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Abstract
J. Yang, Xi Tang, Z.
Wang. 2007. Water quality and ecotoxicity as
influenced by phosphate and biosolid treatments in
lead-contaminated soil and mine waste. JEMREST
3:21-33
DOI: 10.4029/2007jemrest3no115
Elevated metals such as lead (Pb) in soil are well known to pose human health and
ecological risks. In-situ phosphate
treatments are being evaluated as a cost-effective remedial alternative for
reducing metal risk in contaminated soil through in situ
immobilization reactions. Field experiments
were conducted in the urban and mining areas of the Jasper County Superfund
Site, Missouri,
to assess water quality and ecotoxicity as
influenced by soil treatments using phosphate amendments. Urban soil and mining wastes containing
~4000 mg Pb kg-1 were treated
with various phosphate amendments, including phosphoric acid and
phosphate-enriched biosolids. Soils and surface or shallow ground waters
in both treated and untreated areas were collected five years post
treatment. The soils were analyzed for
in vitro Pb bioavailability and chemical
speciation, and the water samples were measured for aqueous Pb and P concentrations and ecotoxicity. Phosphate treatments using either H3PO4 or biosolids have
shown to effectively reduce the bioavailability of soil Pb
and result in aqueous Pb concentrations below the
EPA regulatory standard. Water ecotoxicity was significantly improved due to reduced
aqueous Pb.
Although phosphate leaching was enhanced by the treatments, the P
enrichment in waters was minimal. The
risk reductions of soil Pb to human health and
water quality were accomplished by transforming labile Pb
species to relatively insoluble forms, as a result of the phosphate
treatments. This study also demonstrates that the treatment effects are long-term,
and the biosolid treatments would be
environmentally sound in context of P enrichment in surface and ground
waters.
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