Fire impact on forest soils evaluated using near-infrared spectroscopy and multivariate calibration

L'évaluation des propriétés physicochimiques des sols forestiers affectés par des feux a été réalisée en utilisant la spectroscopie proche infra-rouge (SPIR) couplée avec des méthodes chimiométriques. Pour décrire les propriétés du sol, les mesures prises comprennent le carbone organique total sur phase solide, le contenu d'azote total, le carbone organique et l'absorbance spécifique à 254 et 280nm des substances humiques, le carbone organique dans des acides humiques et fulviques, des concentrations de NH4+, Ca2+, Mg2+, K+ et le phosphore en plus des spectres de PIR. Un indice de répétition d'incendies a été défini et calculé selon les régimes de feux affectant des sols. Ce calcul inclut l'occurrence des incendies et le temps écoulé depuis le dernier feu. Cette étude montre que la spectroscopie PIR pourrait être utilisée pour le contrôle de qualité des sols, particulièrement pour la prédiction quantitative du carbone organique total, l'azote total, le carbone organique dans les substances humiques, les concentrations de phosphore, Mg2 +, Ca2 + et NH4 + et des substances humiques UVSA254. Une nouvelle validation dans ce domaine est nécessaire cependant pour une bonne prédictions de K+, du carbone organique dans des acides humiques et fulviques et les substances humiques UVSA280. De plus, la SPIR couplée avec la régression PLS peut aussi être utile pour prévoir l'indice de répétition de feu et pour déterminer sa variabilité spatiale. Aussi cette méthode peut être utilisée pour dresser la carte de secteurs plus ou moins brûlés et pour adapter les techniques de réhabilitation, comme la reconstitution de l'humus avec des enrichissements organiques (composts) ou le reboisement. Finalement, on peut considérer que notre indice de répétition est représentatif de l'état des sols. / The assessment of physico-chemical properties in forest soils affected by fires was evaluated using near infrared reflectance (NIR) spectroscopy coupled with chemometric methods. In order to describe the soil properties, measurements were taken of the total organic carbon on solid phase, the total nitrogen content, the organic carbon and the specific absorbences at 254 and 280nm of humic substances, organic carbon in humic and fulvic acids, concentrations of NH4+, Ca2+,Mg2+, K+ and phosphorus in addition to NIR spectra. Then, a fire recurrence index was defined and calculated according to the different fires extents affecting soils. This calculation includes the occurrence of fires as well as the time elapsed since the last fire. This study shows that NIR spectroscopy could be considered as a tool for soil monitoring, particularly for the quantitative prediction of the total organic carbon, total nitrogen content, organic carbon in humic substances, concentrations of phosphorus, Mg2+, Ca2+ and NH4+ and humic substances UVSA254. Further validation in this field is necessary however, to try and make successful predictions of K+, organic carbon in humic and fulvic acids and the humic substances UVSA280. Moreover, NIR coupled with PLS can also be useful to predict the fire recurrence index in order to determine the spatial variability. Also this method can be used to map more or less burned areas and possibly to apply adequate rehabilitation techniques, like soil litter reconstitution with organic enrichments (industrial composts) or reforestation. Finally, the proposed recurrence index can be considered representative of the state of the soils

Apport de leinfrarouge a transformee de Fourier et du couplage chromatographie gazeuse/infrarouge a transformee de Fourier a l'etude de systemes chimiques complexes

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Solid/Liquid partitioning coefficient of hydrophobic persistent organic pollutants (POP) for different sediments with passive sampler

International audienceThe dredged contaminated sediment are considered as waste and landfilled. Use as public work material (filling, noise protection slope, landscape mound) is considered. The environmental impact must be assessed, and in particular the emission of persistent organic pollutants (POP) in percolating water. The assessment of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) is problematic since their concentration in water in equilibrium with the sediment is below the limit of quantification of routine water analysis. This work describes a laboratory method for evaluation of hydrophobic POPs concentration in water by passive sampling, and a non-linear partition coefficient model between the sediment solid phase and the aqueous phase

Cinétiques de désorption des composés organiques hydrophobes pour différents sédiments dragués contaminés

Dredged contaminated sediments are considered as waste and landfilled. Reuse in public works is considered. The environmental impact must be assessed, and in particular the emission of persistent organic pollutants (POPs) in percolating water. The kinetics of desorption of POPs from soil or sediment particles is important both from environmental and analytical points of view. Desorption rates of POPs are important in predicting the transport of these compounds between different environmental media, their bioavailability, and the effect of remediation processes at contaminated sites. It has been shown that a large part of POPs (generally over 50 %) are strongly adsorbed to the condensed organic matter (char or soot - also called black carbon) with very slow desorption kinetics. However, today the risk assessment and the regulations are based on the total POPs content. For high contamination, reuse is there from not allowed (in fill, building materials, bricks, and mounds). A kinetic desorption approach could reassess management of contaminated materials taking into account the labile (rapidly-desorbed) fraction instead of the total POP content

Mobility of PAHs, PCBs and TPHs from Fresh and Aged Dredged Sediments

International audienc

Etude de la composition phospholipidique de bactéries hydrocarbonoclastes marines cultivées sur différentes sources de carbone et application in situ

Les phospholipides sont les principaux constituants des membranes bactériennes. Par ailleurs, les croissances in vitro sur des xénobiotiques comme les n-alcanes, les composés aromatiques et les alcools aboutissent généralement à une réponse adaptative des membranes bactériennes. Cette réponse est révélée par une modification majeure de la composition des acides gras phospholipidiques. À propos de ce travail, nous avons étudié différentes souches bactériennes hydrocarbonoclastes cultivées in vitro sur des substrats qui étaient soit solubles, soit hydrophobes, et ce afin de déterminer les effets des xénobiotiques sur les acides gras phospholipidiques mais également sur les phospholipides intacts. Par la suite, nous avons proposé une expérimentation in situ impliquant l'élucidation structurale et l'analyse quantitative des acides gras et des lipides polaires extraits de sédiments marins. Ces sédiments ont été prélevés à proximité d'une raffinerie durant l'hiver et la fin du printemps afin d'estimer les influences respectives des teneurs en hydrocarbures et de la contribution lipidique des macrophytes au cours des saisons.AIX-MARSEILLE3-BU Sc.St Jérô (130552102) / SudocSudocFranceF

Passive sampling to assess the availability of hydrophobic organic pollutants in fresh and matured contaminated sediments

Dredged contaminated sediments are considered as waste. Traditional solutions to the management of these sediments are dumping at sea, disposal to landfills or use as public work materials (back-filling, noise protection slope, landscape mound). To assess its potential impacts on human health and the environment, dredged material must be characterized, particularly with respect to the emission of persistent organic pollutants in percolating water. Some questions arise concerning the effect of disposal duration on the fate and bioavailability of persistent organic contaminants. Our study aims to determine the availability of persistent organic contaminants (16 polycyclic aromatic hydrocarbons - PAHs and 40 polychlorinated biphenyls -PCBs) in 3 fresh or matured (1.5 year) dredged sediments. Sediments were characterized in terms of texture, organic carbon content, black carbon content and oil content. The free dissolved concentration of contaminants in pore water was determined by passive samplers with low-density polyethylene (LDPE). The ratio of the total concentration (determined by classical solvent extraction) with the free dissolved concentration gives the sediment-water partition coefficient (Kd) of these contaminants in fresh or matured sediment. Apparently, higher partition coefficients are observed for matured sediments. A similar conclusion emergr from complementary tests (Tenax desorption and standard percolation test) carried on fresh and matured sediments. Oxydation phenomenon of minerals, inclusion into nanopores, enhancement of weathering degree of oil and ageing phenomenon (incorporation into organic carbon matrix) could explain the higher partition coefficient for matured sediments. The suitability of LDPE passive samplers to assess the difference in sorption capacity of fresh and matured sediment will be presented

Structural characterization of Argania spinosa Moroccan wooden artifacts during natural degradation progress using infrared spectroscopy (ATR-FTIR) and X-Ray diffraction (XRD)

International audienceThe present work is focused on spectroscopic study of four samples of Argan wooden artifact pertaining to the 17 th , 18 th , 20 th and 21 st centuries. The objective is to characterize their unknown structures by the study of their non degraded parts and to investigate changes occurred in their degraded parts due to the natural degradation process. Attenuated total reflectance Fourier transform infrared spectroscopy gauges the presence of many functional groups related to cellulose I and/or II (OH, CO -C and-CH 2), hemicelluloses (particularly C¼O acetoxy ester band at 1732 cm À1), and lignin (OH phenolic, C ar-O and C¼C ar) and provides qualitative information on the state of wood alteration by informing on the evolution of new former C¼O bands. The degree of conversion to carbonyl group, especially quinone or p-quinone at 1650 cm À1 , is correlated to lignin degradation, while the absence of the C¼O acetoxy absorption is ascribable to occurred deterioration in hemicelluloses, and partial degradation of cellulose with enhancement of the C¼O region between 1730-1630 cm À1. X-ray diffraction determines the presence of two forms of cellulose; amorphous cellulose at 18.5 2θ and predominant crystalline cellulose I β at 2θ ¼ 22.6 which characterized by an intense peak. The decrease of crystallinity index values confirms the deterioration level and obvious changes in crystallinity level. However, the microcrystalline structure appears unaltered because no significant changes were observed for calculated cristallite seize. The obtained results depend on the prolonged time of ageing, natural deterioration phenomena, and wood part (internal or external) that is exposed to degradation. The combination of these two methods is useful for an accurate estimation of the degradation level of argan wood

Polyethylene passive samplers to determine sediment–pore water distribution coefficients of persistent organic pollutants in five heavily contaminated dredged sediments

Pore concentration and partition coefficients of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were determined in sediments from five distinct contaminated sites in France (marine harbour, rivers canals and highway sedimentation tank). The assessment of the risk caused by such micropollutants requires, in most cases, the measurement of their availability. To assess this availability, low density polyethylene (LDPE) membrane samplers were exposed to these sediments under constant and low-level agitation over a period of 46 days. Freely dissolved pore water contaminant concentrations were estimated from the concentration at equilibrium in the LDPE membrane. The depletion of contaminants in the sediments was monitored by the use of performance reference compounds (PRCs). Marked differences in freely dissolved PAH and PCB concentrations and resulting sediment–pore water partition coefficients between these five sediments were observed. Data set was tested onto different empirical and mechanistic models. As final findings, triple domain sorption (a total organic carbon, black carbon and oil phase model) could model PCB data successfully whereas the best fitting for PAH partitioning was obtained by Raoult's Law model