| Heavy metal accumulated in the vegetables, in addition to cause changes in soil quality, influence the growth of vegetables and led to the reduction of production, but also through the food chain enters the human body, accumulate in the body, which Produce amplification hazard. There are many output path of soil heavy metals, after heavy metals accumulated, in addition to enter the food chain, but also by surface runoff to migrate and down seepage to pollute the groundwater, through plants’volatiling into the atmosphere and so on.Therefore, this study through the time changes and space changes of Chongqing City Soil and vegetable determining mainly heavy metal pollution, followed by study on the source apportionment of soil heavy metal in vegetables, analysis each contribution coefficient of the input and the output path, providing a reference for the improvement of the prevention and control of soil heavy metals.This research is divided into three parts. The first part is the study of the spatial variations in heavy metals of Chongqing city soil-vegetable. The second part is the study of the time variations in heavy metals of Chongqing city soil-vegetable.The third part is the main pollution of the source of heavy metals.The main experimental results are as follows:(1)The Chongqing city vegetable sample monitoring shows that the pollution degree of heavy metals in vegetables has reached alarming levels, the pollution degree of heavy metals in tuber vegetables has reached the light pollution level, the comprehensive index of Pb in vegetables has reached the level of light pollution; the content of soil heavy metals Cd, Cu, Hg, Pb and Zn decreased with the deepening of the depth of the soil, especially Pb, Cd, Hg layered showed that Cd has reached The light pollution level, Pb, Ni has reached the warning level; Hg in irrigation water has reached the warning level; The vegetable accumulating heavy metal ability was little difference in different distribution of Chongqing City, The vegetable accumulating heavy metal ability was big difference in different vegetable; overall look, the enrichment ability of heavy metals in vegetables is slightly higher than that of tuber vegetables. Considering the pollution situation of vegetable, soil and irrigation water in vegetable base, determine the main pollution of heavy metal was Pb, Cd.(2) Through single season heavy metal input and output path of point vegetable the results show that, vegetable heavy metal Cd single season input was 0.556mg/m2, single season output was 0.479mg/m2. Soil Cd Single Season cumulanting amount was 73.46ug/m2 and effective Cd single season cumulanting amount was 39.75ug/m2. Main input path of vegetable heavy metal Cd were atmospheric wet deposition,which was 85.99% of the total input; for the proportion of 5 kinds of input path from big to small order was:atmospheric wet deposition> chemical fertilizer> atmospheric dry deposition of irrigation water> seed>; main output path was plant residues, vegetables, and so can food absorbing and seepage, three output paths accounted for 89.27% of total output. Vegetable Pb single season input was 17.28mg/m2, single season output was 5.69mg/m2, Pb single season cumulants amount was 11.04mg/m2. Soil single season cumulative amount of effective Pb was 1.94mg/m2. The main vegetable Pb input path were atmospheric wet deposition, which for the total input accounted for 68.76% of the total input; for the proportion of 5 kinds of input path from big to small order: atmospheric wet deposition> chemical fertilizer> atmospheric dry deposition of irrigation water> seed>; vegetable Pb main output path were subsurface flow and surface runoff, two output paths accounted for 90.31% of total output. |
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