Phytoremediation of cadmium and lead-polluted watersheds.

Abandoned hard rock mines and the resulting acid mine drainage (AMD) are a source of vast, environmental degradation that are toxic threats to plants, animals, and humans. Cadmium (Cd) and lead (Pb) are metal contaminants often found in AMD. In our mine outwash water samples, Cd and Pb concentrations were 300 and 40 times greater than EPA Aquatic Life Use water quality standards, respectively. We tested the phytoremediation characteristics, accumulation and tolerance of Cd and Pb contamination, for annual aboveground biomass harvest of three montane willows native to the Rocky Mountains: Salix drummondiana, S. monticola, and S. planifolia. We found S. monticola best suited for Pb remediation based on greater growth and tolerance in response to the low Pb treatment compared to the high Pb treatment. Salix monticola stems also contained higher Pb concentrations in control treatment compared to S. planifolia. We found S. planifolia and S. drummondiana best suited for Cd remediation. Salix drummondiana accumulated higher concentrations of Cd in stems than both S. monticola and S. planifolia. Salix planifolia accumulated nearly 2.5 times greater concentrations of Cd in stems in control treatment than did S. drummondiana. Salix planifolia also contained more total Cd in stems than did S. monticola in Cd treatments. Based on our results, S. drummondiana and S. planifolia could aid in reduction of Cd in watersheds, and S. monticola is better suited than is S. planifolia for aboveground accumulation and tolerance of Pb pollution.