Frescholtz Toby E, Gustin Mae S, Schorran David E, Fernandez George C J
Department of Environmental and Resource Sciences, University of Nevada-Reno, ERS Department, MS 370, Reno, Nevada 89557, USA.
Environ Toxicol Chem. 2003 Sep;22(9):2114-9.
Foliar accumulation of mercury has been demonstrated to occur as plants leaf out, yet the primary source of this mercury is not known. Using closed-system growth chambers, uptake of mercury by quaking aspen (Populus tremuloides) foliage was measured over time as a function of soil mercury concentrations (0.01, 6.2, and 25.6 microg/g) and atmospheric mercury exposure concentrations (1.4, 14.9, and 68.5 ng/m3). Foliar mercury concentrations increased as a function of time for all exposures. Twice during the experiment, leaf washes were analyzed for mercury to assess surface deposition, and little mercury was removed (0.02-0.04 ng/m2), suggesting that direct deposition to the leaf surface was not significant during this experiment. At the end of the four-month experiment, whole-plant mercury concentrations were determined. It was found that whereas mercury in the atmosphere primarily influenced foliar uptake, root concentrations were related to the soil mercury concentration. The implication of this study is that litterfall may serve as a pathway for new, atmospherically derived mercury to be deposited to forest soils. This has significant implications for watershed management of ecosystems where mercury is of concern.
研究表明，随着植物长出新叶，汞会在叶片中积累，但这种汞的主要来源尚不清楚。利用封闭系统生长室，测量了不同时间内震颤白杨（Populus tremuloides）叶片对汞的吸收情况，该吸收情况是土壤汞浓度（0.01、6.2和25.6微克/克）以及大气汞暴露浓度（1.4、14.9和68.5纳克/立方米）的函数。在所有暴露情况下，叶片汞浓度均随时间增加。在实验过程中对叶片进行了两次冲洗，分析冲洗液中的汞以评估表面沉积情况，结果发现去除的汞很少（0.02 - 0.04纳克/平方米），这表明在该实验期间，汞直接沉积到叶片表面的情况并不显著。在为期四个月的实验结束时，测定了整株植物的汞浓度。结果发现，大气中的汞主要影响叶片吸收，而根部汞浓度与土壤汞浓度有关。该研究的意义在于，凋落物可能成为大气中新增汞沉积到森林土壤的一条途径。这对于关注汞问题的生态系统流域管理具有重要意义。
