Evaluating stereoselective sorption by soils of 17α-estradiol and 17β-estradiol

The application of manure and biosolids onto agricultural land has increased the risk of estrogenic exposure to aquatic systems. Both αE2 and βE2 have been routinely detected in surface and ground waters with higher concentrations reported near concentrated animal feeding operations and agricultural fields. Although movement through the soil to a water body is highly dependent on hormone-soil interactions, to date, only the interaction of βE2 with soils has been characterized despite αE2 often being the more common form excreted by livestock such as beef cattle and dairy. In predicting the transport of estradiol, sorption characteristics for the stereoisomers have been assumed to be the same. To evaluate this assumption, sorption of αE2 and βE2 was measured on seven surface soils representing a range in soil properties. Soils were autoclave-sterilized to minimize loss due to biotransformation, and both solution and soil phase concentrations were measured. Overall, E2 sorption is best correlated to soil organic carbon (OC) with an average log OC-normalized distribution coefficient (log Koc, L kgoc-1) of 2.97 ± 0.13 for αE2 and 3.14 ± 0.16 for βE2 with βE2 consistently exhibiting higher sorption than αE2 with the highest β/α sorption ratio of 1.9. Assuming that the two isomers sorb the same is not a conservative decision making approach. The lower sorption affinity of αE2 increases the likelihood that it will be leached from agricultural fields.