不同种类氨基酸在氯化后形成三卤甲烷和卤乙酸潜能特性

Trihalomethanes and haloacetic acids formation upon chlorination of typical amino acids

水体中的氨基酸作为饮用水消毒副产物(DBPs)的重要前驱体之一,已成为环境毒理学研究的焦点问题.本文对典型的20种氨基酸进行模拟氯化消毒实验,确定其耗氯量,以甲基叔丁基醚(MTBE)萃取消毒副产物三卤甲烷(THMs)、卤乙酸(HAAs)和三氯硝基甲烷(TCNM),并用气相色谱仪测试分析THMs、HAAs和TCNM的生成势,同时通过数理统计方法分析不同氨基酸的化学结构与生成消毒副产物浓度的关系.结果表明:(1)各氨基酸的耗氯能力与其结构密切相关,侧链上具有芳香性环状结构的氨基酸的耗氯量较大,其中芳香环上有羟基和氮取代基的酪氨酸和色氨酸分别表现出较高的耗氯量(13.58、14.10 mg·mg^(-1)),而没有官能团的苯丙氨酸耗氯量低(4.24 mg·mg^(-1)).(2)20种氨基酸氯化过程中DBPs生成能力的差异与氨基酸侧链官能团的结构与性质有一定关系,其中侧链上具有芳香性环状结构、羟基、氨基和硫自由基等官能团结构的氨基酸可形成较高浓度DBPs;氯化色氨酸生成THMs能力最强,其生成三卤甲烷量达338.5μg·L^(-1).天冬氨酸生成HAAs(390.61μg·L^(-1))能力最强,酪氨酸生成TCNM(56.38μg·L^(-1))能力最强.(3)通过回归分析得出20种氨基酸在氯化消毒过程中HAAs生成能力大小与耗氯量大小具有较明显的相关性,耗氯量较大的氨基酸生成的HAAs也较高.

Amino acids are important precursors of disinfection by-products in drinking water,which has become a focus of research in environmental toxicology.Twenty typical amino acids with different structures were chlorinated and examined for the formation potentials of trihalomethanes（THMs）,haloacetic acids（HAAs）and trichloronitromethane（TCNM）during chlorination.The main results were summarized as follow.Chlorine consumption ability are closely related to the structure of amino acid.Tyrosine and tryptophan,with hydroxyl and nitrogen substituents in the aromatic ring,showed higher Chlorine consumption（13.58,14.10 mg·mg-1）,while phenylalanine without functional groups showed a lower Chlorine consumption（4.24 mg·mg-1）.The production of DBPs during the chlorination of 20 amino acids were related to the structure and properties of the amino acid functional groups.The amino acids with a ring structure,—OH,—NH2,or—S—in the branched chain showed higher DBPs production.Tryptophan showed a high THM yields（338.5μg·L-1）,aspartic acid showed a high HAA yields（390.61μg·L-1）,and tyrosine showed a high TCNM yields（56.38μg·L-1）.Regression analysis showed that the HAAs production was significantly correlated with the chlorine consumption during chlorination disinfection of 20 amino acids.Results showed that Amino acids with relative high chlorine demand possessed a high HAA formation.