Comparison of two alkaline treatments in the extraction of organic compounds associated with water repellency in soil under Pinus taeda

• Published in: Geoderma 2008-12, Vol.148 (2), p.167-172
• Main Authors: Hansel, Fabricio A., Aoki, Cristiane T., Maia, Claudia M.B.F., Cunha, Anildo, Dedecek, Renato A.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Biopolymer; Cutin; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Geochemistry; Hydrolysis; Lipids; Soil and rock geochemistry; Soils; Suberin; Surficial geology; Water repellent soil
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/j.geoderma.2008.10.002

Isopropanol:NH 3 and Methanol:KOH (saponification) alkaline treatments are usually applied in the study of soil organic matter. The first is used in studies of soil water repellency, and the latter in the extraction of ester-bound lipids from soil. In this study, isopropanol:NH 3 and methanol:KOH treatments were applied separately in a solvent extracted repellent soil, in order to compare their efficiency in the extraction of water repellent compounds. The soil sample was taken from a site under a 16 year old Pinus taeda stand. The amount and class of organic compounds released by each treatment were compared using gas chromatography-mass spectrometry (GC-MS). Both treatments resulted in wettable soil after alkaline extraction. In general, alkaline treatments yielded extracts with the same class of organic compounds. Alkanoic acids, α,ω-alkanedioic acids, hydroxyalkanoic acids, aromatic compounds, and alkanols were identified, indicating the preservation of suberin and cutin biopolyester in the soil. Large differences were observed in the amounts of ω-hydroxyalkanoic acids, as well as in the quantity and distribution of dihydroxyalkanoic and trihydroxyalkanoic acids. In contrast to methanol:KOH, isopropanol:NH 3 was not efficient in the extraction of whole aliphatic biopolyesters, mainly pine cutin-related products. Methanol:KOH was more effective in hydrolysis. The presence of biopolyesters in water repellent soil under the P. taeda stand seems to play an important role in water repellency.