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Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt in Southeastern Missouri, 2018–21

Kendra M. Markland, Camille E. Buckley, R. Charlton, B.E. Davis, J.V. Davis, R.W. Bell · U.S. Geological Survey

USGS Publications · Papers · License: Public Domain

downstream element lead missouri river sediment southeastern transport

usgs, geological survey, united states, science, government publication, usgs scientific investigations report, 2024, 5085, suspended, sediment, trace, element, transport, big, river, downstream, old, lead, belt, southeastern, missouri, 2018

Prepared in cooperation with the U.S. Environmental Protection Agency

Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt in Southeastern Missouri, 2018–21

Scientific Investigations Report 2024–5085

U.S. Department of the Interior U.S. Geological Survey

Cover.

Photograph of the Big River in Missouri, taken by the U.S. Geological Survey.

Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt in Southeastern Missouri, 2018–21 By Kendra M. Markland and Camille E. Buckley

Prepared in cooperation with the U.S. Environmental Protection Agency

Scientific Investigations Report 2024–5085

U.S. Department of the Interior U.S. Geological Survey

U.S. Geological Survey, Reston, Virginia: 2024

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit https://www.usgs.gov or call 1–888–392–8545. For an overview of USGS information products, including maps, imagery, and publications, visit https://store.usgs.gov/ or contact the store at 1–888–275–8747. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Suggested citation: Markland, K.M., and Buckley, C.E., 2024, Suspended sediment and trace element transport in the Big River downstream from the Old Lead Belt in southeastern Missouri, 2018–21: U.S. Geological Survey Scientific Investigations Report 2024–5085, 45 p., https://doi.org/10.3133/sir20245085. Associated data for this publication: Markland, K.M., Mills, C.T., Schumacher, J.G., Stricker, C.A., Knott, K., Kane, T.J., Lueckenhoff, L., and Campbell, K.M., 2024, Geochemical analyses of water, mine tailings, fluvial suspended sediments, fluvial bed sediments, and fluvial flood deposit sediments from the Big River and Meramec River drainage basins, Missouri: U.S. Geological Survey data release, https://doi.org/10.5066/P1B8YS78. U.S. Geological Survey [USGS], 2023, USGS water data for the Nation: U.S. Geological Survey National Water Information System database, https://doi.org/10.5066/F7P55KJN. ISSN 2328-0328 (online)

iii

Acknowledgments The authors would like to thank the U.S. Environmental Protection Agency for providing technical guidance. The authors also would like to acknowledge the staff from the U.S. Geological Survey Central Midwest Water Science Center who supported the project by assisting with data collection, administration, and technical reviews.

Contents Acknowledgments��iii Abstract��1 Introduction��2 Purpose and Scope��4 Description of Study Area��5 Methods��6 Continuous Stage and Water-Quality Data Collection��6 Discrete Suspended Sediment Sample Collection��6 Passive Suspended Sediment Sample Collection��6 Suspended Sediment Laboratory Methods��7 Quality Assurance and Quality Control��7 Data Analysis and Reporting��8 Surface-Water Quality��14 Streamflow Conditions��14 Continuous Water-Quality Parameters��14 Suspended Sediment Transport��21 Daily Suspended Sediment Concentrations and Loads��21 Event-Based Suspended Sediment Concentrations, Loads, and Yields��21 Trace Element Transport��29 Selected Trace Element Concentrations in Suspended Sediments��29 Selected Trace Element Concentrations in Suspended Sediments from Passive Samplers��37 Summary��41 References Cited��42 Appendixes 1–2. Model Archives Summaries for Regression Models��45

Figures 1. 2. 3.

Map showing study site and location of the Big River Basin��3 Graph showing turbidity duration curve for the study site at the Big River below Bonne Terre, Missouri, October 2018–September 2021��10 Graph showing instantaneous turbidity in relation to discrete suspended sediment concentrations used to develop a regression model for the computation of suspended sediment concentrations and loads for the Big River below Bonne Terre, Missouri, October 2018–September 2021��11 Graph showing instantaneous streamflow in relation to discrete suspended sediment concentrations used to develop a regression model for the computation of estimated suspended sediment concentrations and loads for the Big River below Bonne Terre, Missouri, October 2018–September 2021��12 Graph showing total monthly precipitation at the National Oceanic and Atmospheric Administration DeSoto, Missouri, climate station near the Big River Basin, Mo., October 2018–September 2021��15 Graph showing daily mean streamflow during the study period at the Big River below Bonne Terre, Missouri, October 2018–September 2021��17

7. 8. 9.

10. 11. 12.

13.

14.

Graph showing daily mean water temperature measured at the Big River below Bonne Terre, Missouri, October 2018–September 2021��19 Graph showing daily mean turbidity measured at the Big River below Bonne Terre, Missouri, October 2018–September 2021��20 Graph showing continuous streamflow and discrete suspended sediment concentration samples collected at the Big River below Bonne Terre, Missouri, October 2018–September 2021��24 Graph showing daily mean suspended sediment concentrations computed at the Big River below Bonne Terre, Missouri, October 2018–September 2021��25 Graph showing daily mean suspended sediment loads computed at the Big River below Bonne Terre, Missouri, October 2018–September 2021��26 Graphs showing trace element concentrations in two suspended sediment size fractions collected during stormflow events at the Big River below Bonne Terre, Missouri, October 2018–September 2021��32 Boxplot showing comparison of trace element concentrations in the fine sediment size fraction for stormflow events collected at the Big River below Bonne Terre, Missouri, October 2011–September 2013, and October 2018– September 2021��34 Boxplot showing trace element concentrations in suspended sediment collected with passive samplers and collected as discrete samples during stormflow events at the Big River below Bonne Terre, Missouri, October 2011– September 2013, and October 2018–September 2021��39

Tables 1. 2.

4. 5. 6. 7.

8. 9.

10.

Location information for the study site at the Big River below Bonne Terre, Missouri��5 Reporting limits of laboratory analyses for suspended sediment samples analyzed by the U.S. Geological Survey Mineral Research Laboratory contracted laboratory��8 Percent recoveries of select trace elements in standard reference samples submitted with suspended sediment samples for analysis by the U.S. Geological Survey Mineral Research Laboratory contracted laboratory��9 Summary statistics of model-calibration datasets for the Big River below Bonne Terre, Missouri, October 2018–September 2021��12 Streamflow statistics for the Big River below Bonne Terre, Missouri, October 2011–September 2013 and October 2018–September 2021��16 Water-quality statistics for the Big River below Bonne Terre, Missouri, October 2018–September 2021��18 Concentrations and particle-size distributions of suspended sediment in discrete samples collected at Big River below Bonne Terre, Missouri, October 2018–September 2021��22 Summary of suspended sediment concentration and load statistics by water year at the Big River below Bonne Terre, Missouri, October 2018–September 2021��27 Suspended sediment concentrations, load, and yields from sampled stormflow events at the Big River below Bonne Terre, Missouri, October 2018– September 2021��28 Streamflow, suspended sediment concentrations and particle-size distributions, and selected total trace element concentrations in suspended

vii

11.

12. 13.

14.

15.

sediments collected during stormflow events at the Big River below Bonne Terre, Missouri, October 2018–September 2021��30 Selected trace element concentrations in suspended sediment collected during stormflow events at the Big River below Bonne Terre, Missouri, October 2018–September 2021��31 Consensus-based sediment quality guidelines for selected trace elements��34 Selected trace element concentrations, loads, and yields in suspended sediments collected during stormflow events at the Big River below Bonne Terre, Missouri, October 2018–September 2021��35 Particle-size distribution and selected trace element concentrations in suspended sediments collected with passive samplers at the Big River below Bonne Terre, Missouri, October 2018–September 2021��38 Annual loads of selected trace elements in suspended sediments collected with passive samplers at the Big River below Bonne Terre, Missouri, October 2018–September 2021��40

Conversion Factors U.S. customary units to the International System of Units

Multiply

To obtain

Length inch (in.)

2.54

centimeter (cm)

foot (ft)

0.3048

meter (m)

mile (mi)

1.609

kilometer (km)

Area acre square mile (mi2) square mile (mi2)

4,047

square meter (m2)

2.590 259.0

square kilometer (km2) hectare (ha)

Flow rate cubic foot per second (ft3/s)

0.02832

cubic meter per second (m3/s)

foot per second (ft/s)

0.3048

meter per second (m/s)

gallon (gal)

3.785

liter (L)

cubic foot (ft3)

0.02832

cubic meter (m3)

cubic yard (yd3)

0.7646

cubic meter (m3)

Volume

Mass ton, short (2,000 lb)

0.9072

metric ton (t)

pound, avoirdupois (lb)

0.4536

kilogram (kg)

pound per square mile per hour (lb/mi2/hr)

0.1751

pound per cubic foot (lb/ft3)

16.02

Yield kilogram per square kilometer per hour (kg/km2/hr)

Density kilogram per cubic meter (kg/m3)

viii

International System of Units to U.S. customary units

Multiply

To obtain

Length millimeter (mm)

0.03937

inch (in.)

meter (m)

3.281

foot (ft)

Volume cubic meter (m3)

1.308

cubic yard (yd3)

liter (L)

33.81402

ounce, fluid (fl. oz)

Mass gram (g)

0.03527

ounce, avoirdupois (oz)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: °F=(1.8×°C)+32

Datum Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Supplemental Information Concentrations of chemical constituents in water are given in milligrams per liter (mg/L) or micrograms per liter (µg/L). Concentrations of chemical constituents in sediments are given in milligrams per kilogram (mg/ kg) or parts per million (ppm). Turbidity is given in formazin nephelometric units (FNU). A water year is the period from October 1 to September 30 and is designated by the year in which it ends; for example, water year 2021 was from October 1, 2020, to September 30, 2021.

Abbreviations <

less than

CMWSC

Central Midwest Water Science Center

EPA

U.S. Environmental Protection Agency

EWI

equal-width increment

FNU

formazin nephelometric units

MRL

Mineral Research Laboratory

NOAA

National Oceanic and Atmospheric Administration

NWIS

National Water Information System

OLB

Old Lead Belt

PEC

probable effect concentration

PVC

polyvinyl chloride

quality assurance

SSC

suspended sediment concentration

SSL

suspended sediment load

TEC

threshold effect concentration

TET

toxic effect threshold

USGS

U.S. Geological Survey

YSI

Yellow Springs Instruments

Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt in Southeastern Missouri, 2018–21 By Kendra M. Markland1 and Camille E. Buckley2

Abstract The Big River in southeast Missouri drains the Old Lead Belt, an area of major lead mining from the 1860s until 1972 where more than 8.5 million tons of lead were mined. After active mining ceased, the effects of mining activities persisted in the Big River system because of large mine waste pile erosion, and floodplain sediment and streambank contamination along several tributaries and the main stem of the Big River. Lead-contaminated streambed and floodplain sediments extend more than 90 miles from the Old Lead Belt to the confluence of the Big River with the Meramec River. The waste piles and mine-waste contaminated streambed and floodplain sediments have been sources of high concentrations of several trace elements, primarily cadmium, lead, and zinc. The U.S. Environmental Protection Agency Region 7 has made several efforts to prevent further erosion of contaminated sediments into the Big River including the capping of major mine waste piles, reclaiming sediment deposits along the floodplains, and monitoring soil conditions of croplands and residential properties. A cooperative effort began in 2011 between the U.S. Geological Survey and the U.S. Environmental Protection Agency Region 7 to characterize suspended sediment quantity and quality in the Big River downstream from the Old Lead Belt as reclamation activities in the drainage basin progressed. The study was completed in two phases, and each phase included continuous stage, turbidity, and water temperature monitoring at the Big River below Bonne Terre, Missouri, streamgage and sampling station. Periodic suspended sediment samples also were collected manually (discrete samples) during base flow and selected stormflow events. Continuous streamflow, turbidity, and discrete suspended sediment data were used to develop regression models to compute daily suspended sediment concentrations and loads. During both phases, the discrete stormflow event samples were also evaluated to determine particle size distribution and concentrations of select trace elements. Phase one 1U.S. Geological Survey. 2Formerly U.S. Geological Survey.

was completed from October 2011 through September 2013, and phase two, which is the primary focus of this report, was completed from October 2018 through September 2021. Phase two also included time-integrated suspended sediment samples collected using passive samplers. Discrete samples (collected during stormflow events) and passive samples were analyzed for concentrations of barium, cadmium, lead, and zinc in two sediment size fractions (when possible) to estimate trace element loads. Suspended sediment concentrations and loads and select trace element concentration results computed during phase one were compared to those computed during phase two to identify trends in the Big River Basin during the full study period. The concentrations of cadmium, lead, and zinc in nearly all discrete stormflow event suspended sediment samples and passive suspended sediment samples exceeded the threshold effect concentrations and the probable effect concentrations, which are two sediment quality guidelines. Most samples also exceeded the toxic effect threshold, the level at which sediment is considered to be heavily contaminated and problematic for sediment-dwelling organisms. Bulk cadmium concentrations (median of 7.90 milligrams per kilogram [mg/ kg]) exceeded the toxic effect threshold (3.0 mg/kg) in 17 discrete stormflow event samples, and bulk lead concentrations (median of 1,070 mg/kg) exceeded the toxic effect threshold (170 mg/kg) in all 18 discrete stormflow event samples. Bulk zinc concentrations (median of 500 mg/kg) exceeded the toxic effect threshold (540 mg/kg) in eight discrete stormflow event samples. Bulk concentrations of these trace elements in passive suspended sediment samples were slightly greater, with concentrations of cadmium (median of 14.0 mg/kg) and lead (median of 1,860 mg/kg) exceeding the toxic effect threshold in all 18 samples. Bulk concentrations of zinc (median of 733 mg/kg) exceeded the toxic effect threshold in 15 passive samples. Compared to phase one (water years 2012–13), phase two (water years 2019–21) concentrations of lead and cadmium in the fine fraction of discrete suspended sediment samples collected at Big River below Bonne Terre were statistically similar; concentrations of barium and zinc were statistically smaller in samples collected during phase two (water years 2018–21).

2 Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt, 2018–21 Sediment quality data from passive samples and daily mean suspended sediment loads from the regression model were used to calculate annual oads of barium, cadmium, lead, and zinc at the Bonne Terre streamgage. Water year 2019 had the largest loads of barium, cadmium, lead, and zinc (58.6, 1.43, 194, and 76.5 tons, respectively). The total loads of barium, cadmium, lead, and zinc for phase two (water years 2019–21) were 149, 4.00, 520, and 213 tons, respectively. Less than 5 percent of the total lead load calculated for the study period was transported when daily mean streamflow was less than 455 cubic feet per second, which is the approximate flow at which the passive samplers were inundated and began sampling. This highlights that most of the lead load is transported during stormflow events and the effectiveness of using passive samplers for ongoing monitoring of the Big River. Annual suspended sediment loads at the Bonne Terre streamgage computed using the regression model were 113,000 tons in water year 2019, 83,400 tons in water year 2020, and 96,500 tons in water year 2021. The event-based suspended sediment loads for the eight sampled stormflow events ranged from 45.3 to 32,500 tons. Although only a portion of all stormflow events during phase two were sampled, the loads accounted for during these eight stormflow events represented approximately 30.9 percent of the total suspended sediment load calculated for the study period, confirming that a large part of suspended sediments continue to be transported in the Big River during stormflow events. Event-based loads of barium, cadmium, lead, and zinc were greatest during the stormflow events sampled in January 2020 (event 4) and March 2021 (event 8). Event-based loads calculated for event 4 for barium, cadmium, lead, and zinc were 17.1, 0.206, 27.2, and 14.5 tons, respectively. During event 8, an estimated 15.6 tons of barium, 0.239 tons of cadmium, 34.0 tons of lead, and 13.6 tons of zinc were transported in suspended sediments. The continued high concentrations of lead in suspended sediments in the Big River, despite reclamation activities, is likely because of the continual transport from streambed and stream banks of lead-enriched sediment, which remain in the system from historical mining activities.

Introduction The Southeast Missouri Mining District contains part of the world’s largest known lead deposits, and organized lead mining has taken place in the region since the mid-1860s (Pavlowsky and others, 2010). Initial mining in the region was mostly small, scattered surface excavations that began in the 1700s. In the 1860s, mining practices expanded substantially to large scale, multilevel subterranean mining when St. Joseph Lead Company purchased 964 acres of land near Bonne Terre, Missouri, in what would become known as the Old Lead Belt (OLB) subdistrict (fig. 1). At one time, the company operated the largest lead mill in the world (Federal Mill No. 3), and by the early 1900s, 15 companies were mining within the OLB

(Missouri Department of Natural Resources, 2020, 2021). From 1869 through 1972, the OLB was the global leader in lead production (Pavlowsky and others, 2010). More than 8.5 million tons of lead were mined within the OLB before the last operation closed in 1972 (Missouri Department of Natural Resources, 2020, 2021). More than 200 years of intense mining in the OLB and vicinity resulted in the disposal of mine waste that has been subject to wind and water erosion. Some mine waste was mechanically transported around the region and used in construction, such as in haul roads and rail spurs (U.S. Environmental Protection Agency [EPA], 2021). Early mining and mill methods were small operations that ground the ore into sand- to gravel-sized fragments, and the denser lead ore was gravity separated from the waste rock using large gigs or shaker tables (Mugel, 2017). Wastes from these early years of mining were called chat, and numerous small operations were scattered across the region. After the discovery of rich subsurface deposits in the 1860s near the towns now known as Bonne Terre and Park Hills, the scale of the mining and milling operations increased substantially. Ore was ground into smaller sizes, and larger gravity operations were used to concentrate the lead ore. The volume of mine waste increased as mining activities intensified, resulting in large waste piles as much as several hundred feet tall. Beginning in the early 1900s, the floatation process was introduced, which greatly improved the recovery of lead. Floatation required the grinding or milling of ore to fine powder (silt to fine sand). Waste from the floatation process, called tailings, was slurred into large impoundments, where the water eventually decanted. The tailings ponds were either constructed by building a dam across a tributary using coarser chat or building large berms along streams to hold the tailings (Pavlowsky and others, 2010). Seven of the major mine waste areas within the OLB are located along the Big River or its tributaries and cover more than 2,800 acres (fig. 1) with an estimated volume of more than 39 million cubic yards (yd3; Mosby and Weber, 2009). The proximity of these waste areas to streams resulted in a continuous source of contamination to the drainage basin since the mid-1860s. Contaminants of interest include the trace elements cadmium, lead, and zinc. Lead is of greatest concern because it was the primary mined metal and is toxic with negative physical and neurological effects for humans, especially young children (EPA, 2022). Sediments from the mine waste areas and surrounding contaminated soils transported as wind and storm runoff resulted in these toxic metals entering the Big River and its tributaries. Because of a period of heavy rainfall in 1977, about 38,000 cubic meters (m3) of mine waste from the Desloge tailings pile slumped and was released into the Big River (EPA, 2021; fig. 1). Several studies have investigated the extent of trace element contamination in the region since the 1970s, and metal-contaminated streambed and floodplain sediments have been documented along the approximately 90 miles (mi) of the Big River downstream from the OLB to the confluence with

Introduction 3 90°30'

91°00' 38°30'

ST LOUIS

EXPLANATION

FRANKLIN

JEFFERSON

St. Louis

Major mine waste area Major lead mined area

r ve

ram

Major barite mined area

Extent of the Big River Basin Big River near Byrnesville 07018500

Old Lead Belt boundary area Big River, main stem 07018500

U.S. Geological Survey streamgage and identifier Missouri Department of Conservation access at Cherokee Landing

MISSOURI

CRAWFORD

FRANKLIN

ILLINOIS

Big River near Richwo ods 07018100

WASHINGTON

Big River below Bonne Terre 07017610 JEFFERSON

Cherokee landing

Cr ee

Mineral Point

Bonne Terre

M ill

38°00'

er al

rk Fo

Big River near Desloge 07017260

BONNE TERRE

DESLOGE HAYDEN Big River near CREEK

ST GENEVIEVE

Park Hills

Desloge

NATIONAL

ELVINS

FEDERAL

Irondale 07017200

LEADWOOD

Rive

Map area

ST FRANCOIS

WASHINGTON IRON

ST FRANCOIS

IRON Base from Environmental Systems Research Institute basemap, 2017, 1:100,000 National Hydrologic dataset, 2011, 1:100,000 U.S. Geological Survey digital data, 1:100,000, 1995 Universal Transverse Mercator projection, Zone 15 North

0 0

Figure 1. Study site and location of the Big River Basin.

5 5

10 10

MISSOURI

MADISON

15 20 KILOMETERS

20 MILES

Mining data from Mugel (2017)

4 Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt, 2018–21 the Meramec River. A study by the U.S. Geological Survey (USGS) and the Missouri Department of Natural Resources included sampling of the Meramec River upstream and downstream from the Big River confluence. Samples collected downstream from the Big River-Meramec River confluence contained higher concentrations of lead than samples collected upstream from the confluence, indicating that contaminated sediments from the Big River were also moving into the Meramec River (Barr, 2016). Lead concentrations more than 1,000 milligrams per kilogram (mg/kg) were present in floodplain sediment along the lower Meramec River, and concentrations as large as 334 mg/kg have been recorded in recent floods (Pearson and Hanes, 2016). A study of channel sediment and floodplain deposits along 106 river miles of the Big River (from Leadwood, Mo., to the confluence with the Meramec River) concluded that approximately 3,700,000 m3 of contaminated sediment was stored in the channel and 86,800,000 m3 was stored in the floodplain. Floodplain sediments were contaminated above the residential soil threshold limits for lead (400 parts per million [ppm]) along the entire stretch of the Big River study area to a depth of 1–4 meters (m) or more (Pavlowsky and others, 2010). The EPA and responsible parties have completed remedial actions at six of the eight major mine waste areas in the OLB. Remediation included reducing and stabilizing slopes, capping waste piles, and revegetating the areas to prevent further release of mine waste. Mine waste area remediation projects completed to date include: the Bonne Terre (2007); the Elvins pile (2009); the Leadwood pile (2010); the National pile (2012); and the Federal Pile (2021; EPA, 2021). The former Desloge pile (site of the 1977 release) was stabilized in 2000 and currently (2023) is being used as an onsite soil repository for lead-contaminated soils, as is the eastern area of the former Bonne Terre pile (EPA, 2023). All six of these remediation projects have taken place at mine waste areas next to the Big River or its tributaries. The EPA continues to test and cleanup lead-contaminated surficial soils at thousands of residential yards in the region. The EPA is assessing remedial actions for the contaminated streambed and floodplain sediment. Remedial actions for mine wastes used in construction, such as in railroad lines and spurs in the region, also are being assessed (EPA, 2021). Both phases of this study sought to quantify suspended sediment and trace element contamination downstream from the OLB. During phase one (water years 2012 and 2013 [October 1, 2011, through September 30, 2013]), suspended sediment concentrations (SSCs) were measured and suspended sediment loads (SSLs) were computed at two sampling sites on the Big River. During stormflow events, select trace element concentrations also were measured and loads were calculated (Barr, 2016). Phase one sought to understand sediment transport processes and develop a baseline for suspended sediment and trace element loads as the six major mine waste areas were remediated. During phase one (water years 2012–13), nearly 30 percent of the total SSL

at the downstream and upstream sites was accounted for in the six sampled stormflow events indicating that rain events transported a large portion of the sediment in the Big River. Additionally, trace element yields were higher at the upstream site indicating that contaminated sediments were more readily available in that area of the Big River drainage basin (Barr, 2016). The phase one study ended as the major mine waste pile remediation was being completed and thus was unable to quantify the effects of mine-waste pile remedial efforts. This, in addition to ongoing remedial activities in the drainage basin and legacy mine-waste contaminated streambed and floodplain sediments, necessitated continued data collection at the Big River below Bonne Terre sampling site to better quantify the effect of remediation on suspended sediment quantity and quality. Using methods similar to those used by Barr (2016), the purpose of phase two was to continue monitoring the quantity and quality of suspended sediments transported in the Big River downstream from the OLB. The USGS, in cooperation with the EPA Region 7, completed this second phase of the intensive effort (water years 2019–21) to assess suspended sediment and trace element transport as remedial efforts continued; phase two used one station from the phase one study. Regression models were used to compute daily SSC and SSL for each study period. Discrete suspended sediment samples were obtained during base-flow and stormflow conditions. Suspended sediment quality was assessed by analyzing samples obtained during stormflow events for select trace element concentrations. Loads and yields of sediment and select trace elements also were calculated for the sampled stormflow events. Phase two incorporated passive samplers in the collection of sediment, from which samples were analyzed for trace element concentrations and were used to calculate loads of barium, cadmium, lead, and zinc.

Purpose and Scope The purpose of this study was to monitor the quantity and quality of suspended sediments transported in the Big River downstream from the OLB as reclamation activities in the drainage basin progressed. Suspended sediment and trace element data were collected during water years 2019–21 (October 1, 2018, through September 30, 2021; phase two) downstream from the OLB at the Big River below Bonne Terre, Missouri (USGS site number 07017610; hereinafter referred to as the study site; table 1). This report describes the methods and techniques used in the collection and analysis of water quality samples during water years 2019–21 and presents the results and interpretations of that data. Comparisons of these data to results from phase one (water years 2012–13; Barr, 2016) also are presented to determine whether trace element concentrations have changed significantly in the Big River drainage basin in the OLB after major mine waste area remediation efforts.

Introduction 5

Description of Study Area The Big River drainage basin drains 955 square miles (mi2) of southeast Missouri (fig. 1) and is a tributary to the Meramec River. Land use within the Big River drainage basin is primarily forest and pasture, with some agriculture and urban land uses (Missouri Department of Conservation, 1997). The Big River headwaters are northeast of the city of Ironton, Iron County (not shown), where the river is as narrow as 50 feet (ft). The rugged topography and steep drainage divides create a streambed composed of mainly cobble, gravel, and sand. As the river meanders north towards the confluence with the Meramec River in Jefferson County, it widens to nearly

100 ft in some locations. The downstream topography transitions to floodplains, and the streambed changes to sand and silt (Barr, 2016). The study site was chosen for consistency with phase one (Barr, 2016). The site is approximately 3 mi north of the city of Bonne Terre and is at the bridge crossing at County Highway E (fig. 1, Highway E not shown; table 1). The orifice line for the pressure transducer and continuous water-quality monitor is housed underneath the bridge and on the left riverbank (facing downstream). The site drains 409 mi2, and the river channel is 2–3 ft deep and as much as 60 ft wide during base-flow conditions. The riverbed is composed of fine sands, gravels, cobbles, and some boulders (Barr, 2016).

Table 1. Location information for the study site at the Big River below Bonne Terre, Missouri. [Data are from the U.S. Geological Survey National Water Information System database (U.S. Geological Survey, 2023). Coordinates are given degrees, minutes, seconds. USGS, U.S. Geological Survey; mi2, square mile]

USGS site number (fig. 1) 07017610

Station name

Latitude

Longitude

Big River below Bonne Terre, Missouri

37°57'54.9"

90°34'28.2"

Drainage area (mi2) 409

County St. Francois

Period of streamflow record used in this study October 2011– September 2021

6 Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt, 2018–21

Methods To quantify the transport of sediment and select trace elements in the Big River, continuous stage and water-quality data and discrete and passive suspended sediment samples were collected at the study site. Field, laboratory, quality assurance, quality control, and data analysis methods are described.

Continuous Stage and Water-Quality Data Collection During the entire study period (water years 2012–21 [October 1, 2011, through September 30, 2021]), the sampling site was equipped with a streamgaging station to measure streamflow and continuous water quality. Measurements of stage, temperature, and turbidity were recorded every 15 minutes although some periods are missing because of intermittent funding, equipment failures, low-flow conditions, biofouling, and (or) data corrections that exceeded calibration criteria. Continuous data collected during this study are available through the USGS National Water Information System (NWIS; USGS, 2023) database. Streamflow measurements were obtained every 4–6 weeks and during selected stormflow events using an acoustic Doppler current profiler. This information was used to maintain the stage-discharge relation following standard USGS methods and techniques (Rantz and others, 1982; Oberg and others, 2005; Turnipseed and Sauer, 2010; Mueller and others, 2013). Water temperature and turbidity were measured in phase one using a Yellow Springs Instruments (YSI) 6-series sonde and then upgraded in 2015 to an EXO2 sonde, which includes a central wiper. The temperature probe measures degrees Celsius (°C) and is calibrated using a three-point calibration with a National Institute of Standards and Technology thermometer. The turbidity probe measures formazin nephelometric units (FNU) and is calibrated using a three-point calibration and YSI’s calibration standards (Wagner and others, 2006). The YSI EXO2 was serviced approximately every 8–12 weeks, which included cleaning the sonde and calibration checks on the turbidity sensor. The temperature sensor calibration was checked approximately every 12 months. The streamgage was equipped with a data collection platform that stored data from the pressure transducer that measured stage and the sonde that measured water temperature and turbidity. Data were transmitted hourly via satellite telemetry. The sonde was deployed using a polyvinyl chloride (PVC) pipe with several 1-inch (in.) holes drilled in it. Water from the river was able to flow through the pipe and around the sensors reducing issues associated with measuring stagnant water in the pipe.

Discrete Suspended Sediment Sample Collection Traditional cross-sectional sampling methods were used to collect suspended sediment samples during base-flow and high flow conditions. During base-flow conditions, suspended sediment samples were collected approximately 40 ft upstream from the bridge by wading the stream and using the equalwidth increment (EWI) method (USGS, 2006). The EWI method involves sampling at a minimum of 10 equally spaced locations (verticals) across the full width of the stream channel. A US DH-81, a depth-integrated and isokinetic sampler (a sampler in which stream water approaching and entering the sampling nozzle have the same velocity) was used. The US DH–81 consists of a 1-liter (L) sampling bottle with a 1/4-in. Teflon or polypropylene nozzle mounted on the end of a sampling rod. Samples were collected at each vertical with a consistent transit rate (vertical speed). The samples at each vertical were composited into one or more sampling bottles. If the minimum mean stream velocity was less than 1.5 feet per second (ft/s), the sample was collected using grab sample methodology because of the lack of isokinetic conditions (USGS, 2006). The equipment used are described in Wilde and others (2014). Streamflow measurements were collected in the same location as the sediment sample. During stormflow events, measurements and samples were collected from the downstream side of the bridge deck on Highway E using the same EWI method. Samples were collected across the hydrologic event, targeting the rising limb, peak, and falling limb when possible. Streamflow was measured nearest to the peak as possible. Depending on stream conditions, either a US DH–95 or US DH–2 sampler was used. USGS personnel operated the sampler, which was attached to a reel and cable mechanism mounted on a vehicle. The sampler was raised and lowered at a constant speed according to the transit rate, which is calculated from the maximum stream velocity and depth. It should be noted that an unsampled zone exists when using these samplers (4 in. for the DH–81 and DH–2 and 4.8 in. for the DH–95; Davis, 2005; Wilde and others, 2014). The unsampled zone includes the area closest to the streambed that cannot be reached by the nozzle; this area can transport a higher concentration of coarse sediment than the rest of the water column. This part of unsampled suspended sediment may or may not account for a substantial portion of the total suspended sediment and is dependent upon stream velocity, depth, and turbulence (Edwards and Glysson, 1999).

Passive Suspended Sediment Sample Collection Suspended sediment samples were collected passively during the duration of high-flow events using Walling tube samplers (Phillips and others, 2000). Passive sampling is ideal in situations when sampling teams cannot be onsite to collect suspended sediment. In some instances, smaller hydrologic events can happen quickly and without enough time to prepare

Methods 7 for physical sampling. A Walling tube sampler can be set at a fixed height, and when inundated by the stream during an event, sediments are trapped inside as the velocity slows when water moves through the tube. Placement of the samplers at or near a streamgage allows for sampling a part of a hydrologic event. Samples collected by passive samplers are considered a general representation of a hydrologic event. The sampling tubes were constructed from 1 m in length schedule 40 PVC well casings with an inner diameter of 98 millimeters (mm). A conical head is installed on the receiving end of the tube (facing upstream) that threads into the main tube body. A hole was drilled into the end of the conical head and threaded to accept a 1/4-in. USGS D–96 or D–74 sampler nozzle. A 4-in. PVC cleanout with a threaded plug was glued to the other end of the tube, and a 1/4-in. diameter hole was drilled in the center of the plug. Two samplers were secured to metal posts on the left stream bank (nozzles facing upstream) several feet above base-flow stage such that the lower sampler became inundated at a stage of about 4.82 ft (streamflow of approximately 445 cubic feet per second [ft3/s], per rating curve [relation between river stage flow] current for the deployment period) and the upper sampler was inundated at a stage of approximately 5.52 ft (streamflow of approximately 715 ft3/s). If an event happened that would have inundated the samplers, a service visit was done to collect any suspended sediment trapped in the tube during the event(s). During servicing, the nozzle was removed and both openings on the sampler tubes were temporarily plugged before removing the samplers from the mounting posts and rocking them slowly to resuspend sediment within the tube. The tube was then held vertically, and the sediment slurry allowed to drain out the conical end into a clean 1- or 2-gallon plastic container. The plug on the rear of the tube was removed, and the inside of the tube was rinsed with 200–300 milliliters (mL) of native stream water using a small plastic 1-L sprayer. Sediment from the two samplers was composited before submission to the Central Midwest Water Science Center (CMWSC) Sediment Laboratory in Rolla, Mo., for further processing.

Suspended Sediment Laboratory Methods All suspended sediment samples collected during this study were sent to the USGS CMWSC Sediment Laboratory in Rolla, Mo., for particle-size analyses, and all results are available via NWIS (USGS, 2023). Routine discrete samples were analyzed only for SSC using a filtration method (Guy, 1969). Discrete and passive stormflow event samples were analyzed for SSC and particle-size distribution of sands (2–0.063 mm) and fines (less than [<] 0.063 mm). All suspended sediment samples received at the laboratory were allowed to settle before excess water was decanted. Discrete stormflow event samples were analyzed for particle-size distribution using the wet-sieve method (Guy, 1969). Nylon sieves were used to reduce trace element contamination that could be

introduced from the traditional brass sieves. Each portion was placed into separate glass dishes to dry at 80 °C and then for an hour at 103 °C (Guy, 1969). Passive sample sediments were analyzed for particle-size distribution by the dry-sieve method (Guy, 1969) also using nylon sieves after being air-dried and disaggregated. Dried parts of sands and fines from discrete and passive samples were retained after analysis to be used for trace element analyses. The dried fractions of sediments from the passive samplers were split into two equal parts using a stainless-steel universal sample splitter. One portion was submitted for trace element analysis to the USGS Mineral Research Laboratory (MRL) in Denver, Colorado, and the other portion was retained and archived. Any discrete or passive stormflow event sample that had a mass of sands or fines larger than 0.5 gram was sent for trace element analysis on the individual fraction. If any dried size fraction did not meet the minimum mass requirement for trace element analysis, the two fractions were recombined and submitted as a bulk sample (sediment <2 mm in size). Samples were shipped in sealed plastic bags. Submitted samples were analyzed for 49 major and trace elements by inductively coupled plasma mass-spectrometry (Taggart, 2002). The results for the trace elements barium, cadmium, lead, and zinc are presented in this report. Results for the additional major and trace elements are available from the NWIS database (USGS, 2023) or Markland and others (2024).

Quality Assurance and Quality Control Quality assurance (QA) and quality control protocols were followed during this study to ensure data met USGS quality standards. A QA plan, which is summarized here, was created to document techniques and methods. The study site was previously selected by Barr (2016) to reduce fouling, presence of low-flow conditions, and damage from flooding or vandalism. Data transmissions to NWIS were reviewed daily for erroneous data. All site visit and sampling information, including a description of tasks completed and additional notes, was documented and archived. Laboratory analysis request forms were used for the sediment laboratory and MRL for tracking and documentation purposes. Streamflow and stage data from the streamgage were used to monitor and predict the need for stormflow event sampling and servicing of the continuous water-quality equipment. Calibration and maintenance of equipment was completed following USGS methods described by Wagner and others (2006). During each visit, equipment was cleaned and checked for damage and calibration drift. Corrections for calibration drift, fouling corrections, or both were applied to data as needed. If corrections exceeded USGS criteria, the erroneous data were removed from the record (Wagner and others, 2006). Precautions were taken to minimize contamination of samples from sampling equipment, vehicles, and surroundings. The “clean hands/dirty hands” sampling technique was

8 Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt, 2018–21 followed during sediment sampling (USGS, 2006). Sample containers were kept sealed and protected in a large plastic bag to prevent contamination by airborne debris introduced by wind, vehicle traffic, sampling equipment, bridge railings, and precipitation. To identify and quantify any bias and variability associated with the sampling and processing techniques, quality control samples were collected in the form of field replicates, laboratory replicates, equipment blanks, and analysis of standard reference samples of known chemistry. Field replicate samples for the passive samples were collected by treating each Walling tube as a separate sample for selected periods, with one sample assigned as the regular sample and the other as the field replicate. Field blanks were not collected; however, pure silica and silica powder were used to prepare a source blank “sediment,” which was submitted to the USGS CMWSC Sediment Laboratory in Rolla, Mo., and to the MRL. In the sediment laboratory, the silica blanks were dried, sieved, and split in an identical manner to the environmental samples. A sample of the pure silica powder also was submitted as a source blank. Splits from the silica blanks were submitted to the MRL for chemical analysis. All USGS sediment laboratories undergo biannual QA tests to maintain consistency for all laboratories. Results from the QA tests are available from the USGS Branch of Quality Systems at https://bqs.usgs.gov/ SLQA/. The MRL splits 10 percent of samples into split replicates and submits samples of known composition with each batch of samples submitted to the contract laboratory. Additional information on the methods used at the MRL can be found at https://minerals.cr.usgs.gov/. The reporting limits for laboratories used during the study are provided in table 2. Each batch of samples analyzed at the MRL contract laboratory included the analysis of a standard reference sample with preferred/expected concentrations for barium, cadmium, lead, and zinc. The goal of the MRL program is for values in the reference samples to be reported within 15 percent of the preferred/expected value (recovery between 85 and 115 percent). The mean recoveries for the four trace elements ranged from 93.0 to 106 percent (table 3). It was noted that the analytical batch associated with most of the analyzed passive

samples had reported maximum recoveries of barium and lead in the reference samples that were 117 and 129 percent of the expected/preferred values, respectively (table 3). The results of the replicate passive samples (n=9) had barium, cadmium, lead, and zinc relative percent differences of 5.2, 7.4, 6.0, and 4.9 percent, respectively. The results from the silica source blanks (n=12) that were processed in an identical manner to the environmental samples had average barium, cadmium, lead, and zinc concentrations of 12.6, <0.02, 6.1, and 5.3 mg/kg, respectively. The range of concentrations in the blanks were 8–23 mg/kg for barium, <0.02–0.03 mg/kg for cadmium, 1.4–34.5 mg/kg for lead, and 2.6–9.2 mg/kg for zinc. The lead concentration of 34.5 mg/kg was anomalous, as the lead concentration in the other 11 silica blanks sample results were less than 8 mg/kg. The results of the pure silica source material that was not processed but was submitted directly to the MRL for chemical analysis (n=3) had mean barium, cadmium, lead, and zinc concentrations of 10.7, 0.1, 12.6, and 10.9 mg/kg, respectively (Markland and others, 2024).

Data Analysis and Reporting Streamflow, water temperature, and turbidity were recorded every 15 minutes during the study period, and these measurements were used to calculate daily mean, monthly mean, and annual mean values. Additionally, SSC and SSL data were used to compute daily, monthly, and annual mean values. Statistics for all daily data collected by USGS during the study period are available from the NWIS database (USGS, 2023). Monthly precipitation information used in this report was gathered from the National Oceanic and Atmospheric Administration (NOAA) and are cumulative monthly precipitation measurements (NOAA, 2022). This study used turbidity, streamflow, and discrete SSC data from stormflow event and routine base-flow samples to develop regression models to estimate continuous (15-minute) SSCs and SSLs. Because the magnitude of turbidity in riverine systems is typically proportional to the SSC (Rasmussen and others, 2009), continuous turbidity measurements can be used to develop a regression model between turbidity and discrete

Table 2. Reporting limits of laboratory analyses for suspended sediment samples analyzed by the U.S. Geological Survey Mineral Research Laboratory contracted laboratory. [ppm, part per million; mg/L, milligram per liter; USGS SDMO, U.S. Geological Survey Missouri Sediment Laboratory, mm, millimeter; %, percent]

Analyzing laboratory

Analytical reference

Barium (Ba)

Constituent

1 ppm

aAGAT Labs

Taggart, 2002

Cadmium (Cd)

0.02 ppm

aAGAT Labs

Taggart, 2002

Lead (Pb)

0.1 ppm

aAGAT Labs

Taggart, 2002

Zinc (Zn)

0.5 ppm

aAGAT Labs

Taggart, 2002

Suspended sediment concentration (SSC)

0.5 mg/L

USGS SDMO

Guy, 1969

Suspended sediment, percent finer than 0.063 mm

USGS SDMO

Guy, 1969

aU.S. Geological Survey contracted laboratory.

Reporting limit

Methods 9 Table 3. Percent recoveries of select trace elements in standard reference samples submitted with suspended sediment samples for analysis by the U.S. Geological Survey Mineral Research Laboratory contracted laboratory. [Data are from Markland and others, 2024. ppm, part per million]

Reference material

Number of analytical batches

aSAR-L.1 (Preferred/expected value)

Minimum recovery, in percent

Barium (ppm)

Cadmium (ppm)

Lead (ppm)

Zinc (ppm)

879

578

420

87.9

92.7

90.7

90.2

117

112

114

129

Mean recovery, in percent

102

101

SAR-M.1 (Preferred/expected value)

764

Maximum recovery, in percent

Minimum recovery, in percent

101

106

4.76

900

890

98.3

91.3

93.7

108

116

94.9

96.4

Mean recovery, in percent

103

104

SAR-H (Preferred/expected value)

866

25.0

98.0

101

Maximum recovery, in percent

Mean recovery, in percent

93.0 3,890

95.5 3,680

94.9

101

aIncluded the analytical batch associated with 12 of the 16 passive samples submitted March 2019 through March 2021.

SSC samples collected during base-flow conditions and stormflow events. Collection of suspended sediment samples across a range of hydrologic conditions increases the robustness of the regression models and confidence in the results (Rasmussen and others, 2009). Outliers were identified in the dataset after reviewing data for erroneous entries and errors in sampling or laboratory methods. Duration curves of turbidity data indicate that turbidity remained within the range of sensor accuracy (1,000 FNU) during the entirety of phase two (fig. 2). During phase two (water years 2019–21), 40 discrete suspended sediment samples were collected, although only 35 were used in the development of the turbidity-derived regression model because of missing turbidity data from the sensor at the time of discrete sampling. Graphing nontransformed SSC against turbidity values identified a strong relation between the two properties. Inspection of the data and residual plots identified no outliers. The 35 data pairs were used to calibrate the SSC-turbidity model and are plotted on a log-log scale (fig. 3; table 4), with the final regression model as follows: SSC = 2.7435 × Turb0.999,(1) where

SSC

is suspended sediment concentration, in milligrams per liter; and

Turb

is turbidity, in formazin nephelometric units, measured with a YSI EXO2.

The model information is as follows:

• number of calibration measurements=35; • adjusted coefficient of determination=0.96; • root mean squared error=0.153; and • bias-correction factor=1.06. This regression model using phase two data was compared to the regression model from phase one. An analysis of covariance was used to compare the two regression lines and whether they were significantly different with respect to either slope or intercept (defined as p-value <0.05). The slopes of the two regression models were not significantly different (p-value equal to 0.815), but the intercepts were different from each other (p-value <0.001). Because of the significant difference between the two regression models, the phase two model replaced the phase one model for SSC and SSL calculations for phase two of the study period. The shift in the regression between the two phases could be because of a change in the nature or grain-size of the sediment. For periods when instantaneous turbidity was not available, a gap-fill framework was used by computing SSC using a secondary regression model based on instantaneous streamflow. Graphing the relation between SSC and streamflow identified a less statistically significant relation than the turbidity relation (fig. 4). Streamflow-derived regression models tend to have greater uncertainty than turbidity-derived regression models (Rasmussen and others, 2009). Suspended sediment concentrations computed using the streamflow-derived model (approximately 42 percent of the record) were flagged as estimated values. The suspended sediment model derived from streamflow is as follows:

10 Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt, 2018–21 10,000

Turbidity, in formazin nephelometric units

1,000

100

0.1

0.01

Percentage of time value was equaled or exceeded

Figure 2. Turbidity duration curve for the study site at the Big River below Bonne Terre, Missouri, October 2018– September 2021. Data are from the U.S. Geological Survey National Water Information System database for site number 07017610 (U.S. Geological Survey, 2023).

100

Methods 11 10,000

Discrete suspended sediment concentration, in milligrams per liter

EXPLANATION Best-fit regression model 1,000

Data pair used in model

100

y =2.7435(x)0.999, where y is the suspended sediment concentration and x is the instantaneous turbidity

Adjusted coefficient of determination: 0.96 n=35 0.1 0.1

100

1,000

Instantaneous turbidity, in formazin nephelometric units

Figure 3. Instantaneous turbidity in relation to discrete suspended sediment concentrations used to develop a regression model for the computation of suspended sediment concentrations and loads for the Big River below Bonne Terre, Missouri, October 2018–September 2021. Data are from the U.S. Geological Survey National Water Information System database for site number 07017610 (U.S. Geological Survey, 2023).

12 Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt, 2018–21 Table 4. Summary statistics of model-calibration datasets for the Big River below Bonne Terre, Missouri, October 2018– September 2021. [Data are from the U.S. Geological Survey National Water Information System database for site number 07017610 (U.S. Geological Survey, 2023). FNU, formazin nephelometric units; mg/L, milligram per liter; ft3/s, cubic foot per second; --, no data; n/a, not applicable]

Time-series dataset (105,078 15-minute values)

Calibration dataset Summary statistic

Turbidity (FNU)

Suspended sediment concentration (mg/L)

Streamflow (ft3/s)

Turbidity (FNU)

Streamflow (ft3/s)

0.6

38.5

Minimum Maximum

551

1,740

15,100

965

16,000

Mean

124

299

3,444

17.1

517

Median

132

1,277

6.3

243

Standard deviation

133

390

4,213

998

Missing values

46,560

Turbidity values greater than maximum sensor limit

n/a

Number of data values used in model (sample n)

n/a

10,000

Discrete suspended sediment concentration, in milligrams per liter

EXPLANATION Best-fit regression model Data pair used in model

1,000

100

y =0.1592(x )0.953, where y is the suspended sediment concentration and x is the instantaneous turbidity

Adjusted coefficient of determination: 0.80 n=40 0.1

100

1,000

10,000

100,000

Instantaneous streamflow, in cubic feet per second

Figure 4. Instantaneous streamflow in relation to discrete suspended sediment concentrations used to develop a regression model for the computation of estimated suspended sediment concentrations and loads for the Big River below Bonne Terre, Missouri, October 2018–September 2021. Data are from the U.S. Geological Survey National Water Information System database for site number 07017610 (U.S. Geological Survey, 2023).

Methods 13

The model information is as follows: • number of calibration measurements=40; • adjusted coefficient of determination=0.80; • root mean squared error=0.38; and • bias-correction factor=1.38. Streamflow and the regression-computed SSCs were used to compute daily mean SSLs. These SSC and SSL results are available via NWIS (USGS, 2023). To understand the effect of sampled events on sediment transport, event-based SSLs were computed using the runoff volumes and regression-computed SSCs. The total runoff volume is the sum of the 15-minute interval streamflow during the stormflow event divided by the duration of the event. The beginning of a stormflow event was generally determined as the time 1 hour before the streamflow doubled, and the end of a stormflow event was generally defined as when the streamflow decreased consistently by approximately 20 ft3/s during each 15-minute measurement for a continuous 2-hour period. Event-based SSL was computed using the following equation for each 15-minute interval, followed by a summation of all intervals:

ESSL

is event-based suspended sediment load, in pounds;

is drainage area, in square miles; and

is stormflow event duration, in hours.

Event-based loads and yields of barium, cadmium, lead, and zinc were computed from concentrations of the trace elements in the suspended sediment samples. Both sand and fine sediment size fractions were used to compute a bulk mass accumulation (sediment less than 2 mm in size) using the following equation: Conctotal = [(ConcS × (%S/100)) + (ConcF × (%F/100))],(5) where Conctotal

ConcS

is the trace element concentration in the sand fraction, in milligrams per kilogram;

is the percent of mass in total samples considered sands (particles greater than 0.063 millimeter);

ConcF

is the trace element concentration in the fine fraction, in milligrams per kilogram; and

is the percent mass in total samples considered fines (particles less than 0.063 millimeter).

ESSL = EMSSC × RV × (6.245 × 10−5),(3) where

ESSL

is event-based suspended sediment load, in pounds;

EMSSC

is event-based suspended sediment concentration, in milligrams per liter;

RV 6.24 × 10−5

is runoff volume, in cubic feet; and is a conversion from milligrams per liter to pounds per cubic foot.

Sediment yield is the amount of land surface erosion during a period of time per unit area of the hydrologic basin. Sediment yield normalizes SSL by including basin size and stormflow event duration. Event-based suspended sediment yield was computed using the following equation: EYield = ESSL / (DA × ED),(4) where EYield

is event-based suspended sediment yield, in pounds per square mile per hour;

is the total trace element concentration in the suspended sediments, in milligrams per kilogram;

In instances when only enough mass was available for trace element analysis on the bulk sample (rather than the separate size fractions), the bulk sample was analyzed, and the bulk concentrations were used. The arithmetic mean of the trace element concentrations for each stormflow event were computed from the suspended sediment samples collected during the event. The mean stormflow event concentration of each trace element was then expressed as a concentration in milligrams per liter using the SSC derived from the regression model for each 15-minute value. The following equation was used: Concmg/L = (Conctotal × SSC)/1,000,000(6) where Concmg/L Conctotal

is trace element concentration in suspended sediments, in milligrams per liter; is the total trace element concentration in the suspended sediments, in milligrams per kilogram;

14 Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt, 2018–21 conditions in water year 2013 (annual mean streamflow of 695 ft3/s) during phase one were comparable to the conditions in water year 2019 during phase two (annual mean streamflow of 640 ft3/s). Overall, streamflow during phase two was more consistent than in phase one (water years 2012–13).

Continuous Water-Quality Parameters yields in equations 3 and 4.

Surface-Water Quality The quality of a stream can be affected by many factors, including land use, topography, and weather conditions such as droughts and floods. These conditions were assessed to understand the surface-water quality of the Big River through computing the loads and yields of suspended sediment and associated trace elements.

Streamflow Conditions Precipitation can greatly affect streamflow conditions. Monthly precipitation data were obtained from the DeSoto, Mo., climate station, which is about 13 mi north of the study site (NOAA, 2022; fig. 5). During phase two, total monthly precipitation ranged from 1.0 in. (September 2020) to 7.23 in. (May 2019). The normal annual precipitation amount for the climate station (years 1991–2020) is 44.73 in. All water years during phase two exceeded the normal annual precipitation. Water year 2019 had the most precipitation (56.29 in.) followed by water year 2020 (48.79 in.). The driest year of phase two was water year 2021 (46.04 in.; NOAA, 2022). Phase two consisted of wetter conditions and higher mean streamflows than the first year of phase one (table 5; Barr, 2016). Annual mean streamflows during phase one were 189 ft3/s in water year 2012 and 695 ft3/s in water year 2013. Annual mean streamflows during phase two were 640 ft3/s in water year 2019, 450 ft3/s in water year 2020, and 461 ft3/s in water year 2021 (table 5). In comparison, the mean annual streamflow measured while the streamgage has been operational (water years 2012–21) was 508 ft3/s (USGS, 2023). During phase one, daily mean streamflow was typically highest in the winter and spring months and lowest in the fall (fig. 6). The maximum daily mean streamflow for phase two was 12,000 ft3/s, which happened on January 11, 2020 (fig. 6, table 5). The minimum daily mean streamflow was 40.3 ft3/s on October 10, 2019. The maximum peak flow for each water year was 10,200 ft3/s (water year 2019), 16,000 ft3/s (water year 2020), and 13,100 ft3/s (water year 2021; table 5, fig. 6). The historical maximum peak streamflow was 41,100 ft3/s recorded on April 30, 2017 (table 5). A comparison of streamflow to the previous report by Barr (2016) highlights the drier conditions during water year 2012 (annual mean streamflow of 189 ft3/s). Streamflow

Water temperature data were collected at the study site because of its importance in monitoring sonde operations, such as indications of biological activity, streamflow conditions, and human influences (Wilde, 2006). Additionally, sediment transport efficiency is affected by water temperature because of its relation with viscosity (Charlton, 2008). The maximum water temperature recorded at the study site was 31.3 °C on July 9, 2020, and August 12, 2021 (table 6). The minimum water temperature recorded was −1.0 °C on several days (table 6). Water temperatures generally followed the expected diurnal and seasonal patterns (fig. 7). A few periods of the temperature record were removed during QA review. Suspended sediment transport in the Big River may be better understood with the use of continuous turbidity data as turbidity can be used as a surrogate for SSC. The daily mean turbidity during phase two ranged from 0.4 FNU on November 17, 2018, and February 12–13, 2021, to 263 FNU on January 11, 2020 (table 6; fig. 8). The turbidity record is fragmentary in nature (missing approximately 44 percent of daily mean turbidity values) because of instrument biofouling during warmer months and siltation of the deployment pipe during stormflow event flows, as well as calibration drift and instrument malfunction (fig. 8). Whereas increases in turbidity correlated with increases in streamgage height and streamflow, the rate at which each increased was not always consistent. Peaks in turbidity typically precede streamflow peaks for the same stormflow event (Mather and Johnson, 2014). The lag time between the peaks increased with higher flow events. As an example, the maximum turbidity for the study period (965 FNU on November 22, 2020; table 6) did not correlate with the maximum streamflow (16,000 ft3/s on January 12, 2020; table 5). External factors such as timing of previous stormflow events, runoff amounts, and location of rainfall can affect sediment availability and observed turbidity during stormflow events. Turbidity observed during a stormflow event is the result of several factors, including sediment washed into the stream via runoff, increased suspended sediment transport, and erosion of streambanks because of higher stream velocities. When multiple stormflow events happen within a short time span, subsequent events can have reduced amounts of suspended sediment and turbidity as sediment becomes less available because it was transported from the land surface, stream bed, and streambank during prior events. The location and intensity of rainfall and where it falls within the drainage basin also may affect turbidity.

Total monthly precipitation, in inches

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

2018

2019

2020

2021

Date

Figure 5. Total monthly precipitation at the National Oceanic and Atmospheric Administration DeSoto, Missouri, climate station near the Big River Basin, Mo., October 2018– September 2021 (National Oceanic and Atmospheric Administration, 2022).

Surface-Water Quality 15

[Data are from the U.S. Geological Survey National Water Information System for site number 07017610 (U.S. Geological Survey, 2023). ft3/s, cubic foot per second; ft, foot; in., inch; --, no data]

Water yeara

Maximum daily mean streamflow (ft3/s)

Maximum daily mean streamflow date

Minimum daily mean streamflow (ft3/s)

Minimum daily mean streamflow date

Maximum peak streamflow (ft3/s)

Maximum peak streamflow date

Maximum peak stage date

Annual mean streamflow (ft3/s)

Annual runoff (in.)

Phase one study period b,c2012

2,390

March 17, 2012

9.9

August 11, 2012

4,810

March 16, 2012

12.0

March 16, 2012

189

6.27

b2013

18,600

March 18, 2013

September 14, 2013

21,900

April 19, 2013

26.5

April 19, 2013

695

23.06

Phase two study period 2019

8,380

December 15, 2018

49.1

September 30, 2019

d10,200

December 15, 2018

d17.6

December 15, 2018

640

21.2

2020

12,000

January 11, 2020

40.3

October 10, 2019

d16,000

January 12, 2020

d22.4

January 11, 2020

450

15.0

2021

11,100

March 12, 2021

46.1

October 13, 2020

13,100

March 12, 2021

20.2

March 12, 2021

460

15.3

35.8

April 30, 2017

Phases one and two study periods 2012–13 35,600 and 2019–21

April 30, 2017

9.94

August 11, 2012

41,100

April 30, 2017

aWater year is defined as the 12-month period beginning October 1 and ending September 30 of the calendar year in which it ends (water year 2021 is the period October 1, 2020, through September 30, 2021). bStatistics indicated for water years 2012–13 for comparison to the previous study period (Barr, 2016). cStatistics for water year 2012 computed with incomplete data because the streamgage was not in operation until October 13, 2011. dRevised data.

16 Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt, 2018–21

Table 5. Streamflow statistics for the Big River below Bonne Terre, Missouri, October 2011–September 2013 and October 2018–September 2021.

100,000

Daily mean streamflow, in cubic feet per second

10,000

1,000

100

EXPLANATION

Approximate streamflow at which passive samplers began sampling Daily mean streamflow 1 Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

2019

2020

2021

Date

Figure 6. Daily mean streamflow during the study period at the Big River below Bonne Terre, Missouri, October 2018–September 2021. Data are from the U.S. Geological Survey National Water Information System database for site number 07017610 (U.S. Geological Survey, 2023).

Surface-Water Quality 17

2018

[Data are from the U.S. Geological Survey National Water Information System for site number 07017610 (U.S. Geological Survey, 2023)]

Water yeara

Maximum daily mean value

Maximum daily mean value date

Minimum daily mean value

Minimum daily mean value date

Maximum recorded value

Maximum recorded value date

Minimum recorded value

Minimum recorded value date

Water temperature, in degrees Celsius 2019

28 .1

July 21, 2019

0.6

January 31, 2019

31.2

May 29, 2019

January 31, 2019

2020

29.2

July 9 and 12, 2020

0.4

February 20, 2020

31.3

July 9, 2020

−1

February 15, 18, 26 and March 7, 2020

2021

29.2

August 12, 2021

February 11 and 13–21, 2021

31.3

August 12, 2021

−1

February 3, 2021

2019

172

March 14, 2019

0.4

November 17, 2018

519

June 26, 2019

0.2

November 16 and 17, 2018

January 18, 2020

b0.0

October 9, 2019

November 22, 2020

b0.0

February 13 and 14, 2021

Turbidity, in formazin nephelometric units 2020

263

January 11, 2020

1.3

September 22–23, 2020

b743

2021

160

March 18, 2021

0.4

February 12–13, 2021

b965

18 Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt, 2018–21

Table 6. Water-quality statistics for the Big River below Bonne Terre, Missouri, October 2018–September 2021.

Daily mean water temperature, in degrees Celsisus

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

2019

2020

2021

Date

Figure 7. Daily mean water temperature measured at the Big River below Bonne Terre, Missouri, October 2018–September 2021. Data are from the U.S. Geological Survey National Water Information System database for site number 07017610 (U.S. Geological Survey, 2023).

Surface-Water Quality 19

2018

Daily mean turbidity, in formazin nephelometric units

100

Gaps indicate periods in which no data are available. Periods of missing data (gaps) are due to equipment issues, low water conditions, extreme fouling, or exceedance of correction criteria, in which case data are deleted. 0.1

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

2018

2019

2020

2021

Date

Figure 8. Daily mean turbidity measured at the Big River below Bonne Terre, Missouri, October 2018–September 2021. Data are from the U.S. Geological Survey National Water Information System database for site number 07017610 (U.S. Geological Survey, 2023).

20 Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt, 2018–21

1,000

Suspended Sediment Transport 21

Suspended Sediment Transport Forty suspended sediment samples were collected during phase two. These samples included 15 base-flow and 25 stormflow event samples collected during 8 stormflow events (table 7; fig. 9). During water year 2019, five base-flow samples and three sets of stormflow event samples were collected. During water year 2020, two base-flow samples and two sets of stormflow event samples were collected. Eight base-flow samples and three sets of stormflow event samples were collected in 2021 (table 7; fig. 9). Stormflow SSC during phase 2 ranged from 41 to 1,740 mg/L with a median value of 389 mg/L. Base-flow SSC during phase 2 ranged from 1 mg/L to 30 mg/L with a median value of 10 mg/L (table 7; fig. 9). When compared to the phase one study by Barr (2016), the median base-flow SSC during water years 2012–13 (10 mg/L) was the same as phase two. These values also closely align with a prior study within the Ozark Plateaus by Davis and Bell (1998) in similar streams to the Big River where median baseflow SSC ranged from 3 to 28 mg/L with increases during increased streamflow events.

Daily Suspended Sediment Concentrations and Loads Daily SSCs and SSLs were computed using the regression models and followed similar patterns during the phase two study period, with maximum and minimum daily mean SSCs and SSLs frequently happening on the same dates (figs. 10 and 11). The daily mean SSL ranged from a minimum of 0.4 ton on September 24, 2020, to a maximum of 24,900 tons on March 13, 2021. During water year 2019, the maximum daily mean SSC of 816 mg/L and maximum daily mean SSL of 19,400 tons were measured on December 16, 2018 (table 8), which happened during the same stormflow event as the maximum daily mean streamflow for that water year (table 5). During water year 2020, the maximum daily mean SSC of 716 mg/L and maximum daily mean SSL of 22,600 tons were measured on January 12, 2020 (table 8), which was also during the same stormflow event as the maximum daily mean streamflow for water year 2020 (table 5). The maximum daily mean SSC and SSL (1,010 mg/L and 24,900 tons, respectively) during water year 2021 happened on separate dates (maximum concentration on November 23, 2020, and maximum load on March 13, 2021; table 8). The maximum daily mean streamflow for water year 2021 coincided with the same stormflow event as the maximum daily mean SSL in March 2021 (tables 5 and 8). The duration and magnitude of the stormflow event and availability of suspended sediment in the system likely played a role in the differing occurrences of the maximum daily mean concentrations and loads in water year 2021. The estimated annual SSL at the study site varied during phase two and was correlated with the annual mean streamflow with the largest mass of 113,000 tons transported during

water year 2019 (annual mean streamflow of 640 ft3/s; tables 5 and 8). Water years 2020 and 2021 had annual SSLs of 83,400 and 96,500 tons, respectively (table 8). The lowest annual SSL for phase two (83,400 tons) happened during water year 2020, which coincided with the lowest annual mean streamflow (450 ft3/s; tables 5 and 8). Additionally, more turbidity record was missing during water year 2020 when compared to water years 2019 and 2021, which resulted in more of the SSC and SSL record for water year 2020 being estimated using the secondary streamflow-derived regression model. The secondary regression model underestimates the SSC more often than the primary regression model based on turbidity. Approximately 58 percent of the calculated (15-minute) SSCs for the study period were determined using the turbidity-based regression model; the remaining 42 percent of the record was calculated using the secondary streamflow-derived regression model.

Event-Based Suspended Sediment Concentrations, Loads, and Yields Eight stormflow events were sampled during the phase two study period. Mean stormflow event SSCs and total stormflow event SSLs calculated using the regression model are reported for each of the individual events. Mean estimated stormflow event SSCs ranged from 50 to 717 mg/L, and total SSLs ranged from 45.3 to 32,500 tons (table 9). Events lasted an average of about 47 hours. Event runoff volumes ranged from 26,600,000 ft3 (event 5 on August 31–September 2, 2020) to 1,770,000,000 ft3 (event 4 on January 10–13, 2020). Event-based yields normalize each stormflow event based on the drainage area and the event duration. Sediment yield ranged from 5.03 pounds per square mile per hour (lb/mi2/ hr) to 3,460 lb/mi2/hr (table 9). The stormflow events with the largest runoff volumes generally had the largest sediment yields. Sediment availability and rainfall intensity play critical roles in sediment transport in the Big River. Similar-size stormflow events (similar peak or total streamflow volume) are not always comparable. Events 2, 3, and 7 had comparable event runoff volumes, and they also had similar average SSCs (398, 471, and 491 mg/L, respectively; table 9); however, the two largest stormflow events—event 4 (6th highest peak streamflow for period of record) and event 8 (8th highest peak streamflow for period of record)—had differing mean SSCs (table 9). The mean estimated SSC during event 4 was 475 mg/L; the mean for event 8 was 717 mg/L. The timing and magnitude of prior stormflow events and the characteristics of each rainfall event can affect the transport of suspended sediment and associated trace elements. The total SSL for the eight sampled stormflow events during phase two was computed as about 90,400 tons and accounted for 30.9 percent of the total SSL calculated using the regression models for phase two. To estimate a representative base-flow SSL for the phase two study period, the median base-flow SSC (10 mg/L; table 7) and the median of the daily

22 Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt, 2018–21 Table 7. Concentrations and particle-size distributions of suspended sediment in discrete samples collected at Big River below Bonne Terre, Missouri, October 2018–September 2021. [Data are from the U.S. Geological Survey National Water Information System database for site number 07017610 (U.S. Geological Survey, 2023). Dates are given in month/day/year. Times are given in hours:minutes (military). g, gram; mg/L, milligram per liter; %, percent; <, less than; mm, millimeter; -- no data; n/a, not applicable]

Sample date and time

Hydrologic condition

Total sample dry mass (g)

Suspended sediment concentration (mg/L)

Percent fine suspended sediment (% <0.063 mm)

Daily mean streamflow on day of base-flow sampling

11/29/2018 8:00

Base flow

156

12/14/2018 12:00

Base flow

0.0624

296

2/7/2019 12:20

Rise

6.3494

826

n/a

2/7/2019 16:40

Peak

4.2341

554

n/a

2/8/2019 10:25

Fall

1.0472

185

n/a

3/14/2019 10:52

Rise

3.7970

492

n/a

3/14/2019 13:59

Peak

4.696

597

n/a

3/15/2019 10:22

Fall

0.3468

105

n/a

4/14/2019 7:25

Rise

4.6079

582

n/a

4/14/2019 8:54

Peak

3.4587

472

n/a

4/14/2019 10:04

Fall

2.565

359

n/a

7/11/2019 11:00

Base flow

0.0157

130

9/5/2019 12:30

Base flow

0.0518

107

9/5/2019 13:00

Base flow

0.0533

107

11/13/2019 9:30

Base flow

0.0299

99.2

12/5/2019 9:30

Base flow

0.0336

314

1/11/2020 9:00

Rise

4.0523

587

n/a

1/11/2020 10:34

Rise

0.8492

297

n/a

1/11/2020 12:13

Peak

1.1184

389

n/a

1/13/2020 12:34

Fall

0.4817

105

n/a

9/1/2020 12:00

Rise

0.1198

n/a

9/1/2020 16:05

Peak

0.2068

n/a

10/26/2020 11:00

Base flow

0.019

10/29/2020 12:30

Rise

0.9045

160

n/a

10/30/2020 3:05

Peak

1.1183

215

n/a

10/30/2020 15:10

Fall

0.3825

n/a

1/12/2021 11:30

Base flow

0.0628

208

Suspended Sediment Transport 23 Table 7. Concentrations and particle-size distributions of suspended sediment in discrete samples collected at Big River below Bonne Terre, Missouri, October 2018–September 2021.—Continued [Data are from the U.S. Geological Survey National Water Information System database for site number 07017610 (U.S. Geological Survey, 2023). Dates are given in month/day/year. Times are given in hours:minutes (military). g, gram; mg/L, milligram per liter; %, percent; <, less than; mm, millimeter; -- no data; n/a, not applicable]

Sample date and time

Hydrologic condition

Total sample dry mass (g)

Suspended sediment concentration (mg/L)

Percent fine suspended sediment (% <0.063 mm)

Daily mean streamflow on day of base-flow sampling

1/25/2021 12:30

Rise

4.2979

808

n/a

1/26/2021 3:15

Peak

2.5309

472

n/a

1/26/2021 9:20

Fall

1.049

192

n/a

3/11/2021 19:35

Rise

11.9188

1,740

n/a

3/11/2021 21:00

Rise

10.522

1,460

n/a

3/12/2021 0:15

Rise

4.6504

704

n/a

3/12/2021 21:00

Fall

1.2119

282

n/a

5/19/2021 10:00

Base flow

0.0982

478

6/29/2021 11:35

Base flow

0.1195

250

7/29/2021 11:25

Base flow

0.0302

117

8/19/2021 11:15

Base flow

0.0703

9/2/2021 12:00

Base flow

0.1144

152

9/10/2021 10:45

Base flow

0.0385

119

Minimum base flow

Maximum base flow

478

Median base flow

130

Minimum stormflow

n/a

Maximum stormflow

1,740

n/a

Median stormflow

389

n/a

Minimum base flow

n/a

Maximum base flow

n/a

Median base flow

n/a

Minimum stormflow

n/a

Maximum stormflow

1,090

n/a

Median stormflow

228

n/a

Phase two study period (water years 2019–21)

Phase one study period (water years 2012–13)

10,000

Daily mean streamflow, in cubic feet per second

10,000

100

1,000

100

Suspended sediment concentration, in milligrams per liter

1,000

0.1 Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

2018

2019

2020

2021

Date EXPLANATION Daily mean streamflow Discrete suspended sediment sample, base-flow conditions Discrete suspended sediment sample, stormflow conditions

Figure 9. Continuous streamflow and discrete suspended sediment concentration samples collected at the Big River below Bonne Terre, Missouri, October 2018– September 2021. Data are from the U.S. Geological Survey National Water Information System database for site number 07017610 (U.S. Geological Survey, 2023).

24 Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt, 2018–21

100,000

Daily mean suspended sediment concentration, estimated by regression equations, in milligrams per liter

10,000

1,000

100

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

2018

2019

Date

2020

2021

Figure 10. Daily mean suspended sediment concentrations computed at the Big River below Bonne Terre, Missouri, October 2018–September 2021. Data are from the U.S. Geological Survey National Water Information System database for site number 07017610 (U.S. Geological Survey, 2023).

Suspended Sediment Transport 25

0.1

Daily mean suspended sediment load, estimated by regression equations, in tons

10,000

1,000

100

0.1 Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

2018

2019

Date

2020

2021

Figure 11. Daily mean suspended sediment loads computed at the Big River below Bonne Terre, Missouri, October 2018–September 2021. Data are from the U.S. Geological Survey National Water Information System database for site number 07017610 (U.S. Geological Survey, 2023).

26 Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt, 2018–21

100,000

Table 8. Summary of suspended sediment concentration and load statistics by water year at the Big River below Bonne Terre, Missouri, October 2018–September 2021. [Data are from the U.S. Geological Survey National Water Information System database for site number 07017610 (U.S. Geological Survey, 2023). mg/L, milligram per liter]

Water yeara

Maximum daily mean suspended sediment concentration (mg/L)

Maximum daily mean suspended sediment concentration date

Minimum daily mean suspended sediment concentration (mg/L)

Minimum daily mean suspended sediment concentration date

Maximum daily mean suspended sediment load (tons)

Maximum daily mean suspended sediment load date

Minimum daily mean suspended sediment load (tons)

Minimum daily mean suspended sediment load date

Annual suspended sediment load (tons)

2019

816

Dec. 16, 2018

Nov. 18, 2018

19,400

Dec. 16, 2018

0.5

Nov. 18, 2018

113,000

2020

716

Jan. 12, 2020

Sept. 24, 2020

22,600

Jan. 12, 2020

0.4

Sept. 24, 2020

83,400

2021

1,010

Nov. 23, 2020

Feb. 14, 2021

24,900

March 13, 2021

0.6

Feb. 14, 2021

96,500

Suspended Sediment Transport 27

[Data are from the U.S. Geological Survey National Water Information System database for site number 07017610 (U.S. Geological Survey, 2023). hr, hour; ft3, cubic foot; mg/L, milligram per liter; lb, pound; lb/mi2/hr, pound per square mile per hour]

Suspended sediment Number of event samples

Event duration (hr)

Event runoff volume (ft3)

Mean event sample concentration (mg/L)

Mean estimated event concentration (mg/L)

Load

Event number

Water yeara

Event date

2019

Feb. 6–9, 2019

54.25

823,000,000

522

Mar. 13–15, 2019

40.25

554,000,000

Apr. 14–15, 2019

40.25

613,000,000

Jan. 10–13, 2020

62.75

1,770,000,000

Aug. 31–Sept. 2, 2020

26,600,000

90,500

45.3

5.03

Oct. 29–31, 2020

49.75

110,000,000

147

107

773,000

387

38.0

Jan. 25–26, 2021

41.5

525,000,000

491

338

2,900,000

6,440

758

Mar. 11–13, 2021

1,280,000,000

1,050

717

63,700,000

31,800

3,460

2020

5 6

2021

(lb)

(ton)

Yield (lb/mi2/hr)

286

17,900,000

8,960

807

398

368

14,800,000

7,390

898

471

184

5,810,000

2,910

252

264

475

64,900,000

32,500

2,530

28 Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt, 2018–21

Table 9. Suspended sediment concentrations, load, and yields from sampled stormflow events at the Big River below Bonne Terre, Missouri, October 2018–September 2021.

Trace Element Transport 29 mean streamflows associated with each base-flow sample during phase two were used (130 ft3/s; table 7). The estimated base-flow SSL was 3,840 tons, which accounted for 1.31 percent of the total SSL. This highlights that most suspended sediments in the Big River are transported during stormflow events as was concluded in phase one (Barr, 2016).

Trace Element Transport A total of 18 stormflow event suspended sediment samples were analyzed for trace element concentrations during phase two (October 2018 to September 2021). When sufficient mass was available in sand (2–0.063 mm) and fine (<0.063 mm) fractions, separate trace element analyses were performed on each fraction. In instances when the mass of one or both fractions was less than the minimum required (0.5 g), the two fractions were recombined and submitted to MRL for trace element analysis as a bulk sample. Trace elements selected for this report include barium, cadmium, lead, and zinc. Concentrations of the select trace elements were used to determine trace element loads during storm events. These results were compared to phase one (October 2011 to September 2013) to determine if significant changes have happened during the entire study period. In addition, the sediments collected by the passive samplers during stormflow events also were analyzed for select trace elements and aided in determining trace element loads. Additional trace element results are available via NWIS (USGS, 2023) and Markland and others (2024).

Selected Trace Element Concentrations in Suspended Sediments Stormflow event samples were analyzed separately for trace element concentrations among the sand and fine fractions except for samples collected during event 6 and a single sample from both events 1 and 7. All stormflow event samples analyzed for trace element concentrations were made up of mostly fines (median of 74 percent fines) with a range of 63 to 98 percent fines (table 10). Although samples collected during event 6, as well as a single sample from both events 1 and 7, were analyzed for trace elements in bulk, the samples were analyzed for particle-size distribution before chemical analysis, which indicated these samples also were predominately fines (88–90 percent fines for event 6; 70–75 percent fines for bulk-analyzed samples from events 1 and 7; table 10). In general, the fine fractions had higher concentrations of barium, cadmium, lead, and zinc than the sand fractions except for some samples collected during event 8. Barium concentrations in the fine fractions were about twice the concentrations of the sand fractions for all stormflow event samples. Differences in concentrations among sand and fine fractions for cadmium, lead, and zinc were less, with cadmium concentrations being most similar in the two size fractions (fig. 12; table 11).

Trace element concentrations of cadmium, lead, and zinc in suspended sediment from stormflow event samples generally were consistent throughout the duration of each individual event, except events 1 and 8, which indicated a general increase in concentrations within the fine fractions during the event (table 11; fig. 12). These two stormflow events were larger events, with the highest mean event sample SSCs during phase two (522 mg/L for event 1 and 1,050 mg/L for event 8; table 9). This general pattern could indicate new contributions of mine waste material with high concentrations of trace elements that were mobilized from the landscape upstream from the Big River below Bonne Terre, Mo., as the result of the large storm event. Concentrations of barium were generally consistent throughout the duration of each individual event. Two samples were collected during event 6, which happened on October 29–30, 2020. The samples from event 6 were bulk analysis samples because of the lack of sediment mass between the two size fractions. Both bulk samples had the highest concentrations of cadmium (23.8 and 24.1 mg/kg), lead (3,060 and 2,820 mg/kg), and zinc (1,660 and 1,630 mg/ kg) from all event samples during the phase two study (fig. 12, table 11). Suspended sediment samples collected during event 6 were 88–90 percent fines with SSCs ranging from 67 to 215 mg/L, which were low compared to other sampled stormflow events (table 10). Event 6 was the second smallest event (by event runoff volume) sampled during phase two (table 9); however, the heaviest rainfall was localized (average of 2.1 in.) to the immediate area of the major mine waste piles within the OLB (Federal, Desloge, Elvins, and National mine waste piles) within and just west of Park Hills. During the same period, the mean rainfall across the entire 409-mi2 drainage basin upstream from the streamgage below Bonne Terre was less than 1.5 in. Digital raster data of 24-hour rainfall estimates using NOAA Multi-Radar Multi-Sensor System data were obtained from the Iowa Environmental Mesonet (Iowa State University, 2023). One hypothesis is that the localized heavier rainfall and resulting runoff during event 6 eroded and suspended mine-waste contaminated sediments primarily in the area of the major mine waste piles within the OLB. These highly contaminated sediments were not diluted by runoff containing uncontaminated sediments from upstream in nonmined areas of the drainage basin. These signature high trace element concentrations from mine-waste contaminated sediments are likely present during all stormflow events, but they are diluted by runoff from other areas of the drainage basin during the larger stormflow events typically sampled. A second hypothesis is that this smaller event transported primarily fine bed sediments deposited from a previous event. Because the small event only transported the fine, more-contaminated bed material, the suspended sediment samples consisted of mostly these materials and were not diluted by coarser, lower concentration materials. Cadmium, lead, and zinc are considered toxic to aquatic life at certain concentrations in bed sediments (MacDonald and others, 2000). Because the suspended sediments collected during this study were mobilized from bed sediments

30 Suspended Sediment and Trace Element Transport in the Big River Downstream from the Old Lead Belt, 2018–21 Table 10. Streamflow, suspended sediment concentrations and particle-size distributions, and selected total trace element concentrations in suspended sediments collected during stormflow events at the Big River below Bonne Terre, Missouri, October 2018– September 2021. [Data are from the U.S. Geological Survey National Water Information System database for site number 07017610 (U.S. Geological Survey, 2023) and Markland and others, 2024. Dates are given in month/day/year. Times are given in hours: minutes (military). ft3/s, cubic foot per second; mg/L, milligram per liter; %, percent; >, greater than; mm, millimeter; <, less than; --, no data]

Event number or summary statistic

Sample date

2/7/2019

12:20

2/7/2019

16:40

2/8/2019 2

Trace element in suspended sediments, expressed as whole water concentration (mg/L)

Suspended sediment Sample Streamflow time (ft3/s)

Concentration (mg/L)

Sands (% >0.063 mm)

Fines (% <0.063 mm)

Barium

Cadmium

Lead

Zinc

6,120

826

0.390

0.005

0.739

0.310

7,270

554

0.234

0.003

0.469

0.229

10:25

3,790

185

0.085

0.002

0.224

0.110

3/14/2019

10:52

5,070

492

0.236

0.004

0.520

0.280

3/14/2019

13:59

5,930

597

0.309

0.006

0.648

0.341

3/15/2019

10:22

1,790

105

4/14/2019

7:25

4,300

582

0.267

0.004

0.494

0.265

4/14/2019

8:54

4,620

472

0.207

0.003

0.408

0.218

4/14/2019

10:04

4,520

359

0.149

0.002

0.298

0.170

1/11/2020

9:00

13,600

587

0.309

0.004

0.492

0.262

1/11/2020