目的:掌握内蒙古自治区居民饮用水砷含量分布情况，为制定饮水型地方性砷中毒精细化防治措施提供科学依据。方法:2017 - 2019年，在内蒙古自治区12个盟市103个旗（县、区）的全部自然村开展水砷调查工作，按不同供水方式（工程供水、理化改水、分散供水）对居民饮用水进行采样。其中，工程供水：每个改水工程在枯水期、丰水期各采集1份出厂水；在工程覆盖的历史砷中毒病区/高砷暴露村采集1份末梢水。理化改水：每户理化改水的居民家庭采集1份水样。分散供水：在历史砷中毒病区/高砷暴露村，每户家庭采集1份水样；在历史水砷合格村，按照东、南、西、北、中5个方位各选择1户居民家庭，每户家庭采集1份水样。采用原子荧光法检测水砷含量，ArcGIS 10.2软件绘制水砷超标水样分布图。结果:共采集水样90 455份，其中工程供水31 617份、理化改水2 702份、分散供水56 136份。工程供水、理化改水、分散供水水砷中位数分别为1.00、1.00、0.50 μg/L，不同供水方式间比较差异有统计学差异（χn 2 = 1 147.831，n P < 0.05）。共检出486份水砷超标水样，检出率为0.54%（486/90 455）。其中，工程供水、分散供水水砷超标检出率分别为1.48%（469/31 617）、0.03%（17/56 136），工程供水水砷超标检出率高于分散供水（χ n 2 = 775.401，n P < 0.05）；理化改水无水砷超标水样检出。全区水砷超标检出率前3位的地区分别为巴彦淖尔市[15.38%（343/2 230）]、呼和浩特市[2.00%（86/4 293）]、鄂尔多斯市[0.85%（50/5 848）]。ArcGIS 10.2软件显示，水砷超标水样主要在西部地区呈灶状、块状分布，东部地区仅零星存在。n 结论:内蒙古自治区工程供水水砷超标检出率较高，水砷超标水样主要在西部地区呈灶状、块状分布，东部地区仅零星存在。要加强对工程供水的管理与监督，对这些地区应采取改换水源、增加净水设备、改进净水工艺等理化改水途径减轻砷危害，确保居民饮用合格水。“,”Objective:To investigate the distribution of arsenic content in drinking water of residents in Inner Mongolia Autonomous Region, and to provide a scientific basis for formulation of detailed prevention and control measures for endemic arsenic poisoning.Methods:From 2017 to 2019, water arsenic survey was carried out in all natural villages in 103 banners (counties, districts) of 12 leagues (cities) in Inner Mongolia Autonomous Region, and drinking water samples were collected according to different water supply modes (engineering water supply, physical and chemical water purification, decentralized water supply). Among them, engineering water supply: one factory water sample was collected from each water modification project in dry season and wet season; and one terminal water sample was collected in historical arsenism area/high arsenic exposed villages covered by the project. Physical and chemical water purification: one water sample was collected from each household. Decentralized water supply: in historical arsenism area/high arsenic exposed villages, one water sample was collected from each household; in the villages with historical qualified water arsenic, one household was selected according to the five directions of east, south, west, north and middle, and one water sample was collected from each household. The content of arsenic in water was detected by atomic fluorescence spectrometry and a distribution map of water samples with excessive arsenic was drawn using ArcGIS 10.2 software.Results:A total of 90 455 water samples were collected, including 31 617 water samples for engineering water supply, 2 702 water samples for physical and chemical water purification, and 56 136 water samples for decentralized water supply. The medians of water arsenic content of engineering water supply, physical and chemical water purification, and decentralized water supply were 1.00, 1.00 and 0.50 μg/L, respectively, and the differences among different water supply modes were statistically significant (χ n 2 = 1 147.831, n P < 0.05). A total of 486 water samples with excessive arsenic were detected, the detection rate was 0.54% (486/90 455). The detection rates of water samples with excessive arsenic in engineering water supply and decentralized water supply were 1.48% (469/31 617) and 0.03% (17/56 136), the detection rate of water samples with excessive arsenic in engineering water supply was higher than that in decentralized water supply (χ n 2 = 775.401, n P < 0.05); there was no water samples with excessive arsenic in physical and chemical water purification. The top three areas with the detection rates of water samples with excessive arsenic were Bayannaoer [15.38% (343/2 230)], Hohhot [2.00% (86/4 293)], and Ordos [0.85% (50/5 848)]. ArcGIS 10.2 software showed that the water samples with excessive arsenic were mainly distributed in the western region in the shape of focal and block, and only existed sporadically in the eastern region.n Conclusions:The detection rate of water samples with excessive arsenic in engineering water supply in Inner Mongolia Autonomous Region is high, the water samples with excessive arsenic are mainly distributed in the western region in the shape of focal and block, and sporadically in the eastern region. The management and supervision of engineering water supply should be strengthened, in areas where the water arsenic exceeds the standard, we should take physical and chemical water purification measures, such as change water sources, increase water purification equipment, and improve water purification technology to reduce arsenic hazards, so as to ensure that residents can drink qualified water.