| Heavy metals are common polluting elements in soil and plants, accumulation of heavy metals in soil and plants may result in negative effects on human health. Meanwhile, concentrations of heavy metals in soil and plants can also indicate the quality of the environment. In recent years, as industrialization and urbanization develops rapidly in China, heavy metal pollution in soil has been detected in more and more locations. Wheat (Triticum aestivum Linn.) samples and soil and Euonymus japonicus Thunb. leaf samples were collected from the vicinity of a lead smelter in the North China Plain and Zhengzhou City, analyzed for concentrations of heavy metals, methods of rinsing of the polluted wheat grain were also explored. The results indicated that,i) The average concentrations in the wheat grain collected from the vicinity of the lead smelter of nickel (Ni), chromium (Cr), copper (Cu) and lead (Pb) were 2.31, 24.8, 7.86 and 59.5 mg kg-1, respectively, all above the national standard of wheat quality. The lead smelter contributes to the high content of heavy metals in the wheat grain. Higher concentration of heavy metal was found in wheat grain than in straw.ii) Elimination rates by rinsing of different metals ranked Cr> Pb>Cu>Ni>Zn, the results suggested that the heavy metals in wheat grain was predominantly absorbed through wheat leaves other than root. Elimination rate of EDTA, pure water, detergent solvent and dilute nitric acid were 79.95%, 66.67%, 64.41%, 61.88% and 60.41%, respectively.iii) The average concentrations of Ni, Pb, Cr and Zn of urban soils of Zhengzhou City were 34.1, 49.5, 65.3 and 62.5 mg kg-1, apparent accumulation of Pb, Ni, Cr existed in urban soil of Zhengzhou City, while average concentration of Zn was lower than the background value. Comparison of heavy metals in urban soil with different land uses indicated that commercial activity, vehicle transportation and industrial plant are the main sources of heavy metal accumulation in urban soils of Zhengzhou City. Heavy metal pollution in urban soil is leas serious, compared with other big cities in China. Value of the integrated pollution index (IPI) was in the Middle Grade.iv)The average concentration of available Zn, Pb, Cr and Ni (extracted with DTPA) in urban soil of Zhengzhou City were 3.17, 2.73, 1.05 and 0.25 mg kg-1, respectively. Samples collected near bus stations had higher concentrations of available Ni and Zn, those from yard of organizations had higher concentrations of available Pb, Cr and Zn, those from street side greenbelt had high concentrations of available Cr. These values are higher than those of local farming soils, but lower than those of many developed big cities.v) Average concentrations of Ni, Pb, Cr and Zn of leaf of Euonymus japonicus Thunb. were 6.83, 8.38, 13.6 and 21.1 mg kg-1, respectively. Bioconcentraions indices of leaves were 0.20, 0.17, 0.23 and 0.34 for these four metals. Higher contents of Ni and Cr were found in leaf samples from industrial area, higher contents of Zn from samples from street side, while higher contents of Pb were found in leaves from residential community. Pollution indices ranked industrial area >> residential area, bus station > yard of organization>street side>>commercial area. The results indicated that leaves of Euonymus japonicus Thunb. of Zhengzhou City were polluted with Ni, Pb, Cr and Zn. The main pathway for Euonymus japonicus Thunb. leaves to accumulate heavy metals is not root. |
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