Validation of Cryogenic Vacuum Extraction of Pore Water from Volcanic Soils for Isotopic Analysis

Rivera, Diego; Gutierrez, Karen; Valdivia-Cea, Walter; Zambrano-Bigiarini, Mauricio; Godoy-Faúndez, Alex; Álvez, Amaya; Farías, Laura

Keywords: volcanic soils, Isotopic analysis, cryogenic vacuum extraction


Andean headwater catchments are key components of the hydrological cycle, given that they capture moisture, store water and release it for Chilean cities, industry, agriculture, and cities in Chile. However, knowledge about within-Andean catchment processes is far from clear. Most soils in the Andes derive from volcanic ash Andosols and Arenosols presenting high organic matter, high-water retention capacity and fine pores; and are very dry during summer. Despite their importance, there is little research on the hillslope hydrology of Andosols. Environmental isotopes such as Deuterium and 18-O are direct tracers for water and useful on analyzing water-soil interactions. This work explores, for the first time, the efficiency of cryogenic vacuum extraction to remove water from two contrasting soil types (Arenosols, Andosols) at five soil water retention energies (from -1500 to -33 kPa). Two experiments were carried out to analyse the impact of extraction time, and initial water content on the amount of extracted water, while a third experiment tested whether the cryogenic vacuum extraction changed the isotopic ratios after extraction. Minimum extraction times to recover over 90% of water initially in the soil samples were 40-50 min and varied with soil texture. Minimum volume for very dry soils were 0.2 mL (loamy sand) and 1 mL (loam). After extraction, the difference between the isotope standard and the isotopic values after extraction was acceptable. Thus, we recommend this procedure for soils derived from volcanic ashes.

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Título según WOS: Validation of Cryogenic Vacuum Extraction of Pore Water from Volcanic Soils for Isotopic Analysis
Título según SCOPUS: Validation of cryogenic vacuum extraction of pore water from volcanic soils for isotopic analysis
Título de la Revista: WATER
Volumen: 11
Número: 11
Editorial: MDPI Open Access Publishing
Fecha de publicación: 2019
Idioma: English
Financiamiento/Sponsor: We acknowledge the financial support from the Fondo Nacional de Desarrollo Científico y Tecnológico trough grant FONDECYT 1160656, that covered analyses, travels and material, as well publication costs. D Rivera also thanks financial support from CONICYT/