Institute of Environmental Engineering, National Sun Yat-sen University, Kaohsiung 804, Taiwan.
Environ Sci Process Impacts. 2015 Dec;17(12):2092-100. doi: 10.1039/c5em00308c.
The objective of this study was to investigate the formation of different nitrosamines during chlorination or chloramination (chlor(am)ination) of five phenylurea herbicides (fluometuron, diuron, linuron, metobromuron, and propanil), with the effects of disinfection approaches, additional inorganic nitrogen, and reaction pH being studied. By analyzing six nitrosamines, N-nitrosodimethylamine (NDMA) and N-nitrosopyrrolidine (NPYR) formation was observed. The dimethylamine functional group was the key to determining whether a particular phenylurea herbicide was an important nitrosamine precursor, as the NDMA conversion ratio was much higher. Chlorination with ammonium or dichloramination enhanced the NDMA formation. NPYR formation from the herbicides that did not form NDMA was detected and was more vigorous during dichloramination or in the presence of either ammonium or nitrite. The NPYR formation was possibly related to the aniline molecular fragment from the phenylurea herbicides. Both NDMA and NPYR formation were higher at pH 8. Overall, the maximum nitrosamine conversions decreased in the order: fluometuron > diuron > propanil > metobromuron > linuron (up to 0.99%, 0.46%, 0.005%, 0.004%, and 0.003% molar conversion rates, respectively) during chlorination or chloramination and dichloramine > free chlorine > monochloramine (up to 0.99%, 0.41%, and 0.005% molar conversion rates, respectively) for given herbicide, chlorine, and nitrogen doses. Applying the results of this study, phenylurea herbicide concentrations ranging from several to tens of μg L(-1) will yield a NDMA concentration in drinking water above the level for a theoretical 10(-6) lifetime cancer risk. NPYR formation will increase the risk of these phenylurea herbicide concentrations to downstream water users. The true adverse environmental impacts of these phenylurea herbicides are important to emphasize given their high loadings as non-point source pollutants and their typical environmental scenarios (e.g., at neutral pH or with the co-occurrence of inorganic nitrogen), likely resulting in more efficient nitrosamine formation.
本研究旨在探讨五种苯脲类除草剂（氟乐灵、敌草隆、利谷隆、灭草隆和丙草胺）在氯化或氯胺化（氯（氨）化）过程中不同亚硝胺的形成情况，并研究了消毒方法、外加无机氮和反应 pH 值的影响。通过分析六种亚硝胺，发现了 N-亚硝基二甲胺（NDMA）和 N-亚硝基吡咯烷（NPYR）的形成。二甲基胺官能团是决定特定苯脲类除草剂是否为重要亚硝胺前体的关键，因为 NDMA 的转化率要高得多。加铵或二氯胺化会增强 NDMA 的形成。在未形成 NDMA 的除草剂中检测到 NPYR 的形成，并且在二氯胺化或存在铵或亚硝酸盐时更为剧烈。NPYR 的形成可能与苯脲类除草剂中的苯胺分子片段有关。在 pH8 时，NDMA 和 NPYR 的形成均较高。总体而言，亚硝胺的最大转化率顺序为：氟乐灵>敌草隆>丙草胺>灭草隆>利谷隆（氯化或氯胺化和二氯胺化时分别为 0.99%、0.46%、0.005%和 0.004%和 0.003%摩尔转化率），而对于给定的除草剂、氯和氮剂量，二氯胺化>自由氯>单氯胺化（分别为 0.99%、0.41%和 0.005%摩尔转化率）。根据本研究的结果，浓度为数μg/L 到数十μg/L 的苯脲类除草剂会导致饮用水中 NDMA 浓度超过理论上 10-6 致癌风险的水平。NPYR 的形成会增加下游用水者接触这些苯脲类除草剂的风险。鉴于这些苯脲类除草剂作为非点源污染物的高负荷以及它们的典型环境情况（例如，中性 pH 值或与无机氮的共同存在），强调这些苯脲类除草剂的真正不利的环境影响很重要，因为这可能导致更有效的亚硝胺形成。
