U.S. Geological Survey, 5957 Lakeside Boulevard, Indianapolis, IN 46278, USA.
Environ Pollut. 2012 Feb;161:284-90. doi: 10.1016/j.envpol.2011.06.005. Epub 2011 Jun 28.
Mercury (Hg) in autumn litterfall from predominately deciduous forests was measured in 3 years of samples from 23 Mercury Deposition Network sites in 15 states across the eastern USA. Annual litterfall Hg dry deposition was significantly higher (median 12.3 micrograms per square meter (μg/m(2)), range 3.5-23.4 μg/m(2)) than annual Hg wet deposition (median 9.6 μg/m(2), range 4.4-19.7 μg/m(2)). The mean ratio of dry to wet Hg deposition was 1.3-1. The sum of dry and wet Hg deposition averaged 21 μg/m(2) per year and 55% was litterfall dry deposition. Methylmercury was a median 0.8% of Hg in litterfall and ranged from 0.6 to 1.5%. Annual litterfall Hg and wet Hg deposition rates differed significantly and were weakly correlated. Litterfall Hg dry deposition differed among forest-cover types. This study demonstrated how annual litterfall Hg dry deposition rates approximate the lower bound of annual Hg dry fluxes.
美国东部 15 个州的 23 个汞沉降网络站点采集了 3 年的秋季凋落叶样本，对样本中的汞（Hg）含量进行了测量。每年凋落叶 Hg 的干沉降量（中位数为 12.3 微克/平方米（μg/m(2)），范围为 3.5-23.4 μg/m(2)）明显高于每年 Hg 的湿沉降量（中位数为 9.6 μg/m(2)，范围为 4.4-19.7 μg/m(2)）。干沉降 Hg 与湿沉降 Hg 的平均比值为 1.3-1. 每年干沉降 Hg 和湿沉降 Hg 的总和平均为 21 μg/m(2)，其中 55%为凋落叶干沉降。凋落叶中的甲基汞平均占 Hg 的 0.8%，范围为 0.6-1.5%。每年凋落叶 Hg 和湿 Hg 的沉降速率差异显著，且相关性较弱。凋落叶 Hg 的干沉降量因森林覆盖类型而异。本研究表明，每年凋落叶 Hg 的干沉降速率接近每年 Hg 干通量的下限。
