Biofilm Hydrous Manganese Oxyhydroxides and Metal Dynamics in Acid Rock Drainage

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• 作者：Elizabeth A. Haack and Lesley A. Warren
• 刊名：Environmental Science & Technology
• 出版年：2003
• 出版时间：September 15, 2003
• 年：2003
• 卷：37
• 期：18
• 页码：4138 - 4147
• 全文大小：190K
• 年卷期：v.37,no.18(September 15, 2003)
• ISSN：1520-5851

文摘

Biofilms in shallow, tailings-associated acid rock drainage(ARD) accumulated metals from May to September,indicating scavenging is stable within these biologicalsolids over seasonal time frames. Results indicate a doubling(Mn, Cr) to over a 6-fold increase (Ni, Co) in biofilmmetal concentrations. Biofilm oxygen and pH gradientsmeasured over diel time scales with microelectrodes wereobserved to be both spatially and temporally variable,indicating that biofilms are highly dynamic geochemicalenvironments. Biofilm metal retention and affinities wereelement specific indicating different processes control theirsequestration. Metals were specifically scavenged bythe organic constituents of the biofilm itself (Ni, Co) andassociated biominerals of amorphous Mn oxyhydroxides(HMO; Ni, Co, and Cr). Results are consistent with sorptionand coprecipitation processes controlling Ni and Cobiofilm association, while Cr dynamics appear linked tothose of Mn through redox processes. Biofilm HMOconcentrations increased seasonally but showed significantdiel fluctuations, indicating that both formation anddissolution processes occurred over rapid time scales inthese biofilms. Biofilm HMO concentrations increasednocturnally but decreased during daylight hours to lateafternoon minima. Under the geochemical conditions of thestreams, observed HMO formation rates can only beexplained by microbial catalysis. These results are thefirst to quantitatively examine microbial biofilm metal dynamicsusing microscale, geochemical techniques at both dieland seasonal time scales. They provide strong evidencefor the significant role that microbial activity can play inmetal geochemistry in natural environments.