Analytical pyrolysis of bulk sandy soils and sieved fractions. Research on soil water repellency

Soil water repellency (WR) is normally induced by organic substances covering the surface of mineral particles and aggregates or that are present in interstitial spaces within the soil matrix. Despite the relevance of this phenomenon for soil functioning, there is little information about nature and molecular structure of organics related with WR. Soil samples were collected under selected species growing in a sandy soil from the Doñana National Park (SW Spain), Coak oak (Quercus suber, QS), Eagle fern (Pteridium aquilinum, PA), Pinus (Pinus pinea, PP) and Rockrose (Halimium halimifolium, HH). Soil WR and physical chemical characteristics including SOM content were assessed in fine earth soil samples (PA>PP>HH. A positive correlation was observed between WR from each sieve size fraction and soil organic matter (SOM) content. Despite the ¿a priori¿ low complexity of the soils studied, more than 200 organic compounds were released after a direct analytical pyrolysis (Py-GC/MS at 500 ºC) of soil samples and size fractions. The relation between organics in the pyrolysates and soil WR is studied using chemometric analysis that include principal component analysis (PCA) of pyrolysis compounds and groupings according to chemical family and potential biotic precursors (unspecific aromatic compounds, alkane/alkene pairs, fatty acids, lignin derived, polysaccharide derived, protein/polypeptide derived and steranes).
European Regional Development Fund and the European Bioenergy Research Institute .-- Interreg and BioenNW.-- SUPERGEN Bioenergy Hub .-- Aston University.-- Gerstel.-- CDS Analytical.-- SHIMADZU.-- Frontier Lab.-- Gas Data.-- PyroLab.-- SciMed.-- Elsevier