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Occurrence, biotransformation and bioavailability of endocrine disrupting compounds in sediment
Abstract
Endocrine disrupting compounds (EDCs) receive continuing concerns due to the ecological toxicity and potential adverse effect on public health. A number of EDCs has been listed as candidate contaminants by U. S. Environmental Protection Agency. EDCs enter the environment from municipal, agricultural and industrial sources, and widely spread through various biogeochemical processes. Knowledge of their partitioning, transport, and attenuation processes is of great importance to assess and control the risk posed by EDCs. This dissertation investigates the impact of stereoselective biotransformation and particle size on the persistence of steroid hormones, one of the most potent category of EDCs, in aquatic sediment. Results show that 17β-estradiol (17β-E2) and 17β-trenbolone (17β-TB) generally decay more rapidly than the α-isomers in saturated sediment. Co-occurrence of α- and β-isomers decreases the biotransformation rates of both isomers in a sandy sediment indicating carbon source and/or nutrient limited condition may enhance the competition between stereoisomers. Sediment particle size does not dramatically affect the decay rates of 17β-E2 and 17β-TB in the early stage of biotransformation. However, 17β-E2 and 17β-TB residues are more persistent in silt and clay relative to in sand. Estrone (E1) and trendione (TD) are detected as biotransformation products of 17β-E2 and 17β-TB, respectively. In most cases, E1 and TD decay faster in the fine fractions compared to the sand fraction. Fine particles determine the overall persistence of E1 and TD in the whole sediment probably due to larger sorption capacity of and preferential sorption by fine particles. An on-site fish exposure study was also conducted to evaluate the endocrine disrupting effect of sediment-associated agrochemicals including steroid hormones and pesticides. Both anti-estrogenic and anti-androgenic effects are observed in female fathead minnows exposed to spring agrochemical pulses. The overall driver for molecular defeminization in fish is direct exposure to the sediment-associated compounds, indicating that endocrine disrupting effects observed in organisms in turbid water could be attributed to direct exposure of contaminated sediment.
Subject Area
Environmental science|Environmental engineering
Recommended Citation
Zhang, Yun, "Occurrence, biotransformation and bioavailability of endocrine disrupting compounds in sediment" (2016). ETD collection for University of Nebraska-Lincoln. AAI10102680.
https://digitalcommons.unl.edu/dissertations/AAI10102680