| BackgroundThe government has always been highly concerned about the safety of drinking water.Rural areas due to their own conditions,the quality of its water is lower than urban areas.In recent years,with the promotion of rural water projects and the upgrading of water supply systems,the qualified rate of water in rural areas has increased year by year,but some rural areas still exist in the water technology was not complete,disinfection was not standardized.With the development of economy,many chemical enterprises transferred to rural areas,the discharge of pollutants or leakage caused serious pollution of the surrounding environment,combined with agricultural production,domestic waste emissions seriously threaten the rural areas of drinking water safety,the possibility and extent of chemical contaminant caused by chemical pollutants in human drinking water in rural areas need to be scientifically estimated and evaluated.Objective1.To understand the status of drinking water quality in rural areas of Chongqing in 2015,to explore the influencing factors of water quality in factories and provide improvement measures and suggestions to ensure the safety of drinking water in rural areas.2.To understand the exposure level and distribution characteristics of chemical pollutants in drinking water in some rural areas of Chongqing in 2015,to evaluate the potential harm of rural drinking water in Chongqing,and to provide scientific basis for drinking water risk management of the relevant departments.Methods1.According to the different regions of Chongqing,population,economy,geography,water type and other characteristics,with a stratified random sampling,in the city’s 38 districts and counties,each county selected 70% of the town,each town(including the village)select 1-2 rural water plants as a monitoring point.A total of 846 water plants were selected as monitoring points in 2015 and the basic situation was investigated.20 water quality indicators of the factory water were tested and evaluated during the dry season and the wet season.Using Excel to build a database,data analysis using SAS 9.13.Qualitative data and grade data using the frequency and composition ratio for statistical description,two groups and multiple groups between the pass rate using Chi square test,the test level α = 0.05.2.In 2015,22 districts and counties in Chongqing were selected to carry out the rural water monitoring in wet season.A total of 489 samples were collected and analyzed.The health risk assessment was carried out on 17 chemical pollution indexes.Health risk assessment using cancer risk assessment model,non-carcinogenic risk assessment model and the total risk assessment model.Results1.846 rural water plants monitored in 2015 covered the total population of 566.47 million people,mainly to surface water,accounting for 83.92% of the total number of water plants,covering 92.88% of the total population.Most water supply capacity was 200-1000m3/day,accounting for 43.97%.78.72% of water plants treatment process were the completely processed,there were 21 water plants did not do any treatment of water.The use of chlorine dioxide disinfection of rural water plants accounted for 56.62%,17.85% of a total of 151 water plants did not take any disinfection measures.2.A total of 1691 water samples were monitored in 2015,of which the qualified rate was 28.72% in the wet season and 38.11% in the dry season.The qualified rates of microbiological indicators,disinfectant margin indicators and turbidity were less than 70%,and the remaining indicators were higher than 90%.In the same water period,the qualified rate of river water was higher than other sources,and the qualified rate of complete treatment was higher than that of other treatments.The qualified rate of chlorine dioxide disinfection was higher than other methods,and the difference was statistically significant(P <0.05).In 2015,the qualified rate of water quality of factory water in rural water plant in Chongqing was very low.The different water period,water source,water supply capacity,treatment process and disinfection method are the influencing factors of water quality.3.The total risk of rural finished water in the wet season in Chongqing in 2015 was 1.59×10-6(a-1),which does not exceed the maximum acceptable risk level of 5×10-5(a-1)recommended by IARC,slightly greater than the maximum acceptable risk level of 1×10-6(a-1)recommended by the Swedish Environmental Protection Agency.4.Among the 489 water plants participating in the health risk assessment,the water of 237 water plants had a total risk ranging from 1 ×10-6 to 1×10-5(a-1),accounting for 48.47%,the water of 252 water plants had a total risk ranging from 1×10-6 to 1×10-7(a-1),accounting for 51.53%.The health risks of the factory water in 489 water plants were less than the maximum acceptable risk level of 5×10-5(a-1)recommended by IARC,but only 252 were in the maximum acceptable risk level of 1×10-6(a-1)recommended by the Swedish Environmental Protection Agency.5.The total risk of drinking water in Chongqing was ranked as chromium> arsenic> trichloromethane,the proportion was 48.5%,45.4%,5.2%.Conclusion1.Strengthen the water plant monitoring and management of the water supply capacity <1000m3/d of rural areas in Chongqing,in the wet season should increase the amount of disinfectant,add the water plant disinfection facilities and strictly in accordance with the requirements,regulate the water treatment process and procedures,while paying attention to the management and protection of water sources,to avoid the epidemic or outbreaks of waterborne infectious diseases.2.In accordance with the standards recommended by IARC,the total risk of drinking water in rural areas of Chongqing is within the acceptable range and will not have an impact on human health.However,with reference to the Swedish Environmental Protection Agency recommended standards,the total risk of drinking water in Chongqing rural water plant slightly higher than the maximum acceptable risk level,need to pay attention.3.According to the health risk assessment,the chemical pollutants which should be given priority control in Chongqing rural waterworks are: chromium,arsenic,trichloromethane and other pollution indicators. |
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