The relationship between soil organic matter (SOM) content and organic molecular assemblages (n‐alkane/alkenes pairs and n‐fatty acids) with soil water repellency (WR) in different sieve fractions (1–2, 0·25–1, 0·05–0·5 and <0·05 mm) was studied in sandy soils from the Doñana National Park (SW Spain) under four vegetation species: Quercus suber (QS), Pteridium aquilinum (PA), Pinus pinea (PP) and Halimium halimifolium (HH). The severity of soil WR [assessed according to the water drop penetration time (WDPT) test] was ordered according to the sequence QS > PA > PP > HH. A positive correlation was found between soil WR from each sieve fraction and SOM content. Most severe soil WR was detected in QS for all sieve fractions, followed by the finer fractions (<0·05 mm) from PA, PP and HH samples. The finer fraction had the highest SOM content, ranging between 20·9% (PP) and 46·9% (QS). Coarser PA, PP and HH soil fractions (1–2 mm) showed the highest long‐chain‐even C numbered fatty acids in the order PP > PA > HH. A significant correlation was observed between SOM content and the severity of soil WR in QS samples and finer fractions of soil under other vegetation (PA, PP and HH). Coarser fractions (1–2 mm) from PP, PA and HH 1–2 mm sieve fractions showed high severity of WR and relatively low SOM contents that could be explained by a low degree of evolution of the organic residues as seen by analytical pyrolysis, that is, higher alkane/alkene carbon preference index values and the presence of a higher diversity of fatty acid structures. Copyright © 2014 John Wiley & Sons, Ltd.

No abstract

No abstract

No abstract

No abstract

No abstract

This study comprises an innovative approach based on the combination of chromatography (analytical pyrolysis and pyrolysis compound-specific isotope analysis (Py-CSIA)), light stable isotopes, microscopy and mineralogy analyses to characterize the internal layering of coralloid speleothems from the Ana Heva lava tube in Easter Island (Chile). This multidisciplinary proxy showed that the speleothems consist of banded siliceous materials of low crystallinity with different mineralogical compositions and a significant contribution of organic carbon. Opal-A constitutes the outermost grey layer of the coralloids, whereas calcite and amorphous Mg hydrate silicate are the major components of the inner whitish and honey-brown layers, respectively. The differences found in the mineralogical, elemental, molecular and isotopic composition of these distinct coloured layers are related to environmental changes during speleothem development. Stable isotopes and analytical pyrolysis 3 suggested alterations in the water regime, pointing to wetter conditions during the formation of the Ca-rich layer and a possible increase in the amount of water dripping into the cave. The trend observed for δ 15 N values suggested an increase in the average temperature over time, which is consistent with the so-called climate warming during the Holocene.The pyrolysis compound-specific isotope analysis of each speleothem layer showed a similar trend with the bulk δ 13 C values pointing to the appropriateness of direct Py-CSIA in paleoenvironmental studies. The δ 13 C values for n-alkanes reinforced the occurrence of a drastic environmental change, indicating that the outermost Opal layer was developed under drier and more arid environmental conditions.

8Polyethylene is probably the most used plastic material in daily life and its accurate analysis is 9 of importance. In this communication the chemical structure of polyethylenes is studied in 10 detail using conventional analytical pyrolysis (Py-GC/MS), bulk stable isotopic analysis (IRMS) 11 and pyrolysis compound specific stable isotopic analysis (Py-CSIA) to measure stable isotope 12 proportions (δ reported. To the best of our knowledge this is the first application Py-CSIA to the study of a 21 synthetic polymer. This hyphenated analytical technique is a promising tool to study synthetic 22 materials, providing not only a fingerprinting, but also allowing the traceability of the 23 polymerization process and the origin of the materials. 24 25