Fast decomposition of typical endocrine disturbing compounds in microdroplets under sunlight irradiation in the presence of ozone

Water microdroplets are ubiquitous in atmospheric environment, where photo-irradiation and O₃ are available, while photo-decomposition of trace organic pollutants in microdroplets and the impact of atmospheric environmental factors on the photo-chemistry remain unclear. In this study, photochemical generation of reactive oxygen species and degradation of typical endocrine disturbing compounds (EDCs) in microdroplets were investigated under various atmospheric conditions (O₃, inorganic anions and fulvic acid). The experimental results demonstrate that EDCs can be degraded in microdroplets, and the degradation efficiency is further improved under the stimulated solar irradiation. The degradation efficiency of estrone (E1), estradiol (E2), ethinyl estradiol (EE2), testosterone (T) exposing to sunlight irradiation is 55.45 %, 64.11 %, 89.72 %, and 24.72 %, respectively. The degradation of EDCs is attributed to the generation of hydroxyl and superoxide radicals at or near the microdroplets interface. In addition, with O₃, the degradation efficiency of EDCs in microdroplets increased to 100 %, 100 %, 100 %, and 83.87 %, respectively. Common inorganic ions (Cl^-, NO₃^-, SO₄^2-, and HCO₃^-) and fulvic acid exhibit positive effects for degradation of EDCs at varying extents. Overall, these findings shed light on the generation of reactive oxygen species and degradation patthways of trace EDCs in microdroplets and improve the understanding of the effect associated with relevant environmental factors in atmospheric microdroplets.