Abstract: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 measured in 5 year increments, respectively. Surface soil beneath sampled trees at Xiqiaoshan had 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 for 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 in the periods after 1990. It was suggested that the recent increase of the heavy metals in soil and atmosphere in the Delta be the main cause contributed to the elevation of the heavy metals in the pine rings. In the rings formed in the same period, content of Cu, Cr and Pb at Xiqiaoshan were relatively constantly higher, whereas Zn, Ni and Cd, constantly 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 in soil and atmospheric heavy metals in the Delta.
