Spatio-temporal distribution and transformation of 17α- and 17β-estradiol in sterilized soil: A column experiment

The environmental behaviors of steroid estrogens (SEs) associated with land irrigation and application are of critical concern worldwide. Understanding the spatio-temporal distribution and transformation process of these estrogenic compounds in soil is greatly significant. In this study, laboratory soil column experiments were conducted to investigate and explore the migration and abiotic transformation of 17 alpha-estradiol (17 alpha-E2) and 17 beta-estradiol (17 beta-E2) over spatial and time scales. Results indicated that the migration tendency of 17 alpha-E2 and 17 beta-E2 was similar. Discrepancies in transport for different SEs groups might be due to the competitive sorption and isomeric transformation in the binary-solute system. 17 alpha-E2 and 17 beta-E2 can also undergo the abiotic transformation during soil column transport. The soil with naturally abundant mineral substances (e.g., iron and manganese oxides) indicated that E2 isomers tended to mineral-promoted racemization, oxidation, reduction, and radical coupling reactions. Some possible transformation products (e.g., SE239, E-2378, and SE dimer(476)) were identified and proposed in soil samples. Compared to the single compound tests, the estimated 17 beta-estradiol equivalency (EEQ) values of E2 mixture were higher during SEs migration process.