Air-surface exchange of gaseous mercury over permafrost soil: an investigation at a high-altitude (4700 m a.s.l.) and remote site in the central Qinghai-Tibet Plateau
Air-surface exchange of gaseous mercury over permafrost soil: an investigation at a high-altitude (4700 m a.s.l.) and remote site in the central Qinghai-Tibet Plateau
复制标题
DOI：
10.5194/acp-16-14741-2016
复制
发表时间：
2016-11-25
影响因子：
6.3
通讯作者：
Zhang, Xiaoshan
中科院分区：
文献类型：
--
作者：
Ci, Zhijia;Peng, Fei;Zhang, Xiaoshan
由于青藏高原气温低、温差大、太阳辐射强、冻土冻融过程明显，大气-地面气态汞（主要是Hg（0））交换模式可能具有独特性。然而，在QTP的空气-地面Hg（0）通量的研究很少。利用动态通量室技术，对4700 Ma高空大气-地面Hg（0）交换通量、时间变化及影响因素进行了野外观测和控制野外实验研究。S.（图中为L.）和远程站点。结果表明，在整个研究过程中，表层土壤是Hg（0）的净排放源（2.86 ngm（-2）h（-1）或25.05 mu gm（-2）yr（-1））。Hg（0）通量具有明显的季节性，在温暖季节净排放量较高（2014年6月：4.95 ngm（-2）h（-1）; 2014年9月：5.16 ngm（-2）h（-1）; 2015年5月至6月：1.95 ngm（-2）h（-1））和冬季活动中的净低沉积（2014年12月：0.62 ngm 2 h 1 /，也表现出白天排放，夜间沉积的日变化模式，尤其是在无降水的日子。干旱土壤上的降雨事件导致Hg（0）排放量立即大幅增加。降雪事件没有引起Hg（0）排放的脉冲，但融雪导致Hg（0）排放的立即增加。雨、雪天的Hg（0）日通量高于无降水日。控制现场实验表明，水除了干燥的土壤显着增加汞（0）排放的短（分钟）和相对较长的时间尺度（小时），他们还表明，紫外线辐射主要归因于汞（0）排放在白天。我们的研究结果表明，温暖的气候和环境变化可能会促进汞释放的冻土陆地生态系统中的QTP。
The pattern of air-surface gaseous mercury (mainly Hg(0)) exchange in the Qinghai-Tibet Plateau (QTP) may be unique because this region is characterized by low temperature, great temperature variation, intensive solar radiation, and pronounced freeze-thaw process of permafrost soils. However, the air-surface Hg(0) flux in the QTP is poorly investigated. In this study, we performed field measurements and controlled field experiments with dynamic flux chambers technique to examine the flux, temporal variation and influencing factors of air-surface Hg(0) exchange at a high-altitude (4700ma. s. l.) and remote site in the central QTP. The results of field measurements showed that surface soils were the net emission source of Hg(0) in the entire study (2.86 ngm(-2) h(-1) or 25.05 mu gm(-2) yr(-1)).Hg(0) flux showed remarkable seasonality with net high emission in the warm campaigns (June 2014: 4.95 ngm(-2) h(-1); September 2014: 5.16 ngm(-2) h(-1); and May-June 2015: 1.95 ngm(-2) h(-1)) and net low deposition in the winter campaign (December 2014: 0.62 ngm 2 h 1 /and also showed a diurnal pattern with emission in the daytime and deposition in nighttime, especially on days without precipitation. Rainfall events on the dry soils induced a large and immediate increase in Hg(0) emission. Snowfall events did not induce the pulse of Hg(0) emission, but snowmelt resulted in the immediate increase in Hg(0) emission. Daily Hg(0) fluxes on rainy or snowy days were higher than those of days without precipitation. Controlled field experiments suggested that water addition to dry soils significantly increased Hg(0) emission both on short (minutes) and relatively long (hours) timescales, and they also showed that UV radiation was primarily attributed to Hg(0) emission in the daytime. Our findings imply that a warm climate and environmental change could facilitate Hg release from the permafrost terrestrial ecosystem in the QTP.