An oxygen isotope study of seasonal trends in soil water fluxes at two sites along a climate gradient in Washington state (USA)
An oxygen isotope study of seasonal trends in soil water fluxes at two sites along a climate gradient in Washington state (USA)
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DOI：
10.1016/j.jhydrol.2005.12.031
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发表时间：
2006-08
影响因子：
6.4
通讯作者：
J. A. Robertson;C. Gazis
中科院分区：
文献类型：
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作者：
J. A. Robertson;C. Gazis
在喀斯喀特山脉（美国华盛顿）东侧气候梯度沿线的两个地点监测了降水和土壤水中的氧同位素。这两个地点的降水量均以冬季降雪为主。降水 δ18O 值显示出典型的季节变化，在西部站点（克利埃勒姆），从冬季的约-17‰到夏季的约-8‰，而东部站点（埃伦斯堡）的值略低。土壤水同位素组成和含水量与水文季节有关：（1）夏末至秋季——降温，土壤湿度增加； (2)冬季——积雪； (3)冬末春初——积雪融化，土壤和地下水补给； (4) 晚春——土壤初干。使用保存同位素和质量的简单质量平衡模型来限制这些水文季节期间由于蒸发和非分馏损失（蒸腾和向下渗透）而导致的水损失率。春季期间，两个地点的非分级损失相似，约为 0.8-1.0 毫米/天。相比之下，在秋季，这些非分级损失在干燥地点（埃伦斯堡）接近于零，而在湿润地点（克莱埃勒姆）则保持在约 0.8 毫米/天。该模型得出的埃伦斯堡蒸发率在 0.01 到 0.2 毫米/天之间，克莱埃勒姆的蒸发率在 0.2 到 0.9 毫米/天之间。
Oxygen isotopes in precipitation and soil water were monitored at two sites along a climate gradient on the east side of the Cascade Mountains (Washington, USA). Precipitation at both sites is dominated by snowfall in the winter months. δ18O values of precipitation show a typical seasonal variation from around −17‰ in the winter to around −8‰ in the summer at the western site (Cle Elum), and slightly lower values at the eastern site (Ellensburg). Soil water isotope composition and moisture contents relate to hydrological season: (1) late summer to fall – cooling, increased soil moisture; (2) winter – snow cover; (3) late winter to early spring – snow melts, recharge of soils and groundwater; (4) late spring – initial drying of soils. A simple mass balance model that conserves isotopes and mass is used to constrain the rates of water loss due to evaporation and non-fractionating losses (transpiration and downward percolation) during these hydrological seasons. Non-fractionating losses at both sites are similar during the spring at approximately 0.8–1.0mm/day. In contrast, during the fall, these non-fractionating losses are near zero at the drier site (Ellensburg) and remain at ≈0.8mm/day at the wetter site (Cle Elum). The model yields evaporation rates between 0.01 and 0.2mm/day for Ellensburg and between 0.2 and 0.9mm/day for Cle Elum.