HYPER-ALKALINE AQUIFERS OF CALUMET WETLANDS (SOUTH CHICAGO, IL): BIODIVERSITY AND REMEDIATION STUDY

The microorganisms of the Lake Calumet wetlands, Chicago, IL, have been described as one of the world's most extreme alkaliphiles. Over 100 years, large wetland areas have been infilled with steel slags from local blast furnace mills. The slags were comprised primarily of high-temperature calcium silicate minerals and contained as much as 50% metallic iron, manganese, and other steel additives (Cr, Mo, V). The weathering of the calcium silicates formed an aquifer with groundwater pH up to 12.8. The objective of this project is to determine the composition and structure of the microbial communities at different locations of the Calumet area, and their response to varying conditions. Preliminary results show promising potential for further study: (1) in-situ measurements of physicochemical parameters suggest the pH buffering system is highly sensitive to temperature changes, (2) chemical analysis of sediment and groundwater revealed extreme concentrations of heavy metals, (3) incubation of samples using sole source carbon utilization plates (BiologTMEcoplates) revealed moderate microbial diversity, and (4) screening of environmental DNA fingerprint using Ribosomal Intergenic Spacer Analysis (RISA) showed fairly large microbial diversity. With additional gathering of data clearer conclusions will be drawn on temporal shifts in microbial composition of sites, and differences between particular sites according to heavy metal composition.

The second part of this project (starting January 2011) will focus on laboratory remediation column experiments in which sediment together with three different permeable reactive barriers (silica sand, dolomite, apatite) will be incubated. These materials are reported to be capable of decreasing the pH (silica), or the heavy metal concentration (apatite), or both (dolomite). Incubating the columns under defined temperatures (4º and 25º C) will resemble the most striking differences from field. The columns will be continuously flushed with water from the site and subsequently amended with nutrients (C, N, P).

The multidisciplinary character of this project will significantly enhance the field of environmental hydrogeology and extremophile microbiology by novel findings about microbial response to pH and heavy metal remediation efforts.