U.S. Geological Survey
By Laurie S. Balistrieri,1 Larry P. Gough,2 R.C. Severson,2 and Andrew Archuleta3
The chemical composition of sediment, water, and rooted aquatic vegetation from wetlands in the San Luis Valley, Colorado is used to assess whether acidic, metal-bearing waters carried by the Alamosa River have influenced the biogeochemistry of wetlands near or within the Alamosa National Wildlife Refuge. Acid drainage from mineralized areas and mines, including the Summitville Mine, is characterized by low pH values, elevated concentrations of sulfate, Al, Fe, Mn, Co, Cu, Ni, and Zn in the water, and high concentrations of As, Cr, Cu, Pb, and Zn in the stream sediments. The behavior of two of these elements, Cu and Zn, is examined in the wetlands. Water in all of the studied wetlands has basic pH values and is very low in dissolved metal concentrations. Sediments and aquatic plants in wetlands receiving Alamosa River water have higher concentrations of Cu and Zn than wetlands receiving water from other sources. Accumulation rates of Cu and Zn in a wetland receiving Alamosa River water are between two and four times greater than in one receiving Rio Grande River water.
1 U.S. Geological Survey, University of Washington, School of Oceanography, Box 357940, Seattle, WA 98195
2 U.S. Geological Survey, Box 25046, MS-973, Denver Federal Center, Denver, CO, 80225-0046
3 U.S. Fish and Wildlife Service, 730 Simms Street, Suite 290, Golden, CO, 80401