Superfund Research Program
Novel Approaches to Studying the in situ Bioremediation of Complex Mixtures
Project Leader: Rolf Ulrich Halden
Grant Number: R01ES015445
Funding Period: 2006-2009
The vast majority of Superfund sites in the U.S. and the Baltimore/Chesapeake Bay area contain mixtures of organic and inorganic compounds that contaminate underlying aquifers. The environmental fate of these contaminants, and ultimately human exposure to them, is governed primarily by their interactions with microorganisms, which-individually or as a community-drive the process of in situ bioremediation. Whereas single pollutant/microorganism interactions can be determined easily in the lab, no satisfactory tools exist for predicting the fate of mixtures in the environment. Halden and his research team's long-term goal is to improve the success rate of bioremediation at sites containing complex chemical mixtures by using in situ microcosm array (ISMA) technology. The ISMA is a field-deployable, miniaturized laboratory consisting of a large number of small microcosms arranged in parallel. Upon deployment, incubation, and retrieval from a ground water well, the ISMA can be analyzed to reveal the impact of mixture components on the rates of pollutant degradation and on the structure and function of microbial communities.
The research team used computer-aided design (CAD) and instrument machine shops to build two embodiments of the ISMA technology. The first one was based on a 96-well-plate format and informed the initial laboratory studies using the dioxindegrading bacterium Sphingomonas wittichii Strain RW1. A second, larger version of the ISMA was produced at ASU. This newer device has a reduced number of microcosms (12) and an increased size of over 20-feet in length to accommodate the requirement of fluid storage during long-term field experiments. The unit also includes an injection module funded through an NIEHS technology transfer supplement. The ISMA technology consequently was tested and refined at multiple Superfund and hazardous waste sites in Northern and Southern California and in Arizona.
The work concluded in 2012 with two field demonstrations in California and Arizona, where the researchers demonstrated for the first time the feasibility of performing anaerobic bioremediation reactions in aerobic aquifers using the ISMA technology. These field campaigns included a technology deployment at a San Diego subsurface site where the complete reductive dechlorination of trichloroethene (TCE) to ethene was demonstrated, enabled by a strict anaerobic consortium of bacteria the team had obtained with collaborators near a Superfund site in Baltimore, MD.
The research team also employed modern sequencing techniques and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and tandem mass spectrometry to perform genetic and proteomic characterizations of microorganisms of importance to bioremediation.
The researchers employed proteomic mass spectrometry skills initially developed for microbiological and biochemical pathway elucidation work, to investigate proteomic changes in exposed humans, and more specifically in cord blood from newborns. This work resulted in the very first map of the human cord blood proteome and biomarkers of exposure detectable therein.
Humans are regularly exposed to mixtures of Superfund priority pollutants and other compounds from the use of personal care products such as soaps, cosmetics, toothpaste, and from frequent contact with other consumer goods. Since little is known about low-level exposure to these compounds and their associated effects, the researchers also studied the occurrence of environmental exposures during vulnerable periods of human development, such as in newborns.
Understanding how anthropogenic activities impact subsurface biogeochemistry is key to managing groundwater resources upon which billions of people rely worldwide. The laboratory-to-go array technology introduced by the research team in this project hands scientists a carte blanche to modify conditions and to perform subsurface experiments at zero risk of environmental release. For the exploration of Earth and extraterrestrial bodies alike, this new tool is poised to answer many of today’s pressing questions, such as gauging the vulnerability of America’s drinking water resources to hydraulic fracturing fluids, and the risks posed by environmental release of nanomaterials, agricultural chemicals and genetically modified organisms into the biosphere.
The work also shed new light on the frequency and extent of mixture contamination in environmental media and biota, including human adults and newborns. Progress achieved in proteomic analysis strategies will aid in understanding the impact of these environmental exposures on human health and wellbeing.