Understanding the mechanisms that drive spatial and temporal triple oxygen isotope (Δ′O) variations in modern precipitation is the first step to expanding the utility of these measurements as an environmental tracer jointly with traditional stable isotope parameters δD, δO, and d-excess. However, “totalizers” designed to collect a single precipitation sample pooled over a calendar month and minimize evaporation and associated isotopic fractionation of the sample during that time have not been tested for Δ′O. We conducted a 30-day laboratory experiment comparing mass losses and isotopic shifts in four totalizers: 1) the OPEnS (Openly Published Environmental Sensing) totalizer, 2) the classic oil-based totalizer, 3) the commercial tube dip-in/pressure equilibration totalizer (Palmex Ltd. RS1), and 4) a reference totalizer (the control, lacking any evaporation reduction mechanism). The OPEnS totalizer was designed as being readily user built with parts costs of about $10, oil-free to facilitate quick and easy sample preparation and risk-free sample analysis, and its collection device expands as it fills to maintain a small gas/water ratio and minimize internal evaporative losses. All totalizers were filled to 12 % of their 3-L volume and placed in a modified laboratory oven with a diurnal temperature change of 23 to 40 °C and an average relative humidity of 9.1 % to simulate extreme evaporative conditions. The OPEnS totalizer experienced the smallest mass loss of water (0.21 %) and smallest isotopic shifts ( < 0.05 for δO and d-excess), which were all within measurement error. The oil, tube, and reference totalizers showed larger mass losses (0.41, 1.37, and 1.61 %, respectively) and evaporative enrichment with respect to δD (+0.3, +0.8, and + 2.1 ‰), δO (+0.16, +0.23, and + 0.83 ‰), and d-excess (−0.9, −1.0, and − 4.5 ‰). The Δ′O variations for all totalizers were within measurement error, so we suggest that in less harsh climates their triple oxygen isotope changes during secondary evaporation would be more acceptable. To test the OPEnS totalizer in field settings, we installed it alongside oil totalizers to collect monthly precipitation over three years in the towns of Jolly and San Antonio, Texas, with mean annual precipitation, temperature, and windspeed values of 556 and 563 mm, 18.7 and 21.9 °C, and 5.0 and 3.5 m/s, respectively. Results indicate that the OPEnS and oil totalizers can produce similar isotopic data in the field, but modifications to OPEnS have been implemented to minimize under-catch and stabilize the collection component where high winds are present and additional testing under a variety of environmental conditions is ongoing. OPEnS is scalable according to expected monthly precipitation amounts, providing a cost-effective, high-performance device for quantification of total rainfall and its isotopic composition without oil contamination risks.

中文翻译：

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与传统的每月降雨量收集器相比，测试新型 OPEnS 累加器中三氧同位素的保存情况


了解驱动现代降水中三氧同位素 (Δ′O) 空间和时间变化的机制，是扩展这些测量作为环境示踪剂与传统稳定同位素参数 δD、δO 和 d-过量的用途的第一步。然而，“累加器”的设计目的是收集一个日历月内汇集的单个降水样本，并最大限度地减少该时间段内样本的蒸发和相关同位素分馏，但尚未对 Δ′O 进行测试。我们进行了为期 30 天的实验室实验，比较了四种累加器的质量损失和同位素变化：1) OPEnS（公开发布的环境传感）累加器，2) 经典的油基累加器，3) 商用管浸入/压力平衡累加器（Palmex Ltd. RS1），以及 4) 参考累加器（控制装置，缺乏任何蒸发减少机制）。 OPEnS 累加器的设计易于用户构建，零件成本约为 10 美元，无油，便于快速轻松地进行样品制备和无风险样品分析，其收集装置在填充时会扩展，以保持较小的气/水比并最大限度地减少内部蒸发损失。所有累加器均填充至 3 L 体积的 12%，并放置在经过改造的实验室烘箱中，昼夜温度变化为 23 至 40 °C，平均相对湿度为 9.1%，以模拟极端蒸发条件。 OPEnS 累加器经历了最小的水质量损失 (0.21%) 和最小的同位素位移（δ18O 和 d-excess 为 < 0.05），这些都在测量误差范围内。油、管和参考累加器显示出较大的质量损失（分别为 0.41、1.37 和 1.61%）和相对于 δD（+0.3、+0.8 和 + 2.1 ‰）、δO（+0.16、+0）的蒸发富集。 。23 和 + 0.83 ‰），以及 d 过量（−0.9、−1.0 和 − 4.5 ‰）。所有累加器的 Δ′O 变化均在测量误差范围内，因此我们建议，在不太恶劣的气候下，二次蒸发过程中三氧同位素的变化更容易接受。为了在现场环境中测试 OPEnS 累加器，我们将其与石油累加器一起安装，以收集德克萨斯州乔利镇和圣安东尼奥镇三年来的月降水量，年平均降水量、温度和风速值为 556 毫米和 563 毫米，18.7和 21.9 °C，以及 5.0 和 3.5 m/s。结果表明，OPEnS 和石油累加器可以在现场产生类似的同位素数据，但已经对 OPEnS 进行了修改，以最大限度地减少捕获不足并稳定存在强风的收集部分，并且正在进行各种环境条件下的额外测试。 OPEnS 可根据预期的每月降水量进行扩展，为量化总降雨量及其同位素组成提供了一种经济高效的高性能设备，且没有石油污染风险。