Sources of Sulfate Supporting Anaerobic Metabolism in a Contaminated Aquifer
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- 作者：Glenn A. Ulrich ; George N. Breit ; Isabelle M. Cozzarelli ; and Joseph M. Suflita
- 刊名：Environmental Science & Technology
- 出版年：2003
- 出版时间：March 15, 2003
- 年：2003
- 卷：37
- 期：6
- 页码：1093 - 1099
- 全文大小：244K
- 年卷期：v.37,no.6(March 15, 2003)
- ISSN：1520-5851
文摘
Field and laboratory techniques were used to identify thebiogeochemical factors affecting sulfate reduction in ashallow, unconsolidated alluvial aquifer contaminated withlandfill leachate. Depth profiles of 35S-sulfate reductionrates in aquifer sediments were positively correlated withthe concentration of dissolved sulfate. Manipulation ofthe sulfate concentration in samples revealed a Michaelis-Menten-like relationship with an apparent Km and Vmaxof approximately 80 and 0.83 
M SO4-2·day-1, respectively.The concentration of sulfate in the core of the leachateplume was well below 20 M and coincided with very lowreduction rates. Thus, the concentration and availabilityof this anion could limit in situ sulfate-reducing activity.Three sulfate sources were identified, including iron sulfideoxidation, barite dissolution, and advective flux of sulfate.The relative importance of these sources varied withdepth in the alluvium. The relatively high concentration ofdissolved sulfate at the water table is attributed to themicrobial oxidation of iron sulfides in response to fluctuationsof the water table. At intermediate depths, barite dissolvesin undersaturated pore water containing relatively highconcentrations of dissolved barium (~100 M) and lowconcentrations of sulfate. Dissolution is consistent with thesurface texture of detrital barite grains in contact withleachate. Laboratory incubations of unamended and barite-amended aquifer slurries supported the field observationof increasing concentrations of barium in solution when sulfatereached low levels. At a deeper highly permeableinterval just above the confining bottom layer of theaquifer, sulfate reduction rates were markedly higherthan rates at intermediate depths. Sulfate is supplied tothis deeper zone by advection of uncontaminated groundwaterbeneath the landfill. The measured rates of sulfatereduction in the aquifer also correlated with the abundanceof accumulated iron sulfide in this zone. This suggeststhat the current and past distributions of sulfate-reducingactivity are similar and that the supply of sulfate hasbeen sustained at these sites.
M SO4-2·day-1, respectively.The concentration of sulfate in the core of the leachateplume was well below 20 M and coincided with very lowreduction rates. Thus, the concentration and availabilityof this anion could limit in situ sulfate-reducing activity.Three sulfate sources were identified, including iron sulfideoxidation, barite dissolution, and advective flux of sulfate.The relative importance of these sources varied withdepth in the alluvium. The relatively high concentration ofdissolved sulfate at the water table is attributed to themicrobial oxidation of iron sulfides in response to fluctuationsof the water table. At intermediate depths, barite dissolvesin undersaturated pore water containing relatively highconcentrations of dissolved barium (~100 M) and lowconcentrations of sulfate. Dissolution is consistent with thesurface texture of detrital barite grains in contact withleachate. Laboratory incubations of unamended and barite-amended aquifer slurries supported the field observationof increasing concentrations of barium in solution when sulfatereached low levels. At a deeper highly permeableinterval just above the confining bottom layer of theaquifer, sulfate reduction rates were markedly higherthan rates at intermediate depths. Sulfate is supplied tothis deeper zone by advection of uncontaminated groundwaterbeneath the landfill. The measured rates of sulfatereduction in the aquifer also correlated with the abundanceof accumulated iron sulfide in this zone. This suggeststhat the current and past distributions of sulfate-reducingactivity are similar and that the supply of sulfate hasbeen sustained at these sites.