Environment Research Institute, Shandong University, Qingdao 266237, China.
Marine Ecology Research Center, First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China.
Sci Total Environ. 2021 Sep 10;786:147449. doi: 10.1016/j.scitotenv.2021.147449. Epub 2021 Apr 30.
The photodegradation of dissolved organic sulfur (DOS) is a potential source of aqueous sulfate and its chemical precursors in surface water. However, the photochemical fate of DOS and factors that control its fate still remain unclear. Herein, we employed a DOS model featuring a photosensitizer (humic acids, HA) to investigate the photochemical degradation pathways of DOS in various natural water sources, from which we observed the substantial photosensitized formation of sulfate, methanesulfonic acid (MSA), carbonyl sulfide (COS), and carbon disulfide (CS). However, the photochemical production of sulfate and MSA tends to be more efficient than COS and CS. The formation of sulfur-containing photodegradation products was also strongly affected by the identity of the organic sulfur precursor, the oxygen concentration, and the pH, while the salinity did not significantly influence the production ratios. Our results revealed that the photosensitization of DOS contributed significantly to the overall production of sulfate and MSA production, especially in acidic and oxygen-enriched environments, which was attributed to the photochemical production of reactive intermediates, such as excited CDOM (CDOM*) and reactive oxygen species (ROS). Considering the coexistence of DOS and photosensitizers in aquatic environments, photochemistry may play an essential role in the fate of aquatic DOS.
溶解态有机硫（DOS）的光降解是地表水硫酸盐及其化学前体的潜在来源。然而，DOS 的光化学命运及其控制因素仍不清楚。在此，我们采用一种含有光敏剂（腐殖酸，HA）的 DOS 模型来研究各种天然水源中 DOS 的光化学降解途径，从中我们观察到硫酸盐、甲烷磺酸（MSA）、羰基硫（COS）和二硫化碳（CS）的大量光敏形成。然而，硫酸盐和 MSA 的光化学生成往往比 COS 和 CS 更有效。含硫光降解产物的形成也受到有机硫前体的特性、氧浓度和 pH 的强烈影响，而盐度对生成比没有显著影响。我们的结果表明，DOS 的光敏化对硫酸盐和 MSA 的总体生成，尤其是在酸性和富氧环境中，这归因于活性中间体（如激发态 CDOM（CDOM*）和活性氧物质（ROS））的光化学生成，对 DOS 的命运起着重要作用。考虑到 DOS 和光敏剂在水生环境中的共存，光化学可能在水生 DOS 的命运中起着至关重要的作用。
