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Sample records for organic matter remineralization

  1. Inventory of released inorganic carbon from organic matter remineralization in the deeper Arabian Sea

    NASA Astrophysics Data System (ADS)

    Hupe, Axel; Thomas, Helmuth; Ittekkot, Venugopalan; Lendt, Ralf

    2001-12-01

    An attempt is made to quantify the biological carbon pump in Arabian Sea subsurface waters by estimating the total concentrations of remineralized dissolved inorganic carbon (DICrem) and its water column inventory. The influence of different sets of -ΔO2/ΔCorg ratios, which are either constant or variable with depth, on the estimate is assessed. Throughout the water column the horizontally mapped DICrem concentrations increase northward due to enlarged export fluxes of organic matter and subsequently enhanced remineralization processes as well as to the accumulation of remineralization products along the trajectory path of the water masses ventilating the Arabian Sea from the southern Indian Ocean. The choice of the remineralization ratios generates significant differences in the DICrem concentrations at specific depth horizons. The DICrem inventory of the Arabian Sea between 500 and 4500 m in the years 1995-1997 amounts to ˜39-44 Gt C depending on the applied remineralization ratios.

  2. Organic Matter Remineralization Predominates Phosphorus Cycling in the Mid-Bay Sediments in the Chesapeake Bay

    SciTech Connect

    Sunendra, Joshi R.; Kukkadapu, Ravi K.; Burdige, David J.; Bowden, Mark E.; Sparks, Donald L.; Jaisi, Deb P.

    2015-05-19

    The Chesapeake Bay, the largest and most productive estuary in the US, suffers from varying degrees of water quality issues fueled by both point and non–point source nutrient sources. Restoration of the bay is complicated by the multitude of nutrient sources, their variable inputs and hydrological conditions, and complex interacting factors including climate forcing. These complexities not only restrict formulation of effective restoration plans but also open up debates on accountability issues with nutrient loading. A detailed understanding of sediment phosphorus (P) dynamics enables one to identify the exchange of dissolved constituents across the sediment- water interface and aid to better constrain mechanisms and processes controlling the coupling between the sediments and the overlying waters. Here we used phosphate oxygen isotope ratios (δ18Op) in concert with sediment chemistry, XRD, and Mössbauer spectroscopy on the sediment retrieved from an organic rich, sulfidic site in the meso-haline portion of the mid-bay to identify sources and pathway of sedimentary P cycling and to infer potential feedback effect on bottom water hypoxia and surface water eutrophication. Isotope data indicate that the regeneration of inorganic P from organic matter degradation (remineralization) is the predominant, if not sole, pathway for authigenic P precipitation in the mid-bay sediments. We interpret that the excess inorganic P generated by remineralization should have overwhelmed any bottom-water and/or pore-water P derived from other sources or biogeochemical processes and exceeded saturation with respect to authigenic P precipitation. It is the first research that identifies the predominance of remineralization pathway against remobilization (coupled Fe-P cycling) pathway in the Chesapeake Bay. Therefore, these results are expected to have significant implications for the current understanding of P cycling and benthic-pelagic coupling in the bay, particularly on the

  3. Organic matter remineralization predominates phosphorus cycling in the mid-Bay sediments in the Chesapeake Bay.

    PubMed

    Joshi, Sunendra R; Kukkadapu, Ravi K; Burdige, David J; Bowden, Mark E; Sparks, Donald L; Jaisi, Deb P

    2015-05-19

    Chesapeake Bay, the largest and most productive estuary in the U.S., suffers from varying degrees of water quality issues fueled by both point and nonpoint nutrient sources. Restoration of the Bay is complicated by the multitude of nutrient sources, their variable inputs, and complex interaction between imported and regenerated nutrients. These complexities not only restrict formulation of effective restoration plans but also open up debates on accountability issues with nutrient loading. A detailed understanding of sediment phosphorus (P) dynamics provides information useful in identifying the exchange of dissolved constituents across the sediment-water interface as well as helps to better constrain the mechanisms and processes controlling the coupling between sediments and the overlying waters. Here we used phosphate oxygen isotope ratios (δ(18)O(P)) in concert with sediment chemistry, X-ray diffraction, and Mössbauer spectroscopy on sediments retrieved from an organic rich, sulfidic site in the mesohaline portion of the mid-Bay to identify sources and pathway of sedimentary P cycling and to infer potential feedbacks on bottom water hypoxia and surface water eutrophication. Authigenic phosphate isotope data suggest that the regeneration of inorganic P from organic matter degradation (remineralization) is the predominant, if not sole, pathway for authigenic P precipitation in the mid-Bay sediments. This indicates that the excess inorganic P generated by remineralization should have overwhelmed any pore water and/or bottom water because only a fraction of this precipitates as authigenic P. This is the first research that identifies the predominance of remineralization pathway and recycling of P within the Chesapeake Bay. Therefore, these results have significant implications on the current understanding of sediment P cycling and P exchange across the sediment-water interface in the Bay, particularly in terms of the sources and pathways of P that sustain hypoxia

  4. Organic matter remineralization predominates phosphorus cycling in the mid-Bay sediments in the Chesapeake Bay.

    PubMed

    Joshi, Sunendra R; Kukkadapu, Ravi K; Burdige, David J; Bowden, Mark E; Sparks, Donald L; Jaisi, Deb P

    2015-05-19

    Chesapeake Bay, the largest and most productive estuary in the U.S., suffers from varying degrees of water quality issues fueled by both point and nonpoint nutrient sources. Restoration of the Bay is complicated by the multitude of nutrient sources, their variable inputs, and complex interaction between imported and regenerated nutrients. These complexities not only restrict formulation of effective restoration plans but also open up debates on accountability issues with nutrient loading. A detailed understanding of sediment phosphorus (P) dynamics provides information useful in identifying the exchange of dissolved constituents across the sediment-water interface as well as helps to better constrain the mechanisms and processes controlling the coupling between sediments and the overlying waters. Here we used phosphate oxygen isotope ratios (δ(18)O(P)) in concert with sediment chemistry, X-ray diffraction, and Mössbauer spectroscopy on sediments retrieved from an organic rich, sulfidic site in the mesohaline portion of the mid-Bay to identify sources and pathway of sedimentary P cycling and to infer potential feedbacks on bottom water hypoxia and surface water eutrophication. Authigenic phosphate isotope data suggest that the regeneration of inorganic P from organic matter degradation (remineralization) is the predominant, if not sole, pathway for authigenic P precipitation in the mid-Bay sediments. This indicates that the excess inorganic P generated by remineralization should have overwhelmed any pore water and/or bottom water because only a fraction of this precipitates as authigenic P. This is the first research that identifies the predominance of remineralization pathway and recycling of P within the Chesapeake Bay. Therefore, these results have significant implications on the current understanding of sediment P cycling and P exchange across the sediment-water interface in the Bay, particularly in terms of the sources and pathways of P that sustain hypoxia

  5. Carbon cycling in a continental margin sediment: contrasts between organic matter characteristics and remineralization rates and pathways

    NASA Astrophysics Data System (ADS)

    Arnosti, C.; Holmer, M.

    2003-09-01

    Although particulate organic carbon (POC) in sediments is derived from diverse sources, characteristics of bulk POC are frequently used as indicators of the 'quality' of organic matter potentially available to sedimentary microbial communities. In order to investigate the extent to which characteristics of POC relate to sedimentary metabolism, the rates of the initial and terminal steps of organic carbon remineralization (extracellular enzymatic hydrolysis, and sulfate, iron, and manganese reduction, respectively) were compared at three sites in Skagerrak dominated by different terminal remineralization processes. In parallel, dissolved organic carbon (DOC) inventories and bulk POC characteristics were assessed. At all three sites, bulk characteristics of POC were similar, with C/N close to 12, low sedimentary amino acid content, and moderate concentrations of total hydrolyzable carbohydrates. On average, just 12% of POC was characterizable as carbohydrates or amino acids. These characteristics are frequently considered typical of unreactive or 'low quality' organic matter. At all three sites, however, organic carbon remineralization (measured as CO 2 production and sediment O 2 uptake) was quite high relative to other locations with similar bulk characteristics. A comparison of DOC inventories with rates of terminal remineralization demonstrated that at the three sites, on average 27, 8, and 31% of the sedimentary DOC pool must be turned over on a daily basis in order to support terminal respiration. Extracellular enzymatic activity, calculated as potential carbon turnover, was sufficient to support these rates. At these sites, standard chemical characterization of bulk POC does not reflect the reactivity and availability of substrates to the sedimentary microbial community. Carbon remineralization is likely fueled by a small fraction of POC, not distinguishable by measurement of bulk parameters, which is rapidly cycled through the DOC pool.

  6. Organic matter remineralization and porewater exchange rates in permeable South Atlantic Bight continental shelf sediments

    NASA Astrophysics Data System (ADS)

    Jahnke, Richard; Richards, Mary; Nelson, James; Robertson, Charles; Rao, Alexandra; Jahnke, Deborah

    2005-08-01

    South Atlantic Bight (SAB) continental shelf sediments are characterized by high permeabilities, substantial benthic microalgal photosynthesis, and rapid tidally driven bottom currents. Primary productivity by benthic microalgae rivals water column production for much of the shelf area for most of the year and porewater exchange proceeds at rates of 2-100 (mean 34) times that of molecular diffusion. In this environment, traditional techniques of porewater diffusion calculations and benthic flux chamber incubations do not yield accurate estimates of integrated sedimentary reaction and metabolic rates. Between 1995 and 2001, porewater nutrient distributions have been determined on sediment cores recovered on 24 separate expeditions to the central shelf. Measurements demonstrate that standing stocks of porewater nutrients vary significantly seasonally. Replicate whole core incubations from 1999-2001 conducted over a seasonal cycle reveal that remineralization rates vary seasonally by more than a factor of 18, in response to changes in bottom temperature and possibly organic carbon input. These results suggest that changes in remineralization rate and not changes in porewater advective transport rate are the primary factor accounting for the observed seasonal differences in porewater nutrient inventories. Integrating the observed remineralization rates over the shelf area and throughout an annual cycle implies that approximately 3.8 Tg C, equivalent to 17% of the integrated mid-shelf water column production, is recycled annually in the sediments below the surface benthic microalgal layer of the South Atlantic Bight. Including respiration associated with the sediment surface photosynthetic community implies that the sediments account for approximately half of the total metabolic carbon turnover in this shelf system.

  7. Geochemical ecosystem engineering by the mud shrimp Upogebia pugettensis (Crustacea: Thalassinidae) in Yaquina Bay, Oregon: density-dependent effects on organic matter remineralization and nutrient cycling

    EPA Science Inventory

    We investigated the effect of the thalassinid mud shrimp Upogebia pugettensis on organic matter and nutrient cycling on Idaho Flat, an intertidal flat in the Yaquina River estuary, Oregon. Field studies were conducted to measure carbon and nitrogen remineralization rates and bent...

  8. Barium in twilight zone suspended matter as a potential proxy for particulate organic carbon remineralization: Results for the North Pacific

    NASA Astrophysics Data System (ADS)

    Dehairs, F.; Jacquet, S.; Savoye, N.; Van Mooy, B. A. S.; Buesseler, K. O.; Bishop, J. K. B.; Lamborg, C. H.; Elskens, M.; Baeyens, W.; Boyd, P. W.; Casciotti, K. L.; Monnin, C.

    2008-07-01

    This study focuses on the fate of exported organic carbon in the twilight zone at two contrasting environments in the North Pacific: the oligotrophic ALOHA site (22°45'N, 158°W; Hawaii; studied during June-July 2004) and the mesotrophic Subarctic Pacific K2 site (47°N, 161°W; studied during July-August 2005). Earlier work has shown that non-lithogenic, excess particulate Ba (Ba xs) in the mesopelagic water column is a potential proxy of organic carbon remineralization. In general, Ba xs contents were significantly larger at K2 than at ALOHA. At ALOHA, the Ba xs profiles from repeated sampling (five casts) showed remarkable consistency over a period of three weeks, suggesting that the system was close to being at steady state. In contrast, more variability was observed at K2 (six casts sampled), reflecting the more dynamic physical and biological conditions prevailing in this environment. While for both sites Ba xs concentrations increased with depth, at K2 a clear maximum was present between the base of the mixed layer at around 50 and 500 m, reflecting production and release of Ba xs. Larger mesopelagic Ba xs contents and larger bacterial production in the twilight zone at the K2 site indicate that more material was exported from the upper mixed layer for bacterial degradation deeper, compared to the ALOHA site. Furthermore, application of a published transfer function [Dehairs, F., Shopova, D., Ober, S., Veth, C., Goeyens, L., 1997. Particulate barium stocks and oxygen consumption in the Southern Ocean mesopelagic water column during spring and early summer: relationship with export production. Deep-Sea Research II 44(1-2), 497-516] relating oxygen consumption to the observed Ba xs data indicated that the latter were in good agreement with bacterial respiration, calculated from bacterial production. These results corroborate earlier findings highlighting the potential of Ba xs as a proxy for organic carbon remineralization. The range of POC remineralization

  9. Barium in Twilight Zone suspended matter as a potential proxy for particulate organic carbon remineralization: Results for the North Pacific

    SciTech Connect

    Dehairs, F.; Jacquet, S.; Savoye, N.; Van Mooy, B.A.S.; Buesseler, K.; Bishop, J.K.B.; Lamborg, C.H.; Elskens, M.; Baeyens, W.; Boyd, P.W.; Casciotti, K.L.; Monnin, C.

    2008-04-10

    This study focuses on the fate of exported organic carbon in the twilight zone at two contrasting environments in the North Pacific: the oligotrophic ALOHA site (22 degrees 45 minutes N 158 degrees W; Hawaii; studied during June-July 2004) and the mesotrophic Subarctic Pacific K2 site (47 degrees N, 161 degrees W; studied during July-August 2005). Earlier work has shown that non-lithogenic, excess particulate Ba (Ba{sub xs}) in the mesopelagic water column is a potential proxy of organic carbon remineralization. In general Ba{sub xs} contents were significantly larger at K2 than at ALOHA. At ALOHA the Ba{sub xs} profiles from repeated sampling (5 casts) showed remarkable consistency over a period of three weeks, suggesting that the system was close to being at steady state. In contrast, more variability was observed at K2 (6 casts sampled) reflecting the more dynamic physical and biological conditions prevailing in this environment. While for both sites Ba{sub xs} concentrations increased with depth, at K2 a clear maximum was present between the base of the mixed layer at around 50m and 500m, reflecting production and release of Ba{sub xs}. Larger mesopelagic Ba{sub xs} contents and larger bacterial production in the twilight zone at the K2 site indicate that more material was exported from the upper mixed layer for bacterial degradation deeper, compared to the ALOHA site. Furthermore, application of a published transfer function (Dehairs et al., 1997) relating oxygen consumption to the observed Ba{sub xs} data indicated that the latter were in good agreement with bacterial respiration, calculated from bacterial production. These results corroborate earlier findings highlighting the potential of Ba{sub xs} as a proxy for organic carbon remineralization. The range of POC remineralization rates calculated from twilight zone excess particulate Ba contents did also compare well with the depth dependent POC flux decrease as recorded by neutrally buoyant sediment traps

  10. Variations in the elemental ratio of organic matter in the central Baltic Sea: Part I-Linking primary production to remineralization

    NASA Astrophysics Data System (ADS)

    Kreus, Markus; Schartau, Markus; Engel, Anja; Nausch, Monika; Voss, Maren

    2015-06-01

    For most marine ecosystems the growth of diazotrophic cyanobacteria and the associated amount of nitrogen fixation are regulated by the availability of phosphorus. The intensity of summer blooms of nitrogen (N2) fixing algae in the Baltic Sea is assumed to be determinable from a surplus of dissolved inorganic phosphorus (DIP) that remains after the spring bloom has ended. But this surplus DIP concentration is observed to continuously decrease at times when no appreciable nitrogen fixation is measured. This peculiarity is currently discussed and has afforded different model interpretations for the Baltic Sea. In our study we propose a dynamical model solution that explains these observations with variations of the elemental carbon-to-nitrogen-to-phosphorus (C:N:P) ratio during distinct periods of organic matter production and remineralization. The biogeochemical model resolves seasonal C, N and P fluxes with depth at the Baltic Sea monitoring site BY15, based on three assumptions: (1) DIP is utilized by algae though not needed for immediate growth, (2) the uptake of dissolved inorganic nitrogen (DIN) is hampered when the algae's phosphorus (P) quota is low, and (3) carbon assimilation continues at times of nutrient depletion. Model results describe observed temporal variations of DIN, DIP and chlorophyll-a concentrations along with partial pressure of carbon dioxide (pCO2). In contrast to other model studies, our solution does not require N2 fixation to occur shortly after the spring bloom to explain DIP drawdown and pCO2 levels. Model estimates of annual N2 fixation are 297 ± 24 mmol Nm-2a-1. Estimates of total production are 14200 ± 700 mmol Cm-2a-1, 1400 ± 70 mmol Nm-2a-1, and 114 ± 5 mmol Pm-2a-1 for the upper 50 m. The models C, N and P fluxes disclose preferential remineralization of P and of organic N that was introduced via N2 fixation. Our results are in support of the idea that P uptake by phytoplankton during the spring bloom contributes to the

  11. Burial, remineralization and utilization of organic matter at the sea floor under a strong western boundary current. Final report, May 1, 1992--April 30, 1995

    SciTech Connect

    Jahnke, R.A.

    1995-08-24

    The overall goals of this project were to quantify the rates of organic carbon export from the southern mid-Atlantic Bight and to quantify the rates at which carbon is exchanged between the inorganic and organic pools within the bottom sediments. This information is necessary to constrain the role of the oceans in the control of carbon dioxide released to the atmosphere in association with energy production. During this project, in situ benthic flux chamber incubations have been performed at six sites on the continental slope and rise adjacent to Cape Hatteras. Based on the analysis of the time-series samples recovered during each experiment, the sea floor exchange rates of the major biogenic elements, oxygen, carbon, nitrogen, phosphorus and silicon were calculated. From the estimated benthic flux rates and the ancillary pore water and sediment analyses, the deposition, remineralization and burial rates of organic carbon to the sea floor in this area was evaluated. This information has been incorporated into regional and global assessments of organic carbon fluxes to the deep sea.

  12. Temporal variation and stoichiometric ratios of organic matter remineralization in bottom waters of the northern Gulf of Mexico during late spring and summer

    NASA Astrophysics Data System (ADS)

    Xue, Jianhong; Cai, Wei-Jun; Hu, Xinping; Huang, Wei-Jen; Lohrenz, Steven E.; Gundersen, Kjell

    2015-12-01

    An improved extended optimum multiparameter (eOMP) analysis was applied to hydrographic (temperature and salinity), and water chemistry data, including dissolved oxygen (O2), nutrients (nitrate plus nitrite, phosphate, and silicate), dissolved inorganic carbon (DIC), and total alkalinity (TAlk) data collected during late spring and summer from 2006 to 2012 in bottom waters off the Louisiana coast, to explore the dynamics and stoichiometry of DIC production during the development and maintenance of summer hypoxia. Our analysis demonstrated that DIC in bottom water was relatively low from April to June, but increased significantly in July, peaked in August, and dropped slightly in September. Furthermore, DIC production resulted from both aerobic organic carbon (OC) respiration and denitrification, as well as substantial loss due to vertical mixing with surface water. The average summer gross OC respiration rate was estimated to be 0.19 g C m-2 d-1, with the highest values occurring in late summer when hypoxic conditions dominated. We also found that Corg/N/P/-O2 remineralization ratios for aerobic respiration were generally consistent with the classic Redfield ratio (106/16/1/138) except individual C/N and C/P ratios were slightly lower, indicating that marine OC was the major source of the DIC production in the bottom water. This study quantified the role of temporal bottom-water microbial respiration to seasonal DIC dynamics and provided a means for studying the stoichiometry of biogeochemical processes in coastal waters.

  13. Characterization of the Rate and Temperature Sensitivities of Bacterial Remineralization of Dissolved Organic Phosphorus Compounds by Natural Populations

    PubMed Central

    White, Angelicque E.; Watkins-Brandt, Katie S.; Engle, Morgan A.; Burkhardt, Brian; Paytan, Adina

    2012-01-01

    Production, transformation, and degradation are the principal components of the cycling of dissolved organic matter (DOM) in marine systems. Heterotrophic Bacteria (and Archaea) play a large part in this cycling via enzymatic decomposition and intracellular transformations of organic material to inorganic carbon (C), nitrogen (N), and phosphorus (P). The rate and magnitude of inorganic nutrient regeneration from DOM is related to the elemental composition and lability of DOM substrates as well as the nutritional needs of the mediating organisms. While many previous efforts have focused on C and N cycling of DOM, less is known in regards to the controls of organic P utilization and remineralization by natural populations of bacteria. In order to constrain the relative time scales and degradation of select dissolved organic P (DOP) compounds we have conducted a series of experiments focused on (1) assessment of the short-term lability of a range of DOP compounds, (2) characterization of labile DOP remineralization rates, and (3) examination of temperature sensitivities of labile DOP remineralization for varying bacterial populations. Results reinforce previous findings of monoester and polyphosphate lability and the relative recalcitrance of a model phosphonate: 2-aminoethylphosphonate. High resolution time-series of P-monoester remineralization indicates decay constants on the order of 0.67–7.04 day−1 for bacterial populations isolated from coastal and open ocean surface waters. The variability of these rates is predictably related to incubation temperature and initial concentrations of heterotrophic bacteria. Additional controls on DOP hydrolysis included seasonal shifts in bacterial populations and the physiological state of bacteria at the initiation of DOP addition experiments. Composite results indicate that bacterial hydrolysis of P-monoesters exceeds bacterial P demand and thus DOP remineralization efficiency may control P availability to autotrophs

  14. Total and methylated mercury in the Beaufort Sea: the role of local and recent organic remineralization.

    PubMed

    Wang, Feiyue; Macdonald, Robie W; Armstrong, Debbie A; Stern, Gary A

    2012-11-01

    Mercury is a major contaminant in the Arctic marine ecosystem. While extensive studies have been conducted on mercury in the Arctic's atmosphere and biota, far less is known about the distribution and dynamics of mercury species in the Arctic Ocean. Here, we present vertical profiles for total mercury (Hg(T)) and total methylated mercury (MeHg(T), sum of monomethylmercury and dimethylmercury) from the Beaufort Sea of the Arctic Ocean at locations with differing sea ice conditions. The concentration of Hg(T) ranged from 0.40 to 2.9 pM, with a surface enrichment that can be attributed to a combination of sea ice-modified atmospheric deposition and riverine input. The concentration of MeHg(T) ranged from <0.04 to 0.59 pM, with a subsurface peak occurring at the same depth as a nutrient maximum with lower dissolved oxygen, which is consistent with the recent findings in the Pacific Ocean, Southern Ocean, and Mediterranean Sea. However, unlike the interior ocean regions, the nutrient maximum in the Beaufort Sea is predominantly an advective feature produced over the Chukchi Shelf. On the basis of the short lifetime of monomethylmercury in seawater, we propose that the MeHg(T) profile in the Beaufort Sea reflects the local, short-term remineralization of labile organic matter, and not the larger signal of organic remineralization advected from the Chukchi Sea in the halocline. The finding that MeHg(T) is produced locally, reflecting recent strength of organic matter cycling, not only explains wide variance in MeHg(T) in seawater and biota over time and space, but also implies that MeHg(T) could be used as an indicator of the recent export flux of labile organic matter. PMID:23025753

  15. Sources and Distribution of Organic Matter in Sediments of the Louisiana Continental Shelf

    EPA Science Inventory

    Both riverine and marine sources of organic matter (OM) contribute to sediment organic pools, and either source can contribute significantly to sediment accumulation, burial, and remineralization rates on river dominated continental shelf systems. For the Louisiana continental sh...

  16. Preferential remineralization of dissolved organic phosphorus and non-Redfield DOM dynamics in the global ocean: Impacts on marine productivity, nitrogen fixation, and carbon export

    NASA Astrophysics Data System (ADS)

    Letscher, Robert T.; Moore, J. Keith

    2015-03-01

    Selective removal of nitrogen (N) and phosphorus (P) from the marine dissolved organic matter (DOM) pool has been reported in several regional studies. Because DOM is an important advective/mixing pathway of carbon (C) export from the ocean surface layer and its non-Redfieldian stoichiometry would affect estimates of marine export production per unit N and P, we investigated the stoichiometry of marine DOM and its remineralization globally using a compiled DOM data set. Marine DOM is enriched in C and N compared to Redfield stoichiometry, averaging 317:39:1 and 810:48:1 for C:N:P within the degradable and total bulk pools, respectively. Dissolved organic phosphorus (DOP) is found to be preferentially remineralized about twice as rapidly with respect to the enriched C:N stoichiometry of marine DOM. Biogeochemical simulations with the Biogeochemical Elemental Cycling model using Redfield and variable DOM stoichiometry corroborate the need for non-Redfield dynamics to match the observed DOM stoichiometry. From our model simulations, preferential DOP remineralization is found to increase the strength of the biological pump by ~9% versus the case of Redfield DOM cycling. Global net primary productivity increases ~10% including an increase in marine nitrogen fixation of ~26% when preferential DOP remineralization and direct utilization of DOP by phytoplankton are included. The largest increases in marine nitrogen fixation, net primary productivity, and carbon export are observed within the western subtropical gyres, suggesting the lateral transfer of P in the form of DOP from the productive eastern and poleward gyre margins may be important for sustaining these processes downstream in the subtropical gyres.

  17. Photodissolution of soil organic matter

    USGS Publications Warehouse

    Mayer, L.M.; Thornton, K.R.; Schick, L.L.; Jastrow, J.D.; Harden, J.W.

    2012-01-01

    Sunlight has been shown to enhance loss of organic matter from aquatic sediments and terrestrial plant litter, so we tested for similar reactions in mineral soil horizons. Losses of up to a third of particulate organic carbon occurred after continuous exposure to full-strength sunlight for dozens of hours, with similar amounts appearing as photodissolved organic carbon. Nitrogen dissolved similarly, appearing partly as ammonium. Modified experiments with interruption of irradiation to include extended dark incubation periods increased loss of total organic carbon, implying remineralization by some combination of light and microbes. These photodissolution reactions respond strongly to water content, with reaction extent under air-dry to fully wet conditions increasing by a factor of 3-4 fold. Light limitation was explored using lamp intensity and soil depth experiments. Reaction extent varied linearly with lamp intensity. Depth experiments indicate that attenuation of reaction occurs within the top tens to hundreds of micrometers of soil depth. Our data allow only order-of-magnitude extrapolations to field conditions, but suggest that this type of reaction could induce loss of 10-20% of soil organic carbon in the top 10. cm horizon over a century. It may therefore have contributed to historical losses of soil carbon via agriculture, and should be considered in soil management on similar time scales. ?? 2011 Elsevier B.V.

  18. Reactive-transport modeling of iron diagenesis and associated organic carbon remineralization in a Florida (USA) subterranean estuary

    USGS Publications Warehouse

    Roy, Moutusi; Martin, Jonathan B.; Smith, Christopher G.; Cable, Jaye E.

    2011-01-01

    Iron oxides are important terminal electron acceptors for organic carbon (OC) remineralization in subterranean estuaries, particularly where oxygen and nitrate concentrations are low. In Indian River Lagoon, Florida, USA, terrestrial Fe-oxides dissolve at the seaward edge of the seepage face and flow upward into overlying marine sediments where they precipitate as Fe-sulfides. The dissolved Fe concentrations vary by over three orders of magnitude, but Fe-oxide dissolution rates are similar across the 25-m wide seepage face, averaging around 0.21 mg/cm2/yr. The constant dissolution rate, but differing concentrations, indicate Fe dissolution is controlled by a combination of increasing lability of dissolved organic carbon (DOC) and slower porewater flow velocities with distance offshore. In contrast, the average rate constants of Fe-sulfide precipitation decrease from 21.9 × 10-8 s-1 to 0.64 × 10-8 s-1 from the shoreline to the seaward edge of the seepage face as more oxygenated surface water circulates through the sediment. The amount of OC remineralized by Fe-oxides varies little across the seepage face, averaging 5.34 × 10-2 mg/cm2/yr. These rates suggest about 3.4 kg of marine DOC was remineralized in a 1-m wide, shore-perpendicular strip of the seepage face as the terrestrial sediments were transgressed over the past 280 years. During this time, about 10 times more marine solid organic carbon (SOC) accumulated in marine sediments than were removed from the underlying terrestrial sediments. Indian River Lagoon thus appears to be a net sink for marine OC.

  19. Reactive-transport modeling of iron diagenesis and associated organic carbon remineralization in a Florida (USA) subterranean estuary

    NASA Astrophysics Data System (ADS)

    Roy, Moutusi; Martin, Jonathan B.; Smith, Christopher G.; Cable, Jaye E.

    2011-04-01

    Iron oxides are important terminal electron acceptors for organic carbon (OC) remineralization in subterranean estuaries, particularly where oxygen and nitrate concentrations are low. In Indian River Lagoon, Florida, USA, terrestrial Fe-oxides dissolve at the seaward edge of the seepage face and flow upward into overlying marine sediments where they precipitate as Fe-sulfides. The dissolved Fe concentrations vary by over three orders of magnitude, but Fe-oxide dissolution rates are similar across the 25-m wide seepage face, averaging around 0.21 mg/cm 2/yr. The constant dissolution rate, but differing concentrations, indicate Fe dissolution is controlled by a combination of increasing lability of dissolved organic carbon (DOC) and slower porewater flow velocities with distance offshore. In contrast, the average rate constants of Fe-sulfide precipitation decrease from 21.9 × 10 - 8 s - 1 to 0.64 × 10 - 8 s - 1 from the shoreline to the seaward edge of the seepage face as more oxygenated surface water circulates through the sediment. The amount of OC remineralized by Fe-oxides varies little across the seepage face, averaging 5.34 × 10 - 2 mg/cm 2/yr. These rates suggest about 3.4 kg of marine DOC was remineralized in a 1-m wide, shore-perpendicular strip of the seepage face as the terrestrial sediments were transgressed over the past 280 years. During this time, about 10 times more marine solid organic carbon (SOC) accumulated in marine sediments than were removed from the underlying terrestrial sediments. Indian River Lagoon thus appears to be a net sink for marine OC.

  20. soil organic matter fractionation

    NASA Astrophysics Data System (ADS)

    Osat, Maryam; Heidari, Ahmad

    2010-05-01

    Carbon is essential for plant growth, due to its effects on other soil properties like aggregation. Knowledge of dynamics of organic matter in different locations in the soil matrix can provide valuable information which affects carbon sequestration and soil the other soil properties. Extraction of soil organic matter (SOM) fractions has been a long standing approach to elucidating the roles of soil organic matter in soil processes. Several kind fractionation methods are used and all provide information on soil organic matter function. Physical fractionation capture the effects on SOM dynamics of the spatial arrangement of primary and secondary organomineral particles in soil while chemical fractionation can not consider the spatial arrangement but their organic fractions are suitable for advanced chemical characterization. Three method of physical separation of soil have been used, sieving, sedimentation and densitometry. The distribution of organic matter within physical fractions of the soil can be assessed by sieving. Sieving separates soil particles based strictly on size. The study area is located on north central Iran, between 35° 41'- 36° 01' N and 50° 42'- 51° 14' E. Mean annual precipitation about 243.8 mm and mean annual air temperature is about 14.95 °C. The soil moisture and temperature regime vary between aridic-thermic in lower altitudes to xeric-mesic in upper altitudes. More than 36 surface soil samples (0-20 cm) were collected according to land-use map units. After preliminary analyzing of samples 10 samples were selected for further analyses in five size fractions and three different time intervals in September, January and April 2008. Fractionation carried out by dry sieving in five classes, 1-2 mm, 0.5-1 mm, 270 μm-0.5mm, 53-270 μm and <53 μm. Organic matter and C/N ratio were determined for all fractions at different time intervals. Chemical fractionation of organic matter also carried out according to Tan (2003), also Mineralogical

  1. Is old organic matter simple organic matter?

    NASA Astrophysics Data System (ADS)

    Nunan, Naoise; Lerch, Thomas; Pouteau, Valérie; Mora, Philippe; Changey, Fréderique; Kätterer, Thomas; Herrmann, Anke

    2016-04-01

    Bare fallow soils that have been deprived of fresh carbon inputs for prolonged periods contain mostly old, stable organic carbon. In order to shed light on the nature of this carbon, the functional diversity profiles (MicroResp™, Biolog™ and enzyme activity spectra) of the microbial communities of long-term barefallow soils were analysed and compared with those of the microbial communities from their cultivated counterparts. The study was based on the idea that microbial communities adapt to their environment and that therefore the catabolic and enzymatic profiles would reflect the type of substrates available to the microbial communities. The catabolic profiles suggested that the microbial communities in the long-term bare-fallow soil were exposed to a less diverse range of substrates and that these substrates tended to be of simpler molecular forms. Both the catabolic and enzyme activity profiles suggested that the microbial communities from the long-term bare-fallow soils were less adapted to using polymers. These results do not fit with the traditional view of old, stable carbon being composed of complex, recalcitrant polymers. An energetics analysis of the substrate use of the microbial communities for the different soils suggested that the microbial communities from the long-term bare-fallow soils were better adapted to using readily oxidizable,although energetically less rewarding, substrates. Microbial communities appear to adapt to the deprivation of fresh organic matter by using substrates that require little investment.

  2. Remineralization and accumulation of organic carbon and nitrogen in marine sediments of eutrophic bays: the case of the Bay of Concepcion, Chile

    NASA Astrophysics Data System (ADS)

    Farías, Laura

    2003-08-01

    The Bay of Concepcion (36°40'S; 73°02'W) is a semi-enclosed and shallow embayment in which biogeochemical processes are seasonally coupled to coastal upwelling during the austral spring and summer. The nutrient cycle in the bay is complex due to the combined effects of a pronounced O 2 minimum layer and high nutrient concentrations both originating from subsurface equatorial water during coastal upwelling and a rapid rate of sediment nutrient recycling. The sediments are characterized by a high content of organic matter mainly due to the extremely high rates of phytoplankton production and deposition. During the upwelling period, a black flocculent layer frequently covers the sediment-water interface in the inner part of the bay where an extensive mat of Beggiatoa spp. develops. Three approaches are used to analyse the extent to which the benthic system recycles or retains nutrients at two stations, located at the centre (station C, St. C) and mouth (station B, St. B) of the bay for a 1-year period (March 1996-1997): (1) estimation of C and N remineralization rates based on SO 42- reduction measurements, (2) calculation of C and N turnover rates using a diagenetic model applied to total organic carbon and total nitrogen vertical distributions and, (3) construction of C and N budgets from direct measurements of sedimentation (from a sediment trap) and estimates of the C and N burial rates. Depth-integrated SO 42- reduction rates varied between 3.4 (winter) and 25.5 (summer) mmol m -2 d -1. Estimated C and N oxidation rates ranged between 7.9 and 87.8 mol C m -2 yr -1 and between 0.9 and 6.9 mol N m -2 yr -1, respectively. Each approach yielded minor differences in the C and N remineralization rates (and also minor differences between both studied stations), except when the kinetic model was applied to C and N distribution without including the presence of the flocculent layer. The rates of carbon oxidation and sulphate reduction were considerably higher than in

  3. Biomechanical Perspective on the Remineralization of Dentin

    PubMed Central

    Bertassoni, L.E.; Habelitz, S.; Kinney, J.H.; Marshall, S.J.; Marshall, G.W.

    2009-01-01

    The objective of this article is to critically evaluate the methods that are used to assess outcomes of remineralization of dentin. Currently, the most used assessment methods fall either into quantitative analysis of the mineral content of the remineralized structures or dry measurements of their mechanical properties. Properties obtained from the dehydrated organic dentin matrix may not reflect the true mechanical behavior of the remineralized tissue under physiological and hydrated conditions. Here we seek to clarify the biomechanical aspects of remineralization of dentin, pointing out the effects of hydration and dehydration on the mechanical properties of treated tissues. We also emphasize that a more appropriate endpoint to evaluate the effectiveness of remineralization in dentin should be associated with the recovery of the mechanical properties of the hydrated tissue, which is presumed to correlate well with its overall functionality. PMID:19208991

  4. Variations of iron flux and organic carbon remineralization in a subterranean estuary caused by interannual variations in recharge

    USGS Publications Warehouse

    Roy, Moutusi; Martin, Jonathan B.; Cable, Jaye E.; Smith, Christopher G.

    2013-01-01

    We determine the inter-annual variations in diagenetic reaction rates of sedimentary iron (Fe ) in an east Florida subterranean estuary and evaluate the connection between metal fluxes and recharge to the coastal aquifer. Over the three-year study period (from 2004 to 2007), the amount of Fe-oxides reduced at the study site decreased from 192 g/yr to 153 g/yr and associated organic carbon (OC) remineralization decreased from 48 g/yr to 38 g/yr. These reductions occurred although the Fe-oxide reduction rates remained constant around 1 mg/cm2/yr. These results suggest that changes in flow rates of submarine groundwater discharge (SGD) related to changes in precipitation may be important to fluxes of the diagenetic reaction products. Rainfall at a weather station approximately 5 km from the field area decreased from 12.6 cm/month to 8.4 cm/month from 2004 to 2007. Monthly potential evapotranspiration (PET) calculated from Thornthwaite’s method indicated potential evapotranspiration cycled from about 3 cm/month in the winter to about 15 cm/month in the summer so that net annual recharge to the aquifer decreased from 40 cm in 2004 to -10 cm in 2007. Simultaneously, with the decrease in recharge of groundwater, freshwater SGD decreased by around 20% and caused the originally 25 m wide freshwater seepage face to decrease in width by about 5 m. The smaller seepage face reduced the area under which Fe-oxides were undergoing reductive dissolution. Consequently, the observed decrease in Fe flux is controlled by hydrology of the subterranean estuary. These results point out the need to better understand linkages between temporal variations in diagenetic reactions and changes in flow within subterranean estuaries in order to accurately constrain their contribution to oceanic fluxes of solutes from subterranean estuaries.

  5. Estimation of Particle Flux and Remineralization Rate from Radioactive Disequilibrium

    SciTech Connect

    Michael P. Bacon; Roger Francois

    2004-05-24

    Reactive radionuclides, such as the thorium isotopes, show measurable deficiencies in the oceanic water column because of their removal by chemical scavenging due to the particle flux. Measurement of the deficiency, coupled with measurement of the radionuclide concentration in particles, allows a determination of the effective particle sinking velocity. Results to date suggest that the effective particle sinking velocity is remarkably invariant with depth. This leads to the tentative suggestion that POC concentration profiles may, to a good approximation, be used directly to determine length scales for the remineralization of sinking organic matter. Further measurements are in progress to test this idea and to evaluate its limitations. Knowledge of the remineralization length scale is essential to an evaluation of the efficiency of the biological pump as a means for deep sequestering of carbon in the ocean.

  6. Organic Matter Management

    SciTech Connect

    Izaurralde, Roberto C.; Cerri, Carlos C.

    2002-01-01

    Soil organic matter (S)M) is an essential attribute of soil quality with a key role in soil conservation and sustainable agriculture. Many practices-some involving land use changes-have been shown to increase SOM and thus received considerable attention for their possible role in climate change mitigation. Carbon sequestration in managed soils occurs when there is a net removal of atmospheric CO2 because of the balance between carbon inputs (net primary productivity) and outputs (soil respiration, management-related C emissions). Soil C sequestration has the additional appeal that all its practices conform to principles of sustainable agriculture (e.g., reduced tillage, erosion control, diverse cropping systems, improved soil fertility). Long-term field experiments have been instrumental to increase our understanding of SOM dynamics. This chapter presents fundamental concepts to guide readers on the role of SOM in sustainable agriculture and climate change mitigation.

  7. Arctic River organic matter transport

    NASA Astrophysics Data System (ADS)

    Raymond, Peter; Gustafsson, Orjan; Vonk, Jorien; Spencer, Robert; McClelland, Jim

    2016-04-01

    Arctic Rivers have unique hydrology and biogeochemistry. They also have a large impact on the Arctic Ocean due to the large amount of riverine inflow and small ocean volume. With respect to organic matter, their influence is magnified by the large stores of soil carbon and distinct soil hydrology. Here we present a recap of what is known of Arctic River organic matter transport. We will present a summary of what is known of the ages and sources of Arctic River dissolved and particulate organic matter. We will also discuss the current status of what is known about changes in riverine organic matter export due to global change.

  8. Biomimetic remineralization of dentin

    PubMed Central

    Niu, Li-na; Zhang, Wei; Pashley, David H.; Breschi, Lorenzo; Mao, Jing; Chen, Ji-hua; Tay, Franklin R.

    2013-01-01

    Objectives Remineralization of demineralized dentin is important for improving dentin bonding stability and controlling primary and secondary caries. Nevertheless, conventional dentin remineralization strategy is not suitable for remineralizing completely-demineralized dentin within hybrid layers created by etch-and-rinse and moderately aggressive self-etch adhesive systems, or the superficial part of a caries-affected dentin lesion left behind after minimally invasive caries removal. Biomimetic remineralization represents a different approach to this problem by attempting to backfill the demineralized dentin collagen with liquid-like amorphous calcium phosphate nanoprecursor particles that are stabilized by biomimetic analogs of noncollagenous proteins. Methods This paper reviewed the changing concepts in calcium phosphate mineralization of fibrillar collagen, including the recently discovered, non-classical particle-based crystallization concept, formation of polymer-induced liquid- precursors (PILP), experimental collagen models for mineralization, and the need for using phosphate-containing biomimetic analogs for biomimetic mineralization of collagen. Published work on the remineralization of resin-dentin bonds and artificial caries-like lesions by various research groups was then reviewed. Finally, the problems and progress associated with the translation of a scientifically-sound concept into a clinically-applicable approach are discussed. Results and Significance The particle-based biomimetic remineralization strategy based on the PILP process demonstrates great potential in remineralizing faulty hybrid layers or caries-like dentin. Based on this concept, research in the development of more clinically feasible dentin remineralization strategy, such as incorporating poly(anionic) acid-stabilized amorphous calcium phosphate nanoprecursor-containing mesoporous silica nanofillers in dentin adhesives, may provide a promising strategy for increasing of the

  9. Effect of crab bioturbation on organic matter processing in South West Atlantic intertidal sediments

    NASA Astrophysics Data System (ADS)

    Fanjul, Eugenia; Escapa, Mauricio; Montemayor, Diana; Addino, Mariana; Alvarez, María Fernanda; Grela, María A.; Iribarne, Oscar

    2015-01-01

    Organic matter (OM) remineralization plays a key role in controlling the biogeochemistry of marine sediments. Through their burrowing activities, bioturbating macrofauna not only induces physical, chemical and biological modifications, which can affect microbial communities responsible for organic matter remineralization, but it could also directly affect the distribution and bioavailability of sedimentary organic matter. Through in situ experiments manipulating crab and burrow density in intertidal soft-bottoms, we assessed if crab-bioturbation affects benthic metabolism, and the amount, distribution, and bioavailability of sedimentary OM. Crab-bioturbation enhanced overall benthic metabolism and benthic flux of dissolved OM toward the water column at both mudflat and saltmarsh zones. Moreover, our results revealed that bioturbation also changes the quality, bioavailability and distribution of sedimentary OM in mudflats and saltmarshes. Overall, bioturbation enhanced the proportion of labile organic carbon of bioturbated sediments and homogenized the sediment column in terms of their proportion of labile organic carbon. However, crabs also generated biogenic structures (e.g., mounds) that could promote spatial heterogeneity of high nutritional-value OM. Bioturbation-induced changes on benthic metabolism and on OM availability would result in a reduction of the storage capacity of carbon in our intertidal systems. Previous works indicated that crab-burrows trap detritus and OM-rich sediments. Our results suggest that detritus are efficiently remineralized at bioturbated sediment, and finally they are quickly exported to the water column as CO2 and DOC. Thus, crabs are modifying the OM processing at intertidal soft bottoms, and the ways in which carbon is exported to coastal waters.

  10. Interstellar organic matter in meteorites

    NASA Technical Reports Server (NTRS)

    Yang, J.; Epstein, S.

    1983-01-01

    Deuterium-enriched hydrogen is present in organic matter in such meteorites as noncarbonaceous chondrites. The majority of the unequilibrated primitive meteorites contain hydrogen whose D/H ratios are greater than 0.0003, requiring enrichment (relative to cosmic hydrogen) by isotope exchange reactions taking place below 150 K. The D/H values presented are the lower limits for the organic compounds derived from interstellar molecules, since all processes subsequent to their formation, including terrestrial contamination, decrease their D/H ratios. In contrast, the D/H ratios of hydrogen associated with hydrated silicates are relatively uniform for the meteorites analyzed. The C-13/C-12 ratios of organic matter, irrespective of D/H ratio, lie well within those observed for the earth. Present findings suggest that other interstellar material, in addition to organic matter, is preserved and is present in high D/H ratio meteorites.

  11. ENHANCED ORGANIC MATTER REMINERALIZATION AND NUTRIENT TURNOVER BY POPULATIONS OF BURROWING SHRIMP IN YAQUINA BAY, OR

    EPA Science Inventory

    Burrowing, or thalassinid, shrimp structure large areas of intertidal habitat of Pacific Northwest estuaries. This field study utilized a combination of anoxic incubations, porewater dialysis peepers, and benthic chambers to quantify the role of burrowing shrimp species on OM dec...

  12. Early diagenetic remineralization of sedimentary organic C in the Gulf of Papua deltaic complex (Papua New Guinea): Net loss of terrestrial C and diagenetic fractionation of C isotopes

    NASA Astrophysics Data System (ADS)

    Aller, Robert C.; Blair, Neal E.

    2004-04-01

    Oceania supplies ˜40% of the global riverine flux of organic carbon, approximately half of which is injected onto broad continental shelves and processed in shallow deltaic systems. The Gulf of Papua, on the south coast of the large island of New Guinea, is one such deltaic clinoform complex. It receives ˜4 Mt yr -1 particulate terrestrial organic carbon with initial particle C org loading ˜0.7 mg m -2. C org loading is reduced to ˜0.3 mg m -2 in the topset-upper foreset zones of the delta despite additional inputs of mangrove and planktonic detritus, and high net sediment accumulation rates of 1-4 cm yr -1. Carbon isotopic analyses (δ 13C, Δ 14C) of ΣCO 2 and C org demonstrate rapid (<100 yr) remineralization of both terrestrial (δ 13C <-28.6) and marine C org (δ 13C ˜-20.5) ranging in average age from modern (bomb) (Δ 14C ˜60) to ˜1000 yr (Δ 14C ˜-140). Efficient and rapid remineralization in the topset-upper foreset zone is promoted by frequent physical reworking, bioturbation, exposure, and reoxidation of deposits. The seafloor in these regions, particularly <20 m, apparently functions as a periodically mixed, suboxic batch reactor dominated by microbial biomass. Although terrestrial sources can be the primary metabolic substrates at inshore sites, relatively young marine C org often preferentially dominates pore water ΣCO 2 relative to bulk C org in the upper foreset. Thus a small quantity of young, rapidly recycled marine organic material is often superimposed on a generally older, less reactive terrestrial background. Whereas the pore water ΣCO 2 reflects both rapidly cycled marine and terrestrial sources, terrestrial material dominates the slower overall net loss of C org from particles in the topset-upper foreset zone (i.e. recycled marine C org leaves little residue). Preferential utilization of C org subpools and diagenetic fractionation of C isotopes supports the reactive continuum model as a conceptual basis for net decomposition

  13. Burial-nutrient feedbacks amplify the sensitivity of carbon dioxide to changes in organic matter remineralisation

    NASA Astrophysics Data System (ADS)

    Roth, R.; Ritz, S. P.; Joos, F.

    2014-04-01

    Changes in the marine remineralization of particulate organic carbon (POC) and calcium carbonate potentially provide a positive feedback under climate change. The responses to changes in remineralization length scales are systematically mapped with the Bern3D ocean-sediment model for CO2 and tracer fields for which observations and palaeoproxies exist. Spatio-temporal evolutions are captured by empirical orthogonal functions. Results show that the "sediment burial-nutrient feedback" amplifies the initial response in atmospheric CO2 by a factor of four to seven. A temporary imbalance between the weathering flux and the burial of organic matter and calcium carbonate lead to sustained changes the ocean's phosphate and alkalinity inventory and in turn in surface nutrient availability, marine productivity, and atmospheric CO2. It takes decades to centuries to reorganize tracers and fluxes within the ocean, many millennia to approach equilibrium for burial fluxes, while δ13C signatures are still changing 200 000 years after the perturbation. CO2 sensitivity is with 1.7 ppm m-1 about fifty times larger for a unit change in the remineralisation depth of POC than of calcium carbonate. The results highlight the role of organic matter burial for atmospheric CO2 and the substantial impacts of seemingly small changes in POC remineralisation.

  14. Bacteria-organic matter coupling and its significance for oceanic carbon cycling.

    PubMed

    Azam, F; Smith, D C; Steward, G F; Hagström, A

    1994-09-01

    This paper synthesizes current ideas on the role of the microbial loop in carbon fluxes in the ocean and proposes some directions for future research. Organic matter flux into bacteria is highly variable, which can significantly influence the pathways of carbon flow in the ocean. A goal for future research is to elucidate the mechanistic bases of bacteria-organic matter coupling. This research should take into consideration the micrometer-scale distribution of bacteria and the composition, structure, and dynamics of the organic matter field in the bacterium's microhabitat. The ideas on the interactions of bacteria with the particulate organic phase need to be revised in view of recent findings of highly abundant, previously unknown particles ranging in size from nanometers to hundreds of micrometers. The "hot-spots" in the distribution of organic matter and remineralized nutrients can influence the rates as well as the direction of biogeochemical fluxes. Slow-to-degrade dissolved organic matter (DOM) may be produced because of loose bacteria-organic matter coupling resulting in DOM storage. Its use at a later time and place has profound implications for carbon fluxes and food web dynamics. A fundamental research need for the future is to understand the ecological interactions among the members of the microbial loop in an appropriate microhabitat context. While this goal was previously intractable, new molecular and optical techniques should make it possible to understand the biogeochemical activities of the microbial loop in terms of the ecology and evolution of pelagic microbial communities.

  15. N/P re-mineralization ratios across forests worldwide

    NASA Astrophysics Data System (ADS)

    Marklein, A. R.; Houlton, B. Z.

    2012-12-01

    Decomposition of leaf litter is the primary mechanism by which nutrients are recycled in forests. Forests are a sink for atmospheric CO2, but nitrogen (N) and phosphorus (P) could limit or eliminate this ecosystem service in the future. Nutrient cycling during mineralization supplies the vast majority of nutrients to enable forest growth. Therefore, elucidating patterns by which organic N and P are mineralized by decomposing organisms or immobilized in microbial biomass is crucial to establishing controls on plant nutrient availability. Here, we compare re-mineralization N/P ratios to the stoichiometry of the initial material. We performed a meta-analysis of N and P mineralization from leaves and needles in forest ecosystems and included 112 studies, 511 litterbag sequences, and 3225 observations. Of the compiled data, net mineralization occurred in 54 studies, 372 litterbag sequences, and 1308 observations. We compare re-mineralization ratios across temperate and tropical forest systems to elucidate patterns across latitudes. We report strong and systematic regularities between decomposing litter N/P and the N/P of re-mineralization across global forests. Overall, the N/P of mineralization scales at a slope close to unity (slope = 1.4, R2=0.53, n=372), with a tendency toward higher N/P in tropical vs. temperate forests. The N/P of tropical forest re-mineralization is equal to 30/1 (R2=0.55; n=691), corresponding with the high N/P of plant foliage and litter within this biome. In contrast, the N/P of mineralization is equal to 5/1 in temperate forests (R2=0.34; n=617). A modal anomaly analysis further reveals the central tendency of mineralization N/P on that of litter, with departures from the average case tending toward a lower N/P of mineralization compared to litter substrates. These deviations suggest the potential for preferential N retention or enhanced P mineralization, or both, as opposed to more rapid N releases from decomposing organic matter. The

  16. Extraterrestrial organic matter: a review.

    PubMed

    Irvine, W M

    1998-10-01

    We review the nature of the widespread organic material present in the Milky Way Galaxy and in the Solar System. Attention is given to the links between these environments and between primitive Solar System objects and the early Earth, indicating the preservation of organic material as an interstellar cloud collapsed to form the Solar System and as the Earth accreted such material from asteroids, comets and interplanetary dust particles. In the interstellar medium of the Milky Way Galaxy more than 100 molecular species, the bulk of them organic, have been securely identified, primarily through spectroscopy at the highest radio frequencies. There is considerable evidence for significantly heavier organic molecules, particularly polycyclic aromatics, although precise identification of individual species has not yet been obtained. The so-called diffuse interstellar bands are probably important in this context. The low temperature kinetics in interstellar clouds leads to very large isotopic fractionation, particularly for hydrogen, and this signature is present in organic components preserved in carbonaceous chondritic meteorites. Outer belt asteroids are the probable parent bodies of the carbonaceous chondrites, which may contain as much as 5% organic material, including a rich variety of amino acids, purines, pyrimidines, and other species of potential prebiotic interest. Richer in volatiles and hence less thermally processed are the comets, whose organic matter is abundant and poorly characterized. Cometary volatiles, observed after sublimation into the coma, include many species also present in the interstellar medium. There is evidence that most of the Earth's volatiles may have been supplied by a 'late' bombardment of comets and carbonaceous meteorites, scattered into the inner Solar System following the formation of the giant planets. How much in the way of intact organic molecules of potential prebiotic interest survived delivery to the Earth has become an

  17. Extraterrestrial organic matter: a review

    NASA Technical Reports Server (NTRS)

    Irvine, W. M.

    1998-01-01

    We review the nature of the widespread organic material present in the Milky Way Galaxy and in the Solar System. Attention is given to the links between these environments and between primitive Solar System objects and the early Earth, indicating the preservation of organic material as an interstellar cloud collapsed to form the Solar System and as the Earth accreted such material from asteroids, comets and interplanetary dust particles. In the interstellar medium of the Milky Way Galaxy more than 100 molecular species, the bulk of them organic, have been securely identified, primarily through spectroscopy at the highest radio frequencies. There is considerable evidence for significantly heavier organic molecules, particularly polycyclic aromatics, although precise identification of individual species has not yet been obtained. The so-called diffuse interstellar bands are probably important in this context. The low temperature kinetics in interstellar clouds leads to very large isotopic fractionation, particularly for hydrogen, and this signature is present in organic components preserved in carbonaceous chondritic meteorites. Outer belt asteroids are the probable parent bodies of the carbonaceous chondrites, which may contain as much as 5% organic material, including a rich variety of amino acids, purines, pyrimidines, and other species of potential prebiotic interest. Richer in volatiles and hence less thermally processed are the comets, whose organic matter is abundant and poorly characterized. Cometary volatiles, observed after sublimation into the coma, include many species also present in the interstellar medium. There is evidence that most of the Earth's volatiles may have been supplied by a 'late' bombardment of comets and carbonaceous meteorites, scattered into the inner Solar System following the formation of the giant planets. How much in the way of intact organic molecules of potential prebiotic interest survived delivery to the Earth has become an

  18. Tracing the long-term microbial production of recalcitrant fluorescent dissolved organic matter in seawater

    NASA Astrophysics Data System (ADS)

    Jørgensen, Linda; Stedmon, Colin A.; Granskog, Mats A.; Middelboe, Mathias

    2014-04-01

    The majority of dissolved organic matter (DOM) in the ocean is resistant to microbial degradation, yet its formation remains poorly understood. The fluorescent fraction of DOM can be used to trace the formation of recalcitrant DOM (RDOM). A long-term (> 1 year) experiment revealed 27-52% removal of dissolved organic carbon and a nonlinear increase in RDOM fluorescence associated with microbial turnover of semilabile DOM. This fluorescence was also produced using glucose as the only initial carbon source, suggesting that degradation of prokaryote remnants contributes to RDOM. Our results indicate that the formation of a fluorescent RDOM component depends on the bioavailability of the substrate: the less labile, the larger the production of fluorescent RDOM relative to organic carbon remineralized. The anticipated increase in microbial carbon demand due to ocean warming can potentially force microbes to degrade less labile substrates, thereby increasing RDOM production and stimulating ocean carbon storage.

  19. Sedimentary organic matter distributions, burrowing activity, and biogeochemical cycling: Natural patterns and experimental artifacts

    NASA Astrophysics Data System (ADS)

    Michaud, Emma; Aller, Robert, C.; Stora, Georges

    2010-11-01

    resources or in sediment mechanical properties associated with treatments, the latter in part coupled to remineralization processes such as exopolymer production, may explain the burrowing responses. In addition to demonstrating how species may respond to physical sedimentation events (substrate homogenization) and patterns of reactive organic matter redistribution, these experiments suggest that infaunal species interactions in microcosms, including the absolute and relative fluxes of remineralized solutes, may be subject to artifacts depending on exactly how sediments are introduced experimentally. Nonlocal transport and cylinder microenvironment transport - reaction models readily demonstrate how the multiple interactions between burrowing patterns and remineralization rate distributions can alter relative flux balances, decomposition pathways, and time to steady state.

  20. Biogeochemical and hydrographic controls on chromophoric dissolved organic matter distribution in the Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Swan, Chantal M.; Siegel, David A.; Nelson, Norman B.; Carlson, Craig A.; Nasir, Elora

    2009-12-01

    Recent in situ observations of chromophoric dissolved organic material (CDOM) in the Pacific Ocean reveal the biogeochemical controls on CDOM and indicate predictive potential for open-ocean CDOM in diagnosing particulate organic matter (POM) remineralization rates within ocean basins. Relationships between CDOM and concentrations of dissolved oxygen, nutrients and inorganic carbon in the subthermocline waters of the Pacific reflect the relative influences of water mass ventilation and water-column oxidative remineralization. Apparent in situ oxygen utilization (AOU) accounts for 86% and 61% of variance in CDOM abundance, respectively, in Antarctic Intermediate Water and North Pacific Intermediate Water. In the deep waters of the Pacific below the zone of remineralization, AOU explains 26% of CDOM variability. The AOU-CDOM relationship results from competing biogeochemical and advective processes within the ocean interior. Dissolved organic carbon (DOC) is not statistically linked to the CDOM or AOU distributions, indicating that the majority of CDOM production occurs during the remineralization of sinking POM and thus potentially provides key information about carbon export. Once formed in the ocean interior, CDOM is relatively stable until it reaches the surface ocean where it is destroyed by solar bleaching. Susceptibility to bleaching confers an additional tracer-like quality for CDOM in water masses with active convection, such as mode waters that appear as subsurface CDOM minima. In the surface ocean, atypically low CDOM abundance highlights a region of unusually extreme oligotrophy: the subtropical South Pacific gyre. For these hyper-oligotrophic waters, the present CDOM observations are consistent with analysis of in situ radiometric observations of light attenuation and reflectance, demonstrating the accuracy of the CDOM spectrophotometric observations. Overall, we illustrate how CDOM abundance in the ocean interior can potentially diagnose rates of

  1. The contentious nature of soil organic matter.

    PubMed

    Lehmann, Johannes; Kleber, Markus

    2015-12-01

    The exchange of nutrients, energy and carbon between soil organic matter, the soil environment, aquatic systems and the atmosphere is important for agricultural productivity, water quality and climate. Long-standing theory suggests that soil organic matter is composed of inherently stable and chemically unique compounds. Here we argue that the available evidence does not support the formation of large-molecular-size and persistent 'humic substances' in soils. Instead, soil organic matter is a continuum of progressively decomposing organic compounds. We discuss implications of this view of the nature of soil organic matter for aquatic health, soil carbon-climate interactions and land management.

  2. The contentious nature of soil organic matter.

    PubMed

    Lehmann, Johannes; Kleber, Markus

    2015-12-01

    The exchange of nutrients, energy and carbon between soil organic matter, the soil environment, aquatic systems and the atmosphere is important for agricultural productivity, water quality and climate. Long-standing theory suggests that soil organic matter is composed of inherently stable and chemically unique compounds. Here we argue that the available evidence does not support the formation of large-molecular-size and persistent 'humic substances' in soils. Instead, soil organic matter is a continuum of progressively decomposing organic compounds. We discuss implications of this view of the nature of soil organic matter for aquatic health, soil carbon-climate interactions and land management. PMID:26595271

  3. Priming of native soil organic matter by pyrogenic organic matter

    NASA Astrophysics Data System (ADS)

    DeCiucies, Silene; Dharmakeerthi, Saman; Whitman, Thea; Woolf, Dominic; Lehmann, Johannes

    2015-04-01

    Priming, in relation to pyrogenic organic matter (PyOM), describes the change in mineralization rate of non-pyrogenic ("native") soil organic matter (nSOM) due to the addition of PyOM. Priming may be 'positive', in that the addition of pyC increases the mineralization rate of native SOM, or 'negative', in that the mineralization rate of nSOM is decreased. Reasons for increased mineralization may include: (i) co-metabolism: microbial decomposition of labile C-additions increases microbial activity, and facilitates additional decomposition of npSOC by active enzymes; (ii) stimulation: substrate additions result in lifted pH, nutrient, oxygen, or water constraints resulting in increased microbial activity. Decreased mineralization may be a result of: (i) inhibition: the opposite of stimulation whereby constraints are aggravated by substrate addition. Substrate addition may also cause inhibition by interfering with enzymes or signaling compounds; (ii) preferential substrate utilization: labile fraction of PyOM additions are preferentially used up by microbes thus causing a decrease in nSOC decomposition; (iii) sorption: organic compounds are adsorbed onto PyOM surfaces, decreasing their rate of mineralization; (iv) stabilization: formation of organo-mineral associations forms stable SOC pools. We have conducted a suite of experiments to investigate these potential interactions. In a seven year long incubation study, PyOM additions increased total OM mineralization for the first 2.5 years, was equal to control after 6.2 years, and was 3% lower after 7.1 years. Cumulative nSOM mineralization was 23% less with the PyOM additions than without, and over 60% of the added PyOM was present in the labile soil fraction after the 7.1 year incubation. Two additional incubation studies, one with and without plants, showed greater nSOM mineralization in the short term and lower nSOM mineralization over the long term. Increased nSOC mineralization due to the presence of plants was

  4. Dissolved Organic Carbon Distribution, Export and Subsequent Remineralization in the Mesopelagic and Bathypelagic Realms of the North Atlantic Basin

    NASA Astrophysics Data System (ADS)

    Carlson, C. A.; Hansell, D. A.; Nelson, N. B.; Siegel, D. A.; Smethie, W. M.; Khatiwala, S.

    2010-12-01

    Dissolved organic carbon (DOC) was measured for three meridional transects in the North Atlantic as part of the US CLIVAR Repeat Hydrography program in 2003.The hydrographic sections covered a latitudinal range of 6°S to 63° N along longitudes 20°W (CLIVAR line A16), 52°W (A20) and 66°W (A22). Over 3700 individual measurements reveal unprecedented detail in the DOC distribution and systematic variations in the mesopelagic and bathypelagic zones of the North Atlantic basin. Latitudinal gradients in DOC concentrations combined with published estimates of ventilation rates for the main thermocline and North Atlantic Deep Water (NADW) indicate a net DOC export rate of 0.081 Pg C yr-1 from of the epipelagic zone into the mesopelagic and bathypelagic zones. Model II regression and multiple linear regression models applied to pairwise measures of DOC and chlorofluorocarbon (CFC-12) ventilation age, retrieved from major water masses within the main thermocline and NADW, indicate decay rates for exported DOC ranging from 0.13 to 0.94 µmol kg-1 yr-1, with higher DOC concentrations driving higher rates. The contribution of DOC oxidation to oxygen consumption ranged from 5 to 29% while mineralization of sinking biogenic particles drove the balance of the apparent oxygen utilization.

  5. Dissolved organic carbon export and subsequent remineralization in the mesopelagic and bathypelagic realms of the North Atlantic basin

    NASA Astrophysics Data System (ADS)

    Carlson, Craig A.; Hansell, Dennis A.; Nelson, Norman B.; Siegel, David A.; Smethie, William M.; Khatiwala, Samar; Meyers, Meredith M.; Halewood, Elisa

    2010-08-01

    Dissolved organic carbon (DOC) data are presented from three meridional transects conducted in the North Atlantic as part of the US Climate Variability (CLIVAR) Repeat Hydrography program in 2003. The hydrographic sections covered a latitudinal range of 6°S to 63°N along longitudes 20°W (CLIVAR line A16), 52°W (A20) and 66°W (A22). Over 3700 individual measurements reveal unprecedented detail in the DOC distribution and systematic variations in the mesopelagic and bathypelagic zones of the North Atlantic basin. Latitudinal gradients in DOC concentrations combined with published estimates of ventilation rates for the main thermocline and North Atlantic Deep Water (NADW) indicate a net DOC export rate of 0.081 Pg C yr -1 from the epipelagic zone into the mesopelagic and bathypelagic zones. Model II regression and multiple linear regression models applied to pairwise measures of DOC and chlorofluorocarbon (CFC-12) ventilation age, retrieved from major water masses within the main thermocline and NADW, indicate decay rates for exported DOC ranging from 0.13 to 0.94 μmol kg -1 yr -1, with higher DOC concentrations driving higher rates. The contribution of DOC oxidation to oxygen consumption ranged from 5 to 29% while mineralization of sinking biogenic particles drove the balance of the apparent oxygen utilization.

  6. Environmental factors regulating soil organic matter chlorination

    NASA Astrophysics Data System (ADS)

    Svensson, Teresia; Montelius, Malin; Reyier, Henrik; Rietz, Karolina; Karlsson, Susanne; Lindberg, Cecilia; Andersson, Malin; Danielsson, Åsa; Bastviken, David

    2016-04-01

    Natural chlorination of organic matter is common in soils. Despite the widespread abundance of soil chlorinated soil organic matter (SOM), frequently exceeding soil chloride abundance in surface soils, and a common ability of microorganisms to produce chlorinated SOM, we lack fundamental knowledge about dominating processes and organisms responsible for the chlorination. To take one step towards resolving the terrestrial chlorine (Cl) puzzle, this study aims to analyse how environmental factors influence chlorination of SOM. Four factors were chosen for this study: soil moisture (W), nitrogen (N), chloride (Cl) and organic matter quality (C). These factors are all known to be important for soil processes. Laboratory incubations with 36Cl as a Cl tracer were performed in a two soil incubation experiments. It was found that addition of chloride and nitrogen seem to hamper the chlorination. For the C treatment, on the other hand, the results show that chlorination is enhanced by increased availability of labile organic matter (glucose and maltose). Even higher chlorination was observed when nitrogen and water were added in combination with labile organic matter. The effect that more labile organic matter strongly stimulated the chlorination rates was confirmed by the second separate experiment. These results indicate that chlorination was not primarily a way to cut refractory organic matter into digestible molecules, representing one previous hypothesis, but is related with microbial metabolism in other ways that will be further discussed in our presentation.

  7. Chemodestructive fractionation of soil organic matter

    NASA Astrophysics Data System (ADS)

    Popov, A. I.; Rusakov, A. V.

    2016-06-01

    The method of chemodestructive fractionation is suggested to assess the composition of soil organic matter. This method is based on determination of the resilience of soil organic matter components and/or different parts of organic compounds to the impact of oxidizing agents. For this purpose, a series of solutions with similar concentration of the oxidant (K2Cr2O7), but with linearly increasing oxidative capacity was prepared. Chemodestructive fractionation showed that the portion of easily oxidizable (labile) organic matter in humus horizons of different soil types depends on the conditions of soil formation. It was maximal in hydromorphic soils of the taiga zone and minimal in automorphic soils of the dry steppe zone. The portion of easily oxidizable organic matter in arable soils increased with an increase in the rate of organic fertilizers application. The long-lasting agricultural use of soils and burying of the humus horizons within the upper one-meter layer resulted in the decreasing content of easily oxidizable organic matter. It was found that the portion of easily oxidizable organic matter decreases by the mid-summer or fall in comparison with the spring or early summer period.

  8. Controls on the preservation of buried organic matter in an anoxic coastal marine sediment

    SciTech Connect

    Haddad, R.I. ); Martens, C.S. )

    1992-01-01

    Previous work detailing the carbon budget for the upper meter of sediments at Station A-1, Cap Lookout Bight, N.C., indicates that of the 165 [+-] 20 mol C/m[sup 2]y buried below the sediment-water interface, 71 [+-] 14% survives remineralization on a ten-year time scale. Whether this high degree of preservation is due to the nature of the system or to the nature of the organic matter (OM) itself is of considerable interest to geochemists interested in either the dynamics of global element cycling or the prediction of ancient deposition of hydrocarbon-prone organic facies. Organic geochemical measurements have been made to evaluate and compare the carbon budget in terms of the biochemically recognizable carbon fraction (BRC). Results from this study show that the BRC fraction accounts for < 30% of the TOC in the 0--5cm surface interval and that this decreases to 18 [+-] 8% by a depth of 100cm. In terms of carbon preservation, it appears that approximately 50% of the buried BRC fraction survives early diagenesis. Evaluation of the CHS fraction indicates that aside from some possible incorporation of labile biochemicals within the fulvic acids, elemental analysis and CP/MAS 13C-NMR results support a marine/algal/bacterial source for the bulk of the humic organic matter. Comparative microbial sulfate reduction studies employing independent manipulation of both the organic matter and sulfate oxidant concentrations were performed in order to evaluate the effect of inorganic oxidant availability on organic matter preservation. The authors conclude that while the buried organic matter is predominantly derived from microbially-reactive algal/bacterial sources, pre-depositional diagenetic processes effectively transform it into a microbial unreactive form.

  9. Efficient export of carbon to the deep ocean through dissolved organic matter.

    PubMed

    Hopkinson, Charles S; Vallino, Joseph J

    2005-01-13

    Oceanic dissolved organic carbon (DOC) constitutes one of the largest pools of reduced carbon in the biosphere. Estimated DOC export from the surface ocean represents 20% of total organic carbon flux to the deep ocean, which constitutes a primary control on atmospheric carbon dioxide levels. DOC is the carbon component of dissolved organic matter (DOM) and an accurate quantification of DOM pools, fluxes and their controls is therefore critical to understanding oceanic carbon cycling. DOC export is directly coupled with dissolved organic nitrogen and phosphorus export. However, the C:N:P stoichiometry (by atoms) of DOM dynamics is poorly understood. Here we study the stoichiometry of the DOM pool and of DOM decomposition in continental shelf, continental slope and central ocean gyre environments. We find that DOM is remineralized and produced with a C:N:P stoichiometry of 199:20:1 that is substantially lower than for bulk pools (typically >775:54:1), but greater than for particulate organic matter (106:16:1--the Redfield ratio). Thus for a given mass of new N and P introduced into surface water, more DOC can be exported than would occur at the Redfield ratio. This may contribute to the excess respiration estimated to occur in the interior ocean. Our results place an explicit constraint on global carbon export and elemental balance via advective pathways. PMID:15650735

  10. Rapid organic matter sulfurization in sinking particles from the Cariaco Basin water column

    NASA Astrophysics Data System (ADS)

    Raven, Morgan Reed; Sessions, Alex L.; Adkins, Jess F.; Thunell, Robert C.

    2016-10-01

    Organic matter (OM) burial in marine sediments is a potentially important control on global climate and the long-term redox state of the earth's surface. Still, we have only a limited understanding of the processes that stabilize OM and facilitate its preservation in the geologic record. Abiotic reactions with (poly)sulfides can enhance the preservation potential of OM, but for this process to be significant it needs to compete with OM remineralization, the majority of which occurs before sinking particles reach the sea floor. Here we investigate whether OM sulfurization occurs within sinking particles in the Cariaco Basin, a modern sulfidic marine environment with high rates of OM burial. Proto-kerogen in sinking particles is frequently more sulfur-rich and 34S-depleted than expectations for biomass, with a composition that is difficult to explain by mixing with resuspended or terrigenous material. Instead, it appears that sulfur is being incorporated into OM on a timescale of days in sinking particles. The flux of this abiogenic organic S from particles is equivalent to approximately two-thirds of the total amount of proto-kerogen S at 10 cm depth in underlying sediments (ODP Core 1002B); after 6000 years of more gradual sulfurization reactions, potential water column sources are still equivalent to nearly half of the total proto-kerogen S in Cariaco sediments. Water column sulfurization is most extensive during periods of upwelling and high primary productivity and appears to involve elemental S, possibly via polysulfides. This process has the potential to deliver large amounts of OM to the sediments by making it less available for remineralization, generating OM-rich deposits. It represents a potentially dynamic sink in the global carbon cycle that can respond to changes in environmental conditions, including the size and intensity of O2-depleted environments. Water column OM sulfurization could also have played a more significant role in the carbon cycle

  11. Factors Regulating Soil Organic Matter Chlorination

    NASA Astrophysics Data System (ADS)

    Svensson, T.; Gustavsson, M.; Reyier, H.; Rietz, K.; Karlsson, S.; Göransson, C.; Andersson, M.; Öberg, G.; Bastviken, D.

    2013-12-01

    Natural chlorination of organic matter is a common process in various soils. Despite the widespread abundance of soil organic chlorine, knowledge on the processes and regulation of soil organic matter chlorination are modest. The purpose of this study is to elucidate how environmental factors may influence chlorination of organic matter in soil. Four factors were chosen for this study; water content, and nitrogen, organic carbon, and chloride concentrations. The variables are all known in different ways as important for microbes and transformation of chlorine in soil. The soil was collected from 5-15 cm depth in a coniferous forest southeast of Sweden. To test how the selected factors influenced chlorination of organic matter, we used soil laboratory incubations using 36Cl-chloride as a radioisotopic marker. A multivariate factorial design with two levels of i) soil moisture, ii) chloride amendment, iii) nitrogen amendment, and iv) glucose and maltose addition was used to simultaneously test for possible combination effects for all factors. A known radioactivity of 36chloride was added to the soil samples and incubated with four different factor treatments during an incubation period of 15 and 60 days. This presentation will discuss the results of this study including what combination of factors enhanced or hampered chlorination and thereby discuss previous observed variability of organic chlorine and chloride in soil.

  12. Remineralization VS Reductive Dissolution Pathway of Phosphorus Cycling: a Case Study in the Chesapeake Bay

    NASA Astrophysics Data System (ADS)

    Jaisi, D. P.; Joshi, S.; Kukkadapu, R. K.; Burdige, D.; Sparks, D. L.

    2015-12-01

    Coastal hypoxia have spread exponentially worldwide due to increased anthropogenic loading of nutrients in coastal waters. Hypoxia exerts an influence on the stability of minerals and organic debris, direction of nutrient flux at the sediment-water interface, and the extent of benthic-pelagic coupling. This study aimed to address fundamental questions related to sediment phosphorus (P) dynamics in response to transient bottom water hypoxia particularly on P effluxes at the sediment-water interface and P burial (as authigenic/vivianite P) under two pathways: remineralization of organic P (coupled C-P pathway) and reductive dissolution of ferric Fe-bound P (coupled Fe-P pathway). Authigenic phosphate isotope data suggest that the regeneration of inorganic P in the sediment from organic matter degradation (remineralization) is the predominant, if not sole, pathway for authigenic P precipitation in the sediments. Interestingly, ferric Fe-bound phosphate oxygen isotopes are heavier than equilibrium. This means that the ferric Fe-bound P pool in these sediments is largely composed of particulate P from terrestrial sources composed primarily of Fe phyllosilicates plus potentially vivianite that are largely resistant against dissolution in the anoxic sediment column. These results collectively support the predominance of coupled C-P pathway of P cycling, rather than Fe-P coupling, in hypoxic environment in the Chesapeake Bay.

  13. Control of organic matter on the magnetic properties of surficial marine sediments. A simple kinetic model

    NASA Astrophysics Data System (ADS)

    Mohamed Falcon, K. J.; Andrade, A.; Rey, D.; Rubio, B.

    2014-12-01

    Magnetic properties of marine sediments in the Galician Rias, in NW Spain, have shown that in these shallow marine settings the magnetic mineral assemblage, and its bulk magnetic properties, is controlled by grain size, wave climate, and organic matter content. The grain size effect is explained by concentration of diamagnetic biogenic carbonates in the coarse fraction, which dilutes the concentration-dependent magnetic properties. Furthermore, this effect is enhanced by the hydrodynamic sorting of the heavy minerals, like magnetite, that become concentrated in the finer fractions. Waves on the other hand concentrate the coarser bioclasts in the shallower areas along the coastal margins of the rias, and consequently these areas show the lowest magnetic mineral concentrations. Magnetic minerals are therefore more abundant in the deeper central axis and towards the external, more oceanic, areas of the rias. Another effect of waves is periodic resuspension of fine sediments, which allows them to be reoxigenated preventing the onset of reductive diagenesis. This effect is best seen in sediment cores, where organic matter remineralization promotes dissolution of magnetic iron oxides and oxyhydroxides. Areas where resuspension is frequent and/or deeper areas where sediments stay in the water column for longer have lower degrees of reductive early diagenesis. In addition to its downcore effect, organic matter also controls the magnetic properties of surficial sediments. Our results in the Ria de Muros, at the north of our study area, have shown that a simple kinetic model is enough to quantify the effect of organic matter content on the dissolution of magnetite. We have found that a Total Organic Carbon increase of 0.35% reduces magnetite concentration of surface samples by half. These effects observed in the Ria de Muros have also been confirmed for published results in the southern Rias Baixas previously studied by our research group.

  14. Carbon remineralization in the Amazon Guianas tropical mobile mudbelt: A sedimentary incinerator

    NASA Astrophysics Data System (ADS)

    Aller, Robert C.; Blair, Neal E.

    2006-11-01

    The Amazon River spawns a vast mobile mudbelt extending ˜1600 km from the equator to the Orinoco delta. Deposits along the Amazon-Guianas coastline are characterized by some of the highest C org remineralization rates reported for estuarine, deltaic, or shelf deposits, however, paradoxically, except where stabilized by mangroves or intertidal algal mats, they are usually suboxic and nonsulfidic. A combination of tides, wind-driven waves, and coastal currents forms massive fluid muds and mobile surface sediment layers ˜0.5-2 m thick which are dynamically refluxed and frequently reoxidized. Overall, the seabed functions as a periodically mixed batch reactor, efficiently remineralizing organic matter in a gigantic sedimentary incinerator of global importance. Amazon River material entering the head of this dynamic dispersal system carries an initial terrestrial sedimentary C org loading of ˜ 0.7 mg C m -2 particle surface area. Total C org loading is lowered to ˜ 0.2 mg C m -2 in the proximal delta topset, ˜60-70% of which remains of terrestrial origin. Loading decreases further to 0.12-0.14 mg C m -2 (˜60% terrestrial) in mudbanks ˜600 km downdrift along French Guiana, values comparable to those found in the oligotrophic deepsea. DOC/ΣCO 2 ratios in pore waters of French Guiana mudbanks indicate that >90% of metabolized organic substrates are completely oxidized. Within the Amazon delta topset at the head of the dispersal system, both terrestrial and marine organic matter contribute substantially to early diagenetic remineralization, although reactive marine substrate dominates (˜60-70%). The conditional rate constant for terrestrial C org in the delta topset is ˜0.2 a -1. As sedimentary C org is depleted during transit, marine sources become virtually the exclusive substrate for remineralization except very near the mangrove shoreline. The δ13C and Δ 14C values of pore water ΣCO 2 in mudbanks demonstrate that the primary source of remineralized organic

  15. Large-scale variations in the stoichiometry of marine organic matter respiration

    NASA Astrophysics Data System (ADS)

    Devries, Tim; Deutsch, Curtis

    2014-12-01

    The elemental composition of marine organic matter governs resource competition among plankton, and couples the global cycles of carbon, nutrients and oxygen. Observations have revealed systematic large-scale variation in the ratios of these essential elements removed from surface waters by phytoplankton. However, an impact of this variability on deep ocean properties has not been detected. Here we use a data-constrained ocean circulation model and observed long-term mean distributions of dissolved oxygen and the nutrient phosphate to show that there is a threefold variation across latitudes in the amount of dissolved oxygen consumed per unit of phosphate released during organic matter respiration. This pattern of remineralization ratios is shown to significantly modify the extent and distribution of low-oxygen water masses in the interior ocean. We also find that ocean biomes with distinct light and nutrient availability are characterized by different regional stoichiometries. These findings suggest that in a more stratified ocean, an increase in light exposure and decrease in nutrient concentration could raise the C:P ratio of phytoplankton, and the associated carbon storage by the ocean’s biological pump.

  16. Organic Matter Loading Affects Lodgepole Pine Seedling Growth

    NASA Astrophysics Data System (ADS)

    Wei, Xiaohua; Li, Qinglin; Waterhouse, M. J.; Armleder, H. M.

    2012-06-01

    Organic matter plays important roles in returning nutrients to the soil, maintaining forest productivity and creating habitats in forest ecosystems. Forest biomass is in increasing demand for energy production, and organic matter has been considered as a potential supply. Thus, an important management question is how much organic matter should be retained after forest harvesting to maintain forest productivity. To address this question, an experimental trial was established in 1996 to evaluate the responses of lodgepole pine seedling growth to organic matter loading treatments. Four organic matter loading treatments were randomly assigned to each of four homogeneous pine sites: removal of all organic matter on the forest floor, organic matter loading quantity similar to whole-tree-harvesting residuals left on site, organic matter loading quantity similar to stem-only-harvesting residuals, and organic matter loading quantity more similar to what would be found in disease- or insect-killed stands. Our 10-year data showed that height and diameter had 29 and 35 % increase, respectively, comparing the treatment with the most organic matter loading to the treatment with the least organic matter loading. The positive response of seedling growth to organic matter loading may be associated with nutrients and/or microclimate change caused by organic matter, and requires further study. The dynamic response of seedling growth to organic matter loading treatments highlights the importance of long-term studies. Implications of those results on organic matter management are discussed in the context of forest productivity sustainability.

  17. Functional remineralization of carious dentin

    NASA Astrophysics Data System (ADS)

    Pugach, Megan Kardon

    A primary goal of dental tissue engineering is the biological reconstruction of tooth substrate destroyed by caries or other diseases affecting tooth mineralization. Traditionally, dentists treat caries by using invasive techniques to remove the diseased dental tissue and restore the lesion, ideally preventing further progression of decay. Success in strategies associated with remineralization of enamel and root caries have contributed to the less invasive prospect of remineralization of dentinal carious lesions. The central hypothesis of this dissertation is that carious dentin lesions can be remineralized if the lesions contain residual mineral. Caries Detector (CD) stained zones (pink, light pink, transparent and normal) of arrested carious dentin lesions were characterized according to microstructure by atomic force microscopy (AFM) imaging, mineral content by digital transverse microradiography, and nanomechanical properties by AFM-based nanoindentation. CD-stained and unstained zones had significantly different microstructure, mineral content and nanomechanical properties. Furthermore, the most demineralized carious zone contained residual mineral. To obtain reproducible, standardized dentin caries lesions, we characterized the lesions from an artificial carious dentin lesion model using a 0.05M acetate demineralization buffer. The artificial caries-like lesions produced by the buffer had similar mineral content and nanomechanical properties in the stained and unstained zones as natural dentin lesions. Both natural and artificial lesions had significant correlations between mineral content and nanomechanical properties. Mineral crystallite size and shape was examined by small angle x-ray scattering. Both natural and artificial carious dentin had different mineral sizes than normal dentin. Collagen in natural and artificial carious dentin lesions was examined by trichrome stain, AFM high-resolution imaging, and UV resonance Raman spectroscopy, to determine if

  18. Organic matter of urban soils: A review

    NASA Astrophysics Data System (ADS)

    Vodyanitskii, Yu. N.

    2015-08-01

    Urban environment exerts an ambiguous effect on the organic pool of soils; it may decrease (as compared to the background values) in some parts of a city and increase in other parts. The organic matter accumulation in urban soils is promoted by the input of aerial organic pollutants; slowed down mineralization of plant residues under the influence of contamination; and increased productivity of the plants owing to elevated temperatures, high content of carbon dioxide in the air, and maintenance of green zones (sodding of vast areas in cities, application of peat, irrigation and drainage of soils.)

  19. Shallow Remineralization in the Sargasso Sea Estimated from Seasonal Variations in Oxygen and Dissolved Inorganic Carbon

    NASA Technical Reports Server (NTRS)

    Ono, S.; Ennyu, A.; Najjar, R. G.; Bates, N.

    1998-01-01

    A diagnostic model of the mean annual cycles of dissolved inorganic carbon (DIC) and oxygen below the mixed layer at the Bermuda Atlantic Time-series Study (BATS) site is presented and used to estimate organic carbon remineralization in the seasonal thermocline. The model includes lateral and vertical advection as well as vertical, diffusion. Very good agreement is found for the remineralization estimates based on oxygen and DIC. Net remineralization averaged from mid-spring to early fall is found to be a maximum between 120 and 140 in. Remineralization integrated between 100 (the compensation depth) and 250 m during this period is estimated to be about 1 mol C/sq m. This flux is consistent with independent estimates of the loss of particulate and dissolved organic carbon.

  20. Organic matters: investigating the sources, transport, and fate of organic matter in Fanno Creek, Oregon

    USGS Publications Warehouse

    Sobieszczyk, Steven; Keith, Mackenzie; Goldman, Jami H.; Rounds, Stewart A.

    2015-01-01

    The U.S. Geological Survey (USGS), in cooperation with Clean Water Services, recently completed an investigation into the sources, transport, and fate of organic matter in the Fanno Creek watershed. The information provided by this investigation will help resource managers to implement strategies aimed at decreasing the excess supply of organic matter that contributes to low dissolved-oxygen levels in Fanno Creek and downstream in the Tualatin River during summer. This fact sheet summarizes the findings of the investigation.

  1. Organic matter and sandstone-type uranium deposits: a primer

    USGS Publications Warehouse

    Leventhal, Joel S.

    1979-01-01

    Organic material is intimately associated with sandstone-type uranium deposits in the western United States.. This report gives details of the types of organic matter and their possible role in producing a uranium deposit. These steps include mobilization of uranium from igneous rocks, transportation from the surface, concentration by organic matter, reduction by organic matter, and preservation of the uranium deposit.

  2. Quantitative measurements of remineralization of incipient caries.

    PubMed

    Linton, J L

    1996-12-01

    White demineralized areas after the removal of orthodontic appliances remain a problem for clinicians and patients. The main objective of this study is to assess clinical photography as a method for the evaluation of caries and white spots and the in vivo study of remineralization of carious lesions. The secondary objective was to compare the effect of different levels of both experimental and commercial fluoride solutions on the remineralization of enamel carious lesions. White spot lesions were created with an acid solution on extracted permanent human teeth, and the lesions were remineralized in remineralizing solutions with or without fluoride ions. The changes in the enamel surface during the demineralization and the remineralization processes were recorded with a 35 mm clinical camera. Photographs were taken of the experimentally created white spots, the samples were sectioned for microradiography testing, and the actual mineral contents of the white spot lesions were calculated from the microradiographs. The enamel lesions were further analyzed by powder x-ray diffraction to confirm whether fluoride was incorporated into the lesions during the remineralization period. From this experiment it can be concluded: (1) clinical photography as currently practiced is not an adequate method of monitoring the remineralization of white spots with large lesion depths and (2) the experimental solution that contains 50 ppm fluoride had a higher efficacy for remineralization than the control solution or the commercial mouth rinse, which contained 225 ppm fluoride.

  3. Subaerial weathering of sedimentary organic matter

    USGS Publications Warehouse

    Clayton, J.L.; Swetland, P.J.

    1978-01-01

    Small diameter core samples were taken from outcrops of the Permian Phosphoria Formation and the Cretaceous Pierre Shale of the Western United States to determine the effects of weathering on organic matter in shale outcrops. While the Pierre Shale core showed no evidence of weathering, the Phosphoria Formation showed significant reduction of overall organic content and pronounced changes in organic composition over the near-surface interval of the core. Total organic carbon is lower by as much as 60% over the upper 2 ft of the core. Chloroform-soluble organic matter and total hydrocarbon (C15+) concentrations are 50% lower over this same interval. The ratio of saturated to aromatic hydrocarbons decreases steadily with core depth over the upper 2.6 ft of the core. Aromatic hydrocarbons are enriched in the stable carbon-13 isotope by an average of 1.7%. over this same interval. Shallow core samples also show a loss of n-paraffins relative to branched/cyclic compounds in the saturated C15+ fraction. Although the extent of weathering is variable, certain characteristic effects are recognizable and can be applied to the interpretation of outcrop data in organic geochemical studies. ?? 1978.

  4. Isotopic analysis of cometary organic matter

    NASA Astrophysics Data System (ADS)

    Kerridge, J. F.

    1991-04-01

    Carbon isotope ratios have been measured for CN in the coma of Comet Halley and for several CHON particles emitted by Halley. Of these, only the CHON-particle data may be reasonably related to organic matter in the cometary nucleus, but the true range of (C-13)/(C-12) values in those particles is quite uncertain. The D/H ratio in H2O in the Halley coma resembles that in Titan/Uranus.

  5. Isotopic analysis of cometary organic matter

    NASA Technical Reports Server (NTRS)

    Kerridge, John F.

    1991-01-01

    Carbon isotope ratios have been measured for CN in the coma of Comet Halley and for several CHON particles emitted by Halley. Of these, only the CHON-particle data may be reasonably related to organic matter in the cometary nucleus, but the true range of (C-13)/(C-12) values in those particles is quite uncertain. The D/H ratio in H2O in the Halley coma resembles that in Titan/Uranus.

  6. Analysis of Organic matter from cloud particles

    NASA Astrophysics Data System (ADS)

    Bank, Shelton; Castillo, Raymond

    1987-03-01

    Organic matter collected from filtration of two separate cloud events was analysed by Fourier Transform Infrared Spectroscopy. Particles collected from different size filters were separated by color and each type of particle gave rise to a characteristic spectrum. The major constituents were identified as complex proteins and cellulose. Additionally, some degraded material (likely protein) and an unidentified orange-brown material were present. Finally some trace components were identified as wax, oil, silicon oil, polyvinyl chloride, calcium carbonate, clay, sand and polyethylene.

  7. Dissolved Organic Matter in Headwater Streams: Compositional Variability across Climatic Regions of North America

    NASA Astrophysics Data System (ADS)

    Jaffé, R.; Yamashita, Y.; Maie, N.; Cooper, W. T.; Dittmar, T.; Dodds, W. K.; Jones, J. B.; Myoshi, T.; Ortiz-Zayas, J. R.; Podgorski, D. C.; Watanabe, A.

    2012-10-01

    Dissolved organic matter (DOM) represents the largest organic matter pool in freshwater systems, but much of it remains molecularly uncharacterized. Although freshwater systems cover only a small area of the earth's surface, inland waters are an important component of the global carbon cycle. The traditional idea that rivers are simply conduits for refractory carbon delivery to coastal areas is inconsistent with carbon flux estimates, and streams have been shown to serve as reactors for DOM cycling. The overall quality of DOM, and its associated reactivity, can be related to its chemical composition and molecular structure. However, the variability of DOM composition in freshwater ecosystems, particularly in headwater streams, is poorly characterized. Detailed molecular studies of DOM from small streams across climatic regions, which could provide critical information regarding carbon dynamics on a more global scale, have not been performed. To address these issues, this study applies a multi-method analytical approach in an attempt to assess molecular characteristics of DOM and ultrafiltered DOM (UDOM) in headwater streams from different climatic regions in North America. In general terms the chemical and molecular characteristics of UDOM from six different biomes were determined in unsurpassed detail to feature some clear general similarities but also specific differences. While the degree of similarity is remarkable, and suggests similar source strengths, such as soil-derived organic matter and/or similar diagenetic degradation processes for DOM from vastly different environments, each sample was clearly unique in its overall composition, featuring some distinct molecular patterns for at least one or more of the analytical determinations. Molecular and compositional differences of DOM from headwater streams should result from variations in DOM sources and localized environmental conditions, and consequently feature different photo- and bio-reactivity and

  8. Variable C : N : P stoichiometry of dissolved organic matter cycling in the Community Earth System Model

    DOE PAGES

    Letscher, R. T.; Moore, J. K.; Teng, Y. -C.; Primeau, F.

    2015-01-12

    Dissolved organic matter (DOM) plays an important role in the ocean's biological carbon pump by providing an advective/mixing pathway for ~ 20% of export production. DOM is known to have a stoichiometry depleted in nitrogen (N) and phosphorus (P) compared to the particulate organic matter pool, a fact that is often omitted from biogeochemical ocean general circulation models. However the variable C : N : P stoichiometry of DOM becomes important when quantifying carbon export from the upper ocean and linking the nutrient cycles of N and P with that of carbon. Here we utilize recent advances in DOM observationalmore » data coverage and offline tracer-modeling techniques to objectively constrain the variable production and remineralization rates of the DOM C : N : P pools in a simple biogeochemical-ocean model of DOM cycling. The optimized DOM cycling parameters are then incorporated within the Biogeochemical Elemental Cycling (BEC) component of the Community Earth System Model (CESM) and validated against the compilation of marine DOM observations. The optimized BEC simulation including variable DOM C : N : P cycling was found to better reproduce the observed DOM spatial gradients than simulations that used the canonical Redfield ratio. Global annual average export of dissolved organic C, N, and P below 100 m was found to be 2.28 Pg C yr-1 (143 Tmol C yr-1, 16.4 Tmol N yr-1, and 1 Tmol P yr-1, respectively, with an average export C : N : P stoichiometry of 225 : 19 : 1 for the semilabile (degradable) DOM pool. Dissolved organic carbon (DOC) export contributed ~ 25% of the combined organic C export to depths greater than 100 m.« less

  9. Isolation and chemical characterization of dissolved and colloidal organic matter

    USGS Publications Warehouse

    Aiken, G.; Leenheer, J.

    1993-01-01

    Commonly used techniques for the concentration and isolation of organic matter from water, such as preparative chromatography, ultrafiltration and reverse osmosis, and the methods used to analyze the organic matter obtained by these methods are reviewed. The development of methods to obtain organic matter that is associated with fractions of the dissolved organic carbon other than humic substances, such as organic bases, hydrophilic organic acids and colloidal organic matter are discussed. Methods specifically used to study dissolved organic nitrogen and dissolved organic phosphorous are also discussed. -from Authors

  10. How do natural, uncultivated microbes interact with organic matter? Insights from single cell genomics and metagenomics

    NASA Astrophysics Data System (ADS)

    Lloyd, K. G.; Bird, J.; Schreiber, L.; Petersen, D.; Kjeldsen, K.; Schramm, A.; Stepanauskas, R.; Jørgensen, B. B.

    2013-12-01

    Since most of the microbes in marine sediments remain uncultured, little is known about the mechanisms by which these natural communities degrade organic matter (OM). Likewise, little is known about the make-up of labile OM in marine sediments beyond general functional classes such as proteins, carbohydrates, and lipids, measured as monomers. However, microbes have complex interactions with specific polymers within these functional classes, which can be indicated by a microbe's enzymatic toolkit. We found that four single cell genomes of archaea have very different peptidase compositions than four single cells of bacteria, suggesting that archaea and bacteria may play different roles in OM degradation. We also found that predicted extracellular cysteine peptidases, which require chemically reducing conditions, were common in IMG database metagenomes from marine sediments, and absent in those from seawater. This suggests that the pathways, and not just the rates, of OM degradation may differ between seawater and sediments. By comparing enzyme classes in different organisms, or in different types of marine environments, we present an emerging view of the microbial potential for specific carbon remineralization pathways in marine sediments. In addition, the methods we present hold promise for characterizing OM degradation in any environment where genomic information is available.

  11. Abiotic Bromination of Soil Organic Matter.

    PubMed

    Leri, Alessandra C; Ravel, Bruce

    2015-11-17

    Biogeochemical transformations of plant-derived soil organic matter (SOM) involve complex abiotic and microbially mediated reactions. One such reaction is halogenation, which occurs naturally in the soil environment and has been associated with enzymatic activity of decomposer organisms. Building on a recent finding that naturally produced organobromine is ubiquitous in SOM, we hypothesized that inorganic bromide could be subject to abiotic oxidations resulting in bromination of SOM. Through lab-based degradation treatments of plant material and soil humus, we have shown that abiotic bromination of particulate organic matter occurs in the presence of a range of inorganic oxidants, including hydrogen peroxide and assorted forms of ferric iron, producing both aliphatic and aromatic forms of organobromine. Bromination of oak and pine litter is limited primarily by bromide concentration. Fresh plant material is more susceptible to bromination than decayed litter and soil humus, due to a labile pool of mainly aliphatic compounds that break down during early stages of SOM formation. As the first evidence of abiotic bromination of particulate SOM, this study identifies a mechanistic source of the natural organobromine in humic substances and the soil organic horizon. Formation of organobromine through oxidative treatments of plant material also provides insights into the relative stability of aromatic and aliphatic components of SOM.

  12. Soil organic matter composition affected by potato cropping managements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Organic matter is a small but important soil component. As a heterogeneous mixture of geomolecules and biomolecules, soil organic matter (SOM) can be fractionated into distinct pools with different solubility and lability. Water extractable organic matter (WEOM) fraction is the most labile and mobil...

  13. Variable C : N : P stoichiometry of dissolved organic matter cycling in the Community Earth System Model

    DOE PAGES

    Letscher, R. T.; Moore, J. K.; Teng, Y. -C.; Primeau, F.

    2014-06-16

    Dissolved organic matter (DOM) plays an important role in the ocean's biological carbon pump by providing an advective/mixing pathway for ~ 20% of export production. DOM is known to have a stoichiometry depleted in nitrogen (N) and phosphorus (P) compared to the particulate organic matter pool, a~fact that is often omitted from biogeochemical-ocean general circulation models. However the variable C : N : P stoichiometry of DOM becomes important when quantifying carbon export from the upper ocean and linking the nutrient cycles of N and P with that of carbon. Here we utilize recent advances in DOM observational data coveragemore » and offline tracer-modeling techniques to objectively constrain the variable production and remineralization rates of the DOM C / N / P pools in a simple biogeochemical-ocean model of DOM cycling. The optimized DOM cycling parameters are then incorporated within the Biogeochemical Elemental Cycling (BEC) component of the Community Earth System Model and validated against the compilation of marine DOM observations. The optimized BEC simulation including variable DOM C : N : P cycling was found to better reproduce the observed DOM spatial gradients than simulations that used the canonical Redfield ratio. Global annual average export of dissolved organic C, N, and P below 100 m was found to be 2.28 Pg C yr-1 (143 Tmol C yr-1), 16.4 Tmol N yr-1, and 1 Tmol P yr-1, respectively with an average export C : N : P stoichiometry of 225 : 19 : 1 for the semilabile (degradable) DOM pool. DOC export contributed ~ 25% of the combined organic C export to depths greater than 100 m.« less

  14. The surface area of soil organic matter

    USGS Publications Warehouse

    Chiou, C.T.; Lee, J.-F.; Boyd, S.A.

    1990-01-01

    The previously reported surface area for soil organic matter (SOM) of 560-800 m2/g as determined by the ethylene glycol (EG) retention method was reexamined by the standard BET method based on nitrogen adsorption at liquid nitrogen temperature. Test samples consisted of two high organic content soils, a freeze-dried soil humic acid, and an oven-dried soil humic acid. The measured BET areas for these samples were less than 1 m2/g, except for the freeze-dried humic acid. The results suggest that surface adsorption of nonionic organic compounds by SOM is practically insignificant in comparison to uptake by partition. The discrepancy between the surface areas of SOM obtained by BET and EG methods was explained in terms of the 'free surface area' and the 'apparent surface area' associated with these measurements.The previously reported surface area for soil organic matter (SOM) of 560-800 m2/g as determined by the ethylene glycol (EG) retention method was reexamined by the standard BET method based on nitrogen adsorption at liquid nitrogen temperature. Test samples consisted of two high organic content soils, a freeze-dried soil humic acid, and an oven-dried soil humic acid. The measured BET areas for these samples were less than 1 m2/g, except for the freeze-dried humic acid. The results suggest that surface adsorption of nonionic organic compounds by SOM is practically insignificant in comparison to uptake by partition. The discrepancy between the surface areas of SOM obtained by BET and EG methods was explained in terms of the 'free surface area' and the 'apparent surface area' associated with these measurements.

  15. Organic geochemical analysis of sedimentary organic matter associated with uranium

    USGS Publications Warehouse

    Leventhal, J.S.; Daws, T.A.; Frye, J.S.

    1986-01-01

    Samples of sedimentary organic matter from several geologic environments and ages which are enriched in uranium (56 ppm to 12%) have been characterized. The three analytical techniqyes used to study the samples were Rock-Eval pyrolysis, pyrolysis-gas chromatography-mass spectrometry, and solid-state C-13 nuclear magnetic resonance (NMR) spectroscopy. In samples with low uranium content, the pyrolysis-gas chromatography products contain oxygenated functional groups (as hydroxyl) and molecules with both aliphatic and aromatic carbon atoms. These samples with low uranium content give measurable Rock-Eval hydrocarbon and organic-CO2 yields, and C-13 NMR values of > 30% aliphatic carbon. In contrast, uranium-rich samples have few hydrocarbon pyrolysis products, increased Rock-Eval organic-CO2 contents and > 70% aromatic carbon contents from C-13 NMR. The increase in aromaticity and decrease in hydrocarbon pyrolysis yield are related to the amount of uranium and the age of the uranium minerals, which correspond to the degree of radiation damage. The three analytical techniques give complementary results. Increase in Rock-Eval organic-CO2 yield correlates with uranium content for samples from the Grants uranium region. Calculations show that the amount of organic-CO2 corresponds to the quantity of uranium chemically reduced by the organic matter for the Grants uranium region samples. ?? 1986.

  16. Remineralization rates, recycling, and storage of carbon in Amazon shelf sediments

    NASA Astrophysics Data System (ADS)

    Aller, R. C.; Blair, N. E.; Xia, Q.; Rude, P. D.

    1996-04-01

    Diagenetic reactions and redox properties of Amazon shelf sediments are characterized by extensive vertical and lateral regions of Fe and Mn cycling. This is in contrast to many temperate estuarine and shelf deposits where S can dominate early diagenesis, but may be typical of wet-tropical regions draining highly weathered terrain with energetic coastlines. Although the major pathways of C org remineralization in surfical sediments apparently differ from previously studied areas, the absolute magnitude and relative importance of benthic decomposition on the Amazon shelf are comparable to many shallow water regions of equivalent depth range (10-40 m). Net ΣC0 2 production over the upper ˜1-2 m of deposits is >50 mmol m -2 d -1 and has a predominantly planktonic isotopic composition (δ 13C˜-21to-22%‰), indicating that marine organic matter largely drives diagenesic reactions and that >20% of average water-column primary production is metabolized on the seafloor. The ΣCO 2 production rates in the upper 0-5 cm of sediment tend to increase slightly alongshelf away from the turbid river mouth, but are relatively uniform within cross-shelf transects any given season and independent of net sedimentation rate. Near uniformity in surface decomposition rates, despite substantial offshore increases in water-column productivity and net accumulation at the delta front, implies rapid cross-shelf particle exchange by estuarine circulation and tidal currents. Build-up patterns of pore-water ΣCO 2 indicate in some cases that the upper ˜20 cm was deposited only a few days prior to core collection. Benthic ΣC0 2 production is highest during periods of low or falling river flow, but no dramatic seasonality occurs. O 2 penetrates ˜2-4 mm into sediments and diffusive OZ uptake averages ˜13 mmol m -2 d -1 annually. Anaerobic metabolism accounts for >75% of sedimentary remineralization, but C/S burial ratios are usually >6 (average world shelf |2.8). Seasonal patterns in

  17. Fluorescent organic matter in carbonaceous chondrites.

    PubMed

    Murae, T

    1999-01-01

    Fluorescent organic matter in carbonaceous chondrites was investigated using a microscope equipped with a fluorescence spectrophotometer. Fluorescent particles were observed in powdered CM2 carbonaceous chondrites (Y-74662, Y-7791198, and Murchison) without carbon enrichment by acid treatments. Although it was difficult to find fluorescent particles in powdered sample of C3 chondrites (ALH-77307, Y-791717, and Allende) without acid treatments, many fluorescent particles were observed after carbon enrichment by acid treatments. Fluorescence of coronene and shock-altered graphite were observed using the same microscope and the same conditions as those for carbonaceous chondrites.

  18. Mapping Soil Organic Matter with Hyperspectral Imaging

    NASA Astrophysics Data System (ADS)

    Moni, Christophe; Burud, Ingunn; Flø, Andreas; Rasse, Daniel

    2014-05-01

    Soil organic matter (SOM) plays a central role for both food security and the global environment. Soil organic matter is the 'glue' that binds soil particles together, leading to positive effects on soil water and nutrient availability for plant growth and helping to counteract the effects of erosion, runoff, compaction and crusting. Hyperspectral measurements of samples of soil profiles have been conducted with the aim of mapping soil organic matter on a macroscopic scale (millimeters and centimeters). Two soil profiles have been selected from the same experimental site, one from a plot amended with biochar and another one from a control plot, with the specific objective to quantify and map the distribution of biochar in the amended profile. The soil profiles were of size (30 x 10 x 10) cm3 and were scanned with two pushbroomtype hyperspectral cameras, one which is sensitive in the visible wavelength region (400 - 1000 nm) and one in the near infrared region (1000 - 2500 nm). The images from the two detectors were merged together into one full dataset covering the whole wavelength region. Layers of 15 mm were removed from the 10 cm high sample such that a total of 7 hyperspectral images were obtained from the samples. Each layer was analyzed with multivariate statistical techniques in order to map the different components in the soil profile. Moreover, a 3-dimensional visalization of the components through the depth of the sample was also obtained by combining the hyperspectral images from all the layers. Mid-infrared spectroscopy of selected samples of the measured soil profiles was conducted in order to correlate the chemical constituents with the hyperspectral results. The results show that hyperspectral imaging is a fast, non-destructive technique, well suited to characterize soil profiles on a macroscopic scale and hence to map elements and different organic matter quality present in a complete pedon. As such, we were able to map and quantify biochar in our

  19. The fate of airborne polycyclic organic matter.

    PubMed Central

    Nielsen, T; Ramdahl, T; Bjørseth, A

    1983-01-01

    Biological tests have shown that a significant part of the mutagenicity of organic extracts of collected airborne particulate matter is not due to polycyclic aromatic hydrocarbons (PAH). It is possible that part of these unknown compounds are transformation products of PAH. This survey focuses on the reaction of PAH in the atmosphere with other copollutants, such as nitrogen oxides, sulfur oxides, ozone and free radicals and their reaction products. Photochemically induced reactions of PAH are also included. The reactivity of particle-associated PAH is discussed in relation to the chemical composition and the physical properties of the carrier. Recommendations for future work are given. PMID:6825615

  20. Organic Matter in the Outer Solar System

    NASA Technical Reports Server (NTRS)

    Cruiskshank, Dale P.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    Many solid bodies in the outer Solar System are covered with ices of various compositions, including water, carbon dioxide, methane, nitrogen, and other molecules that are solid at the low temperatures that prevail there. These ices have all been detected by remote sensing observations made with telescopes on Earth, or more recently, spacecraft in orbit (notably Galileo at Jupiter). The data also reveal other solid materials that could be minerals or complex carbon-bearing organic molecules. A study in progress using large ground-based telescopes to acquire infrared spectroscopic data, and laboratory results on the optical properties of complex organic matter, seeks to identify the non-icy materials on several satellites of Saturn, Uranus, and Neptune. The work on the satellites of Saturn is in part preparatory to the Cassini spacecraft investigation of the Saturn system, which will begin in 2004 and extend for four years.

  1. Short-Term Dynamics of North Sea Bacterioplankton-Dissolved Organic Matter Coherence on Molecular Level

    PubMed Central

    Lucas, Judith; Koester, Irina; Wichels, Antje; Niggemann, Jutta; Dittmar, Thorsten; Callies, Ulrich; Wiltshire, Karen H.; Gerdts, Gunnar

    2016-01-01

    Remineralization and transformation of dissolved organic matter (DOM) by marine microbes shape the DOM composition and thus, have large impact on global carbon and nutrient cycling. However, information on bacterioplankton-DOM interactions on a molecular level is limited. We examined the variation of bacterial community composition (BCC) at Helgoland Roads (North Sea) in relation to variation of molecular DOM composition and various environmental parameters on short-time scales. Surface water samples were taken daily over a period of 20 days. Bacterial community and molecular DOM composition were assessed via 16S rRNA gene tag sequencing and ultrahigh resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), respectively. Environmental conditions were driven by a coastal water influx during the first half of the sampling period and the onset of a summer phytoplankton bloom toward the end of the sampling period. These phenomena led to a distinct grouping of bacterial communities and DOM composition which was particularly influenced by total dissolved nitrogen (TDN) concentration, temperature, and salinity, as revealed by distance-based linear regression analyses. Bacterioplankton-DOM interaction was demonstrated in strong correlations between specific bacterial taxa and particular DOM molecules, thus, suggesting potential specialization on particular substrates. We propose that a combination of high resolution techniques, as used in this study, may provide substantial information on substrate generalists and specialists and thus, contribute to prediction of BCC variation. PMID:27014241

  2. Soil organic matter mineralization in frozen soils

    NASA Astrophysics Data System (ADS)

    Harrysson Drotz, S.; Sparrman, T.; Schleucher, J.; Nilsson, M.; Öquist, M. G.

    2009-12-01

    Boreal forest soils are frozen for a large part of the year and soil organic matter mineralization during this period has been shown to significantly influence the C balance of boreal forest ecosystems. Mineralization proceeds through heterotrophic microbial activity, but the understanding of the environmental controls regulating soil organic matter mineralization under frozen conditions is poor. Through a series of investigations we have addressed this issue in order to elucidate to what extent a range of environmental factors control mineralization processes in frozen soils and also the microbial communities potential to oxidize organic substrates and grow under such conditions. The unfrozen water content in the frozen soils was shown to be an integral control on the temperature response of biogenic CO2 production across the freezing point of bulk soil water. We found that osmotic potential was an important contributor to the total water potential and, hence, the unfrozen water content of frozen soil. From being low and negligible in an unfrozen soil, the osmotic potential was found to contribute up to 70% of the total water potential in frozen soil, greatly influencing the volume of liquid water. The specific factors of how soil organic matter composition affected the unfrozen water content and CO2 production of frozen soil were studied by CP-MAS NMR. We concluded that abundance of aromatics and recalcitrant compounds showed a significant positive correlation with unfrozen water content and these were also the major soil organic fractions that similarly correlated with the microbial CO2 production of the frozen soils. Thus, the hierarchy of environmental factors controlling SOM mineralization changes as soils freeze and environmental controls elucidated from studies of unfrozen systems can not be added on frozen conditions. We have also investigated the potential activity of soil microbial communities under frozen conditions in order to elucidate temperature

  3. Stability of Ferrihydrite and Organic Matter in Ferrihydrite-Organic Matter Associations

    NASA Astrophysics Data System (ADS)

    Eusterhues, K.; Totsche, K. U.

    2015-12-01

    Iron oxides can bind particularly large amounts of organic matter (OM) and seem to be an important control on OM storage in many soils. To better understand the interactions between Fe oxides and OM, we produced ferrihydrite-OM associations by adsorption and coprecipitation in laboratory experiments. Because ferrihydrites are often formed in OM-rich solutions, we assume that coprecipitation is a common process in nature. In contrast to adsorption on pre-existing ferrihydrite surfaces, coprecipitation involves adsorption, occlusion (physical entrapment of OM), formation of Fe-OM complexes, and poisoning of ferrihydrite growth. The reactivity of coprecipitates may therefore differ from ferriydrites with adsorbed OM. Incubation experiments with an inoculum extracted from a Podzol forest-floor were carried out to quantify the mineralization of the adsorbed and coprecipitated organic matter. These experiments showed that the association with ferrihydrite stabilized the associated organic matter, but that differences in the degradability of adsorbed and coprecipitated organic matter were small. We therefore conclude that coprecipitation does not lead to a significant formation of microbial inaccessible organic matter domains. Microbial reduction experiments were performed using Geobacter bremensis. We observed that increasing amounts of associated OM led to decreasing initial reaction rates and a decreasing degree of dissolution. Reduction of coprecipitated ferrihydrites was faster than reduction of ferrihydrites with adsorbed OM. Our data demonstrate that the association with ferrihydrite can effectively stabilize labile polysaccharides. Vice versa, these polysaccharides may protect ferrihydrite from reduction by Geobacter-like bacteria. However, a challenge for future studies will be to link formation and degradation of mineral-organic associations to natural porous systems, that is, to the complex interplay of mass transport and microbial distribution in the

  4. Hydrological and biogeochemical Controls on Absorption and Fluorescence of Dissolved Organic Matter in the Northern South China Sea

    NASA Astrophysics Data System (ADS)

    Guo, Weidong; Wang, Chao; Li, Yan; Li, Yizhen; Song, Guodong; Wang, Lei; Cheng, Yuanyue

    2016-04-01

    Absorption and fluorescence of dissolved organic matter (DOM) were investigated in the northern South China Sea (SCS) and adjacent Kuroshio section of the West Philippine Sea (WPS). Two humic-like (C1, C2) and three protein-like (C3-C5) fluorescent components were identified using parallel factor analysis (PARAFAC). chromophoric DOM (CDOM) and fluorescent DOM (FDOM) in the northern SCS showed similar distribution patterns to the adjacent Kuroshio section and global open ocean, yet exhibited higher values in the whole water column. An isopycnal mixing model was adopted to quantify the difference in CDOM and FDOM in the euphotic zone between the northern SCS and WPS. Results showed that CDOM and humic-like FDOM were mainly modulated by Kuroshio intrusion, while protein-like FDOM were more affected by biological activities. At mid-depth, significant linear relationships between a350, C1, C2 and apparent oxygen utilization (AOU) suggested that CDOM and humic-like FDOM were produced in situ coupled to remineralization of biogenic sinking particle. Excess humic-like FDOM in the intermediate water of northern SCS were determined and more proportion of high molecular weight organic carbon was exported to the open ocean interior. In addition, regional distribution patterns of CDOM and FDOM were also tuned by mesoscale processes in the northern SCS. Different CDOM and FDOM components in the euphotic zone have apparently different responses for changes of biological activity and vertical mixing driven by eddies. Moreover, cold eddy could capture more sinking particles and finally increase the accumulation of bio-refractory CDOM and humic-like FDOM in the dark ocean. Finally, we demonstrated that the ratio of two humic-like FDOM (C1:C2, or peak C:M) may be a good indicator of water mixing, evolution of mesoscale eddies, photochemistry in the upper water and remineralization in the deeper layer.

  5. Positive priming of terrestrially derived dissolved organic matter in a freshwater microcosm system

    NASA Astrophysics Data System (ADS)

    Bianchi, Thomas S.; Thornton, Daniel C. O.; Yvon-Lewis, Shari A.; King, Gary M.; Eglinton, Timothy I.; Shields, Michael R.; Ward, Nicholas D.; Curtis, Jason

    2015-07-01

    The role of priming processes in the remineralization of terrestrially derived dissolved organic carbon (TDOC) in aquatic systems has been overlooked. We provide evidence for TDOC priming using a lab-based microcosm experiment in which TDOC was primed by the addition of 13C-labeled algal dissolved organic carbon (ADOC) or a 13C-labeled disaccharide (trehalose). The rate of TDOC remineralization to carbon dioxide (CO2) occurred 4.1 ± 0.9 and 1.5 ± 0.3 times more rapidly with the addition of trehalose and ADOC, respectively, relative to experiments with TDOC as the sole carbon source over the course of a 301 h incubation period. Results from these controlled experiments provide fundamental evidence for the occurrence of priming of TDOC by ADOC and a simple disaccharide. We suggest that priming effects on TDOC should be considered in carbon budgets for large-river deltas, estuaries, lakes, hydroelectric reservoirs, and continental shelves.

  6. Sources, behaviors and degradation of dissolved organic matter in the East China Sea

    NASA Astrophysics Data System (ADS)

    Chen, Yan; Yang, Gui-Peng; Liu, Li; Zhang, Peng-Yan; Leng, Wei-Song

    2016-03-01

    Concentrations of dissolved organic carbon (DOC), dissolved inorganic nitrogen (DIN), dissolved organic nitrogen (DON) and its major compound classes-total hydrolysable amino acids (THAA) were measured at 4 cross-shelf transects of the East China Sea in July 2011. Surface concentrations of DOC, DIN, DON and THAA at the nearshore stations were mostly in excess of those found at the offshore sites, indicating either substantial autochthonous production or allochthonous inputs from the Changjiang River. The vertical distributions of DOC, DON and THAA showed similar trends with higher values in the surface layer, whereas the elevated concentrations of DIN were observed in the bottom layer. Major constituents of THAA presented in the study area were glycine, serine, alanine, glutamic acid, aspartic acid and valine. The mole percentages of neutral amino acids increased from surface water to bottom water, whereas acidic and hydroxy amino acids decreased with the water depth. Concentrations of DOC and THAA were negatively correlated to the ΔDIN values (the difference between the real concentration and theoretical concentration), respectively, indicating the coupling relation between dissolved organic matter (DOM) remineralization and nutrient regeneration in the water column. The C/N ratios in the water column exhibited different characteristics with elevated values appearing in the surface and bottom layers. Box and whisker plots showed that both degradation index (DI) values and THAA yields displayed a decreasing trend from the surface layer to the bottom layer, implying increasing degradation with the water depth. Our data revealed that glycine and alanine increased in relative abundance with decreasing DI, while tyrosine, valine, phenylalanine and isoleucine increased with increasing DI.

  7. Soil Organic Matter and Management of Plant-Parasitic Nematodes

    PubMed Central

    Widmer, T. L.; Mitkowski, N. A.; Abawi, G. S.

    2002-01-01

    Organic matter and its replenishment has become a major component of soil health management programs. Many of the soil's physical, chemical, and biological properties are a function of organic matter content and quality. Adding organic matter to soil influences diverse and important biological activities. The diversity and number of free-living and plant-parasitic nematodes are altered by rotational crops, cover crops, green manures, and other sources of organic matter. Soil management programs should include the use of the proper organic materials to improve soil chemical, physical, and biological parameters and to suppress plant-parasitic nematodes and soilborne pathogens. It is critical to monitor the effects of organic matter additions on activities of major and minor plant-parasitic nematodes in the production system. This paper presents a general review of information in the literature on the effects of crop rotation, cover crops, and green manures on nematodes and their damage to economic crops. PMID:19265946

  8. Sensitivity of soil organic matter in anthropogenically disturbed organic soils

    NASA Astrophysics Data System (ADS)

    Säurich, Annelie; Tiemeyer, Bärbel; Bechtold, Michel; Don, Axel; Freibauer, Annette

    2016-04-01

    Drained peatlands are hotspots of carbon dioxide (CO2) emissions from agriculture. However, the variability of CO2 emissions increases with disturbance, and little is known on the soil properties causing differences between seemingly similar sites. Furthermore the driving factors for carbon cycling are well studied for both genuine peat and mineral soil, but there is a lack of information concerning soils at the boundary between organic and mineral soils. Examples for such soils are both soils naturally relatively high in soil organic matter (SOM) such as Humic Gleysols and former peat soils with a relative low SOM content due to intensive mineralization or mixing with underlying or applied mineral soil. The study aims to identify drivers for the sensitivity of soil organic matter and therefore for respiration rates of anthropogenically disturbed organic soils, especially those near the boundary to mineral soils. Furthermore, we would like to answer the question whether there are any critical thresholds of soil organic carbon (SOC) concentrations beyond which the carbon-specific respiration rates change. The German agricultural soil inventory samples all agricultural soils in Germany in an 8x8 km² grid following standardized protocols. From this data and sample base, we selected 120 different soil samples from more than 80 sites. As reference sites, three anthropogenically undisturbed peatlands were sampled as well. We chose samples from the soil inventory a) 72 g kg-1 SOC and b) representing the whole range of basic soil properties: SOC (72 to 568 g kg-1), total nitrogen (2 to 29 g kg-1), C-N-ratio (10 to 80) bulk density (0.06 to 1.41 g/cm³), pH (2.5 to 7.4), sand (0 to 95 %) and clay (2 to 70 %) content (only determined for samples with less than 190 g kg-1 SOC) as well as the botanical origin of the peat (if determinable). Additionally, iron oxides were determined for all samples. All samples were sieved (2 mm) and incubated at standardized water content and

  9. Spectrophotometric discrimination of river dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Baker, Andy

    2002-11-01

    There is a need to be able to differentiate the dissolved organic matter (DOM) fraction in river waters. Research in the 1970s and 1980s has attempted to utilize both absorbance and fluorescence to distinguish between DOM fractions in river waters, but both were limited by the available technology. Total organic carbon content has, therefore, been widely used as a standard method of measuring DOM concentration, although it has little power to differentiate DOM fractions. Recent advances in fluorescence spectrophotometry enable rapid and optically precise analysis of DOM. Here, we show how a combination of both fluorescence and absorbance can be used to discriminate statistically between spatial variations of DOM in tributaries in a small catchment of the Ouseburn, NE England. The results of the discriminant analysis suggest that about 70% of the samples can be correctly classified to its tributary. Discriminant function 1 explains 60·8% of the variance in the data and the fulvic-like fluorescence intensity has the largest absolute correlation within this function; discriminant function 2 explains a further 21·5% of the variance and the fulvic-like fluorescence emission wavelength has the largest absolute correlation within this function. The discriminant analysis does not correctly classify all tributaries every time, and successfully discriminates between the different tributaries 70% of the time. Occasions when the tributary waters are less well discriminated are due to either episodic pollution events (at two sites) or due to tributaries that have strong seasonal trends in spectrophotometric parameters, which allows the sites to be misclassified. Results suggest that spectrophotometric techniques have considerable potential in the discrimination of DOM in rivers.

  10. The evolution of organic matter in space.

    PubMed

    Ehrenfreund, Pascale; Spaans, Marco; Holm, Nils G

    2011-02-13

    Carbon, and molecules made from it, have already been observed in the early Universe. During cosmic time, many galaxies undergo intense periods of star formation, during which heavy elements like carbon, oxygen, nitrogen, silicon and iron are produced. Also, many complex molecules, from carbon monoxide to polycyclic aromatic hydrocarbons, are detected in these systems, like they are for our own Galaxy. Interstellar molecular clouds and circumstellar envelopes are factories of complex molecular synthesis. A surprisingly high number of molecules that are used in contemporary biochemistry on the Earth are found in the interstellar medium, planetary atmospheres and surfaces, comets, asteroids and meteorites and interplanetary dust particles. Large quantities of extra-terrestrial material were delivered via comets and asteroids to young planetary surfaces during the heavy bombardment phase. Monitoring the formation and evolution of organic matter in space is crucial in order to determine the prebiotic reservoirs available to the early Earth. It is equally important to reveal abiotic routes to prebiotic molecules in the Earth environments. Materials from both carbon sources (extra-terrestrial and endogenous) may have contributed to biochemical pathways on the Earth leading to life's origin. The research avenues discussed also guide us to extend our knowledge to other habitable worlds.

  11. Evolution of Mineral-Organic Matter Associations in Sediments: From (Bio)mineralization to Burial

    NASA Astrophysics Data System (ADS)

    Estes, E.; Nordlund, D.; Wankel, S. D.; Hansel, C. M.

    2014-12-01

    Physical and chemical associations with mineral surfaces may protect organic matter (OM) from oxidative degradation and allow its preservation in soils and sediments. This study evaluates the mechanism of mineral-based preservation (MBP) and the time scale on which MBP is operative by tracking the co-evolution of oxide minerals and associated OM during mineral precipitation and ripening. Scanning transmission X-ray microscopy coupled to near edge X-ray absorption fine structure spectroscopy (STXM-NEXAFS) as well as bulk NEXAFS demonstrate that, in laboratory systems using cell-free filtrate from pure bacterial cultures, an association between OM and biogenic manganese oxides is rapidly established. OM associated with freshly precipitated biominerals consists of proteinaceous carbon and nitrogen consistent with a microbial origin; this composition remains constant over the course of 96 hours, despite mineral aggregation and structural evolution from hexagonal to triclinic birnessite. We predict that, in natural systems, oxide minerals simultaneously drive remineralization and offer MBP. Different minerals will promote a different balance between the two, imparting a mineral-specific signature on the concentration and composition of preserved OM. We test this idea by conducting incubations of natural estuary waters spiked with compositionally and structurally diverse synthetic oxide minerals. The concentration and composition of mineral-associated OM were tracked by element analyzer-isotope ratio mass spectrometry (EA-IRMS) and STXM-NEXAFS in multiple experiments lasting between 4 weeks and 1 year. Results from incubation experiments are contrasted with natural sediment samples from a range of depositional environments in order to evaluate the potential for long-term sequestration of organic carbon in sediments facilitated by minerals.

  12. Complexation of trace metals by adsorbed natural organic matter

    USGS Publications Warehouse

    Davis, J.A.

    1984-01-01

    The adsorption behavior and solution speciation of Cu(II) and Cd(II) were studied in model systems containing colloidal alumina particles and dissolved natural organic matter. At equilibrium a significant fraction of the alumina surface was covered by adsorbed organic matter. Cu(II) was partitioned primarily between the surface-bound organic matter and dissolved Cu-organic complexes in the aqueous phase. Complexation of Cu2+ with the functional groups of adsorbed organic matter was stronger than complexation with uncovered alumina surface hydroxyls. It is shown that the complexation of Cu(II) by adsorbed organic matter can be described by an apparent stability constant approximately equal to the value found for solution phase equilibria. In contrast, Cd(II) adsorption was not significantly affected by the presence of organic matter at the surface, due to weak complex formation with the organic ligands. The results demonstrate that general models of trace element partitioning in natural waters must consider the presence of adsorbed organic matter. ?? 1984.

  13. Benthic fluxes of dissolved organic nitrogen in the Lower St. Lawrence Estuary and implications for selective organic matter degradation

    NASA Astrophysics Data System (ADS)

    Alkhatib, M.; del Giorgio, P. A.; Gelinas, Y.; Lehmann, M. F.

    2013-05-01

    The distribution of dissolved organic nitrogen (DON) and carbon (DOC) in sediment pore waters was determined at nine locations along the St. Lawrence Estuary and in the Gulf of St. Lawrence. The study area is characterized by gradients in the sedimentary particulate organic matter (POM) reactivity, bottom water oxygen concentrations, as well as benthic respiration rates. Based on pore water profiles we estimated the benthic diffusive fluxes of DON and DOC. Our results show that DON fluxed out of the sediments at significant rates (110 to 430 μmol m-2 d-1). DON fluxes were positively correlated with sedimentary POM reactivity and sediment oxygen exposure time (OET), suggesting direct links between POM quality, aerobic remineralization and the release of DON to the water column. DON fluxes were on the order of 30% to 64% of the total benthic inorganic fixed N loss due to denitrification, and often exceeded the diffusive nitrate fluxes into the sediments. Hence they represented a large fraction of the total benthic N exchange. This result is particularly important in light of the fact that DON fluxes are usually not accounted for in estuarine and coastal zone nutrient budgets. The ratio of the DON to nitrate flux increased from 0.6 in the Lower Estuary to 1.5 in the Gulf. In contrast to DON, DOC fluxes did not show any significant spatial variation along the Laurentian Channel (LC) between the Estuary and the Gulf (2100 ± 100μmol m-2 d-1), suggesting that production and consumption of labile DOC components proceed at similar rates, irrespective of the overall benthic characteristics and the reactivity of POM. As a consequence, the molar C/N ratio of dissolved organic matter (DOM) in pore water and the overlying bottom water varied significantly along the transect, with lowest C/N in the Lower Estuary (5-6) and highest C/N (> 10) in the Gulf. We observed large differences between the C/N of pore water DOM with respect to POM, and the degree of the C- versus -N

  14. Methane and organic matter as sources for excess carbon dioxide in intertidal surface sediments of the German Wadden Sea

    NASA Astrophysics Data System (ADS)

    Böttcher, M. E.; Al-Raei, A. M.; Walpersdorf, E. C.; Heuer, V.; Hinrichs, K.; Hilker, Y.; Engelen, B.; Volkenborn, N.; Segl, M.

    2009-12-01

    The tidal areas of the German Wadden Sea form an important transition zone between the terrestrial and marine environment. Tidal areas represent highly productive marine coastal ecosystems that are under additional influence of riverine inputs. The re-mineralization of organic matter is coupled to reductive processes using oxygen, nitrate, Mn,Fe oxy(hydroxi)des and sulfate as final electron acceptors. Sulfate reduction is involved in the oxidation of DOC and methane, and is the most important anaerobic process leading to a re-flux of CO2 into the water column. CH4 and CO2 are important greenhouse gases. Both are produced in marine sediments but methane fluxes from marine sediments to the water column or the atmosphere are often limited by oxidation. Upon oxidation of organic matter and methane, carbon dioxide is added to pore waters, and both, carbon dioxide and methane may be liberated from intertidal surface sediments into the bottom waters or the atmosphere. Sizes and quality of OM pools and methane concentrations, transport properties as well as biogeochemical processs in intertidal sediments differ in different sediment types (sands, mixed and mud flats). Pore waters and surface sediments from the intertidal of the German Wadden Sea, North Sea, have been analyzed on a seasonal base for a number of (bio)geochemical parameters as, for instance, the contents and isotope composition of TOC, DIC, methane, sulphate reduction rates (SRR), sulfate, sulfide, pyrite, AVS. The typical sediments of the tidal area of Spiekeroog Island have been considered, as sands, mixed and mud flats. The C-13/C-12 partitioning was used to identify the major sources of DIC and key reactions in the coupled C-S cycles. SRR showed a control by season (temperature) and organic matter contents. Bulk organic matter in the surface sediments showed stable carbon isotope data between about -19 and -25 per mil with lighter data found in mixed and mud flats, indicating mixtures between marine and

  15. Subcritical water extraction of organic matter from sedimentary rocks.

    PubMed

    Luong, Duy; Sephton, Mark A; Watson, Jonathan S

    2015-06-16

    Subcritical water extraction of organic matter containing sedimentary rocks at 300°C and 1500 psi produces extracts comparable to conventional solvent extraction. Subcritical water extraction of previously solvent extracted samples confirms that high molecular weight organic matter (kerogen) degradation is not occurring and that only low molecular weight organic matter (free compounds) are being accessed in analogy to solvent extraction procedures. The sedimentary rocks chosen for extraction span the classic geochemical organic matter types. A type I organic matter-containing sedimentary rock produces n-alkanes and isoprenoidal hydrocarbons at 300°C and 1500 psi that indicate an algal source for the organic matter. Extraction of a rock containing type II organic matter at the same temperature and pressure produces aliphatic hydrocarbons but also aromatic compounds reflecting the increased contributions from terrestrial organic matter in this sample. A type III organic matter-containing sample produces a range of non-polar and polar compounds including polycyclic aromatic hydrocarbons and oxygenated aromatic compounds at 300°C and 1500 psi reflecting a dominantly terrestrial origin for the organic materials. Although extraction at 300°C and 1500 psi produces extracts that are comparable to solvent extraction, lower temperature steps display differences related to organic solubility. The type I organic matter produces no products below 300°C and 1500 psi, reflecting its dominantly aliphatic character, while type II and type III organic matter contribute some polar components to the lower temperature steps, reflecting the chemical heterogeneity of their organic inventory. The separation of polar and non-polar organic compounds by using different temperatures provides the potential for selective extraction that may obviate the need for subsequent preparative chromatography steps. Our results indicate that subcritical water extraction can act as a suitable

  16. Extraterrestrial Organic Matter and the Detection of Life

    NASA Astrophysics Data System (ADS)

    Sephton, Mark A.; Botta, Oliver

    A fundamental goal of a number of forthcoming space missions is the detection and characterization of organic matter on planetary surfaces. Successful interpretation of data generated by in situ experiments will require discrimination between abiogenic and biogenic organic compounds. Carbon-rich meteorites provide scientists with examples of authentic extraterrestrial organic matter generated in the absence of life. Outcomes of meteorite studies include clues to protocols that will enable the unequivocal identification of organic matter derived from life. In this chapter we summarize the diagnostic abiogenic features of key compound classes involved in life detection and discuss their implications for analytical instruments destined to fly on future spacecraft missions.

  17. Extraterrestrial Organic Matter and the Detection of Life

    NASA Astrophysics Data System (ADS)

    Sephton, Mark A.; Botta, Oliver

    2008-03-01

    A fundamental goal of a number of forthcoming space missions is the detection and characterization of organic matter on planetary surfaces. Successful interpretation of data generated by in situ experiments will require discrimination between abiogenic and biogenic organic compounds. Carbon-rich meteorites provide scientists with examples of authentic extraterrestrial organic matter generated in the absence of life. Outcomes of meteorite studies include clues to protocols that will enable the unequivocal identification of organic matter derived from life. In this chapter we summarize the diagnostic abiogenic features of key compound classes involved in life detection and discuss their implications for analytical instruments destined to fly on future spacecraft missions.

  18. Subcritical water extraction of organic matter from sedimentary rocks.

    PubMed

    Luong, Duy; Sephton, Mark A; Watson, Jonathan S

    2015-06-16

    Subcritical water extraction of organic matter containing sedimentary rocks at 300°C and 1500 psi produces extracts comparable to conventional solvent extraction. Subcritical water extraction of previously solvent extracted samples confirms that high molecular weight organic matter (kerogen) degradation is not occurring and that only low molecular weight organic matter (free compounds) are being accessed in analogy to solvent extraction procedures. The sedimentary rocks chosen for extraction span the classic geochemical organic matter types. A type I organic matter-containing sedimentary rock produces n-alkanes and isoprenoidal hydrocarbons at 300°C and 1500 psi that indicate an algal source for the organic matter. Extraction of a rock containing type II organic matter at the same temperature and pressure produces aliphatic hydrocarbons but also aromatic compounds reflecting the increased contributions from terrestrial organic matter in this sample. A type III organic matter-containing sample produces a range of non-polar and polar compounds including polycyclic aromatic hydrocarbons and oxygenated aromatic compounds at 300°C and 1500 psi reflecting a dominantly terrestrial origin for the organic materials. Although extraction at 300°C and 1500 psi produces extracts that are comparable to solvent extraction, lower temperature steps display differences related to organic solubility. The type I organic matter produces no products below 300°C and 1500 psi, reflecting its dominantly aliphatic character, while type II and type III organic matter contribute some polar components to the lower temperature steps, reflecting the chemical heterogeneity of their organic inventory. The separation of polar and non-polar organic compounds by using different temperatures provides the potential for selective extraction that may obviate the need for subsequent preparative chromatography steps. Our results indicate that subcritical water extraction can act as a suitable

  19. Dissolved Organic Matter and Emerging Contaminants in Urban Stream Ecosystems

    NASA Astrophysics Data System (ADS)

    Kaushal, S. S.; Findlay, S.; Groffman, P.; Belt, K.; Delaney, K.; Sides, A.; Walbridge, M.; Mayer, P.

    2009-05-01

    We investigated the effects of urbanization on the sources, bioavailability and forms of natural and anthropogenic organic matter found in streams located in Maryland, U.S.A. We found that the abundance, biaoavailability, and enzymatic breakdown of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and dissolved organic phosphorus (DOP) increased in streams with increasing watershed urbanization suggesting that organic nutrients may represent a growing form of nutrient loading to coastal waters associated with land use change. Organic carbon, nitrogen, and phosphorus in urban streams were elevated several-fold compared to forest and agricultural streams. Enzymatic activities of stream microbes in organic matter decomposition were also significantly altered across watershed land use. Chemical characterization suggested that organic matter in urban streams originated from a variety of sources including terrestrial, sewage, and in-stream transformation. In addition, a characterization of emerging organic contaminants (polyaromatic cyclic hydrocarbons, organochlorine pesticides, and polybrominated diphenyl ether flame retardents), showed that organic contaminants and dissolved organic matter increase with watershed urbanization and fluctuate substantially with changing climatic conditions. Elucidating the emerging influence of urbanization on sources, transport, and in-stream transformation of organic nutrients and contaminants will be critical in unraveling the changing role of organic matter in urban degraded and restored stream ecosystems.

  20. Changes in River Organic Matter Through Time.

    NASA Astrophysics Data System (ADS)

    Hudson, N.; Baker, A.; Ward, D.

    2006-12-01

    fluorescence, as an increase in pH was also observed in these samples. This work illustrates the dynamic character of river organic matter within a timescale and under conditions that are representative of the natural system.

  1. Spatial Complexity of Soil Organic Matter Forms at Nanometre Scales

    SciTech Connect

    Lehmann,J.; Solomon, D.; Kinyangi, J.; Dathe, L.; Wirick, S.; Jacobsen, C.

    2008-01-01

    Organic matter in soil has been suggested to be composed of a complex mixture of identifiable biopolymers1 rather than a chemically complex humic material2. Despite the importance of the spatial arrangement of organic matter forms in soil3, its characterization has been hampered by the lack of a method for analysis at fine scales. X-ray spectromicroscopy has enabled the identification of spatial variability of organic matter forms, but was limited to extracted soil particles4 and individual micropores within aggregates5, 6. Here, we use synchrotron-based near-edge X-ray spectromicroscopy7 of thin sections of entire and intact free microaggregates6 to demonstrate that on spatial scales below 50 nm resolution, highly variable yet identifiable organic matter forms, such as plant or microbial biopolymers, can be found in soils at distinct locations of the mineral assemblage. Organic carbon forms detected at this spatial scale had no similarity to organic carbon forms of total soil. In contrast, we find that organic carbon forms of total soil were remarkably similar between soils from several temperate and tropical forests with very distinct vegetation composition and soil mineralogy. Spatial information on soil organic matter forms at the scale provided here could help to identify processes of organic matter cycling in soil, such as carbon stability or sequestration and responses to a changing climate.

  2. Deformation behaviors of peat with influence of organic matter.

    PubMed

    Yang, Min; Liu, Kan

    2016-01-01

    Peat is a kind of special material rich in organic matter. Because of the high content of organic matter, it shows different deformation behaviors from conventional geotechnical materials. Peat grain has a non-negligible compressibility due to the presence of organic matter. Biogas can generate from peat and can be trapped in form of gas bubbles. Considering the natural properties of peat, a special three-phase composition of peat is described which indicates the existence of organic matter and gas bubbles in peat. A stress-strain-time model is proposed for the compression of organic matter, and the surface tension effect is considered in the compression model of gas bubbles. Finally, a mathematical model has been developed to simulate the deformation behavior of peat considering the compressibility of organic matter and entrapped gas bubbles. The deformation process is the coupling of volume variation of organic matter, gas bubbles and water drainage. The proposed model is used to simulate a series of peat laboratory oedometer tests, and the model can well capture the test results with reasonable model parameters. Effects of model parameters on deformation of peat are also analyzed. PMID:27247870

  3. Deformation behaviors of peat with influence of organic matter.

    PubMed

    Yang, Min; Liu, Kan

    2016-01-01

    Peat is a kind of special material rich in organic matter. Because of the high content of organic matter, it shows different deformation behaviors from conventional geotechnical materials. Peat grain has a non-negligible compressibility due to the presence of organic matter. Biogas can generate from peat and can be trapped in form of gas bubbles. Considering the natural properties of peat, a special three-phase composition of peat is described which indicates the existence of organic matter and gas bubbles in peat. A stress-strain-time model is proposed for the compression of organic matter, and the surface tension effect is considered in the compression model of gas bubbles. Finally, a mathematical model has been developed to simulate the deformation behavior of peat considering the compressibility of organic matter and entrapped gas bubbles. The deformation process is the coupling of volume variation of organic matter, gas bubbles and water drainage. The proposed model is used to simulate a series of peat laboratory oedometer tests, and the model can well capture the test results with reasonable model parameters. Effects of model parameters on deformation of peat are also analyzed.

  4. Pyrogenic organic matter can alter microbial communication

    NASA Astrophysics Data System (ADS)

    Masiello, Caroline; Gao, Xiaodong; Cheng, Hsiao-Ying; Silberg, Jonathan

    2016-04-01

    Soil microbes communicate with each other to manage a large range of processes that occur more efficiently when microbes are able to act simultaneously. This coordination occurs through the continuous production of signaling compounds that are easily diffused into and out of cells. As the number of microbes in a localized environment increases, the internal cellular concentration of these signaling compounds increases, and when a threshold concentration is reached, gene expression shifts, leading to altered (and coordinated) microbial behaviors. Many of these coordinated behaviors have biogeochemically important outcomes. For example, methanogenesis, denitrification, biofilm formation, and the development of plant-rhizobial symbioses are all regulated by a simple class of cell-cell signaling molecules known as acyl homoserine lactones (AHLs). Pyrogenic organic matter in soils can act to disrupt microbial communication through multiple pathways. In the case of AHLs, charcoal's very high surface area can sorb these signaling compounds, preventing microbes from detecting each others' presence (Masiello et al., 2014). In addition, the lactone ring in AHLs is vulnerable to pH increases accompanying PyOM inputs, with soil pH values higher than 7-8 leading to ring opening and compound destabilization. Different microbes use different classes of signaling compounds, and not all microbial signaling compounds are pH-vulnerable. This implies that PyOM-driven pH increases may trigger differential outcomes for Gram negative bacteria vs fungi, for example. A charcoal-driven reduction in microbes' ability to detect cell-cell communication compounds may lead to a shift in the ability of microbes to participate in key steps of C and N cycling. For example, an increase in an archaeon-specific AHL has been shown to lead to a cascade of metabolic processes that eventually results in the upregulation of CH4 production (Zhang et al., 2012). Alterations in similar AHL compounds leads to

  5. Enamel alteration following tooth bleaching and remineralization.

    PubMed

    Coceska, Emilija; Gjorgievska, Elizabeta; Coleman, Nichola J; Gabric, Dragana; Slipper, Ian J; Stevanovic, Marija; Nicholson, John W

    2016-06-01

    The purpose of this study was to compare the effects of professional tooth whitening agents containing highly concentrated hydrogen peroxide (with and without laser activation), on the enamel surface; and the potential of four different toothpastes to remineralize any alterations. The study was performed on 50 human molars, divided in two groups: treated with Opalescence(®) Boost and Mirawhite(®) Laser Bleaching. Furthermore, each group was divided into five subgroups, a control one and 4 subgroups remineralized with: Mirasensitive(®) hap+, Mirawhite(®) Gelleѐ, GC Tooth Mousse™ and Mirafluor(®) C. The samples were analysed by SEM/3D-SEM-micrographs, SEM/EDX-qualitative analysis and SEM/EDX-semiquantitative analysis. The microphotographs show that both types of bleaching cause alterations: emphasized perikymata, erosions, loss of interprizmatic substance; the laser treatment is more aggressive and loss of integrity of the enamel is determined by shearing off the enamel rods. In all samples undergoing remineralization deposits were observed, those of toothpastes based on calcium phosphate technologies seem to merge with each other and cover almost the entire surface of the enamel. Loss of integrity and minerals were detected only in the line-scans of the sample remineralized with GC Tooth Mousse™. The semiquantitative EDX analysis of individual elements in the surface layer of the enamel indicates that during tooth-bleaching with HP statistically significant loss of Na and Mg occurs, whereas the bleaching in combination with a laser leads to statistically significant loss of Ca and P. The results undoubtedly confirm that teeth whitening procedures lead to enamel alterations. In this context, it must be noted that laser bleaching is more aggressive for dental substances. However, these changes are reversible and can be repaired by application of remineralization toothpastes. PMID:27197087

  6. Spectral band selection for classification of soil organic matter content

    NASA Technical Reports Server (NTRS)

    Henderson, Tracey L.; Szilagyi, Andrea; Baumgardner, Marion F.; Chen, Chih-Chien Thomas; Landgrebe, David A.

    1989-01-01

    This paper describes the spectral-band-selection (SBS) algorithm of Chen and Landgrebe (1987, 1988, and 1989) and uses the algorithm to classify the organic matter content in the earth's surface soil. The effectiveness of the algorithm was evaluated comparing the results of classification of the soil organic matter using SBS bands with those obtained using Landsat MSS bands and TM bands, showing that the algorithm was successful in finding important spectral bands for classification of organic matter content. Using the calculated bands, the probabilities of correct classification for climate-stratified data were found to range from 0.910 to 0.980.

  7. Interstellar chemistry recorded in organic matter from primitive meteorites.

    PubMed

    Busemann, Henner; Young, Andrea F; Alexander, Conel M O'd; Hoppe, Peter; Mukhopadhyay, Sujoy; Nittler, Larry R

    2006-05-01

    Organic matter in extraterrestrial materials has isotopic anomalies in hydrogen and nitrogen that suggest an origin in the presolar molecular cloud or perhaps in the protoplanetary disk. Interplanetary dust particles are generally regarded as the most primitive solar system matter available, in part because until recently they exhibited the most extreme isotope anomalies. However, we show that hydrogen and nitrogen isotopic compositions in carbonaceous chondrite organic matter reach and even exceed those found in interplanetary dust particles. Hence, both meteorites (originating from the asteroid belt) and interplanetary dust particles (possibly from comets) preserve primitive organics that were a component of the original building blocks of the solar system. PMID:16675696

  8. Assessment of soil organic matter fluxes at the EU level

    NASA Astrophysics Data System (ADS)

    Gobin, Anne; Campling, Paul

    2010-05-01

    Soil has a complex relationship with climate change. Soil helps take carbon dioxide out of the air and as such it absorbs millions of tons each year, but with the Earth still warming micro-organisms grow faster, consume more soil organic matter and release carbon dioxide. The net result is a relative decline in soil organic carbon. With a growing population and higher bio-energy demands, more land is likely to be required for settlement, for commercial activity and for bio-energy production. Conversions from terrestrial ecosystems to urban and commercial activity will alter both the production and losses of organic matter, and have an indirect impact on potential SOM levels. Conversions between different terrestrial ecosystems have a direct impact on SOM levels. Net SOM losses are reported for several land conversions, e.g. from grassland to arable land, from wetlands to drained agricultural land, from crop rotations to monoculture, reforestation of agricultural land. In the context of looking for measures to support best practices to manage soil organic matter in Europe we propose a method to assess soil organic matter fluxes at the EU level. We adopt a parsimonious approach that is comparable to the nutrient balance approaches developed by the OECD and Eurostat. We describe the methodology and present the initial results of a European carbon balance indicator that uses existing European statistical and land use change databases. The carbon balance consists of the following components: organic matter production (I), organic matter losses (O), land use changes that effect both production and losses (E). These components are set against the (mostly legislative) boundary conditions that determine the maximum input potential (MIP) for soil organic matter. In order to budget SOM losses due to mineralisation, runs will be made with a multi-compartment SOM model that takes into account management practices, climate and different sources of organic matter.

  9. Demineralization–remineralization dynamics in teeth and bone

    PubMed Central

    Abou Neel, Ensanya Ali; Aljabo, Anas; Strange, Adam; Ibrahim, Salwa; Coathup, Melanie; Young, Anne M; Bozec, Laurent; Mudera, Vivek

    2016-01-01

    Biomineralization is a dynamic, complex, lifelong process by which living organisms control precipitations of inorganic nanocrystals within organic matrices to form unique hybrid biological tissues, for example, enamel, dentin, cementum, and bone. Understanding the process of mineral deposition is important for the development of treatments for mineralization-related diseases and also for the innovation and development of scaffolds. This review provides a thorough overview of the up-to-date information on the theories describing the possible mechanisms and the factors implicated as agonists and antagonists of mineralization. Then, the role of calcium and phosphate ions in the maintenance of teeth and bone health is described. Throughout the life, teeth and bone are at risk of demineralization, with particular emphasis on teeth, due to their anatomical arrangement and location. Teeth are exposed to food, drink, and the microbiota of the mouth; therefore, they have developed a high resistance to localized demineralization that is unmatched by bone. The mechanisms by which demineralization–remineralization process occurs in both teeth and bone and the new therapies/technologies that reverse demineralization or boost remineralization are also scrupulously discussed. Technologies discussed include composites with nano- and micron-sized inorganic minerals that can mimic mechanical properties of the tooth and bone in addition to promoting more natural repair of surrounding tissues. Turning these new technologies to products and practices would improve health care worldwide. PMID:27695330

  10. Demineralization–remineralization dynamics in teeth and bone

    PubMed Central

    Abou Neel, Ensanya Ali; Aljabo, Anas; Strange, Adam; Ibrahim, Salwa; Coathup, Melanie; Young, Anne M; Bozec, Laurent; Mudera, Vivek

    2016-01-01

    Biomineralization is a dynamic, complex, lifelong process by which living organisms control precipitations of inorganic nanocrystals within organic matrices to form unique hybrid biological tissues, for example, enamel, dentin, cementum, and bone. Understanding the process of mineral deposition is important for the development of treatments for mineralization-related diseases and also for the innovation and development of scaffolds. This review provides a thorough overview of the up-to-date information on the theories describing the possible mechanisms and the factors implicated as agonists and antagonists of mineralization. Then, the role of calcium and phosphate ions in the maintenance of teeth and bone health is described. Throughout the life, teeth and bone are at risk of demineralization, with particular emphasis on teeth, due to their anatomical arrangement and location. Teeth are exposed to food, drink, and the microbiota of the mouth; therefore, they have developed a high resistance to localized demineralization that is unmatched by bone. The mechanisms by which demineralization–remineralization process occurs in both teeth and bone and the new therapies/technologies that reverse demineralization or boost remineralization are also scrupulously discussed. Technologies discussed include composites with nano- and micron-sized inorganic minerals that can mimic mechanical properties of the tooth and bone in addition to promoting more natural repair of surrounding tissues. Turning these new technologies to products and practices would improve health care worldwide.

  11. High resolution profiles of vertical particulate organic matter export off Cape Blanc, Mauritania: Degradation processes and ballasting effects

    NASA Astrophysics Data System (ADS)

    Iversen, Morten Hvitfeldt; Nowald, Nicolas; Ploug, Helle; Jackson, George A.; Fischer, Gerhard

    2010-06-01

    Vertical carbon fluxes between the surface and 2500 m depth were estimated from in situ profiles of particle size distributions and abundances me/asured off Cape Blanc (Mauritania) related to deep ocean sediment traps. Vertical mass fluxes off Cape Blanc were significantly higher than recent global estimates in the open ocean. The aggregates off Cape Blanc contained high amounts of ballast material due to the presence of coccoliths and fine-grained dust from the Sahara desert, leading to a dominance of small and fast-settling aggregates. The largest changes in vertical fluxes were observed in the surface waters (<250 m), and, thus, showing this site to be the most important zone for aggregate formation and degradation. The degradation length scale ( L), i.e. the fractional degradation of aggregates per meter settled, was estimated from vertical fluxes derived from the particle size distribution through the water column. This was compared with fractional remineralization rate of aggregates per meter settled derived from direct ship-board measurements of sinking velocity and small-scale O 2 fluxes to aggregates measured by micro-sensors. Microbial respiration by attached bacteria alone could not explain the degradation of organic matter in the upper ocean. Instead, flux feeding from zooplankton organisms was indicated as the dominant degradation process of aggregated carbon in the surface ocean. Below the surface ocean, microbes became more important for the degradation as zooplankton was rare at these depths.

  12. Investigation of the organic matter in inactive nuclear tank liquids

    SciTech Connect

    Schenley, R.L.; Griest, W.H.

    1990-08-01

    Environmental Protection Agency (EPA) methodology for regulatory organics fails to account for the organic matter that is suggested by total organic carbon (TOC) analysis in the Oak Ridge National Laboratory (ORNL) inactive nuclear waste-tank liquids and sludges. Identification and measurement of the total organics are needed to select appropriate waste treatment technologies. An initial investigation was made of the nature of the organics in several waste-tank liquids. This report details the analysis of ORNL wastes.

  13. Characterizing Variability In Ohio River Natural Organic Matter

    EPA Science Inventory

    Surface water contains natural organic matter (NOM) which reacts with disinfectants creating disinfection byproducts (DBPs), some of which are USEPA regulated contaminants. Characterizing NOM can provide important insight on DBP formation and water treatment process adaptation t...

  14. Soil organic matter dynamics and the global carbon cycle

    SciTech Connect

    Post, W.M.; Emanuel, W.R.; King, A.W.

    1992-01-01

    The large size and potentially long residence time of the soil organic matter pool make it an important component of the global carbon cycle. Net terrestrial primary production of about 60 Pg C[center dot]yr[sup -1] is, over a several-year period of time, balanced by an equivalent flux of litter production and subsequent decomposition of detritus and soil organic matter. We will review many of the major factors that influence soil organic matter dynamics that need to be explicitly considered in development of global estimates of carbon turnover in the world's soils. We will also discuss current decomposition models that are general enough to be used to develop a representation of global soil organic matter dynamics.

  15. Soil organic matter dynamics and the global carbon cycle

    SciTech Connect

    Post, W.M.; Emanuel, W.R.; King, A.W.

    1992-12-01

    The large size and potentially long residence time of the soil organic matter pool make it an important component of the global carbon cycle. Net terrestrial primary production of about 60 Pg C{center_dot}yr{sup -1} is, over a several-year period of time, balanced by an equivalent flux of litter production and subsequent decomposition of detritus and soil organic matter. We will review many of the major factors that influence soil organic matter dynamics that need to be explicitly considered in development of global estimates of carbon turnover in the world`s soils. We will also discuss current decomposition models that are general enough to be used to develop a representation of global soil organic matter dynamics.

  16. Seasonal Changes in Arctic Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Boot, C. M.; Wallenstein, M. D.; Schimel, J.

    2011-12-01

    The Arctic is a landscape in flux. Temperatures are shifting upward and plant communities are transitioning from tussock to shrub tundra in some regions. Decomposition processes sensitive to temperature, moisture, and plant inputs are controls on the source/sink dynamics of the Arctic C pool. The response of decomposition to warming will, in part, determine if the Arctic C pool feeds back positively or negatively to climate change. The portion of the C pool immediately available to decomposers is dissolved organic matter (DOM). The aim of this is study is to examine the molecular composition of DOM to determine which components vary seasonally in soil pore water among three vegetation types at Toolik Field Station in Alaska. Vegetation types include wet sedge (Carex aquatilis and Eriophorum angustifolium), moist acidic tussock (E. vaginatum) and shrub tundra (Betula nana and Salix sp.). These sites were sampled during winter/summer transitions in 2010 in order to capture both growing season and winter dynamics. We expected the chemical composition of DOM in pore water to be distinct among plant communities due to differences in root exudates, litter chemistry and microbial community; and vary seasonally due to shifting temperature and water availability and their impacts on decomposition of DOM. Soil pore water was isolated through centrifugation and is being characterized with ultra high performance liquid chromatography (UPLC) in line with a quadrupole time of flight mass spectrometer (QTOF-MS) as well as with specific UV absorbance at 254 nm (SUVA), and excitation emission matrices (EEMs) generated by fluorescence spectroscopy. The DOM concentrations across vegetation types show consistent seasonal patterns, spiking at thaw, and declining through late summer. As soils freeze these patterns diverge-in tussock soils DOM concentration decreases slightly, while in shrub and wet sedge sites it increases. SUVA values (indicator of aromaticity) were consistent among

  17. Surface microanalysis and chemical imaging of early dentin remineralization.

    PubMed

    Toledano, Manuel; Cabello, Inmaculada; Vílchez, Miguel Angel Cabrerizo; Fernández, Miguel Angel; Osorio, Raquel

    2014-02-01

    This study reports physical and chemical changes that occur at early dentin remineralization stages. Extracted human third molars were sectioned to obtain dentin discs. After polishing the dentin surfaces, three groups were established: (1) untreated dentin (UD), (2) 37% phosphoric acid application for 15 s (partially demineralized dentin-PDD), and (3) 10% phosphoric acid for 12 h at 25° C (totally demineralized dentin-TDD). Five different remineralizing solutions were used: chlorhexidine (CHX), artificial saliva (AS), phosphate solution (PS), ZnCl2, and ZnO. Wettability (contact angle), ζ potential and Raman spectroscopy analysis were determined on dentin surfaces. Demineralization of dentin resulted in a higher contact angle. Wettability decreased after immersion in all solutions. ζ potential analysis showed dissimilar performance ranging from -6.21 mV (TDD + AS) up to 3.02 mV (PDD + PS). Raman analysis showed an increase in mineral components after immersing the dentin specimens, in terms of crystallinity, mineral content, and concentration. This confirmed the optimal incorporation and deposition of mineral on dentin collagen. Organic content reflected scarce changes, except in TDD that appeared partially denatured. Pyridinium, as an expression of cross-linking, appeared in all spectra except in specimens immersed in PS. PMID:24160361

  18. Composition and reactivity of ferrihydrite-organic matter associations

    NASA Astrophysics Data System (ADS)

    Eusterhues, Karin; Hädrich, Anke; Neidhardt, Julia; Küsel, Kirsten; Totsche, Kai

    2014-05-01

    The formation of organo-mineral associations affects many soil forming processes. On the one hand, it will influence soil organic matter composition and development, because the complex organic matter mixtures usually fractionate during their association with mineral surfaces. Whereas the associated fraction is supposed to be stabilized, the non-associated fraction remains mobile and available to degradation by microorganisms. On the other hand, the organic coating will completely change the interface properties of Fe oxides such as solubility, charge and hydrophobicity. This in turn will strongly influence their reactivity towards nutrients and pollutants, the adsorption of new organic matter, and the availability of ferric Fe towards microorganisms. To better understand such processes we produced ferrihydrite-organic matter associations by adsorption and coprecipitation in laboratory experiments. As a surrogate for dissolved soil organic matter we used the water-extractable fraction of a Podzol forest-floor layer under spruce. Sorptive fractionation of the organic matter was investigated by 13C NMR and FTIR. Relative to the original forest-floor extract, the ferrihydrite-associated OM was enriched in polysaccharides but depleted in aliphatic C and carbonyl C, especially when adsorption took place. Liquid phase incubation experiments were carried out with an inoculum extracted from the podzol forest-floor under oxic conditions at pH 4.8 to quantify the mineralization of the adsorbed and coprecipitated organic matter. These experiments showed that the association with ferrihydrite stabilized the associated organic matter, but that differences in the degradability of adsorbed and coprecipitated organic matter were small. We therefore conclude that coprecipitation does not lead to a significant formation of microbial inaccessible organic matter domains. Microbial reduction experiments were performed using Geobacter bremensis. We observed that increasing amounts of

  19. Hydroxyapatite-anchored dendrimer for in situ remineralization of human tooth enamel.

    PubMed

    Wu, Duo; Yang, Jiaojiao; Li, Jiyao; Chen, Liang; Tang, Bei; Chen, Xingyu; Wu, Wei; Li, Jianshu

    2013-07-01

    In situ remineralization of hydroxyapatite (HA) on human tooth enamel surface induced by organic matrices is of great interest in the fields of material science and stomatology. In order to mimic the organic matrices induced biomineralization process in developing enamel and enhance the binding strength at the remineralization interface, carboxyl-terminated poly(amido amine) (PAMAM-COOH)-alendronate (ALN) conjugate (ALN-PAMAM-COOH) was synthesized and characterized. PAMAM-COOH has a highly ordered architecture and is capable of promoting the HA crystallization process. ALN is conjugated on PAMAM-COOH due to its specific adsorption on HA (the main component of tooth enamel), resulting in increased binding strength which is tight enough to resist phosphate buffered saline (PBS) rinsing as compared with that of PAMAM-COOH alone. While incubated in artificial saliva, ALN-PAMAM-COOH could induce in situ remineralization of HA on acid-etched enamel, and the regenerated HA has the nanorod-like crystal structure similar to that of human tooth enamel. The hardness of acid-etched enamel samples treated by ALN-PAMAM-COOH can recover up to 95.5% of the original value with strong adhesion force. In vivo experiment also demonstrates that ALN-PAMAM-COOH is effective in repairing acid-etched enamel in the oral cavity. Overall, these results suggest that ALN-PAMAM-COOH is highly promising as a restorative biomaterial for in situ remineralization of human tooth enamel.

  20. The search for indigenous lunar organic matter.

    NASA Technical Reports Server (NTRS)

    Sagan, C.

    1972-01-01

    It is argued that the absence of organic compounds from returned lunar samples is to be expected even for a lunar history rich in primordial organics. The sites most likely to yield lunar organic compounds have not been investigated, and there may be an area of investigation conceivably critical to problems in prebiological chemistry and the early history of the solar system awaiting continued lunar exploration, manned or unmanned.

  1. Natural organic matter properties in Swedish agricultural streams

    NASA Astrophysics Data System (ADS)

    Bieroza, Magdalena; Kyllmar, Katarina; Bergström, Lars; Köhler, Stephan

    2016-04-01

    We have analysed natural organic matter (NOM) properties in 18 agricultural streams in Sweden covering a broad range of environmental (climate, soil type), land use and water quality (nutrient and concentrations, pH, alkalinity) characteristics. Stream water samples collected every two weeks within an ongoing Swedish Monitoring Programme for Agriculture have been analysed for total/dissolved organic carbon, absorbance and fluorescence spectroscopy. A number of quantitative and qualitative spectroscopic parameters was calculated to help to distinguish between terrestrially-derived, refractory organic material and autochthonous, labile material indicative of biogeochemical transformations of terrestrial NOM and recent biological production. The study provides insights into organic matter properties and carbon budgets in agricultural streams and improves understanding of how agricultural catchments transform natural and anthropogenic fluxes of organic matter and nutrients to signals observed in receiving waters.

  2. High dimensional reflectance analysis of soil organic matter

    NASA Technical Reports Server (NTRS)

    Henderson, T. L.; Baumgardner, M. F.; Franzmeier, D. P.; Stott, D. E.; Coster, D. C.

    1992-01-01

    Recent breakthroughs in remote-sensing technology have led to the development of high spectral resolution imaging sensors for observation of earth surface features. This research was conducted to evaluate the effects of organic matter content and composition on narrowband soil reflectance across the visible and reflective infrared spectral ranges. Organic matter from four Indiana agricultural soils, ranging in organic C content from 0.99 to 1.72 percent, was extracted, fractionated, and purified. Six components of each soil were isolated and prepared for spectral analysis. Reflectance was measured in 210 narrow bands in the 400- to 2500-nm wavelength range. Statistical analysis of reflectance values indicated the potential of high dimensional reflectance data in specific visible, near-infrared, and middle-infrared bands to provide information about soil organic C content, but not organic matter composition. These bands also responded significantly to Fe- and Mn-oxide content.

  3. Modeling organic matter stabilization during windrow composting of livestock effluents.

    PubMed

    Oudart, D; Paul, E; Robin, P; Paillat, J M

    2012-01-01

    Composting is a complex bioprocess, requiring a lot of empirical experiments to optimize the process. A dynamical mathematical model for the biodegradation of the organic matter during the composting process has been developed. The initial organic matter expressed by chemical oxygen demand (COD) is decomposed into rapidly and slowly degraded compartments and an inert one. The biodegradable COD is hydrolysed and consumed by microorganisms and produces metabolic water and carbon dioxide. This model links a biochemical characterization of the organic matter by Van Soest fractionating with COD. The comparison of experimental and simulation results for carbon dioxide emission, dry matter and carbon content balance showed good correlation. The initial sizes of the biodegradable COD compartments are explained by the soluble, hemicellulose-like and lignin fraction. Their sizes influence the amplitude of the carbon dioxide emission peak. The initial biomass is a sensitive variable too, influencing the time at which the emission peak occurs. PMID:23393964

  4. Defining the quality of soil organic matter

    EPA Science Inventory

    Soils represent the largest terrestrial pool of carbon (C) and hold approximately two-thirds of all C held in these ecosystems. However, not all C in soils is of equal quality. Some fractions of the organic forms, i.e., soil organic carbon (SOC) have long residence times while ...

  5. Effects of Crayfish on Quality of Fine Particulate Organic Matter

    NASA Astrophysics Data System (ADS)

    Montemarano, J. J.; Kershner, M. W.; Leff, L. G.

    2005-05-01

    The origin and ontogeny of detritus often determines its bioavailability. Crayfish shred and consume detrital organic matter, influencing fine particulate organic matter (FPOM) availability, composition and quality. Given consumption of FPOM by many invertebrates, crayfish can indirectly affect these organisms by altering FPOM bioavailability through organic matter fragmentation, biofilm disturbance, and defecation. These effects may or may not vary among coarse particulate organic matter (CPOM) from different leaf species. To assess crayfish effects on FPOM quality, crayfish were fed stream-conditioned maple or oak leaves in hanging 1-mm mesh-bottom baskets in aquaria. After 12 h, crayfish and remaining leaves were removed. FPOM fragments that fell through the mesh were vacuum filtered and analyzed for percent organic matter, C:N ratio, and bacterial abundance. The same analyses were conducted on crayfish feces collected using finger cots encasing crayfish abdomens. C:N ratios did not differ between feces and maple leaf CPOM, but were lower in FPOM produced through fragmentation and disturbance (P = 0.023). Overall, crayfish alter the ontogeny of detritus, which may, in turn, affect stream FPOM dynamics.

  6. Soil organic matter contribution to the NW Mediterranean (Invited)

    NASA Astrophysics Data System (ADS)

    Kim, J.; Buscail, R.; Blokker, J.; Kerhervé, P.; Schouten, S.; Ludwig, W.; Sinninghe Damsté, J. S.

    2009-12-01

    The BIT (Branched and Isoprenoid Tetraether) index has recently been introduced as a proxy for soil organic matter input and is based on the relative abundance of non-isoprenoidal glycerol dialkyl glycerol tetraethers (GDGTs) derived from organisms living in terrestrial environments versus a structurally related isoprenoid GDGT “crenarchaeol” produced by marine Crenarchaeota (Hopmans et al., 2004). In this study, detailed spatial distribution patterns of BIT index were investigated in combination with other organic parameters in the continental margin of the north western Mediterranean. Based on a transect sampling strategy from source (land) to sink (sea) via river, we analysed a variety of soils from the Têt and Rhône basins, suspended particulate matter in waters of the Têt and Rhône rivers flowing into the Gulf of Lions, and marine surface sediments from the Gulf of Lions collected before and after a flood occurred in June 2008. Our study allows us to track BIT values along the transport pathway of soil organic matter and thus to estimate soil organic matter contribution in marine sediments in the Gulf of Lions (NW Mediterranean), a river-dominated continental margin. Hopmans, E.C., Weijers, J.W.H., Schefuss, E., Herfort, L., Sinninghe Damsté, J.S., Schouten, S., 2004. A novel proxy for terrestrial organic matter in sediments based on branched and isoprenoidtetraether lipids. Earth and Planetary Science Letters 224, 107-116.

  7. Dissolved Organic Matter in the Hudson River Plume

    NASA Astrophysics Data System (ADS)

    Chen, R. F.; Gardner, G. B.

    2004-12-01

    As part of the LATTE (Lagrangian Transport and Transformation Experiment) program, dissolved organic carbon (DOC), total nitrogen (TN), and chromophoric dissolved organic matter (CDOM) were measured in the Hudson River Estuary and Plume. As revealed by high resolution measurements from the Integrated Coastal Observation System (ICOS), dissolved organic matter has several sources within the estuary including the Hudson and Raritan Rivers, and a yet unidentified anthropogenic source off Manhattan. The quantity of dissolved organic matter that is exported from the Hudson River Estuary is significantly greater than that which the Hudson River can supply by simply conservative mixing with coastal seawater. In May, 2004, rhodamine dye was injected at the surface as the plume flowed out onto the New York/New Jersey shelf, once as the plume turned north towards Long Island, and once as the plume flowed south along the New Jersey coast. The ECOShuttle (a towed-undulating vehicle) carrying a rhodamine fluorometer was able to track these dye patches. An examination of dissolved organic matter transformations that occurred over these two to two and one-half day Lagrangian experiments will be discussed. In addition seasonal distributions of dissolved organic matter distributions will be presented from cruises in June 2003, June 2004 and September 2004 under different river flow and wind conditions.

  8. Black Carbon in Estuarine and Coastal Ocean Dissolved Organic Matter

    NASA Technical Reports Server (NTRS)

    Mannino, Antonio; Harvey, H. Rodger

    2003-01-01

    Analysis of high-molecular-weight dissolved organic matter (DOM) from two estuaries in the northwest Atlantic Ocean reveals that black carbon (BC) is a significant component of previously uncharacterized DOM, suggesting that river-estuary systems are important exporters of recalcitrant dissolved organic carbon to the ocean.

  9. Organic Matter Application Can Reduce Copper Toxicity in Tomato Plants

    ERIC Educational Resources Information Center

    Campbell, Brian

    2010-01-01

    Copper fungicides and bactericides are often used in tomato cultivation and can cause toxic Cu levels in soils. In order to combat this, organic matter can be applied to induce chelation reactions and form a soluble complex by which much of the Cu can leach out of the soil profile or be taken up safely by plants. Organic acids such as citric,…

  10. PHOTOCHEMICAL TRANSFORMATIONS OF DISSOLVED ORGANIC MATTER IN A BLACKWATER RIVER

    EPA Science Inventory

    We examined photochemical alterations of dissolved organic matter (DOM) from the Satilla River, a high DOC (10-40 mg/liter) blackwater river of southeast Georgia. Water samples were filtered to remove most organisms, placed in quartz tubes, and incubated under natural sunlight a...

  11. Pedogenesis evolution of mine technosols: focus onto organic matter implication

    NASA Astrophysics Data System (ADS)

    Grégoire, Pascaud; Marilyne, Soubrand; Laurent, Lemee; Husseini Amelène, El-Mufleh Al; Marion, Rabiet; Emmanuel, Joussein

    2014-05-01

    Keywords: Mine technosols, pedogenesis, organic matter, environmental impact, pyr-GC-MS Technosols include soils subject to strong anthropogenic pressure and particularly to soil influenced by human transformed materials. In this context, abandoned mine sites contain a large amount of transformed waste materials often enriched with metals and/or metalloids. The natural evolution of technosols (pedogenesis) may induces the change in contaminants behaviour in term of stability of bearing phases, modification of pH oxydo-reduction conditions, organic matter turnover, change in permeability, or influence of vegetation cover. The fate of these elements in the soil can induce major environmental problems (contamination of biosphere and water resource). This will contribute to a limited potential use of these soils, which represent yet a large area around the world. The initial contamination of the parental material suggests that the pedological cover would stabilize the soil; however, the chemical reactivity must be taken in consideration particularly with respect to potential metal leachings. In this case, it is quite important to understand the development of soil in this specific context. Consequently, the global aims of this study are to understand the functioning of mine Technosols focusing onto the organic matter implication in their pedogenesis. Indeed, soil organic matter constitutes an heterogeneous fraction of organic compounds that plays an important role in the fate and the transport of metals and metalloids in soils. Three different soil profiles were collected representative to various mining context (contamination, time, climat), respectively to Pb-Ag, Sn and Au exploitations. Several pedological parameters were determined like CEC, pH, %Corg, %Ntot, C/N ratio, grain size distribution and chemical composition. The evolution of the nature of organic matter in Technosol was studied by elemental analyses and thermochemolysis was realized on the total and

  12. Remineralization of demineralized enamel via calcium phosphate nanocomposite.

    PubMed

    Weir, M D; Chow, L C; Xu, H H K

    2012-10-01

    Secondary caries remains the main problem limiting the longevity of composite restorations. The objective of this study was to investigate the remineralization of demineralized human enamel in vitro via a nanocomposite containing nanoparticles of amorphous calcium phosphate (NACP). NACP were synthesized by a spray-drying technique and incorporated into a dental resin. First, caries-like subsurface enamel lesions were created via an acidic solution. Then, NACP nanocomposite or a commercial fluoride-releasing control composite was placed on the demineralized enamel, along with control enamel without a composite. These specimens were then treated with a cyclic demineralization/remineralization regimen for 30 days. Quantitative microradiography showed typical enamel subsurface demineralization before cyclic demineralization/remineralization treatment, and significant remineralization in enamel under the NACP nanocomposite after the demineralization/remineralization treatment. The NACP nanocomposite had the highest enamel remineralization (mean ± SD; n = 6) of 21.8 ± 3.7%, significantly higher than the 5.7 ± 6.9% for fluoride-releasing composite (p < 0.05). The enamel group without composite had further demineralization of -26.1 ± 16.2%. In conclusion, a novel NACP nanocomposite was effective in remineralizing enamel lesions in vitro. Its enamel remineralization was 4-fold that of a fluoride-releasing composite control. Combined with the good mechanical and acid-neutralization properties reported earlier, the new NACP nanocomposite is promising for remineralization of demineralized tooth structures. PMID:22933607

  13. Interstellar and Solar System Organic Matter Preserved in Interplanetary Dust

    NASA Astrophysics Data System (ADS)

    Messenger, Scott R.; Nakamura-Messenger, Keiko

    2015-08-01

    Interplanetary dust particles (IDPs) collected in the Earth’s stratosphere derive from collisions among asteroids and by the disruption and outgassing of short-period comets. Chondritic porous (CP) IDPs are among the most primitive Solar System materials. CP-IDPs have been linked to cometary parent bodies by their mineralogy, textures, C-content, and dynamical histories. CP-IDPs are fragile, fine-grained (< um) assemblages of anhydrous amorphous and crystalline silicates, oxides and sulfides bound together by abundant carbonaceous material. Ancient silicate, oxide, and SiC stardust grains exhibiting highly anomalous isotopic compositions are abundant in CP-IDPs, constituting 0.01 - 1 % of the mass of the particles. The organic matter in CP-IDPs is isotopically anomalous, with enrichments in D/H reaching 50x the terrestrial SMOW value and 15N/14N ratios up to 3x terrestrial standard compositions. These anomalies are indicative of low T (10-100 K) mass fractionation in cold molecular cloud or the outermost reaches of the protosolar disk. The organic matter shows distinct morphologies, including sub-um globules, bubbly textures, featureless, and with mineral inclusions. Infrared spectroscopy and mass spectrometry studies of organic matter in IDPs reveals diverse species including aliphatic and aromatic compounds. The organic matter with the highest isotopic anomalies appears to be richer in aliphatic compounds. These materials also bear similarities and differences with primitive, isotopically anomalous organic matter in carbonaceous chondrite meteorites. The diversity of the organic chemistry, morphology, and isotopic properties in IDPs and meteorites reflects variable preservation of interstellar/primordial components and Solar System processing. One unifying feature is the presence of sub-um isotopically anomalous organic globules among all primitive materials, including IDPs, meteorites, and comet Wild-2 samples returned by the Stardust mission. We will present

  14. GROUNDWATER TRANSPORT OF HYDROPHOBIC ORGANIC COMPOUNDS IN THE PRESENCE OF DISSOLVED ORGANIC MATTER

    EPA Science Inventory

    The effects of dissolved organic matter (DOM) on the transport of hydrophobic organic compounds in soil columns were investigated. Three compounds (naphthalene, phenanthrene and DDT) that spanned three orders of magnitude in water solubility were used. Instead of humic matter, mo...

  15. Influence of nutrient utilization and remineralization stoichiometry on phytoplankton species and carbon export: A modeling study at BATS

    NASA Astrophysics Data System (ADS)

    Salihoglu, B.; Garçon, V.; Oschlies, A.; Lomas, M. W.

    2008-01-01

    The primary objective of this research is to understand the underlying mechanisms of the time-varying flux of carbon in the Sargasso Sea. To address this objective, a one-dimensional multi-component lower trophic level ecosystem model that includes detailed algal physiology as well as nutrient cycles is used at the Bermuda Atlantic Time-series Study (BATS, 31∘40'N, 64∘10'W) site. In this model autotrophic growth is represented by three algal groups and the cell quota approach is used to estimate algal growth and nutrient uptake. This model is tested and evaluated for year 1998 using the bimonthly BATS cruise data. Results show that phosphorus and dissolved organic matter (DOM) are necessary compartments to correctly simulate organic elemental cycles at the BATS site. Model results show that autotrophic eukaryotes and cyanobacteria (i.e. Prochlorococcus and Synechococcus) are the most abundant algal groups and are responsible for 63% and 33% of carbon production in the region, respectively. Sensitivity analyses show that the annual contribution of nitrogen fixation and atmospheric nitrogen deposition to new production is approximately 9% and 3%, respectively. However, the recycled nitrogen and phosphorus are important components of the ecosystem dynamics because sustained growth of algal groups depends on remineralized nutrients which accounts for 75% of the annual carbon production. Nutrient uptake and remineralization stoichiometry can play an important role in determining the surface ocean nutrient distribution. Model results suggest phosphate limitation even during the spring bloom. Phosphate may thus limit the growth of all algal groups throughout the year.

  16. The impact of remineralization depth on the air-sea carbon balance

    NASA Astrophysics Data System (ADS)

    Kwon, Eun Young; Primeau, François; Sarmiento, Jorge L.

    2009-09-01

    As particulate organic carbon rains down from the surface ocean it is respired back to carbon dioxide and released into the ocean's interior. The depth at which this sinking carbon is converted back to carbon dioxide-known as the remineralization depth-depends on the balance between particle sinking speeds and their rate of decay. A host of climate-sensitive factors can affect this balance, including temperature, oxygen concentration, stratification, community composition and the mineral content of the sinking particles. Here we use a three-dimensional global ocean biogeochemistry model to show that a modest change in remineralization depth can have a substantial impact on atmospheric carbon dioxide concentrations. For example, when the depth at which 63% of sinking carbon is respired increases by 24m globally, atmospheric carbon dioxide concentrations fall by 10-27ppm. This reduction in atmospheric carbon dioxide concentration results from the redistribution of remineralized carbon from intermediate waters to bottom waters. As a consequence of the reduced concentration of respired carbon in upper ocean waters, atmospheric carbon dioxide is preferentially stored in newly formed North Atlantic Deep Water. We suggest that atmospheric carbon dioxide concentrations are highly sensitive to the potential changes in remineralization depth that may be caused by climate change.

  17. Compartmental model for organic matter digestion in facultative ponds.

    PubMed

    Giraldo, E; Garzón, A

    2002-01-01

    A model has been developed for the digestion of organic matter in facultative ponds in tropical regions. Complete mixing has been assumed for the aerobic and anaerobic compartments. Settling, aerobic layer oxidation, and anaerobic layer methanogenesis are the main processes for organic matter removal in the water column. Exchange processes between layers are dispersive or soluble exchange, solubilization and transport of organic matter from sediments to water column are also taken into account. Degradation of organic matter in the sediments produces gaseous emissions to the water column. The exchange between bubbles ascending and the water column was measured. The model was calibrated with data obtained from a pilot facultative pond built in Muña Reservoir in Bogotá. The pond was sampled during 4 months to compare data between its water hyacinth covered section and uncovered section. The results clearly show the relative importance of different BOD removal processes in facultative ponds and suggest modifications to further improve performance. The results from the model suggest that internal loadings to facultative ponds due to solubilization and return of organic matter from the sediments to the aerobic layer greatly influence the soluble BOD effluent concentration. Aerobic degradation activity in the facultative pond does not affect significantly the effluent concentration. Anaerobic degradation activity in the facultative pond can more easily achieve increases in the removal efficiencies of BOD.

  18. Compartmental model for organic matter digestion in facultative ponds.

    PubMed

    Giraldo, E; Garzón, A

    2002-01-01

    A model has been developed for the digestion of organic matter in facultative ponds in tropical regions. Complete mixing has been assumed for the aerobic and anaerobic compartments. Settling, aerobic layer oxidation, and anaerobic layer methanogenesis are the main processes for organic matter removal in the water column. Exchange processes between layers are dispersive or soluble exchange, solubilization and transport of organic matter from sediments to water column are also taken into account. Degradation of organic matter in the sediments produces gaseous emissions to the water column. The exchange between bubbles ascending and the water column was measured. The model was calibrated with data obtained from a pilot facultative pond built in Muña Reservoir in Bogotá. The pond was sampled during 4 months to compare data between its water hyacinth covered section and uncovered section. The results clearly show the relative importance of different BOD removal processes in facultative ponds and suggest modifications to further improve performance. The results from the model suggest that internal loadings to facultative ponds due to solubilization and return of organic matter from the sediments to the aerobic layer greatly influence the soluble BOD effluent concentration. Aerobic degradation activity in the facultative pond does not affect significantly the effluent concentration. Anaerobic degradation activity in the facultative pond can more easily achieve increases in the removal efficiencies of BOD. PMID:11833730

  19. Transplanting an organization: how does culture matter.

    PubMed

    Munich, Richard L

    2011-01-01

    Cultural differences are often cited as a major obstacle to the successful transition/integration into new situations of organizations. In this contribution, the author details the changing cultural factors impacting the operation and move of the Menninger Clinic from autonomous status to an affiliation with and first year of operation in the Baylor College of Medicine and Methodist Hospital Health Care System. Both functional and dysfunctional consequences are outlined, and specific examples illustrate how the organization's leadership and staff struggled to adapt during this complicated process. Based on the experience within the Clinic, general recommendations for managing such an acculturation are provided.

  20. Removal of dissolved organic matter by anion exchange: Effect of dissolved organic matter properties

    USGS Publications Warehouse

    Boyer, T.H.; Singer, P.C.; Aiken, G.R.

    2008-01-01

    Ten isolates of aquatic dissolved organic matter (DOM) were evaluated to determine the effect that chemical properties of the DOM, such as charge density, aromaticity, and molecular weight, have on DOM removal by anion exchange. The DOM isolates were characterized asterrestrial, microbial, or intermediate humic substances or transphilic acids. All anion exchange experiments were conducted using a magnetic ion exchange (MIEX) resin. The charge density of the DOM isolates, determined by direct potentiometric titration, was fundamental to quantifying the stoichiometry of the anion exchange mechanism. The results clearly show that all DOM isolates were removed by anion exchange; however, differences among the DOM isolates did influence their removal by MIEX resin. In particular, MIEX resin had the greatest affinity for DOM with high charge density and the least affinity for DOM with low charge density and low aromaticity. This work illustrates that the chemical characteristics of DOM and solution conditions must be considered when evaluating anion exchange treatment for the removal of DOM. ?? 2008 American Chemical Society.

  1. Organic matter on asteroid 130 Elektra

    NASA Technical Reports Server (NTRS)

    Cruikshank, D. P.; Brown, R. H.

    1987-01-01

    Infrared absorption spectra of a low-albedo water-rich asteroid appear to show a weak 3.4-micrometer carbon-hydrogen stretching mode band, which suggests the presence of hydrocarbons on asteroid 130 Elektra. The organic extract from the primitive carbonaceous chondritic Murchison meteorite shows similar spectral bands.

  2. Organic matter in the Saturn system

    NASA Technical Reports Server (NTRS)

    Sagan, C.; Khare, B. N.; Lewis, J. S.

    1984-01-01

    Theoretical and experimental predictions of the formation (and outgassing) of organic molecules in the outer solar system are compared with Voyager IRIS spectral data for the Titan atmosphere. The organic molecules of Titan are of interest because the species and processes within the atmosphere of that moon may have had analogs in the early earth atmosphere 4 Gyr ago. The spacecraft data confirmed the presence of alkanes, ethane, propane, ethylene, alkynes, acetylene, butadiene, methylacetylene, nitriles, hydrogen cyanide, cyanoacetylene, and cyanogen, all heavier than the dominant CH4. Experimental simulation of the effects of UV photolysis, alpha and gamma ray irradiation, electrical discharges and proton and electron bombardment of similar gas mixtures has shown the best promise for modeling the reactions producing the Titan atmosphere chemicals.

  3. River export of nutrients and organic matter from the North Slope of Alaska to the Beaufort Sea

    NASA Astrophysics Data System (ADS)

    McClelland, J. W.; Townsend-Small, A.; Holmes, R. M.; Pan, Feifei; Stieglitz, M.; Khosh, M.; Peterson, B. J.

    2014-02-01

    While river-borne materials are recognized as important resources supporting coastal ecosystems around the world, estimates of river export from the North Slope of Alaska have been limited by a scarcity of water chemistry and river discharge data. This paper quantifies water, nutrient, and organic matter export from the three largest rivers (Sagavanirktok, Kuparuk, and Colville) that drain Alaska's North Slope and discusses the potential importance of river inputs for biological production in coastal waters of the Alaskan Beaufort Sea. Together these rivers export ˜297,000 metric tons of organic carbon and ˜18,000 metric tons of organic nitrogen each year. Annual fluxes of nitrate-N, ammonium-N, and soluble reactive phosphorus are approximately 1750, 200, and 140 metric tons per year, respectively. Constituent export from Alaska's North Slope is dominated by the Colville River. This is in part due to its larger size, but also because constituent yields are greater in the Colville watershed. River-supplied nitrogen may be more important to productivity along the Alaskan Beaufort Sea coast than previously thought. However, given the dominance of organic nitrogen export, the potential role of river-supplied nitrogen in support of primary production depends strongly on remineralization mechanisms. Although rivers draining the North Slope of Alaska make only a small contribution to overall river export from the pan-arctic watershed, comparisons with major arctic rivers reveal unique regional characteristics as well as remarkable similarities among different regions and scales. Such information is crucial for development of robust river export models that represent the arctic system as a whole.

  4. Biogeochemistry of dissolved organic matter in an anoxic intertidal creek bank

    NASA Astrophysics Data System (ADS)

    Seidel, Michael; Beck, Melanie; Riedel, Thomas; Waska, Hannelore; Suryaputra, I. G. N. A.; Schnetger, Bernhard; Niggemann, Jutta; Simon, Meinhard; Dittmar, Thorsten

    2014-09-01

    Seawater circulation in permeable coastal sediments is driven by tidal changes in hydraulic gradients. The resulting submarine groundwater discharge is a source of nutrients and dissolved organic matter (DOM) to the water column. Yet, little is known about the cycling of DOM within tidal sediments, because the molecular DOM characterization remains analytically challenging. One technique that can dissect the multitude of molecules in DOM is ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). To aim at a high resolution DOM analysis we study the seasonal turnover and marine and terrestrial sources of DOM in an intertidal creek bank of the southern North Sea down to 3 m depth and link the biogeochemical processes to FT-ICR-MS data and the analyses of inorganic porewater chemistry, δ13C of solid-phase extracted dissolved organic carbon (SPE-DOC), dissolved black carbon (DBC) and dissolved carbohydrates (DCHO). Increasing concentrations of dissolved Fe, Mn, P, total alkalinity, dissolved nitrogen, DOC and a concomitant decrease of sulfate along the seawater circulation path from the upper tidal flat to the tidal flat margin indicate continuous microbial activity. The relative increase of Si concentrations, unsaturated aliphatics, peptide molecular formulae and isotopically more 13C-enriched SPE-DOC towards the tidal flat margin suggests that remineralization processes mobilize DOM from buried algal (diatoms) and microbial biomass. Porewater in sediments <100 cm depth contains 13C-depleted SPE-DOC and highly unsaturated compounds which are probably derived from eroded peats, suggesting rapid removal of bioavailable marine DOM such as DCHO from the water column and selective enrichment of terrestrial DOM. DBC concentrations are highest in the discharging porewater close to the tidal creek suggesting that the intertidal flat is an important DBC source to the coastal ocean. Porewater DOM accumulating at the low water line is

  5. Scavenging of soluble organic matter from the prebiotic oceans.

    PubMed

    Nissenbaum, A

    1976-12-01

    The existence of hot or cold "nutrient broth" or "primeval soup" is challenged on the basis of the recent geochemistry of soluble organic carbon in the oceans. Most of the dissolved organic carbon is recycled quickly by organisms, but the residual, biologically refractive, organic matter is efficiently scavenged from the oceans (residence time of 1000 to 3500 years) by nonbiologically mediated chemical and physical processes, such as adsorption on sinking minerals, polymerization and aggregation to humic type polymers or by aggregation to particulate matter through bubbling and sinking of this material to the ocean bottom. Since there is no reason to believe that such nonbiological scavenging was not operative in the prebiotic oceans as well, then the prolonged existence of "organic soup" is very doubtful. The question of the origin of life is thus assumed to be related to solid-liquid interfacial activity, and the answer may be associated with sediment-water interaction rather than with solution chemistry.

  6. Detection of organic matter in interstellar grains.

    PubMed

    Pendleton, Y J

    1997-06-01

    Star formation and the subsequent evolution of planetary systems occurs in dense molecular clouds, which are comprised, in part, of interstellar dust grains gathered from the diffuse interstellar medium (DISM). Radio observations of the interstellar medium reveal the presence of organic molecules in the gas phase and infrared observational studies provide details concerning the solid-state features in dust grains. In particular, a series of absorption bands have been observed near 3.4 microns (approximately 2940 cm-1) towards bright infrared objects which are seen through large column densities of interstellar dust. Comparisons of organic residues, produced under a variety of laboratory conditions, to the diffuse interstellar medium observations have shown that aliphatic hydrocarbon grains are responsible for the spectral absorption features observed near 3.4 microns (approximately 2940 cm-1). These hydrocarbons appear to carry the -CH2- and -CH3 functional groups in the abundance ratio CH2/CH3 approximately 2.5, and the amount of carbon tied up in this component is greater than 4% of the cosmic carbon available. On a galactic scale, the strength of the 3.4 microns band does not scale linearly with visual extinction, but instead increases more rapidly for objects near the Galactic Center. A similar trend is noted in the strength of the Si-O absorption band near 9.7 microns. The similar behavior of the C-H and Si-O stretching bands suggests that these two components may be coupled, perhaps in the form of grains with silicate cores and refractory organic mantles. The ubiquity of the hydrocarbon features seen in the near infrared near 3.4 microns throughout out Galaxy and in other galaxies demonstrates the widespread availability of such material for incorporation into the many newly forming planetary systems. The similarity of the 3.4 microns features in any organic material with aliphatic hydrocarbons underscores the need for complete astronomical observational

  7. Influence of organic matter on collembolan communities in reedbed habitats

    NASA Astrophysics Data System (ADS)

    Uteseny, K.; Drapela, T.; Frouz, J.

    2009-04-01

    The combination of the organic matter, micro-climatic environments and plant cover belongs to important factors for the distribution of soil meso-fauna, especially Collembola. There are no studies attending to these factors on collembolan communities in reedbed vegetation. The main goals of our investigation were therefore to compare diversity of Collembola in redbed habitats of Lake Neudsiedl, eastern Austria, and to assess particularly the role of organic matter with regard to the collembolan community structure. Soil samples were taken from April 1997 to October 1997 at fifteen study sites covered with Phragmatis australis of different age. Changes in the structure and composition of the assemblages of Collembola were examined.

  8. Isotopic composition of hydrogen in insoluble organic matter from cherts

    NASA Technical Reports Server (NTRS)

    Krishnamurthy, R. V.; Epstein, S.

    1991-01-01

    Robert (1989) reported the presence of unusually enriched hydrogen in the insoluble HF-HCl residue extracted from two chert samples of Eocene and Pliocene ages. Since the presence of heavy hydrogen might be due to the incorporation of extraterrestrial materials, we desired to reexamine the same samples to isolate the D-rich components. Our experiments did not reveal any D-rich components, but the hydrogen isotope composition of the insoluble residue of the two chert samples was well within the range expected for terrestrial organic matter. We also describe a protocol that needs to be followed in the hydrogen isotope analysis of any insoluble organic matter.

  9. Andic soils : mineralogical effect onto organic matter dynamics, organic matter effect onto mineral dynamics, or both?

    NASA Astrophysics Data System (ADS)

    Basile-Doelsch, Isabelle; Amundson, Ronald; Balesdent, Jérome; Borschneck, Daniel; Bottero, Jean-Yves; Colin, Fabrice; de Junet, Alexis; Doelsch, Emmanuel; Legros, Samuel; Levard, Clément; Masion, Armand; Meunier, Jean-Dominique; Rose, Jérôme

    2014-05-01

    From a strictly mineralogical point of view, weathering of volcanic glass produces secondary phases that are short range ordered alumino-silicates (SRO-AlSi). These are imogolite tubes (2 to 3 nm of diameter) and allophane supposedly spheres (3.5 to 5 nm). Their local structure is composed of a curved gibbsite Al layer and Si tetrahedra in the vacancies (Q0). Proto-imogolites have the same local structure but are roof-shape nanoparticles likely representing the precursors of imogolite and allophanes (Levard et al. 2010). These structures and sizes give to the SRO-AlSi large specific surfaces and high reactivities. In some natural sites, imogolites and allophanes are formed in large quantities. Aging of these phases may lead to the formation of more stable minerals (halloysite, kaolinite and gibbsite) (Torn et al 1997). In natural environments, when the weathering of volcanic glass is associated with the establishment of vegetation, the soils formed are generally andosols. These soils are particularly rich in organic matter (OM), which is explained by the high ability of SRO-AlSi mineral phases to form bonds with organic compounds. In a first order "bulk" approach, it is considered that these bonds strongly stabilize the organic compounds as their mean age can reach more than 10 kyrs in some studied sites (Basile-Doelsch et al. 2005; Torn et al. 1997). However, the structure of the mineral phases present in andosols deserves more attention. Traditionally, the presence in the SRO-AlSi andosols was shown by selective dissolution approaches by oxalate and pyrophosphate. Using spectroscopic methods, mineralogical analysis of SRO-AlSi in andosols samples showed that these mineral phases were neither imogolites nor allophanes as originally supposed, but only less organized structures remained in a state of proto-imogolites (Basile-Doelsch al. 2005 ; Levard et al., 2012). The presence of OM would have an inhibitory effect on the formation of secondary mineral phases, by

  10. Composition of dissolved organic matter in groundwater

    NASA Astrophysics Data System (ADS)

    Longnecker, Krista; Kujawinski, Elizabeth B.

    2011-05-01

    Groundwater constitutes a globally important source of freshwater for drinking water and other agricultural and industrial purposes, and is a prominent source of freshwater flowing into the coastal ocean. Therefore, understanding the chemical components of groundwater is relevant to both coastal and inland communities. We used electrospray ionization coupled with Fourier-transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) to examine dissolved organic compounds in groundwater prior to and after passage through a sediment-filled column containing microorganisms. The data revealed that an unexpectedly high proportion of organic compounds contained nitrogen and sulfur, possibly due to transport of surface waters from septic systems and rain events. We matched 292 chemical features, based on measured mass:charge ( m/z) values, to compounds stored in the Kyoto Encyclopedia of Genes and Genomes (KEGG). A subset of these compounds (88) had only one structural isomer in KEGG, thus supporting tentative identification. Most identified elemental formulas were linked with metabolic pathways that produce polyketides or with secondary metabolites produced by plants. The presence of polyketides in groundwater is notable because of their anti-bacterial and anti-cancer properties. However, their relative abundance must be quantified with appropriate analyses to assess any implications for public health.

  11. Interstellar and Solar System Organic Matter Preserved in Interplanetary Dust

    NASA Technical Reports Server (NTRS)

    Messenger, Scott; Nakamura-Messenger, Keiko

    2015-01-01

    Interplanetary dust particles (IDPs) collected in the Earth's stratosphere derive from collisions among asteroids and by the disruption and outgassing of short-period comets. Chondritic porous (CP) IDPs are among the most primitive Solar System materials. CP-IDPs have been linked to cometary parent bodies by their mineralogy, textures, C-content, and dynamical histories. CP-IDPs are fragile, fine-grained (less than um) assemblages of anhydrous amorphous and crystalline silicates, oxides and sulfides bound together by abundant carbonaceous material. Ancient silicate, oxide, and SiC stardust grains exhibiting highly anomalous isotopic compositions are abundant in CP-IDPs, constituting 0.01 - 1 % of the mass of the particles. The organic matter in CP-IDPs is isotopically anomalous, with enrichments in D/H reaching 50x the terrestrial SMOW value and 15N/14N ratios up to 3x terrestrial standard compositions. These anomalies are indicative of low T (10-100 K) mass fractionation in cold molecular cloud or the outermost reaches of the protosolar disk. The organic matter shows distinct morphologies, including sub-um globules, bubbly textures, featureless, and with mineral inclusions. Infrared spectroscopy and mass spectrometry studies of organic matter in IDPs reveals diverse species including aliphatic and aromatic compounds. The organic matter with the highest isotopic anomalies appears to be richer in aliphatic compounds. These materials also bear similarities and differences with primitive, isotopically anomalous organic matter in carbonaceous chondrite meteorites. The diversity of the organic chemistry, morphology, and isotopic properties in IDPs and meteorites reflects variable preservation of interstellar/primordial components and Solar System processing. One unifying feature is the presence of sub-um isotopically anomalous organic globules among all primitive materials, including IDPs, meteorites, and comet Wild-2 samples returned by the Stardust mission.

  12. Caracterisation of anthropogenic contribution to the coastal fluorescent organic matter

    NASA Astrophysics Data System (ADS)

    El Nahhal, Ibrahim; Nouhi, Ayoub; Mounier, Stéphane

    2015-04-01

    It is known that most of the coastal fluorescent organic matter is of a terrestrial origin (Parlanti, 2000; Tedetti, Guigue, & Goutx, 2010). However, the contribution of the anthropogenic organic matter to this pool is not well defined and evaluated. In this work the monitoring of little bay (Toulon Bay, France) was done in the way to determine the organic fluorescent response during a winter period. The sampling campaign consisted of different days during the month of December, 2014 ( 12th, 15th, 17th, 19th) on 21 different sampling sites for the fluorescence measurements (without any filtering of the samples) and the whole month of December for the bacterial and the turbidity measurements. Excitation Emission Matrices (EEMs) of fluorescence (from 200 to 400 nm and 220 to 420 nm excitation and emission range) were treated by parallel factor analysis (PARAFAC).The parafac analysis of the EEM datasets was conducted using PROGMEEF software in Matlab langage. On the same time that the turbidity and bacterial measurement (particularly the E.Coli concentration) were determined. The results gives in a short time range, information on the the contribution of the anthropogenic inputs to the coastal fluorescent organic matter. In addition, the effect of salinity on the photochemical degradation of the anthropogenic organic matter (especially those from wastewater treatment plants) will be studied to investigate their fate in the water end member by the way of laboratory experiments. Parlanti, E. (2000). Dissolved organic matter fluorescence spectroscopy as a tool to estimate biological activity in a coastal zone submitted to anthropogenic inputs. Organic Geochemistry, 31(12), 1765-1781. doi:10.1016/S0146-6380(00)00124-8 Tedetti, M., Guigue, C., & Goutx, M. (2010). Utilization of a submersible UV fluorometer for monitoring anthropogenic inputs in the Mediterranean coastal waters. Marine Pollution Bulletin, 60(3), 350-62. doi:10.1016/j.marpolbul.2009.10.018

  13. Pre-biotic organic matter from comets and asteroids.

    PubMed

    Anders, E

    1989-11-16

    Several authors have suggested that comets or carbonaceous asteroids contributed large amounts of organic matter to the primitive Earth, and thus possibly played a vital role in the origin of life. But organic matter cannot survive the extremely high temperatures (>10(4) K) reached on impact, which atomize the projectile and break all chemical bonds. Only fragments small enough to be gently decelerated by the atmosphere--principally meteors of 10(-12)-10(-6) g--can deliver their organic matter intact. The amount of such 'soft-landed' organic carbon can be estimated from data for the infall rate of meteoritic matter. At present rates, only approximately 0.006 g cm-2 intact organic carbon would accumulate in 10(8) yr, but at the higher rates of approximately 4 x 10(9) yr ago, about 20 g cm-2 may have accumulated in the few hundred million years between the last cataclysmic impact and the beginning of life. It may have included some biologically important compounds that did not form by abiotic synthesis on Earth.

  14. Adsorption combined with ultrafiltration to remove organic matter from seawater.

    PubMed

    Tansakul, Chatkaew; Laborie, Stéphanie; Cabassud, Corinne

    2011-12-01

    Organic fouling and biofouling are the major severe types of fouling of reverse osmosis (RO) membranes in seawater (SW) desalination. Low pressure membrane filtration such as ultrafiltration (UF) has been developed as a pre-treatment before reverse osmosis. However, UF alone may not be an effective enough pre-treatment because of the existence of low-molecular weight dissolved organic matter in seawater. Therefore, the objective of the present work is to study a hybrid process, powdered activated carbon (PAC) adsorption/UF, with real seawater and to evaluate its performance in terms of organic matter removal and membrane fouling. The effect of different PAC types and concentrations is evaluated. Stream-activated wood-based PAC addition increased marine organic matter removal by up to 70% in some conditions. Moreover, coupling PAC adsorption with UF decreased UF membrane fouling and the fouling occurring during short-term UF was totally reversible. It can be concluded that the hybrid PAC adsorption/UF process performed in crossflow filtration mode is a relevant pre-treatment process before RO desalination, allowing organic matter removal of 75% and showing no flux decline for short-term experiments. PMID:21996607

  15. Adsorption combined with ultrafiltration to remove organic matter from seawater.

    PubMed

    Tansakul, Chatkaew; Laborie, Stéphanie; Cabassud, Corinne

    2011-12-01

    Organic fouling and biofouling are the major severe types of fouling of reverse osmosis (RO) membranes in seawater (SW) desalination. Low pressure membrane filtration such as ultrafiltration (UF) has been developed as a pre-treatment before reverse osmosis. However, UF alone may not be an effective enough pre-treatment because of the existence of low-molecular weight dissolved organic matter in seawater. Therefore, the objective of the present work is to study a hybrid process, powdered activated carbon (PAC) adsorption/UF, with real seawater and to evaluate its performance in terms of organic matter removal and membrane fouling. The effect of different PAC types and concentrations is evaluated. Stream-activated wood-based PAC addition increased marine organic matter removal by up to 70% in some conditions. Moreover, coupling PAC adsorption with UF decreased UF membrane fouling and the fouling occurring during short-term UF was totally reversible. It can be concluded that the hybrid PAC adsorption/UF process performed in crossflow filtration mode is a relevant pre-treatment process before RO desalination, allowing organic matter removal of 75% and showing no flux decline for short-term experiments.

  16. A marine sink for chlorine in natural organic matter

    NASA Astrophysics Data System (ADS)

    Leri, Alessandra C.; Mayer, Lawrence M.; Thornton, Kathleen R.; Northrup, Paul A.; Dunigan, Marisa R.; Ness, Katherine J.; Gellis, Austin B.

    2015-08-01

    Chloride--the most abundant ion in sea water--affects ocean salinity, and thereby seawater density and ocean circulation. Its lack of reactivity gives it an extremely long residence time. Other halogens are known to be incorporated into marine organic matter. However, evidence of similar transformations of seawater chloride is lacking, aside from emissions of volatile organochlorine by marine algae. Here we report high organochlorine concentrations from 180 to 700 mg kg-1 in natural particulate organic matter that settled into sediment traps at depths between 800 and 3,200 m in the Arabian Sea, taken between 1994 and 1995. X-ray spectromicroscopic imaging of chlorine bonding reveals that this organochlorine exists primarily in concentrated aliphatic forms consistent with lipid chlorination, along with a more diffuse aromatic fraction. High aliphatic organochlorine in particulate material from cultured phytoplankton suggests that primary production is a source of chlorinated organic matter. We also found that particulate algal detritus can act as an organic substrate for abiotic reactions involving Fe2+, H2O2 or light that incorporate chlorine into organic matter at levels up to several grams per kilogram. We conclude that transformations of marine chloride to non-volatile organochlorine through biological and abiotic pathways represent an oceanic sink for this relatively unreactive element.

  17. Search for Organic Matter in Leonid Meteoroids

    NASA Technical Reports Server (NTRS)

    Rairden, Richard L.; Jenniskens, Peter; Laux, Christophe O.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    Near-ultraviolet 300-410 nm spectra of Leonid meteors were obtained in an effort to measure the strong B to X emission band of the radical CN in Leonid meteor spectra at 387 nm. CN is an expected product of ablation of nitrogen containing organic carbon in the meteoroids as well as a possible product of the aerothermochemistry induced by the kinetic energy of the meteor. A slitless spectrograph with objective grating was deployed on FISTA during the 1999 Leonid Multi-Instrument Aircraft Campaign. Fifteen first-order UV spectra were captured near the 02:00 UT meteor storm peak on November 18. It is found that neutral iron lines dominate the spectrum, with no clear sign of the CN band. The meteor plasma contains less than one CN molecule per three Fe atoms at the observed altitude of about 100 km.

  18. Aggregation of organic matter by pelagic tunicates

    SciTech Connect

    Pomeroy, L.R.; Deibel, D.

    1980-07-01

    Three genera of pelagic tunicates were fed concentrates of natural seston and an axenic diatom culture. Fresh and up to 4-day-old feces resemble flocculent organic aggregates containing populations of microorganisms, as described from highly productive parts of the ocean, and older feces resemble the nearly sterile flocculent aggregates which are ubiquitous in surface waters. Fresh feces consist of partially digested phytoplankton and other inclusions in an amorphous gelatinous matrix. After 18 to 36 h, a population of large bacteria develops in the matrix and in some of the remains of phytoplankton contained in the feces. From 48 to 96 h, protozoan populations arise which consume the bacteria and sometimes the remains of the phytoplankton in the feces. Thereafter only a sparse population of microorganisms remains, and the particles begin to fragment. Water samples taken in or below dense populations of salps and doliolids contained greater numbers of flocculent aggregates than did samples from adjacent stations.

  19. Organic matter subducted to the seasonal thermocline supports summertime heterotrophy in the lower euphotic zone of the North Atlantic subtropical gyre

    NASA Astrophysics Data System (ADS)

    Chen, H.

    2015-12-01

    In the oligotrophic subtropical gyre of the North Atlantic, summertime surface drawdown of dissolved inorganic carbon (DIC) and build-up of oxygen (O2) in the absence of nutrients to support primary productivity has been an unresolved puzzle for decades. We use 4 years of biogeochemical data from profiling floats in the northwestern subtropical North Atlantic and 24 years of bottle samples from the BATS timeseries to address this puzzle. We show that oxygen-rich, low-nitrate surface waters are subducted into the seasonal thermocline after the spring bloom. These waters are trapped on isopyncals that are progressively displaced downward over the season. Because of this downward displacement, a 50-100m depth-integrated O2 anomaly appears at an average rate of 1.64 ± 0.60 mol/m2 from May to October. Similarly and apparent nitrate loss occurs at an average rate of -0.028 ± 0.022 mol/m2. Organic matter is also subducted to these isopycnals and its remineralization counters the tendencies towards oxygen build-up and nitrate loss in the lower euphotic zone. This compensation, however, is incomplete (70-80%). The result is a positive rate of change in the O2 anomaly from May to October (0.32 ± 0.15 mol/m2) despite net heterotrophy. For Bermuda, 30-50% of positive net community production (NCP) within the mixed layer could be supported by vertical supply of the nutrients remineralized at 50-100m.

  20. Analysis of the Organic Matter in Interplanetary Dust Particles: Clues to the Organic Matter in Comets, Asteroids, and Interstellar Grains

    NASA Technical Reports Server (NTRS)

    Flynn, G. J.; Keller, L. P.

    2003-01-01

    Reflection spectroscopy suggests the C- , P-, and D-types of asteroids contain abundant carbon, but these Vis-nearIR spectra are featureless, providing no information on the type(s) of carbonaceous matter. Infrared spectroscopy demonstrates that organic carbon is a significant component in comets and as grains or grain coatings in the interstellar medium. Most of the interplanetary dust particles (IDPs) recovered from the Earth s stratosphere are believed to be fragments from asteroids or comets, thus characterization of the carbon in IDPs provides the opportunity to determine the type(s) and abundance of organic matter in asteroids and comets. Some IDPs exhibit isotopic excesses of D and N-15, indicating the presence of interstellar material. The characterization of the carbon in these IDPs, and particularly any carbon spatially associated with the isotopic anomalies, provides the opportunity to characterize interstellar organic matter.

  1. Influence of freshwater inflow on the inorganic nutrient and dissolved organic matter within coastal sea ice and underlying waters in the Gulf of Finland (Baltic Sea)

    NASA Astrophysics Data System (ADS)

    Granskog, Mats A.; Kaartokallio, Hermanni; Thomas, David N.; Kuosa, Harri

    2005-10-01

    A study was conducted to measure the biogeochemical characteristics of freshwater plumes underlying Baltic Sea land-fast ice, and the overlying sea ice. A 40-km long transect was conducted in the northern Baltic Sea in March 2003, following a freshwater plume from its source into the fully mixed open-sea area. The spreading of river outflow below the ice resulted in a well-stratified low-salinity surface layer further out than normally occurs in the open-water period. The freshwaters were high in dissolved organic matter (DOC, DON and CDOM), and inorganic nutrients (ammonium, nitrate and silicate), although the levels of phosphate were low. In general these parameters changed concurrently with salinity in such a way that mixing was conservative. The characteristics of the ice varied from the freshwater source to the open water, with increasing salinity and brine volumes (porosity) occurring in the more open-sea stations. Coinciding with the changes in ice properties there was an increase in sea-ice algal growth in the more marine stations along the transect. Biological activity in the ice was largely confined to bottom ice assemblages. In contrast to the conditions in the underlying water, no relationship between salinity, inorganic nutrients and organic matter was observed in the ice. In particular ammonium, phosphate, DOC and DON were present in excess of those levels predicted from the dilution curves, indicating the presence of considerable DOM production by ice assemblages, inorganic nutrient uptake and remineralization within the ice.

  2. The Relationship Between Dissolved Organic Matter Composition and Organic Matter Optical Properties in Freshwaters

    NASA Astrophysics Data System (ADS)

    Aiken, G.; Spencer, R. G.; Butler, K.

    2010-12-01

    Dissolved organic matter (DOM) chemistry and flux are potentially useful, albeit, underutilized, indicators of watershed characteristics, climate influences on watershed hydrology and soils, and changes associated with resource management. Source materials, watershed geochemistry, oxidative processes and hydrology exert strong influences on the nature and reactivity of DOM in aquatic systems. The molecules that comprise DOM, in turn, control a number of environmental processes important for ecosystem function including light penetration and photochemistry, microbial activity, mineral dissolution/precipitation, and the transport and reactivity of hydrophobic compounds and metals (e.g. Hg). In particular, aromatic molecules derived from higher plants exert strong controls on aquatic photochemistry, and on the transport and biogeochemistry of metals. Assessment of DOM composition and transport, therefore, can provide a basis for understanding watershed processes and biogeochemistry of rivers and streams. Here we present results of multi-year studies designed to assess the seasonal and spatial variability of DOM quantity and quality for 57 North American Rivers. DOM concentrations and composition, based on DOM fractionation on XAD resins, ultraviolet (UV)/visible absorption and fluorescence spectroscopic analyses, and specific compound analyses, varied greatly both between sites and seasonally within a given site. DOM in these rivers exhibited a wide range of concentration (<80 to >4000 µM C* L-1) and specific ultra-violet absorbance at 254 nm (SUVA254) (0.6 to 5 L *mg C-1 *m-1), an optical measurement that is an indicator of aromatic carbon content. In almost all systems, UV absorbance measured at specific wavelengths (e.g. 254 nm) correlated strongly with DOM and hydrophobic organic acid (HPOA) content (aquatic humic substances). The relationships between dissolved organic carbon (DOC) concentration and absorbance for the range of systems were quite variable due to

  3. Calculation of the enthalpy of formation of coal organic matter

    SciTech Connect

    A.M. Gyul'maliev; M.Ya. Shpirt

    2008-10-15

    The enthalpy of formation for the organic matter of coals in the coal rank series was calculated from the heat of the complete combustion reaction. Three variants were considered in which the experimental heating values and the values found from the correlation equation or calculated using the Mendeleev formula were taken as the heat of the complete combustion of coals.

  4. Photoproduction of Carbon Monoxide from Natural Organic Matter

    EPA Science Inventory

    Pioneering studies by Valentine provided early kinetic results that used carbon monoxide (CO) production to evaluate the photodecomposition of aquatic natural organic matter (NOM) . (ES&T 1993 27 409-412). Comparatively few kinetic studies have been conducted of the photodegradat...

  5. Lyophilization and Reconstitution of Reverse Osmosis Concentrated Natural Organic Matter

    EPA Science Inventory

    Disinfection by-product (DBP) research can be complicated by difficulties in shipping large water quantities and changing natural organic matter (NOM) characteristics over time. To overcome these issues, it is advantageous to have a reliable method for concentrating and preservin...

  6. Quenching and Sensitizing Fullerene Photoreactions by Natural Organic Matter

    EPA Science Inventory

    Effects of natural organic matter (NOM) on the photoreaction kinetics of fullerenes (i.e., C60 and fullerenol) were investigated using simulated sunlight and monochromatic radiation (365 nm). NOM from several sources quenched (slowed) the photoreaction of C60 aggregates in water ...

  7. Organic matter in a coal ball: Peat or coal?

    USGS Publications Warehouse

    Hatcher, P.G.; Lyons, P.C.; Thompson, C.L.; Brown, F.W.; Maciel, G.E.

    1982-01-01

    Chemical analyses of morphologically preserved organic matter in a Carboniferous coal ball reveal that the material is coalified to a rank approximately equal to that of the surrounding coal. Hence, the plant tissues in the coal ball were chemically altered by coalification processes and were not preserved as peat. Copyright ?? 1982 AAAS.

  8. Fractionation of halogenated organic matter present in rain and snow

    PubMed

    Laniewski; Boren; Grimvall

    1999-01-01

    Organic matter in samples of rain and snow from Sweden, Poland, Germany and the Republic of Ireland was fractionated by employing a series of filtration, purging, evaporation and extraction steps. Determinations of the group parameter AOX (adsorbable organic halogens) in aqueous phases and EOX (extractable organic halogens) in organic phases showed that halogenated organic matter present in bulk precipitation is composed of several different groups of compounds. The largest amounts of organically bound halogens were found in fractions of relatively polar and non-volatile to semivolatile compounds. In particular, a significant part of the AOX could be attributed to alkaline-labile organic bases. Gas chromatographic analysis of different organic extracts in the chlorine channel of an atomic emission detector (AED) resulted in chromatograms with few distinct peaks, and analysis in the bromine channel did not produce any distinct peaks. Chlorinated acetic acids were the most abundant halogenated organic acids, and chlorinated alkyl phosphates were normally responsible for the largest peaks in the chlorine chromatogram of neutral, hexane-extractable compounds. When analysing volatiles, 1,4-dichlorobenzene and a thus far unidentified chloroorganic compound often caused the largest response in the chlorine channel of the AED system.

  9. CHROMOPHORIC DISSOLVED ORGANIC MATTER (CDOM) DERIVED FROM DECOMPOSITION OF VARIOUS VASCULAR PLANT AND ALGAL SOURCES

    EPA Science Inventory

    Chromophoric dissolved organic (CDOM) in aquatic environments is derived from the microbial decomposition of terrestrial and microbial organic matter. Here we present results of studies of the spectral properties and photoreactivity of the CDOM derived from several organic matter...

  10. Organic and Inorganic Matter in Louisiana Coastal Waters: Vermilion, Atchafalaya, Terrebonne, Barataria, and Mississippi Regions.

    EPA Science Inventory

    Chromophoric dissolved organic matter (CDOM) spectral absorption, dissolved organic carbon (DOC) concentration, and the particulate fraction of inorganic (PIM) and organic matter (POM) were measured in Louisiana coastal waters at Vermilion, Atchafalaya, Terrebonne, Barataria, and...

  11. Molecular characterization of soil organic matter: a historic overview

    NASA Astrophysics Data System (ADS)

    Kögel-Knabner, Ingrid; Rumpel, Cornelia

    2014-05-01

    The characterization of individual molecular components of soil organic matter started in the early 19th century, but proceeded slowly. The major focus at this time was on the isolation and differentiation of different humic and fulvic acid fractions, which were considered to have a defined chemical composition and structure. The isolation and structural anlysis of specific individual soil organic matter components became more popular in the early 20th century. In 1936 40 different individual compounds had been isolated and a specific chemical strucutre had been attributed. These structural attributions were confirmed later for some, but not all of these individual compounds. In the 1950 much more individual compounds could be isolated and characterized, using complicated and time consuming chromatography. It became obvious that soil also contains a number of compounds of microbial origin, such as e.g., amino sugars and lipids. With the improvement of chrmoatographic separation techniques and the use of gas chromatography in combination with thin layerchromatography in the 1960 hundreds of individual compounds have been isolated and identified, most of them after chemical degradation of humic or fulvic acids. The chemical degradative techniques were amended with analytical pyrolysis in the 1970s. More and more, bulk soil organic matter was analyzed with these techniques and the advent of solid-stae 13C NMR spectroscopy around the 1980s allowed for the characterization of the composition of bulk soil organic matter. The gas chromatographic separation of organic matter can nowadays be combined with specific detectors, such that specific attributes ofindividual molecules can be analyzed, e.g. the radiocarbon content or the stable isotope composition.

  12. Organic matter variations in transgressive and regressive shales

    USGS Publications Warehouse

    Pasley, M.A.; Gregory, W.A.; Hart, G.F.

    1991-01-01

    Organic matter in the Upper Cretaceous Mancos Shale adjacent to the Tocito Sandstone in the San Juan Basin of New Mexico was characterized using organic petrology and organic geochemistry. Differences in the organic matter found in these regressive and transgressive offshore marine sediments have been documented and assessed within a sequence stratigraphic framework. The regressive Lower Mancos Shale below the Tocito Sandstone contains abundant well preserved phytoclasts and correspondingly low hydrogen indices. Total organic carbon values for the regressive shale are low. Sediments from the transgressive systems tract (Tocito Sandstone and overlying Upper Mancos Shale) contain less terrestrially derived organic matter, more amorphous non-structured protistoclasts, higher hydrogen indices and more total organic carbon. Advanced stages of degradation are characteristic of the phytoclasts found in the transgressive shale. Amorphous material in the transgressive shale fluoresces strongly while that found in the regressive shale is typically non-fluorescent. Data from pyrolysis-gas chromatography confirm these observations. These differences are apparently related to the contrasting depositional styles that were active on the shelf during regression and subsequent transgression. It is suggested that data from organic petrology and organic geochemistry provide greater resolution in sedimentologic and stratigraphic interpretations, particularly when working with basinward, fine-grained sediments. Petroleum source potential for the regressive Lower Mancos Shale below the Tocito Sandstone is poor. Based on abundant fluorescent amorphous material, high hydrogen indices, and high total organic carbon, the transgressive Upper Mancos Shale above the Tocito Sandstone possesses excellent source potential. This suggests that appreciable source potential can be found in offshore, fine-grained sediments of the transgressive systems tract below the condensed section and associated

  13. Characterisation of the organic matter pool in manures.

    PubMed

    Moral, R; Moreno-Caselles, J; Perez-Murcia, M D; Perez-Espinosa, A; Rufete, B; Paredes, C

    2005-01-01

    In this research, different types of animal manure were evaluated with respect to organic matter (OM), total organic carbon (C(ot)), total N (N(t)), C(ot)/N(t) ratio, water-soluble organic carbon (C(w)), organic N (N(org)), carbohydrates, C(w)/N(org) ratio, humic acid-like carbon (C(ha)), fulvic acid-like carbon (C(fa)), humification index ((C(ha)/C(ot))x100) (HI) and the C(ha)/C(fa) and NH(4)(+)-N/NO(3)(-)-N ratios. In comparison with the limits set by the Spanish legislation for organic fertilisers, most of the manures had high OM contents, moderate N(org) concentrations (except in the case of the chicken and pig manures where this parameter was high) and C(ot)/N(t) ratios above the value stated in the legislation. The study of the different fractions of organic matter showed that the horse, pig and rabbit manures had the greatest content of C(ot). However, the fraction of easily-biodegradable organic compounds (C(w)) was significantly higher in the horse, goat and chicken manures. The study also showed that, in most cases, the percentage of fulvic acid-like C was greater than that of the humic acid-like C, indicating that the organic matter of these wastes is not completely humified. Values of HI ((C(ha)/C(ot))x100) and C(ha)/C(fa) ratio in the studied manures were not significantly different. Regarding the parameters related to the organic matter stability such as C(w), carbohydrates and the C(ot)/N(t), C(w)/N(org) and NH(4)(+)-N/NO(3)(-)-N ratios, it has been determined that the organic matter of these materials was not completely stabilised. The heterogeneity in OM composition of the studied manures did not allow the formulation of simple equations for evaluation of the composition of these wastes from easily-determined parameters.

  14. Cumulative effects of biochar, mineral and organic fertilizers on soil organic matter

    NASA Astrophysics Data System (ADS)

    Plaza, César; López-de-Sá, Esther G.; Gascó, Gabriel; Méndez, Ana; Zaccone, Claudio

    2016-04-01

    We investigated the effect of three consecutive annual applications of biochar at rates of 0 and 20 t ha-1, in a factorial combination with a mineral fertilizer (NPK and nitrosulfate) and two types of organic amendment (municipal solid waste compost and sewage sludge), on soil organic matter in a field experiment under Mediterranean conditions. Biochar increased significantly soil organic C content and C/N ratio. In biochar-amended soils, soil organic C increased significantly with the addition of municipal solid waste compost and sewage sludge. To capture organic matter protection mechanisms related to aggregation and mineral interaction, the soil samples will be fractionated into free (unprotected), intra-macroaggregate, intra-microaggregate, and mineral-associated organic matter pools, and the isolated fractions will be subjected to further chemical and spectroscopic analysis.

  15. Pre-biotic organic matter from comets and asteroids

    NASA Technical Reports Server (NTRS)

    Anders, Edward

    1989-01-01

    Only meteoritic fragments small enough to be gently decelerated by the atmosphere (10 to the -12th g to 10 to the -6th g) can deliver organic matter intact. The amount of such 'soft-landed' organic carbon can be estimated from data for the infall rate of meteoritic matter. At present rates, only about 0.0006 g/sq cm intact organic carbon would accumulate in 100 million years, but at the higher rates of about four billion yr ago, about 20 g/sq cm may have accumulated in the few hundred million years between the last cataclysmic impact and the beginning of life. It may have included some biologically important compounds that did not form by abiotic synthesis on earth.

  16. Bacterial biomarkers thermally released from dissolved organic matter

    USGS Publications Warehouse

    Greenwood, P.F.; Leenheer, J.A.; McIntyre, C.; Berwick, L.; Franzmann, P.D.

    2006-01-01

    Hopane biomarker products were detected using microscale sealed vessel (MSSV) pyrolysis gas chromatography-mass spectrometry (GC-MS) analysis of dissolved organic matter from natural aquatic systems colonised by bacterial populations. MSSV pyrolysis can reduce the polyhydroxylated alkyl side chain of bacteriohopanepolyols, yielding saturated hopane products which are more amenable to GC-MS detection than their functionalised precursors. This example demonstrates how the thermal conditions of MSSV pyrolysis can reduce the biologically-inherited structural functionality of naturally occurring organic matter such that additional structural fragments can be detected using GC methods. This approach complements traditional analytical pyrolysis methods by providing additional speciation information useful for establishing the structures and source inputs of recent or extant organic material. ?? 2006.

  17. Nature of particulate organic matter in the River Indus, Pakistan

    NASA Astrophysics Data System (ADS)

    Ittekkot, Venugopalan; Arain, Rafee

    1986-08-01

    Suspended sediments from the Indus River collected during 1981 through 1983 were analyzed for POC and its constituent fractions including amino acids, amino sugars and sugars. Percentage of POC decreased with increasing suspended matter concentrations, which suggested dilution of organic matter by mineral matter. The concentrations of amino acids, amino sugars and sugars varied, respectively, between 180 and 2000 μg/l, 5 and 125 μg/l, and 60 and 1100 μg/l. Their contributions to POC varied between 2 and 60% for amino acids and amino sugars, and between 2 and 15% for sugars. They were high during low sediment discharge (February to June), and low during high sediment discharge (August and September). Suspended sediments associated with high sediment discharge periods were characterized by low ratios of: (i) aspartic acid:β-alanine (ii) glutamic acid:γ-aminobutyric acid (iii) amino acids:amino sugars (iv) hexoses:pentoses. These and the relative distribution pattern of the monosaccharides such as galactose, arabinose, mannose and xylose indicated that, not only dilution, but also differences in the sources and processes affect the POC transport in the Indus River. These result in transport of biodegraded organic matter during high sediment discharge periods: this appears to be common to other major rivers of the region, with depositional centers in deep sea areas. These rivers, with their high sediment loads, could contribute up to 8 to 11% of the global annual organic carbon burial in marine sediments.

  18. Loss of organic matter from riverine particles in deltas

    SciTech Connect

    Keil, R.G.; Quay, P.D.; Richey, J.E.

    1997-04-01

    In order to examine the transport and burial of terrigenous organic matter along the coastal zones of large river systems, we assessed organic matter dynamics in coupled river/delta systems using mineral surface area as a conservative tracer for discharged riverine particulate organic matter (POM). Most POM in the rivers studied (n = 6) is tightly associated with suspended mineral materiaL e.g., it is sorbed to mineral surfaces. Average organic loadings in the Amazon River (0.67 - 0.14 Mg C m{sup -2}), the river for which we have the largest dataset, are approximately twice that of sedimentary minerals from the Amazon Delta (-0.35 mg C m{sup -2}). Stable carbon isotope analysis indicate that approximately two-thirds of the total carbon on the deltaic particles is terrestrial. The combined surface-normalized, isotope-distinguished estimate is that >70% of the Amazon fluvial POM is not buried in the delta consistent with other independent evidence. Losses of terrestrial POM have also been quantified for the river/delta systems of Columbia in the USA, Fly in New Guinea. and Huange-He in China. If the losses of riverine POM observed in these river/delta systems are representative of rivers worldwide, then the surface-constrained analyses point toward a global loss of fluvial POM in delta regions of {approximately}0.1 x 10{sup 15} g C y{sup -1}. 28 refs., 2 figs., 1 tab.

  19. Surficial bioturbation and rapid benthic remineralization in the Cape Hatteras shelf/slope region. Final report

    SciTech Connect

    Robert C. Aller; Josephine Y. Aller; C. Lee; J. Kirk Cochran

    1999-03-17

    This is a final report for the DOE of grant DE-FG02-92ER61464 ''Surficial bioturbation and rapid benthic remineralization in the Cape Hatteras shelf slope region''. Over the past 6 years we have participated in a multidisciplinary field study called the Ocean margins Program (OMP) to examine the importance of continental margins in the global carbon cycle. Specifically, we have focused on the southern portion of the Mid-Atlantic Bight between Cape Hatteras and Chesapeake Bay where a large flux of freshwater and organic carbon enters the North Atlantic Ocean. Additionally, during the first stage of this project, we developed the use of CM-a distributions in sediments as a quantitative indicator of benthic C flux and remineralization rates. The primary objective of our research group has been to understand mechanisms and quantify biogeochemical processes in the seabed that affect cycling, flux, and storage of carbon on the ocean margin of the Mid-Atlantic Bight.

  20. Role of organic matter in framboidal pyrite oxidation.

    PubMed

    Rigby, P A; Dobos, S K; Cook, F J; Goonetilleke, A

    2006-08-31

    An experimental system has been set up to investigate the reaction kinetics of framboidal pyrite oxidation in real, reactive acid sulfate soil assemblages. This study was undertaken to determine the degree to which pyrite oxidation rates are reduced by bacteriological reactions and organic matter, which both modify the net reaction mechanisms and compete for available oxygen. The results from these experimental runs not only confirm the role of organic matter in mitigating pyrite oxidation but indicate that at least initially, the acidity produced is consumed or otherwise ameliorated by parallel reactions. Tracking pH or [H+] in both a reactor and in soil does not accurately reflect reaction progress and may not correctly indicate the true level of risk. In comparison, the tracking of pyrite oxidation with the concentration of sulfate in solution is not affected by side reactions or precipitation and is therefore a better indicator for the rate of pyrite destruction. PMID:16839593

  1. Carbon isotopic studies of organic matter in precambrian rocks.

    PubMed

    Oehler, D Z; Schopf, J W; Kvenvolden, K A

    1972-03-17

    Reduced carbon in early Precambrian cherts of the Fig Tree and upper and middle Onverwacht groups of South Africa is isotopically similar (the average value of delta(13)C(PDB) is -28.7 per mil) to photosynthetically produced organic matter of younger geological age. Reduced carbon in lower Onverwacht cherts (Theespruit formation) is anomalously heavy (the average value of delta(13)C(PDB) is -16.5 per mil). This discontinuity may reflect a major event in biological evolution.

  2. Photochemical Degradation of Persistent Organic Pollutants: A Study of Ice Photochemistry Mediated by Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Bobby, R.; Pagano, L.; Grannas, A. M.

    2012-12-01

    It is well established that ice is a reactive medium in the environment and that active photochemistry occurs in frozen systems. Snow and ice contain a number of absorbing species including nitrate, peroxide and organic matter. Upon irradiation, they can generate a variety of reactive intermediates such as hydroxyl radical and singlet oxygen. It has been shown that dissolved organic matter is a ubiquitous component of snow and ice and plays an important role in overall light absorption properties of the sample. Additionally, the reactive intermediates produced can further react with contaminants present and alter their fate in the environment. Unfortunately, the role of dissolved organic matter in ice photochemistry has received little attention. Here we present results from laboratory-based studies aimed at elucidating the role of dissolved organic matter photochemistry on contaminant degradation in ice. Aqueous samples of our target pollutant, aldrin (20 μg/L), in liquid and frozen phases, were irradiated under Q-Panel 340 lamps to simulate the UV radiation profile of natural sunlight. Results indicated that frozen samples degraded more quickly than liquid samples and that the addition of dissolved organic matter increases the aldrin degradation rate significantly. Both terrestrial (Suwannee River, U.S.) and microbial sources (Pony Lake, Antarctica) of DOM were able to sensitize aldrin loss in ice. Scavengers of singlet oxygen, such as furfuryl alcohol and β-carotene, were also added to DOM solutions. Based on the type of organic matter present, the scavengers had different effects on the photochemical degradation of aldrin. Our results indicate that natural organic matter present in ice is an important component of ice photochemical processes.

  3. Thermodynamics of uranium/organic matter interactions in hydrothermal systems

    NASA Astrophysics Data System (ADS)

    Richard, L.

    2003-04-01

    Organic matter is commonly encountered in and around uranium and other ore deposits, which raises the question of the role played by organic compounds in the formation of these deposits (Landais and Gize, 1997). One of the best known examples is the observation of uraninite crystals entrapped within solid bitumens in the Oklo natural reactors. This observation led Nagy et al. (1991) to propose that a liquid, aliphatic-rich bitumen may have acted as a reductant to precipitate uraninite from hydrothermal solutions according to the reaction VIUO2+2(aq)+H_2O(l)=IVUO2(c)+2H^+(aq)+0.5 O2(g). The liquid bitumen was simultaneously oxidized into a polyaromatic solid, which may be represented by the reaction 2.7n- C20H42(l) + 17.85 O2(g) = C54H42(c)+35.7 H_2O(l) where n-C20H42(l) denotes n-eicosane present in the liquid bitumen, and C54H42(c) represents an idealized polyaromatic solid. Recent advances in theoretical organic geochemistry made it possible to generate a comprehensive thermodynamic database for hundreds of crystalline, liquid, gas and aqueous organic compounds of geochemical interest (Shock and Helgeson, 1990; Shock, 1995; Amend and Helgeson, 1997; Helgeson et al., 1998; Richard and Helgeson, 1998; Richard, 2001), which can be used together with thermodynamic properties for uranium-bearing minerals and aqueous species (Grenthe et al., 1992; Shock et al., 1997) to characterize uranium/organic matter interactions in hydrothermal systems as a function of temperature, pressure, oxygen fugacity, and organic matter composition. Activity-fO_2 diagrams have been constructed at a series of temperatures and pressures to investigate possible genetic relationships between uranium mineralizations and solid bitumens of various compositions.

  4. Xiphinema americanum as Affected by Soil Organic Matter and Porosity.

    PubMed

    Ponchillia, P E

    1972-07-01

    The effects of four soil types, soil porosity, particle size, and organic matter were tested on survival and migration of Xiphinema americanum. Survival and migration were significantly greater in silt loam than in clay loam and silty clay soils. Nematode numbers were significantly greater in softs planted with soybeans than in fallow softs. Nematode survival was greatest at the higher of two pore space levels in four softs. Migration of X. americanum through soft particle size fractions of 75-150, 150-250, 250-500, 500-700, and 700-1,000 mu was significantly greater in the middle three fractions, with the least occurring in the smallest fraction. Additions of muck to silt loam and loamy sand soils resulted in reductions in survival and migration of the nematode. The fulvic acid fraction of muck, extracted with sodium hydroxide, had a deleterious effect on nematode activity. I conclude that soils with small amounts of air-filled pore space, extremes in pore size, or high organic matter content are deleterious to the migration and survival of X. americanum, and that a naturally occurring toxin affecting this species may be present in native soft organic matter.

  5. Temperature sensitivity of organic-matter decay in tidal marshes

    USGS Publications Warehouse

    Kirwan, Matthew L.; Guntenspergen, Glenn R.; Langley, J.A.

    2014-01-01

    Approximately half of marine carbon sequestration takes place in coastal wetlands, including tidal marshes, where organic matter contributes to soil elevation and ecosystem persistence in the face of sea-level rise. The long-term viability of marshes and their carbon pools depends, in part, on how the balance between productivity and decay responds to climate change. Here, we report the sensitivity of labile soil organic-matter decay in tidal marshes to seasonal and latitudinal variations in temperature measured over a 3-year period. We find a moderate increase in decay rate at warmer temperatures (3-6% per °C, Q10 = 1.3-1.5). Despite the profound differences between microbial metabolism in wetlands and uplands, our results indicate a strong conservation of temperature sensitivity. Moreover, simple comparisons with organic-matter production suggest that elevated atmospheric CO2 and warmer temperatures will accelerate carbon accumulation in marsh soils, and potentially enhance their ability to survive sea-level rise.

  6. Matrix protected organic matter in a river dominated margin: A possible mechanism to sequester terrestrial organic matter?

    NASA Astrophysics Data System (ADS)

    Mead, Ralph N.; Goñi, Miguel A.

    2008-06-01

    The provenance of organic matter in surface sediments from the northern Gulf of Mexico was investigated by analyzing the compositions of lipid biomarkers ( n-alkanes, fatty acids, sterols) liberated after a series of chemical treatments designed to remove different organo-mineral matrix associations (i.e. freely extractable, base-hydrolyzable, unhydrolyzable). Bulk analyses of the organic matter (carbon content, carbon:nitrogen ratios, stable and radiocarbon isotopic analyses) were also performed on the intact sediments and their non-hydrolyzable, demineralized residue. We found recognizable lipids from distinct sources, including terrestrial vascular plants, bacteria and marine algae and zooplankton, within each of the isolated fractions. Based on the lipid signatures and bulk compositions, the organic matter within the unhydrolyzable fractions appeared to be the most diagenetically altered, was the oldest in age, and had the highest abundance of terrigenous lipids. In contrast, the base-hydrolyzable fraction was the most diagentically unaltered, had the youngest ages and was most enriched in N and marine lipids. Our results indicate that fresh, autochthonous organic matter is the most important contributor to base-hydrolyzable lipids, whereas highly altered allochthonous sources appear to be predominant source of unhydrolyzable lipids in the surface sediments from the Atchafalaya River shelf. Overall, the lipid biomarker signatures of intact sediments were biased towards the autochthonous source because many of the organic compounds indicative of degraded, terrigenous sources were protected from extraction and saponification by organo-mineral matrices. It is only after these protective matrices were removed by treatment with HCl and HF that these compounds became evident.

  7. Carbon isotopic studies of organic matter in Precambrian rocks.

    NASA Technical Reports Server (NTRS)

    Oehler, D. Z.; Schopf, J. W.; Kvenvolden, K. A.

    1972-01-01

    A survey has been undertaken of the carbon composition of the total organic fraction of a suite of Precambrian sediments to detect isotopic trends possibly correlative with early evolutionary events. Early Precambrian cherts of the Fig Tree and upper and middle Onverwacht groups of South Africa were examined for this purpose. Reduced carbon in these cherts was found to be isotopically similar to photosynthetically produced organic matter of younger geological age. Reduced carbon in lower Onverwacht cherts was found to be anomalously heavy; it is suggested that this discontinuity may reflect a major event in biological evolution.

  8. Comments on D/H ratios in chondritic organic matter

    NASA Astrophysics Data System (ADS)

    Smith, J. W.; Rigby, D.

    1981-06-01

    D/H ratios in chondritic organic matter are investigated. Demineralized organic residues obtained from previous experiments were dried in a quartz reaction vessel under vacuum for 60 minutes at 250-300 C and then combusted in oxygen for 20 minutes at 850 C. The apparatus is described and the results of the experiments such as D/H ratios in water and measurements on total carbon dioxide are given. Atomic H/C ratios calculated directly from the quantities of carbon dioxide and water recovered, are reported according to Standard Mean Ocean Water and Pee Dee Belemnite, using the customary notation.

  9. Organic matter in meteorites and comets - Possible origins

    NASA Technical Reports Server (NTRS)

    Anders, Edward

    1991-01-01

    At least six extraterrestrial environments may have contributed organic compounds to meteorites and comets: solar nebula, giant-planet subnebulae, asteroid interiors containing liquid water, carbon star atmospheres, and diffuse or dark interstellar clouds. The record in meteorites is partly obscured by pervasive reheating that transformed much of the organic matter to kerogen; nonetheless, it seems that all six formation sites contributed. For comets, the large abundance of HCHO, HCN, and unsaturated hydrocarbons suggests an interstellar component of 50 percent or more, but the contributions of various interstellar processes, and of a solar-nebula component, are hard to quantify. A research program is outlined that may help reduce these uncertainties.

  10. Flood Pulse Influence on Export of Terrestrial Organic Matter

    NASA Astrophysics Data System (ADS)

    Dalzell, B. J.; Harbor, J. M.; Filley, T. R.

    2004-12-01

    While much attention has been placed on characterizing Terrestrial Organic Matter (TOM) export from large rivers, recent research has shown that in-stream processing of TOM in smaller streams and rivers over shorter time scales can be an important upland component of regional carbon budgets not detected at the outlets of large rivers. With predictions of climate change accompanied by more intense rainfall patterns in some areas, it is important to understand the linkage between flood events and watershed export of TOM. To this end, we have collected water samples from Big Pine Creek watershed, an 850km2 watershed located in west central Indiana. Organic carbon in dissolved, colloidal, and particulate size fractions has been described with molecular and stable carbon isotope techniques to track source, quantity, and compositional changes of TOM over changing flow conditions. Results from these samples show that flood conditions export dramatically more TOM; not only from increases in discharge, but also from increases in concentration of terrestrial organic carbon to all size fractions. While molecular biomarkers show increases in terrestrial organic matter, bulk stable carbon isotope values show that the sources of TOM do not remain constant. Rather, relative contributions from C4 plants (corn in this study area) increase during flood conditions by up to 40 percent. Finally, increases in rainfall intensity are likely to disproportionately increase organic carbon export from terrestrial systems, especially from smaller watersheds where short duration and high intensity flow events dominate annual discharge.

  11. Why dissolved organic matter (DOM) enhances photodegradation of methylmercury

    SciTech Connect

    Qian, Yun; Yin, Xiangping Lisa; Brooks, Scott C; Liang, Liyuan; Gu, Baohua

    2014-01-01

    Methylmercury (MeHg) is known to degrade photochemically, but it remains unclear what roles naturally dissolved organic matter (DOM) and complexing organic ligands play in MeHg photodegradation. Here we investigate the rates and mechanisms of MeHg photodegradation using DOM samples with varying oxidation states and origins as well as organic ligands with known molecular structures. All DOM and organic ligands increased MeHg photodegradation under solar irradiation, but the first-order rate constants varied depending on the oxidation state of DOM and the type and concentration of the ligands. Compounds containing both thiols and aromatics (e.g., thiosalicylate and reduced DOM) increased MeHg degradation rates far greater than those containing only aromatic or thiol functional groups (e.g., salicylate or glutathione). Our results suggest that, among other factors, the synergistic effects of thiolate and aromatic moieties in DOM greatly enhance MeHg photodegradation.

  12. SOIL NITROGEN TRANSFORMATIONS AND ROLE OF LIGHT FRACTION ORGANIC MATTER IN FOREST SOILS

    EPA Science Inventory

    Depletion of soil organic matter through cultivation may alter substrate availability for microbes, altering the dynamic balance between nitrogen (N) immobilization and mineralization. Soil light fraction (LF) organic matter is an active pool that decreases upon cultivation, and...

  13. Soil Quality of Restinga Forest: Organic Matter and Aluminum Saturation

    NASA Astrophysics Data System (ADS)

    Rodrigues Almeida Filho, Jasse; Casagrande, José Carlos; Martins Bonilha, Rodolfo; Soares, Marcio Roberto; Silva, Luiz Gabriel; Colato, Alexandre

    2013-04-01

    The restinga vegetation (sand coastal plain vegetation) consists of a mosaic of plant communities, which are defined by the characteristics of the substrates, resulting from the type and age of the depositional processes. This mosaic complex of vegetation types comprises restinga forest in advanced (high restinga) and medium regeneration stages (low restinga), each with particular differentiating vegetation characteristics. Of all ecosystems of the Atlantic Forest, restinga is the most fragile and susceptible to anthropic disturbances. The purpose of this study was evaluating the organic matter and aluminum saturation effects on soil quality index (SQI). Two locations were studied: State Park of the Serra do Mar, Picinguaba, in the city of Ubatuba (23°20' e 23°22' S / 44°48' e 44°52' W), and State Park of Cardoso Island in the city of Cananéia (25°03'05" e 25°18'18" S / 47°53'48" e 48° 05'42" W). The soil samples were collect at a depth of 0-10 cm, where concentrate 70% of vegetation root system. Was studied an additive model to evaluate soil quality index. The shallow root system development occurs due to low calcium levels, whose disability limits their development, but also can reflect on delay, restriction or even in the failure of the development vegetation. The organic matter is kept in the soil restinga ecosystem by high acidity, which reduces the decomposition of soil organic matter, which is very poor in nutrients. The base saturation, less than 10, was low due to low amounts of Na, K, Ca and Mg, indicating low nutritional reserve into the soil, due to very high rainfall and sandy texture, resulting in high saturation values for aluminum. Considering the critical threshold to 3% organic matter and for aluminum saturation to 40%, the IQS ranged from 0.95 to 0.1 as increased aluminum saturation and decreased the soil organic matter, indicating the main limitation to the growth of plants in this type of soil, when deforested.

  14. Dissolved organic matter in the ocean: recalcitrant or simply too diverse for bio-degradation?

    NASA Astrophysics Data System (ADS)

    Kattner, Gerhard; Koch, Boris P.

    2010-05-01

    The amount of carbon in the dissolved organic matter (DOM) pool in the ocean is estimated to be 700 Pg C, whereas the particulate marine organic carbon accounts only for about 30 Pg C. Dissolved organic carbon (DOC) is almost as much as the amount of carbon in atmospheric CO2 (~800 Pg) or terrestrial biomass (~610 Pg). The majority of DOC in the ocean has an average age of 4000 to 6000 years. Thus, DOM must be extremely resistant against biotic and abiotic degradation and remineralization and/or unusable for microorganisms. However, the mechanisms of generation of recalcitrant DOM are still unclear. DOM is produced by primary producers, is actively released or originates from a huge variety of biological and chemical processes. This originally labile DOM is transformed to semi-labile and finally to recalcitrant DOM. These transformations proceed on time scales of days to month and probably over very long periods of time. Without knowledge on molecular structures it is impossible to discern why DOM is so resistant against biotic and abiotic decomposition. Tools for the chemical characterization of DOM in the ocean are limited, and thus, the molecular structure of marine DOM remains largely unknown. The present molecular level determination of DOM in seawater is essentially restricted to carbohydrates, amino acids, lipids and aminosugars. These compounds represent less than 10% of the open ocean DOC, and because they are usually determined after considerable chemical treatment the chemical structure they are embedded is also unknown. Other data on molecular level characterization are obtained by the combination of analytical techniques with various methods of isolation and fractionation of DOM such as solid phase extraction and ultrafiltration. However, it has to be considered that only a method-dependent fraction can be isolated from the total DOM. In the past few years, Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS) enabled to determine the

  15. Using Riverine Natural Organic Matter to Test the Hypothesis that Soil Organic Matter is Modified by Contact with Sodium Hydroxide

    NASA Astrophysics Data System (ADS)

    Perdue, E. Michael; Driver, Shamus; Hertkorn, Norbert; Harir, Mourad; Schmitt-Kopplin, Philippe

    2016-04-01

    It has been postulated by some scientists that soil humic acids and fulvic acids are an artifact of alkaline extractions of soil. Riverine natural organic matter (NOM) is obtained in part by dissolution and transport of organic matter from soils by meteoric waters at acidic to circumneutral pH. The NOM may be fractionated into humic acid (HA), fulvic acid (FA), and hydrophilic NOM by adsorption of HA and FA onto XAD-8 resin at pH < 2, followed by their desorption with NaOH at pH 13. Alternatively, riverine NOM may be concentrated using reverse osmosis (RO) and desalted by cation exchange. Several properties of Suwannee River NOM prior to its isolation, after concentration by RO, and after the XAD-8 process are compared to detect modifications that might have resulted from exposure of the sample to low and high pH.

  16. The composition and degradability of upland dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Moody, Catherine; Worrall, Fred; Clay, Gareth

    2016-04-01

    In order to assess controls on the degradability of DOM in stream water, samples of dissolved organic matter (DOM) and particulate organic matter (POM) were collected every month for a period of 24 months from an upland, peat-covered catchment in northern England. Each month the degradability of the DOM was assessed by exposing river water to light for up to 24 hours, and the change in the dissolved organic carbon (DOC) concentration in the water was measured. To provide context for the analysis of DOM and its degradability, samples of peat, vegetation, and litter were also taken from the same catchment and analysed. The organic matter samples were analysed by several methods including: elemental analysis (CHN and O), bomb calorimetry, thermogravimetric analysis, pyrolysis GC/MS, ICP-OES, stable isotope analysis (13C and 15N) and 13C solid state nuclear magnetic resonance (NMR). The water samples were analysed for pH, conductivity, absorbance at 400nm, anions, cations, particulate organic carbon (POC) and DOC concentrations. River flow conditions and meteorology were also recorded at the site and included in the analysis of the composition and degradability of DOM. The results of multiple regression models showed that the rates of DOC degradation were affected by the N-alkyl, O-alkyl, aldehyde and aromatic relative intensities, gross heat, OR and C:N. Of these, the N-alkyl relative intensity had the greatest influence, and this in turn was found to be dependent on the rainfall and soil temperature in the week before sampling.

  17. Isotopic constraints on the origin of meteoritic organic matter

    NASA Technical Reports Server (NTRS)

    Kerridge, J. F.

    1991-01-01

    Salient features of the isotopic distribution of H, C and N in the organic material found in carbonaceous meteorites are noted. Most organic fractions are strongly enriched in D with respect to the D/H ratio characteristic of H2 in the protosolar system; substantial variations in C-13/C-12 ratio are found among different molecular species, with oxidised species tending to be C-13 enriched relative to reduced species; some homologous series reveal systematic decrease in C-13/C-12 with increasing C number; considerable variation in N-15/N-14 ratio is observed within organic matter, though no systematic pattern to its distribution has yet emerged; no interelement correlations have been observed between isotope enrichments for the different biogenic elements. The isotopic complexity echoes the molecular diversity observed in meteoritic organic matter and suggests that the organic matter was formed by multiple processes and/or from multiple sources. However, existence of a few systematic patterns points towards survival of isotopic signatures characteristic of one or more specific processes. The widespread D enrichment implies either survival of many species of interstellar molecule or synthesis from a reservoir containing a significant interstellar component. Several of the questions raised above can be addressed by more detailed determination of the distribution of the H, C and N isotopes among different well-characterized molecular fractions. Thus, the present study is aimed at discovering whether the different amino acids have comparable D enrichments, which would imply local synthesis from a D-enriched reservoir, or very viable D enrichments, which would imply survival of some interstellar amino acids. The same approach is also being applied to polycyclic aromatic hydrocarbons. Because the analytical technique employed (secondary ion mass spectrometry) can acquire data for all three isotopic systems from each molecular fraction, any presently obscured interelement

  18. Soil organic matter regulates molybdenum storage and mobility in forests

    USGS Publications Warehouse

    Marks, Jade A; Perakis, Steven; King, Elizabeth K; Pett-Ridge, Julie

    2015-01-01

    The trace element molybdenum (Mo) is essential to a suite of nitrogen (N) cycling processes in ecosystems, but there is limited information on its distribution within soils and relationship to plant and bedrock pools. We examined soil, bedrock, and plant Mo variation across 24 forests spanning wide soil pH gradients on both basaltic and sedimentary lithologies in the Oregon Coast Range. We found that the oxidizable organic fraction of surface mineral soil accounted for an average of 33 %of bulk soil Mo across all sites, followed by 1.4 % associated with reducible Fe, Al, and Mn-oxides, and 1.4 % in exchangeable ion form. Exchangeable Mo was greatest at low pH, and its positive correlation with soil carbon (C) suggests organic matter as the source of readily exchangeable Mo. Molybdenum accumulation integrated over soil profiles to 1 m depth (τMoNb) increased with soil C, indicating that soil organic matter regulates long-term Mo retention and loss from soil. Foliar Mo concentrations displayed no relationship with bulk soil Mo, and were not correlated with organic horizon Mo or soil extractable Mo, suggesting active plant regulation of Mo uptake and/or poor fidelity of extractable pools to bioavailability. We estimate from precipitation sampling that atmospheric deposition supplies, on average, over 10 times more Mo annually than does litterfall to soil. In contrast, bedrock lithology had negligible effects on foliar and soil Mo concentrations and on Mo distribution among soil fractions. We conclude that atmospheric inputs may be a significant source of Mo to forest ecosystems, and that strong Mo retention by soil organic matter limits ecosystem Mo loss via dissolution and leaching pathways.

  19. The role of remineralizing agents in dentistry: a review.

    PubMed

    Rao, Arathi; Malhotra, Neeraj

    2011-01-01

    Minimal intervention is a key phrase in today's dental practice. Minimal intervention dentistry (MID) focuses on the least invasive treatment options possible in order to minimize tissue loss and patient discomfort. Concentrating mainly on prevention and early intervention of caries, MID's first basic principle is the remineralization of early carious lesions, advocating a biological or therapeutic approach rather than the traditional surgical approach for early surface lesions. One of the key elements of a biological approach is the usage and application of remineralizing agents to tooth structure (enamel and dentin lesions). These agents are part of a new era of dentistry aimed at controlling the demineralization/ remineralization cycle, depending upon the microenvironment around the tooth. This article details the various agents that enhance and/or promote remineralization and discusses their clinical implications.

  20. Remineralization of enamel caries can decrease optical reflectivity.

    PubMed

    Jones, R S; Fried, D

    2006-09-01

    The remineralization of enamel caries can lead to distinct optical changes within a lesion. We hypothesized that the restoration of mineral volume would result in a measurable decrease in the depth-resolved reflectivity of polarized light from the lesion. To test this hypothesis, we measured optical changes in artificial caries undergoing remineralization as a function of depth, using Polarization-sensitive Optical Coherence Tomography (PS-OCT). Lesions were imaged non-destructively before and after exposure to a remineralization regimen. After imaging, microradiographs of histological thin sections indicated that the significant reflectivity reduction measured by PS-OCT accurately represented the increase in mineral content within a larger repaired surface zone. Mineral volume changes arising from remineralization can be measured on the basis of the optical reflectivity of the lesion. PMID:16931861

  1. Differences in spectroscopic characteristics between dissolved and particulate organic matters in sediments: Insight into distribution behavior of sediment organic matter.

    PubMed

    He, Wei; Jung, Heonjae; Lee, Jong-Hyun; Hur, Jin

    2016-03-15

    In this study, we examined the distribution behavior of sediment organic matter (SOM) between dissolved and particulate phases and the potential influencing factors by comparing the spectroscopic features of pore water organic matter (PWOM) and alkaline-extractable organic matter (AEOM) of river sediments. The characteristics of SOM were described by several selected spectral indicators and fluorescence excitation emission matrix (EEM)-parallel factor analysis (PARAFAC). The spectral indicators showed that larger sized SOM molecules with a higher aromatic content were more enriched in sediment particles than in pore water. The relative ratios of humification index between dissolved and particulate phases revealed that the SOM constituents with a higher degree of structural condensation were preferentially distributed onto sediment particles. EEM-PARAFAC demonstrated different distribution behaviors of protein-like (tyrosine-like and tryptophan-like) and humic-like substances in sediments. The relative abundance of tyrosine-like component was much higher in PWOM than in AEOM, whereas the other three components tended to be more abundant in AEOM. The predominant presence of tyrosine-like component suggests its potential operation as a discriminant indicator between PWOM and AEOM. Spearman correlations and non-metric multidimensional scaling further revealed that distribution of protein-like components onto sediment particles might be associated with reductive environments, aluminum minerals, and anthropogenic activities of upstream watersheds. This study demonstrated a successful application of using EEM-PARAFAC to examine the distribution behavior of different SOM constitutes between dissolved and solid phases.

  2. Early diagenesis of recently deposited organic matter: a 9-yr time-series study of a flood deposit

    NASA Astrophysics Data System (ADS)

    Tesi, T.; Goñi, M. A.; Langone, L.; Wheatcroft, R. A.; Miserocchi, S.; Bertotti, L.

    2012-04-01

    Because the preservation of organic carbon (OC) in river-dominated margins accounts for a significant fraction of OC burial in the ocean, biochemical studies must find novel ways to explicitly address the non-steadiness of these settings. In this study, we approached this issue by collecting event-beds soon after their emplacement (event-response sampling) and following their evolution with time (time-series analysis). In Fall 2000, the Po River (Italy) experienced a 100-yr return period flood that resulted in a thick deposit in the adjacent prodelta. Cores collected in the central prodelta after the flood event and over the following 9 years (8 sediment cores), allowed characterization of the event-strata in their initial state and documentation of their subsequent evolution. The characterization of sedimentary organic matter (OM) collected soon after the flood deposit emplacement and the description of its subsequent evolution with time provided extraordinary opportunity to investigate the reactivity of OM on a 9-yr time scale. Our analysis included the evaluation of the whole spectrum of CuO reaction products such as lignin phenols, p-hydroxy benzenes, benzoic acids, cutin-derived products, dicarboxylic acids, and fatty acids, as well as bulk organic carbon, nitrogen and carbon stable isotopes. Sedimentological characteristics were investigated using x-radiographs and sediment texture analyses whereas the evolution of sedimentary OM was evaluated via inventories of bulk elements and biomarkers. Remineralization of organic nitrogen and organic carbon occurred at similar rates (% change ~-17%) indicating that the overall elemental composition of sedimentary OM remained stable with time. This steadiness was confirmed by lack of temporal changes of the OC/TN ratio. Despite the steady OC/TN ratio, changes in δ13C revealed preferential loss of isotopically enriched organic material. Biomarker inventories indicated selective degradation during diagenesis, consistent

  3. Organic matter oxidation and aragonite diagenesis in a coral reef

    SciTech Connect

    Tribble, G.W. Univ. of Hawaii, Honolulu )

    1993-05-01

    A combination of field and theoretical work is used to study controls on the saturation state of aragonite inside a coral-reef framework. A closed-system ion-speciation model is used to evaluate the effect of organic-matter oxidation on the saturation state of aragonite. The aragonite saturation state initially drops below 1 but becomes oversaturated during sulfate reduction. The C:N ratio of the organic matter affects the degree of oversaturation with N-poor organic material resulting in a system more corrosive to aragonite. Precipitation of sulfide as FeS strongly affects the aragonite saturation state, and systems with much FeS formation will have a stronger tendency to become oversaturated with respect to aragonite. Both precipitation and dissolution of aragonite are predicted at different stages of the organic reaction pathway if the model system is maintained at aragonite saturation. Field data from a coral-reef framework indicate that the system maintains itself at aragonite saturation, and model-predicted changes in dissolved calcium follow those observed in the interstitial waters of the reef. Aragonite probably acts as a solid-phase buffer in regulating the pH of interstitial waters. Because interstitial water in the reef has a short residence time, the observed equilibration suggests rapid kinetics.

  4. Organic matter and nutrient inputs to the Humber Estuary, England.

    PubMed

    Boyes, Suzanne; Elliott, Michael

    2006-01-01

    Estuaries are sinks for organic matter and nutrients entering both from their catchments and also from the adjacent lands and urban areas and in turn they are sources of such materials to the adjacent coast. The present paper quantifies the relative amounts of natural and anthropogenic organic matter and nutrients entering the Humber Estuary, Eastern England, including the allochthonous and autochthonous materials, those from urban and industrial sewage and from the catchment drainage of arable land. These data thus give a budget for the estuary which in turn answers questions fundamental to the management of the estuary. The estimations within the study have been carried out against a background of designating estuaries under the European Union Urban Waste-water Treatment Directive and the EU Nitrates Directive. The assessment has particularly addressed the question, related to the former Directive, of whether the Humber Estuary is eutrophic or likely to become eutrophic unless management measures are taken. Thus the paper indicates the nature and value of control measures such as treatment plant upgrading and the designation of Nitrate Vulnerable Zones. The paper includes the recent national and European discussions on the designation of areas under these Directives. Finally, the study has allowed a quantification of the present organic inputs to the estuary in comparison to those entering prior to large scale land-claim which had removed natural organic-producing wetlands.

  5. Remote monitoring of organic matter in the ocean

    NASA Astrophysics Data System (ADS)

    Niccolai, Filippo; Bazzani, Marco; Cecchi, Giovanna; Innamorati, Mario; Massi, Luca; Nuccio, Caterina; Santoleri, Rosalia

    1999-12-01

    The monitoring of organic matter, suspended or dissolved in the water column, is relevant for the study of the aquatic environment. Actually, the Dissolved Organic Matter (DOM) represents a major reservoir of reactive carbon in the global carbon cycle, thus influencing significantly the marine ecosystem. Due to the strong absorption in the near ultraviolet, DOM reduces considerably the extinction path of solar light in the water column, affecting phytoplankton population and its vertical distribution. The measurement of the DOM absorption coefficient has to be regarded as a good parameter for the monitoring of water quality. This paper deals with the measurements carried out during the oceanographic campaign 'Marine Fronts,' which took place in the Western Mediterranean Sea and Atlantic Ocean from July 14 to August 5, 1998. In this measurement campaign, a high spectral resolution fluorescence lidar (FLIDAR) was installed on the rear-deck of the O/V 'Urania,' acquiring remote fluorescence spectra both in ship motion and in stations. A particular attention was devoted to the monitoring of DOM distribution in the different water masses in marine frontal areas. The lidar data were compared and integrated with SST satellite data and biological samplings. The results show that FLIDAR data agree with satellite imagery, particularly for marine front detection. The comparison with water sample data gave indications for retrieving the DOM absorption coefficient directly from fluorescence remote spectra. In addition, a protein like fluorescence band was detected in the measurements carried out on total suspended matter filtered from the water samplings.

  6. Remineralization of Artificial Dentin Lesions via the Polymer-Induced Liquid-Precursor (PILP) Process.

    PubMed

    Thula-Mata, Taili; Burwell, Anora; Gower, Laurie B; Habeliz, Stefan; Marshall, Grayson W

    2011-01-01

    Acid-etched dentin samples with a zone of demineralized dentin were remineralized via the polymer-induced liquid-precursor (PILP) process. Poly-L-aspartic acid was used as the polymeric process-directing agent. Samples were incubated in the mineralization solution for 1-4 weeks. Dentin samples remineralized by the PILP process presented a surface morphology very similar to the intact mineralized dentin's architecture, in contrast to samples mineralized via the conventional nucleation and growth method (without polymer additive), which led to a superficial crust of randomly organized mineral crystals. Energy dispersive x-ray spectroscopy analysis of the PILP-mineralized samples showed the presence of calcium and phosphate ions at high levels. Since no hydroxyapatite (HA) clusters were observed on the surface of the PILP-mineralized samples, we could conclude the signal was produced from the mineral embedded within the dentin matrix. TEM and diffraction analyses suggest that both intrafibrillar and interfibrillar remineralization occurred in the demineralized dentin matrix.

  7. Remineralization of Artificial Dentin Lesions via the Polymer-Induced Liquid-Precursor (PILP) Process

    PubMed Central

    Thula-Mata, Taili; Burwell, Anora; Gower, Laurie B.; Habeliz, Stefan; Marshall, Grayson W.

    2011-01-01

    Acid-etched dentin samples with a zone of demineralized dentin were remineralized via the polymer-induced liquid-precursor (PILP) process. Poly-L-aspartic acid was used as the polymeric process-directing agent. Samples were incubated in the mineralization solution for 1–4 weeks. Dentin samples remineralized by the PILP process presented a surface morphology very similar to the intact mineralized dentin’s architecture, in contrast to samples mineralized via the conventional nucleation and growth method (without polymer additive), which led to a superficial crust of randomly organized mineral crystals. Energy dispersive x-ray spectroscopy analysis of the PILP-mineralized samples showed the presence of calcium and phosphate ions at high levels. Since no hydroxyapatite (HA) clusters were observed on the surface of the PILP-mineralized samples, we could conclude the signal was produced from the mineral embedded within the dentin matrix. TEM and diffraction analyses suggest that both intrafibrillar and interfibrillar remineralization occurred in the demineralized dentin matrix. PMID:24839340

  8. Organic speciation of size-segregated atmospheric particulate matter

    NASA Astrophysics Data System (ADS)

    Tremblay, Raphael

    Particle size and composition are key factors controlling the impacts of particulate matter (PM) on human health and the environment. A comprehensive method to characterize size-segregated PM organic content was developed, and evaluated during two field campaigns. Size-segregated particles were collected using a cascade impactor (Micro-Orifice Uniform Deposit Impactor) and a PM2.5 large volume sampler. A series of alkanes and polycyclic aromatic hydrocarbons (PAHs) were solvent extracted and quantified using a gas chromatograph coupled with a mass spectrometer (GC/MS). Large volume injections were performed using a programmable temperature vaporization (PTV) inlet to lower detection limits. The developed analysis method was evaluated during the 2001 and 2002 Intercomparison Exercise Program on Organic Contaminants in PM2.5 Air Particulate Matter led by the US National Institute of Standards and Technology (NIST). Ambient samples were collected in May 2002 as part of the Tampa Bay Regional Atmospheric Chemistry Experiment (BRACE) in Florida, USA and in July and August 2004 as part of the New England Air Quality Study - Intercontinental Transport and Chemical Transformation (NEAQS - ITCT) in New Hampshire, USA. Morphology of the collected particles was studied using scanning electron microscopy (SEM). Smaller particles (one micrometer or less) appeared to consist of solid cores surrounded by a liquid layer which is consistent with combustion particles and also possibly with particles formed and/or coated by secondary material like sulfate, nitrate and secondary organic aerosols. Source apportionment studies demonstrated the importance of stationary sources on the organic particulate matter observed at these two rural sites. Coal burning and biomass burning were found to be responsible for a large part of the observed PAHs during the field campaigns. Most of the measured PAHs were concentrated in particles smaller than one micrometer and linked to combustion sources

  9. Photochemical production of singlet oxygen from particulate organic matter.

    PubMed

    Appiani, Elena; McNeill, Kristopher

    2015-03-17

    Dissolved organic matter is established as one of the most relevant photosensitizers in aquatic environments, producing singlet oxygen (1O2) alongside other photochemically produced reactive intermediates. While the production of 1O2 from DOM has been well studied, the relative importance of particulate organic matter (POM) to the overall 1O2 production is less well understood. POM is known to play an important role in pollutant fate through the sorption and transport of hydrophobic pollutants. If POM is directly involved in 1O2 production, sorbed molecules would be expected to undergo enhanced photodegradation. In this work, synthetic POM was prepared by coating silica particles with commercial humic acid. The photochemical behavior of these POM samples was compared to dissolved commercial humic acids (DOM). Suspended natural sediment was also studied to test the environmental relevance of the synthetic POM model. Synthetic POM particles appear to simulate well the 1O2-production of suspended sediment. The 1O2 concentrations experienced by POM-sorbed probe molecules was up to 30% higher than experienced by DOM-sorbed ones, even though the aqueous concentration of 1O2 in irradiated POM suspensions was much lower than the analogous DOM solutions. These results were interpreted with a reaction-diffusion model, which suggested that the production rate of 1O2 by POM is lower than DOM, but the loss of 1O2 from the POM-phase is also lower than DOM. Based on the experimental results of this study, calculations were conducted to estimate the impact of removing POM on 1O2-mediated processes. These calculations indicate that compounds with a log Koc value near 4 will be most affected by removal of POM and that the magnitude of the effect is proportional to the fraction of the total organic matter represented by POM. This study demonstrates that particles can play an important role in the degradation of organic compounds via aquatic photochemistry.

  10. Missing links in the root-soil organic matter continuum.

    SciTech Connect

    O'Brien, S. L.; Iversen, C. M.; Biosciences Division; ORNL

    2009-01-01

    The soil environment remains one of the most complex and poorly understood research frontiers in ecology. Soil organic matter (SOM), which spans a continuum from fresh detritus to highly processed, mineral-associated organic matter, is the foundation of sustainable terrestrial ecosystems. Heterogeneous SOM pools are fueled by inputs from living and dead plants, driven by the activity of micro- and mesofauna, and are shaped by a multitude of abiotic factors (Fig. 1). The specialization required to measure unseen processes that occur on a wide range of spatial and temporal scales has led to the partitioning of soil ecology research across several disciplines. In the organized oral session 'Missing links in the root-soil organic matter continuum' at the annual Ecological Society of America meeting in Albuquerque, NM, USA, we joined the call for greater communication and collaboration among ecologists who work at the root-soil interface (e.g. Coleman, 2008). Our goal was to bridge the gap between scientific disciplines and to synthesize disconnected pieces of knowledge from root-centric and soil-centric studies into an integrated understanding of belowground ecosystem processes. We focused this report around three compelling themes that arose from the session: (1) the influence of the rhizosphere on SOM cycling, (2) the role of soil heterotrophs in driving the transformation of root detritus to SOM, and (3) the controlling influence of the soil environment on SOM dynamics. We conclude with a discussion of new approaches for gathering data to bridge gaps in the root-SOM continuum and to inform the next generation of ecosystem models.

  11. Competitive Sorption and Desorption of Chlorinated Organic Solvents (DNAPLs) in Engineered Natural Organic Matter

    SciTech Connect

    Tang, Jixin; Weber, Walter J., Jr.

    2004-03-31

    The effects of artificially accelerated geochemical condensation and maturation of natural organic matter on the sorption and desorption of trichloroethylene (TCE) and tetrachloroethylene (PCE) were studied. The sorption and desorption of TCE in the presence and absence of the competing PCE and 1,2-dichlorobenzene (DCB) were also examined. A sphagnum peat comprising geologically young organic matter was artificially ''aged'' using superheated water, thus increasing the aromaticity and the degree of condensation of its associated organic matter. The sorption of all solutes tested were increased remarkably and their respective desorptions reduced, by the aged peat. The sorption capacities and isotherm nonlinearities of the peat for both TCE and PCE were found to increase as treatment temperature increased. In the competitive sorption studies, both PCE and DCB were found to depress TCE sorption, with PCE having greater effects than DCB, presumably because the molecular structure o f the former is more similar to that of TCE.

  12. Application of organic geochemistry to detect signatures of organic matter in the Haughton impact structure

    NASA Astrophysics Data System (ADS)

    Parnell, John; Lee, Pascal; Osinski, Gordon R.; Cockell, Charles S.

    2005-12-01

    Organic geochemistry applied to samples of bedrock and surface sediment from the Haughton impact structure detects a range of signatures representing the impact event and the transfer of organic matter from the crater bedrock to its erosion products. The bedrock dolomite contains hydrocarbon-bearing fluid inclusions which were incorporated before the impact event. Comparison of biomarker data from the hydrocarbons in samples inside and outside of the crater show the thermal signature of an impact. The occurrence of hydrocarbon inclusions in hydrothermal mineral samples shows that organic matter was mobilized and migrated in the immediate aftermath of the impact. The hydrocarbon signature was then transferred from bedrock to the crater-fill lacustrine deposits and present-day sediments in the crater, including wind-blown detritus in snow/ice. Separate signatures are detected from modern microbial life in crater rock and sediment samples. Signatures in Haughton crater samples are readily detectable because they include hydrocarbons generated by the burial of organic matter. This type of organic matter is not expected in crater samples on other planets, but the Haughton data show that, using very high resolution detection of organic compounds, any signature of primitive life in the crater rocks could be transferred to surface detritus and so extend the sampling medium.

  13. Modelling of organic matter dynamics during the composting process.

    PubMed

    Zhang, Y; Lashermes, G; Houot, S; Doublet, J; Steyer, J P; Zhu, Y G; Barriuso, E; Garnier, P

    2012-01-01

    Composting urban organic wastes enables the recycling of their organic fraction in agriculture. The objective of this new composting model was to gain a clearer understanding of the dynamics of organic fractions during composting and to predict the final quality of composts. Organic matter was split into different compartments according to its degradability. The nature and size of these compartments were studied using a biochemical fractionation method. The evolution of each compartment and the microbial biomass were simulated, as was the total organic carbon loss corresponding to organic carbon mineralisation into CO(2). Twelve composting experiments from different feedstocks were used to calibrate and validate our model. We obtained a unique set of estimated parameters. Good agreement was achieved between the simulated and experimental results that described the evolution of different organic fractions, with the exception of some compost because of a poor simulation of the cellulosic and soluble pools. The degradation rate of the cellulosic fraction appeared to be highly variable and dependent on the origin of the feedstocks. The initial soluble fraction could contain some degradable and recalcitrant elements that are not easily accessible experimentally. PMID:21978424

  14. Redox effects on the microbial degradation of refractory organic matter in marine sediments

    NASA Astrophysics Data System (ADS)

    Reimers, Clare E.; Alleau, Yvan; Bauer, James E.; Delaney, Jennifer; Girguis, Peter R.; Schrader, Paul S.; Stecher, Hilmar A.

    2013-11-01

    Microbially mediated reduction-oxidation (redox) reactions are often invoked as being the mechanisms by which redox state influences the degradation of sedimentary organic matter (OM) in the marine environment. To evaluate the effects of elevated, oscillating and reduced redox potentials on the fate of primarily aged, mineral-adsorbed OM contained in continental shelf sediments, we used microbial fuel cells to control redox state within and around marine sediments, without amending the sediments with reducing or oxidizing substances. We subsequently followed electron fluxes in the redox elevated and redox oscillating treatments, and related sediment chemical, isotopic and bacterial community changes to redox conditions over a 748-day experimental period. The electron fluxes of the elevated and oscillating redox cells were consistent with models of organic carbon (OC) oxidation with time-dependent first-order rate constants declining from 0.023 to 0.005 y-1, in agreement with rate constants derived from typical OC profiles and down core ages of offshore sediments, or from sulfate reduction rate measurements in similar sediments. Moreover, although cumulative electron fluxes were higher in the continuously elevated redox treatment, incremental rates of electron harvesting in the two treatments converged over the 2 year experiment. These similar rates were reflected in chemical indicators of OM metabolism such as dissolved OC and ammonia, and particulate OC concentrations, which were not significantly different among all treatments and controls over the experimental time-scale. In contrast, products of carbonate and opal dissolution and metal mobilization showed greater enrichments in sediments with elevated and oscillating redox states. Microbial community composition in anode biofilms and surrounding sediments was assessed via high-throughput 16S rRNA gene sequencing, and these analyses revealed that the elevated and oscillatory redox treatments led to the

  15. Organic Matter Sulfurization in the Cariaco Water Column Revealed by High-Sensitivity and Compound-Specific d34S Analyses.

    NASA Astrophysics Data System (ADS)

    Raven, M. R.; Sessions, A. L.; Adkins, J. F.; Thunell, R.

    2015-12-01

    Organic matter burial in marine sediments is a major process in the global carbon cycle, and enhanced organic matter burial is often associated with periods of global climatic and ecological change. Still, we have only a limited understanding of the processes that drive enhanced OM burial during oxygen-deficient conditions. Abiotic OM sulfurization has the potential to enhance the preservation of OM, but for this process to be significant it must compete with heterotrophic remineralization, most of which occurs before sinking particles reach the sea floor. We investigate the sources of sulfur to sinking particles in a modern marine basin using samples from the CARIACO fixed sediment trap time-series, applying recently developed methods for d34S analysis of small (≥20 nmol) sulfur pools and individual volatile organosulfur compounds. Relative to expectations for planktonic biomass, we find that sinking particles are both sulfur-rich and 34S-depleted. Higher apparent fluxes of 34S-depleted organic sulfur are associated with high OM export from the surface ocean, low terrestrial inputs, and high concentrations of both elemental S and the dominant non-polar organosulfur compound, C20 thiophene. We conclude that OM sulfurization is occurring in particles sinking through the Cariaco water column on timescales of days or less. Depending on the frequency of high OM export events, we estimate that this rapid sulfurization delivers roughly half of the total organic S present at 5 cm depth in underlying sediments. Accordingly, many OM-rich deposits in the geologic record may represent the products of water column sulfurization. This process provides a strong mechanistic feedback between oxygen deficiency and OM preservation.

  16. Soft X-Ray Photoionizing Organic Matter from Comet Wild 2: Evidence for the Production of Organic Matter by Impact Processes

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael E.; Wirick, S.; Flynn, G. J.; Jacobsen, C.; Na

    2011-01-01

    The Stardust mission collected both mineral and organic matter from Comet Wild 2 [1,2,3,4]. The organic matter discovered in Comet Wild 2 ranges from aromatic hydrocarbons to simple aliphatic chains and is as diverse and complex as organic matter found in carbonaceous chondrites and interplanetary dust particles.[3,5,6,7,8,9]. Compared to insoluble organic matter from carbonaceous chondrites the organic matter in Comet Wild 2 more closely resembles organic matter found in the IDPS both hydrous and anhydrous. Common processes for the formation of organic matter in space include: Fischer-Tropsch, included with this aqueous large body and moderate heating alterations; UV irradiation of ices; and; plasma formation and collisions. The Fischer-Tropsch could only occur on large bodies processes, and the production of organic matter by UV radiation is limited by the penetration depth of UV photons, on the order of a few microns or less for most organic matter, so once organic matter coats the ices it is formed from, the organic production process would stop. Also, the organic matter formed by UV irradiation would, by the nature of the process, be in-sensitive to photodissocation from UV light. The energy of soft X-rays, 280-300 eV occur within the range of extreme ultraviolet photons. During the preliminary examination period we found a particle that nearly completely photoionized when exposed to photons in the energy range 280-310eV. This particle experienced a long exposure time to the soft x-ray beam which caused almost complete mass loss so little chemical information was obtain. During the analysis of our second allocation we have discovered another particle that photoionized at these energies but the exposure time was limited and more chemical information was obtained.

  17. ENVIRONMENTAL RESEARCH BRIEF: CHARACTERIZATION OF ORGANIC MATTER IN SOIL AND AQUIFER SOLIDS

    EPA Science Inventory

    The focus of this work was the evaluation of analytical methods to determine and characterize fractions of subsurface organic matter. Major fractions of total organic carbon (TOC) include: particulate organic carbon (POC) in aquifer material, dissolved organic carbon (DOC) and ...

  18. Mercury dilution by autochthonous organic matter in a fertilized mangrove wetland.

    PubMed

    Machado, Wilson; Sanders, Christian J; Santos, Isaac R; Sanders, Luciana M; Silva-Filho, Emmanoel V; Luiz-Silva, Wanilson

    2016-06-01

    A dated sediment core from a highly-fertilized mangrove wetland located in Cubatão (SE Brazil) presented a negative correlation between mercury (Hg) and organic carbon contents. This is an unusual result for a metal with well-known affinity to organic matter. A dilution of Hg concentrations by autochthonous organic matter explained this observation, as revealed by carbon stable isotopes signatures (δ(13)C). Mercury dilution by the predominant mangrove-derived organic matter counterbalanced the positive influences of algal-derived organic matter and clay contents on Hg levels, suggesting that deleterious effects of Hg may be attenuated. Considering the current paradigm on the positive effect of organic matter on Hg concentrations in coastal sediments and the expected increase in mangrove organic matter burial due to natural and anthropogenic stimulations of primary production, predictions on the influences of organic matter on Hg accumulation in mangrove wetlands deserve caution.

  19. Organic Matter as an Indicator of Soil Degradation

    NASA Astrophysics Data System (ADS)

    Romero Diaz, Asuncion; Damian Ruiz Sinoga, Jose

    2010-05-01

    Numerous and expensive physical-chemical tests are often carried out to determine the level of soil degration. This study was to find one property, as Organic Matter, which is usually analyzed for determine the soil degradation status. To do this 19 areas in the south and southeast of the Iberian Peninsula (provinces of Málaga, Granada, Almería y Murcia) were selected and a wide sampling process was carried out. Sampling points were spread over a wide pluviometric gradient (from 1100 mm/yr to 232 mm/yr) covering the range from Mediterranean wet to dry. 554 soil surface samples were taken from soil (0-10 cm) and the following properties were analyzed: Texture, Organic Matter (OM), Electric Conductivity (EC), Aggregate Stability (AE) y Cation Exchange Capacity (CEC). These properties were intercorrelated and also with rainfall and the K factor of soil erosion, calculated for each sampling point. Los results obtained by applying the Pearson correlation coefficient to the database shows how as rainfall increases so does OM content (0,97) and la CEC (0,89), but K factor (-0,80) reacts inversely. The content of OM in the soil is related to its biological activity and this in turn is the result of available wáter within the system and, consequently, rainfall. This is specially important in fragile and complex ecogeomorphological systems as is the case of the Mediterranean, where greater or lesser rainfall is similarly reflected in the levels of increase or decrease of soil organic matter. This affirmation is reinforced by linking the organic matter of the soil with other indicative properties such as CEC and erosion, as has been shown by various authors (Imeson y Vis, 1984; De Ploey & Poesen, 1985; Le Bissonnais, 1996; Boix-Fayos et al., 2001; Cammeraat y Imeson, 1998; Cerdá, 1998). As has been stated, there is a direct relationship between rainfall, organic matter content, cation exchange capacity, structural stability, and the resistence to soil erosion factor

  20. Unraveling the chemical space of terrestrial and meteoritic organic matter

    NASA Astrophysics Data System (ADS)

    Schmitt-Kopplin, Philippe; Harir, Mourad; Hertkorn, Norbert; Kanawati, Basem; Ruf, Alexander; Quirico, Eric; Bonal, Lydie; Beck, Pierre; Gabelica, Zelimir

    2015-04-01

    In terrestrial environments natural organic matter (NOM) occurs in soils, freshwater and marine environments, in the atmosphere and represents an exceedingly complex mixture of organic compounds that collectively exhibits a nearly continuous range of properties (size-reactivity continuum). In these materials, the "classical" biogeosignatures of the (biogenic and geogenic) precursor molecules, like lipids, lignins, proteins and natural products have been attenuated, often beyond recognition, during a succession of biotic and abiotic (e.g. photo- and redox chemistry) reactions. Because of this loss of biochemical signature, these materials can be designated non-repetitive complex systems. The access to extra-terrestrial organic matter is given i.e. in the analysis of meteoritic materials. Numerous descriptions of organic molecules present in organic chondrites have improved our understanding of the early interstellar chemistry that operated at or just before the birth of our solar system. However, many molecular analyses are so far targeted toward selected classes of compounds with a particular emphasis on biologically active components in the context of prebiotic chemistry. Here we demonstrate that a non-targeted ultrahigh-resolution molecular analysis of the solvent-accessible organic fraction of meteorite extracted under mild conditions allows one to extend its indigenous chemical diversity to tens of thousands of different molecular compositions and likely millions of diverse structures. The description of the molecular complexity provides hints on heteroatoms chronological assembly, shock and thermal events and revealed recently new classes of thousands of novel organic, organometallic compounds uniquely found in extra-terrestrial materials and never described in terrestrial systems. This high polymolecularity suggests that the extraterrestrial chemodiversity is high compared to terrestrial relevant biological and biogeochemical-driven chemical space. (ultra

  1. Lead sequestration and species redistribution during soil organic matter decomposition.

    PubMed

    Schroth, Andrew W; Bostick, Benjamin C; Kaste, James M; Friedland, Andrew J

    2008-05-15

    The turnover of soil organic matter (SOM) maintains a dynamic chemical environment in the forest floor that can impact metal speciation on relatively short timescales. Here we measure the speciation of Pb in controlled and natural organic (O) soil horizons to quantify changes in metal partitioning during SOM decomposition in different forest litters. We provide a link between the sequestration of pollutant Pb in O-horizons, estimated by forest floor Pb inventories, and speciation using synchrotron-based X-rayfluorescence and X-ray absorption spectroscopy. When Pb was introduced to fresh forest O(i) samples, it adsorbed primarily to SOM surfaces, but as decomposition progressed over two years in controlled experiments, up to 60% of the Pb was redistributed to pedogenic birnessite and ferrihydrite surfaces. In addition, a significant fraction of pollutant Pb in natural soil profiles was associated with similar mineral phases (approximately 20-35%) and SOM (-65-80%). Conifer forests have at least 2-fold higher Pb burdens in the forest floor relative to deciduous forests due to more efficient atmospheric scavenging and slower organic matter turnover. We demonstrate that pedogenic minerals play an important role in surface soil Pb sequestration, particularly in deciduous forests, and should be considered in any assessment of pollutant Pb mobility.

  2. Complexation of lead by organic matter in Luanda Bay, Angola.

    PubMed

    Leitão, Anabela; Santos, Ana Maria; Boaventura, Rui A R

    2015-10-01

    Speciation is defined as the distribution of an element among different chemical species. Although the relation between speciation and bioavailability is complex, the metal present as free hydrated ion, or as weak complexes able to dissociate, is usually more bioavailable than the metal incorporated in strong complexes or adsorbed on colloidal or particulate matter. Among the analytical techniques currently available, anodic stripping voltammetry (ASV) has been one of the most used in the identification and quantification of several heavy metal species in aquatic systems. This work concerns the speciation study of lead, in original (natural, non-filtered) and filtered water samples and in suspensions of particulate matter and sediments from Luanda Bay (Angola). Complexes of lead with organics were identified and quantified by differential pulse anodic stripping voltammetry technique. Each sample was progressively titrated with a Pb(II) standard solution until complete saturation of the organic ligands. After each addition of Pb(II), the intensity, potential and peak width of the voltammetric signal were measured. The results obtained in this work show that more than 95 % of the lead in the aquatic environment is bound in inert organic complexes, considering all samples from different sampling sites. In sediment samples, the lead is totally (100 %) complexed with ligands adsorbed on the particles surface. Two kinds of dominant lead complexes, very strong (logK >11) and strong to moderately strong (8< logK <11), were found, revealing the lead affinity for the stronger ligands. PMID:27624745

  3. Lead sequestration and species redistribution during soil organic matter decomposition

    USGS Publications Warehouse

    Schroth, A.W.; Bostick, B.C.; Kaste, J.M.; Friedland, A.J.

    2008-01-01

    The turnover of soil organic matter (SOM) maintains a dynamic chemical environment in the forest floor that can impact metal speciation on relatively short timescales. Here we measure the speciation of Pb in controlled and natural organic (O) soil horizons to quantify changes in metal partitioning during SOM decomposition in different forest litters. We provide a link between the sequestration of pollutant Pb in O-horizons, estimated by forest floor Pb inventories, and speciation using synchrotron-based X-ray fluorescence and X-ray absorption spectroscopy. When Pb was introduced to fresh forest Oi samples, it adsorbed primarily to SOM surfaces, but as decomposition progressed over two years in controlled experiments, up to 60% of the Pb was redistributed to pedogenic birnessite and ferrihydrite surfaces. In addition, a significant fraction of pollutant Pb in natural soil profiles was associated with similar mineral phases (???20-35%) and SOM (???65-80%). Conifer forests have at least 2-fold higher Pb burdens in the forest floor relative to deciduous forests due to more efficient atmospheric scavenging and slower organic matter turnover. We demonstrate that pedogenic minerals play an important role in surface soil Pb sequestration, particularly in deciduous forests, and should be considered in any assessment of pollutant Pb mobility. ?? 2008 American Chemical Society.

  4. Lead Sequestration And Species Redistribution During Soil Organic Matter Decomposition

    SciTech Connect

    Schroth, A.W.; Bostick, B.C.; Kaste, J.M.; Friedland, A.J.

    2009-05-27

    The turnover of soil organic matter (SOM) maintains a dynamic chemical environment in the forest floor that can impact metal speciation on relatively short timescales. Here we measure the speciation of Pb in controlled and natural organic (O) soil horizons to quantify changes in metal partitioning during SOM decomposition in different forest litters. We provide a link between the sequestration of pollutant Pb in O-horizons, estimated by forest floor Pb inventories, and speciation using synchrotron-based X-rayfluorescence and X-ray absorption spectroscopy. When Pb was introduced to fresh forest O{sub i} samples, it adsorbed primarily to SOM surfaces, but as decomposition progressed over two years in controlled experiments, up to 60% of the Pb was redistributed to pedogenic birnessite and ferrihydrite surfaces. In addition, a significant fraction of pollutant Pb in natural soil profiles was associated with similar mineral phases ({approx}20--35%) and SOM ({approx}65--80%). Conifer forests have at least 2-fold higher Pb burdens in the forest floor relative to deciduous forests due to more efficient atmospheric scavenging and slower organic matter turnover. We demonstrate that pedogenic minerals play an important role in surface soil Pb sequestration, particularly in deciduous forests, and should be considered in any assessment of pollutant Pb mobility.

  5. Lead Sequestration and Species Redistribution During Soil Organic Matter Decomposition

    SciTech Connect

    Schroth,A.; Bostick, B.; Kaste, J.; Friedland, A.

    2008-01-01

    The turnover of soil organic matter (SOM) maintains a dynamic chemical environment in the forest floor that can impact metal speciation on relatively short timescales. Here we measure the speciation of Pb in controlled and natural organic (O) soil horizons to quantify changes in metal partitioning during SOM decomposition in different forest litters. We provide a link between the sequestration of pollutant Pb in O-horizons, estimated by forest floor Pb inventories, and speciation using synchrotron-based X-ray fluorescence and X-ray absorption spectroscopy. When Pb was introduced to fresh forest Oi samples, it adsorbed primarily to SOM surfaces, but as decomposition progressed over two years in controlled experiments, up to 60% of the Pb was redistributed to pedogenic birnessite and ferrihydrite surfaces. In addition, a significant fraction of pollutant Pb in natural soil profiles was associated with similar mineral phases ({approx}20-35%) and SOM ({approx}65-80%). Conifer forests have at least 2-fold higher Pb burdens in the forest floor relative to deciduous forests due to more efficient atmospheric scavenging and slower organic matter turnover. We demonstrate that pedogenic minerals play an important role in surface soil Pb sequestration, particularly in deciduous forests, and should be considered in any assessment of pollutant Pb mobility.

  6. Missing links in the root-soil organic matter continuum

    SciTech Connect

    O'Brien, Sarah L.; Iversen, Colleen M

    2009-01-01

    The soil environment remains one of the most complex and poorly understood research frontiers in ecology. Soil organic matter (SOM), which spans a continuum from fresh detritus to highly processed, mineral-associated organic matter, is the foundation of sustainable terrestrial ecosystems. Heterogeneous SOM pools are fueled by inputs from living and dead plants, driven by the activity of micro- and mesofauna, and are shaped by a multitude of abiotic factors. The specialization required to measure unseen processes that occur on a wide range of spatial and temporal scales has led to the partitioning of soil ecology research across several disciplines. In the organized oral session 'Missing links in the root-soil organic matter continuum' at the annual Ecological Society of America meeting in Albuquerque, NM, USA, we joined the call for greater communication and collaboration among ecologists who work at the root-soil interface (e.g. Coleman, 2008). Our goal was to bridge the gap between scientific disciplines and to synthesize disconnected pieces of knowledge from root-centric and soil-centric studies into an integrated understanding of belowground ecosystem processes. We focused this report around three compelling themes that arose from the session: (1) the influence of the rhizosphere on SOM cycling, (2) the role of soil heterotrophs in driving the transformation of root detritus to SOM, and (3) the controlling influence of the soil environment on SOM dynamics. We conclude with a discussion of new approaches for gathering data to bridge gaps in the root-SOM continuum and to inform the next generation of ecosystem models. Although leaf litter has often been considered to be the main source of organic inputs to soil, Ann Russell synthesized a convincing body of work demonstrating that roots, rather than surface residues, control the accumulation of SOM in a variety of ecosystems. Living roots, which are chemically diverse and highly dynamic, also influence a wide

  7. Priming of soil organic matter decomposition in cryoturbated Arctic soils

    NASA Astrophysics Data System (ADS)

    Richter, A.; Wild, B.; Schnecker, J.; Rusalimova, O.

    2012-12-01

    The Arctic is subjected to particularly high rates of warming, with profound consequences for the carbon cycle: on the one hand plant productivity and C storage in plant biomass have been shown to increase strongly in many parts of the Arctic, on the other hand, increasing rates of soil organic matter (SOM) decomposition have been reported. One of the possibilities that could reconcile these observations is, that increased plant growth may lead to increased root exudation rates, which are known to stimulate microbial turnover of organic matter under certain circumstances, in a process termed "priming" of SOM. Two mechanisms have been brought forward that may be responsible for priming: first, easily assimilable material exuded by plant roots may help microbes to overcome their energy limitation and second, this input of labile carbon could lead to a nitrogen limitation of the microbial community and lead to nitrogen mining, i.e. decomposition of N-rich SOM. We here report on an incubation study with arctic soil investigating potential priming of SOM decomposition in organic topsoil horizons, cryoturbated organic matter and subsoil mineral horizons of tundra soil from the Taymyr peninsula in Siberia. We used arctic soils, that are characterized by cryoturbation (mixing of soil layers due to freezing and thawing), for this study. Turbated cryosols store more than 580 Gt C globally, a significant proportion of which is stored in the cryoturbated organic matter. We hypothesized that an increased availability of labile compounds would increase SOM decomposition rates, and that this effect would be strongest in horizons with a low natural availability of labile C, i.e. in the mineral subsoil. We amended soils with 13C labelled glucose, cellulose, amino acids or proteins, and measured the mineralization of SOM C as well as microbial community composition and potential activities of extracellular enzymes. Our results demonstrate that topsoil organic, cryoturbated and

  8. Aquatic Organic Matter Fluorescence - from phenomenon to application

    NASA Astrophysics Data System (ADS)

    Reynolds, Darren

    2014-05-01

    The use of fluorescence to quantify and characterise aquatic organic matter in river, ocean, ground water and drinking and waste waters has come along way since its discovery as a phenomenon in the early 20th century. For example, there are over 100 papers published each year in international peer reviewed journals, an order of magnitude increase since a decade ago (see Figure taken from ISI database from 1989 to 2007 for publications in the fields of river water and waste water). Since then it has been extensively used as a research tool since the 1990's by scientists and is currently used for a wide variety of applications within a number of sectors. Universities, organisations and companies that research into aquatic organic matter have either recently readily use appropriate fluorescence based techniques and instrumentation. In industry and government, the technology is being taken up by environmental regulators and water and wastewater companies. This keynote presentation will give an overview of aquatic organic matter fluorescence from its conception as a phenomenon through to its current use in a variety of emerging applications within the sectors concerned with understanding, managing and monitoring the aquatic environment. About the Speaker Darren Reynolds pioneered the use of fluorescence spectroscopy for the analysis of wastewaters in the 1990's. He currently leads a research group within the Centre for Research in Biosciences and sits on the Scientific Advisory Board for the Institute of Bio-Sensing Technology at the University of the West of England, Bristol. He is a multidisciplinary scientist concerned with the development of technology platforms for applications in the fields of environment/agri-food and health. His current research interests include the development of optical technologies and techniques for environmental and biological sensing and bio-prospecting applications. He is currently involved in the development and use of synthetic biology

  9. Persistence of soil organic matter as an ecosystem property

    SciTech Connect

    Schmidt, M.W.; Torn, M. S.; Abiven, S.; Dittmar, T.; Guggenberger, G.; Janssens, I.A.; Kleber, M.; Kögel-Knabner, I.; Lehmann, J.; Manning, D.A.C.; Nannipieri, P.; Rasse, D.P.; Weiner, S.; Trumbore, S.E.

    2011-08-15

    Globally, soil organic matter (SOM) contains more than three times as much carbon as either the atmosphere or terrestrial vegetation. Yet it remains largely unknown why some SOM persists for millennia whereas other SOM decomposes readily—and this limits our ability to predict how soils will respond to climate change. Recent analytical and experimental advances have demonstrated that molecular structure alone does not control SOM stability: in fact, environmental and biological controls predominate. Here we propose ways to include this understanding in a new generation of experiments and soil carbon models, thereby improving predictions of the SOM response to global warming.

  10. Particulate organic matter sinks and sources in high Arctic fjord

    NASA Astrophysics Data System (ADS)

    Kuliński, Karol; Kędra, Monika; Legeżyńska, Joanna; Gluchowska, Marta; Zaborska, Agata

    2014-11-01

    The main aim of this paper is to present results on concentrations, fluxes and isotopic composition (δ13Corg) of particulate and sedimentary organic carbon (measures of particulate and sedimentary organic matter, respectively) in Kongsfjorden, Spitsbergen. The terrestrial particulate organic carbon (POC) input to the Kongsfjorden reached 760 · 106 ± 145 · 106 g Corg y- 1, forced mostly by the glaciers' activity. This constituted 5-10% of the bulk POC supplied to the system. Marine primary production was the main source of the remaining 90-95% of POC. Organic carbon burial rates amounted to 9 ± 1 g Corg m- 2 y- 1 in the central and 13 ± 1 g Corg m- 2 y- 1 in the outer part of the fjord. Two terrestrial POM δ13Corg end members were identified: the ancient organic matter (OM) supplied by glaciers and rivers fed by water discharged from the glaciers (from - 25.4‰ to - 25.1‰), and the fresh terrestrial POM (from - 26.7‰ to - 26.6‰). Marine OM was characterized by a wide range of δ13Corg signatures: from ≤ - 26.1‰ for the phytoplankton depleted in 13Corg to ca. - 15.8‰ for debris of marine phytobenthos. The lack of distinct marine δ13Corg end member and the resemblance of phytoplankton δ13Corg signatures to the terrestrial POM δ13Corg end member precluded the use of the two δ13Corg end member mixing model to trace the terrestrial OM in Kongsfjorden, which is also very likely to happen in other Arctic regions.

  11. Association of organic matter and ferrihydrite: adsorption versus coprecipitation

    NASA Astrophysics Data System (ADS)

    Eusterhues, K.; Rennert, T.; Knicker, H.; Totsche, K. U.

    2009-04-01

    Ferrihydrite (Fh) - even if present at low concentrations - may control the available surface area and therefore, the behaviour of nutrients and pollutants in soils. Its precipitation often takes place in the presence of dissolved organic matter (OM). This involves processes such as adsorption, but also coprecipitation, flocculation/coagulation and poisoning of crystal growth. In this study, we compare coprecipitation of organic matter and ferrihydrite with pure adsorption of OM on ferrihydrite. We therefore prepared an adsorption series and a coprecipitation series using (i) water extractable organic matter from a forest topsoil and (ii) sulfite extractable lignin from paper. Products were investigated by N2-adsorption, XRD and FTIR. In coprecipitation experiments with both types of OM we observed a strong interference of the organic molecules with crystal growth leading to smaller Fh crystals, increased lattice spacings and a lower crystallinity. The highest achieved C loadings were found at approximately 200 mg C per g Fh for the adsorption and coprecipitation of the soil extract as well as for the adsorption of lignin. Coprecipitation of lignin, in contrast, resulted in a much higher maximum loading of 360 mg C per g Fh. The FTIR spectrum of the unreacted soil extract is mainly characterized by carboxyl C and polysaccharide C, with a smaller contribution of phenolic C. Spectra of the adsorbed or coprecipitated soil extract reveal weaker bands and lowered wave numbers indicating removal from solution followed by the formation of chemical bonds between the organic species and Fh by inner-sphere surface complexes. The FTIR spectrum of the lignin material shows a strong contribution of carboxyl C, polysaccharide C, and several aromatic C species. Again, all of these C species seem to form surface complexes after reaction with Fh in adsorption and coprecipitation experiments. Interestingly, at low initial C concentrations in all experiments the sorption of carboxyl

  12. Conservative or reactive? Mechanistic chemical perspectives on organic matter stability

    NASA Astrophysics Data System (ADS)

    Koch, Boris

    2016-04-01

    Carbon fixation by terrestrial and marine primary production has a fundamental seasonal effect on the atmospheric carbon content and it profoundly contributes to long-term carbon storage in form of organic matter (OM) in soils, water, and sediments. The efficacy of this sequestration process strongly depends on the degree of OM persistence. Therefore, one of the key issues in dissolved and particulate OM research is to assess the stability of reservoirs and to quantify their contribution to global carbon fluxes. Incubation experiments are helpful to assess OM stability during the first, early diagenetic turnover induced by sunlight or microbes. However, net carbon fluxes within the global carbon cycle also act on much longer time scales, which are not amenable in experiments. It is therefore critical to improve our mechanistic understanding to be able to assess potential future changes in the organic matter cycle. This session contribution highlights some achievements and open questions in the field. An improved mechanistic understanding of OM turnover particularly depends on the molecular characterization of biogeochemical processes and their kinetics: (i) in soils and sediments, aggregation/disaggregation of OM is primarily controlled by its molecular composition. Hence, the chemical composition determines the transfer of organic carbon from the large particulate to the small dissolved organic matter reservoir - an important substrate for microbial metabolism. (ii) In estuaries, dissolved organic carbon gradients usually suggest conservative behavior, whereas molecular-level studies reveal a substantial chemical modification of terrestrial DOM along the land-ocean interface. (iii) In the ocean, previous studies have shown that the recalcitrance of OM depends on bulk concentration and energy yield. However, ultrahigh resolution mass spectrometry in combination with radiocarbon analyses also emphasized that stability is tightly connected to molecular composition

  13. Do organic matter matter? Contribution of organic matter on scavenging and fractionation of natural radionuclides in the Oceanic Flux Program (OFP) site of Bermuda

    NASA Astrophysics Data System (ADS)

    Chuang, C.; Santschi, P. H.; Conte, M. H.; Schumann, D.; Ayranov, M.

    2012-12-01

    Natural particle-reactive radionuclides, 234Th, 233Pa, 210Po, 210Pb and 7Be, have been used for estimating particulate organic carbon (POC) export flux in the ocean for decades. However, by simply relying on empirically determined isotope ratios to POC and other parameters, sometimes results from field studies are puzzling and become controversial (e.g., one is summarized in Li, 2005). The picture becomes clearer when it was noticed that a missing fraction, e.g., natural organic matter, could be the cause. For example, a series of field and lab studies demonstrated that biopolymers excreted by marine micro-organisms are likely carrier molecules for a number of these isotopes (e.g., Guo et al., 2002; Quigley et al., 2002; Santschi et al., 2003; Roberts et al., 2009; Hung et al., 2010; Xu et al., 2011; Hung et al., 2012; Yang et al., 2012). To examine the effect of organic composition of the particle on the scavenging and fractionation of selected natural radionuclides (e.g., Th, Pa, Pb, Po, Be), organic composition (e.g., protein, polysaccharides, uronic acid, siderophore and amino acid contents, and etc.) and particle-water partition coefficients (Kd) were determined for sediment trap material collected in the Oceanic Flux Program (OFP) site of Bermuda (500, 1500 and 3200 m). Results showed that different organic components contribute differently to the fractionation of different radionuclides from the three depths. We conclude that natural organic matter control on the particle-water partition coefficients cannot be ignored.

  14. Influence of dissolved organic carbon content on modelling natural organic matter acid-base properties.

    PubMed

    Garnier, Cédric; Mounier, Stéphane; Benaïm, Jean Yves

    2004-10-01

    Natural organic matter (NOM) behaviour towards proton is an important parameter to understand NOM fate in the environment. Moreover, it is necessary to determine NOM acid-base properties before investigating trace metals complexation by natural organic matter. This work focuses on the possibility to determine these acid-base properties by accurate and simple titrations, even at low organic matter concentrations. So, the experiments were conducted on concentrated and diluted solutions of extracted humic and fulvic acid from Laurentian River, on concentrated and diluted model solutions of well-known simple molecules (acetic and phenolic acids), and on natural samples from the Seine river (France) which are not pre-concentrated. Titration experiments were modelled by a 6 acidic-sites discrete model, except for the model solutions. The modelling software used, called PROSECE (Programme d'Optimisation et de SpEciation Chimique dans l'Environnement), has been developed in our laboratory, is based on the mass balance equilibrium resolution. The results obtained on extracted organic matter and model solutions point out a threshold value for a confident determination of the studied organic matter acid-base properties. They also show an aberrant decreasing carboxylic/phenolic ratio with increasing sample dilution. This shift is neither due to any conformational effect, since it is also observed on model solutions, nor to ionic strength variations which is controlled during all experiments. On the other hand, it could be the result of an electrode troubleshooting occurring at basic pH values, which effect is amplified at low total concentration of acidic sites. So, in our conditions, the limit for a correct modelling of NOM acid-base properties is defined as 0.04 meq of total analysed acidic sites concentration. As for the analysed natural samples, due to their high acidic sites content, it is possible to model their behaviour despite the low organic carbon concentration.

  15. The abiotic degradation of soil organic matter to oxalic acid

    NASA Astrophysics Data System (ADS)

    Studenroth, Sabine; Huber, Stefan; Schöler, H. F.

    2010-05-01

    The abiotic degradation of soil organic matter to volatile organic compounds was studied intensely over the last years (Keppler et al., 2000; Huber et al., 2009). It was shown that soil organic matter is oxidised due to the presence of iron (III), hydrogen peroxide and chloride and thereby produces diverse alkyl halides, which are emitted into the atmosphere. The formation of polar halogenated compounds like chlorinated acetic acids which are relevant toxic environmental substances was also found in soils and sediments (Kilian et al., 2002). The investigation of the formation of other polar halogenated and non-halogenated compounds like diverse mono- and dicarboxylic acids is going to attain more and more importance. Due to its high acidity oxalic acid might have impacts on the environment e.g., nutrient leaching, plant diseases and negative influence on microbial growth. In this study, the abiotic formation of oxalic acid in soil is examined. For a better understanding of natural degradation processes mechanistic studies were conducted using the model compound catechol as representative for structural elements of the humic substances and its reaction with iron (III) and hydrogen peroxide. Iron is one of the most abundant elements on earth and hydrogen peroxide is produced by bacteria or through incomplete reduction of oxygen. To find suitable parameters for an optimal reaction and a qualitative and quantitative analysis method the following reaction parameters are varied: concentration of iron (III) and hydrogen peroxide, time dependence, pH-value and influence of chloride. Analysis of oxalic acid was performed employing an ion chromatograph equipped with a conductivity detector. The time dependent reaction shows a relatively fast formation of oxalic acid, the optimum yield is achieved after 60 minutes. Compared to the concentration of catechol an excess of hydrogen peroxide as well as a low concentration of iron (III) are required. In absence of chloride the

  16. Effect of Green and White Tea Pretreatment on Remineralization of Demineralized Dentin by CPP-ACFP-An Invitro Microhardness Analysis

    PubMed Central

    Jose, Poornima; Sekar, Mahalaxmi

    2016-01-01

    Introduction Mechanical performance of dentine is of major significance for the overall function of the teeth. Remineralization of carious dentine is the ultimate goal in re-establishing the functionality of the affected tissue so as to regain and maintain the mechanical properties of dentine. Functional remineralization of the affected dentin involves stabilization of both inorganic and organic component, but Caesin Phosphopeptide Amorphous Calcium Flurophosphate (CPP-ACFP) stabilizes only inorganic content. Hence to stabilize organic content and to bring in functional remineralization the use of anticollagenolytic and antielastastic agent was considered for this study. Aim To assess and compare the remineralization of artificial carious dentin pre treated with white and green tea, before and after application of CPP-ACFP using microhardness test. Null hypothesis was that both teas did not have any effect on remineralization potential of CPP ACFP. Materials and Methods Forty specimens were subjected to artificial caries lesions and were randomly divided into 4 groups based on the application of tea extract followed by CPP-ACFP (groups A & B) and CPP-ACFP followed by tea extracts (groups C & D). All the specimens were subjected to two pH cycling regimen. The specimens were subjected to Vickers microhardness test to obtain the microhardness values. The values were statistically analysed using one-way ANOVA and multiple comparisons with Tukey’s HSD procedure. Results After the 1st and 2nd pH cycling in groups A and B, Group B showed significant increase in microhardness values (35.79± 3.12 VHN). But after the pH cycling regimen in groups C and D, microhardness values increased in 1st pH cycling (50.03± 3.64 VHN); (50.03±3.64 VHN), respectively but decreased during the 2nd pH cycling, (33.94±6.45 VHN); (33.11±6.11 VHN) respectively with the level of significance <0.05. Conclusion The results of this study rejects the hypothesis tested and showed that both the

  17. Morphological Study of Insoluble Organic Matter Residues from Primitive

    NASA Technical Reports Server (NTRS)

    Changela, H. G.; Stroud, R. M.; Peeters, Z.; Nittler, L. R.; Alexander, C. M. O'D.; DeGregorio, B. T.; Cody, G. D.

    2012-01-01

    Insoluble organic matter (IOM) constitutes a major proportion, 70-99%, of the total organic carbon found in primitive chondrites [1, 2]. One characteristic morphological component of IOM is nanoglobules [3, 4]. Some nanoglobules exhibit large N-15 and D enrichments relative to solar values, indicating that they likely originated in the ISM or the outskirts of the protoplanetary disk [3]. A recent study of samples from the Tagish Lake meteorite with varying levels of hydrothermal alteration suggest that nanoglobule abundance decreases with increasing hydrothermal alteration [5]. The aim of this study is to further document the morphologies of IOM from a range of primitive chondrites in order to determine any correlation of morphology with petrographic grade and chondrite class that could constrain the formation and/or alteration mechanisms.

  18. Nature and transformation of dissolved organic matter in treatment wetlands

    USGS Publications Warehouse

    Barber, L.B.; Leenheer, J.A.; Noyes, T.I.; Stiles, E.A.

    2001-01-01

    This investigation into the occurrence, character, and transformation of dissolved organic matter (DOM) in treatment wetlands in the western United States shows that (i) the nature of DOM in the source water has a major influence on transformations that occur during treatment, (ii) the climate factors have a secondary effect on transformations, (iii) the wetlands receiving treated wastewater can produce a net increase in DOM, and (iv) the hierarchical analytical approach used in this study can measure the subtle DOM transformations that occur. As wastewater treatment plant effluent passes through treatment wetlands, the DOM undergoes transformation to become more aromatic and oxygenated. Autochthonous sources are contributed to the DOM, the nature of which is governed by the developmental stage of the wetland system as well as vegetation patterns. Concentrations of specific wastewaterderived organic contaminants such as linear alkylbenzene sulfonate, caffeine, and ethylenediaminetetraacetic acid were significantly attenuated by wetland treatment and were not contributed by internal loading.

  19. Literature review of organic matter transport from marshes

    NASA Technical Reports Server (NTRS)

    Dow, D. D.

    1982-01-01

    A conceptual model for estimating a transport coefficient for the movement of nonliving organic matter from wetlands to the adjacent embayments was developed in a manner that makes it compatible with the Earth Resources Laboratory's Productive Capacity Model. The model, which envisages detritus movement from wetland pixels to the nearest land-water boundary followed by movement within the water column from tidal creeks to the adjacent embayment, can be transposed to deal with only the interaction between tidal water and the marsh or to estimate the transport from embayments to the adjacent coastal waters. The outwelling hypothesis postulated wetlands as supporting coastal fisheries either by exporting nutrients, such as inorganic nitrogen, which stimulated the plankton-based grazing food chain in the water column, or through the export of dissolved and particulate organic carbon which provided a benthic, detritus-based food web which provides the food source for the grazing food chain in a more indirect fashion.

  20. Carbon isotope fractionation of sapropelic organic matter during early diagenesis

    USGS Publications Warehouse

    Spiker, E. C.; Hatcher, P.G.

    1984-01-01

    Study of an algal, sapropelic sediment from Mangrove Lake, Bermuda shows that the mass balance of carbon and stable carbon isotopes in the major organic constituents is accounted for by a relatively straightforward model of selective preservation during diagenesis. The loss of 13C-enriched carbohydrates is the principal factor controlling the intermolecular mass balance of 13C in the sapropel. Results indicate that labile components are decomposed leaving as a residual concentrate in the sediment an insoluble humic substance that may be an original biochemical component of algae and associated bacteria. An overall decrease of up to about 4??? in the ?? 13C values of the organic matter is observed as a result of early diagenesis. ?? 1984.

  1. Ironing out the details of soil organic matter cycling: The unique role of Fe-bearing minerals in regulating organic matter transformation in soils

    NASA Astrophysics Data System (ADS)

    Heckman, K. A.; Lawrence, C. R.; Harden, J. W.; Crate, J.; Swanston, C.

    2015-12-01

    Interest in the influence of mineral chemistry on soil organic matter cycling has been steadily growing, with the role of iron specifically garnering a great deal of attention. Empirical evidence from both lab and field based studies suggest that the interactions of Fe-bearing minerals and colloidal Fe species are unique from the interactions of the soil mineral matrix as a whole and may have a disproportionate influence on soil organic matter. We present results from a suite of studies examining Fe-organic matter interactions which utilize a broad range of technical approaches and highlight the use of radiocarbon analysis in terrestrial carbon cycle studies. Data suggests that interaction of organics with Fe-bearing moieties induces consistent partitioning of organics between dissolved and surface bound organic matter pools, including significant consequences for N and P availability and biodegradability of soil organic matter. Selective dissolution techniques have revealed that Fe-humus complexes comprise a significant pool of soil organic matter which cycles on a shorter-term basis across a variety of ecosystems types, while sequential density separation combined with x-ray diffraction imply concentration and long-term preservation of N-rich organics on Fe-bearing crystalline mineral surfaces. Our results explore the unique and multifaceted roles of Fe in regulating organic matter transformation and preservation in a range of soil types.

  2. Dissolved organic matter photolysis in Canadian arctic thaw ponds

    NASA Astrophysics Data System (ADS)

    Laurion, Isabelle; Mladenov, Natalie

    2013-09-01

    The abundant thaw lakes and ponds in the circumarctic receive a new pool of organic carbon as permafrost peat soils degrade, which can be exposed to significant irradiance that potentially increases as climate warms and ice cover shortens. Exposure to sunlight is known to accelerate the transformation of dissolved organic matter (DOM) into molecules that can be more readily used by microbes. We sampled the water from two common classes of ponds found in the ice-wedge system of continuous permafrost regions of Canada, polygonal and runnel ponds, and followed the transformation of DOM over 12 days by looking at dissolved organic carbon (DOC) concentration and DOM absorption and fluorescence properties. The results indicate a relatively fast decay of color (3.4 and 1.6% loss d-1 of absorption at 320 nm for the polygonal and runnel pond, respectively) and fluorescence (6.1 and 8.3% loss d-1 of total fluorescent components, respectively) at the pond surface, faster in the case of humic-like components, but insignificant losses of DOC over the observed period. This result indicates that direct DOM mineralization (photochemical production of CO2) is apparently minor in thaw ponds compared to the photochemical transformation of DOM into less chromophoric and likely more labile molecules with a greater potential for microbial mineralization. Therefore, DOM photolysis in arctic thaw ponds can be considered as a catalytic mechanism, accelerating the microbial turnover of mobilized organic matter from thawing permafrost and the production of greenhouse gases, especially in the most shallow ponds. Under a warming climate, this mechanism will intensify as summers lengthen.

  3. Terrestrial and marine perspectives on modeling organic matter degradation pathways.

    PubMed

    Burd, Adrian B; Frey, Serita; Cabre, Anna; Ito, Takamitsu; Levine, Naomi M; Lønborg, Christian; Long, Matthew; Mauritz, Marguerite; Thomas, R Quinn; Stephens, Brandon M; Vanwalleghem, Tom; Zeng, Ning

    2016-01-01

    Organic matter (OM) plays a major role in both terrestrial and oceanic biogeochemical cycles. The amount of carbon stored in these systems is far greater than that of carbon dioxide (CO2 ) in the atmosphere, and annual fluxes of CO2 from these pools to the atmosphere exceed those from fossil fuel combustion. Understanding the processes that determine the fate of detrital material is important for predicting the effects that climate change will have on feedbacks to the global carbon cycle. However, Earth System Models (ESMs) typically utilize very simple formulations of processes affecting the mineralization and storage of detrital OM. Recent changes in our view of the nature of this material and the factors controlling its transformation have yet to find their way into models. In this review, we highlight the current understanding of the role and cycling of detrital OM in terrestrial and marine systems and examine how this pool of material is represented in ESMs. We include a discussion of the different mineralization pathways available as organic matter moves from soils, through inland waters to coastal systems and ultimately into open ocean environments. We argue that there is strong commonality between aspects of OM transformation in both terrestrial and marine systems and that our respective scientific communities would benefit from closer collaboration. PMID:26015089

  4. Photochemical and Nonphotochemical Transformations of Cysteine with Dissolved Organic Matter.

    PubMed

    Chu, Chiheng; Erickson, Paul R; Lundeen, Rachel A; Stamatelatos, Dimitrios; Alaimo, Peter J; Latch, Douglas E; McNeill, Kristopher

    2016-06-21

    Cysteine (Cys) plays numerous key roles in the biogeochemistry of natural waters. Despite its importance, a full assessment of Cys abiotic transformation kinetics, products and pathways under environmental conditions has not been conducted. This study is a mechanistic evaluation of the photochemical and nonphotochemical (dark) transformations of Cys in solutions containing chromophoric dissolved organic matter (CDOM). The results show that Cys underwent abiotic transformations under both dark and irradiated conditions. Under dark conditions, the transformation rates of Cys were moderate and were highly pH- and temperature-dependent. Under UVA or natural sunlight irradiations, Cys transformation rates were enhanced by up to two orders of magnitude compared to rates under dark conditions. Product analysis indicated cystine and cysteine sulfinic acid were the major photooxidation products. In addition, this study provides an assessment of the contributions of singlet oxygen, hydroxyl radical, hydrogen peroxide, and triplet dissolved organic matter to the CDOM-sensitized photochemical oxidation of Cys. The results suggest that another unknown pathway was dominant in the CDOM-sensitized photodegradation of Cys, which will require further study to identify. PMID:27172378

  5. Terrestrial and marine perspectives on modeling organic matter degradation pathways.

    PubMed

    Burd, Adrian B; Frey, Serita; Cabre, Anna; Ito, Takamitsu; Levine, Naomi M; Lønborg, Christian; Long, Matthew; Mauritz, Marguerite; Thomas, R Quinn; Stephens, Brandon M; Vanwalleghem, Tom; Zeng, Ning

    2016-01-01

    Organic matter (OM) plays a major role in both terrestrial and oceanic biogeochemical cycles. The amount of carbon stored in these systems is far greater than that of carbon dioxide (CO2 ) in the atmosphere, and annual fluxes of CO2 from these pools to the atmosphere exceed those from fossil fuel combustion. Understanding the processes that determine the fate of detrital material is important for predicting the effects that climate change will have on feedbacks to the global carbon cycle. However, Earth System Models (ESMs) typically utilize very simple formulations of processes affecting the mineralization and storage of detrital OM. Recent changes in our view of the nature of this material and the factors controlling its transformation have yet to find their way into models. In this review, we highlight the current understanding of the role and cycling of detrital OM in terrestrial and marine systems and examine how this pool of material is represented in ESMs. We include a discussion of the different mineralization pathways available as organic matter moves from soils, through inland waters to coastal systems and ultimately into open ocean environments. We argue that there is strong commonality between aspects of OM transformation in both terrestrial and marine systems and that our respective scientific communities would benefit from closer collaboration.

  6. Photosensitizing properties of water-extractable organic matter from soils.

    PubMed

    Nkhili, Ezzhora; Boguta, Patrycja; Bejger, Romualda; Guyot, Ghislain; Sokołowska, Zofia; Richard, Claire

    2014-01-01

    Water-extractable organic matter (WEOM) was extracted using pure water from two black soils and from the Elliott reference soil of the International Humic Substances Society (IHSS). WEOMs were characterized by chemical and spectroscopic methods. The apparent quantum yields of singlet oxygen, triplet excited states and hydroxyl radicals formation upon irradiation within the wavelength range 290-450 nm were determined using chemical probes and compared to those of standard Elliott humic substances. In general, the aromatic content, as measured by the SUVA value, was close in WEOMs and humic substances, while the E2/E3 was higher and the humification index lower in the former. Quantum yield values measured for WEOMs fell within the range of those found for basic medium extracted humic substances or were even higher in one case. Thus, water soluble aromatic moiety of the soil organic matter, especially those with low humification degree, is important for the photosensitizing properties. We also found that WEOMs sensitized the bisphenol A phototransformation with rates of the same order of magnitude for all the samples.

  7. Synergy of fresh and accumulated organic matter to bacterial growth.

    PubMed

    Farjalla, Vinicius F; Marinho, Claudio C; Faria, Bias M; Amado, André M; Esteves, Francisco de A; Bozelli, Reinaldo L; Giroldo, Danilo

    2009-05-01

    The main goal of this research was to evaluate whether the mixture of fresh labile dissolved organic matter (DOM) and accumulated refractory DOM influences bacterial production, respiration, and growth efficiency (BGE) in aquatic ecosystems. Bacterial batch cultures were set up using DOM leached from aquatic macrophytes as the fresh DOM pool and DOM accumulated from a tropical humic lagoon. Two sets of experiments were performed and bacterial growth was followed in cultures composed of each carbon substrate (first experiment) and by carbon substrates combined (second experiment), with and without the addition of nitrogen and phosphorus. In both experiments, bacterial production, respiration, and BGE were always higher in cultures with N and P additions, indicating a consistent inorganic nutrient limitation. Bacterial production, respiration, and BGE were higher in cultures set up with leachate DOM than in cultures set up with humic DOM, indicating that the quality of the organic matter pool influenced the bacterial growth. Bacterial production and respiration were higher in the mixture of substrates (second experiment) than expected by bacterial production and respiration in single substrate cultures (first experiment). We suggest that the differences in the concentration of some compounds between DOM sources, the co-metabolism on carbon compound decomposition, and the higher diversity of molecules possibly support a greater bacterial diversity which might explain the higher bacterial growth observed. Finally, our results indicate that the mixture of fresh labile and accumulated refractory DOM that naturally occurs in aquatic ecosystems could accelerate the bacterial growth and bacterial DOM removal. PMID:18985269

  8. Black Carbon - Soil Organic Matter abiotic and biotic interactions

    NASA Astrophysics Data System (ADS)

    Cotrufo, Francesca; Boot, Claudia; Denef, Karolien; Foster, Erika; Haddix, Michelle; Jiang, Xinyu; Soong, Jennifer; Stewart, Catherine

    2014-05-01

    Wildfires, prescribed burns and the use of char as a soil amendment all add large quantities of black carbon to soils, with profound, yet poorly understood, effects on soil biology and chemical-physical structure. We will present results emerging from our black carbon program, which addresses questions concerning: 1) black carbon-soil organic matter interactions, 2) char decomposition and 3) impacts on microbial community structure and activities. Our understanding derives from a complementary set of post-fire black carbon field surveys and laboratory and field experiments with grass and wood char amendments, in which we used molecular (i.e., BPCA, PLFA) and isotopic (i.e., 13C and 15N labelled char) tracers. Overall, emerging results demonstrate that char additions to soil are prone to fast erosion, but a fraction remains that increases water retention and creates a better environment for the microbial community, particularly favoring gram negative bacteria. However, microbial decomposition of black carbon only slowly consumes a small fraction of it, thus char still significantly contributes to soil carbon sequestration. This is especially true in soils with little organic matter, where black carbon additions may even induce negative priming.

  9. Wastewater disinfection and organic matter removal using ferrate (VI) oxidation.

    PubMed

    Bandala, Erick R; Miranda, Jocelyn; Beltran, Margarita; Vaca, Mabel; López, Raymundo; Torres, Luis G

    2009-09-01

    The use of iron in a +6 valence state, (Fe (VI), as FeO4(-2)) was tested as a novel alternative for wastewater disinfection and decontamination. The removal of organic matter (OM) and index microorganisms present in an effluent of a wastewater plant was determined using FeO4(-2) without any pH adjustment. It was observed that concentrations of FeO4(-2) ranging between 5 and 14 mg l(-1) inactivated up to 4-log of the index microorganisms (initial concentration c.a. 10(6) CFU/100 ml) and achieved OM removal up to almost 50%. The performance of FeO4(-2) was compared with OM oxidation and disinfection using hypochlorite. It was observed that hypochlorite was less effective in OM oxidation and coliform inactivation than ferrate. Results of this work suggest that FeO4(-2) could be an interesting oxidant able to deactivate pathogenic microorganisms in water with high OM content and readily oxidize organic matter without jeopardizing its efficiency on microorganism inactivation.

  10. Wastewater disinfection and organic matter removal using ferrate (VI) oxidation.

    PubMed

    Bandala, Erick R; Miranda, Jocelyn; Beltran, Margarita; Vaca, Mabel; López, Raymundo; Torres, Luis G

    2009-09-01

    The use of iron in a +6 valence state, (Fe (VI), as FeO4(-2)) was tested as a novel alternative for wastewater disinfection and decontamination. The removal of organic matter (OM) and index microorganisms present in an effluent of a wastewater plant was determined using FeO4(-2) without any pH adjustment. It was observed that concentrations of FeO4(-2) ranging between 5 and 14 mg l(-1) inactivated up to 4-log of the index microorganisms (initial concentration c.a. 10(6) CFU/100 ml) and achieved OM removal up to almost 50%. The performance of FeO4(-2) was compared with OM oxidation and disinfection using hypochlorite. It was observed that hypochlorite was less effective in OM oxidation and coliform inactivation than ferrate. Results of this work suggest that FeO4(-2) could be an interesting oxidant able to deactivate pathogenic microorganisms in water with high OM content and readily oxidize organic matter without jeopardizing its efficiency on microorganism inactivation. PMID:19491501

  11. Photochemical and Nonphotochemical Transformations of Cysteine with Dissolved Organic Matter.

    PubMed

    Chu, Chiheng; Erickson, Paul R; Lundeen, Rachel A; Stamatelatos, Dimitrios; Alaimo, Peter J; Latch, Douglas E; McNeill, Kristopher

    2016-06-21

    Cysteine (Cys) plays numerous key roles in the biogeochemistry of natural waters. Despite its importance, a full assessment of Cys abiotic transformation kinetics, products and pathways under environmental conditions has not been conducted. This study is a mechanistic evaluation of the photochemical and nonphotochemical (dark) transformations of Cys in solutions containing chromophoric dissolved organic matter (CDOM). The results show that Cys underwent abiotic transformations under both dark and irradiated conditions. Under dark conditions, the transformation rates of Cys were moderate and were highly pH- and temperature-dependent. Under UVA or natural sunlight irradiations, Cys transformation rates were enhanced by up to two orders of magnitude compared to rates under dark conditions. Product analysis indicated cystine and cysteine sulfinic acid were the major photooxidation products. In addition, this study provides an assessment of the contributions of singlet oxygen, hydroxyl radical, hydrogen peroxide, and triplet dissolved organic matter to the CDOM-sensitized photochemical oxidation of Cys. The results suggest that another unknown pathway was dominant in the CDOM-sensitized photodegradation of Cys, which will require further study to identify.

  12. CO2 Losses from Terrestrial Organic Matter through Photodegradation

    NASA Astrophysics Data System (ADS)

    Rutledge, S.; Campbell, D. I.; Baldocchi, D. D.; Schipper, L. A.

    2010-12-01

    Net ecosystem exchange (NEE) is the sum of CO2 uptake by plants and CO2 losses from both living plants and dead organic matter. In all but a few ecosystem scale studies on terrestrial carbon cycling, losses of CO2 from dead organic matter are assumed to be the result of microbial respiration alone. Here we provide evidence for an alternative, previously largely underestimated mechanism for ecosystem-scale CO2 emissions. The process of photodegradation, the direct breakdown of organic matter by solar radiation, was found to contribute substantially to the ecosystem scale CO2 losses at both a bare peatland in New Zealand, and a summer-dead grassland in California. Comparisons of daytime eddy covariance (EC) data with data collected at the same time using an opaque chamber and the CO2 soil gradient technique, or with night-time EC data collected during similar moisture and temperature conditions were used to quantify the direct effect of exposure of organic matter to solar radiation. At a daily scale, photodegradation contributed up to 62% and 92% of summer mid-day CO2 fluxes at the de-vegetated peatland and at the grassland during the dry season, respectively. Irradiance-induced CO2 losses were estimated to be 19% of the total annual CO2 loss at the peatland, and almost 60% of the dry season CO2 loss at the grassland. Small-scale measurements using a transparent chamber confirmed that CO2 emissions from air-dried peat and grass occurred within seconds of exposure to light when microbial activity was inhibited. Our findings imply that photodegradation could be important for many ecosystems with exposed soil organic matter, litter and/or standing dead material. Potentially affected ecosystems include sparsely vegetated arid and semi-arid ecosystems (e.g. shrublands, savannahs and other grasslands), bare burnt areas, agricultural sites after harvest or cultivation (especially if crop residues are left on the surface), deciduous forests after leaf fall, or ecosystems

  13. Land Application of Wastes: An Educational Program. Organic Matter - Module 17, Objectives, and Script.

    ERIC Educational Resources Information Center

    Clarkson, W. W.; And Others

    This module sketches out the impact of sewage organic matter on soils. For convenience, that organic matter is separated into the readily decomposable compounds and the more resistant material (volatile suspended solids, refractory organics, and sludges). The fates of those organics are reviewed along with loading rates and recommended soil…

  14. Climate Change Impacts on Soil Organic Matter: New Insights from Molecular-Level Studies

    NASA Astrophysics Data System (ADS)

    Simpson, M. J.; Feng, X.; Simpson, A.

    2009-05-01

    Natural organic matter is ubiquitously found in the environment and plays a critical role in several biogeochemical processes such as the regulation of atmospheric CO2, agricultural sustainability, and the fate and transport of problematic organic chemicals in the environment. Organic matter preserved within the sedimentary record also holds key information about early life on earth, insights into past climates, and the presence of specific organic matter structures is often used in the search for life on other planets. Despite the importance of natural organic matter in several disciplines, the vast majority of organic matter remains "molecularly uncharacterized" (Hedges et al. 2000, Org. Geochem. 31:945-958). The lack of organic matter structural information is mostly due to the complex nature and uniqueness of organic matter but also due to the lack of sophisticated analytical strategies designed specifically for the study of organic matter structure and environmental reactivity. Organic matter is a collection of compounds from various plant, microbial, and anthropogenic sources, all at various stages of oxidation (decomposition) and represents the most naturally occurring complex mixture on earth. Organic geochemists have long used biomarker methods to study the sources, structures, and stage of organic matter oxidation however biomarker methods only extract and measure a small fraction of the total organic matter composition. Nuclear magnetic resonance (NMR), namely solid-state 13C NMR spectroscopy, has been used extensively to study organic matter structure but suffers from poor spectral resolution due to organic matter heterogeneity and strong dipolar coupling in solids. This presentation will highlight the development of molecular-level analytical methods for organic matter and demonstrate their utility in studying soil organic matter biogeochemistry with global warming. The use of biomarker methods with conventional and innovative NMR methods in tandem

  15. Sulfur species behavior in soil organic matter during decomposition

    USGS Publications Warehouse

    Schroth, A.W.; Bostick, B.C.; Graham, M.; Kaste, J.M.; Mitchell, M.J.; Friedland, A.J.

    2007-01-01

    Soil organic matter (SOM) is a primary re??servoir of terrestrial sulfur (S), but its role in the global S cycle remains poorly understood. We examine S speciation by X-ray absorption near-edge structure (XANES) spectroscopy to describe S species behavior during SOM decomposition. Sulfur species in SOM were best represented by organic sulfide, sulfoxide, sulfonate, and sulfate. The highest fraction of S in litter was organic sulfide, but as decomposition progressed, relative fractions of sulfonate and sulfate generally increased. Over 6-month laboratory incubations, organic sulfide was most reactive, suggesting that a fraction of this species was associated with a highly labile pool of SOM. During humification, relative concentrations of sulfoxide consistently decreased, demonstrating the importance of sulfoxide as a reactive S phase in soil. Sulfonate fractional abundance increased during humification irrespective of litter type, illustrating its relative stability in soils. The proportion of S species did not differ systematically by litter type, but organic sulfide became less abundant in conifer SOM during decomposition, while sulfate fractional abundance increased. Conversely, deciduous SOM exhibited lesser or nonexistent shifts in organic sulfide and sulfate fractions during decomposition, possibly suggesting that S reactivity in deciduous litter is coupled to rapid C mineralization and independent of S speciation. All trends were consistent in soils across study sites. We conclude that S reactivity is related to spqciation in SOM, particularly in conifer forests, and S species fractions in SOM change, during decomposition. Our data highlight the importance of intermediate valence species (sulfoxide and sulfonate) in the pedochemical cycling of organic bound S. Copyright 2007 by the American Geophysical Union.

  16. Potential enzyme activities in cryoturbated organic matter of arctic soils

    NASA Astrophysics Data System (ADS)

    Schnecker, J.; Wild, B.; Rusalimova, O.; Mikutta, R.; Guggenberger, G.; Richter, A.

    2012-12-01

    An estimated 581 Gt organic carbon is stored in arctic soils that are affected by cryoturbtion, more than in today's atmosphere (450 Gt). The high amount of organic carbon is, amongst other factors, due to topsoil organic matter (OM) that has been subducted by freeze-thaw processes. This cryoturbated OM is usually hundreds to thousands of years old, while the chemical composition remains largely unaltered. It has therefore been suggested, that the retarded decomposition rates cannot be explained by unfavourable abiotic conditions in deeper soil layers alone. Since decomposition of soil organic material is dependent on extracellular enzymes, we measured potential and actual extracellular enzyme activities in organic topsoil, mineral subsoil and cryoturbated material from three different tundra sites, in Zackenberg (Greenland) and Cherskii (North-East Siberia). In addition we analysed the microbial community structure by PLFAs. Hydrolytic enzyme activities, calculated on a per gram dry mass basis, were higher in organic topsoil horizons than in cryoturbated horizons, which in turn were higher than in mineral horizons. When calculated on per gram carbon basis, the activity of the carbon acquiring enzyme exoglucanase was not significantly different between cryoturbated and topsoil organic horizons in any of the three sites. Oxidative enzymes, i.e. phenoloxidase and peroxidase, responsible for degradation of complex organic substances, showed higher activities in topsoil organic and cryoturbated horizons than in mineral horizons, when calculated per gram dry mass. Specific activities (per g C) however were highest in mineral horizons. We also measured actual cellulase activities (by inhibiting microbial uptake of products and without substrate addition): calculated per g C, the activities were up to ten times as high in organic topsoil compared to cryoturbated and mineral horizons, the latter not being significantly different. The total amount of PLFAs, as a proxy for

  17. DETOXIFICATION OF OUTFALL WATER USING NATURAL ORGANIC MATTER

    SciTech Connect

    Halverson, N.; Looney, B.; Millings, M.; Nichols, R.; Noonkester, J.; Payne, B.

    2010-07-13

    To protect stream organisms in an ephemeral stream at the Savannah River Site, a proposed National Pollutant Discharge Elimination System (NPDES) permit reduced the copper limit from 25 {micro}g/l to 6 {micro}g/l at Outfall H-12. Efforts to reduce copper in the wastewater and stormwater draining to this outfall did not succeed in bringing copper levels below this limit. Numerous treatment methods were considered, including traditional methods such as ion exchange and natural treatment alternatives such as constructed wetlands and peat beds, all of which act to remove copper. However, the very low target metal concentration and highly variable outfall conditions presented a significant challenge for these treatment technologies. In addition, costs and energy use for most of these alternatives were high and secondary wastes would be generated. The Savannah River National Laboratory developed an entirely new 'detoxification' approach to treat the outfall water. This simple, lower-cost detoxification system amends outfall water with natural organic matter to bind up to 25 {micro}g/l copper rather than remove it, thereby mitigating its toxicity and protecting the sensitive species in the ecosystem. The amendments are OMRI (Organic Materials Review Institute) certified commercial products that are naturally rich in humic acids and are commonly used in organic farming.

  18. Spectroscopic characterization of dissolved organic matter isolated from rainwater.

    PubMed

    Santos, Patrícia S M; Otero, Marta; Duarte, Regina M B O; Duarte, Armando C

    2009-02-01

    Rainwater is a matrix containing extremely low concentrations (in the range of muM C) of dissolved organic carbon (DOC) and for its characterization, an efficient extraction procedure is essential. A recently developed procedure based on adsorption onto XAD-8 and XAD-4 resins in series was used in this work for the extraction and isolation of rainwater dissolved organic matter (DOM). Prior to the isolation and fractionation of DOM, and to obtain sufficient mass for the spectroscopic analyses, individual rainwater samples were batched together according to similar meteorological conditions on a total of three composed samples. The results of the isolation procedure indicated that the resin tandem procedure is not applicable for rainwater DOM since the XAD-4 resin caused samples contamination. On the other hand, the XAD-8 resin allowed DOM recoveries of 39.9-50.5% of the DOC of the original combined samples. This recovered organic fraction was characterized by UV-visible, molecular fluorescence, FTIR-ATR and 1H NMR spectroscopies. The chemical characterization of the rainwater DOM showed that the three samples consist mostly of hydroxylated and carboxylic acids with a predominantly aliphatic character, containing a minor component of aromatic structures. The obtained results suggest that the DOM in rainwater, and consequently in the precursor atmospheric particles, may have a secondary origin via the oxidation of volatile organic compounds from different origins.

  19. Iron traps terrestrially derived dissolved organic matter at redox interfaces.

    PubMed

    Riedel, Thomas; Zak, Dominik; Biester, Harald; Dittmar, Thorsten

    2013-06-18

    Reactive iron and organic carbon are intimately associated in soils and sediments. However, to date, the organic compounds involved are uncharacterized on the molecular level. At redox interfaces in peatlands, where the biogeochemical cycles of iron and dissolved organic matter (DOM) are coupled, this issue can readily be studied. We found that precipitation of iron hydroxides at the oxic surface layer of two rewetted fens removed a large fraction of DOM via coagulation. On aeration of anoxic fen pore waters, >90% of dissolved iron and 27 ± 7% (mean ± SD) of dissolved organic carbon were rapidly (within 24 h) removed. Using ultra-high-resolution MS, we show that vascular plant-derived aromatic and pyrogenic compounds were preferentially retained, whereas the majority of carboxyl-rich aliphatic acids remained in solution. We propose that redox interfaces, which are ubiquitous in marine and terrestrial settings, are selective yet intermediate barriers that limit the flux of land-derived DOM to oceanic waters. PMID:23733946

  20. Hydrogen and carbon isotopes of petroleum and related organic matter

    NASA Astrophysics Data System (ADS)

    Yeh, Hsueh-Wen; Epstein, Samuel

    1981-05-01

    D/H and 13C /12C ratios were measured for 114 petroleum samples and for several samples of related organic matter. δD of crude oil ranges from -85 to -181‰, except for one distillate (-250‰) from the Kenai gas field; δ13C of crude oil ranges from -23.3 to -32.5‰, Variation in δD and δ13C values of compound-grouped fractions of a crude oil is small, 3 and 1.1%., respectively, and the difference in δD and δ13C between oil and coeval wax is slight. Gas fractions are 53-70 and 22.6-23.2‰ depleted in D and 13C, respectively, relative to the coexisting oil fractions. The δD and δ13C values of the crude oils appear to be largely determined by the isotopic compositions of their organic precursors. The contribution of terrestrial organic debris to the organic precursors of most marine crude oils may be significant.

  1. Alterations in enamel remineralization in vitro induced by blue light

    NASA Astrophysics Data System (ADS)

    Kato, I. T.; Zezell, D. M.; Mendes, F. M.; Wetter, N. U.

    2010-06-01

    Blue light, especially from LED devices, is a very frequently used tool in dental procedures. However, the investigations of its effects on dental enamel are focused primarily on enamel demineralization and fluoride retention. Despite the fact that this spectral region can inhibit enamel demineralization, the effects of the irradiation on demineralized enamel are not known. For this reason, we evaluated the effects of blue LED on remineralization of dental enamel. Artificial lesions were formed in bovine dental enamel blocks by immersing the samples in undersaturated acetate buffer. The lesions were irradiated with blue LED (455 nm, 1.38 W/cm2, 13.75 J/cm2, and 10 s) and remineralization was induced by pH-cycling process. Cross-sectional hardness was used to asses mineral changes after remineralization. Non-irradiated enamel lesions presented higher mineral content than irradiated ones. Furthermore, the mineral content of irradiated group was not significantly different from the lesion samples that were not submitted to the remineralization process. Results obtained in the present study show that the blue light is not innocuous for the dental enamel and inhibition of its remineralization can occur.

  2. The impact of meter-scale oxygen gradients in the selective degradation of organic matter: implications for proxy interpretation

    NASA Astrophysics Data System (ADS)

    Bogus, K.; Zonneveld, K. A.; Fischer, D.; Kasten, S.; Versteegh, G.

    2010-12-01

    The reconstruction of upper oceanographic conditions is often founded on organic matter-based proxies that have their origin within the photic zone and measurably reflect these conditions. It is well known that only a fraction of the organic matter that is produced in the upper water column reaches the sea floor where it is further degraded by aerobic and anaerobic remineralization processes. During the last decades it has become clear that preservation is highly selective and can, depending on the proxy used, severely influence the proxy outcome. One of the main factors that can influence the preservation of organic matter is the presence of oxygen. Therefore, for an adequate interpretation of proxy signals, it is essential to obtain insight as to how the extent of oxygen availability might alter the proxy outcome. Until now, the majority of studies investigating the impact of selective aerobic degradation on organic matter-based proxies have suffered from a priori environmental spatial heterogeneity. In other words, a large distance between sample locations introduces a source of error in that additional factors, such as lateral transport and differing photic zone conditions, cannot be completely discounted as contributing reasons for a change in proxy ratios during interpretation. This degree of uncertainty makes it difficult to separate initial environmentally-induced heterogeneity, such as varying temperatures and nutrient levels, from those induced by selective aerobic degradation. In order to constrain these problems and evaluate the extent of early selective aerobic degradation on proxies in surface sediments, we restricted sampling distance to meter-scale oxygen gradients existing on the margins of cold seeps in the northeastern Arabian Sea. These samples were retrieved along a gradient from the methane pocket to the outer rim of the methane-influenced area by computer-steered push coring using the ROV Quest during RV Meteor cruise M74/3 in November 2007

  3. Measuring Organic Matter with COSIMA on Board Rosetta

    NASA Astrophysics Data System (ADS)

    Briois, C.; Baklouti, D.; Bardyn, A.; Cottin, H.; Engrand, C.; Fischer, H.; Fray, N.; Godard, M.; Hilchenbach, M.; von Hoerner, H.; Höfner, H.; Hornung, K.; Kissel, J.; Langevin, Y.; Le Roy, L.; Lehto, H.; Lehto, K.; Orthous-Daunay, F. R.; Revillet, C.; Rynö, J.; Schulz, R.; Silen, J. V.; Siljeström, S.; Thirkell, L.

    2014-12-01

    Comets are believed to contain the most pristine material of our Solar System materials and therefore to be a key to understand the origin of the Solar System, and the origin of life. Remote sensing observations have led to the detection of more than twenty simple organic molecules (Bockelée-Morvan et al., 2004; Mumma and Charnley, 2011). Experiments on-board in-situ exploration missions Giotto and Vega and the recent Stardust sample return missions have shown that a significant fraction of the cometary grains consists of organic matter. Spectra showed that both the gaseous (Mitchell et al., 1992) and the solid phase (grains) (Kissel and Krueger, 1987) contained organic molecules with higher masses than those of the molecules detected by remote sensing techniques in the gaseous phase. Some of the grains analyzed in the atmosphere of comet 1P/Halley seem to be essentially made of a mixture of carbon, hydrogen, oxygen and nitrogen (CHON grains, Fomenkova, 1999). Rosetta is an unparalleled opportunity to make a real breakthrough into the nature of cometary matter, both in the gas and in the solid phase. The dust mass spectrometer COSIMA on Rosetta will analyze organic and inorganic phases in the dust. The organic phases may be refractory, but some organics may evaporate with time from the dust and lead to an extended source in the coma. Over the last years, we have prepared the cometary rendezvous by the analysis of various samples with the reference model of COSIMA. We will report on this calibration data set and on the first results of the in-situ analysis of cometary grains as captured, imaged and analyzed by COSIMA. References : Bockelée-Morvan, D., et al. 2004. (Eds.), Comets II. the University of Arizona Press, Tucson, USA, pp. 391-423 ; Fomenkova, M.N., 1999. Space Science Reviews 90, 109-114 ; Kissel, J., Krueger, F.R., 1987. Nature 326, 755-760 ; Mitchell, et al. 1992. Icarus 98, 125-133 ; Mumma, M.J., Charnley, S.B., 2011. Annual Review of Astronomy and

  4. Organic matter loss from cultivated peat soils in Sweden

    NASA Astrophysics Data System (ADS)

    Berglund, Örjan; Berglund, Kerstin

    2015-04-01

    The degradation of drained peat soils in agricultural use is an underestimated source of loss of organic matter. Oxidation (biological degradation) of agricultural peat soils causes a loss of organic matter (OM) of 11 - 22 t ha-1 y-1 causing a CO2 emission of 20 - 40 t ha-1 y-1. Together with the associated N2O emissions from mineralized N this totals in the EU to about 98.5 Mton CO2 eq per year. Peat soils are very prone to climate change and it is expected that at the end of this century these values are doubled. The degradation products pollute surface waters. Wind erosion of peat soils in arable agriculture can cause losses of 3 - 30 t ha-1 y-1 peat also causing air pollution (fine organic particles). Subsidence rates are 1 - 2 cm per year which leads to deteriorating drainage effect and make peat soils below sea or inland water levels prone to flooding. Flooding agricultural peat soils is in many cases not possible without high costs, high GHG emissions and severe water pollution. Moreover sometimes cultural and historic landscapes are lost and meadow birds areas are lost. In areas where the possibility to regulate the water table is limited the mitigation options are either to increase biomass production that can be used as bioenergy to substitute some fossil fuel, try to slow down the break-down of the peat by different amendments that inhibit microbial activity, or permanent flooding. The negative effects of wind erosion can be mitigated by reducing wind speed or different ways to protect the soil by crops or fiber sheets. In a newly started project in Sweden a typical peat soil with and without amendment of foundry sand is cropped with reed canary grass, tall fescue and timothy to investigate the yield and greenhouse gas emissions from the different crops and how the sand effect the trafficability and GHG emissions.

  5. BiOMAS: Biochip for Organic Matter Analysis in Space

    NASA Astrophysics Data System (ADS)

    Dobrijevic, Michel; Incerti, Sebastien; Baque, Mickael; Le Postollec, Aurelie; Coussot, Gaelle; Moretto, Philippe; Vandenabeele Trambouze, Odile

    The search for the first steps of a prebiotic chemistry and the detection of life in the Solar System are ones of the great challenges of new upcoming space missions. In particular, some instruments will be designed to detect traces of organic matter on extra-terrestrial objects like Mars, Titan, comets, etc. A new and promising technique based on biochips is recommended by space agencies (ESA and NASA). A biochip is a miniaturized device composed of biological sensitive systems grafted on a slide. It allows the quantification of numerous target molecules simultaneously (from hundreds to thousands). With the support of the French space agency (CNES), our team currently develops a biochip especially designed for planetary exploration. The BiOMAS (Biochip for Organic Matter Analysis in Space) project, in progress for four years, has an interdisciplinary dimension bringing together specialists evolving in different area (planetology, physics, chemistry, biology and materials science) and developing complementary competences. A space biochip should be highly sensitive, specific and robust, allowing the detection of traces of various organic molecules (individuals and families). Since the conception of the biochip is at the heart of the instrumental specification, our aim is to optimize all the components (including the slide material, the ligands, the chemical bonds and the detection system) in order to meet both analytical and space constraints. Two different types of ligands (antibodies and aptamers) are under study to reach this objective. In space conditions, a lot of constraints might alter the efficiency of this analytical tool (irradiation by cosmic rays, temperature variations, vacuum, long duration mission, etc). Therefore, designing such a biochip requires testing the resistance of all its components to space conditions. Main concepts and current developments of the project are presented.

  6. Significance of Isotopically Labile Organic Hydrogen in Thermal Maturation of Organic Matter

    SciTech Connect

    Arndt Schimmelmann; Maria Mastalerz

    2010-03-30

    Isotopically labile organic hydrogen in fossil fuels occupies chemical positions that participate in isotopic exchange and in chemical reactions during thermal maturation from kerogen to bitumen, oil and gas. Carbon-bound organic hydrogen is isotopically far less exchangeable than hydrogen bound to nitrogen, oxygen, or sulfur. We explore why organic hydrogen isotope ratios express a relationship with organic nitrogen isotope ratios in kerogen at low to moderate maturity. We develop and apply new techniques to utilize organic D/H ratios in organic matter fractions and on a molecular level as tools for exploration for fossil fuels and for paleoenvironmental research. The scope of our samples includes naturally and artificially matured substrates, such as coal, shale, oil and gas.

  7. SNC Meteorites, Organic Matter and a New Look at Viking

    NASA Technical Reports Server (NTRS)

    Warmflash, David M.; Clemett, Simon J.; McKay, David S.

    2001-01-01

    Recently, evidence has begun to grow supporting the possibility that the Viking GC-MS would not have detected certain carboxylate salts that could have been present as metastable oxidation products of high molecular weight organic species. Additionally, despite the instrument's high sensitivity, the possibility had remained that very low levels of organic matter, below the instrument's detection limit, could have been present. In fact, a recent study indicates that the degradation products of several million microorganisms per gram of soil on Mars would not have been detected by the Viking GC-MS. Since the strength of the GC-MS findings was considered enough to dismiss the biology packet, particularly the LR results, any subsequent evidence suggesting that organic molecules may in fact be present on the Martian surface necessitates a re-evaluation of the Viking LR data. In addition to an advanced mass spectrometer to look for isotopic signatures of biogenic processes, future lander missions will include the ability to detect methane produced by methanogenic bacteria, as well as techniques based on biotechnology. Meanwhile, the identification of Mars samples already present on Earth in the form of the SNC meteorites has provided us with the ability to study samples of the Martian upper crust a decade or more in advance of any planned sample return missions. While contamination issues are of serious concern, the presence of indigenous organic matter in the form of polycyclic aromatic hydrocarbons has been detected in the Martian meteorites ALH84001 and Nakhla, while there is circumstantial evidence for carbonaceous material in Chassigny. The radiochronological ages of these meteorites are 4.5 Ga, 1.3 Ga, and 165 Ma respectively representing a span of time in Earth history from the earliest single-celled organisms to the present day. Given this perspective on organic material, a biological interpretation to the Viking LR results can no longer be ruled out. In the LR

  8. Quality of fresh organic matter affects priming of soil organic matter and substrate utilization patterns of microbes

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Boutton, Thomas W.; Xu, Wenhua; Hu, Guoqing; Jiang, Ping; Bai, Edith

    2015-05-01

    Changes in biogeochemical cycles and the climate system due to human activities are expected to change the quantity and quality of plant litter inputs to soils. How changing quality of fresh organic matter (FOM) might influence the priming effect (PE) on soil organic matter (SOM) mineralization is still under debate. Here we determined the PE induced by two 13C-labeled FOMs with contrasting nutritional quality (leaf vs. stalk of Zea mays L.). Soils from two different forest types yielded consistent results: soils amended with leaf tissue switched faster from negative PE to positive PE due to greater microbial growth compared to soils amended with stalks. However, after 16 d of incubation, soils amended with stalks had a higher PE than those amended with leaf. Phospholipid fatty acid (PLFA) results suggested that microbial demand for carbon and other nutrients was one of the major determinants of the PE observed. Therefore, consideration of both microbial demands for nutrients and FOM supply simultaneously is essential to understand the underlying mechanisms of PE. Our study provided evidence that changes in FOM quality could affect microbial utilization of substrate and PE on SOM mineralization, which may exacerbate global warming problems under future climate change.

  9. Quality of fresh organic matter affects priming of soil organic matter and substrate utilization patterns of microbes.

    PubMed

    Wang, Hui; Boutton, Thomas W; Xu, Wenhua; Hu, Guoqing; Jiang, Ping; Bai, Edith

    2015-01-01

    Changes in biogeochemical cycles and the climate system due to human activities are expected to change the quantity and quality of plant litter inputs to soils. How changing quality of fresh organic matter (FOM) might influence the priming effect (PE) on soil organic matter (SOM) mineralization is still under debate. Here we determined the PE induced by two (13)C-labeled FOMs with contrasting nutritional quality (leaf vs. stalk of Zea mays L.). Soils from two different forest types yielded consistent results: soils amended with leaf tissue switched faster from negative PE to positive PE due to greater microbial growth compared to soils amended with stalks. However, after 16 d of incubation, soils amended with stalks had a higher PE than those amended with leaf. Phospholipid fatty acid (PLFA) results suggested that microbial demand for carbon and other nutrients was one of the major determinants of the PE observed. Therefore, consideration of both microbial demands for nutrients and FOM supply simultaneously is essential to understand the underlying mechanisms of PE. Our study provided evidence that changes in FOM quality could affect microbial utilization of substrate and PE on SOM mineralization, which may exacerbate global warming problems under future climate change. PMID:25960162

  10. Quality of fresh organic matter affects priming of soil organic matter and substrate utilization patterns of microbes.

    PubMed

    Wang, Hui; Boutton, Thomas W; Xu, Wenhua; Hu, Guoqing; Jiang, Ping; Bai, Edith

    2015-01-01

    Changes in biogeochemical cycles and the climate system due to human activities are expected to change the quantity and quality of plant litter inputs to soils. How changing quality of fresh organic matter (FOM) might influence the priming effect (PE) on soil organic matter (SOM) mineralization is still under debate. Here we determined the PE induced by two (13)C-labeled FOMs with contrasting nutritional quality (leaf vs. stalk of Zea mays L.). Soils from two different forest types yielded consistent results: soils amended with leaf tissue switched faster from negative PE to positive PE due to greater microbial growth compared to soils amended with stalks. However, after 16 d of incubation, soils amended with stalks had a higher PE than those amended with leaf. Phospholipid fatty acid (PLFA) results suggested that microbial demand for carbon and other nutrients was one of the major determinants of the PE observed. Therefore, consideration of both microbial demands for nutrients and FOM supply simultaneously is essential to understand the underlying mechanisms of PE. Our study provided evidence that changes in FOM quality could affect microbial utilization of substrate and PE on SOM mineralization, which may exacerbate global warming problems under future climate change.

  11. Influence of land use on soil organic matter

    NASA Astrophysics Data System (ADS)

    Rogeon, H.; Lemée, L.; Chabbi, A.; Ambles, A.

    2009-04-01

    Soil organic matter (SOM) is actually of great environmental interest as the amount of organic matter stored in soils represents one of the largest reservoirs of organic carbon on the global scale [1]. Indeed, soil carbon storage capacity represents 1500 to 2000 Gt for the first meter depth, which is twice the concentration of atmospheric CO2 [2]. Furthermore, human activities, such as deforestation (which represents a flux of 1.3 Gt C/year), contribute to the increase in atmospheric CO2 concentration for about one percent a year [3]. Therefore, carbon dioxide sequestration in plant and carbon storage in soil and biomass could be considered as a complementary solution against climate change. The stock of carbon in soils is greatly influenced by land use (ca 70 Gt for a forest soil or a grassland against 40 Gt for an arable land). Furthermore the molecular composition of SOM should be also influenced by vegetation. In this context, four horizons taken between 0-120 cm from the same profile of a soil under grassland and forest located in the vicinity of Poitiers (INRA Lusignan, ORE Prairie) were compared. For the surface horizon, the study is improved with the results from the cultivated soil from INRA Versailles. Soil organic matter was characterized using IR spectroscopy, elemental analysis and thermal analysis. Granulometric fractionation into sand (50-2000 μm), silt (2-50 μm) and clay (<2 μm) was conducted. The organic matter associated with the mineral fractions was thus characterized using thermochemolysis coupled with gas chromatography and mass spectrometry (Py-GC/MS). The total lipidic fractions were extracted with CH2Cl2/MeOH using an accelerated solvent extraction (ASE). In the three soils, lipids are concentrated into the superficial horizon (0-30 cm) which indicates a low mobilisation. Lipids from the superficial horizon are more abundant for the arable soil (1010 ppm) than for the two other (400 ppm). Lipids from the forest and the grassland were

  12. Storage and turnover of organic matter in soil

    SciTech Connect

    Torn, M.S.; Swanston, C.W.; Castanha, C.; Trumbore, S.E.

    2008-07-15

    Historically, attention on soil organic matter (SOM) has focused on the central role that it plays in ecosystem fertility and soil properties, but in the past two decades the role of soil organic carbon in moderating atmospheric CO{sub 2} concentrations has emerged as a critical research area. This chapter will focus on the storage and turnover of natural organic matter in soil (SOM), in the context of the global carbon cycle. Organic matter in soils is the largest carbon reservoir in rapid exchange with atmospheric CO{sub 2}, and is thus important as a potential source and sink of greenhouse gases over time scales of human concern (Fischlin and Gyalistras 1997). SOM is also an important human resource under active management in agricultural and range lands worldwide. Questions driving present research on the soil C cycle include: Are soils now acting as a net source or sink of carbon to the atmosphere? What role will soils play as a natural modulator or amplifier of climatic warming? How is C stabilized and sequestered, and what are effective management techniques to foster these processes? Answering these questions will require a mechanistic understanding of how and where C is stored in soils. The quantity and composition of organic matter in soil reflect the long-term balance between plant carbon inputs and microbial decomposition, as well as other loss processes such as fire, erosion, and leaching. The processes driving soil carbon storage and turnover are complex and involve influences at molecular to global scales. Moreover, the relative importance of these processes varies according to the temporal and spatial scales being considered; a process that is important at the regional scale may not be critical at the pedon scale. At the regional scale, SOM cycling is influenced by factors such as climate and parent material, which affect plant productivity and soil development. More locally, factors such as plant tissue quality and soil mineralogy affect

  13. Organic matter and metamorphic history of CO chondrites

    NASA Astrophysics Data System (ADS)

    Bonal, Lydie; Bourot-Denise, Michèle; Quirico, Eric; Montagnac, Gilles; Lewin, Eric

    2007-03-01

    The metamorphic grades of a series of eight CO3 chondrites (ALHA77307, Colony, Kainsaz, Felix, Lancé, Ornans, Warrenton and Isna) have been quantified. The method used was based on the structural grade of the organic matter trapped in the matrix, which is irreversibly transformed by thermal metamorphism. The maturation of the organic matter is independent with respect to the mineralogical context and aqueous alteration. This metamorphic tracer is thus valid whatever the chemical class of chondrites. Moreover, it is sensitive to the peak metamorphic temperature. The structural grade of the organic matter was used along with other metamorphic tracers such as petrography of opaque minerals, Fa and Fs silicate composition in type I chondrules, presolar grains and noble gas (P3 component) abundance. The deduced metamorphic hierarchy and the attributed petrographic types are the following: ALHA77307 (3.03) < Colony (3.1) < Kainsaz (3.6) < Felix (3.6 (1)) < Ornans (3.6 (2)) < Lancé (3.6 (3)) < Warrenton (3.7 (1)) < Isna (3.7 (2)). For most metamorphosed objects, the peak metamorphic temperature can be estimated using a geothermometer calibrated with terrestrial metasediments [Beyssac O., Goffe B., Chopin C., and Rouzaud J. N. (2002) Raman spectrum of carbonaceous material in metasediments: a new geothermometer. J. Metamorph. Geol., 20, 859-871]. A value of 330 °C was obtained for Allende (CV chondrite), Warrenton and Isna, consistent with temperatures estimated from Fe diffusion [Weinbruch S., Armstrong J., and Palme H. (1994). Constraints on the thermal history of the Allende parent body as derive from olivine-spinel thermometry and Fe/Mg interdiffusion in olivine. Geochim. Cosmochim. Acta58(2), 1019-1030.], from the Ni content in sulfide-metal assemblages [Zanda B., Bourot-Denise M., and Hewins R. (1995) Condensate sulfide and its metamorphic transformations in primitive chondrites. Meteorit. Planet. Sci.30, A605.] and from the d002 interlayer spacing in poorly

  14. Repair of Artificial Lesions using an Acidic Remineralization Model Monitored with Cross – Polarization Optical Coherence Tomography

    PubMed Central

    Kang, Hobin; Darling, Cynthia L.; Fried, Daniel

    2011-01-01

    It is difficult to completely remineralize carious lesions because diffusion into the interior of the lesion is inhibited as new mineral is deposited in the outermost layers. In previous remineralization studies employing polarization sensitive optical coherence tomography (PS-OCT), two models of remineralization were employed and in both models there was preferential deposition of mineral in the outer most layer. In this study we attempted to remineralize the entire lesion using an acidic remineralization model and demonstrate that this remineralization can be monitored using PS-OCT. Artificial lesions approximately 100–150 μm in-depth were exposed to an acidic remineralization regimen and the integrated reflectivity from the lesions was measured before and after remineralization. Automated integration routines worked well for assessing the integrated reflectivity for the lesion areas after remineralization. Although there was a higher degree of remineralization, there was still incomplete remineralization of the body of the lesion. PMID:21785533

  15. Sources, Ages, and Alteration of Organic Matter in Estuaries.

    PubMed

    Canuel, Elizabeth A; Hardison, Amber K

    2016-01-01

    Understanding the processes influencing the sources and fate of organic matter (OM) in estuaries is important for quantifying the contributions of carbon from land and rivers to the global carbon budget of the coastal ocean. Estuaries are sites of high OM production and processing, and understanding biogeochemical processes within these regions is key to quantifying organic carbon (Corg) budgets at the land-ocean margin. These regions provide vital ecological services, including nutrient filtration and protection from floods and storm surge, and provide habitat and nursery areas for numerous commercially important species. Human activities have modified estuarine systems over time, resulting in changes in the production, respiration, burial, and export of Corg. Corg in estuaries is derived from aquatic, terrigenous, and anthropogenic sources, with each source exhibiting a spectrum of ages and lability. The complex source and age characteristics of Corg in estuaries complicate our ability to trace OM along the river-estuary-coastal ocean continuum. This review focuses on the application of organic biomarkers and compound-specific isotope analyses to estuarine environments and on how these tools have enhanced our ability to discern natural sources of OM, trace their incorporation into food webs, and enhance understanding of the fate of Corg within estuaries and their adjacent waters. PMID:26407145

  16. Sources, Ages, and Alteration of Organic Matter in Estuaries.

    PubMed

    Canuel, Elizabeth A; Hardison, Amber K

    2016-01-01

    Understanding the processes influencing the sources and fate of organic matter (OM) in estuaries is important for quantifying the contributions of carbon from land and rivers to the global carbon budget of the coastal ocean. Estuaries are sites of high OM production and processing, and understanding biogeochemical processes within these regions is key to quantifying organic carbon (Corg) budgets at the land-ocean margin. These regions provide vital ecological services, including nutrient filtration and protection from floods and storm surge, and provide habitat and nursery areas for numerous commercially important species. Human activities have modified estuarine systems over time, resulting in changes in the production, respiration, burial, and export of Corg. Corg in estuaries is derived from aquatic, terrigenous, and anthropogenic sources, with each source exhibiting a spectrum of ages and lability. The complex source and age characteristics of Corg in estuaries complicate our ability to trace OM along the river-estuary-coastal ocean continuum. This review focuses on the application of organic biomarkers and compound-specific isotope analyses to estuarine environments and on how these tools have enhanced our ability to discern natural sources of OM, trace their incorporation into food webs, and enhance understanding of the fate of Corg within estuaries and their adjacent waters.

  17. Sources, Ages, and Alteration of Organic Matter in Estuaries

    NASA Astrophysics Data System (ADS)

    Canuel, Elizabeth A.; Hardison, Amber K.

    2016-01-01

    Understanding the processes influencing the sources and fate of organic matter (OM) in estuaries is important for quantifying the contributions of carbon from land and rivers to the global carbon budget of the coastal ocean. Estuaries are sites of high OM production and processing, and understanding biogeochemical processes within these regions is key to quantifying organic carbon (Corg) budgets at the land-ocean margin. These regions provide vital ecological services, including nutrient filtration and protection from floods and storm surge, and provide habitat and nursery areas for numerous commercially important species. Human activities have modified estuarine systems over time, resulting in changes in the production, respiration, burial, and export of Corg. Corg in estuaries is derived from aquatic, terrigenous, and anthropogenic sources, with each source exhibiting a spectrum of ages and lability. The complex source and age characteristics of Corg in estuaries complicate our ability to trace OM along the river-estuary-coastal ocean continuum. This review focuses on the application of organic biomarkers and compound-specific isotope analyses to estuarine environments and on how these tools have enhanced our ability to discern natural sources of OM, trace their incorporation into food webs, and enhance understanding of the fate of Corg within estuaries and their adjacent waters.

  18. Impact of natural organic matter (NOM) on freshwater amphipods.

    PubMed

    Timofeyev, Maxim A; Wiegand, Claudia; Kent Burnison, B; Shatilina, Zhanna M; Pflugmacher, Stephan; Steinberg, Christian E W

    2004-02-01

    Natural organic matter (NOM) isolated from the eutrophic Sanctuary Pond (Point Pelee National Park, Canada) has an adverse impact on amphipod species (Gammarus tigrinus and Chaetogammarus ischnus from Lake Müggelsee, Germany, and Eulimnogammarus cyaneus, from Lake Baikal, Russia). Increases in amphipod mortality, changes in peroxidase activity and increases of heat shock protein (hsp70) expression were observed upon exposure to NOM. The highest resistance to the adverse impact of NOM was observed with the endemic Baikalian amphipod E. cyaneus. However, the mechanisms behind this finding remains obscure. If differences in the sensitivity of the hsp70 antibody may be excluded, different modes of action may be postulated: because the adverse impact of NOM may be caused by reactive oxygen species (ROS) and the NOM itself, the observed differences may be due to the action of ROS alone (with E. cyaneus) and a combination of both adverse modes of action (European species). PMID:14967505

  19. Modeling of natural organic matter transport processes in groundwater.

    PubMed Central

    Yeh, T C; Mas-Pla, J; McCarthy, J F; Williams, T M

    1995-01-01

    A forced-gradient tracer test was conducted at the Georgetown site to study the transport of natural organic matter (NOM) in groundwater. In particular, the goal of this experiment was to investigate the interactions between NOM and the aquifer matrix. A detailed three-dimensional characterization of the hydrologic conductivity heterogeneity of the site was obtained using slug tests. The transport of a conservative tracer (chloride) was successfully reproduced using these conductivity data. Despite the good simulation of the flow field, NOM breakthrough curves could not be reproduced using a two-site sorption model with spatially constant parameters. Preliminary results suggest that different mechanisms for the adsorption/desorption processes, as well as their spatial variability, may significantly affect the transport and fate of NOM. PMID:7621798

  20. [Dissolved organic matter (DOM) dynamics in karst aquifer systems].

    PubMed

    Yao, Xin; Zou, Sheng-Zhang; Xia, Ri-Yuan; Xu, Dan-Dan; Yao, Min

    2014-05-01

    Dissolved organic matter (DOM) and nutrients have a unique way of producing, decomposing and storing in southwest karst water systems. To understand the biogeochemical cycle of DOM in karst aquifer systems, we investigated the behavioral changes of DOM fluorescence components in Zhaidi karst river system. Two humic-like components (C1 and C2), and one autochthonous tyrosine-like component (C4) were identified using the parallel factor analysis (PARAFAC) model. Compared with the traditional physical and chemical indicators, spatial heterogeneity of DOM was more obvious, which can reflect the subtle changes in groundwater system. Traditional indicators mainly reflect the regional characteristics of karst river system, while DOM fluorescence components reflect the attribute gaps of sampling types.

  1. Systematic approaches to comprehensive analyses of natural organic matter

    USGS Publications Warehouse

    Leenheer, Jerry A.

    2009-01-01

    The more that is learned of the chemistry of aquatic natural organic matter (NOM) the greater is the scientific appreciation of the vast complexity of this subject. This complexity is due not only to a multiplicity of precursor molecules in any environment but to their associations with each other and with other components of local environments such as clays, mineral acids and dissolved metals. In addition, this complex system is subject to constant change owing to environmental variables and microbial action. Thus, there is a good argument that no two NOM samples are exactly the same even from the same source at nearly the same time. When ubiquity of occurrence, reaction with water treatment chemicals, and subsequent human exposure are added to the list of NOM issues, one can understand the appeal that this subject holds for a wide variety of environmental scientists.

  2. New monoaromatic steroids in organic matter of the apocatagenesis zone

    NASA Astrophysics Data System (ADS)

    Kashirtsev, V. A.; Fomin, A. N.; Shevchenko, N. P.; Dolzhenko, K. V.

    2016-08-01

    According to the materials of geochemical study in the core of the ultradeep hole SV-27 of aromatic fractions of bitumoids of the Vilyui syneclise (East Siberia) by the method of chromatography-mass spectrometry, starting from the depth of >5000 m, four diastereomers of previously unknown hydrocarbons, which become predominant in the fraction at a depth of ˜6500 m, were distinguished. Similar hydrocarbons were found in organic matter of Upper Paleozoic rocks of the Kharaulakh anticlinorium in the Verkhoyansk folded area. According to the intense molecular ion m/z 366 and the character of the basic fragmental ions (m/z 238, 309, and 323), the major structure of the compounds studied was determined as 17-desmethyl-23-methylmonoaromatic steroid C27. The absence of such steroids in oil of the Vilyui syneclise shows that deep micro-oils did not participate in the formation of oil fringes of gas condensate deposits of the region.

  3. A search for presolar organic matter in meteorite

    NASA Technical Reports Server (NTRS)

    Yang, J.; Epstein, S.

    1985-01-01

    The D/H ratios and the C-13/C-12 ratios of acid-insoluble organic matter of 4 meteorites, Ochansk (H4), Plainview (H5), Gladstone (H6) and Odessa (IA), were measured. delta-D values for hydrogen extracted by stepwise combustion were negative, down to -280 deg/infinity. delta-C-13 values were also negative except in the case of the carbon coming off at the highest temperature steps for Plainview and Odessa meteorites. The concentrations of C-13-rich carbon were 3-5 orders of magnitude smaller than those found in Murchison meteorite, suggesting that relic grains of stellar condensates were mostly destroyed in the meteorites examined.

  4. Grown organic matter as a fuel raw material resource

    NASA Technical Reports Server (NTRS)

    Roller, W. L.; Keener, H. M.; Kline, R. D.; Mederski, H. J.; Curry, R. B.

    1975-01-01

    An extensive search was made on biomass production from the standpoint of climatic zones, water, nutrients, costs and energy requirements for many species. No exotic species were uncovered that gave hope for a bonanza of biomass production under culture, location, and management markedly different from those of existing agricultural concepts. A simulation analysis of biomass production was carried out for six species using conventional production methods, including their production costs and energy requirements. These estimates were compared with data on food, fiber, and feed production. The alternative possibility of using residues from food, feed, or lumber was evaluated. It was concluded that great doubt must be cast on the feasibility of producing grown organic matter for fuel, in competition with food, feed, or fiber. The feasibility of collecting residues may be nearer, but the competition for the residues for return to the soil or cellulosic production is formidable.

  5. Priming-induced Changes in Permafrost Soil Organic Matter Decomposition

    NASA Astrophysics Data System (ADS)

    Pegoraro, E.; Schuur, E.; Bracho, R. G.

    2015-12-01

    Warming of tundra ecosystems due to climate change is predicted to thaw permafrost and increase plant biomass and litter input to soil. Additional input of easily decomposable carbon can alter microbial activity by providing a much needed energy source, thereby accelerating soil organic matter decomposition. This phenomenon, known as the priming effect, can increase CO2 flux from soil to the atmosphere. However, the extent to which this mechanism can decrease soil carbon stocks in the Arctic is unknown. This project assessed priming effects on permafrost soil collected from a moist acidic tundra site in Healy, Alaska. We hypothesized that priming would increase microbial activity by providing microbes with a fresh source of carbon, thereby increasing decomposition of old and slowly decomposing carbon. Soil from surface and deep layers were amended with multiple pulses of uniformly 13C labeled glucose and cellulose, and samples were incubated at 15° C to quantify whether labile substrate addition increased carbon mineralization. We quantified the proportion of old carbon mineralization by measuring 14CO2. Data shows that substrate addition resulted in higher respiration rates in amended soils; however, priming was only observed in deep layers, where 30% more soil-derived carbon was respired compared to control samples. This suggests that microbes in deep layers are limited in energy, and the addition of labile carbon increases native soil organic matter decomposition, especially in soil with greater fractions of slowly decomposing carbon. Priming in permafrost could exacerbate the effects of climate change by increasing mineralization rates of carbon accumulated over the long-term in deep layers. Therefore, quantifying priming effect in permafrost soils is imperative to understanding the dynamics of carbon turnover in a warmer world.

  6. Molecular characterization of dissolved organic matter (DOM): a critical review.

    PubMed

    Nebbioso, Antonio; Piccolo, Alessandro

    2013-01-01

    Advances in water chemistry in the last decade have improved our knowledge about the genesis, composition, and structure of dissolved organic matter, and its effect on the environment. Improvements in analytical technology, for example Fourier-transform ion cyclotron (FT-ICR) mass spectrometry (MS), homo and hetero-correlated multidimensional nuclear magnetic resonance (NMR) spectroscopy, and excitation emission matrix fluorimetry (EEMF) with parallel factor (PARAFAC) analysis for UV-fluorescence spectroscopy have resulted in these advances. Improved purification methods, for example ultrafiltration and reverse osmosis, have enabled facile desalting and concentration of freshly collected DOM samples, thereby complementing the analytical process. Although its molecular weight (MW) remains undefined, DOM is described as a complex mixture of low-MW substances and larger-MW biomolecules, for example proteins, polysaccharides, and exocellular macromolecules. There is a general consensus that marine DOM originates from terrestrial and marine sources. A combination of diagenetic and microbial processes contributes to its origin, resulting in refractory organic matter which acts as carbon sink in the ocean. Ocean DOM is derived partially from humified products of plants decay dissolved in fresh water and transported to the ocean, and partially from proteinaceous and polysaccharide material from phytoplankton metabolism, which undergoes in-situ microbial processes, becoming refractory. Some of the DOM interacts with radiation and is, therefore, defined as chromophoric DOM (CDOM). CDOM is classified as terrestrial, marine, anthropogenic, or mixed, depending on its origin. Terrestrial CDOM reaches the oceans via estuaries, whereas autochthonous CDOM is formed in sea water by microbial activity; anthropogenic CDOM is a result of human activity. CDOM also affects the quality of water, by shielding it from solar radiation, and constitutes a carbon sink pool. Evidence in support

  7. Effects of warming on stream biofilm organic matter use capabilities.

    PubMed

    Ylla, Irene; Canhoto, Cristina; Romaní, Anna M

    2014-07-01

    The understanding of ecosystem responses to changing environmental conditions is becoming increasingly relevant in the context of global warming. Microbial biofilm communities in streams play a key role in organic matter cycling which might be modulated by shifts in flowing water temperature. In this study, we performed an experiment at the Candal stream (Portugal) longitudinally divided into two reaches: a control half and an experimental half where water temperature was 3 °C above that of the basal stream water. Biofilm colonization was monitored during 42 days in the two stream halves. Changes in biofilm function (extracellular enzyme activities and carbon substrate utilization profiles) as well as chlorophyll a and prokaryote densities were analyzed. The biofilm in the experimental half showed a higher capacity to decompose cellulose, hemicellulose, lignin, and peptidic compounds. Total leucine-aminopeptidase, cellobiohydrolase and β-xylosidase showed a respective 93, 66, and 61% increase in activity over the control; much higher than would be predicted by only the direct temperature physical effect. In contrast, phosphatase and lipase activity showed the lowest sensitivity to temperature. The biofilms from the experimental half also showed a distinct functional fingerprint and higher carbon usage diversity and richness, especially due to a wider use of polymers and carbohydrates. The changes in the biofilm functional capabilities might be indirectly affected by the higher prokaryote and chlorophyll density measured in the biofilm of the experimental half. The present study provides evidence that a realistic stream temperature increase by 3 °C changes the biofilm metabolism to a greater decomposition of polymeric complex compounds and peptides but lower decomposition of lipids. This might affect stream organic matter cycling and the transfer of carbon to higher trophic levels.

  8. Ocean warming-acidification synergism undermines dissolved organic matter assembly.

    PubMed

    Chen, Chi-Shuo; Anaya, Jesse M; Chen, Eric Y-T; Farr, Erik; Chin, Wei-Chun

    2015-01-01

    Understanding the influence of synergisms on natural processes is a critical step toward determining the full-extent of anthropogenic stressors. As carbon emissions continue unabated, two major stressors--warming and acidification--threaten marine systems on several scales. Here, we report that a moderate temperature increase (from 30°C to 32°C) is sufficient to slow--even hinder--the ability of dissolved organic matter, a major carbon pool, to self-assemble to form marine microgels, which contribute to the particulate organic matter pool. Moreover, acidification lowers the temperature threshold at which we observe our results. These findings carry implications for the marine carbon cycle, as self-assembled marine microgels generate an estimated global seawater budget of ~1016 g C. We used laser scattering spectroscopy to test the influence of temperature and pH on spontaneous marine gel assembly. The results of independent experiments revealed that at a particular point, both pH and temperature block microgel formation (32°C, pH 8.2), and disperse existing gels (35°C). We then tested the hypothesis that temperature and pH have a synergistic influence on marine gel dispersion. We found that the dispersion temperature decreases concurrently with pH: from 32°C at pH 8.2, to 28°C at pH 7.5. If our laboratory observations can be extrapolated to complex marine environments, our results suggest that a warming-acidification synergism can decrease carbon and nutrient fluxes, disturbing marine trophic and trace element cycles, at rates faster than projected.

  9. Ocean warming-acidification synergism undermines dissolved organic matter assembly.

    PubMed

    Chen, Chi-Shuo; Anaya, Jesse M; Chen, Eric Y-T; Farr, Erik; Chin, Wei-Chun

    2015-01-01

    Understanding the influence of synergisms on natural processes is a critical step toward determining the full-extent of anthropogenic stressors. As carbon emissions continue unabated, two major stressors--warming and acidification--threaten marine systems on several scales. Here, we report that a moderate temperature increase (from 30°C to 32°C) is sufficient to slow--even hinder--the ability of dissolved organic matter, a major carbon pool, to self-assemble to form marine microgels, which contribute to the particulate organic matter pool. Moreover, acidification lowers the temperature threshold at which we observe our results. These findings carry implications for the marine carbon cycle, as self-assembled marine microgels generate an estimated global seawater budget of ~1016 g C. We used laser scattering spectroscopy to test the influence of temperature and pH on spontaneous marine gel assembly. The results of independent experiments revealed that at a particular point, both pH and temperature block microgel formation (32°C, pH 8.2), and disperse existing gels (35°C). We then tested the hypothesis that temperature and pH have a synergistic influence on marine gel dispersion. We found that the dispersion temperature decreases concurrently with pH: from 32°C at pH 8.2, to 28°C at pH 7.5. If our laboratory observations can be extrapolated to complex marine environments, our results suggest that a warming-acidification synergism can decrease carbon and nutrient fluxes, disturbing marine trophic and trace element cycles, at rates faster than projected. PMID:25714090

  10. Response of Dissolved Organic Matter to Warming and Nitrogen Addition

    NASA Astrophysics Data System (ADS)

    Choi, J. H.; Nguyen, H.

    2014-12-01

    Dissolved Organic Matter (DOM) is a ubiquitous mixture of soluble organic components. Since DOM is produced from the terrestrial leachate of various soil types, soil may influence the chemistry and biology of freshwater through the input of leachate and run-off. The increased temperature by climate change could dramatically change the DOM characteristics of soils through enhanced decomposition rate and losses of carbon from soil organic matter. In addition, the increase in the N-deposition affects DOM leaching from soils by changing the carbon cycling and decomposition rate of soil decay. In this study, we conducted growth chamber experiments using two types of soil (wetland and forest) under the conditions of temperature increase and N-deposition in order to investigate how warming and nitrogen addition influence the characteristics of the DOM leaching from different soil types. This leachate controls the quantity and quality of DOM in surface water systems. After 10 months of incubation, the dissolved organic carbon (DOC) concentrations decreased for almost samples in the range of 7.6 to 87.3% (ANOVA, p<0.05). The specific UV absorption (SUVA) values also decreased for almost samples after the first 3 months and then increased gradually afterward in range of 3.3 to 108.4%. Both time and the interaction between time and the temperature had the statistically significant effects on the SUVA values (MANOVA, p<0.05). Humification index (HIX) showed the significant increase trends during the duration of incubation and temperature for almost the samples (ANOVA, p<0.05). Higher decreases in the DOC values and increases in HIX were observed at higher temperatures, whereas the opposite trend was observed for samples with N-addition. The PARAFAC results showed that three fluorescence components: terrestrial humic (C1), microbial humic-like (C2), and protein-like (C3), constituted the fluorescence matrices of soil samples. During the experiment, labile DOM from the soils was

  11. Geochemical drivers of organic matter decomposition in Arctic tundra soils

    SciTech Connect

    Herndon, Elizabeth M.; Yang, Ziming; Graham, David E.; Wullschleger, Stan D.; Gu, Baohua; Liang, Liyuan; Bargar, John; Janot, Noemie; Regier, Tom Z.

    2015-12-07

    Climate change is warming tundra ecosystems in the Arctic, resulting in the decomposition of previously-frozen soil organic matter (SOM) and release of carbon (C) to the atmosphere; however, the processes that control SOM decomposition and C emissions remain highly uncertain. In this study, we evaluate geochemical factors that influence anaerobic production of carbon dioxide (CO2) and methane (CH4) in the active layers of four ice-wedge polygons. Surface and soil pore waters were collected during the annual thaw season over a two-year period in an area containing waterlogged, low-centered polygons and well-drained, high-centered polygons. We report spatial and seasonal patterns of dissolved gases in relation to the geochemical properties of Fe and organic C as determined using spectroscopic and chromatographic techniques. Iron was present as Fe(II) in soil solution near the permafrost boundary but enriched as Fe(III) in the middle of the active layer, similar to dissolved aromatic-C and organic acids. Dissolved CH4 increased relative to dissolved CO2 with depth and varied with soil moisture in the middle of the active layer in patterns that were positively correlated with the proportion of dissolved Fe(III) in transitional and low-centered polygon soils but negatively correlated in the drier flat- and high-centered polygons. These results suggest that microbial-mediated Fe oxidation and reduction influence respiration/fermentation of SOM and production of substrates (e.g., low-molecular-weight organic acids) for methanogenesis. As a result, we infer that geochemical differences induced by water saturation dictate microbial products of SOM decomposition, and Fe geochemistry is an important factor regulating methanogenesis in anoxic tundra soils.

  12. Geochemical drivers of organic matter decomposition in Arctic tundra soils

    DOE PAGES

    Herndon, Elizabeth M.; Yang, Ziming; Graham, David E.; Wullschleger, Stan D.; Gu, Baohua; Liang, Liyuan; Bargar, John; Janot, Noemie; Regier, Tom Z.

    2015-12-07

    Climate change is warming tundra ecosystems in the Arctic, resulting in the decomposition of previously-frozen soil organic matter (SOM) and release of carbon (C) to the atmosphere; however, the processes that control SOM decomposition and C emissions remain highly uncertain. In this study, we evaluate geochemical factors that influence anaerobic production of carbon dioxide (CO2) and methane (CH4) in the active layers of four ice-wedge polygons. Surface and soil pore waters were collected during the annual thaw season over a two-year period in an area containing waterlogged, low-centered polygons and well-drained, high-centered polygons. We report spatial and seasonal patterns ofmore » dissolved gases in relation to the geochemical properties of Fe and organic C as determined using spectroscopic and chromatographic techniques. Iron was present as Fe(II) in soil solution near the permafrost boundary but enriched as Fe(III) in the middle of the active layer, similar to dissolved aromatic-C and organic acids. Dissolved CH4 increased relative to dissolved CO2 with depth and varied with soil moisture in the middle of the active layer in patterns that were positively correlated with the proportion of dissolved Fe(III) in transitional and low-centered polygon soils but negatively correlated in the drier flat- and high-centered polygons. These results suggest that microbial-mediated Fe oxidation and reduction influence respiration/fermentation of SOM and production of substrates (e.g., low-molecular-weight organic acids) for methanogenesis. As a result, we infer that geochemical differences induced by water saturation dictate microbial products of SOM decomposition, and Fe geochemistry is an important factor regulating methanogenesis in anoxic tundra soils.« less

  13. Adsorption of paraquat on soil organic matter: effect of exchangeable cations and dissolved organic carbon.

    PubMed

    Gondar, Dora; López, Rocío; Antelo, Juan; Fiol, Sarah; Arce, Florencio

    2012-10-15

    Herbicides that interact with soil organic matter do so with both the solid and the dissolved fractions, so that the distribution of herbicide between the soil solution and solid phases is determined by competitive effects. In the present study, adsorption experiments were carried out with the cationic herbicide paraquat and untreated and acid-washed samples of a peat soil, at different values of pH and ionic strength. Less herbicide was adsorbed onto the untreated peat than onto the acid-washed peat; the difference was due to the presence of exchangeable cations, as demonstrated in experiments carried out by adding Ca(2+) to suspensions of acid-washed peat. The results were interpreted by an electrostatic model and the fitting parameters indicated that the adsorption constants were the same for both samples of peat, although the number of binding sites available was different. Simultaneous resolution of the adsorption equilibrium of paraquat for the soil organic matter (SOM) and of the binding equilibrium between paraquat and dissolved organic matter (DOM) enabled the distribution of paraquat between the solid and solution phases to be determined. The increased solubility of the SOM with increasing pH led to a decrease in the fraction of paraquat retained on the peat surface above pH 5.5, which favors the mobility of the herbicide in the soil.

  14. Partition of nonpolar organic pollutants from water to soil and sediment organic matters

    USGS Publications Warehouse

    Chiou, C.T.

    1995-01-01

    The partition coefficients (Koc) of carbon tetrachloride and 1,2-dichlorobenzene between normal soil/sediment organic matter and water have been determined for a large set of soils, bed sediments, and suspended solids from the United States and the People's Republic of China. The Koc values for both solutes are quite invariant either for the soils or for the bed sediments; the values on bed sediments are about twice those on soils. The similarity of Koc values between normal soils and between normal bed sediments suggests that natural organic matters in soils (or sediments) of different geographic origins exhibit comparable polarities and possibly comparable compositions. The results also suggest that the process that converts eroded soils into bed sediments brings about a change in the organic matter property. The difference between soil and sediment Koc values provides a basis for identifying the source of suspended solids in river waters. The very high Koc values observed for some special soils and sediments are diagnostic of severe anthropogenic contamination.

  15. Molecular-level dynamics of refractory dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Niggemann, J.; Gerdts, G.; Dittmar, T.

    2012-04-01

    Refractory dissolved organic matter (DOM) accounts for most of the global oceanic organic carbon inventory. Processes leading to its formation and factors determining its stability are still largely unknown. We hypothesize that refractory DOM carries a universal molecular signature. Characterizing spatial and temporal variability in this universal signature is a key to understanding dynamics of refractory DOM. We present results from a long-term study of the DOM geo-metabolome in the open North Sea. Geo-metabolomics considers the entity of DOM as a population of compounds, each characterized by a specific function and reactivity in the cycling of energy and elements. Ten-thousands of molecular formulae were identified in DOM by ultrahigh resolution mass spectrometry analysis (FT-ICR-MS, Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry). The DOM pool in the North Sea was influenced by a complex interplay of processes that produced, transformed and degraded dissolved molecules. We identified a stable fraction in North Sea DOM with a molecular composition similar to deep ocean DOM. Molecular-level changes in this stable fraction provide novel information on dynamics and interactions of refractory DOM.

  16. Removal of bromide and natural organic matter by anion exchange.

    PubMed

    Hsu, Susan; Singer, Philip C

    2010-04-01

    Bromide removal by anion exchange was explored for various water qualities, process configurations, and resin characteristics. Simulated natural waters containing different amounts of natural organic matter (NOM), bicarbonate, chloride, and bromide were treated with a polyacrylate-based magnetic ion exchange (MIEX) resin on a batch basis to evaluate the effectiveness of the resin for removal of bromide. While bromide removal was achieved to some degree, alkalinity (bicarbonate), dissolved organic carbon (DOC), and chloride were shown to inhibit bromide removal in waters with bromide concentrations of 100 and 300 microg/L. Water was also treated using a two-stage batch MIEX process. Two-stage treatment resulted in only a slight improvement in bromide removal compared to single-stage treatment, presumably due to competition with the high concentration of chloride which is present along with bromide in natural waters. In view of the relatively poor bromide removal results for the MIEX resin, a limited set of experiments was performed using polystyrene resins. DOC and bromide removal were compared by treating model waters with MIEX and two polystyrene resins, Ionac A-641 and Amberlite IRA910. The two polystyrene resins were seen to be more effective for bromide removal, while the MIEX resin was more effective at removing DOC.

  17. Precipitates in landfill leachate mediated by dissolved organic matters.

    PubMed

    Li, Zhenze; Xue, Qiang; Liu, Lei; Li, Jiangshan

    2015-04-28

    Clogging of landfill leachate collection system is so ubiquitous that it causes problems to landfills. Although precipitations of calcite and other minerals have been widely observed, the mechanism of precipitation remains obscure. We examined the clog composition, dissolved organic matters, leachate chemical compositions and the correlation of these variables in view of the precipitation process. It is shown that Dissolved Organic Carbon (DOC) inhibits precipitation of landfill leachate. Using the advanced NICA-Donnan model, the analysis of aqueous chemical reactions between Mg-Ca-DOC-CO2 suggests a good agreement with experimental observations. Calcite and dolomite are both found to be oversaturated in most of the landfill leachate samples. DOC is found to preferentially bind with Mg than Ca, leading to more likely precipitation of Calcite than dolomite from landfill leachate. The NICA-Donnan model gives a reasonable estimation of dolomite saturation index in a wide range of DOC. Modeling confirms the major precipitation mechanism in terms of alkaline earth metal carbonate. Uncertainties in model parameters are discussed with particular focus on DOC composition, functional group types and density concentration and the influential factors. PMID:25661175

  18. Transformation of organic matters in animal wastes during composting.

    PubMed

    Wang, Ke; He, Chao; You, Shijie; Liu, Weijie; Wang, Wei; Zhang, Ruijun; Qi, Huanhuan; Ren, Nanqi

    2015-12-30

    The transformation of organic matters in swine, cow and chicken manures was compared and evaluated using elemental analysis, FTIR, (13)C NMR, pyrolysis/GC/MS, Biolog and multiple fluorochrome over 60 days composting. The results revealed that cow manure exhibited the greatest C/N and aromaticity, whereas chicken manure exhibited the highest nitrogen and sulfur contents. O-alkyl-C was predominant carbon structure in the three manures. Alkyl-C and carboxyl-C were decomposed dramatically in initial 10 days, and mineralization of O-alkyl-C dominated the curing stage. During pyrolysis of chicken, cow, and swine manures, the majority products were fatty acids, phenols and cholestene derivatives, respectively, however, phenols and cholestene derivatives were strongly reduced in the mature manures. Furthermore, microorganisms in the raw cow, chicken and swine manure demonstrated the highest degradation capabilities for carbohydrates, lipids and amino acids, respectively. Spatial differences in the contents of solid organics in the manure particles were negligible through detection by multiple staining methods during composting.

  19. Effects of pressure on thermal evolution of organic matter

    SciTech Connect

    Goffe, B.; Domine, F. )

    1989-09-01

    In the internal metamorphic zones of the French Alps, organic matter-bearing terrestrial sediments of Dogger age underwent an Eocene high-pressure metamorphic event (607 kbar at 300{degree}-330{degree}C). These metasediments now contain, trapped in metamorphic minerals, low evolved kerogen (small extent of molecular orientation), heavy hydrocarbon compounds (aromatic and aliphatic up to C{sup 30} with traces of pristane and phytane molecules), and gases with low C{sup 1}/C{sup 2}-C{sup 6} ratios. However, the degree of organic maturation (equivalent to catagenesis) is much less than that predicted by classical models. This field example indicates that the oil window opens with increasing pressure. Experimental pyrolysis of supercritical hexane performed in a closed, constant-pressure gold reactor at 210-15,600 bars pressure range and 290{degree}-365{degree}C, clearly demonstrates the important influence of pressure on the product distribution of hexane pyrolysis: as pressure is increased, relative light product yields decrease and heavy products increase. This can be interpreted mainly by considering the activation volumes of the reactions involved. In conclusion, the experimental and natural examples presented here indicate that the rate of thermal maturation decreases with pressure.

  20. Transformation of organic matters in animal wastes during composting.

    PubMed

    Wang, Ke; He, Chao; You, Shijie; Liu, Weijie; Wang, Wei; Zhang, Ruijun; Qi, Huanhuan; Ren, Nanqi

    2015-12-30

    The transformation of organic matters in swine, cow and chicken manures was compared and evaluated using elemental analysis, FTIR, (13)C NMR, pyrolysis/GC/MS, Biolog and multiple fluorochrome over 60 days composting. The results revealed that cow manure exhibited the greatest C/N and aromaticity, whereas chicken manure exhibited the highest nitrogen and sulfur contents. O-alkyl-C was predominant carbon structure in the three manures. Alkyl-C and carboxyl-C were decomposed dramatically in initial 10 days, and mineralization of O-alkyl-C dominated the curing stage. During pyrolysis of chicken, cow, and swine manures, the majority products were fatty acids, phenols and cholestene derivatives, respectively, however, phenols and cholestene derivatives were strongly reduced in the mature manures. Furthermore, microorganisms in the raw cow, chicken and swine manure demonstrated the highest degradation capabilities for carbohydrates, lipids and amino acids, respectively. Spatial differences in the contents of solid organics in the manure particles were negligible through detection by multiple staining methods during composting. PMID:26311195

  1. Chromophoric dissolved organic matter export from U.S. rivers

    NASA Astrophysics Data System (ADS)

    Spencer, Robert G. M.; Aiken, George R.; Dornblaser, Mark M.; Butler, Kenna D.; Holmes, R. Max; Fiske, Greg; Mann, Paul J.; Stubbins, Aron

    2013-04-01

    Chromophoric dissolved organic matter (CDOM) fluxes and yields from 15 major U.S. rivers draining an assortment of terrestrial biomes are presented. A robust relationship between CDOM and dissolved organic carbon (DOC) loads is established (e.g., a350 versus DOC; r2 = 0.96, p < 0.001). Calculated CDOM yields are also correlated to watershed percent wetland (e.g. a350; r2 = 0.81, p < 0.001) providing a method for the estimation of CDOM export from ungauged watersheds. A large variation in CDOM yields was found across the rivers. The two rivers in the north-eastern U.S. (Androscoggin and Penobscot), the Edisto draining into the South Atlantic Bight, and some rivers draining into the Gulf of Mexico (Atchafalaya and Mobile) exhibit the highest CDOM yields, linked to extensive wetlands in these watersheds. If the Edisto CDOM yield is representative of other rivers draining into the South Atlantic Bight, this would result in a CDOM load equivalent to that of the Mississippi from a region of approximately 10% of the Mississippi watershed, indicating the importance of certain regions with respect to the role of terrigenous CDOM in ocean color budgets.

  2. Chromophoric Dissolved Organic Matter Export from U.S. Rivers

    NASA Astrophysics Data System (ADS)

    Spencer, R. G.; Aiken, G.; Dornblaser, M.; Butler, K. D.; Holmes, R. M.; Fiske, G.; Mann, P. J.; Stubbins, A.

    2012-12-01

    Chromophoric dissolved organic matter (CDOM) fluxes and yields from 15 major U.S. rivers draining an assortment of terrestrial biomes are presented. Utilizing CDOM and dissolved organic carbon (DOC) flux data we establish a robust universal relationship between CDOM and DOC loads. The application of this relationship allows future studies to derive DOC loads from CDOM utilizing emerging in-situ or remote sensing technologies and thus refine river-to-ocean DOC fluxes, as well as exploit historic imagery to examine how fluxes may have changed. Calculated CDOM yields from the 15 U.S. rivers highlight the importance of certain regions with respect to CDOM flux to the coastal ocean. This approach indicates that future studies might predict CDOM and DOC yields for different watershed types that could then be readily converted to loads providing for the estimation of CDOM and DOC export from ungauged watersheds. Examination of CDOM yields also highlights important geographical regions for future study with respect to the role of terrigenous CDOM in ocean color budgets and CDOM's role in biogeochemical processes.

  3. Toward an experimental synthesis of the chondritic insoluble organic matter

    NASA Astrophysics Data System (ADS)

    Biron, Kasia; Derenne, Sylvie; Robert, FrançOis; Rouzaud, Jean-NoëL.

    2015-08-01

    Based on the statistical model proposed for the molecular structure of the insoluble organic matter (IOM) isolated from the Murchison meteorite, it was recently proposed that, in the solar T-Tauri disk regions where (photo)dissociation of gaseous molecules takes place, aromatics result from the cyclization/aromatization of short aliphatics. This hypothesis is tested in this study, with n-alkanes being submitted to high-frequency discharge at low pressure. The contamination issue was eliminated using deuterated precursor. IOM was formed and studied using solid-state nuclear magnetic resonance, pyrolysis coupled to gas chromatography and mass spectrometry, RuO4 oxidation, and high-resolution transmission electron microscopy. It exhibits numerous similarities at the molecular level with the hydrocarbon backbone of the natural IOM, reinforcing the idea that the initial precursors of the IOM were originally chains in the gas. Moreover, a fine comparison between the chemical structure of several meteorite IOM suggests either that (i) the meteorite IOMs share a common precursor standing for the synthetic IOM or that (ii) the slight differences between the meteorite IOMs reflect differences in their environment at the time of their formation i.e., related to plasma temperature that, in turn, dictates the dissociation-recombination rates of organic fragments.

  4. Precipitates in landfill leachate mediated by dissolved organic matters.

    PubMed

    Li, Zhenze; Xue, Qiang; Liu, Lei; Li, Jiangshan

    2015-04-28

    Clogging of landfill leachate collection system is so ubiquitous that it causes problems to landfills. Although precipitations of calcite and other minerals have been widely observed, the mechanism of precipitation remains obscure. We examined the clog composition, dissolved organic matters, leachate chemical compositions and the correlation of these variables in view of the precipitation process. It is shown that Dissolved Organic Carbon (DOC) inhibits precipitation of landfill leachate. Using the advanced NICA-Donnan model, the analysis of aqueous chemical reactions between Mg-Ca-DOC-CO2 suggests a good agreement with experimental observations. Calcite and dolomite are both found to be oversaturated in most of the landfill leachate samples. DOC is found to preferentially bind with Mg than Ca, leading to more likely precipitation of Calcite than dolomite from landfill leachate. The NICA-Donnan model gives a reasonable estimation of dolomite saturation index in a wide range of DOC. Modeling confirms the major precipitation mechanism in terms of alkaline earth metal carbonate. Uncertainties in model parameters are discussed with particular focus on DOC composition, functional group types and density concentration and the influential factors.

  5. Global effects of agriculture on fluvial dissolved organic matter.

    PubMed

    Graeber, Daniel; Boëchat, Iola G; Encina-Montoya, Francisco; Esse, Carlos; Gelbrecht, Jörg; Goyenola, Guillermo; Gücker, Björn; Heinz, Marlen; Kronvang, Brian; Meerhoff, Mariana; Nimptsch, Jorge; Pusch, Martin T; Silva, Ricky C S; von Schiller, Daniel; Zwirnmann, Elke

    2015-11-06

    Agricultural land covers approximately 40% of Earth's land surface and affects hydromorphological, biogeochemical and ecological characteristics of fluvial networks. In the northern temperate region, agriculture also strongly affects the amount and molecular composition of dissolved organic matter (DOM), which constitutes the main vector of carbon transport from soils to fluvial networks and to the sea, and is involved in a large variety of biogeochemical processes. Here, we provide first evidence about the wider occurrence of agricultural impacts on the concentration and composition of fluvial DOM across climate zones of the northern and southern hemispheres. Both extensive and intensive farming altered fluvial DOM towards a more microbial and less plant-derived composition. Moreover, intensive farming significantly increased dissolved organic nitrogen (DON) concentrations. The DOM composition change and DON concentration increase differed among climate zones and could be related to the intensity of current and historical nitrogen fertilizer use. As a result of agriculture intensification, increased DON concentrations and a more microbial-like DOM composition likely will enhance the reactivity of catchment DOM emissions, thereby fuelling the biogeochemical processing in fluvial networks, and resulting in higher ecosystem productivity and CO2 outgassing.

  6. Mineral surface-organic matter interactions: basics and applications

    NASA Astrophysics Data System (ADS)

    Valdrè, G.; Moro, D.; Ulian, G.

    2012-03-01

    The ability to control the binding of biological and organic molecules to a crystal surface is central in several fields; for example, in biotechnology, catalysis, molecular microarrays, biosensors preparation and environmental sciences. The nano-morphology and nanostructure at the surface may have physico-chemical properties that are very different from those of the underlying mineral substrate. Recent developments in scanning probe microscopy (SPM) have widened the spectrum of possible investigations that can be performed at the nanometric level on the surface of minerals. They range from the study of physical properties such as surface potential, electric field topological determination, Brønsted-Lowry site distributions, to chemical and spectroscopic analysis in air, in liquid or in gaseous environments. After an introduction to SPM modes of operation and new SPM-based technological developments, we will present recent examples of applications in the study of interactions between organic matter and mineral surface and report on the advances in knowledge that have been made by the use of scanning probe microscopy.

  7. Effects of agricultural practices on organic matter degradation in ditches

    PubMed Central

    Hunting, Ellard R.; Vonk, J. Arie; Musters, C.J.M.; Kraak, Michiel H.S.; Vijver, Martina G.

    2016-01-01

    Agricultural practices can result in differences in organic matter (OM) and agricultural chemical inputs in adjacent ditches, but its indirect effects on OM composition and its inherent consequences for ecosystem functioning remain uncertain. This study determined the effect of agricultural practices (dairy farm grasslands and hyacinth bulb fields) on OM degradation by microorganisms and invertebrates with a consumption and food preference experiment in the field and in the laboratory using natural OM collected from the field. Freshly cut grass and hyacinths were also offered to control for OM composition and large- and small mesh-sizes were used to distinguish microbial decomposition and invertebrate consumption. Results show that OM decomposition by microorganisms and consumption by invertebrates was similar throughout the study area, but that OM collected from ditches adjacent grasslands and freshly cut grass and hyacinths were preferred over OM collected from ditches adjacent to a hyacinth bulb field. In the case of OM collected from ditches adjacent hyacinth bulb fields, both microbial decomposition and invertebrate consumption were strongly retarded, likely resulting from sorption and accumulation of pesticides. This outcome illustrates that differences in agricultural practices can, in addition to direct detrimental effects on aquatic organisms, indirectly alter the functioning of adjacent aquatic ecosystems. PMID:26892243

  8. Role of dissolved organic matter in ice photochemistry.

    PubMed

    Grannas, Amanda M; Pagano, Lisa P; Pierce, Brittany C; Bobby, Rachel; Fede, Alexis

    2014-09-16

    In this study, we provide evidence that dissolved organic matter (DOM) plays an important role in indirect photolysis processes in ice, producing reactive oxygen species (ROS) and leading to the efficient photodegradation of a probe hydrophobic organic pollutant, aldrin. Rates of DOM-mediated aldrin loss are between 2 and 56 times faster in ice than in liquid water (depending on DOM source and concentration), likely due to a freeze-concentration effect that occurs when the water freezes, providing a mechanism to concentrate reactive components into smaller, liquid-like regions within or on the ice. Rates of DOM-mediated aldrin loss are also temperature dependent, with higher rates of loss as temperature decreases. This also illustrates the importance of the freeze-concentration effect in altering reaction kinetics for processes occurring in environmental ices. All DOM source types studied were able to mediate aldrin loss, including commercially available fulvic and humic acids and an authentic Arctic snow DOM sample isolated by solid phase extraction, indicating the ubiquity of DOM in indirect photochemistry in environmental ices. PMID:25157605

  9. Effects of agricultural practices on organic matter degradation in ditches.

    PubMed

    Hunting, Ellard R; Vonk, J Arie; Musters, C J M; Kraak, Michiel H S; Vijver, Martina G

    2016-01-01

    Agricultural practices can result in differences in organic matter (OM) and agricultural chemical inputs in adjacent ditches, but its indirect effects on OM composition and its inherent consequences for ecosystem functioning remain uncertain. This study determined the effect of agricultural practices (dairy farm grasslands and hyacinth bulb fields) on OM degradation by microorganisms and invertebrates with a consumption and food preference experiment in the field and in the laboratory using natural OM collected from the field. Freshly cut grass and hyacinths were also offered to control for OM composition and large- and small mesh-sizes were used to distinguish microbial decomposition and invertebrate consumption. Results show that OM decomposition by microorganisms and consumption by invertebrates was similar throughout the study area, but that OM collected from ditches adjacent grasslands and freshly cut grass and hyacinths were preferred over OM collected from ditches adjacent to a hyacinth bulb field. In the case of OM collected from ditches adjacent hyacinth bulb fields, both microbial decomposition and invertebrate consumption were strongly retarded, likely resulting from sorption and accumulation of pesticides. This outcome illustrates that differences in agricultural practices can, in addition to direct detrimental effects on aquatic organisms, indirectly alter the functioning of adjacent aquatic ecosystems. PMID:26892243

  10. Role of dissolved organic matter in ice photochemistry.

    PubMed

    Grannas, Amanda M; Pagano, Lisa P; Pierce, Brittany C; Bobby, Rachel; Fede, Alexis

    2014-09-16

    In this study, we provide evidence that dissolved organic matter (DOM) plays an important role in indirect photolysis processes in ice, producing reactive oxygen species (ROS) and leading to the efficient photodegradation of a probe hydrophobic organic pollutant, aldrin. Rates of DOM-mediated aldrin loss are between 2 and 56 times faster in ice than in liquid water (depending on DOM source and concentration), likely due to a freeze-concentration effect that occurs when the water freezes, providing a mechanism to concentrate reactive components into smaller, liquid-like regions within or on the ice. Rates of DOM-mediated aldrin loss are also temperature dependent, with higher rates of loss as temperature decreases. This also illustrates the importance of the freeze-concentration effect in altering reaction kinetics for processes occurring in environmental ices. All DOM source types studied were able to mediate aldrin loss, including commercially available fulvic and humic acids and an authentic Arctic snow DOM sample isolated by solid phase extraction, indicating the ubiquity of DOM in indirect photochemistry in environmental ices.

  11. Global effects of agriculture on fluvial dissolved organic matter

    PubMed Central

    Graeber, Daniel; Boëchat, Iola G.; Encina-Montoya, Francisco; Esse, Carlos; Gelbrecht, Jörg; Goyenola, Guillermo; Gücker, Björn; Heinz, Marlen; Kronvang, Brian; Meerhoff, Mariana; Nimptsch, Jorge; Pusch, Martin T.; Silva, Ricky C. S.; von Schiller, Daniel; Zwirnmann, Elke

    2015-01-01

    Agricultural land covers approximately 40% of Earth’s land surface and affects hydromorphological, biogeochemical and ecological characteristics of fluvial networks. In the northern temperate region, agriculture also strongly affects the amount and molecular composition of dissolved organic matter (DOM), which constitutes the main vector of carbon transport from soils to fluvial networks and to the sea, and is involved in a large variety of biogeochemical processes. Here, we provide first evidence about the wider occurrence of agricultural impacts on the concentration and composition of fluvial DOM across climate zones of the northern and southern hemispheres. Both extensive and intensive farming altered fluvial DOM towards a more microbial and less plant-derived composition. Moreover, intensive farming significantly increased dissolved organic nitrogen (DON) concentrations. The DOM composition change and DON concentration increase differed among climate zones and could be related to the intensity of current and historical nitrogen fertilizer use. As a result of agriculture intensification, increased DON concentrations and a more microbial-like DOM composition likely will enhance the reactivity of catchment DOM emissions, thereby fuelling the biogeochemical processing in fluvial networks, and resulting in higher ecosystem productivity and CO2 outgassing. PMID:26541809

  12. Organic matter in the ancient Alpine Tethyan Ocean Continental Transition

    NASA Astrophysics Data System (ADS)

    Mateeva, Tsvetomila; Wolff, George; Kusznir, Nick; Wheeler, John; Manataschal, Gianreto

    2016-04-01

    Studies of hydrothermal vents in modern ocean settings suggest that methane produced by serpentinization can support methanotrophic bio-systems. Are such bio-systems locally restricted to hydrothermal vents or are more pervasive, being linked with the geology of serpentinized mantle in the subsurface? Answering this question has implications for our understanding of the global importance of hidden sub-surface bio-systems, the fate of methane and the carbon cycle. The ocean-continent transition (OCT) of magma-poor rifted continental margins, exhumed within mountain belts by continent collision, provides an opportunity to investigate this question. Initial data from the Totalp unit in the Eastern Swiss Alps, representing exhumed OCT of the Alpine Tethyan rifted continental margin, shows the presence of various hydrocarbons (Mateeva et al., in prep.). Samples from other Tethyan OCT locations, consisting of the Tasna nappe and Platta unit of the Eastern Swiss Alps and Chenaillet in the Western Alps, have also been analysed to investigate the presence or absence of methanotrophic biosystems within serpentinized exhumed mantle and associated ophicalcite and syn-rift sediments. Samples from these remnant Tethyan OCT locations are characterized by low and varied organic carbon concentrations that reflect the large lithological diversity of this area. The samples contain hydrocarbons in the form of n-alkanes mostly in the range C20 - C32, polynuclear aromatic hydrocarbons (PAHs) and various biomarkers (e.g. steranes, hopanes). A typical sample from the hydrothermal system in Platta shows the lithological characteristics of a black smoker, but with no indication of a more developed biosystem. Preliminary results from the examined Tethyan OCT locations (Tasna, Platta, Chenaillet) show evidence for the preservation of marine organic matter in the serpentinized mantle and overlying sediments, although there is no unequivocal indication that the organic matter is generated from

  13. Do Long-Term Changes in Organic Matter Inputs to Forest Soils Affect Dissolved Organic Matter Chemistry and Export?

    NASA Astrophysics Data System (ADS)

    Lajtha, K.; Strid, A.; Lee, B. S.

    2014-12-01

    Dissolved organic matter (DOM) production and transport play an important role in regulating organic matter (OM) distribution through a soil profile and ultimately, OM stabilization or export to aquatic systems. The contributions of varying OM inputs to the quality and amount of DOM as it passes through a soil profile remain relatively unknown. The Detrital Input and Removal Treatment (DIRT) site at the H. J. Andrews Experimental Forest in Oregon has undergone 17 years of litter, wood and root input manipulations and allows us to guage shifts in DOM chemistry induced by long-term changes to aboveground and belowground OM additions and exclusions. Using fluorescence and UV spectroscopy to characterize fluorescent properties, extent of decomposition, and sources of DOM in streams and soil solutions collected with lysimeters and soil extractions, we have assessed the importance of fresh OM inputs to DOM chemistry. Soil extracts from DIRT plots had a higher fluorescence index (FI) than lysimeter solutions or stream water. A high FI in surface water is generally interpreted as indicative of a high proportion of microbially-derived DOM. However, we suspect that the high FI in soil extracts is due to a higher proportion of non-aromatic DOM from fresh soil that microorganisms consume in transit through the soil profile to lysimeters or to streams. High redox index (RI) values were observed in lysimeters from the April 2014 sampling compared with the November 2013 sampling. These RI values show evidence of more reducing conditions at the end of the rainy season in the spring compared to the onset of the rainy season in the fall. Lysimeter water collected in No Input, No Litter, and No Root treatments contained high proportions of protein, suggesting the absence of carbon inputs changes activities of the microbial community. Observed variations reflect the viability of using fluorescent properties to explore the terrestrial-aquatic interface.

  14. Key soil functional properties affected by soil organic matter - evidence from published literature

    NASA Astrophysics Data System (ADS)

    Murphy, Brian

    2015-07-01

    The effect of varying the amount of soil organic matter on a range of individual soil properties was investigated using a literature search of published information largely from Australia, but also included relevant information from overseas. Based on published pedotransfer functions, soil organic matter was shown to increase plant available water by 2 to 3 mm per 10 cm for each 1% increase in soil organic carbon, with the largest increases being associated with sandy soils. Aggregate stability increased with increasing soil organic carbon, with aggregate stability decreasing rapidly when soil organic carbon fell below 1.2 to 1.5 5%. Soil compactibility, friability and soil erodibility were favourably improved by increasing the levels of soil organic carbon. Nutrient cycling was a major function of soil organic matter. Substantial amounts of N, P and S become available to plants when the soil organic matter is mineralised. Soil organic matter also provides a food source for the microorganisms involved in the nutrient cycling of N, P, S and K. In soils with lower clay contents, and less active clays such as kaolinites, soil organic matter can supply a significant amount of the cation exchange capacity and buffering capacity against acidification. Soil organic matter can have a cation exchange capacity of 172 to 297 cmol(+)/kg. As the cation exchange capacity of soil organic matter varies with pH, the effectiveness of soil organic matter to contribute to cation exchange capacity below pH 5.5 is often minimal. Overall soil organic matter has the potential to affect a range of functional soil properties.

  15. Soil organic matter on citrus plantation in Eastern Spain

    NASA Astrophysics Data System (ADS)

    Cerdà, Artemi; Pereira, Paulo; Novara, Agata; Prosdocimi, Massimo

    2015-04-01

    Citrus plantations in Eastern Spain are the main crop and Valencia region is the largest world exporter. The traditional plantation are located on flood irrigated areas and the new plantation are located on slopes were drip irrigation is the source of the wetting. It has been demonstrate that the citrus plantations contribute to high erosion rates on slopes (Cerdà et al., 2009b) as it is usual on agriculture land (Cerdà et al., 2009a), but when organic farming is present the soil erosion is much lower (Cerdà and Jurgensen, 2008; Cerdà et al., 2009; Cerdà and Jurgensen, 2011). This is a worldwide phenomenon (Wu et al., 2007; Wu et al., 2011; Xu et al., 2010; Xu et al., 2012a; Xu et al., 2012b), which are a key factor of the high erosion rates in rural areas (García Orenes et al., 2009: García Orenes et al., 20010; García Orenes et al., 2012; Haregewyn et al., 2013; Zhao et al., 2013). The key factor of the contrasted response of soils to the rain in citrus is the organic matter cover. This is why the Soil Erosion and Degradation Research Team developed a survey to determine the soil erosion rates on citrus orchards under different managements. A hundred of samples were collected in a citrus plantation on slope under conventional management (Chemical management), one on organic farming, one on traditional flood irrigated organic farming and one on traditional chemical flooding farm. The organic farming soils were treated with 10000 Kg ha-1 of manure yearly. The results show that the mean soil organic matter content was 1.24 %, 3.54%, 5,43% and 2.1% respectively, which show a clear impact of organic farming in the recovery of the soil organic matter. meanwhile the on the slopes and the flood-irrigated soils are Acknowledgements The research projects GL2008-02879/BTE, LEDDRA 243857 and PREVENTING AND REMEDIATING DEGRADATION OF SOILS IN EUROPE THROUGH LAND CARE (RECARE)FP7- ENV-2013- supported this research. References Cerdà, A., Flanagan, D.C., le Bissonnais

  16. The flux of organic matter through a peatland ecosystem - evidence from thermogravimetric analysis

    NASA Astrophysics Data System (ADS)

    Worrall, Fred; Moody, Catherine; Clay, Gareth

    2016-04-01

    Carbon budgets of peatlands are now common and studies have considered nitrogen, oxygen and energy budgets, but no study has considered the whole composition of the organic matter as it transfers through and into a peatland. Organic matter samples were taken from each organic matter reservoir found in and each fluvial flux from a peatland and analysed the samples by thermogravimetric analysis. The samples analysed were: aboveground, belowground, heather, mosses and sedges, litter layer, a peat core, and monthly samples of particulate and dissolved organic matter. All organic matter samples were taken from a 100% peat catchment within Moor House National Nature Reserve in the North Pennines, UK, and collected samples were compared to standards of lignin, cellulose, humic acid and plant protein. Results showed that the thermogravimetric trace of the sampled organic matter were distinctive with the DOM traces being marked out by very low thermal stability relative other organic matter types. The peat profile shows a significant trend with depth from vegetation- to lignin-like composition. When all traces are weighted according to the observed dry matter and carbon budgets for the catchment then it is possible to judge what has been lost in the transition through and into the ecosystem. By plotting this "lost" trace it possible to assess its composition which is either 97% cellulose and 3% humic acid or 92% and 8% lignin. This has important implications for what controls the organic matter balance of peatlands and it suggests that the oxidation state (OR) of peatland is less than 1.

  17. Vehicular emissions of organic particulate matter in Sao Paulo, Brazil

    NASA Astrophysics Data System (ADS)

    Oyama, B. S.; Andrade, M. F.; Herckes, P.; Dusek, U.; Röckmann, T.; Holzinger, R.

    2015-12-01

    Vehicular emissions have a strong impact on air pollution in big cities. Many factors affect these emissions: type of vehicle, type of fuel, cruising velocity, and brake use. This study focused on emissions of organic compounds by Light (LDV) and Heavy (HDV) duty vehicle exhaust. The study was performed in the city of Sao Paulo, Brazil, where vehicles run on different fuels: gasoline with 25 % ethanol (called gasohol), hydrated ethanol, and diesel (with 5 % of biodiesel). The vehicular emissions are an important source of pollutants and the principal contribution to fine particulate matter (smaller than 2.5 μm, PM2.5) in Sao Paulo. The experiments were performed in two tunnels: Janio Quadros (TJQ) where 99 % of the vehicles are LDV, and Rodoanel Mario Covas (TRA) where up to 30 % of the fleet was HDV. The PM2.5 samples were collected on quartz filters in May and July 2011 at TJQ and TRA, respectively, using two samplers operating in parallel. The samples were analyzed by Thermal-Desorption Proton-Transfer-Reaction Mass-Spectrometry (TD-PTR-MS), and by Thermal-Optical Transmittance (TOT). The organic aerosol (OA) desorbed at TD-PTR-MS represented around 30 % of the OA estimated by the TOT method, mainly due to the different desorption temperatures, with a maximum of 870 and 350 °C for TOT and TD-PTR-MS, respectively. Average emission factors (EF) organic aerosol (OA) and organic carbon (OC) were calculated for HDV and LDV fleet. We found that HDV emitted more OA and OC than LDV, and that OC emissions represented 36 and 43 % of total PM2.5 emissions from LDV and HDV, respectively. More than 700 ions were identified by TD-PTR-MS and the EF profiles obtained from HDV and LDV exhibited distinct features. Nitrogen-containing compounds measured in the desorbed material up to 350 °C contributed around 20 % to the EF values for both types of vehicles, possibly associated with incomplete fuel burning. Additionally, 70 % of the organic compounds measured from the aerosol

  18. Chemical composition of dissolved organic matter draining permafrost soils

    NASA Astrophysics Data System (ADS)

    Ward, Collin P.; Cory, Rose M.

    2015-10-01

    Northern circumpolar permafrost soils contain roughly twice the amount of carbon stored in the atmosphere today, but the majority of this soil organic carbon is perennially frozen. Climate warming in the arctic is thawing permafrost soils and mobilizing previously frozen dissolved organic matter (DOM) from deeper soil layers to nearby surface waters. Previous studies have reported that ancient DOM draining deeper layers of permafrost soils was more susceptible to degradation by aquatic bacteria compared to modern DOM draining the shallow active layer of permafrost soils, and have suggested that DOM chemical composition may be an important control for the lability of DOM to bacterial degradation. However, the compositional features that distinguish DOM drained from different depths in permafrost soils are poorly characterized. Thus, the objective of this study was to characterize the chemical composition of DOM drained from different depths in permafrost soils, and relate these compositional differences to its susceptibility to biological degradation. DOM was leached from the shallow organic mat and the deeper permafrost layer of soils within the Imnavait Creek watershed on the North Slope of Alaska. DOM draining both soil layers was characterized in triplicate by coupling ultra-high resolution mass spectrometry, 13C solid-state NMR, and optical spectroscopy methods with multi-variate statistical analyses. Reproducibility of replicate mass spectra was high, and compositional differences resulting from interfering species or isolation effects were significantly smaller than differences between DOM drained from each soil layer. All analyses indicated that DOM leached from the shallower organic mat contained higher molecular weight, more oxidized, and more unsaturated aromatic species compared to DOM leached from the deeper permafrost layer. Bacterial production rates and bacterial efficiencies were significantly higher for permafrost compared to organic mat DOM

  19. Do aggregate stability and soil organic matter content increase following organic inputs?

    NASA Astrophysics Data System (ADS)

    Lehtinen, Taru; Gísladóttir, Guðrún; van Leeuwen, Jeroen P.; Bloem, Jaap; Steffens, Markus; Vala Ragnarsdóttir, Kristin

    2014-05-01

    Agriculture is facing several challenges such as loss of soil organic matter (SOM); thus, sustainable farming management practices are needed. Organic farming is growing as an alternative to conventional farming; in Iceland approximately 1% and in Austria 16% of utilized agricultural area is under organic farming practice. We analyzed the effect of different farming practices (organic, and conventional) on soil physicochemical and microbiological properties in grassland soils in Iceland and cropland soils in Austria. Organic farms differed from conventional farms by absence of chemical fertilizers and pesticide use. At these farms, we investigated soil physicochemical (e.g. soil texture, pH, CAL-extractable P and K) and microbiological properties (fungal and bacterial biomass and activity). The effects of farming practices on soil macroaggregate stability and SOM quantity, quality and distribution between different fractions were studied following a density fractionation. In Iceland, we sampled six grassland sites on Brown (BA) and Histic (HA) Andosols; two sites on extensively managed grasslands, two sites under organic and two sites under conventional farming practice. In Austria, we sampled four cropland sites on Haplic Chernozems; two sites under organic and two sites under conventional farming practice. We found significantly higher macroaggregate stability in the organic compared to the conventional grasslands in Iceland. In contrast, slightly higher macroaggregation in conventional compared to the organic farming practice was found in croplands in Austria, although the difference was not significant. Macroaggregates were positively correlated with fungal biomass in Iceland, and with Feo and fungal activity in Austria. In Austria, SOM content and nutrient status (except for lower CAL-extractable P at one site) were similar between organic and conventional farms. Our results show that the organic inputs may have enhanced macroaggregation in organic farming

  20. Vertical transport of particulate organic matter regulated by fjord topography

    NASA Astrophysics Data System (ADS)

    Erlandsson, Carina P.

    2008-03-01

    The deepwater in many areas with restricted water exchange suffers from low oxygen concentrations due to degradation of organic matter. The objective of this study was to investigate how topography may influence the vertical transport, Fc, of particulate organic matter, POM, to the deepwater. A conceptual/analytical model for Fc was developed covering the combination of the three possible sources of POM/nutrients to an enclosed area; the coastal water, local supply, and nutrient rich local deepwater. The mathematical formulation of the conceptual model includes several factors describing to which degree various physical mechanisms in the fjord are influencing Fc. The model consists of submodels for the different sources of POM/nutrients. A one-dimensional process oriented numerical model was used to test the conceptual model. Restricted water exchange with the coastal water led to decreased import of POM and thereby decreased vertical transport, Fc, of coastal POM. The contribution to Fc by local input of nutrients to the surface layer was described by a function of the residence time of the water above sill level, Tsw and the time Tp it takes for POM produced in the surface layer to settle below sill level. The recirculation of POM produced due to basin water renewals was shown to be a function of several factors: The relation between the depth of photic zone, Hp and the sill depth, Ht, the vertical velocity of the rising nutrient rich water mass versus the settling velocity of POM, etc. The results based on the conceptual submodels agreed well with the results from the process oriented numerical model. Methods to identify the trophic state of coastal waters, and also simple models to calculate the effect of a local point source, can be found in literature. However, using the model developed in this paper the effects of nutrient enrichment from different sources can be quantified in a simple and more efficient way than earlier. The model can thus be used to

  1. Heavy metals fractionation and organic matter mineralisation in contaminated calcareous soil amended with organic materials.

    PubMed

    Clemente, Rafael; Escolar, Angeles; Bernal, M Pilar

    2006-10-01

    Degradation of organic matter (OM) from organic amendments used in the remediation of metal contaminated soils leads to changes in soil chemical properties shortly after their addition, which may affect the soil metal distribution. The effects of two differing organic amendments on OM mineralisation and fractionation of heavy metals in a contaminated soil were investigated in an incubation experiment. The treatments were: control unamended soil, soil amended with fresh cow manure, and soil amended with a compost having a high maturity degree. The soil used was characteristic of the mining area at La Unión (Murcia, Spain) with 28% CaCO(3) and sandy-loam texture (pH 7.7; 2602 mg kg(-1)Zn; 1572 mg kg(-1)Pb). Manure and compost C-mineralisation after 56 days (24% and 3.8%, respectively) were below values reported previously for uncontaminated soils. Both amendments favoured Zn and Pb fixation, particularly the manure. Mn solubility increased at the beginning of the experiment due to a pH effect, and only Cu solubility increased through organic matter chelation in both amended soils.

  2. The Isiokpo oil-pipeline leakage: total organic carbon/organic matter contents of affected soils.

    PubMed

    Osuji, Leo C; Adesiyan, Samuel O

    2005-08-01

    The environmental impact of the 1997 leakage of the high-pressure crude-oil pipeline at Isiokpo in the Niger Delta in the southeast of Nigeria was evaluated, with particular reference to total-organic-carbon (TOC) and total-organic-matter (TOM) contents of soils within the vicinity of the oil spillage. The soils, taken from depths of 0-15 cm (surface) and 15-30 cm (subsurface), were found to be more acidic (pH 4.2-5.6) than the unpolluted soils, with a high average moisture content of 6.8%. The extractable hydrocarbon content ranged from 2.71-3.48 mg/kg, indicating hydrocarbon contamination. However, contrary to expectation, the TOC and TOM contents of the polluted soils did not show any significant increase in concentration, supposedly due to natural rehabilitation of the affected mat layer of soils. Thus, notwithstanding the possible proliferation of heterotrophic organisms by the presence of the added petroleum hydrocarbons, environmental conditions such as weathering and climatic predispositions, as well as physico-chemical parameters such as pH, moisture content, and temperature must have encumbered the carbon-mineralizing capacity of the heterotrophs, thereby reducing the turnover of carbon and the decomposition of organic matter. The restrictions by high moisture content might not come directly from H(2)O itself, but are probably a consequence of hindered soil ventilation, which reduces O(2) supply and gaseous diffusion, conditions that might have been substantially aggravated by the added petroleum hydrocarbons.

  3. Electron Shuttling Capacity of Solid-Phase Organic Matter in Forest Soils

    NASA Astrophysics Data System (ADS)

    Patel, A.; Zhao, Q.; Yang, Y.

    2015-12-01

    Soil organic matter, as an electron shuttle, plays an important role in regulating the biogeochemical cycles of metals, especially the redox reactions for iron. Microorganisms can reduce soil organic matter under anaerobic conditions, and biotically-reduced soil organic matter can abiotically donate electrons to ferric oxides. Such soil organic matter-mediated electron transport can facilitate the interactions between microorganisms and insoluble terminal electron acceptors, i.e. iron minerals. Most previous studies have been focused on the electron shuttling processes through dissolved soil organic matter, and scant information is available for solid-phase soil organic matter. In this study, we aim to quantify the electron accepting capacity for solid-phase organic matter in soils collected from four different forests in the United States, including Truckee (CA), Little Valley (NV), Howland (ME) and Hart (MI). We used Shewanella oneidensisMR-1 to biotically reduce soil slurries, and then quantified the electrons transferred to solid-phase and solution-phase organic matter by reacting them with Fe(III)-nitrilotriacetic acid (Fe(III)-NTA). The generation of Fe(II) was measured by a ferrozine assay to calculate the electron accepting capacity of soil organic matter. Our preliminary results showed that the Truckee soil organic matter can accept 0.51±0.07 mM e-/mol carbon. We will measure the electron accepting capacity for four different soils and correlate them to the physicochemical properties of soils. Potential results will provide information about the electron accepting capacity of solid-phase soil organic matter and its governing factors, with broad implication on the coupled biogeochemical cycles of carbon and iron.

  4. Effects of Natural Organic Matter on Stability, Transport and Deposition of Engineered Nano-particles in Porous Media

    EPA Science Inventory

    The interaction of nano-particles and organic substances, like natural organic matter, could have significant influence on the fate, transport and bioavailability of toxic substances. Natural organic matter (NOM) is a mixture of chemically complex polyelectrolytes with varying m...

  5. In vitro enamel remineralization by low-fluoride toothpaste with calcium citrate and sodium trimetaphosphate.

    PubMed

    Hirata, Edo; Danelon, Marcelle; Freire, Isabelle Rodrigues; Delbem, Alberto Carlos Botazzo

    2013-01-01

    The objective of this study was to evaluate in vitro the effect of a low fluoride toothpaste (450 µgF/g, NaF) combined with calcium citrate (Cacit) and sodium trimetaphosphate (TMP) on enamel remineralization. Bovine enamel blocks had the enamel surface polished sequentially to determine the surface hardness. After production of artificial carious lesions, the blocks selected by their surface hardness were submitted to remineralization pH cycling and daily treatment with dentifrice suspensions (diluted in deionized water or artificial saliva): placebo, 275, 450, 550 and 1,100 µgF/g and commercial dentifrice (positive control, 1,100 µgF/g). Finally, the surface and cross-section hardness was determined for calculating the change of surface hardness (%SH) and mineral content (%∆Z). Fluoride in enamel was also determined. The data from %SH, %∆Z and fluoride were subjected to two-way analysis of variance followed by Student-Newman-Keuls's test (p<0.05). The mineral gain (%SH and %∆Z) was higher for toothpastes diluted in saliva (p<0.05), except for the 450 µgF/g dentifrice with Cacit/TMP (p>0.05). The 450 Cacit/TMP toothpaste and the positive control showed similar results (p>0.05) when diluted in water. A dose-response was observed between fluoride concentration in toothpastes and fluoride present in enamel, regardless of dilution. It was concluded that it is possible to enhance the remineralization capacity of low F concentration toothpaste by of organic (Cacit) and inorganic (TMP) compounds with affinity to hydroxyapatite.

  6. In vitro enamel remineralization by low-fluoride toothpaste with calcium citrate and sodium trimetaphosphate.

    PubMed

    Hirata, Edo; Danelon, Marcelle; Freire, Isabelle Rodrigues; Delbem, Alberto Carlos Botazzo

    2013-01-01

    The objective of this study was to evaluate in vitro the effect of a low fluoride toothpaste (450 µgF/g, NaF) combined with calcium citrate (Cacit) and sodium trimetaphosphate (TMP) on enamel remineralization. Bovine enamel blocks had the enamel surface polished sequentially to determine the surface hardness. After production of artificial carious lesions, the blocks selected by their surface hardness were submitted to remineralization pH cycling and daily treatment with dentifrice suspensions (diluted in deionized water or artificial saliva): placebo, 275, 450, 550 and 1,100 µgF/g and commercial dentifrice (positive control, 1,100 µgF/g). Finally, the surface and cross-section hardness was determined for calculating the change of surface hardness (%SH) and mineral content (%∆Z). Fluoride in enamel was also determined. The data from %SH, %∆Z and fluoride were subjected to two-way analysis of variance followed by Student-Newman-Keuls's test (p<0.05). The mineral gain (%SH and %∆Z) was higher for toothpastes diluted in saliva (p<0.05), except for the 450 µgF/g dentifrice with Cacit/TMP (p>0.05). The 450 Cacit/TMP toothpaste and the positive control showed similar results (p>0.05) when diluted in water. A dose-response was observed between fluoride concentration in toothpastes and fluoride present in enamel, regardless of dilution. It was concluded that it is possible to enhance the remineralization capacity of low F concentration toothpaste by of organic (Cacit) and inorganic (TMP) compounds with affinity to hydroxyapatite. PMID:23969915

  7. Coupled Ocean-Atmosphere Loss of Refractory Marine Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Kieber, D. J.; Keene, W. C.; Frossard, A. A.; Long, M. S.; Russell, L. M.; Maben, J. R.; Kinsey, J. D.; Tyssebotn, I. M.; Quinn, P.; Bates, T. S.

    2013-12-01

    Marine aerosol produced in the oceans from bursting bubbles and breaking waves is number dominated by submicron aerosol that are highly enriched in marine organic matter relative to seawater. Recent studies suggest that these organic-rich, submicron aerosol have a major impact on tropospheric chemistry and climate. It has been assumed this marine-derived aerosol organic matter is of recent origin stemming from biological activity in the photic zone. However, we deployed a marine aerosol generator on a recent cruise in the Sargasso Sea with seawater collected from 2500 m and showed that the aerosol generated from this seawater was enriched with organic matter to the same level as observed in surface Sargasso seawater, implying that the marine organic matter flux from the oceans into atmospheric aerosol is partly due to marine organic matter not of recent origin. We propose that marine aerosol production and subsequent physical and photochemical atmospheric evolution is the main process whereby old, refractory organic matter is removed from the oceans, thereby closing the carbon budget in the oceans and solving a long-standing conundrum regarding the removal mechanism for this organic matter in the sea. The implications of this study for couplings in the ocean-atmosphere cycling of organic matter will be discussed.

  8. Enhancement of the natural organic matter removal from drinking water by nanofiltration.

    PubMed

    Matilainen, A; Liikanen, R; Nyström, M; Lindqvist, N; Tuhkanen, T

    2004-03-01

    Finnish surface waters are abundant in natural organic matter. Natural organic matter can be removed from drinking water in a water treatment process by coagulation and filtration. The standard treatment operations are not able to remove the smallest molar mass fraction of organic matter and the intermediate molar mass matter is only partly removed. The removal of residual natural organic matter from drinking water by nanofiltration was evalueted in this study. Three different nanofiltration membranes were compared in filtering six pre-treated surface waters. The total organic carbon content of the feed waters varied from 2.0 to 4.2 mg l(-1). Other water quality parameters measured were conductivity, alkalinity, hardness, UV-absorbance, SUVA, E2/E3 value and molecular size distribution by high-performance size-exclusion chromatography. The natural organic matter removal efficiencies of the membranes were good and varied between 100% and 49%, and between 85% and 47% according to molecular size distribution and total organic carbon measurements, respectively. Removal of different molecular size fractions varied from 100% to 56%, 100% to 54% and 88% to 19%, regarding high molar mass, intermediate molar mass and low molar mass organic matter, respectively. The Desal-5 DL membrane produced the highest natural organic matter removals.

  9. Influence of soil organic matter composition on the partition of organic compounds

    USGS Publications Warehouse

    Rutherford, D.W.; Chiou, C.T.; Klle, D.E.

    1992-01-01

    The sorption at room temperature of benzene and carbon tetrachloride from water on three high-organic-content soils (muck, peat, and extracted peat) and on cellulose was determined in order to evaluate the effect of sorbent polarity on the solute partition coefficients. The isotherms are highly linear for both solutes on all the organic matter samples, which is consistent with a partition model. For both solutes, the extracted peat shows the greatest sorption capacity while the cellulose shows the lowest capacity; the difference correlates with the polar-to-nonpolar group ratio [(O + N)/C] of the sorbent samples. The relative increase of solute partition coefficient (Kom) with a decrease of sample polar content is similar for both solutes, and the limiting sorption capacity on a given organic matter sample is comparable between the solutes. This observation suggests that one can estimate the polarity effect of a sample of soil organic matter (SOM) on Kom of various nonpolar solutes by determining the partition coefficient of single nonpolar solute when compositional analysis of the SOM is not available. The observed dependence of Kom on sample polarity is used to account for the variation of Kom values of individual compounds on different soils that results from change in the polar group content of SOM. On the assumption that the carbon content of SOM in "ordinary soils" is 53-63%, the calculated variation of Kom is a factor of ???3. This value is in agreement with the limit of variation of most Kom data with soils of relatively high SOM contents.

  10. The effects of organic matter-mineral interactions and organic matter chemistry on diuron sorption across a diverse range of soils.

    PubMed

    Smernik, Ronald J; Kookana, Rai S

    2015-01-01

    Sorption of non-ionic organic compounds to soil is usually expressed as the carbon-normalized partition coefficient (KOC), because it is assumed that the main factor that influences the amount sorbed is the organic carbon content of the soil. However, KOC can vary by a factor of at least ten across a range of soils. We investigated two potential causes of variation in diuron KOC - organic matter-mineral interactions and organic matter chemistry - for a diverse set of 34 soils from Sri Lanka, representing a wide range of soil types. Treatment with hydrofluoric acid (HF-treatment) was used to concentrate soil organic matter. HF-treatment increased KOC for the majority of soils (average factor 2.4). We attribute this increase to the blocking of organic matter sorption sites in the whole soils by minerals. There was no significant correlation between KOC for the whole soils and KOC for the HF-treated soils, indicating that the importance of organic matter-mineral interactions varied greatly amongst these soils. There was as much variation in KOC across the HF-treated soils as there was across the whole soils, indicating that the nature of soil organic matter is also an important contributor to KOC variability. Organic matter chemistry, determined by solid-state (13)C nuclear magnetic resonance (NMR) spectroscopy, was correlated with KOC for the HF-treated soils. In particular, KOC increased with the aromatic C content (R=0.64, p=1×10(-6)), and decreased with O-alkyl C (R=-0.32, p=0.03) and alkyl C (R=-0.41, p=0.004) content.

  11. The effects of organic matter-mineral interactions and organic matter chemistry on diuron sorption across a diverse range of soils.

    PubMed

    Smernik, Ronald J; Kookana, Rai S

    2015-01-01

    Sorption of non-ionic organic compounds to soil is usually expressed as the carbon-normalized partition coefficient (KOC), because it is assumed that the main factor that influences the amount sorbed is the organic carbon content of the soil. However, KOC can vary by a factor of at least ten across a range of soils. We investigated two potential causes of variation in diuron KOC - organic matter-mineral interactions and organic matter chemistry - for a diverse set of 34 soils from Sri Lanka, representing a wide range of soil types. Treatment with hydrofluoric acid (HF-treatment) was used to concentrate soil organic matter. HF-treatment increased KOC for the majority of soils (average factor 2.4). We attribute this increase to the blocking of organic matter sorption sites in the whole soils by minerals. There was no significant correlation between KOC for the whole soils and KOC for the HF-treated soils, indicating that the importance of organic matter-mineral interactions varied greatly amongst these soils. There was as much variation in KOC across the HF-treated soils as there was across the whole soils, indicating that the nature of soil organic matter is also an important contributor to KOC variability. Organic matter chemistry, determined by solid-state (13)C nuclear magnetic resonance (NMR) spectroscopy, was correlated with KOC for the HF-treated soils. In particular, KOC increased with the aromatic C content (R=0.64, p=1×10(-6)), and decreased with O-alkyl C (R=-0.32, p=0.03) and alkyl C (R=-0.41, p=0.004) content. PMID:24972176

  12. Sorptive stabilization of organic matter by amorphous Al hydroxide

    NASA Astrophysics Data System (ADS)

    Schneider, M. P. W.; Scheel, T.; Mikutta, R.; van Hees, P.; Kaiser, K.; Kalbitz, K.

    2010-03-01

    Amorphous Al hydroxides (am-Al(OH) 3) strongly sorb and by this means likely protect dissolved organic matter (OM) against microbial decay in soils. We carried out batch sorption experiments (pH 4.5; 40 mg organic C L -1) with OM extracted from organic horizons under a Norway spruce and a European beech forest. The stabilization of OM by sorption was analyzed by comparing the CO 2 mineralized during the incubation of sorbed and non-sorbed OM. The mineralization of OM was evaluated based in terms of (i) the availability of the am-Al(OH) 3, thus surface OM loadings, (ii) spectral properties of OM, and (iii) the presence of phosphate as a competitor for OM. This was done by varying the solid-to-solution ratio (SSR = 0.02-1.2 g L -1) during sorption. At low SSRs, hence limited am-Al(OH) 3 availability, only small portions of dissolved OM were sorbed; for OM from Oa horizons, the mineralization of the sorbed fraction exceeded that of the original dissolved OM. The likely reason is competition with phosphate for sorption sites favouring the formation of weak mineral-organic bindings and the surface accumulation of N-rich, less aromatic and less complex OM. This small fraction controlled the mineralization of sorbed OM even at higher SSRs. At higher SSRs, i.e., with am-Al(OH) 3 more available, competition of phosphate decreased and aromatic compounds were sorbed selectively, which resulted in pronounced resistance of sorbed OM against decay. The combined OC mineralization of sorbed and non-sorbed OM was 12-65% less than that of the original DOM. Sorbed OM contributed only little to the overall OC mineralization. Stabilization of OC increased in direct proportion to am-Al(OH) 3 availability, despite constant aromatic C (˜30%). The strong stabilization at higher mineral availability is primarily governed by strong Al-OM bonds formed under less competitive conditions. Due to these strong bonds and the resulting strong stabilization, the surface loading, a proxy for the

  13. Sustaining effect of soil warming on organic matter decomposition

    NASA Astrophysics Data System (ADS)

    Hou, Ruixing; Ouyang, Zhu; Dorodnikov, Maxim; Wilson, Glenn; Kuzyakov, Yakov

    2015-04-01

    Global warming affects various parts of carbon (C) cycle including acceleration of soil organic matter (SOM) decomposition with strong feedback to atmospheric CO2 concentration. Despite many soil warming studies showed changes of microbial community structure, only very few were focused on sustainability of soil warming on microbial activity associated with SOM decomposition. Two alternative hypotheses: 1) acclimation because of substrate exhaustion and 2) sustaining increase of microbial activity with accelerated decomposition of recalcitrant SOM pools were never proven under long term field conditions. This is especially important in the nowadays introduced no-till crop systems leading to redistribution of organic C at the soil surface, which is much susceptible to warming effects than the rest of the profile. We incubated soil samples from a four-year warming experiment with tillage (T) and no-tillage (NT) practices under three temperatures: 15, 21, and 27 °C, and related the evolved total CO2 efflux to changes of organic C pools. Warmed soils released significantly more CO2 than the control treatment (no warming) at each incubation temperature, and the largest differences were observed under 15 °C (26% increase). The difference in CO2 efflux from NT to T increase with temperature showing high vulnerability of C stored in NT to soil warming. The Q10 value reflecting the sensitivity of SOM decomposition to warming was lower for warmed than non-warmed soil indicating better acclimation of microbes or lower C availability during long term warming. The activity of three extracellular enzymes: β-glucosidase, chitinase, sulphatase, reflecting the response of C, N and S cycles to warming, were significantly higher under warming and especially under NT compared to two other respective treatments. The CO2 released during 2 months of incubation consisted of 85% from recalcitrant SOM and the remaining 15% from microbial biomass and extractable organic C based on the

  14. Macroinvertebrate and organic matter export from headwater tributaries of a Central Appalachian stream

    EPA Science Inventory

    Headwater streams export organisms and other materials to their receiving streams and macroinvertebrate drift can shape colonization dynamics in downstream reaches while providing food for downstream consumers. Spring-time macroinvertebrate drift and organic matter export was me...

  15. Tillage, crop rotation, and organic amendment effect on changes in soil organic matter.

    PubMed

    Rickman, R; Douglas, C; Albrecht, S; Berc, J

    2002-01-01

    Carbon sequestration in agricultural soils is controlled by the balance of added organic residues and microbial oxidation of both residues and native organic matter (OM) as moderated by management and tillage. The PC-based model CQESTR predicts decomposition of residues, organic amendments and soil OM, based on cropping practices. CQESTR uses RUSLE (Revised Universal Soil Loss Equation) crop rotation and management practice, crop production, and operation databases. These data are supplemented with residue nitrogen and soil OM, bulk density, and layer thickness. CQESTR was calibrated with soil carbon data from 70-year-long experiments at the Research Center at Pendleton, OR. The calibrated model provides estimates with a 95% confidence interval of 0.33% OM. Validation at 11 independent sites resulted in a matching of observed with calculated OM with a 95% confidence interval of 0.55% OM. A 12th site, with a history of severe erosion, provided a poor match.

  16. Variation in assimilable organic carbon formation during chlorination of Microcystis aeruginosa extracellular organic matter solutions.

    PubMed

    Sun, Xingbin; Yuan, Ting; Ni, Huishan; Li, Yanpeng; Hu, Yang

    2016-07-01

    This study investigated the chlorination of Microcystis aeruginosa extracellular organic matter (EOM) solutions under different conditions, to determine how the metabolites produced by these organisms affect water safety and the formation of assimilable organic carbon (AOC). The effects of chlorine dosages, coagulant dosage, reaction time and temperature on the formation of AOC were investigated during the disinfection of M.aeruginosa metabolite solutions. The concentration of AOC followed a decreasing and then increasing pattern with increasing temperature and reaction time. The concentration of AOC decreased and then increased with increasing chlorination dosage, followed by a slight decrease at the highest level of chlorination. However, the concentration of AOC decreased continuously with increasing coagulant dosage. The formation of AOC can be suppressed under appropriate conditions. In this study, chlorination at 4mg/L, combined with a coagulant dose of 40mg/L at 20°C over a reaction time of 12hr, produced the minimum AOC. PMID:27372113

  17. Photodegradation of dissolved organic matter in ice under solar irradiation.

    PubMed

    Xue, Shuang; Wang, Chao; Zhang, Zhaohong; Song, Youtao; Liu, Qiang

    2016-02-01

    The photodegradation behavior of dissolved organic matter (DOM) with different origins in ice under solar irradiation was investigated. Exposure to sunlight at 2.7 × 10(5) J m(-2) resulted in dissolved organic carbon (DOC) reductions of 22.1-36.5% in ice. The naturally occurring DOM had higher photodegradation potentials than the wastewater-derived DOM in ice. Ultraviolet (UV)-absorbing compounds in DOM, regardless of DOM origin, had much higher photodegradation potentials than gross DOC in ice. The susceptibility of UV-absorbing compounds with natural origin to sunlight exposure in ice was higher than those derived from wastewater. Trihalomethane (THM) precursors were more susceptible to photochemical reactions than gross DOC and haloacetic acid (HAA) precursors in ice. THM precursors in naturally occurring DOM were more photoreactive than those in wastewater-derived DOM in ice, while the photoreactivity of HAA precursors in ice was independent of DOM origin. In ice, the photoreactivity of humic-like fluorescent materials, regardless of DOM origin, was higher than that of gross DOC and protein-like fluorescent materials. DOC reductions caused by sunlight irradiation were found to be negatively correlated to DOC levels, and positively correlated to the aromaticity of DOM. The photodegradation of both wastewater-derived and naturally occurring DOM in ice was significantly facilitated at both acid and alkaline pH, as compared to neutral pH. The photodegradation of DOM in ice, regardless of the origin, was facilitated by nitrate ion [Formula: see text] , nitrite ion [Formula: see text] , ferric ion (Fe(3+)) and ferrous ion (Fe(2+)), and on the other hand, was inhibited by chloridion ion (Cl(-)) and copper ion (Cu(2+)).

  18. Natural organic matter fouling behaviors on superwetting nanofiltration membranes.

    PubMed

    Shan, Linglong; Fan, Hongwei; Guo, Hongxia; Ji, Shulan; Zhang, Guojun

    2016-04-15

    Nanofiltration has been widely recognized as a promising technology for the removal of micro-molecular organic components from natural water. Natural organic matter (NOM), a very important precursor of disinfection by-products, is currently considered as the major cause of membrane fouling. It is necessary to develop a membrane with both high NOM rejection and anti-NOM fouling properties. In this study, both superhydrophilic and superhydrophobic nanofiltration membranes for NOM removal have been fabricated. The fouling behavior of NOM on superwetting nanofiltration membranes has been extensively investigated by using humic acid (HA) as the model foulant. The extended Derjaguin-Landau-Verwey-Overbeek approach and nanoindentor scratch tests suggested that the superhydrophilic membrane had the strongest repulsion force to HA due to the highest positive total interaction energy (ΔG(TOT)) value and the lowest critical load. Excitation emission matrix analyses of natural water also indicated that the superhydrophilic membrane showed resistance to fouling by hydrophobic substances and therefore high removal thereof. Conversely, the superhydrophobic membrane showed resistance to fouling by hydrophilic substances and therefore high removal capacity. Long-term operation suggested that the superhydrophilic membrane had high stability due to its anti-NOM fouling capacity. Based on the different anti-fouling properties of the studied superwetting membranes, a combination of superhydrophilic and superhydrophobic membranes was examined to further improve the removal of both hydrophobic and hydrophilic pollutants. With a combination of superhydrophilic and superhydrophobic membranes, the NOM rejection (RUV254) and DOC removal rates (RDOC) could be increased to 83.6% and 73.3%, respectively. PMID:26900973

  19. Chemodiversity of dissolved organic matter in the Amazon Basin

    NASA Astrophysics Data System (ADS)

    Gonsior, Michael; Valle, Juliana; Schmitt-Kopplin, Philippe; Hertkorn, Norbert; Bastviken, David; Luek, Jenna; Harir, Mourad; Bastos, Wanderley; Enrich-Prast, Alex

    2016-07-01

    Regions in the Amazon Basin have been associated with specific biogeochemical processes, but a detailed chemical classification of the abundant and ubiquitous dissolved organic matter (DOM), beyond specific indicator compounds and bulk measurements, has not yet been established. We sampled water from different locations in the Negro, Madeira/Jamari and Tapajós River areas to characterize the molecular DOM composition and distribution. Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) combined with excitation emission matrix (EEM) fluorescence spectroscopy and parallel factor analysis (PARAFAC) revealed a large proportion of ubiquitous DOM but also unique area-specific molecular signatures. Unique to the DOM of the Rio Negro area was the large abundance of high molecular weight, diverse hydrogen-deficient and highly oxidized molecular ions deviating from known lignin or tannin compositions, indicating substantial oxidative processing of these ultimately plant-derived polyphenols indicative of these black waters. In contrast, unique signatures in the Madeira/Jamari area were defined by presumably labile sulfur- and nitrogen-containing molecules in this white water river system. Waters from the Tapajós main stem did not show any substantial unique molecular signatures relative to those present in the Rio Madeira and Rio Negro, which implied a lower organic molecular complexity in this clear water tributary, even after mixing with the main stem of the Amazon River. Beside ubiquitous DOM at average H / C and O / C elemental ratios, a distinct and significant unique DOM pool prevailed in the black, white and clear water areas that were also highly correlated with EEM-PARAFAC components and define the frameworks for primary production and other aspects of aquatic life.

  20. Chemotaxis toward phytoplankton drives organic matter partitioning among marine bacteria

    PubMed Central

    Smriga, Steven; Fernandez, Vicente I.; Mitchell, James G.; Stocker, Roman

    2016-01-01

    The microenvironment surrounding individual phytoplankton cells is often rich in dissolved organic matter (DOM), which can attract bacteria by chemotaxis. These “phycospheres” may be prominent sources of resource heterogeneity in the ocean, affecting the growth of bacterial populations and the fate of DOM. However, these effects remain poorly quantified due to a lack of quantitative ecological frameworks. Here, we used video microscopy to dissect with unprecedented resolution the chemotactic accumulation of marine bacteria around individual Chaetoceros affinis diatoms undergoing lysis. The observed spatiotemporal distribution of bacteria was used in a resource utilization model to map the conditions under which competition between different bacterial groups favors chemotaxis. The model predicts that chemotactic, copiotrophic populations outcompete nonmotile, oligotrophic populations during diatom blooms and bloom collapse conditions, resulting in an increase in the ratio of motile to nonmotile cells and in the succession of populations. Partitioning of DOM between the two populations is strongly dependent on the overall concentration of bacteria and the diffusivity of different DOM substances, and within each population, the growth benefit from phycospheres is experienced by only a small fraction of cells. By informing a DOM utilization model with highly resolved behavioral data, the hybrid approach used here represents a new path toward the elusive goal of predicting the consequences of microscale interactions in the ocean. PMID:26802122

  1. Dissolved organic matter reduces algal accumulation of methylmercury

    USGS Publications Warehouse

    Luengen, Allison C.; Fisher, Nicholas S.; Bergamaschi, Brian A.

    2012-01-01

    Dissolved organic matter (DOM) significantly decreased accumulation of methylmercury (MeHg) by the diatom Cyclotella meneghiniana in laboratory experiments. Live diatom cells accumulated two to four times more MeHg than dead cells, indicating that accumulation may be partially an energy-requiring process. Methylmercury enrichment in diatoms relative to ambient water was measured by a volume concentration factor (VCF). Without added DOM, the maximum VCF was 32 x 104, and the average VCF (from 10 to 72 h) over all experiments was 12.6 x 104. At very low (1.5 mg/L) added DOM, VCFs dropped by approximately half. At very high (20 mg/L) added DOM, VCFs dropped 10-fold. Presumably, MeHg was bound to a variety of reduced sulfur sites on the DOM, making it unavailable for uptake. Diatoms accumulated significantly more MeHg when exposed to transphilic DOM extracts than hydrophobic ones. However, algal lysate, a labile type of DOM created by resuspending a marine diatom in freshwater, behaved similarly to a refractory DOM isolate from San Francisco Bay. Addition of 67 μM L-cysteine resulted in the largest drop in VCFs, to 0.28 x 104. Although the DOM composition influenced the availability of MeHg to some extent, total DOM concentration was the most important factor in determining algal bioaccumulation of MeHg.

  2. Results of the 2008 dissolved organic matter fluorescence intercalibration study

    NASA Astrophysics Data System (ADS)

    Murphy, K. R.; Butler, K.; Spencer, R. G.; Boehme, J.; Aiken, G.

    2009-12-01

    In 2008, 20 laboratories around the world participated in an intercalibration study of organic matter fluorescence measurements via Excitation-Emission Matrix Spectroscopy (EEMS). The goal was to assess the variability of fluorescence measurements obtained for identical samples (n = 5 natural samples, Suwanee River Fulvic Acid, quinine sulphate and four Starna Fluorescence Reference cells) by different laboratories, and to examine potential sources of this variability. Operator error was found to be a significant source of variability, with 6 laboratories submitting erroneous EEMs in an initial round. Uncorrected EEMs were significantly different from corrected EEMs, particularly at relatively low and relatively high excitation (λex) and emission (λem) wavelengths. When data from each lab were corrected according to a standard set of algorithms, the variability between EEMs for the same sample measured by different labs was wavelength dependent, with EEMs normalized to raman areas more similar at low λex and λem, and EEMs normalized to quinine sulphate equivalents more similar at higher wavelengths. The results confirm the importance of (1) applying spectral corrections prior to comparing fluorescence data acquired on different instruments, (2) full reporting of correction procedures and implementation according to an agreed standard protocol, and (3) strict implementation of quality assurance protocols prior to reporting EEMs.

  3. Soil microstructure and organic matter: keys for chlordecone sequestration.

    PubMed

    Woignier, T; Fernandes, P; Soler, A; Clostre, F; Carles, C; Rangon, L; Lesueur-Jannoyer, M

    2013-11-15

    Past applications of chlordecone, a persistent organochlorine pesticide, have resulted in diffuse pollution of agricultural soils, and these have become sources of contamination of cultivated crops as well as terrestrial and marine ecosystems. Chlordecone is a very stable and recalcitrant molecule, mainly present in the solid phase, and has a strong affinity for organic matter. To prevent consumer and ecosystem exposure, factors that influence chlordecone migration in the environment need to be evaluated. In this study, we measured the impact of incorporating compost on chlordecone sequestration in andosols as a possible way to reduce plant contamination. We first characterized the transfer of chlordecone from soil to plants (radish, cucumber, and lettuce). Two months after incorporation of the compost, soil-plant transfers were reduced by a factor of 1.9-15 depending on the crop. Our results showed that adding compost modified the fractal microstructure of allophane clays thus favoring chlordecone retention in andosols. The complex structure of allophane and the associated low accessibility are important characteristics governing the fate of chlordecone. These results support our proposal for an alternative strategy that is quite the opposite of total soil decontamination: chlordecone sequestration.

  4. [Effects of dissolved organic matter on copper absorption by ryegrass].

    PubMed

    Tang, Chao; Wang, Bin; Liu, Man-Qiang; Hu, Feng; Li, Hui-Xin; Jiao, Jia-Guo

    2012-08-01

    In this study, dissolved organic matter (DOM) was extracted from earthworm casts and from the cattle manure with which the earthworms were fed, and a water culture experiment was conducted to study the effects of the DOM on the copper (Cu2+) absorption by ryegrass in the presence of different concentration Cu2+ (0, 5 and 10 mg x L(-1)). With the increasing concentration of Cu2+ in the medium, there was a gradual decrease in the dry mass of ryegrass shoots and roots and in the root length, surface area, volume, and tip number. In the presence of medium Cu2+, DOM increased the biomass of shoots and roots and the root length, surface area, volume, and tip number significantly. DOM reduced the Cu2+ concentration in roots, promoted the Cu2+ translocation from roots to shoots, and significantly increased the Cu2+ accumulation in shoots. The DOM from earthworm casts had better effects than that from cattle manure, and high concentration DOM had better effects than low concentration DOM. PMID:23189712

  5. Soil microstructure and organic matter: keys for chlordecone sequestration.

    PubMed

    Woignier, T; Fernandes, P; Soler, A; Clostre, F; Carles, C; Rangon, L; Lesueur-Jannoyer, M

    2013-11-15

    Past applications of chlordecone, a persistent organochlorine pesticide, have resulted in diffuse pollution of agricultural soils, and these have become sources of contamination of cultivated crops as well as terrestrial and marine ecosystems. Chlordecone is a very stable and recalcitrant molecule, mainly present in the solid phase, and has a strong affinity for organic matter. To prevent consumer and ecosystem exposure, factors that influence chlordecone migration in the environment need to be evaluated. In this study, we measured the impact of incorporating compost on chlordecone sequestration in andosols as a possible way to reduce plant contamination. We first characterized the transfer of chlordecone from soil to plants (radish, cucumber, and lettuce). Two months after incorporation of the compost, soil-plant transfers were reduced by a factor of 1.9-15 depending on the crop. Our results showed that adding compost modified the fractal microstructure of allophane clays thus favoring chlordecone retention in andosols. The complex structure of allophane and the associated low accessibility are important characteristics governing the fate of chlordecone. These results support our proposal for an alternative strategy that is quite the opposite of total soil decontamination: chlordecone sequestration. PMID:24056248

  6. The Organic Matter Biogeochemistry of the Congo River

    NASA Astrophysics Data System (ADS)

    Spencer, R. G.; Hernes, P.; Wabakanghanzi, J.; Bienvenu, D. J.; Six, J.

    2015-12-01

    Organic matter (OM) represents a fundamental link between terrestrial and aquatic carbon cycles and plays an essential role in aquatic ecosystem biogeochemistry. The Congo River, which drains pristine tropical forest and savannah is the second largest exporter of terrestrial carbon to the ocean, and represents a historically understudied basin. Our ongoing projects in the Congo Basin aim to provide pertinent information on transport and emissions of carbon by rivers that need to be incorporated into carbon budgets of terrestrial ecosystems. To date the Congo Basin has seen only limited perturbation but the carbon locked away in the Congo, as in other tropical rainforests is increasingly vulnerable to release into the aquatic system and the atmosphere. However, riverine carbon transport (both of OM to the oceans and release of CO2 to the atmosphere) as a driver of global carbon cycling is still largely overlooked. Here we present data from a multi-season field campaign to quantify the transport fluxes, mineralization fluxes, and chemical character of Congo River OM, and to elucidate how these properties relate to each other and vary seasonally driven by hydrology within the Congo Basin. Existing data demonstrates that although tropical rivers do not experience the seasonal climatic extremes of temperate or northern high-latitude rivers, they all demonstrate similar effects due to changing hydrologic inputs with respect to OM dynamics. Specifically flushing periods appear to warrant further study as maximal export of reactive freshly leached plant material occurs during this time period.

  7. Chemotaxis toward phytoplankton drives organic matter partitioning among marine bacteria.

    PubMed

    Smriga, Steven; Fernandez, Vicente I; Mitchell, James G; Stocker, Roman

    2016-02-01

    The microenvironment surrounding individual phytoplankton cells is often rich in dissolved organic matter (DOM), which can attract bacteria by chemotaxis. These "phycospheres" may be prominent sources of resource heterogeneity in the ocean, affecting the growth of bacterial populations and the fate of DOM. However, these effects remain poorly quantified due to a lack of quantitative ecological frameworks. Here, we used video microscopy to dissect with unprecedented resolution the chemotactic accumulation of marine bacteria around individual Chaetoceros affinis diatoms undergoing lysis. The observed spatiotemporal distribution of bacteria was used in a resource utilization model to map the conditions under which competition between different bacterial groups favors chemotaxis. The model predicts that chemotactic, copiotrophic populations outcompete nonmotile, oligotrophic populations during diatom blooms and bloom collapse conditions, resulting in an increase in the ratio of motile to nonmotile cells and in the succession of populations. Partitioning of DOM between the two populations is strongly dependent on the overall concentration of bacteria and the diffusivity of different DOM substances, and within each population, the growth benefit from phycospheres is experienced by only a small fraction of cells. By informing a DOM utilization model with highly resolved behavioral data, the hybrid approach used here represents a new path toward the elusive goal of predicting the consequences of microscale interactions in the ocean.

  8. Chemotaxis toward phytoplankton drives organic matter partitioning among marine bacteria.

    PubMed

    Smriga, Steven; Fernandez, Vicente I; Mitchell, James G; Stocker, Roman

    2016-02-01

    The microenvironment surrounding individual phytoplankton cells is often rich in dissolved organic matter (DOM), which can attract bacteria by chemotaxis. These "phycospheres" may be prominent sources of resource heterogeneity in the ocean, affecting the growth of bacterial populations and the fate of DOM. However, these effects remain poorly quantified due to a lack of quantitative ecological frameworks. Here, we used video microscopy to dissect with unprecedented resolution the chemotactic accumulation of marine bacteria around individual Chaetoceros affinis diatoms undergoing lysis. The observed spatiotemporal distribution of bacteria was used in a resource utilization model to map the conditions under which competition between different bacterial groups favors chemotaxis. The model predicts that chemotactic, copiotrophic populations outcompete nonmotile, oligotrophic populations during diatom blooms and bloom collapse conditions, resulting in an increase in the ratio of motile to nonmotile cells and in the succession of populations. Partitioning of DOM between the two populations is strongly dependent on the overall concentration of bacteria and the diffusivity of different DOM substances, and within each population, the growth benefit from phycospheres is experienced by only a small fraction of cells. By informing a DOM utilization model with highly resolved behavioral data, the hybrid approach used here represents a new path toward the elusive goal of predicting the consequences of microscale interactions in the ocean. PMID:26802122

  9. Pyrolysis-combustion 14C dating of soil organic matter

    USGS Publications Warehouse

    Wang, Hongfang; Hackley, Keith C.; Panno, S.V.; Coleman, D.D.; Liu, J.C.-L.; Brown, J.

    2003-01-01

    Radiocarbon (14C) dating of total soil organic matter (SOM) often yields results inconsistent with the stratigraphic sequence. The onerous chemical extractions for SOM fractions do not always produce satisfactory 14C dates. In an effort to develop an alternative method, the pyrolysis-combustion technique was investigated to partition SOM into pyrolysis volatile (Py-V) and pyrolysis residue (Py-R) fractions. The Py-V fractions obtained from a thick glacigenic loess succession in Illinois yielded 14C dates much younger but more reasonable than the counterpart Py-R fractions for the soil residence time. Carbon isotopic composition (??13C) was heavier in the Py-V fractions, suggesting a greater abundance of carbohydrate- and protein-related constituents, and ??13C was lighter in the Py-R fractions, suggesting more lignin- and lipid-related constituents. The combination of 14C dates and ??13C values indicates that the Py-V fractions are less biodegradation resistant and the Py-R fractions are more biodegradation resistant. The pyrolysis-combustion method provides a less cumbersome approach for 14C dating of SOM fractions. With further study, this method may become a useful tool for analyzing unlithified terrestrial sediments when macrofossils are absent. ?? 2003 University of Washington. Published by Elsevier Inc. All rights reserved.

  10. Natural organic matter enhanced mobility of nano zerovalent iron.

    PubMed

    Johnson, Richard L; Johnson, Graham O'Brien; Nurmi, James T; Tratnyek, Paul G

    2009-07-15

    Column studies showed that the mobility of nanometer-sized zerovalent iron (nZVI) through granular media is greatly increased in the presence of natural organic matter (NOM). At NOM concentrations of 20 mg/L or greater, the nZVI was highly mobile during transport experiments in 0.15-m long columns packed with medium sand. Below 20 mg/L NOM, mobility of the nZVI was less; however, even at 2 mg/L the nZVI showed significantly increased mobility compared to the no-NOM case. Spectrophotometric and aggregation studies of nZVI suspensions in the presence of NOM suggest that sorption of the NOM onto the nZVI, resulting in a reduced sticking coefficient, may be the primary mechanism of enhanced mobility. Modeling the mobility of nZVI in porous media with filtration theory is challenging, but calibration of a simple model with experimental results from the column experiments reported here allows simulation of transport distances during injection. The simulation results show that the increased mobility due to NOM combined with the decrease in mobility due to decreased velocity with distance from an injection well could produce an injection zone that is wide enough to be useful for remediation but small enough to avoid reaching unwanted receptors. PMID:19708381

  11. The chemical ecology of soil organic matter molecular constituents.

    PubMed

    Simpson, Myrna J; Simpson, André J

    2012-06-01

    Soil organic matter (OM) contains vast stores of carbon, and directly supports microbial, plant, and animal life by retaining essential nutrients and water in the soil. Soil OM plays important roles in biological, chemical, and physical processes within the soil, and arguably plays a major role in maintaining long-term ecological stability in a changing world. Despite its importance, there is a great deal still unknown about soil OM chemical ecology. The development of sophisticated analytical methods have reshaped our understanding of soil OM composition, which is now believed to be comprised of plant and microbial products at various stages of decomposition. The methods also have recently been applied to study environmental change in various settings and have provided unique insight with respect to soil OM chemical ecology. The goal of this review is to highlight the methods used to characterize soil OM structure, source, and degradation that have enabled precise observations of OM and associated ecological shifts. Although the chemistry of soil OM is important in its overall fate in ecosystems, the studies conducted to date suggest that ecological function is not defined by soil OM chemistry alone. The long-standing questions regarding soil OM stability and recalcitrance will likely be answered when several molecular methods are used in tandem to closely examine structure, source, age, degradation stage, and interactions of specific OM components in soil.

  12. Mercury reduction and complexation by natural organic matter

    SciTech Connect

    Gu, Baohua; Bian, Yongrong; Miller, Carrie L; Dong, Wenming; Jiang, Xin; Liang, Liyuan

    2011-01-01

    Mercuric Hg(II) species form complexes with natural dissolved organic matter (DOM) such as humic acid (HA), and this binding is known to affect the chemical and biological transformation and cycling of mercury in aquatic environments. Dissolved elemental mercury, Hg(0), is also widely observed in sediments and water. However, reactions between Hg(0) and DOM have rarely been studied in anoxic environments. Here, under anoxic dark conditions we show strong interactions between reduced HA and Hg(0) through thiol-ligand induced oxidative complexation with an estimated binding capacity of about 3.5 umol Hg(0)/g HA and a partitioning coefficient greater than 10^6 mL/g. We further demonstrate that Hg(II) can be effectively reduced to Hg(0) in the presence of as little as 0.2 mg/L reduced HA, whereas production of purgeable Hg(0) is inhibited by complexation as HA concentration increases. This dual role played by DOM in the reduction and complexation of mercury is likely widespread in anoxic sediments and water and can be expected to significantly influence the mercury species transformations and biological uptake that leads to the formation of toxic methylmercury.

  13. Biochemical composition of organic matter in UK Midlands catchments: implications for drinking water treatment

    NASA Astrophysics Data System (ADS)

    Bieroza, M.; Bridgeman, J.; Baker, A.

    2007-12-01

    Insufficient removal of natural organic matter at treatment works can lead to the formation of potentially carcinogenic disinfection by-products (mainly trihalomethanes and haloacetic acids, THMs and HAAs) due to reactions of residual organic matter with chlorine added at the disinfection stage of water treatment process. However, the total organic carbon (TOC) removal efficiency is controlled by the content and character of organic matter in treated water, spatially and temporally dependent (e.g. the ratio of hydrophylic and hydrophobic fractions). Thus, a better understanding of organic matter composition can affect the treatment process strategies, improving the THM formation prediction and the quantification of coagulant and disinfection dosages. Fluorescence analysis of organic matter composition and treatment efficiency has been carried out on raw and partially-treated water samples from catchments in the Midlands region of the UK. The catchments cover an area of different water sources, ranging from upland, peaty-rich subcatchments with coloured, young waters, to agriculturally transformed lowland subcatchments. From the spectrophotometric analysis of raw water it was found that, the abstraction from river with water storage in reservoirs corresponds with a hydrophilic character of organic matter, rather high microbial fraction and high TOC. Opposite properties (hydrophobic, low microbial and variable TOC) are specific for sites with abstraction and storage processes within reservoirs. For direct abstraction from rivers, without water storing in reservoir, a common pattern is intermediate character of organic matter. The fluorescence excitation-emission matrix (EEM) technique was used for the assessment of water treatment works performance (TOC removal) and organic matter characterization. The freshwater organic matter exhibits specific fluorescence properties, with increased intensities of fluorescence in some regions of the EEM, resulting from the water

  14. Occurrence and abundance of carbohydrates and amino compounds in sequentially extracted labile soil organic matter fractions.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study aimed to investigate the content of carbohydrates and amino compounds in three labile fraction of soil organic matter (SOM). Soil samples were collected from two agricultural fields in southern Italy and the light fraction (LF), the 500–53-µm particulate organic matter (POM) and the mobil...

  15. Contribution of plant lignin to the soil organic matter formation and stabilization

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lignin is the third most abundant plant constituent after cellulose and hemicellulose and thought to be one of the building blocks for soil organic matter formation. Lignin can be used as a predictor for long-term soil organic matter stabilization and C sequestration. Soils and humic acids from fo...

  16. FACTORS INFLUENCING PHOTOREACTIONS OF DISSOLVED ORGANIC MATTER IN A COASTAL RIVER OF THE SOUTHEASTERN UNITED STATES

    EPA Science Inventory

    Photoreactions of dissolved organic matter can affect the oxidizing capacity, nutrient dynamics, trace gas exchange, and color of surface waters. This study focuses on factors that affect the photoreactions of the colored dissolved organic matter (CDOM) in the Satilla River, a co...

  17. Advances in understanding the molecular structure of soil organic matter: Implications for interactions in the environment

    EPA Science Inventory

    We take a historic approach to explore how concepts of the chemical and physical nature of soil organic matter have evolved over time. We emphasize conceptual and analytical achievements in organic matter research over the last two decades and demonstrate how these developments h...

  18. Cosorption study of organic pollutants and dissolved organic matter in a soil.

    PubMed

    Flores-Céspedes, F; Fernández-Pérez, M; Villafranca-Sánchez, M; González-Pradas, E

    2006-08-01

    In this study we have evaluated the effects of dissolved organic matter (DOM) on sorption of imidacloprid, 3,4-dichloroaniline (3,4-DCA) and 4-bromoaniline (4-BA) on a typical calcareous soil (Luvic Xerosol) from south-eastern Spain. Two different types of DOM were used, that is to say, dissolved natural organic matter extracts from a commercial peat (DNOM) and a high-purity tannic acid (TA) solution. The experiments were carried out in a 0.01 M CaCl2 aqueous medium at 25 degrees C. The results indicated that the presence of both DNOM and TA, over a concentration range of 15-100 mg L(-1), produced an increase in the amount of 3,4-DCA and 4-BA sorbed and a decrease in the amount of imidacloprid retained on the soil studied. A modified distribution coefficient, K(doc), has been proposed as a safer parameter for soil sorption predictions of organic pollutants and it could be of help to model the fate of these in the environment.

  19. Abiotic emissions of methane and reduced organic compounds from organic matter

    NASA Astrophysics Data System (ADS)

    Roeckmann, T.; Keppler, F.; Vigano, I.; Derendorp, L.; Holzinger, R.

    2012-12-01

    Recent laboratory studies show that the important greenhouse gas methane, but also other reduced atmospheric trace gases, can be emitted by abiotic processes from organic matter, such as plants, pure organic compounds and soils. It is very difficult to distinguish abiotic from biotic emissions in field studies, but in laboratory experiments this is easier because it is possible to carefully prepare/sterilize samples, or to control external parameters. For example, the abiotic emissions always show a strong increase with temperature when temperatures are increased to 70C or higher, well above the temperature optimum for bacterial activity. UV radiation has also been clearly shown to lead to emission of methane and other reduced gases from organic matter. Interesting information on the production mechanism has been obtained from isotope studies, both at natural abundance and with isotope labeling. For example, the methoxyl groups of pectin were clearly identified to produce methane. However, analysis of the isotopic composition of methane from natural samples clearly indicates that there must be other molecular mechanisms that lead to methane production. Abiotic methane generation could be a ubiquitous process that occurs naturally at low rates from many different sources.

  20. Soil organic matter on citrus plantation in Eastern Spain

    NASA Astrophysics Data System (ADS)

    Cerdà, Artemi; Pereira, Paulo; Novara, Agata; Prosdocimi, Massimo

    2015-04-01

    Citrus plantations in Eastern Spain are the main crop and Valencia region is the largest world exporter. The traditional plantation are located on flood irrigated areas and the new plantation are located on slopes were drip irrigation is the source of the wetting. It has been demonstrate that the citrus plantations contribute to high erosion rates on slopes (Cerdà et al., 2009b) as it is usual on agriculture land (Cerdà et al., 2009a), but when organic farming is present the soil erosion is much lower (Cerdà and Jurgensen, 2008; Cerdà et al., 2009; Cerdà and Jurgensen, 2011). This is a worldwide phenomenon (Wu et al., 2007; Wu et al., 2011; Xu et al., 2010; Xu et al., 2012a; Xu et al., 2012b), which are a key factor of the high erosion rates in rural areas (García Orenes et al., 2009: García Orenes et al., 20010; García Orenes et al., 2012; Haregewyn et al., 2013; Zhao et al., 2013). The key factor of the contrasted response of soils to the rain in citrus is the organic matter cover. This is why the Soil Erosion and Degradation Research Team developed a survey to determine the soil erosion rates on citrus orchards under different managements. A hundred of samples were collected in a citrus plantation on slope under conventional management (Chemical management), one on organic farming, one on traditional flood irrigated organic farming and one on traditional chemical flooding farm. The organic farming soils were treated with 10000 Kg ha-1 of manure yearly. The results show that the mean soil organic matter content was 1.24 %, 3.54%, 5,43% and 2.1% respectively, which show a clear impact of organic farming in the recovery of the soil organic matter. meanwhile the on the slopes and the flood-irrigated soils are Acknowledgements The research projects GL2008-02879/BTE, LEDDRA 243857 and PREVENTING AND REMEDIATING DEGRADATION OF SOILS IN EUROPE THROUGH LAND CARE (RECARE)FP7- ENV-2013- supported this research. References Cerdà, A., Flanagan, D.C., le Bissonnais

  1. Where is DNA preserved in soil organic matter?

    NASA Astrophysics Data System (ADS)

    Zaccone, Claudio; Beneduce, Luciano; Plaza, César

    2015-04-01

    Deoxyribonucleic acid (DNA) consists of long chains of alternating sugar and phosphate residues twisted in the form of a helix. Upon decomposition of plant and animal debris, this nucleic acid is released into the soil, where its fate is still not completely understood. In fact, although DNA is one of the organic compounds from living cells that is apparently broken down rapidly in soils, it is also potentially capable of being incorporated in (or interact with) the precursors of humic molecules. In order to track DNA occurrence in soil organic matter (SOM) fractions, an experiment was set up as a randomized complete block design with two factors, namely biochar addition and organic amendment. In particular, biochar (BC), applied at a rate of 20 t/ha, was combined with municipal solid waste compost (BC+MC) at a rate equivalent to 75 kg/ha of potentially available N, and with sewage sludge (BC+SS) at a rate equivalent to 75 kg/ha of potentially available N. Using a physical fractionation method, free SOM located between aggregates (unprotected C pool; FR), SOM occluded within macroaggregates (C pool weakly protected by physical mechanisms; MA), SOM occluded within microaggregates (C pool strongly protected by physical mechanisms; MI), and SOM associated with the mineral fractions (chemically-protected C pool; MIN) were separated from soil samples. DNA was then isolated from each fraction of the two series, as well as from the unamended soil (C) and from the bulk soils (WS), using Powersoil DNA isolation kit (MoBio, CA, USA) with a modified protocol. Data clearly show that the DNA survived the SOM fractionation, thus suggesting that physical fractionation methods create less artifacts compared to the chemical ones. Moreover, in both BC+MC and BC+SS series, most of the isolated DNA was present in the FR fraction, followed by the MA and the MI fractions. No DNA was recovered from the MIN fraction. This finding supports the idea that most of the DNA occurring in the SOM

  2. Soil Organic Matter Effects on Phosphorus Sorption: a Path Analysis

    SciTech Connect

    Kang, J.; Hesterberg, D; Osmond, D

    2009-01-01

    While P sorption in mineral soils has been extensively studied, P sorption behavior in organic-rich soils is less known. This study was conducted to determine the relationships between Langmuir P sorption maxima (S{sub max}) and selected physicochemical properties of soils, with particular emphasis on organic matter (OM) content. The S{sub max} values were determined for 72 soil samples from the North Carolina Coastal Plain, along with pH, clay and OM contents, oxalate-extractable P (P{sub ox}), Al (Al{sub ox}), and Fe (Fe{sub ox}), and Mehlich 3 extractable P (P{sub M3}), Al (Al{sub M3}), and Fe (Fe{sub M3}). Path analysis was used to examine direct and indirect effects of soil properties on S{sub max}. In the oxalate path analysis, the direct effects of clay, Al{sub ox}, and Fe{sub ox} on S{sub max} were significant in the order Al{sub ox} > clay > Fe{sub ox} (P < 0.05). The S{sub max} was highly influenced by the indirect effect of Al{sub ox} and Fe{sub ox} through OM content. A two-piece segmented linear relationship existed between S{sub max} and OM and the regression slope in soils with OM {le} 49 g kg{sup -1} was 10-fold greater than that for soils with OM > 49 g kg{sup -1}. This finding suggested that noncrystalline or organically bound Al and Fe in the soils with OM > 49 g kg{sup -1} is less effective for P sorption than in the soils with lower OM content. In the Mehlich 3 path analysis, the direct effects of clay, OM, and Al{sub M3} on S{sub max} were significant in the order Al{sub M3} > OM > clay (P < 0.05) while the direct effect of Fe{sub M3} on S{sub max} was not significant. Oxalate may be better suited than Mehlich 3 as an extractant for predicting P sorption capacity in the Coastal Plain soils.

  3. Dissolved organic matter in anoxic pore waters from Mangrove Lake, Bermuda

    USGS Publications Warehouse

    Orem, W.H.; Hatcher, P.G.; Spiker, E. C.; Szeverenyi, N.M.; Maciel, G.E.

    1986-01-01

    Dissolved organic matter and dissolved inorganic chemical species in anoxic pore water from Mangrove Lake, Bermuda sediments were studied to evaluate the role of pore water in the early diagenesis of organic matter. Dissolved sulphate, titration alkalinity, phosphate, and ammonia concentration versus depth profiles were typical of many nearshore clastic sediments and indicated sulphate reduction in the upper 100 cm of sediment. The dissolved organic matter in the pore water was made up predominantly of large molecules, was concentrated from large quantities of pore water by using ultrafiltration and was extensively tudied by using elemental and stable carbon isotope analysis and high-resolution, solid state 13C nuclear magnetic resonance and infrared spectroscopy. The results indicate that this material has a predominantly polysaccharide-like structure and in addition contains a large amount of oxygen-containing functional groups (e.g., carboxyl groups). The 13C nulcear magnetic resonance spectra of the high-molecular-weight dissolved organic matter resemble those of the organic matter in the surface sediments of Mangrove Lake. We propose that this high-molecular-weight organic matter in pore waters represents the partially degraded, labile organic components of the sedimentary organic matter and that pore waters serve as a conduit for removal of these labile organic components from the sediments. The more refractory components are, thus, selectively preserved in the sediments as humic substances (primarily humin). ?? 1986.

  4. Quantitative retrieving of soil organic matter using field spectrometer and hyperspectral remote sensing

    NASA Astrophysics Data System (ADS)

    Zhuo, Luo; Liu, Yaolin; Chen, Jie; Hu, Changji; Wu, Jian

    2008-12-01

    As the important component of soil, soil organic matter not only provides every nutrient element for crop, but also has determinant effect for forming of soil structure and melioration the soil physical character. Mapping and dating soil organic matter is of great importance in soil use and evaluation. In this study we examine the feasibility of soil organic matter content by using Hyperspectrally reflective remote sensing methodology. This technique was tested in Xiaochang County located in Hubei province. The soil reflectance properties of samples were measured in the laboratory by ASD field spectrometer. The correlation analysis related with organic matter content was processed from three factors: the spectral reflectance parameter ((lgρ)', ρ/ ρ450-750 and (1/lgρ623)'/ (1/lgρ564)'). The results show that the correlation coefficients of r values were: organic matter identification index (ρ/ ρ450-750) > logarithmic first derivative of reflectivity ((lgρ)') > organic matter mix identification index ((1/lgρ623)'/(1/lgρ564)'). Knowing these correlations we were able to use the best prominence correlation of organic matter identification index of 1850nm wavelength as the variable regression to build up statistical regression analysis. We used five model types (Linear Function, Logarithmic Function, Quadratic Function, Power Function and Exponential Function) to forecast the soil organic matter content Hyperion model. The accuracy assessment (R2= 0.8484) by relating forecasted organic matter values with Quadratic Function regression showed that the model is reliable and significantly correlative with known stabilization processes throughout the study area. The quantitative methodology developed in this study for refutations soil organic matter content can be adapted to other regions throughout the world.

  5. Estimating toxic damage to soil ecosystems from soil organic matter profiles

    USGS Publications Warehouse

    Beyer, W.N.

    2001-01-01

    Concentrations of particulate and total organic matter were measured in upper soil profiles at 26 sites as a potential means to identify toxic damage to soil ecosystems. Because soil organic matter plays a role in cycling nutrients, aerating soil, retaining water, and maintaining tilth, a significant reduction in organic matter content in a soil profile is not just evidence of a change in ecosystem function, but of damage to that soil ecosystem. Reference sites were selected for comparison to contaminated sites, and additional sites were selected to illustrate how variables other than environmental contaminants might affect the Soil organic matter profile. The survey was undertaken on the supposition that environmental contaminants and other stressors reduce the activity of earthworms and other macrofauna, inhibiting the incorporation of organic matter into the soil profile. The profiles of the unstressed soils showed a continuous decrease in organic matter content from the uppermost mineral soil layer (0-2.5 cm) down to 15 cm. Stressed soils showed an abrupt decrease in soil organic matter content below a depth of 2.5 cm. The 2.5-5.0 cm layer of stressed soils--such as found in a pine barren, an orchard, sites contaminated with zinc, and a site with compacted soil--had less than 4% total organic matter and less than 1% particulate organic matter. However, damaged soil ecosystems were best identified by comparison of their profiles to the profiles of closely matched reference soils, rather than by comparison to these absolute values. The presence or absence of earthworms offered a partial explanation of observed differences in soil organic matter profiles.

  6. Transport of organic contaminants in subsoil horizons and effects of dissolved organic matter related to organic waste recycling practices.

    PubMed

    Chabauty, Florian; Pot, Valérie; Bourdat-Deschamps, Marjolaine; Bernet, Nathalie; Labat, Christophe; Benoit, Pierre

    2016-04-01

    Compost amendment on agricultural soil is a current practice to compensate the loss of organic matter. As a consequence, dissolved organic carbon concentration in soil leachates can be increased and potentially modify the transport of other solutes. This study aims to characterize the processes controlling the mobility of dissolved organic matter (DOM) in deep soil layers and their potential impacts on the leaching of organic contaminants (pesticides and pharmaceutical compounds) potentially present in cultivated soils receiving organic waste composts. We sampled undisturbed soil cores in the illuviated horizon (60-90 cm depth) of an Albeluvisol. Percolation experiments were made in presence and absence of DOM with two different pesticides, isoproturon and epoxiconazole, and two pharmaceutical compounds, ibuprofen and sulfamethoxazole. Two types of DOM were extracted from two different soil surface horizons: one sampled in a plot receiving a co-compost of green wastes and sewage sludge applied once every 2 years since 1998 and one sampled in an unamended plot. Results show that DOM behaved as a highly reactive solute, which was continuously generated within the soil columns during flow and increased after flow interruption. DOM significantly increased the mobility of bromide and all pollutants, but the effects differed according the hydrophobic and the ionic character of the molecules. However, no clear effects of the origin of DOM on the mobility of the different contaminants were observed.

  7. Dynamics of dissolved organic matter in fjord ecosystems: Contributions of terrestrial dissolved organic matter in the deep layer

    NASA Astrophysics Data System (ADS)

    Yamashita, Youhei; McCallister, S. Leigh; Koch, Boris P.; Gonsior, Michael; Jaffé, Rudolf

    2015-06-01

    Annually, rivers and inland water systems deliver a significant amount of terrestrial organic matter (OM) to the adjacent coastal ocean in both particulate and dissolved forms; however, the metabolic and biogeochemical transformations of OM during its seaward transport remains one of the least understood components of the global carbon cycle. This transfer of terrestrial carbon to marine ecosystems is crucial in maintaining trophic dynamics in coastal areas and critical in global carbon cycling. Although coastal regions have been proposed as important sinks for exported terrestrial materials, most of the global carbon cycling data, have not included fjords in their budgets. Here we present distributional patterns on the quantity and quality of dissolved OM in Fiordland National Park, New Zealand. Specifically, we describe carbon dynamics under diverse environmental settings based on dissolved organic carbon (DOC) depth profiles, oxygen concentrations, optical properties (fluorescence) and stable carbon isotopes. We illustrate a distinct change in the character of DOC in deep waters compared to surface and mid-depth waters. Our results suggest that, both, microbial reworking of terrestrially derived plant detritus and subsequent desorption of DOC from its particulate counterpart (as verified in a desorption experiment) are the main sources of the humic-like enriched DOC in the deep basins of the studied fjords. While it has been suggested that short transit times and protection of OM by mineral sorption may ultimately result in significant terrestrial carbon burial and preservation in fjords, our data suggests the existence of an additional source of terrestrial OM in the form of DOC generated in deep, fjord water.

  8. Determination of organic-matter content of Appalachian Devonian shales from gamma-ray logs.

    USGS Publications Warehouse

    Schmoker, J.W.

    1981-01-01

    The organic-matter content of the Devonian shale of the Appalachian basin is important for assessing natural-gas resources. In most of the western part of the Appalachian basin the organic-matter content of the Devonian shale can be estimated from gamma-ray wire-line logs. Organic-matter contents estimated using these logs are compared with determinations from direct laboratory analyses of organic carbon for 74 intervals of varying thickness from 12 widely separated wells. The cumulative pool of gamma-ray logs for the Devonian shale forms a large and geographically broad data base. The approach may also be applicable to other formations.-from Author

  9. Jellyfish Lake, Palau: early diagenesis of organic matter in sediments of an anoxic marine lake

    USGS Publications Warehouse

    Orem, W.H.; Burnett, W.C.; Landing, W.M.; Lyons, W.B.; Showers, W.

    1991-01-01

    The major postdepositional change in the sedimentary organic matter is carbohydrate biodegradation. Lignin and aliphatic substances are preserved in the sediments. Dissolved organic matter in pore waters is primarily composed of carbohydrates, reflecting the degradation of sedimentary carbohydrates. Rate constants for organic carbon degradation and sulfate reduction in sediments of the lake are about 10?? lower than in other anoxic sediments. This may reflect the vascular plant source and partly degraded nature of the organic matter reaching the sediments of the lake. -from Authors

  10. Characterization of organic matter in lake sediments from Minnesota and Yellowstone National Park

    USGS Publications Warehouse

    Dean, Walter E.

    2006-01-01

    Samples of sediment from lakes in Minnesota and Yellowstone National Park (YNP) were analyzed for organic carbon (OC), hydrogen richness by Rock-Eval pyrolysis, and stable carbon- and nitrogen-isotope composition of bulk organic matter. Values of delta 13C of lake plankton tend to be around -28 to -32 parts per thousand (0/00). Organic matter with values of delta 13C in the high negative 20s overlap with those of organic matter derived from C3 higher terrestrial plants but are at least 10 0/00 more depleted in 13C than organic matter derived from C4 terrestrial plants. If the organic matter is produced mainly by photosynthetic plankton and is not oxidized in the water column, there may be a negative correlation between H-richness (Rock-Eval pyrolysis H-index) and delta 13C, with more H-rich, algal organic matter having lower values of delta 13C. However, if aquatic organic matter is oxidized in the water column, or if the organic matter is a mixture of terrestrial and aquatic organic matter, then there may be no correlation between H-richness and carbon-isotopic composition. Values of delta 13C lower than about -28 0/00 probably indicate a contribution of bacterial biomass produced in the hypolimnion by chemoautotrophy or methanotrophy. In highly eutrophic lakes in which large amounts of 13C-depleted organic matter is continually removed from the epilimnion by photosynthesis throughout the growing season, the entire carbon reservoir in the epilimnion may become severely 13C-enriched so that 13C-enriched photosynthetic organic matter may overprint 13C-depleted chemosynthetic bacterial organic matter produced in the hypolimnon. Most processes involved with the nitrogen cycle in lakes, such as production of ammonia and nitrate, tend to produce 15N-enriched values of delta 15N. Most Minnesota lake sediments are 15N-enriched. However, some of the more OC-rich sediments have delta 15N values close to zero (delta 15N of air), suggesting that organic matter production is

  11. Nanoscale Structure of Organic Matter Could Explain Litter Decomposition

    NASA Astrophysics Data System (ADS)

    Papa, G.; Adani, F.

    2014-12-01

    According to the literature biochemical catalyses are limited in their actions because of the complex macroscopic and, above all, microscopic structures of cell wall that limit mass transportation (i.e. 3D structure). Our study on energy crop showed that plant digestibility increased by modifying the 3D cell wall microstructure. Results obtained were ascribed to the enlargement, such as effectively measured, of the pore spaces between cellulose fibrils. Therefore we postulated that 3 D structure of plant residues drives degradability in soil determining its recalcitrance in short time. Here we focused on the drivers of short-term decomposition of organic matter (plant residues) in soils evaluating the architecture of plant tissues, captured via measurements of the microporosiy of the cell walls. Decomposition rates of a wide variety of biomass types were studied conducting experiments in both aerobic and anaerobic environments. Different analytical approaches were applied in order to characterize biomass at both chemical and physical level. Combined statistical approaches were used to examine the relationships between carbon mineralization and chemical/physical characteristics. The results revealed that degradation was significantly and negatively correlated with the micro-porosity surface (MiS) (surface of pores of 0.3-1.5 nm of diameter). The multiple regressions performed by using partial least square model enabled describing biomass biodegradability under either aerobic and anaerobic condition by using micro-porosity and aromatic-C content (assumed to be representative of lignin) as independent variables (R2 =0.97, R2cv =0.95 for aerobic condition; R2 =0.99, R2cv =0.98 for anaerobic condition, respectively). These results corroborate the hypothesis that plant tissues are physically protected from enzymatic attack by a microporous "sheath" that limit penetration into cell wall, and demonstrate the key role played by aromatic carbon, because of its chemical

  12. Hydrological controls on rate of organic matter mineralization in peats

    NASA Astrophysics Data System (ADS)

    Ghezzehei, Teamrat; Arnold, Chelsea; Asefaw Berhe, Asmeret

    2016-04-01

    The predominant factor that ties together the formation and persistence of peat soils across regions is their dependence on localized hydrology. Hydrology also plays a dominant role in the relative strength of peatlands as sinks for atmospheric carbon dioxide and sources of methane, and thus on peatland net climate impact. Drying of peat soils by climate change and/or drainage is typically followed by reduction in methane emissions. However, this may easily be offset by the increase in carbon dioxide production. Therefore, mechanistic understanding of peatland hydrology and its association with carbon cycling is a prerequisite for assessing vulnerability of peats to disturbances and for incorporating the associated feedbacks in carbon-climate models. We will present physically based model that ties together the structure of peat soils (mainly pore size distribution and mechanical stability) to rates of aerobic and anaerobic decomposition over a wide range of soil water potentials. Peats consist of hierarchical structure with clear separation of the pores into a population of micropores within clumps of organic matter and/or soil aggregates and a group of macropores between clumps and/or aggregates. This essentially partitions the carbon stock in peat soils in to multiple pools that become mineralizable at disparate water potential ranges. While the carbon in macropores can readily be decomposed by aerobic microorganisms when the soil is only slightly drained, the carbon in fine pores remains largely protected from aerobic microbes until the water potential exceeds a threshold that lets in oxygen. In this presentation we will show the mathematical development of the model and illustrative examples that compare projections with data derived from the literature.

  13. Concurrent photolytic degradation of aqueous methylmercury and dissolved organic matter

    USGS Publications Warehouse

    Fleck, Jacob A.; Gill, Gary W.; Bergamaschi, Brian A.; Kraus, Tamara E.C.; Downing, Bryan D.; Alpers, Charles N.

    2014-01-01

    Monomethyl mercury (MeHg) is a potent neurotoxin that threatens ecosystem viability and human health. In aquatic systems, the photolytic degradation of MeHg (photodemethylation) is an important component of the MeHg cycle. Dissolved organic matter (DOM) is also affected by exposure to solar radiation (light exposure) leading to changes in DOM composition that can affect its role in overall mercury (Hg) cycling. This study investigated changes in MeHg concentration, DOM concentration, and the optical signature of DOM caused by light exposure in a controlled field-based experiment using water samples collected from wetlands and rice fields. Filtered water from all sites showed a marked loss in MeHg concentration after light exposure. The rate of photodemethylation was 7.5 × 10-3 m2 mol-1 (s.d. 3.5 × 10-3) across all sites despite marked differences in DOM concentration and composition. Light exposure also caused changes in the optical signature of the DOM despite there being no change in DOM concentration, indicating specific structures within the DOM were affected by light exposure at different rates. MeHg concentrations were related to optical signatures of labile DOM whereas the percent loss of MeHg was related to optical signatures of less labile, humic DOM. Relationships between the loss of MeHg and specific areas of the DOM optical signature indicated that aromatic and quinoid structures within the DOM were the likely contributors to MeHg degradation, perhaps within the sphere of the Hg-DOM bond. Because MeHg photodegradation rates are relatively constant across freshwater habitats with natural Hg–DOM ratios, physical characteristics such as shading and hydrologic residence time largely determine the relative importance of photolytic processes on the MeHg budget in these mixed vegetated and open-water systems.

  14. Biogeochemical Processes That Produce Dissolved Organic Matter From Wheat Straw

    USGS Publications Warehouse

    Wershaw, Robert L.; Rutherford, David W.; Leenheer, Jerry A.; Kennedy, Kay R.; Cox, Larry G.; Koci, Donald R.

    2003-01-01

    The chemical reactions that lead to the formation of dissolved organic matter (DOM) in natural waters are poorly understood. Studies on the formation of DOM generally are complicated because almost all DOM isolates have been derived from mixtures of plant species composed of a wide variety of different types of precursor compounds for DOM formation. This report describes a study of DOM derived mainly from bales of wheat straw that had been left in a field for several years. During this period of time, black water from the decomposing wheat straw accumulated in pools in the field. The nuclear magnetic resonance and infrared spectra of the black water DOM indicate that it is composed almost entirely of lignin and carbohydrate polymeric units. Analysis by high-performance size-exclusion chromatography with multi-angle laser-light scattering detection indicates that the number average molecular weight of the DOM is 124,000 daltons. The results presented in this report indicate that the black water DOM is composed of hemicellulose chains cross-linked to lignin oligomers. These types of structures have been shown to exist in the hemicellulose matrix of plant cell walls. The cross-linked lignin-hemicellulose complexes apparently were released from partially degraded wheat-straw cell walls with little alteration. In solution in the black water, these lignin-hemicellulose polymers fold into compact globular particles in which the nonpolar parts of the polymer form the interiors of the particles and the polar groups are on the exterior surfaces of the particles. The tightly folded, compact conformation of these particles probably renders them relatively resistant to microbial degradation. This should be especially the case for the aromatic lignin structures that will be buried in the interiors of the particles.

  15. Effects of Fe on Physicochemical Characteristics of Natural Organic Matter

    NASA Astrophysics Data System (ADS)

    Maurice, P. A.; Pullin, M. J.; Anthony, C.

    2003-12-01

    Natural organic matter (NOM) is ubiquitous in aquatic and terrestrial environments, and it plays an important role in controlling many biogeochemical processes. NOM molecular weight (MW) is a key property that affects NOM reactivity. Polyvalent metals such as Fe and Al bind strongly to NOM and also can cause its coagulation. Thus, we hypothesized that the presence of Fe would affect NOM MW determinations, even at relatively low Fe and NOM concentrations. This hypothesis was tested by adding increasing amounts of Fe(III) to aqueous solutions of NOM isolate (XAD-8) at pH 5.5, in the dark, and following changes in the NOM MW (measured by size exclusion chromatography), absorbance, and fluorescence. No change in MW was observed to 3 uM total Fe concentration, but at 10 uM total Fe concentration, there was a loss of low MW components and an increase in higher MW components. The weight average MW increased from 3661 Da to 3975 Da. Absorbance at 254 nm (typically monitored in water treatment processes) was unchanged by added Fe, but absorbance increase over parts of the visible spectrum (350-600 nm), and decreased in the far UV (200-225 nm), thus altering spectral slope. The two fluorescence maxima observed for this sample (Ex 325, Em 450; Ex 230, Em 435) decreased in intensity with increasing Fe concentration, with no shift in peak location. These results have important implications for our understanding of the concept of 'molecular weight' as applied to NOM, and for NOM reactivity including bioavailability, adsorption, and other processes.

  16. Spatial Arrangement of Organic Compounds on a Model Mineral Surface: Implications for Soil Organic Matter Stabilization

    NASA Astrophysics Data System (ADS)

    Ambaye, Haile; Petridis, Loukas; Jagadamma, Sindhu; Kilbey, Michael; Lauter, Valeria; Lokitz, Bradley; Mayes, Melanie

    2015-03-01

    Stability of organic carbon compounds in soil is important for global climate futures which could be affected by the complexity of the mineral-organic carbon interfaces. We examined the nanoscale structure of model interfaces by depositing films of organic carbon compounds of contrasting chemical character, hydrophilic glucose, deuterated-amphiphilic stearic acid (SA) and Natural Organic Matters (NOM) onto a soil mineral analogue (Al2O3) . The NOM was separated into its constituent components such as NOM-Philic and NOM-Phobic when it is deposited onto the soil mineral. We used Neutron Reflectivity technique to understand the depth organization of the thin films. The result indicates that glucose molecules reside in a layer between Al2O3 and stearic acid and SA self-assembles. No self-assembly of SA was observed when SA and NOM-Phobic was deposited on the mineral soil. Molecular dynamics simulations reveal the thermodynamic driving force behind glucose partitioning on the mineral interface. Funded by ORNL Director's Research and Development Program. Research at ORNL was sponsored by the BES, DOE.

  17. Temperature Dependence of Photodegradation of Dissolved Organic Matter to Dissolved Inorganic Carbon and Particulate Organic Carbon

    PubMed Central

    Porcal, Petr; Dillon, Peter J.; Molot, Lewis A.

    2015-01-01

    Photochemical transformation of dissolved organic matter (DOM) has been studied for more than two decades. Usually, laboratory or “in-situ” experiments are used to determine photodegradation variables. A common problem with these experiments is that the photodegradation experiments are done at higher than ambient temperature. Five laboratory experiments were done to determine the effect of temperature on photochemical degradation of DOM. Experimental results showed strong dependence of photodegradation on temperature. Mathematical modeling of processes revealed that two different pathways engaged in photochemical transformation of DOM to dissolved inorganic carbon (DIC) strongly depend on temperature. Direct oxidation of DOM to DIC dominated at low temperatures while conversion of DOM to intermediate particulate organic carbon (POC) prior to oxidation to DIC dominated at high temperatures. It is necessary to consider this strong dependence when the results of laboratory experiments are interpreted in regard to natural processes. Photodegradation experiments done at higher than ambient temperature will necessitate correction of rate constants. PMID:26106898

  18. Natural organic matter and the event horizon of mass spectrometry.

    PubMed

    Hertkorn, N; Frommberger, M; Witt, M; Koch, B P; Schmitt-Kopplin, Ph; Perdue, E M

    2008-12-01

    Soils, sediments, freshwaters, and marine waters contain natural organic matter (NOM), an exceedingly complex mixture of organic compounds that collectively exhibit a nearly continuous range of properties (size-reactivity continuum). NOM is composed mainly of carbon, hydrogen, and oxygen, with minor contributions from heteroatoms such as nitrogen, sulfur, and phosphorus. Suwannee River fulvic acid (SuwFA) is a fraction of NOM that is relatively depleted in heteroatoms. Ultrahigh resolution Fourier transform ion cyclotron (FTICR) mass spectra of SuwFA reveal several thousand molecular formulas, corresponding in turn to several hundred thousand distinct chemical environments of carbon even without accountancy of isomers. The mass difference deltam among adjoining C,H,O-molecules between and within clusters of nominal mass is inversely related to molecular dissimilarity: any decrease of deltam imposes an ever growing mandatory difference in molecular composition. Molecular formulas that are expected for likely biochemical precursor molecules are notably absent from these spectra, indicating that SuwFA is the product of diagenetic reactions that have altered the major components of biomass beyond the point of recognition. The degree of complexity of SuwFA can be brought into sharp focus through comparison with the theoretical limits of chemical complexity, as constrained and quantized by the fundamentals of chemical binding. The theoretical C,H,O-compositional space denotes the isomer-filtered complement of the entire, very vast space of molecular structures composed solely of carbon, hydrogen, and oxygen. The molecular formulas within SuwFA occupy a sizable proportion of the theoretical C,H,O-compositional space. A 100 percent coverage of the theoretically feasible C,H,O-compositional space by SuwFA molecules is attained throughout a sizable range of mass and H/C and O/C elemental ratios. The substantial differences between (and complementarity of) the SuwFA molecular

  19. Colored dissolved organic matter in Tampa Bay, Florida

    USGS Publications Warehouse

    Chen, Z.; Hu, C.; Conmy, R.N.; Muller-Karger, F.; Swarzenski, P.

    2007-01-01

    Absorption and fluorescence of colored dissolved organic matter (CDOM) and concentrations of dissolved organic carbon (DOC), chlorophyll and total suspended solids in Tampa Bay and its adjacent rivers were examined in June and October of 2004. Except in Old Tampa Bay (OTB), the spatial distribution of CDOM showed a conservative relationship with salinity in June, 2004 (aCDOM(400) = − 0.19 × salinity + 6.78, R2 = 0.98, n = 17, salinity range = 1.1–32.5) with little variations in absorption spectral slope and fluorescence efficiency. This indicates that CDOM distribution was dominated by mixing. In October, 2004, CDOM distribution was nonconservative with an average absorption coefficient (aCDOM(400), ∼ 7.76 m-1) about seven times higher than that in June (∼ 1.11 m-1). The nonconservative behavior was caused largely by CDOM removal at intermediate salinities (e.g., aCDOM(400) removal > 15% at salinity ∼ 13.0), which likely resulted from photobleaching due to stronger stratification. The spatial and seasonal distributions of CDOM in Tampa Bay showed that the two largest rivers, the Alafia River (AR) and Hillsborough River (HR) were dominant CDOM sources to most of the bay. In OTB, however, CDOM showed distinctive differences: lower absorption coefficient, higher absorption spectral slopes, and lower ratios of CDOM absorption to DOC and higher fluorescence efficiency. These differences may have stemmed from (1) changes in CDOM composition by more intensive photobleaching due to the longer residence time of water mass in OTB; (2) other sources of CDOM than the HR/AR inputs, such as local creeks, streams, groundwater, and/or bottom re-suspension. Average CDOM absorption in Tampa Bay at 443 nm, aCDOM(443), was about five times higher in June and about ten times higher in October than phytoplankton pigment absorption, aph(443), indicating that blue light attenuation in the water column was dominated by CDOM rather than by phytoplankton absorption throughout the

  20. The Contribution of Fungal Necromass to Soil Organic Matter Storage

    NASA Astrophysics Data System (ADS)

    Schreiner, K. M.; Blair, N. E.; Buiser, A.; Egerton-Warburton, L.

    2013-12-01

    Saprotrophic fungi have the ability to degrade the three most important biopolymers: cellulose, lignin, and chitin, and therefore are key moderators of a globally important flow of carbon. However, little is known about how that carbon is transformed and/or stored in soil organic matter (SOM). Fungi are also known to produce a variety of biopolymers, such as chitin, melanin, glucan, and mucus-like exudates, and it is likely that these compounds contribute to long-term storage of SOM. In fact, recent work with ectomycorrhizal fungi has shown that a portion of the fungal necromass survives after degradation times of a few weeks to one month (e.g. Drigo et al. 2012, Clemmenson et al. 2013). Until now, the potential contribution of other abundant fungi to recalcitrant SOM has been unknown. Soil incubations have been performed with the common saprotrophic fungus, Fusarium avencum. Approximately 80% of the fungal material was found to turnover over on a time period of days, but 15% of the original biomass was left over at the end of the two-month degradation experiment in both laboratory experiments and in situ in the Dixon Prairie of the Chicago Botanic Garden. In both experiments, degradation was performed by a natural soil microbial consortium. Residual fungal material at each point in the decomposition sequence was analyzed using FTIR and thermochemolysis-GCMS with tetramethyl ammonium hydroxide. The recalcitrant fraction contained carbohydrate and amide-linked functional groups, which is consistent with the chitin or chitosan biopolymer. The breakdown of more labile organic carbon (including proteins and ester-linked groups) appears to occur on a more rapid time scale. Additionally, lipid biomarker analyses revealed a succession of microbial degraders in the degradation process. This is the first time a study of this kind has been performed using a widely distributed saprotrophic fungus, and indicates that these fungi are potentially important in long-term C

  1. Evolution of soil organic matter changes using pyrolysis and metabolic indices: a comparison between organic and mineral fertilization.

    PubMed

    Marinari, S; Masciandaro, G; Ceccanti, B; Grego, S

    2007-09-01

    The aim of this study was to evaluate chemical and biochemical changes of organic matter in fertilized (ammonium nitrate) and amended (vermicompost and manure) soils using pyrolysis and metabolic indices. The metabolic potential [dehydrogenase (DH-ase)/water soluble organic carbon (WSOC)], the metabolic quotient (qCO2) and the microbial quotient (Cmic:Corg) were calculated as indices of soil organic matter evolution. Pyrolysis-gas chromatography (Py-GC) was used to study structural changes in the organic matter. Carbon forms and microbial biomass have been measured by dichromate oxidation and fumigation-extraction methods, respectively. Dehydrogenase activity has been tested using INT (p-Iodonitrotetrazolium violet) as substrate. The results showed that organic amendment increased soil microbial biomass and its activity which were strictly related to pyrolytic mineralization and humification indices (N/O, B/E3). Mineral fertilization caused a greater alteration of native soil organic matter than the organic amendments, in that a high release of WSOC and relatively large amounts of aliphatic pyrolytic products, were observed. Therefore, the pyrolysis and metabolic indices provided similar and complementary information on soil organic matter changes after mineral and organic fertilization.

  2. Quantifying the degradation of organic matter in marine sediments: A review and synthesis

    NASA Astrophysics Data System (ADS)

    Arndt, Sandra; Jørgensen, B. B.; LaRowe, D. E.; Middelburg, J. J.; Pancost, R. D.; Regnier, P.

    2013-08-01

    Quantifying the rates of biogeochemical processes in marine sediments is essential for understanding global element cycles and climate change. Because organic matter degradation is the engine behind benthic dynamics, deciphering the impact that various forces have on this process is central to determining the evolution of the Earth system. Therefore, recent developments in the quantitative modeling of organic matter degradation in marine sediments are critically reviewed. The first part of the review synthesizes the main chemical, biological and physical factors that control organic matter degradation in sediments while the second part provides a general review of the mathematical formulations used to model these processes and the third part evaluates their application over different spatial and temporal scales. Key transport mechanisms in sedimentary environments are summarized and the mathematical formulation of the organic matter degradation rate law is described in detail. The roles of enzyme kinetics, bioenergetics, temperature and biomass growth in particular are highlighted. Alternative model approaches that quantify the degradation rate constant are also critically compared. In the third part of the review, the capability of different model approaches to extrapolate organic matter degradation rates over a broad range of temporal and spatial scales is assessed. In addition, the structure, functions and parameterization of more than 250 published models of organic matter degradation in marine sediments are analyzed. The large range of published model parameters illustrates the complex nature of organic matter dynamics, and, thus, the limited transferability of these parameters from one site to another. Compiled model parameters do not reveal a statistically significant correlation with single environmental characteristics such as water depth, deposition rate or organic matter flux. The lack of a generic framework that allows for model parameters to be

  3. Bioavailability of organic matter in a highly disturbed Estuary: The role of detrital and algal resources

    USGS Publications Warehouse

    Sobczak, W.V.; Cloern, J.E.; Jassby, A.D.; Muller-Solger, A. B.

    2002-01-01

    The importance of algal and detrital food supplies to the planktonic food web of a highly disturbed, estuarine ecosystem was evaluated in response to declining zooplankton and fish populations. We assessed organic matter bioavailability among a diversity of habitats and hydrologic inputs over 2 years in San Francisco Estuary's Sacramento-San Joaquin River Delta. Results show that bioavailable dissolved organic carbon from external riverine sources supports a large component of ecosystem metabolism. However, bioavailable particulate organic carbon derived primarily from internal phytoplankton production is the dominant food supply to the planktonic food web. The relative importance of phytoplankton as a food source is surprising because phytoplankton production is a small component of the ecosystem's organic-matter mass balance. Our results indicate that management plans aimed at modifying the supply of organic matter to riverine, estuarine, and coastal food webs need to incorporate the potentially wide nutritional range represented by different organic matter sources.

  4. Bioavailability of organic matter in a highly disturbed estuary: The role of detrital and algal resources

    PubMed Central

    Sobczak, William V.; Cloern, James E.; Jassby, Alan D.; Müller-Solger, Anke B.

    2002-01-01

    The importance of algal and detrital food supplies to the planktonic food web of a highly disturbed, estuarine ecosystem was evaluated in response to declining zooplankton and fish populations. We assessed organic matter bioavailability among a diversity of habitats and hydrologic inputs over 2 years in San Francisco Estuary's Sacramento–San Joaquin River Delta. Results show that bioavailable dissolved organic carbon from external riverine sources supports a large component of ecosystem metabolism. However, bioavailable particulate organic carbon derived primarily from internal phytoplankton production is the dominant food supply to the planktonic food web. The relative importance of phytoplankton as a food source is surprising because phytoplankton production is a small component of the ecosystem's organic-matter mass balance. Our results indicate that management plans aimed at modifying the supply of organic matter to riverine, estuarine, and coastal food webs need to incorporate the potentially wide nutritional range represented by different organic matter sources. PMID:12060756

  5. Optical properties and bioavailability of dissolved organic matter along a flow-path continuum from soil pore waters to the Kolyma River mainstem, East Siberia

    NASA Astrophysics Data System (ADS)

    Frey, Karen E.; Sobczak, William V.; Mann, Paul J.; Holmes, Robert M.

    2016-04-01

    The Kolyma River in northeast Siberia is among the six largest Arctic rivers and drains a region underlain by vast deposits of Holocene-aged peat and Pleistocene-aged loess known as yedoma, most of which is currently stored in ice-rich permafrost throughout the region. These peat and yedoma deposits are important sources of dissolved organic matter (DOM) to inland waters that in turn play a significant role in the transport and ultimate remineralization of organic carbon to CO2 and CH4 along the terrestrial flow-path continuum. The turnover and fate of terrigenous DOM during offshore transport largely depends upon the composition and amount of carbon released to inland and coastal waters. Here, we measured the ultraviolet-visible optical properties of chromophoric DOM (CDOM) from a geographically extensive collection of waters spanning soil pore waters, streams, rivers, and the Kolyma River mainstem throughout a ˜ 250 km transect of the northern Kolyma River basin. During the period of study, CDOM absorption coefficients were found to be robust proxies for the concentration of DOM, whereas additional CDOM parameters such as spectral slopes (S) were found to be useful indicators of DOM quality along the flow path. In particular, the spectral slope ratio (SR) of CDOM demonstrated statistically significant differences between all four water types and tracked changes in the concentration of bioavailable DOC, suggesting that this parameter may be suitable for clearly discriminating shifts in organic matter characteristics among water types along the full flow-path continuum across this landscape. However, despite our observations of downstream shifts in DOM composition, we found a relatively constant proportion of DOC that was bioavailable ( ˜ 3-6 % of total DOC) regardless of relative water residence time along the flow path. This may be a consequence of two potential scenarios allowing for continual processing of organic material within the system, namely (a

  6. Optical properties and bioavailability of dissolved organic matter along a flow-path continuum from soil pore waters to the Kolyma River, Siberia

    NASA Astrophysics Data System (ADS)

    Frey, K. E.; Sobczak, W. V.; Mann, P. J.; Holmes, R. M.

    2015-08-01

    The Kolyma River in Northeast Siberia is among the six largest arctic rivers and drains a region underlain by vast deposits of Holocene-aged peat and Pleistocene-aged loess known as yedoma, most of which is currently stored in ice-rich permafrost throughout the region. These peat and yedoma deposits are important sources of dissolved organic matter (DOM) to inland waters that in turn play a significant role in the transport and ultimate remineralization of organic carbon to CO2 and CH4 along the terrestrial flow-path continuum. The turnover and fate of terrigenous DOM during offshore transport will largely depend upon the composition and amount of carbon released to inland and coastal waters. Here, we measured the optical properties of chromophoric DOM (CDOM) from a geographically extensive collection of waters spanning soil pore waters, streams, rivers, and the Kolyma River mainstem throughout a ∼ 250 km transect of the northern Kolyma River basin. During the period of study, CDOM absorbance values were found to be robust proxies for the concentration of DOM, whereas additional CDOM parameters such as spectral slopes (S) were found to be useful indicators of DOM quality along the flow-path. In particular, CDOM absorption at 254 nm showed a strong relationship with dissolved organic carbon (DOC) concentrations across all water types (r2 = 0.958, p < 0.01). The spectral slope ratio (SR) of CDOM demonstrated statistically significant differences between all four water types and tracked changes in the concentration of bioavailable DOC, suggesting that this parameter may be suitable for clearly discriminating shifts in organic matter characteristics among water types along the full flow-path continuum across this landscape. The heterogeneity of environmental characteristics and extensive continuous permafrost of the Kolyma River basin combine to make this a critical region to investigate and monitor. With ongoing and future permafrost degradation, peat and yedoma

  7. Sediment organic matter content as a confounding factor in toxicity tests with Chironomus tentans

    SciTech Connect

    Lacey, R.; Watzin, M.C.; McIntosh, A.W.

    1999-02-01

    Physicochemical characteristics of sediment unrelated to contaminant levels and bioavailability may influence the outcome of toxicity tests. In particular, sediment organic matter content has the potential to be a confounding factor in toxicity tests using the midge larva Chironomus tentans because the larvae are infaunal and feed on organic matter in the sediments. To examine the possibility, the authors conducted a series of tests using formulated sediments with varying organic matter contents following the standard US Environmental Protection Agency (US EPA) 10-day C. tentans growth and survival protocol. Formulated sediments made with peat moss, {alpha}-cellulose, and maple leaves were tested. An organic-rich natural sediment diluted with formulated sediment to achieve a range of organic matter contents was also examined. In a final experiment, sediments containing each of the four organic matter sources at the same concentration were tested against one another. Survival was not greatly affected by concentration of organic matter, except at the lowest concentrations in natural sediment, where survival dipped below 70%. In experiments using peat moss, {alpha}-cellulose, and maple leaves, significant differences in C. tentans growth were found at different organic matter concentrations. In contrast, concentration of organic matter in the natural sediment dilution series had little effect on growth, perhaps because much of this material was highly refractory. In the comparison experiment, growth differed significantly among the four sediments, with best growth achieved with {alpha}-cellulose and leaves. These results suggest that both organic matter quantity and quality can be confounding factors in toxicity tests using C. tentans.

  8. Effect of water saturation in soil organic matter on the partition of organic compounds

    USGS Publications Warehouse

    Rutherford, D.W.; Chlou, G.T.

    1992-01-01

    The sorption of benzene, trichloroethylene, and carbon tetrachloride at room temperature from water solution and from vapor on two high-organic-content soils (peat and muck) was determined in order to evaluate the effect of water saturation on the solute partition in soil organic matter (SOM). The uptake of water vapor was similarly determined to define the amounts of water in the saturated soil samples. In such high-organic-content soils the organic vapor sorption and the respective solute sorption from water exhibit linear isotherms over a wide range of relative concentrations. This observation, along with the low BET surface areas of the samples, suggests that partition in the SOM of the samples is the dominant process in the uptake of these liquids. A comparison of the sorption from water solution and from vapor phase shows that water saturation reduces the sorption (partition) efficiency of SOM by ?? 42%; the saturated water content is ??38% by weight of dry SOM. This reduction is relatively small when compared with the almost complete suppression by water of organic compound adsorption on soil minerals. While the effect of water saturation on solute uptake by SOM is much expected in terms of solute partition in SOM, the influence of water on the solubility behavior of polar SOM can be explained only qualitatively by regular solution theory. The results suggest that the major effect of water in a drying-wetting cycle on the organic compound uptake by normal low-organic-content soils (and the associated compound's activity) is the suppression of adsorption by minerals rather than the mitigation of the partition effect in SOM.

  9. Mobilization of stable organic carbon in thawing permafrost by fresh organic matter from recent vegetation

    NASA Astrophysics Data System (ADS)

    Knoblauch, C.; Beer, C.; Pfeiffer, E. M.

    2015-12-01

    Permafrost affected soils contain 1,300 Pg organic carbon which is about twice the amount of the global vegetation. Most of this carbon (C) is locked in the perennially frozen ground (permafrost) and only a minor part is stored in the seasonal surface thaw layer (active layer). Rising arctic temperatures will cause deeper active layer thaw and permafrost degradation, which liberates additional soil organic matter (SOM) for microbial mineralization. After thaw, old permafrost C will be mixed with fresh organic matter from plant residues, e.g. by cryoturbation or leaching. Recent incubation studies have increased our understanding on how fast permafrost SOM may be mineralized to the greenhouse gases (GHG) carbon dioxide (CO2) and methane (CH4). After initial maximum GHG production from labile SOM components (labile C pool) mineralization rates slow down since the remaining SOM is more recalcitrant (stable C pool). The current study investigates if this stabile C pool may be mobilized by fresh organic matter from recent vegetation ("priming effect"). Therefore, permafrost samples (14C ages 0.1 - 17 ka BP) from the Siberian tundra were spiked with a 13C-labeled sedge (Carex aquatilis) after the samples were pre-incubated for 4 years. The amount of C released from permafrost SOM was calculated from the δ13C-values of produced GHG using a mixing model. Under aerobic conditions, all samples showed an accelerated mineralization of SOM after the addition of C. aquatilis (positive priming). After 4 months, which is about one vegetation period, the measured CO2 production exceeded the estimated CO2 release without labile plant material by 60 ± 28%. Under anaerobic conditions, priming was more pronounced increasing CO2 production by 100 ± 67% and CH4 production by 33 ± 32%. The CO2/CH4 ratio increased from 0.9 before priming to 1.3 after priming. The total mineralization of SOM over 4 months was significantly higher under aerobic (14.2 ± 6.1 μmol CO2-C gdw-1) than under

  10. Effect of organic matter on the sorption activity of heavy loamy soils for volatile organic compounds under low moisture conditions

    NASA Astrophysics Data System (ADS)

    Breus, I. P.; Mishchenko, A. A.; Shinkarev, A. A.; Neklyudov, S. A.; Breus, V. A.

    2014-12-01

    The diverse effect of the organic matter content on the sorption of vapors of aromatic and aliphatic hydrocarbons in soils under low moisture (<10.5%) has been revealed in sorption experiments using profile samples from two virgin heavy loamy dark gray forest soils characterized by relatively stable contents of finely dispersed mineral components. The decrease of the hydrocarbon sorption with increasing the content of organic matter under dry conditions (in the moisture range from 0 to 5-6%) indicates its lower sorption activity than that of the clay components and the blocking of the sorption sites on soil minerals by organic matter. At moisture contents above 5-6%, the effect of the soil composition on the sorption activity changes radically: it increases with increasing the content of organic matter. This is due to the inversion of the ratio between the activities of the soil components because of the hydrophilization of the surface of the mineral soil component. As a result, the sorption of water on the minerals reduces the mineral sorption activity to hydrocarbons to a lower level than the activity of organic matter. The maximum manifestation of the revealed blocking effect has been observed for the low-humus soils and this effect decreased with the accumulation of soil organic matter.

  11. Integrating Organic Matter Structure with Ecosystem Function using Advanced Analytical Chemistry Techniques

    NASA Astrophysics Data System (ADS)

    Boot, C. M.

    2012-12-01

    Microorganisms are the primary transformers of organic matter in terrestrial and aquatic ecosystems. The structure of organic matter controls its bioavailability and researchers have long sought to link the chemical characteristics of the organic matter pool to its lability. To date this effort has been primarily attempted using low resolution descriptive characteristics (e.g. organic matter content, carbon to nitrogen ratio, aromaticity, etc .). However, recent progress in linking these two important ecosystem components has been advanced using advanced high resolution tools (e.g. nuclear magnetic resonance (NMR) spectroscopy, and mass spectroscopy (MS)-based techniques). A series of experiments will be presented that highlight the application of high resolution techniques in a variety of terrestrial and aquatic ecosystems with the focus on how these data explicitly provide the foundation for integrating organic matter structure into our concept of ecosystem function. The talk will highlight results from a series of experiments including: an MS-based metabolomics and fluorescence excitation emission matrix approach evaluating seasonal and vegetation based changes in dissolved organic matter (DOM) composition from arctic soils; Fourier transform ion cyclotron resonance (FTICR) MS and MS metabolomics analysis of DOM from three lakes in an alpine watershed; and the transformation of 13C labeled glucose track with NMR during a rewetting experiment from Colorado grassland soils. These data will be synthesized to illustrate how the application of advanced analytical techniques provides novel insight into our understanding of organic matter processing in a wide range of ecosystems.

  12. Insight into dissolved organic matter fractions in Lake Wivenhoe during and after a major flood.

    PubMed

    Aryal, Rupak; Grinham, Alistair; Beecham, Simon

    2016-03-01

    Dissolved organic matter is an important component of biogeochemical processes in aquatic environments. Dissolved organic matter may consist of a myriad of different fractions and resultant processing pathways. In early January 2011, heavy rainfall occurred across South East Queensland, Australia causing significant catchment inflow into Lake Wivenhoe, which is the largest water supply reservoir for the city of Brisbane, Australia. The horizontal and vertical distributions of dissolved organic matter fractions in the lake during the flood period were investigated and then compared with stratified conditions with no catchment inflows. The results clearly demonstrate a large variation in dissolved organic matter fractions associated with inflow conditions compared with stratified conditions. During inflows, dissolved organic matter concentrations in the reservoir were fivefold lower than during stratified conditions. Within the dissolved organic matter fractions during inflow, the hydrophobic and humic acid fractions were almost half those recorded during the stratified period whilst low molecular weight neutrals were higher during the flood period compared to during the stratified period. Information on dissolved organic matter and the spatial and vertical variations in its constituents' concentrations across the lake can be very useful for catchment and lake management and for selecting appropriate water treatment processes.

  13. Insight into dissolved organic matter fractions in Lake Wivenhoe during and after a major flood.

    PubMed

    Aryal, Rupak; Grinham, Alistair; Beecham, Simon

    2016-03-01

    Dissolved organic matter is an important component of biogeochemical processes in aquatic environments. Dissolved organic matter may consist of a myriad of different fractions and resultant processing pathways. In early January 2011, heavy rainfall occurred across South East Queensland, Australia causing significant catchment inflow into Lake Wivenhoe, which is the largest water supply reservoir for the city of Brisbane, Australia. The horizontal and vertical distributions of dissolved organic matter fractions in the lake during the flood period were investigated and then compared with stratified conditions with no catchment inflows. The results clearly demonstrate a large variation in dissolved organic matter fractions associated with inflow conditions compared with stratified conditions. During inflows, dissolved organic matter concentrations in the reservoir were fivefold lower than during stratified conditions. Within the dissolved organic matter fractions during inflow, the hydrophobic and humic acid fractions were almost half those recorded during the stratified period whilst low molecular weight neutrals were higher during the flood period compared to during the stratified period. Information on dissolved organic matter and the spatial and vertical variations in its constituents' concentrations across the lake can be very useful for catchment and lake management and for selecting appropriate water treatment processes. PMID:26837382

  14. Organic matter and thermochemical sulfate reduction in the Viburnum Trend, southeast Missouri

    USGS Publications Warehouse

    Leventhal, J.S.

    1990-01-01

    The role of organic matter in Mississippi Valley-type Pb-Zn deposits has been studied by systematically sampling and characterizing various types of organic matter in the Upper Cambrian Bonneterre Formation in lead-zinc mines from the Viburnum Trend and from rocks as far as 20 km away from the Trend. Organic matter that is several kilometers from ore consists of insoluble disseminated kerogen in carbonates. Within meters to centimeters of ore in the Milliken mine, at the south end of the Viburnum Trend, organic matter occurs as solid, partly soluble tacky bitumen and insoluble hard blebs of millimeter to centimeter size. The solid insoluble organic matter in intimate contact (intergrown) with ore (galena and chalcopyrite) is friable and brittle. The sulfur content of solid organic matter from the Milliken mine varies and is lowest for tacky material away from ore, intermediate for blebs near ore, and highest for friable material in intimate contact with ore. Pyrolysis-gas chromatography of this sample suite documents the progression of kerogen (far from ore) through solid petroleumlike material (near ore) to degraded organic matter (in contact with ore). -from Author

  15. Organic matter quality of deep permafrost carbon - a study from Arctic Siberia

    NASA Astrophysics Data System (ADS)

    Strauss, J.; Schirrmeister, L.; Mangelsdorf, K.; Eichhorn, L.; Wetterich, S.; Herzschuh, U.

    2014-11-01

    The organic carbon (OC) pool accumulated in Arctic permafrost (perennially frozen ground) equals the carbon stored in the recent atmosphere. To give an idea of how Yedoma region permafrost could respond under future climatic warming, we conducted a study to quantify the organic matter quality for future decomposition of late Pleistocene (Yedoma) and Holocene (thermokarst) deposits on the Buor Khaya Peninsula, northeast Siberia. The objective of this study was to develop a stratigraphic classified organic matter quality characterization. For this purpose the degree of organic matter decomposition was estimated by using a multiproxy approach. We applied sedimentological (grain-size analyses, bulk density, ice content) and geochemical parameters (total OC, stable carbon isotopes (δ13C), carbon : nitrogen (C / N) ratios) as well as lipid biomarkers (n-alkanes, n-fatty acids, hopanes, triterpenoids, and biomarker proxies/indices: average chain length, carbon preference index (CPI), and higher plant fatty acid index (HPFA)). Our results show that the Yedoma and thermokarst organic matter qualities exhibit no obvious degradation - depth trend. The C / N, δ13C, and hop-17(21)-ene values and the HPFA index show a better quality of the organic matter stored in thermokarst deposits compared to Yedoma deposits, but the CPI points in the other direction. As the ranges of the proxies mostly overlap, we interpret this as to indicate similar quality for both kind of deposits with perhaps slightly better thermokarst organic matter quality. Supported by principal component analyses, the sediment parameters and quality proxies of Yedoma and thermokarst deposits could not be clearly separated from each other. This lack of clear quality differences revealed that the organic matter vulnerability is heterogeneous, independent from radiocarbon age and depends on different decomposition trajectories and the previous decomposition and preservation history. Elucidating this was one of the

  16. Recovery of crystallographic texture in remineralized dental enamel.

    PubMed

    Siddiqui, Samera; Anderson, Paul; Al-Jawad, Maisoon

    2014-01-01

    Dental caries is the most prevalent disease encountered by people of all ages around the world. Chemical changes occurring in the oral environment during the caries process alter the crystallography and microstructure of dental enamel resulting in loss of mechanical function. Little is known about the crystallographic effects of demineralization and remineralization. The motivation for this study was to develop understanding of the caries process at the crystallographic level in order to contribute towards a long term solution. In this study synchrotron X-ray diffraction combined with scanning electron microscopy and scanning microradiography have been used to correlate enamel crystallography, microstructure and mineral concentration respectively in enamel affected by natural caries and following artificial demineralization and remineralization regimes. In particular, the extent of destruction and re-formation of this complex structure has been measured. 2D diffraction patterns collected at the European Synchrotron Radiation Facility were used to quantify changes in the preferred orientation (crystallographic texture) and position of the (002) Bragg reflection within selected regions of interest in each tooth slice, and then correlated with the microstructure and local mineral mass. The results revealed that caries and artificial demineralization cause a large reduction in crystallographic texture which is coupled with the loss of mineral mass. Remineralization restores the texture to the original level seen in healthy enamel and restores mineral density. The results also showed that remineralization promotes ordered formation of new crystallites and growth of pre-existing crystallites which match the preferred orientation of healthy enamel. Combining microstructural and crystallographic characterization aids the understanding of caries and erosion processes and assists in the progress towards developing therapeutic treatments to allow affected enamel to regain

  17. Recovery of Crystallographic Texture in Remineralized Dental Enamel

    PubMed Central

    Siddiqui, Samera; Anderson, Paul; Al-Jawad, Maisoon

    2014-01-01

    Dental caries is the most prevalent disease encountered by people of all ages around the world. Chemical changes occurring in the oral environment during the caries process alter the crystallography and microstructure of dental enamel resulting in loss of mechanical function. Little is known about the crystallographic effects of demineralization and remineralization. The motivation for this study was to develop understanding of the caries process at the crystallographic level in order to contribute towards a long term solution. In this study synchrotron X-ray diffraction combined with scanning electron microscopy and scanning microradiography have been used to correlate enamel crystallography, microstructure and mineral concentration respectively in enamel affected by natural caries and following artificial demineralization and remineralization regimes. In particular, the extent of destruction and re-formation of this complex structure has been measured. 2D diffraction patterns collected at the European Synchrotron Radiation Facility were used to quantify changes in the preferred orientation (crystallographic texture) and position of the (002) Bragg reflection within selected regions of interest in each tooth slice, and then correlated with the microstructure and local mineral mass. The results revealed that caries and artificial demineralization cause a large reduction in crystallographic texture which is coupled with the loss of mineral mass. Remineralization restores the texture to the original level seen in healthy enamel and restores mineral density. The results also showed that remineralization promotes ordered formation of new crystallites and growth of pre-existing crystallites which match the preferred orientation of healthy enamel. Combining microstructural and crystallographic characterization aids the understanding of caries and erosion processes and assists in the progress towards developing therapeutic treatments to allow affected enamel to regain

  18. Dissolved organic carbon and chromophoric dissolved organic matter properties of rivers in the USA

    NASA Astrophysics Data System (ADS)

    Spencer, Robert G. M.; Butler, Kenna D.; Aiken, George R.

    2012-09-01

    Dissolved organic carbon (DOC) concentration and chromophoric dissolved organic matter (CDOM) parameters were measured over a range of discharge in 30 U.S. rivers, covering a diverse assortment of fluvial ecosystems in terms of watershed size and landscape drained. Relationships between CDOM absorption at a range of wavelengths (a254, a350, a440) and DOC in the 30 watersheds were found to correlate strongly and positively for the majority of U.S. rivers. However, four rivers (Colorado, Colombia, Rio Grande and St. Lawrence) exhibited statistically weak relationships between CDOM absorption and DOC. These four rivers are atypical, as they either drain from the Great Lakes or experience significant impoundment of water within their watersheds, and they exhibited values for dissolved organic matter (DOM) parameters indicative of autochthonous or anthropogenic sources or photochemically degraded allochthonous DOM and thus a decoupling between CDOM and DOC. CDOM quality parameters in the 30 rivers were found to be strongly correlated to DOM compositional metrics derived via XAD fractionation, highlighting the potential for examining DOM biochemical quality from CDOM measurements. This study establishes the ability to derive DOC concentration from CDOM absorption for the majority of U.S. rivers, describes characteristics of riverine systems where such an approach is not valid, and emphasizes the possibility of examining DOM composition and thus biogeochemical function via CDOM parameters. Therefore, the usefulness of CDOM measurements, both laboratory-based analyses and in situ instrumentation, for improving spatial and temporal resolution of DOC fluxes and DOM dynamics in future studies is considerable in a range of biogeochemical studies.

  19. Dissolved organic carbon and chromophoric dissolved organic matter properties of rivers in the USA

    USGS Publications Warehouse

    Spencer, Robert G.M.; Butler, Kenna D.; Aiken, George R.

    2012-01-01

    Dissolved organic carbon (DOC) concentration and chromophoric dissolved organic matter (CDOM) parameters were measured over a range of discharge in 30 U.S. rivers, covering a diverse assortment of fluvial ecosystems in terms of watershed size and landscape drained. Relationships between CDOM absorption at a range of wavelengths (a254, a350, a440) and DOC in the 30 watersheds were found to correlate strongly and positively for the majority of U.S. rivers. However, four rivers (Colorado, Colombia, Rio Grande and St. Lawrence) exhibited statistically weak relationships between CDOM absorption and DOC. These four rivers are atypical, as they either drain from the Great Lakes or experience significant impoundment of water within their watersheds, and they exhibited values for dissolved organic matter (DOM) parameters indicative of autochthonous or anthropogenic sources or photochemically degraded allochthonous DOM and thus a decoupling between CDOM and DOC. CDOM quality parameters in the 30 rivers were found to be strongly correlated to DOM compositional metrics derived via XAD fractionation, highlighting the potential for examining DOM biochemical quality from CDOM measurements. This study establishes the ability to derive DOC concentration from CDOM absorption for the majority of U.S. rivers, describes characteristics of riverine systems where such an approach is not valid, and emphasizes the possibility of examining DOM composition and thus biogeochemical function via CDOM parameters. Therefore, the usefulness of CDOM measurements, both laboratory-based analyses and in situ instrumentation, for improving spatial and temporal resolution of DOC fluxes and DOM dynamics in future studies is considerable in a range of biogeochemical studies.

  20. Variations in the elemental ratio of organic matter in the central Baltic Sea: Part II - Sensitivities of annual mass flux estimates to model parameter variations

    NASA Astrophysics Data System (ADS)

    Kreus, Markus; Schartau, Markus

    2015-06-01

    This study describes a sensitivity analysis that allows the parameters of a one-dimensional ecosystem model to be ranked according to their specificity in determining biochemical key fluxes. Key fluxes of interest are annual (a) total production (TP), (b) remineralization above the halocline (RM), and (c) export at 50 m (EX) at the Baltic Sea monitoring site BY15 located in the Gotland Deep basin. The model resolves mass flux of carbon (C), nitrogen (N), and phosphorous (P), while considering nitrogen fixation explicitly. Our first null hypothesis is that the variation of the value of every single model parameter affects each annual C, N, and P budget simultaneously. Our second null hypothesis states that the variation of every parameter value induces changes at least in either of the annual C, N or P budgets. Our analyses falsify both null hypotheses and reveal that 8 out of 36 parameters must be regarded redundant, as their variation neither alter annual key fluxes nor produce considerable time-shifts in model trajectories at the respective site. Seven parameters were found to induce substantial changes in annual C, N, and P flux estimates simultaneously. The assimilation efficiency of zooplankton turned out to be of vital importance. This parameter discriminates between the assimilation and destruction of algal prey during grazing. The fraction of unassimilated dead algal cells is critical for the amount of organic matter exported out of the euphotic zone. The maximum cellular N:C quota of diazotrophs and the degradation/hydrolysis rate of detrital carbon are two parameters that will likely remain unconstrained by time series data, but both affect the annual C budget considerably. Overall, our detailed specification of model sensitivities to parameter variations will facilitate the formulation of a well-posed inverse problem for the estimation of C, N and P fluxes from stock observations at the Gotland Deep.

  1. Multidecadal accumulation of anthropogenic and remineralized dissolved inorganic carbon along the Extended Ellett Line in the northeast Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Humphreys, Matthew P.; Griffiths, Alex M.; Achterberg, Eric P.; Holliday, N. Penny; Rérolle, Victoire M. C.; Menzel Barraqueta, Jan-Lukas; Couldrey, Matthew P.; Oliver, Kevin I. C.; Hartman, Susan E.; Esposito, Mario; Boyce, Adrian J.

    2016-02-01

    Marine carbonate chemistry measurements have been carried out annually since 2009 during UK research cruises along the Extended Ellett Line (EEL), a hydrographic transect in the northeast Atlantic Ocean. The EEL intersects several water masses that are key to the global thermohaline circulation, and therefore the cruises sample a region in which it is critical to monitor secular physical and biogeochemical changes. We have combined results from these EEL cruises with existing quality-controlled observational data syntheses to produce a hydrographic time series for the EEL from 1981 to 2013. This reveals multidecadal increases in dissolved inorganic carbon (DIC) throughout the water column, with a near-surface maximum rate of 1.80 ± 0.45 µmol kg-1 yr-1. Anthropogenic CO2 accumulation was assessed, using simultaneous changes in apparent oxygen utilization (AOU) and total alkalinity (TA) as proxies for the biogeochemical processes that influence DIC. The stable carbon isotope composition of DIC (δ13CDIC) was also determined and used as an independent test of our method. We calculated a volume-integrated anthropogenic CO2 accumulation rate of 2.8 ± 0.4 mg C m-3 yr-1 along the EEL, which is about double the global mean. The anthropogenic CO2 component accounts for only 31 ± 6% of the total DIC increase. The remainder is derived from increased organic matter remineralization, which we attribute to the lateral redistribution of water masses that accompanies subpolar gyre contraction. Output from a general circulation ecosystem model demonstrates that spatiotemporal heterogeneity in the observations has not significantly biased our multidecadal rate of change calculations and indicates that the EEL observations have been tracking distal changes in the surrounding North Atlantic and Nordic Seas.

  2. PATTERNS AND CONTROLS OF DISSOLVED ORGANIC MATTER EXPORT BY MAJOR RIVERS: A NEW SEASONAL, SPATIALLY EXPLICIT, GLOBAL MODEL

    EPA Science Inventory

    River-derived dissolved organic matter (DOM) influences metabolism, light attenuation, and bioavailability of metals and nutrients in coastal ecosystems. Recent work suggests that DOM concentrations in surface waters vary seasonally because different organic matter pools are mobi...

  3. NITROGEN DEPOSITION AND ORGANIC MATTER MANIPULATIONS AFFECT GROSS AND NET NITROGEN TRANSFORMATIONS IN TWO TEMPERATE FORESTS SOILS

    EPA Science Inventory

    Soil nitrogen transformations are intricately linked to carbon transformations. We utilized two existing organic matter manipulation sites in western Oregon, USA and Hungary to investigate these linkages. Our questions were: 1) Does the quantity and quality of organic matter af...

  4. PHOTOREACTIVITY OF CHROMOPHORIC DISSOLVED ORGANIC MATTER (CDOM) DERIVED FROM DECOMPOSITION OF VARIOUS VASCULAR PLANT AND ALGAL SOURCES

    EPA Science Inventory

    Chromophoric dissolved organic matter (CDOM) in aquatic environments is derived from the microbial decomposition of terrestrial and microbial organic matter. Here we present results of studies of the spectral properties and photoreactivity of the CDOM derived from several organi...

  5. Effect of organic matter amendment, arsenic amendment and water management regime on rice grain arsenic species.

    PubMed

    Norton, Gareth J; Adomako, Eureka E; Deacon, Claire M; Carey, Anne-Marie; Price, Adam H; Meharg, Andrew A

    2013-06-01

    Arsenic accumulation in rice grain has been identified as a major problem in some regions of Asia. A study was conducted to investigate the effect of increased organic matter in the soil on the release of arsenic into soil pore water and accumulation of arsenic species within rice grain. It was observed that high concentrations of soil arsenic and organic matter caused a reduction in plant growth and delayed flowering time. Total grain arsenic accumulation was higher in the plants grown in high soil arsenic in combination with high organic matter, with an increase in the percentage of organic arsenic species observed. The results indicate that the application of organic matter should be done with caution in paddy soils which have high soil arsenic, as this may lead to an increase in accumulation of arsenic within rice grains. Results also confirm that flooding conditions substantially increase grain arsenic. PMID:23466730

  6. Sustainable Water Supplies:Reducing The Organic Matter Content of Potable Water

    NASA Astrophysics Data System (ADS)

    Sohn, Mary

    2009-07-01

    As freshwater becomes a limiting factor in sustainable development, water treatment processes which can efficiently oxidize both anthropogenic and natural sources of organic matter are becoming crucial. While many anthropogenic organic compounds found in freshwater pose a direct risk to human health, natural organic matter such as humic acids, pose an indirect risk through the production of disinfection byproducts resulting from chlorination. Removal of dissolved natural organic matter before disinfection of potable water is recommended for the production of potable water in water treatment facilities. Several promising developments in dissolved organic matter oxidation are described including hydroxyl radical, advanced oxidation processes and ferrate (VI). The feasibility of applying these processes to water treatment on a large scale is largely dependent on cost.

  7. Role of bacteria in organic matter fluxes in the Southern California Coastal Zone: (Progress report)

    SciTech Connect

    Not Available

    1988-07-01

    The fate of organic matter in the sea, whether produced in situ or introduced from land, is greatly influenced by the metabolic trophic activities of the resident biota. Until recently it was thought that much of the primary production is consumed by the herbivores, making them the main determinants of fate of organic matter. It now appears that the microbial component of marine foodweb also plays a significant role in the decomposition, distribution, and vertical flux of organic material in seawater. The goal of the proposed research is to quantify this role of the microbial foodweb as part of a DOE-sponsored interdisciplinary study. We are testing the hypothesis that organic matter utilization by heterotrophic bacterioplankton represents a major sink for organic matter in the Southern California Coastal Zone.

  8. Effect of organic matter amendment, arsenic amendment and water management regime on rice grain arsenic species.

    PubMed

    Norton, Gareth J; Adomako, Eureka E; Deacon, Claire M; Carey, Anne-Marie; Price, Adam H; Meharg, Andrew A

    2013-06-01

    Arsenic accumulation in rice grain has been identified as a major problem in some regions of Asia. A study was conducted to investigate the effect of increased organic matter in the soil on the release of arsenic into soil pore water and accumulation of arsenic species within rice grain. It was observed that high concentrations of soil arsenic and organic matter caused a reduction in plant growth and delayed flowering time. Total grain arsenic accumulation was higher in the plants grown in high soil arsenic in combination with high organic matter, with an increase in the percentage of organic arsenic species observed. The results indicate that the application of organic matter should be done with caution in paddy soils which have high soil arsenic, as this may lead to an increase in accumulation of arsenic within rice grains. Results also confirm that flooding conditions substantially increase grain arsenic.

  9. Catchment scale molecular composition of hydrologically mobilized dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Raeke, Julia; Lechtenfeld, Oliver J.; Oosterwoud, Marieke R.; Bornmann, Katrin; Tittel, Jörg; Reemtsma, Thorsten

    2016-04-01

    Increasing concentrations of dissolved organic matter (DOM) in rivers of temperate catchments in Europe and North Amerika impose new technical challenges for drinking water production. The driving factors for this decadal increase in DOM concentration are not conclusive and changes in annual temperatures, precipitation and atmospheric deposition are intensely discussed. It is known that the majority of DOM is released by few but large hydrologic events, mobilizing DOM from riparian wetlands for export by rivers and streams. The mechanisms of this mobilization and the resulting molecular composition of the released DOM may be used to infer long-term changes in the biogeochemistry of the respective catchment. Event-based samples collected over two years from streams in three temperate catchments in the German mid-range mountains were analyzed after solid-phase extraction of DOM for their molecular composition by ultra-high resolution mass spectrometry (FT-ICR MS). Hydrologic conditions, land use and water chemistry parameters were used to complement the molecular analysis. The molecular composition of the riverine DOM was strongly dependent on the magnitude of the hydrologic events, with unsaturated, oxygen-enriched compounds being preferentially mobilized by large events. This pattern is consistent with an increase in dissolved iron and aluminum concentrations. In contrast, the relative proportions of nitrogen and sulfur bearing compounds increased with an increased agricultural land use but were less affected by the mobilization events. Co-precipitation experiments with colloidal aluminum showed that unsaturated and oxygen-rich compounds are preferentially removed from the dissolved phase. The precipitated compounds thus had similar chemical characteristics as compared to the mobilized DOM from heavy rain events. Radiocarbon analyses also indicated that this precipitated fraction of DOM was of comparably young radiocarbon age. DOM radiocarbon from field samples

  10. Pyrogenic and Fresh Organic Matter Effects on Soil Microbial Communities

    NASA Astrophysics Data System (ADS)

    Whitman, T.; Buckley, D. H.; Lehmann, J.

    2014-12-01

    Soils hold a globally important stock of carbon (C) and can act as both a C source and sink, depending on management and environmental conditions. Pyrogenic organic matter (PyOM) is produced naturally during fires, and contains relatively stable forms of C. Its intentional production has also been proposed as a mechanism for C management (in such cases PyOM is often referred to as "biochar"). However, the impact of natural or anthropogenic PyOM production on soils is complex and depends on many factors. In particular, PyOM additions to soils may have effects on plant growth and on native soil C cycling. The response of the soil microbial community to PyOM additions is likely key to understanding these interactions, but remains poorly characterized. We studied soil C dynamics and soil microbial communities in a field study with 350°C PyOM from 13C-labelled corn stover, a C3-derived soil, and C4 plants (sudangrass). PyOM additions only temporarily increased total soil CO2 fluxes, dramatically less than the increase associated with the addition of corn stover, which likely increased SOC losses. We used high-throughput sequencing of the 16S region on the MiSeq platform to characterize the initial, 12-day and 82-day soil bacterial communiities. We used three-part stable isotopic partitioning after two months to distinguish 334% higher root-derived CO2 fluxes in the plots with PyOM additions than those without, and 45% lower PyOM-C derived CO2 fluxes in the plots with plants present. The 84% increase in estimated cumulative soil CO2 emissions with stover additions was accompanied by a significant shift in the soil bacterial community on days 12 and 82, while the PyOM additions only resulted in significant changes to the overall community on day 82. We investigate which taxa are driving these community shifts, and how they may relate to the soil CO2 fluxes.

  11. Spatial distribution and transport of soil organic matter through a semi-arid catchment

    NASA Astrophysics Data System (ADS)

    Cammeraat, L. H.

    2009-04-01

    Soil erosion and deposition plays an important role in the transport and reallocation of organic matter in terrestrial carbon dynamics. This study discusses the production, transport and storage of organic material in semi-arid, semi-natural shrubland and forest ecosystem in SE Spain. Goal is to study the faith of organic matter in these land use systems and to reveal their possible importance within the terrestrial carbon cycle and the importance of the spatial redistribution of organic matter through the landscape. The study was carried out at the Alquería field station in the Guadalentín basin in SE Spain on calcareous soils. Measurements were carried out at plant, plot and (sub-) catchment scale incorporating Stipa tenacissima tussock dominated shrublands, Pinus halepensis open forests and almond and cereal fields. The determination of organic matter was based on the production and presence of organic matter on the soil surface, the amount of organic matter incorporated in the soil as present under and around individual plants and scaled up using high resolution aerial photographs and remote sensing images. The standing biomass was determined as well, using allometric methods and scaled up also using high resolution aerial photographs to estimate total plant cover. The transport of organic matter is determined using organic matter collected in classical unbounded plots that have been monitored also for runoff and sediment yield. Sediment stored in a 60 year old retention basin was also studied to reveal the sediment and organic matter fluxes at broader spatio-temporal scales. Furthermore also soil material accumulated behind bench terraces was evaluated for soil organic carbon. The results will be discussed in the context of the sources and sinks of organic matter as well as to their linkage to erosion and hydrological processes. The spatial heterogeneity of the accumulated and transported organic matter is strongly related to the frequency-magnitude of

  12. Effects of peptide concentration on remineralization of eroded enamel.

    PubMed

    Chung, Hsiu-Ying; Huang, Kuo-Chen

    2013-12-01

    Promoting remineralization to repair eroded enamel is a promising therapy in clinics. In this study, biocompatible asparagine-serine-serine (NSS) peptide chelates free ions from artificial saliva through charged functional groups, and subsequently form nano-hydroxyapatite crystals to partially repair erosive lesions. The nanomechanical properties, cross-sectional microstructure, types of deposited minerals, and subsurface microstructure of enamel at various treatment stages were characterized by nanoindentation, scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM), respectively. The results revealed that the nanohardness and elastic modulus of eroded enamel increase with peptide concentration, particularly for the 3NSS peptide system. In contrast, the structure of the 5NSS peptide is larger and longer, leading to increasing difficulty in penetrating to the deep acid-eroded regions; therefore, the remineralization effect was restricted to the top enamel surface. The 3NSS peptide with high concentration promoted the formation of smaller, finer, and staggered nanohydroxyapatite crystals. The enamel remineralized with a 100μM 3NSS exhibited the highest degree of nanohardness recovery (34%), resulting from subsurface crystalline regrowth.

  13. Remineralizing potential of various agents on dental erosion

    PubMed Central

    Somani, Rani; Jaidka, Shipra; Singh, Deepti Jawa; Arora, Vanika

    2014-01-01

    Aim The purpose of this study is to compare the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP, Tooth Mousse) containing and casein phosphopeptide-amorphous calcium phosphate with fluoride (CPP-ACPF, Tooth Mousse Plus) containing pastes on dental erosion. Materials and methods Thirty permanent non-carious premolars indicated for orthodontic extraction were included in this study and were sectioned in mesiodistal direction vertically. After immersion in the carbonated drink for 14 min, samples were treated with various remineralizing pastes which were CPP-ACP containing paste (Tooth Mousse) and CPP-ACPF containing paste (Tooth Mousse Plus) according to the manufacturer's instructions. Vickers Microhardness was recorded at baseline, after exposure to erosive drink and after treatment with remineralizing pastes. Data obtained was statistically analysed using Student t-test with a level of significance set at p < 0.05. Results CPP-ACP (Tooth Mousse) and CPP-ACP with fluoride (Tooth Mousse Plus) resulted in 30.52% and 38.98% increase in post-erosion microhardness values respectively. The remineralizing potential of CPP-ACP with fluoride containing paste (Tooth Mousse Plus) was significantly better than that of CPP-ACP containing paste (Tooth Mousse) (p < 0.05). Conclusion Casein phosphopeptide-amorphous calcium phosphate with fluoride (CPP-ACPF, Tooth Mousse Plus) can be recommended to be used in preventing erosive tooth wear from acidic beverages. PMID:25737926

  14. Defining organic matter quality in sediment systems: a suggested classification scheme

    NASA Astrophysics Data System (ADS)

    Alderson, Danielle; Evans, Martin; Rothwell, James; Boult, Stephen

    2015-04-01

    The quantity and quality of the mineral component of sediments is a core focus of sedimentological investigation in terrestrial systems. This is not to say that the organic component of collected sediments is simply ignored; the organic component is often scrutinised, but in some fields in a restricted manner, limited to basic characteristics such as the ratio of organic to mineral content derived from loss on ignition. There is no doubt that this information is useful; however, these types of analysis indicate the quantity of organic matter relative to a particular temporal scale or volume, rather than treating the organic fraction as a separate entity worthy of substantial investigation. The quality of the organic component is being increasingly considered in a number of fields, with molecular, thermal, spectroscopic and bulk methods being used. However, models and theories on organic matter processing in a variety of environmental systems, have been developed without clearly defining organic matter quality, because most results do not depend on an outright measure of quality (Bosatta and Agren, 1999). With approaches and techniques varying between fields, there is a need to consider a more systematic approach to the analysis and definition of organic matter quality. The disparities in the definition of the quality of organic matter, and thus how it may be measured have vital implications for the study of carbon cycling, biogeochemical processing, and ultimately ecosystem structure and function. The quality and quantity of organic matter have an influence on the chemistry and biology of systems and may reveal a wealth of past or contemporary environmental information. In this paper we provide a classification of organic matter quality and examples of potential applications and suitable techniques for the analysis of the main classes of organic matter character. A more consistent approach to organic matter characterisation has the potential to aid understanding of

  15. High-molecular-weight organic matter in the particles of comet 67P/Churyumov–Gerasimenko

    NASA Astrophysics Data System (ADS)

    Fray, Nicolas; Bardyn, Anaïs; Cottin, Hervé; Altwegg, Kathrin; Baklouti, Donia; Briois, Christelle; Colangeli, Luigi; Engrand, Cécile; Fischer, Henning; Glasmachers, Albrecht; Grün, Eberhard; Haerendel, Gerhard; Henkel, Hartmut; Höfner, Herwig; Hornung, Klaus; Jessberger, Elmar K.; Koch, Andreas; Krüger, Harald; Langevin, Yves; Lehto, Harry; Lehto, Kirsi; Le Roy, Léna; Merouane, Sihane; Modica, Paola; Orthous-Daunay, François-Régis; Paquette, John; Raulin, François; Rynö, Jouni; Schulz, Rita; Silén, Johan; Siljeström, Sandra; Steiger, Wolfgang; Stenzel, Oliver; Stephan, Thomas; Thirkell, Laurent; Thomas, Roger; Torkar, Klaus; Varmuza, Kurt; Wanczek, Karl-Peter; Zaprudin, Boris; Kissel, Jochen; Hilchenbach, Martin

    2016-10-01

    The presence of solid carbonaceous matter in cometary dust was established by the detection of elements such as carbon, hydrogen, oxygen and nitrogen in particles from comet 1P/Halley. Such matter is generally thought to have originated in the interstellar medium, but it might have formed in the solar nebula—the cloud of gas and dust that was left over after the Sun formed. This solid carbonaceous material cannot be observed from Earth, so it has eluded unambiguous characterization. Many gaseous organic molecules, however, have been observed; they come mostly from the sublimation of ices at the surface or in the subsurface of cometary nuclei. These ices could have been formed from material inherited from the interstellar medium that suffered little processing in the solar nebula. Here we report the in situ detection of solid organic matter in the dust particles emitted by comet 67P/Churyumov–Gerasimenko the carbon in this organic material is bound in very large macromolecular compounds, analogous to the insoluble organic matter found in the carbonaceous chondrite meteorites. The organic matter in meteorites might have formed in the interstellar medium and/or the solar nebula, but was almost certainly modified in the meteorites’ parent bodies. We conclude that the observed cometary carbonaceous solid matter could have the same origin as the meteoritic insoluble organic matter, but suffered less modification before and/or after being incorporated into the comet.

  16. Effects of dissolved organic matter on toxicity and bioavailability of copper for lettuce sprouts.

    PubMed

    Inaba, Shoko; Takenaka, Chisato

    2005-05-01

    It is well known that dissolved organic matter in soil solution may affect the toxicity or bioavailability of heavy metals to plants, but existing information on various organic substances is insufficient for treating problems with heavy metal-contaminated soils. To clarify how dissolved organic matter alters the toxicity and bioavailability of metals, we germinated lettuce seeds exposed to solutions containing Cu and several kinds of dissolved organic matters. Low molecular weight organic acids (citric, malic, and oxalic acids) increased the toxicity and bioavailability of Cu, but low concentrations of the synthetic chelators ethylenediamine tetra-acetic acid (EDTA) and diethylenetriamine penta-acetic acid (DTPA) decreased the toxicity and bioavailability of Cu. In contrast, humic acid appeared to be the most effective organic substance for detoxifying Cu, even though it did not significantly decrease the bioavailability of Cu. Consequently, the bioavailability and toxic effects of Cu in soil depend on the nature of coexisting organic substances in the soil solution.

  17. Depletion of 13C in Cretaceous marine organic matter: Source, diagenetic, or environmental sigal?

    USGS Publications Warehouse

    Dean, W.E.; Arthur, M.A.; Claypool, G.E.

    1986-01-01

    Geochemical studies of Cretaceous strata rich in organic carbon (OC) from Deep Sea Drilling Project (DSDP) sites and several land sections reveal several consistent relationships among amount of OC, hydrocarbon generating potential of kerogen (measured by pyrolysis as the hydrogen index, HI), and the isotopic composition of the OC. First, there is a positive correlation between HI and OC in strata that contain more than about 1% OC. Second, percent OC and HI often are negatively correlated with carbon isotopic composition (?? 13C) of kerogen. The relationship between HI and OC indicates that as the amount of organic matter increases, this organic matter tends to be more lipid rich reflecting the marine source of the organic matter. Cretaceous samples that contain predominantly marine organic matter tend to be isotopically lighter than those that contain predominantly terrestrial organic matter. Average ?? 13C values for organic matter from most Cretaceous sites are between -26 and -28???, and values heavier than about -25??? occur at very few sites. Most of the ?? 13C values of Miocene to Holocene OC-rich strata and modern marine plankton are between -16 to -23???. Values of ??13C of modern terrestrial organic matter are mostly between -23 and -33???. The depletion of terrestial OC in 13C relative to marine planktonic OC is the basis for numerous statements in the literature that isotopically light Cretaceous organic matter is of terrestrial origin, even though other organic geochemical and(or) optical indicators show that the organic matter is mainly of marine origin. A difference of about 5??? in ?? 13C between modern and Cretaceous OC-rich marine strata suggests either that Cretaceous marine planktonic organic matter had the same isotopic signature as modern marine plankton and that signature has been changed by diagenesis, or that OC derived from Cretaceous marine plankton was isotopically lighter by about 5??? relative to modern plankton OC. Diagenesis does

  18. Photochemical Flocculation of Terrestrial Dissolved Organic Matter (tDOM) and Iron: Mechanisms and Geochemical Implications

    NASA Astrophysics Data System (ADS)

    Mopper, K.; Helms, J. R.; Mao, J.; Abdulla, H. A.; Schmidt-Rohr, K.

    2013-12-01

    Photoflocculation of DOM has received relatively little attention. No previous studies have examined the chemical composition of the flocs nor investigated the coagulation mechanisms. We observed that, after 30 days of simulated solar UV irradiation of 0.1-um filtered Great Dismal Swamp (Virginia) water, 7.1% of the DOC was converted to POC while 75% was remineralized. Approximately 87% of the iron was removed from the dissolved phase after 30 days, but iron did not flocculate until a major fraction of DOM was removed by photochemical degradation and flocculation (>10 days); thus, during the initial 10 days, there were sufficient organic ligands present and/or the pH was low enough to keep iron in solution. Although photoflocculation of iron did eventually occur, it is not clear if iron is required for the initial flocculation of DOM. Using NMR and FT-IR techniques, we found that photochemically flocculated POM was enriched in aliphatics and amide functionality relative to the residual non-flocculated DOM, while carbohydrate-like material was neither photochemical degraded nor flocculated. Based on this spectroscopic evidence, we propose several mechanisms for the formation of the flocs during irradiation. We also speculate that abiotic photochemical flocculation may remove a significant fraction of tDOM and iron from the upper water column between headwaters and the ocean, including estuaries. Fig. 1. Concentrations of dissolved (gray), particulate (black), and adsorbed (white) material as a function of irradiation time: (a) organic carbon, (b) absorption at 300 nm, (c) total iron by atomic absorption, and (d) total nitrogen. Error bars represent the combined standard deviations of the 'total,' 'dissolved,' and 'adsorbed' terms from which the 'particulate' term was calculated. Total nitrogen was not determined for the 'adsorbed' material

  19. Enhanced binding of hydrophobic organic contaminants by microwave-assisted humification of soil organic matter.

    PubMed

    Hur, Jin; Park, Sung-Won; Kim, Min Chan; Kim, Han S

    2013-11-01

    Enhanced binding of hydrophobic organic contaminants (HOCs) with soil organic matter (SOM) by microwave (MW) irradiation was investigated in this study. We used fluorescence excitation emission matrix, humification index (HIX), and organic carbon partitioning coefficient (Koc) to examine characteristic changes in SOM and its sorptive capacity for HOCs. When MW was irradiated to soils, protein-like fluorescence decreased but fulvic- and humic-like fluorescence increased. The addition of activated carbon in the presence of oxygen facilitated the humification-like alteration of SOM more significantly, evidenced by increases in fulvic- and humic-like fluorescence signals. The extent of SOM-phenanthrene binding also increased with MW treatment, supported by a notable increase in Koc value from 1.8×10(4) to 7.3×10(5)Lkg(-1). Various descriptors indicating the physical and chemical properties of SOM along with the relative percentage of humic-like fluorescence and HIX values demonstrated strong linear relationships with Koc values. These linear relationships indicated that the increased binding affinity of SOM for phenanthrene was attributed to enhanced SOM humification, which was stimulated by MW irradiation. Thus, our results demonstrate that MW irradiation could be effectively used for remediation or for assessing the environmental risks of HOC-contaminated soils and groundwater.

  20. Effects of polar and nonpolar groups on the solubility of organic compounds in soil organic matter

    USGS Publications Warehouse

    Chiou, C.T.; Kile, D.E.

    1994-01-01

    Vapor sorption capacities on a high-organic-content peat, a model for soil organic matter (SOM), were determined at room temperature for the following liquids: n-hexane, 1,4-dioxane, nitroethane, acetone, acetonitrile, 1-propanol, ethanol, and methanol. The linear organic vapor sorption is in keeping with the dominance of vapor partition in peat SOM. These data and similar results of carbon tetrachloride (CT), trichloroethylene (TCE), benzene, ethylene glycol monoethyl ether (EGME), and water on the same peat from earlier studies are used to evaluate the effect of polarity on the vapor partition in SOM. The extrapolated liquid solubility from the vapor isotherm increases sharply from 3-6 wt % for low-polarity liquids (hexane, CT, and benzene) to 62 wt % for polar methanol and correlates positively with the liquid's component solubility parameters for polar interaction (??P) and hydrogen bonding (??h). The same polarity effect may be expected to influence the relative solubilities of a variety of contaminants in SOM and, therefore, the relative deviations between the SOM-water partition coefficients (Kom) and corresponding octanol-water partition coefficients (Kow) for different classes of compounds. The large solubility disparity in SOM between polar and nonpolar solutes suggests that the accurate prediction of Kom from Kow or Sw (solute water solubility) would be limited to compounds of similar polarity.

  1. Investigation of the organic matter in inactive nuclear tank liquids. Environmental Restoration Program

    SciTech Connect

    Schenley, R.L.; Griest, W.H.

    1990-08-01

    Environmental Protection Agency (EPA) methodology for regulatory organics fails to account for the organic matter that is suggested by total organic carbon (TOC) analysis in the Oak Ridge National Laboratory (ORNL) inactive nuclear waste-tank liquids and sludges. Identification and measurement of the total organics are needed to select appropriate waste treatment technologies. An initial investigation was made of the nature of the organics in several waste-tank liquids. This report details the analysis of ORNL wastes.

  2. Experimental Study of Soil Organic Matter Loss From Cultivated Field Plots In The Venezuelan Andes.

    NASA Astrophysics Data System (ADS)

    Bellanger, B.; Huon, S.; Velasquez, F.; Vallès, V.; Girardin A, C.; Mariotti, A. B.

    The question of discriminating sources of organic matter in suspended particles of stream flows can be addressed by using total organic carbon (TOC) concentration and stable isotope (13C, 15N) measurements when constant fluxes of organic matter supply can be assumed. However, little is known on the dynamics of organic matter release during soil erosion and on the temporal stability of its isotopic signature. In this study, we have monitored soil organic carbon loss and water runoff using natural rainfall events on three experimental field plots with different vegetation cover (bare soil, maize and coffee fields), set up on natural slopes of a tropical mountainous watershed in NW Venezuela (09°13'32'' ­ 09°10'00''N, 70°13'49'' ­ 70°18'34''W). Runoff and soil loss are markedly superior for the bare field plot than for the coffee field plot: by a factor 15 ­ 36, respectively, for the five-month experiment, and by a factor 30 ­ 120, respectively, during a single rainfall event experiment. Since runoff and soil organic matter loss are closely linked during most of the flow (at the time scales of this study), TOC concentration in suspended matter is constant. Furthermore, stable isotope compositions reflect those of top-soil organic matter from which they originate.

  3. Sources and Fates of Dissolved Organic Matter in the Mid-Atlantic Bight

    SciTech Connect

    Hopkinson, C. S.

    2000-08-16

    The objectives of the research program were to identify and determine the relative importance of various sources of dissolved organic matter to the continental shelf, and to estimate the net carbon balance for the Middle Atlantic Bight.

  4. Northern Gulf of Mexico estuarine coloured dissolved organic matter derived from MODIS data

    EPA Science Inventory

    Coloured dissolved organic matter (CDOM) is relevant for water quality management and may become an important measure to complement future water quality assessment programmes. An approach to derive CDOM using the Moderate Resolution Imaging Spectroradiometer (MODIS) was developed...

  5. Photobleaching Kinetics of Chromophoric Dissolved Organic Matter Derived from Mangrove Leaf Litter and Floating Sargassum Colonies

    EPA Science Inventory

    We examined the photoreactivity of chromophoric dissolved organic matter (CDOM) derived from Rhizophora mangle (red mangrove) leaf litter and floating Sargassum colonies as these marine plants can be important contributors to coastal and open ocean CDOM pools, respectively. Mangr...

  6. THE ROLE OF NITROGEN IN CHROMOPHORIC AND FLUORESCENT DISSOLVED ORGANIC MATTER FORMATION

    EPA Science Inventory

    Microbial and photochemical processes affect chromophoric dissolved organic matter (CDOM) dynamics in the ocean. Some evidence suggests that dissolved nitrogen plays a role in CDOM formation, although this has received little systematic attention in marine ecosystems. Coastal sea...

  7. CHROMOPHORIC DISSOLVED ORGANIC MATTER (CDOM) SOURCE CHARACTERIZATION IN THE LOUISIANA BIGHT

    EPA Science Inventory

    Chromophoric dissolved organic matter (CDOM) in the Mississippi plume region may have several distinct sources: riverine (terrestrial soils), wetland (terrestrial plants), biological production (phytoplankton, zooplankton, microbial), and sediments. Complex mixing, photodegradati...

  8. Lyophilization, Reconstitution, and DBP Formation in Reverse-Osmosis Concentrated Natural Organic Matter

    EPA Science Inventory

    Drinking water treatment and disinfection byproduct (DBP) research can be complicated by natural organic matter (NOM) temporal variability. NOM preservation by lyophilization (freeze-drying) has been long practiced to address this issue; however, its applicability for drinking w...

  9. REFERENCE MATERIALS AND QUALITY ASSURANCE FOR THE CHARACTERIZATION OF ORGANIC COMPOUNDS IN PARTICULATE MATTER

    EPA Science Inventory

    One of the first environmental matrix Standard Reference Materials (SRMs) developed by the National Institute of Standards and Technology (NIST) for determination of organic species was SRM 1649 Urban Dust, ambient total suspended particulate matter (PM) collected in Washington D...

  10. Natural organic matter (NOM) in a limed lake and its tributaries.

    PubMed

    Andersen, Dag O; Gjessing, Egil T

    2002-05-01

    The chemistry of a limed lake and its main tributaries were studied for 3 years (1992-94) with an emphasis on natural organic matter (NOM). Increased transparency and decreased water colour indicated a general reduction of NOM in the lake. Increased A(254 nm)/A(410 nm) ratios in the epilimnion during summer and early autumn suggested degradation of higher molecular size organic matter into low molecular size NOM. Increase in ammonium and dissolved inorganic carbon concentrations in the lake was possibly due to the NOM degradation. Using budget calculations and the literature values, photodegradation and microbial activity were estimated to be the main mechanisms of the NOM removal. These mechanisms accounted for about 30-35% and 60-65% of the total loss of organic matter, respectively, in the summer and early autumn period. Low sedimentation rates indicate that co-precipitation of organic matter with calcium, aluminium and/or iron was of minor importance in these seasons.

  11. CHANGES IN SPECTRAL AND PHOTOCHEMICAL PROPERTIES OF COLORED DISSOLVED ORGANIC MATTER IN A COASTAL ESTUARY

    EPA Science Inventory

    Colored dissolved organic matter (CDOM) is the primary determinant of UV penetration and exposure in freshwater and coastal environments. CDOM is photochemically reactive and its photoreactions can lead to reductions in UV absorbance and increased UV exposure in aquatic ecosystem...

  12. Trueness, Precision, and Detectability for Sampling and Analysis of Organic Species in Airborne Particulate Matter

    EPA Science Inventory

    Recovery. precision, limits of detection and quantitation, blank levels, calibration linearity, and agreement with certified reference materials were determined for two classes of organic components of airborne particulate matter, polycyclic aromatic hydrocarbons and hopanes usin...

  13. Light-Induced Transformations of the C60 Derivative, Fullerenol: Interactions with Natural Organic Matter

    EPA Science Inventory

    Recent studies have indicated that fullerenes, an important class of nanomaterials, are photodegraded by solar radiation and can sensitize the photoproduction of reactive oxygen species such as singlet oxygen. Because natural organic matter (NOM) can retard photoreactions that a...

  14. CHLORPYRIFOS TRANSFORMATION BY AQUEOUS CHLORINE IN THE PRESENCE OF BROMIDE AND NATURAL ORGANIC MATTER

    EPA Science Inventory

    The aqueous chlorination of chlorpyrifos (CP) was investigated in the presence of bromide and natural organic matter (NOM), which were identified as naturally occurring aqueous constituents that could impact CP transformation rates to the toxic product chlorpyrifos oxon (CPO). Br...

  15. [Spatial heterogeneity of soil organic matter and its response to disturbance in karst peak cluster depressions].

    PubMed

    Ouyang, Zi-Wen; Peng, Wan-Xia; Song, Tong-Qing; Zeng, Fu-Ping; Wang, Ke-Lin; Guan, Xin; Wu, Hai-Yong

    2009-06-01

    By using geostatistic methods, this paper studied the spatial variation and distribution of soil organic matter as well as its ecological processes and related mechanisms in four typical disturbed areas (cropland, man-made forest, secondary forest, and primary forest) of karst peak cluster depressions in northwest Guangxi of China. Eighty soil samples (0-20 cm) were collected from an aligned grid of 10 m x 10 m for the analysis of soil organic matter. The soil organic matter content increased significantly (P < 0.05) with the decrease of disturbance and the vegetation succession from crop to man-made forest to secondary forest to primary forest. Soil organic matter content had good spatial autocorrelation in all of the four typical disturbed areas, but its spatial heterogeneity differed. Gaussian model fitted best to the semivariance functions of soil organic matter content in the study areas except secondary forest area where exponential model fitted well. In cropland area, the spatial autocorrelation of soil organic matter was at medium level, with the C0/(C0 + C) being 26.5%; while in the other three areas, the spatial autocorrelation was at high level, with the C0/(C0 + C) being 9.0%-22.6%. The range and scale of the spatial autocorrelation of soil organic matter in cropland and man-made forest areas were larger than those in the other two areas, possibly due to the strong human disturbance and the homogeneity of low energy. The range of the spatial autocorrelation of soil organic matter in primary forest area was large due to the high vegetation coverage, while that in secondary forest area was the lowest due to the diverse vegetation communities and their uneven distribution. The low fractal value (D) of semivariance functions of soil organic matter in man-made forest and primary forest areas suggested that a strong spatial dependence existed, while the high D in cropland and secondary forest areas suggested a great random variance of spatial distribution of

  16. The fate or organic matter during planetary accretion - Preliminary studies of the organic chemistry of experimentally shocked Murchison meteorite

    NASA Technical Reports Server (NTRS)

    Tingle, Tracy N.; Tyburczy, James A.; Ahrens, Thomas J.; Becker, Christopher H.

    1992-01-01

    The fate of organic matter in carbonaceous meteorites during hypervelocity (1-2 km/sec) impacts is investigated using results of experiments in which three samples of the Murchison (CM2) carbonaceous chondrite were shocked to 19, 20, and 36 GPa and analyzed by highly sensitive thermal-desorption photoionization mass spectrometry (SALI). The thermal-desorptive SALI mass spectra of unshocked CM2 material revealed presence of indigenous aliphatic, aromatic, sulfur, and organosulfur compounds, and samples shocked to about 20 GPa showed little or no loss of organic matter. On the other hand, samples shocked to 36 GPa exhibited about 70 percent loss of organic material and a lower alkene/alkane ratio than did the starting material. The results suggest that it is unlikely that the indigenous organic matter in carbonaceous chondritelike planetesimals could have survived the impact on the earth in the later stages of earth's accretion.

  17. The effects of soil management on subsoil organic matter

    NASA Astrophysics Data System (ADS)

    Gregory, Andrew; Coleman, Kevin; Jenkinson, David; Powlson, David; Poulton, Paul; Whitmore, Andrew

    2010-05-01

    Soil management has a clear effect on the organic matter (OM) content of soils in agricultural systems. For instance, grassland soils tend to have a greater OM content than arable soils due to the difference in the management of the surface vegetation between the two systems. Our knowledge of this is largely restricted to the topsoil however, as this is the part of the profile that is most obviously influenced by the inputs and losses of OM. How agricultural management at the surface affects OM contents in the subsoil is rarely considered, let alone understood. We present the state of our current knowledge of the effect of soil management on subsoil OM based on measurements made on soils from some of the established field experiments at Rothamsted Research, UK. We have examined subsoil OM data collected by us and other scientists at Rothamsted representing different timescales: long-term (Broadbalk wilderness and arable, Geescroft wilderness, and Park Grass: 130 years), medium-term (Highfield ley-arable: 40-60 years), and short-term (Highfield and Geescroft reversion: 2 years). Samples to depths of up to 96 cm in the profile were collected from the field experiments periodically between 1870 and 2009 and analysed for C and N. Both C and N increased in soils converted from arable to long-term woodland and grassland throughout the profile. The C:N ratio also increased in comparison to long-term arable soils which suggested either the preferential accumulation of C or the preferential decomposition of N at depth in grassland and woodland soils, or the converse at depth in the arable soils. Small increases in C and N in both long-term grassland and arable soils were also apparent. In the medium-term, differences in the pattern of soil C and N with depth were found, with homogenisation in the cultivated layer in arable and fallow soils and a more gradual decrease with depth in the grassland soil. In general, differences between soils subjected to different management

  18. Direct Evidence Linking Soil Organic Matter Development to Microbial Communities

    NASA Astrophysics Data System (ADS)

    Kallenbach, C.; Grandy, S.

    2013-12-01

    Despite increasing recognition of microbial contributions to soil organic matter (SOM) formation there is little experimental evidence linking microbial processes to SOM development and the mechanisms responsible remain unclear. Specifically, if stable SOM is largely comprised of microbial products, we need to better understand the soil conditions that influence microbial biomass production and ultimately its stability. Microbial physiology, such as microbial growth efficiency (MGE) and rate (MGR) have direct influences on microbial biomass production and are highly sensitive to resource quality. Therefore, the importance of resource quality on SOM is not necessarily a function of resistance to decay but the degree to which it optimizes microbial biomass production. While resource quality may have an indirect effect on SOM abundance via its influence on microbial physiology, SOM stabilization of labile microbial products may rely heavily on a soil's capacity to form organo-mineral interactions. To examine the relative importance of soil microbial community function, resource quality and mineralogy on direct microbial contributions to SOM formation and stability, an ongoing 15-mo incubation experiment was set up using artificial, initially C- and microbial-free soils. Soil microcosms were constructed by mixing sand with either kaolinite or montmorillonite clays followed with a natural soil microbial inoculum. For both soil mineral treatments, weekly additions of glucose, cellobiose, or syringol are carried out, with an additional treatment of plant leachate to serve as a reference. This simplified system allows us to determine if, in the absence of plant-derived C, microbial products using simple substrates can result in chemically complex SOM similar to natural soils. Over the course of the incubation, MGE, MGR, microbial activity, and SOM accumulation rates are monitored. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) is used to track the microbial

  19. The nature of Cu bonding to natural organic matter

    NASA Astrophysics Data System (ADS)

    Manceau, Alain; Matynia, Anthony

    2010-05-01

    Copper biogeochemistry is largely controlled by its bonding to natural organic matter (NOM) for reasons not well understood. Using XANES and EXAFS spectroscopy, along with supporting thermodynamic equilibrium calculations and structural and steric considerations, we show evidence at pH 4.5 and 5.5 for a five-membered Cu(malate) 2-like ring chelate at 100-300 ppm Cu concentration, and a six-membered Cu(malonate)) 1-2-like ring chelate at higher concentration. A "structure fingerprint" is defined for the 5.0-7.0 Å -1 EXAFS region which is indicative of the ring size and number (i.e., mono- vs. bis-chelate), and the distance and bonding of axial oxygens (O ax) perpendicular to the chelate plane formed by the four equatorial oxygens (O eq) at 1.94 Å. The stronger malate-type chelate is a C 4 dicarboxylate, and the weaker malonate-type chelate a C 3 dicarboxylate. The malate-type chelate owes its superior binding strength to an -OH for -H substitution on the α carbon, thus offering additional binding possibilities. The two new model structures are consistent with the majority of carboxyl groups being clustered and α-OH substitutions common in NOM, as shown by recent infrared and NMR studies. The high affinity of NOM for Cu(II) is explained by the abundance and geometrical fit of the two types of structures to the size of the equatorial plane of Cu(II). The weaker binding abilities of functionalized aromatic rings also is explained, as malate-type and malonate-type structures are present only on aliphatic chains. For example, salicylate is a monocarboxylate which forms an unfavorable six-membered chelate, because the OH substitution is in the β position. Similarly, phthalate is a dicarboxylate forming a highly strained seven-membered chelate. Five-membered Cu(II) chelates can be anchored by a thiol α-SH substituent instead of an alcohol α-OH, as in thio-carboxylic acids. This type of chelate is seldom present in NOM, but forms rapidly when Cu(II) is photoreduced

  20. Characterization of Soil Organic Matter in Peat Soil with Different Humification Levels using FTIR

    NASA Astrophysics Data System (ADS)

    Teong, I. T.; Felix, N. L. L.; Mohd, S.; Sulaeman, A.

    2016-07-01

    Peat soil is defined as an accumulation of the debris and vegetative under the water logging condition. Soil organic matter of peat soil was affected by the environmental, weather, types of vegetative. Peat soil was normally classified based on its level of humification. Humification can be defined as the transformation of numerous group of substances (proteins, carbohydrates, lipids, etc.) and individual molecules present in living organic matter into group of substances with similar properties (humic substances). During the peat transformation process, content of soil organic matter also will change. Hence, that is important to determine out the types of the organic compound. FTIR (Fourier Transform Infrared) is a machine which is used to differential soil organic matter by using infrared. Infrared is a types of low energy which can determine the organic minerals. Hence, FTIR can be suitable as an indicator on its level of humification. The main objective of this study is to identify an optimized method to characterization of the soil organic content in different level of humification. The case study areas which had been chosen for this study are Parit Sulong, Batu Pahat and UCTS, Sibu. Peat soil samples were taken by every 0.5 m depth until it reached the clay layer. However, the soil organic matter in different humification levels is not significant. FTIR is an indicator which is used to determine the types of soil, but it is unable to differentiate the soil organic matter in peat soil FTIR can determine different types of the soil based on different wave length. Generally, soil organic matter was found that it is not significant to the level of humification.

  1. Effect of organic matters on CO2 hydrate phase equilibrium conditions in Na-montmorillonite clay

    NASA Astrophysics Data System (ADS)

    Park, T.; Kyung, D.; Lee, W.

    2013-12-01

    Formation of gas hydrates provides an attractive idea for storing greenhouse gases in a long-term stable geological formation. Since the phase equilibrium conditions of gas hydrates indicate the stability of hydrates, estimation of the phase equilibrium conditions of gas hydrates in marine geological conditions is necessary. In this study, we have identified the effects of organic matters (glycine, glucose, and urea) and solid surface (montmorillonite (MMT)) on the three-phase (liquid-hydrate-vapor) equilibrium conditions of CO2 hydrate. CO2 phase equilibrium experiments were conducted using 0.5mol% organic matter solutions with and without 10g soil mineral were experimentally conducted. Addition of organic matters shifted the phase equilibrium conditions of CO2 hydrate to the higher pressure or lower pressure region because of higher competition of water molecules due to the dissolved organic matters. Presence of MMT also leaded to the higher equilibrium pressure due to the interaction of cations with water molecules. By addition of organic matters to the clay suspension, the hydrate phase equilibrium conditions were less inhibited compared to those of MMT and organic matters independently. The diminished magnitudes by addition of organic matters to the clay suspension (MMT > MMT+urea > MMT+glycine > MMT+glucose > DIW) were different to the order of inhibition degree without MMT (Glucose > glycine > urea > DIW). X-ray diffraction (XRD), scanning electron microscope (SEM), and ion chromatography (IC) analysis were conducted to support the hypothesis that the organic matters interact with cations in MMT interlayer space, and leads to the less inhibition of phase equilibrium conditions. The present study provides basic information for the formation and dissociation of CO2 hydrates in the geological formation when sequestering CO2 as a form of CO2 hydrate.

  2. Effects of Organic Matter on Photochemistry of Pollutants in Ice and at Ice Surfaces

    NASA Astrophysics Data System (ADS)

    Kahan, T.; Malley, P.; Grossman, J.

    2013-12-01

    Ice and snow are important but poorly-characterized reaction media. We have investigated the effects of proxies for environmental organic matter on the photolysis kinetics of aromatic pollutants in laboratory-prepared ice samples. Pollutant reactivity was greater at air-ice interfaces than in liquid regions within the ice bulk such as veins and pockets. Organic matter affected photolysis kinetics in ice samples, even when it did not absorb solar photons.

  3. Chromatographic methods for the isolation, separation and characterisation of dissolved organic matter.

    PubMed

    Sandron, Sara; Rojas, Alfonso; Wilson, Richard; Davies, Noel W; Haddad, Paul R; Shellie, Robert A; Nesterenko, Pavel N; Kelleher, Brian P; Paull, Brett

    2015-09-01

    This review presents an overview of the separation techniques applied to the complex challenge of dissolved organic matter characterisation. The review discusses methods for isolation of dissolved organic matter from natural waters, and the range of separation techniques used to further fractionate this complex material. The review covers both liquid and gas chromatographic techniques, in their various modes, and electrophoretic based approaches. For each, the challenges that the separation and fractionation of such an immensely complex sample poses is critically reviewed. PMID:26290053

  4. Tracing sources of organic matter in adjacent urban streams having different degrees of channel modification.

    PubMed

    Duan, Shuiwang; Amon, Rainer M W; Brinkmeyer, Robin L

    2014-07-01

    Urbanization and stream-channel modifications affect organic matter concentrations and quality in streams, by altering allochthonous organic matter input and in-stream transformation. This study uses multiple tracers (δ(13)C, δ(15)N, C/N ratio, and chlorophyll-a) to track sources of organic matter in two highly urbanized bayous in Houston (Texas, USA). Wastewater treatment plants (WWTPs) are located in headwaters of both bayous and contribute more than 75% to water flow. Low isotopic relatedness to natural end-members and enriched δ(15)N values suggest the influence of WWTPs on the composition of all organic matter fractions. The two bayous differ in degree of channel improvement resulting in different responses to hydrological conditions. During high flow conditions, the influence of terrestrial organic matter and sediment resuspension was much more pronounced in the Buffalo Bayou than in the concrete-lined White Oak Bayou. Particulate organic matter (POM) in White Oak Bayou had similar values of enriched δ(15)N in all subsegments, whereas in Buffalo Bayou, the degree of δ(15)N enrichment was less in the subsegments of the lower watershed. The difference in riparian zone contributions and interactions with sediments/soils was likely responsible for the compositional differences between the two bayous. Phytoplankton inputs were significantly higher in the bayous, especially in slow-flowing sections, relative to the reference sites, and elevated phytoplankton inputs accounted for the observed stable C isotope differences between FPOM and high molecular weight dissolved organic matter (HMW DOM). Relative to POM, HMW DOM in the bayous was similar to WWTP effluents and showed minor longitudinal variability in both streams suggesting that WWTPs contribute much of the DOM in the systems. Urbanization has a major influence on organic matter sources and quality in these urban water bodies and these changes seem further enhanced by stream channel modifications.

  5. In Situ Mapping of the Organic Matter in Carbonaceous Chondrites and Mineral Relationships

    NASA Technical Reports Server (NTRS)

    Clemett, Simon J.; Messenger, S.; Thomas-Keprta, K. L.; Ross, D. K.

    2012-01-01

    Carbonaceous chondrite organic matter represents a fossil record of reactions that occurred in a range of physically, spatially and temporally distinct environments, from the interstellar medium to asteroid parent bodies. While bulk chemical analysis has provided a detailed view of the nature and diversity of this organic matter, almost nothing is known about its spatial distribution and mineralogical relationships. Such information is nevertheless critical to deciphering its formation processes and evolutionary history.

  6. Stable carbon isotope ratios of rock varnish organic matter: a new paleoenvironmental indicator.

    PubMed

    Dorn, R I; Deniro, M J

    1985-03-22

    Stable carbon isotope ratios of organic matter in rock varnishes of Holocene age from western North America and the Middle East show a strong association with the environment. This isotopic variability reflects the abundance of plants with different photosynthetic pathways in adjacent vegetation. Analyses of different layers of varnish on late Pleistocene desert landforms indicate that the carbon isotopic composition of varnish organic matter is a paleoenvironmental indicator. PMID:17777781

  7. [Effects of Tillage on Distribution of Heavy Metals and Organic Matter Within Purple Paddy Soil Aggregates].

    PubMed

    Shi, Qiong-bin; Zhao, Xiu-lan; Chang, Tong-ju; Lu, Ji-wen

    2016-05-15

    A long-term experiment was utilized to study the effects of tillage methods on the contents and distribution characteristics of organic matter and heavy metals (Cu, Zn, Pb, Cd, Fe and Mn) in aggregates with different sizes (including 1-2, 0.25-1, 0.05-0.25 mm and < 0.05 mm) in a purple paddy soil under two tillage methods including flooded paddy field (FPF) and paddy-upland rotation (PR). The relationship between heavy metals and organic matter in soil aggregates was also analyzed. The results showed that the aggregates of two tillage methods were dominated by 0.05-0.25 mm and < 0.05 mm particle size, respectively. The contents of organic matter in each aggregate decreased with the decrease of aggregate sizes, however, compared to PR, FPF could significantly increase the contents of organic matter in soils and aggregates. The tillage methods did not significantly affect the contents of heavy metals in soils, but FPF could enhance the accumulation and distribution of aggregate, organic matter and heavy metals in aggregates with diameters of 1-2 mm and 0.25-1 mm. Correlation analysis found that there was a negative correlation between the contents of heavy metals and organic matter in soil aggregates, but a positive correlation between the amounts of heavy metal and organic matter accumulated in soil aggregates. From the slope of the correlation analysis equations, we could found that the sensitivities of heavy metals to the changes of soil organic matters followed the order of Mn > Zn > Pb > Cu > Fe > Cd under the same tillage. When it came to the same heavy metal, it was more sensitive in PR than in FPF. PMID:27506049

  8. Chromatographic methods for the isolation, separation and characterisation of dissolved organic matter.

    PubMed

    Sandron, Sara; Rojas, Alfonso; Wilson, Richard; Davies, Noel W; Haddad, Paul R; Shellie, Robert A; Nesterenko, Pavel N; Kelleher, Brian P; Paull, Brett

    2015-09-01

    This review presents an overview of the separation techniques applied to the complex challenge of dissolved organic matter characterisation. The review discusses methods for isolation of dissolved organic matter from natural waters, and the range of separation techniques used to further fractionate this complex material. The review covers both liquid and gas chromatographic techniques, in their various modes, and electrophoretic based approaches. For each, the challenges that the separation and fractionation of such an immensely complex sample poses is critically reviewed.

  9. Stable carbon isotope ratios of rock varnish organic matter: a new paleoenvironmental indicator.

    PubMed

    Dorn, R I; Deniro, M J

    1985-03-22

    Stable carbon isotope ratios of organic matter in rock varnishes of Holocene age from western North America and the Middle East show a strong association with the environment. This isotopic variability reflects the abundance of plants with different photosynthetic pathways in adjacent vegetation. Analyses of different layers of varnish on late Pleistocene desert landforms indicate that the carbon isotopic composition of varnish organic matter is a paleoenvironmental indicator.

  10. The Origin of Organic Matter in the Solar System: Evidence from Interplanetary Dust Particles

    NASA Technical Reports Server (NTRS)

    Flynn, G. J.; Keller, L. P.; Jacobsen, C.; Wirick, S.

    2001-01-01

    The origin of the organic matter in interplanetary materials has not been established. A variety of mechanisms have been proposed, with two extreme cases being a Fisher-Tropsch type process operating in the gas phase of the solar nebula or a Miller-Urey type process, which requires interaction with an aqueous fluid, presumably occurring on an asteroid. In the Fisher-Tropsch case, we might expect similar organic matter in hydrated and anhydrous interplanetary materials. However, aqueous alteration is required in the case of the Miller-Urey process, and we would expect to see organic matter preferentially in interplanetary materials that exhibit evidence of aqueous activity, such as the presence of hydrated silicates. The types and abundance of organic matter in meteorites have been used as an indicator of the origin of organic matter in the Solar System. Indigenous complex organic matter, including amino acids, has been found in hydrated carbonaceous chondrite meteorites, such as Murchison. Much lower amounts of complex organic matter, possibly only terrestrial contamination, have been found in anhydrous carbonaceous chondrite meteorites, such as Allende, that contain most of their carbon in elemental form. These results seem to favor production of the bulk of the organic matter in the Solar System by aqueous processing on parent bodies such as asteroids, a Miller-Urey process. However, the hydrated carbonaceous chondrite meteorites have approximately solar abundances of the moderately volatile elements, while all anhydrous carbonaceous chondrite meteorites have significantly lower contents of these moderately volatile elements. Two mechanisms, incomplete condensation or evaporation, both of which involve processing at approx. 1200 C, have been suggested to explain the lower content of the moderately volatile elements in all anhydrous meteorites. Additional information is contained in the original extended abstract.

  11. The Carboniferous carbon isotope record from sedimentary organic matter: can we disentangle the carbon cycle?

    NASA Astrophysics Data System (ADS)

    Davies, S. J.; Bennett, C. E.; Leng, M. J.; Kearsey, T.; Marshall, J. E.; Millward, D.; Reeves, E. J.; Snelling, A.; Sherwin, J. E.

    2014-12-01

    A comprehensive analysis of the δ13C composition of sedimentary organic matter from Euramerican Carboniferous successions indicates there are significant shifts in δ13C through this key time interval. Our studies have revealed that, at an individual location, the source and delivery mechanism of the sediment contribute to the type of organic matter preserved and, in turn this influences the measured δ13C values from bulk sedimentary organic matter of organic matter. In general, where marine-derived organic matter is dominant in these Carboniferous successions then δ13C values are characteristically lower compared to the higher values encountered where terrestrial plant-derived material is most abundant. The implication of these observations is that an apparent carbon isotope excursion identified from the bulk organic matter may reflect a change in transport processes, or depositional environment, rather than a perturbation in the global carbon cycle. In our most recent studies, however, we compare δ13C values from specific wood fragments and bulk sedimentary organic matter from non-marine, marine basinal, and marine shelfal successions from the earliest Mississippian through to the early Pennsylvanian. These data indicate that early Mississippian δ13C of organic matter is far less negative (around -22%0) than material of Late Mississippian age (around -26%0), however by the early Pennsylvanian, δ13C values return to -22%0. There are some δ13C data from brachiopod carbonate from this time interval and similar shifts are indicated. Our data are beginning to address whether we can identify a primary carbon cycle signal from the Carboniferous record using δ13C from a range of sedimentary environments. If we can, there are still questions around what the record is telling us about the global carbon cycle during a period when plant groups, including lycopods and seed ferns, rapidly diversified.

  12. [Effects of Tillage on Distribution of Heavy Metals and Organic Matter Within Purple Paddy Soil Aggregates].

    PubMed

    Shi, Qiong-bin; Zhao, Xiu-lan; Chang, Tong-ju; Lu, Ji-wen

    2016-05-15

    A long-term experiment was utilized to study the effects of tillage methods on the contents and distribution characteristics of organic matter and heavy metals (Cu, Zn, Pb, Cd, Fe and Mn) in aggregates with different sizes (including 1-2, 0.25-1, 0.05-0.25 mm and < 0.05 mm) in a purple paddy soil under two tillage methods including flooded paddy field (FPF) and paddy-upland rotation (PR). The relationship between heavy metals and organic matter in soil aggregates was also analyzed. The results showed that the aggregates of two tillage methods were dominated by 0.05-0.25 mm and < 0.05 mm particle size, respectively. The contents of organic matter in each aggregate decreased with the decrease of aggregate sizes, however, compared to PR, FPF could significantly increase the contents of organic matter in soils and aggregates. The tillage methods did not significantly affect the contents of heavy metals in soils, but FPF could enhance the accumulation and distribution of aggregate, organic matter and heavy metals in aggregates with diameters of 1-2 mm and 0.25-1 mm. Correlation analysis found that there was a negative correlation between the contents of heavy metals and organic matter in soil aggregates, but a positive correlation between the amounts of heavy metal and organic matter accumulated in soil aggregates. From the slope of the correlation analysis equations, we could found that the sensitivities of heavy metals to the changes of soil organic matters followed the order of Mn > Zn > Pb > Cu > Fe > Cd under the same tillage. When it came to the same heavy metal, it was more sensitive in PR than in FPF.

  13. Influence of organic matters on AsIII oxidation by the microflora of polluted soils.

    PubMed

    Lescure, T; Moreau, J; Charles, C; Ben Ali Saanda, T; Thouin, H; Pillas, N; Bauda, P; Lamy, I; Battaglia-Brunet, F

    2016-06-01

    The global AsIII-oxidizing activity of microorganisms in eight surface soils from polluted sites was quantified with and without addition of organic substrates. The organic substances provided differed by their nature: either yeast extract, commonly used in microbiological culture media, or a synthetic mixture of defined organic matters (SMOM) presenting some common features with nat