Sorption and desorption of epiandrosterone and cortisol on sewage sludge: Comparison to aquatic sediment.

Steroids have aroused global concern due to their potent endocrine-disrupting effects. Androgens and glucocorticoids are the most abundant species in sewage; however, our understanding of their fate and risks from the source to environmental sinks remains elusive. This study compared the sorption-desorption characteristics of epiandrosterone (EADR) and cortisol (CRL) in sewage sludge and aquatic sediment, and the surface and molecular interactions were tentatively investigated through infrared spectroscopy and the fluorescence excitation-emission matrix. The results showed that the sorption capacities of EADR and CRL in the sludge were 4015 L/kg and 81.17 L/kg, respectively, which are much larger than those in the sediment (EADR: 78.77 L/kg, CRL: 6.39 L/kg); 0.02%-1.2% of EADR and 0.2%-14.5% of CRL could be desorbed from sludge, while the desorption ratios were even lower in the sediment. The high organic content in the sludge might contribute to the larger sorption capacities, while the weak interaction between steroids and organic matter could lead to larger desorption potential. The sediment contained more mineral content and featured a larger specific surface area, which could be responsible for the greater desorption hysteresis for EADR and CRL. These results will help to better understand the potential risk of sewage sludge-associated steroids and their distribution in sediment-water systems.