Implications of Contrary Creek, Virginia, Acid Mine Drainage on Surrounding Soils and Macroinvertebrate Populations.

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. 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 and the local macroinvertebrates and plants. Aquatic macroinvertebrates are indicators of stream quality, which may be affecting or affected by the surrounding soil.

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 fractions. Macroinvertebrate samples were analyzed for species richness and diversity.

Analysis shows that all the soils 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. Diptera populations, found in compromised ecosystems, had a significant negative correlation with populations of Odonata, a sensitive species, and overall species diversity. Odonata populations displayed a significant negative correlation with aluminum and copper streamwater concentrations, all indicating harmful ecological effects. Interestingly, the small tributary site showed the healthiest water and macroinvertebrate population, but the soils there were just as contaminated as elsewhere.