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Elberling B.,Copenhagen University | Breuning-Madsen H.,Copenhagen University | Knicker H.,Institute for Natural Resources and Agrobiology
Geoderma | Year: 2013

Soil organic carbon (SOC) in tropical forest soils is typically characterized by fast turnover rates but mineralization might be inhibited resulting in long term organic matter protection. This study focuses on SOC trapped in iron oxides in a Paleudult (chromic Acrisol) located in the moist semi-deciduous forest in Ghana by determining the age of the SOC, quantifying the geochemical characteristics of the SOC, and estimating how much of the SOC that is bound so tightly to the oxides that it does not participate in the normal turnover of organic matter in the soil. The SOC has been characterized by using solid-state 13C nuclear magnetic resonance (NMR) spectroscopy and 14C dating. The turnover rate of the reactive SOC was determined by basal soil respiration (BSR) and a ratio between the SOC stock in the soil. The investigation shows that SOC associated with iron nodules has a 14C age of more than 21,000years and the absence of CO2 release during BSR measurements reveals that iron nodules have trapped and immobilized ~21% of SOC stored in the top 1m (~3.4kgCm-2). NMR results indicate that trapped SOC in the iron nodules is more decomposed than the organic matter in the topsoil. © 2013 Elsevier B.V. Source


Kristiansen S.M.,University of Aarhus | Dalsgaard K.,University of Aarhus | Thomsen I.K.,University of Aarhus | Knicker H.,Institute for Natural Resources and Agrobiology | And 3 more authors.
Soil Science Society of America Journal | Year: 2010

The chemistry of wet Spodosols (Aquods) differs from well-drained Spodosols. Two different hypotheses have been suggested to explain the contrasting genesis of wet spodic horizons. This study attempted to determine whether Aquods at a Danish peat-bog wetland site are a result of (i) in situ illuviation under a fluctuating water table, or (ii) degradation of a former Fe-rich, well-drained spodic horizon. Methods included soil surveys, wet chemical analyses, micromorphology, pollen analysis, and radiocarbon dating of soil organic matter (OM) fractions. Aquods, and soil material with spodic features, were exclusively found in sandy material at the margins of or underneath sphagnum peat bogs, whereas Inceptisols were found on well-drained sandy deposits only. Aluminum content was very high and Fe low in spodic materials with ortstein properties. Solid-state 13C nuclear magnetic resonance (NMR) spectra of wet sandy 2Bs horizons were dominated by alkyl C (70%) from water-insoluble OM and were clearly distinct from NMR spectra of overlying 2Bhsm material. Pollen analysis revealed that an open forest with a thick mor layer dominated until shortly after 5000 yr BP, when sphagnum was first recorded. Radiocarbon ages of bulk soil C in the spodic horizons had mean residence times of 4500 to 4400 yr. Accordingly, the spodic B horizon was probably formed by strong in situ illuviation of Al-OM complexes before the sphagnum peat bog formation. This suggests that spodic material formation and thus strong C accumulation underneath this Danish peat bog took place for a limited period, only in susceptible parent material, and at the margins of the expanding peat bog. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA All rights reserved. Source


Sutherland K.,Philadelphia Museum of Art | Del Rio J.C.,Institute for Natural Resources and Agrobiology
Journal of Chromatography A | Year: 2014

A variety of lac resin samples obtained from artists' suppliers, industrial manufacturers, and museum collections were analysed using gas chromatography mass spectrometry (GCMS) and reactive pyrolysis GCMS with quaternary ammonium reagents. These techniques allowed a detailed chemical characterisation of microgram-sized samples, based on the detection and identification of derivatives of the hydroxy aliphatic and cyclic (sesquiterpene) acids that compose the resin. Differences in composition could be related to the nature of the resin, e.g. wax-containing (unrefined), bleached, or aged samples. Furthermore, differences in the relative abundances of aliphatic hydroxyacids appear to be associated with the biological source of the resin. The diagnostic value of newly characterised lac components, including 8-hydroxyacids, is discussed here for the first time. Identification of derivatised components was aided by AMDIS deconvolution software, and discrimination of samples was enhanced by statistical evaluation of data using principal component analysis. The robustness of the analyses, together with the minimal sample size required, make these very powerful approaches for the characterisation of lac resin in museum objects. The value of such analyses for enhancing the understanding of museum collections is illustrated by two case studies of objects in the collection of the Philadelphia Museum of Art: a restorer's varnish on a painting by Luca Signorelli, and a pictorial inlay in an early nineteenth-century High Chest by George Dyer. © 2014 Elsevier B.V. Source


Badia D.,University of Zaragoza | Marti C.,University of Zaragoza | Aguirre A.J.,University of Zaragoza | Aznar J.M.,University of Zaragoza | And 2 more authors.
Catena | Year: 2014

Soil organic carbon and nutrient content are analysed at topsoil cm-scale in a Rendzic Phaeozem from an Aleppo pine forest in semiarid Central Ebro Basin (NE-Spain). Soil depth affected by a severe wildfire is studied immediately after burning and a year later, trying to differentiate the heat shock and the ash/charcoal deposition effects. One week after the wildfire, soil organic carbon content (SOC) on burned topsoil decreases significantly at 0-1. cm soil depth. Wildfire degrades polysaccharides and proteins and eliminates, or at least reduces, biogenic compound markers, derived from lignin and lipids, but only above 2. cm soil depth. A characteristic cracking in the alkane series, as well as the presence of pyrogenic polycyclic aromatic hydrocarbons are also observed in the burned 1st cm topsoil. Below 2. cm the fire has little or no effect in soil organic matter molecular assemblage. Calcium, magnesium, potassium, ammonium, nitrate and phosphorous increased significantly a week after the fire, in the first cm soil depth. These modifications detected immediately after the fire (SOC decrease and nutrient increase) are related to the heat released during the severe wildfire. One year after the wildfire, SOC in the 1st cm of burned topsoil regain the same level to that observed in unburned sites, which could be a consequence of burned residues and black ash incorporation and even new inputs on soil surface derived from the reblooming processes, which starts after the fire. With the exception of nitrates whose concentration is higher in burned plots than the control ones within 0-3. cm of soil depth studied, nutrient concentration relatively decreased one year after the wildfire. Despite this decrease, fire effect (memory) still remains at the 1st cm topsoil, with many nutrients having comparatively high concentration in the burned soils under semiarid climate. © 2013 Elsevier B.V. Source


Simmler M.,Lincoln University at Christchurch | Simmler M.,ETH Zurich | Ciadamidaro L.,Institute for Natural Resources and Agrobiology | Schulin R.,ETH Zurich | And 5 more authors.
Environmental Science and Technology | Year: 2013

Repeated application of Cd-rich phosphate fertilizers can lead to the accumulation of this nonessential element in soil. This can result in increased plant uptake, with possible breaches of food or feed safety standards. We aimed to determine whether lignite (brown coal) can reduce Cd solubility and plant uptake in New Zealand pasture soils. In batch sorption experiments, we tested the capacity of lignite and lignite-soil mixtures to sorb Cd at various soil pH and Cd loadings. Over a pH range of 4-7, Cd sorption by lignite was 1-2 orders of magnitude greater than by a typic immature pallic soil containing 2% carbon. The addition of 5 wt % lignite to a range of soils revealed that lignite addition was most effective in reducing soluble Cd in soils with low pH. In a greenhouse experiment, we tested the effect of lignite on the accumulation of Cd and other elements by perennial ryegrass, Lolium perenne (L.). The addition of just 1 wt % lignite to the aforementioned soil reduced plant Cd uptake by 30%, without adversely affecting biomass or the uptake of essential nutrient elements including copper and zinc. This may be due to preferential binding of Cd to organic sulfur in lignite. © 2013 American Chemical Society. Source

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