Dichlorvos (DDVP) is an organophosphorus pesticide that has been classified as highly hazardous chemical by the World Health organization. In this study, the fate of the pesticide DDVP in natural water compartments was examined under simulated sunlight. Moreover, the effect of UV-254 irradiation on DDVP depletion was also studied. In deionized water, DDVP was photodegraded only in the presence of dissolved molecular oxygen. The photodegradation during the first 6 h of sunlight irradiation occurred with pseudo first-order kinetics, and the rate constants were 0.040 h⁻¹ at pH 7 and 0.064 h⁻¹ at pH 3. A reaction mechanism for the generation of reactive oxygen species (ROS) via DDVP photoabsorption was proposed. Humic acids (HA) played a double role as photosensitizer and inhibitor, observing an enhancement on DDVP photodegradation at low HA concentration (TOC = 2 mg L⁻¹). The depletion of DDVP under 254 nm UV irradiation was ascribed to direct photodegradation and oxygen mediated photoinduced reactions. Direct photodegradation of DDVP decreased with 254 nm irradiation reduction, highlighting the importance of radical mediated mechanisms at low irradiation doses. Based on LC/MS data, the main photoproducts under simulated solar light and UV-C irradiation were identified and potential reaction pathways were postulated. The three main identified products were o-methyl 2,2-dichlorovinyl phosphate, dichloroacetaldehyde and dimethylphosphate. Moreover, the toxicity of samples was evaluated along the irradiation exposure time using Microtox® assays. This study brings new insights into the role of oxygen in the photodegradation of DDVP and the induced and inhibition mechanisms involved in the presence of the humic acids in natural waters.

敌敌畏（DDVP）是一种有机磷农药，已被世界卫生组织（World Health Organization）列为高度危险的化学品。在这项研究中，在模拟的阳光下检查了农药DDVP在天然水室中的去向。此外，还研究了UV-254辐照对DDVP耗竭的影响。在去离子水中，DDVP仅在溶解的分子氧存在下才被光降解。太阳光的照射的前6小时内光降解发生与假一级动力学，且速率常数分别为0.040ħ ^-1在pH 7和0.064ħ ^-1提出了一种通过DDVP光吸收产生活性氧（ROS）的反应机理。腐殖酸（HA）起到了光敏剂和抑制剂的双重作用，在低HA浓度（TOC = 2 mg L ^-1）下观察到DDVP光降解作用增强。DDVP在254 nm UV辐射下的损耗归因于直接光降解和氧介导的光诱导反应。DDVP的直接光降解随着254 nm辐射的减少而降低，突出了自由基介导的机制在低辐射剂量下的重要性。根据LC / MS数据，确定了模拟太阳光和UV-C辐射下的主要光产物，并推测了潜在的反应途径。三个主要的标识产物Ø-甲基2，2-二氯乙烯基磷酸酯，二氯乙醛和磷酸二甲酯。此外，使用Microtox®分析法沿辐照时间评估了样品的毒性。这项研究带来了新的见解，了解氧气在DDVP的光降解中的作用以及天然水中腐殖酸的存在所涉及的诱导和抑制机制。