We present one year of δD, δ18O, d-excess, and Δʹ17O data from monthly precipitation at a Caribbean coastal site in Panama and from tap waters across the country to constrain geographic, climate, and moisture source controls on isotopic variability and better understand the sources and mechanisms of precipitation in Central America, a region facing significant modifications to the annual rainfall cycle due to climate change. Monthly precipitation δD ranged from –52.2 to +14.3 ‰, δ18O from –7.6 to +0.4 ‰, d-excess from +7.1 to +11.6 ‰, and Δ′17O from +11 to +29 per meg. Rainy season precipitation samples were found to have lower δD, δ18O, and d-excess due to Rayleigh distillation during the condensation and rainout of Pacific moisture over the central cordilleras, which results in decoupling between d-excess and Δ′17O. Outlier Δ′17O values during peak dry and rainy months may reflect seasonal changes in water vapor sourcing, from Caribbean to Pacific and/or locally recycled moisture, or may be a result of organic contamination. Tap water δD ranged from –82.3 to –14.3 ‰, δ18O from –11.6 to –2.4 ‰, d-excess from +4.3 to +12.2 ‰ and Δ′17O from –2 to +84 per meg. Tap water δD and δ18O values increase eastward due to lower orographic effects and Pacific and locally recycled moisture contributions to rainfall and greater secondary evaporation. Tap water d-excess and Δ′17O values are also de-coupled but lack clear spatial trends and controls. The results of this study indicate the promise of adding Δ′17O to the isotopic toolkit in tropical mountainous regions with complicated water cycling dynamics and provide a baseline for future triple oxygen isotope investigations.

中文翻译：

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热带山区降水的三重氧同位素变率


我们展示了巴拿马加勒比海沿岸地区每月降水量和全国各地自来水的一年 δD、δ18O、d-过量和 Δ17O 数据，以限制地理、气候和水分来源对同位素变化的控制，并更好地了解中美洲的降水来源和机制，该地区因气候变化而面临年降雨周期的重大变化。月降水量 δD 范围为 –52.2 至 +14.3 ‰，δ18O 范围为 –7.6 至 +0.4 ‰，d-过量范围为 +7.1 至 +11.6 ‰，Δ′17O 范围为 +11 至 +29/meg。发现雨季降水样品具有较低的 δD、δ18O 和 d-过量，这是由于太平洋水分在中央科迪勒拉山脉上空的冷凝和降雨过程中的瑞利蒸馏，导致 d-过量和 Δ′17O 之间的脱钩。在干旱和雨季的高峰期，异常值 Δ′17O 值可能反映了从加勒比海到太平洋和/或当地循环水分的水蒸气来源的季节性变化，或者可能是有机污染的结果。自来水 δD 范围为 –82.3 至 –14.3 ‰，δ18O 范围为 –11.6 至 –2.4 ‰，d-过量范围为 +4.3 至 +12.2 ‰，Δ′17O 范围为 –2 至 +84/meg。由于较低的地形效应以及太平洋和当地循环的水分对降雨和更大的二次蒸发的贡献，自来水 δD 和 δ18O 值向东增加。自来水 d-excess 和 Δ′17O 值也是解耦的，但缺乏明确的空间趋势和控制。这项研究的结果表明，在具有复杂水循环动力学的热带山区，将 Δ′17O 添加到同位素工具包中有望，并为未来的三重氧同位素研究提供基线。