Biogeochemical Processes and Microbial Characteristics across Groundwater-Surface Water Boundaries of the Hanford Reach of the Columbia River

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• 作者：Duane P. Moser ; James K. Fredrickson ; David R. Geist ; Evan V. Arntzen ; Aaron D. Peacock ; Shu-Mei. W. Li ; Tina Spadoni ; and James P. McKinley
• 刊名：Environmental Science & Technology
• 出版年：2003
• 出版时间：November 15, 2003
• 年：2003
• 卷：37
• 期：22
• 页码：5127 - 5134
• 全文大小：199K
• 年卷期：v.37,no.22(November 15, 2003)
• ISSN：1520-5851

文摘

Biogeochemical processes within riverbed hyporheiczones (HZ) can potentially impact the fate and transportof contaminants. We evaluated a modified freeze coretechnique for the collection of intact cobble-bed samplesfrom the Columbia River HZ along a stretch of theHanford Reach in Washington State and investigatedmicrobiological and geochemical parameters of correspondingfrozen and unfrozen samples. During three samplingperiods (March, May, and November 2000), relatively highnumbers of viable aerobic heterotrophic bacteria wererecovered from both unfrozen (10⁶-10⁷ cfu/g) and frozensamples (10⁵-10⁶ cfu/g). Relatively large populations ofsulfate-, nitrate-, and iron-reducing bacteria were present,and significant concentrations of acid-volatile sulfidewere measured in some samples, indicating that anoxicregions exist within this zone. Cr(VI), a priority groundwaterpollutant on adjacent U.S. Department of Energy lands,was probably removed from solution in HZ samples by acombination of microbial activity and chemical reduction,presumably via products of anaerobic microbial metabolism.These results suggest that biogeochemical processesin the Columbia River HZ may contribute to the naturalattenuation of Cr(VI). Although freezing modestly diminishedrecovery of viable bacteria, freeze core techniquesproved reliable for the collection of intact hyporheicsediments.