Fluorine Form In Soils Of Sierozem Area And Fluorine Absorption By Wheat Plants Of Cadmium,Fluorine Combined Pollution

The content and chemical speciation distribution characteristics of fluorine?F?in surface and profile cropland of Baiyin suburb,and the migration and distribution characteristics of F in soil were studied through filed investigation and laboratory analysis.The effects of Cd-F combined pollution on the growth of wheat plant,the transformation and tendency of chemical forms of F in soils,and bioavailability to the wheat plant were studied in this work using pot experiments.In particular,the soil environmental quality index of fluorine in oasis soils from the Northwest arid areas were discussed,the results as below:?1?The soils from Dongdagou stream had higher concentrations for fluorine than the content of typical fluorosis areas of China.It is indicated that the soils in Dongdagou could be considered contaminated and believed to be a source of cause fluorosis in humans;Total F contents of soils from Xidagou stream were within the normal range of soils.when there is a seriously fluoride polluted in sierozem of arid areas,the contents of different fluoride forms were decreased in the order:Res-F?Ws-F>Or-F>Fe/Mn-F>Ex-F.On the contrary,when the total F contents of soils from sierozem were within the normal range of soils,the form of F were influenced by different pollution sources,and changed with the length of the soil balance time.?2?In profile soils,the content of fluorine were mainly enriched in the topsoil and the fifth layer?80-100cm?.Ws-F and Ex-F had the relatively similar distribution with the T-F;Fe/Mn-F had no obvious change rule;As soil depth increasing,the Or-F first decreased,then increased and decreased again.?3?The order of accumulation F in wheat plants of field study and the pot experiment,are found to be roots>leaves>shells>stocks>grains and roots>shells>leaves>grains>stocks,respectively.The contents of F in the grains of wheat plants were higher than the national edible health standard,which suggest that the wheat plant samples studied were contaminated.Soils studied are not fit to plant the wheat crops for human consumption,and pose high potential health risk for human health through food chain.?4?This field study provided F-Cd interactions that occur in soils from the oasis at environmentally relevant concentrations that the interaction effects were more pronounced at high concentrations range and less pronounced at low concentrations.In the pot experiment,when the concentration of F is low,the Cd 40 mg·kg^-1 in soil can increase the content of F in roots;and when the concentration of F is high,the presence of Cd in soil can increase the content of F in roots.It's revealed for the first time that naturally occurring Cd in areas with endemic fluorosis is acting as a critical but hidden health hazard that may underlie the risk of F,possibly even at epidemiological proportions,but further research is required.?5?The environmental quality of soil fluorine of sierozem in arid areas can be evaluated by the total fluorine?the water soluble fluorine and fluorine in water environment.The evaluation criteria for T-F?Ws-F?and fluorine in water environment are 653 mg·kg^-1,8.7mg·kg-l and 1.75mg·L^-1 respectively.If the level of fluorine in the soils or water environments over the limit,it will cause the occurrence of endemic fluorosis in the region.