Analysis on monitoring results of toxicological indicators of rural drinking water in Shaanxi Province from 2016 to 2018

OBJECTIVE To understand the toxicological indexes of rural drinking water quality in 2016-2018 in Shaanxi Province. METHODS From 2016 to2018, rural drinking water monitoring points were set up in all( 102) agriculture-related counties( districts) in Shaanxi Province. Each township selected 1-2 rural water supply systems for terminal water supply and terminal water and waste water for distributed water supply as monitoring points. A total of 18 284 monitoring points were set. Water samples were collected during the dry season from April to June and from July to September, according to the Standard Test Method for Drinking Water( GB/T 5750. 5-2006, GB/T5750. 6-2006, GB/T 5750. 8-2006). Carried out experimental analysis and collected water quality monitoring information through the "National Drinking Water Quality Monitoring Information System ". Experimental analysis according to the Standard Test Method for Drinking Water( GB/T 5750. 5-2006, GB/T 5750. 6-2006, GB/T5750. 8-2006); 11 toxicological indicators of the routine indicators were analyzed and evaluated according to the Standard of Drinking Water Hygiene( GB 5749-2006). RESULTS From 2016 to 2018, the overall compliance rate of drinking water toxicology indicators in rural areas of Shaanxi Province was 81. 02%. The top four indicators exceeding the standard were fluoride( 9. 74%), nitrate nitrogen( 6. 09%) and hexavalent chromium. ( 4. 50%) and arsenic( 1. 44%), the other indicators exceeding the standard exceeds the range of 0. 01%-0. 32%. The difference of water quality compliance rates of cadmium, selenium, cyanide, fluoride and nitrate nitrogen in different years was statistically significant( P<0. 05), and the compliance rate of selenium, cyanide, fluoride and nitrate nitrogen increased with the year. Increasing trend( P<0. 05). The compliance rate of cadmium and selenium in the wet season was higher than that in the dry season, and the compliance rate of nitrate nitrogen in the dry season was higher than that in the wet season, the difference was statistically significant( P<0. 05). The compliance rate of arsenic, cadmium, hexavalent chromium, lead, selenium, fluoride and nitrate nitrogen in surface water were higher than that of groundwater( P < 0. 05). There was a statistically significant difference in the overall compliance rate of water toxicology between different water supply method in centralized water supply projects( P < 0. 001). The highest standard rate of water quality was observed in conventional water treatment, followed by sedimentation and filtration. There were 10, 10 and 4 types of over-standard indicators in Guanzhong, northern Shaanxi and southern Shaanxi, and the regional differences of 7 indicators including arsenic, cadmium, hexavalent chromium, lead, selenium, fluoride and nitrate nitrogen had statistics significance( P<0. 05). CONCLUSION The overall compliance rate of toxicological indicators of drinking water in rural areas of Shaanxi Province is low, fluoride, nitrate nitrogen, hexavalent chromium and arsenic are serious and have obvious regional characteristics. In the future, we should focus on the excessive toxicological indicators, and ensure the safety and hygiene of drinking water from the aspects of water supply and treatment technology.