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Kaal J.,Institute Ciencias del Patrimonio Incipit | Nierop K.G.J.,University Utrecht | Kraal P.,Southern Cross University of Australia | Preston C.M.,Natural Resources Canada
Organic Geochemistry | Year: 2012

Tannins account for a significant proportion of plant biomass and are likely to contribute to the residues formed by incomplete biomass combustion (black carbon, BC). Nonetheless, the molecular properties of thermally modified tannins have not been investigated in laboratory charring experiments. We applied conventional analytical pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and thermally assisted hydrolysis and methylation (THM-GC-MS) to investigate the effects of heat treatment with a muffle furnace on the properties of condensed tannins (CT) from Corsican pine (Pinus nigra) needles. Py-GC-MS showed a decrease in the relative abundance of the 1,2,3-trihydroxybenzenes (pyrogallols) at ≥300 °C and of the dihydroxybenzenes (mainly catechols) at ≥350 °C due to dehydroxylation of the CT B ring. Further dehydroxylation led to formation of monohydroxybenzenes (phenols), which showed a strong enrichment between 350 and 400 °C and, at higher temperatures, to a series of monocyclic and polycyclic aromatics [benzene, alkyl benzenes and polycondensed aromatic hydrocarbons (PAHs)]. Degradation of the A ring could not be recognized via Py-GC-MS, probably because of the poor chromatographic behavior of 1,3,5-trihydroxybenzenes (phloroglucinols). The progressive dehydroxylation and eventual polycondensation of the CT B ring was corroborated using THM-GC-MS. In addition, with THM-GC-MS the thermal rearrangement of CT A rings at 300 °C and higher was inferred from the relative abundance of 1,3,5-trimethoxybenzenes (methylated phloroglucinol derivatives). These compounds were observed at moderate/high temperature (up to 450 °C) and can not be produced from THM of lignin, suggesting that they may be markers of CT in natural BC samples. © 2012 Elsevier Ltd.

Kaal J.,Institute Ciencias del Patrimonio Incipit | Wagner S.,University of Florida | Jaffe R.,Florida International University
Journal of Analytical and Applied Pyrolysis | Year: 2016

This study aimed to assess the molecular properties of dissolved organic matter (DOM) and dissolved black carbon (DBC) using analytical pyrolysis (Py-GC-MS). The sample set was comprised of ultrafiltered DOM (UDOM) from North American headwater streams associated with Long Term Ecological Research network sites. Pyrolysis products for each UDOM sample were categorized as being sourced from non-pyrogenic sources and DBC. Major non-pyrogenic components of the headwater stream UDOM were comprised of phenolic compounds derived from lignin and chitin markers from microbial biomass, and their relative contributions indicated differences in organic matter dynamics of these ecosystems. The DBC pyrolyzates included benzene, PAHs and benzonitriles, which accounted for 12.5. ±. 4.5% of total quantified peak area (TPQA), and decreased in the order Alaskan boreal forest (19%), Alaskan tundra (17%), Appalachian deciduous forest (11%), Colorado alpine tundra (9%), Puerto Rican mountainous tropical rainforest (9%) and Kansas tallgrass prairie (7%). Pyrolysis products were compared to DBC content as determined by the benzenepolycarboxylic acid (BPCA) method. Although Py-GC-MS has quantitative limitations, this technique can detect weakly condensed and other DBC structures which fall outside of the BPCA analytical window. © 2016 Elsevier B.V.

Calvelo Pereira R.,Massey University | Kaal J.,Institute Ciencias del Patrimonio Incipit | Camps Arbestain M.,Massey University | Pardo Lorenzo R.,University of Santiago de Compostela | And 5 more authors.
Organic Geochemistry | Year: 2011

Different analytical techniques were used to find the most reliable and economic method for determining the labile fraction of C in biochar. Biochar was produced from pine, poplar and willow (PI, PO and WI, respectively) at two temperatures (400 and 550°C) and characterised using spectroscopic techniques [solid state 13C nuclear magnetic resonance spectroscopy (NMR)], molecular markers [pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS)], thermogravimetry (TG), elemental composition and wet oxidation (potassium permanganate and potassium dichromate). Short term incubation (110h) of an A horizon from an Umbrisol amended with the biochar samples at two doses (7.5 and 15tha-1) was also carried out to provide supplementary information on the influence of biochar-soil interaction on CO2 evolution. Spectroscopic analysis demonstrated that the degree of biochar carbonisation was influenced by the type of feedstock and heating conditions and followed the order WI-400

Calvelo Pereira R.,Massey University | Camps Arbestain M.,Massey University | Kaal J.,Institute Ciencias del Patrimonio Incipit | Vazquez Sueiro M.,Massey University | And 2 more authors.
European Journal of Soil Science | Year: 2014

The stability of biochar, a form of charcoal intentionally made to be added to soil to sequester carbon (C) and improve its function, remains unclear. As it is not feasible to perform long-term (decades, centuries) laboratory experiments to assess biochar evolution after soil amendment, the study of ancient archaeological charcoals can help to identify characteristics (and possibly molecular markers) associated with the decomposition and preservation dynamics of biochar in specific pedoclimatic environments. In this study, the chemical composition of the organic carbon fractions of three charcoals from pre-European Māori gardens of New Zealand (buried >25cm depth) was thoroughly assessed. Complementary short-term incubations of charcoals in sand were used to (i) evaluate the stability of C in the short-medium term, (ii) model its mineralization processes and (iii) estimate the C turnover. Elemental analysis, thermogravimetric analysis (TG), X-ray photoelectron spectroscopy (XPS), solid-state 13C nuclear magnetic resonance (NMR) and pyrolysis gas chromatography/mass spectroscopy (Py-GC-MS) gave consistent results in describing the charring intensity and the degree of polycondensation of these charcoals. The oldest buried deposit (770±50years BP) still retained un-charred or weakly charred lignocellulosic material, indicating that such material survived decomposition processes for several centuries. The amount of organic C mineralized in 109days was <0.5% of the initial charcoal-C. No differences in MRT among samples were detected in spite of inferred differences in thermal impact. Longer-term incubations are needed to obtain better estimates of C turnover rates in charred material. © 2013 British Society of Soil Science.

Lopez-Merino L.,Brunel University | Silva Sanchez N.,University of Santiago de Compostela | Kaal J.,Institute Ciencias del Patrimonio Incipit | Lopez-Saez J.A.,Institute Historia CCHS | Martinez Cortizas A.,University of Santiago de Compostela
Global and Planetary Change | Year: 2012

There is a wealth of studies dealing with the reconstruction of past environmental changes and their effects on vegetation composition in NW Iberia, but none of them have focused specifically on the post-disturbance dynamics (i.e. the type of response) of the vegetation at different space and time scales. To fill this gap, we analysed the record of pollen and non-pollen palynomorphs (NPP) of a 235-cm thick colluvial sequence spanning the last ~13,900years. The aims were to detect the changes in vegetation, identify the responsible drivers and determine the type of responses to disturbance. To extract this information we applied multivariate statistical techniques (constrained cluster analysis and principal components analysis on transposed matrices, PCA tr) to the local (hydro-hygrophytes and NPP) and regional (land pollen) datasets separately. In both cases the cluster analysis resulted in eight local and regional assemblage zones, while five (local types) and four (regional types) principal components were obtained by PCA tr to explain 94.1% and 96.6% of the total variance, respectively. The main drivers identified were climate change, grazing pressure, fire events and cultivation. The vegetation showed gradual, threshold and elastic responses to these drivers, at different space (local vs. regional) and time scales, revealing a complex ecological history. Regional responses to perturbations were sometimes delayed with respect to the local response. The results also showed an ecosystem resilience, such as the persistence of open Betula-dominated vegetation community for ~1700years after the onset of the Holocene, and elastic responses, such as the oak woodland to the 8200calyr BP dry/cold event. Our results support the notion that palaeoecological research is a valuable tool to investigate ecosystem history, their responses to perturbations and their ability to buffer them. This knowledge is critical for modelling the impact of future environmental change and to help to manage the landscape more sustainably. © 2012 Elsevier B.V.

Kaal J.,Institute Ciencias del Patrimonio Incipit | Schneider M.P.W.,University of Zürich | Schmidt M.W.I.,University of Zürich
Biomass and Bioenergy | Year: 2012

Rice straw and chestnut wood were heated between 200 and 1000 °C (T CHAR) to produce Black C 'thermosequences'. The molecular properties of the charred residues were assessed by pyrolysis-GC/MS to investigate the relation between charring intensity and pyrolysis fingerprint. Samples obtained at T CHAR > 500 °C (wood) or >700 °C (straw) gave low quality pyrograms and poor reproducibility because of high thermal stability, but pyrolysis-GC/MS allowed to track the thermal degradation of the main biocomponents (polysaccharides, lignin, methylene chain-based aliphatics, triterpenoids, chlorophyll and proteins) in the lower temperature range, mostly occurring between T CHAR 250 and 500 °C. With increasing T CHAR, the charred residues of these biocomponents lose characteristic functional groups, aromatise and finally condense into non-pyrolysable biomass. The proportions of the pyrolysis products of unspecific origin (benzene, toluene, PAHs, etc.), increase with charring intensity, while the ratios that reflect the abundance of alkyl cross-linkages between aromatic moieties (e.g. benzene/toluene, naphthalene/alkylnaphthalene) decrease. These results provide the guidelines to using pyrolysis-GC/MS for the molecular characterisation of different components in Black C and biochar, which is an important parameter for predicting Black C/biochar behaviour in soil. Results are consistent with earlier studies of these samples using the BPCA (benzenepolycarboxylic acid) method and the ring current-induced 13C benzene chemical shift NMR (Nuclear Magnetic Resonance) approach. Pyrolysis-GC/MS provides more information on molecular structures in the low temperature range (T CHAR ≤ 500 °C) while the BPCA and NMR ring current methods provide more reliable estimations of charring intensity, especially at higher temperatures (T CHAR ≥ 500 °C). © 2012 Elsevier Ltd.

Suarez-Abelenda M.,University of Santiago de Compostela | Kaal J.,Institute Ciencias Del Patrimonio Incipit | Camps-Arbestain M.,Massey University | Knicker H.,CSIC - Institute of Natural Resources and Agriculture Biology of Seville | MacIas F.,University of Santiago de Compostela
Soil Research | Year: 2014

Samples from a colluvial soil rich in pyrogenic material (black C, BC) in north-west Spain were subjected to K2Cr2O7 and KMnO4 oxidation and the residual soil organic matter (SOM) was NaOH-extracted and analysed using analytical pyrolysis-gas chromatography-mass spectroscopy (Py-GC/MS) and solid-state 13C cross-polarisation magic angle spinning-nuclear magnetic resonance (13C CP MAS-NMR) in order to study the susceptibility of different SOM fractions (fresh, degraded/microbial, BC and aliphatic) towards these oxidising agents. Untreated samples that were NaOH-extracted were also analysed. The Py-GC/MS and 13C NMR indicated that KMnO4 promotes the oxidation of carbohydrate products, mostly from degraded/microbial SOM and lignocellulose, causing a relative enrichment of aliphatic and aromatic structures. Residual SOM after K2Cr2O7 oxidation contained BC, N-containing BC and aliphatic structures. This was corroborated by a relatively intense resonance of aromatic C and some signal of alkyl C in 13C NMR spectra. These results confirm that dichromate oxidation residues contain a non-pyrogenic fraction mainly consisting of aliphatic structures. © 2014 CSIRO.

Kaal J.,Institute Ciencias del Patrimonio Incipit | Schellekens J.,University Of Sa&Tild | Nierop K.G.J.,University Utrecht | Muller J.,Gulf
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2014

The Lynch's Crater (NE Australia) deposit is a key information source on Late-Quaternary palaeoenvironmental change, including human-induced deforestation since the arrival of Aboriginals, megaherbivore extinction and southern hemisphere tropical climate dynamics. This study adds to the important dataset available for the site by assessing the molecular composition of organic matter in the record using pyrolysis-GC-MS to elucidate ecological and hydrological conditions since 55. ka BP.Pyrolysates were dominated by methylene chain compounds (MCCs) and lignin products (methoxyphenols). Concomitant increases in MCCs and aquatic source indicators (biogenic opaline silica, Si:Al ratio, SEM-visible debris of sponges and diatoms and aquatic pollen taxa), which roughly coincide with abrupt climate events in GISP2 δ18O (Heinrich event H3, H1, 8.2ka and oscillations at 33-36ka BP), reflect transitions from peat (dominated by lignin from terrestrial plants) to lacustrine (MCCs from aquatic plants) conditions. The evidence points towards wet conditions causing the accumulation of layers rich in inorganic sediment during H events, favouring the hypothesis of a southward ITCZ shift, rather than an ENSO-induced northward shift, as the underlying mechanism. This contradicts previous studies using the "degree of peat humification" index (DPH). We measured DPH and the extracts and residues by PY-GC-MS, to better understand the validity of this surface moisture proxy. Paradoxically, high DPH corresponds to the relatively young (<15ka) ombrotrophic peat environment, as DPH relies on the proportion of extractable carbohydrates concentrated in this part of the core, while deeper and unarguably more evolved layers are comprised of alkali-inextricable lignin and MCCs. Therefore, DPH does not accurately reflect humidity-controlled degradation/preservation dynamics and its use for studying climate change in complex records, such as Lynch's Crater, is cautioned. Finally, the decoupling of humidity conditions from changes in regional arboreal vegetation supports the hypothesis of an anthropogenic- rather than climate-driven shift towards sclerophyllous vegetation since 45ka, but the hydroseral complexity of the system demands caution on this matter. © 2014 Elsevier B.V.

We present the results of the on-going effort to measure the orientation of a comprehensive number of churches in Galicia. We have measured the orientation of the apse of 25 churches so far. Although the results are still preliminary we can obtain a number of interesting conclusions. The churches in our sample present a similar trend to those of the same period recently measured in the rest of the Iberian Peninsula. There is a general tendency towards orientations slightly north of due equinoctial east. This tendency is consistent with a use of sunrise on March 25th at the time of construction to orientate the building. In this respect, the Cathedral of Santiago may be a paradigmatic case. There are exceptions to this rule and the most interesting would be that early churches do appear to be facing westwards instead of eastward. Finally, the orientation of San Xes de Francelos allows identification with the group of churches of Asturias. © 2015, Associacao Portuguesa para o Desenvolvimento Regional (APDR). All rights reserved.

Kaal J.,Institute Ciencias Del Patrimonio Incipit | Martinez Cortizas A.,University of Santiago de Compostela | Reyes O.,University of Santiago de Compostela | Solino M.,National Institute for Agriculture and Food Research and Technology INIA
Journal of Analytical and Applied Pyrolysis | Year: 2012

Gorse species (Ulex sp.) are ubiquitous in the shrublands of NW Spain and have the potential to become key players in an integral biofuel/biochar program in NW Spain. Here we present molecular characterization (using pyrolysis-GC/MS) of a biochar "thermosequence" obtained by laboratory heating of Ulex europaeus wood in a muffle furnace between 200 and 600°C (T CHAR). Low temperature chars (T CHAR ≤ 350°C) produced significant amounts of pyrolysis products of which the precursor biopolymer could be recognized, while high-temperature chars (T CHAR ≥ 400°C) produced mainly phenols and monocyclic and polycyclic aromatic hydrocarbons, which are not specific for any biopolymer. Carbohydrate could hardly be recognized at T CHAR ≥ 350°C. The thermal rearrangement of polyphenols, mainly lignin, was reflected in more detail (1) C 3-side chain shortening and probably depolymerization (T CHAR 200-350°C), (2) demethoxylation of syringyl and probably also some guaiacyl lignin (T CHAR 300-400°C), (3) elimination of virtually all remaining methoxyl groups (T CHAR 350-400°C), through dehydroxylation and demethoxylation, (4) almost complete dehydroxylation of lignin and other biopolymers (T CHAR 400-500°C), (5) progressive condensation into polyaromatic structures (T CHAR 300-500°C) and (6) partial elimination of alkyl bridges between (poly)aromatic moieties (T CHAR 450-500°C). These results were supported by Fourier transform infrared spectroscopy (FTIR) of the same samples. We conclude that pyrolysis-GC/MS can be used as a rapid molecular screening method of gorse-derived biochar. Molecular properties elucidation is an essential part of predicting the stability and agronomical behavior of gorse-derived biochar after future implementation in soils. © 2012 Elsevier B.V. All rights reserved.

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