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

Microorganisms in the groundwater of 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. The slags were deposited as waste from local blast furnace mills and were comprised primarily of high-temperature calcium silicate minerals and could contain as much as 50% metallic iron, manganese, and other steel additives (Cr, Mo, V) varying in composition within meters of each other. Weathering of the calcium silicates subsequently formed an aquifer with groundwater pH up to 13.3.

The project goal is to determine the composition and structure of microbial communities at different locations of the Calumet area, and their response to varying conditions. Preliminary results show promising potential for further study: (1) monitoring of physicochemical parameters suggests the pH is highly sensitive to temperature changes and discharge rates, (2) chemical analysis of sediment and groundwater revealed extreme concentrations of heavy metals, (3) incubation of samples using sole source carbon utilization plates (Biolog^TM Ecoplates) revealed moderate microbial diversity, and (4) DNA fingerprint using Ribosomal Intergenic Spacer Analysis (RISA) showed large microbial diversity with sample clustering according to spatial distribution and season.

The second part of this project (starting August 2011) will focus on laboratory remediation column experiments in which sediment together with three different permeable reactive barriers (silica sand, dolomite, Apatite II^TM) will be incubated. These materials are reported to be capable of decreasing the pH (silica), or the heavy metal concentration (Apatite II^TM), 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.