Photodegradation of 17α-ethynylestradiol in nitrate aqueous solutions

17α-Ethynylestradiol (EE2) has gotten growing concerns due to its widely detected in the environment and high estrogenic potency. However, the knowledge on the photochemical behaviors of EE2 in natural waters is still limited. Herein, the photodegradation and estrogenic potency variation of EE2 induced nitrate were studied using a sunlight simulator consisted by a 300 W medium pressure mercury lamp and 290 nm cut-off filters. It was found that EE2 could be photodegraded at a rate of 0.0193 h in pure aqueous solutions, and the photodegradation of EE2 could be significantly promoted by nitrate. The photodegradation removal rate of EE2 was increased from 9% in Milli-Q water to 85% in 2.0 mM nitrate solutions. Reactive species scavenging experiments demonstrated that the photogenerated HO contributed about 55% to EE2 degradation. Fe(III), Cl and DHA could inhibit the photodegradation of EE2 by competing the incident light and photogenerated HO, while HCO3 had no influence on EE2 photodegradation. EE2 was determined to be phototransformed into organic chemicals without estrogenic potency by GC-MS and MCF-7 cell proliferation toxicity tests. These findings could extend our knowledge on the photochemical behaviors of steroid estrogens and provide information for ecological risk assessment.