Gilliam Frank S, Adams Mary Beth
a Department of Biological Sciences , Marshall University , Huntington , West Virginia , USA.
b U.S. Department of Agriculture Forest Service, Timber and Watershed Laboratory , Parsons , West Virginia , USA.
J Air Waste Manag Assoc. 1996 Oct;46(10):978-984. doi: 10.1080/10473289.1996.10467533.
Although extensive research on acidic deposition has been directed toward spruce-fir forests, less research has been done on the impacts of air pollution on eastern montane hardwood forests. The purpose of this study was to describe precipitation chemistry for several Appalachian hardwood forest sites at or near the Fernow Experimental Forest (FEF) to assess the potential for problems associated with acidic deposition. Emphasis was placed on seasonal patterns of ionic concentrations (H+, Ca++, NH4+; NO3-, and SO4=) and spatial variability of ionic concentrations and deposition among sites. Seasonal patterns of most ions showed highest concentrations during the summer months and deposition of H+ was especially pronounced during this time. Deposition of all ions was generally greater (related to greater precipitation) at three montane forested sample sites compared to a nonforested riverbottom site. Precipitation chemistry at FEF was similar to other sites throughout the eastern United States and contrasted sharply with mid-western and western sites. Eastern sites, including means for FEF sites, were uniformly 3-4 times higher in H+ and SO4= concentration than the mid-western and western sites. Precipitation at FEF was chronically acidic, more so during the growing season, and highest at higher elevations where environmental stresses can be most severe. Furthermore, there were occasional large discrepancies between the low-elevation site and the higher-elevation forested sites for precipitation chemistry and acidic deposition. These results suggest that synoptic-scale (network) data may greatly underestimate the pollutant conditions to which highelevation forest trees are exposed, since network data rarely take elevation into account and typically are based on annual ionic concentration and deposition means that may be considerably lower than those of the growing season.
尽管针对云杉-冷杉林的酸性沉降已有广泛研究，但空气污染对东部山地阔叶林的影响研究较少。本研究的目的是描述弗诺实验林（FEF）及其附近几个阿巴拉契亚阔叶林站点的降水化学特征，以评估与酸性沉降相关问题的潜在可能性。重点关注离子浓度（H⁺、Ca²⁺、NH₄⁺、NO₃⁻和SO₄²⁻）的季节模式以及各站点间离子浓度和沉降的空间变异性。大多数离子的季节模式显示夏季浓度最高，且此时H⁺的沉降尤为明显。与一个非森林覆盖的河底站点相比，三个山地森林采样站点的所有离子沉降通常更大（与降水量更大有关）。FEF的降水化学特征与美国东部其他站点相似，与中西部和西部站点形成鲜明对比。包括FEF站点平均值在内的东部站点，H⁺和SO₄²⁻浓度比中西部和西部站点统一高出3至4倍。FEF的降水长期呈酸性，生长季节更甚，且在环境压力可能最严重的较高海拔处最高。此外，低海拔站点与高海拔森林站点在降水化学和酸性沉降方面偶尔存在较大差异。这些结果表明，天气尺度（网络）数据可能会极大低估高海拔森林树木所面临的污染物状况，因为网络数据很少考虑海拔因素，通常基于年度离子浓度和沉降平均值，而这些值可能远低于生长季节的值。
