Elemental Speciation Distribution Characteristics And Influencing Factors In Selenium And Iodine Rich Areas

Selenium and iodine are closely related to human health.At present,there are many studies on selenium and iodine at home and abroad,but there are few reports on the elemental speciation distribution characteristics of selenium and iodine in enrich areas.Therefore,it is of great significance to study the speciation distribution and environmental geochemistry of selenium and iodine in enrich areas.In this paper,the total amount of selenium and iodine and speciation analysis methods are established by using High Performance Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry(HPLC-ICPMS),three dimensional fluorescence spectroscopy(3D-EEM)and microwave digestion instrument.On this basis,the distribution characteristics of elemental speciation and influencing factors are studied in selenium enriched regions-Enshi,Hubei,iodine enriched regions-Xilingol League Inner Mongolia and Tacheng Xinjiang.The main conclusions are as follows:1.Establishing the separation methods of six selenium speciation,the results shows that the Thermo C8 column and 0.025%seven flubutyric acid as the mobile phase,and the separation and peak effect are better.The detection limits of six selenium separations such as SeⅥ,SeⅣ,SeCys2,L-SeMC,SeMet and SeEt can reach 0.38 μg/L,0.38 μg/L,0.59 μg/L,0.88μg/L,0.87μg/L and 0.83 μg/L.The area and concentration of various selenium separation shows a good linear relationship,the correlation coefficient is more than 0.9997,and the linear range reached 4 orders of magnitude,the six selenium speciations recovery rate of the added standard is between 84%and 104%.2.In order to analyze selenium speciation distribution and its influencing factors in selenium enrich areas,the samples of water and sediment in 12 villagess of Enshi were collected,and the total selenium and selenium speciation content were measured.The influence of factors such as ground elevation,pH,and redox potential and natural organic matter structure in water on the distribution of selenium were discussed.The study shows that the total selenium content of mountain spring water and river water in Enshi area are relatively high,which rangs from 5 μg/L to 10 μg/L,and the individual point reachs 30μg/L or 90 μg/L.The selenium speciation in the water is mainly inorganic,followed by organic,and the content is SeⅥ>SeMet>L-SeMC>SeIV>SeCys2.The total selenium content increased with the increase of ground elevation.The pH of the sampling points are between 7.1-7.7,and the total selenium content is not significantly changed with the increase of pH.The REDOX potential in the sampling area is concentrated in 175-250 mV,and the accumulation of selenium can only be carried out under certain oxidative conditions.The dissolved organic matter in the spring water is mainly composed of endogenous and microbial processes,and the dissolved organic matter of the river is soil organic or terrestrial plants.There is a positive correlation between dissolved organic matter and total selenium in water.3.In order to analyze iodine speciation distribution and its influencing factors in iodine enrich areas in water,35 surface water and groundwater samples were collected from Xilingol League Inner Mongolia and Tacheng Xinjiang.The distribution patterns of total iodine and iodine speciation were analyzed,and the effects of ground elevation,dissolved oxygen,redox potential and soluble salt on the distribution characteristics of iodine were discussed.Research shows that I-is dominant in Xilingol League Inner Mongolia groundwater and the total iodine is maintained at 200 μg/L,with individual point reaching 600 μg/L or even 1700 μg/L.The content of iodine in Xilingol League groundwater is distributed in a circular pattern,showing a "low-high-low" distribution pattern from northeast to southwest.IO3-is dominant in Tacheng groundwater,with the total iodine content of less than 100 μg/L and the individual poinits are close to 200 μg/L.Moreover,the total iodine content increases gradually from the east to the west,showing a layered distribution.Oxidation condition that is beneficial to the transformation between different iodine speciations;It is not conducive to the iodine enrichment when dissolved oxygen is too high or too low.Iodine will decrease with soluble salt loss.The upstream total iodine content is lower than the downstream total iodine content along the flow direction.There is no significant difference in the total selenium of the sediment samples which the ICPMS has the collision pool or not.The results of the final test have the differeces with the preprocessing of the sealed acid solution and microwave digestion.The total selenium content in the sediment samples is more than 1.0 μg/g;the selenium content of the humus combined state of selenium is about 4 times than that of soluble combined state of selenium in the sediment samples.This study preliminarily explores the effect of environmental factors on selenium and iodine content in water enriched areas.And it has certain guiding role and practical value for the scientific utilization of surface water,groundwater,and prevention of endemic diseases in selenium and iodine enriched areas.