| Arsenic(As)is the most toxic and carcinogenic metal in the environment,and selenium(Se)is a essential trace element in humans and animals.These two elements are currently hot research elements in pedology,hydrogeochemistry,and environmentology.As and Se will eventually enter the human body through the environmental medium,which will have a certain impact on the human body.Many scholars have done a lot of researches on these two elements,such as the remediation of arsenic polluted environment and the development of selenium-rich land.The oasis area on the southeastern edge of the Tarim Basin in Xinjiang is an important red jujube and nut production base in southern Xinjiang.The prevention of As polluted land and the development of characteristic selenium-rich agricultural products have important guiding significance for local economic development.Based on this,this paper selects As and Se elements as target elements,and takes the oasis area of Ruoqiang County-Qiemo County-Minfeng County-Yutian County in the southeast margin of Tarim Basin in Xinj iang as the study area.Combined with the test data of As,Se and other related indexes in groundwater,soil and crops,this paper deeply discusses the migration and enrichment of As and Se elements in groundwater-soil-crop system.This study aims to provide scientific basis for the prevention and control of soil arsenic pollution and develop the green agricultural products;at the same time,it also provides technical support for the development of selenium-enriched land,the improvement of agricultural products' quality and efficiency,and the precise poverty alleviation.The majoy contents and conclusions of study were as follows:(1)The soil environment is generally a weakly alkaline environment,the soil organic matter content is low,and soil weathering degree is gradually increased from east to west in study area.The contents of soil As and Se are generally low.There are significant differences in soil As and Se contents under five comparison conditions,such as surface and deep layers,agricultural and non-agricultural land,different soil formation,soil types,and land use types.(2)According to the Delimitation and the logo for natural selenium-enriched land(Trial)(DD 201910),the number of sampling points in the study area where the Se content of the surface soil reached the selenium-enriched standard was 77,accounting for 2.2%of the total surface soil sampling points,and the area of selenium-enriched land is 152 km2.It is distributed within the range of agricultural land.(3)The content of As and Se in the irrigated groundwater in the study area is relatively low,and it has little effect on the enrichment of As and Se in soil and agricultural products.The background values of soil As and Se content were 8.36 and 0.13 mg/kg,respectively.The total area of soil As and Se content anomaly area was 570.12 km2,which were mainly distributed in cultivated land or garden land.(4)The Moran's indexes of spatial autocorrelation were>0,and the spatial autocorrelation of the two elements is spatially positive correlation,and the main aggregation types of spatial autocorrelation were highhigh and low-low types,which is caused by the superposition of structural factors and random factors.The semi-variogram theoretical models are mainly Gaussian and exponential models.(5)Kriging interpolation has a good effect.From the results of interpolation,the As and Se content in the agricultural land in the study area is higher than that in the non-agricultural land,which is consistent with the statistical results of the content.This result was consistent with autocorrelation analysis results too.In the horizontal direction of As and Se elements,the contents of As and Se in agricultural land are higher than those in non-agricultural land,and the areas with high values of As and Se content are concentrated in patches or scattered in islands.At the same time,the levels of As and Se were unevenly distributed.In the vertical direction,the content of As and Se in each layer of agricultural land is low.The As and Se content of the vertical profiles of the agricultural land in Ruoqiang County and 36 Regiment fluctuated from the surface to depth,whereas those of other counties were relatively stable.(6)From the calculation results of soil As and Se element migration coefficients and leaching ratios,it can be seen that the As and Se elements are not migrate along the soil profile.The calculation results of soil environmental enrichment coefficients show that As and Se elements are at a weakly enriched-natural state level.(7)Correlation analysis method was used to determine the influencing factors of As and Se content in topsoil,including natural factors(parent material,soil type)and human factors(land use).The As contents of surface soil had a significant positive correlation with pH,a significant positive correlation with P,Mn,TC,TN,and Corg and other macronutrients,and a significant positive correlation with Al2O3,Fe2O3,CaO,and MgO.Se content in surface soil is significantly negatively correlated with pH,Al2O3,and SiO2,and significantly positively correlated with oxides such as Fe2O3,Na2O,K2O,CaO,and MgO.At the same time,there was a significant positive correlation between Se content,Corg,TC,TN,P,and other elements.(8)The results of the bioconcentration coefficient calculation showed that the As enrichment ability of crops was ranked as:root vegetables>walnuts>wheat>red dates>corn;the Se enrichment ability of crops was ranked as:walnut>root vegetables>red dates>corn>wheat.The results of correlation analysis and multiple regression analysis showed that the As content of maize root soil was only significantly correlated with soil clay content;the As content of red jujube soil root soil showed significant positive correlation with K,Corg,CEC,B,and clay content;There was no significant correlation between Se content in the root soil of five crops and Se content in agricultural products. |
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