Comparative Foliar Atmospheric Mercury Accumulation across Functional Types in Temperate Trees
Xinyu Zhang, Huhu Kang, Xiaohong Liu, Jun Zhou, Мaodian Liu, Lixin Wang, Xiaoyu Xing, Qiangqiang Lu, Xiaomin Zeng, Na Wei, Shichang Kang
Abstract
Vegetation assimilation of atmospheric gaseous elemental mercury (GEM) represents the largest dry deposition pathway in global terrestrial ecosystems. This study investigated Hg accumulation mechanisms in deciduous broadleaves and evergreen needles, focusing on how ecophysiological strategies─reflected by δ 13 C, δ 18 O, leaf mass per area, and leaf dry matter content-mediated Hg accumulation. Results showed that deciduous leaves exhibited higher total Hg (THg) concentrations and accumulation rates (THg rate ), which were 85.3 ± 17.7 and 110.0 ± 0.3% higher than those in evergreen needles. The two tree types exhibited distinct ecophysiological strategies: deciduous broadleaves, with higher stomatal conductance and photosynthetic rates, rapidly adjust stomata to changes in meteorological and pollutant factors, playing a key role in controlling THg rate . In contrast, evergreen needles featured stable stomatal control, highlighting the direct positive effect of GEM on their THg rate . Precipitation and wind speed negatively influenced foliar THg rate . Correlations between PM 2.5, NO 2, and THg rate in evergreen needles suggested synergistic patterns between atmospheric Hg and pollutants. This study underscores distinct GEM accumulation mechanisms across tree functional types and emphasizes the importance of species-specific foliar ecophysiological strategies. An empirical model linking THg rate with ecophysiological, meteorological, and atmospheric pollution factors was provided, contributing to the refinement of foliar Hg accumulation models.