Department of Civil and Environmental Engineering, University of Catania, Italy.
Water Res. 2013 Oct 15;47(16):5995-6006. doi: 10.1016/j.watres.2013.07.018. Epub 2013 Jul 31.
This study examined effects of bromide on yields and speciation of dihaloacetonitrile (DHAN) species that included dichloro-, bromochloro- and dibromoacetonitriles generated in chlorinated water. Experimental data obtained using two water sources, varying concentrations and characters of Natural Organic Matter (NOM), bromide concentrations, reaction times, chlorine doses, temperatures and pHs were interpreted using a semi-phenomenological model that assumed the presence of three kinetically distinct sites in NOM (denoted as sites S1, S2 and S3) and the occurrence of sequential incorporation of bromine and chlorine into them. One site was found to react very fast with the chlorine and bromine but its contribution in the DHAN generation was very low. The site with the highest contribution to the yield of DHAN (>70%) has the lowest reaction rates. The model introduced dimensionless coefficients (denoted as φ1(DHAN), φ2(DHAN) and φ3(DHAN)) applicable to the initial DHAN generation sites and their monochlorinated and monobrominated products, respectively. These parameters were used to quantify the kinetic preference to bromine incorporation over that of chlorine. Values of these coefficients optimized for DHAN formation were indicative of the strongly preferential incorporation of bromine into the engaged NOM sites. The same set of φ(i)(DHAN) coefficients could be used to model the speciation of DHAN released from their kinetically different precursors. The dimensionless speciation coefficients φ(i)(DHAN) were determined to be site specific and dependent on the NOM content and character as well as pH. The presented model of DHAN formation and speciation can help quantify in more detail the generation of DHAN and provide more insight necessary for further assessment of their potential health effects.
本研究考察了溴化物对二卤乙腈（DHAN）物种产量和形态的影响，这些物种包括在氯化水中生成的二氯、溴氯和二溴乙腈。使用两种水源、不同浓度和特性的天然有机物（NOM）、溴化物浓度、反应时间、氯剂量、温度和 pH 值获得的实验数据，使用一个半经验模型进行了解释，该模型假设 NOM 中存在三个动力学上不同的位点（表示为 S1、S2 和 S3 位点），并且溴和氯依次进入这些位点。发现一个位点与氯和溴反应非常快，但它对 DHAN 生成的贡献非常低。对 DHAN 生成贡献最大（>70%）的位点反应速率最低。该模型引入了无量纲系数（分别表示为 φ1(DHAN)、φ2(DHAN)和 φ3(DHAN)），适用于初始 DHAN 生成位点及其单氯和单溴化产物。这些参数用于量化溴与氯的取代反应动力学偏好。针对 DHAN 形成进行优化的这些系数值表明，溴强烈优先进入参与的 NOM 位点。相同的 φ(i)(DHAN)系数集可用于模拟从其动力学不同的前体释放的 DHAN 的形态。无量纲形态系数 φ(i)(DHAN)被确定为特定于位点的，并且取决于 NOM 含量和特性以及 pH 值。所提出的 DHAN 形成和形态模型可以帮助更详细地量化 DHAN 的生成，并提供对其潜在健康影响进行进一步评估所需的更多见解。
