Long-term sewage sludge application and wastewater irrigation on the mineralization and sorption of 17β-estradiol and testosterone in soils

The disposal of animal manures, wastewater and sewage sludge to agricultural land can lead to the transfer of steroid hormones like 17β-estradiol and testosterone into soils, surface and groundwaters. The objective of this study was to investigate the effects of different site histories like wastewater irrigation and sewage sludge application on hormone mineralization and sorption in soils. Two agricultural sites with different long-term treatment histories with wastewater and sewage sludge were sampled. The mineralization of 14C-17β-estradiol and 14C-testosterone was studied during incubations at 20 °C over three weeks. Despite the structural resemblance of both hormones the mineralization rate of 17β-estradiol was about an order of magnitude lower than that of testosterone in all four soils, reaching 5–7% vs. 50–59%, respectively. Estradiol mineralization was significantly lower in soils with long-term wastewater irrigation than in the corresponding soil with freshwater irrigation. Pre-incubation of the soils with unlabeled hormones or application of the hormones within a wastewater matrix had only minor effects on their mineralization. The results indicate that estradiol mineralization occurs co-metabolically and is limited by sorption, whereas testosterone appears to be utilized directly by soil microorganisms. Sorption of 14C-17β-estradiol and 14C-testosterone to sterile and unsterile soils was determined in batch experiments with CaCl2 or wastewater solution with hormone concentrations of 0.13–0.0013 μg mg−1. FREUNDLICH sorption isotherms and parameters like KF and log Koc values were used to describe the results. The KF values for estradiol sorption were generally about 1.2 to 1.6-fold higher than for testosterone. The SOC-normalized partition coefficients Koc also differ accordingly and indicate quite large differences in soil organic matter qualities relating to hormone sorption between the soils and treatments. When the hormones were added to the soil within a wastewater matrix less estradiol was sorbed in the solid phase than in the controls with pure water, thus indicating that wastewater contains soluble sorbents.