Biogeochemical dynamics in zero-valent iron columns: Implications for permeable reactive barriers

被引:227
作者
Gu, B
Phelps, TJ
Liang, L
Dickey, MJ
Roh, Y
Kinsall, BL
Palumbo, AV
Jacobs, GK
机构
[1] Oak Ridge Natl Lab, Div Environm Sci, Oak Ridge, TN 37831 USA
[2] Oak Ridge Inst Sci & Educ, Oak Ridge, TN 37831 USA
关键词
D O I
10.1021/es981077e
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
The impact of microbiological and geochemical processes has been a major concern for the long-term performance of permeable reactive barriers containing zero-valent iron (Fe-o). To evaluate potential biogeochemical impacts, laboratory studies were performed over a 5-month period using columns containing a diverse microbial community. The conditions chosen for these experiments were designed to simulate high concentrations of bicarbonate (17-33 mM HCO3-) and sulfate (7-20 mM SO42-) containing groundwater regimes. Groundwater chemistry was found to significantly affect corrosion rates of Fe-o filings and resulted in the formation of a suite of mineral precipitates. HCO3- ions in SO42-containing water were particularly corrosive to Fe-o, resulting in the formation of ferrous carbonate and enhanced H-2 gas generation that stimulated the growth of microbial populations and increased SO42- reduction. Major mineral precipitates identified included lepidocrocite; akaganeite, mackinawite, magnetite/maghemite, goethite, siderite, and amorphous ferrous sulfide. Sulfide was formed as a result of microbial reduction of SO42- that became significant after about 2 months of column operations; This study demonstrates that biogeochemical influences on the performance and reaction of Fe-o may be minimal in the short term (e.g., a few weeks or months), necessitating longer-term operations to observe the effects of biogeochemical reactions on the performance of Fe-o barriers. Although major failures of in-ground treatment barriers have not been problematic to date, the accumulation of iron oxyhydroxides, carbonates, and sulfides from biogeochemical processes could reduce the reactivity and permeability of Fe-o beds, thereby decreasing treatment efficiency.
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页码:2170 / 2177
页数:8
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