Search results for "Total organic Carbon"
showing 10 items of 139 documents
A comparison of extraction procedures for water-extractable organic matter in soils
2014
The characteristics of dissolved organic matter (DOM) in soils are often determined through laboratory experiments. Many different protocols can be used to extract organic matter from soil. In this study, we used five air-dried soils to compare three extraction methods for water-extractable organic matter (WEOM) as follows: (i) pressurised hot-water-extractable organic carbon (PH-WEOC), a percolation at high pressure and temperature; (ii) water-extractable organic carbon (WEOC), a 1-hour end-over shaking; and (iii) leaching-extractable organic carbon (LEOC), a leaching of soil columns at ambient conditions. We quantified the extraction yield of organic carbon; the quality of WEOM was charac…
The Use of Carbon Stable Isotopes to Investigate the Origin and Distribution of Suspended and Sedimentary Organic Matter in a Semi-enclosed Mediterra…
2001
The natural stable isotope values of different primary sources have been used to trace the fate of organic carbon that enters in the marine food webs of Stagnone di Marsala (Italy). Water and sediment samples were collected monthly (March 1996 – February 1997) at 3 stations, characterized by different amounts of vegetal cover and analysed to determine total organic matter (OM), phytopigments, biopolymeric organic carbon (BPC) and stable carbon isotopic composition (δ13C), the latter measured also in main primary producers. Sedimentary OM accumulated in summer, while total suspended organic matter reached highest concentrations in May and December. The concentration of chlorophyll-a carbon i…
Origin and distribution of suspended organic matter as inferred from carbon isotope composition in a Mediterranean semi-enclosed marine system
1999
The origin and distribution of suspended organic matter, the trophic features and the stable carbon isotopic composition of particulate organic carbon (POC) were studied monthly in a Western Mediterranean semi-enclosed basin. Sampling stations were selected as a function of wind-exposure and the degree of vegetation cover and then compared with an adjacent unvegetated site. The predominant vegetation was seagrass (Posidonia oceanica and Cymodocea nodosa) and Caulerpa prolifera. Water samples were analyzed for total suspended matter (inorganic and organic fractions), photosynthetic pigments (chlorophyll-a and phaeopigments), dissolved organic carbon, particulate organic carbon and their isot…
Sources of carbon and dietary habits of new Lessepsian entry Brachidontes pharaonis (Bivalvia, Mytilidae) in the western Mediterranean
2003
The sources of carbon and the dietary habits of Brachidontes pharaonis (Mollusca, Bivalvia), a new Lessepsian entry in the western Mediterranean, living in a cooling vat of a saltworks system in western Sicily (MED), were assessed by estimating throughout a season the relative abundance of a stable carbon isotope (δ13C) in particulate organic matter (POM), sedimentary organic matter (SOM), primary organic matter sources (seagrasses, sand microflora, macroalgae), Brachidontes pharaonis and its biodeposition material. In the saltworks the most enriched primary food source potentially fuelling the saltworks food web was Cymodocea nodosa (seasonal average -7.9±0.6‰), Laurencia papillosa and Cys…
In-situ reflectance spectroscopy - analysing techniques for high-resolution pigment logging in sediment cores
2003
The temporal resolution of marine proxy data is limited by analytically required sample size. We present in-situ reflectance spectroscopy techniques (usually applied in remote sensing) to analyse the organic fraction of marine and terrestrial sediment. From absorption band depths, photosynthesis pigment variations are derived for sediments from the upwelling region off Peru, where productivity is related to the annual variability of El Nino strength. Quantitative estimations of diagenetic photosynthesis pigments derived from absorption band analysis in reflectance spectra are highly correlated to organic carbon content. The ratio of pigment fractions is related to chlorine concentration and…
Characterization of organic matter in topsoils under rain forest and pasture in the eastern Brazilian Amazon basin
1999
In topsoils under forest and 7-, 12- and 17-year-old pastures, organic matter was characterized by analysing C and N distribution in particle-size fractions, the C decomposition rates of soil and particle-size fractions and by employing density-fractionation of macro-organic matter (>150 μm). The C and N associated with clay fractions increased with increasing age of pasture. The weight (%) of macro-organic matter and its heavy fractions (>1.37 g cm–3) also increased with increasing age of pasture. However, in a long-term incubation (100 days), these changes seemed to involve an increase in the C decomposition rate in the topsoil of the oldest pasture. Using the C decomposition rates of par…
Comprehensive dataset of shotgun metagenomes from oxygen stratified freshwater lakes and ponds
2021
Stratified lakes and ponds featuring steep oxygen gradients are significant net sources of greenhouse gases and hotspots in the carbon cycle. Despite their significant biogeochemical roles, the microbial communities, especially in the oxygen depleted compartments, are poorly known. Here, we present a comprehensive dataset including 267 shotgun metagenomes from 41 stratified lakes and ponds mainly located in the boreal and subarctic regions, but also including one tropical reservoir and one temperate lake. For most lakes and ponds, the data includes a vertical sample set spanning from the oxic surface to the anoxic bottom layer. The majority of the samples were collected during the open wate…
Modelling biogeochemical processes in sediments from the north-western Adriatic Sea: response to enhanced particulate organic carbon fluxes
2018
This work presents the result of a study carried out in the north-western Adriatic Sea, by combining two different types of biogeochemical models with field sampling efforts. A longline mussel farm was taken as a local source of perturbation to the natural particulate organic carbon (POC) downward flux. This flux was first quantified by means of a pelagic model of POC deposition coupled to sediment trap data, and its effects on sediment bioirrigation capacity and organic matter (OM) degradation pathways were investigated constraining an early diagenesis model by using original data collected in sediment porewater. The measurements were performed at stations located inside and outside the ar…
Dynamics of copper and zinc sedimentation in a lagooning system receiving landfill leachate.
2013
9 pages; International audience; This study characterises the sediment dredged from a lagooning system composed of a settling pond and three lagoons that receive leachates from a municipal solid waste (MSW) landfill in France. Organic carbon, carbonate, iron oxyhydroxides, copper (Cu) and zinc (Zn) concentrations were measured in the sediment collected from upstream to downstream in the lagooning system. In order to complete our investigation of sedimentation mechanisms, leachates were sampled in both dry (spring) and wet (winter) seasonal conditions. Precipitation of calcite and amorphous Fe-oxyhydroxides and sedimentation of organic matter occurred in the settling pond. Since different di…
Les phénols de la lignine et le 13C, traceurs de l'origine des matières organiques du sol
2001
Abstract In spodosols of Gascony (France), conversion of maritime pine stands into maize cropping leads to an incorporation of maize organic matter, which changed the isotopic (δ13C) and phenolic signature in A and L horizons of soil. Hydrolysis of phenol lignin in forests and cultivated soils showed the predominance of vanillic units under forest and the early but moderate incorporation of cinnamic acids. Incorporation of syringic units appeared higher, related to a large maize production of stable syringic phenols. Syringic units represented a long-term marker of maize inputs in soils, whereas vanillic units revealed the degradation of forest organic matter.