Fate of Biosolid Derived Organic Contaminants in Soils and Effects on Soil Microbial Communities

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).0854167GunschWastewater treatment processes do not efficiently remove all types of contaminants. The accumulation of these contaminants in biosolids is a growing concern because approximately 50% of biosolids in the United States are currently land-applied. Thus, there is potential for these pollutants to become mobilized in the environment following land-application of biosolids and cause adverse environmental effects. The principal objective of this proposal is to characterize the chemical fate of several organic contaminants, of various physicochemical properties, in soils and plants following biosolid land application. Furthermore, this project will explore microbial community dynamics and changes in denitrification function resulting from this process. Denitrifiers are key to nitrogen cycling and are linked to primary productivity and carbon decomposition. As such, denitrifying community dynamics are a good indicator of microbial function in soils. The contaminants chosen for this study are: 1) triclosan (a bactericide found in personal care products); 2) nonylphenol (a detergent/surfactant); 3) naproxen (pharmaceutically active compound a.k.a. Aleve) and; 4) two types of brominated flame retardants (BFRs). The working hypothesis of this project is that the rate of biosolid application will affect not only the contaminant fate, but impact microbial community structure and function. A series of experiments will be carried out in batch reactors and specially designed environmental chambers to test this hypothesis. At the conclusion of this study several metrics will be calculated to evaluate biosolid land application on environmental and soil health. These include: 1) soil retention factors of each contaminant ; 2) bioavailability of contaminants to plants cultivated in the soils; 3) the plant biomass production; and 4) by determining the threshold concentrations of each contaminant that is responsible for a significant microbial shift in microbial community structure and a 10% decrease in denitrification rate. This project will serve to further establish and strengthen collaborations between junior Faculty in the Pratt School of Engineering and the Nicholas School of the Environment at Duke University. This research will also enable both graduate and undergraduate students participating in this project to work in an interdisciplinary research team and gain valuable training. In addition, the PIs will continue to develop and implement an outreach program ("Scientists and Engineers for the Future") aimed at introducing underrepresented minority students in middle school to science and engineering so that they may make educated career decisions. The PIs are currently working with several middle school science teachers to develop work plans which integrate the students' curriculum with innovative hands-on activities representative of the biological sciences and environmental engineering. The PIs hope this outreach program will help these students make informed choices about career possibilities in science and engineering.