Selection Of Vegetables Of Low Heavy Metal Accumulation In Mining Areas In Hunan Province

In order to assess the human health risk caused by elevated concentrations of heavy metals and to evaluate heavy metal pollution of vegetables and vegetable planting soils round the two typical mining areas Chenzhou and Hengyang in Hunan Province, common local vegetables were planted in these two areas. Edible parts of the vegetables and their planting soils were tested in the laboratory in mature period. The results could be used to identify vegetable varieties of low heavy metal accumulation and optimize vegetable planting patterns, so as to attain the goal reducing human health risk from heavy metals of vegetables and soils. The primary results of the experiments were as follows:(1) Both mining areas were complexly polluted seriously by Pb, Cd, Cu and Zn. Significant or highly significant positive linear relations were found between exchangeable Pb, Cu and Zn contents and total contents of these metals in the planting soils in Chenzhou. The same results were found for Cd, Cu and Zn in Hengyang planting soils; however, a significant negtive linear relation was obtained for exchangeable Pb contents and total Pb contents in this area.(2) The order for heavy metal contents in edible parts of vegetables was as follows:leaf-vegetables> rootstalk-like vegetables> fruit-vegetables. No serious Cu pollution was found in these vegetables. Five kinds of vegetables were polluted with single Pb (raddish and cabbage in Chenzhou, and pakchoi in Hengyang) or Cd (eggplant and capsicum in both areas), the others were found polluted complexly with Pb/Cd/Zn or Pb/Cd or Pb/Zn.(3) Highly significant positive linear relations were found between Pb and Cd, Pb and Zn, Cd and Zn in edible parts of vegetables in Chenzhou, while there were no significant positive linear relations between Cu and Pb, Cd or Zn. In Hengyang, highly significant positive linear relations were found among all these four elements in edible parts of vegetables.(4) According to the WHO standards for humans with an average body weight of60kg, the value of Pb ADI (average daily intake) is lower than3.570μg·kg-1body wt, and that for Cd ADI is lower than1.000μg·kg-1body wt. For the residents both in Chenzhou and Hengyang, the average ingestion rates of Pb and Cd from vegetables both exceeded the WHO standards. As a result, consuming vegetables, especially leaf-vegetables, appeared to be an important path for the intake of Pb and Cd and might pose a health risk to local residents.(5) In mining aresas with heavy metal pollution, it should be advocated to plant more fruit-vegetables and rootstalk-like vegetables, and less leaf-vegetables. It would be appropriated to plant balsam pear, towel gourd, cucumber, pumpkin, tomato, carob, kidney bean in these mining areas in springs and summers. Although eggplant belongs one of fruit-vegetables, it could easily accumulate Cd from soils, and it should be better not to plant. In autumns and winters, the vegetables are mainly leaf-vegetables which could easily accumulate heavy metals, it should be advocated to plant the vegetables which accumulate less heavy metals, such as radish, brassica campestris var purpurea, and pakchoi.