DOI: 10.5194/hess-20-715-2016
Scopus记录号: 2-s2.0-84958794270
论文题名: In situ unsaturated zone water stable isotope (2H and 18O) measurements in semi-arid environments: A soil water balance
作者: Gaj M ; , Beyer M ; , Koeniger P ; , Wanke H ; , Hamutoko J ; , Himmelsbach T
刊名: Hydrology and Earth System Sciences
ISSN: 10275606
出版年: 2016
卷: 20, 期: 2 起始页码: 715
结束页码: 731
语种: 英语
Scopus关键词: Carbon dioxide
; Evapotranspiration
; Isotopes
; Light measurement
; Soil moisture
; Soil testing
; Soils
; Spectrometers
; Spectroscopic analysis
; Transpiration
; Calibration procedure
; Environmental conditions
; Fractionation effects
; In-situ measurement
; Laser spectrometers
; Semi-arid environments
; Spatial and temporal resolutions
; Water stable isotopes
; Soil surveys
; calibration
; environmental conditions
; evapotranspiration
; experimental study
; hydrogen isotope
; in situ measurement
; oxygen isotope
; soil water
; stable isotope
; vadose zone
; water budget
; Bavaria
; Germany
; Munich
; Namibia
英文摘要: Stable isotopes (deuterium, 2H, and oxygen-18, 18O) of soil water were measured in the field using a liquid water isotope analyzer (tunable off-axis integrated cavity output spectroscope, OA-ICOS, LGR) and commercially available soil gas probes (BGL-30, UMS, Munich) in the semi-arid Cuvelai-Etosha Basin (CEB), Namibia. Results support the applicability of an in situ measurement system for the determination of stable isotopes in soil pore water. High spatial and temporal resolution was achieved in the study area with reasonable accuracy and measurements were in agreement with laboratory-based cryogenic vacuum extraction and subsequent cavity ring-down laser spectroscopic isotope analysis (CRDS, L2120-i, Picarro Inc.). After drift and span correction of the in situ isotope data, precision for over 140 measurements taken during two consecutive field campaigns (June and November 2014) was 1.8 and 0.48 ‰ for δ2H and δ18O, respectively. Mean measurement trueness is determined using quality check standards and was 5 and 0.3 ‰ for δ2H and δ18O, respectively. The isotope depth profiles are used quantitatively to calculate a soil water balance. The contribution of transpiration to total evapotranspiration ranged between 72 and 92 %. Shortly after a rain event, the contribution of transpiration was much lower, at 35 to 50 %. Potential limitations of such an in situ system are related to environmental conditions which could be minimized by using a temperature-controlled chamber for the laser spectrometer. Further, the applicability of the system using previously oven-dried soil material might be limited by physicochemical soil properties (i.e., clay minerals). Uncertainty in the in situ system is suggested to be reduced by improving the calibration procedure and further studying fractionation effects influencing the isotope ratios in the soil water, especially at low water contents. Furthermore, the influence of soil-respired CO2 on isotope values within the root zone could not be deduced from the data. © 2016 Author(s). Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/78912
Appears in Collections: 气候变化事实与影响
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作者单位: Federal Institue for Geosciences and Natural Resources (BGR), Stilleweg, Hanover, Germany; Department of Hydrology, Faculty of Environment and Natural Resources, University of Freiburg, Fahnenbergplatz, Freiburg, Germany; Department of Geology, University of Namibia (UNAM), Windhoek, Namibia
Recommended Citation:
Gaj M,, Beyer M,, Koeniger P,et al. In situ unsaturated zone water stable isotope (2H and 18O) measurements in semi-arid environments: A soil water balance[J]. Hydrology and Earth System Sciences,2016-01-01,20(2)