No abstract

The kinetic fractionation factor (αK) controls to a large extent the isotopic enrichment of surface waters during evaporation (E). In contrast to the well‐known vapor‐to‐liquid isotopic equilibrium fractionation factor, αK has still not yet been properly characterized for soil water evaporation. In this study, we investigated the αK daily dynamics during a series of three laboratory experiments differing in soil water availability and aerodynamic conditions. For this, we applied a commonly used isotopic evaporation model and tested it in two different approaches. First, a two‐end‐member mixing model (Keeling plot) was fitted to the measured isotopic composition of the laboratory air water vapor to obtain αK. In a second approach, αK was obtained from the slope of the evaporation line in a dual isotopic coordinate system. For both methods, the isotopic composition of the soil water was determined nondestructively and online by sampling the soil water vapor with gas‐permeable microporous tubing. Results highlighted the limitation of the first approach, as the determination of the isotopic composition of E with the Keeling plot was challenging with the laboratory setup. The second approach provided αK values within the range ( αK2normalH0.25em= 1.0132 ± 0.0013; αK18normalO = 1.0149 ± 0.0012) reported in the literature and pointed to the prevalence of turbulent water vapor transport under water‐saturated soil conditions but also at soil water content significantly lower than the saturated value. In a third experiment, temporal dynamics of the atmospheric water vapor intrusion in the topmost soil layer could be observed during an isotopic labeling pulse.

Abstract. Disentangling ecosystem evapotranspiration (ET) into evaporation (E) and transpiration (T) is of high relevance for a wide range of applications, from land surface modelling to policymaking. Identifying and analysing the determinants of the ratio of T to ET (T/ET) for various land covers and uses, especially in view of climate change with an increased frequency of extreme events (e.g. heatwaves and floods), is prerequisite for forecasting the hydroclimate of the future and tackling present issues, such as agricultural and irrigation practices. One partitioning method consists of determining the water stable isotopic compositions of ET, E, and T (δET, δE, and δE, respectively) from the water retrieved from the atmosphere, the soil, and the plant vascular tissues. The present work emphasizes the challenges this particular method faces (e.g. the spatial and temporal representativeness of the T/ET estimates, the limitations of the models used, and the sensitivities to their driving parameters) and the progress that needs to be made in light of the recent methodological developments. As our review is intended for a broader audience beyond the isotopic ecohydrological and micrometeorological communities, it also attempts to provide a thorough review of the ensemble of techniques used for determining δET, δE, and δE and solving the partitioning equation for T/ET. From the current state of research, we conclude that the most promising way forward to ET partitioning and capturing the subdaily dynamics of T/ET is by making use of non-destructive online monitoring techniques of the stable isotopic composition of soil and xylem water. Effort should continue towards the application of the eddy covariance technique for high-frequency determination of δET at the field scale as well as the concomitant determination of δET, δE, and δE at high vertical resolution with field-deployable lift systems.

Abstract. Disentangling ecosystem evapotranspiration (ET) into evaporation (E) and transpiration (T) is of high relevance for a wide range of applications, from land surface modelling to policy making. Identifying and analysing the determinants of the ratio of T to ET (T / ET) for various land covers and uses, especially in view of climate change with increased frequency of extreme events (e.g., heatwaves and floods), is prerequisite for forecasting the hydroclimate of the future and tackling present issues, such as agricultural and irrigation practices. A powerful partitioning method consists in determining the water stable isotopic compositions of ET, E, and T (δET, δE, and δT, respectively) from the water retrieved from the atmosphere, the soil, and the plant vascular tissues. The present work emphasises the challenges this particular method faces (e.g., the spatial and temporal representativeness of the T / ET estimates, the limitations of the models used and the sensitivities to their driving parameters) and the progress that needs to be made in light of the recent methodological developments. As our review is intended for a broader audience beyond the isotopic ecohydrological and micrometeorological communities, it also attempts to provide a thorough review of the ensemble of techniques used for determining δET, δE, and δT, and solving the partitioning equation for T / ET. From the current state of research, we conclude that the most promising way forward to ET partitioning and capturing the sub-daily dynamics of T / ET is in making use of non-destructive online monitoring techniques of the stable isotopic composition of soil and xylem water. Effort should continue towards the application of the eddy covariance technique for high-frequency determination of δET at the field scale as well as the concomitant determination of δET, δE, and δT at high vertical resolution with field-deployable lift systems.

Total reflection X-ray fluorescence spectrometry (TXRF) was used to determine residual metal content in metallurgical slag after sulfuric acid extraction. A slag sample provided by a copper smelter industry and submitted to a recycling process with the aim of extracting valuable metals was analyzed. Slurry sampling was evaluated as a simple sample preparation procedure for the determination of major (Si, Fe, K, Ca) and trace elements (Ti, Ni, Cu, Zn, As, Pb, Sr, Rb, Mn) in two certified reference materials (lake and river sediments) to evaluate the accuracy of the procedure. Precision was evaluated as relative standard deviation (%) of three replicates, being usually lower than 10%. Detection limits were in the range of 1.1-1079 μg g À1 . Additionally, it was evaluated to use Sia major component of the slagas intrinsic reference to determine residual elements in the slag residues. A two-element internal standard (Ga + P) was employed to determine all the elements. Ga was used as internal standard for the determination of elements from K to Pb, and P was required for the quantification of Si. The optimal procedure of slurry sampling was applied for the analysis of the original metallurgical slag and the solid residues. It was found that As and Pb are accumulated in the slag, whereas Cu, Zn, and Fe are extracted to a percentage >90% from the slag. This was confirmed by analysis of the sulfuric acid extracts of the metallurgical slag.