School of Environmental Science and Engineering, Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, China.
School of Civil and Environmental Engineering, The University of New South Wales, Sydney, New South Wales 2052, Australia.
Environ Sci Technol. 2020 Aug 18;54(16):9980-9989. doi: 10.1021/acs.est.0c01693. Epub 2020 Jul 29.
Excited triplet states of natural organic matter (NOM*) are important reactive intermediates in phototransformation of organic contaminants in sunlit waters. The main goal of this study was to explore the influence of Cu on triplet-sensitized transformation rates of 20 selected phenolic and amine contaminants. Fourteen of the compounds examined exhibited a marked decrease in their 4-carboxybenzophenone (CBBP)-mediated phototransformation rate in the presence of trace amounts of Cu(II) (25-500 nM). Both mathematical modeling of these rate data and transient absorption spectroscopy measurements support the hypothesis that the decrease in the rate and extent of phototransformation of organic contaminants is due to the reduction of radical intermediates of the contaminants by photochemically formed Cu(I). The Cu-induced inhibition of oxidation of organic contaminants photosensitized by Suwannee River NOM (SRNOM) could also take place in the presence of nanomolar concentrations of Cu. The inhibitory effect of Cu on the oxidation rates of amine contaminants in SRNOM solutions was found to be significantly weaker compared to that in CBBP solutions, but little difference was observed on depletion of phenols. This behavior was attributed to the intrinsic inhibitory effect of the antioxidant moieties present in NOM on phototransformation of amine compounds, partially neutralizing the potential for further Cu inhibition.
天然有机物（NOM*）的激发三重态是阳光下水体中有机污染物光转化的重要反应中间体。本研究的主要目的是探索 Cu 对 20 种选定酚类和胺类污染物的三重态敏化转化速率的影响。在所研究的 14 种化合物中，当存在痕量 Cu(II)（25-500 nM）时，其 4-羧基二苯甲酮（CBBP）介导的光转化速率明显下降。这些速率数据的数学建模和瞬态吸收光谱测量都支持这样的假设，即有机污染物光转化的速率和程度的降低是由于污染物的自由基中间体被光化学形成的 Cu(I)还原。在纳米摩尔浓度的 Cu 存在下，由苏万尼河天然有机物（SRNOM）敏化的有机污染物的氧化也可能发生 Cu 诱导的抑制作用。与 CBBP 溶液相比，发现 Cu 对 SRNOM 溶液中胺类污染物氧化速率的抑制作用要弱得多，但对酚类的消耗几乎没有差异。这种行为归因于 NOM 中存在的抗氧化剂部分对胺类化合物光转化的固有抑制作用，部分中和了进一步 Cu 抑制的潜力。
