Another study examined microbial communities associated with a leachate-contaminated landfill using GeoChip 3.0 (Lu et al., 2012b) . Groundwater samples were collected from wells along a flowpath of the landfill. Communities directly under the landfill and in the closest well had significantly lower functional gene diversity and richness. Genes involved in the anaerobic degradation of organic contaminates such as aromatic acids (bclA, bbs, tutFDG), phenoxyacetic acid herbicides (ftdA) atrazine (atzABC, trzN, trzA, trzE) were detected in all wells. Based on canonical correspondence analysis, the environmental variables (pH, sulfate, ammonia, and dissolved organic carbon) had significant effects on the community structure.