Department of Civil and Environmental Engineering, Stanford University, 473 Via Ortega, Stanford, CA, 94305, United States.
City of Los Angeles, USA.
Chemosphere. 2019 Apr;221:597-605. doi: 10.1016/j.chemosphere.2019.01.053. Epub 2019 Jan 9.
US EPA Method 521 employs activated carbon-based solid phase extraction (SPE) cartridges for analyzing N-nitrosamines. The analysis of N-nitrosamines and their chloramine-reactive and ozone-reactive precursors in nitrified municipal secondary effluent revealed the potential for NDMA to form as an artefact during the analysis. As samples passed through the SPE cartridge, the activated carbon mediated the reaction of nitrite with dimethylamine to form NDMA. The reaction was not significant with tertiary amines. Artefactual NDMA formation was important for nitrite concentrations >0.2 mg/L as N in the Biological Nitrogen Removal (BNR) process effluent. However, it is difficult to define a general threshold for nitrite concentrations, because the importance of the reaction also depends on secondary amine concentrations, which are usually poorly characterized. Pre-treatment of samples with sulfamic acid to destroy nitrite mitigated the artefact. This artefact did not affect NDMA analysis in a nitrified effluent from another facility, likely due to low dimethylamine concentrations. This artefact also did not affect the analysis of primary effluent, due to the lack of nitrite, or the analysis of other N-nitrosamines, likely due to the lack of their secondary amine precursors. Because chloramination does not significantly degrade nitrite, this artefact could affect the analysis of chloramine-reactive N-nitrosamine precursors. Because ozonation rapidly degrades nitrite, it should not affect the analysis of ozone-reactive precursors. However, ozonation at 0.8 mg ozone/mg dissolved organic carbon resulted in significant degradation of all N-nitrosamines, even though simultaneous NDMA formation from ozone-reactive precursors resulted in a net increase in NDMA concentration.
美国环保署方法 521 采用基于活性炭的固相萃取 (SPE) 小柱来分析亚硝胺。在分析硝化城市二级出水时，发现亚硝胺及其与氯胺反应和臭氧反应的前体物可能会在分析过程中形成假象。当样品通过 SPE 小柱时，活性炭介导亚硝酸盐与二甲胺反应形成 NDMA。该反应与叔胺不显著。在生物氮去除 (BNR) 过程出水中，当亚硝酸盐浓度 >0.2mg/L 时，这种假象 NDMA 的形成很重要。然而，由于二级胺浓度通常难以准确描述，因此很难定义一个通用的亚硝酸盐浓度阈值。用氨基磺酸预处理样品以破坏亚硝酸盐可减轻假象。由于二甲胺浓度较低，这种假象不会影响另一个处理设施硝化废水中的 NDMA 分析。由于缺乏亚硝酸盐，这种假象也不会影响初沉出水的分析，或者不会影响其他亚硝胺的分析，可能是因为缺乏它们的二级胺前体物。由于氯化消毒不会显著降解亚硝酸盐，因此这种假象可能会影响对氯胺反应性亚硝胺前体物的分析。由于臭氧氧化会迅速降解亚硝酸盐，因此不会影响对臭氧反应性前体物的分析。然而，当臭氧投加量为 0.8mg 臭氧/mg 溶解有机碳时，所有亚硝胺都会被显著降解，尽管臭氧反应性前体物同时形成 NDMA 会导致 NDMA 浓度净增加。
