Search results for "dissolved organic carbon"
showing 10 items of 124 documents
Modelling the Impacts of Climate Change on Dissolved Organic Carbon
2009
Dissolved organic carbon (DOC) from peat soils has implications both for the ecology of receiving waters and for the quality and treatment costs of water used for human consumption. Fluxes of DOC from peat soils are also relevant in the context of the global carbon cycle. Chapter 12 in this volume has reviewed the evidence for the effects of different environmental factors on the decomposition of peat soils and the export of DOC, drawing on literature and long-term data acquired from a number of European sites. The conclusion from this and many other studies is that, although there may be other influences such as land management and recovery from acid deposition, climate factors are a major…
Multiple-stressor effects on river biofilms under different hydrological conditions
2016
Summary We studied the relative importance of environmental factors (river flow, nutrients, dissolved organic matter) and organic micro-pollutants [herbicides, insecticides, industrial organic compounds, personal care products, antibiotics and pharmaceuticals, (PhCs)] to the structure and function of epilithic biofilms under various hydrological conditions and land uses. Biofilms from four river basins in the Iberian Peninsula (Llobregat, Ebro, Jucar and Guadalquivir) were analysed in summer–autumn during a wet period and base-flow conditions. The sites experienced different levels of pollution. We used variance partitioning (Redundancy Detrended Analysis, RDA) to link environmental stresso…
The influence of preservation method and time on theδ13C value of dissolved inorganic carbon in water samples
2009
The precise delta(13)C value of dissolved inorganic carbon (DIC) is important for various types of ecological studies. Without a preservation agent, microbial degradation of organic compounds continues in water samples and the delta(13)C value of DIC will become more depleted with time. HgCl(2) or acidification is often used to prevent microbial activity in water samples collected for carbon isotope ratio analyses of DIC. Mercury compounds are toxic and result in waste disposal problems. Other inhibiting agents or preservation methods are therefore needed. Two possible solutions are to use copper sulphate (CuSO(4)) as a preservative agent or to acidify water samples with phosphoric acid (H(…
Modelling the interactions of soil microbes and nematodes
2009
Abstract Six different soil food webs, assembled from a bacterium, a bacterial-feeding nematode, a fungus and a fungal-feeding nematode, were established in replicated laboratory microcosms. Glucose was supplied as the sole carbon source for the microbes. Biomasses of the organisms and the concentration of dissolved organic carbon (DOC) were measured ten times during 20 weeks. A discrete dynamic model based on the material flow between system components was fitted to the experimental data. Bacterial-based food chains were largely inactive in the absence of fungi, but mutual facilitation was observed in the systems with both fungus and bacterium. The population dynamics of a fungal-feeding …
Geochemical characterisation of gases along the dead sea rift: Evidences of mantle-co2 degassing
2016
International audience; The Dead Sea Transform (DST) fault system, where a lateral displacement between the African and Arabian plates occurs, is characterised by anomalous heat flux in the Israeli area close to the border with Syria and Jordan. The concentration of He and CO2, and isotopic composition of He and total dissolved inorganic carbon were studied in cold and thermal waters collected along the DST, in order to investigate the source of volatiles and their relationship with the tectonic framework of the DST. The waters with higher temperature (up to 57.2 °C) are characterised by higher amounts of CO2 and helium (up to 55.72 and 1.91 * 10-2 cc l-1, respectively). Helium isotopic dat…
Ocean acidification effects on stable isotope signatures and trophic interactions of polychaete consumers and organic matter sources at a CO2 shallow…
2015
Abstract Stable carbon and nitrogen isotope analysis (SIA) was used to examine trophic interactions in a naturally acidified shallow coastal CO2 area in the Mediterranean Sea. SIA was helpful to determine the potential effects of ocean acidification (OA) on the interactions of organic matter sources and polychaete consumers, which appear to be tolerant to high pCO2. Mesoherbivore consumers, represented by three polychaete species, Platynereis dumerilii (Audouin and Milne Edwards, 1834) (Nereididae), Polyophthalmus pictus (Dujardin, 1839) (Opheliidae) and Syllis prolifera Krohn, 1852 (Syllidae), are abundant in the low pH conditions of the CO2 vents. Samples of consumers and potential organi…
Adsorption of dissolved organic matter on clay minerals as assessed by infra-red, CPMAS 13C NMR spectroscopy and low field T1 NMR relaxometry
2011
Abstract Dissolved organic matter (DOM) is a very important environmental constituent due to its role in controlling factors for soil formation, mineral weathering and pollutant transport in the environment. Prediction of DOM physical–chemical properties is achieved by studying its chemical structure and spatial conformation. In the present study, dissolved organic matter extracted from compost obtained from the organic fraction of urban wastes (DOM-P) has been analysed by FT-IR, CPMAS 13C NMR spectroscopy and 1H T1 NMR relaxometry with fast field cycling (FFC) setup. While the first two spectroscopic techniques revealed the chemical changes of dissolved organic matter after adsorption eith…
Influence of organic amendments on diuron leaching through an acidic and a calcareous vineyard soil using undisturbed lysimeters.
2008
9 pages; International audience; The influence of different organic amendments on diuron leaching was studied through undisturbed vineyard soil columns. Two composts (A and D), the second at two stages of maturity, and two soils (VR and Bj) were sampled. After 1 year, the amount of residues (diuron þ metabolites) in the leachates of the VR soil (0.19e0.71%) was lower than in the Bj soil (4.27e8.23%), which could be explained by stronger diuron adsorption on VR. An increase in the amount of diuron leached through the amended soil columns, compared to the blank, was observed for the Bj soil only. This result may be explained by the formation of mobile complexes between diuron and water-extrac…
Pore water velocity and ionic strength effects on DOC release from peat-sand mixtures: Results from laboratory and field experiments
2017
Organic soils are the most important source of dissolved organic carbon (DOC) in surface water. To date, most studies have focused on natural and re-wetted peatlands, but in Central Europe a large proportion of organic soils are drained and under agricultural use. Furthermore, measures such as deep ploughing or sand addition have been conducted to improve trafficability and have resulted in topsoil horizons consisting of a peat-sand mixture. Very little is known about DOC losses from such soils. Moreover, peat soils frequently feature both mobile zones, characterised by active water and solute transport, and immobile zones, which exchange solutes with the mobile zone by diffusion. Surprisin…
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…