Uptake and transport of steroid estrogens in soil-plant systems and their dissipation in rhizosphere: Influence factors and mechanisms

Residual steroid estrogens (SEs) in soil may be absorbed by plants, and subsequently threaten human health via food chains. However, the environmental behavior of SEs in soil-plant systems remains unclear. In this study, a wheat pot experiment using rhizosphere bags was performed to investigate the uptake and dissipation of target SEs (17 beta-estradiol (E2) and estrone (E1)) in different soils. The results indicated that soils with higher organic matter and silt and clay reduced the plant uptake of estrogens. Compared with E1, E2 was less accumulated in plants, which was mainly correlated with its higher hydrophobicity and shorter half-life. Estrogens tended to concentrate in the plant roots instead of translocating to the shoots. In addition, plant cultivation enhanced estrogen dissipation in the rhizosphere with an improvement of 10-21%. This improvement mainly resulted from stimulating the activities of estrogen-degrading enzymes, increasing the total bacterial populations, and promoting the development of estrogen degraders. Furthermore, this promotion effect will increase with plant growth. These findings will help us understand the characteristics of SEs taken up by plants and the role of the rhizosphere in SEs elimination, and provide theoretical insights into reducing the pollution risk of SEs in agricultural soils.