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ENVIRONMENTAL RESEARCH BRIEF: LONG-TERM PERFORMANCE OF PERMEABLE REACTIVE BARRIERS USING ZERO-VALENT IRON: AN EVALUATION AT TWO SITES
Citation:
Wilkin*, R T., R W. Puls*, AND G W. Sewell*. ENVIRONMENTAL RESEARCH BRIEF: LONG-TERM PERFORMANCE OF PERMEABLE REACTIVE BARRIERS USING ZERO-VALENT IRON: AN EVALUATION AT TWO SITES. U.S. Environmental Protection Agency, Washington, DC, EPA/600/S-02/001, 2002.
Impact/Purpose:
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Description:
Geochemical and microbiological factors that control long-term performance of subsurface permeable reactive barriers were evaluated at the Elizabeth City, NC and the Denver Federal Center, CO sites. These groundwater treatment systems use zero-valent iron filings to intercept and remediate chlorinated hydrocarbon compounds at the Denver Federal Center (funnel-and-gate system) and overlapping plumes of hexavalent chromium and chlorinated hydrocarbons at Elizabeth City (continuous wall system). Zero-valent iron at both sites is a long-term sink for C, S, Ca, Si, N, and Mg. At both sites, consistent patterns of spatially heterogeneous mineral precipitation and microbial activity are observed. Mineral precipitates and microbial biomass accumulate the fastest near the upgradient aquifer-Fe0 interface, where the rate of pore space infilling ranges from 1.4% per year at Elizabeth City to 3.4% per year of the initial available volume at the Denver Federal Center (gate 2). While pore space has been lost due the accumulation of authigenic components, neither site shows evidence of pervasive pore clogging after four years of operation.