水中亚硝胺的测量不确定度模型及HJ-809的水质监测适用性评价

摘要

N-nitrosodimethylamine (NDMA) is frequently detected with higher concentration among nitrosamine compounds in water. Nitrosamines were tested by Gas Chromatography coupled with Fire Ionization Detector (GC-FID) in an issued environmental standard HJ 809-2016. In this study, the uncertainty of NDMA, a typical compound of Nitrosamines, was detailed analyzed and assessed, and the applicability for the testing standard HJ 809-2016 was evaluated. It was reported that Nitrosamines were generally at the level of ng/L in China at present, which is far below the detection limit of HJ 809-2016. Furthermore, according to nitrosamines production process of domestic water plants and its health risk, the water quality safety limit was recommend to be 6~40 ng/L for our country, which is also lower than the detection limit of HJ 809-2016 by an order of magnitude. Therefore, there are great limitation in the application of this testing standard when considering the present situation in water, toxicity, and human health risk of nitrosamines. It is obviously difficult to meet the testing need of lower concentration detection of nitrosamines in drinking water and source water. A better test method with higher sensitivity and lower detection limit, like mass spectrometry used in most testing labs, should be established to satisfy the technology need for nitrosamines in water quality monitoring.%根据《测量不确定度评定与表示》(JJF 1059.1-2012),以气相色谱法(GC-FID)测定水环境中检出率和检出浓度较高的N-亚甲基二甲胺(NDMA)为例,对测量过程的不确定度来源进行详细分析和评定,并对环境标准(HJ 809-2016)方法的适用性进行探讨和评价.目前我国水体中亚硝胺的浓度普遍为ng/L级,均远低于HJ 809-2016的方法检出限0.4~0.6 μg/L.此外,结合国内水厂的生产工艺和亚硝胺的健康风险,我国NDMA的水质安全标准值推荐为6~40 ng/L,也比HJ 809-2016的方法检出限低1~2个数量级.综合考虑水环境中亚硝胺的存在现状、毒性及其人体健康风险,现有的检测方法标准HJ 809-2016存在较大的局限性,无法满足普通地表水或水源水中普遍低浓度的检测,应寻求灵敏度更高、普及率较好的质谱方法,建立检出限更低的检测标准,适应实际的水质监测技术需求.