A simple system for extracting water from soil and plant substrates -effects of substrate-derived exchangeable hydrogen on isotope ratios of extracted water-

Extraction of water from soil and plants for isotope analysis is a key step in hydrological and ecological studies. Current water extraction systems are either inefficient or complex and expensive, and depletion of heavy isotopes such as H-2 (deuterium) in extracted water relative to spiked water is commonly observed. We constructed a simple water extraction system using commercially available parts and assessed its sample capacity and performance. We spiked 1% (HHO)-H-1-H-2 aliquots into soil and plant substrates and analyzed water recovery and isotope exchange of deuterium in spiked water with exchangeable hydrogen in substrates. The water extraction system required 3 days to extract 100% of the spiked water volume when heated at 60 degrees C for plant samples and 100 degrees C for soil samples. Deuterium was depleted in extracted water relative to spiked water due to dilution by substrate-derived exchangeable hydrogen. The exchangeable hydrogen content varied among substrates, causing variation in the degree of deuterium depletion. The simple and low-cost system for water extraction from soil and plant samples decreases barriers to isotope analysis. Estimating substrate-derived exchangeable hydrogen is useful for accounting for deuterium depletion during water extraction.