Distribution Inhomogeneity of Cd Pollution of Farmland Soil on A Plot-scale
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Natural Science Foundation of Jiangsu Province (No.BK20171496), the Key Technology Support Program of Jiangsu Province (No. BE2015708) and the Special Fund No.2015-447 from Land Development and Consolidation of Jiangsu Province

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    Abstract:

    【Objective】In plain areas like the Yangtze River Delta in China, where farmlands are highly fragmented and the contradiction between limited farmland resources and a big population is outstanding, the problem of how to control heavy metal pollutions, especially Cd pollution, of farmland soil has long been an issue attracting extensive attention. The new finding of distribution inhomogeneity of Cd pollution of farmland soil on a plot-scale in the regions is of great reference value to control of the pollution and remediation of the polluted farmlands therein. Though in the literature quite a number of papers can be found systematacially exploring and discussing distribution of heavy metals and trace elements in farmland soil and inhomogeneity of the soil as well, on a plot-scale, few dealt with distribution inhomogeneity of Cd pollution. Hence, this paper is devoted to analysis of the distribution inhomogeneity of Cd pollution in farmland soil on a plot scale.【Method】In this study, a total of 42 soil samples were collected from the topsoil layers (0~20cm) and sedimentary soil profiles (0~220cm) of 5 typical tracts of farmland in the studied areas with the aid of special soil sampling tools for analysis of content distributions and geochemical indices of As Cd, Cu, Pb, Zn, Cr, Ni, Hg, As, Sb,Se, pH and TOC, with the aid of ICP-MS,XRF and some others.【Result】Analysis of the environmental geochemical survey data obtained from the typical farmland soils in the Yangtze River Delta shows that when soil Cd were higher than 1.0 mg.kg-1 in concentration in a farmland plot, significant spatial inhomogeneity of Cd pollution could be observed. In a field less than 0.13 hm2, soil Cd varied sharply in concentration from plot to plot, and differed by dozens of times to the most possible, and that soils mild, moderate and severe in Cd pollution coexisted in a farmland plot. In a long strip of farmland plot, Cd pollution distributed somewhat in an exponentially declining trend. The more serious the closer to the pollutant source, and the more inhomogeneous in upland plots than in paddy plots. Distribution heterogeneity of Cd pollution mainly appeared horizontally, and vertically Cd pollution concentrated mainly in the surface toplayer (0~ 20 cm). Contrast to soil Cd, other heavy metal elements, like Cu, Pb, Zn, As, Cr, and so on, were distributed normally in the farmland plot in a relatively even manner. [Conclusion] The uneven distribution of Cd pollution is universal in farmland soil on a plot-scale in the Yangtze River Delta and similar plain areas, and attributed mainly to differences in micro-topography and farming practices. The knowledge about the characteristics of Cd distribution in the soil on a plot scale is quite practical and helpful to remediation of Cd contaminated farmlands in the Yangtze River Delta and similar areas.

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LIAO Qilin, REN Jinhua, XU Weiwei, LI Wenbo, FAN Jian, JINYang, CUI xiaodan, WANG Yuanyuan. Distribution Inhomogeneity of Cd Pollution of Farmland Soil on A Plot-scale[J]. Acta Pedologica Sinica,2019,56(6):1390-1400.

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History
  • Received:January 23,2019
  • Revised:August 13,2019
  • Adopted:August 14,2019
  • Online: August 27,2019
  • Published: