Ca isotopic composition reflect evapotranspiration and dust inputs in shallow desert soils
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Desert soils cover ~35% of the Earth’s surface and are therefore important in global processes. Despite their wide distribution, however, whether deserts are a source or sink of CO2 to the atmosphere remains unknown . The processes affecting carbonate precipitation in shallow desert soils remain an area of active research, with recent work suggesting that carbonate precipitation may occur at much shallower depths than previously thought . Here, in order to elucidate processes affecting carbonates within shallow desert soils strongly impacted by both evaporation and plant root systems, we measured the Ca isotopic composition of both the exchangeable and carbonate fractions of soil from El Dorado Valley, Nevada. We also measured the Ca isotopic composition of the incoming dust, samples beneath and immediately beside biological soil crusts, and creosote stems, roots, and leaves. Results indicate that the exchangeable fraction is heavier than the carbonate fraction, and that the deeper samples are lighter than the surface samples. Results are consistent with preferential incorporation of lighter isotopes into the carbonates with precipitation, as well as mixing of dust from different sources. Additional work is needed to further understand processes affecting fractionation of Ca isotopes in desert soils, with implications for understanding paleosols and the global carbon cycle.
Hausrath, E. M.,
Downs, B. R.,
Ca isotopic composition reflect evapotranspiration and dust inputs in shallow desert soils.