临安区西径山不同森林中的汞迁移及沉降

Mercury Migration and Deposition in Different Forests in Xijingshan,Lin’an

森林系统,是汞在地球生物化学过程中极为重要的一环。其中,叶片是大气汞与森林交互作用的主要界面。本文以临安地区的典型落叶林、针叶林为例,进行定点监测,探明不同季节落叶林、针叶林中汞在叶片和林下土壤中的分布状况及其影响因素。定点监测实验的结果表明,森林汞在垂直方向上具有明显的分层累积现象,其中土壤中汞浓度最高,含量最多,凋落物其次,新鲜叶最低。且阔叶林在各垂直分层中汞含量均显著高于针叶林。2种森林类型汞均在7—9月达到峰值,这与森林生长发育的季节性与夏季土壤汞的再释放相关。凋落物汞输入是森林土壤汞的主要来源之一,而由土壤所固持的汞主要集中于0~10 cm土层,这与0~10 cm土层中含有的大量具有吸附、固定汞能力的有机质相关。另外,对阔叶林与针叶林的沉降通量估算结果显示,阔叶林沉降通量高于针叶林,这与阔叶林凋落物沉降通量显著高于针叶林相关。本研究的结果有助于了解森林叶片汞浓度以及土壤汞负荷的影响,以及不同季节森林叶片汞和土壤汞时空分布状况。同时,本研究也有利于进一步探明浙江省森林汞地球生物化学循环过程的特征与分布情况。

Forest ecosystems play an extremely important role in the biogeochemical processes of mercury on Earth.Among them,leaves serve as the primary interface for the interaction between atmospheric mercury(Hg)and forests.In this study,typical deciduous and coniferous forests in the Lin’an Region were selected for fixed-point monitoring to investigate the distribution of Hg in leaves and forest soils during different seasons and the influencing factors.The results of the experiments indicate that forest Hg exhibits a significant vertical accumulation pattern.A mong the vertical layers,the highest Hg concentrations were found in the soil,followed by litterfall,and the lowest in fresh leaves.Additionally,broad-leaved forests had significantly higher Hg concentrations in all vertical layers compared to coniferous forests.Both types of forests reached their peak Hg levels from July to September,which is related to the seasonal growth of the forests and the re-release of Hg from soils of summer.Litterfall deposition was identified as the one of primary source of Hg input into forest soils,and the Hg retained by the soil was mainly concentrated in the 0~10 cm soil layer.This is related to the presence of a significant amount of organic matter in the 0~10 cm soil layer,which has adsorption and immobilization capabilities for Hg.Furthermore,the estimated results of deposition flux for broad-leaved and coniferous forests showed that broad-leaved forests had higher deposition flux compared to coniferous forests,which is correlated with the significantly higher litterfall d eposition flux in broad-leaved forests.The potential ecological risk of soil total mercury in broad-leaved forest was significantly higher than that in coniferous forest(P<0.05).The findings of this study contribute to understanding the Hg concentration in forest leaves and the soil Hg load,as well as the spatiotemporal distribution of Hg in forest leaves and soil during different seasons.Additionally,this research is valuable for further exploring the characteristics of the Hg biogeochemical cycle and ecological risk situation in forest ecosystems in Zhejiang Province.