| Estrogens such as 17 β-estradiol (E2) and estrone (E1) have been detected in surface waters at concentrations considered to have a biological impact on fish and amphibians. Many pathways of estrogens to surface waters have been investigated, but those through soil (leaching to karsts, shallow groundwater, or agricultural drains) represent some challenges. Previous research has shown that estrogens preferentially sorb to soil organic matter (SOM), and that they are rapidly degraded in aerobic conditions. Consequently we usually expect little or no leaching and transport of estrogens in soil, but E2 and E1 are still detected in unexpected places. Explanations for this require the influence of preferential flow paths and possibly colloidal materials. Colloids may enhance estrogen transport through soil. This study was designed to investigate the impacts of colloidal material on the interactions of E2 and E1 with soil, highlighting the ability of colloids to sorb E2 and E1, the rate of sorption and degradation, and any effect of suspended colloids on the transport of E2 and E1. Our results show estrogen sorption to soil and colloidal material is dominated by soil organic carbon as the sorbent (hydrophobic partitioning), and organic carbon more concentrated in colloidal material meaning that colloids can sorb more estrogen than soil, by mass. The kinetics of sorption show a rapid phase and a slower phase, with similar rates between the different materials measured. Degradation of estrogens is rapid in soil under aerobic conditions, but can slow, cease, or even reverse under anaerobic conditions. If preferential flow pathways are present, colloidal material can carry estrogens through soil. The presence of colloids and preferential flow paths during transport decreased the time of first detection, and increased both the concentration at peak delivery, and the total estrogen mass fraction transported. |
