Study On The Source And Enrichment Of Arsenic In Arsenic Poisoning Areas In Tuzuoqi, Inner Mongolia

The study area in Tuzuoqi, Inner Mongolia is an old endemic arsenic poisoning area for centuries, villagers suffered from arsenic poisoning disease from generation to generation. We start a 1:50000 ecological geochemistry detailed investigation based on the study area. To find out the sources, enrichment mechanism and influencing factors of the high arsenic groundwater and offer some reasonable comments and suggestions for preventing arsenic poisoning in the arsenic poisoning areas, we visit the villagers and hospitals and collect water, rocks, soil, plants, coal dust, human hair and other samples for comprehensive analysis.The research shows that the amount of arsenic in soil and groundwater have little consistency in space in this area, indicating that the arsenic in the study area has no significant vertical migration from the soil into the groundwater. The arsenic in the coal(ash) isn’t the main source of the arsenic in the groundwater because the arsenic content of the coal(ash) is not high in the study area. The arsenic content of the rocks including sallow adamellite of Archean, gray-green marble and black basalt of the Daqing mountain in the north which is the source of the groundwater recharge in this area is higher than the crustal abundance. The arsenic content of the gray-green marble of Archean which belongs to the arsenic-rich rock series is four times higher than the crustal abundance. These arsenic-rich rock series are the original sources of the arsenic in the groundwater of the study area. Hubao basin is a meso-cenozoic rift basin, which deposited thick Quaternary sediments Q4 fl main consisted of silt and mucky. These sediments rich in organic matters which has a strong arsenic enrichment capability and then developed into high-arsenic groundwater aquifers. They provide a lot of material source for the enrichment of the arsenic.Due to faults, the underground run-off alternate slow and water flow is poor, a closed-semi-enclosed underground environment is formed. The arsenic-rich sediments rich in organic matters are buried in the shallow of the fault zone and in a reducing environment. And also the p H is alkaline, therefore the Fe oxide minerals in the aquifers have been reacted with the dissimilation reduction reaction under the organic matters and the microbe synergy. The dissolved Fe2+ was formed by the reduction of Fe oxide minerals, at the same time the As which adsorbed on the mineral surfaces was immediately released out into the surrounding water and the As was concentrated in the groundwater. The organic matters can reduce As(V) to As(III), increasing the toxicity of arsenic from 60 to 100 times. The study area is classified as an arid evaporation basin. The groundwater recharge mainly through atmospheric precipitation and water streams from the northern mountains. The water leached the As from the surrounding rocks and sediments while it added to the underground. The As in the water was concentrated again because of the evaporation loss. Then the high-arsenic groundwater which can lead to disease are formed.