Environmental bioindication of sulfur in tree rings of Masson pine (Pinus massoniana L.) in the Pearl River Delta of China

Abstract

In order to identify the potential of sulfur (S) content in the rings of Masson pine (Pinus massoniana) in the Pearl River Delta as a bio-indicator of regional history of atmospheric pollution, dendrochemistry was used to determine the temporal distribution of S content in the xylem of Masson pines from Zhaoqing Dinghushan and Nanhai Xiqiaoshan, Guangdong Province, southern China. The results indicated that contents of xylem S increased temporally and peaked in the rings formed in the most recent years at both sites. In the rings formed during the same period before the 1980s, S contents were not significantly different between the two sites, while in the rings formed at the same period after the 1980s, S content at Xiqiaoshan were significantly higher than those at Dinghushan. The chronosequences of the S indices at both sites could be easily marked as three periods: before 1970, during 1971–1985, and during 1986–2002. Based on the temporal changes of the xylem S contents and certain social-economic indices after the 1980s in the Delta, the history of atmospheric pollution at the study sites could be reconstructed as follows: 1) before 1970, a period in which the air was relatively clear, 2) 1971–1985, a period in which the air was gradually polluted, and 3) 1986–2002, a period in which the air was most severely polluted in the Delta.