Technical note: A microcontroller-based automatic rain sampler for stable isotope studies

Nils Michelsen, Gerrit Laube, Jan Friesen, Stephan M. Weise, Ali Bakhit Ali Bait Said, Thomas Müller
2019 Hydrology and Earth System Sciences  
<p><strong>Abstract.</strong> Automatic samplers represent a convenient way to gather rain samples for isotope (<span class="inline-formula"><i>δ</i><sup>18</sup>O</span> and <span class="inline-formula"><i>δ</i><sup>2</sup>H</span>) 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
more » ... lection 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&amp;thinsp;<span class="inline-formula"><sup>∘</sup></span>C) was simulated for 26 weeks. At the end of the test, all bottles had lost less than 1&amp;thinsp;% of the original water amount, and all isotope shifts were within the analytical precision.</p> <p>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.</p>
doi:10.5194/hess-23-2637-2019 fatcat:vibil2gxqzdldlqqpdjejzcjxe