Department of Chemistry, Villanova University , 800 Lancaster Avenue, Villanova, Pennsylvania 19085, United States.
Environ Sci Technol. 2015 Nov 3;49(21):12808-15. doi: 10.1021/acs.est.5b03600. Epub 2015 Oct 21.
Dissolved natural organic matter (DOM) is a ubiquitous component of natural waters and an important photosensitizer. A variety of reactive oxygen species (ROS) are known to be produced from DOM photochemistry, including singlet oxygen, 1O2. Recently, it has been determined that humic-like substances and unknown organic chromophores are significant contributors to sunlight absorption in snowpack; however, DOM photochemistry in snow/ice has received little attention in the literature. We recently showed that DOM plays an important role in indirect photolysis processes in ice, producing ROS and leading to the efficient photodegradation of a probe hydrophobic organic pollutant, aldrin.1 ROS scavenger experiments indicated that 1O2 played a significant role in the indirect photodegradation of aldrin. Here we quantitatively examine 1O2 photochemically produced from DOM in frozen and liquid aqueous solutions. Steady-state 1O2 production is enhanced up to nearly 1000 times in frozen DOM samples compared to liquid samples. 1O2 production is dependent on the concentration of DOM, but the nature of the DOM source (terrestrial vs microbial) does not have a significant effect on 1O2 production in liquid or frozen samples, with different source types producing similar steady-state concentrations of 1O2. The temperature of frozen samples also has a significant effect on steady-state 1O2 production in the range of 228-262 K, with colder samples producing more steady-state 1O2. The large enhancement in 1O2 in frozen samples suggests that it may play a significant role in the photochemical processes that occur in snow and ice, and DOM could be a significant, but to date poorly understood, oxidant source in snow and ice.
溶解的天然有机物（DOM）是自然水体中普遍存在的成分，也是一种重要的光敏剂。已知 DOM 光化学反应会产生多种活性氧物质（ROS），包括单线态氧，1O2。最近，人们已经确定腐殖质样物质和未知的有机发色团是雪包中阳光吸收的重要贡献者；然而，DOM 在雪/冰中的光化学作用在文献中很少受到关注。我们最近表明，DOM 在冰中的间接光解过程中起着重要作用，产生 ROS，并导致探针疏水性有机污染物艾氏剂的有效光降解。1 ROS 清除剂实验表明，1O2 在艾氏剂的间接光降解中起重要作用。在这里，我们定量检查了 DOM 在冷冻和液态水溶液中光化学产生的 1O2。与液态样品相比，冷冻 DOM 样品中 1O2 的稳态产生增加了近 1000 倍。1O2 的产生取决于 DOM 的浓度，但 DOM 来源（陆地与微生物）的性质对液态或冷冻样品中的 1O2 产生没有显著影响，不同来源类型产生相似的稳态 1O2 浓度。冷冻样品的温度对 228-262 K 范围内的稳态 1O2 产生也有显著影响，较冷的样品产生更多的稳态 1O2。冷冻样品中 1O2 的大量增加表明，它可能在雪和冰中发生的光化学过程中发挥重要作用，DOM 可能是雪和冰中重要但迄今为止理解甚少的氧化剂来源。
