Abstract
Three solvent extraction methods (Soxhlet, sonication, and accelerated solvent extraction (ASE)) were investigated to develop an efficient technique for isolating and quantifying water repellency-inducing compounds (saturated long-chain (≥ C14) carboxylic acids, alkanes, alcohols, and sterols) from soils. The Soxhlet method was the most efficient at removing organic material from a deep yellow sand under dryland agriculture and grey sand under an Eucalyptus plantation. Although the sonication and ASE methods are time-efficient and facilitate high sample throughput, they were less effective for organic extraction (8.6% and 2.9% for dryland agriculture, 14.0% and 8.9% for plantation). While a range of chemical species from each of the four classes of soil water repellency-inducing compounds were extracted by the three methods, differences in the efficacies of the techniques were identified. Soxhlet extraction consistently recovered greater amounts of carboxylic acids, alcohols, and steroids, whereas ASE removed the largest amount of alkane. However, compounds from all classes were only identified from Soxhlet extracts of both field soils. The results indicate care is needed when comparing concentrations of compounds reported from extractions of water repellent soils using different extraction techniques.
