水中天然含氮有机物的形成、迁移转化及分布

The formation, transformation and distribution of natural organic nitrogen chemicals in aquatic environment

天然含氮有机物是水环境中的重要组成部分,其在天然水体中的形态及分布对环境质量有显著影响.本文围绕水中天然含氮有机物在氮循环中的地位、迁移转化以及其在国内主要水域中的分布情况,对天然含氮有机物的研究现状进行了梳理.我国不同水域中溶解性含氮有机物(DON)浓度相差较大;其中水体中DON浓度一般在1.0 mg·L^(-1)以下;沉积物中DON浓度通常为几十至几百mg·kg^(-1).水体DON以分子量<1 kDa的有机物为主,主要成分是尿素、氨基酸等物质.沉积物DON以分子量<1 kDa和>30 kDa的有机物为主,其中前者主要由芳构化程度较高的氨基酸等小分子有机物构成,后者以腐殖质类为主.水体中部分胺类物质本身具有一定毒性,游离氨基酸等DON还是卤乙腈、卤代酰胺、卤代硝基甲烷、卤化氰和亚硝胺等含氮消毒副产物的重要前体物.由于水体中许多含氮有机物具有生物可利用性,有机氮可能是引起水体富营养化的重要原因之一.

Natural organic nitrogen(NON) is an important constituent of aquatic environment and its form and distribution have a significant impact on the environmental quality. This review focused on the role of NON in the nitrogen cycle, and the formation, transformation and distribution of NON in major waters across China, then organized the current research of NON. The results indicated that dissolved organic nitrogen(DON) contents in water normally lower than 1 mg·L^(-1), and DON contents in sediments were usually tens to hundreds of mg·kg^(-1). The molecular fractionation results indicated that the molecular weight <1 kDa fraction accounted for the highest percentage in water, which consists of urea, amino acid, etc.. The molecular weight <1 kDa and >30 kDa fractions were the dominant fraction in sediments, and the <1 kDa fraction mainly consists of highly aromatic contents like amino acids and the >30 kDa fraction mainly consists of humic matter. Amines were likely to be toxicological. Free amino acids and amines had the potential to act as precursors in the formation of haloacetonitriles, haloacetamides, halonitromethanes, cyanogen halides and nitrosamines. NON also had the risks of causing eutrophication in waters due to its bio-availability.