某个男人的败北 独伊:Transport of free and conjugated estrogens in runoff from agricultural soils receiving poultry manur

Abstract (Summary)

Land application of animal manure such as poultry litter is a common agricultural management practice, especially in states with surplus manure. However, in addition to beneficial plant nutrients, manure has also been found to contain naturally-occurring steroidal hormones like estrogens. These hormones may pose a threat to aquatic and wildlife species when manure and associated contaminants are transported with agricultural runoff to receiving water bodies and aquatic ecosystems. Our understanding of the fate and transport of estrogens in agricultural runoff is, however, fairly limited. The overall goal of this study was to investigate the fate of estrogens in agricultural runoff at the field and watershed scales. At the field-scale, the impact of agricultural practices such as the type and rate of application of manure and tillage on estrogens was evaluated. At the watershed scale, estrogen concentrations in surface and soil waters were determined for various landscape positions. This study was conducted on agricultural soils in the coastal plain of Delaware. The estrogens that were quantified included both the free (estrone, E1; 17β estradiol, E2β 17α estradiol, E2α estriol, E3) and conjugate forms (glucuronides and sulfates), which differ in their toxicity potential.

Concentrations of estrogens were evaluated in surface runoff from experimental plots (5m x 12 m each) receiving raw and pelletized poultry litter at the rate of 12.6 to 35 Mg/ha ^-1 . Sampling was performed for surface runoff for 10 natural storm events over a four month period (April through July 2008). Estrogen concentrations were screened using enzyme-linked immunosorbent assays (ELISA), followed by quantification using liquid chromatography with tandem mass spectrometry (LC-MS/MS). Exports of estrogens were much lower from soils amended with pelletized poultry litter than the raw form of the litter. The no-tillage management practice also resulted in a lower export of estrogens with surface runoff compared to reduced tillage because less runoff was generated.

For the watershed-scale study, raw poultry litter was applied to a 10 ha watershed with corn as the crop at a rate of 9 Mg/ha ^-1 . Sampling and analyses were performed for surface runoff, soil water, and runoff sediment for nine storm events over 187 days (March-October, 2010) during the summer growing season. Estrogens in runoff were in the form of estrone and sulfate conjugates. Concentrations of estrogens were highest at the field-edge and then declined rapidly for upland and lowland riparian locations. Concentrations of conjugates in runoff were much higher than those of the free form at the edge of the field. We observed the E1 concentrations in the stream samples up to 3 ng/L ^-1 ; whereas, the concentrations considered as potentially toxic in different bioassays where at a range higher than 40 ng/L ^-1 . Overall, this study suggests that the agronomic practices associated with manure application in the present field and watershed studies did not pose substantial threat in terms of release of hormones to runoff waters.

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