Lake water constituents, such as chromophoric dissolved organic matter (CDOM) and nitrate, absorb sunlight which induces an array of photochemical reactions. Although these reactions are a substantial driver of pollutant degradation in lakes they are insufficiently understood, in particular on large scales. Here, we provide for the first time comprehensive photochemical maps covering a large geographic region. Using photochemical kinetics modeling for 1048 lakes across Sweden we simulated the steady-state concentrations of four photoreactive transient species, which are continuously produced and consumed in sunlit lake waters. We then simulated the transient-induced photochemical transformation of organic pollutants, to gain insight into the relevance of the different photoreaction pathways. We found that boreal lakes were often unfavorable environments for photoreactions mediated by hydroxyl radicals (OH) and carbonate radical anions (CO₃⁻), while photoreactions mediated by CDOM triplet states (³CDOM*) and, to a lesser extent, singlet oxygen (¹O₂) were the most prevalent. These conditions promote the photodegradation of phenols, which are used as plastic, medical drug and herbicide precursors. When CDOM concentrations increase, as is currently commonly the case in boreal areas such as Sweden, ³CDOM* will also increase, promoting its importance in photochemical pathways even more.

中文翻译：

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纬度为14度的阳光照射下的北方湖泊的光反应瞬态和有机污染物的光化学转化模拟

湖水成分，例如发色溶解的有机物（CDOM）和硝酸盐，吸收阳光，从而引发一系列光化学反应。尽管这些反应是造成湖泊中污染物降解的主要驱动力，但对它们的了解还不够，特别是在大规模方面。在这里，我们首次提供了覆盖广泛地理区域的综合光化学图。通过对瑞典1048个湖泊的光化学动力学建模，我们模拟了四种光反应性瞬态物种的稳态浓度，这些物种在阳光普照的湖水中不断产生和消耗。然后，我们模拟了瞬态诱导的有机污染物的光化学转化，以了解不同光反应途径的相关性。OH）和碳酸根阴离子（CO ₃ ^-），而由CDOM三重态（³ CDOM *）和较小程度的单线态氧（¹ O ₂）介导的光反应最为普遍。这些条件促进了酚的光降解，酚被用作塑料，医疗药物和除草剂的前体。当CDOM浓度增加时（如瑞典北部地区目前普遍存在的情况），³ CDOM *也将增加，从而进一步提高了其在光化学途径中的重要性。