Foliar exchange of mercury vapor: Evidence for a compensation point
Foliar exchange of mercury vapor: Evidence for a compensation point
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DOI：
10.1007/978-94-011-0153-0_41
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发表时间：
1995-02
期刊：
影响因子：
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通讯作者：
P. Hanson;S. Lindberg;T. A. Tabberer;J. Owens;K. Kim
中科院分区：
文献类型：
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作者：
P. Hanson;S. Lindberg;T. A. Tabberer;J. Owens;K. Kim
对作物和杂草物种的历史研究记录了元素汞蒸气（Hg°）沉积到树叶上的情况，但他们使用的Hg°浓度比目前已知的背景条件下的水平高出几个数量级，可能在大气和景观表面之间人为地造成高梯度。用白色栎（Quercus阿尔巴尔.）红枫（Acer rubrum L.），挪威云杉（Picea abiesL.），和黄杨（Liriodendron tumeferaL.）在开放的气体交换系统中进行叶面试验，该系统允许在受控的环境条件下同时测量CO2、H2O和Hg°交换。当Hg°浓度保持在0.5至1.5 ng m−3时，红枫（Acer rubrum L.），挪威云杉（Picea abiesL.），黄杨（鹅掌楸），和白色栎（Quercus阿尔巴尔.）树叶的平均Hg°排放量分别为5.5、1.7、2.7和5.3 ng m− 2 h −1。当Hg°浓度在9 - 20 ng m− 3之间时，几乎没有观察到Hg°的净交换。然而，当浓度在50 - 70 ng m− 3之间时，Hg°以22 - 38 ng m− 2 h −1的速率沉积到叶子上。这些数据表明，陆地森林景观中干燥的叶面可能是一个动态交换面，可以作为源或汇，取决于当前Hg°浓度的大小。这些数据提供了证据，表明在10-25 ng m− 3的范围内，Hg°沉积到幼苗叶片上的补偿浓度（或补偿点）因物种而异。
Historical studies for crop and weed species documented elemental Hg vapor (Hg°) deposition to foliage, but they used Hg° concentrations that were orders of magnitude higher than levels now known to occur under background conditions, possibly creating artificially high gradients between the atmosphere and landscape surfaces. Measurements of Hg° exchange with white oak (Quercus albaL.), red maple (Acer rubrumL.), Norway spruce (Picea abiesL.), and yellow-poplar (Liriodendron tulipiferaL.) foliage were conducted in an open gas exchange system that allows for simultaneous measurements of CO2, H2O and Hg° exchange under controlled environmental conditions. When Hg° concentrations were held at 0.5 to 1.5 ng m−3, red maple (Acer rubrumL.), Norway spruce (Picea abiesL.), yellow-poplar (Liriodendron tulipiferaL.), and white oak (Quercus albaL.) foliage exhibited mean Hg° emissions of 5.5, 1.7, 2.7, and 5.3 ng m−2h−1, respectively. At Hg° concentrations between 9 and 20 ng m−3little net exchange of Hg° was observed. However at concentrations between 50 and 70 ng m−3the Hg° was deposited to foliage at rates between 22 and 38 ng m−2h−1. These data suggest that dry foliar surfaces in terrestrial forest landscapes may be a dynamic exchange surface that can function as a source or sink dependent on the magnitude of current Hg° concentrations. These data provide evidence of species-specific compensation concentrations (or compensation points) for Hg° deposition to seedling foliage in the 10–25 ng m−3range.