Geochemical Characteristics Of Iodine And Arsenic And Controlling Factors Of Endemic Diseases In Hetao Plain

In view of the Inner Mongolia hetao plain arsenic endemic in the area and the high and low iodine endemic goiter coexisting situation,based on the data of surface soil and shallow groundwater obtained from multi-objective regional geochemical survey in Hetao area,this paper expounds the geochemical characteristics of iodine and arsenic elements in surface soil and shallow groundwater,finds out the causes and correlation of high iodine and high arsenic groundwater at the same time.On this basis,the relationship between the incidence of endemic diseases and surface soil and shallow groundwater was compared,and the control factors of endemic diseases of iodine and arsenic were explored.The results show that:Iodine in surface soil is mainly combined with organic matter or adsorbed by organic matter.Clay content has a great influence on iodine content,while the more acidic environment in surface soil is,the more favorable iodine element exists in soil.The spatial distribution of iodine content in shallow groundwater in Hetao Plain is extremely uneven,material accumulation in palaeogeographic environment and tectonic closed reduction conditions,combined with local arid-semiarid climatic conditions,lead to the enrichment of iodine in shallow groundwater.Based on the analysis results of surface soil and shallow groundwater,11 counties(banner areas)with relatively complete data are divided into four categories: high iodine area,safety area,high and low iodine coexistence area,iodine deficiency area.Endemic iodine diseases are affected by iodine in shallow groundwater and surface soil.Only when two iodine levels are considered comprehensively can the incidence of endemic iodine diseases in the study area be accurately judged.In view of the coexistence of excessive iodine and iodine deficiency in Hetao Plain area,considering the economic and practical effects,iodized salt and drinking water may be a suitable method for supplementing iodine.At the same time,the edible iodized salt should be prohibited in high iodine area,and the source of drinking water should be adjusted to reduce the impact of high iodine water on residents in this area.The arsenic content in surface soil is closely related to the distribution of the river course: the fine grain size and high clay content of the soil on both sides of the river course,and the low content of organic matter leads to a significant higher arsenic content in surface soil.The arsenic in shallow groundwater is related to ferromanganese(hydrogen)oxides,but mainly to iron(hydrogen)oxides.The shallow groundwater environment in the whole Hetao Plain is weak alkaline.The formation of high arsenic groundwater in Hetao Plain of Inner Mongolia is mainly controlled by three aspects: the source of arsenic,the geological conditions conducive to the formation of high arsenic groundwater and the characteristics of local groundwater environment.In Hetao Plain,the arsenic content of shallow groundwater can be used to determine whether there are endemic arsenic diseases in an area,and the arsenic content in surface soil can be used as an indicator of the incidence of endemic arsenic diseases in this area.Groundwater with high iodine and high arsenic was formed in the same palaeogeographic environment,the same material source and the closed reduction condition in structure,and was formed under the influence of the later semi-arid environment,so it has very similar spatial distribution characteristics.In terms of material sources,arsenic mainly comes from the northern mountains and palaeogeographic environment conditions,while iodine mainly depends on the accumulation of the palaeogeographic environment.