Michelsen, Nils ; Laube, Gerrit ; Friesen, Jan ; Weise, Stephan M. ; Bait Said, Ali Bakhit Ali ; Müller, Thomas (2019):
Technical note: A microcontroller-based automatic rain sampler for stable isotope studies.
In: Hydrology and Earth System Sciences, 23 (6), pp. 2637-2645. Copernicus, ISSN 1607-7938,
DOI: 10.5194/hess-23-2637-2019,
[Article]

Abstract

Automatic samplers represent a convenient way to gather rain samples for isotope (δ 18O and δ 2H) and water quality analyses. Yet, most commercial collectors are expensive and do not reduce post-sampling evaporation and the associated isotope fractionation sufficiently. Thus, we have developed a microcontroller-based automatic rain sampler for timer-actuated collection of integral rain samples. Sampling periods are freely selectable (minutes to weeks), and the device is low-cost, simple, robust, and customizable. Moreover, a combination of design features reliably minimizes evaporation from the collection bottles. Evaporative losses were assessed by placing the pre-filled sampler in a laboratory oven with which a diurnal temperature regime (21–31 ◦C) was simulated for 26 weeks. At the end of the test, all bottles had lost less than 1 % of the original water amount, and all isotope shifts were within the analytical precision. These results show that even multi-week field deployments of the device would result in rather small evaporative mass losses and isotope shifts. Hence, we deem our sampler a useful addition to devices that are currently commercially available and/or described in the scientific literature. To enable reproduction, all relevant details on hard- and software are openly accessible.

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