| For a long time,the problem of drinking water safety attracts the attention of researchers at home and abroad.In the process of chlorination and disinfection in the production of tap water,chlorine-containing disinfectants react with organic nitrogen-containing compounds to generate carcinogenic Nitrosoamines?NAs?,which have been detected in many urban water supply networks in China with concentrations as high as tens of ng·L-1.However,at present,the formation mechanism of NAs in the process of chlorination is not clear,and there is still a lack of detection standards for NAs in water in China.Therefore,it is of great practical significance to study the concentration distribution of NAs in tap water and health risks for drinking water safety.Based on SPE?Solid Phase Extraction,the SPE?-gas chromatography mass spectrometry?GC-MS/MS?technology to establish the method for determination of the seven kinds of NAs in tap water,with the aid of the method is tested in the northern city of tap water samples and typical waterworks all processes in and out of the seven kinds of NAs levels in water samples,compared with the pollutant concentration and composition differences at home and abroad,analyzed the formation mechanism of the urban tap water is mainly the NAs and potential health risks.The results show that:1)After optimization of SPE packing and elution solvent,coconut shell activated carbon is finally selected as the adsorption filler and dichloromethane as the elution solvent.The standard recovery rate can reach 88.8%110%.The GC-MS/MS method is used only for quantitative analysis of 7 target substances.The detection limits of 7 substances are all lower than 0.1 ng·L-1,the quantitative limits are all lower than 0.5 ng·L-1,the correlation coefficients are all greater than 0.999,and the relative standard deviation?n=3?is less than6.2%.2)On the basis of the above methods,the tap water samples from the main urban area of a city and the water samples from two typical waterworks in and out of each process are gathered for quantitative analysis.The results show that the NAs concentration in the tap water in the main urban area is between undetected and 3.576 ng·L-1,in which NDBA(average concentration:2.766 ng·L-1)and NDMA(average concentration:2.489 ng·L-1)are100%detected and the average concentration is higher.The concentration in the samples of waterworks ranged from undetected to 2.03 ng·L-1,where NDMA(average concentration:1.32 ng·L-1)detected 100%and the average concentration is higher,the concentration of NAs in the samples of waterworks is generally lower than that in the main urban area,and NDPA and NPIP were only detected at some sampling points.According to the time distribution,the detection rate of NDMA and NMEA are higher in summer,while the detection rate of 7 kinds of NAs is lower in winter than in spring and summer.Concentrations of NAs in all samples are below the limits set by the U.S.environmental protection agency.3)Based on the detection concentration of NAs,the carcinogenic probability?CR?of all samples is evaluated by three pathways:ingestion,inhalation and skin contact.The results show that the potential risk of NAs in the tap water involved is low and do not greater than the maximum acceptable level(10-4)recommended by EPA,and the drinking water of residents is safe to drink. |
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