The Chemical Characteristics Of Groundwater And Risk Assessment Of Fluorine Polluion In The Jilantai Basin

Jilantai Basin is located in the Alxa which has dry climate,scarce precipitation, dunesdiffuse cloth, poor ecological environment. With the rapid development of Industrial andoases agriculture, groundwater resources was exploited deucedly,and then the groundwaterlevel decline everyear, soil salinization, desertification and ecological and environmentalproblems begin to appear, the diving water quality deteriorate. This is a serious threat to thedevelopment of local economy and people’s health, so carrying out the study of groundwaterpollution has become imperative.. The Jilantai basin is divided to Ulan Buh Desert pastoraland Chahal beach oasis agricultural areas, water samples were analyzed at the laboratoryexperiments. In this paper we analysic chemical characteristics and fluorine content of thegroundwater and the distribution and causes of F-in the groundwater,the risk evaluation ofgroundwater fluorine pollution, the main research of this paper are as follows:（1） In the study area, hydrochemical type has obvious zonality along the direction ofgroundwater flow. From the piedmont to the basin, the chemical characteristics ofgroundwater changed from the bicarbonate water to sulfate water to chloride water；Besides,the water quality becomes worse gradually from the Piedmont to the edge of lakebasin to the middle of basin； The eastern part of the study area, diving basic salinity less than1g/l, a depression in the center of the lake basin and mountains salinity in1-3g/l, in someplaces up to3-5g/l even greater than5g/l;（2） It is showed that fluoride distribution has a level and vertical rule. fluoride ioncontent tended to increase from the recharge area to the center of the basin discharge zone, F-in confined water was significantly higher than diving; Fluoride ion content in Chahal Beacharea is less than water standard of0.5mg/l required by the drinking water, that is because ofhigh Ca²⁺and Mg²⁺in the groundwater; The ratio of （K⁺+Na⁺）/(Ca²⁺+Mg²⁺) is proportional tothe fluorine ion content. The causes of high-fluorine water has some connection with the dryclimate, the terrain that is high on all sides and low in the middle and the groundwater runoffconditions.（3）In this paper, the study area was divided into high-risk areas, risk areas and low-riskareas of fluoride pollution in groundwater. High-risk areas concentrated in the center of thebasin and north of Bayan Ul mountain, its area is about3203.51km²and belong to JilantaiTown，In this region, population is concentrated, fluoride ion content is over2mg/l,groundwater flow pathway is long, aquifer lithology is clay-based, groundwater level is shallow, fluoride ions enrichment easily under the action of evaporation and concentration;Fluoride pollution in risk areas is located in the zone around the center of the basin, its area is5842.64km², that is the Bayan Ul mountain piedmont and Bayan Muren hematoxylin andAolunbulage town and the eastern of Wusitai town, In these areas aquifer lithology is mainlysandy clay and clayey sand, fluoride ion content is less2mg/l, evaporation and precipitation isin the middle relative to other regions; low-risk areas is located in Zongbieli town, thesouthern part of Wusitai Town, Bayan Muren hematoxylin, its area is2616.65km², Theseareas are located in the edge of the lake basin, belong to groundwater runoff zone, fluoride ioncontent is less1mg/l,the aquifer containing gravel sand or sand, both fluorine pollution riskand vulnerability are lower.（4） In the center of the basin and north of Bayan Ul mountain,, the source of drinkingwater should be changed, because the fluoride ion content is over2mg/l and the it is fluoridepollution high-risk region, the reverse osmosis unit or electrodialysis fluoride removal unitshould be installed in the centralized drinking water supply area. Low-temperature freezingmethod which is easy and low-cost can be used in sparsely populated areas.