Research On Evaluation And Spatial Distribution Of Heavy Metals In Farmland Soil Of Shihezi Reclamationarea

[Objective] Effects of heavy metal pollution on soil environmental quality has become animportant problem for agricultural product safety and sustainable development of agriculturein China. Soil heavy metal contents of Zn, Cu, Cr, Pb, Cd, Ni, As, and Hg were investigated infarmland of Shihezi reclamation area. Spatial distribution characteristics of heavy metal insoil were analyzed. Soil environmental quality and potential ecological risk of heavy metalwere also evaluated in this study. The objective is to provide basic data and scientific basis forsoil quality construction and agricultural sustainable development of the study area.[Method]200soil samples were collected by using the grid method in farmland of Shihezireclamation area. The heavy metal contents of Zn, Cu, Cr, Pb, Cd, Ni, As, and Hg in soil weremeasured by inductively coupled plasma (ICP), atomic fluorescence spectrometry (AFS)and cold-vapor atomic absorption methods. The spatial distribution characteristic of soilheavy metals were analyzed with geostatistics method. Single factor pollution index andNemerow pollution index were applied to evaluate the environmental quality of heavy metalsin soil. The potential ecological risk of soil heavy metals were also assessed using thepotential ecological risk index method.[Result](1) The average contents of Zn, Cu, Cr, Pb, Cd, Ni, As, and Hg were82.84,28.94,43.77,14.45,0.51,33.89,13.48, and0.08mg kg-1, respectively. The average concentrations of eightheavy metals were below the national standards GradeⅡ, but higher than Xinjiang Regionalsoil background values (except for Cr and Pb). Variation coefficients of eight heavy metalsranged from19%to74%, and belonged to the medium variation.(2) There was a significant correlation among the elements of Zn, Cu, Cr, Pb, Ni, and Cd;while the correlation between Hg and As showed the heterologous characteristic. The spatialdistribution of eight heavy metals belonged to spatial autocorrelation. The element of Ni hadthe biggest variation range, which was mainly caused by the structural variations such astopography and soil parent material; while the remaining7elements showed a relativelysmaller scale in the spatial autocorrelation, which mainly caused by the random factors suchas human activities.(3) The high-value of eight heavy metals were mainly distributed in the northwest,southwest and southeast of the study area. The highest contents of soil Zn, Cu, and Ni in16farms of Shihezi reclamation area were all found in the141thfarm, and Cd was mainlydistributed in the farms133th,134th,135th, and141th. the highest content of As was determinedin the136thfarm, and Hg element was mainly distributed in132th,133th, and142thfarms.(4) In general, the single-factor pollution indexes of8heavy metals followed the order:Cd>Ni> As>Cu>Zn>Hg>Cr>Pb, which belonged to the clean or relative-clean in the studyarea. The single-factor pollution indexes of Cd element ranged from1.0to2.0and belongedto mild pollution in the farms of133th,134th,135th, and141th. The average integrated pollutionindexe of8heavy metals in soil was0.68and belonged to clean level. Among200samplingsites, the soil environment quality of55.5%samples belonged to clean,39%was relative-clean, and5.5%for mild pollution.(5) The order of single-factor potential ecological risk indexes were followed by Hg>Cd>Ni>As>Cu>Pb>Cr>Zn. The element of Hg had the highest potential ecological risk index,40.5%and13%of soil samples reached the extremely-high and high potential ecological risk,respectively. The element of Cd also had high potential ecological risk index, whichrepresented66%and24.5%of soil samples in high and relative-high potential ecological risk.In general, the integrated potential ecological risk of8heavy metals was belonged to therelative high level in farmland soil study aea. The farms of122th,132th,133th,134th,135th,141th,142th,143thand144thwere the relative-high level, and the remainder in medium level.[Conclusion] The average content of eight heavy metals were below the national standardsGradeⅡin farmland soil of Shihezi reclamation area. The high-value of heavy metal contentswere mainly distributed in the northwest, southwest and southeast of the study area. Theenvironmental quality of heavy metals in soil belonged to the clean or relative-clean. Whilethe integrated potential ecological risk of heavy metals in soil reached to the relative highlevel, especially for Hg and Cd had the higher potential ecological risk indexes than otherheavy metals.