Heavy Metal Pollution Evaluation Of Urban Plantations In Harbin City

In order to understand the forest litter floor and soil heavy metals characteristics in different type plantations in Harbin City,litter samples,0-1 Ocm and 10-30cm soil samples were collected from eight mono-cultured plantations (Larix gmelinii, Pinus sylvestris var. mongolica,Pinus tabulaeformis var.mukdensis, Phellodendron amurense,Juglans mandshurica,Fraxinus mandshurica,Betula platyphyllaand Quercus mongolica) and one mixed plantation (P. sylvestris var. mongolica+F. mandshurica+Pinus koraiensis+P. amurense+ B. platyphylla) established in theUrban Forestry Demonstration Research Base of Northeast Forestry University in the 1950s to analyze the concentrations of Cu, Zn, Cd, Ni, Pb, and As. The results showed that litter heavy metals contents were significantly different in plantations and content of Cu,Cd.Pb and Zn in litter of each type of plantation were abviously higher than those in the soil. There existed significant differences in the heavy metals concentration in the same soil layers among different type plantations. In the test plantations, the concentrations of soil heavy metals except As and Ni tended to decrease with soil depth. In the litter and the same soil layers, Zn had the highest concentration (96.09-224.21mg·kg1,62.29-126.35mg·kg-1), while Cd had the lowest one (0.30-0.80 mg·kg-1,0.06-0.47 mg·kg-1). The abundance and accumulation tendency of test heavy metals in the plantations was in the order of Zn>Pb>Cu(Ni)>Ni(Cu)>As>Cd, and Cd>Pb>Zn>Cu>Ni>As, respectively. There existed positive correlations among soil Cu, Zn, Pb, and Cd concentrations in the plantations except F. mandshurica, and the concentrations of these four heavy metals in the plantations except F. mandshurica and Q. mongolica were positively correlated with soil organic matter, N, P, and K. The concentrations of soil Cd, Pb, Zn, and Cu were higher than the background values, suggesting the anthropogenic inputs; while those of Ni and As were similar to or lower than the background values, suggesting the origin from soil materials. The comprehensive pollution index and ecological risk index were used to assess the soil heavy metals pollution in the plantations, based on the background values of black soil in the City. The comprehensive pollution index indicated the plantations' litter and 0-10cm soil were seriously polluted by heavy metals.Heavy metals integrated pollution from high to low was F. mandshurica>B. platyphylla>P. amurense>L. gmelinii>J. mandshurica>P. sylvestris var. mongolica>mixed plantation>Q.mongolica> P. tabulaeformis var.mukdensis. Ecological risk index showed that Cd had the highest potential to cause ecological damage in plantations,followed by the orderCd>Pb>As>Cu>Ni>Zn.The RI of the test plantations was decreased in the order of F. mandshurica>P. amurense>mixed plantation>J. mandshurica>B. platyphylla>L. gmelinii>P. sylvestris var. mongolica>P. tabulaeformis var. mukdensis>Q. mongolica. The results showed that both comprehensive pollution index and ecological risk index were considerably lower in coniferous forest than broad-leaved forest(except Q. mongolica).