| Safe drinking water is the basis of human health, social stability and economic development. N-nitrosamines are emerging disinfection by-products in drinking waters. In recent years, N-nitrosamines have been paid highly attention to by the domestic and foreign scholars for their potential strong carcinogenicity. The California Department of Public Health has established a notification level of10ng/L for N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) in drinking waters, which is8000times lower than the level for trihalomethanes (THMs) and6000times lower than the level for haloacetic acids (HAAs) established by US EPA. Until now, there have been no water-quality standards for N-nitrosamines in China and few research reports on the occurrences of N-nitrosamines in drinking water treatment plants (DWTPs) in Jiangsu province. Therefore it is valuable to study on the levels and sources of N-nitrosamines in DWTPs in Jiangsu province.The N-nitrosamines in waters were extracted by SPE method and analyzed by GC/MS. The detection limits (DLs) for nine N-nitrosamine species ranged from0.8to4.3ng/L. The average recovery of N-nitrosamine species spiked at lOng/L,50ng/L and200ng/L was from86%to97%except for N-nitroso-di-phenylamine (NDPhA). Only two N-nitrosamines including NDMA (n.d.-4.8ng/L) and N-nitrosomorpholine (NMor)(n.d.-36.2ng/L) were detected in ten bottled drinking waters from the local supermarket by using the established analysis method. And Water samples from nine municipal DWTPs in eight cities of Jiangsu Province were analyzed for nine N-nitrosamine species. For the distribution system waters, NDMA (n.d.-5.4ng/L), N-nitrosomethylethylamine (NMEA)(n.d.-9.5ng/L), NDEA (n.d.-2.7ng/L) and N-nitroso-pyrrolidine (NPyr)(n.d.-8.5ng/L) were detected in wet season and NDMA (n.d.-45.3ng/L), NPyr (n.d.-5.2ng/L) and N-nitrosopiperidine (NPip)(n.d.-309ng/L) were detected in dry season.Multiple linear regression analysis between the detected values of raw water quality parameters (pH, DOC, UV254, UV272, SUVA254, SUVA272, NH3-N, NO2--N, NO3--N and DON), the residual chlorine and monochlorine in finished waters and distribution system waters and the total concentrations of nine N-nitrosamines in raw waters, finished waters and distribution system waters in the DWTPs showed that there were positive relationships between DOC concentrations in raw waters and the total concentrations of nine N-nitrosamines in raw waters (r=0.983) and in finished waters (r=0.961). The concentrations of residual monochloramine in finished waters and distribution system waters both had a high correlation coefficient (r=0.988) with the total concentrations of nine N-nitrosamines in distribution system waters.The formation potentials for nine N-nitrosamines species of three kinds of predecessors including two kinds of humic acid from China and a foreign country (HA-G and HA-J) and one kind of quaternary ammonium salt (dodecyldimethylbenzylammonium chloride) were compared, which were disinfected at20℃and pH7.0with chlorine and monochloramine, respectively. The DOC had the same amount of substance with the disinfectants in the initial mixture solution. HA-J had the highest total N-nitrosamines formation potential, while dodecyldimethylbenzylammonium chloride had the lowest total N-nitrosamines formation potential. The NDMA formation potential of dodecyldimethylbenzylammonium chloride disinfected with chlorine was higher than that with monochloramine. However, the NDEA formation potentials of HA-J and HA-G disinfected with chlorine were lower than that with monochloramine and there was no NDMA formed under the two disinfection methods. HA-G consumed less chlorine and monochloramine than HA-J, which was because HA-G contained less aromatic hydrocarbons and organic nitrogen than HA-J according to the characterization results by the fluorescence index, elementary analysis, ultraviolet, fourier transform infrared spectrometer(FTIR),’H-NMR and13C-NMR spectra. |
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