Project Info

This study seeks to systematically investigate aqueous isotope exchange of ¹⁶O-¹⁷O-¹⁸O and H-D between crystal water of hydrated Ca-sulphates (gypsum, bassanite) and principal types of Atacama desert water (water vapor, fog water, salt lakes and plant water). The purpose of this study is to determine if humidity- a key environmental parameter in deserts - can be directly inferred from the isotopic composition of gypsum hydration water (GHW) and plant water. 

After determination of the respective fractionation factors we aim to conduct experiments on possible exchange dynamics between gypsum powder and fog water. Selected transects and profiles will be investigated to test the theoretical and experimental constraints. We hypothesize that the purely mass dependent variation in ¹⁷O-excess can be used as a paleo humidity proxy.

In our pilot study we discovered that not only SO₄ but also gypsum crystal water can carry a massindependent (MIF) ₁₇O signature. This water carries a low δD signature (-100‰) implying that some crystal water in the Atacama is of stratospheric origin. In this project we aim to quantify the proportion of this stratospheric water (and thus gypsum) within natural samples and to determine how resistant this 17O enriched crystal water is to isotopic exchange. Such MIF water is probably only preserved under hyper arid conditions and may serve as a tool to identify (paleo-) hyper arid conditions.

Finally we suggest to analyze plant water to test (1) if plants utilize GHW as a water source and (2) if humidity can be inferred from the ¹⁷O-excess in leaf and stem water.