Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 20, 2012
Publication Date: April 21, 2012
Repository URL: http://www.ars.usda.gov/SP2UserFiles/Place/53102000/pdf_pubs/P2383.pdf
Citation: Zheng, W., Li, X., Yates, S.R., Bradford, S.A. 2012. Anaerobic transformation kinetics and mechanism of steroid estrogenic hormones in dairy lagoon water. Environmental Science and Technology. 46(10):5471-5478. Interpretive Summary: Wastewater reclamation offers a viable and economical water management option and use of treated wastewater for landscape and/or agricultural irrigation is increasing. Wastewater can provide nutrients and organic matter for plant growth and offers an additional water source to reduce the demand for higher quality water. However, water derived from animal feeding operations often contains contaminants such as excess nutrients, salinity, pathogens, heavy metals and organic chemicals, which often include natural and synthetic hormones and veterinary pharmaceuticals. These contaminants pose a potential risk both to the receiving ecosystems and drinking water resources. Dairy farms are an important potential source of wastewater. It has been estimated that dairy cattle contributes approximately 90% of endogenous hormones in the United States. Hormones excreted from livestock species occur as free steroids or as sulfate or glucuronide conjugates. Free steroid estrogenic hormones are classified as highly potent endocrine-disrupting chemicals, whereas most conjugated forms of these hormones are biologically inactive. Sorption and degradation are two primary processes affecting the fate and transport of steroid estrogenic hormones in the environment once they enter the soil and aerobic biodegradation is an important removal mechanism. The objective of this study was to investigate the persistence of hormones in the environment and to address some of the knowledge gaps about the degradation of estrogenic hormones in dairy wastewater. This study provides important information that will help scientists, regulators and land-use manages to understand the various factors affecting antibiotics in surface and ground water.
Technical Abstract: Wastewater from concentrated animal feeding operations (CAFOs) frequently contains high concentrations of steroid estrogenic hormones. Release of these hormones into the environment may occur when CAFO wastewater is applied to agricultural lands as a nutrient and/or water source for crop production. To assess the potential risk of hormone contaminants derived from animal wastewater, we investigated the transformation mechanisms and kinetics of three natural estrogenic hormones (17a-estradiol, 17ß-estradiol, and estrone) in aqueous solutions blended with dairy lagoon water under anaerobic conditions. Initial transformations of the three hormones in the dairy lagoon water were predominated by biodegradation and the degradation rates were temperature-dependent. The total amounts of hormones remaining in the solution after 52 days at 35 oC accounted for approximately 85%, 78%, and 77% of the initial amounts of 17a-estradiol, 17ß-estradiol, and estrone, respectively. This observation suggests that these hormones are relatively stable over time and may accumulate in anaerobic or anoxic environments and anaerobic CAFO lagoons. A racemization reaction between 17a-estradiol and 17ß-estradiol via estrone was observed in aqueous solutions in the presence of CAFO wastewater under anaerobic conditions. A reversible reaction kinetic model was applied to fit the observed transformation dynamics. The degradation and regeneration of the parent hormone and its metabolites were successfully simulated by this model. The information in this study is useful for assessing the environmental risk of steroid hormones released from CAFO wastewater and to better understand why these hormone contaminants persist in many aquatic environments.