Water Research Institute, National Research Council (IRSA-CNR), Via del Mulino 19, Brugherio, MB, Italy.
Water Research Institute, National Research Council (IRSA-CNR), Via del Mulino 19, Brugherio, MB, Italy.
Sci Total Environ. 2014 Jul 1;485-486:681-692. doi: 10.1016/j.scitotenv.2014.03.096. Epub 2014 Apr 22.
We monitored the chemical and isotopic compositions of wet depositions, at the Pyramid International Laboratory (5050 ma.s.l.), and surrounding surface waters, in the Khumbu basin, to understand precipitation chemistry and to obtain insights regarding ecosystem responses to atmospheric inputs. The major cations in the precipitation were NH4(+) and Ca(2+), whereas the main anion was HCO3(-), which constituted approximately 69% of the anions, followed by NO3(-), SO4(2-) and Cl(-). Data analysis suggested that Na(+), Cl(-) and K(+) were derived from the long-range transport of marine aerosols. Ca(2+), Mg(2+) and HCO3(-) were related to rock and soil dust contributions and the NO3(-) and SO4(2-) concentrations were derived from anthropogenic sources. Furthermore, NH4(+) was derived from gaseous NH3 scavenging. The isotopic composition of weekly precipitation ranged from -1.9 to -23.2‰ in δ(18)O, and from -0.8 to -174‰ in δ(2)H, with depleted values characterizing the central part of the monsoon period. The chemical composition of the stream water was dominated by calcite and/or gypsum dissolution. However, the isotopic composition of the stream water did not fully reflect the composition of the monsoon precipitation, which suggested that other water sources contributed to the stream flow. Precipitation contents for all ions were the lowest ones among those measured in high elevation sites around the world. During the monsoon periods the depositions were not substantially influenced by anthropogenic inputs, while in pre- and post-monsoon seasons the Himalayas could not represent an effective barrier for airborne pollution. In the late monsoon phase, the increase of ionic contents in precipitation could also be due to a change in the moisture source. The calculated atmospheric N load (0.30 kg ha(-1) y(-1)) was considerably lower than the levels that were measured in other high-altitude environments. Nevertheless, the NO3(-) concentrations in the surface waters (from 2 to 17 μeq L(-1)) were greater than expected based on the low N inputs from wet deposition.
我们监测了位于昆布盆地（5050 米海拔）的 Pyramid 国际实验室及周边地表水的湿沉降的化学和同位素组成，以了解降水化学，并深入了解生态系统对大气输入的响应。降水中的主要阳离子是 NH4(+)和 Ca(2+)，主要阴离子是 HCO3(-)，约占阴离子的 69%，其次是 NO3(-)、SO4(2-)和 Cl(-)。数据分析表明，Na(+)、Cl(-)和 K(+)来源于海洋气溶胶的长程传输。Ca(2+)、Mg(2+)和 HCO3(-)与岩石和土壤尘埃的贡献有关，NO3(-)和 SO4(2-)浓度则来自人为源。此外，NH4(+)来源于气态 NH3 的吸收。每周降水的同位素组成在 δ(18)O 中为-1.9 到-23.2‰，在 δ(2)H 中为-0.8 到-174‰，其中季风期的中部特征是贫化值。河水的化学组成主要由方解石和/或石膏溶解控制。然而，河水的同位素组成并未完全反映季风降水的组成，这表明其他水源也对河流流量有贡献。所有离子的降水含量均为全球高海拔地区测量值中最低的。在季风期间，沉积作用没有受到人为输入的显著影响，而在季风前和季风后季节，喜马拉雅山脉无法成为空气污染物的有效屏障。在季风后期，降水离子含量的增加也可能是由于水汽源的变化。计算得出的大气 N 负荷（0.30 千克/公顷/年）明显低于其他高海拔环境的测量值。然而，地表水中的 NO3(-)浓度（2 到 17 μeq/L）高于根据湿沉降的低 N 输入所预期的水平。
