Abstract: Samp leswere taken from differentwaterbodies ( groundwater, surface water and tap water) in the Hetao Plain,Inner Mongolia, for analysis of the content and species of As to study distribution ofAs in the waterbodies in that typical area of endemic As disease. Samp les of groundwater atDayingVillage, Shanyin County of Shanxi and of surface water and groundwater at Zhaoyuan District of Shandong were also collected for comparison of pollution features and analysis of sources. Total As was determined with inductively coup led p lasma mass spectrometry ( ICP-MS) and inductively coupled plasma atomic emission spectrometry( ICP-AES). High performance liquid chromatography2inductively coupled plasma mass spectrometry (HPLC-ICP-MS)was used for analysis of arsenic speciation in 16 water samples. It was found that the groundwaters, which are used as drinkingwater, in Hetao Plain and DayingVillage were both rich in arsenic, with an average arsenic content being 368.9 and 443.5μg·L-1 ,respectively. Out of all the 175 groundwater samples collected from the Hetao Plain, about 59%, containedmore than 50μg·L-1 arsenic—the threshold criterion for arsenic in water supp ly for rural area and in groundwater (Grade Ⅲ). Besides, out of the 16 samp les for analysis of arsenic speciation, seven were found to contain arsenite or even arsenite predominates. Furthermore, all the surface and tap water samp les, excep t for a few, were determined to be below 50μg·L-1 ,while some tap water samples over the criterion for arsenic in drinking water.

Key words: groundwater, arsenic, distribution, speciation, Hetao Plain