Abstract
Abstract. Automated field sampling of streamwater or precipitation for subsequent analysis of stable water isotopes (2H and 18O) is often conducted with off-the-shelf automated samplers. However, when water samples are stored in the field for days and weeks in open bottles inside autosamplers, their isotopic signatures can be altered by evaporative fractionation and vapor mixing. We therefore designed an evaporation protection method which modifies autosampler bottles using a syringe housing and silicone tube, and we tested whether this method reduces evaporative fractionation and vapor mixing in water samples stored for up to 24 d in 6712 full-size portable samplers (Teledyne ISCO, Lincoln, USA). Laboratory and field tests under different temperature and humidity conditions showed that water samples in bottles with evaporation protection were far less altered by evaporative fractionation and vapor mixing than samples in conventional open bottles. Our design is a cost-efficient approach to upgrade the 1 L sample bottles of the ISCO autosamplers, allowing secure water sample collection in warm and dry environments. Our design can be readily adapted (e.g., by using a different syringe size) to fit the bottles used by many other field autosamplers.
Highlights
The stable water isotopes deuterium (2H) and oxygen-18 (18O) are used as natural tracers for water flow through the landscape and provide important insights into water sources, flowpaths, and travel times in hydrologic systems (e.g., Gat et al, 2001; Kendall and McDonnell, 1998; Klaus and McDonnell, 2013; McGuire and McDonnell, 2008)
We tested whether retrofitting the 1 L sample bottles of the conventional 6712 full-size portable sampler (Teledyne ISCO, Lincoln, USA) with a modified syringe housing and silicone tube reduces evaporative fractionation and vapor mixing in water samples collected for subsequent stable water isotope analysis
Laboratory and field tests under different temperature and humidity conditions showed that water samples in retrofitted bottles were far less altered by evaporative fractionation and vapor mixing than samples stored in conventional open bottles
Summary
The stable water isotopes deuterium (2H) and oxygen-18 (18O) are used as natural tracers for water flow through the landscape and provide important insights into water sources, flowpaths, and travel times in hydrologic systems (e.g., Gat et al, 2001; Kendall and McDonnell, 1998; Klaus and McDonnell, 2013; McGuire and McDonnell, 2008). Deuterium and oxygen-18 signatures in precipitation and/or streamwater can help to track the movement of atmospheric air masses (Fischer et al, 2017), identify the water sources of plants (Dawson and Ehleringer, 1991), and reconstruct climate records (Shanley et al, 1998). Streamwater is usually collected through instantaneous grab sampling, after which the sample containers are sealed and cooled until laboratory analysis. To prevent evaporative fractionation of the precipitation sample during the sampling period, paraffin oil can be used that
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