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Sources and sinks of hydroxyl radicals upon irradiation of natural water samples

机译：天然水样品辐照时羟基自由基的来源和吸收

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Hydroxyl radical formation rates, steady-state concentration, and overall scavenging rate constant were measured by irradiation of surface lake water samples from Piedmont (NW Italy) and nitrate-rich groundwater samples from Moldova (NE Romania). Dissolved organic matter (DOM) was the main source and sink of center dot OH upon lake water irradiation, with [center dot OH] being independent of DOM amount. Water oxidation by photoexcited DOM is a likely center dot OH source in the presence of very low levels of nitrate and dissolved iron. Under different circumstances it is not possible to exclude other processes, e. g., DOM-enhanced photo-Fenton reactions. Under the hypotheses of no interaction and absence of mutual screening of radiation, nitrate would prevail over DOM as center dot OH source for a NO3-/DOM ratio higher than 3.3 x 10(-5) (mol NO3-) (mg C)(-1), DOM prevailing for lower values. Substantial DOM photolability was observed upon irradiation of nitrate-rich groundwater, mainly due to the elevated center dot OH generation rate. For the first time to our knowledge, evidence was also obtained of the photoformation of potentially toxic and/or mutagenic nitroaromatic compounds upon irradiation of natural lake water and groundwater samples, proportionally to the nitrate levels.
机译：羟基自由基的形成速率，稳态浓度和总清除速率常数是通过辐照来自皮埃蒙特（意大利西北）的地表湖水样品和来自摩尔多瓦（罗马尼亚东北）的富含硝酸盐的地下水样品来测量的。溶解有机物（DOM）是湖水辐照后中心点OH的主要来源和汇，[中心点OH]与DOM量无关。在硝酸盐和铁含量非常低的情况下，光激发DOM引起的水氧化可能是中心点OH源。在不同情况下，不可能排除其他过程，例如例如DOM增强的光芬顿反应。在没有相互作用且没有相互屏蔽辐射的假设下，对于NO3- / DOM比高于3.3 x 10（-5）（mol NO3-）（mg C）（ -1），较低的值以DOM为主。辐照富含硝酸盐的地下水时观察到了相当大的DOM可光化性，这主要归因于中心点OH生成速率的提高。据我们所知，这也是首次获得证据，证明天然湖水和地下水样品辐照时潜在的有毒和/或诱变的硝基芳族化合物的光形成与硝酸盐含量成比例。

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