System for High Throughput Water Extraction from Soil Material for Stable Isotope Analysis of Water

Abstract

A major limitation in the use of stable isotope of water in ecological studies is the time that is required to extract water from soil and plant samples. Using vacuum distillation the extraction time can be less than one hour per sample. Therefore, assembling a distillation system that can process multiple samples simultaneously is advantageous and necessary for ecological or hydrological investigations. Presented here is a vacuum distillation apparatus, having six ports, that can process up to 30 samples per day. The distillation system coupled with the Los Gatos Research DLT-100 Liquid Water Isotope Analyzer is capable of analyzing all of the samples that are generated by vacuum distillation. These two systems allow larger sampling rates making investigations into water movement through an ecological system possible at higher temporal and spatial resolution.

Validation and application of a cryogenic vacuum extraction system for soil and plant water extraction for isotope analysis

“…Because of Rayleigh fractionation, we found progressively less negative values towards the end of the extraction process for both isotopes (exception: δ 18 O after 45 min extraction time). In agreement with the results of West et al (2006) and Goebel and Lascano (2012), we observed no statistically significant changes in the isotopic signatures for extraction times longer than 30 min for hydrogen isotopes and 60 min for oxygen isotopes for this specific soil type. Nevertheless, as already observed in experiment #4 neither δ 2 H nor δ 18 O of extracted water matched the isotopic signature of the applied water.…”

“…Incomplete water extraction in terms of weight was only observed for one sample, with a recovery rate still as high as 99 %. West et al (2006) determined extraction times to obtain an unfractionated water sample for sandy soils of 30 min, and 40 min for clay soils, consistent with the results of Goebel and Lascano (2012) who recommended 30 min extraction duration for a sandy clay loam. Koeniger et al (2011) applied even shorter extraction times (2.5 to 40 min), recovering the original water isotopic signature after 15 min.…”

“…In the past, the performance of extraction systems was in most cases merely verified through water extractions from soils of various grain size, water contents, or extraction duration (Ingraham and Shadel, 1992;Walker et al, 1994;Araguás-Araguás et al, 1995;West et al, 2006;Koeniger et al, 2011), separately tested for the system's extraction ports (Goebel and Lascano, 2012). However, none of the studies tested the functionality of a vacuum extraction system in the same detail as performed here.…”

“…To determine the isotopic signature of water, it is necessary to separate or extract the water from other components of the sample material (plant roots, stems and leaves, soil). In recent decades, several extraction methods have been developed: azeotropic distillation with various toxic substances such as toluene, hexane, and kerosene (Revesz and Woods, 1990;Thorburn et al, 1993), mechanical squeezing (Wershaw et al, 1966;White et al, 1985), cryogenic vacuum extraction (Dalton, 1988;Dawson and Ehleringer, 1993;Sala et al, 2000;West et al, 2006;Goebel and Lascano, 2012), the batch-method for stem water extraction (Vendramini and Sternberg, 2007), the modified vacuum extraction technique of Koeniger et al (2011), centrifugation with or without immiscible heavy liquids (Mubarak and Olsen, 1976;Batley and Giles, 1979;Barrow and Whelan, 1980;Peters and Yakir, 2008) as well as different equilibrium techniques especially for soil samples (Scrimgeour, 1995;Hsieh et al, 1998;McConville et al, 1999;Koehler et al, 2000;. Out of these, cryogenic vacuum extraction is the most widely utilized method (Ingraham and Shadel, 1992;West et al, 2006;Vendramini and Sternberg, 2007;Koeniger et al, 2011).…”

Time for cotton to uptake water of a known isotopic signature as measured in leaf petioles

“…Three petioles were sampled and reduced in size to ~13 mm, placed in an 8 mL glass screw top vial, sealed and stored in the freezer until time for extraction. To begin the extraction procedure the stored vials were removed from the freezer, the caps were removed and both the caps and the vials were placed into an ignition tube (Pyrex ® , 25 × 200 cm) and a rubber stopper was used to seal the ignition tube [33] The tube was then placed in liquid nitrogen (LN 2 ) for 20 minutes prior to placement on the distillation apparatus. The ignition tube was then placed on the distillation apparatus and vacuum was applied until the pressure read <13 Pa.…”