ACID MINE DRAINAGE EFFECTS ON SEDIMENTS AND SURROUNDING SOILS OF CONTRARY CREEK, VIRGINIA

Acid mine drainage (AMD) has greatly affected the 8-km long Contrary Creek, a minor tributary of Lake Anna in Louisa County, Virginia, in the Chesapeake Bay watershed. This area is known for its pyrite (FeS₂), which can be found even today in and along the creek bed. Between the years of 1880 and 1923, the pyrite was mined for the production of sulfuric acid using three shaft mines found around the area of the creek. Most pyrite mines closed in the 1920s, but the EPA conducted only limited remediation in the 1970s on the heaps of tailings left behind. Much of the stream channel was dredged, and the surrounding land received sludge applications, seeding and mulching. A few follow-up studies on the streamwaters, as well as this research, show continuing low pH and high dissolved metal concentrations. This is the first study to look at the impacts of AMD on the surrounding soils, sediments, and the local ecosystem. Soil samples were taken along a transect at each site out to 40 meters from each bank along the stream from a former mine to the mouth of the stream feeding into Lake Anna, including a site at a tributary believed to be unaffected by AMD. Macroinvertebrate population, water, and sediment samples were taken from the creek at each site. Samples were analyzed for pH, organic matter, and the concentrations of metals in various soil and sediment fractions. Macroinvertebrate samples were analyzed for species richness and diversity and levels of bioaccumulation. The concentrations of trace metals As, Cd, Cu, Fe, Mg, Ni, Pb, Se, and Zn in Contrary Creek’s soils, sediments, and macroinvertebrate populations were measured by acid digesting samples and analyzing the extraction solution with an inductively-coupled plasma atomic emission spectrometer (ICP-AES) Thermo Scientific iCAP 6000 Series with CETAC ASX-520 Autosampler. Correlations were performed with SPSS and Excel software. Initial analysis shows that all the soils, sediments, and creek waters still demonstrate high levels of pollution, especially aluminum, lead, and zinc concentrations. Soil pH at all the sites was below 4 or 5, with some improvement at 40m. Interestingly, the small tributary site showed the healthiest water and macroinvertebrate population, but the soils there were just as contaminated as elsewhere.