Formation And Influencing Factors Of Nitrosamines In Drinking Water

N-nitrosamines, as a group of emerging disinfection by-products (DBPs) in drinking water, have recently raised great concerns because of their high carcinogenic potency. Based on the review of concentrations, analytical methods, and formation mechanism of nitrosamines in drinking water, the formation and influencing factors of nitrosamines in drinking water were investigated, which may provide certain theoretical basis to controlling and eliminating nitrosamines in drinking water, safeguarding human health. The main results of this thesis are shown below:(1) The solid phase extraction (SPE) method combination of two SPE cartridges was developed to extract 9 nitrosamines in drinking water simultaneously, and the recoveries of 9 nitrosamines ranged from 83.6% to 99.8%. The high sensitivity LC/MS/MS analytical method was also established, and the detection limits ranged from 0.03-2.5 ng/L. The method improved the analysis level of 9 nitrosamines in drinking water effectively.(2) It was found that chloramination of 9 secondary amines could produce the corresponding nitrosamines, and conversion rate is 0.18%-2.3%. The initial concentration of reactants and solution pH were found to influence the formation of 9 nitrosamines, and the influence of different compounds was various. The solution pH is the key factor in controlling the formation of nitrosamines, the conversion rate of nitrosodiphenylamine (NDPhA) increased rapidly from 0.2% to 73.5% with the solution pH increased from 5.0 to 9.0, while the conversion rate of nitrosodimethylamine (NDMA) changed little, ranging from 1.1% to 2.6%.(3) The formation of a new DBP phenazine was studied and its cytotoxicities on two human cancer cells were also investigated. Phenazine can be produced along with NDPhA from diphenylamine (DPhA) chloramination, and the molar yield was higher than NDPhA. The formation of phenazine had a maximum molar yield from DPhA with solution pH increasing from 5.0 to 9.0. The cytotoxicity assays showed that phenazine had obvious cell-specific toxicity on T24 (bladder cancer cell lines) and HepG2 (hepatic tumor cell lines) cells with IC50 values of 0.50 and 2.04 mmol/L, which were slight lower to that of NDPhA (IC50,0.16 mmol/L and 0.27 mmol/L). The molar yields of phenazine were higher than that of NDPhA in certain conditions suggesting that phenazine in drinking water may play an adverse effect on human health.