HE Chunlu1, GAO Yuan1, LI Yao1, LIU Xu1, WANG Xun2, WANG Yongmin1, WANG Dingyong1

（1. College of Resources and Environment, Southwest University, Chongqing 400715, China;
2. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, State Key Office of environmental geochemistry, Guiyang 550081, China）

Abstract： Tree rings have been regarded as an emerging natural archive to reconstruct historical atmospheric mercury (Hg) trends, but its reliability needs to be further improved. In this study, Schrenk Spruce tree rings in the Tianshan Mountains of China were chosen as the research object to explore the influence of environmental factors and tree age effect on tree-ring Hg concentration. The tree-ring Hg records were also compared with anthropogenic Hg emission data in Xinjiang and tree-ring Hg data of other studies to assess the reliability of Schrenk Spruce tree-ring Hg records. Results showed that there are tree-specific variations in the tree-ring Hg concentration of Schrenk Spruce. Correlation analysis showed that the annual average sunshine hours of the study area were significantly positively correlated with the tree-ring Hg concentration (R2=0.65, P<0.05), indicating that environmental factors can affect the growth of trees, thus affect the tree-ring Hg records. Besides, the temporal variation of atmospheric Hg cannot be reflected well by tree-ring Hg data of the young growth period due to the age effect, but it can be better reconstructed after discarding this part of the data. Finally, combined with the anthropogenic Hg emission data in Xinjiang and the analysis of the trajectory of backward air masses, the increase in atmospheric Hg concentration in Xinjiang is mainly related to the increase of anthropogenic Hg emissions of Xinjiang in the past two decades, as well as the cross-border transmission of atmospheric Hg from central Asian countries adjacent to northwest China into Xinjiang through the westerly wind belt. With further standardization and improvement, the tree ring can become a reliable natural archive for reconstructing the historical atmospheric Hg concentration trends.

Key words：Schrenk Spruce; tree rings; Hg; environmental factors; tree age effect

EARTH AND ENVIRONMENT Vol.51, No.4, Tot No.354, 2023, Page 455