Abstract: Pb pollution, an important type of urban environmental pollution, affects environmental quality and human health and thus has received many concerns. In this study, Pb accumulation in tree rings of Magnolia grandiflora and Ailanthus altissima, two common garden tree species in Hefei City, was measured to understand the temporal dynamics of urban Pb pollution and the underlying reason. The results showed that the average Pb concentration was 1.114±0.055 mg·kg^-1  in the tree rings of Magnolia grandiflorafor 110 years and 0.667±0.037 mg·kg^-1 in Ailanthus altissimafor 60 years. The variations of Pb concentrations in the tree rings of both species showed substantial fluctuation and great similarity. For most of the tree rings, Pb concentrations were at a lower level. The peak of both tree species appeared in the same period. Pb concentration had no significant correlation with tree age and ring width, but was well correlated with annual average precipitation corresponding to tree ring segments, with correlation coefficients of 0.89 and 0.84, respectively. The variation pattern of Pb concentration in both species reflected the historical Pb pollution. The years with Pb concentration in the tree rings higher than the average concurred with war, urban economic growth, and/or urban expansion. During the period of study, the overall trend Pb accumulation in tree rings showed a downward trend, and such trend was significantly greater for Ailanthus altissima than for Magnolia grandiflora.

Key words: climate change, rubber, climatic suitability