de Brito Anton Luana, Silverman Andrea I, Apell Jennifer N
Civil and Urban Engineering Department, Tandon School of Engineering, New York University, Brooklyn, New York 11201, USA.
Environ Sci Process Impacts. 2025 Jul 16;27(7):2116-2127. doi: 10.1039/d5em00199d.
Predicting the environmental fate of anthropogenic chemicals remains a top priority for scientists and regulators; however, these efforts are hindered by the complexity of environmental systems. For example, in aquatic photodegradation, multiple photochemically produced reactive intermediates (PPRI) are present simultaneously, such as hydroxyl radicals (˙OH), singlet oxygen (O), and triplet excited states of chromophoric dissolved organic matter (CDOM*). This makes it difficult to isolate contributions of individual PPRI to overall photodegradation as well as to measure bimolecular reaction rate constants with target contaminants (), which could subsequently be used to predict degradation rates under variable environmental conditions and in engineered water treatment systems. As an alternative approach, simplified model systems can be used to isolate reactions with each PPRI. Yet, a systematic comparison of the results obtained in different model systems has not been conducted. In this study, at least two model systems were used to quantify between each PPRI (, ˙OH, O, and three CDOM* proxies) and each of the 28 pesticides evaluated. Results were consistent for most pesticides across the set of model systems used to evaluate a given PPRI. However, significant discrepancies were observed in some cases. For some pesticides, reactions with ˙OH appeared faster than the diffusion-controlled limit, suggesting additional reactions with unidentified PPRI were occurring. In O model systems, unexpected reactions occurred between some pesticides and the triplet excited states of the model sensitizer. Lastly, there was not a consistent trend between the calculated and the photochemical properties of the three CDOM* proxies evaluated, as suggested in previous studies. Overall, the results from this study showed that model systems are a powerful tool for investigating indirect photodegradation reactions and should be adopted in formal evaluations of the environmental fate of anthropogenic chemicals. Key considerations and recommendations to ensure accurate and reliable use of model systems are provided and areas benefiting from further investigation are identified.
预测人为化学物质的环境归宿仍然是科学家和监管机构的首要任务；然而，这些努力受到环境系统复杂性的阻碍。例如，在水生光降解过程中，多种光化学产生的反应性中间体（PPRI）同时存在，如羟基自由基（˙OH）、单线态氧（O）和发色溶解有机物的三重激发态（CDOM*）。这使得难以分离单个PPRI对整体光降解的贡献，也难以测量与目标污染物的双分子反应速率常数（），而这些常数随后可用于预测可变环境条件下和工程水处理系统中的降解速率。作为一种替代方法，可以使用简化的模型系统来分离与每种PPRI的反应。然而，尚未对不同模型系统中获得的结果进行系统比较。在本研究中，至少使用了两种模型系统来量化每种PPRI（，˙OH，O和三种CDOM替代物）与所评估的28种农药中的每一种之间的（）。在用于评估给定PPRI的一组模型系统中，大多数农药的结果是一致的。然而，在某些情况下观察到了显著差异。对于一些农药，与˙OH的反应似乎比扩散控制极限更快，这表明正在发生与未识别的PPRI的额外反应。在O模型系统中，一些农药与模型敏化剂的三重激发态之间发生了意外反应。最后，如先前研究中所建议的，在所评估的三种CDOM替代物的计算（）和光化学性质之间没有一致的趋势。总体而言，本研究的结果表明，模型系统是研究间接光降解反应的有力工具，应在人为化学物质环境归宿的正式评估中采用。提供了确保准确可靠使用模型系统的关键考虑因素和建议，并确定了受益于进一步研究的领域。
