Department of Forest and Natural Resources Management, State University of New York College of Environmental Science and Forestry, Syracuse, NY, United States of America.
Department of Civil and Environmental Engineering, Syracuse University, Syracuse, NY, United States of America.
PLoS One. 2018 Apr 23;13(4):e0196293. doi: 10.1371/journal.pone.0196293. eCollection 2018.
Mercury (Hg) is deposited from the atmosphere to remote areas such as forests, but the amount of Hg in trees is not well known. To determine the importance of Hg in trees, we analyzed foliage, bark and bole wood of eight tree species at four sites in the northeastern USA (Huntington Forest, NY; Sleepers River, VT; Hubbard Brook, NH; Bear Brook, ME). Foliar concentrations of Hg averaged 16.3 ng g-1 among the hardwood species, which was significantly lower than values in conifers, which averaged 28.6 ng g-1 (p < 0.001). Similarly, bark concentrations of Hg were lower (p < 0.001) in hardwoods (7.7 ng g-1) than conifers (22.5 ng g-1). For wood, concentrations of Hg were higher in yellow birch (2.1-2.8 ng g-1) and white pine (2.3 ng g-1) than in the other species, which averaged 1.4 ng g-1 (p < 0.0001). Sites differed significantly in Hg concentrations of foliage and bark (p = 0.02), which are directly exposed to the atmosphere, but the concentration of Hg in wood depended more on species (p < 0.001) than site (p = 0.60). The Hg contents of tree tissues in hardwood stands, estimated from modeled biomass and measured concentrations at each site, were higher in bark (mean of 0.10 g ha-1) and wood (0.16 g ha-1) than in foliage (0.06 g ha-1). In conifer stands, because foliar concentrations were higher, the foliar pool tended to be more important. Quantifying Hg in tree tissues is essential to understanding the pools and fluxes of Hg in forest ecosystems.
汞（Hg）从大气中沉积到森林等偏远地区，但树木中的汞含量却知之甚少。为了确定汞在树木中的重要性，我们分析了美国东北部四个地点（纽约州亨廷顿森林、佛蒙特州斯利珀斯河、新罕布什尔州哈伯布鲁克、缅因州贝尔布鲁克）的八种树种的树叶、树皮和树干木材。硬木树种的叶片汞浓度平均为 16.3ng g-1，明显低于针叶树种的 28.6ng g-1（p <0.001）。同样，硬木树种的树皮汞浓度也较低（p <0.001）（7.7ng g-1）低于针叶树种（22.5ng g-1）。对于木材，黄桦（2.1-2.8ng g-1）和白松（2.3ng g-1）的汞浓度高于其他树种，平均为 1.4ng g-1（p <0.0001）。直接暴露于大气中的树叶和树皮的汞浓度在各地点之间存在显著差异（p = 0.02），但木材中的汞浓度更多地取决于树种（p <0.001）而不是地点（p = 0.60）。根据每个地点的生物量模型和实测浓度估算的硬木林树木组织中的汞含量，树皮（平均值为 0.10g ha-1）和木材（0.16g ha-1）中的汞含量高于树叶（0.06g ha-1）。在针叶林中，由于叶片浓度较高，叶片库往往更为重要。量化树木组织中的汞对于了解森林生态系统中汞的储量和通量至关重要。
