Historical Changes in Heavy Metals in Tree-rings of Masson Pine (Pinus mossoniana) in the Pearl River Delta, South China
珠江三角洲马尾松年轮重金属含量年代变化

Heavy metals (Cu, Zn, Ni, Cd, Cr and Pb) in the tree-rings of Masson pine (Pinus massoniana) growing in Dinghushan (relatively clean area) and Xiqiaoshan (polluted area) were determined in 5 year increments, respectively. Surface soil beneath the sampled trees at Xiqiaoshan elevated concentrations of Cu, Zn, Cd and Pb compared with their background values in Guangdong Province, whereas at Dinghushan, had lowed metal concentrations in the ranges of the background values except Cd. Contents of Cu, Zn, Ni, Cr and Pb increased steadily in tree-rings from the heart-wood to sap-wood at both sites, reflecting the increase in the bio-availability in the Delta area during the past decades. Peaks in Cu, Zn, Ni and most obviously Cr and Pb, were found in rings formed after 1990. It was suggested that the recent increase of the heavy metals in soil and atmosphere in the Delta was the main source contributed to the elevation of the heavy metals in the pine rings. In the rings formed during the same period, content of Cu, Cr and Pb at Xiqiaoshan were constantly higher, whereas Zn, Ni and Cd, consitantly lower than those at Dinghushan, which was not only related to the difference of the metals content in the environments, but also to the difference of accumulation ability of the metals in the pine. The results indicated that tree ring chemistry of Masson pine could provide information concerning historical changes of heave metals in soil and atmosphere in the Delta.