[Bioaccumulation of Heavy Metals in Twigs and Leaves of at Mount Gongga in China: A Comparison Study Between 1999 and 2014].

The rapid economy growth led to the environmental carrying capacity reaching the maximum level.Given that the time changing trend of heavy metal pollution in the remote forest ecosystems has rarely been reported, we reported the differences of Pb, Hg, Cd, As, Cr, Mn, Cu, Zn and bioaccumulation in twigs and leaves of fir() between samples collected in 1999 and 2014 at the Mt. Gongga, which was located at eastern Tibet Plateau. Our results suggested that the concentrations of Pb, Hg, As, Cd, Mn and Cu in the samples collected in 1999 were significantly higher than those collected in 2014, while the concentrations of Cr, Zn and Ba in samples collected in 2014 were higher than those collected in 1999. The correlation analysis indicated that concentrations of Pb, Hg, Cr, As, Cd, Mn, Cu, Zn and Ba in leaves were positive correlated to the age of the leaves. In addition, Hg was apt to enrich in leaves while the other metals were prone to enrich in twigs. According to the multiple linear regression result, about 70.6% of Hg in leaves and twigs was from air, while the other heavy metals, including Pb, Cr, As, Cd, Cu, Zn, and Ba, were mainly from soil(42.3%-92.2%). These results suggest that there may be different accumulation mechanisms in forest ecosystems between Hg and the other heavy metals.