Cody J. Mertens* - University of Wisconsin- La Crosse
Ryan Perroy, PhD - University of Wisconsin La Crosse
Colin Belby, PhD - University of Wisconsin La Crosse
Sara Erickson - University of Wisconsin La Crosse
Between 1932 and 1963, the La Crosse Gun Club discharged large quantities of lead (Pb) shot into an urban marsh in the heart of La Crosse, Wisconsin. Determining the spatial distribution and potential danger of this legacy contamination is important for protecting both wildlife and the surrounding community that interact with this marsh daily. To quantify the spatial distribution of Pb contamination throughout the shot fallout zone, 30 sediment cores ranging in depth from 0.3 to 0.8 meters (divided into 2 cm sample increments) and 424 surficial (0-5 cm) sediment samples were collected. 1215 total sediment samples were dried and ground prior to X-Ray Fluorescence (XRF) analysis for total Pb concentration at the University of Wisconsin-La Crosse. Sample results were then interpolated in MATLAB to create a three-dimensional model (1m x 1m x 0.02m) of Pb concentration across the study area. 3.9 hectares of surficial sediment surpassed the US EPA's hazard standard of >400 ppm. Volumetric estimates of contaminated sediments were also produced. Depth to maximum Pb concentration (including an overall measured maximum Pb level of 31,100 ppm) varies throughout the study area due to spatially variable sedimentation rates and bioturbation. These findings have guided surface water and biological sampling as we investigate the toxicological effect of this Pb contamination. Our research methodology and findings will benefit other environmental contamination studies and remediation efforts that continue at active and abandoned shooting ranges worldwide.