Sorption of 17alpha-ethynylestradiol in different soil environments

Endocrine Disrupting Compounds (EDCs) have the ability to negatively affect the endocrine system; subsequently, they became the focus of the current research and media awareness. Steroid estrogens (natural and synthetic) have been recognized as endocrine disrupting chemicals a number of studies have correlated these compounds to adverse effects in humans, wildlife and fish. Most of the research done thus far was focused on the fate, behavior and impact of these compounds within living organisms, or during their removal/treatment. However, knowledge about the behavior and partitioning of these compounds or their byproducts once they are released in the environment (particularly in soil media) is not yet very well established. The focus of this study was to identify and evaluate the extent of partitioning of 17alpha-ethynylestradiol (EE2), a synthetic estrogen steroidal hormone, to different soil constituents (clay minerals: illite, montmorillonite, iron oxide: goethite and soil organic humic acid). The study demonstrated the effect of variable experimental conditions, such as pH, oxygen availability and EE2 initial concentration on the degree of sorption of the steroidal estrogen to individual soil components. Moreover, the potential mobility of 17alpha-ethynylestradiol leaching from biosolids and natural fertilizers application was investigated.; Batch-equilibration methods were conducted at the nanogram level in an attempt to emulate current environmental concentrations. The outcome of this research showed that 17alpha-ethynylestradiol showed different affinities of binding to soil constituents. Partitioning onto clay minerals was greater than onto iron oxide or humic acid. Sorption of 17alpha-ethynylestradiol was generally rapid within 1 hour; however, uptake by clay minerals continued to occur over a period of 24 hours. Changes in soil particles' surface-charges as a result of changing pH values were demonstrated to have a great influence on the potential mobility of 17alpha-ethynylestradiol within soil media. Highest sorption values were achieved at the isoelectric points of individual soil constituent. Sorption was primarily governed by hydrophobic interactions with siloxane surfaces, coupled with the interaction of nonpolar 17alpha-ethynylestradiol with uncharged soil surface hydroxyl groups through hydrogen bonding. The results also implied that the affinity of the synthetic estrogen to partition to soil constituents within subsurface media is not expected to differ between aerated top soil regions and deep ground levels of air deficiency. Moreover, the introduction of leachate was found to reduce the affinity of 17alpha-ethynylestradiol to partition into illite, natural soil, and goethite; however, it increased the degree of sorption to montmorillonite. Finally, this study results suggest that montmorillonite possessed the greatest sorption capacities under a wide range of environmental conditions. Although adsorbing EE2 to clay minerals is expected to diminish the potential hazard of leaching out to groundwater, surface water bodies are still vulnerable to contamination through runoff.