Constituent Concentrations in Sediment of Selected Gravel Bars along the Big River, Southeast Missouri, 2011

Historic mining activity in the Old Lead Belt has led to substantial influx of lead and zinc mining waste into the channel of the Big River in southeastern Missouri. The primary objectives of this data collection was to determine the depth of heavy-metal contamination at five gravel bars along the Big River to verify and supplement findings by Pavlowsky and Owen (2010). A secondary objective of the study was to develop and implement methods for use in other Natural Resource Damage Assessment projects, such as the Tri-State Mining District (TSMD) project (Smith, 2016). This data was collected in cooperation with the Ozarks Environmental and Water Resources Institute, Missouri State University, and U.S. Fish and Wildlife Service (USFWS). Five gravel bars along the Big River were selected for this study. Three boreholes were drilled on each gravel bar with the exception of bar A. Due to the smaller surface area of bar A, two boreholes were drilled. Surface samples were collected in the unsaturated zone by hand methods for each boring location. A stainless steel hand scoop was used to collect sediment from 0 to 1 foot. A shovel was used to collect deeper samples in the unsaturated zone. Once a hole was excavated with a shovel, disturbed sediment was cleared away to access undisturbed sediment and a sample would be collected with a stainless steel hand scoop. A freeze method similar to that used by Lisle and Eads (1971) was used to collect the saturated samples for the project. Methods used in this study implemented a hollow sampler and was driven by means of Geoprobe direct push sampling equipment. In this study, liquid carbon dioxide was injected into the hollow sampler and sediment was frozen to the outside of the sampler. The length-wise fins on the outside of the sampler protected the frozen sample during removal by pushing coarse material away from the sampler during the retrieval process. More information about the sampler design and methods is described by Smith (2016). The frozen sample was then rinsed with deionized water while still frozen to the sampler. This removed any particles from upper layers that may have attached to the frozen sediment during retrieval. This left a solid frozen sediment sample taken from the depth at which the sample was frozen. The sediment was then scraped and rinsed into a stainless steel pan. All samples were stored in labeled double zippered plastic bags and transported to the Rolla, Missouri US Geological Survey (USGS) office. Samples were stored in the USGS repository and allowed to air dry. Once the samples were dry, the initial mass was recorded and sieved using a single #10 (2 millimeter) sieve. The two size fractions were placed in separate labeled zippered plastic bags and their masses were recorded. The less than 2 millimeter size fraction was scanned by USFWS personnel in Columbia, Missouri using a handheld x-ray fluorescence (XRF) unit to determine metal concentrations. The samples were scanned 3 times and the average concentration of the three scans for each constituent was calculated as a best representation of the constituent concentration. The individual samples were hand mixed within the bag before each scan to ensure homogeneity. Pavlowsky, R.T., Owen, M.R. and Martin, D.J., 2010, Distribution, geochemistry, and storage of mining sediment in channel and floodplain deposits of the Big River System in St. Francois, Washington, and Jefferson counties, Missouri, The Ozarks Environmental and Water Resources Institute (OEWRI), Missouri State University, 141 p., https://oewri.missouristate.edu/assets/OEWRI/Big_River_Report.pdf Smith, D.C., 2016, Occurrence, distribution, and volume of metals-contaminated sediment of selected streams draining the Tri-State Mining District, Missouri, Oklahoma, and Kansas, 2011-12: U.S. Geological Survey Scientific Investigations Report 2016-5144, 86 p., http://dx.doi.org/10.3133/sir20165144. Lisle, T.E., and Eads, R.E., 1971, Methods to measure sedimentation of spawning gravels: U.S. Department of Agriculture, Forest Service, Pacific Southwest Forest and Range Experiment Station Research Note PSW-RN-411, 7 p.