Effects of Long‐Term Application of Biosolids for Mine Land Reclamation on Groundwater Chemistry: Trace Metals

Abstract

Data collected for 35 yr from a 1790-ha strip mine reclamation site in Fulton County, Illinois, where biosolids were applied from 1972 to 2004, were used to evaluate the impacts of long-term biosolids application on metal concentrations in groundwater. Groundwater samples were collected between 1972 and 2006 from wells installed in seven strip-mined fields treated with biosolids at cumulative loading rates of 801 to 1815 dry Mg ha and from another seven fields (also strip mined) treated with mineral fertilizer. Samples were collected monthly between 1972 and 1986 and quarterly between 1987 and 2004 and were analyzed for total metals. The concentrations of metals in groundwater were generally below regulatory limits. Lead, Cd, Cu, Cr, Ni, and Hg concentrations in groundwater were similar for the biosolids-amended and fertilizer-treated sites across all sampling intervals. Zinc concentration was increased by biosolids application only for samples collected before the 1993 promulgation of the USEPA 40 CFR Part 503 rule. Iron and Mn were the only metals that were consistently increased after biosolids application; however, Mn concentrations did not exceed the 10 mg L regulatory limits. Zinc, Cu, Cd, Pb, Fe, Al, and Mn concentrations in groundwater decreased with time, coupled with the change from pre-part 503 to post-Part 503 biosolids. The concentrations of other metals, including Ni, Cr, and Hg, did not increase in groundwater with the prolonged biosolids application. The study suggests that the long-term application of biosolids at high loading rates does not result in trace metal pollution of groundwater.