GeoChip-Based Analysis\nof Microbial Functional Gene\nDiversity in a Landfill Leachate-Contaminated Aquifer

Abstract

The functional gene diversity and structure of microbial\ncommunities\nin a shallow landfill leachate-contaminated aquifer were assessed\nusing a comprehensive functional gene array (GeoChip 3.0). Water samples\nwere obtained from eight wells at the same aquifer depth immediately\nbelow a municipal landfill or along the predominant downgradient groundwater\nflowpath. Functional gene richness and diversity immediately below\nthe landfill and the closest well were considerably lower than those\nin downgradient wells. Mantel tests and canonical correspondence analysis\n(CCA) suggested that various geochemical parameters had a significant\nimpact on the subsurface microbial community structure. That is, leachate\nfrom the unlined landfill impacted the diversity, composition, structure,\nand functional potential of groundwater microbial communities as a\nfunction of groundwater pH, and concentrations of sulfate, ammonia,\nand dissolved organic carbon (DOC). Historical geochemical records\nindicate that all sampled wells chronically received leachate, and\nthe increase in microbial diversity as a function of distance from\nthe landfill is consistent with mitigation of the impact of leachate\non the groundwater system by natural attenuation mechanisms.