Search results for "Total organic Carbon"

Pedogenesis and carbon sequestration in transformed agricultural soils of Sicily

2021

The increasing atmospheric CO2 concentration is a consequence of human activities leading to severe environmental deteriorations. Techniques are thus needed to sequester and reduce atmospheric carbon. One of the proposed techniques is the transformation or construction of new soils into which more organic carbon can be sequestered and CO2 be consumed by increased weathering. By using a chronosequence of new and transformed soils on crushed limestone (0–48 years) in a Mediterranean area (Sicily), we tried to quantify the amount of organic carbon that could be additionally sequestered and to derive the corresponding rates. A further aim was to trace chemical weathering and related CO2 consump…

Revisiting the disappearance of terrestrial dissolved organic matter in the ocean: a <i>δ</i><sup>13&lt…

2014

Abstract. Organic carbon (OC) depleted in 13C is a widely used tracer for terrestrial organic matter (OM) in aquatic systems. Photochemical reactions can, however, change δ13C of dissolved organic carbon (DOC) when chromophoric, aromatic-rich terrestrial OC is selectively mineralized. We assessed the robustness of the δ13C signature of DOC (δ13CDOC) as a tracer for terrestrial OM by estimating its change during the photobleaching of chromophoric DOM (CDOM) from 10 large rivers. These rivers cumulatively account for approximately one-third of the world's freshwater discharge to the global ocean. Photobleaching of CDOM by simulated solar radiation was associated with the photochemical mineral…

Differences of stabilized organic carbon fractions and microbiological activity along Mediterranean Vertisols and Alfisols profiles

2010

This study examined the chemical and structural properties of humic substances and microbiological activity in order to verify differences in carbon dynamics along soil profiles in two Vertisols (Typic Haploxerert and Xeric Epiaquert) and two Alfisols (Mollic Haploxeralf and Ultic Haploxeralf) developed under Mediterranean climate in Italy. Humification parameters, thermal methods, including differential scanning calorimetry (DSC) and thermogravimetry (TG), together with Fourier transform infrared (FT-IR) and fluorescence spectroscopies were used to characterize humic acids (HA). Microbiological activity of soils was assessed by basal respiration, metabolic quotient (qCO2) and Cmic:Corg rat…

Phosphorus Loss in Overfertilized Soils: The Selective P Partitioning and Redistribution Between Particle Size Separates

2007

Using 12 well-characterised European soils contrasting in their physical and chemical properties, we demonstrate significant differences in the partitioning of phosphorus (P) between various particle size separates. Samples of each soil were subjected to one of three methods of increasingly aggressive dispersion in the order water (WD), mechanical (MD) or chemical (CD). A general, although not exclusive, inverse relationship existed between the concentration of various attributes (these included organic carbon, oxalate and dithionite iron contents, total P, resin and water extractable P) and particle size. The quantity, composition and physico-chemical properties of individual size separate…

Role of terrestrial carbon in aquatic UV exposure and photoprotective pigmentation of meiofauna in subarctic lakes

2015

Summary Aquatic organisms are adversely influenced by ultraviolet radiation (UV) and utilise photoprotective strategies, including pigmentation. We examined UV-protective melanin pigmentation of aquatic meiofauna (Cladocera) in relation to the UV exposure across 25 tree line lakes in Finland to address the potential effects of increased UV and altered input of UV-screening terrestrial dissolved organic carbon (DOC) on aquatic organisms. Bio-optical parameters, including concentration of DOC, the coloured dissolved organic matter (CDOM) fraction, a suite of carbon quality indices and chlorophyll a, were analysed from lake water, and their role in controlling underwater UV environment (measur…

Terrestrial carbon and intraspecific size-variation shape lake ecosystems

2007

Conceptual models of lake ecosystem structure and function have generally assumed that energy in pelagic systems is derived from in situ photosynthesis and that its use by higher trophic levels depends on the average properties of individuals in consumer populations.These views are challenged by evidence that allochthonous subsidies of organic carbon greatly influence energy mobilization and transfer and the trophic structure of pelagic food webs, and that size variation within consumer species has major ramifications for lake communitydynamics and structure. These discoveries represent conceptual shifts that have yet to be integrated into current views on lake ecosystems. Here, we assess k…

Energy use in the A and B horizons of the soil under a pine and a cedar stand

2002

Publisher Summary This chapter discusses a study that compares organic carbon content, availability of substrates, and microbial metabolism in two afforested sites in Sicily (Italy) developed under the same climatic and physical conditions but underlying different tree species. Given the key role of the soil microbiota in promoting energy exchanges and transformations in the soil profile, an analysis of the microbial activity and of organic carbon pools was performed on twenty profiles. The parameters considered in this study were based on microbial activity, organic carbon fractions, and kinetics of organic C mineralization. In the two systems studied, the competition for available energy …

Uptake of chlorohydrocarbons from soil by lipid-containing semipermeable membrane devices (SPMDs)

1998

Chlorohydrocarbons (CHCs) were surveyed in contaminated lake shore soil in Central Finland with polyethylene membranes containing synthetic triolein (SPMDs). High levels of hexachlorobenzene (HCBz) and PCBs were found in a significant number of the SPMDs exposed 28 days to 35 soil sampling locations along the 350 meter long shoreline. Distributions of HCBz and PCBs were different as demonstrated by two maximas of HCBz and four maximas of PCBs observed. Soil was also analyzed at selected locations for concentrations of CHCs, organic carbon (OC) and moisture. Steady state environmental fate modeling and simple equilibrium partition estimates based on analytical results both gave the same stea…

Global health burden of PM2.5, black and organic carbon aerosols

2021

Paléoenvironnements et caractérisation des roches mères pétrolières des séries pré-salifères du bassin intérieur du Gabon

2003

Resume Le bassin interieur du Gabon, dont l'histoire est liee a la separation des continents Sud-Americain et Africain, comprend des depots continentaux fluvio-lacustres, localement glaciaires, dates du Precambrien superieur a l'Aptien p.p., surmontes par des facies marins aptiens et albiens. L'analyse par pyrolyse Rock–Eval d'echantillons d'affleurements et de forages preleves dans ce bassin met en evidence la presence de facies siliciclastiques riches en matiere organique (jusqu'a 25 % de carbone organique total) de types I et II. Ces niveaux, qui se rencontrent dans le Permien, le Neocomien-Barremien ainsi que dans l'Aptien, constituent d'excellentes roches meres et sont a l'origine des …