Tracing hydrocarbon contamination through hyperalkaline environments in the Calumet region of Southeastern Chicago

Abstract

The Calumet region of Southeastern Chicago was once known for industrialization, which left pollution as its legacy. Disposal of slag and other industrial wastes occurred in nearby wetlands in attempt to create areas suitable for future development. The waste creates an unpredictable, heterogeneous geology and a unique hyperalkaline environment. Upgradient to the field site is a former coking facility, where coke, creosote, and coal weather openly on the ground. Hydrocarbons weather into characteristic polycyclic aromatic hydrocarbons (PAHs), which can be used to create a fingerprint and correlate them to their original parent compound. This investigation identified PAHs present in the nearby surface and groundwaters through use of gas chromatography/mass spectrometry (GC/MS), as well as investigated the relationship between the alkaline environment and the organic contamination. PAH ratio analysis suggests that the organic contamination is not mobile in the groundwater, and instead originated from the air. 16S rDNA profiling suggests that some microbial communities are influenced more by pH, and some are influenced more by the hydrocarbon pollution. BIOLOG Ecoplates revealed that most communities have the ability to metabolize ring structures similar to the shape of PAHs. Analysis with bioinformatics using PICRUSt demonstrates that each community has microbes thought to be capable of hydrocarbon utilization. The field site, as well as nearby areas, are targets for habitat remediation and recreational development. In order for these remediation efforts to be successful, it is vital to understand the geochemistry, weathering, microbiology, and distribution of known contaminants. Many PAHs are toxic in both the environment and to humans, and are known to be both carcinogenic as well as bioaccumulate. Thus, understanding the relationship of PAHs to the geochemistry of this field site provides critical information for ongoing research and future remediation efforts.