Variation Of Five Heavy Metals Content In Larch Tree Rings, Xilin, Yichun, China

Five kinds of heavy metal (lead-Pb, cadmium-Cd, zinc-Zn, copper-Cu, and manganese-Mn) concentration in tree rings of Larix gmelini of three sample plots near Xilin Lead-zinc Mine, Yichun, China were measured and analyzed by using dendro-environmental methods. The results show that Mn concentration in tree rings of Larix gmelini is the highest of the five heavy metals, while Cd is the lowest. Concentrations of Zn and Cu in Larix gmelini tree rings near the ground of P2are significantly higher than those at the breast height, while the concentrations of Cd and Zn of P1is on the contrary and the difference of other heavy metals concentration near the ground or at the breast height is not significant. During the period of1966-2010, there is a downtrend for heavy metal concentration of P2while other heavy metal concentrations is on the increase. The decrease of Cd concentration of P2is the most obvious; the fluctuation of Pb is quite drastic in the overall change; the fluctuation of Zn in some years is obvious. With the increase of tree ring width, the concentration of Pb decreases; the concentration of Cd decreases at P1and increases at P2; the concentration of Zn, Cu and Mn increase at P1and P2; there are both increase and decrease at P3. There exist some differences of the concentration of Pb and other heavy metals near the ground or at the breast height. The concentration of Pb and other four mentals near the ground show the positive correlation, especially at P1which shows the significant positive correlation. However, breast height is not significant, except Cd was positively correlated, and Cd concentration decreased significantly with the Pb concentration increased. The concentration of P1and P3has close relationship with the amount of precipitation. The figure of P2is relatively bad with Pb, Cd and Cu shows the trend of changing with the amount of precipitation. In terms of temperature, except Cu that is synchronous with temperature, there is no obvious change of other heavy metals. Variations of heavy metal concentrations in tree rings of Larix gmelini may be influenced by the production and mining activities of of Xilin Lead-zinc Mine, so the Pb concentration can be used to reconstruct the mining history. In present, Pb concentration has polluted surrounding environments near Xilin Lead-zinc Mine. Therefore, heavy metals processing in the tailings should be strengthened if the Mine continues to be mined.