Present Situation And Evaluation Of Heavy Metal Pollution Of Vegetable Garden Soils And Vegetables In Nanning City Suburbs

In this thesis, the present situation of heavy metal (CiK Zn> Cd> PbN Ci\ Ni) pollution of vegetable garden soils and vegetables in Nanning city suburbs was investigated and evaluated. The results were showed as follows:1 .The vegetables in Nanning city suburbs were polluted by Pb and Cd. Pb pollution was the most serious, following by Cd, but the vegetables were not polluted by Cu> Zn^ Cr. Pb contents of vegetables except garlic ^ yard-long beam balsampear and vegetablesponge were beyond the restricted standard. The rate of exceeding standard of Pb in field sowthisle reached to 76.92%, which was highest among those vegetables. Cd contents of vegetables except red vinespinach> onionN garlicx yard-long beanN eggplanU balsampear and vegetablesponge were beyond the restricted standard in a different degrees. The rate of exceeding standard of Cd in swamp cabbage reached to 57.14%, which was highest among those vegetables. According to the average rate of exceeding standard and the synthetic pollution index of vegetables, the pollution order of heavy metals among investigated vegetables was as follows:leaf vegetable root and tuber vegetable>melon and fruit vegetable .2. The average contents of QK Zn Cd Pb Ni except Cr in Nanning city suburbs' vegetable garden soils were higher than the background values of Nanning city soils. The vegetable garden soils have been polluted by Zn and Cd. Cd pollution was critical, and rate of exceeding standard of Cd and Zn was 38.6% and 10.5%, respectively. The pollution tendency was in the following orders:near suburbs>distant suburbs.3.Correlation analysis indicated that there were significant or highly significant positive correlations between total heavy metals in soils except that of Ni and Pb or Pb and Cr. There were highly significant positive correlations between available and total contents of heavy metals except Cr.