| Along with the rapid development of social economy, the heavy metal pollution in soil as a world environmental problem was concerned by the scholars both at home and abroad especially the impact of heavy metals in the soil located in mining on surrounding environment and human health. To explore the pollution characteristics and health risks of heavy metals in the cultivated land located in the nickel ore district of Jilin province, the samples of 52 farm land soils, 1 ash and 38 corn plant including root, stem, leaf and grain were obtained in the nickel ore districts of Hongqiling and Piaohechuan belong to Jilin Province in this paper. The pollution characteristics of heavy metals(Cu, Zn, Ni, Cr, Pb, Cd and As) in farm land soils was evaluated using the method of single factor pollution index, comprehensive pollution index and potential ecological risk index, the distribution and activity of the heavy metals were discussed using the method of DTPA extraction and Tessier five steps sequential, the migration and accumulation of heavy metals in corn plant were also studied by determing the contents of heavy metals in the root, stem, leaf and grain. The results were as follows:(1) Soil p H was from 3.82 to 7.40, and organic matter content was from 2.01% to 9.37% with an average of 4.44%. The average content of soil heavy metals Cu, Zn, Ni, Cr, Pb, Cd and As in farmland soils in the nickel mining area was in the order of Zn(96.32 mg / kg) > Ni(93.58 mg / kg) > Cu(50.86 mg / kg) > Pb(25.71 mg / kg) > Cr(15.10 mg / kg) >As(10.69 mg / kg) > Cd(0.13 mg / kg). Compared with the soil background value of Jilin Province, the average content of the heavy metals were 2.97, 1.20, 4.37, 0.32, 0.89, 1.34 and 1.25 times for Cu, Zn, Ni, Cr, Pb, Cd and As, respectively, which indicting that the soil being polluted by Cu, Zn, Ni, Cd and As to different degrees. Besides the content of Cr, Pb and As in all sampling points did not exceed the national secondary standard(GB15618-1995), the other heavy metals were 36.54%, 1.92%, 65.38% and 7.69% of all the sampling points exceeding the secondary standard for Cu, Zn, Ni and Cd, respectively. The result from the single factor pollution index evaluation showed that the soils were all polluted serously by Ni and Cu, and accompanied with Cd and Zn; the results from Nemerow index evaluation showed that there were 46.2% of cultivated land soil sampling points being safety or alert level, and 13.4% of the sampling sites being heavy pollution level; the result from compound ecological risk hazard evaluation index showed that the farm land soils were in mild ecological harm degree.(2) Copper, Zn and Ni in the soils were mainly in the forms of residual and organic bound, and Pb was mainly in the forms of residual and Fe-Mn oxide bound. The activity of the heavy metals in the soils were in the order of Cd > Ni > Cu > Zn > Pb according to the DTPA-extraction rate.(3) The accumulationg of the hevvy metals in corn plant was in the order of leaf > root > stem > grain for Cu and Pb, leaf > seed > root > stem for Zn, root > leaf > stem > grain for Ni, root > leaf > stem ≈ grain for Cd, respectively. The result of comprehensive pollution index showed that 52.6% of the corn grains were polluted by heavy metals in the study area. Heavy metal content in corn plant was not correlated with the soil p H, however, the contents of Ni in roots, stems and grains, and that of Pb in leaves were significantly negative correlation with soil organic matter. The relationship between the contents of heavy metals in corn plant and in the soils were not significantly, but the contents of heavy metals in root increased significantly with the increase of DTPA extractable amounts of heavy metals in the soils. Except for the contents of Ni in the root, stem, leaf of corn plant correlated significantly positively, there were no significant correlation between the contents of Cu, Pb and Zn and all forms of heavy metals obtained by the sequential extraction method. |
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