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Sample records for modelling dissolved organic

  1. Mathematical modeling of wastewater-derived biodegradable dissolved organic nitrogen.

    PubMed

    Simsek, Halis

    2016-11-01

    Wastewater-derived dissolved organic nitrogen (DON) typically constitutes the majority of total dissolved nitrogen (TDN) discharged to surface waters from advanced wastewater treatment plants (WWTPs). When considering the stringent regulations on nitrogen discharge limits in sensitive receiving waters, DON becomes problematic and needs to be reduced. Biodegradable DON (BDON) is a portion of DON that is biologically degradable by bacteria when the optimum environmental conditions are met. BDON in a two-stage trickling filter WWTP was estimated using artificial intelligence techniques, such as adaptive neuro-fuzzy inference systems, multilayer perceptron, radial basis neural networks (RBNN), and generalized regression neural networks. Nitrite, nitrate, ammonium, TDN, and DON data were used as input neurons. Wastewater samples were collected from four different locations in the plant. Model performances were evaluated using root mean square error, mean absolute error, mean bias error, and coefficient of determination statistics. Modeling results showed that the R(2) values were higher than 0.85 in all four models for all wastewater samples, except only R(2) in the final effluent sample for RBNN modeling was low (0.52). Overall, it was found that all four computing techniques could be employed successfully to predict BDON.

  2. THERMODYNAMIC MODELING OF LIQUID AEROSOLS CONTAINING DISSOLVED ORGANICS AND ELECTROLYTES

    EPA Science Inventory

    Many tropospheric aerosols contain large fractions of soluble organic material, believed to derive from the oxidation of precursors such alpha-pinene. The chemical composition of aerosol organic matter is complex and not yet fully understood.

    The key properties of solu...

  3. THERMODYNAMIC MODELING OF LIQUID AEROSOLS CONTAINING DISSOLVED ORGANICS AND ELECTROLYTES

    EPA Science Inventory

    Many tropospheric aerosols contain large fractions of soluble organic material, believed to derive from the oxidation of precursors such alpha-pinene. The chemical composition of aerosol organic matter is complex and not yet fully understood.

    The key properties of solu...

  4. Three-phase modeling of polycyclic aromatic hydrocarbon association with pore-water-dissolved organic carbon

    SciTech Connect

    Mitra, S. ); Dickhut, R.M. )

    1999-06-01

    Log-log plots of measured organic carbon-normalized sediment pore-water distribution coefficients (K[prime][sub OC]s) for several polycyclic aromatic hydrocarbons (PAHs) versus their octanol-water partition coefficients (K[prime][sub OW]s) at two sites in the Elizabeth River, Virginia, show large deviations from linearity. Organic-carbon normalized distribution coefficients for these PAHs between sediments and pore waters decreased by more than two orders of magnitude with depth as well. To determine to what extent pore water dissolved and colloidal organic carbon (DOC) was responsible for the observed nonlinearity and decrease in K[prime][sub OC], a three-phase model was used to estimate pore-water PAH-DOC binding coefficients (K[sub DOC]). Partitioning of PAHs to pore-water DOC (i.e., K[sub DOC])enhances the observed dissolved phase PAH concentration, especially for high-K[sub OW] compounds, contributing to the nonlinearity in K[prime][sub OC]-K[sub OW] plots. However, the application of the three-phase partitioning model to these data indicate that, at most, pore-water PAH-DOC binding accounts for one order of magnitude of the observed decrease in K[prime][sub OC] with depth in the sediment bed. The results of this study are consistent with three-phase partitioning theory for hydrophobic organic compounds between sediment organic matter, pore-water DOC, and freely dissolved aqueous phases in natural systems.

  5. 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.; ...

    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

  6. Dynamics of dissolved organic carbon in hillslope discharge: Modeling and challenges

    NASA Astrophysics Data System (ADS)

    Dusek, Jaromir; Vogel, Tomas; Dohnal, Michal; Barth, Johannes A. C.; Sanda, Martin; Marx, Anne; Jankovec, Jakub

    2017-03-01

    Reliable quantitative prediction of water movement and fluxes of dissolved substances - specifically organic carbon - at both the hillslope and the catchment scales remains a challenge due to complex boundary conditions and soil spatial heterogeneity. In addition, microbially mediated transformations of dissolved organic carbon (DOC) are recognized to determine the balance of DOC in soils. So far, only few studies utilized stable water isotope information in modeling and even fewer linked dissolved carbon fluxes to mixing and/or transport models. In this study, stormflow dynamics of 18O/16O ratios in the water molecules (expressed as δ18O) and DOC were analyzed using a physically-based modeling approach. A one-dimensional dual-continuum vertical flow and transport model was used to simulate the subsurface transport processes in a forest hillslope soil over a period of 2.5 years. The model was applied to describe the transformation of input signals of δ18O and DOC into output signals observed in the hillslope stormflow. To quantify uncertainty associated with the model parameterization, Monte Carlo analysis in conjunction with Latin hypercube sampling was applied. δ18O variations in hillslope discharge and in soil pore water were predicted reasonably well. Despite the complex nature of microbial transformations that caused uncertainty in model parameters and subsequent prediction of DOC transport, the simulated temporal patterns of DOC concentration in stormflow showed similar behavior to that reflected in the observed DOC fluxes. Due to preferential flow, the contribution of the hillslope DOC export was higher than the amounts that are usually found in the available literature.

  7. Modeling studies of dissolved organic matter cycling in Santa Barbara Basin (CA, USA) sediments

    NASA Astrophysics Data System (ADS)

    Burdige, David J.; Komada, Tomoko; Magen, Cédric; Chanton, Jeffrey P.

    2016-12-01

    Here we describe new reaction-transport models for the cycling of dissolved organic matter (DOM, both dissolved organic carbon [DOC] and dissolved organic nitrogen [DON]) in anoxic marine sediments, and apply these models to data from Santa Barbara Basin sediment cores (maximum depth of 4.6 m). Model results show that most organic carbon (and nitrogen) flow in the sediments occurs through reactive DOM intermediates that turn over rapidly to produce inorganic remineralization end-products. Refractory DOM is also produced, and the vast majority of this refractory DOM is not remineralized and either escapes as a benthic flux across the sediment-water interface or is buried. Except near the sediment surface, refractory DOM represents >95% of the total pore water DOM. Pore water DOM appears to be consistently depleted in nitrogen as compared to its source organic matter, which may be the result of differential production of carbon- versus nitrogen-containing refractory DOM during remineralization. Refractory DOC (DOCr) in Santa Barbara Basin sediment pore waters is largely produced from degradation of sediment particulate organic carbon (POC). In addition, there is an upward basal flux of DOCr that is strongly depleted in 14C (-810‰). The Δ14C value of DOCr varies according to its source, ranging from +60‰ (a component of surface sediment POC enriched with radiocarbon from nuclear weapons testing in the 1960's) to -810‰ (the basal DOC flux). Each contributes to the DOCr benthic flux, which has a weighted-average Δ14C value of -40‰. The model-determined DOCr benthic flux is roughly half of the total DOC benthic flux, consistent with observations in the literature that sediments are a source of both labile and refractory DOC to bottom waters. These results support previous arguments that sediment benthic fluxes represent an important source of refractory DOC to the oceans. The benthic flux of refractory DOC from these sediments may also contribute pre-aged DOC

  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.; ...

    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

  9. 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.

  10. Simple models for the release kinetics of dissolved organic carbon from woody filtration media.

    PubMed

    McLaughlan, Robert G; Al-Mashaqbeh, Othman

    2009-05-01

    The mechanisms and kinetics of dissolved organic carbon (DOC) release from woody materials (pine, hardwood and compost) under non-equilibrium leaching conditions was examined through batch and column tests. Mechanistically based kinetic models (first and second order) had a low predictive power for DOC release compared to those based solely on regression (Elovitch, power law). The DOC release data showed a bi-phasic response, with an early period of rapid release (<24h) controlled by film diffusion followed by a slower rate controlled by intra-particle diffusion. After flow interruption, DOC release was primarily controlled by intra-particle diffusion; however, the specific rate parameters generally varied with each flow cycle and between different wood types.

  11. Experimental investigation and modeling of dissolved organic carbon removal by coagulation from seawater.

    PubMed

    Jeong, Sanghyun; Sathasivan, Arumugam; Kastl, George; Shim, Wang Geun; Vigneswaran, Saravanamuthu

    2014-01-01

    Coagulation removes colloidal matters and dissolved organic carbon (DOC) which can cause irreversible membrane fouling. However, how DOC is removed by coagulant is not well-known. Jar test was used to study the removal of hydrophobic and hydrophilic DOC fractions at various doses (0.5-8.0 mg-Fe(+3) L(-1)) of ferric chloride (FeCl3) and pH (5.0-9.0). Natural organic matter (NOM) in seawater and treated seawater were fractionated by liquid chromatography-organic carbon detector (LC-OCD). Compared to surface water, the removal of DOC in seawater by coagulation was remarkably different. Majority of DOC could be easily removed with very low coagulant dose (<5.0 mg-Fe(+3) L(-1)) and the removal efficiency did not vary with pH, but the DOC composition in treated water had significantly changed. Hydrophobic fraction (HB) was better removed at high pH while hydrophilic fraction (HF) was better removed at low pH. A modified model of Kastl et al. (2004) which assumed that the removal occurred by adsorption of un-dissociated compounds onto ferric hydroxide was formulated and successfully validated against the jar test data.

  12. Hydrochemical Modeling of Dissolved Organic Carbon in a Small, Undisturbed, Forested Watershed in Southern Chile

    NASA Astrophysics Data System (ADS)

    Valdivia, M. V.; Walter, M. T.; Salmon, C. D.; Hedin, L. O.; Walter, M. F.

    2004-12-01

    The objective of the present study is to model Dissolved Organic Carbon (DOC) concentrations in a stream draining a small, undisturbed, old-growth forested watershed in Southern Chile and test model results against measured data. DOC plays an important role in several processes in terrestrial and aquatic ecosystems. For example, through the formation of organic complexes, DOC can influence nutrient availability, affect the solubility, mobility, and toxicity of metals, and control the absorption of pesticides to soils. DOC also influences biological activity by absorbing UV-B radiation and can contribute significantly to freshwater acidity. Additionally, DOC is linked to the formation of trihalomethanes as by-products of the disinfection of drinking water with chlorine, which constitutes a potentially serious threat to human health. Despite plentiful research on biogeochemical processes controlling DOC production and consumption, there is little information from minimally impacted environments, which can provide valuable baseline information from which to evaluate the more impacted ecosystems. Our study focused on a virtually unpolluted old-growth forested watershed in Southern Chile. We developed a conceptual model that assumes DOC production in forest soils is a function of temperature and DOC transport from soil to stream water is a function of discharge and hydrological flow paths. The hydrological response of the catchment under study was simulated using a simple lumped model, based on two years of meteorological data previously collected. Three different equations were used to simulate DOC concentrations in soil water as a function of temperature, and ultimately to derive DOC concentrations in streamflow. Model results were tested against two years of measured DOC concentrations in streamflow, and all three models provided a reasonably good representation of the DOC response of the small studied watershed and a better agreement to the observed DOC than

  13. Copper(II) binding by dissolved organic matter: importance of the copper-to-dissolved organic matter ratio and implications for the biotic ligand model.

    PubMed

    Craven, Alison M; Aiken, George R; Ryan, Joseph N

    2012-09-18

    The ratio of copper to dissolved organic matter (DOM) is known to affect the strength of copper binding by DOM, but previous methods to determine the Cu(2+)-DOM binding strength have generally not measured binding constants over the same Cu:DOM ratios. In this study, we used a competitive ligand exchange-solid-phase extraction (CLE-SPE) method to determine conditional stability constants for Cu(2+)-DOM binding at pH 6.6 and 0.01 M ionic strength over a range of Cu:DOM ratios that bridge the detection windows of copper-ion-selective electrode and voltammetry measurements. As the Cu:DOM ratio increased from 0.0005 to 0.1 mg of Cu/mg of DOM, the measured conditional binding constant ((c)K(CuDOM)) decreased from 10(11.5) to 10(5.6) M(-1). A comparison of the binding constants measured by CLE-SPE with those measured by copper-ion-selective electrode and voltammetry demonstrates that the Cu:DOM ratio is an important factor controlling Cu(2+)-DOM binding strength even for DOM isolates of different types and different sources and for whole water samples. The results were modeled with Visual MINTEQ and compared to results from the biotic ligand model (BLM). The BLM was found to over-estimate Cu(2+) at low total copper concentrations and under-estimate Cu(2+) at high total copper concentrations.

  14. Comparing Modeled and Measured Mercury Speciation in Contaminated Groundwater: Importance of Dissolved Organic Matter Composition.

    PubMed

    Richard, Jan-Helge; Bischoff, Cornelia; Biester, Harald

    2016-07-19

    In addition to analytical speciation, reliable Hg species modeling is crucial for predicting the mobility and toxicity of Hg, but geochemical speciation codes have not yet been tested for their prediction accuracy. Our study compares analyses of Hg species in highly Hg-contaminated groundwater (Hgtot: 0.02-4 μmol·L(-1)) at three sites with predictions of Hg speciation obtained from three geochemical codes (WHAM, Visual MINTEQ, PHREEQC) with and without implementation of Hg complexation by dissolved organic matter (DOM). Samples were analyzed for chemical composition, elemental, inorganic, and DOM-bound Hg (Hg(0), Hginorg, HgDOM). Hg-DOM complexation was modeled using three approaches: binding to humic/fulvic acids, binding to thiol-groups, or a combination of both. Results of Hg(0) modeling were poor in all scenarios. Prediction accuracy for Hginorg and HgDOM strongly depended on the assumed DOM composition. Best results were achieved when weaker binding sites, simulated by WHAMs DOM submodel, were combined with strongly binding thiol groups. Indications were found that thiol-DOM ratios in groundwater are likely to be lower than in surface water, highlighting the need for analytical thiol quantification in groundwater DOM. This study shows that DOM quality is a crucial parameter for prediction of Hg speciation in groundwater by means of geochemical modeling.

  15. Modeling subsurface fluxes of dissolved organic carbon at the hillslope scale

    NASA Astrophysics Data System (ADS)

    Dusek, Jaromir; Vogel, Tomas; Dohnal, Michal; Barth, Johannes A. C.; Sanda, Martin; Marx, Anne; Jankovec, Jakub

    2017-04-01

    Reliable quantitative prediction of water movement and fluxes of dissolved organic carbon (DOC) at both hillslope and catchment scales remains a challenge due to complex boundary conditions and soil spatial heterogeneity. In this study, a one-dimensional dual-continuum vertical flow and transport model was used to analyze subsurface transport processes in a forest hillslope soil over a period of 2.5 years. Among the processes determining the DOC distribution in the soil profile the microbially mediated transformations of DOC, dependent on soil moisture and soil temperature conditions, were considered. To quantify uncertainty associated with the model parameterization, Monte Carlo analysis was performed. The model was applied to describe the transformation of DOC source into output signal observed in the hillslope stormflow. Despite the complex nature of microbial transformations that caused uncertainty in model parameters and subsequent prediction of DOC transport, the simulated temporal patterns of DOC concentration in stormflow showed similar behavior to that reflected in the observed DOC fluxes. Due to preferential flow, the hillslope DOC export was higher than the amounts that are usually found in the available literature.

  16. Representation of Dissolved Organic Carbon in the JULES Dynamic Global Vegetation Model

    NASA Astrophysics Data System (ADS)

    Nakhavali, Mahdi; Friedlingstein, Pierre; Guenet, Bertrand; Ciais, Philip

    2017-04-01

    Current global models of the carbon cycle consider only vertical gas exchanges between terrestrial or oceanic reservoirs and the atmosphere, hence not considering lateral transport of carbon from the continent to the oceans. This also means that such models implicitly consider that all the CO2 which is not respired to the atmosphere is stored on land, hence overestimating the land sink of carbon. Moving toward a boundless carbon cycle that is integrating the whole continuum from land to ocean to atmosphere is needed in order to better understand Earth's carbon cycle and to make more reliable projection of its future. Here we present an original representation of Dissolved Organic Carbon (DOC) processes in the Joint UK Land Environment Simulator (JULES). The standard version of JULES represent energy, water and carbon cycles and exchanges with the atmosphere, but only account for water run-off, not including export of carbon from terrestrial ecosystems to the aquatic environments. The aim of the project is to include in JULES a representation of DOC production in terrestrial soils, due to incomplete decomposition of organic matter, its decomposition to the atmosphere, and its export to the river network by leaching. In new developed version of JULES (JULES-DOCM), DOC pools, based on their decomposition rate, are classified into labile and recalcitrant within 3 meters of soil. Based on turnover rate, DOC coming from plant material pools and microbial biomass is directed to labile pool, while DOC from humus is directed to recalcitrant pool. Both of these pools have free (dissolved) and locked (adsorbed) form where just the free pool is subjected to decomposition and leaching. DOC production and decomposition are controlled by rate modifiers (moisture, temperature, vegetation fraction and decomposition rate) at each soil layer. Decomposed DOC is released to the atmosphere following a fixed carbon use efficiency. Leaching accounts for both surface (runoff) and

  17. Molecular Simulation of Copper Complexation by a Model of Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Newton, A. G.; Sposito, G.

    2008-12-01

    The coadsorption of cations and organic matter to mineral surfaces has been proposed as a mechanism to stabilize soil organic carbon and explain enhanced cation adsorption in soils. Spectroscopic investigations of coadsorption in copper (Cu)-organic ligand-mineral systems have provided conclusive evidence that ternary surface complexes do occur in instances where the simple organic ligand possesses a minimal number of homogeneous binding sites. Although the results of many experimental and spectroscopic investigations of ternary systems with dissolved organic matter (DOM) suggest that ternary surface complexes may be present, unambiguous conclusions cannot be drawn due to the nature of DOM and the heterogeneity of DOM binding sites. Molecular simulations of ternary surface complexes are powerful tools that can be used in the interpretation of spectroscopic data from these experimental systems. Molecular simulations of Cu-DOM coadsorption at mineral surfaces require a model of Cu-DOM that adequately reproduces the physical-chemical behavior of natural Cu-DOM. The Cu-saturated Schulten DOM molecule, whose charge from deprotonated carboxyl groups was balanced by Cu2+ ions, was modeled using the COMPASS forcefield and energy minimization and molecular dynamics algorithms. Compared to previous simulations of Na- and Ca-saturated Schulten DOM, the Cu-DOM was more compact and spherical, as demonstrated by the decreases in the surface area, surface area: volume ratio, porosity, and radius of gyration and by an increase in the volume. The Cu-DOM complex is more polar than Ca-DOM and less polar than Na-DOM, as indicated by the dipole moment and extent of hydrogen bonding. The Cu2+ ion coordination environment contains an average of four oxygen atoms at 2.04 Å from the metal center. These first shell atoms are primarily water and carboxylate oxygen, although oxygen atoms from carbonyl, phenolic, and esters functionalities as well as nitrogen groups are also present. The DOM

  18. Effects of asynchronous snowmelt on flushing of dissolved organic carbon: A mixing model approach

    USGS Publications Warehouse

    Boyer, E.W.; Hornberger, G.M.; Bencala, K.E.; McKnight, Diane M.

    2000-01-01

    In many snowmelt-dominated catchments, stream dissolved organic carbon (DOC) levels typically increase rapidly as spring melt commences, peak before maximum discharge, and decrease quickly as melting continues. We present data from Deer Creek (Summit County, CO) that shows this distinctive flushing response of DOC during snowmelt runoff, with DOC stored in landscape soils flushed to the stream in response to infiltrating melt waters. Our prior studies show that asynchronous melting of the snowpack across the landscape causes the spring DOC flush to be initiated at different times throughout the catchment. In this study we quantify characteristics of the asynchronous melt and its effect on DOC flushing. We investigated whether a simple mixing model can be used to capture the essentials of the asynchronous melting of a seasonal snowpack and its controls on DOC transport. We divided the catchment into zones of aspect and elevation, which largely determine spatial and temporal variations in the distribution of snow. TOPMODEL was used to simulate the hydrology in each zone, and the simulated flow paths were routed through a simple DOC mixing model to predict contributions of DOC to the stream. The zonal responses were aggregated to give a predicted response of hydrology and DOC fluxes for the entire catchment. Our results indicate that asynchronous melting-which determines the timing of contributions of discharge and DOC to streamflow from different areas of the landscape-can be quantified using a simple modeling approach. Copyright ?? 2000 John Wiley & Sons, Ltd.

  19. pH modeling for maximum dissolved organic matter removal by enhanced coagulation.

    PubMed

    Xie, Jiankun; Wang, Dongsheng; van Leeuwen, John; Zhao, Yanmei; Xing, Linan; Chow, Christopher W K

    2012-01-01

    Correlations between raw water characteristics and pH after enhanced coagulation to maximize dissolved organic matter (DOM) removal using four typical coagulants (FeCl3, Al2(SO4)3, polyaluminum chloride (PACl) and high performance polyaluminum chloride (HPAC)) without pH control were investigated. These correlations were analyzed on the basis of the raw water quality and the chemical and physical fractionations of DOM of thirteen Chinese source waters over three seasons. It was found that the final pH after enhanced coagulation for each of the four coagulants was influenced by the content of removable DOM (i.e. hydrophobic and higher apparent molecular weight (AMW) DOM), the alkalinity and the initial pH of raw water. A set of feed-forward semi-empirical models relating the final pH after enhanced coagulation for each of the four coagulants with the raw water characteristics were developed and optimized based on correlation analysis. The established models were preliminarily validated for prediction purposes, and it was found that the deviation between the predicted data and actual data was low. This result demonstrated the potential for the application of these models in practical operation of drinking water treatment plants.

  20. Copper(II) binding by dissolved organic matter: Importance of the copper-to-dissolved organic matter ratio and implications for the Biotic Ligand Model

    USGS Publications Warehouse

    Craven, Alison M.; Aiken, George R.; Ryan, Joseph N.

    2012-01-01

    The ratio of copper to dissolved organic matter (DOM) is known to affect the strength of copper binding by DOM, but previous methods to determine the Cu2+–DOM binding strength have generally not measured binding constants over the same Cu:DOM ratios. In this study, we used a competitive ligand exchange–solid-phase extraction (CLE-SPE) method to determine conditional stability constants for Cu2+–DOM binding at pH 6.6 and 0.01 M ionic strength over a range of Cu:DOM ratios that bridge the detection windows of copper-ion-selective electrode and voltammetry measurements. As the Cu:DOM ratio increased from 0.0005 to 0.1 mg of Cu/mg of DOM, the measured conditional binding constant (cKCuDOM) decreased from 1011.5 to 105.6 M–1. A comparison of the binding constants measured by CLE-SPE with those measured by copper-ion-selective electrode and voltammetry demonstrates that the Cu:DOM ratio is an important factor controlling Cu2+–DOM binding strength even for DOM isolates of different types and different sources and for whole water samples. The results were modeled with Visual MINTEQ and compared to results from the biotic ligand model (BLM). The BLM was found to over-estimate Cu2+ at low total copper concentrations and under-estimate Cu2+ at high total copper concentrations.

  1. Modeling the Dynamics and Export of Dissolved Organic Matter in the Northeastern U.S. Continental Shelf

    NASA Technical Reports Server (NTRS)

    Druon, J.N.; Mannino, A.; Signorini, Sergio R.; McClain, Charles R.; Friedrichs, M.; Wilkin, J.; Fennel, K.

    2009-01-01

    Continental shelves are believed to play a major role in carbon cycling due to their high productivity. Particulate organic carbon (POC) burial has been included in models as a carbon sink, but we show here that seasonally produced dissolved organic carbon (DOC) on the shelf can be exported to the open ocean by horizontal transport at similar rates (1-2 mol C/sq m/yr) in the southern U.S. Mid-Atlantic Bight (MAB). The dissolved organic matter (DOM) model imbedded in a coupled circulation-biogeochemical model reveals a double dynamics: the progressive release of dissolved organic nitrogen (DON) in the upper layer during summer increases the regenerated primary production by 30 to 300%, which, in turns ; enhances the DOC production mainly from phytoplankton exudation in the upper layer and solubilization of particulate organic matter (POM) deeper in the water column. This analysis suggests that DOM is a key element for better representing the ecosystem functioning and organic fluxes in models because DOM (1) is a major organic pool directly related to primary production, (2) decouples partially the carbon and nitrogen cycles (through carbon excess uptake, POM solubilization and DOM mineralization) and (3) is intimately linked to the residence time of water masses for its distribution and export.

  2. Photoproduction of hydrogen peroxide in aqueous solution from model compounds for chromophoric dissolved organic matter (CDOM).

    PubMed

    Clark, Catherine D; de Bruyn, Warren; Jones, Joshua G

    2014-02-15

    To explore whether quinone moieties are important in chromophoric dissolved organic matter (CDOM) photochemistry in natural waters, hydrogen peroxide (H2O2) production and associated optical property changes were measured in aqueous solutions irradiated with a Xenon lamp for CDOM model compounds (dihydroquinone, benzoquinone, anthraquinone, napthoquinone, ubiquinone, humic acid HA, fulvic acid FA). All compounds produced H2O2 with concentrations ranging from 15 to 500 μM. Production rates were higher for HA vs. FA (1.32 vs. 0.176 mM h(-1)); values ranged from 6.99 to 0.137 mM h(-1) for quinones. Apparent quantum yields (Θ app; measure of photochemical production efficiency) were higher for HA vs. FA (0.113 vs. 0.016) and ranged from 0.0018 to 0.083 for quinones. Dihydroquinone, the reduced form of benzoquinone, had a higher production rate and efficiency than its oxidized form. Post-irradiation, quinone compounds had absorption spectra similar to HA and FA and 3D-excitation-emission matrix fluorescence spectra (EEMs) with fluorescent peaks in regions associated with CDOM.

  3. Riverine Dissolved Organic Matter Degradation Modeled Through Microbial Incubations of Vascular Plant Leachates

    NASA Astrophysics Data System (ADS)

    Harfmann, J.; Hernes, P.; Chuang, C. Y.

    2015-12-01

    Dissolved organic matter (DOM) contains as much carbon as is in the atmosphere, provides the main link between terrestrial and marine carbon reservoirs, and fuels the microbial food web. The fate and removal of DOM is a result of several complex conditions and processes, including photodegradation, sorption/desorption, dominant vascular plant sources, and microbial abundance. In order to better constrain factors affecting microbial degradation, laboratory incubations were performed using Sacramento River water for microbial inoculums and vascular plant leachates. Four vascular plant sources were chosen based on their dominance in the Sacramento River Valley: gymnosperm needles from Pinus sabiniana (foothill pine), angiosperm dicot leaves from Quercus douglassi (blue oak), angiosperm monocot mixed annual grasses, and angiosperm monocot mixed Schoenoplectus acutus (tule) and Typha spp. (cattails). Three concentrations of microbial inoculum were used for each plant material, ranging from 0.2% to 10%. Degradation was monitored as a function of time using dissolved organic carbon (DOC), UV-Vis absorbance, and fluorescent dissolved organic matter (fDOM), and was compared across vascular plant type and inoculum concentration.

  4. Modeling priming effects on microbial consumption of dissolved organic carbon in rivers

    NASA Astrophysics Data System (ADS)

    Hotchkiss, E. R.; Hall, R. O.; Baker, M. A.; Rosi-Marshall, E. J.; Tank, J. L.

    2014-05-01

    Rivers receive and process large quantities of terrestrial dissolved organic carbon (DOC). Biologically available (unstable) DOC leached from primary producers may stimulate (i.e., prime) the consumption of more stable terrestrially derived DOC by heterotrophic microbes. We measured microbial DOC consumption (i.e., decay rates) from contrasting C sources in 10 rivers in the western and Midwestern United States using short-term bioassays of river water, soil and algal leachates, glucose, and commercial humate. We added inorganic nutrients (ammonium and phosphorus) to a subset of bioassays. We also amended a subset of river, soil, and commercial humate bioassays with glucose or algal leachates to test the hypothesis that unstable DOC primes consumption of more stable DOC. We used prior measurements of source-specific DOC bioavailability, linked with a Bayesian process model, to estimate means and posterior probability distributions for source-specific DOC decay rates in multisource bioassays. Modeled priming effects ranged from a -130 to +370% change in more stable DOC decay when incubated with unstable DOC. Glucose increased modeled river DOC decay by an average of 87% among all rivers. Glucose and algal leachates increased soil leachate and commercial humate decay by an average of 25% above background rates. Inorganic nutrient additions did not have consistent effects on DOC decay, likely because most of the study rivers had high ambient background nutrients. Our results demonstrate that the priming effect can augment DOC decay in rivers. In addition, Bayesian models can be used to estimate mechanisms driving aquatic ecosystem processes that are difficult to measure directly.

  5. Modeling the production, decomposition, and transport of dissolved organic carbon in boreal soils

    USGS Publications Warehouse

    Fan, Zhaosheng; Neff, Jason C.; Wickland, Kimberly P.

    2010-01-01

    The movement of dissolved organic carbon (DOC) through boreal ecosystems has drawn increased attention because of its potential impact on the feedback of OC stocks to global environmental change in this region. Few models of boreal DOC exist. Here we present a one-dimensional model with simultaneous production, decomposition, sorption/desorption, and transport of DOC to describe the behavior of DOC in the OC layers above the mineral soils. The field-observed concentration profiles of DOC in two moderately well-drained black spruce forest sites (one with permafrost and one without permafrost), coupled with hourly measured soil temperature and moisture, were used to inversely estimate the unknown parameters associated with the sorption/desorption kinetics using a global optimization strategy. The model, along with the estimated parameters, reasonably reproduces the concentration profiles of DOC and highlights some important potential controls over DOC production and cycling in boreal settings. The values of estimated parameters suggest that humic OC has a larger potential production capacity for DOC than fine OC, and most of the DOC produced from fine OC was associated with instantaneous sorption/desorption whereas most of the DOC produced from humic OC was associated with time-dependent sorption/desorption. The simulated DOC efflux at the bottom of soil OC layers was highly dependent on the component and structure of the OC layers. The DOC efflux was controlled by advection at the site with no humic OC and moist conditions and controlled by diffusion at the site with the presence of humic OC and dry conditions.

  6. Modelling hydrological processes and dissolved organic carbon dynamics in a rehabilitated Sphagnum-dominated peatland

    NASA Astrophysics Data System (ADS)

    Bernard-Jannin, Léonard; Binet, Stéphane; Gogo, Sébastien; Leroy, Fabien; Perdereau, Laurent; Laggoun-Défarge, Fatima

    2017-04-01

    Sphagnum-dominated peatlands represent a global major stock of carbon (C). Dissolved organic carbon (DOC) exports through runoff and leaching could reduce their potential C sink function and impact downstream water quality. DOC production in peatlands is strongly controlled by the hydrology, especially water table depth (WTD). Therefore, disturbances such as drainage can lead to increase DOC exports by lowering the WTD. Hydrological restoration (e.g. rewetting) can be undertaken to restore peatland functioning with an impact on DOC exports. The objective of this study is to assess the impact of drainage and rewetting on hydrological processes and their interactions with DOC dynamics in a Sphagnum dominated peatland. A hydrological model has been applied to a drained peatland (La Guette, France) which experienced a rewetting action on February 2014 and where WTD has been recorded in four piezometers at a 15 min time step since 2009. In addition, DOC concentrations in the peatland have been measured 6 times a year since 2014. The hydrological model is a WTD dependent reservoir model composed by two reservoirs representing the micro and macro porosity of the peatland (Binet et al., 2013). A DOC production module in both reservoirs was implemented based on temperature and WTD. The model was calibrated against WTD and DOC concentrations for each piezometer. The results show that the WTD in the study area is strongly affected by local meteorological conditions that could hide the effect of the rewetting action. The preliminary results evidenced that an additional source of water, identified as groundwater supply originating from the surrounding sandy layer aquifer, is necessary to maintain the water balance, especially during wet years (NS>0.8). Finally, the DOC module was able to describe DOC concentrations measured in the peatland and could be used to assess the impact of rewetting on DOC dynamics at different locations and to identify the factors of control of DOC

  7. A variable reaction rate model for chlorine decay in drinking water due to the reaction with dissolved organic matter.

    PubMed

    Hua, Pei; Vasyukova, Ekaterina; Uhl, Wolfgang

    2015-05-15

    A second order kinetic model for simulating chlorine decay in bulk water due to the reaction with dissolved organic matter (DOM) was developed. It takes into account the decreasing reactivity of dissolved organic matter using a variable reaction rate coefficient (VRRC) which decreases with an increasing conversion. The concentration of reducing species is surrogated by the maximum chlorine demand. Temperature dependency, respectively, is described by the Arrhenius-relationship. The accuracy and adequacy of the proposed model to describe chlorine decay in bulk water were evaluated and shown for very different waters and different conditions such as water mixing or rechlorination by applying statistical tests. It is thus very well suited for application in water quality modeling for distribution systems.

  8. Understanding and modelling the variability in Dissolved Organic Carbon concentrations in catchment drainage

    NASA Astrophysics Data System (ADS)

    Coleman, Martin; Waldron, Susan; Scott, Marian; Drew, Simon

    2013-04-01

    Our knowledge of dynamic natural habitats could be improved through the deployment of automated sensor technology. Dissolved organic carbon concentrations, [DOC], are of interest to water companies as purification removes this pool and currently in environmental science, due in part to rising DOC levels and also as respiration of this C pool can lead to an increased CO2 efflux. Manual sampling of catchment drainage systems has revealed seasonal patterns in DOC (Williams, P.J.L., 1995) and that hydrological events export most DOC(Raymond, P.A. and J.E. Saiers, 2010). However, manual sampling precludes detailed characterisation of the dynamic fluctuation of DOC over shorter but important time periods e.g. immediately prior to an event; the transition from base flow to a surface run-off dominated system as surface flow pathways defrost. Such insight is only gained through deployment of continuous-monitoring equipment. Since autumn 2010 we have deployed an S::CAN Spectrolyser (which from absorbance gives a measurement of [DOC]) in a 7.5 kilometre squared peaty catchment draining Europe's largest windfarm, Whitelee. Since autumn 2011, we have an almost complete time series of [DOC] every 30. Here [DOC] has ranged from 12.2 to 58.4 mg/l C and during event flow DOC had a maximum variation of 23.5 mg/l within a single day. Simultaneously with the Spectrolyser, we have logged stage height, pH and conductivity using an In-Situ Inc MD Troll 9000. Generally there is an inverse relationship between [DOC] and both pH and conductivity, but a positive relationship (albeit with seasonal differences) with [DOC] and stage height, from which we can infer hydrological changes in the source of the DOC. Here, in addition to presenting the time series of the data, and a more accurate export budget estimate, I will explore statistical methods for the handling of large datasets. Trends in the data of such large and dynamic data sets are challenging to model. Simple relationships with stage

  9. Uranium isotopes and dissolved organic carbon in loess permafrost: Modeling the age of ancient ice

    USGS Publications Warehouse

    Ewing, Stephanie A.; Paces, James B.; O'Donnell, J.A.; Jorgenson, M.T.; Kanevskiy, M.Z.; Aiken, George R.; Shur, Y.; Harden, Jennifer W.; Striegl, Robert G.

    2015-01-01

    fluctuations in climate, fire disturbance and vegetation. Radiocarbon (14C) analysis of dissolved organic carbon (DOC) in thaw waters supports ages greater than ∼40 ky BP below 10 m. DOC concentrations in thaw waters increased with depth to maxima of >1000 ppm, despite little change in ice content or cryostructures. These relations suggest time-dependent production of old DOC that will be released upon permafrost thaw at a rate that is mediated by sediment transport, among other factors.

  10. Uranium isotopes and dissolved organic carbon in loess permafrost: Modeling the age of ancient ice

    NASA Astrophysics Data System (ADS)

    Ewing, S. A.; Paces, J. B.; O'Donnell, J. A.; Jorgenson, M. T.; Kanevskiy, M. Z.; Aiken, G. R.; Shur, Y.; Harden, J. W.; Striegl, R.

    2015-03-01

    climate, fire disturbance and vegetation. Radiocarbon (14C) analysis of dissolved organic carbon (DOC) in thaw waters supports ages greater than ∼40 ky BP below 10 m. DOC concentrations in thaw waters increased with depth to maxima of >1000 ppm, despite little change in ice content or cryostructures. These relations suggest time-dependent production of old DOC that will be released upon permafrost thaw at a rate that is mediated by sediment transport, among other factors.

  11. Recalcitrant dissolved organic carbon fractions.

    PubMed

    Hansell, Dennis A

    2013-01-01

    Marine dissolved organic carbon (DOC) exhibits a spectrum of reactivity, from very fast turnover of the most bioavailable forms in the surface ocean to long-lived materials circulating within the ocean abyss. These disparate reactivities group DOC by fractions with distinctive functions in the cycling of carbon, ranging from support of the microbial loop to involvement in the biological pump to a hypothesized major source/sink of atmospheric CO(2) driving paleoclimate variability. Here, the major fractions constituting the global ocean's recalcitrant DOC pool are quantitatively and qualitatively characterized with reference to their roles in carbon biogeochemistry. A nomenclature for the fractions is proposed based on those roles.

  12. Dissolved organic C export is highly dynamic - capturing this variability and challenges in modelling

    NASA Astrophysics Data System (ADS)

    Waldron, S.; Coleman, M.; Scott, E. M.; Drew, S.

    2013-12-01

    High resolution, field-deployable sensors offer opportunities to deepen our understanding of natural environmental systems, and measure the ';riverine pulse'. Studies utilising high-resolution equipment have demonstrated that sampling hydrological variables on traditional low frequency rates (such as once a week) creates a simplified picture of conditions that does not capture a true reflection of how fluvial systems operate. Dissolved organic carbon (DOC) represents a large and diverse mixture of compounds (including sugars, amino acids and humic substances) and concentration and composition of this pool varies globally. Understanding transport of this C pool in fluvial systems is important as it 1) represents the lateral export of C no longer sequestered in the terrestrial system, 2) surface water concentrations have been observed to have increased globally and we need to know if this trend is continuing and 3) when water is abstracted the purification processes removing DOC from the water, can create harmful by-products and so prior knowledge of inflow loading is valuable. Traditionally [DOC] has been measured using manual sampling methods, where a water sample would be collected in the field and returned to the lab. This approach can provide reliable data but the resource required to sustain this make it nearly impossible to measure the ';riverine pulse' through the information in long and detailed time series. In recent years new technology designed to estimate [DOC] in-situ has been developed. We have used one of these devices, which measures absorption in both the visible and UV wavelength regions of the electromagnetic spectrum and from this absorbance profile an algorithm estimates [DOC]. We have deployed this system in the field environment and after overcoming initial challenges have an almost continuous time series of [DOC], measured at 30 minute intervals, since May 2012. The logger has been functioning over a temperature range of 0.5 - 23 °C and a

  13. Degradation dynamics and bioavailability of land-based dissolved organic nitrogen in the Bohai Sea: Linking experiment with modeling.

    PubMed

    Li, Keqiang; Ma, Yunpeng; Dai, Aiquan; Wang, Xiulin

    2017-02-24

    Dissolved organic nitrogen (DON) is the major nitrogen form in the Bohai Sea. Land-based DON is released into the nitrogen pool and degraded by planktonic microbiota in coastal ocean. In this study, we evaluated the degradation of land-based DON, particularly its dynamics and bioavailability, in coastal water by linking experiment and modeling. Results showed that the degradation rate constant of DON from sewage treatment plant was significantly faster than those of other land-based sources (P<0.05). DON was classified into three categories based on dynamics and bioavailability. The supply of dissolved inorganic nitrogen (DIN) pool from the DON pool of Liao River, Hai River, and Yellow River was explored using a 3D hydrodynamic multi-DON biogeochemical model in the Bohai Sea. In the model, large amounts of DIN were supplied from DON of Liao River than the other rivers because of prolonged flushing time in Liaodong Bay.

  14. Characterizing dissolved organic matter using PARAFAC modeling of fluorescence spectroscopy: a comparison of two models

    Treesearch

    Jason B. Fellman; Mathew P. Miller; Rose M. Cory; David V. D' Amore; Dan White

    2009-01-01

    We evaluated whether fitting fluorescence excitation-emission matrices (EEMs) to a previously validated PARAFAC model is an acceptable alternative to building an original model. To do this, we built a l0-component model using 307 EEMscollected from southeast Alaskan soil and streamwater. All 307 EEMs were then fit to the existing model (CM) presented in Cory and...

  15. Speciation of rare earth elements in natural terrestrial waters: assessing the role of dissolved organic matter from the modeling approach

    NASA Astrophysics Data System (ADS)

    Tang, Jianwu; Johannesson, Karen H.

    2003-07-01

    Humic Ion-Binding Model V, which focuses on metal complexation with humic and fulvic acids, was modified to assess the role of dissolved natural organic matter in the speciation of rare earth elements (REEs) in natural terrestrial waters. Intrinsic equilibrium constants for cation-proton exchange with humic substances (i.e., p KMHA for type A sites, consisting mainly of carboxylic acids), required by the model for each REE, were initially estimated using linear free-energy relationships between the first hydrolysis constants and stability constants for REE metal complexation with lactic and acetic acid. p KMHA values were further refined by comparison of calculated Model V "fits" to published data sets describing complexation of Eu, Tb, and Dy with humic substances. A subroutine that allows for the simultaneous evaluation of REE complexation with inorganic ligands (e.g., Cl -, F -, OH -, SO 42-, CO 32-, PO 43-), incorporating recently determined stability constants for REE complexes with these ligands, was also linked to Model V. Humic Ion-Binding Model V's ability to predict REE speciation with natural organic matter in natural waters was evaluated by comparing model results to "speciation" data determined previously with ultrafiltration techniques (i.e., organic acid-rich waters of the Nsimi-Zoetele catchment, Cameroon; dilute, circumneutral-pH waters of the Tamagawa River, Japan, and the Kalix River, northern Sweden). The model predictions compare well with the ultrafiltration studies, especially for the heavy REEs in circumneutral-pH river waters. Subsequent application of the model to world average river water predicts that organic matter complexes are the dominant form of dissolved REEs in bulk river waters draining the continents. Holding major solute, minor solute, and REE concentrations of world average river water constant while varying pH, the model suggests that organic matter complexes would dominate La, Eu, and Lu speciation within the pH ranges of 5

  16. 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...

  17. 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...

  18. Modeling nonequilibrium adsorption of MIB and sulfamethoxazole by powdered activated carbon and the role of dissolved organic matter competition.

    PubMed

    Shimabuku, Kyle K; Cho, Hyukjin; Townsend, Eli B; Rosario-Ortiz, Fernando L; Summers, R Scott

    2014-12-02

    This study demonstrates that the ideal adsorbed solution theory-equivalent background compound (IAST-EBC) as a stand-alone model can simulate and predict the powdered activated carbon (PAC) adsorption of organic micropollutants found in drinking water sources in the presence of background dissolved organic matter (DOM) under nonequilibrium conditions. The IAST-EBC represents the DOM competitive effect as an equivalent background compound (EBC). When adsorbing 2-methylisoborneol (MIB) with PAC, the EBC initial concentration was a similar percentage, on average 0.51%, of the dissolved organic carbon in eight nonwastewater impacted surface waters. Using this average percentage in the IAST-EBC model yielded good predictions for MIB removal in two nonwastewater impacted waters. The percentage of competitive DOM was significantly greater in wastewater impacted surface waters, and varied markedly in DOM size fractions. Fluorescence parameters exhibited a strong correlation with the percentage of competitive DOM in these waters. Utilizing such correlations in the IAST-EBC successfully modeled MIB and sulfamethoxazole adsorption by three different PACs in the presence of DOM that varied in competitive effect. The influence of simultaneous coagulant addition on PAC adsorption of micropollutants was also investigated. Coagulation caused the DOM competitive effect to increase and decrease with MIB and sulfamethoxazole, respectively.

  19. Understanding drivers of the export of dissolved organic carbon from a German headwater catchment using Generalised Additive Models

    NASA Astrophysics Data System (ADS)

    Selle, Benny; Musolff, Andreas; Tittel, Jörg

    2016-04-01

    In the literature, several causes of recently increasing concentrations of dissolved organic carbon (DOC) in headwaters across eastern North America and northern and central Europe have been debated. One likely driver of the widespread increase of DOC concentrations since the early 1990s are decreasing depositions of acid rain resulting in an increased solubility of organic carbon compounds including humic acids. Here, we tested the hypothesis if the reduced availability of nitrate stimulated the microbial reduction of ferric iron soil minerals and the mobilisation of DOC. Forested catchments are relatively unaffected by agricultural and urban nitrate inputs. In these catchments, decreasing depositions often resulted in a reduced availability of nitrate, which are preferred electron acceptors in microbial decomposition processes. As ferric iron minerals act as efficient sorbents of organic compounds in soils its reduction may cause a release of humic substances and hence an export of DOC. To test this hypothesis, time series of DOC, dissolved iron and nitrate from a forested headwater catchment in Germany were examined using Generalised Additive Models. We found that rising DOC concentrations most likely resulted from a reductive dissolution of iron(III) minerals in soils and the associated mobilisation of adsorbed organic carbon. Phosphate, which can trigger undesired algal growth and is also known to be adsorbed by particulate iron(III), was released as well.

  20. Understanding drivers of the export of dissolved organic carbon from headwater catchments in Germany using Generalised Additive Models

    NASA Astrophysics Data System (ADS)

    Selle, Benny; Tittel, Jörg; Musolff, Andreas

    2015-04-01

    In the literature, several causes of recently increasing concentrations of dissolved organic carbon (DOC) in headwaters across eastern North America and northern and central Europe have been debated. One likely driver of the widespread increase of DOC concentrations since the early to mid 1990s are decreasing depositions of acid rain resulting in an increased solubility of organic carbon compounds including humic acids. Here, we tested the hypothesis if the reduced availability of both nitrate and sulfate stimulated the reduction of ferric iron soil minerals and the mobilisation of DOC. Decreasing depositions often resulted in a reduced availability of both nitrate and sulphate, which are preferred electron acceptors in microbial decomposition processes. As iron minerals act as efficient sorbents of organic compounds in soils its reduction may have caused a release of humic substances and hence an increasing export of DOC from headwater catchments. To test this hypothesis, time series of DOC, dissolved iron, sulfate and nitrate from several German headwater catchments were examined using Generalised Additive Models. Using this modelling technique, discharge corrected time series of concentrations were represented as a sum of a seasonal and a non-linear trend component. Both, the computed trends and seasonalities supported the redox hypothesis.

  1. First dynamic model of dissolved organic carbon derived directly from high-frequency observations through contiguous storms.

    PubMed

    Jones, Timothy D; Chappell, Nick A; Tych, Wlodek

    2014-11-18

    The first dynamic model of dissolved organic carbon (DOC) export in streams derived directly from high frequency (subhourly) observations sampled at a regular interval through contiguous storms is presented. The optimal model, identified using the recently developed RIVC algorithm, captured the rapid dynamics of DOC load from 15 min monitored rainfall with high simulation efficiencies and constrained uncertainty with a second-order (two-pathway) structure. Most of the DOC export in the four headwater basins studied was associated with the faster hydrometric pathway (also modeled in parallel), and was soon exhausted in the slower pathway. A delay in the DOC mobilization became apparent as the ambient temperatures increased. These features of the component pathways were quantified in the dynamic response characteristics (DRCs) identified by RIVC. The model and associated DRCs are intended as a foundation for a better understanding of storm-related DOC dynamics and predictability, given the increasing availability of subhourly DOC concentration data.

  2. Dissolved organic nitrogen measurement using dialysis pretreatment.

    PubMed

    Lee, Wontae; Westerhoff, Paul

    2005-02-01

    Dissolved organic nitrogen (DON) is important for ecological and engineering researches. Quantification of low DON concentrations in waters with elevated dissolved inorganic nitrogen (DIN) using existing methods is inaccurate. In this study, a dialysis-based pretreatment technique was optimized and adopted to reduce the interference from DIN to the quantification of DON in natural water. A cellulose ester dialysis tube (nominal molecular weight cutoff = 100 Da) was used in batch and continuous-flow dialysis steps with model compounds, natural organic matter isolates, and bulk waters to develop a dialysis pretreatment approach that selectively reduces DIN from solutions containing DON. By reducing DIN concentrations, propagation of analytical variance in total dissolved nitrogen (TDN) and DIN species concentrations allows more accurate determination of DON (DON = TDN - NO3 - NO2- - NH3/NH4+). Dialysis for 24 h against continuously flowing distilled water reduced DIN species by 70%. With dialysis pretreatment, DON recoveries of more than 95% were obtained for surface water and finished drinking water, but wastewater experienced a slight loss (approximately 10%) of DON possibly due to the adsorption of organics onto the dialysis membrane, permeation of low molecular weight fractions, or biodegradation. Dialysis experiments using surface water spiked with different DIN/TDN ratios concluded that dialysis pretreatment leads to more accurate DON determination than no dialysis when DIN/TDN ratios exceed 0.6 mg of N/mg of N.

  3. Experimental and modeling approach to study sorption of dissolved hydrophobic organic contaminants to microbial biofilms.

    PubMed

    Wicke, Daniel; Böckelmann, Uta; Reemtsma, Thorsten

    2007-05-01

    A biofilm reactor was developed to investigate the sorption of polycyclic aromatic hydrocarbons (PAH) as model compounds for hydrophobic organic contaminants (HOC) to intact microbial biofilms at environmentally realistic concentrations. When operated as a differential column batch reactor, the system can be used to study the thermodynamics as well as the kinetics of the exchange of HOC between an aqueous phase and microbial biofilms. Organic carbon normalized partition coefficients (K(oc)) for phenanthrene, fluoranthene and pyrene were at the lower end of those known for other organic sorbents. Intra-biofilm diffusion coefficients (D) were calculated from decrease in solute concentration over time using a model for diffusion through a plane sheet and ranged from 0.23 to 0.45x10(-9)cm(2)s(-1) for the three PAH. These diffusion coefficients are about four orders of magnitude lower than those reported in literature for free aqueous solution. These data and the experimental approach presented here are useful to assess the importance of microbial biofilms for exchange processes of HOC in heterogeneous systems such as water distribution systems, membranes and aquifers, sewer systems or surface soils.

  4. Reactive transport modeling of dissolved organic matter and iron in the Bengal Basin and Mahomet Bedrock Valley aquifers

    NASA Astrophysics Data System (ADS)

    Mladenov, N.; Kulkarni, H. V.; Steward, D. R.; Datta, S.

    2016-12-01

    Despite their different geography, geology and hydrology, Bengal Basin (BB) and Mahomet Bedrock Valley (MBV) aquifers have some key processes in common that mobilize arsenic (As) into groundwater. Groundwater flow, transport of sedimentary labile carbon and dissolved organic matter (DOM) through a multi-layer aquifer system, and microbial interactions together play an important role in the discontinuous As distribution. This study characterized and compared the DOM in high and low As groundwaters in BB and MBV aquifers and developed refined hydrogeological flow models for each of the aquifers. Fluorescence indices suggested substantially more humified and decomposed DOM character in high As (>50 ppb) zones than in low As (<50 ppb) zones in both aquifers. Modeling results indicate North-West to South-East flow with velocity of 7.2 cm/day for the BB aquifer and South-East to North-West with velocity of 35 cm/day for the MBV aquifer. A transport model including advection, dispersion, sorption and reaction was developed to understand the distribution of dissolved iron (Fe) in domains. A modified Monod rate law was used to simulate acetotrophic Fe reduction influenced by the presence of humic-like DOM, based on experimental data. The model produced a Fe2+ distribution, which was similar to that observed in high and low As sites in the BB aquifer. Meanwhile, in the MBV aquifer model, the dispersion of Fe2+ was found to be lower due to higher hydraulic gradient. Model results further indicated that in 30 years these processes would mobilize Fe2+ up to 1.4 km and 5 km in BB and MBV aquifers, respectively. While the quality of DOM in the two aquifers showed similarities, diverse flow and transport conditions may result in more localized and widespread distributions of Fe2+ and As in the BB and MBV aquifers respectively.

  5. Simple model of dissolved oxygen consumption in a bay within high organic loading: an applied remediation tool.

    PubMed

    Ahumada, Ramón; Vargas, José; Pagliero, Liliana

    2006-07-01

    San Vicente Bay is a coastal shallow embayment in Central Chile with multiple uses, one of which is receiving wastewater from industrial fisheries, steel mill effluents, and domestic sewage. A simulation model was developed and applied to dissolved oxygen consumption by organic residues released into this embayment. Three compartments were established as function of: depth, circulation and outfall location. The model compartments had different volumes, and their oxygen saturation value was used as baseline. The parameters: (a) BOD5 of the industrial and urban effluents, (b) oxygen demand by organic sediments, (c) respiration, (d) photosynthesis and (e) re-aeration were included in the model. Iteration results of the model showed severe alterations in Compartment 1, with a decrease of 65% in the oxygen below saturation. Compartment 2 showed a small decline (10%) and compartment 3 did not show apparent changes in oxygen values. Measures recommended for remediation were to decrease the BOD5 loading by 30% in the affected sector. Iteration of the model for 200 h following recommendations derived from the preceding results produced an increase in saturation of 60% (5 ml O2 L(-1)), which suggested an improvement of the environmental conditions.

  6. Modeling 400-500-kyr Pleistocene carbon isotope cyclicity through variations in the dissolved organic carbon pool

    NASA Astrophysics Data System (ADS)

    Ma, Wentao; Wang, Pinxian; Tian, Jun

    2017-05-01

    The carbon isotope (δ13C) record from the Plio-Pleistocene shows prominent 400-kyr cycles with maximum values at eccentricity minima during the Pliocene. The period extends to 500 kyr in the Pleistocene after 1.6 Ma. Five δ13C maxima occurred at 0.2, 0.5, 1.0, 1.5 and 1.9 Ma over the last 2 Ma. Although several hypotheses have been suggested to explain why the 400-500-kyr cycles are so strong in δ13C records and how they may have originated, the mechanism is still not clear. The aim of this study was to test the dissolved organic carbon (DOC) hypothesis, which was proposed recently to explain this 400-500-kyr cycle in deeper time. We used an intermediate complexity box model that is computationally efficient for studies involving longer timescales. The model incorporates sophisticated microbial processes, dividing the oceanic carbon cycle into a rapid and a slow cycle. The model result suggests that when more nutrients enter the surface ocean, the rapid carbon cycle is more active, and less refractory DOC (RDOC) is produced. The opposite sequence occurs when fewer nutrients enter the ocean. The modeled RDOC concentration and the δ13C of dissolved inorganic carbon (DIC) are anti-correlated with riverine nutrient input. According to mass conservation, the release of isotopically lighter carbon from the RDOC pool leads to lighter DIC δ13C while an increase in the RDOC pool enriches it. The transient simulations produced a one-to-one correspondence between modeled and measured δ13C. This study supports the hypothesis that chemical weathering-induced variations in the DOC pool act as a pacemaker for δ13C changes over 400-500-kyr cycles.

  7. Influence of dissolved organic matter and manganese oxides on metal speciation in soil solution: A modelling approach.

    PubMed

    Schneider, Arnaud R; Ponthieu, Marie; Cancès, Benjamin; Conreux, Alexandra; Morvan, Xavier; Gommeaux, Maxime; Marin, Béatrice; Benedetti, Marc F

    2016-06-01

    Trace element (TE) speciation modelling in soil solution is controlled by the assumptions made about the soil solution composition. To evaluate this influence, different assumptions using Visual MINTEQ were tested and compared to measurements of free TE concentrations. The soil column Donnan membrane technique (SC-DMT) was used to estimate the free TE (Cd, Cu, Ni, Pb and Zn) concentrations in six acidic soil solutions. A batch technique using DAX-8 resin was used to fractionate the dissolved organic matter (DOM) into four fractions: humic acids (HA), fulvic acids (FA), hydrophilic acids (Hy) and hydrophobic neutral organic matter (HON). To model TE speciation, particular attention was focused on the hydrous manganese oxides (HMO) and the Hy fraction, ligands not considered in most of the TE speciation modelling studies in soil solution. In this work, the model predictions of free ion activities agree with the experimental results. The knowledge of the FA fraction seems to be very useful, especially in the case of high DOM content, for more accurately representing experimental data. Finally, the role of the manganese oxides and of the Hy fraction on TE speciation was identified and, depending on the physicochemical conditions of the soil solution, should be considered in future studies.

  8. Kinetics of peat soil dissolved organic carbon release to surface water. Part 2. A chemodynamic process model.

    PubMed

    Thibodeaux, L J; Aguilar, L

    2005-09-01

    Temporary water reservoirs built upon peat soil may exhibit water quality impairment from elevated dissolved organic carbon (DOC). Microbiological decay of the organic carbon in the bed with subsequent release produces "tea" colored water which may require treatment prior to use. This paper contains a process-based mathematical model that quantifies the DOC release from the bed and its build-up in the water column. The model elements are based on microbial DOC production rates and bed sediment transport kinetics describing its' release from the organic soil systems. It relies on laboratory data obtained from an experimental study, Part 1, designed to simulate the DOC chemodynamics of aquatic reservoirs built upon peat soils. A two-step DOC release process was structured based on the experimental findings. The model mechanism assumes a quick release fraction that characterizes the upper soil surface layers as a "tea bag" type release process. This is followed by a fraction that is continuously produced and then released at a constant rate overtime by on-going microbial processes within the upper soil layers. The depth of the active layer, selected as h* = 0.3 cm, is the single adjustable parameter in the model. Concentration predictions of the are consistent with the laboratory simulations and field observations. Measured vs. model-calculated DOC concentrations for both in the microcosm bed and water column are used to test critical features of the proposed model. As conceived and structured it appears to be a realistic first step in quantifying the DOC release consequences for the water column of a reservoir sited upon a peat-soil bed. The development ends with an application to a hypothetical reservoir in order to illustrate model strengths and uncertainties.

  9. Effect on pCO2 by phytoplankton uptake of dissolved organic nutrients in the Central and Northern Baltic Sea, a model study

    NASA Astrophysics Data System (ADS)

    Edman, Moa K.; Anderson, Leif G.

    2014-11-01

    Dissolved organic matter (DOM) has been added to an existing biogeochemical model and the phytoplankton were allowed to utilize the dissolved organic nutrients for primary production. The results show typical vertical structures for dissolved organic carbon (DOC), and improved or maintained model skill for both mean vertical profiles and mean seasonal variation of biogeochemical variables, evaluated by objective skill metrics. Due to scarce DOM measurements in the Baltic Sea it was hard to validate the new variables, but the model can recreate the general magnitude and distribution of terrestrial and in situ produced DOC, DON, and DOP, as far as we know them. The improvements are especially clear for the total nutrient levels and in recreating the biological drawdown of CO2 in the Eastern Gotland basin. Without phytoplankton uptake of dissolved organic nitrogen and phosphate, CO2 assimilation is lower during the summer months and the partial pressure of CO2 increases by about 200 μatm in the Eastern Gotland Basin, while in the Bothnian Bay, both the duration and magnitude of CO2 assimilation are halved. Thus the phytoplankton uptake of dissolved organic nutrients lowers pCO2 in both basins. Variations in the river transported DOM concentration mainly affect the magnitude of the summer cyanobacteria bloom.

  10. Experimental verification of a model describing solid phase microextraction (SPME) of freely dissolved organic pollutants in sediment porewater.

    PubMed

    Yang, Ze-Yu; Maruya, Keith A; Greenstein, Darrin; Tsukada, David; Zeng, Eddy Y

    2008-08-01

    To verify a theoretical mass balance and multiple compartment partitioning model developed to predict freely dissolved concentrations (FDCs) of hydrophobic organic chemicals (HOCs) using negligible depletion-solid phase microextraction (nd-SPME), a series of sediment slurry experiments were performed using disposable poly(dimethyl)siloxane (PDMS) coated-SPME fibers and (14)C-radiolabeled HOC analogs. First, pre-calibration of disposable PDMS coated fibers for four model compounds (phenanthrene, PCB 52, PCB 153 and p,p'-DDE) with good precision (model [Yang, Z.-Y., Zeng, E.Y., Maruya, K.A., Mai, B.-X., Ran, Y., 2007b. Predicting organic contaminant concentrations in sediment porewater using solid-phase microextraction. Chemosphere 66, 1408-1414]. Moreover, the SPME-measured FDCs (C(pw,SPME)) followed the order of phenanthrene>PCB 52>PCB 153, and the measured and predicted C(pw) values were not substantially different from empirically determined values except for p,p'-DDE.

  11. Dissolved organic carbon fluxes in the Middle Atlantic Bight: An integrated approach based on satellite data and ocean model products

    NASA Astrophysics Data System (ADS)

    Mannino, Antonio; Signorini, Sergio R.; Novak, Michael G.; Wilkin, John; Friedrichs, Marjorie A. M.; Najjar, Raymond G.

    2016-02-01

    Continental margins play an important role in global carbon cycle, accounting for 15-21% of the global marine primary production. Since carbon fluxes across continental margins from land to the open ocean are not well constrained, we undertook a study to develop satellite algorithms to retrieve dissolved organic carbon (DOC) and combined these satellite data with physical circulation model products to quantify the shelf boundary fluxes of DOC for the U.S. Middle Atlantic Bight (MAB). Satellite DOC was computed through seasonal relationships of DOC with colored dissolved organic matter absorption coefficients, which were derived from an extensive set of in situ measurements. The multiyear time series of satellite-derived DOC stocks (4.9 Teragrams C; Tg) shows that freshwater discharge influences the magnitude and seasonal variability of DOC on the continental shelf. For the 2010-2012 period studied, the average total estuarine export of DOC into the MAB shelf is 0.77 Tg C yr-1 (year). The integrated DOC tracer fluxes across the shelf boundaries are 12.1 Tg C yr-1 entering the MAB from the southwest alongshore boundary, 18.5 Tg C yr-1 entering the MAB from the northeast alongshore boundary, and 29.0 Tg C yr-1 flowing out of the MAB across the entire length of the 100 m isobath. The magnitude of the cross-shelf DOC flux is quite variable in time (monthly) and space (north to south). The highly dynamic exchange of water along the shelf boundaries regulates the DOC budget of the MAB at subseasonal time scales.

  12. Effect of chemical oxidation on the sorption tendency of dissolved organic matter to a model hydrophobic surface.

    PubMed

    Zeng, Teng; Wilson, Corey J; Mitch, William A

    2014-05-06

    The application of chemical oxidants may alter the sorption properties of dissolved organic matter (DOM), such as humic and fulvic acids, proteins, polysaccharides, and lipids, affecting their fate in water treatment processes, including attachment to other organic components, activated carbon, and membranes (e.g., organic fouling). Similar reactions with chlorine (HOCl) and bromine (HOBr) produced at inflammatory sites in vivo affect the fate of biomolecules (e.g., protein aggregation). In this study, quartz crystal microbalance with dissipation monitoring (QCM-D) was used to evaluate changes in the noncovalent interactions of proteins, polysaccharides, fatty acids, and humic and fulvic acids with a model hydrophobic surface as a function of increasing doses of HOCl, HOBr, and ozone (O3). All three oxidants enhanced the sorption tendency of proteins to the hydrophobic surface at low doses but reduced their sorption tendency at high doses. All three oxidants reduced the sorption tendency of polysaccharides and fatty acids to the hydrophobic surface. HOCl and HOBr increased the sorption tendency of humic and fulvic acids to the hydrophobic surface with maxima at moderate doses, while O3 decreased their sorption tendency. The behavior observed with two water samples was similar to that observed with humic and fulvic acids, pointing to the importance of these constituents. For chlorination, the highest sorption tendency to the hydrophobic surface was observed within the range of doses typically applied during water treatment. These results suggest that ozone pretreatment would minimize membrane fouling by DOM, while chlorine pretreatment would promote DOM removal by activated carbon.

  13. A runoff model of dissolved organic carbon considering soil infiltration and river runoff processes in a forested watershed

    NASA Astrophysics Data System (ADS)

    Ebata, K.; Ichikawa, Y.; Ishidaira, H.; Matsumoto, Y.; Nishida, K.

    2016-12-01

    Estimation of dissolved organic carbon (DOC) runoff load in forested watershed is important for the assessment of the global carbon cycle as well as for the control of regional water environments. A few process-based models have been proposed to estimate the DOC loads to water environments, which assume DOC source in topsoil and transport processes to the river, however, these models exhibited difficulties with the availability of input data and applicability to short time-scale rainfall-runoff processes in the Asian monsoon area. With the six years' data from middle stream (98ha) and downstream (1798ha) in the Mizugaki Experimental Watershed, Yamanashi, Japan, this study developed a new process-based model that consists of two separate systems for determining DOC loads enforced by DOC Source Area (DSA) concept. For the runoff system, a semi-distributed hydrological modelling unit (`modified-TOPMODEL') was installed, by which surface and subsurface water flows, representing for DSA, were sequentially simulated. For the soil system, a wet-dry cycle was successfully simulated by an advection-diffusion and dissolution formulation as well as seasonal temperature effect, integrated with root-zone water fluxes calculated by modified-TOPMODEL. The results of storm event calculation showed that the model performed well for the middle stream while the simulated DOC loadings were overestimated at downstream, implying the need of improvement for DSA calculation with a large gap in topographic characteristics.

  14. Modeling the photo-oxidation of dissolved organic matter by ultraviolet radiation in freshwater lakes: implications for mercury bioavailability.

    PubMed

    Haverstock, Sarah; Sizmur, Tom; Murimboh, John; O'Driscoll, Nelson J

    2012-08-01

    Uncertainties in projected ultraviolet (UV) radiation may lead to future increases in UV irradiation of freshwater lakes. Because dissolved organic carbon (DOC) is the main binding phase for mercury (Hg) in freshwater lakes, an increase in DOC photo-oxidation may affect Hg speciation and bioavailability. We quantified the effect of DOC concentration on the rate of abiotic DOC photo-oxidation for five lakes (DOC=3.27-12.3 mg L(-1)) in Kejimkujik National Park, Canada. Samples were irradiated with UV-A or UV-B radiation over a 72-h period. UV-B radiation was found to be 2.36 times more efficient at photo-oxidizing DOC than UV-A, with energy-normalized rates of dissolved inorganic carbon (DIC) production ranging from 3.8×10(-5) to 1.1×10(-4) mg L(-1)J(-1) for UV-A, and from 6.0×10(-5) to 3.1×10(-4) mg L(-1)J(-1) for UV-B. Energy normalized rates of DIC production were positively correlated with DOC concentrations. Diffuse integrated attenuation coefficients were quantified in situ (UV-A K(d)=0.056-0.180 J cm(-1); UV-B K(d)=0.015-0.165 J cm(-1)) and a quantitative depth-integrated model for yearly DIC photo-production in each lake was developed. The model predicts that, UV-A produces between 3.2 and 100 times more DIC (1521-2851 mg m(-2) year(-1)) than UV-B radiation (29.17-746.7 mg m(-2) year(-1)). Future increases in UV radiation may increase DIC production and increase Hg bioavailability in low DOC lakes to a greater extent than in high DOC lakes. Copyright © 2012 Elsevier Ltd. All rights reserved.

  15. 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

  16. The Biogeochemistry of Chromophoric Dissolved Organic Matter in Coastal Waters

    DTIC Science & Technology

    2016-06-07

    processes controlling the fate and distribution of DOM in coastal waters will allow detailed modeling of the fate of contaminants such as hydrophobic...The Biogeochemistry of Chromophoric Dissolved Organic Matter in Coastal Waters Robert F. Chen Environmental, Coastal and Ocean Sciences University of...coastal waters . Of particular interest is the fate of terrigenous and anthropogenic dissolved organic matter in marine systems. OBJECTIVES 1

  17. Associations Between the Molecular and Optical Properties of Dissolved Organic Matter in the Florida Everglades, a Model Coastal Wetland System

    PubMed Central

    Wagner, Sasha; Jaffé, Rudolf; Cawley, Kaelin; Dittmar, Thorsten; Stubbins, Aron

    2015-01-01

    Optical properties are easy-to-measure proxies for dissolved organic matter (DOM) composition, source, and reactivity. However, the molecular signature of DOM associated with such optical parameters remains poorly defined. The Florida coastal Everglades is a subtropical wetland with diverse vegetation (e.g., sawgrass prairies, mangrove forests, seagrass meadows) and DOM sources (e.g., terrestrial, microbial, and marine). As such, the Everglades is an excellent model system from which to draw samples of diverse origin and composition to allow classically-defined optical properties to be linked to molecular properties of the DOM pool. We characterized a suite of seasonally- and spatially-collected DOM samples using optical measurements (EEM-PARAFAC, SUVA254, S275−295, S350−400, SR, FI, freshness index, and HIX) and ultrahigh resolution mass spectrometry (FTICR-MS). Spearman's rank correlations between FTICR-MS signal intensities of individual molecular formulae and optical properties determined which molecular formulae were associated with each PARAFAC component and optical index. The molecular families that tracked with the optical indices were generally in agreement with conventional biogeochemical interpretations. Therefore, although they represent only a small portion of the bulk DOM pool, absorbance, and fluorescence measurements appear to be appropriate proxies for the aquatic cycling of both optically-active and associated optically-inactive DOM in coastal wetlands. PMID:26636070

  18. Associations between the molecular and optical properties of dissolved organic matter in the Florida Everglades, a model coastal wetland system

    NASA Astrophysics Data System (ADS)

    Wagner, Sasha; Jaffe, Rudolf; Cawley, Kaelin; Dittmar, Thorsten; Stubbins, Aron

    2015-11-01

    Optical properties are easy-to-measure proxies for dissolved organic matter (DOM) composition, source and reactivity. However, the molecular signature of DOM associated with such optical parameters remains poorly defined. The Florida coastal Everglades is a subtropical wetland with diverse vegetation (e.g., sawgrass prairies, mangrove forests, seagrass meadows) and DOM sources (e.g., terrestrial, microbial and marine). As such, the Everglades is an excellent model system from which to draw samples of diverse origin and composition to allow classically-defined optical properties to be linked to molecular properties of the DOM pool. We characterized a suite of seasonally- and spatially-collected DOM samples using optical measurements (EEM-PARAFAC, SUVA254, S275-295, S350-400, SR, FI, freshness index and HIX) and ultrahigh resolution mass spectrometry (FTICR-MS). Spearman’s rank correlations between FTICR-MS signal intensities of individual molecular formulae and optical properties determined which molecular formulae were associated with each PARAFAC component and optical index. The molecular families that tracked with the optical indices were generally in agreement with conventional biogeochemical interpretations. Therefore, although they represent only a small portion of the bulk DOM pool, absorbance and fluorescence measurements appear to be appropriate proxies for the aquatic cycling of both optically-active and associated optically-inactive DOM in coastal wetlands.

  19. Associations Between the Molecular and Optical Properties of Dissolved Organic Matter in the Florida Everglades, a Model Coastal Wetland System.

    PubMed

    Wagner, Sasha; Jaffé, Rudolf; Cawley, Kaelin; Dittmar, Thorsten; Stubbins, Aron

    2015-01-01

    Optical properties are easy-to-measure proxies for dissolved organic matter (DOM) composition, source, and reactivity. However, the molecular signature of DOM associated with such optical parameters remains poorly defined. The Florida coastal Everglades is a subtropical wetland with diverse vegetation (e.g., sawgrass prairies, mangrove forests, seagrass meadows) and DOM sources (e.g., terrestrial, microbial, and marine). As such, the Everglades is an excellent model system from which to draw samples of diverse origin and composition to allow classically-defined optical properties to be linked to molecular properties of the DOM pool. We characterized a suite of seasonally- and spatially-collected DOM samples using optical measurements (EEM-PARAFAC, SUVA254, S275-295, S350-400, SR, FI, freshness index, and HIX) and ultrahigh resolution mass spectrometry (FTICR-MS). Spearman's rank correlations between FTICR-MS signal intensities of individual molecular formulae and optical properties determined which molecular formulae were associated with each PARAFAC component and optical index. The molecular families that tracked with the optical indices were generally in agreement with conventional biogeochemical interpretations. Therefore, although they represent only a small portion of the bulk DOM pool, absorbance, and fluorescence measurements appear to be appropriate proxies for the aquatic cycling of both optically-active and associated optically-inactive DOM in coastal wetlands.

  20. Modeling the transport of freshwater and dissolved organic carbon in the Neuse River Estuary, NC, USA following Hurricane Irene (2011)

    NASA Astrophysics Data System (ADS)

    Brown, Matthew M.; Mulligan, Ryan P.; Miller, Richard L.

    2014-02-01

    Numerical models are useful tools that aid in understanding complex flows and the distribution of suspended material over large geographic areas and during extreme weather events. Here we describe the use of a three-dimensional numerical model (Delft3D) to simulate freshwater and dissolved organic carbon (DOC) transport over a 3-week period, following intense precipitation that led to high river discharge into the brackish Neuse River Estuary (NRE), NC, from Hurricane Irene (Aug. 2011). The model was calibrated and validated using field measurements of water level elevations, vertical salinity profiles, and surface DOC concentrations in the estuary. DOC was simulated as a conservative tracer over the study period. Model results indicate differences in the intensity of the freshwater and DOC-laden plumes as they propagated along estuary due to a one week time lag between the maximum discharge of 540 m3 s-1 and maximum DOC concentration of 29.85 mg L-1 entering the NRE from the river. In the upper estuary, the surface DOC concentration increased by 18 mg L-1 above the pre-storm value of 7 mg L-1; the maximum concentration occurred 10 days after the passage of the storm. In the lower estuary, the outer edge of the DOC plume reached Pamlico Sound after 3 weeks with a surface DOC concentration that was 3 mg L-1 above the pre-storm value. Results also indicate cross-channel salinity differences up to 10 ppt and DOC concentration differences up to 15 mg L-1 in the upper NRE to due to wind-driven motion of the estuary. The methods described here could be applied to other coastal plain estuarine systems to simulate and characterize flow rates and DOC transport during and succeeding storm events where field measurements are often limited.

  1. Peer reviewed: Characterizing aquatic dissolved organic matter

    USGS Publications Warehouse

    Leenheer, Jerry A.; Croué, Jean-Philippe

    2003-01-01

    Whether it causes aesthetic concerns such as color, taste, and odor; leads to the binding and transport of organic and inorganic contaminants; produces undesirable disinfection byproducts; provides sources and sinks for carbon; or mediates photochemical processes, the nature and properties of dissolved organic matter (DOM) in water are topics of significant environmental interest. DOM is also a major reactant in and product of biogeochemical processes in which the material serves as a carbon and energy source for biota and controls levels of dissolved oxygen, nitrogen, phosphorus, sulfur, numerous trace metals, and acidity.

  2. Toxicity to embryo and adult zebrafish of copper complexes with two malonic acids as models for dissolved organic matter

    SciTech Connect

    Palmer, F.B.; Evans, C.W.; Butler, C.A.; Timperley, M.H.

    1998-08-01

    The toxicity to embryo and adult zebrafish (Danio rerio) of Cu complexes with two substituted malonic acids, benzyl- and n-hexadecyl-, chosen as models for low-molecular-weight natural dissolved organic matter, were investigated. Toxicity test solutions at pH 6.5 {+-} 0.1 with the required Cu ion-specific electrode. In the absence of malonic acids, concentrations of Cu{sup 2+} up to 1.13 {mu}mol/L increased the embryo hatching time from approx. 2 d in control solutions (no Cu or malonic acid) and solutions containing malonic acids without Cu to approx. 8 d. The Cu-benzylmalonic acid complex in the presence of inorganic Cu species did not delay hatching beyond that attributable to Cu{sup 2+}. In contrast, 0.60 {mu}mol/L Cu-n-hexadecylmalonic complexes delayed hatching by 5.5 d in excess of that attributable to 1.13 {mu}mol/L Cu{sup 2+}, assuming that the hatching delays caused by the different Cu species were additive, possibly because of Cu entry into the embryo as the lipophilic Cu-n-hexadecylmalonic complex. None of the Cu-malonic acid complexes was acutely toxic to adult zebrafish at concentrations up to 1.4 {mu}mol/L, possibly because Cu was removed from the Cu-malonic acid complexes by stronger chelating groups at the gill surface. Substituted malonic acids with similar proton and Cu association constants can be readily prepared with a variety of simple substituents, radiolabeled if required. Their results show that these acids could be useful ligands for investigating intracellular transport and metabolism of metal-organic complexes.

  3. Response surface modeling for optimization heterocatalytic Fenton oxidation of persistence organic pollution in high total dissolved solid containing wastewater.

    PubMed

    Sekaran, G; Karthikeyan, S; Boopathy, R; Maharaja, P; Gupta, V K; Anandan, C

    2014-01-01

    The rice-husk-based mesoporous activated carbon (MAC) used in this study was precarbonized and activated using phosphoric acid. N2 adsorption/desorption isotherm, X-ray powder diffraction, electron spin resonance, X-ray photoelectron spectroscopy and scanning electron microscopy, transmission electron microscopy, (29)Si-NMR spectroscopy, and diffuse reflectance spectroscopy were used to characterize the MAC. The tannery wastewater carrying high total dissolved solids (TDS) discharged from leather industry lacks biodegradability despite the presence of dissolved protein. This paper demonstrates the application of free electron-rich MAC as heterogeneous catalyst along with Fenton reagent for the oxidation of persistence organic compounds in high TDS wastewater. The heterogeneous Fenton oxidation of the pretreated wastewater at optimum pH (3.5), H2O2 (4 mmol/L), FeSO4[Symbol: see text]7H2O (0.2 mmol/L), and time (4 h) removed chemical oxygen demand, biochemical oxygen demand, total organic carbon and dissolved protein by 86, 91, 83, and 90%, respectively.

  4. Conceptual hydrogeological model of flow and transport of dissolved organic carbon in a small Jura karst system

    NASA Astrophysics Data System (ADS)

    Charlier, Jean-Baptiste; Bertrand, Catherine; Mudry, Jacques

    2012-08-01

    SummaryThis paper aims at characterizing infiltration and solute transport processes in a karst system during flood events in order to build a conceptual model of hydrogeological functioning. The study site is the small karst system of Fertans in the French Jura. Soil cover, rock matrix, and a small spring were monitored to measure hydrological and hydrochemical parameters, and particularly a continuous dissolved organic carbon (DOC) signal, which is a relevant environmental tracer of fast infiltration. We used two combined approaches. First, from hydrodynamic and hydrochemical data, we identified the system structure (consistent with a dual porosity scheme) and characterized the main processes occurring during flood events. Second, on the basis of this scheme, we built a new conceptual hydrogeological model coupled with DOC transport to numerically validate the hydrological functioning. This modelling approach is based on a rainfall-discharge model to simulate spring flow. Solute transport is modelled using mixing equations, including an empirical retardation factor, as well as a first order solute decay. The model was calibrated and validated on a set of nineteen flood events, showing its performances in simulating spring hydrographs and delayed DOC signals during flood events with various rainfall intensities. We showed that the recharge area of the karst system varied largely with low and high groundwater periods, which was attributed to the state of hydraulic connectivity in the unsaturated zone. The soil cover appeared to play an important role of mixing and transfer for the recharge water. The model simulated the contributions of pre-event and event waters during flood events and allowed a better quantification of the available resource. It showed, in particular, that total discharge of some flood events during low water periods is mainly composed of pre-event water via piston flow-type processes. Finally, this study shows that the mixing model can simulate

  5. Coupled cycling of dissolved organic nitrogen and carbon in a forest stream

    Treesearch

    E.N. Jack Brookshire; H. Maurice Valett; Steven A. Thomas; Jackson R. Webster

    2005-01-01

    Dissolved organic nitrogen (DON) is an abundant but poorly understood pool of N in many ecosystems. We assessed DON cycling in a N-limited headwater forest stream via whole-ecosystem additions of dissolved inorganic nitrogen (DIN) and labile dissolved organic matter (DOM), hydrologic transport and biogeochemical modeling, and laboratory experiments with native...

  6. An integrated Dissolved Organic Carbon Dynamics Model (DOCDM 1.0): model development and a case study in the Alaskan Yukon River Basin

    NASA Astrophysics Data System (ADS)

    Lu, X.; Zhuang, Q.

    2015-12-01

    Quantitative understanding of the variation in dissolved organic carbon (DOC) is important to studying the terrestrial ecosystem carbon cycle. This study presents a process-based, dissolved organic carbon dynamics model (DOCDM 1.0) that couples the soil heat conduction, water flow, DOC production, mineralization and transport in both surface and subsurface of soil profile to quantify DOC dynamics in boreal terrestrial ecosystems. The model is first evaluated and then applied for a watershed in Alaska to investigate its DOC production and transport. We find that 42 and 27 % of precipitation infiltrates to soils in 2004, a warmer year, and in 1976, a colder year, respectively. Under warming conditions, DOC transported via overland flow does not show the expected decrease trend while the overland DOC yield shows a 4 % increase. The horizontal subsurface flow only accounts for 1-2 % of total water flux, but transports 30-50 % of DOC into rivers. Water flush due to water infiltration controls DOC transport. Snowmelt plays a noticeable role in DOC flush-out and DOC transport significantly depends on flowpaths in the study region. High soil temperature stimulates DOC production. The overland DOC export does not necessarily follow the DOC downward trend in surface water transport. Overall, this study shows that DOC export behavior is complex under changing temperature and hydrological conditions in cold-region watersheds. To adequately quantify DOC dynamics in northern high latitudes, more DOC and hydrological data are needed to better parameterize and test the developed model before extrapolating it to the region.

  7. ESTIMATING DISSOLVED ORGANIC CARBON PARTITION COEFFICIENTS FOR NONIONIC ORGANIC CHEMICALS

    EPA Science Inventory

    A literature search was performed for dissolved organic carbon/water partition coefficients for nonionic chemicals (Kdoc) and Kdoc data was taken from more than sixty references. The Kdoc data were evaluated as a function of the n-octanol/water partition coefficients (Kow). A pre...

  8. ESTIMATING DISSOLVED ORGANIC CARBON PARTITION COEFFICIENTS FOR NONIONIC ORGANIC CHEMICALS

    EPA Science Inventory

    A literature search was performed for dissolved organic carbon/water partition coefficients for nonionic chemicals (Kdoc) and Kdoc data was taken from more than sixty references. The Kdoc data were evaluated as a function of the n-octanol/water partition coefficients (Kow). A pre...

  9. Application of Bayesian belief net in modelling the origin and effects of terrigenous dissolved organic matter in a boreal aquatic ecosystem

    NASA Astrophysics Data System (ADS)

    Rahikainen, Mika; Hoikkala, Laura; Soinne, Helena

    2013-04-01

    models of different environmental compartments (soil chemistry, agricultural management practices, aquatic processes, costs and benefits for society) with explicit treatment of uncertainty. In order to achieve policy relevance, these models have to be integrated into resource management. We use a Bayesian belief net to describe the probabilistic dependencies among the driving forces, processes, and impacts relevant to dissolved organic matter in boreal waterways.

  10. Hydrological mobilization of mercury and dissolved organic carbon in a snow-dominated, forested watershed: Conceptualization and modeling

    NASA Astrophysics Data System (ADS)

    Schelker, J.; Burns, D. A.; Weiler, M.; Laudon, H.

    2011-03-01

    The mobilization of mercury and dissolved organic carbon (DOC) during snowmelt often accounts for a major fraction of the annual loads. We studied the role of hydrological connectivity of riparian wetlands and upland/wetland transition zones to surface waters on the mobilization of Hg and DOC in Fishing Brook, a headwater of the Adirondack Mountains, New York. Stream water total mercury (THg) concentrations varied strongly (mean = 2.25 ± 0.5 ng L-1), and the two snowmelt seasons contributed 40% (2007) and 48% (2008) of the annual load. Methyl mercury (MeHg) concentrations ranged up to 0.26 ng L-1, and showed an inverse log relationship with discharge. TOPMODEL-simulated saturated area corresponded well with wetland areas, and the application of a flow algorithm based elevation-above-creek approach suggests that most wetlands become well connected during high flow. The dynamics of simulated saturated area and soil storage deficit were able to explain a large part of the variation of THg concentrations (r2 = 0.53 to 0.72). In contrast, the simulations were not able to explain DOC variations and DOC and THg concentrations were not correlated. These results indicate that all three constituents, THg, MeHg, and DOC, follow different patterns at the outlet: (1) the mobilization of THg is primarily controlled by the saturation state of the catchment, (2) the dilution of MeHg suggests flushing from a supply limited pool, and (3) DOC dynamics follow a pattern different from THg dynamics, which likely results from differing gain and/or loss processes for THg and/or DOC within the Fishing Brook catchment.

  11. Hydrological mobilization of mercury and dissolved organic carbon in a snow-dominated, forested watershed: Conceptualization and modeling

    USGS Publications Warehouse

    Schelker, J.; Burns, Douglas A.; Weiler, M.; Laudon, H.

    2011-01-01

    The mobilization of mercury and dissolved organic carbon (DOC) during snowmelt often accounts for a major fraction of the annual loads. We studied the role of hydrological connectivity of riparian wetlands and upland/wetland transition zones to surface waters on the mobilization of Hg and DOC in Fishing Brook, a headwater of the Adirondack Mountains, New York. Stream water total mercury (THg) concentrations varied strongly (mean = 2.25 ?? 0.5 ng L -1), and the two snowmelt seasons contributed 40% (2007) and 48% (2008) of the annual load. Methyl mercury (MeHg) concentrations ranged up to 0.26 ng L-1, and showed an inverse log relationship with discharge. TOPMODEL-simulated saturated area corresponded well with wetland areas, and the application of a flow algorithm based elevation-above-creek approach suggests that most wetlands become well connected during high flow. The dynamics of simulated saturated area and soil storage deficit were able to explain a large part of the variation of THg concentrations (r2 = 0.53 to 0.72). In contrast, the simulations were not able to explain DOC variations and DOC and THg concentrations were not correlated. These results indicate that all three constituents, THg, MeHg, and DOC, follow different patterns at the outlet: (1) the mobilization of THg is primarily controlled by the saturation state of the catchment, (2) the dilution of MeHg suggests flushing from a supply limited pool, and (3) DOC dynamics follow a pattern different from THg dynamics, which likely results from differing gain and/or loss processes for THg and/or DOC within the Fishing Brook catchment. Copyright 2011 by the American Geophysical Union.

  12. 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

  13. Evaluation and modelling of dissolved organic matter reactivity toward As(III) and As(V) – implication in environmental arsenic speciation.

    PubMed

    Lenoble, V; Dang, D H; Loustau Cazalet, M; Mounier, S; Pfeifer, H-R; Garnier, C

    2015-03-01

    Many studies have been carried out to identify dissolved organic matter-trace metals interactions, as organic matter (OM) was demonstrated to be a governing parameter of metals speciation. Concerning arsenic (As), such OM-As studies are scarce and concluded that, when As binding occurred, it was probably through cationic bridges or, in some cases, directly. Yet, analytical proofs remained complex to obtain. In this work, As binding with Suwanee River Humic Acid (SRHA), as an example of dissolved organic matter, was studied, considering both As(III) and As(V), at various pH and in absence/presence of Na and Ca. Dialysis, fluorescence measurements and PHREEQC modelling were performed to identify and characterize the mechanisms at work for the various performed experiments. It was observed that As(III) binding on SRHA occurred through direct SRHA-As(III) binding and that neither Na nor Ca presence modify this mechanism. As(V) appeared to be also bound by SRHA through direct interaction, but suffered from the competition of Na for the SRHA binding sites. Oppositely, in presence of Ca, the overall As(V)-SRHA binding was significantly enhanced, Ca acting as an efficient cationic bridge through the formation of an SRHA-Ca-As(V) ternary complex. All the obtained data were satisfactorily simulated using a unique set of binding parameters which can therefore be implemented in any speciation code to better address As behaviour in environmental conditions.

  14. Relating dissolved organic matter fluorescence to functional properties

    NASA Astrophysics Data System (ADS)

    Tipping, E.; Baker, A.; Thacker, S.; Gondar, D.

    2007-12-01

    The fluorescence excitation emission matrix properties of dissolved organic matter from three rivers and one lake in NW England are analysed. Sites are sampled in duplicate and for some sites seasonally to cover variations in dissolved organic matter composition, river flow, and carbon isotopic (13C, 14C) variability. Results are compared to the functional properties of the dissolved organic matter, the functional assays provide quantitative information on light absorption, fluorescence, photochemical fading, pH buffering, copper binding, benzo[a]pyrene binding, hydrophilicity and adsorption to alumina. Fluorescence characterization of the dissolved organic matter samples demonstrates that peak C fluorescence emission wavelength, the ratio of peak T to peak C fluorescence intensity, and the fluorescence : absorbance ratio best differentiate different dissolved organic matter samples. These parameters correspond to dissolved organic matter aromaticity, the ratio of labile to recalcitrant organic matter, and dissolved organic matter molecular weight. Peak C fluorescence emission wavelength, the ratio of peak T to peak C fluorescence intensity, and the fluorescence : absorbance ratio fluorescence parameters also have strong correlations with several of the functional assays, in particular the extinction coefficients, benzo(a)pyrene binding and alumina adsorption, and buffering capacity. In many cases, regression equations with a correlation coefficient >0.9 are obtained, suggesting that dissolved organic matter functional character can be predicted from DOM fluorescence properties. For one site, the relationship between dissolved organic matter source, fluorescence, function and carbon isotopic composition is discussed.

  15. 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.

  16. Utilization of PARAFAC-Modeled Excitation-Emission Matrix (EEM) Fluorescence Spectroscopy to Identify Biogeochemical Processing of Dissolved Organic Matter in a Northern Peatland.

    PubMed

    Tfaily, Malak M; Corbett, Jane E; Wilson, Rachel; Chanton, Jeffrey P; Glaser, Paul H; Cawley, Kaelin M; Jaffé, Rudolf; Cooper, William T

    2015-01-01

    In this study, we contrast the fluorescent properties of dissolved organic matter (DOM) in fens and bogs in a Northern Minnesota peatland using excitation emission matrix fluorescence spectroscopy with parallel factor analysis (EEM-PARAFAC). EEM-PARAFAC identified four humic-like components and one protein-like component and the dynamics of each were evaluated based on their distribution with depth as well as across sites differing in hydrology and major biological species. The PARAFAC-EEM experiments were supported by dissolved organic carbon measurements (DOC), optical spectroscopy (UV-Vis), and compositional characterization by ultrahigh resolution Fourier transform ion cyclotron resonance mass spectroscopy (FT-ICR MS). The FT-ICR MS data indicate that metabolism in peatlands reduces the molecular weights of individual components of DOM, and oxygen-rich less aromatic molecules are selectively biodegraded. Our data suggest that different hydrologic and biological conditions within the larger peat ecosystem drive molecular changes in DOM, resulting in distinctly different chemical compositions and unique fluorescent fingerprints. PARAFAC modeling of EEM data coupled with ultrahigh resolution FT-ICR MS has the potential to provide significant molecular-based information on DOM composition that will support efforts to better understand the composition, sources, and diagenetic status of DOM from different terrestrial and aquatic systems.

  17. Net community production of dissolved organic carbon

    NASA Astrophysics Data System (ADS)

    Hansell, Dennis A.; Carlson, Craig A.

    1998-09-01

    Each year large amounts of carbon, with a residence time of months, accumulate in the surface layer of the ocean as semilabile dissolved organic carbon (DOC). This material is transported long distances, contributing to the interhemispheric transfer and deep ocean export of carbon. The fraction of net community production resulting in the accumulation of semilabile DOC is estimated here by mass balance during periods of net phytoplankton production in three diverse environments: the Ross Sea polynya, the Equatorial Pacific Ocean, and the Sargasso Sea. In the eutrophic systems of the Ross Sea and the Equatorial Pacific, net DOC production generally fell between 10 and 20% of net community production. For the 1995 spring bloom in the Sargasso Sea, net DOC production was 59-70% of the net community production. Net DOC production was maximal during the period of deep convective overturn of the water column, indicating linkage between the processes. Following the Sargasso Sea spring bloom and into the summer period, net DOC production was nil over the upper 250 m so that net DOC production was reduced to ˜8% of net community production on a seasonal timescale. Consideration of the various types of production regimes in the ocean indicates that the global net production of semilabile DOC is ˜17% of global new production. Regions of the world's oceans with the greatest contributions to global net community production, such as equatorial and coastal upwelling areas, contribute most to the global production of semilabile DOC.

  18. Atmospheric forcing and marsh dissolved organic matter fluxes: Modeling and observations from a Chesapeake Bay tidal marsh-estuary ecosystem

    NASA Astrophysics Data System (ADS)

    Clark, J. B.; Long, W.; Tzortziou, M.; Neale, P.; Hood, R. R.

    2016-02-01

    Biogeochemical processes on the fringes of estuaries are relatively unconstrained especially in terms of tidal marsh-estuary exchanges and carbon budgets. A three-dimensional biogeochemical simulation can be a valuable tool to augment the observations on these exchanges and can provide insights into the carbon fluxes and organic matter fate. The Finite Volume Community Ocean Model (FVCOM) coupled with CE-QUAL-ICM for water quality is used to simulate the physical and biogeochemical characteristics in the year 2005 for the Kirkpatrick Marsh and Rhode River, a sub-estuary of Chesapeake Bay, MD, USA. The Rhode River hydrodynamic simulation (rhodeFVM) accurately recreates the temperature and salinity in the shallow water sub-estuary and includes a marsh grass drag model that gives realistic marsh water flow. Data analysis from spring 2015 shows a strong negative correlation between marsh creek salinity and DOM fluxes, with wind velocity being an important factor driving large amplitude variation. Model results are consistent with observations revealing sub-tidal variability of marsh creek salinity associated with non-linear interactions between wind velocity and precipitation events. A newly developed three-dimensional marsh DOM model that includes chromophoric DOM provides insights into the spatial and temporal variability of DOM being exported to the estuary.

  19. 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.

  20. Bioavailability and characterization of dissolved organic nitrogen and dissolved organic phosphorus in wastewater effluents.

    PubMed

    Qin, Chao; Liu, Haizhou; Liu, Lei; Smith, Scott; Sedlak, David L; Gu, April Z

    2015-04-01

    There is still a great knowledge gap in the understanding of characteristics and bioavailability of dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) in wastewater effluents, which surmise implications related to both discharge regulation and treatment practice. In this study, we simultaneously investigated the characteristics and bioavailability of both DON and DOP, with separated hydrophilic versus hydrophobic fractions, in highly-treated wastewater effluents for the first time. The tertiary effluents from two wastewater treatment plants were separated into two fractions by XAD-8 resin coupled with anion exchange resin based on the hydrophobicity. Results showed that the majority of DON was present in hydrophilic forms while more DOP existed in hydrophobic forms. Hydrophilic DON contributed to 64.0%-72.2% of whole DON, while hydrophobic DOP accounted for 61.4%-80.7% of total DOP for the two plants evaluated. The effluents and their fractions were then subject to bioavailability assay based on 14-day algae growth. The results indicated that majority (~73-75%) of the effluent DOP, particularly the hydrophobic fraction with lower C/P ratio was more likely to be bioavailable for algal growth. The bioavailable fraction of DON varied widely (28%-61%) for the two plants studied and the hydrophilic fraction with lower C/N ratio seemed to exhibit higher bioavailability than the hydrophobic portion. The differences in bioavailable DON and DOP distributions of effluents from those two plants could be attributed to different receiving effluent compositions and wastewater treatment processes. In addition, fluorescence excitation-emission matrices (EEMs) combined with parallel factor analysis (PARAFAC) were used to characterize the dissolved organic matter (DOM) in wastewater effluent, which provided insights into the nature of organic matter in wastewater samples with different characteristics and originating sources.

  1. Dissolved organic carbon release by marine macrophytes

    NASA Astrophysics Data System (ADS)

    Barrón, C.; Apostolaki, E. T.; Duarte, C. M.

    2012-02-01

    Estimates of dissolved organic carbon (DOC) release by marine macrophyte communities (seagrass meadows and macroalgal beds) were obtained experimentally using in situ benthic chambers. The effect of light availability on DOC release by macrophyte communities was examined in two communities both by comparing net DOC release under light and dark, and by examining the response of net DOC release to longer-term (days) experimental shading of the communities. All most 85% of the seagrass communities and almost all of macroalgal communities examined acted as net sources of DOC. There was a weak tendency for higher DOC fluxes under light than under dark conditions in seagrass meadow. There is no relationship between net DOC fluxes and gross primary production (GPP) and net community production (NCP), however, this relationship is positive between net DOC fluxes and community respiration. Net DOC fluxes were not affected by shading of a T. testudinum community in Florida for 5 days, however, shading of a mixed seagrass meadow in the Philippines led to a significant reduction on the net DOC release when shading was maintained for 6 days compared to only 2 days of shading. Based on published and unpublished results we also estimate the global net DOC production by marine macrophytes. The estimated global net DOC flux, and hence export, from marine macrophyte is about 0.197 ± 0.015 Pg C yr-1 or 0.212 ± 0.016 Pg C yr-1 depending if net DOC flux by seagrass meadows was estimated by taking into account the low or high global seagrass area, respectively.

  2. 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.

  3. 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.

  4. Production of fluorescent dissolved organic matter in Arctic Ocean sediments

    PubMed Central

    Chen, Meilian; Kim, Ji-Hoon; Nam, Seung-Il; Niessen, Frank; Hong, Wei-Li; Kang, Moo-Hee; Hur, Jin

    2016-01-01

    Little is known about the production of fluorescent dissolved organic matter (FDOM) in the anoxic oceanic sediments. In this study, sediment pore waters were sampled from four different sites in the Chukchi-East Siberian Seas area to examine the bulk dissolved organic carbon (DOC) and their optical properties. The production of FDOM, coupled with the increase of nutrients, was observed above the sulfate-methane-transition-zone (SMTZ). The presence of FDOM was concurrent with sulfate reduction and increased alkalinity (R2 > 0.96, p < 0.0001), suggesting a link to organic matter degradation. This inference was supported by the positive correlation (R2 > 0.95, p < 0.0001) between the net production of FDOM and the modeled degradation rates of particulate organic carbon sulfate reduction. The production of FDOM was more pronounced in a shallow shelf site S1 with a total net production ranging from 17.9 to 62.3 RU for different FDOM components above the SMTZ depth of ca. 4.1 mbsf, which presumably underwent more accumulation of particulate organic matter than the other three deeper sites. The sediments were generally found to be the sources of CDOM and FDOM to the overlying water column, unearthing a channel of generally bio-refractory and pre-aged DOM to the oceans. PMID:27982085

  5. Production of fluorescent dissolved organic matter in Arctic Ocean sediments.

    PubMed

    Chen, Meilian; Kim, Ji-Hoon; Nam, Seung-Il; Niessen, Frank; Hong, Wei-Li; Kang, Moo-Hee; Hur, Jin

    2016-12-16

    Little is known about the production of fluorescent dissolved organic matter (FDOM) in the anoxic oceanic sediments. In this study, sediment pore waters were sampled from four different sites in the Chukchi-East Siberian Seas area to examine the bulk dissolved organic carbon (DOC) and their optical properties. The production of FDOM, coupled with the increase of nutrients, was observed above the sulfate-methane-transition-zone (SMTZ). The presence of FDOM was concurrent with sulfate reduction and increased alkalinity (R(2) > 0.96, p < 0.0001), suggesting a link to organic matter degradation. This inference was supported by the positive correlation (R(2) > 0.95, p < 0.0001) between the net production of FDOM and the modeled degradation rates of particulate organic carbon sulfate reduction. The production of FDOM was more pronounced in a shallow shelf site S1 with a total net production ranging from 17.9 to 62.3 RU for different FDOM components above the SMTZ depth of ca. 4.1 mbsf, which presumably underwent more accumulation of particulate organic matter than the other three deeper sites. The sediments were generally found to be the sources of CDOM and FDOM to the overlying water column, unearthing a channel of generally bio-refractory and pre-aged DOM to the oceans.

  6. Dissolved Organic Phosphorus In Shelf Sediment Pore-waters

    NASA Astrophysics Data System (ADS)

    Statham, P. J.; Homoky, W. B.

    2016-02-01

    Marine sediments are a major reservoir for the macronutrient phosphorus (P). The cycling, fate and form of P in pore-waters has focussed almost exclusively on the easy to measure soluble reactive (SRP) forms. There are, however, very few data available for the "dissolved organic" forms of P, i.e. the difference between the total dissolved P and SRP. Preliminary data on "DOP" and SRP forms of P in shelf sediments around the UK show that the organic fraction can be important (up to 30% of the size of the SRP pool), and the magnitude of this "organic" signal varies with season and delivery of post bloom organic matter to the sediment. A limited number of oceanic samples show a sequence of decreasing DOP concentrations in pore-waters on moving off shelf that decrease to undetectable levels in deep-water oxic sediments. Present budgets and diagenetic models ignore this "organic" pool that represents an important intermediary in the benthic cycling of P.

  7. Production of fluorescent dissolved organic matter in Arctic Ocean sediments

    NASA Astrophysics Data System (ADS)

    Chen, Meilian; Kim, Ji-Hoon; Nam, Seung-Il; Niessen, Frank; Hong, Wei-Li; Kang, Moo-Hee; Hur, Jin

    2016-12-01

    Little is known about the production of fluorescent dissolved organic matter (FDOM) in the anoxic oceanic sediments. In this study, sediment pore waters were sampled from four different sites in the Chukchi-East Siberian Seas area to examine the bulk dissolved organic carbon (DOC) and their optical properties. The production of FDOM, coupled with the increase of nutrients, was observed above the sulfate-methane-transition-zone (SMTZ). The presence of FDOM was concurrent with sulfate reduction and increased alkalinity (R2 > 0.96, p < 0.0001), suggesting a link to organic matter degradation. This inference was supported by the positive correlation (R2 > 0.95, p < 0.0001) between the net production of FDOM and the modeled degradation rates of particulate organic carbon sulfate reduction. The production of FDOM was more pronounced in a shallow shelf site S1 with a total net production ranging from 17.9 to 62.3 RU for different FDOM components above the SMTZ depth of ca. 4.1 mbsf, which presumably underwent more accumulation of particulate organic matter than the other three deeper sites. The sediments were generally found to be the sources of CDOM and FDOM to the overlying water column, unearthing a channel of generally bio-refractory and pre-aged DOM to the oceans.

  8. Developing and improving a simple runoff model of dissolved organic carbon considering soil infiltration and river runoff processes in a forested watershed

    NASA Astrophysics Data System (ADS)

    Ebata, K.; Ichikawa, Y.; Matsumoto, Y.; Nishida, K.

    2015-12-01

    Estimation of dissolved organic carbon (DOC) runoff from forested watershed is important for carbon cycle researches and water quality control. Recently, a few process-based models have been proposed to estimate DOC loading to water environments, which assume DOC source in topsoil and transport process to the river. However, the models require large number of input data and are not designed for short time scale calculation of intensive rainfall runoff with in Asian monsoon area. We proposed a new DOC runoff model with both soil and river runoff processes enforced by DOC Source Area (DSA) concept. The data were collected at middle stream (98ha) and downstream (1798ha) in the Mizugaki Experimental Watershed, Yamanashi, Japan from 2009 to 2012. Dry-wet cycle and long-term variation in soil were successfully simulated by advection-diffusion and dissolution formulations of the Soil Submodel. Runoff Submodel included hydrological calculation unit, TOPMODEL, to separately quantify base flow (Qb), subsurface flow (Qsf) and overland flow (Qof). Qsf and Qof were assumed to represent for DSA, and the DOC loading was calculated by Qsf, Qof and the estimated DOC concentration from the Soil Submodel. The results showed that the model performed well for 4 among 11 events at the middle stream while the simulated DOC loadings were overestimated for all 8 events downstream. The reason of the low performance of the model was attributed to the error of Qsf and Qof calculated by TOPMODEL.

  9. Dissolved Organic Matter Export from a Forested Watershed during Hurricane Irene

    NASA Astrophysics Data System (ADS)

    Yoon, B.; Raymond, P.

    2012-12-01

    We incorporate high resolution time-series data to calculate the total amount of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) transported during Hurricane Irene in Esopus Creek in New York (August 2011). During this 200-yr event the Esopus Creek experienced a 330-fold discharge increase and a 4-fold increase in concentration, resulting in the export of roughly 43% and 31% of its average annual DOC and DON fluxes in just 5 days, respectively. The source of this large dissolved organic matter (DOM) flux also shifted during its course and showed an increased contribution of aromatic organic matter. We conclude that more frequent large events due to climate change will increase the export of terrigenous dissolved organic matter, and potentially impact the water quality and biogeochemistry of lakes and coastal systems. In addition, we show that the use of conventional models for extreme events lead to erroneous flux calculations, if not supported by high resolution data collected during the events.easured and modeled dissolved organic matter concentrations, and specific UV-Absorbance for the study watershed during Hurricane Irene (A: dissolved organic carbon; B: dissolved organic nitrogen; C: SUVA).

  10. Possible method for dissolved organic carbon speciation in forest soils

    NASA Astrophysics Data System (ADS)

    Drabek, O.; Tejnecký, V.; Ash, C.; Hubova, P.; Boruvka, L.

    2013-12-01

    Dissolved organic carbon (DOC) is a natural part of dissolved organic matter and it plays an important role in the biogeochemistry of soil processes. Low Molecular Mass Organic Acids (LMMOA) are an essential part of DOC. These acids play a key role in chemical processes that affect the entire soil environment. Knowing the amount of DOC and the speciation of LMMOA is required for realistic equilibrium modelling of soil chemical processes and transport mechanisms. There have been a number of proposed methods for the quantitative analysis of DOC and for speciation of LMMOA. The first aim of this contribution is to introduce and test a modified spectroscopic method for the determination of water-extractable organic carbon (WEOC) from forest soils. In general this method is based on the oxidization of WEOC by chromium-sulphuric acid. The presented method can be used as an economical alternative to the classical, more financially demanding elemental analysis. However, the main aim is to test the reliability of the method for LMMOA speciation. Ion exchange chromatography (IC) with hydroxide elution has proven to be a useful tool for the determination of LMMOA in many different water-based samples. However, the influence of multivalent cations (often present in environmental samples) on IC results has not yet been sufficiently studied. In order to assess the influence of Al, Fe, Mn, Mg and Ca on the amount of LMMOA determined by IC, an extensive set of model solutions was prepared and immediately analysed by means of IC. Moreover, the influence of pH on determined amounts of LMMOA in model solutions and representative soil aqueous extracts was investigated. These experimental results were compared to expected values and also to results provided by the chemical equilibrium model - PHREEQC. Based on the above listed research, some modifications to the common IC method for LMMOA speciation are presented.

  11. Modelling seasonal and long-term patterns in stream dissolved organic carbon concentration in mire and forest dominated landscape elements at Svartberget, Sweden using INCA-C

    NASA Astrophysics Data System (ADS)

    Futter, M.; Koehler, S. J.; Bishop, K. H.

    2009-04-01

    We present an application of the INCA-C (Integrated Catchments model for Carbon) to the Svartberget catchment in central Sweden. The INCA-C model is a catchment-scale, semi-distributed, process-based model of dissolved organic carbon (DOC) that has been used previously to simulate intra- and inter-annual patterns in surface water DOC concentration and flux in boreal and temperate forested catchments (Futter et al. 2007). The 50 ha Svartberget catchment provides an ideal location for evaluating the performance of INCA-C as it contains two mire and upland landscape elements, where the output from each element has been monitored separately for a decade. Previous work has shown that these two landscape elements have markedly different intra-annual patterns of DOC concentration and export as well as the importance of the riparian zone in controlling surface water DOC concentration from the forested sub-catchment (Köhler et al. 2008). The 19 ha mire sub-catchment is dominated by bog communities with Scots pine in the upland areas. The 13 ha forested sub-catchment stream joins the main stem of the stream just above the confluence. It is dominated by Scots pine and Norway spruce. A third sub-catchment between the mire and the catchment outflow has a similar vegetation cover to that of the forested sub-catchment. INCA is designed to model different landscape elements, and combine them to simulate downstream locations. Like most complex, process-based models, however, INCA-C is over-determined. Insufficient data are available to constrain all processes and pool-sizes. As a result, similar in-stream DOC concentrations may be obtained by varying either aquatic or terrestrial rate parameters. The Svartberget catchment provides an opportunity to constrain the model parameter space for the entire catchment as there is information for the two major constituent elements, forest and mire. Additionally soil solution data from the riparian zone in the forest area together with a

  12. The combined effects of hardness, pH, and dissolved organic carbon on the chronic toxicity of Zn to D. magna: development of a surface response model.

    PubMed

    Heijerick, D G; Janssen, C R; De Coen, W M

    2003-02-01

    The effect of changes in pH, hardness, and dissolved organic carbon (DOC) and the possible interactions among these parameters on the chronic toxicity of zinc to D. magna were investigated. Based on a Central Composite Design, models were developed that can explain the observed variation in EC(10) and EC(50) as a function of these toxicity modifying factors. All three parameters significantly altered the observed effect concentrations based on net reproductive rate. The largest differences in 21-day EC(10)s and EC(50)s caused by these factors were 10.1 and 4.9, respectively. An increase in pH and/or DOC decreased zinc toxicity. The significant interaction between pH and DOC on observed chronic Zn toxicity is in accordance with earlier reported increased sorption efficiency of Zn to humic substances at higher pH levels. Lowest Zn toxicity was observed in tests performed with moderately hard test media (between 200 and 300 mg/L as CaCO(3)). Lower or higher hardness of the test medium resulted in lower effect concentrations. Based on physico-chemical characteristics of the test media, developed models can be used to explain the variation between reported NOECs for Zn and may improve current environmental risk assessment procedures of metals.

  13. 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.

  14. Colored Dissolved Organic Matter Dynamics in the Northern Gulf of Mexico from Ocean Color and Numerical Model Results

    DTIC Science & Technology

    2013-12-18

    model simula- tions. Various factors such as winds , river discharges, and detached eddies from the Loop Current can contribute to the generation of...indicate that a large component of transport over the inner shelf is produced by wind (40–48%), with river discharge (28–33%) and Loop Current (LC...eddies (19–33%) accounting for the rest (Oey, 1995). Two seasonal current patterns that depend on wind characteristics are distinguishable over the shelf

  15. Recent advances in structure and reactivity of dissolved organic matter: radiation chemistry of non-isolated natural organic matter and selected model compounds.

    PubMed

    Ayatollahi, Shakiba; Kalnina, Daina; Song, Weihua; Cottrell, Barbara A; Gonsior, Michael; Cooper, William J

    2012-01-01

    The importance of natural organic matter (NOM) as a source of carbon in natural waters, as the source of reactive oxygen species, or for the complications its presence causes in treatment of natural waters, is undeniable. Recent studies have also pointed to the major photochemical role of triplet excited state of natural organic matter in the environmental fate of pharmaceutical and personal care products (PPCPs) in waters. However, the characterization of NOM is problematic due to its complex molecular structure. One approach to better understand NOM chemistry is the use of model compounds. As the condensation of a plant's phenolic compounds leads to humification and the formation of NOM, a structurally broad group of nine phenolic compounds were selected as model compounds for this study. With methods used in the discipline of radiation chemistry, the oxidative chemistry and transient spectra of these phenols were studied. In addition, the oxidative chemistry and transient spectra of a sample of NOM from the Black River, North Carolina, USA, was characterized. This natural water sample was used as received and represents the first studies of non-isolated NOM by pulsed radiolysis. The results of the transient spectra of the NOM revealed that the radical intermediates were very long lived. This phenomenon was not captured using the nine model compounds suggesting that more complex compounds are needed to further our understanding of the oxidation chemistry of NOM.

  16. Carbon cycle: Ocean dissolved organics matter

    NASA Astrophysics Data System (ADS)

    Amon, Rainer M. W.

    2016-12-01

    Large quantities of organic carbon are stored in the ocean, but its biogeochemical behaviour is elusive. Size-age-composition relations now quantify the production of tiny organic molecules as a major pathway for carbon sequestration.

  17. Influence of dissolved organic materials on turbid water optical properties and remote-sensing reflectance

    NASA Technical Reports Server (NTRS)

    Witte, W. G.; Whitlock, C. H.; Harriss, R. C.; Usry, J. W.; Poole, L. R.; Houghton, W. M.; Morris, W. D.; Gurganus, E. A.

    1982-01-01

    The effects of dissolved organic materials on turbid-water optical properties are assessed, by means of field measurements and laboratory simulations in which upwelled reflectance, attenuation, absorption, and backscatter spectral properties at wavelengths from 450 to 800 nm are examined in relation to water chemistry. The data show that dissolved organic materials decrease upwelled reflectance from turbid waters, and that the decrease in reflectance is a nonlinear function of concentration with the largest gradients at low carbon concentrations, depending on wavelength. Upwelled reflectance is found to be highly correlated with two backscatter-absorption parameters used in some optical models, which are nonlinear with dissolved organic material concentration change.

  18. 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.

  19. Hydrology controls dissolved organic matter (DOM) quality and dynamics

    NASA Astrophysics Data System (ADS)

    Fasching, Christina; Schelker, Jakob; Ulseth, Amber; Singer, Gabriel; Steniczka, Gertraud; Battin, Tom

    2014-05-01

    Headwater streams are major contributors to carbon cycling. It is therefore of utmost importance to understand the dynamics of dissolved organic matter (DOM) and its drivers in these ecosystems. Here we present data from more than 4,000 individual DOM measurements from Oberer Seebach, a 3rd-order stream draining a largely pristine alpine catchment (Lunz am See, Austria). We determined the concentration of streamwater and hyporheic dissolved organic carbon and a suite of optical properties of DOM based on a diurnal sampling design over almost three years; we also monitored various hydrological and climate parameters over that same time. Optical properties were determined from absorbance measurements and parallel factor analysis (PARAFAC) modelling of Excitation emission matrices. We also estimated DOM export fluxes from Oberer Seebach and the contributions of the various chromophoric and fluorescent components to these exports. Preliminary results suggest that DOM in Oberer Seebach was largely of terrigenous origin throughout the year. However during periods of low discharge autochthonous DOM export increased, indicating freshly produced DOM possibly from benthic algae. Hyphoreic and streamwater DOM composition and its dynamics were tightly coupled in time at baseflow, yet displaying higher variability as discharge increased. Our timeseries studies highlight the relevance of the flow regime on the dynamics, origin and composition of DOM in a headwater stream. We discuss these findings in the context of extreme hydrological events on carbon fluxes.

  20. Simulating dissolved organic carbon dynamics at the swedish integrated monitoring sites with the integrated catchments model for carbon, INCA-C.

    PubMed

    Futter, M N; Löfgren, S; Köhler, S J; Lundin, L; Moldan, F; Bringmark, L

    2011-12-01

    Surface water concentrations of dissolved organic carbon ([DOC]) are changing throughout the northern hemisphere due to changes in climate, land use and acid deposition. However, the relative importance of these drivers is unclear. Here, we use the Integrated Catchments model for Carbon (INCA-C) to simulate long-term (1996-2008) streamwater [DOC] at the four Swedish integrated monitoring (IM) sites. These are unmanaged headwater catchments with old-growth forests and no major changes in land use. Daily, seasonal and long-term variations in streamwater [DOC] driven by runoff, seasonal temperature and atmospheric sulfate (SO₄(2-)) deposition were observed at all sites. Using INCA-C, it was possible to reproduce observed patterns of variability in streamwater [DOC] at the four IM sites. Runoff was found to be the main short-term control on [DOC]. Seasonal patterns in [DOC] were controlled primarily by soil temperature. Measured SO₄(2-) deposition explained some of the long-term [DOC] variability at all sites.

  1. Snowball Earth prevention by dissolved organic carbon remineralization.

    PubMed

    Peltier, W Richard; Liu, Yonggang; Crowley, John W

    2007-12-06

    The 'snowball Earth' hypothesis posits the occurrence of a sequence of glaciations in the Earth's history sufficiently deep that photosynthetic activity was essentially arrested. Because the time interval during which these events are believed to have occurred immediately preceded the Cambrian explosion of life, the issue as to whether such snowball states actually developed has important implications for our understanding of evolutionary biology. Here we couple an explicit model of the Neoproterozoic carbon cycle to a model of the physical climate system. We show that the drawdown of atmospheric oxygen into the ocean, as surface temperatures decline, operates so as to increase the rate of remineralization of a massive pool of dissolved organic carbon. This leads directly to an increase of atmospheric carbon dioxide, enhanced greenhouse warming of the surface of the Earth, and the prevention of a snowball state.

  2. Ocean metabolism and dissolved organic matter: How do small dissolved molecules persist in the ocean?

    NASA Astrophysics Data System (ADS)

    Benner, Ronald

    2010-05-01

    The ocean reservoir of dissolved organic matter (DOM) is among the largest global reservoirs (~700 Pg C) of reactive organic carbon. Marine primary production (~50 Pg C/yr) by photosynthetic microalgae and cyanobacteria is the major source of organic matter to the ocean and the principal substrate supporting marine food webs. The direct release of DOM from phytoplankton and other organisms as well as a variety of other processes, such as predation and viral lysis, contribute to the ocean DOM reservoir. Continental runoff and atmospheric deposition are relatively minor sources of DOM to the ocean, but some components of this material appear to be resistant to decomposition and to have a long residence time in the ocean. Concentrations of DOM are highest in surface waters and decrease with depth, a pattern that reflects the sources and diagenesis of DOM in the upper ocean. Most (70-80%) marine DOM exists as small molecules of low molecular weight (<1 kDalton). Surprisingly, high-molecular-weight (>1 kDalton) DOM is relatively enriched in major biochemicals, such as combined neutral sugars and amino acids, and is more bioavailable than low-molecular-weight DOM. The observed relationships among the size, composition, and reactivity of DOM have led to the size-reactivity continuum model, which postulates that diagenetic processes lead to the production of smaller molecules that are structurally altered and resistant to microbial degradation. The radiocarbon content of these small dissolved molecules also indicates these are the most highly aged components of DOM. Chemical signatures of bacteria are abundant in DOM and increase during diagenesis, indicating bacteria are an important source of slowly cycling biochemicals. Recent analyses of DOM isolates by ultrahigh-resolution mass spectrometry have revealed an incredibly diverse mixture of molecules. Carboxyl-rich alicyclic molecules are abundant in DOM, and they appear to be derived from diagenetically

  3. Measurement and Modeling of Optical, Physical, and Photochemical Processes in the Open-Ocean Mixed Layer: Peroxide and Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Sikorski, Richard J.

    The goals of this work were to model H _2O_2 cycling in aquatic systems, and to study the photoproperties of bulk dissolved organic matter (DOM). H_2O _2 is produced photochemically from DOM with an "apparent" quantum yield (AQY; normalized to DOM absorbance) which decreases exponentially as wavelength increases. The primary task of this project was to develop a vertical-flux model of undersea irradiance (300-500 nm). The model varied the path-length and geometry of undersea light with solar zenith angle according to scattering in the atmosphere and water column, and according to the ratio of collimated light to diffuse light. This optical model was then combined with a one-dimensional model of marine surface mixing, which derived structure and dynamics by applying empirically determined stability limits to calculated bulk turbulent kinetic energy and shear turbulence. Using data collected in the eastern Caribbean during 1988, modeled H_2O _2 mixed-layer depth and diel distributions were controlled by mixing dynamics. Preliminary model results made it possible to identify two classes of photoproductive waters, based on the ratio of UV DOM absorption, 330 nm, to visible absorption, 460 nm. H_2O _2 photoproduction was primarily due to 320-360 nm irradiance in the model, while a surprisingly significant fraction of total production occurred at wavelengths greater than 400 nm at depth and at zenith angles greater than 15 degrees. The diel photoproduction of H _2O_2 was notably deeper at midday than would be predicted in a simple non -scattering optical model. DOM fluorescence decayed with irradiation above 330 nm, and intensified with irradiation below 330 nm. The processes were partially photo-reversible, and also reversed slowly in the dark. For new river input, irradiation at 296.7 nm initially bleached fluorescence, with re-intensification occurring upon longer irradiation at the same wavelength. Full -spectral solar irradiation bleached fluorescence. The rates of

  4. 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.

  5. 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.

  6. Do soils loose phosphorus with dissolved organic matter?

    NASA Astrophysics Data System (ADS)

    Kaiser, K.; Brödlin, D.; Hagedorn, F.

    2014-12-01

    During ecosystem development and soil formation, primary mineral sources of phosphorus are becoming increasingly depleted. Inorganic phosphorus forms tend to be bound strongly to or within secondary minerals, thus, are hardly available to plants and are not leached from soil. What about organic forms of phosphorus? Since rarely studied, little is known on the composition, mobility, and bioavailability of dissolved organic phosphorus. There is some evidence that plant-derived compounds, such as phytate, bind strongly to minerals as well, while microbial compounds, such as nucleotides and nucleic acids, may represent more mobile fractions of soil phosphorus. In some weakly developed, shallow soils, leaching losses of phosphorus seem to be governed by mobile organic forms. Consequently, much of the phosphorus losses observed during initial stages of ecosystem development may be due to the leaching of dissolved organic matter. However, the potentially mobile microbial compounds are enzymatically hydrolysable. Forest ecosystems on developed soils already depleted in easily available inorganic phosphorus are characterized by rapid recycling of organic phosphors. That can reduce the production of soluble forms of organic phosphorus as well as increase the enzymatic hydrolysis and subsequent plant uptake of phosphorus bound within dissolved organic matter. This work aims at giving an outlook to the potential role of dissolved organic matter in the cycling of phosphorus within developing forest ecosystems, based on literature evidence and first results of ongoing research.

  7. 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...

  8. 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...

  9. The molecular geography of dissolved organic matter in the Atlantic Ocean can largely be explained by a simple two-source mixing model.

    NASA Astrophysics Data System (ADS)

    Seibt, M.; Niggemann, J.; Osterholz, H.; Dittmar, T.

    2016-02-01

    Marine dissolved organic matter (DOM) is one of the largest active carbon reservoirs on Earth, similar in size to atmospheric CO2. The primary source for marine DOM is photosynthesis, but a wide variety of biotic and abiotic processes shape the DOM pool over time. With ultrahigh-resolution analytical techniques such as Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) it is possible to characterize DOM on the molecular level in unprecedented detail. Despite the geographical diversity of primary producers, microbial community structures, variety of abiotic conditions and ecosystem types, marine molecular DOM composition is exceptionally similar across the globe, even when analyzed at highest analytical resolution. Molecular dissimilarities of DOM occur mainly between the surface mixed layer and the deep sea. Here we hypothesize that this observed dissimilarity can largely be explained by a simple two-source mixing model of freshly produced and old background DOM. Furthermore, we hypothesize that the two endmembers in this model each carry a universal molecular signature. To test these hypotheses, we mixed deep sea DOM with increasing proportions of DOM produced in the laboratory by a marine microbial community over the course of two years. The molecular composition of these artificial mixtures was compared via FT-ICR-MS with >300 natural samples across the entire Atlantic Ocean. In support of our hypotheses, the addition of laboratory-created DOM made deep sea DOM molecularly more similar to surface DOM. We conclude that much of the observed molecular differences across water masses and between surface and deep sea is simply explained by mixing of two endmembers, i. e. freshly produced DOM and aged background DOM. The two endmembers have characteristic and universal molecular features. Our results also show that additional processes at the sea surface, such as photochemistry, influence the molecular composition of DOM beyond simple mixing.

  10. Modeling Fish Growth in Low Dissolved Oxygen

    ERIC Educational Resources Information Center

    Neilan, Rachael Miller

    2013-01-01

    This article describes a computational project designed for undergraduate students as an introduction to mathematical modeling. Students use an ordinary differential equation to describe fish weight and assume the instantaneous growth rate depends on the concentration of dissolved oxygen. Published laboratory experiments suggest that continuous…

  11. Modeling Fish Growth in Low Dissolved Oxygen

    ERIC Educational Resources Information Center

    Neilan, Rachael Miller

    2013-01-01

    This article describes a computational project designed for undergraduate students as an introduction to mathematical modeling. Students use an ordinary differential equation to describe fish weight and assume the instantaneous growth rate depends on the concentration of dissolved oxygen. Published laboratory experiments suggest that continuous…

  12. [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.

  13. Assessing chromophoric dissolved organic matter (CDOM) distribution, stocks, and fluxes in Apalachicola Bay using combined field, VIIRS ocean color, and model observations

    DOE PAGES

    Joshi, Ishan D.; D'Sa, Eurico J.; Osburn, Christopher L.; ...

    2017-02-06

    Understanding the role of estuarine-carbon fluxes is essential to improve estimates of the global carbon budget. Dissolved organic matter (DOM) plays an important role in aquatic carbon cycling. Here, the chromophoric fraction of DOM (CDOM) can be readily detected via in situ and remotely-sensed optical measurements. DOM properties, including CDOM absorption coefficient at 412 nm (ag412) and dissolved organic carbon (DOC) concentrations were examined in Apalachicola Bay, a national estuarine research reserve located in the northeast Gulf of Mexico, using in situ and satellite observations during the spring and fall of 2015. Synoptic and accurate representation of estuarine-scale processes usingmore » satellite ocean color imagery necessitates the removal of atmospheric contribu- tion (~90%) to signals received by satellite sensors to successfully link to in situ observations. Three atmospheric correction schemes (e.g., Standard NIR correction, Iterative NIR correction, and SWIR correction) were tested first to find a suitable correction scheme for the VIIRS imagery in low to moderately turbid Apalachicola Bay. The iterative NIR correction performed well, and validation showed high correlation (R2 = 0.95, N = 25) against in situ light measurements. A VIIRS-based CDOM algorithm was developed (R2 = 0.87, N = 9) and validated (R2 = 0.76, N = 20, RMSE = 0.29 m-1) against in situ observations. Subsequently, ag412 was used as a proxy of DOC in March (DOC = 1.08 + 0.94 × ag412,R2 =0.88, N = 13)and in November (DOC= 1.61 + 1.33 × ag412, R2 = 0.83, N = 24) to derive DOC maps that provided synoptic views of DOC distribution, sources, and their transport to the coastal waters during the wet and dry seasons. The estimated DOC stocks were ~3.71 × 106 kg C in March and ~4.07 × 106 kg C in November over an area of ~560 km2. Volume flux (out of the bay) almost doubled for March 24 (735 m3 s-1) relative to November 4 (378 m3 s-1). However, estimates of DOC fluxes exported out

  14. Effects of dissolved organic matter from a eutrophic lake on the freely dissolved concentrations of emerging organic contaminants.

    PubMed

    Xiao, Yi-Hua; Huang, Qing-Hui; Vähätalo, Anssi V; Li, Fei-Peng; Chen, Ling

    2014-08-01

    The authors studied the effects of dissolved organic matter (DOM) on the bioavailability of bisphenol A (BPA) and chloramphenicol by measuring the freely dissolved concentrations of the contaminants in solutions containing DOM that had been isolated from a mesocosm in a eutrophic lake. The abundance and aromaticity of the chromophoric DOM increased over the 25-d mesocosm experiment. The BPA freely dissolved concentration was 72.3% lower and the chloramphenicol freely dissolved concentration was 56.2% lower using DOM collected on day 25 than using DOM collected on day 1 of the mesocosm experiment. The freely dissolved concentrations negatively correlated with the ultraviolent absorption coefficient at 254 nm and positively correlated with the spectral slope of chromophoric DOM, suggesting that the bioavailability of these emerging organic contaminants depends on the characteristics of the DOM present. The DOM-water partition coefficients (log KOC ) for the emerging organic contaminants positively correlated with the aromaticity of the DOM, measured as humic acid-like fluorescent components C1 (excitation/emission=250[313]/412 nm) and C2 (excitation/emission=268[379]/456 nm). The authors conclude that the bioavailability of emerging organic contaminants in eutrophic lakes can be affected by changes in the DOM.

  15. Loss of nitrogenous dissolved organic matter from small lakes

    USGS Publications Warehouse

    Manny, Bruce A.; Otsuki, Akira

    1981-01-01

    To determine how much organic nitrogen is lost from lakes during winter by natural processes, we collected water in fall and winter from six small lakes (area, 5-822 hectares) and separated organic matter dissolved in the water with n-butanol into three fractions--yellow organic acids, a white precipitate, and aqueous (nonextractable) organic matter. The nitrogen content of each fraction was measured by ultraviolet photolysis. About 25-30% of the yellow acid and white precipitate fractions were lost from the water column in each of the lakes during winter. More than 80% of the organic nitrogen dissolved in the lake water samples was found in the aqueous fraction. We believe the white precipitate is part of the humin material in lake waters because it was relatively insoluble in acidic and alkaline solutions.

  16. Effluent dissolved organic nitrogen and dissolved phosphorus removal by enhanced coagulation and microfiltration.

    PubMed

    Arnaldos, Marina; Pagilla, Krishna

    2010-10-01

    Plants aiming to achieve very low effluent nutrient levels (<3 mg N/L for N, and <0.1 mg P/L for P) need to consider removal of effluent fractions hitherto not taken into account. Two of these fractions are dissolved organic nitrogen (DON) and dissolved non-reactive phosphorus (DNRP) (mainly composed of organic phosphorus). In this research, enhanced coagulation using alum (at doses commonly employed in tertiary phosphorus removal) followed by microfiltration (using 0.22 μm pore size filters) was investigated for simultaneous effluent DON and dissolved phosphorus (DP) fractions removal. At an approximate dose of 3.2 mg Al(III)/L, corresponding to 1.5 Al(III)/initial DON-N and 3.8 Al(III)/initial DP-P molar ratios, maximum simultaneous removal of DON and DP was achieved (69% for DON and 72% for DP). At this dose, residual DON and DP concentrations were found to be 0.3 mg N/L and 0.25 mg P/L, respectively. Analysis of the trends of removal revealed that the DNRP removal pattern was similar to that commonly reported for dissolved reactive phosphorus. Since this study involved intensive analytical work, a secondary objective was to develop a simple and accurate measurement protocol for determining dissolved N and P species at very low levels in wastewater effluents. The protocol developed in this study, involving simultaneous digestion for DON and DNRP species, was found to be very reliable and accurate based on the results.

  17. Copper binding by dissolved organic matter. II. Variation in type and source of organic matter

    SciTech Connect

    Cabaniss, S.E.; Shuman, M.S.

    1988-01-01

    Copper binding properties of several fulvic acid (FA) and whole water samples are compared by means of an empirical model that was calibrated using Suwannee River FA. Within the calibration limits of the model (pH 5.0-8.5, total Cu concentration 0.1-100 ..mu..M, ionic strength 0.1, and dissolved organic carbon, DOC, 1-10 mg C/1), pCu in solutions of a variety of FA samples are predicted with < 0.2 pCu units root mean square error (RMSE). Within the calibration limits, many whole water sample pCu's are predicted with < 0.3 pCu units RMSE if only one-half of the dissolved organic carbon is assumed to bind Cu. Agreement between prediction and experiment at lower ionic strength is not as good. Variations in Cu binding among different sources of dissolved organic matter appear to be much smaller than those due to chemical factors such as pH and ionic strength.

  18. Measurement and importance of dissolved organic carbon. Chapter 13

    Treesearch

    Randall Kolka; Peter Weishampel; Mats. Froberg

    2008-01-01

    The flux of dissolved organic carbon (DOC) from an ecosystem can be a significant component of carbon (C) budgets especially in watersheds containing wetlands. Although internal ecosystem cycling of DOC is generally greater than the fluxes to ground or surface waters, it is the transport out of the system that is a main research focus for carbon accounting. In...

  19. DISSOLVED ORGANIC MATTER AND METALS: EFFECTS OF PH ON PARTITIONING

    EPA Science Inventory

    Eighteen Dutch soils were extracted in aqueous solutions at varying pH. Extracts were analyzed for Cd, Cu, Ni, Pb, and Zn by ICP-AES. Extract dissolved organic carbon (DOC) was fractionated into three operationally defined fractions: hydrophilic acids (Hyd), fulvic acids (FA), an...

  20. Labile dissolved organic carbon supply limits hyporheic denitrification

    Treesearch

    Jay P. Zarnetske; Roy Haggerty; Steven M. Wondzell; Michelle A. Baker

    2012-01-01

    We used an in situ steady state 15N-labeled nitrate and acetate well-to-wells injection experiment to determine how the availability of labile dissolved organic carbon as acetate influences microbial denitrification in the hyporheic zone of an upland (third-order) agricultural stream.

  1. DISSOLVED ORGANIC MATTER AND METALS: EFFECTS OF PH ON PARTITIONING

    EPA Science Inventory

    Eighteen Dutch soils were extracted in aqueous solutions at varying pH. Extracts were analyzed for Cd, Cu, Ni, Pb, and Zn by ICP-AES. Extract dissolved organic carbon (DOC) was fractionated into three operationally defined fractions: hydrophilic acids (Hyd), fulvic acids (FA), an...

  2. Photochemical Reactivity of Dissolved Organic Matter in Boreal Lakes

    NASA Astrophysics Data System (ADS)

    Gu, Y.; Vuorio, K.; Tiirola, M.; Perämäki, S.; Vahatalo, A.

    2016-12-01

    Boreal lakes are rich in dissolved organic matter (DOM) that terrestrially derived from forest soil and wetland, yet little is known about potential for photochemical transformation of aquatic DOM in boreal lakes. Transformation of chromophoric dissolved organic matter (CDOM) can decrease water color and enhance microbial mineralization, affecting primary production and respiration, which both affect the CO2 balance of the lakes. We used laboratory solar radiation exposure experiments with lake water samples collected from 54 lakes located in Finland and Sweden, representing different catchment composition and watershed location to assess photochemical reactivity of DOM. The pH of water samples ranged from 5.4 to 8.3, and the concentrations of dissolved iron (Fe) were between < 0.06 and 22 μmol L-1. The filtered water samples received simulated solar radiation corresponding to a daily dose of sunlight, and photomineralization of dissolved organic carbon (DOC) to dissolved inorganic carbon (DIC) was measured for determination of spectral apparent quantum yields (AQY). During irradiation, photobleaching decreased the absorption coefficients of CDOM at 330 nm between 4.9 and 79 m-1 by 0.5 to 11 m-1. Irradiation generated DIC from 2.8 to 79 μmol C L-1. The AQY at 330 nm ranged between 31 and 273 ×10-6 mol C mol photons-1 h-1, which was correlated positively with concentration of dissolved Fe, and negatively with pH. Further statistical analyze indicated that the interaction between pH and Fe may explain much of the photochemical reactivity of DOM in the examined lakes, and land cover concerns main catchment areas also can have impact on the photoreaction process. This study may suggest how environmental conditions regulate DOM photomineralization in boreal lakes.

  3. Dissolved Organic Matter: a Master Variable for Predicting and Modeling the Effects of Climatic and Environmental Change on Mercury Transport and Reactivity

    NASA Astrophysics Data System (ADS)

    Aiken, G.

    2013-12-01

    It is known that dissolved organic matter (DOM) exerts strong controls on the transport and reactivity of Hg in aquatic systems. Our research has demonstrated that DOM binds Hg strongly, interacts with nanoparticulate HgS to stabilize and enhance reactivity, and controls, in part, the availability of Hg for methylation by micro-organisms. In many rivers and streams, DOM and dissolved Hg concentrations are strongly positively correlated and DOM optical properties have been shown to be excellent proxies for Hg concentration. Of particular importance is the hydrophobic acid fraction of DOM that contains primarily terrestrially derived aquatic humic substances. This fraction is derived, in large part, from watershed soils and plant litter, is chromophore-rich, and strongly influences DOM optical properties, such as ultraviolet (UV) absorbance, fluorescence, and specific UV absorbance (SUVA - an indicator of DOM aromaticity). In most rivers and streams studied by our group, the relationships between total dissolved Hg concentration and hydrophobic organic acid (HPOA) content are often stronger than those observed between dissolved Hg and DOM. These results and those of lab studies support the hypothesis that interactions between Hg and the HPOA fraction are important drivers for the transport and reactivity of dissolved Hg in aquatic systems. Therefore, understanding how climate or land use related changes may influence DOM and HPOA export and yield within a particular watershed is key to predicting in the fate and bioaccumulation of Hg in that system. Watershed hydrology, the nature of source materials, and biogeochemical processes throughout the entire ecosystem drive DOM composition. In particular, the abundance of wetlands within a river basin is an excellent indicator of DOM concentration, DOM optical properties, and the concentration of HPOA. For instance, for 17 major North American rivers we found significant positive correlations between basin wetland-cover and

  4. Uptake of allochthonous dissolved organic matter from soil and salmon in coastal temperate rainforest streams

    Treesearch

    Jason B. Fellman; Eran Hood; Richard T. Edwards; Jeremy B. Jones

    2009-01-01

    Dissolved organic matter (DOM) is an important component of aquatic food webs. We compare the uptake kinetics for NH4-N and different fractions of DOM during soil and salmon leachate additions by evaluating the uptake of organic forms of carbon (DOC) and nitrogen (DON), and proteinaceous DOM, as measured by parallel factor (PARAFAC) modeling of...

  5. Yucca Mountain Area Saturated Zone Dissolved Organic Carbon Isotopic Data

    SciTech Connect

    Thomas, James; Decker, David; Patterson, Gary; Peterman, Zell; Mihevc, Todd; Larsen, Jessica; Hershey, Ronald

    2007-06-25

    Groundwater samples in the Yucca Mountain area were collected for chemical and isotopic analyses and measurements of water temperature, pH, specific conductivity, and alkalinity were obtained at the well or spring at the time of sampling. For this project, groundwater samples were analyzed for major-ion chemistry, deuterium, oxygen-18, and carbon isotopes of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC). The U.S. Geological Survey (USGS) performed all the fieldwork on this project including measurement of water chemistry field parameters and sample collection. The major ions dissolved in the groundwater, deuterium, oxygen-18, and carbon isotopes of dissolved inorganic carbon (DIC) were analyzed by the USGS. All preparation and processing of samples for DOC carbon isotopic analyses and geochemical modeling were performed by the Desert Research Institute (DRI). Analysis of the DOC carbon dioxide gas produced at DRI to obtain carbon-13 and carbon-14 values was conducted at the University of Arizona Accelerator Facility (a NSHE Yucca Mountain project QA qualified contract facility). The major-ion chemistry, deuterium, oxygen-18, and carbon isotopes of DIC were used in geochemical modeling (NETPATH) to determine groundwater sources, flow paths, mixing, and ages. The carbon isotopes of DOC were used to calculate groundwater ages that are independent of DIC model corrected carbon-14 ages. The DIC model corrected carbon-14 calculated ages were used to evaluate groundwater travel times for mixtures of water including water beneath Yucca Mountain. When possible, groundwater travel times were calculated for groundwater flow from beneath Yucca Mountain to down gradient sample sites. DOC carbon-14 groundwater ages were also calculated for groundwaters in the Yucca Mountain area. When possible, groundwater travel times were estimated for groundwater flow from beneath Yucca Mountain to down gradient groundwater sample sites using the DOC calculated

  6. [Effects of dissolved organic matter on phenanthrene adsorption by soil].

    PubMed

    Xiong, Wei; Ling, Wan-ting; Gao, Yan-zheng; Li, Qiu-ling; Dai, Jing-yu

    2007-02-01

    This paper studied the effects of exotic and native dissolved organic matter (DOM) on the phenanthrene adsorption by three soils differed in soil organic carbon content (foc). The exotic DOM came from decayed rice straw, while the native DOM was extracted from the test soils. In all cases, the adsorption of phenanthrene by treated soils could be well described with linear-type model, and there was a positive correlation between adsorption coefficient (Kd) and foc Compared with the control, the Kd value of test soils after native DOM removed was increased by 7. 08% -21. 4% , and the increment (deltaKd) was positively correlated with fo,, indicating that the presence of soil native DOM impeded the phenanthrene adsorption by soil. The effects of exotic DOM on phenanthrene adsorption had a close relation with its added concentration in soil-water system. Within the range of 0-106 mg DOC x L(-1) , the K, value increased first, and then decreased with the increase of added exotic DOM concentration. Lower concentrations of added exotic DOM promoted the phenanthrene adsorption by soil, while higher concentrations ( I> or =52 mg DOC x L(-1)) of it obviously impeded this adsorption. These effects of exotic and native DOM on soil phenanthrene adsorption were considered to be related to the association of phenanthrene with DOM in solution, and the ' cumulative adsorption effect' between soil solid and aqueous phases.

  7. Seasonal changes in photochemical properties of dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Porcal, P.; Dillon, P. J.; Molot, L. A.

    2013-03-01

    The fate of dissolved organic matter (DOM) in lakes and streams is significantly affected by photochemical transformation of DOM. A series of laboratory photochemical experiments was conducted to describe long-term changes in photochemical properties of DOM. The stream samples used in this study originated from three different catchments on the southern-most part of the Boreal ecozone near Dorset, Ontario, Canada. A first-order kinetics equation was used to model photochemical degradation of DOM and the kinetic rate constant, K, was used as an indicator of photochemical properties of DOM. Highest Kwas observed in samples from the catchment dominated by coniferous forest while the lowest K was measured in the deciduous catchment. Kinetic rate constants from all three catchments showed a sinusoidal pattern during the hydrological year. K increased steadily during autumn and winter and decreased during spring and summer. The highest values were observed during spring melt events when DOM was flushed from terrestrial sources by high flows. The minimum rate constants were found in summer when discharge was lowest. DOM molecular weight and specific absorbance at 254 nm also exhibited annual cycles corresponding to the seasonal cycles of terrestrial organic matter but the relationships between these properties and K was probably affected by previous exposure to solar radiation during transit from the catchment as well as pH and iron.

  8. Quenching of excited triplet states by dissolved natural organic matter.

    PubMed

    Wenk, Jannis; Eustis, Soren N; McNeill, Kristopher; Canonica, Silvio

    2013-11-19

    Excited triplet states of aromatic ketones and quinones are used as proxies to assess the reactivity of excited triplet states of the dissolved organic matter ((3)DOM*) in natural waters. (3)DOM* are crucial transients in environmental photochemistry responsible for contaminant transformation, production of reactive oxygen species, and potentially photobleaching of DOM. In recent photochemical studies aimed at clarifying the role of DOM as an inhibitor of triplet-induced oxidations of organic contaminants, aromatic ketones have been used in the presence of DOM, and the question of a possible interaction between their excited triplet states and DOM has emerged. To clarify this issue, time-resolved laser spectroscopy was applied to measure the excited triplet state quenching of four different model triplet photosensitizers induced by a suite of DOM from various aquatic and terrestrial sources. While no quenching for the anionic triplet sensitizers 4-carboxybenzophenone (CBBP) and 9,10-anthraquinone-2,6-disulfonic acid (2,6-AQDS) was detected, second-order quenching rate constants with DOM for the triplets of 2-acetonaphthone (2AN) and 3-methoxyacetophenone (3MAP) in the range of 1.30-3.85 × 10(7) L mol(C)(-1) s(-1) were determined. On the basis of the average molecular weight of DOM molecules, the quenching for these uncharged excited triplet molecules is nearly diffusion-controlled, but significant quenching (>10%) in aerated water is not expected to occur below DOM concentrations of 22-72 mg(C) L(-1).

  9. Fluorescence characteristics and biodegradability of dissolved organic matter in forest and wetland soils from coastal temperate watersheds in southeast Alaska

    Treesearch

    Jason B. Fellman; David V. D' Amore; Eran Hood; Richard D. Boone

    2008-01-01

    Understanding how the concentration and chemical quality of dissolved organic matter (DOM) varies in soils is critical because DOM influences an array of biological, chemical, and physical processes. We used PARAFAC modeling of excitation-emission fluorescence spectroscopy, specific UV absorbance (SUVA254) and biodegradable dissolved organic...

  10. Production of Dissolved Organic Matter During Doliolid Feeding

    NASA Astrophysics Data System (ADS)

    Castellane, N. J.; Paffenhofer, G. A.; Stubbins, A.

    2016-02-01

    The biological carbon pump (BCP) draws carbon dioxide out of the atmosphere and buries it at the seafloor. The efficiency of the BCP is determined in part by the sinking rates of particulate organic carbon (POC) from ocean surface waters. Zooplankton can package POC into fecal pellets with higher sinking rates than their food source (e.g. phytoplankton), increasing the efficiency of the BCP. However, dissolved organic carbon (DOC) is also produced as zooplankton ingest and egest food, reducing the efficiency of BCP. The pelagic tunicate Dolioletta gegenbauri (doliolid) is a gelatinous zooplankton found at high concentrations in shelf waters, including our study site: the South Atlantic Bight. Doliolids are efficient grazers capable of stripping large quantities of phytoplankton from the water column. To determine the balance between pellet formation and DOC production during feeding, doliolids (6-7 mm gonozooids) were placed in natural seawater amended with a live phytoplankton food source and incubated on a plankton wheel. Dissolved organic matter (DOM) released directly to the water as well as the water soluble fraction of pellet organic matter were quantified and optically characterized. Colored dissolved organic matter (CDOM) absorbance and fluorescence spectra revealed that doliolid feeding produces DOM with optical properties that are commonly indicative of newly produced, highly biolabile DOM of microbial origin. Based upon these optical characteristics, doliolid-produced DOM is expected to be highly bio-labile in the environment and therefore rapidly degraded by surface ocean microbes shunting phytoplankton-derived organic carbon out of the BCP and back to dissolved inorganic carbon.

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

    PubMed Central

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

    2013-01-01

    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

  12. Utilizing chromophoric dissolved organic matter measurements to derive export and reactivity of dissolved organic carbon exported to the Arctic Ocean: A case study of the Yukon River, Alaska

    USGS Publications Warehouse

    Spencer, R.G.M.; Aiken, G.R.; Butler, K.D.; Dornblaser, M.M.; Striegl, R.G.; Hernes, P.J.

    2009-01-01

    The quality and quantity of dissolved organic matter (DOM) exported by Arctic rivers is known to vary with hydrology and this exported material plays a fundamental role in the biogeochemical cycling of carbon at high latitudes. We highlight the potential of optical measurements to examine DOM quality across the hydrograph in Arctic rivers. Furthermore, we establish chromophoric DOM (CDOM) relationships to dissolved organic carbon (DOC) and lignin phenols in the Yukon River and model DOC and lignin loads from CDOM measurements, the former in excellent agreement with long-term DOC monitoring data. Intensive sampling across the historically under-sampled spring flush period highlights the importance of this time for total export of DOC and particularly lignin. Calculated riverine DOC loads to the Arctic Ocean show an increase from previous estimates, especially when new higher discharge data are incorporated. Increased DOC loads indicate decreased residence times for terrigenous DOM in the Arctic Ocean with important implications for the reactivity and export of this material to the Atlantic Ocean. Citation: Spencer, R. G. M., G. R. Aiken, K. D. Butler, M. M. Dornblaser, R. G. Striegl, and P. J. Hernes (2009), Utilizing chromophoric dissolved organic matter measurements to derive export and reactivity of dissolved organic carbon exported to the Arctic Ocean: A case study of the Yukon River, Alaska, Geophys. Res. Lett., 36, L06401, doi:10.1029/ 2008GL036831. Copyright 2009 by the American Geophysical Union.

  13. Characterization Of Dissolved Organic Mattter In The Florida Keys Ecosystem

    NASA Astrophysics Data System (ADS)

    Adams, D. G.; Shank, G. C.

    2009-12-01

    Over the past few decades, Scleractinian coral populations in the Florida Keys have increasingly experienced mortality due to bleaching events as well as microbial mediated illnesses such as black band and white band disease. Such pathologies seem to be most correlated with elevated sea surface temperatures, increased UV exposures, and shifts in the microbial community living on the coral itself. Recent studies indicate that corals’ exposure to UV in the Florida Keys is primarily controlled by the concentration of CDOM (Chromophoric Dissolved Organic Matter) in the water column. Further, microbial community alterations may be linked to changes in concentration and chemical composition of the larger DOM (Dissolved Organic Matter) pool. Our research characterized the spatial and temporal properties of DOM in Florida Bay and along the Keys ecosystems using DOC analyses, in-situ water column optical measurements, and spectral analyses including absorbance and fluorescence measurements. We analyzed DOM characteristics along transects running from the mouth of the Shark River at the southwest base of the Everglades, through Florida Bay, and along near-shore Keys coastal waters. Two 12 hour time-series samplings were also performed at the Seven-Mile Bridge, the primary Florida Bay discharge channel to the lower Keys region. Photo-bleaching experiments showed that the chemical characteristics of the DOM pool are altered by exposure to solar radiation. Results also show that DOC (~0.8-5.8 mg C/L) and CDOM (~0.5-16.5 absorbance coefficient at 305nm) concentrations exhibit seasonal fluctuations in our study region. EEM analyses suggest seasonal transitions between primarily marine (summer) and terrestrial (winter) sources along the Keys. We are currently combining EEM-PARAFAC analysis with in-situ optical measurements to model changes in the spectral properties of DOM in the water column. Additionally, we are using stable δ13C isotopic analysis to further characterize DOM

  14. Effects of iron on optical properties of dissolved organic matter

    USGS Publications Warehouse

    Poulin, Brett; Ryan, Joseph N.; Aiken, George R.

    2014-01-01

    Iron is a source of interference in the spectroscopic analysis of dissolved organic matter (DOM); however, its effects on commonly employed ultraviolet and visible (UV–vis) light adsorption and fluorescence measurements are poorly defined. Here, we describe the effects of iron(II) and iron(III) on the UV–vis absorption and fluorescence of solutions containing two DOM fractions and two surface water samples. In each case, regardless of DOM composition, UV–vis absorption increased linearly with increasing iron(III). Correction factors were derived using iron(III) absorption coefficients determined at wavelengths commonly used to characterize DOM. Iron(III) addition increased specific UV absorbances (SUVA) and decreased the absorption ratios (E2:E3) and spectral slope ratios (SR) of DOM samples. Both iron(II) and iron(III) quenched DOM fluorescence at pH 6.7. The degree and region of fluorescence quenching varied with the iron:DOC concentration ratio, DOM composition, and pH. Regions of the fluorescence spectra associated with greater DOM conjugation were more susceptible to iron quenching, and DOM fluorescence indices were sensitive to the presence of both forms of iron. Analyses of the excitation–emission matrices using a 7- and 13-component parallel factor analysis (PARAFAC) model showed low PARAFAC sensitivity to iron addition.

  15. Effects of iron on optical properties of dissolved organic matter.

    PubMed

    Poulin, Brett A; Ryan, Joseph N; Aiken, George R

    2014-09-02

    Iron is a source of interference in the spectroscopic analysis of dissolved organic matter (DOM); however, its effects on commonly employed ultraviolet and visible (UV-vis) light adsorption and fluorescence measurements are poorly defined. Here, we describe the effects of iron(II) and iron(III) on the UV-vis absorption and fluorescence of solutions containing two DOM fractions and two surface water samples. In each case, regardless of DOM composition, UV-vis absorption increased linearly with increasing iron(III). Correction factors were derived using iron(III) absorption coefficients determined at wavelengths commonly used to characterize DOM. Iron(III) addition increased specific UV absorbances (SUVA) and decreased the absorption ratios (E2:E3) and spectral slope ratios (SR) of DOM samples. Both iron(II) and iron(III) quenched DOM fluorescence at pH 6.7. The degree and region of fluorescence quenching varied with the iron:DOC concentration ratio, DOM composition, and pH. Regions of the fluorescence spectra associated with greater DOM conjugation were more susceptible to iron quenching, and DOM fluorescence indices were sensitive to the presence of both forms of iron. Analyses of the excitation-emission matrices using a 7- and 13-component parallel factor analysis (PARAFAC) model showed low PARAFAC sensitivity to iron addition.

  16. Measuring the bioavailability of two hydrophobic organic compounds in the presence of dissolved organic matter.

    PubMed

    Akkanen, Jarkko; Kukkonen, Jussi V K

    2003-03-01

    Bioavailability of benzo[a]pyrene (BaP) and 3,3',4,4'-tetrachlorobiphenyl (TCB) was studied in natural lake water containing dissolved organic matter (DOM). Lake water was diluted to give a dissolved organic carbon (DOC) range of 1 to 20 mg/L. Partition coefficients for the model compounds were assessed at different DOM concentrations and over time with three different methods, namely equilibrium dialysis and reverse-phase and liquid-liquid extraction. In addition, biological partition coefficients were estimated from the difference in the bioconcentration of the model compounds in Daphnia magna in the presence and absence of DOM. Results showed that bioavailability of the model compounds was reduced by the presence of DOM. The equilibrium dialysis method gave the best estimates for bioavailability of the model compounds when compared with biologically determined values. Both the reverse-phase and the liquid-liquid extraction overestimated the bioavailable fraction. The more pronounced overestimation of bioavailable fraction of TCB suggested that the sorption of TCB was not only lower but the interaction was also weaker than that of BaP. Increasing DOM concentration produced lower partition coefficients and the effect seemed to be more pronounced when measured by the reverse-phase and the extraction methods.

  17. The Impact of Microbial Metabolism on Marine Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Kujawinski, Elizabeth B.

    2011-01-01

    Microbes mediate global biogeochemical cycles through their metabolism, and all metabolic processes begin with the interaction between the microbial cell wall or membrane and the external environment. For all heterotrophs and many autotrophs, critical growth substrates and factors are present within the dilute and heterogeneous mixture of compounds that constitutes dissolved organic matter (DOM). In short, the microbe-molecule interaction is one of the fundamental reactions within the global carbon cycle. Here, I summarize recent findings from studies that examine DOM-microbe interactions from either the DOM perspective (organic geochemistry) or the microbe perspective (microbial ecology). Gaps in our knowledge are highlighted and future integrative research directions are proposed.

  18. Algal uptake of dissolved organic nitrogen in wastewater treatment plants.

    PubMed

    Zhang, Jingtian; Su, Mingzhou; Xi, Beidou; Qian, Guangren; Liu, Jianyong; Hua, Fei; Huo, Shouliang

    2016-12-01

    The algal uptake of dissolved organic nitrogen (DON) in the anaerobic-anoxic-oxic (A2O) process was investigated in this study. Anaerobic, aerobic and effluent DON samples from two wastewater treatment plants (WWTPs) were separated into hydrophilic and hydrophobic fractions using a DAX-8 resin coupled with an anion exchange resin and a nanofiltration (NF) pretreatment. Hydrophilic DON accounted for 66.66%-88.74% of the entire DON for the two plants evaluated. After a 15-day incubation, 16.95%-91.75% DON was bioavailable for algal growth, and untreated samples exhibited higher DON bioavailability, with 52.83% DON average uptake rates, compared with the hydrophilic and hydrophobic fractions (45.53% and 44.40%, respectively) because the pretreatment caused the inorganic salt to be resistant to algae. Anaerobic untreated samples, hydrophilic fractions and hydrophobic fractions showed higher DON reduction rates and higher biomass accumulation compared with the other DON fractions due to the decomposition of resistant organics by anaerobic and anoxic bacteria. DON in aerobic and effluent samples of plant A was more bioavailable than that of plant B with usages of 27.49%-55.26% DON. DON bioavailability in the anaerobic-anoxic-oxic process decreased in the following order: anaerobic>effluent>aerobic. The DON contents were reduced after anaerobic treatment in the two plants. The EEM-PARAFAC model identified three DON components, including two humic acid-like substances and one protein-like substance in plant A and two protein-like substances and one humic acid-like substance in plant B. Copyright © 2016. Published by Elsevier B.V.

  19. Meridional fluxes of dissolved organic matter in the North Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    Walsh, John J.; Carder, Kendall L.; Mueller-Karger, Frank E.

    1992-01-01

    Biooptical estimates of gelbstoff and a few platinum measurements of dissolved organic carbon (DOCpt) are used to construct a budget of the meridional flux of DOC and dissolved organic nitrogen (DON) across 36 deg 25 min N in the North Atlantic from previous inverse models of water and element transport. Distinct southward subsurface fluxes of dissolved organic matter within subducted shelf water, cabelled slope water, and overturned basin water are inferred. Within two cases of a positive gradient of DOCpt between terrestrial/shelf and offshore stocks, the net equatorward exports of O2 and DOCpt from the northern North Atlantic yield molar ratios of 2.1 to 9.1, compared to the expected Redfield O2/C ratio of 1.3. It is concluded that some shelf export of DOC, with a positive gradient between coastal and oceanic stocks, as well as falling particles, are required to balance carbon, nitrogen, and oxygen budgets of the North Atlantic.

  20. Meridional fluxes of dissolved organic matter in the North Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    Walsh, John J.; Carder, Kendall L.; Mueller-Karger, Frank E.

    1992-01-01

    Biooptical estimates of gelbstoff and a few platinum measurements of dissolved organic carbon (DOCpt) are used to construct a budget of the meridional flux of DOC and dissolved organic nitrogen (DON) across 36 deg 25 min N in the North Atlantic from previous inverse models of water and element transport. Distinct southward subsurface fluxes of dissolved organic matter within subducted shelf water, cabelled slope water, and overturned basin water are inferred. Within two cases of a positive gradient of DOCpt between terrestrial/shelf and offshore stocks, the net equatorward exports of O2 and DOCpt from the northern North Atlantic yield molar ratios of 2.1 to 9.1, compared to the expected Redfield O2/C ratio of 1.3. It is concluded that some shelf export of DOC, with a positive gradient between coastal and oceanic stocks, as well as falling particles, are required to balance carbon, nitrogen, and oxygen budgets of the North Atlantic.

  1. Quantifying litter decomposition losses to dissolved organic carbon and respiration

    NASA Astrophysics Data System (ADS)

    Soong, J.; Parton, W. J.; Calderon, F. J.; Guilbert, K.; Cotrufo, M.

    2013-12-01

    As litter decomposes its carbon is lost from the litter layer, largely through microbial processing. However, much of the carbon lost from the surface litter layer during decomposition is not truly lost from the ecosystem but gets transferred to the soil through fragmentation and leaching of dissolved organic carbon (DOC). This DOC in the soil acts as a stock of soil organic matter (SOM) to be utilized by soil microbes, stabilized in the soil, or leached further through the soil profile. The total amount of C that ends up leaching from litter to the soil, as well as its chemical composition, has important implications on the residence time of decomposing litter C in the soil and is not currently well parameterized in models. In this study we aim to quantify the proportional relationship between CO2 efflux and DOC partitioning during decomposition of fresh leaf litter with distinct structural and chemical composition. The results from this one-year laboratory incubation show a clear relationship between the lignin to cellulose ratios of litter and DOC to CO2 partitioning during four distinct phases of litter decomposition. For example, bluestem grass litter with a low lignin to cellulose ratio loses almost 50% of its C as DOC whereas pine needles with a high lignin to cellulose ratio loses only 10% of its C as DOC, indicating a potential ligno-cellulose complexation effect on carbon use efficiency during litter decomposition. DOC production also decreases with time during decomposition, correlating with increasing lignin to cellulose ratios as decomposition progresses. Initial DOC leaching can be predicted based on the amount of labile fraction in each litter type. Field data using stable isotope labeled bluestem grass show that about 18% of the surface litter C lost in 18 months of decomposition is stored in the soil, and that over 50% of this is recovered in mineral-associated heavy SOM fractions, not as litter fragments, confirming the relative importance of the

  2. Selective Sorption of Dissolved Organic Carbon Compounds by Temperate Soils

    SciTech Connect

    Jagadamma, Sindhu; Mayes, Melanie; Phillips, Jana Randolph

    2012-01-01

    Physico-chemical sorption of dissolved organic carbon (DOC) on soil minerals is one of the major processes of organic carbon (OC) stabilization in soils, especially in deeper layers. The attachment of C on soil solids is related to the reactivity of the soil minerals and the chemistry of the sorbate functional groups, but the sorption studies conducted without controlling microbial activity may overestimate the sorption potential of soil. This study was conducted to examine the sorptive characteristics of a diverse functional groups of simple OC compounds (D-glucose, L-alanine, oxalic acid, salicylic acid, and sinapyl alcohol) on temperate climate soil orders (Mollisols, Ultisols and Alfisols) with and without biological degradative processes. Equilibrium batch experiments were conducted using 0-100 mg C L-1 at a solid-solution ratio of 1:60 for 48 hrs and the sorption parameters were calculated by Langmuir model fitting. The amount of added compounds that remained in the solution phase was detected by high performance liquid chromatography (HPLC) and total organic C (TOC) analysis. Soil sterilization was performed by -irradiation technique and experiments were repeated to determine the contribution of microbial degradation to apparent sorption. Overall, Ultisols did not show a marked preference for apparent sorption of any of the model compounds, as indicated by a narrower range of maximum sorption capacity (Smax) of 173-527 mg kg soil-1 across compounds. Mollisols exhibited a strong preference for apparent sorption of oxalic acid (Smax of 5290 mg kg soil-1) and sinapyl alcohol (Smax of 2031 mg kg soil-1) over the other compounds. The propensity for sorption of oxalic acid is mainly attributed to the precipitation of insoluble Ca-oxalate due to the calcareous nature of most Mollisol subsoils and its preference for sinapyl alcohol could be linked to the polymerization of this lignin monomer on 2:2 mineral dominated soils. The reactivity of Alfisols to DOC was in

  3. Importance of Dissolved Organic Nitrogen to Water Quality in Narragansett Bay

    EPA Science Inventory

    This preliminary analysis of the importance of the dissolved organic nitrogen (DON) pool in Narragansett Bay is being conducted as part of a five-year study of Narragansett Bay and its watershed. This larger study includes water quality and ecological modeling components that foc...

  4. 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.

  5. Dissolved oxygen as an indicator of bioavailable dissolved organic carbon in groundwater

    USGS Publications Warehouse

    Chapelle, Francis H.; Bradley, Paul M.; McMahon, Peter B.; Kaiser, Karl; Benner, Ron

    2012-01-01

    Concentrations of dissolved oxygen (DO) plotted vs. dissolved organic carbon (DOC) in groundwater samples taken from a coastal plain aquifer of South Carolina (SC) showed a statistically significant hyperbolic relationship. In contrast, DO-DOC plots of groundwater samples taken from the eastern San Joaquin Valley of California (CA) showed a random scatter. It was hypothesized that differences in the bioavailability of naturally occurring DOC might contribute to these observations. This hypothesis was examined by comparing nine different biochemical indicators of DOC bioavailability in groundwater sampled from these two systems. Concentrations of DOC, total hydrolysable neutral sugars (THNS), total hydrolysable amino acids (THAA), mole% glycine of THAA, initial bacterial cell counts, bacterial growth rates, and carbon dioxide production/consumption were greater in SC samples relative to CA samples. In contrast, the mole% glucose of THNS and the aromaticity (SUVA254) of DOC was greater in CA samples. Each of these indicator parameters were observed to change with depth in the SC system in a manner consistent with active biodegradation. These results are uniformly consistent with the hypothesis that the bioavailability of DOC is greater in SC relative to CA groundwater samples. This, in turn, suggests that the presence/absence of a hyperbolic DO-DOC relationship may be a qualitative indicator of relative DOC bioavailability in groundwater systems.

  6. Dissolved oxygen as an indicator of bioavailable dissolved organic carbon in groundwater.

    PubMed

    Chapelle, Francis H; Bradley, Paul M; McMahon, Peter B; Kaiser, Karl; Benner, Ron

    2012-01-01

    Concentrations of dissolved oxygen (DO) plotted vs. dissolved organic carbon (DOC) in groundwater samples taken from a coastal plain aquifer of South Carolina (SC) showed a statistically significant hyperbolic relationship. In contrast, DO-DOC plots of groundwater samples taken from the eastern San Joaquin Valley of California (CA) showed a random scatter. It was hypothesized that differences in the bioavailability of naturally occurring DOC might contribute to these observations. This hypothesis was examined by comparing nine different biochemical indicators of DOC bioavailability in groundwater sampled from these two systems. Concentrations of DOC, total hydrolysable neutral sugars (THNS), total hydrolysable amino acids (THAA), mole% glycine of THAA, initial bacterial cell counts, bacterial growth rates, and carbon dioxide production/consumption were greater in SC samples relative to CA samples. In contrast, the mole% glucose of THNS and the aromaticity (SUVA(254)) of DOC was greater in CA samples. Each of these indicator parameters were observed to change with depth in the SC system in a manner consistent with active biodegradation. These results are uniformly consistent with the hypothesis that the bioavailability of DOC is greater in SC relative to CA groundwater samples. This, in turn, suggests that the presence/absence of a hyperbolic DO-DOC relationship may be a qualitative indicator of relative DOC bioavailability in groundwater systems.

  7. Spatial and temporal variation of dissolved organic matter in the Changjiang: Fluvial transport and flux estimation

    NASA Astrophysics Data System (ADS)

    Bao, Hongyan; Wu, Ying; Zhang, Jing

    2015-09-01

    The Changjiang is the most important source of freshwater and dissolved organic matter (DOM) for the East China Sea. However, knowledge regarding the sources, seasonal fluxes, and fluvial transport of terrigenous DOM (tDOM) in the Changjiang is lacking. To fill this knowledge gap, we measured dissolved organic carbon (DOC) and dissolved lignin in water samples collected in the middle and lower Changjiang under different hydrological conditions. Additional samples were collected biweekly in the lower Changjiang. Through comparisons with other rivers, we found that the DOC in the Changjiang is mainly from soil organic matter and has a higher fraction of tDOM during flood. Mass balance model results indicate that approximately 33% of the dissolved lignin discharged into the middle and lower Changjiang is removed during its transport to the lower reach during both low-discharge and flood periods. Based on a comparison of the removal rates under these two contrasting hydrological conditions and considering the lower organic carbon content and fine grain size of the Changjiang's suspended particles, we speculate that the major process for the removal of dissolved lignin is sorption, and potentially flocculation by suspended particles. Changjiang discharges 1.4 ± 0.10 Tg yr-1 and 8.6 ± 0.30 Gg yr-1 DOC and dissolved lignin to the estuary during the period of July 2010 to June 2011, respectively. Seasonal distributions of DOC and dissolved lignin fluxes are controlled by water discharge, which will be affected by future climate change and the Three Gorges Dam.

  8. Dissolved organic matter enhances microbial mercury methylation under sulfidic conditions

    USGS Publications Warehouse

    Graham, Andrew M.; Aiken, George R.; Gilmour, Cynthia

    2012-01-01

    Dissolved organic matter (DOM) is generally thought to lower metal bioavailability in aquatic systems due to the formation of metal–DOM complexes that reduce free metal ion concentrations. However, this model may not be pertinent for metal nanoparticles, which are now understood to be ubiquitous, sometimes dominant, metal species in the environment. The influence of DOM on Hg bioavailability to microorganisms was examined under conditions (0.5–5.0 nM Hg and 2–10 μM sulfide) that favor the formation of β-HgS(s) (metacinnabar) nanoparticles. We used the methylation of stable-isotope enriched 201HgCl2 by Desulfovibrio desulfuricans ND132 in short-term washed cell assays as a sensitive, environmentally significant proxy for Hg uptake. Suwannee River humic acid (SRHA) and Williams Lake hydrophobic acid (WLHPoA) substantially enhanced (2- to 38-fold) the bioavailability of Hg to ND132 over a wide range of Hg/DOM ratios (9.4 pmol/mg DOM to 9.4 nmol/mg DOM), including environmentally relevant ratios. Methylmercury (MeHg) production by ND132 increased linearly with either SRHA or WLHPoA concentration, but SRHA, a terrestrially derived DOM, was far more effective at enhancing Hg-methylation than WLHPoA, an aquatic DOM dominated by autochthonous sources. No DOM-dependent enhancement in Hg methylation was observed in Hg–DOM–sulfide solutions amended with sufficient l-cysteine to prevent β-HgS(s) formation. We hypothesize that small HgS particles, stabilized against aggregation by DOM, are bioavailable to Hg-methylating bacteria. Our laboratory experiments provide a mechanism for the positive correlations between DOC and MeHg production observed in many aquatic sediments and wetland soils.

  9. Selective Sorption of Dissolved Organic Carbon Compounds by Temperate Soils

    PubMed Central

    Jagadamma, Sindhu; Mayes, Melanie A.; Phillips, Jana R.

    2012-01-01

    Background Physico-chemical sorption onto soil minerals is one of the major processes of dissolved organic carbon (OC) stabilization in deeper soils. The interaction of DOC on soil solids is related to the reactivity of soil minerals, the chemistry of sorbate functional groups, and the stability of sorbate to microbial degradation. This study was conducted to examine the sorption of diverse OC compounds (D-glucose, L-alanine, oxalic acid, salicylic acid, and sinapyl alcohol) on temperate climate soil orders (Mollisols, Ultisols and Alfisols). Methodology Equilibrium batch experiments were conducted using 0–100 mg C L−1 at a solid-solution ratio of 1∶60 for 48 hrs on natural soils and on soils sterilized by γ-irradiation. The maximum sorption capacity, Qmax and binding coefficient, k were calculated by fitting to the Langmuir model. Results Ultisols appeared to sorb more glucose, alanine, and salicylic acid than did Alfisols or Mollisols and the isotherms followed a non-linear pattern (higher k). Sterile experiments revealed that glucose and alanine were both readily degraded and/or incorporated into microbial biomass because the observed Qmax under sterile conditions decreased by 22–46% for glucose and 17–77% for alanine as compared to non-sterile conditions. Mollisols, in contrast, more readily reacted with oxalic acid (Qmax of 886 mg kg−1) and sinapyl alcohol (Qmax of 2031 mg kg−1), and no degradation was observed. The reactivity of Alfisols to DOC was intermediate to that of Ultisols and Mollisols, and degradation followed similar patterns as for Ultisols. Conclusion This study demonstrated that three common temperate soil orders experienced differential sorption and degradation of simple OC compounds, indicating that sorbate chemistry plays a significant role in the sorptive stabilization of DOC. PMID:23209742

  10. Chromophoric Dissolved Organic Matter in Southwestern Greenland Lakes

    NASA Astrophysics Data System (ADS)

    Osburn, C. L.; Giles, M. E.; Underwood, G. J. C.

    2014-12-01

    Dissolved organic matter (DOM) is an important property of Arctic lake ecosystems, originating from allochthonous inputs from catchments and autochthonous production by plankton in the water column. Little is known about the quality of DOM in Arctic lakes that lack substantial inputs from catchments and such lakes are abundant in southwestern Greenland. Colored dissolved organic matter (CDOM), the fraction that absorbs ultraviolet (UV) and visible light, is the controlling factor for the optical properties of many surface waters and as well informs on the quality of DOM. We examined the quality of CDOM in 21 lakes in southwestern Greenland, from the ice sheet to the coast, as part of a larger study examining the role of DOM in regulating microbial communities in these lakes. DOM was size fractioned and absorbance and fluorescence was measured on each size fraction, as well as on bulk DOM. The specific ultraviolet absorbance (SUVA) at 254 nm (SUVA254), computed by normalizing absorption (a254) to dissolved organic carbon (DOC) concentration, provided an estimate of the aromatic carbon content of DOM. SUVA values were generally <2, indicating low aromatic content. Parallel factor analysis (PARAFAC) of CDOM fluorescence was used to determine the relative abundance of allochthonous and autochthonous DOM in all size fractions. Younger lakes near the ice sheet and lakes near the coast had lower amounts of CDOM and appeared more microbial in quality. However, lakes centrally located between the ice sheet and the coast had the highest CDOM concentrations and exhibited strong humic fluorescence. Overall distinct differences in CDOM quality were observed between lake locations and among DOM size fractions.

  11. Production of Dissolved Organic Matter During Fungal Wood Rot Decay

    NASA Astrophysics Data System (ADS)

    Filley, T. R.; Jellison, J.; Goodell, B.; Kelley, S.; Davis, M.

    2002-12-01

    Dissolved organic matter mediates numerous biogeochemical processes in soil systems impacting subsurface microbial activity, redox chemistry, soil structure, and carbon and nitrogen sequestration. The structure and chemistry of DOM is a function of the inherited chemistry of the source material, the type of microbial action that has occurred, and selective interaction with mineral substrates. The type of fungal decomposition imparted to woody tissue is a major factor in determining the nature of DOM in forest soils. In order to investigate the relationship between fungal decomposition and the nature of DOM in coniferous forest soils we conducted 32-week inoculation studies on spruce sapwood with basidiomycete brown-rot wood decay fungi where leachable dissolved and colloidal organic matter was separated from decayed residue. A detailed examination of the organic fractions was conducted using 13C-labeled tetramethylammonium hydroxide thermochemolysis, solid-state 13C-NMR, and electrospray mass spectrometry. The progressive stages of microbial decay (cellulolytic and ligninolytic) were manifested in the chemical composition of the DOM which showed an evolution from a composition initially polysaccharide rich to one dominated by mildly oxidized and demethylated lignin. Upon removal of all polysaccharides at 16 weeks the DOM (up to 10% by weight of the original tissue) looked chemically distinct from the degraded residue

  12. 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.

  13. Characterization of Biologically Produced Colored Dissolved Organic Matter in Seawater

    DTIC Science & Technology

    2005-11-29

    Seritti, A. Environ. Tech. 1993, 14, 94.1-948. (19) Lombardi, A.T.; Jardim, W.F. Water Research. 1999, 33, 512-520. (20) Parlanti, E .; Morin , B.; Vacher...REPORT DOCUMENTATION PAGE Form Approved Public reporting burden for this collection of I•mo,,ation , e dlat ed to average hour per response. ind•uding... e -mail: drepeta(atwhoi.edu Grant# N00014-98-1-0579 & N00014-03-1-0387 Chromophoric, or colored dissolved organic matter (CDOM), influences the

  14. Effects of water hardness and dissolved organic material on bioavailability of selected organic chemicals.

    PubMed

    Akkanen, J; Kukkonen, J V

    2001-10-01

    The influence of water hardness and dissolved organic matter (DOM) on bioavailability of organic chemicals to Daphnia magna was studied by using benzo[a]pyrene (BaP), pyrene, atrazine, and 3,3',4,4'-tetrachlorobiphenyl (TCB) as model compounds. Two types of DOM were used, namely Lake Kontiolampi, Joensuu, Finland water (KL) and Nordic reference fulvic acid (NoFA) dissolved in artificial freshwater. Binding of the four contaminants by KL DOM decreased with increasing water hardness. Furthermore, increasing hardness reduced the binding of BaP and pyrene to NoFA. The binding of atrazine and TCB by NoFA was low and was not significantly affected by water hardness. In the DOM-free samples, the bioconcentration of the four contaminants in D. magna usually was not affected by water hardness. In the presence of DOM, the bioconcentration factors (BCFs) were lower (except for atrazine) than in the DOM-free controls. In the presence of both types of DOM, increasing water hardness resulted in higher BCFs for BaP. The bioconcentration of pyrene and TCB increased with increasing water hardness in the presence of KL DOM. In conclusion, the effects of DOM and water hardness on bioavailability of hydrophobic chemicals depend on the type of chemical and on the properties of DOM.

  15. Dissolved organic matter export from a forested watershed during Hurricane Irene

    NASA Astrophysics Data System (ADS)

    Yoon, Byungman; Raymond, Peter A.

    2012-09-01

    We incorporate high-resolution time-series data to calculate the total amount of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) transported during Hurricane Irene in Esopus Creek in New York (August 2011). During this 200-yr event the Esopus Creek experienced a 330-fold discharge increase and a 4-fold increase in concentration, resulting in the export of roughly 43% and 31% of its average annual DOC and DON fluxes, respectively, in just 5 days. The source of this large dissolved organic matter (DOM) flux also shifted during its course and showed an increased contribution of aromatic organic matter. We conclude that more frequent large events due to climate change will increase the export of terrigenous dissolved organic matter, and potentially impact the water quality and biogeochemistry of lakes and coastal systems. In addition, we show that the use of conventional models for extreme events lead to erroneous flux calculations, unless supported by high resolution data collected during the events.

  16. First-order kinetics-controlled multiple species reactive transport of dissolved organic compounds in groundwater: Development and application of a numerical model

    SciTech Connect

    McNab, W.W. Jr.

    1990-05-01

    Reactive chemical transport models developed over the past decade have generally relied on the assumption that local thermodynamic equilibrium is achieved at all times between aqueous species in a given system. Consequently, homogeneous aqueous systems characterized by a number of kinetically slow reactions, particularly problems involving organic species, cannot be satisfactorily modeled. In this study, we present a prototype computer model, KINETRAN, which is designed to handle kinetically-controlled homogeneous reactions in the aqueous phase, along with the transport of the various species involved, through geologic media. 31 refs., 53 figs., 10 tabs.

  17. Acid-base properties of Baltic Sea dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Hammer, Karoline; Schneider, Bernd; Kuliński, Karol; Schulz-Bull, Detlef E.

    2017-09-01

    Calculations related to the marine CO2 system that are based on alkalinity data may be strongly biased if the contributions of organic compounds are ignored. In coastal seas, concentrations of dissolved organic matter (DOM) are frequently high and alkalinity from inorganic compounds is low. In this study, based on measurements of total alkalinity, total CO2, and pH, we determined the organic alkalinity, Aorg, in water from the central Baltic Sea. The maximum Aorg measured in the surface mixed layer during the spring bloom was > 50 μmol/kg-SW but the Aorg decreased with depth and approached zero below the permanent halocline. This behavior could be attributed to the decreased pH of deeper water layers. The data were used to calculate the bulk dissociation constant, KDOM, for marine DOM and the fraction f of dissolved organic carbon (DOC) that acts as a carrier for acid-base functional groups. The p KDOM (7.27) agreed well with the value (7.34) previously estimated in a preliminary study of organic alkalinity in the Baltic Sea. The fraction of carbon atoms carrying acid-base groups was 17% and was somewhat higher than previously reported (12%). Spike experiments performed using artificial seawater and three different humic/fulvic substances tested whether the acid-base properties of these substances explain the results of our field study. Specifically, Aorg was determined at different concentrations (DOC) of the added humic/fulvic substances. The relationship between Aorg and the DOC concentrations indicated that humic/fulvic substances are more acidic (p KDOM < 6.5) than the bulk DOC natural occurring in the Baltic Sea.

  18. Low photolability of yedoma permafrost dissolved organic carbon

    NASA Astrophysics Data System (ADS)

    Stubbins, Aron; Mann, Paul J.; Powers, Leanne; Bittar, Thais B.; Dittmar, Thorsten; McIntyre, Cameron P.; Eglinton, Timothy I.; Zimov, Nikita; Spencer, Robert G. M.

    2017-01-01

    Vast stores of arctic permafrost carbon that have remained frozen for millennia are thawing, releasing ancient dissolved organic carbon (DOC) to arctic inland waters. Once in arctic waters, DOC can be converted to CO2 and emitted to the atmosphere, accelerating climate change. Sunlight-driven photoreactions oxidize DOC, converting a portion to CO2 and leaving behind a photomodified pool of dissolved organic matter (DOM). Samples from the Kolyma River, its tributaries, and streams draining thawing yedoma permafrost were collected. Irradiation experiments and radiocarbon dating were employed to assess the photolability of ancient permafrost-DOC in natural and laboratory generated samples containing a mix of modern and ancient DOC. Photolabile DOC was always modern, with no measurable photochemical loss of ancient permafrost-DOC. However, optical and ultrahigh resolution mass spectrometric measurements revealed that both modern river DOM and ancient permafrost-DOM were photomodified during the irradiations, converting aromatic compounds to less conjugated compounds. These findings suggest that although sunlight-driven photoreactions do not directly mineralize permafrost-DOC, photomodification of permafrost-DOM chemistry may influence its fate and ecological functions in aquatic systems.

  19. Global effects of agriculture on fluvial dissolved organic matter

    NASA Astrophysics Data System (ADS)

    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

    2015-11-01

    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.

  20. Contaminant-mediated photobleaching of wetland chromophoric dissolved organic matter.

    PubMed

    Langlois, Maureen C; Weavers, Linda K; Chin, Yu-Ping

    2014-09-20

    Photolytic transformation of organic contaminants in wetlands can be mediated by chromophoric dissolved organic matter (CDOM), which in turn can lose its reactivity from photobleaching. We collected water from a small agricultural wetland (Ohio), Kawai Nui Marsh (Hawaii), the Everglades (Florida), and Okefenokee Swamp (Georgia) to assess the effect of photobleaching on the photofate of two herbicides, acetochlor and isoproturon. Analyte-spiked water samples were irradiated using a solar simulator and monitored for changes in CDOM light absorbance and dissolved oxygen. Photobleaching did not significantly impact the indirect photolysis rates of either herbicide over 24 hours of irradiation. Surprisingly, the opposite effect was observed with isoproturon, which accelerated DOM photobleaching. This phenomenon was more pronounced in higher-CDOM waters, and we believe that the redox pathway between triplet-state CDOM and isoproturon may be responsible for our observations. By contrast, acetochlor indirect photolysis was dependent on reaction with the hydroxyl radical and did not accelerate photobleaching of wetland water as much as isoproturon. Finally, herbicide indirect photolysis rate constants did not correlate strongly to any one chemical or optical property of the sampled waters.

  1. 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.

  2. 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

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

    USGS Publications Warehouse

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

    2013-01-01

    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.

  4. Groundwater-transported dissolved organic nitrogen exports from coastal watersheds

    USGS Publications Warehouse

    Kroeger, K.D.; Cole, Marci L.; Valiela, I.

    2006-01-01

    We analyzed groundwater-transported nitrogen (N) exports from 41 watershed segments that comprised 10 Cape Cod, Massachusetts watersheds to test the hypotheses that chemical form of N exports is related to land use and to length of flow paths through watersheds. In the absence of human habitation, these glacial outwash-plain watersheds exported largely dissolved organic N (DON) but at relatively low annual rate. Addition of people to watersheds increased rates of both total dissolved N (TDN) and DON export through groundwater. Percent of TDN as DON in groundwater was negatively related to path length of groundwater through aquifers, but %DON was not significantly related to population density on the watersheds. DON was often the dominant form of N exported from the watersheds, even at high population densities. Our results suggest that natural sources are not entirely responsible for organic N exports from watersheds, but, instead, a substantial portion of anthropogenic N introduced to watersheds is exported as DON. This finding is in disagreement with previous results, which suggest that anthropogenic N is exported from watersheds largely as NO 3- and that DON exported from watersheds is from natural sources. ?? 2006, by the American Society of Limnology and Oceanography, Inc.

  5. 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.

  6. Carbon isotopic exchange between dissolved inorganic and organic carbon

    NASA Astrophysics Data System (ADS)

    Thomas, B.; Freeman, K. H.; House, C. H.; Arthur, M. A.

    2009-12-01

    The pools of inorganic and organic carbon are often considered to be separate and distinct. Isotopic exchange between the inorganic and organic carbon pools in natural waters is rarely considered plausible at low temperatures owing to kinetic barriers to exchange. In certain circumstances, however carboxyl carbon of dissolved organic matter (DOM) may be subject to exchange with the dissolved inorganic carbon (DIC) pool. We report results from an isotopic labeling experiment that resulted in rapid methanogen-catalyzed isotopic exchange between DIC and the carboxyl carbon of acetate. This exchange rapidly mixes the isotopic composition of the DIC pool into the dissolved organic carbon (DOC) acetate pool. This exchange is likely associated with the reversible nature of the carbon monoxide dehydrogenase enzyme. In nature, many decarboxylase enzymes are also reversible and some can be shown to facilitate similar exchange reactions. Those decarboxylase enzymes that are important in lignin decomposition and other organic carbon (OC) transformations may help to mask the isotopic composition of the precursor DOC with as much as 15% contribution from DIC. Though this dilution is unlikely to matter in soils where DOC and DIC are similar in composition, this exchange may be extremely important in systems where the stable or radioisotope composition of DOC and DIC differ significantly. As an example of the importance of this effect, we demonstrate that the stable and radiocarbon isotopic composition of fluvial DOC could be altered by mixing with marine DIC to produce a DOC composition similar to those observed in the deep marine DOC pool. We hypothesize that this exchange resolves the conundrum of apparently old (>5 kyr) marine-derived DOC. If most of the carboxyl carbon of pre-aged, terrestrial-derived DOC (15% of total carbon) is subject to exchange with marine DIC, the resulting carbon isotopic composition of deep DOC will be similar to that observed in deep marine studies

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

    PubMed

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

    2001-12-15

    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 wastewater-derived organic contaminants such as linear alkylbenzene sulfonate, caffeine, and ethylenediaminetetraacetic acid were significantly attenuated by wetland treatment and were not contributed by internal loading.

  8. 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.

  9. Aged black carbon identified in marine dissolved organic carbon

    NASA Astrophysics Data System (ADS)

    Ziolkowski, L. A.; Druffel, E. R. M.

    2010-08-01

    Produced on land by incomplete combustion of organic matter, black carbon (BC) enters the ocean by aerosol and river deposition. It has been postulated that BC resides in the marine dissolved organic carbon (DOC) pool before sedimentary deposition and may attribute to its great 14C age (1500-6500 14C years). Here we report the first radiocarbon measurements of BC in high molecular weight DOC (UDOM). BC exported from rivers is highly aromatic and <500 14C years old, while open ocean samples contain less aromatic BC and have an age of 18,000 ± 3,000 14C years. The low abundance of BC in UDOM (0.5-3.5%) suggests that it is more labile than presently believed and/or the low molecular weight DOC contains a larger proportion of aged BC.

  10. 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.

  11. 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...

  12. 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...

  13. Use of Passive Samplers to Measure Dissolved Organic Contaminants in a Temperate Estuary

    EPA Science Inventory

    Measuring dissolved concentrations of organic contaminants can be challenging given their low solubilities and high particle association. However, to perform accurate risk assessments of these chemicals, knowing the dissolved concentration is critical since it is considered to b...

  14. Use of Passive Samplers to Measure Dissolved Organic Contaminants in a Temperate Estuary

    EPA Science Inventory

    Measuring dissolved concentrations of organic contaminants can be challenging given their low solubilities and high particle association. However, to perform accurate risk assessments of these chemicals, knowing the dissolved concentration is critical since it is considered to b...

  15. 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.

  16. Optical Characterization of Dissolved Organic Matter in Maine Rivers

    NASA Astrophysics Data System (ADS)

    White, D. P.; Roesler, C. S.; Bourakovsky, A.; Drapeau, S.; Huntington, T. G.; Billmire, M.; Camill, P.

    2014-12-01

    The coastal waters of the Gulf of Maine are significantly impacted by the input of fresh water from a distributed river system. In this study, we focus on the four largest watersheds (Androscoggin, Kennebec, Penobscot and St. John) that contribute to the freshwater inputs. In particular, we investigated the input of dissolved organic carbon via PARAFAC analysis of excitation/emission matrix fluorescence spectroscopy. Monthly sampling of over 65 stations for three years has yielded a wealth of information about tributary characteristics. Specifically, we investigated the role of water quality properties and landscape coverage in the mobilization and flux of different components of DOC and how those properties vary spatially across the landscape and temporally over seasons and between years. Across all rivers, humic-like materials were the most prevalent components at the river mouths; accumulating along the rivers due to sequential tributary inputs. The concentration of humic-like materials increased latitudinally from the Androscoggin to St John, a geographic progression in source material also correlated to climate variations, land coverage or bedrock acidity. Dissolved proteins displayed positive relationships with climatological Chlorophyll a and total Nitrogen values. In all rivers, peak fluorescence of dissolved proteins was observed during summer months, with the maximum intensity observed in the Androscoggin River. The magnitude and pattern of seasonal flux of fluorescent materials into the Gulf of Maine was very similar between the Penobscot and the Kennebec rivers. The flux of all DOM components was highest during the spring freshet, with a secondary peak during fall precipitation maxima and lowest during August, likely due to both low mobilization and photo degradation of river borne materials.

  17. Improved automation of dissolved organic carbon sampling for organic-rich surface waters.

    PubMed

    Grayson, Richard P; Holden, Joseph

    2016-02-01

    In-situ UV-Vis spectrophotometers offer the potential for improved estimates of dissolved organic carbon (DOC) fluxes for organic-rich systems such as peatlands because they are able to sample and log DOC proxies automatically through time at low cost. In turn, this could enable improved total carbon budget estimates for peatlands. The ability of such instruments to accurately measure DOC depends on a number of factors, not least of which is how absorbance measurements relate to DOC and the environmental conditions. Here we test the ability of a S::can Spectro::lyser™ for measuring DOC in peatland streams with routinely high DOC concentrations. Through analysis of the spectral response data collected by the instrument we have been able to accurately measure DOC up to 66 mg L(-1), which is more than double the original upper calibration limit for this particular instrument. A linear regression modelling approach resulted in an accuracy >95%. The greatest accuracy was achieved when absorbance values for several different wavelengths were used at the same time in the model. However, an accuracy >90% was achieved using absorbance values for a single wavelength to predict DOC concentration. Our calculations indicated that, for organic-rich systems, in-situ measurement with a scanning spectrophotometer can improve fluvial DOC flux estimates by 6 to 8% compared with traditional sampling methods. Thus, our techniques pave the way for improved long-term carbon budget calculations from organic-rich systems such as peatlands.

  18. Effect of Dissolved Organic Matter on Basalt Weathering Rates under Flow Conditions

    NASA Astrophysics Data System (ADS)

    Dontsova, K.; Steefel, C. I.; Chorover, J. D.

    2009-12-01

    Rock weathering is an important aspect of soil formation that is tightly coupled to the progressive colonization of grain surfaces by microorganisms and plant tissue, both of which are associated with the exudation of complexing ligands and reducing equivalents that are incorporated into dissolved organic matter. As part of a larger hillslope experimental study being designed for Biosphere 2 (Oracle, AZ), we seek to determine how the presence and concentration of dissolved organic matter affects the incongruent dissolution rates of basaltic tuff. Saturated flow column experiments are being conducted using plant-derived soluble organic matter solutions of variable concentrations, and comparisons are being made to experiments conducted with malic acid, a low-molecular weight organic acid commonly exuded into the rhizosphere. Dissolved organic matter was extracted from Ponderosa Pine forest floor and was characterized for aqueous geochemical parameters (pH, EC, ion balance, DOC/TN) and also for DOC composition (UV-Vis, FTIR spectroscopy). Column effluents are being analyzed for major and trace cations, anions, silica and organic solutes. Dissolution rates of primary minerals and precipitation rates of secondary phases will be estimated by fitting the data to a numerical reactive transport model, CrunchFlow2007. At the end of the fluid flow experiment, column materials will be analyzed for biogeochemical composition to detect preferential dissolution of specific phases, the precipitation of new ones, and to monitor the associated formation of biofilms. The influence of organic solutions on weathering patterns of basalt will be discussed.

  19. Structuring of bacterioplankton communities by specific dissolved organic carbon compounds.

    PubMed

    Gómez-Consarnau, Laura; Lindh, Markus V; Gasol, Josep M; Pinhassi, Jarone

    2012-09-01

    The main role of microorganisms in the cycling of the bulk dissolved organic carbon pool in the ocean is well established. Nevertheless, it remains unclear if particular bacteria preferentially utilize specific carbon compounds and whether such compounds have the potential to shape bacterial community composition. Enrichment experiments in the Mediterranean Sea, Baltic Sea and the North Sea (Skagerrak) showed that different low-molecular-weight organic compounds, with a proven importance for the growth of marine bacteria (e.g. amino acids, glucose, dimethylsulphoniopropionate, acetate or pyruvate), in most cases differentially stimulated bacterial growth. Denaturing gradient gel electrophoresis 'fingerprints' and 16S rRNA gene sequencing revealed that some bacterial phylotypes that became abundant were highly specific to enrichment with specific carbon compounds (e.g. Acinetobacter sp. B1-A3 with acetate or Psychromonas sp. B3-U1 with glucose). In contrast, other phylotypes increased in relative abundance in response to enrichment with several, or all, of the investigated carbon compounds (e.g. Neptuniibacter sp. M2-A4 with acetate, pyruvate and dimethylsulphoniopropionate, and Thalassobacter sp. M3-A3 with pyruvate and amino acids). Furthermore, different carbon compounds triggered the development of unique combinations of dominant phylotypes in several of the experiments. These results suggest that bacteria differ substantially in their abilities to utilize specific carbon compounds, with some bacteria being specialists and others having a more generalist strategy. Thus, changes in the supply or composition of the dissolved organic carbon pool can act as selective forces structuring bacterioplankton communities.

  20. 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...

  1. 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...

  2. 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

  3. Adsorption of Compounds that Mimic Urban Stormwater Dissolved Organic Nitrogen.

    PubMed

    Mohtadi, Mehrdad; James, Bruce R; Davis, Allen P

    2017-02-01

      Stormwater runoff carrying nitrogen can accelerate eutrophication. Bioretention facilities are among low impact development systems which are commonly used to manage urban stormwater quality and quantity. They are, however, not designed to remove dissolved organic nitrogen (DON) and may become a net DON exporter. Adsorption of seven organic nitrogenous compounds onto several adsorbents was examined. Batch adsorption study revealed that coal activated carbon (AC) exhibited the best performance in adsorption of the selected organic nitrogenous compounds. The highest adsorption capacity of coal AC was 0.4 mg N/g for pyrrole at an equilibrium concentration of 0.02 mg N/L, while adsorption was not detectable for urea at the same equilibrium concentration. The fastest compound to reach equilibrium adsorption capacity onto the coal AC was pyrrole (1 hour). The adsorption capacity of the coal AC for pyrrole and N-acetyl-d-glucosamine and 1-hour contact time is recommended for designing bioretention systems targeting organic nitrogenous compounds.

  4. Climate Variability, Dissolved Organic Carbon, UV Exposure, and Amphibian Decline

    NASA Astrophysics Data System (ADS)

    Brooks, P. D.; O'Reilly, C. M.; Diamond, S.; Corn, S.; Muths, E.; Tonnessen, K.; Campbell, D. H.

    2001-12-01

    Increasing levels of UV radiation represent a potential threat to aquatic organisms in a wide range of environments, yet controls on in situ variability on UV exposure are relatively unknown. The primary control on the penetration of UV radiation in surface water environments is the amount of photoreactive dissolved organic carbon (DOC). Consequently, biogeochemical processes that control the cycling of DOC also affect the exposure of aquatic organisms to UV radiation. Three years of monitoring UV extinction and DOC composition in Rocky Mountain, Glacier, Sequoia/ Kings Canyon, and Olympic National Parks demonstrate that the amount of fulvic acid DOC is much more important than the total DOC pool in controlling UV attenuation. This photoreactive component of DOC originates primarily in soil, and is subject both to biogeochemical controls (e.g. temperature, moisture, vegetation, soil type) on production, and hydrologic controls on transport to surface water and consequently UV exposure to aquatic organisms. Both of these controls are positively related to precipitation with greater production and transport associated with higher precipitation amounts. For example, an approximately 20 percent reduction in precipitation from 1999 to 2000 resulted in a 27% - 59% reduction in the amount of photoreactive DOC at three sites in Rocky Mountain National Park. These differences in the amount of hydrophobic DOC result in an increase in UV exposure in the aquatic environment by a factor of 2 or more. Implications of these findings for observed patterns of amphibian decline will be discussed.

  5. Refractory dissolved organic nitrogen accumulation in high-elevation lakes.

    PubMed

    Goldberg, S J; Ball, G I; Allen, B C; Schladow, S G; Simpson, A J; Masoom, H; Soong, R; Graven, H D; Aluwihare, L I

    2015-02-23

    The role of dissolved organic matter (DOM) as either a sink for inorganic nutrients or an additional nutrient source is an often-neglected component of nutrient budgets in aquatic environments. Here, we examined the role of DOM in reactive nitrogen (N) storage in Sierra Nevada (California, USA) lakes where atmospheric deposition of N has shifted the lakes toward seasonal phosphorus (P)-limitation. Nuclear magnetic resonance (NMR) spectroscopy and isotope analyses performed on DOM isolated from Lake Tahoe reveal the accumulation of refractory proteinaceous material with a 100-200-year residence time. In contrast, smaller lakes in the same watershed contain DOM with typical terrestrial characteristics, indicating that proteins in Lake Tahoe are autochthonously produced. These data support the role of DOM as a possible sink for reactive N in these lake ecosystems and identify a potential role for DOM in affecting the inorganic nutrient stoichiometry of these environments.

  6. Dissolved Organic Carbon in the North Atlantic Meridional Overturning Circulation

    PubMed Central

    Fontela, Marcos; García-Ibáñez, Maribel I.; Hansell, Dennis A.; Mercier, Herlé; Pérez, Fiz F.

    2016-01-01

    The quantitative role of the Atlantic Meridional Overturning Circulation (AMOC) in dissolved organic carbon (DOC) export is evaluated by combining DOC measurements with observed water mass transports. In the eastern subpolar North Atlantic, both upper and lower limbs of the AMOC transport high-DOC waters. Deep water formation that connects the two limbs of the AMOC results in a high downward export of non-refractory DOC (197 Tg-C·yr−1). Subsequent remineralization in the lower limb of the AMOC, between subpolar and subtropical latitudes, consumes 72% of the DOC exported by the whole Atlantic Ocean. The contribution of DOC to the carbon sequestration in the North Atlantic Ocean (62 Tg-C·yr−1) is considerable and represents almost a third of the atmospheric CO2 uptake in the region. PMID:27240625

  7. Dissolved organic matter uptake by Trichodesmium in the Southwest Pacific

    PubMed Central

    Benavides, Mar; Berthelot, Hugo; Duhamel, Solange; Raimbault, Patrick; Bonnet, Sophie

    2017-01-01

    The globally distributed diazotroph Trichodesmium contributes importantly to nitrogen inputs in the oligotrophic oceans. Sites of dissolved organic matter (DOM) accumulation could promote the mixotrophic nutrition of Trichodesmium when inorganic nutrients are scarce. Nano-scale secondary ion mass spectrometry (nanoSIMS) analyses of individual trichomes sampled in the South Pacific Ocean, showed significant 13C-enrichments after incubation with either 13C-labeled carbohydrates or amino acids. These results suggest that DOM could be directly taken up by Trichodesmium or primarily consumed by heterotrophic epibiont bacteria that ultimately transfer reduced DOM compounds to their host trichomes. Although the addition of carbohydrates or amino acids did not significantly affect bulk N2 fixation rates, N2 fixation was enhanced by amino acids in individual colonies of Trichodesmium. We discuss the ecological advantages of DOM use by Trichodesmium as an alternative to autotrophic nutrition in oligotrophic open ocean waters. PMID:28117432

  8. Dissolved organic matter uptake by Trichodesmium in the Southwest Pacific

    NASA Astrophysics Data System (ADS)

    Benavides, Mar; Berthelot, Hugo; Duhamel, Solange; Raimbault, Patrick; Bonnet, Sophie

    2017-01-01

    The globally distributed diazotroph Trichodesmium contributes importantly to nitrogen inputs in the oligotrophic oceans. Sites of dissolved organic matter (DOM) accumulation could promote the mixotrophic nutrition of Trichodesmium when inorganic nutrients are scarce. Nano-scale secondary ion mass spectrometry (nanoSIMS) analyses of individual trichomes sampled in the South Pacific Ocean, showed significant 13C-enrichments after incubation with either 13C-labeled carbohydrates or amino acids. These results suggest that DOM could be directly taken up by Trichodesmium or primarily consumed by heterotrophic epibiont bacteria that ultimately transfer reduced DOM compounds to their host trichomes. Although the addition of carbohydrates or amino acids did not significantly affect bulk N2 fixation rates, N2 fixation was enhanced by amino acids in individual colonies of Trichodesmium. We discuss the ecological advantages of DOM use by Trichodesmium as an alternative to autotrophic nutrition in oligotrophic open ocean waters.

  9. 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+)). Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Dissolved organic carbon and its potential predictors in eutrophic lakes.

    PubMed

    Toming, Kaire; Kutser, Tiit; Tuvikene, Lea; Viik, Malle; Nõges, Tiina

    2016-10-01

    Understanding of the true role of lakes in the global carbon cycle requires reliable estimates of dissolved organic carbon (DOC) and there is a strong need to develop remote sensing methods for mapping lake carbon content at larger regional and global scales. Part of DOC is optically inactive. Therefore, lake DOC content cannot be mapped directly. The objectives of the current study were to estimate the relationships of DOC and other water and environmental variables in order to find the best proxy for remote sensing mapping of lake DOC. The Boosted Regression Trees approach was used to clarify in which relative proportions different water and environmental variables determine DOC. In a studied large and shallow eutrophic lake the concentrations of DOC and coloured dissolved organic matter (CDOM) were rather high while the seasonal and interannual variability of DOC concentrations was small. The relationships between DOC and other water and environmental variables varied seasonally and interannually and it was challenging to find proxies for describing seasonal cycle of DOC. Chlorophyll a (Chl a), total suspended matter and Secchi depth were correlated with DOC and therefore are possible proxies for remote sensing of seasonal changes of DOC in ice free period, while for long term interannual changes transparency-related variables are relevant as DOC proxies. CDOM did not appear to be a good predictor of the seasonality of DOC concentration in Lake Võrtsjärv since the CDOM-DOC coupling varied seasonally. However, combining the data from Võrtsjärv with the published data from six other eutrophic lakes in the world showed that CDOM was the most powerful predictor of DOC and can be used in remote sensing of DOC concentrations in eutrophic lakes. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Dissolved Organic Matter in the Yukon River Basin

    NASA Astrophysics Data System (ADS)

    Aiken, G.; Striegl, R.; Schuster, P.

    2004-12-01

    Source materials, watershed geochemistry, oxidative processes and hydrology exert strong influences on the nature and reactivity of dissolved organic matter (DOM) in aquatic systems. At present, a critical question in carbon cycling is how climate change could alter the fate and chemical nature of dissolved organic carbon (DOC) released from watersheds, particularly those underlain by permafrost, and transported to rivers, lakes, estuaries and coastal waters. The spatial and temporal variability of DOM in surface waters associated with the Yukon River are being studied to better define processes controlling DOM in this system. Like many northern ecosystems, the Yukon River Basin is experiencing melting permafrost, drying of upland soils and changing wetland environments. Study results indicate that the transport of DOM in the river and its major tributaries is strongly seasonally dependent. Specific ultraviolet absorbance (SUVA) data, an excellent indicator of aromatic carbon content of DOM, also indicate a large variation in the chemical nature of the organic matter transported by the river. Lowest DOC concentrations and SUVA values were observed for samples collected in the winter under low flow conditions and for tributaries dominated by ground water inputs. Greatest DOC concentrations and SUVA values were measured on samples collected during the spring on the leading part of the hydrograph. High SUVA values are indicative of greater amounts of organic material originating from higher plants that are present in upper soil horizons and wetlands of the watershed. Aquatic humic substances collected from the Yukon River during the snowmelt period were found to have low nitrogen contents and greater amounts of aromatic C relative to samples from other aquatic environments. Low N content and high aromaticity are indicative of humic substances evolved from higher plant sources with little alteration resulting from microbial degradation or soil interactions. In addition

  12. Characterization of dissolved organic carbon leached from a woodchip bioreactor.

    PubMed

    Abusallout, Ibrahim; Hua, Guanghui

    2017-09-01

    Woodchip bioreactors are increasingly being applied to remove nitrate from agricultural subsurface drainage. However, dissolved organic carbon (DOC) released from woodchips may negatively affect the aquatic ecosystems and drinking water supplies. The objective of this study was to evaluate the leaching characteristics, disinfection byproduct (DBP) formation potentials, and treatability of DOC derived from a laboratory woodchip bioreactor. Initial flush of woodchips resulted in the release of high organic content from woodchips. The DOC concentration in the bioreactor effluent decreased rapidly from 71.8 to 20.7 mg/L during the first week of operation, and then gradually decreased to 3.0 mg/L after 240 days of operation under a hydraulic retention time of 24 h. A recycled steel chip filter removed an average of 44.2% of the DOC in the bioreactor effluent. Hydrophobic carbons and organic compounds with molecular weight of 10-100 KDa were the most abundant organic fractions in the DOC released from woodchips. These two DOC fractions were also the most important precursors to the formation of total organic halogen (TOX) during chlorination and chloramination. The TOX yields of woodchip DOC were similar to those of Suwannee River Fulvic Acid, suggesting that organic compounds released from woodchips have great potentials for DBP formation. Alum and polyaluminium chloride were more effective at removing woodchip DOC than ferric chloride during coagulation. Drinking water treatment plants may need to adjust coagulant types and doses in order to remove woodchip DOC in the source water to reduce the DBP formation potential. Published by Elsevier Ltd.

  13. Effects of Dissolved Organic Matter Source on Wetland Bacterial Metabolism

    NASA Astrophysics Data System (ADS)

    Ward, A. K.

    2005-05-01

    Wetlands are rich environments for organic matter production from a variety of wetland plant types. Investigations of the Talladega Wetland Ecosystem (TWE) in the southeastern U.S. show that bacterioplankton productivity is driven by dissolved organic carbon derived from wetland plants. The TWE is formed from a small coastal plain stream that has been dammed by beaver activity and resides in a forested catchment. In this study, bacterioplankton communities sampled from the wetland were amended with leachate from two different plants common in the TWE, the soft rush, Juncus effusus, and hazel alder, Alnus serrulata, and compared to unamended controls. The bacterioplankton response was examined by measuring bacterial carbon productivity and by an array of fluorescent microscope techniques used to distinguish metabolically active and non-active cells. Both plant leachates elicited rapid and significant increases in productivity and numbers of metabolically active bacterial cells. However, the timeframe of response, the magnitude of response, and the bacterial morphotypes varied depending on the leachate source. This study suggests that wetland bacterial communities contain different sub-component populations that may generally occur in low numbers, but that can adapt and respond rapidly to different sources of organic matter native to the wetland.

  14. 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

  15. Abiotic Addition of Sulfide to Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Poulin, B. A.; Ryan, J. N.; Nagy, K.; Stubbins, A.; Dittmar, T.; Aiken, G.

    2016-02-01

    Sulfur-containing functional groups in dissolved organic matter (DOM) play important roles in controlling the chemical speciation and geochemistry of trace metals in surface waters, wetland soils, and pore waters. The abiotic addition of sulfide to DOM is recognized as an important mechanism responsible for the elevated concentration of sulfur and high relative abundance of reduced sulfur groups in DOM. Despite these observations, there is little experimental information on the organic molecules that sulfur incorporates into and the speciation of the incorporated sulfur. We present results from laboratory and field efforts that characterize changes in organic sulfur chemistry under sulfidic conditions. In the laboratory, Suwannee River hydrophobic organic acid (HPOA) was reacted with sulfide at an environmentally relevant sulfide-to-DOM concentration ratio (0.06 mol S2-(mol C)-1). Elemental composition and sulfur K-edge X-ray absorption near-edge structure (XANES) spectra of Suwannee River samples show a 55% molar increase in reduced sulfur accompanied by a shift in reduced sulfur speciation from primarily heterocyclic (75% of reduced S) to predominantly exocyclic (90% of reduced S) following sulfide exposure. An analysis of samples by Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) reveals an increase in molecular formula assignments with sulfur heteroatoms (e.g., CHOS, CHONS) likely due to reactions with sulfide. For the field component, the HPOA fraction of DOM was isolated from surface and pore water samples collected from four locations across a sulfate gradient in the Florida Everglades. Elemental composition and FTICR-MS spectra of DOM samples show that the (1) organic sulfur content and (2) percentage of molecular formula assignments containing sulfur heteroatoms correspond with the aqueous sulfide concentration. The results provide insight into the alteration of DOM in sulfidic environments and its implications for sulfur cycling.

  16. Association of Dissolved Mercury with Dissolved Organic Carbon in Rivers and Streams: The Role of Watershed Soil Organic Carbon

    NASA Astrophysics Data System (ADS)

    Stoken, O.; Riscassi, A.; Scanlon, T. M.

    2014-12-01

    Surface waters are an important pathway for the transport of atmospherically deposited mercury (Hg) from terrestrial watersheds. Dissolved Hg (HgD) is thought to be more bioavailable than particulate Hg and has been found to be strongly correlated with dissolved organic carbon (DOC) in numerous watersheds. The ratio of HgD to DOC is highly variable from site to site, which we hypothesize is strongly dependent on local environmental factors such as atmospheric deposition and soil organic carbon (SOC). Sixteen watersheds throughout the United States were used in this study to determine the relationship between the ratio of HgD:DOC, Hg wet deposition, and SOC. The Soil Survey Geographic database (SSURGO) and Northern Circumpolar Soil Carbon Database (NCSCD) were used to determine SOC values while HgD:DOC values were obtained from previous studies. Hg wet deposition was reported by the Mercury Deposition Network. There was no correlation found between atmospheric mercury wet deposition and HgD:DOC (r2 = 0.04; p = 0.44) but SOC was able to explain about 71% of the variation in the HgD:DOC ratio (r2 = 0.71; p < 0.01). A mathematical framework was developed to explain the power-law relationship between SOC and HgD:DOC based on soil carbon pools. The framework infers that the amount of Hg adsorbed to SOC does not increase in proportion to SOC at high SOC levels and points towards a Hg supply limitation for adsorption to soils with relatively deep carbon pools. Overall, this study identifies SOC as a first-order control on the association of HgD and DOC and indicates that globally available SOC datasets can be utilized to predict Hg transport in stream systems.

  17. Changes in dissolved organic matter during stream drying and rewetting

    NASA Astrophysics Data System (ADS)

    von Schiller, D.; Acuña, V.; Graeber, D.; Martí, E.; Ribot, M.; Sabater, S.; Timoner, X.; Tockner, K.

    2012-04-01

    Dissolved organic matter (DOM) is a complex mixture of organic compounds, which represents an essential source of carbon (C) and nutrients in aquatic ecosystems. In addition, DOM can play a key ecological role by modifying the optical properties of waters, mediating the availability of metals and influencing trophic food web structure. While the effects of drying and rewetting on DOM dynamics in terrestrial soils is a well studied subject, less is known about its effects in aquatic ecosystems, especially in streams. This is an important gap of knowledge since temporary streams that naturally cease to flow are found worldwide. Moreover, many streams with perennial flow are currently facing flow intermittency due to the effects of water extraction or changes in land-use and climate. The aim of this study was to evaluate the effects of stream flow intermittency on the spatial and temporal variability of DOM. The study was performed in a 300-m long reach of the Fuirosos stream (Catalonia, NE Spain) during the drying (June to July) and rewetting (October to November) phases. We sampled at several points along the study reach every 3 to 4 days. We assessed DOM amount by measuring the concentration of dissolved organic C and nitrogen (N). We characterized DOM composition using spectroscopic measurements, size-exclusion chromatography and C:N stoichiometry. Results showed two markedly distinct biogeochemical shifts between the drying and the rewetting phases. During the transition from continuous to fragmented flow we observed an increase in the magnitude and spatial variability of DOM concentrations and DOM was dominated by compounds from aquatic origin. After flow recovery, we also observed a pronounced increase in DOM concentration, but during this hydrologic phase DOM was dominated by compounds of terrestrial origin. Taken together, these results emphasize the relevance of flow intermittency in regulating stream DOM dynamics not only in terms of its availability but

  18. 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.

  19. 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...

  20. 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...

  1. Influence of dissolved organic matter on the complexation of mercury under sulfidic conditions.

    PubMed

    Miller, Carrie L; Mason, Robert P; Gilmour, Cynthia C; Heyes, Andrew

    2007-04-01

    The complexation of Hg under sulfidic conditions influences its bioavailability for microbial methylation. Neutral dissolved Hg-sulfide complexes are readily available to Hg-methylating bacteria in culture, and thermodynamic models predict that inorganic Hg-sulfide complexes dominate dissolved Hg speciation under natural sulfidic conditions. However, these models have not been validated in the field. To examine the complexation of Hg in natural sulfidic waters, octanol/water partitioning methods were modified for use under environmentally relevant conditions, and a centrifuge ultrafiltration technique was developed. These techniques demonstrated much lower concentrations of dissolved Hg-sulfide complexes than predicted. Furthermore, the study revealed an interaction between Hg, dissolved organic matter (DOM), and sulfide that is not captured by current thermodynamic models. Whereas Hg forms strong complexes with DOM under oxic conditions, these complexes had not been expected to form in the presence of sulfide because of the stronger affinity of Hg for sulfide relative to its affinity for DOM. The observed interaction between Hg and DOM in the presence of sulfide likely involves the formation of a DOM-Hg-sulfide complex or results from the hydrophobic partitioning of neutral Hg-sulfide complexes into the higher-molecular-weight DOM. An understanding of the mechanism of this interaction and determination of complexation coefficients for the Hg-sulfide-DOM complex are needed to adequately assess how our new finding affects Hg bioavailability, sorption, and flux.

  2. Relationships between Nitrate and Dissolved Organic Nitrogen and Watershed Characteristics in a Rural Temperate Basin

    NASA Astrophysics Data System (ADS)

    Daley, M. L.; McDowell, W. H.

    2002-05-01

    Global models have been developed to predict nitrate export, a main component of dissolved inorganic nitrogen (DIN) export, based on human population density and human activity. Controls on dissolved organic nitrogen (DON) export are largely unknown. We tested several global nitrate models and examined potential sources of riverine DON in the Lamprey River basin (479 km2) located in rural southeastern New Hampshire, and 11 of its sub-catchments. Dissolved organic nitrogen dominated total N export. Export of nitrate and DON from the Lamprey was 0.53 and 1.28 kg/ha/yr respectively. Mean annual nitrate and DON concentration in the Lamprey was 0.11 and 0.30 mg/L respectively. The global nitrate models over predicted (>200% difference) nitrate export for the Lamprey and all its sub-catchments except for the smallest most populated catchment. Population density (R2>0.89, p<0.00001) and riparian percentage agriculture (R2>0.90, p<0.00001) showed strong positive relationships with nitrate concentration and export. Dissolved organic nitrogen was not related to factors that control inorganic nitrogen (human population density or percentage agriculture). Non-purgeable organic carbon (NPOC) concentration and export (R2>0.84, p<0.0001), percentage wetland (R2=0.79, p<0.001) and riparian carbon storage (R2=0.84, p<0.0001) all showed strong positive relationships with DON. We conclude from the results of this study that human population density and activity are the main factors controlling DIN export and that wetlands and riparian soils are main sources of DON.

  3. Data-based mechanistic modeling of dissolved organic carbon load through storms using continuous 15-minute resolution observations within UK upland watersheds

    NASA Astrophysics Data System (ADS)

    Jones, T.; Chappell, N. A.

    2013-12-01

    Few watershed modeling studies have addressed DOC dynamics through storm hydrographs (notable exceptions include Boyer et al., 1997 Hydrol Process; Jutras et al., 2011 Ecol Model; Xu et al., 2012 Water Resour Res). In part this has been a consequence of an incomplete understanding of the biogeochemical processes leading to DOC export to streams (Neff & Asner, 2001, Ecosystems) & an insufficient frequency of DOC monitoring to capture sometimes complex time-varying relationships between DOC & storm hydrographs (Kirchner et al., 2004, Hydrol Process). We present the results of a new & ongoing UK study that integrates two components - 1/ New observations of DOC concentrations (& derived load) continuously monitored at 15 minute intervals through multiple seasons for replicated watersheds; & 2/ A dynamic modeling technique that is able to quantify storage-decay effects, plus hysteretic, nonlinear, lagged & non-stationary relationships between DOC & controlling variables (including rainfall, streamflow, temperature & specific biogeochemical variables e.g., pH, nitrate). DOC concentration is being monitored continuously using the latest generation of UV spectrophotometers (i.e. S::CAN spectro::lysers) with in situ calibrations to laboratory analyzed DOC. The controlling variables are recorded simultaneously at the same stream stations. The watersheds selected for study are among the most intensively studied basins in the UK uplands, namely the Plynlimon & Llyn Brianne experimental basins. All contain areas of organic soils, with three having improved grasslands & three conifer afforested. The dynamic response characteristics (DRCs) that describe detailed DOC behaviour through sequences of storms are simulated using the latest identification routines for continuous time transfer function (CT-TF) models within the Matlab-based CAPTAIN toolbox (some incorporating nonlinear components). To our knowledge this is the first application of CT-TFs to modelling DOC processes

  4. Photolytic processing of secondary organic aerosols dissolved in cloud droplets.

    PubMed

    Bateman, Adam P; Nizkorodov, Sergey A; Laskin, Julia; Laskin, Alexander

    2011-07-14

    The effect of UV irradiation on the molecular composition of aqueous extracts of secondary organic aerosol (SOA) was investigated. SOA was prepared by the dark reaction of ozone and d-limonene at 0.05-1 ppm precursor concentrations and collected with a particle-into-liquid sampler (PILS). The PILS extracts were photolyzed by 300-400 nm radiation for up to 24 h. Water-soluble SOA constituents were analyzed using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) at different stages of photolysis for all SOA precursor concentrations. Exposure to UV radiation increased the average O/C ratio and decreased the average double bond equivalent (DBE) of the dissolved SOA compounds. Oligomeric compounds were significantly decreased by photolysis relative to the monomeric compounds. Direct pH measurements showed that acidic compounds increased in abundance upon photolysis. Methanol reactivity analysis revealed significant photodissociation of molecules containing carbonyl groups and the formation of carboxylic acids. Aldehydes, such as limononaldehyde, were almost completely removed. The removal of carbonyls was further confirmed by the UV/Vis absorption spectroscopy of the SOA extracts where the absorbance in the carbonyl n→π* band decreased significantly upon photolysis. The effective quantum yield (the number of carbonyls destroyed per photon absorbed) was estimated as ∼0.03. The total concentration of peroxides did not change significantly during photolysis as quantified with an iodometric test. Although organic peroxides were photolyzed, the likely end products of photolysis were smaller peroxides, including hydrogen peroxide, resulting in a no net change in the peroxide content. Photolysis of dry limonene SOA deposited on substrates was investigated in a separate set of experiments. The observed effects on the average O/C and DBE were similar to the aqueous photolysis, but the extent of chemical change was smaller in dry SOA. Our results suggest

  5. 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

  6. The soil organic carbon content of anthropogenically altered organic soils effects the dissolved organic matter quality, but not the dissolved organic carbon concentrations

    NASA Astrophysics Data System (ADS)

    Frank, Stefan; Tiemeyer, Bärbel; Bechtold, Michel; Lücke, Andreas; Bol, Roland

    2016-04-01

    Dissolved organic carbon (DOC) is an important link between terrestrial and aquatic ecosystems. This is especially true for peatlands which usually show high concentrations of DOC due to the high stocks of soil organic carbon (SOC). Most previous studies found that DOC concentrations in the soil solution depend on the SOC content. Thus, one would expect low DOC concentrations in peatlands which have anthropogenically been altered by mixing with sand. Here, we want to show the effect of SOC and groundwater level on the quantity and quality of the dissolved organic matter (DOM). Three sampling sites were installed in a strongly disturbed bog. Two sites differ in SOC (Site A: 48%, Site B: 9%) but show the same mean annual groundwater level of 15 and 18 cm below ground, respectively. The SOC content of site C (11%) is similar to Site B, but the groundwater level is much lower (-31 cm) than at the other two sites. All sites have a similar depth of the organic horizon (30 cm) and the same land-use (low-intensity sheep grazing). Over two years, the soil solution was sampled bi-weekly in three depths (15, 30 and 60 cm) and three replicates. All samples were analyzed for DOC and selected samples for dissolved organic nitrogen (DON) and delta-13C and delta-15N. Despite differences in SOC and groundwater level, DOC concentrations did not differ significantly (A: 192 ± 62 mg/L, B: 163 ± 55 mg/L and C: 191 ± 97 mg/L). At all sites, DOC concentrations exceed typical values for peatlands by far and emphasize the relevance even of strongly disturbed organic soils for DOC losses. Individual DOC concentrations were controlled by the temperature and the groundwater level over the preceding weeks. Differences in DOM quality were clearer. At site B with a low SOC content, the DOC:DON ratio of the soil solution equals the soil's C:N ratio, but the DOC:DON ratio is much higher than the C:N ratio at site A. In all cases, the DOC:DON ratio strongly correlates with delta-13C. There is no

  7. Study of fouling and scaling in capacitive deionisation by using dissolved organic and inorganic salts.

    PubMed

    Mossad, Mohamed; Zou, Linda

    2013-01-15

    In this work, fouling, scaling and cleaning of the capacitive deionisation (CDI) with activated carbon electrodes were systematically investigated for the first time. Electrode fouling caused by dissolved organic matter using sodium salt of humic acid as a model foulant (measured by total organic carbon concentration, TOC) and inorganic salt (NaCl, MgCl(2), CaCl(2) and FeCl(3)) in the CDI feed solutions was investigated in a series of controlled fouling experiments. After each CDI experiment, a series of cleaning steps was performed to understand the reversibility of fouling accumulated on the electrode surface by analysing the cleaning solutions. The higher the TOC concentration in the CDI feed solution, the more the reduction of salt removal efficiency, declination in the production rate and energy consumption. Dissolved organic matter is the main cause of electrode fouling, as it blocks the activated carbon pores and reduces their electrosorption capacitance. Ca and Mg have no noticeable effect on the CDI treatment performance. However, Fe seemed to have a greater effect on CDI electrode fouling. Alkaline and acid cleaning solutions were able to restore the recovery of the CDI performance from fouling. Pre-treatment to reduce the dissolved organic matter levels is recommended to achieve sustainable treatment performance. Copyright © 2012 Elsevier B.V. All rights reserved.

  8. Towards an understanding of feedbacks between plant productivity, acidity and dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Rowe, Ed; Tipping, Ed; Davies, Jessica; Monteith, Don; Evans, Chris

    2014-05-01

    The recent origin of much dissolved organic carbon (DOC) (Tipping et al., 2010) implies that plant productivity is a major control on DOC fluxes. However, the flocculation, sorption and release of potentially-dissolved organic matter are governed by pH, and widespread increases in DOC concentrations observed in northern temperate freshwater systems seem to be primarily related to recovery from acidification (Monteith et al., 2007). We explore the relative importance of changes in productivity and pH using a model, MADOC, that incorporates both these effects (Rowe et al., 2014). The feedback whereby DOC affects pH is included. The model uses an annual timestep and relatively simple flow-routing, yet reproduces observed changes in DOC flux and pH in experimental (Evans et al., 2012) and survey data. However, the first version of the model probably over-estimated responses of plant productivity to nitrogen (N) deposition in upland semi-natural ecosystems. There is a strong case that plant productivity is an important regulator of DOC fluxes, and theoretical reasons for suspecting widespread productivity increases in recent years due not only to N deposition but to temperature and increased atmospheric CO2 concentrations. However, evidence that productivity has increased in upland semi-natural ecosystems is sparse, and few studies have assessed the major limitations to productivity in these habitats. In systems where phosphorus (P) limitation prevails, or which are co-limited, productivity responses to anthropogenic drivers will be limited. We present a revised version of the model that incorporates P cycling and appears to represent productivity responses to atmospheric N pollution more realistically. Over the long term, relatively small fluxes of nutrient elements into and out of ecosystems can profoundly affect productivity and the accumulation of organic matter. Dissolved organic N (DON) is less easily intercepted by plants and microbes than mineral N, and DON

  9. A Predictable Terrestrial Signature to Riverine Dissolved Organic Carbon?

    NASA Astrophysics Data System (ADS)

    Sanderman, J.; Amundson, R.; Baldock, J. A.

    2007-12-01

    In small mountainous watersheds, the majority of dissolved organic carbon (DOC) is derived from terrigenous sources; however, there is much debate over the age and recalcitrance of these organic materials. To determine controls on the age and recalcitrance of DOC found in stream waters, we measured DOC composition in stream and soil water samples, using isotopic (13C and 14C) and spectroscopic (UV and 13C NMR) analyses, in conjunction with soil hydrometric conditions in two first-order watersheds with contrasting vegetation in northern California. In a low-gradient coastal prairie stream, we found low concentrations of old (Δ14C = -200 permil) DOC that most resembled stabilized soil organic matter found deep within the mineral soil during baseflow. In contrast, during storm events where saturation overland flow dominated runoff, we found high concentrations of young (Δ14C = +75 permil) DOC resembling fresher organic matter. These results contrast with observations from a high-gradient coniferous forest where there is a much narrower range in age and chemistry of stream DOC over time. In the forest, runoff generation is dominated by subsurface stormflow with little if any overland flow and there is a much narrower range of stream DOC concentration, age and chemistry DOC, all of which is comparable to that of older, stabilized soil organic matter. At both of these locations DOC in soil water varies with increasing depth: young to old and labile to recalcitrant - due to rapid exchange with surficially-bound organic matter on soil solids. Given this range in soil DOC properties, it appears that the flowpath of water through soils determines the age and composition of DOC as water enters the stream network. During throughflow conditions, the soil acts as a filter for fresh plant-derived DOC, releasing only aged and highly altered DOC to the stream. Shallow flowpaths will largely bypass this filter, resulting in the export of high concentrations of young and labile DOC

  10. Analysis of spatial distribution characteristics of dissolved organic matter in typical greenhouse soil of northern China using three dimensional fluorescence spectra technique and parallel factor analysis model.

    PubMed

    Pan, Hong-wei; Lei, Hong-jun; Han, Yu-ping; Xi, Bei-dou; He, Xiao-song; Xu, Qi-gong; Li, Dan

    2014-06-01

    The aim of the present work is to study the soil DOM characteristics in the vegetable greenhouse with a long-term of cultivation. Results showed that the soil DOM mainly consisted of three components, fulvic acid-like (C1), humic acid-like (C2) and protein-like (C3), with C1 as the majority one. The distribution of DOM in space was also studied. In vertical direction, C1 and C2 decreased significantly with the increase in soil depth, while C3 component decreased after increased. The humification coefficient decreased fast from 0-20 to 30-40 cm, and then increased from 30-40 to 40-50 cm. In the horizontal direction, the level of C2 component varied greatly in space, while that of C1 component changed little, and that of C3 component fell in between the above two. The change in the humification degree of each soil layer significantly varied spatially. Humification process of soil organic matter mainly occurred in the surface soil layer. In addition, the humification degree in space also changed significantly. The new ideas of this study are: (1) Analyze the composition and spatial heterogeneity of soil DOM in the vegetable greenhouse; (2) Use three dimensional fluorescence spectra technology and parallel factor analysis model successfully to quantify the components of soil DOM, which provides a new method for the soil DOM analysis.

  11. 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

  12. 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.

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

    NASA Technical Reports Server (NTRS)

    Mannino, Antonio; Harvey, H. Rodger

    2003-01-01

    Black carbon (BC) in ultrafiltered high-molecular-weight DOM (UDOM) was measured in surface waters of Delaware Bay, Chesapeake Bay and the adjacent Atlantic Ocean (USA) to ascertain the importance of riverine and estuarine DOM as a source of BC to the ocean. BC comprised 5-72% of UDOM-C (27+/-l7%) and on average 8.9+/-6.5% of dissolved organic carbon (DOC) with higher values in the turbid region of the Delaware Estuary and lower yields in the river and coastal ocean. The spatial and seasonal distributions of BC along the salinity gradient of Delaware Bay suggest that the higher levels of BC in surface water UDOM originated from localized sources, possibly from atmospheric deposition or released from resuspended sediments. Black carbon comprised 4 to 7% of the DOC in the coastal Atlantic Ocean, revealing that river-estuary systems are important exporters of colloidal BC to the ocean. The annual flux of BC from Delaware Bay UDOM to the Atlantic Ocean was estimated at 2.4x10(exp 10) g BC yr(exp -1). The global river flux of BC through DOM to the ocean could be on the order of 5.5x1O(exp 12)g BC yr (exp -1). These results support the hypothesis that the DOC pool is the intermediate reservoir in which BC ages prior to sedimentary deposition.

  14. Hidden cycle of dissolved organic carbon in the deep ocean.

    PubMed

    Follett, Christopher L; Repeta, Daniel J; Rothman, Daniel H; Xu, Li; Santinelli, Chiara

    2014-11-25

    Marine dissolved organic carbon (DOC) is a large (660 Pg C) reactive carbon reservoir that mediates the oceanic microbial food web and interacts with climate on both short and long timescales. Carbon isotopic content provides information on the DOC source via δ(13)C and age via Δ(14)C. Bulk isotope measurements suggest a microbially sourced DOC reservoir with two distinct components of differing radiocarbon age. However, such measurements cannot determine internal dynamics and fluxes. Here we analyze serial oxidation experiments to quantify the isotopic diversity of DOC at an oligotrophic site in the central Pacific Ocean. Our results show diversity in both stable and radio isotopes at all depths, confirming DOC cycling hidden within bulk analyses. We confirm the presence of isotopically enriched, modern DOC cocycling with an isotopically depleted older fraction in the upper ocean. However, our results show that up to 30% of the deep DOC reservoir is modern and supported by a 1 Pg/y carbon flux, which is 10 times higher than inferred from bulk isotope measurements. Isotopically depleted material turns over at an apparent time scale of 30,000 y, which is far slower than indicated by bulk isotope measurements. These results are consistent with global DOC measurements and explain both the fluctuations in deep DOC concentration and the anomalous radiocarbon values of DOC in the Southern Ocean. Collectively these results provide an unprecedented view of the ways in which DOC moves through the marine carbon cycle.

  15. Hidden cycle of dissolved organic carbon in the deep ocean

    PubMed Central

    Follett, Christopher L.; Repeta, Daniel J.; Rothman, Daniel H.; Xu, Li; Santinelli, Chiara

    2014-01-01

    Marine dissolved organic carbon (DOC) is a large (660 Pg C) reactive carbon reservoir that mediates the oceanic microbial food web and interacts with climate on both short and long timescales. Carbon isotopic content provides information on the DOC source via δ13C and age via Δ14C. Bulk isotope measurements suggest a microbially sourced DOC reservoir with two distinct components of differing radiocarbon age. However, such measurements cannot determine internal dynamics and fluxes. Here we analyze serial oxidation experiments to quantify the isotopic diversity of DOC at an oligotrophic site in the central Pacific Ocean. Our results show diversity in both stable and radio isotopes at all depths, confirming DOC cycling hidden within bulk analyses. We confirm the presence of isotopically enriched, modern DOC cocycling with an isotopically depleted older fraction in the upper ocean. However, our results show that up to 30% of the deep DOC reservoir is modern and supported by a 1 Pg/y carbon flux, which is 10 times higher than inferred from bulk isotope measurements. Isotopically depleted material turns over at an apparent time scale of 30,000 y, which is far slower than indicated by bulk isotope measurements. These results are consistent with global DOC measurements and explain both the fluctuations in deep DOC concentration and the anomalous radiocarbon values of DOC in the Southern Ocean. Collectively these results provide an unprecedented view of the ways in which DOC moves through the marine carbon cycle. PMID:25385632

  16. Light-mediated release of dissolved organic carbon by phytoplankton

    NASA Astrophysics Data System (ADS)

    Cherrier, Jennifer; Valentine, SarahKeith; Hamill, Barbara; Jeffrey, Wade H.; Marra, John F.

    2015-07-01

    Laboratory and field studies were carried out to examine the effects of irradiance variability on dissolved organic carbon (DOC) extracellular release by phytoplankton (ER) and the response of natural bacteria assemblages. In axenic laboratory cultures, ER was 3× greater in cultures shifted to 330 μmol photons m-2 s-1 compared to cultures kept at their cultured irradiance, 110 μmol photons m-2 s-1. Natural bacterial assemblages incubated in the dark for 24 h in algal-free culture filtrate generated from both light treatments consumed the DOC from the high-light treatment at a faster rate than that for the low-light treatment. Field measurements in the coastal waters of the northeastern Gulf of Mexico (GOM) and the Eastern North Pacific (ENP) mirrored the laboratory findings, with short-term increases in DOC concentrations occurring concurrently with short-term increases in irradiance, followed by rapid consumption by bacteria. Where no diurnal irradiance increase was observed (overcast skies), no increase in DOC concentration was observed. An experiment using 14C as a tracer for plankton interactions (GOM) was consistent with data on bulk DOC concentrations. For all the field measurements, the rate of irradiance change was correlated with the quantity of DOC released. Collectively these results indicated that release of DOC by phytoplankton populations as a function of incident irradiance can be significant and may have important implications for estimates of ocean carbon flux.

  17. 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.

  18. 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.

  19. Photolytic processing of secondary organic aerosols dissolved in cloud droplets

    SciTech Connect

    Bateman, Adam P; Nizkorodov, Serguei; Laskin, Julia; Laskin, Alexander

    2011-05-26

    The effect of UV irradiation on the molecular composition of aqueous extracts of secondary organic aerosol (SOA) was investigated. SOA was prepared by the dark reaction of ozone and d-limonene at 0.05 - 1 ppm precursor concentrations and collected with a particle-into-liquid sampler (PILS). The PILS extracts were photolyzed by 300 - 400 nm radiation for up to 24 hours. Water-soluble SOA constituents were analyzed using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) at different stages of photolysis for all SOA precursor concentrations. Exposure to UV radiation increased the average O/C ratio and decreased the average double bond equivalent (DBE) of the dissolved SOA compounds. Oligomeric compounds were significantly reduced by photolysis relative to the monomeric compounds. Direct pH measurements showed that compounds containing carboxylic acids increased upon photolysis. Methanol reactivity analysis revealed significant photodissociation of molecules containing carbonyl groups and formation of carboxylic acids. Aldehydes, such as limononaldehyde, were almost completely removed. The removal of carbonylswas confirmed by the UV-Vis absorption spectroscopy of the SOA extracts where the absorbance in the carbonyl n→π* band decreased significantly upon photolysis. The effective quantum yield (the number of carbonyls destroyed per photon absorbed) was estimated as ~ 0.03. The concentration of peroxides did not change significantly during photolysis as quantified with an iodometric test. Although organic peroxides were photolyzed, the likely end products of photolysis were smaller peroxides, including hydrogen peroxide, resulting in a no net change in the peroxide content.

  20. Ocean Warming–Acidification Synergism Undermines Dissolved Organic Matter Assembly

    PubMed Central

    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

  1. 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.

  2. Fluxes of dissolved organic carbon from Chesapeake Bay sediments

    SciTech Connect

    Burdige, D.J.; Homstead, J. )

    1994-08-01

    Benthic fluxes of dissolved organic carbon (DOC) were measured over an annual cycle at two contrasting sites in Chesapeake Bay. At an organic-rich, sulfidic site in the mesohaline portion of the Bay (site M) DOC fluxes from the sediments ranged from 1.4 to 2.9 mmol/m[sup 2]/d. Measured benthic DOC fluxes at site M corresponded to [approximately]3-13% of the depth-integrated benthic C remineralization rates ([Sigma]OCR), and agreed well with calculated diffusive DOC fluxes based on porewater DOC profiles. This agreement suggests that DOC fluxes from site M sediments were likely controlled by molecular diffusion. The second site that was studied is a heavily bioturbated site in the southern Bay (site S). The activity of macrobenthos did not appear to enhance DOC fluxes from these sediments, since measured benthic DOC fluxes (>0.5 mmol/m[sup 2]/d) were lower than those at site M. The ratios of benthic DOC fluxes to [Sigma]OCR values at site S were also slightly smaller than those observed at site M. Benthic DOC fluxes from Chesapeake Bay sediments do not appear to significantly affect the transport of DOC through this estuary, although uncertainties in the reactivity of DOC in estuaries makes this conclusion somewhat tentative at this time. However, when these results are used to make a lower limit estimate of the globally integrated benthic DOC flux from marine sediments, a value similar to that previously calculated by Burdige et al. is obtained. This observation further supports suggestions in this paper about the importance of benthic DOC fluxes in the oceanic C cycle.

  3. Dissolved Organic Carbon In Precipitation At A Coastal Rural Site

    NASA Astrophysics Data System (ADS)

    Liptzin, D.; Daley, M.; Sive, B. C.; Talbot, R. W.; McDowell, W. H.

    2013-12-01

    Dissolved organic carbon (DOC) is a ubiquitous component of precipitation. This DOC is a complex mixture of compounds from biogenic and anthropogenic sources. The amount and chemistry of the DOC in precipitation has been studied for a variety of reasons: as a source of acidity, as a source of C to marine and terrestrial ecosystems, or to track the fate of individual compounds or pollutants. In most cases, past studies have focused on particular compounds or a limited number of precipitation events. Very little is known about the temporal trends in DOC or the relationship between DOC and other constituents of precipitation. We collected precipitation events for more than five years at a rural coastal site in New Hampshire. We evaluated the seasonal patterns and compared the DOC concentrations to other typical measures of the wet atmospheric deposition (ammonium, nitrate, sulfate, and chloride). In addition, we compared the DOC in precipitation to the concentrations of various organic constituents of the atmosphere. The volume weighted mean C concentration was 0.75 mg C/L with concentrations in the summer significantly higher than in the other three seasons. The DOC concentration was most strongly associated with ammonium concentrations (r=0.81), but was also significantly related to nitrate (r=0.50) and sulfate (r=0.63) concentrations. There was no significant association between DOC and chloride concentrations. Preliminary regression tree analysis suggests that the DOC concentration in precipitation was best predicted by the atmospheric concentration of methyl vinyl ketone, an oxidation product of isoprene. These results suggest that both terrestrial biogenic and anthropogenic sources may be important precursors to the C removed from the atmosphere during precipitation events.

  4. The characteristics of dissolved organic matter (DOM) and chromophoric dissolved organic matter (CDOM) in Antarctic sea ice

    NASA Astrophysics Data System (ADS)

    Norman, Louiza; Thomas, David N.; Stedmon, Colin A.; Granskog, Mats A.; Papadimitriou, Stathys; Krapp, Rupert H.; Meiners, Klaus M.; Lannuzel, Delphine; van der Merwe, Pier; Dieckmann, Gerhard S.

    2011-05-01

    An investigation of coloured dissolved organic matter (CDOM) and its relationships to physical and biogeochemical parameters in Antarctic sea ice and oceanic water have indicated that ice melt may both alter the spectral characteristics of CDOM in Antarctic surface waters and serve as a likely source of fresh autochthonous CDOM and labile DOC. Samples were collected from melted bulk sea ice, sea ice brines, surface gap layer waters, and seawater during three expeditions: one during the spring to summer and two during the winter to spring transition period. Variability in both physical (temperature and salinity) and biogeochemical parameters (dissolved and particulate organic carbon and nitrogen, as well as chlorophyll a) was observed during and between studies, but CDOM absorption coefficients measured at 375 nm (a 375) did not differ significantly. Distinct peaked absorption spectra were consistently observed for bulk ice, brine, and gap water, but were absent in the seawater samples. Correlation with the measured physical and biogeochemical parameters could not resolve the source of these peaks, but the shoulders and peaks observed between 260 and 280 nm and between 320 to 330 nm respectively, particularly in the samples taken from high light-exposed gap layer environment, suggest a possible link to aromatic and mycosporine-like amino acids. Sea ice CDOM susceptibility to photo-bleaching was demonstrated in an in situ 120 hour exposure, during which we observed a loss in CDOM absorption of 53% at 280 nm, 58% at 330 nm, and 30% at 375 nm. No overall coincidental loss of DOC or DON was measured during the experimental period. A relationship between the spectral slope (S) and carbon-specific absorption (a *375) indicated that the characteristics of CDOM can be described by the mixing of two broad end-members; and aged material, present in brine and seawater samples characterised by high S values and low a *375; and a fresh material, due to elevated in situ

  5. Effect of organic fertilizers derived dissolved organic matter on pesticide sorption and leaching.

    PubMed

    Li, Kun; Xing, Baoshan; Torello, William A

    2005-03-01

    Incorporation of organic fertilizers/amendments has been, and continues to be, a popular strategy for golf course turfgrass management. Dissolved organic matter (DOM) derived from these organic materials may, however, facilitate organic chemical movement through soils. A batch equilibrium technique was used to evaluate the effects of organic fertilizer-derived DOM on sorption of three organic chemicals (2,4-D, naphthalene and chlorpyrifos) in USGA (United States Golf Association) sand, a mixed soil (70% USGA sand and 30% native soil) and a silt loam soil (Typic Fragiochrept). DOM was extracted from two commercial organic fertilizers. Column leaching experiments were also performed using USGA sand. Sorption experiments showed that sorption capacity was significantly reduced with increasing DOM concentration in solution for all three chemicals. Column experimental results were consistent with batch equilibrium data. These results suggest that organic fertilizer-derived DOM might lead to enhanced transport of applied chemicals in turf soils.

  6. Dissolved organic carbon and sulfur in southwestern Quebec lakes: Relationships with catchment and lake properties

    SciTech Connect

    Houle, D.; Carignan, R.; Lachance, M.

    1995-06-01

    In 59 southwestern Quebec lakes, dissolved organic S (DOS) concentration averages 185{+-}92 {mu}g liter{sup -1} (9.2% of total S) and ranges from undetectable to 437 {mu}g liter{sup -1} (22% of total S). DOS can be predicted from dissolved organic C (DOC) concentrations: DOS ({mu}g liter{sup -1}) = 2.20 log{sub 10}(DOC) + 7, r{sup 2} = 0.55. When applied to 1,238 lakes from five Quebec regions, this relationship indicates that DOS can account for 8.5% (Ottawa) to 22.2% (North Shore) of total S. These results stress the importance of evaluating DOS concentrations in studies of catchment S budgets. Multiple regression models using lake and catchment properties as independent variables respectively explain 75, 43, 49, and 69% of the variance in DOC, DOS, DOC: DOS, and color. The regressions found for DOC, color, and DOS include a flowpath index, accounting for dissolved organic matter (DOM) leaching from the catchment, and a term for in-lake losses. The DOC:DOS regression includes the flowpath index, lake perimeter, and altitude and suggests that DOM supply and composition also depend on catchment properties. 23 refs., 3 figs., 5 tabs.

  7. Dissolved Organic Matter, Organic Matter Optical Properties and Mercury in Rivers and Streams

    NASA Astrophysics Data System (ADS)

    Aiken, G. R.; Brigham, M. E.; Shanley, J. B.; Krabbenhoft, D. P.

    2008-12-01

    Interactions of mercury (Hg) with dissolved organic matter (DOM) play important roles in controlling concentrations, reactivity, bioavailability and transport of Hg in aquatic systems. Recent studies have shown that DOM influences Hg solubility through strong binding interactions and the stabilization of nanocolloidal mercuric sulfide. In this paper we present the results of watershed based studies associated with US Geological Survey NAWQA and WEBB Programs designed to better define the factors controlling the export of Hg in stream systems. We investigated the seasonal and spatial variability of dissolved organic matter quantity and quality, and the concentrations of dissolved Hg and methylmercury (MeHg) in 12 rivers and streams representing a range of watershed types that varied in climate, landscape, Hg deposition and water chemistry. DOM concentrations and composition, based on DOM fractionation and ultraviolet/visible absorption spectroscopic analyses, varied greatly both between sites, and seasonally within sites. Strong relationships were found between DOM and total dissolved Hg concentrations in almost all of the systems. The relationships between total dissolved Hg concentration and hydrophobic organic acid (HPOA) content (aquatic humic substances) were stronger than those observed between Hg and DOM, supporting the hypothesis that interactions between Hg and the HPOA fraction are important drivers for the transport of dissolved Hg in aquatic systems. The relationships between MeHg and DOM and HPOA content were not as strong as those observed with Hg. In all systems, UV absorbance measured at 254 nm correlated strongly with DOM, HPOA content and Hg concentrations. The relationships between DOM concentration and absorbance for the range of systems were quite variable because not all of the dissolved organic carbon in a given sample absorbs UV light to the same degree and each system exhibited a different relationship. However, the relationship between HPOA

  8. 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...

  9. Bioavailable and biodegradable dissolved organic nitrogen in activated sludge and trickling filter wastewater treatment plants

    USDA-ARS?s Scientific Manuscript database

    A study was carried out to understand the fate of biodegradable dissolved organic nitrogen (BDON) and bioavailable dissolved organic nitrogen (ABDON) along the treatment trains of a wastewater treatment facility (WWTF) equipped with an activated sludge (AS) system and a WWTF equipped with a two-stag...

  10. Stream dissolved organic matter bioavailability and composition in watersheds underlain with discontinuous permafrost

    Treesearch

    Kelly L. Balcarczyk; Jeremy B. Jones; Rudolf Jaffe; Nagamitsu Maie

    2009-01-01

    We examined the impact of permafrost on dissolved organic matter (DOM) composition in Caribou-Poker Creeks Research Watershed (CPCRW), a watershed underlain with discontinuous permafrost, in interior Alaska. The stream draining the high permafrost watershed had higher DOC and dissolved organic nitrogen (DON) concentrations, higher DOCDON and greater specific...

  11. DISSOLVED ORGANIC CARBON (DOC) CONCENTRATIONS IN SMALL STREAMS OF THE GEORGIA PIEDMONT

    EPA Science Inventory

    Dissolved organic matter (DOM) supports microbial activity and contributes to transport of N and P in streams. We have studied the impact of land uses on dissolved organic carbon (DOC) concentrations in 17 Georgia Piedmont headwater streams since January 2001. We classified the w...

  12. 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...

  13. DISSOLVED ORGANIC CARBON (DOC) CONCENTRATIONS IN SMALL STREAMS OF THE GEORGIA PIEDMONT

    EPA Science Inventory

    Dissolved organic matter (DOM) supports microbial activity and contributes to transport of N and P in streams. We have studied the impact of land uses on dissolved organic carbon (DOC) concentrations in 17 Georgia Piedmont headwater streams since January 2001. We classified the w...

  14. Seasonal changes in the chemical quality and biodegradability of dissolved organic matter exported from soils to streams in coastal temperate rainforest watersheds

    Treesearch

    Jason B. Fellman; Eran Hood; David V. D' Amore; Richard T. Edwards; Dan White

    2009-01-01

    The composition and biodegradability of streamwater dissolved organic matter (DOM) varies with source material and degree of transformation. We combined PARAFAC modeling of fluorescence excitation-emission spectroscopy and biodegradable dissolved organic carbon (BDOC) incubations to investigate seasonal changes in the lability of DOM along a soil-stream continuum in...

  15. Complexation with dissolved organic matter and solubility control of heavy metals in a sandy soil.

    PubMed

    Weng, Liping; Temminghoff, Erwin J M; Lofts, Stephen; Tipping, Edward; Van Riemsdijk, Willem H

    2002-11-15

    The complexation of heavy metals with dissolved organic matter (DOM) in the environment influences the solubility and mobility of these metals. In this paper, we measured the complexation of Cu, Cd, Zn, Ni, and Pb with DOM in the soil solution at pH 3.7-6.1 using a Donnan membrane technique. The results show that the DOM-complexed species is generally more significant for Cu and Pb than for Cd, Zn, and Ni. The ability of two advanced models for ion binding to humic substances, e.g., model VI and NICA-Donnan, in the simulation of metal binding to natural DOM was assessed by comparing the model predictions with the measurements. Using the default parameters of fulvic and humic acid, the predicted concentrations of free metal ions from the solution speciation calculation using the two models are mostly within 1 order of magnitude difference from the measured concentrations, except for Ni and Pb in a few samples. Furthermore, the solid-solution partitioning of the metals was simulated using a multisurface model, in which metal binding to soil organic matter, dissolved organic matter, clay, and iron hydroxides was accounted for using adsorption and cation exchange models (NICA-Donnan, Donnan, DDL, CD-MUSIC). The model estimation of the dissolved concentration of the metals is mostly within 1 order of magnitude difference from those measured except for Ni in some samples and Pb. The solubility of the metals depends mainly on the metal loading over soil sorbents, pH, and the concentration of inorganic ligands and DOM in the soil solution.

  16. Long-term dynamics of dissolved organic carbon: implications for drinking water supply.

    PubMed

    Ledesma, José L J; Köhler, Stephan J; Futter, Martyn N

    2012-08-15

    Surface waters are the main source of drinking water in many regions. Increasing organic carbon concentrations are a cause for concern in Nordic countries since both dissolved and particulate organic carbon can transport contaminants and adversely affect drinking water treatment processes. We present a long-term study of dynamics of total (particulate and dissolved) organic carbon (TOC) concentrations in the River Fyris. This river supplies drinking water to approximately 200000 people in Uppsala, Sweden. The River Fyris is a main tributary to Lake Mälaren, which supplies drinking water to approximately 2 million people in the greater Stockholm area. Utilities responsible for drinking water supply in both Uppsala and Stockholm have expressed concerns about possible increases in TOC. We evaluate organic carbon dynamics within the Fyris catchment by calculating areal mass exports using observed TOC concentrations and modeled flows and by modeling dissolved organic carbon (as a proxy for TOC) using the dynamic, process based INCA-C model. Exports of TOC from the catchment ranged from 0.8 to 5.8 g m(-2) year(-1) in the period 1995-2010. The variation in annual exports was related to climatic variability which influenced seasonality and amount of runoff. Exports and discharge uncoupled at the end of 2008. A dramatic increase in TOC concentrations was observed in 2009, which gradually declined in 2010-2011. INCA-C successfully reproduced the intra- and inter-annual variation in concentrations during 1996-2008 and 2010-2011 but failed to capture the anomalous increase in 2009. We evaluated a number of hypotheses to explain the anomaly in 2009 TOC values, ultimately none proved satisfactory. We draw two main conclusions: there is at least one unknown or unmeasured process controlling or influencing surface water TOC and INCA-C can be used as part of the decision-making process for current and future use of rivers for drinking water supply.

  17. Determining Passive Sampler Partition Coefficients for Dissolved-phase Organic Contaminants

    EPA Science Inventory

    Passive samplers are used for environmental and analytical purposes to measure dissolved nonionic organic contaminants (NOCs) by absorption from a contaminated medium into a clean phase, usually in the form of a synthetic organic film. Recently developed passive sampler techniqu...

  18. Determining Passive Sampler Partition Coefficients for Dissolved-phase Organic Contaminants

    EPA Science Inventory

    Passive samplers are used for environmental and analytical purposes to measure dissolved nonionic organic contaminants (NOCs) by absorption from a contaminated medium into a clean phase, usually in the form of a synthetic organic film. Recently developed passive sampler techniqu...

  19. 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.

  20. Concurrent photolytic degradation of aqueous methylmercury and dissolved organic matter.

    PubMed

    Fleck, Jacob A; Gill, Gary; Bergamaschi, Brian A; Kraus, Tamara E C; Downing, Bryan D; Alpers, Charles N

    2014-06-15

    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)m(2)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.

  1. 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.

  2. [Spectral Characteristic of Dissolved Organic Matter in Xiaohe River, Hebei].

    PubMed

    Yu, Min-da; Zhang, Hui; He, Xiao-song; Tan, Wen-bing; Zhang, Yuan; Ma, Li-na; Xi, Bei-dou; Dang, Qiu-ling; Gao, Ru-tai

    2015-09-01

    The spectral characteristic of dissolved organic matter (DOM) in Xiaohe River, Hebei, was investigated by fluorescence spectroscopy, ultraviolet-visible absorption spectroscopy, and basic chemical water quality indicators. The data was then statistical analyzed using principal component analysis and correlation analysis method. The result based on 3D excitation-emission matrix fluorescence spectroscopy showed that DOM in Xiaohe River contained both protein-like and humus-like components. DOM and N-containing compounds were obviously correlated with COD, especially between NH4+ -N and humic-like component, indicating that COD of water in Xiaohe River can be reduced by removing NH4+ -N and DOM, which could be good indicators for monitoring water quality in the future. The relative content of protein-like component reduces gradually along the downstream, while that of humic-like component showed an increasing trend. DOM in samples S1 and S2 was mainly consisted of humic-like components with larger molecular weight and higher aromaticity, while that in samples S3 and S6 was mainly consisted of protein-like components with smaller molecular weight, lower aromaticity, which are easier to be degraded. Therefore, in order to enhance the remove of refractory humic-like substances, sewage treatment plants of S1 and S2 or improved membrane treatment equipment with better removal effect of macromolecules should be provide. On the other hand, the anaerobic and aerobic biological treatment processes should be optimized in S3 and S6, so as to better remove these degradable protein-like substances.

  3. Seqestration of dissolved organic carbon in the deep sea

    SciTech Connect

    Daniel J. Repeta

    2006-03-01

    There are 600 GT of dissolved organic carbon (DOC) sequestered in seawater. The marine inventory of DOC is set by its concentration in the deep sea, which is nearly constant at 35+2µM C, irrespective of sample location or depth. Isotopic measurements show deep sea DOC to be depleted in radiocarbon, with an apparent radiocarbon age of between 4000ybp (Atlantic) and 6000ybp (Pacific). From the radiocarbon data, we can infer that deep sea DOC is inert and does not cycle on less than millennial time scales. However, high precision DOC measurements show deep sea concentrations are variable at the + 1-2µM DOC level, suggesting a fraction of deep sea DOC, equivalent to 15-30Gt C, is cycling on short time scales, acting as a sink for new, atmospheric carbon. This project is designed to identify and quantify the biological and physical processes that sequester DOM in the deep sea by making compound specific radiocarbon measurements on sugars and proteins extracted from deep sea DOC. Our Hawaii surface seawater sample has a DIC Δ14C value of 72 + 7 ‰ and shows the influence of bomb radiocarbon on surface water DIC values. HMWDOC Δ14C is 10 ‰, significantly depleted in radiocarbon relative to DIC. Purification of HMWDOC by reverse phase HPLC yields seven neutral sugars with radiocarbon values of 47 – 67‰. Assuming the radiocarbon determinations of individual sugars in HMWDOC serve as replicates, then the average Δ14C for neutral sugars in HMWDOC is 57 + 6 ‰(1 SD, n=11), only slightly depleted in 14C relative to DIC. There has been a sharp decrease in radiocarbon values for DIC in the North Pacific Ocean over the past few decades. If neutral sugars cycle more slowly than DIC, we would expect them to have correspondingly higher radiocarbon values. Previous studies have modeled upper ocean DOC as a two component mixture of newly synthesized DOC with a radiocarbon value equal to DIC, and an old component with a radiocarbon value equal to deep sea DO14C. In order to

  4. Biogeochemical modelling of dissolved oxygen in a changing ocean.

    PubMed

    Andrews, Oliver; Buitenhuis, Erik; Le Quéré, Corinne; Suntharalingam, Parvadha

    2017-09-13

    Secular decreases in dissolved oxygen concentration have been observed within the tropical oxygen minimum zones (OMZs) and at mid- to high latitudes over the last approximately 50 years. Earth system model projections indicate that a reduction in the oxygen inventory of the global ocean, termed ocean deoxygenation, is a likely consequence of on-going anthropogenic warming. Current models are, however, unable to consistently reproduce the observed trends and variability of recent decades, particularly within the established tropical OMZs. Here, we conduct a series of targeted hindcast model simulations using a state-of-the-art global ocean biogeochemistry model in order to explore and review biases in model distributions of oceanic oxygen. We show that the largest magnitude of uncertainty is entrained into ocean oxygen response patterns due to model parametrization of pCO2-sensitive C : N ratios in carbon fixation and imposed atmospheric forcing data. Inclusion of a pCO2-sensitive C : N ratio drives historical oxygen depletion within the ocean interior due to increased organic carbon export and subsequent remineralization. Atmospheric forcing is shown to influence simulated interannual variability in ocean oxygen, particularly due to differences in imposed variability of wind stress and heat fluxes.This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'. © 2017 The Author(s).

  5. Fate of dissolved organic nitrogen in two stage trickling filter process.

    PubMed

    Simsek, Halis; Kasi, Murthy; Wadhawan, Tanush; Bye, Christopher; Blonigen, Mark; Khan, Eakalak

    2012-10-15

    Dissolved organic nitrogen (DON) represents a significant portion of nitrogen in the final effluent of wastewater treatment plants (WWTPs). Biodegradable portion of DON (BDON) can support algal growth and/or consume dissolved oxygen in the receiving waters. The fate of DON and BDON has not been studied for trickling filter WWTPs. DON and BDON data were collected along the treatment train of a WWTP with a two-stage trickling filter process. DON concentrations in the influent and effluent were 27% and 14% of total dissolved nitrogen (TDN). The plant removed about 62% and 72% of the influent DON and BDON mainly by the trickling filters. The final effluent BDON values averaged 1.8 mg/L. BDON was found to be between 51% and 69% of the DON in raw wastewater and after various treatment units. The fate of DON and BDON through the two-stage trickling filter treatment plant was modeled. The BioWin v3.1 model was successfully applied to simulate ammonia, nitrite, nitrate, TDN, DON and BDON concentrations along the treatment train. The maximum growth rates for ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria, and AOB half saturation constant influenced ammonia and nitrate output results. Hydrolysis and ammonification rates influenced all of the nitrogen species in the model output, including BDON. Copyright © 2012 Elsevier Ltd. All rights reserved.

  6. Impact of dataset diversity on accuracy and sensitivity of parallel factor analysis model of dissolved organic matter fluorescence excitation-emission matrix

    NASA Astrophysics Data System (ADS)

    Yu, Huarong; Liang, Heng; Qu, Fangshu; Han, Zheng-Shuang; Shao, Senlin; Chang, Haiqing; Li, Guibai

    2015-05-01

    Parallel factor (PARAFAC) analysis enables a quantitative analysis of excitation-emission matrix (EEM). The impact of a spectral variability stemmed from a diverse dataset on the representativeness of the PARAFAC model needs to be examined. In this study, samples from a river, effluent of a wastewater treatment plant, and algae secretion were collected and subjected to PARAFAC analysis. PARAFAC models of global dataset and individual datasets were compared. It was found that the peak shift derived from source diversity undermined the accuracy of the global model. The results imply that building a universal PARAFAC model that can be widely available for fitting new EEMs would be quite difficult, but fitting EEMs to existing PARAFAC model that belong to a similar environment would be more realistic. The accuracy of online monitoring strategy that monitors the fluorescence intensities at the peaks of PARAFAC components was examined by correlating the EEM data with the maximum fluorescence (Fmax) modeled by PARAFAC. For the individual datasets, remarkable correlations were obtained around the peak positions. However, an analysis of cocktail datasets implies that the involvement of foreign components that are spectrally similar to local components would undermine the online monitoring strategy.

  7. Impact of dataset diversity on accuracy and sensitivity of parallel factor analysis model of dissolved organic matter fluorescence excitation-emission matrix

    PubMed Central

    Yu, Huarong; Liang, Heng; Qu, Fangshu; Han, Zheng-shuang; Shao, Senlin; Chang, Haiqing; Li, Guibai

    2015-01-01

    Parallel factor (PARAFAC) analysis enables a quantitative analysis of excitation-emission matrix (EEM). The impact of a spectral variability stemmed from a diverse dataset on the representativeness of the PARAFAC model needs to be examined. In this study, samples from a river, effluent of a wastewater treatment plant, and algae secretion were collected and subjected to PARAFAC analysis. PARAFAC models of global dataset and individual datasets were compared. It was found that the peak shift derived from source diversity undermined the accuracy of the global model. The results imply that building a universal PARAFAC model that can be widely available for fitting new EEMs would be quite difficult, but fitting EEMs to existing PARAFAC model that belong to a similar environment would be more realistic. The accuracy of online monitoring strategy that monitors the fluorescence intensities at the peaks of PARAFAC components was examined by correlating the EEM data with the maximum fluorescence (Fmax) modeled by PARAFAC. For the individual datasets, remarkable correlations were obtained around the peak positions. However, an analysis of cocktail datasets implies that the involvement of foreign components that are spectrally similar to local components would undermine the online monitoring strategy. PMID:25958786

  8. Hydropedological hotspots for dissolved organic carbon loading to streams along the perhumid temperate rainforest coastal margin of Alaska.

    NASA Astrophysics Data System (ADS)

    D'Amore, D. V.; Edwards, R.; Herendeen, P. A.; Fellman, J.; Hood, E. W.

    2015-12-01

    Integrating terrestrial and aquatic biogeochemical research is essential for understanding the amount of material exported from terrestrial systems to streams and coastal margins. Integrated models are needed to elucidate how shifts in vegetation communities driven by soil moisture can predict plant community composition and biomass changes that alter the balance of carbon cycling and export to aquatic systems. Soil saturation has long been recognized as an important control on many ecological and biogeochemical relationships in coastal rainforests. However, the lack of working models for soil drainage with enough precision to provide accurate site assessments has limited interpretations of biogeochemical fluxes from terrestrial ecosystems to coastal zones. We have established a hydropedological model that can be used to identify the spatial distribution and seasonal fluctuations of soil saturation and associated anaerobic conditions in soils. Periods of critical DOC loading and peak export associated with these conditions highlight the ability of rainforest soils to produce copious quantities of dissolved organic carbon export to streams. The loading of dissolved organic carbon to streams is closely coupled to seasonal temperature cycles, but constrained by the flow of water through the soil matrix. Episodic storm surges produce varying amounts of dissolved organic carbon flow depending on antecedent conditions. The largest amount of dissolved organic carbon loading to streams occurs after peak temperature and coincident with higher storm surges. Dissolved organic carbon flows more frequently and in higher quantities from wetland soils, but is also produced in large quantities from upland soils. These advances in modeling hydropedologic functions and dissolved organic carbon export establish a framework for climate change vulnerability assessments in rainforest soils.

  9. Applications of Fluorescence Spectroscopy for dissolved organic matter characterization in wastewater treatment plants

    NASA Astrophysics Data System (ADS)

    Goffin, Angélique; Guérin, Sabrina; Rocher, Vincent; Varrault, Gilles

    2016-04-01

    Dissolved organic matter (DOM) influences wastewater treatment plants efficiency (WTTP): variations in its quality and quantity can induce a foaming phenomenon and a fouling event inside biofiltration processes. Moreover, in order to manage denitrification step (control and optimization of the nitrate recirculation), it is important to be able to estimate biodegradable organic matter quantity before biological treatment. But the current methods used to characterize organic matter quality, like biological oxygen demand are laborious, time consuming and sometimes not applicable to directly monitor organic matter in situ. In the context of MOCOPEE research program (www.mocopee.com), this study aims to assess the use of optical techniques, such as UV-Visible absorbance and more specifically fluorescence spectroscopy in order to monitor and to optimize process efficiency in WWTP. Fluorescence excitation-emission matrix (EEM) spectroscopy was employed to prospect the possibility of using this technology online and in real time to characterize dissolved organic matter in different effluents of the WWTP Seine Centre (240,000 m3/day) in Paris, France. 35 sewage water influent samples were collected on 10 days at different hours. Data treatment were performed by two methods: peak picking and parallel factor analysis (PARAFAC). An evolution of DOM quality (position of excitation - emission peaks) and quantity (intensity of fluorescence) was observed between the different treatment steps (influent, primary treatment, biological treatment, effluent). Correlations were found between fluorescence indicators and different water quality key parameters in the sewage influents. We developed different multivariate linear regression models in order to predict a variety of water quality parameters by fluorescence intensity at specific excitation-emission wavelengths. For example dissolved biological oxygen demand (r2=0,900; p<0,0001) and ammonium concentration (r2=0,898; p<0

  10. Surprising results from abiotic enzyme digestion of dissolved organic matter at the molecular scale

    NASA Astrophysics Data System (ADS)

    Hess, N. J.; Tfaily, M. M.; Heredia-Langnar, A.; Rodriguez, L.; Purvine, E.; Todd-Brown, K. E.

    2016-12-01

    Sometimes even the simplest of experiments leads to unexpected results and new understanding. We extract dissolved organic matter using water from peat soil obtained from the S1 bog at the Marcell Experimental Forest in northern Minnesota. We characterized the dissolved organic matter in the water extract before and after adding glucosidase, peroxidase and β-N-Acetylglucosaminidase enzymes using electrospray Fourier transform ion cyclotron resonance mass spectrometry in negative ion mode. Based on mass measurement accuracy of less than 1 ppm for singly charged ions, we assigned putative chemical formula to greater than 80% of the measured mass spectrometry features. For each enzyme tested we are able to easily distinguish between the types and composition of dissolved organic molecules that are susceptible to enzyme degradation - and those that are not - based on the presence new compounds in reacted extracts and loss of compounds from the initial water extract. Next, we created a consensus molecular network analysis based on the neutral mass loss between the measured compounds for each enzyme. The connectivity within these networks suggested a unique, distinctive chemistry for each enzyme. Some results were expected, like the nondiscriminatory oxidation of organic molecules by peroxidase and preferential loss of lignin and tannin-like molecules by glucosidase. However, surprising results include the apparent reactivity of glucosidase enzymatic products to reassemble, forming larger mass organic molecules. While these experiments were conducted abiotically, these molecular-resolved results suggest that biotic enzymatic processes may result in product compounds with unexpected chemistry and reactivity, implying that our current conceptual model of microbial enzymatic activity may be overly simplistic.

  11. 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.

  12. Influence of dissolved organic substances in groundwater on sorption behavior of americium and neptunium

    SciTech Connect

    Boggs, S. Jr.; Seitz, M.G.

    1984-01-01

    Groundwaters typically contain dissolved organic carbon consisting largely of high molecular weight compounds of humic and fulvic acids. To evaluate whether these dissolved organic substances can enhance the tranport of radionuclides through the groundwater system, experiments were conducted to examine the sorption of americium and neptunium onto crushed basalt in the presence of dissolved humic- and fulvic-acid organic carbon introduced into synthetic groundwater. The partitioning experiments with synthetic groundwater show that increasing the concentration of either humic or fulvic acid in the water has a significant inhibiting effect on sorption of both americium and neptunium. At 22/sup 0/C, adsorption of these radionuclides, as measured by distribution ratios (the ratio of nuclide sorbed onto the solid to nuclide in solution at the end of the experiment), decreased by 25% to 50% by addition of as little as 1 mg/L dissolved organic carbon and by one to two orders of magnitude by addition of 100 to 200 mg/L dissolved organic carbon. Distribution ratios measured in solutions reacted at 90/sup 0/C similarly decreased with the addition of dissolved organic carbon but generally ranged from one to two orders of magnitude higher than those determined in the 22/sup 0/C experiment. These results suggest that organic carbon dissolved in deep groundwaters may significantly enhance the mobility of radionuclides of americium and neptunium. 23 references, 5 figures, 11 tables.

  13. Analytical Determinations of the Phenolic Content of Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Pagano, T.; Kenny, J. E.

    2010-12-01

    Indicators suggest that the amount of dissolved organic matter (DOM) in natural waters is increasing. Climate Change has been proposed as a potential contributor to the trend, and under this mechanism, the phenolic content of DOM may also be increasing. We have explored the possibility of assessing the phenolic character of DOM using fluorescence spectroscopy as a more convenient alternative to wet chemistry methods. In this work, parallel factor analysis (PARAFAC) was applied to fluorescence excitation emission matrices (EEMs) of humic samples in an attempt to analyze their phenolic content. The PARAFAC results were correlated with phenol concentrations derived from the Folin-Ciocalteau reagent-based method. The reagent-based method showed that the phenolic content of five International Humic Substance Society (IHSS) DOM samples vary from approximately 5 to 22 ppm Tannic Acid Equivalents (TAE) in phenol concentration. A five-component PARAFAC fit was applied to the EEMs of the IHSS sample dataset and it was determined by PARAFAC score correlations with phenol concentrations from the reagent-based method that components C1 (R2=0.78), C4 (R2=0.82), and C5 (R2=0.88) have the highest probability of containing phenolic groups. Furthermore, when the scores of components C4 and C5 were summed, the correlation improved (R2=0.99). Likewise, when the scores of C1, C4, and C5 were summed, their correlations were stronger than their individual parts (R2=0.89). Since the reagent-based method is providing an indicator of “total phenol” amount, regardless of the exact molecular structure of C1, C4, and C5, it seems reasonable that each of these components individually contributes a portion to the summed “total phenol” profile, and that the sum of their phenol-related spectral parts represents a larger portion of the “total phenol” index. However, when the sum of all five components were plotted against the reagent-based phenol concentrations, due to the considerable

  14. Composition of dissolved organic nitrogen in rivers associated with wetlands.

    PubMed

    Watanabe, Akira; Tsutsuki, Kiyoshi; Inoue, Yudzuru; Maie, Nagamitsu; Melling, Lulie; Jaffé, Rudolf

    2014-09-15

    As basic information for assessing reactivity and functionality of wetland-associated dissolved organic matter (DOM) based on their composition and structural properties, chemical characteristics of N in ultrafiltered DOM (UDON; >1 kD) isolated from wetland-associated rivers in three climates (cool-temperate, Hokkaido, Japan; sub-tropical, Florida, USA; tropical, Sarawak, Malaysia) were investigated. The UDON was isolated during dry and wet seasons, or during spring, summer, and autumn. The proportion of UDON present as humic substances, which was estimated as the DAX-8 adsorbed fraction, ranged from 47 to 91%, with larger values in the Sarawak than at the other sites. The yield of hydrolyzable amino acid N ranged 1.24 to 7.01 mg g(-1), which correlated positively to the total N content of UDOM and tended to be larger in the order of Florida>Hokkaido>Sarawak samples. X-ray photoelectron N1s spectra of UDON showed a strong negative correlation between the relative abundances of amide/peptide N and primary amine N. The relative abundances of amide/peptide N and primary amine N in the Sarawak samples were smaller (70-76%) and larger (20-23%) respectively compared to those (80-88% and 4-9%) in the Florida and Hokkaido samples. Assuming terminal amino groups and amide N of peptides as major constituents of primary amine N and amide/peptide N, respectively, the average molecular weight of peptides was smaller in the Sarawak samples than that in the Florida and Hokkaido samples. Seasonal variations in UDON composition were scarce in the Sarawak and Florida samples, whereas the distribution of humic substance-N and nonhumic substance-N and compositions of amino acids and N functional groups showed a clear seasonality in the Hokkaido samples. While aromatic N increased from spring to autumn, contributions from fresh proteinaceous materials were also enhanced during autumn, resulting in the highest N content of UDOM for this season. Copyright © 2014 Elsevier B.V. All rights

  15. Dissolved organic carbon pools and export from the coastal ocean

    NASA Astrophysics Data System (ADS)

    Barrón, Cristina; Duarte, Carlos M.

    2015-10-01

    The distribution of dissolved organic carbon (DOC) concentration across coastal waters was characterized based on the compilation of 3510 individual estimates of DOC in coastal waters worldwide. We estimated the DOC concentration in the coastal waters that directly exchange with open ocean waters in two different ways, as the DOC concentration at the edge of the shelf break and as the DOC concentration in coastal waters with salinity close to the average salinity in the open ocean. Using these estimates of DOC concentration in the coastal waters that directly exchange with open ocean waters, the mean DOC concentration in the open ocean and the estimated volume of water annually exchanged between coastal and open ocean, we estimated a median ± SE (and average ± SE) global DOC export from coastal to open ocean waters ranging from 4.4 ± 1.0 Pg C yr-1 to 27.0 ± 1.8 Pg C yr-1 (7.0 ± 5.8 Pg C yr-1 to 29.0 ± 8.0 Pg C yr-1) depending on the global hydrological exchange. These values correspond to a median and mean median (and average) range between 14.7 ± 3.3 to 90.0 ± 6.0 (23.3 ± 19.3 to 96.7 ± 26.7) Gg C yr-1 per km of shelf break, which is consistent with the range between 1.4 to 66.1 Gg C yr-1 per km of shelf break of available regional estimates of DOC export. The estimated global DOC export from coastal to open ocean waters is also consistent with independent estimates of the net metabolic balance of the coastal ocean. The DOC export from the coastal to the open ocean is likely to be a sizeable flux and is likely to be an important term in the carbon budget of the open ocean, potentially providing an important subsidy to support heterotrophic activity in the open ocean.

  16. Bioavailability of dissolved organic nitrogen (DON) in wastewaters from animal feedlots and storage lagoons

    USDA-ARS?s Scientific Manuscript database

    Dissolved organic nitrogen (DON) transport from animal agriculture to surface waters can lead to eutrophication and dissolved oxygen depletion. Biodegradable DON (BDON) is a portion of DON that is mineralized by bacteria while bioavailable DON (ABDON) is utilized by bacteria and/or algae. This stu...

  17. Determination of the Fate of Dissolved Organic Nitrogen in the Three Wastewater Treatment Plants, Jordan

    ERIC Educational Resources Information Center

    Wedyan, Mohammed; Al Harahsheh, Ahmed; Qnaisb, Esam

    2016-01-01

    This research aimed to assess the composition of total dissolved nitrogen (TDN) species, particularly dissolved organic nitrogen (DON), over the traditional wastewater treatment operations in three biological nutrient removal (BNR) wastewater treatment plants (WWTPs) in Jordan. It had been found that the DON percentage was up to 30% of TDN within…

  18. Pulsed, cross-shelf export of terrigenous dissolved organic carbon to the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Fichot, Cédric G.; Lohrenz, Steven E.; Benner, Ronald

    2014-02-01

    The export of terrigenous dissolved organic carbon (tDOC) and other river-borne material across the continental shelf boundary has important ramifications for biological productivity and the cycling of continentally derived bioelements in the ocean. Recent studies revealed the 275-295 nm spectral slope coefficient of chromophoric dissolved organic matter (CDOM), S275-295, is a reliable tracer for terrigenous dissolved organic carbon (tDOC) in river-influenced ocean margins. Here an empirical algorithm for the accurate retrieval of S275-295 from ocean color was developed and validated using in situ optical properties collected seasonally in the northern Gulf of Mexico. This study also demonstrated S275-295 is a robust proxy for tDOC concentration in this environment, thereby providing a means to derive surface tDOC concentrations on synoptic scales and in quasi-real time using remote sensing. The resulting tDOC-algorithm was implemented using Aqua-MODIS in a retrospective analysis of surface tDOC concentrations over the northern Gulf of Mexico between July 2002 and June 2013. Large pulses of tDOC were observed in continental-slope surface waters off the Mississippi River delta, indicating cross-shelf export of tDOC was sporadic and exhibited considerable interannual variability. Favorable winds following an anomalously high discharge from the Mississippi-Atchafalaya river system always coincided with a major export event, and in general, cross-shelf export was enhanced during years of anomalously high discharge. The tDOC-algorithm will find applicability in the assessment of future climate- and human-induced changes in tDOC export, in biogeochemical models of the continental shelf, and in the validation of high-resolution coastal models of buoyancy-driven shelf circulation.

  19. EFFECTS OF REVERSE OSMOSIS ISOLATION ON REACTIVITY OF NATURALLY OCCURRING DISSOLVED ORGANIC MATTER IN PHYSICOCHEMICAL PROCESSES. (R828045)

    EPA Science Inventory

    A field reverse osmosis system was used to isolate dissolved organic matter (DOM) from two lacustrine and two riverine surface water sources. The rejection of DOM was on the order of 99% and did not vary significantly with pressure. A simple mass balance model using a single m...

  20. EFFECTS OF REVERSE OSMOSIS ISOLATION ON REACTIVITY OF NATURALLY OCCURRING DISSOLVED ORGANIC MATTER IN PHYSICOCHEMICAL PROCESSES. (R828045)

    EPA Science Inventory

    A field reverse osmosis system was used to isolate dissolved organic matter (DOM) from two lacustrine and two riverine surface water sources. The rejection of DOM was on the order of 99% and did not vary significantly with pressure. A simple mass balance model using a single m...

  1. Dissolved organic carbon source integration in an agricultural watershed

    NASA Astrophysics Data System (ADS)

    Hernes, P. J.; Spencer, R. G.; Dyda, R. Y.; Pellerin, B. A.; Bachand, P. A.; Bergamaschi, B. A.

    2012-12-01

    The dissolved organic carbon (DOC) chemistry and concentration at the mouth of a watershed represents an integrated signal of all sources and process that occur upstream of the mouth, however, the relative contributions of all those sources and processes to the chemistry and concentration is not equal. We sampled an agricultural watershed in the Sacramento River valley in California synoptically on multiple occasions in order to better identify the most important contributors to DOC chemistry. Our samples included headwater samples from native grasslands in three sub-catchments, samples within the agricultural portions of those sub-watersheds, samples near the conjunctions, and irrigation field inputs and outputs. DOC concentrations increase considerably in the agricultural portion of the watershed, demonstrating the impacts of anthropogenic disturbance of landscapes as well as the potential for local landscapes to contribute significantly to the overall DOC concentration and chemistry. The central sub-catchment in particular had significantly greater DOC concentrations, which appears to correspond to the much greater proportion of flood irrigation land management in this portion, as our field runoff measurements indicate much higher added DOC during flood irrigation than during furrow irrigation. Flow-weighted averaging of the three sub-catchment DOC concentrations does not replicate concentrations at the mouth (1-6 km downstream of the confluences), indicating the importance of in-stream processing and/or source inputs from riparian zones even along the mainstem. Optical characterization of DOC demonstrates changing chemistry from season to season, and differences in chemistry from different areas of the catchment. The storm-influenced spring sampling yielded higher carbon-specific UV absorbance at 254 nm (SUVA254), indicating a higher proportion of aromaticity, while the southern sub-catchment consistently yielded the highest spectral slope values, which

  2. Reading the molecular signature of ecosystems in dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Simon, Carsten; Roth, Vanessa-Nina; Dittmar, Thorsten; Gleixner, Gerd

    2017-04-01

    To make forecasts about the behavior, origin and fate of dissolved organic matter (DOM) in the environment, we need further insights into the molecular composition of this complex mixture. The development of soft ionization procedures and mass spectrometers capable of ultrahigh resolution (Fourier-Transform Mass Spectrometry, FTMS) have opened important new horizons in this regard. However, the application of such systems is restricted due to high purchase and maintenance costs. The introduction of the improved version of the Orbitrap FTMS analyzer ("Elite") in 2011 could open new perspectives for the molecular-level investigation of DOM, as it combines high performance with lower overall costs. We compared the Orbitrap with an established FT-ICR-MS (ion cyclotron resonance, 15 Tesla) to assess the potential of this analyzer on a broad set of 17 terrestrial and aquatic DOM samples prepared by solid phase extraction (SPE-DOM, Dittmar et al. 2008). The dataset included groundwater, soil water from different depths and vegetation covers (forests, grassland), as well as bog, river, lake and marine waters. We here show that the Orbitrap analyzer is able to detect hard-to-resolve nitrogen and sulfur containing compounds (triplet signal [CHO]N2O2, [CHO]C5, [CHO]C2H4S) up to a mass-to-charge ratio of 430 and well retrieves the intensity information of the FT-ICR-MS. Both points have been recently reported as major obstacles in the detailed molecular-level analyses of DOM by Orbitrap systems (Hawkes et al. 2016). In our data, slight deviations in intensity representation were only found in samples characterized by stronger aromaticity, and especially in the lower mass range (below m/z 250). A subset of > 6000 formulae detected in both sets was used to further characterize the sample set on a molecular level. The derived ecological information, as assessed by ordination and post-ordination gradient fitting, was highly consistent among both datasets. A dominating first

  3. Exoenzyme activities as indicators of dissolved organic matter composition in the hyporheic zone of a floodplain river

    Treesearch

    Sandra M. Clinton; Rick T. Edwards; Stuart E.G. Findlay

    2010-01-01

    We measured the hyporheic microbial exoenzyme activities in a floodplain river to determine whether dissolved organic matter (DOM) bioavailability varied with overlying riparian vegetation patch structure or position along flowpaths. Particulate organic matter (POM), dissolved organic carbon (DOC), dissolved oxygen (DO), electrical conductivity and temperature were...

  4. Characteristics and transformations of dissolved organic nitrogen in municipal biological nitrogen removal wastewater treatment plants

    NASA Astrophysics Data System (ADS)

    Huo, Shouliang; Xi, Beidou; Yu, Honglei; Qin, Yanwen; Zan, Fengyu; Zhang, Jingtian

    2013-12-01

    Dissolved organic nitrogen (DON) represents most of the dissolved nitrogen in the effluent of biological nitrogen removal (BNR) wastewater treatment plants (WWTPs). The characteristics of wastewater-derived DON in two different WWTPs were investigated by several different methods. The major removals of DON and biodegradable dissolved organic nitrogen (BDON) along the treatment train were observed in the anaerobic process. Dissolved combined amino acids (DCAA) and dissolved free amino acids (DFAA) in the effluent accounted approximately for less than 4% and 1% of the effluent DON, respectively. Approximately half of wastewater-derived DON was capable of passing through a 1 kDa ultrafilter, and low MW DON cannot effectively be removed by BNR processes. More than 80% of effluent DON was composed of hydrophilic compounds, which stimulate algal growth. The study provided important information for future upgrading of WWTPs or the selection of DON removal systems to meet more demanding nitrogen discharge limits.

  5. Methane hydrate-bearing seeps as a source of aged dissolved organic carbon to the oceans

    USGS Publications Warehouse

    Pohlman, J.W.; Bauer, J.E.; Waite, W.F.; Osburn, C.L.; Chapman, N.R.

    2011-01-01

    Marine sediments contain about 500-10,000 Gt of methane carbon, primarily in gas hydrate. This reservoir is comparable in size to the amount of organic carbon in land biota, terrestrial soils, the atmosphere and sea water combined, but it releases relatively little methane to the ocean and atmosphere. Sedimentary microbes convert most of the dissolved methane to carbon dioxide. Here we show that a significant additional product associated with microbial methane consumption is methane-derived dissolved organic carbon. We use ??14 C and ??13 C measurements and isotopic mass-balance calculations to evaluate the contribution of methane-derived carbon to seawater dissolved organic carbon overlying gas hydrate-bearing seeps in the northeastern Pacific Ocean. We show that carbon derived from fossil methane accounts for up to 28% of the dissolved organic carbon. This methane-derived material is much older, and more depleted in 13 C, than background dissolved organic carbon. We suggest that fossil methane-derived carbon may contribute significantly to the estimated 4,000-6,000 year age of dissolved organic carbon in the deep ocean, and provide reduced organic matter and energy to deep-ocean microbial communities. ?? 2011 Macmillan Publishers Limited. All rights reserved.

  6. Methane hydrate-bearing seeps as a source of aged dissolved organic carbon to the oceans

    USGS Publications Warehouse

    Pohlman, John; Waite, William F.; Bauer, James E.; Osburn, Christopher L.; Chapman, N. Ross

    2011-01-01

    Marine sediments contain about 500–10,000 Gt of methane carbon1, 2, 3, primarily in gas hydrate. This reservoir is comparable in size to the amount of organic carbon in land biota, terrestrial soils, the atmosphere and sea water combined1, 4, but it releases relatively little methane to the ocean and atmosphere5. Sedimentary microbes convert most of the dissolved methane to carbon dioxide6, 7. Here we show that a significant additional product associated with microbial methane consumption is methane-derived dissolved organic carbon. We use Δ14C and δ13C measurements and isotopic mass-balance calculations to evaluate the contribution of methane-derived carbon to seawater dissolved organic carbon overlying gas hydrate-bearing seeps in the northeastern Pacific Ocean. We show that carbon derived from fossil methane accounts for up to 28% of the dissolved organic carbon. This methane-derived material is much older, and more depleted in 13C, than background dissolved organic carbon. We suggest that fossil methane-derived carbon may contribute significantly to the estimated 4,000–6,000 year age of dissolved organic carbon in the deep ocean8, and provide reduced organic matter and energy to deep-ocean microbial communities.

  7. Effect of dissolved organic matter source on phytotoxicity to Lemna aequinoctialis.

    PubMed

    Shoji, Ryo

    2008-05-01

    The effect of dissolved organic matter (DOM) on metal toxicity to aquatic organisms has been reported. Biotic ligand model (BLM) can account for this factor to predict metal toxicity. However, few attempts have been made to assess the effect of the DOM on metal phytotoxicity to duckweeds. The objectives of this study were to examine the effect of DOM on copper toxicity to the duckweed Lemna aequinoctialis, and to determine if DOM concentration alone, regardless of DOM source, is an acceptable input parameter for the BLM for copper. Nine different DOM isolates from nine different sites in Japan were used in this study. A significant difference was observed between the lowest and the highest copper binding capacity. Phytotoxicity for copper decreased with increasing DOM concentration. These observations support use of the copper biotic ligand model (BLM) with AFA% (active fulvic acid percent) as a regulatory tool to predict copper phytotoxicity on duckweeds.

  8. 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...

  9. 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...

  10. 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...

  11. DISSOLVED ORGANIC CARBON TRENDS RESULTING FROM CHANGES IN ATMOSPHERIC DEPOSITION CHEMISTRY

    EPA Science Inventory

    Several hypotheses have been proposed to explain recent, widespread increases in concentrations of dissolved organic carbon (DOC) in the surface waters of glaciated landscapes across eastern North America and northern and central Europe. Some invoke anthropogenic forcing through ...

  12. 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.

  13. Impact of solids retention time on dissolved organic nitrogen and its biodegradability in treated wastewater

    USDA-ARS?s Scientific Manuscript database

    Dissolved organic nitrogen (DON) and its biodegradability in treated wastewater have recently gained attention because DON potentially causes oxygen depletion and/or eutrophication in receiving waters. Laboratory scale chemostat experiments were conducted at 9 different solids retention times (SRTs)...

  14. 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...

  15. 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...

  16. 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...

  17. PHOTOCHEMICALLY-INDUCED TRANSFORMATIONS OF DISSOLVED ORGANIC MATTER IN RIVERINE WATERS

    EPA Science Inventory

    We demonstrated that exposure of riverine water to natural sunlight initiated degradation and corresponding alteration to the stable carbon isotope ratio and biochemical composition of the associated dissolved organic carbon (DOC). Water samples were collected from two distinct ...

  18. Influence of carbonization methods on the aromaticity of pyrogenic dissolved organic carbon

    USDA-ARS?s Scientific Manuscript database

    Dissolved organic carbon (DOC) components of soil amendments such as biochar will influence the fundamental soil chemistry including the metal speciation, nutrient availability, and microbial activity. Quantitative correlation is necessary between (i) pyrogenic DOC components of varying aromaticity...

  19. 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...

  20. DISSOLVED ORGANIC CARBON TRENDS RESULTING FROM CHANGES IN ATMOSPHERIC DEPOSITION CHEMISTRY

    EPA Science Inventory

    Several hypotheses have been proposed to explain recent, widespread increases in concentrations of dissolved organic carbon (DOC) in the surface waters of glaciated landscapes across eastern North America and northern and central Europe. Some invoke anthropogenic forcing through ...

  1. Optical Proxies for Dissolved Organic Matter in Estuaries and Coastal Waters

    NASA Astrophysics Data System (ADS)

    Osburn, C. L.; Montgomery, M. T.; Boyd, T. J.; Bianchi, T. S.; Coffin, R. B.; Paerl, H. W.

    2016-02-01

    The flux of terrestrial dissolved organic carbon (DOC) into the coastal ocean from rivers and estuaries is a major part of the ocean's carbon cycle. Absorbing and fluorescing properties of chromophoric dissolved organic matter (CDOM) often are used to fingerprint its sources and to track fluxes of terrestrial DOM into the ocean. They also are used as proxies for organic matter to calibrate remote sensing observations from air and space and from in situ platforms. In general, strong relationships hold for large river dominated estuaries (e.g., the Mississippi River) but little is known about how widely such relationships can be developed in estuaries that have relatively small or multiple riverine inputs. Results are presented from a comparison of six diverse estuarine systems: the Atchafalaya River (ARE), the Mackenzie River (MRE), the Chesapeake Bay (CBE), Charleston Harbor (CHE), Puget Sound (PUG), and the Neuse River (NRE). Mean DOM concentrations ranged from 100 to 700 µM and dissolved lignin concentrations ranged from ca. 3-30 µg L-1. Overall trends were linear between CDOM measured at 350 nm (a350) and DOC concentration (R2=0.77) and between a350 and lignin (R2=0.87). Intercepts of a350 vs lignin were not significantly different from zero (P=0.43) suggesting that most of the CDOM was terrestrial in nature. Deviations from these regressions were strongest in the Neuse River Estuary, the most eutrophic of the six estuaries studied. After this calibration procedure, fluorescence modeling via parallel factor analysis (PARAFAC) was used to make estimates of terrigenous and planktonic DOC in these estuaries.

  2. 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.

  3. Influence of dissolved organic matter on dissolved vanadium speciation in the Churchill River estuary (Manitoba, Canada).

    PubMed

    Shi, Yong Xiang; Mangal, Vaughn; Guéguen, Céline

    2016-07-01

    Diffusive gradients in thin films (DGT) devices were used to investigate the temporal and spatial changes in vanadium (V) speciation in the Churchill estuary system (Manitoba). Thirty-six DGT sets and 95 discrete water samples were collected at 8 river and 3 estuary sites during spring freshet and summer base flow. Dissolved V concentration in the Churchill River at summer base flow was approximately 5 times higher than those during the spring high flow (27.3 ± 18.9 nM vs 4.8 ± 3.5 nM). DGT-labile V showed an opposite trend with greater values found during the spring high flow (2.6 ± 1.8 nM vs 1.4 ± 0.3 nM). Parallel factor analysis (PARAFAC) conducted on 95 excitation-emission matrix spectra validated four humic-like (C1C4) and one protein-like (C5) fluorescent components. Significant positive relationship was found between protein-like DOM and DGT-labile V (r = 0.53, p < 0.05), indicating that protein-like DOM possibly affected the DGT-labile V concentration in Churchill River. Sediment leachates were enriched in DGT-labile V and protein-like DOM, which can be readily released when river sediment began to thaw during spring freshet. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Mechanisms of dissolved organic carbon cycling in an ocean margin. Final technical report

    SciTech Connect

    Benner, R.

    1997-11-24

    Dissolved organic carbon (DOC) is the largest reservoir of organic carbon in the ocean, and the objectives of this project were to investigate the mechanisms and pathways of DOC formation and consumption in seawater. Carbohydrates are the most abundant form of DOC, and this project included measurements of dissolved carbohydrates as well as DOC to help delineate the cycling of DOC. Many of the methods and approaches for investigating DOC production were developed as part of this project.

  5. [Sources of dissolved organic carbon and the bioavailability of dissolved carbohydrates in the tributaries of Lake Taihu].

    PubMed

    Ye, Lin-Lin; Wu, Xiao-Dong; Kong, Fan-Xiang; Liu, Bo; Yan, De-Zhi

    2015-03-01

    Surface water samples of Yincungang and Chendonggang Rivers were collected from September 2012 to August 2013 in Lake Taihu. Water temperature, Chlorophyll a and bacterial abundance were analyzed, as well as dissolved organic carbon (DOC) concentrations, stable carbon isotope of DOC (Δ13C(DOC)), specific UV absorbance (SUVA254 ) and dissolved carbohydrates concentrations. Δ13C(DOC) ranged from -27.03% per thousand ± 0.30% per thousand to -23.38%per thousand ± 0.20% per thousand, indicating a terrestrial source. Both the autochthonous and allochthonous sources contributed to the carbohydrates pool in the tributaries. Significant differences in PCHO (polysaccharides) and MCHO (monosaccharides) concentrations were observed between spring-summer and autumn-winter (P < 0.01, n = 12; P < 0.01, n = 12), which might be caused by the variation in the sources and bioavailability of carbohydrates. PCHO contributed a major fraction to TCHO (total dissolved carbohydrates) in autumn and winter, which could be explained by the accumulation of undegradable PCHO limited by the low water temperature; MCHO contributed a major fraction to TCHO in spring and summer, which might be caused by the transformation from PCHO by microbes at high water temperature.

  6. PHOTOCHEMICAL ALTERATION OF DISSOLVED ORGANIC MATTER: EFFECTS ON THE CONCENTRATION AND ACIDITIES OF IONIZABLE SITES IN DISSOLVED ORGANIC MATTER IN THE SATILLA RIVER OF GEORGIA, USA

    EPA Science Inventory

    The acid-base properties of humic substances, the major component of dissolved organic matter (DOM), area major control on the alkalinity, or acid neutralizing capacity of freshwater systems. Alkalinity is one of the fundamental parameters measured in aquatic sciences, and is an ...

  7. PHOTOCHEMICAL ALTERATION OF DISSOLVED ORGANIC MATTER: EFFECTS ON THE CONCENTRATION AND ACIDITIES OF IONIZABLE SITES IN DISSOLVED ORGANIC MATTER IN THE SATILLA RIVER OF GEORGIA, USA

    EPA Science Inventory

    The acid-base properties of humic substances, the major component of dissolved organic matter (DOM), area major control on the alkalinity, or acid neutralizing capacity of freshwater systems. Alkalinity is one of the fundamental parameters measured in aquatic sciences, and is an ...

  8. Effect of dissolved organic matter from treated effluents on sorption of atrazine and prometryn by soils

    SciTech Connect

    Seol, Y.; Lee, L.S.

    2000-01-02

    The apparent enhanced transport of soil-applied atrazine following irrigation of treated effluents has been hypothesized to be from complexation of atrazine with effluent-borne dissolved organic matter (DOM). Under long-term effluent irrigation, even small DOM-induced decreases in pesticide sorption can result in significant enhanced pesticide movement due to cumulative effects. The effect of atrazine and prometryn association with DOM extracted from municipal wastewater (MW), swine-derived lagoon wastewater (SW), and dissolved Aldrich humic acid (HA) on sorption by two soils was measured in batch equilibration studies. Individual association of pesticides to DOM, sorption of DOM to soil, and pesticide sorption by soil were also quantified. Pesticide association to DOM normalized to organic carbon (OC) ranged from 30 to 1000 L/kg OC. DOM sorption by soil ranged from 1.5 to 10 L/kg with a silt loam having a higher affinity for the DOM than the sandy loam. DOM up to 150 mg OC/L did not significantly suppress sorption by soils of either atrazine or prometryne in agreement with predictions using the independently measured binary distribution coefficients in a model that assumed linear equilibrium behavior among pesticide, soil, and DOM. A sensitivity analysis was performed using the same model to identify what combination of soil, pesticide, and DOC variables may suppress sorption, resulting in facilitated transport. Results from the sensitivity analysis are presented and the potential for effluent properties other than DOM to facilitate pesticide transport is discussed.

  9. Photobleaching of dissolved organic material from a tidal marsh-estuarine system of the Chesapeake Bay.

    PubMed

    Tzortziou, Maria; Osburn, Christopher L; Neale, Patrick J

    2007-01-01

    Wetlands and tidal marshes in the Rhode River estuary of the Chesapeake Bay act as important sources of dissolved organic carbon and strongly absorbing dissolved organic matter (DOM) for adjacent estuarine waters. The effects of solar exposure on the photochemical degradation of colored DOM (CDOM) were examined for material derived from different sources (estuarine and freshwater parts of the Rhode River, sub-watershed stream, marshes) in this estuarine ecosystem. Consistent with changes in fluorescence emission, absorption loss upon exposure to different portions of the solar spectrum (i.e. different long-pass cut-off filters) occurred across the entire spectrum but the wavelength of maximum photobleaching decreased as the cut-off wavelength of the filter decreased. Our results illustrate that solar exposure can cause either an increase or a decrease in the CDOM absorption spectral slope, S(CDOM), depending on the spectral quality of irradiation and, thus, on the parameters (e.g. atmospheric composition, concentration of UV-absorbing water constituents) that affect the spectral characteristics of the light to which CDOM is exposed. We derived a simple spectral model for describing the effects of solar exposure on CDOM optical quality. The model accurately, and consistently, predicted the observed dependence of CDOM photobleaching on the spectral quality of solar exposure.

  10. The removal kinetics of dissolved organic matter and the optical clarity of groundwater

    NASA Astrophysics Data System (ADS)

    Chapelle, Francis H.; Shen, Yuan; Strom, Eric W.; Benner, Ronald

    2016-09-01

    Concentrations of dissolved organic matter (DOM) and ultraviolet/visible light absorbance decrease systematically as groundwater moves through the unsaturated zones overlying aquifers and along flowpaths within aquifers. These changes occur over distances of tens of meters (m) implying rapid removal kinetics of the chromophoric DOM that imparts color to groundwater. A one-compartment input-output model was used to derive a differential equation describing the removal of DOM from the dissolved phase due to the combined effects of biodegradation and sorption. The general solution to the equation was parameterized using a 2-year record of dissolved organic carbon (DOC) concentration changes in groundwater at a long-term observation well. Estimated rates of DOC loss were rapid and ranged from 0.093 to 0.21 micromoles per liter per day (μM d-1), and rate constants for DOC removal ranged from 0.0021 to 0.011 per day (d-1). Applying these removal rate constants to an advective-dispersion model illustrates substantial depletion of DOC over flow-path distances of 200 m or less and in timeframes of 2 years or less. These results explain the low to moderate DOC concentrations (20-75 μM; 0.26-1 mg L-1) and ultraviolet absorption coefficient values ( a 254 < 5 m-1) observed in groundwater produced from 59 wells tapping eight different aquifer systems of the United States. The nearly uniform optical clarity of groundwater, therefore, results from similarly rapid DOM-removal kinetics exhibited by geologically and hydrologically dissimilar aquifers.

  11. 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.

  12. Chemical characterization of dissolved organic compounds from coastal sea surface microlayers (Baltic Sea, Germany).

    PubMed

    van Pinxteren, Manuela; Müller, Conny; Iinuma, Yoshiteru; Stolle, Christian; Herrmann, Hartmut

    2012-10-02

    The physicochemical properties of the sea surface microlayer (SML), i.e. the boundary layer between the air and the sea, and its impact on air-sea exchange processes have been investigated for decades. However, a detailed description about these processes remains incomplete. In order to obtain a better chemical characterization of the SML, in a case study three pairs of SML and corresponding bulk water samples were taken in the southern Baltic Sea. The samples were analyzed for dissolved organic carbon and dissolved total nitrogen, as well as for several organic nitrogen containing compounds and carbohydrates, namely aliphatic amines, dissolved free amino acids, dissolved free monosaccharides, sugar alcohols, and monosaccharide anhydrates. Therefore, reasonable analytical procedures with respect to desalting and enrichment were established. All aliphatic amines and the majority of the investigated amino acids (11 out of 18) were found in the samples with average concentrations between 53 ng L(-1) and 1574 ng L(-1). The concentrations of carbohydrates were slightly higher, averaging 2900 ng L(-1). Calculation of the enrichment factor (EF) between the sea surface microlayer and the bulk water showed that dissolved total nitrogen was more enriched (EF: 1.1 and 1.2) in the SML than dissolved organic carbon (EF: 1.0 and 1.1). The nitrogen containing organic compounds were generally found to be enriched in the SML (EF: 1.9-9.2), whereas dissolved carbohydrates were not enriched or even depleted (EF: 0.7-1.2). Although the investigated compounds contributed on average only 0.3% to the dissolved organic carbon and 0.4% to the total dissolved nitrogen fraction, these results underline the importance of single compound analysis to determine SML structure, function, and its potential for a transfer of compounds into the atmosphere.

  13. Calibration of an in situ membrane inlet mass spectrometer for measurements of dissolved gases and volatile organics in seawater.

    PubMed

    Bell, Ryan J; Short, R Timothy; van Amerom, Friso H W; Byrne, Robert H

    2007-12-01

    Use of membrane inlet mass spectrometers (MIMS) for quantitative measurements of dissolved gases and volatile organics over a wide range of ocean depths requires characterization of the influence of hydrostatic pressure on the permeability of MIMS inlet systems. To simulate measurement conditions in the field, a laboratory apparatus was constructed for control of sample flow rate, temperature, pressure, and the concentrations of a variety of dissolved gases and volatile organic compounds. MIMS data generated with this apparatus demonstrated thatthe permeability of polydimethylsiloxane (PDMS) membranes is strongly dependent on hydrostatic pressure. For the range of pressures encountered between the surface and 2000 m ocean depths, the pressure dependent behavior of PDMS membranes could not be satisfactorily described using previously published theoretical models of membrane behavior. The observed influence of hydrostatic pressure on signal intensity could, nonetheless, be quantitatively modeled using a relatively simple semiempirical relationship between permeability and hydrostatic pressure. The semiempirical MIMS calibration developed in this study was applied to in situ underwater mass spectrometer (UMS) data to generate high-resolution, vertical profiles of dissolved gases in the Gulf of Mexico. These measurements constitute the first quantitative observations of dissolved gas profiles in the oceans obtained by in situ membrane inlet mass spectrometry. Alternative techniques used to produce dissolved gas profiles were in good accord with UMS measurements.

  14. Dynamics of dissolved organic carbon in a stream during a quarter century of forest succession

    Treesearch

    Judy L. Meyer; Jackson Webster; Jennifer Knoepp; E.F. Benfield

    2014-01-01

    Dissolved organic carbon (DOC) is a heterogeneous mixture of compounds that makes up a large fraction of the organic matter transported in streams. It plays a significant role in many ecosystems. Riverine DOC links organic carbon cycles of continental and oceanic ecosystems. It is a significant trophic resource in stream food webs. DOC imparts color to lakes,...

  15. Photoproduction of dissolved organic carbon and inorganic nutrients from resuspended lake sediments.

    PubMed

    Hu, Bin; Wang, Peifang; Zhang, Nannan; Wang, Chao; Ao, Yanhui

    2016-11-01

    Sediments exposed to simulated solar radiation can serve as an important source of dissolved organic carbon (DOC) to surrounding waters. However, it is still unclear if dissolved nutrients can be photoproduced from lake sedimentary organic matter. In this study, a series of laboratory-based experiments was conducted to address the photoproduction of dissolved inorganic nutrients and DOC from resuspended Taihu Lake sediments. Dissolved inorganic nutrients and DOC were photoproduced after 8-h irradiation. The released NH4(+), NOx(-), and DOC levels ranged from 3.57 to 12.14, 1.43 to 6.43, and 24.17 to 69.17 μmol L(-1), respectively. The variation in the amount released indicated that sediment source had an effect on DOC and nutrient photorelease. More DOC and nutrients were released from higher concentration suspensions. However, due to the light absorption by suspended sediment, less DOC and nutrients were released from per gram of suspended sediment in high concentration suspensions. The decrease in DOC and increase in dissolved inorganic nitrogen during the last 2-h irradiation indicated that the photoproduction of inorganic nutrients proceeded via direct photodissolution of suspended sediments and subsequent photodegradation of the produced dissolved organic matter. Our results demonstrated that the photoproduction flux of NH4(+) and NOx(-) accounts for 12.3 and 6.5 % of wet deposition, respectively, which suggest that the photodissolution of suspended sediment could be a potential source of DOC and dissolved nutrients in shallow water ecosystems.

  16. Landscape controls on dissolved nutrients, organic matter and major ions in a suburbanizing watershed

    NASA Astrophysics Data System (ADS)

    Daley, M. L.; McDowell, W. H.

    2010-12-01

    differently to hydrologic events. Concentrations of DON were negatively correlated with discharge (r2= 0.06, p < 0.01), but DOC concentrations did not respond to discharge, suggesting there is much to learn about the decoupling of C and N rich dissolved organic matter (DOM). Our landscape models do not account for spatial variability in dissolved inorganic carbon (DIC), dissolved organic P (DOP) or particulate C, N and P; however, at our site with the longest record, the Lamprey River, DIC and particulate C account for only 25% and 5% respectively of the total C flux. Among three sites ranging from 3-16% development, particulate N only accounted for 12-18% of total N, but particulate P accounted for 30-50% and DOP accounted for an additional 40-50% of total P. Landscape characteristics may in fact be better predictors of spatial variability in particulate-P and DOP than PO4-P. Nonetheless, the landscape models that we have developed for DIN and DOM flux can be used by local watershed managers to predict changes in water quality in response to changes in land use.

  17. Direct estimation of dissolved organic carbon using synchronous fluorescence and independent component analysis (ICA): advantages of a multivariate calibration.

    PubMed

    De Almeida Brehm, Franciane; de Azevedo, Julio Cesar R; da Costa Pereira, Jorge; Burrows, Hugh D

    2015-11-01

    Dissolved organic carbon (DOC) is frequently used as a diagnostic parameter for the identification of environmental contamination in aqueous systems. Since this organic matter is evolving and decaying over time. If samples are collected under environmental conditions, some sample stabilization process is needed until the corresponding analysis can be made. This may affect the analysis results. This problem can be avoided using the direct determination of DOC. We report a study using in situ synchronous fluorescence spectra, with independent component analysis to retrieve relevant major spectral contributions and their respective component contributions, for the direct determination of DOC. Fluorescence spectroscopy is a very powerful and sensitive technique to evaluate vestigial organic matter dissolved in water and is thus suited for the analytical task of direct monitoring of dissolved organic matter in water, thus avoiding the need for the stabilization step. We also report the development of an accurate calibration model for dissolved organic carbon determinations using environmental samples of humic and fulvic acids. The method described opens the opportunity for a fast, in locus, DOC estimation in environmental or other field studies using a portable fluorescence spectrometer. This combines the benefits of the use of fresh samples, without the need of stabilizers, and also allows the interpretation of various additional spectral contributions based on their respective estimated properties. We show how independent component analysis may be used to describe tyrosine, tryptophan, humic acid and fulvic acid spectra and, thus, to retrieve the respective individual component contribution to the DOC.

  18. Predicting Sources of Dissolved Organic Nitrogen to an Estuary from an Agro-Urban Coastal Watershed.

    PubMed

    Osburn, Christopher L; Handsel, Lauren T; Peierls, Benjamin L; Paerl, Hans W

    2016-08-16

    Dissolved organic nitrogen (DON) is the nitrogen (N)-containing component of dissolved organic matter (DOM) and in aquatic ecosystems is part of the biologically reactive nitrogen pool that can degrade water quality in N-sensitive waters. Unlike inorganic N (nitrate and ammonium) DON is comprised of many different molecules of variable reactivity. Few methods exist to track the sources of DON in watersheds. In this study, DOM excitation-emission matrix (EEM) fluorescence of eight discrete DON sources was measured and modeled with parallel factor analysis (PARAFAC) and the resulting model ("FluorMod") was fit to 516 EEMs measured in surface waters from the main stem of the Neuse River and its tributaries, located in eastern North Carolina. PARAFAC components were positively correlated to DON concentration. Principle components analysis (PCA) was used to confirm separation of the eight sources and model validation was achieved by measurement of source samples not included in the model development with an error of <10%. Application of FluorMod to surface waters of streams within the Neuse River Basin showed that while >70% of DON was attributed to natural sources, nonpoint sources, such as soil and poultry litter leachates and street runoff, accounted for the remaining 30%. This result was consistent with changes in land use from urbanized Raleigh metropolitan area to the largely agricultural Southeastern coastal plain. Overall, the predicted fraction of nonpoint DON sources was consistent with previous reports of increased organic N inputs in this river basin, which are suspected of impacting the water quality of its estuary.

  19. Inhibition of hydroxyl radical reaction with aromatics by dissolved natural organic matter

    SciTech Connect

    Lindsey, M.E.; Tarr, M.A.

    2000-02-01

    Remediation of hydrophobic pollutants is complicated by sorption of these compounds to hydrophobic sites of dissolved natural organic matter (NOM), suspended particulates, soil, and sediment. This sorption causes the pollutants to be less easily degraded by remediation techniques. Reaction of aromatic compounds with hydroxyl radical is inhibited by dissolved natural organic matter (NOM). The degree of inhibition is significantly greater than that expected based on a simple model in which aromatic compound molecules bound to NOM are considered to be unreactive. In this study, hydroxyl radical was produced at steady-state concentrations using Fenton chemistry (H{sub 2}O{sub 2} + Fe{sup 2+} {yields} Fe{sup 3+} + HO{sup {minus}} + HO{sm_bullet}). Suwannee River fulvic acid and humic acid were used as NOM. The most likely mechanism for the observed inhibition is that hydroxyl radical formation occurs in microenvironmental sites remote from the aromatic compounds. In addition to changes in kinetics, pyrene hydroxyl radical reaction also exhibited a mechanistic change in the presence of fulvic acid. The mechanism changed from a reaction that was apparently first-order in pyrene to one that was apparently second-order in pyrene, indicating that pyrene self-reaction may have become the dominant mechanism in the presence of fulvic acid. Dissolved NOM causes significant changes in the rate and mechanism of hydroxyl radical degradation of aromatic compounds. Consequently, literature rate constants measured in pure water will not be useful for predicting the degradation of pollutants in environmental systems. The kinetic and mechanistic information in this study will be useful for developing improved degradation methods involving Fenton chemistry.

  20. The Delivery Of Dissolved Organic Carbon From Forest Soils To A Head Water Stream

    NASA Astrophysics Data System (ADS)

    Mei, Y.; Hornberger, G. M.; Kaplan, L.; Newbold, J. D.; Aufdenkampe, A. K.

    2010-12-01

    The temporal variation of the delivery of dissolved organic carbon (DOC), a complex mixture of compounds, from hillslopes to the adjacent streams is determined by hydrological and biogeochemical processes that have not been completely quantified. In particular, processes involving differences in the fate and transport of the easily biodegradable fraction of dissolved organic carbon (BDOC) and the more recalcitrant fraction of DOC are of ecological importance. We conducted leaching experiments on two vertically oriented in-situ soil cores with different lengths to explore the dynamics of behavior of BDOC and DOC on a forested hillslope at White Clay Creek in southeastern Pennsylvania. A dual-permeability model based on a one-dimensional Richards’ equation coupled with reactive convection-dispersion equations and a heat transport model to characterize the temperature pattern along the core was developed, and used to interpret the experimental data. We also collected storm DOC samples from the stream and from piezometers and wells along a hillslope transect. A two dimensional saturated-unsaturated finite element flow model coupled with a two-dimensional reactive transport model was developed to describe the soil and groundwater flow and the DOC and BDOC responses to precipitation events. Parameters for both the flow and transport models were selected using trial and error calibration first, and then refined using UCODE (USGS). The results show that the models can match the main features of the observed DOC and BDOC patterns under transient soil water flux conditions. Both the simulation and experimental results from this work suggest that the DOC flux declines with depth in the soil profile. DOC, and particularly BDOC, transported from soils to the stream is predominantly from the riparian zone.

  1. High molecular weight dissolved organic matter enrichment selects for methylotrophs in dilution to extinction cultures

    PubMed Central

    Sosa, Oscar A; Gifford, Scott M; Repeta, Daniel J; DeLong, Edward F

    2015-01-01

    The role of bacterioplankton in the cycling of marine dissolved organic matter (DOM) is central to the carbon and energy balance in the ocean, yet there are few model organisms available to investigate the genes, metabolic pathways, and biochemical mechanisms involved in the degradation of this globally important carbon pool. To obtain microbial isolates capable of degrading semi-labile DOM for growth, we conducted dilution to extinction cultivation experiments using seawater enriched with high molecular weight (HMW) DOM. In total, 93 isolates were obtained. Amendments using HMW DOM to increase the dissolved organic carbon concentration 4x (280 μM) or 10x (700 μM) the ocean surface water concentrations yielded positive growth in 4–6% of replicate dilutions, whereas <1% scored positive for growth in non-DOM-amended controls. The majority (71%) of isolates displayed a distinct increase in cell yields when grown in increasing concentrations of HMW DOM. Whole-genome sequencing was used to screen the culture collection for purity and to determine the phylogenetic identity of the isolates. Eleven percent of the isolates belonged to the gammaproteobacteria including Alteromonadales (the SAR92 clade) and Vibrio. Surprisingly, 85% of isolates belonged to the methylotrophic OM43 clade of betaproteobacteria, bacteria thought to metabolically specialize in degrading C1 compounds. Growth of these isolates on methanol confirmed their methylotrophic phenotype. Our results indicate that dilution to extinction cultivation enriched with natural sources of organic substrates has a potential to reveal the previously unsuspected relationships between naturally occurring organic nutrients and the microorganisms that consume them. PMID:25978545

  2. High molecular weight dissolved organic matter enrichment selects for methylotrophs in dilution to extinction cultures.

    PubMed

    Sosa, Oscar A; Gifford, Scott M; Repeta, Daniel J; DeLong, Edward F

    2015-12-01

    The role of bacterioplankton in the cycling of marine dissolved organic matter (DOM) is central to the carbon and energy balance in the ocean, yet there are few model organisms available to investigate the genes, metabolic pathways, and biochemical mechanisms involved in the degradation of this globally important carbon pool. To obtain microbial isolates capable of degrading semi-labile DOM for growth, we conducted dilution to extinction cultivation experiments using seawater enriched with high molecular weight (HMW) DOM. In total, 93 isolates were obtained. Amendments using HMW DOM to increase the dissolved organic carbon concentration 4x (280 μM) or 10x (700 μM) the ocean surface water concentrations yielded positive growth in 4-6% of replicate dilutions, whereas <1% scored positive for growth in non-DOM-amended controls. The majority (71%) of isolates displayed a distinct increase in cell yields when grown in increasing concentrations of HMW DOM. Whole-genome sequencing was used to screen the culture collection for purity and to determine the phylogenetic identity of the isolates. Eleven percent of the isolates belonged to the gammaproteobacteria including Alteromonadales (the SAR92 clade) and Vibrio. Surprisingly, 85% of isolates belonged to the methylotrophic OM43 clade of betaproteobacteria, bacteria thought to metabolically specialize in degrading C1 compounds. Growth of these isolates on methanol confirmed their methylotrophic phenotype. Our results indicate that dilution to extinction cultivation enriched with natural sources of organic substrates has a potential to reveal the previously unsuspected relationships between naturally occurring organic nutrients and the microorganisms that consume them.

  3. Effects of pore size and dissolved organic matters on diffusion of arsenate in aqueous solution.

    PubMed

    Wang, Yulong; Wang, Shaofeng; Wang, Xin; Jia, Yongfeng

    2017-02-01

    Presented here is the influence of membrane pore size and dissolved organic matters on the diffusion coefficient (D) of aqueous arsenate, investigated by the diffusion cell method for the first time. The pH-dependent diffusion coefficient of arsenate was determined and compared with values from previous studies; the coefficient was found to decrease with increasing pH, showing the validity of our novel diffusion cell method. The D value increased dramatically as a function of membrane pore size at small pore sizes, and then increased slowly at pore sizes larger than 2.0μm. Using the ExpAssoc model, the maximum D value was determined to be 11.2565×10(-6)cm(2)/sec. The presence of dissolved organic matters led to a dramatic increase of the D of arsenate, which could be attributed to electrostatic effects and ionic effects of salts. These results improve the understanding of the diffusion behavior of arsenate, especially the important role of various environmental parameters in the study and prediction of the migration of arsenate in aquatic water systems.

  4. Distinct Optical Chemistry of Dissolved Organic Matter in Urban Pond Ecosystems

    PubMed Central

    McEnroe, Nicola A.; Williams, Clayton J.; Xenopoulos, Marguerite A.; Porcal, Petr; Frost, Paul C.

    2013-01-01

    Urbanization has the potential to dramatically alter the biogeochemistry of receiving freshwater ecosystems. We examined the optical chemistry of dissolved organic matter (DOM) in forty-five urban ponds across southern Ontario, Canada to examine whether optical characteristics in these relatively new ecosystems are distinct from other freshwater systems. Dissolved organic carbon (DOC) concentrations ranged from 2 to 16 mg C L-1 across the ponds with an average value of 5.3 mg C L-1. Excitation-emission matrix (EEM) spectroscopy and parallel factor analysis (PARAFAC) modelling showed urban pond DOM to be characterized by microbial-like and, less importantly, by terrestrial derived humic-like components. The relatively transparent, non-humic DOM in urban ponds was more similar to that found in open water, lake ecosystems than to rivers or wetlands. After irradiation equivalent to 1.7 days of natural solar radiation, DOC concentrations, on average, decreased by 38% and UV absorbance decreased by 25%. Irradiation decreased the relative abundances of terrestrial humic-like components and increased protein-like aspects of the DOM pool. These findings suggest that high internal production and/or prolonged exposure to sunlight exerts a distinct and significant influence on the chemistry of urban pond DOM, which likely reduces its chemical similarity with upstream sources. These properties of urban pond DOM may alter its biogeochemical role in these relatively novel aquatic ecosystems. PMID:24348908

  5. Geomorphic controls on riparian zone hydrology, carbon pools and fluxes of dissolved organic carbon

    NASA Astrophysics Data System (ADS)

    Grabs, T.; Ledesma, J.; Laudon, H.; Seibert, J.; Kohler, S. J.; Bishop, K. H.

    2014-12-01

    Near stream (riparian) zones are an important link between terrestrial and aquatic ecosystems and influence a wide range of processes including solute transport or hydrologic behavior of headwater catchments. Understanding the links between geomorphology and riparian soils, vegetation and hydrology is, thus, a prerequisite for relating small scale processes to observations at the watershed scale. Geographic information systems (GIS) have traditionally been used to study links between geomorphology and properties of terrestrial ecosystems. Applying this approach to riparian zones, however, has only recently become feasible with the availability of high-resolution digital elevation models and the new development of suitable computational methods. In this study we present links between geomorphology and riparian zone hydrology, carbon pools and fluxes of dissolved organic carbon. Geomorphometric attributes were successfully used to predict (1) riparian groundwater levels and flow pathways, (2) the size of riparian soil carbon pools, (3) the vertical variation of dissolved organic carbon (DOC) in riparian soil profiles, as well as (4) riparian carbon fluxes and turnover times.

  6. Radioacarbon in dissolved organic carbon, a possible groundwater dating method: Case studies from western Canada

    SciTech Connect

    Wassenaar, L.; Aravena, R. ); Hendry, J. ); Fritz, P. )

    1991-08-01

    This paper explores the feasibility of using {sup 14}C in dissolved organic carbon (DOC) as an alternative isotopic groundwater dating method. Two hydrogeologically contrasting groundwater systems were tested; the Cretaceous age Milk River aquifer, and low-permeability, organic rich, Wisconsinan age Prairie tills in southern Alberta, Canada. Comparisons of radiocarbon data were made between DOC fractions, dissolved inorganic carbon (DIC), and several DIC geochemical age correction models along well defined flow paths. The data presented demonstrate that {sup 14}C dating of DOC fractions can indeed provide an alternative method for determining isotopic groundwater ages, under suitable conditions. However, detailed information may be required regarding (1) the geologic nature of the aquifer and its flow system, (2) the isotopically conservative behavior of DOC, (3) the initial {sup 14}C activity of DOC in recharge, and (4) the effect of bacterial redox processes on the {sup 14}C activity of DOC. In the Milk River aquifer, DOC {sup 14}C ages were successfully used to estimate groundwater residence times, as well as to further refine input parameter assumptions for the DIC method. In the Prairie tills, DOC {sup 14}C ages were used to establish a maximum age for the pore waters in an environment where the DIC method is especially problematic.

  7. Distinct optical chemistry of dissolved organic matter in urban pond ecosystems.

    PubMed

    McEnroe, Nicola A; Williams, Clayton J; Xenopoulos, Marguerite A; Porcal, Petr; Frost, Paul C

    2013-01-01

    Urbanization has the potential to dramatically alter the biogeochemistry of receiving freshwater ecosystems. We examined the optical chemistry of dissolved organic matter (DOM) in forty-five urban ponds across southern Ontario, Canada to examine whether optical characteristics in these relatively new ecosystems are distinct from other freshwater systems. Dissolved organic carbon (DOC) concentrations ranged from 2 to 16 mg C L(-1) across the ponds with an average value of 5.3 mg C L(-1). Excitation-emission matrix (EEM) spectroscopy and parallel factor analysis (PARAFAC) modelling showed urban pond DOM to be characterized by microbial-like and, less importantly, by terrestrial derived humic-like components. The relatively transparent, non-humic DOM in urban ponds was more similar to that found in open water, lake ecosystems than to rivers or wetlands. After irradiation equivalent to 1.7 days of natural solar radiation, DOC concentrations, on average, decreased by 38% and UV absorbance decreased by 25%. Irradiation decreased the relative abundances of terrestrial humic-like components and increased protein-like aspects of the DOM pool. These findings suggest that high internal production and/or prolonged exposure to sunlight exerts a distinct and significant influence on the chemistry of urban pond DOM, which likely reduces its chemical similarity with upstream sources. These properties of urban pond DOM may alter its biogeochemical role in these relatively novel aquatic ecosystems.

  8. Triplet state dissolved organic matter in aquatic photochemistry: reaction mechanisms, substrate scope, and photophysical properties.

    PubMed

    McNeill, Kristopher; Canonica, Silvio

    2016-11-09

    Excited triplet states of chromophoric dissolved organic matter ((3)CDOM*) play a major role among the reactive intermediates produced upon absorption of sunlight by surface waters. After more than two decades of research on the aquatic photochemistry of (3)CDOM*, the need for improving the knowledge about the photophysical and photochemical properties of these elusive reactive species remains considerable. This critical review examines the efforts to date to characterize (3)CDOM*. Information on (3)CDOM* relies mainly on the use of probe compounds because of the difficulties associated with directly observing (3)CDOM* using transient spectroscopic methods. Singlet molecular oxygen ((1)O2), which is a product of the reaction between (3)CDOM* and dissolved oxygen, is probably the simplest indicator that can be used to estimate steady-state concentrations of (3)CDOM*. There are two major modes of reaction of (3)CDOM* with substrates, namely triplet energy transfer or oxidation (via electron transfer, proton-coupled electron transfer or related mechanisms). Organic molecules, including several environmental contaminants, that are susceptible to degradation by these two different reaction modes are reviewed. It is proposed that through the use of appropriate sets of probe compounds and model photosensitizers an improved estimation of the distribution of triplet energies and one-electron reduction potentials of (3)CDOM* can be achieved.

  9. Overstory vegetation influence nitrogen and dissolved organic carbon flux from the atmosphere to the forest floor: Boreal Plain, Canada

    Treesearch

    David E. Pelster; Randall K. Kolka; Ellie E. Prepas

    2009-01-01

    Nitrate, ammonium, total dissolved nitrogen (TDN), dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) concentrations and flux were measured for one year in bulk deposition and throughfall from three stand types (upland deciduous, upland conifer and wetland conifer) on the Boreal Plain, Canada. Annual (November 2006 to October 2007 water year) flux...

  10. Strong colloidal and dissolved organic ligands binding copper and zinc in rivers.

    PubMed

    Hoffmann, Stephen R; Shafer, Martin M; Armstrong, David E

    2007-10-15

    The speciation or physicochemical form of copper and zinc in freshwater plays an important role in reactivity, bioavailability, and toxicity. Strong metal-binding ligands, which determine speciation, were detected by voltammetric methods, both anodic stripping voltammetry (ASV) and competitive ligand equilibration adsorptive stripping voltammetry (CLE-AdSV); the latter technique can detect nanomolar levels of extremely strong (log K' > 13) ligands. Through careful field site selection and the investigation of ultrafiltration permeate samples, natural organic ligands were measured with limited interferences of colloidal inorganic iron- and aluminum-based trace metal-binding phases. Furthermore, ultrafiltration allowed measurement of colloidal and dissolved ligands independently, and differences of ligand abundance and strength in different size classes are reported. For copper, ultrafilterable (<3 kDa) organic ligand site concentrations (expressed normalized to dissolved organic carbon) were on average 33% of the colloidal level, but ultrafilterable ligand log K' values were 0.5 log units stronger than those of the 0.4 microm filterable concentration. The ultrafilterable copper-binding ligand concentration showed a smaller variation across the rivers (25% rsd) than zinc-binding ligands (90% rsd). For all field sites and size fractions, strong ligand sites greatly exceeded metal concentrations; subsequently, equilibrium speciation modeling predict picomolar levels of free metal. Modeling also indicated that the very strong ligands (detected by CLE-AdSV) predominate, so modeling based solely on ASV data in freshwater may be inadequate. Competition experiments indicated that the very strong ligand sites are metal specific for copper and zinc.

  11. Removal of bulk dissolved organic carbon (DOC) and trace organic compounds by bank filtration and artificial recharge.

    PubMed

    Grünheid, Steffen; Amy, Gary; Jekel, Martin

    2005-09-01

    Bank filtration and artificial recharge provide an important drinking water source to the city of Berlin. Due to the practice of water recycling through a semi-closed urban water cycle, the introduction of effluent organic matter (EfOM) and persistent trace organic pollutants in the drinking water is of potential concern. In the work reported herein, the research objectives are to study the removal of bulk and trace organics at bank filtration and artificial recharge sites and to assess important factors of influence for the Berlin area. The monthly analytical program is comprised of dissolved organic carbon (DOC), UV absorbance (UVA254), liquid chromatography with organic carbon detection (LC-OCD), differentiated adsorbable organic halogens (AOX) and single organic compound analysis of a few model compounds. More than 1 year of monitoring was conducted on observation wells located along the flowpaths of the infiltrating water at two field sites that have different characteristics regarding redox conditions, travel time, and travel distance. Two transects are highlighted: one associated with a bank filtration site dominated by anoxic/anaerobic conditions with a travel time of up to 4-5 months, and another with an artificial recharge site dominated by aerobic conditions with a travel time of up to 50 days. It was found that redox conditions and travel time significantly influence the DOC degradation kinetics and the efficiency of AOX and trace compound removal.

  12. Inhibition of hydroxyl radical reaction with aromatics by dissolved natural organic matter

    USGS Publications Warehouse

    Lindsey, M.E.; Tarr, M.A.

    2000-01-01

    Reaction of aromatic compounds with hydroxyl radical is inhibited by dissolved natural organic matter (NOM). The degree of inhibition is significantly greater than that expected based on a simple model in which aromatic compound molecules bound to NOM are considered to be unreactive. In this study, hydroxyl radical was produced at steady-state concentrations using Fenton chemistry (H2O2 + Fe2+ ??? Fe3+ + HO- + HO??). Suwannee River fulvic acid and humic acid were used as NOM. The most likely mechanism for the observed inhibition is that hydroxyl radical formation occurs in microenvironmental sites remote from the aromatic compounds. In addition to changes in kinetics, pyrene hydroxyl radical reaction also exhibited a mechanistic change in the presence of fulvic acid. The mechanism changed from a reaction that was apparently firstorder in pyrene to one that was apparently secondorder in pyrene, indicating that pyrene self-reaction may have become the dominant mechanism in the presence of fulvic acid. Dissolved NOM causes significant changes in the rate and mechanism of hydroxyl radical degradation of aromatic compounds. Consequently, literature rate constants measured in pure water will not be useful for predicting the degradation of pollutants in environmental systems. The kinetic and mechanistic information in this study will be useful for developing improved degradation methods involving Fenton chemistry.Reaction of aromatic compounds with hydroxyl radical is inhibited by dissolved natural organic matter (NOM). The degree of inhibition is significantly greater than that expected based on a simple model in which aromatic compounds molecules bounds to NOM are considered to be unreactive. In this study, hydroxyl radical was produced at steady-state concentrations using Fenton chemistry (H2O2 + Fe2+ ??? Fe3+ + HO- + HO??). Suwannee River fulvic acid and humic acid were used as NOM. The most likely mechanisms for the observed inhibition is that hydroxyl radical

  13. Characterization and origin of polar dissolved organic matter from the Great Salt Lake

    USGS Publications Warehouse

    Leenheer, J.A.; Noyes, T.I.; Rostad, C.E.; Davisson, M.L.

    2004-01-01

    Polar dissolved organic matter (DOM) was isolated from a surface-water sample from the Great Salt Lake by separating it from colloidal organic matter by membrane dialysis, from less-polar DOM fractions by resin sorbents, and from inorganic salts by a combination of sodium cation exchange followed by precipitation of sodium salts by acetic acid during evaporative concentration. Polar DOM was the most abundant DOM fraction, accounting for 56% of the isolated DOM. Colloidal organic matter was 14C-age dated to be about 100% modern carbon and all of the DOM fractions were 14C-age dated to be between 94 and 95% modern carbon. Average structural models of each DOM fraction were derived that incorporated quantitative elemental and infrared, 13C-NMR, and electrospray/mass spectrometric data. The polar DOM model consisted of open-chain N-acetyl hydroxy carboxylic acids likely derived from N-acetyl heteropolysaccharides that constituted the colloidal organic matter. The less polar DOM fraction models consisted of aliphatic alicyclic ring structures substituted with carboxyl, hydroxyl, ether, ester, and methyl groups. These ring structures had characteristics similar to terpenoid precursors. All DOM fractions in the Great Salt Lake are derived from algae and bacteria that dominate DOM inputs in this lake.

  14. Effects of sulfate deposition on pore water dissolved organic carbon, nutrients, and microbial enzyme activities in a northern peatland

    EPA Science Inventory

    Export of dissolved organic carbon from lakes and streams has increased throughout Europe and North America over the past several decades. One possible cause is altered deposition chemistry; specifically, decreasing sulfate inputs leading to changes in ionic strength and dissolve...

  15. DISTRIBUTION AND COMPOSITION OF DISSOLVED AND PARTICULATE ORGANIC CARBON IN NORTHERN SAN FRANCISCO BAY DURING LOW FRESHWATER FLOW CONDITIONS

    EPA Science Inventory

    The distribution of organic matter was studied in northern San Francisco Bay monthly through spring and summer 1996 along the salinity gradient from the Sacramento River to Central Bay. Dissolved constituents included monosaccharides (MONO), total carbohydrates (TCHO), dissolved ...

  16. DISTRIBUTION AND COMPOSITION OF DISSOLVED AND PARTICULATE ORGANIC CARBON IN NORTHERN SAN FRANCISCO BAY DURING LOW FRESHWATER FLOW CONDITIONS

    EPA Science Inventory

    The distribution of organic matter was studied in northern San Francisco Bay monthly through spring and summer 1996 along the salinity gradient from the Sacramento River to Central Bay. Dissolved constituents included monosaccharides (MONO), total carbohydrates (TCHO), dissolved ...

  17. Effects of sulfate deposition on pore water dissolved organic carbon, nutrients, and microbial enzyme activities in a northern peatland

    EPA Science Inventory

    Export of dissolved organic carbon from lakes and streams has increased throughout Europe and North America over the past several decades. One possible cause is altered deposition chemistry; specifically, decreasing sulfate inputs leading to changes in ionic strength and dissolve...

  18. Spatial and temporal variation in dissolved organic carbon composition in a peaty catchment draining a windfarm

    NASA Astrophysics Data System (ADS)

    Zheng, Ying; Waldron, Susan; Flowers, Hugh

    2015-04-01

    Peatlands are an important terrestrial carbon reserve and a principal source of dissolved organic carbon (DOC) to the fluvial environment (Wallage et al. 2006). Recently it has been observed that DOC concentrations [DOC] in surface waters have increased in Europe and North America (Monteith et al. 2007). This has been attributed primarily to reduced acid deposition. However, land use change can also release C from peat soils. A significant land use change in Scotland is hosting windfarms. Whether windfarm construction causes such impacts has been a research focus, particularly considering fluvial losses, but usually assessing if there are changes in DOC concentration rather than composition. Our study area is a peaty catchment that hosts wind turbines, has peat restoration activities and forest felling and is drained by two streams. We are using UV-visible and fluorescence spectrophotometry to assess if there are differences between the two steams or temporal changes in DOC composition. We will present data from samples collected since February 2014. The parameters we are focusing on are SUVA254, E4/E6 and E2/E4 ratios as these are indicators of DOC aromaticity, humic acid (HA): fulvic acid (FA) ratio and the proportion of humic substances in DOC (Weishaar, 2003; Spencer et al. 2007; Graham et al. 2012). To assess these we have measured UV-visible absorbance spectra from 200 nm to 800 nm. Meanwhile sample fluorescence emission and excitation matrix (EEM) will be applied with the PARAFAC model to obtain more information about the variations in humic substances in this catchment. Our current analysis indicates spatial differences not only in DOC concentration but also in composition. For example, the mainstem draining the windfarm area had a smaller [DOC] but higher E4/E6 and lower E2/E4 ratio values than the tributary draining an area of felled forestry. This may be indicative of more HAs in the mainstem DOC. Seasonal variations have also been observed. Both streams

  19. Colored dissolved organic matter in shallow estuaries: relationships between carbon sources and light attenuation

    USGS Publications Warehouse

    Oestreich, W.K.; Ganju, Neil K.; Pohlman, John; Suttles, Steven E.

    2016-01-01

    Light availability is of primary importance to the ecological function of shallow estuaries. For example, benthic primary production by submerged aquatic vegetation is contingent upon light penetration to the seabed. A major component that attenuates light in estuaries is colored dissolved organic matter (CDOM). CDOM is often measured via a proxy, fluorescing dissolved organic matter (fDOM), due to the ease of in situ fDOM sensor measurements. Fluorescence must be converted to CDOM absorbance for use in light attenuation calculations. However, this CDOM–fDOM relationship varies among and within estuaries. We quantified the variability in this relationship within three estuaries along the mid-Atlantic margin of the eastern United States: West Falmouth Harbor (MA), Barnegat Bay (NJ), and Chincoteague Bay (MD/VA). Land use surrounding these estuaries ranges from urban to developed, with varying sources of nutrients and organic matter. Measurements of fDOM (excitation and emission wavelengths of 365 nm (±5 nm) and 460 nm (±40 nm), respectively) and CDOM absorbance were taken along a terrestrial-to-marine gradient in all three estuaries. The ratio of the absorption coefficient at 340 nm (m−1) to fDOM (QSU) was higher in West Falmouth Harbor (1.22) than in Barnegat Bay (0.22) and Chincoteague Bay (0.17). The CDOM : fDOM absorption ratio was variable between sites within West Falmouth Harbor and Barnegat Bay, but consistent between sites within Chincoteague Bay. Stable carbon isotope analysis for constraining the source of dissolved organic matter (DOM) in West Falmouth Harbor and Barnegat Bay yielded δ13C values ranging from −19.7 to −26.1 ‰ and −20.8 to −26.7 ‰, respectively. Concentration and stable carbon isotope mixing models of DOC (dissolved organic carbon) indicate a contribution of 13C-enriched DOC in the estuaries. The most likely source of 13C-enriched DOC for the systems we investigated is Spartina cordgrass. Comparison of

  20. Colored dissolved organic matter in shallow estuaries: relationships between carbon sources and light attenuation

    NASA Astrophysics Data System (ADS)

    Oestreich, W. K.; Ganju, N. K.; Pohlman, J. W.; Suttles, S. E.

    2016-02-01

    Light availability is of primary importance to the ecological function of shallow estuaries. For example, benthic primary production by submerged aquatic vegetation is contingent upon light penetration to the seabed. A major component that attenuates light in estuaries is colored dissolved organic matter (CDOM). CDOM is often measured via a proxy, fluorescing dissolved organic matter (fDOM), due to the ease of in situ fDOM sensor measurements. Fluorescence must be converted to CDOM absorbance for use in light attenuation calculations. However, this CDOM-fDOM relationship varies among and within estuaries. We quantified the variability in this relationship within three estuaries along the mid-Atlantic margin of the eastern United States: West Falmouth Harbor (MA), Barnegat Bay (NJ), and Chincoteague Bay (MD/VA). Land use surrounding these estuaries ranges from urban to developed, with varying sources of nutrients and organic matter. Measurements of fDOM (excitation and emission wavelengths of 365 nm (±5 nm) and 460 nm (±40 nm), respectively) and CDOM absorbance were taken along a terrestrial-to-marine gradient in all three estuaries. The ratio of the absorption coefficient at 340 nm (m-1) to fDOM (QSU) was higher in West Falmouth Harbor (1.22) than in Barnegat Bay (0.22) and Chincoteague Bay (0.17). The CDOM : fDOM absorption ratio was variable between sites within West Falmouth Harbor and Barnegat Bay, but consistent between sites within Chincoteague Bay. Stable carbon isotope analysis for constraining the source of dissolved organic matter (DOM) in West Falmouth Harbor and Barnegat Bay yielded δ13C values ranging from -19.7 to -26.1 ‰ and -20.8 to -26.7 ‰, respectively. Concentration and stable carbon isotope mixing models of DOC (dissolved organic carbon) indicate a contribution of 13C-enriched DOC in the estuaries. The most likely source of 13C-enriched DOC for the systems we investigated is Spartina cordgrass. Comparison of DOC source to CDOM : f

  1. Leaching of Particulate and Dissolved Organic Carbon from Compost Applied to Bioretention Systems

    NASA Astrophysics Data System (ADS)

    Iqbal, Hamid; Flury, Markus; Mullane, Jessica; Baig, Muhammad

    2015-04-01

    Compost is used in bioretention systems to improve soil quality, to promote plant growth, and to remove metal contaminants from stormwater. However, compost itself, particularly when applied freshly, can be a source of contamination of the stormwater. To test the potential contamination caused by compost when applied to bioretention systems, we continuously leached a compost column with water under unsaturated conditions and characterized dissolved and particulate organic matter in the leachate. Freshly applied, mature compost leached up to 400 mg/L of dissolved organic carbon and 2,000 mg/L of suspended particulate organic carbon. It required a cumulative water flux of 4,000 mm until concentrations of dissolved and particulate organic carbon declined to levels typical for surface waters. Although, dissolved and particulate organic carbon are not contaminants per se, they can facilitate the movement of metals, thereby enhancing the mobility of toxic metals present in stormwater. Therefore, we recommended that compost is washed before it is applied to bioretention systems. Keywords compost; leachate; alkali extract; dissolved organic carbon; flux

  2. Dissolved organic matter transport reflects hillslope to stream connectivity during snowmelt in a montane catchment

    NASA Astrophysics Data System (ADS)

    Burns, Margaret A.; Barnard, Holly R.; Gabor, Rachel S.; McKnight, Diane M.; Brooks, Paul D.

    2016-06-01

    Dissolved organic matter (DOM) transport is a key biogeochemical linkage across the terrestrial-aquatic interface in headwater catchments, and quantifying the biological and hydrological controls on DOM composition provides insight into DOM cycling at the catchment scale. We evaluated the mobility of DOM components during snowmelt in a montane, semiarid catchment. DOM composition was evaluated on a near-daily basis within the soil and the stream during snowmelt, and was compared to groundwater samples using a site-specific parallel factor analysis (PARAFAC) model derived from soil extracts. The fluorescent component loadings in the interstitial soil water and in the groundwater were significantly different and did not temporally change during snowmelt. In the stream, a transition occurred during snowmelt from fluorescent DOM with higher contributions of amino acid-like components indicative of groundwater to higher humic-like contributions indicative of soil water. Furthermore, we identified a humic-like fluorescent component in the soil water and the stream that is typically only observed in extracted water soluble organic matter from soil which may suggest hillslope to stream connectivity over very short time scales. Qualitative interpretations of changes in stream fluorescent DOM were supported by two end-member mixing analyses of conservative tracers. After normalizing fluorescent DOM loadings for dissolved organic carbon (DOC) concentration, we found that the peak in DOC concentration in the stream was driven by the nonfluorescent fraction of DOM. This study demonstrated how PARAFAC analysis can be used to refine our conceptual models of runoff generation sources, as well as provide a more detailed understanding of stream chemistry dynamics.

  3. Dissolved organic matter composition of Arctic rivers: Linking permafrost and parent material to riverine carbon

    NASA Astrophysics Data System (ADS)

    O'Donnell, Jonathan A.; Aiken, George R.; Swanson, David K.; Panda, Santosh; Butler, Kenna D.; Baltensperger, Andrew P.

    2016-12-01

    Recent climate change in the Arctic is driving permafrost thaw, which has important implications for regional hydrology and global carbon dynamics. Permafrost is an important control on groundwater dynamics and the amount and chemical composition of dissolved organic matter (DOM) transported by high-latitude rivers. The consequences of permafrost thaw for riverine DOM dynamics will likely vary across space and time, due in part to spatial variation in ecosystem properties in Arctic watersheds. Here we examined watershed controls on DOM composition in 69 streams and rivers draining heterogeneous landscapes across a broad region of Arctic Alaska. We characterized DOM using bulk dissolved organic carbon (DOC) concentration, optical properties, and chemical fractionation and classified watersheds based on permafrost characteristics (mapping of parent material and ground ice content, modeling of thermal state) and ecotypes. Parent material and ground ice content significantly affected the amount and composition of DOM. DOC concentrations were higher in watersheds underlain by fine-grained loess compared to watersheds underlain by coarse-grained sand or shallow bedrock. DOC concentration was also higher in rivers draining ice-rich landscapes compared to rivers draining ice-poor landscapes. Similarly, specific ultraviolet absorbance (SUVA254, an index of DOM aromaticity) values were highest in watersheds underlain by fine-grained deposits or ice-rich permafrost. We also observed differences in hydrophobic organic acids, hydrophilic compounds, and DOM fluorescence across watersheds. Both DOC concentration and SUVA254 were negatively correlated with watershed active layer thickness, as determined by high-resolution permafrost modeling. Together, these findings highlight how spatial variations in permafrost physical and thermal properties can influence riverine DOM.

  4. Dissolved organic matter composition of Arctic rivers: Linking permafrost and parent material to riverine carbon

    USGS Publications Warehouse

    O’Donnell, Jonathan A.; Aiken, George R.; Swanson, David K.; Santosh, Panda; Butler, Kenna; Baltensperger, Andrew P.

    2016-01-01

    Recent climate change in the Arctic is driving permafrost thaw, which has important implications for regional hydrology and global carbon dynamics. Permafrost is an important control on groundwater dynamics and the amount and chemical composition of dissolved organic matter (DOM) transported by high-latitude rivers. The consequences of permafrost thaw for riverine DOM dynamics will likely vary across space and time, due in part to spatial variation in ecosystem properties in Arctic watersheds. Here we examined watershed controls on DOM composition in 69 streams and rivers draining heterogeneous landscapes across a broad region of Arctic Alaska. We characterized DOM using bulk dissolved organic carbon (DOC) concentration, optical properties, and chemical fractionation and classified watersheds based on permafrost characteristics (mapping of parent material and ground ice content, modeling of thermal state) and ecotypes. Parent material and ground ice content significantly affected the amount and composition of DOM. DOC concentrations were higher in watersheds underlain by fine-grained loess compared to watersheds underlain by coarse-grained sand or shallow bedrock. DOC concentration was also higher in rivers draining ice-rich landscapes compared to rivers draining ice-poor landscapes. Similarly, specific ultraviolet absorbance (SUVA254, an index of DOM aromaticity) values were highest in watersheds underlain by fine-grained deposits or ice-rich permafrost. We also observed differences in hydrophobic organic acids, hydrophilic compounds, and DOM fluorescence across watersheds. Both DOC concentration and SUVA254 were negatively correlated with watershed active layer thickness, as determined by high-resolution permafrost modeling. Together, these findings highlight how spatial variations in permafrost physical and thermal properties can influence riverine DOM.

  5. Dissolved organic sulfur in the ocean: Biogeochemistry of a petagram inventory.

    PubMed

    Ksionzek, Kerstin B; Lechtenfeld, Oliver J; McCallister, S Leigh; Schmitt-Kopplin, Philippe; Geuer, Jana K; Geibert, Walter; Koch, Boris P

    2016-10-28

    Although sulfur is an essential element for marine primary production and critical for climate processes, little is known about the oceanic pool of nonvolatile dissolved organic sulfur (DOS). We present a basin-scale distribution of solid-phase extractable DOS in the East Atlantic Ocean and the Atlantic sector of the Southern Ocean. Although molar DOS versus dissolved organic nitrogen (DON) ratios of 0.11 ± 0.024 in Atlantic surface water resembled phytoplankton stoichiometry (sulfur/nitrogen ~ 0.08), increasing dissolved organic carbon (DOC) versus DOS ratios and decreasing methionine-S yield demonstrated selective DOS removal and active involvement in marine biogeochemical cycles. Based on stoichiometric estimates, the minimum global inventory of marine DOS is 6.7 petagrams of sulfur, exceeding all other marine organic sulfur reservoirs by an order of magnitude. Copyright © 2016, American Association for the Advancement of Science.

  6. Dust inputs and bacteria influence dissolved organic matter in clear alpine lakes

    PubMed Central

    Mladenov, N.; Sommaruga, R.; Morales-Baquero, R.; Laurion, I.; Camarero, L.; Diéguez, M.C.; Camacho, A.; Delgado, A.; Torres, O.; Chen, Z.; Felip, M.; Reche, I.

    2011-01-01

    Remote lakes are usually unaffected by direct human influence, yet they receive inputs of atmospheric pollutants, dust, and other aerosols, both inorganic and organic. In remote, alpine lakes, these atmospheric inputs may influence the pool of dissolved organic matter, a critical constituent for the biogeochemical functioning of aquatic ecosystems. Here, to assess this influence, we evaluate factors related to aerosol deposition, climate, catchment properties, and microbial constituents in a global dataset of 86 alpine and polar lakes. We show significant latitudinal trends in dissolved organic matter quantity and quality, and uncover new evidence that this geographic pattern is influenced by dust deposition, flux of incident ultraviolet radiation, and bacterial processing. Our results suggest that changes in land use and climate that result in increasing dust flux, ultraviolet radiation, and air temperature may act to shift the optical quality of dissolved organic matter in clear, alpine lakes. PMID:21792184

  7. Dissolved organic sulfur in the ocean: Biogeochemistry of a petagram inventory

    NASA Astrophysics Data System (ADS)

    Ksionzek, Kerstin B.; Lechtenfeld, Oliver J.; McCallister, S. Leigh; Schmitt-Kopplin, Philippe; Geuer, Jana K.; Geibert, Walter; Koch, Boris P.

    2016-10-01

    Although sulfur is an essential element for marine primary production and critical for climate processes, little is known about the oceanic pool of nonvolatile dissolved organic sulfur (DOS). We present a basin-scale distribution of solid-phase extractable DOS in the East Atlantic Ocean and the Atlantic sector of the Southern Ocean. Although molar DOS versus dissolved organic nitrogen (DON) ratios of 0.11 ± 0.024 in Atlantic surface water resembled phytoplankton stoichiometry (sulfur/nitrogen ~ 0.08), increasing dissolved organic carbon (DOC) versus DOS ratios and decreasing methionine-S yield demonstrated selective DOS removal and active involvement in marine biogeochemical cycles. Based on stoichiometric estimates, the minimum global inventory of marine DOS is 6.7 petagrams of sulfur, exceeding all other marine organic sulfur reservoirs by an order of magnitude.

  8. Dissolving and melting phenomena of inorganic and organic crystals by addition of third or second components

    NASA Astrophysics Data System (ADS)

    Funakoshi, Kunio; Negishi, Rina; Nakagawa, Hiroshi; Kawasaki, Rentaro

    2017-06-01

    Dissolution of potassium sulphate (K2SO4) crystals was decelerated or stopped since the trivalent chrome ions (Cr(III)) or the iron ions were added into a K2SO4 aqueous solution, but inhibition mechanism of crystal dissolving by additives is not discussed well. Moreover, the melting inhibition of organic compound crystals by addition of the second components is not reported. In this study, inorganic or organic compound crystals are dissolved in a solution added the third component or were melted in a melt added the second one, and the dissolving and melting inhibition phenomena of the inorganic and organic crystals with additives are discussed. The dissolving rates of K2SO4 crystals decreased with the increasing of the amount of Cr(III) added into an K2SO4 unsaturated solution. The melting rates of m-chloronitrobenzene (CNB) crystals were also decreased by addition of p-CNB. The dissolving rates of a K2SO4 mother crystal and the melting rates of a m-CNB mother crystal were scattered during experiments and the dissolving and the melting phenomena would be caused by adsorption and detachments of additives on and from crystal surfaces.

  9. Amount, composition and seasonality of dissolved organic carbon and nitrogen export from agriculture in contrasting climates

    NASA Astrophysics Data System (ADS)

    Graeber, Daniel; Meerhof, Mariana; Zwirnmann, Elke; Ovesen, Niels; Gelbrecht, Jörg; Teixeira de Mello, Franco; González-Bergonzoni, Ivan; Jeppesen, Erik; Kronvang, Brian

    2014-05-01

    Agricultural catchments are potentially important but often neglected sources of dissolved organic matter (DOM), of which a large part is dissolved organic carbon (DOC) and nitrogen (DON). DOC is an important source of aquatic microbial respiration and DON may be an important source of nitrogen to aquatic ecosystems. However, there is still a lack of comprehensive studies on the amount, composition and seasonality of DOM export from agricultural catchments in different climates. The aim of our study was to assess the amount, composition and seasonality of DOM in a total of four streams in the wet-temperate and subtropical climate of Denmark and Uruguay, respectively. In each climate, we investigated one stream with extensive agriculture (mostly pasture) and one stream with intensive agriculture (mostly intensively used arable land) in the catchment. We sampled each stream taking grab samples fortnightly for two years and measured DOC and DON concentration, as well as molecular composition by size-exclusion chromatography. We used absorbance, fluorescence and parallel factor analysis to gather additional information on the sources and composition of the DOM. The results were coupled to measurements of precipitation, water temperature, discharge, water residence time and physicochemical data measured at each study site to investigate the effects these environmental variables have on the amount and composition of DOM in the streams. Average annual DOM concentration and seasonality were highest in the stream with intensive agriculture in Uruguay and lowest in the stream with extensive agriculture in Denmark. In all streams, the molecular-size composition of DOC and DON were similar and most DOC and DON were exported as humic substances with low C:N ratio, which indicates high bioavailability. Moreover, DON was of higher relative importance in the Uruguayan streams than in the Danish streams, as can be seen from the lower dissolved inorganic to total dissolved nitrogen

  10. On the borderline of dissolved and particulate organic matter: partitioning and bioavailability of polycyclic aromatic hydrocarbons.

    PubMed

    Akkanen, Jarkko; Tuikka, Anita; Kukkonen, Jussi V K

    2012-04-01

    The functionality of dissolved organic matter (DOM) was studied by assessing the availability of polycyclic aromatic hydrocarbons (PAHs) spiked in pore water samples separated from sediments by water extraction and centrifugation with or without subsequent filtration. The purpose was to compare the effects of traditionally defined DOM (0.45-μm cut off) and larger colloidal material present in the separated pore water samples on the partitioning and bioavailability of PAHs. The tested PAHs included phenanthrene (Phe), fluoranthene (Flu), pyrene (Pyr) and benzo[a]pyrene (BaP). Bioavailability of the selected PAHs was tested with two ecologically different organisms: pelagic filter feeder Daphnia magna and sediment-dwelling deposit feeder Lumbriculus variegatus. Sorption to DOM (i.e. in filtered samples) was clearly higher for BaP than for the other PAH. This was also reflected in significantly reduced bioavailability for both model organisms in the filtered samples compared to DOM-free conditions. For the other PAHs the sorption was significant only in the unfiltered samples indicating the importance of larger colloidal material. Thus, the bioavailability of PAHs was also more effectively reduced by the colloidal material. This holds true for both the model organisms, indicating that the ecological differences i.e. filter feeder vs. deposit feeder do not affect in this respect. It appears that considering only traditionally defined DOM, material that may be present in environmental samples and is important for the speciation and bioavailability of contaminants is ignored.

  11. Dissolved Organic Matter Dynamics in a Suburbanizing Watershed: The Importance of Wetlands, People, and Flowpaths

    NASA Astrophysics Data System (ADS)

    Koenig, L.; Daley, M. L.; Potter, J.; McDowell, W. H.

    2013-12-01

    Human development of a watershed often yields fundamental and quantifiable changes in water quality and inorganic nutrient cycling. The effects of suburban development on the cycling of dissolved organic matter (DOM), however, have received relatively less attention, and the understanding of local dissolved organic matter dynamics is rarely a stated goal of watershed management. In this study, we examine the effects of suburbanization on concentrations of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) as well as the optical properties of DOM using 17 study sites in the Lamprey River watershed, NH that integrate varying levels of human development and population density. We show that concentration of DOC and DON is related to wetland cover but is not correlated with population density. Further, we observed no response in DOC concentration with increased flow at the mainstem site, while DON concentration is diluted. The optical properties of dissolved organic matter, however, showed different trends. Fluorescence Index (FI) decreases with increasing wetland cover and lower population density. We show that in a coastal watershed, while DOM quantity is driven by the presence of wetlands, DOM quality changes with both wetland cover and human development. The decoupling of DOM quantity and quality in this suburbanizing watershed indicate that DOM quality may be an important yet overlooked control on watershed-scale biogeochemical cycling and nutrient export.

  12. Linking aboveground net primary productivity to soil carbon and dissolved organic carbon in complex terrain

    Treesearch

    F.S. Peterson; K. Lajtha

    2013-01-01

    Factors influencing soil organic matter (SOM) stabilization and dissolved organic carbon (DOC) content in complex terrain, where vegetation, climate, and topography vary over the scale of a few meters, are not well understood. We examined the spatial correlations of lidar and geographic information system-derived landscape topography, empirically measured soil...

  13. FACTORS AFFECTING COLORED DISSOLVED ORGANIC MATTER IN AQUATIC ENVIRONMENTS OF THE SOUTHEASTERN UNITED STATES

    EPA Science Inventory

    The sunlight-absorbing (colored) component of dissolved organic matter (CDOM) in aquatic environments is widely distributed in freshwaters and coastal regions where it influences the fate and transport of toxic organic substances and biologically-important metals such as mercury,...

  14. Characterization of Plant-derived Dissolved Organic Matter by Multiple Spectroscopic Techniques

    USDA-ARS?s Scientific Manuscript database

    Dissolved organic matter (DOM) derived from fresh or early-stage decomposing soil amendment materials may play an important role in the process of organic matter accumulation. In this study, eight DOM samples from alfalfa, corn, crimson clover, hairy vetch, lupin, soybean, wheat and dairy manure wer...

  15. Dispersion of kaolinite by dissolved organic matter from Douglas-fir roots

    Treesearch

    Philip B. Durgin; Jesse G. Chaney

    1984-01-01

    The organic constituents of water extracts from Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. menziesii) roots that cause kaolinite dispersion were investigated. The dissolved organic matter was fractionated according to molecular size and chemical characteristics into acids, neutrals, and bases of the hydrophilic and hydrophobic groups.

  16. FACTORS AFFECTING COLORED DISSOLVED ORGANIC MATTER IN AQUATIC ENVIRONMENTS OF THE SOUTHEASTERN UNITED STATES

    EPA Science Inventory

    The sunlight-absorbing (colored) component of dissolved organic matter (CDOM) in aquatic environments is widely distributed in freshwaters and coastal regions where it influences the fate and transport of toxic organic substances and biologically-important metals such as mercury,...

  17. Bioavailability and export of dissolved organic matter from a tropical river during base- and stormflow conditions

    Treesearch

    Tracy N. Wiegner; Randee L. Tubal; Richard A. MacKenzie

    2009-01-01

    Concentrations, bioavailability, and export of dissolved organic matter (DOM), particulate organic matter (POM), and nutrients from the Wailuku River, Hawai'i, U.S.A., were examined under base- and stormflow conditions. During storms, DOM and POM concentrations increased approximately by factors of 2 and 11, respectively, whereas NO3...

  18. Effects of Low Dissolved Oxygen on Organisms Used in Freshwater Sediment Toxicity Tests

    EPA Science Inventory

    This manuscript describes the results of tests to determine the tolerance of three benthic organisms to reduced dissolved oxygen (DO). These three organisms are those recommended by EPA for use in toxicity testing of contaminated sediments. The results of the exposures indicate ...

  19. Effects of Low Dissolved Oxygen on Organisms Used in Freshwater Sediment Toxicity Tests

    EPA Science Inventory

    This manuscript describes the results of tests to determine the tolerance of three benthic organisms to reduced dissolved oxygen (DO). These three organisms are those recommended by EPA for use in toxicity testing of contaminated sediments. The results of the exposures indicate ...

  20. Spatial connectivity in a large river system: resolving the sources and fate of dissolved organic matter.

    PubMed

    Massicotte, Philippe; Frenette, Jean-Jacques

    2011-10-01

    Large rivers are generally heterogeneous and productive systems that receive important inputs of dissolved organic matter (DOM) from terrestrial and in situ sources. Thus, they are likely to play a significant role in the biogeochemical cycling of the DOM flowing to the oceans. The asymmetric spatial gradient driven by directional flow and environmental heterogeneity contributes to the fate of DOM flowing downstream. Yet, the relative effects of spatial connectivity and environmental heterogeneity on DOM dynamics are poorly understood. For example, since environmental variables show spatial heterogeneity, the variation explained by environmental and spatial variables may be redundant. We used the St. Lawrence River (SLR) as a representative large river to resolve the unique influences of environmental heterogeneity and spatial connectivity on DOM dynamics. We used three-dimensional fluorescence matrices combined with parallel factor analysis (PARAFAC) to characterize the DOM pool in the SLR. Seven fluorophores were modeled, of which two were identified to be of terrestrial origin and three from algal exudates. We measured a set of environmental variables that are known to drive the fate of DOM in aquatic systems. Additionally, we used asymmetric eigenvector map (AEM) modeling to take spatial connectivity into account. The combination of spatial and environmental models explained 85% of the DOM variation. We show that spatial connectivity is an important driver of DOM dynamics, as a large fraction of environmental heterogeneity was attributable to the asymmetric spatial gradient. Along the longitudinal axis, we noted a rapid increase in dissolved organic carbon (DOC), mostly controlled by terrestrial input of DOM originating from the tributaries. Variance partitioning demonstrated that freshly produced protein-like DOM was found to be the preferential substrate for heterotrophic bacteria undergoing rapid proliferation, while humic-like DOM was more correlated to the

  1. 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.

  2. Transport of dissolved organic carbon from soil to surface water: Identifying the transport pathways

    NASA Astrophysics Data System (ADS)

    Van Gaelen, Nele

    2013-04-01

    Over the last decades, increasing concentrations of dissolved organic carbon (DOC) have been found in surface waters. It has also become clear that land use is an important driver for DOC export. However, causal factors controlling this temporal and spatial variation are not clear. Efforts to model DOC export on a catchment scale are rare. In this research, we aim to determine the factors controlling variations in DOC concentration and quality in surface waters. Secondly, the importance of the different pathways (surface runoff, subsurface flow and groundwater flow) for the transport of dissolved organic matter from the soil to the surface water is investigated. Six headwater catchments (100 - 400 ha) were selected in Belgium, representing three different types of land use, namely forest, grassland and arable land. At the outlet of each catchment, a flow-proportional sampler has been collecting samples of base flow and peak discharge since January 2010. In addition, samples of groundwater, subsurface water and precipitation water were collected on a regular base in three of the catchments. Samples were analyzed for DOC, specific UV absorbance (SUVA) and dissolved silica (DSi). Elemental analysis was carried out using ICP-OES. Since 2012, precipitation water and a selection of river water samples was also analyzed for O and H isotopes. Overall, DOC concentrations were highest in forest catchments and lowest in grassland catchments. For all land use types, measured DOC concentrations were highest during peak discharge. The rise in DOC concentrations was associated with a change in DOC quality. During periods of greater discharge, higher SUVA values were measured, indicating DOC with higher aromaticity (humic and fulvic fractions) reaches the outlet. ICP and DSi results also showed a significant difference in geochemical composition of the river water if peak events are compared to base flow samples. During an event, Ca, Mg, Na, S and DSi concentrations were lowered

  3. Dissolved organic carbon concentrations and compositions, and trihalomethane formation potentials in waters from agricultural peat soils, Sacramento-San Joaquin Delta, California; implications for drinking-water quality

    USGS Publications Warehouse

    Fujii, Roger; Ranalli, Anthony J.; Aiken, George R.; Bergamaschi, Brian A.

    1998-01-01

    . Dissolved organic carbon concentration, trihalomethane formation potential, and ultraviolet absorbance were all highly correlated, showing that trihalomethane precursors increased with increasing dissolved organic carbon and ultraviolet absorbance for whole water samples. Contrary to the generally accepted conceptual model for trihalomethane formation that assumes that aromatic forms of carbon are primary precursors to trihalomethanes, results from this study indicate that dissolved organic carbon aromaticity appears unrelated to trihalomethane formation on a carbon-normalized basis. Thus, dissolved organic carbon aromaticity alone cannot fully explain or predict trihalomethane precursor content, and further investigation of aromatic and nonaromatic forms of carbon will be needed to better identify trihalomethane precursors.

  4. Terrestrial C sequestration at elevated CO2 and temperature: the role of dissolved organic N loss

    USGS Publications Warehouse

    Rastetter, Edward B.; Perakis, Steven S.; Shaver, Gaius R.; Agren, Goran I.

    2005-01-01

    We used a simple model of carbona??nitrogen (Ca??N) interactions in terrestrial ecosystems to examine the responses to elevated CO2 and to elevated CO2 plus warming in ecosystems that had the same total nitrogen loss but that differed in the ratio of dissolved organic nitrogen (DON) to dissolved inorganic nitrogen (DIN) loss. We postulate that DIN losses can be curtailed by higher N demand in response to elevated CO2, but that DON losses cannot. We also examined simulations in which DON losses were held constant, were proportional to the amount of soil organic matter, were proportional to the soil C:N ratio, or were proportional to the rate of decomposition. We found that the mode of N loss made little difference to the short-term (<60 years) rate of carbon sequestration by the ecosystem, but high DON losses resulted in much lower carbon sequestration in the long term than did low DON losses. In the short term, C sequestration was fueled by an internal redistribution of N from soils to vegetation and by increases in the C:N ratio of soils and vegetation. This sequestration was about three times larger with elevated CO2 and warming than with elevated CO2 alone. After year 60, C sequestration was fueled by a net accumulation of N in the ecosystem, and the rate of sequestration was about the same with elevated CO2 and warming as with elevated CO2 alone. With high DON losses, the ecosystem either sequestered C slowly after year 60 (when DON losses were constant or proportional to soil organic matter) or lost C (when DON losses were proportional to the soil C:N ratio or to decomposition). We conclude that changes in long-term C sequestration depend not only on the magnitude of N losses, but also on the form of those losses.

  5. Dissolved Organic Matter Composition of Arctic Rivers: Linking Permafrost, Parent Material, and Groundwater to Riverine Carbon

    NASA Astrophysics Data System (ADS)

    O'Donnell, J. A.; Aiken, G.; Butler, K. D.; Swanson, D. K.

    2015-12-01

    Recent warming in the Arctic is modifying the chemical composition of riverine dissolved organic matter (DOM) through changes in growing season length, wildfire, and permafrost thaw. In arctic rivers, DOM composition is an important control on nutrient availability, trace metal mobilization, and greenhouse gas emissions. As a result, shifts in DOM associated with a changing arctic landscape may alter how aquatic ecosystems function in this region. Here, we examined spatial variation in DOM composition in 72 rivers in the Brooks Range and Seward Peninsula of northern Alaska. We characterized DOM using a suite of techniques, including dissolved organic carbon (DOC) concentration, absorbance spectra, fluorescence, and chemical fractionation. Watersheds were classified based on traits that influence subsurface hydrology, including parent material (volcanic deposits, loess, sand, glacial moraine, bedrock) and permafrost extent (continuous vs. discontinuous zone) and state (ice-rich vs. ice-poor). We observed considerable variability in DOM composition across rivers. DOC concentrations were lowest in rivers influenced by glacial deposits (<2 mgC L-1) and highest in rivers draining lowland tundra or extensive wetlands (>10 mgC L-1). Specific ultraviolet absorbance (SUVA254), which serves as an index of DOM aromaticity, was also variable across rivers; spring-fed mountain streams had the lowest SUVA254 values (<1.5 L mgC-1 m-1), whereas tundra and wetland-dominated streams had the highest values (>4 L mgC-1 m-1). While hydrophobic organic acids were the dominant DOM fraction in all rivers, we observed a significant increase in the proportion of hydrophilic compounds during winter flow and in groundwater-fed systems. We also observed variation in DOM composition with permafrost extent and ground ice distribution across the region. Model projections over the next century suggest a heterogeneous response of DOM to thaw, likely mediated by spatial variations in ground ice and

  6. Non-conservative behavior of fluorescent dissolved organic matter (FDOM) within a subterranean estuary

    NASA Astrophysics Data System (ADS)

    Suryaputra, I. G. N. A.; Santos, I. R.; Huettel, M.; Burnett, W. C.; Dittmar, T.

    2015-11-01

    The role of submarine groundwater discharge (SGD) in releasing fluorescent dissolved organic matter (FDOM) to the coastal ocean and the possibility of using FDOM as a proxy for dissolved organic carbon (DOC) was investigated in a subterranean estuary in the northeastern Gulf of Mexico (Turkey Point, Florida). FDOM was continuously monitored for three weeks in shallow beach groundwater and in the adjacent coastal ocean. Radon (222Rn) was used as a natural groundwater tracer. FDOM and DOC correlated in groundwater and seawater samples, implying that FDOM may be a proxy of DOC in waters influenced by SGD. A mixing model using salinity as a seawater tracer revealed FDOM production in the high salinity region of the subterranean estuary. This production was probably a result of infiltration and transformation of labile marine organic matter in the beach sediments. The non-conservative FDOM behavior in this subterranean estuary differs from most surface estuaries where FDOM typically behaves conservatively. At the study site, fresh and saline SGD delivered about 1800 mg d-1 of FDOM (quinine equivalents) to the coastal ocean per meter of shoreline. About 11% of this input was related to fresh SGD, while 89% were related to saline SGD resulting from FDOM production within the shallow aquifer. If these fluxes are representative of the Florida Gulf Coast, SGD-derived FDOM fluxes would be equivalent to at least 18% of the potential regional riverine FDOM inputs. To reduce uncertainties related to the scarcity of FDOM data, further investigations of river and groundwater FDOM inputs in Florida and elsewhere are necessary.

  7. Removal of dissolved organic matter in water-hyacinth waste-water treatment lagoons

    SciTech Connect

    Victoria-Rueda, C.H.

    1991-01-01

    Secondary treatment of domestic wastewater in water hyacinth lagoons was evaluated under experimental conditions to assess the role of the roots' bacterial biofilm in the removal of dissolved organic matter (DOM). Research was conducted to (1) quantify removal rates by the biofilm as a function of bulk DOM concentration, (2) formulate an analytical model of DOM removal incorporating biofilm activity, and (3) test the model response to variable organic loads in a pilot-scale plant. Removal of DOM by the biofilm was quantified in continuous-flow water hyacinth tanks at ten concentrations ranging from 45 to 330 g COD m {sup {minus}3} . Total DOM removal in the denitrifying, acetate-based experimental system was measured and partitioned into two fractions associated with the activity of biofilm and suspended bacteria. Calculated DOM removal by the biofilm was adjusted for the release of organic compounds by debris decomposition. Values of DOM removal were used to calculate oxygen transfer rates from the water hyacinth roots. A model of DOM removal in water hyacinth lagoons was formulated. The model, composed of four differential equations, was solved at steady-state conditions and the validity of its simulation results was tested in pilot-scale tanks. Hydraulic detection times ranging from 2 to 28 days were evaluated using biofilm density and concentrations of DOM and particulate organics as monitoring parameters of the model response. The observed decrease of suspended bacterial biomass along the tank was correctly simulated by the model, but predictions of effluent concentrations were not always consistent. Predicted values of biofilm bacterial mass were similar to those measured in the tanks, except when large algal populations were present in the film.

  8. Estuarine Export of Dissolved Organic Carbon to the Mid-Atlantic Bight

    NASA Astrophysics Data System (ADS)

    Signorini, S. R.; Mannino, A.; Friedrichs, M. A.; Wilkin, J.; Tabatabai, A.

    2016-02-01

    Estuaries play an important role in transforming riverine nutrients and carbon before they are exported to the adjacent continental shelf. Land-estuarine-ocean biogeochemical modeling systems, evaluated with in situ and satellite data, are invaluable tools to quantify riverine nitrogen and carbon inputs, within-estuary nitrogen/carbon transformation processes and the ultimate export of nitrogen and carbon to the coastal ocean. In this study, we developed satellite algorithms to retrieve estuarine dissolved organic carbon (DOC) concentrations, and combined these surface DOC estimates with output from physical circulation models based on the Regional Ocean Modeling System (ROMS) to quantify coastal DOC fluxes. This study specifically focuses on the export of DOC from two major estuaries, Chesapeake Bay and Delaware Bay, to the U.S. Middle Atlantic Bight (MAB) using newly developed higher resolution models. DOC profiles required to compute the tracer fluxes at the mouths of the estuaries were derived using a feed forward neural networks model trained with in situ data (salinity, temperature, and DOC).The seasonal and interannual variability of estuarine DOC export are analyzed based on multi-year model runs for Delaware Bay and Chesapeake Bay, combined with surface DOC concentrations derived from the satellite retrievals. Fluxes derived from coupled biogeochemical-circulation modeling systems are compared with these off-line model-satellite tracer fluxes. Results from this study will be used to improve the assessment of the total carbon budget for the MAB.

  9. Black Carbon in Marine Dissolved Organic Carbon: Abundance and Radiocarbon Measurements in the Global Ocean

    NASA Astrophysics Data System (ADS)

    Coppola, A. I.; Walker, B. D.; Druffel, E. R. M.

    2014-12-01

    Compound specific radiocarbon analysis is a powerful tool for understanding the cycling of individual components, such as black carbon (BC) produced from biomass burning and fossil fuel combustion, within bulk pools, like the marine dissolved organic carbon pool. Here, we use a solid phase extraction method and a wide range of solvent polarities to concentrate dissolved organic carbon from seawater. Then we isolate BC in sufficient quantities for radiocarbon analysis. We report the radiocarbon age of BC, concentrations and its relative structure, from coastal and open ocean surface samples. We will discuss our progress towards measuring these quantities in dissolved organic carbon collected from the Pacific and Atlantic oceans to understand the fate, transformation and cycling of BC in the world ocean. These measurements are paired with bulk DOC Δ14C profiles, providing insight into the role of BC as a missing sink in the ultra-refractory DOC pool.

  10. Effects of pH, dissolved organic matter, and salinity on ibuprofen sorption on sediment.

    PubMed

    Oh, Sanghwa; Shin, Won Sik; Kim, Hong Tae

    2016-11-01

    Ibuprofen is well known as one of the most frequently detected pharmaceuticals and personal care products (PPCPs) in rivers. However, sorption of ibuprofen onto sediment has not been considered in spite of its high K ow (3.5). In this study, the effects of various environmental conditions such as pH (4, 5.3, and 7), the concentrations of dissolved organic matters (0 to 1.0 mM citrate and urea), salinity (0, 10, 20, and 30 part per thousand), and presence of other PPCP (salicylic acid) on ibuprofen sorption were investigated. Linear model mainly fitted the experimental data for analysis. The distribution coefficient (K d) in the linear model decreased from 6.76 at pH 4 to near zero at pH 7, indicating that neutral form of ibuprofen at pH below pKa (5.2) was easily sorbed onto the sediment whereas the sorption of anionic form at pH over pKa was not favorable. To investigate the effect of dissolved organic matters (DOMs) on ibuprofen sorption, citrate and urea were used as DOMs. As citrate concentration increased, the K d value decreased but urea did not interrupt the ibuprofen sorption. Citrate has three carboxyl functional groups which can attach easily ibuprofen and hinder its sorption onto sediment. Salinity also affected ibuprofen sorption due to decrease of the solubility of ibuprofen as salinity increased. In competitive sorption experiment, the addition of salicylic acid also led to enhance ibuprofen sorption. Conclusively, ibuprofen can be more easily sorbed onto the acidified sediments of river downstream, especially estuaries or near-shore environment with low DOM concentration.

  11. Relationships between land cover and dissolved organic matter change along the river to lake transition

    USGS Publications Warehouse

    Larson, James H.; Frost, Paul C.; Xenopoulos, Marguerite A.; Williams, Clayton J.; Morales-Williams, Ana M.; Vallazza, Jonathan M.; Nelson, J. C.; Richardson, William B.

    2014-01-01

    Dissolved organic matter (DOM) influences the physical, chemical, and biological properties of aquatic ecosystems. We hypothesized that controls over spatial variation in DOM quantity and composition (measured with DOM optical properties) differ based on the source of DOM to aquatic ecosystems. DOM quantity and composition should be better predicted by land cover in aquatic habitats with allochthonous DOM and related more strongly to nutrients in aquatic habitats with autochthonous DOM. Three habitat types [rivers (R), rivermouths (RM), and the nearshore zone (L)] associated with 23 tributaries of the Laurentian Great Lakes were sampled to test this prediction. Evidence from optical indices suggests that DOM in these habitats generally ranged from allochthonous (R sites) to a mix of allochthonous-like and autochthonous-like (L sites). Contrary to expectations, DOM properties such as the fluorescence index, humification index, and spectral slope ratio were only weakly related to land cover or nutrient data (Bayesian R 2 values were indistinguishable from zero). Strongly supported models in all habitat types linked DOM quantity (that is, dissolved organic carbon concentration [DOC]) to both land cover and nutrients (Bayesian R2 values ranging from 0.55 to 0.72). Strongly supported models predicting DOC changed with habitat type: The most important predictor in R sites was wetlands whereas the most important predictor at L sites was croplands. These results suggest that as the DOM pool becomes more autochthonous-like, croplands become a more important driver of spatial variation in DOC and wetlands become less important.

  12. Coextracted dissolved organic carbon has a suppressive effect on the acetylcholinesterase inhibition assay.

    PubMed

    Neale, Peta A; Escher, Beate I

    2013-07-01

    The acetylcholinesterase (AChE) inhibition assay is frequently applied to detect organophosphates and carbamate pesticides in different water types, including dissolved organic carbon (DOC)-rich wastewater and surface water. The aim of the present study was to quantify the effect of coextracted DOC from different water samples on the commonly used enzyme-based AChE inhibition assay. Approximately 40% to 70% of DOC is typically recovered by solid-phase extraction, and this comprises not only organic micropollutants but also natural organic matter. The inhibition of the water extracts in the assay differed greatly from the expected mixture effects based on chemical analysis of organophosphates and carbamates. Binary mixture experiments with the known AChE inhibitor parathion and the water extracts showed reduced toxicity in comparison with predictions using the mixture models of concentration addition and independent action. In addition, the extracts and reference organic matter had a suppressive effect on a constant concentration of parathion. The present study thus indicated that concentrations of DOC as low as 2 mg carbon/L can impair the AChE inhibition assay and, consequently, that only samples with a final DOC concentration of less than 2 mgC /L are suitable for this assay. To check for potential suppression in environmental samples, standard addition experiments using an AChE-inhibiting reference compound are recommended.

  13. Inorganic and suspended/dissolved-organic nitrogen in Sierra Nevada soil core leachates

    SciTech Connect

    Marcus, J.A.; Miller, W.W.; Blank, R.R.

    1998-07-01

    Watershed disturbance has been suggested as a possible mechanism for accelerated nutrient input into Lake Tahoe, California/Nevada. However, little is known regarding how nutrient discharge is coupled to physicochemical watershed processes. Recent investigations in the Lake Tahoe Basin have suggested that suspended/dissolved-organic nutrient transport may play an important role in lake and tributary water quality. The mobility of inorganic and suspended/dissolved-organic N in soils of a Lake Tahoe watershed was assessed using constant head permeameter leaching experiments with intact soil cores. The authors evaluated the interaction of plot condition on magnitude and form of N discharge. Incremental leachate discharge was analyzed for concentrations of inorganic (NH{sub 4}-N and NO{sub 3}-N) and suspended/dissolved-organic N. Leachate from the riparian soil cores had significantly higher concentrations and total discharge NO{sub 3}-N than that from the nonforested or forested areas. Loading of NH{sub 4}-N was more consistent among vegetative cover types, but the riparian leachate again contributed a significantly greater amount. Suspended/dissolved-organic N was mobile and the most dominant form of N for nonforested and forested soil cores with discharge loading ratios of 17:1 and 7:1, respectively. Although the loading ratio was approximately 1:1 for the riparian soil cores, the amount of suspended/dissolved-organic N discharged was greatest. The mobility and presence of significant amounts of suspended/dissolved-organic N indicate that this once unrecognized nutrient form is an important component in at least one Sierra Nevada watershed, and should be more fully investigated elsewhere.

  14. Enhanced dissolution of cinnabar (mercuric sulfide) by dissolved organic matter isolated from the Florida Everglades

    USGS Publications Warehouse

    Ravichandran, Mahalingam; Aiken, George R.; Reddy, Michael M.; Ryan, Joseph N.

    1998-01-01

    Organic matter isolated from the Florida Everglades caused a dramatic increase in mercury release (up to 35 μM total dissolved mercury) from cinnabar (HgS), a solid with limited solubility. Hydrophobic (a mixture of both humic and fulvic) acids dissolved more mercury than hydrophilic acids and other nonacid fractions of dissolved organic matter (DOM). Cinnabar dissolution by isolated organic matter and natural water samples was inhibited by cations such as Ca2+. Dissolution was independent of oxygen content in experimental solutions. Dissolution experiments conducted in DI water (pH = 6.0) had no detectable (<2.5 nM) dissolved mercury. The presence of various inorganic (chloride, sulfate, or sulfide) and organic ligands (salicylic acid, acetic acid, EDTA, or cysteine) did not enhance the dissolution of mercury from the mineral. Aromatic carbon content in the isolates (determined by 13C NMR) correlated positively with enhanced cinnabar dissolution. ζ-potential measurements indicated sorption of negatively charged organic matter to the negatively charged cinnabar (pHpzc = 4.0) at pH 6.0. Possible mechanisms of dissolution include surface complexation of mercury and oxidation of surface sulfur species by the organic matter.

  15. Effect of pH on dynamic and equilibrium surface tension of dissolve organic matter

    NASA Astrophysics Data System (ADS)

    Arye, Gilboa; Trifonov, Pavel; Ilani, Talli

    2014-05-01

    Dissolved organic matter (DOM) in the terrestrial environment may originate from the decomposition of soil organic matter accumulated from the degradation of vegetative residues, the release of root exudates, the lysis of microorganisms and addition of organic wastes, such as livestock manure, biosolids, and different composted organic residues, or from irrigation with wastewater. The structure of DOM macromolecules is known to vary with the following aqueous solution properties: ionic strength, the nature of the inorganic ions, pH and dissolved organic carbon (DOC) concentration. In aqueous solution, the DOM molecules are amphiphilic, that is, it possesses both hydrophilic and hydrophobic functional groups in the same molecule. This simultaneous presence, gave rise to the conceptual surfactant like model for DOM which has been studies in conjunction with the equilibrium surface tension at the liquid-air interface (STeq, mN/m). Measurements of STeq of DOM solution were reported in a relatively small number of studies for the conditions of the aqueous solution (e.g., temperature, pH, ionic strength, the valence of the metal ions, and DOC concentration). All studies demonstrate the decrease in STeq with increase aqueous concentration of the DOC. The effect of pH, however, exhibit contradictory results. Specifically, for a given DOC concentration, the patterns reported for STeq versus pH were different. With increasing pH values, STeq has been reported to decrease, increase or exhibit a minimum. These contradictory results have been attributed to the different DOC concentration examined in each of the studies. In current study we hypothesized that the inconsistent results of STeq vs. pH may also stem from the adsorption kinetics of the DOM amphiphilic molecules at the liquid air interface, which can be evaluated form dynamic surface tension measurements (STt). The STt is approaching STeq values and commonly exhibiting an exponential decay pattern. If for different p

  16. Dissolved Trace Metal and Organic Matter Relationships over Various Fluvial Scales

    NASA Astrophysics Data System (ADS)

    Shiller, A. M.; Bianchi, T. S.; Aiken, G. R.

    2006-05-01

    The fluvial mobilization of many dissolved trace elements is affected by dissolved organic matter, primarily through complexation. We have examined the metal-DOC relationship through various means including: a) metal-DOC comparisons over large scales, b) metal-DOC comparisons between watersheds of differing landscapes, and c) an incubation experiment designed to see how changing DOC composition affects metal speciation. Our compilation of data includes time series samples from the lower Mississippi River, the Loch Vale Watershed, the Pearl River (MS), and the Yukon River as well as short time series and grab samples from a wide variety of streams and rivers in the Yukon Basin. When pooled together, overall relationships between DOC and the concentrations of certain trace elements (e.g., Fe, Cu, Zn) are observed. In many cases this probably reflects competition between adsorption and organic complexation and suggests the possibility that complexation and adsorption constants in these systems vary less than the amounts of organic matter and adsorbing surfaces. In other words, it may be possible to develop a simple one-site, one- ligand model to approximately (or, at least, conceptually) describe fluvial trace element behavior. We also observe, when comparing watersheds of the Yukon River Basin, differences in both DOC and associated dissolved metal concentrations. If DOC is truly a master variable for these trace elements, then prediction of how climate change will affect DOC mobilization from various environments will lead to predictions of dissolved trace elements will also be affected. However, some caution is required for these generalizations. Because DOC tends to vary inversely with pH and conductivity on global fluvial scales, the importance of other controlling factors cannot be ignored. To further investigate DOC metal relationships we have also used column partitioning methods the examine metal speciation during a photo-incubation experiment. The

  17. Characteristics of dissolved organic matter (DOM) and relationship with dissolved mercury in Xiaoqing River-Laizhou Bay estuary, Bohai Sea, China.

    PubMed

    Jiang, Tao; Skyllberg, Ulf; Björn, Erik; Green, Nelson W; Tang, Jianhui; Wang, Dingyong; Gao, Jie; Li, Chuxian

    2017-04-01

    Because of heterogeneous properties, dissolved organic matter (DOM) is known to control the environmental fate of a variety of organic pollutants and trace metals in aquatic systems. Here we report absorptive and fluorescence properties of DOM, in concurrence with concentrations of dissolved mercury (Hg), along the Xiaoqing River-Laizhou Bay estuary system located in the Bohai Sea of China. A mixing model consisting of the two end-members terrestrial and aquatic DOM demonstrated that terrestrial signatures decreased significantly from the river into the estuary. Quasi-conservative mixing behavior of DOM sources suggests that the variations in the average DOM composition were governed by physical processes (e.g., dilution) rather than by new production and/or degradation processes. In contrast to some previous studies of river-estuary systems, the Xiaoqing River-Laizhou Bay estuary system displayed a non-significant correlation between DOM and Hg quantities. Based on this and the variation of Hg concentration along the salinity gradient, we concluded that Hg showed a non-conservative mixing behavior of suggested end-member sources. Thus, rather than mixing, Hg concentration variations seemed to be controlled by biogeochemical processes.

  18. The Fluorescent Properties of Dissolved Organic Matter and Assessment of Total Nitrogen in Overlying Water with Different Dissolved Oxygen Conditions.

    PubMed

    Zhang Hua; Kuan, Wang; Song, Jian; Zhang, Yong; Huang, Ming; Huang, Jian; Zhu, Jing; Huang, Shan; Wang, Meng

    2016-03-01

    This paper used excitation-emission matrix spectroscopy (EEMs) to probe the fluorescence properties of dissolved organic matter (DOM) in the overlying water with different dissolved oxygen (DO) conditions, investigating the relationship between protein-like fluorescence intensity and total nitrogen concentration. The resulting fluorescence spectra revealed three protein-like components (high-excitation wavelength tyrosine, low-excitation wavelength tyrosine, low-excitation wavelength tryptophan) and two fulvic-like components (ultraviolet fulvic-like components, visible fulvic-like components) in the overlying water. Moreover, the protein-like components were dominant in the overlying water's DOM. The fluorescence intensity of the protein-like components decreased significantly after aeration. Two of the protein-like components--the low-excitation wavelength tyrosine and the low-excitation wavelength tryptophan--were more susceptible to degradation by microorganisms within the degradable organic matter with respect to the high-excitation wavelength tyrosine. In contrast, the ultraviolet and visible fulvic-like fluorescence intensity increased along with increasing DO concentration, indicating that the fulvic-like components were part of the refractory organics. The fluorescence indices of the DOM in the overlying water were between 1.65-1.80, suggesting that the sources of the DOM were related to terrigenous sediments and microbial metabolic processes, with the primary source being the contribution from microbial metabolism. The fluorescence indices increased along with DO growth, which showed that microbial biomass and microbial activity gradually increased with increasing DO while microbial metabolism also improved, which also increased the biogenic components in the overlying water. The fluorescence intensity of the high-excitation wavelength tyrosine peak A showed a good linear relationship with the total nitrogen concentration at higher DO concentrations of 2

  19. Marine methane paradox explained by bacterial degradation of dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Repeta, Daniel J.; Ferrón, Sara; Sosa, Oscar A.; Johnson, Carl G.; Repeta, Lucas D.; Acker, Marianne; Delong, Edward F.; Karl, David M.

    2016-12-01

    Biogenic methane is widely thought to be a product of archaeal methanogenesis, an anaerobic process that is inhibited or outcompeted by the presence of oxygen and sulfate. Yet a large fraction of marine methane delivered to the atmosphere is produced in high-sulfate, fully oxygenated surface waters that have methane concentrations above atmospheric equilibrium values, an unexplained phenomenon referred to as the marine methane paradox. Here we use nuclear magnetic resonance spectroscopy to show that polysaccharide esters of three phosphonic acids are important constituents of dissolved organic matter in seawater from the North Pacific. In seawater and pure culture incubations, bacterial degradation of these dissolved organic matter phosphonates in the presence of oxygen releases methane, ethylene and propylene gas. Moreover, we found that in mutants of a methane-producing marine bacterium, Pseudomonas stutzeri, disrupted in the C-P lyase phosphonate degradation pathway, methanogenesis was also disabled, indicating that the C-P lyase pathway can catalyse methane production from marine dissolved organic matter. Finally, the carbon stable isotope ratio of methane emitted during our incubations agrees well with anomalous isotopic characteristics of seawater methane. We estimate that daily cycling of only about 0.25% of the organic matter phosphonate inventory would support the entire atmospheric methane flux at our study site. We conclude that aerobic bacterial degradation of phosphonate esters in dissolved organic matter may explain the marine methane paradox.

  20. Dissolved Organic Matter Composition in Waters Draining Permafrost Landscapes - a Circumpolar Synthesis

    NASA Astrophysics Data System (ADS)

    O'Donnell, J. A.; Aiken, G.; Abbott, B. W.; Butler, K. D.; Ewing, S. A.; Olefeldt, D.; Spencer, R. G.; Striegl, R. G.; Vonk, J.; Wickland, K.

    2016-12-01

    The flux of dissolved organic matter (DOM) from terrestrial to freshwater aquatic and marine ecosystems represents an important component of the carbon (C) balance in Arctic and sub-Arctic watersheds. Recent warming and permafrost thaw have altered DOM fluxes in rivers, both through the release of old permafrost C and by shifting hydrologic transport and cycling of DOM in soils. The fate of DOM along the soil-river-ocean continuum is closely linked to its chemical composition, which governs photochemical and microbially mediated transformations and therefore C-cycle feedbacks to the atmosphere. Given the complexity of these issues, large uncertainties exist with respect to DOM fate under future warming and permafrost thaw. To better constrain DOM turnover and fate, we synthesized DOM composition data from 48 published studies and additional unpublished data from across the northern circumpolar permafrost region. Our database includes over 4000 water samples spanning different regions (North America, Eurasia), permafrost zones (continuous, discontinuous), site types (soils, rivers, lakes, ocean), and disturbances (i.e., thermokarst activity). DOM was characterized using a broad range of analytical approaches, including bulk dissolved organic carbon (DOC) and nitrogen concentrations, optical properties, chemical fractionation, and C isotopes (δ13C, Δ14C). Preliminary findings highlight broad spatial variation in DOM composition along the soil-to-ocean continuum, reflecting DOM processing as a function of transport time. DOC concentrations were highest in waters draining upland and peatland thermokarst features, but generally declined in larger downstream basins. While DOM age in ground ice and permafrost-thaw waters was old (> 10k y BP), DOM in streams and rivers was generally modern, likely reflecting the bio-lability and rapid turnover of permafrost C, as well as dilution of old DOM by young carbon inputs moving down the hydrologic network. We will present

  1. Similarities in Photodegradation of Cyanobacteria-Derived and Marine Fluorescent Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Ianiri, H. L.; Timko, S.; Gonsior, M.

    2016-02-01

    Marine dissolved organic matter (DOM) is one of the largest reduced carbon reservoirs on Earth, yet we only have a limited understanding of its production, cycling, degradation, and overall structure. It was previously believed that a significant portion of refractory dissolved organic carbon (RDOC) in the ocean was derived from terrestrial sources, however recent studies indicated that the majority of marine DOM might be produced in situ by marine biota. Previous research has found that terrestrial and microbial DOM fluorescent signatures are similar, complicating the identification of the origins of marine fluorescent DOM (FDOM). However, photodegradation kinetics of terrestrial and microbial-derived DOM are expected to be different due to their assumed different chemical compositions. In this study we analyzed for the first time the photodegradation kinetics of microbial-derived DOM originating from different cyanobacteria strains. Cyanobacterial-derived DOM were exposed to simulated sunlight for a total of 20 hours while recording excitation emission matrix (EEM) fluorescence every twenty minutes to observe the photodegradation of this specific FDOM. Parallel Factor Analysis (PARAFAC) was applied to deconvolute the EEM matrices into six separate components. The photodegradation kinetics was then calculated for each component and compared with previously obtained photodegradation data of marine and terrestrial FDOM. This six component PARAFAC model was similar to those generated from open ocean data and global DOM data sets. The "humic-like" FDOM was also found in cyanobacteria FDOM and showed similar fluorescence intensities and percent fluorescence loss when compared to marine DOM. The degradation kinetics of the "humic-like" component of microbial-derived DOM was faster than that of terrestrial-derived DOM, and marine FDOM samples showed degradation kinetics more similar to microbial-derived FDOM. This indicates marine FDOM is more similar in chemical

  2. Fluorescence Excitation-Emission Matrix Regional Integration to Quantify Spectra for Dissolved Organic Matter

    USGS Publications Warehouse

    Chen, W.; Westerhoff, P.; Leenheer, J.A.; Booksh, K.

    2003-01-01

    Excitation-emission matrix (EEM) fluorescence spectroscopy has been widely used to characterize dissolved organic matter (DOM) in water and soil. However, interpreting the >10,000 wavelength-dependent fluorescence intensity data points represented in EEMs has posed a significant challenge. Fluorescence regional integration, a quantitative technique that integrates the volume beneath an EEM, was developed to analyze EEMs. EEMs were delineated into five excitation-emission regions based on fluorescence of model compounds, DOM fractions, and marine waters or freshwaters. Volumetric integration under the EEM within each region, normalized to the projected excitation-emission area within that region and dissolved organic carbon concentration, resulted in a normalized region-specific EEM volume (??i,n). Solid-state carbon nuclear magnetic resonance (13C NMR), Fourier transform infrared (FTIR) analysis, ultraviolet-visible absorption spectra, and EEMs were obtained for standard Suwannee River fulvic acid and 15 hydrophobic or hydrophilic acid, neutral, and base DOM fractions plus nonfractionated DOM from wastewater effluents and rivers in the southwestern United States. DOM fractions fluoresced in one or more EEM regions. The highest cumulative EEM volume (??T,n = ????i,n) was observed for hydrophobic neutral DOM fractions, followed by lower ??T,n values for hydrophobic acid, base, and hydrophilic acid DOM fractions, respectively. An extracted wastewater biomass DOM sample contained aromatic protein- and humic-like material and was characteristic of bacterial-soluble microbial products. Aromatic carbon and the presence of specific aromatic compounds (as indicated by solid-state 13C NMR and FTIR data) resulted in EEMs that aided in differentiating wastewater effluent DOM from drinking water DOM.

  3. Temporal patterns of dissolved organic matter biodegradability are similar across three rivers of varying size

    NASA Astrophysics Data System (ADS)

    Coble, Ashley A.; Marcarelli, Amy M.; Kane, Evan S.; Toczydlowski, David; Stottlemyer, Robert

    2016-06-01

    Dissolved organic matter (DOM) composition may be an important determinant of its fate in freshwaters, but little is known about temporal variability in DOM composition and the biodegradability of DOM in northern temperate watersheds. We measured biodegradable dissolved organic carbon (BDOC) via incubation assays and DOM composition using optical indices on 11 dates in three Lake Superior tributaries. Percent BDOC (%BDOC) and BDOC concentrations were seasonally synchronous across these watersheds, despite that they vary in size by orders of magnitude (1.7 to 3400 km2). Relative to %BDOC, BDOC concentrations were more tightly constrained among sites on any given date. BDOC also varied within seasons; for example, %BDOC on two different dates in winter were among the highest (29% and 54%) and lowest (0%) values observed for each site (overall %BDOC range: 0 to 72%). DOM composition varied the most among tributaries during a summer storm event when BDOC (both as percent and concentration) was elevated but was remarkably similar among tributaries during fall, spring, and winter. Multivariate models identified humic-like and tryptophan-like fluorophores as predictors of %BDOC, but DOM composition only described 21% of the overall variation in %BDOC. Collectively, these three rivers exported ~18 Gg C yr-1 as DOC and ~2 Gg C yr-1 as BDOC, which corresponded to 9 to 17% of annual DOC exported in biodegradable form. Our results suggest much of the C exported from these northern temperate watersheds may be biodegradable within 28 days and that large pulses of labile DOM can be exported during storm events and spring snowmelt.

  4. A molecular perspective on the ageing of marine dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Flerus, R.; Lechtenfeld, O. J.; Koch, B. P.; McCallister, S. L.; Schmitt-Kopplin, P.; Benner, R.; Kaiser, K.; Kattner, G.

    2012-06-01

    Dissolved organic matter (DOM) was extracted by solid-phase extraction (SPE) from 137 water samples from different climate zones and different depths along an eastern Atlantic Ocean transect. The extracts were analyzed with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with electrospray ionization (ESI). Δ14C analyses were performed on subsamples of the SPE-DOM. In addition, the amount of dissolved organic carbon was determined for all water and SPE-DOM samples as well as the yield of amino sugars for selected samples. Linear correlations were observed between the magnitudes of 43 % of the FT-ICR mass peaks and the extract Δ14C values. Decreasing SPE-DOM Δ14C values went along with a shift in the molecular composition to higher average masses (m/z) and lower hydrogen/carbon (H/C) ratios. The correlation was used to model the SPE-DOM Δ14C distribution for all 137 samples. Based on single mass peaks, a degradation index (IDEG) was developed to compare the degradation state of marine SPE-DOM samples analyzed with FT-ICR MS. A correlation between Δ14C, IDEG, DOC values and amino sugar yield supports that SPE-DOM analyzed with FT-ICR MS reflects trends of bulk DOM. DOM weighted normalized mass peak magnitudes were used to compare aged and recent SPE-DOM on a semi-quantitative molecular basis. The magnitude comparison showed a continuum of different degradation rates for the detected compounds. A high proportion of the compounds should persist, possibly modified by partial degradation, in the course of thermohaline circulation. Prokaryotic (bacterial) production, transformation and accumulation of this very stable DOM occur primarily in the upper ocean. This DOM is an important contribution to very old DOM, showing that production and degradation are dynamic processes.

  5. A molecular perspective on the ageing of marine dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Flerus, R.; Koch, B. P.; Lechtenfeld, O. J.; McCallister, S. L.; Schmitt-Kopplin, P.; Benner, R.; Kaiser, K.; Kattner, G.

    2011-11-01

    Dissolved organic matter (DOM) was extracted with solid phase extraction (SPE) from 137 water samples from different climate zones and different depths along an Eastern Atlantic Ocean transect. The extracts were analyzed with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with electrospray ionization (ESI). Δ14C analyses were performed on subsamples of the SPE-DOM. In addition, the amount of dissolved organic carbon was determined for all water and SPE-DOM samples as well as the yield of amino sugars for selected samples. Linear correlations were observed between the magnitudes of 43 % of the FT-ICR mass peaks and the extract Δ14C values. Decreasing SPE-DOM Δ14C values went along with a shift in the molecular composition to higher average masses (m/z) and lower hydrogen/carbon (H/C) ratios. The correlation was used to model the SPE-DOM Δ14C distribution for all 137 samples. Based on single mass peaks a degradation index was developed to compare the degradation state of marine SPE-DOM samples analyzed with FT-ICR MS. A correlation between Δ14C, degradation index, DOC values and amino sugar yield supports that SPE-DOM analyzed with FT-ICR MS reflects trends of bulk DOM. A relative mass peak magnitude ratio was used to compare aged SPE-DOM and fresh SPE-DOM regarding single mass peaks. The magnitude ratios show a continuum of different reactivities for the single compounds. Only few of the compounds present in the FT-ICR mass spectra are expected to be highly degraded in the oldest water masses of the Pacific Ocean. All other compounds should persist partly thermohaline circulation. Prokaryotic (bacterial) production, transformation and accumulation of this very stable DOM occurs probably primarily in the upper ocean. This DOM is an important contribution to very old DOM, showing that production and degradation are dynamic processes.

  6. Stream Dissolved Organic Matter Quantity and Quality Along a Wetland-Cropland Catchment Gradient

    NASA Astrophysics Data System (ADS)

    McDonough, O.; Hosen, J. D.; Lang, M. W.; Oesterling, R.; Palmer, M.

    2012-12-01

    Wetlands may be critical sources of dissolved organic matter (DOM) to stream networks. Yet, more than half of wetlands in the continental United States have been lost since European settlement, with the majority of loss attributed to agriculture. The degree to which agricultural loss of wetlands impacts stream DOM is largely unknown and may have important ecological implications. Using twenty headwater catchments on the Delmarva Peninsula (Maryland, USA), we investigated the seasonal influence of wetland and cropland coverage on downstream DOM quantity and quality. In addition to quantifying bulk downstream dissolved organic carbon (DOC) concentration, we used a suite of DOM UV-absorbance metrics and parallel factor analysis (PARAFAC) modeling of excitation-emission fluorescence spectra (EEMs) to characterize DOM composition. Percent bioavailable DOC (%BDOC) was measured during the Spring sampling using a 28-day incubation. Percent wetland coverage and % cropland within the watersheds were significantly negatively correlated (r = -0.93, p < 0.001). Results show that % wetland coverage was positively correlated with stream DOM concentration, molecular weight, aromaticity, humic-like fluorescence, and allochthonous origin. Conversely, increased wetland coverage was negatively correlated with stream DOM protein-like fluorescence. Percent BDOC decreased with DOM humic-like fluorescence and increased with protein-like fluorescence. We observed minimal seasonal interaction between % wetland coverage and DOM concentration and composition across Spring, Fall, and Winter sampling seasons. However, principal component analysis suggested more pronounced seasonal differences exist in stream DOM. This study highlights the influence of wetlands on downstream DOM in agriculturally impacted landscapes where loss of wetlands to cultivation may significantly alter stream DOM quantity and quality.

  7. Adsorption kinetics of dissolve organic matter at the water-air interface

    NASA Astrophysics Data System (ADS)

    Arye, Gilboa; Zhang, Wei

    2017-04-01

    The surface active nature of humic substances and naturally occurring dissolved organic matter (DOM), has been confirmed by a growing number of studies. The main quantity from which the surface activity has been deduced obtained from measurements of surface-tension (ST, mN m-1) at the water/air interface. All studies demonstrated the decay in the ST of water (72.5 mN m-1 at 25C) with increased aqueous concentrations of dissolved organic carbon (DOC). The ST values reported for DOM should be defined as equilibrium ST, when the adsorption and orientation of the amphipathic molecule at the water/air interface have reached equilibrium state. However, for any amphipathic molecule the adsorption kinetics at the water/air interface is not reached instantaneously and may range from seconds up to several hours. The time depended ST started from the time where a new water/air interface is formed. Thereafter, amphipathic molecules need first to diffuse from the bulk solution to the interface, subsequently adsorb and simultaneously achieving the correct orientation at the interface. The consequence of this process will be expressed in a decay of the ST as a function of time until it will reach the equilibrium the surface tension. The main objective of this study was to quantify the rate and extent of DOM adsorption kinetics at the water-air interface through dynamic surface tension measurement, using the pendant drop method. The applicability of a diffusion-only model to describe the results will be presented and discussed.

  8. Contaminant transport in riverbank filtration in the presence of dissolved organic matter and bacteria: a kinetic approach

    NASA Astrophysics Data System (ADS)

    Kim, Song-Bae; Corapcioglu, M. Yavuz

    2002-09-01

    In riverbank filtration, the removal of organic contaminants is an important task for the production of good quality drinking water. The transport of an organic contaminant in riverbank filtration can be retarded by sorption on to the solid matrix and facilitated by the presence of mobile colloids. In the presence of dissolved organic matter (DOM) and bacteria, the subsurface environment can be modeled as a four-phase porous medium: two mobile colloidal phases, an aqueous phase, and a solid matrix. In this study, a kinetic model is developed to simulate the contaminant transport in riverbank filtration in the presence of DOM and bacteria. The bacterial deposition and the contaminant sorption on bacteria and DOM are expressed with kinetic expressions. The model equations are solved numerically with a fully implicit finite difference method. Simulation results show that the contaminant mobility increases greatly in riverbank filtration due to the presence of DOM. The mobility can be enhanced further when the bacteria and DOM are present together in the aquifer. In this system, the total aqueous phase contaminant concentration, Cct+, includes the contaminant dissolved in the aqueous phase, Cc+, the contaminant sorbed to DOM, σcd+, and the contaminant sorbed to mobile bacteria, Cb+σcbm+, (i.e. Cct+= Cc++ σcd++ Cb+σcbm+). Sensitivity analysis illustrates that the distribution of the total aqueous phase contaminants among the dissolved phase, DOM and bacteria is changed significantly with various Damköhler numbers related to the contaminant sorption on mobile colloids.

  9. Using 18O as a Tracer of Oxygen in the Photochemical Alteration of Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Davis, J. A.; Stubbins, A.; Helms, J.; Dias, R. F.; Mopper, K.

    2006-12-01

    The biogeochemical cycling of dissolved organic matter (DOM) in natural waters is affected by numerous processes, including photochemical alteration. Photochemical processes result in the net oxidation and mineralization of DOM concomitant with dissolved oxygen consumption and production of dissolved inorganic carbon (DIC; principally CO2). The photochemical oxygen budget is not well constrained while DIC production accounts for nearly all the dissolved oxygen consumed, conflicting data suggests that more than half of the oxygen consumed is required to account for observed DOM oxidation and hydrogen peroxide production. An alternate source of oxygen is required to balance this budget; water itself may provide the answer. In order to determine the source of oxygen, a number of time series irradiations were performed using Great Dismal Swamp water (southeast Virginia) with 18O enrichments as either dissolved oxygen or water. Early results, upon irradiation in a UV solar simulator, show significant incorporation of 18O-enriched oxygen into high molecular weight (HMW) DOM from both sources. While the majority of the incorporated oxygen originated from the dissolved oxygen, at least 5 percent originated from water. Data will be presented showing the rate and degree of incorporation of 18O-enriched oxygen from both sources as well as the production of 18O-enriched carbon dioxide. The movement of 18O label will be discussed in relation to shifts in spectral qualities, including photobleaching and spectral slope, of the irradiated samples and selective incorporation as detailed by FT-ICRMS.

  10. Production of photo-oxidants by dissolved organic matter during UV water treatment.

    PubMed

    Lester, Yaal; Sharpless, Charles M; Mamane, Hadas; Linden, Karl G

    2013-10-15

    Dissolved organic matter (DOM) irradiated by sunlight generates photo-oxidants that can accelerate organic contaminant degradation in surface waters. However, the significance of this process to contaminant removal during engineered UV water treatment has not been demonstrated, partly due to a lack of suitable methods in the deep UV range. This work expands methods previously established to detect (1)O2, HO•, H2O2, and DOM triplet states ((3)DOM*) at solar wavelengths to irradiation at 254 nm, typical of UV water treatment. For transient intermediates, the methods include a photostable probe combined with selective scavengers. Quantum yields for (1)O2, (3)DOM* and H2O2 were in the same range as for solar-driven reactions but were an order of magnitude higher for HO•, which other experiments indicate is due to H2O2 reduction. With the quantum yields, the degradation of metoxuron was successfully predicted in a DOM solution irradiated at 254 nm. Further modeling showed that the contribution of DOM sensitization to organic contaminant removal during UV treatment should be significant only at high UV fluence, characteristic of advanced oxidation processes. Of the reactive species studied, (3)DOM* is predicted to have the greatest general influence on UV degradation of contaminants.

  11. Is the composition of dissolved organic carbon changing in upland acidic streams?

    PubMed

    Dawson, Julian J C; Malcolm, Iain A; Middlemas, Stuart J; Tetzlaff, Doerthe; Soulsby, Chris

    2009-10-15

    The quantity and composition of dissolved organic carbon (DOC) exported from upland soils to surface waters is a key link in the global carbon cycle and economically important for treating potable waters. The relationship between ultraviolet (UV) absorbance and DOC concentrations can be used to infer changes in the proportion of hydrophobic (aromatic, recalcitrant) carbon and hence biodegradability of DOC. This study describes a significant change in the relationship between UV absorbance and DOC over 22 years at two upland moorland catchments in Scotland, UK. Despite increases in long-term DOC concentrations, analysis suggests that the proportion of hydrophobic material has declined. A statistical mixed-effect modeling approach was used to examine the likely mechanisms that could explain these observations. Annual nonmarine sulfate load was the only significant forcing factor that could explain the observed long-term trend in the UV absorbance-DOC relationship at both sites. It is hypothesized that enhanced heterotrophic decomposition of organic matter and increased solubility of carbon compounds in soils where sulfate driven acidification is being reversed are the dominant mechanisms behind this change in DOC composition. These trends will impact on carbon substrate dynamics by potentially increasing biodegradability of exported organic matter, influencing carbon cycling in terrestrial and aquatic ecosystems.

  12. Interactions between dissolved organic matter and mercury in the Florida Everglades

    USGS Publications Warehouse

    Aiken, G.; Haitzer, M.; Ryan, J.N.; Nagy, K.; ,

    2003-01-01

    Experiments were conducted using organic matter isolated from various surface waters in the Florida Everglades to study the interactions between dissolved organic matter (DOM) and Hg(II). Conditional distribution coefficients (KDOM???), obtained using an equilibrium dialysis ligand exchange method, were strongly affected by the Hg/DOM concentration ratio. Very strong interactions (KDOM??? = 1023.2??0.5 L kg-1), indicative of Hg-thiol bonds, were observed at Hg/DOM ratios below approximately 1 ??g per mg DOM. Above approximately 10 ??g Hg per mg DOM much lower KDOM??? values (1010.7??0.5 L kg-1) were obtained DOM-Hg interactions were also studied by HgS (log Ksp = -52.4) dissolution and precipitation experiments. In the dissolution experiments, a significant amount of Hg was released from cinnabar in the presence of DOM, suggesting strong interactions. Conversely, precipitation of HgS was strongly inhibited in the presence of low concentrations (???3 mg C/L) of DOM. In both the dissolution and precipitation experiments, organic matter rich in aromatic moieties was more reactive with HgS than less aromatic fractions and sulfur-containing model compounds. These results suggest that DOM can influence the geochemistry of inorganic complexes of Hg in the Everglades, especially HgS, by strong Hg-DOM binding and colloidal stabilization.

  13. Functional and Structural Responses of Hyporheic Biofilms to Varying Sources of Dissolved Organic Matter

    PubMed Central

    Wagner, Karoline; Bengtsson, Mia M.; Besemer, Katharina; Sieczko, Anna; Burns, Nancy R.; Herberg, Erik R.

    2014-01-01

    Headwater streams are tightly connected with the terrestrial milieu from which they receive deliveries of organic matter, often through the hyporheic zone, the transition between groundwater and streamwater. Dissolved organic matter (DOM) from terrestrial sources (that is, allochthonous) enters the hyporheic zone, where it may mix with DOM from in situ production (that is, autochthonous) and where most of the microbial activity takes place. Allochthonous DOM is typically considered resistant to microbial metabolism compared to autochthonous DOM. The composition and functioning of microbial biofilm communities in the hyporheic zone may therefore be controlled by the relative availability of allochthonous and autochthonous DOM, which can have implications for organic matter processing in stream ecosystems. Experimenting with hyporheic biofilms exposed to model allochthonous and autochthonous DOM and using 454 pyrosequencing of the 16S rRNA (targeting the “active” community composition) and of the 16S rRNA gene (targeting the “bulk” community composition), we found that allochthonous DOM may drive shifts in community composition whereas autochthonous DOM seems to affect community composition only transiently. Our results suggest that priority effects based on resource-driven stochasticity shape the community composition in the hyporheic zone. Furthermore, measurements of extracellular enzymatic activities suggest that the additions of allochthonous and autochthonous DOM had no clear effect on the function of the hyporheic biofilms, indicative of functional redundancy. Our findings unravel possible microbial mechanisms that underlie the buffering capacity of the hyporheic zone and that may confer stability to stream ecosystems. PMID:25063654

  14. Dissolving efficacy of some organic solvents on gutta-percha.

    PubMed

    Magalhães, Bianca Silva; Johann, Julia Elis; Lund, Rafael Guerra; Martos, Josué; Del Pino, Francisco Augusto Burkert

    2007-01-01

    The aim of this study was to evaluate the solubility of gutta-percha in four organic solvents used in endodontics. The solubility of gutta-percha (Dentsply) was assessed in xylol, orange oil, eucalyptol, chloroform and distilled water. A hundred and fifty samples of gutta-percha were prepared using a standardized stainless steel mould and divided into five groups for immersion in the different solvents tested and in distilled water (control group) for 2, 5 and 10 minutes. The means of gutta-percha dissolution in the solvents were obtained by the difference between the pre-immersion original weight and the post-immersion weight in a digital analytical scale (Gehaka-AG2000). Data were statistically analyzed by Analysis of Variance (ANOVA) and multiple comparisons with Scheffes test (p<0.05). The best solvency capacity was obtained with xylol. Chloroform, orange oil and eucalyptol presented similar results, and distilled water did not promote alterations in the gutta-percha.

  15. Dissolving efficacy of organic solvents on root canal sealers.

    PubMed

    Martos, J; Gastal, M T; Sommer, L; Lund, R G; Del Pino, F A B; Osinaga, P W R

    2006-03-01

    The aim of this study was to evaluate the solubility of three types of root canal sealers in three organic solvents used in endodontics. The solubility of calcium-hydroxide-based (Sealer 26), silicon-polydimethylsiloxane-based (RoekoSeal), and zinc-oxide-eugenol based (Endofill and Intrafill) sealers was assessed in eucalyptol, xylol, orange oil, and distilled water. Eighty samples of each filling material were prepared according to the manufacturers' instructions and then divided into four groups for immersion in solvent for 2 or 10 min. The means of sealer dissolution in solvents were obtained by the difference between the original preimmersion weight and the postimmersion weight in a digital analytical scale. Data were statistically analyzed with the Student's t test, and multiple comparisons were performed with Student-Newman-Keuls. Xylol and orange oil showed similar effects, with significant solubilization (P<0.05) of the tested cements. Endofill and Sealer 26 did not show any significant difference in solubilization at the two immersion times, whereas RoekoSeal and Intrafill showed a more pronounced solubility at 10 min. The lowest levels of solubilization occurred in RoekoSeal, Sealer 26, Endofill, and Intrafill. It is concluded that xylol and orange oil presented similar solvent effects with a significant solubility of the tested cements.

  16. Freshwater processing of terrestrial dissolved organic matter: What governs lability?

    NASA Astrophysics Data System (ADS)

    D'Andrilli, J.; Smith, H. J.; Junker, J. R.; Scholl, E. A.; Foreman, C. M.

    2016-12-01

    Aquatic and terrestrial ecosystems are linked through the transfer of energy and materials. Allochthonous organic matter (OM) is central to freshwater ecosystem function, influencing local food webs, trophic state, and nutrient availability. In order to understand the nature and fate of OM from inland headwaters to the open ocean, it is imperative to understand the links between OM lability and ecosystem function. Thus, biological, chemical, and physical factors need to be evaluated together to inform our understanding of environmental lability. We performed a laboratory processing experiment on naturally occurring OM leachates from riparian leaves, grasses, and pine needles. Measures of water chemistry, OM optical and molecular characterization, bacterial abundances, microbial assemblage composition, respiration, and C:N:P were integrated to discern the nature and fate of labile and recalcitrant OM in a freshwater stream. Peak processing of all OM sources in the stream water occurred after two days, with spikes in bacterial cell abundances, respiration rates, microbial assemblage shifts, and maximum C utilization. Respiration rates and microbial assemblages were dependent on the degree of lability of the OM molecular composition. Within the first few days, no differences in respiration rates were observed between leachate sources, however, beyond day five, the rates diverged with C processing efficiency correlated with OM lability. Originally comprised of amino acid-like, labile fluorescent species, the inoculated stream water OM became more recalcitrant after 16 days, indicating humification processing over time. Our study highlights the importance of interdisciplinary approaches for understanding the processing and fate of OM in aquatic ecosystems.

  17. Fluorescence-based proxies for lignin in freshwater dissolved organic matter

    USGS Publications Warehouse

    Hernes, Peter J.; Bergamaschi, Brian A.; Eckard, Robert S.; Spencer, Robert G.M.

    2009-01-01

    Lignin phenols have proven to be powerful biomarkers in environmental studies; however, the complexity of lignin analysis limits the number of samples and thus spatial and temporal resolution in any given study. In contrast, spectrophotometric characterization of dissolved organic matter (DOM) is rapid, noninvasive, relatively inexpensive, requires small sample volumes, and can even be measured in situ to capture fine-scale temporal and spatial detail of DOM cycling. Here we present a series of cross-validated Partial Least Squares models that use fluorescence properties of DOM to explain up to 91% of lignin compositional and concentration variability in samples collected seasonally over 2 years in the Sacramento River/San Joaquin River Delta in California, United States. These models were subsequently used to predict lignin composition and concentration from fluorescence measurements collected during a diurnal study in the San Joaquin River. While modeled lignin composition remained largely unchanged over the diurnal cycle, changes in modeled lignin concentrations were much greater than expected and indicate that the sensitivity of fluorescence-based proxies for lignin may prove invaluable as a tool for selecting the most informative samples for detailed lignin characterization. With adequate calibration, similar models could be used to significantly expand our ability to study sources and processing of DOM in complex surface water systems.

  18. Optical assessment of colored dissolved organic matter and its related parameters in dynamic coastal water systems

    NASA Astrophysics Data System (ADS)

    Shanmugam, Palanisamy; Varunan, Theenathayalan; Nagendra Jaiganesh, S. N.; Sahay, Arvind; Chauhan, Prakash

    2016-06-01

    Prediction of the curve of the absorption coefficient of colored dissolved organic matter (CDOM) and differentiation between marine and terrestrially derived CDOM pools in coastal environments are hampered by a high degree of variability in the composition and concentration of CDOM, uncertainties in retrieved remote sensing reflectance and the weak signal-to-noise ratio of space-borne instruments. In the present study, a hybrid model is presented along with empirical methods to remotely determine the amount and type of CDOM in coastal and inland water environments. A large set of in-situ data collected on several oceanographic cruises and field campaigns from different regional waters was used to develop empirical methods for studying the distribution and dynamics of CDOM, dissolved organic carbon (DOC) and salinity. Our validation analyses demonstrated that the hybrid model is a better descriptor of CDOM absorption spectra compared to the existing models. Additional spectral slope parameters included in the present model to differentiate between terrestrially derived and marine CDOM pools make a substantial improvement over those existing models. Empirical algorithms to derive CDOM, DOC and salinity from remote sensing reflectance data demonstrated success in retrieval of these products with significantly low mean relative percent differences from large in-situ measurements. The performance of these algorithms was further assessed using three hyperspectral HICO images acquired simultaneously with our field measurements in productive coastal and lagoon waters on the southeast part of India. The validation match-ups of CDOM and salinity showed good agreement between HICO retrievals and field observations. Further analyses of these data showed significant temporal changes in CDOM and phytoplankton absorption coefficients with a distinct phase shift between these two products. Healthy phytoplankton cells and macrophytes were recognized to directly contribute to the

  19. Dissolved organic sulfur in streams draining forested catchments in southern China.

    PubMed

    Wang, Zhanyi; Zhang, Xiaoshan; Wang, Zhangwei; Zhang, Yi; Li, Bingwen; Vogt, Rolf

    2012-01-01

    Dissolved organic sulfur (DOS) is an important fraction for sulfur mobilization in ecosystem. In this work stream waters were sampled in 25 forested sites in southern China to study the dissolved sulfur fractions. Dissolved sulfur was fractionated into dissolved organic sulfur (DOS) and inorganic sulfate (SO4(2-)) for 95 stream water samples. The results showed that the concentration of DOS ranged from 0 to 13.1 mg/L (average 1.3 mg/L) in all the streams. High concentrations of DOS in stream waters were found in the sites with high concentrations of sulfate. DOS constituted less than 60.1% of dissolved sulfur (average 17.9%). Statistical analysis showed that DOS concentration was correlated with SO4(2-) in streams waters and total sulfur in surface layer soils. The results also showed that DOS concentration in stream waters had a seasonal variation, but no trends were found with it. The implication was that the long term sulfur deposition had led the increase of the concentration and fraction of DOS in stream waters in acid rain prevailing regions

  20. Fe-binding dissolved organic ligands near the Kerguelen Archipelago in the Southern Ocean (Indian sector)

    NASA Astrophysics Data System (ADS)

    Gerringa, L. J. A.; Blain, S.; Laan, P.; Sarthou, G.; Veldhuis, M. J. W.; Brussaard, C. P. D.; Viollier, E.; Timmermans, K. R.

    2008-03-01

    During the Kerguelen Ocean and Plateau compared Study (KEOPS; January-February 2005) cruise, the area southeast of the Kerguelen Archipelago in the Indian sector of the Southern Ocean was investigated to identify the mechanisms of natural iron fertilization of the Kerguelen Plateau. In this study, the organic speciation of Fe is described. Samples were determined immediately on board using competing ligand-adsorptive cathodic stripping voltammetry (CL-AdCSV). The dissolved organic ligands were always in excess of the dissolved Fe concentration, increasing the residence time in the water column and the potential availability for phytoplankton. The concentration of the dissolved organic ligands ranged from 0.44 to 1.61 nEq of M Fe (=complexation site for Fe), with an average concentration of 0.91 nEq of M Fe (S.D.=0.28, n=113) and a mean logarithm of conditional stability constant (log K') of 21.7 (S.D.=0.28, n=113). A second weaker dissolved organic ligand group was detected in 32% of the samples, with Fe-binding characteristics at the edge of the detection window of the applied method. The occurrence of the highest concentrations of dissolved organic ligands in the wind-mixed surface layer and near the sediment at the bottom of the water column indicated that both phytoplankton and the sediment act as sources. Both sources are in concert with the general conclusions from the KEOPS research on the sources of Fe, where Fe was regenerated, organic Fe-binding ligands were formed in the upper layers, and both Fe and ligands were supplied by the sediment.

  1. Response of soil dissolved organic matter to microplastic addition in Chinese loess soil.

    PubMed

    Liu, Hongfei; Yang, Xiaomei; Liu, Guobin; Liang, Chutao; Xue, Sha; Chen, Hao; Ritsema, Coen J; Geissen, Violette

    2017-10-01

    Plastic debris is accumulating in agricultural land due to the increased use of plastic mulches, which is causing serious environmental problems, especially for biochemical and physical properties of the soil. Dissolved organic matter (DOM) plays a central role in driving soil biogeochemistry, but little information is available on the effects of plastic residues, especially microplastic, on soil DOM. We conducted a soil-incubation experiment in a climate-controlled chamber with three levels of microplastic added to loess soil collected from the Loess Plateau in China: 0% (control, CK), 7% (M1) and 28% (M2) (w/w). We analysed the soil contents of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), NH4(+), NO3(-), dissolved organic phosphorus (DOP), and PO4(3-) and the activities of fluorescein diacetate hydrolase (FDAse) and phenol oxidase. The higher level of microplastic addition significantly increased the nutrient contents of the DOM solution. The lower level of addition had no significant effect on the DOM solution during the first seven days, but the rate of DOM decomposition decreased in M1 between days 7 and 30, which increased the nutrient contents. The microplastic facilitated the accumulation of high-molecular-weight humic-like material between days 7 and 30. The DOM solutions were mainly comprised of high-molecular-weight humic-like material in CK and M1 and of high-molecular-weight humic-like material and tyrosine-like material in M2. The Microplastic stimulated the activities of both enzymes. Microplastic addition thus stimulated enzymatic activity, activated pools of organic C, N, and P, and was beneficial for the accumulation of dissolved organic C, N and P. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Removal of terrestrial dissolved organic carbon in aquatic ecosystems of a temperate river network.

    NASA Astrophysics Data System (ADS)

    Wollheim, W. M.; Stewart, R. J.; Aiken, G.; Butler, K. D.; Morse, N.; Salisbury, J.

    2015-12-01

    Surface waters play an important role in the global carbon balance. Dissolved organic carbon (DOC) fluxes are a major transfer of terrestrial carbon to river systems, and the net removal of terrestrial DOC in aquatic systems is poorly constrained. We used a combination of spatially distributed sampling of three DOC fractions, nitrate, and chloride in streams of different size throughout a river network and modeling to quantify the net removal of terrestrial DOC relative to other constituents during a summer base flow period. The approach was applied to the 400 km2 Ipswich River watershed, MA, USA. We found that aquatic reactivity of terrestrial DOC leading to net loss is low, closer to conservative chloride than to reactive nitrogen. Net removal of DOC occurred mainly from the hydrophobic organic acid fraction, while hydrophilic and transphilic acids showed no net change. Model fits were improved using the different DOC fractions than when using bulk DOC, indicating that partitioning of bulk DOC into different fractions is critical for understanding terrestrial DOC removal. These findings suggest that river systems may have only a modest ability to alter the amounts of terrestrial DOC delivered to coastal zones.

  3. Method for removing and decolorizing aqueous waste effluents containing dissolved or dispersed organic matter

    DOEpatents

    Case, F.N.; Ketchen, E.E.

    1975-10-14

    A method is provided for treating organic waste material dissolved or dispersed in an aqueous effluent, which comprises contacting the effluent with an inert particulate carbonaceous sorbent at an oxygen pressure up to 2000 psi, irradiating the resultant mixture with high energy radiation until a decolorized liquid is produced, and then separating the decolorized liquid.

  4. Dissolved organic carbon in Alaskan boreal forest: sources, chemical characteristics, and biodegradability

    Treesearch

    Kimberly P. Wickland; Jason C. Neff; George R. Aiken

    2007-01-01

    The fate of terrestrially-derived dissolved organic carbon (DOC) is important to carbon (C) cycling in both terrestrial and aquatic environments, and recent evidence suggests that climate warming is influencing DOC dynamics in northern ecosystems. To understand what determines the fate of terrestrial DOC, it is essential to quantify the chemical nature and potential...

  5. TREATMENT OF URBAN STORMWATER FOR DISSOLVED POLLUTANTS: A COMPARATIVE STUDY OF THREE NATURAL ORGANIC MEDIA

    EPA Science Inventory

    The feasibility of using hard and soft wood tree mulch and processed jute fiber, as filter media, for treating mixtures of dissolved pollutants (toxic organic compounds and heavy metals) in urban stormwater (SW) runoff was evaluated. Copper (Cu), cadmium (Cd), chromium (Cr+6), l...

  6. Production of Chromophoric Dissolved Organic Matter from Mangrove Leaf Litter and Floating Sargassum Colonies

    EPA Science Inventory

    Chromophoric dissolved organic matter (CDOM) strongly absorbs solar radiation in the blue-green and serves as the primary attenuator of water column ultraviolet radiation (UV-R). CDOM interferes with remote sensing of ocean chlorophyll and can control UV-R-induced damage to light...

  7. ISOTOPIC BIOGEOCHEMISTRY OF DISSOLVED ORGANIC NITROGEN: A NEW TECHNIQUE AND APPLICATION. (R825151)

    EPA Science Inventory

    We present a new technique for isolating and isotopically characterizing dissolved organic nitrogen (DON) for non-marine waters, 15N values for DON from lacustrine samples and data suggesting that this technique will be a...

  8. TREATMENT OF URBAN STORMWATER FOR DISSOLVED POLLUTANTS: A COMPARATIVE STUDY OF THREE NATURAL ORGANIC MEDIA

    EPA Science Inventory

    The feasibility of using hard and soft wood tree mulch and processed jute fiber, as filter media, for treating mixtures of dissolved pollutants (toxic organic compounds and heavy metals) in urban stormwater (SW) runoff was evaluated. Copper (Cu), cadmium (Cd), chromium (Cr+6), l...

  9. Dissolved organic carbon loading from the field to watershed scale in tile-drained landscapes

    USDA-ARS?s Scientific Manuscript database

    Dissolved organic carbon (DOC) is an integral part to the functioning of aquatic ecosystems; yet, there is a paucity of data on DOC delivery and management in tile-drained agricultural headwater watersheds. The objective of this study was to quantify the contribution of subsurface tile drains to wat...

  10. Quantifying the production of dissolved organic nitrogen in headwater streams using 15N tracer additions

    Treesearch

    Laura T. Johnson; Jennifer L. Tank; Robert O. Hall; Patrick J. Mullholland; Stephen K. Hamilton; H. Maurice Valett; Jackson R. Webster; Melody J. Bernot; William H. McDowell; Bruce J. Peterson; Suzanne M. Thomas

    2013-01-01

    Most nitrogen (N) assimilation in lake and marine ecosystems is often subsequently released via autochthonous dissolved organic nitrogen (DON) production, but autochthonous DON production has yet to be quantified in flowing waters. We measured in-stream DON production following 24 h 15N-nitrate (NO3-...

  11. Dissolved organic carbon fluxes from hydropedologic units in Alaskan coastal temperate rainforest watersheds

    Treesearch

    David V. D' Amore; Rick T. Edwards; Paul A. Herendeen; Eran Hood; Jason B. Fellman

    2015-01-01

    Dissolved organic C (DOC) transfer from the landscape to coastal margins is a key component of regional C cycles. Hydropedology provides a conceptual and observational framework for linking soil hydrologic function to landscape C cycling. We used hydropedology to quantify the export of DOC from the terrestrial landscape and understand how soil temperature and water...

  12. Pathways and mechanisms for removal of dissolved organic carbon from leaf leachate in streams

    Treesearch

    Clifford N. Dahm

    1981-01-01

    Removal of dissolved organic carbon (DOC) from water resulting from adsorption and microbial uptake was examined to determine the importance of biotic and abiotic pathways. Physical–chemical adsorption to components of the stream sediment or water and biotic assimilation associated with the microbial population was determined in recirculating chambers utilizing...

  13. PHOTOCHEICAL PRODUCTION OF HYDROXYL RADICAL IN NATURAL WATER - THE ROLE OF IRON AND DISSOLVED ORGANIC MATTER

    EPA Science Inventory

    Photochemical hydroxyl radical (OH) production was measured in several natural waters to investigate the importance of colored dissolved organic matter (CDOM) and iron-CDOM complexes as sources of OH. High rates of OH photoproduction in highly colored, iron-rich, acidic waters a...

  14. PHOTOCHEMICAL MINERALIZATION OF DISSOLVED ORGANIC NITROGEN TO AMMONIUM IN THE BALTIC SEA

    EPA Science Inventory

    Solar radiation-induced photochemistry can be considered as a new source of nutrients when photochemical reactions release bioavailable nitrogen from biologically non-reactive dissolved organic nitrogen (DON). Pretreatments of Baltic Sea waters in the dark indicated that >72% of ...

  15. Comment on “Dissolved organic sulfur in the ocean: Biogeochemistry of a petagram inventory”

    NASA Astrophysics Data System (ADS)

    Dittmar, Thorsten; Stubbins, Aron; Ito, Takamitsu; Jones, Daniel C.

    2017-05-01

    Ksionzek et al. (Reports, 28 October 2016, p. 456) provide important data describing the distribution of dissolved organic sulfur (DOS) in the Atlantic Ocean. Here, we show that mixing between water masses is sufficient to explain the observed distribution of DOS, concluding that the turnover time of refractory DOS that Ksionzek et al. present cannot be deduced from their data.

  16. INFLUENCE OF DISSOLVED ORGANIC MATTER ON AGROCHEMICAL PHOTOREACTIONS IN AQUATIC ENVIRONMENTS

    EPA Science Inventory

    Pioneering studies by Don Crosby and co-workers demonstrated that the sunlight-induced dissipation of agrochemicals in water often is strongly affected by natural constituents in the water such as nitrate and dissolved organic matter. In this presentation, the focus is on the rol...

  17. Influence of Dissolved Organic Matter and Fe (II) on the Abiotic Reduction of Pentachloronitrobenzene

    EPA Science Inventory

    Nitroaromatic pesticides (NAPs) are hydrophobic contaminants that can accumulate in sediments by the deposition of suspended solids from surface waters. Fe(II) and dissolved organic matter (DOM), present in suboxic and anoxic zones of freshwater sediments, can transform NAPs in n...

  18. CONSTANTS FOR MERCURY BINDING BY DISSOLVED ORGANIC MATTER ISOLATES FROM THE FLORIDA EVERGLADES. (R827653)

    EPA Science Inventory

    Dissolved organic matter (DOM) has been implicated as an important complexing agent for Hg that can affect its mobility and bioavailability in aquatic ecosystems. However, binding constants for natural Hg-DOM complexes are not well known. We employed a competitive ligand appro...

  19. Production of Chromophoric Dissolved Organic Matter from Mangrove Leaf Litter and Floating Sargassum Colonies

    EPA Science Inventory

    Chromophoric dissolved organic matter (CDOM) strongly absorbs solar radiation in the blue-green and serves as the primary attenuator of water column ultraviolet radiation (UV-R). CDOM interferes with remote sensing of ocean chlorophyll and can control UV-R-induced damage to light...

  20. ISOTOPIC BIOGEOCHEMISTRY OF DISSOLVED ORGANIC NITROGEN: A NEW TECHNIQUE AND APPLICATION. (R825151)

    EPA Science Inventory

    We present a new technique for isolating and isotopically characterizing dissolved organic nitrogen (DON) for non-marine waters, 15N values for DON from lacustrine samples and data suggesting that this technique will be a...

  1. Comment on "Dilution limits dissolved organic carbon utilization in the deep ocean".

    PubMed

    Jiao, Nianzhi; Legendre, Louis; Robinson, Carol; Thomas, Helmuth; Luo, Ya-Wei; Dang, Hongyue; Liu, Jihua; Zhang, Rui; Tang, Kai; Luo, Tingwei; Li, Chao; Wang, Xiaoxue; Zhang, Chuanlun

    2015-12-18

    Arrieta et al. (Reports, 17 April 2015, p. 331) propose that low concentrations of labile dissolved organic carbon (DOC) preclude prokaryotic consumption of a substantial fraction of DOC in the deep ocean and that this dilution acts as an alternative mechanism to recalcitrance for long-term DOC storage. Here, we show that the authors' data do not support their claims.

  2. Response to Comment on "Dilution limits dissolved organic carbon utilization in the deep ocean".

    PubMed

    Arrieta, Jesús M; Mayol, Eva; Hansman, Roberta L; Herndl, Gerhard J; Dittmar, Thorsten; Duarte, Carlos M

    2015-12-18

    Our recent finding that dilution limits dissolved organic carbon (DOC) utilization in the deep ocean has been criticized based on the common misconception that lability equates to rapid and complete utilization. Even when considering the redefinition of recalcitrant DOC recently proposed by Jiao et al., the dilution hypothesis best explains our experimental observations.

  3. Effect of dissolved organic carbon in recycled wastewaters on boron adsorption by soils

    USDA-ARS?s Scientific Manuscript database

    In areas of water scarcity, recycled municipal wastewaters are being used as water resources for non-potable applications, especially for irrigation. Such wastewaters often contain elevated levels of dissolved organic carbon (DOC) and solution boron (B). Boron adsorption was investigated on eight ...

  4. Comment on “Dilution limits dissolved organic carbon utilization in the deep ocean”

    NASA Astrophysics Data System (ADS)

    Jiao, Nianzhi; Legendre, Louis; Robinson, Carol; Thomas, Helmuth; Luo, Ya-Wei; Dang, Hongyue; Liu, Jihua; Zhang, Rui; Tang, Kai; Luo, Tingwei; Li, Chao; Wang, Xiaoxue; Zhang, Chuanlun

    2015-12-01

    Arrieta et al. (Reports, 17 April 2015, p. 331) propose that low concentrations of labile dissolved organic carbon (DOC) preclude prokaryotic consumption of a substantial fraction of DOC in the deep ocean and that this dilution acts as an alternative mechanism to recalcitrance for long-term DOC storage. Here, we show that the authors’ data do not support their claims.

  5. INFLUENCE OF DISSOLVED ORGANIC MATTER ON AGROCHEMICAL PHOTOREACTIONS IN AQUATIC ENVIRONMENTS

    EPA Science Inventory

    Pioneering studies by Don Crosby and co-workers demonstrated that the sunlight-induced dissipation of agrochemicals in water often is strongly affected by natural constituents in the water such as nitrate and dissolved organic matter. In this presentation, the focus is on the rol...

  6. PRODUCTION OF HYDRATED ELECTRONS FROM PHOTOIONIZATION OF DISSOLVED ORGANIC MATTER IN NATURAL WATERS

    EPA Science Inventory

    Under UV irradiation, an important primary photochemical reaction of colored dissolved organic matter (CDOM) is electron ejection, producing hydrated electrons (e-aq). The efficiency of this process has been studied in both fresh and seawater samples with both steady-state scave...

  7. CONSTANTS FOR MERCURY BINDING BY DISSOLVED ORGANIC MATTER ISOLATES FROM THE FLORIDA EVERGLADES. (R827653)

    EPA Science Inventory

    Dissolved organic matter (DOM) has been implicated as an important complexing agent for Hg that can affect its mobility and bioavailability in aquatic ecosystems. However, binding constants for natural Hg-DOM complexes are not well known. We employed a competitive ligand appro...

  8. PRODUCTION OF HYDRATED ELECTRONS FROM PHOTOIONIZATION OF DISSOLVED ORGANIC MATTER IN NATURAL WATERS

    EPA Science Inventory

    Under UV irradiation, an important primary photochemical reaction of colored dissolved organic matter (CDOM) is electron ejection, producing hydrated electrons (e-aq). The efficiency of this process has been studied in both fresh and seawater samples with both steady-state scave...

  9. Effects of watershed history on dissolved organic matter characteristics in headwater streams

    Treesearch

    Youhei Yamashita; Brian D. Kloeppel; Jennifer Knoepp; Gregory L. Zausen; Rudolf Jaffe'

    2011-01-01

    Dissolved organic matter (DOM) is recognized as a major component in the global carbon cycle and is an important driver in aquatic ecosystem function. Climate, land use, and forest cover changes all impact stream DOM and alter biogeochemical cycles in terrestrial environments. We determined the temporal variation in DOM quantity and quality in headwater streams at a...

  10. PHOTOCHEICAL PRODUCTION OF HYDROXYL RADICAL IN NATURAL WATER - THE ROLE OF IRON AND DISSOLVED ORGANIC MATTER

    EPA Science Inventory

    Photochemical hydroxyl radical (OH) production was measured in several natural waters to investigate the importance of colored dissolved organic matter (CDOM) and iron-CDOM complexes as sources of OH. High rates of OH photoproduction in highly colored, iron-rich, acidic waters a...

  11. PHOTOCHEMICAL MINERALIZATION OF DISSOLVED ORGANIC NITROGEN TO AMMONIUM IN THE BALTIC SEA

    EPA Science Inventory

    Solar radiation-induced photochemistry can be considered as a new source of nutrients when photochemical reactions release bioavailable nitrogen from biologically non-reactive dissolved organic nitrogen (DON). Pretreatments of Baltic Sea waters in the dark indicated that >72% of ...

  12. Organic carbon and dissolved oxygen budgets for a commerical-size, in-pond raceway system

    USDA-ARS?s Scientific Manuscript database

    Intensive production of Ictalurid catfish in the United States has increased over the past several years and a better understanding of the amount of organic carbon (OC) and dissolved oxygen (DO) in these culture environments is needed. Budgets for OC and DO were estimated over a production season (M...

  13. Pyrolysis temperature-dependent release of dissolved organic carbon from plant, manure, and biorefinery wastes

    USDA-ARS?s Scientific Manuscript database

    Limited information is available to understand the chemical structure of biochar’s labile dissolved organic carbon (DOC) fraction that will change amended soil’s DOC composition. This study utilized the high sensitivity of fluorescence excitation-emission (EEM) spectrophotometry to understand the s...

  14. Dissolved organic matter dynamics in surface waters affected by oil spill pollution: Results from the Serious Game exercise

    NASA Astrophysics Data System (ADS)

    Gonnelli, M.; Galletti, Y.; Marchetti, E.; Mercadante, L.; Retelletti Brogi, S.; Ribotti, A.; Sorgente, R.; Vestri, S.; Santinelli, C.

    2016-11-01

    Dissolved organic carbon (DOC), chromophoric and fluorescent dissolved organic matter (CDOM and FDOM, respectively) surface distribution was studied during the Serious Game exercise carried out in the Eastern Ligurian Sea, where an oil spill was localized by using satellite images and models. This paper reports the first DOC, CDOM and FDOM data for this area together with an evaluation of fluorescence as a fast and inexpensive tool for early oil spill detection in marine waters. The samples collected in the oil spill showed a fluorescence intensity markedly higher ( 5 fold) than all the other samples. The excitation-emission matrixes, coupled with parallel factor analysis (PARAFAC), allowed for the identification in the FDOM pool of a mixture of polycyclic aromatic hydrocarbons, humic-like and protein-like fluorophores.

  15. Photochemical and microbial transformation of terrestrial dissolved organic matter - Lena River vs. rivers in mid and low latitudes

    NASA Astrophysics Data System (ADS)

    Vähätalo, A. V.; Aarnos, H.; Paolucci, E. M.; Musibono, D. E.; Khan, S. R.; Gelinas, Y.; Shantz, A.; Huang, Q.; Schneider, W.; Rezende, C. E.; Petrescu, E.; Reader, H. E.

    2012-04-01

    The aim of this study was to assess the fate of riverine dissolved organic matter (DOM) in coastal ocean. In that environment after the sedimentation of terrestrial particulate matter and the advective mixing of river water to optically clear marine water, the photochemical transformation of riverine DOM has a large potential for decomposing riverine DOM. For this study, we collected water samples from ten large rivers and carried out laboratory experiments with the river water samples. The potential for the photochemical decomposition of riverine dissolved organic matter was assessed by exposing sterile-filtered river waters to simulated solar radiation. Dark control samples we treated similarly but were not irradiated. The exposures were designed to decompose photochemically chromophoric dissolved organic matter, the major absorber of UV-vis radiation and the primary initiator of the direct photoreactions of DOM. In the end of irradiation, the difference in the concentration of dissolved organic carbon between the irradiated and the dark control sample corresponded to that portion of dissolved organic carbon (DOC) decomposable through direct photoreactions to carbon dioxide. In order to assess the amount of DOC phototransformed into biologically available forms, the irradiated and the dark control water samples received indigenous inoculums of riverine microbes and were incubated in the darkness. After a month, the difference in the concentration of DOC between the irradiated and dark control sample was considered to represent the photoreactive portion of DOC, while the residual DOC made up the DOC resistant to photochemical reactions. The photoreactive portion of DOC varied among rivers and was related to the amount of chromophoric dissolved organic matter in the water samples. The biological decomposition experiments were extended to last up to one year and predictions about the biodegradability of irradiated and dark control DOM were made by fitting a

  16. Characterization of dissolved organic matter in an urbanized estuary located in Northeastern Brazil.

    PubMed

    Arguelho, Maria de Lara Palmeira de Macedo; Alves, José do Patrocínio Hora; Monteiro, Adnívia Santos Costa; Garcia, Carlos Alexandre Borges

    2017-06-01

    The Sal River estuary, which is located in the state of Sergipe, Northeastern Brazil, stands out as an urban estuary, anthropogenically impacted by untreated and treated wastewater discharge. Synchronous fluorescence spectroscopy and measurement of dissolved organic carbon (DOC) were used for characterization of dissolved organic matter (DOM) in the estuarine water. Dissolved organic carbon concentrations ranged from 7.5 to 19.0 mg L(-1) and, in general, the highest values were recorded during dry season. For both seasons (dry and rainy), DOC presented an inverse linear relationship with salinity, which indicates a conservative dilution of organic matter coming into the estuary. During rainy season, anthropogenic organic constituents and humic substances from land-based sources predominated in DOM composition, carried by river flow. Whereas during the dry season, it has been observed a significant increase of products generated by microbial degradation of anthropogenic organic matter. The relationships between fluorescence intensity and salinity suggest a conservative behavior during rainy season and a non-conservative behavior during dry season, with addition of fluorescent organic matter into the intermediate zone of the estuary. Photodegradation by action of sunlight caused a decrease in fluorescence intensity of humic and tryptophan-like constituents and the release of photoproducts, resulting in an increase in fluorescence intensity of protein-like constituents.

  17. Cross-scale ensemble projections of dissolved organic carbon dynamics in boreal forest streams

    NASA Astrophysics Data System (ADS)

    Oni, Stephen K.; Futter, Martyn N.; Teutschbein, Claudia; Laudon, Hjalmar

    2014-05-01

    Climate is an important driver of dissolved organic carbon (DOC) dynamics in boreal catchments characterized by networks of streams within forest-wetland landscape mosaics. In this paper, we assess how climate change may affect stream DOC concentrations ([DOC]) and export from boreal forest streams with a multi-model ensemble approach. First, we apply an ensemble of regional climate models (RCMs) to project soil temperatures and stream-flows. These data are then used to drive two biogeochemical models of surface water DOC: (1) The Integrated Catchment model for Carbon (INCA-C), a detailed process-based model of DOC operating at the catchment scale, and (2) The Riparian Integration Model (RIM), a simple dynamic hillslope scale model of stream [DOC]. All RCMs project a consistent increase in temperature and precipitation as well as a shift in spring runoff peaks from May to April. However, they present a considerable range of possible future runoff conditions with an ensemble median increase of 31 % between current and future (2061-2090) conditions. Both biogeochemical models perform well in describing the dynamics of present-day stream [DOC] and fluxes, but disagree in their future projections. Here, we assess possible futures in three boreal catchments representative of forest, mire and mixed landscape elements. INCA-C projects a wider range of stream [DOC] due to its temperature sensitivity, whereas RIM gives consistently larger inter-annual variation and a wider range of exports due to its sensitivity to hydrological variations. The uncertainties associated with modeling complex processes that control future DOC dynamics in boreal and temperate catchments are still the main limitation to our understanding of DOC mechanisms under changing climate conditions. Novel, currently overlooked or unknown drivers may appear that will present new challenges to modelling DOC in the future.

  18. Biodegradability of dissolved organic carbon within and among hillslopes along a chronosequence of landscape age in arctic Alaska

    NASA Astrophysics Data System (ADS)

    Whittinghill, K. A.; Finlay, J. C.; Hobbie, S. E.

    2009-12-01

    A thorough understanding of the influence of landscape heterogeneity on arctic soil organic matter processing is necessary to predict how arctic carbon cycling will change with future climate. Large variation in geology, topography, vegetation, and permafrost extent exists throughout the circumpolar region. In the Kuparuk River region of northern Alaska, significant differences in mineralization of soil organic matter and production of dissolved organic carbon exist among landscapes with different glaciation histories which cannot be explained entirely by geochemical differences among these landscapes. In addition to variation among landscape ages, previous research in the region has demonstrated significant differences in soil water dissolved organic carbon concentrations within hillslope toposequences. We hypothesized that differences in biodegradability of dissolved organic matter within hillslopes or across landscapes of different age may drive observed variability in soil water dissolved organic carbon concentrations, dissolved organic carbon production, and soil respiration. To test this hypothesis we examined dissolved organic carbon extracted (with water) from soils within hillslopes across a chronosequence of landscapes with different glacial histories using four direct and indirect indices of dissolved organic matter biodegradability: 1) specific UV absorbance, 2) fluorescence index, 3) respiration measured by oxygen consumption rates, and 4) a long-term incubation of dissolved organic mater consumption. We selected three replicate hillslopes within four distinct landscape ages near the Kuparuk River. Within each hillslope we extracted dissolved organic matter from three organic soil samples collected from each of three transects: a) adjacent to the stream, b) along the vegetation boundary between upslope and streamside vegetation, and c) within upslope tussock tundra vegetation. Soil extract dissolved organic carbon concentrations were significantly

  19. Numerical modeling of dissolved oxygen in an ultra-urban best management practice.

    PubMed

    Bai, Sen

    2009-04-01

    Stormvault (Jensen Precast, Sparks, Nevada) is a retention-type ultra-urban best management practice, which has been tested extensively for pollutant reduction. As the first step to understand the internal water quality change during a dry-weather condition, dissolved oxygen was monitored in a Stormvault system. A diffusion-reaction model was developed to diagnose the contributions of organic materials floating on the water surface, in the water column, and in the sediment, to dissolved oxygen decrease. The mathematical model was calibrated using the observed dissolved oxygen data recorded at a 0.15-m interval along the water column depth. Three scenarios were simulated, and the results confirmed that sediment oxygen demand (SOD) is the governing factor controlling a dissolved oxygen decrease in the system. The SOD rate reaches 0.8 g m(-2) d(-1) at 20 degrees C, with an average sediment accumulation depth of 0.05 m, which is lower than the recommended cleanup depth of 0.15 m.

  20. Production and stabilization of dissolved organic matter throughout the entire soil profile

    NASA Astrophysics Data System (ADS)

    Kalbitz, Karsten; Kaiser, Klaus

    2010-05-01

    Dissolved organic matter (DOM) is the most mobile and rapidly cycling organic fraction in soil, affecting biogeochemical processes and linking terrestrial and aquatic ecosystems. Although representing just a small portion of total organic, it seems to be a key player in processes ultimately resulting in stabilization of organic matter against microbial decay. Recent studies have pointed out that up to 90% of the organic C in the mineral soil could derive from DOM. Most studies assume DOM to derive from surface horizons having large contents of organic matter such as peats, forest floor layers and mineral topsoils. Once biologically produced or physico-chemically released, DOM is transported into the subsoils characterized by smaller contents of organic matter. Here, DOM is retained by adsorption and/or (co)precipitation, resulting in stabilization against microbial decay. This concept assumes, DOM exported to the hydrosphere is that portion of DOM either not respired or not stabilized within the mineral soil. We think that this conceptual model is oversimplified and not made up to explain all aspects of organic matter transport and stabilization in soils. All organic matter in soil derives from primary production, entering the soil as leaves, roots and root exudates. The biological decomposition of the primary sources will provide a large variety of compounds of differing reactivity, solubility and stability, with microbial metabolites representing a prominent part of the stable fraction. Microbial decomposition will not ultimately convert all organic material into CO2 but render a certain portion soluble. Also, DOM seems capable to replace sorbed organic matter, thus allowing also for retention in parts of the mineral soil with large contents of organic matter. Therefore, we think that throughout the entire soil profile, production and release of DOM is possible, as well as retention and stabilization. In organic-rich horizons, especially those close or at the

  1. Release dynamics of dissolved organic matter in soil amended with biosolids

    NASA Astrophysics Data System (ADS)

    Trifonov, Pavel; Ilani, Talli; Arye, Gilboa

    2014-05-01

    Among the soil organic matter (SOM) components, dissolved organic matter (DOM) is the link between the solid phase and the soil solution. Previous studies emphasize the turnover of dissolved organic carbon (DOC) and nitrogen (DON) in soils as major pathways of element cycling. In addition to DOM contribution to carbon, nitrogen and other nutrient budgets, it also influence soil biological activity, reduces metal-ion toxicity, increase the transport of some compounds and contribute to the mineral weathering. Amending soils with biosolids originated from sludge have become very popular in the recent years. Those additions significantly affect the quantity and the composition of the DOM in agricultural soils. It should be noted that under most irrigation habitants, the soil is subjected to drying and re-wetting cycles, inducing a complex changes of soil structure, aggregation, SOM quality and micro-flora. However, most studies that addressed the above issues (directly or indirectly) are engaged with soils under cover of naturally occurring forests of relatively humid areas rather than agricultural soils in arid areas. In the current study we examined the DOC and DON release dynamic of sand and loess soils sampled from the Negev Desert of Israel. Each one of the soils were mixing with 5% (w/w) of one of the biosolids and packed into a Plexiglass column (I.d. 5.2 cm, L=20 cm). The flow-through experiments were conducted under low (1 ml/min) or high (10 ml/min) flow rates in a continuous or interrupted manner. The leachates were collected in time intervals equivalent to about 0.12 pore volume of a given soil-biosolids mixture. The established leaching curves of DOC, DON, NO3-, NH4+ and Cl- are analyzed by water flow and solute transport model for saturate (continuous runs) or variably saturate water flow conditions (interrupted runs). The chemical equilibrium or non-equilibrium (i.e. equilibrium and/or kinetics adsorption/desorption) versions of the convection dispersion

  2. Investigation of organic carbon transformation in soils of dominant dissolved organic carbon source zones

    NASA Astrophysics Data System (ADS)

    Pissarello, Anna; Miltner, Anja; Oosterwoud, Marieke; Fleckenstein, Jan; Kästner, Matthias

    2014-05-01

    Over the past 20 years both a decrease in soil organic matter (SOM) and an increase in the dissolved organic carbon (DOC) concentrations in surface water bodies, including drinking water reservoirs, have been recorded in the northern hemisphere. This development has severe consequences for soil fertility and for drinking water purification. As both processes occur simultaneously, we assume that microbial SOM degradation, which transforms SOM into CO2 and DOC, is a possible source of the additional DOC in the surface water. In addition we speculate that both processes are initially triggered by physical mechanisms, resulting in a modification of the organic matter solubility equilibria and thus in higher SOM availability and DOC mobilization. The general hypothesis of the study is therefore that SOM loss and DOC increase are combined consequences of enhanced microbial degradation of SOM and that this is a result of climate variations and global change, e.g. the increase of the temperature, the alteration of the water regime (i.e. increase of the frequency of drying and rewetting cycles and a higher number of heavy rain events), but also the decrease of the atmospheric acid deposition resulting in an increase of soil pH values. The general goal of the study is the identification of the dominant processes and controlling factors involved in soil microbial carbon turnover and mobilization of DOC in soils from catchment areas that contribute DOC to the receiving waters and the downstream Rappbode reservoir, which showed a pronounced increase in DOC concentration in recent years. This reservoir is the source of drinking water for about one million people in northern Germany. Preliminary screening experiments, consisting of 65-day soil batch incubation experiments, have been conducted in order to select the parameters (and the parameter ranges) of relevance for further in-depth experiments. During the experiments, different soil systems were exposed to different

  3. A watershed-scale characterication of dissolved organic carbon and nutrients on the South Carolina Coastal Plain

    Treesearch

    Daniel L. Tufford; Setsen Alton-Ochir; Warren Hankinson

    2016-01-01

    Dissolved organic matter (DOM) is recognized as a major component in the global carbon cycle and is an important driver of numerous biogeochemical processes in aquatic ecosystems, both in-stream and downstream in estuaries. This study sought to characterize chromophoric DOM (CDOM), dissolved organic carbon (DOC), and dissolved nutrients in major rivers and their...

  4. A watershed-scale characterization of dissolved organic carbon and nutrients on the South Carolina Coastal Plain

    Treesearch

    Daniel Tufford; Setsen Alton-Ochir

    2016-01-01

    Dissolved organic matter (DOM) is recognized as a major component in the global carbon cycle and is an important driver of numerous biogeochemical processes in aquatic ecosystems, both in-stream and downstream in estuaries. This study sought to characterize chromophoric DOM (CDOM), dissolved organic carbon (DOC), and dissolved nutrients in major rivers and their...

  5. Understanding dissolved organic matter reactivity in a global context: tribute to Dr. George Aiken's many contributions

    NASA Astrophysics Data System (ADS)

    McKnight, Diane

    2017-04-01

    As Dr. George Aiken emphasized throughout his distinguished research career, the diversity of sources of dissolved organic material (DOM) is associated with a diversity of dissolved organic compounds with a range of chemistries and reactivities that are present in the natural environment. From a limnological perspective, dissolved organic matter (DOM) can originate from allochthonous sources on the landscape which drains into a lake, river, wetland, coastal region, or other aquatic ecosystem, or from autochthonous sources within the given aquatic ecosystem. In many landscapes, the precursor organic materials that contribute to the DOM of the associated aquatic ecosystem can be derived from diverse sources, e.g. terrestrial plants, plant litter, organic material in different soil horizons, and the products of microbial growth and decay. Yet, through his focus on the underlying chemical processes a clear, chemically robust foundation for understanding DOM reactivity has emerged from Aiken's research. These processes include the enhancement in solubility due to ionized carboxylic acid functional groups and the reactions of organic sulfur groups with mercury. This approach has advanced understand of carbon cycling in the lakes of the Mars-like barren landscapes of the McMurdo Dry Valleys in Antarctica and the rivers draining the warming tundra of the Arctic.

  6. Enhanced dissolution of cinnabar (mercuric sulfide) by dissolved organic matter isolated from the Florida Everglades

    SciTech Connect

    Ravichandran, M.; Ryan, J.N.; Aiken, G.R.; Reddy, M.M.

    1998-11-01

    Organic matter isolated from the Florida Everglades caused a dramatic increase in mercury release from cinnabar (HgS), a solid with limited solubility. Hydrophobic (a mixture of both humic and fulvic) acids dissolved more mercury than hydrophilic acids and other nonacid fractions of dissolved organic matter (DOM). Cinnabar dissolution by isolated organic matter and natural water samples was inhibited by cations such as Ca{sup 2+}. Dissolution was independent of oxygen content in experimental solutions. Dissolution experiments conducted in Dl water had no detectable dissolved mercury. The presence of various inorganic (chloride, sulfate, or sulfide) and organic ligands (salicylic acid, acetic acid, EDTA, or cysteine) did not enhance the dissolution of mercury from the mineral. Aromatic carbon content in the isolates correlated positively with enhanced cinnabar dissolution. {zeta}-potential measurements indicated sorption of negatively charged organic matter to the negatively charged cinnabar at pH 6.0. Possible mechanisms of dissolution include surface complexation of mercury and oxidation of surface sulfur species by the organic matter.

  7. Investigating the Chemical Composition and Bioavailability of Arctic River Dissolved Organic Matter (DOM) Using Biomarkers

    NASA Astrophysics Data System (ADS)

    Canedo-Oropeza, M. F.; Kaiser, K.; Amon, R. M. W.

    2016-02-01

    Arctic rivers are the dominant pathways for the transport of terrestrial dissolved organic matter to the Arctic Ocean, but knowledge of sources, transformations and transfer of organic carbon and nitrogen in Arctic river watersheds is extremely limited. This study uses chemical analyses of carbohydrates and enantiomeric amino acids to investigate the bioavailability of dissolved organic matter in five major Arctic river watersheds. In addition, existing measurements of lignin, mono/di-hydroxy benzenes, and radiocarbon contents were integrated to track the decomposition of the major organic constituents of riverine DOM and identify DOM sources. Carbohydrate-based indicators are sensitive to polysaccharide components derived from all plant sources; hydroxyproline and D-amino acids indicate plant and bacterial nitrogen, respectively; and lignin and mono/di-hydroxy benzenes track the phenolic constituents of vascular plants, mosses and lichens. The results show the bioavailability of DOM in Arctic rivers is strongly correlated with seasons, vegetation topography and water residence time in the watersheds. Pulses of bioavailable DOM were observed in the Siberian Rivers during the spring flood, whereas the Mackenzie River showed extensively degraded DOM throughout all stages of the hydrograph. Δ14C-DOC was not correlated to higher carbohydrate yields possibly indicating export of recently mobilized ancient permafrost organic carbon. Freshet samples showed significant input of plant-derived N, whereas bacterially-derived N dominated the dissolved organic nitrogen (DON) pool during low water discharge.

  8. Molecular Weight Distribution of Dissolved Organic Phosphorus in Euphotic Zone at South China Sea

    NASA Astrophysics Data System (ADS)

    Wen, L. S.; Lee, C. P.; Cheng, C. Y.

    2016-02-01

    Colloidal organic phosphorus (COP) plays an important role in marine P cycle; however, studies on COP are still scarce. This study focused on the distribution and variation of dissolved and colloidal organic phosphorus in euphotic zone of South China Sea. Seawater samples were separated into total dissolved (≤0.4μm), truly dissolved (≤1kDa), and colloidal (1 kDa 0.4 μm) fractions by in-line filtration of 0.4 μm-size capsule filter and then Cross-Flow Ultrafiltration (1kDa). After separation, each fractions were digested by a high temperature oxidation method and analyzed by phosphomolybdate-blue spectrophotometry. Therefore, different fractions of both inorganic and organic phosphorus were determined. Our results shown that the COP accounted for a significant amount (63±18%) of total dissolved P in the euphotic zone. It was also found that the depths of COP maximum concentration correlated well with the depths of chlorophyll a maximum, varies between day time and night hours. All these evidences highlight the strong biological effect on production and assimilation of COP and its vital importance in marine P cycle.

  9. Continuous Dissolved Oxygen Measurements and Modelling Metabolism in Peatland Streams

    PubMed Central

    Dick, Jonathan J.; Soulsby, Chris; Birkel, Christian; Malcolm, Iain; Tetzlaff, Doerthe

    2016-01-01

    Stream water dissolved oxygen was monitored in a 3.2km2 moorland headwater catchment in the Scottish Highlands. The stream consists of three 1st order headwaters and a 2nd order main stem. The stream network is fringed by peat soils with no riparian trees, though dwarf shrubs provide shading in the lower catchment. Dissolved oxygen (DO) is regulated by the balance between atmospheric re-aeration and the metabolic processes of photosynthesis and respiration. DO was continuously measured for >1 year and the data used to calibrate a mass balance model, to estimate primary production, respiration and re-aeration for a 1st order site and in the 2nd order main stem. Results showed that the stream was always heterotrophic at both sites. Sites were most heterotrophic in the summer reflecting higher levels of stream metabolism. The 1st order stream appeared more heterotrophic which was consistent with the evident greater biomass of macrophytes in the 2nd order stream, with resulting higher primary productivity. Comparison between respiration, primary production, re-aeration and potential physical controls revealed only weak relationships. However, the most basic model parameters (e.g. the parameter linking light and photosynthesis) controlling ecosystem processes resulted in significant differences between the sites which seem related to the stream channel geometry. PMID:27556278

  10. Continuous Dissolved Oxygen Measurements and Modelling Metabolism in Peatland Streams.

    PubMed

    Dick, Jonathan J; Soulsby, Chris; Birkel, Christian; Malcolm, Iain; Tetzlaff, Doerthe

    2016-01-01

    Stream water dissolved oxygen was monitored in a 3.2km2 moorland headwater catchment in the Scottish Highlands. The stream consists of three 1st order headwaters and a 2nd order main stem. The stream network is fringed by peat soils with no riparian trees, though dwarf shrubs provide shading in the lower catchment. Dissolved oxygen (DO) is regulated by the balance between atmospheric re-aeration and the metabolic processes of photosynthesis and respiration. DO was continuously measured for >1 year and the data used to calibrate a mass balance model, to estimate primary production, respiration and re-aeration for a 1st order site and in the 2nd order main stem. Results showed that the stream was always heterotrophic at both sites. Sites were most heterotrophic in the summer reflecting higher levels of stream metabolism. The 1st order stream appeared more heterotrophic which was consistent with the evident greater biomass of macrophytes in the 2nd order stream, with resulting higher primary productivity. Comparison between respiration, primary production, re-aeration and potential physical controls revealed only weak relationships. However, the most basic model parameters (e.g. the parameter linking light and photosynthesis) controlling ecosystem processes resulted in significant differences between the sites which seem related to the stream channel geometry.

  11. 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

  12. The Effects of Acid Rock Drainage (ARD) on Fluorescent Dissolved Organic Matter (DOM)

    NASA Astrophysics Data System (ADS)

    Lee, R. H.; Gabor, R. S.; SanClements, M.; McKnight, D. M.

    2011-12-01

    Located in the Rocky Mountains of central Colorado, the catchments drained by the headwaters of the Snake River are dominated by metal- and sulfide-rich bedrock. The breakdown of these minerals results in acidic metal-rich waters in the Snake (pH ~3) that persist until the confluence with Deer Creek (pH ~7). Previous research has been conducted examining the interactions of acid-rock drainage (ARD) and dissolved organic matter (DOM), but the effects of ARD on DOM production is not as well understood. In a synoptic study, samples of creek water were collected at evenly spaced intervals along the length of a tributary to the Snake River which drains an area with ARD. At each sampling location, water samples were collected and pH, conductivity, and temperature were measured. Water samples were analyzed for metal chemistry, and the DOM was analyzed with UV-Vis and fluorescence spectroscopy. The character of the DOM was described using PARAFAC and index calculations. This work demonstrates that the introduction of acid and dissolved metal species has notable effects on DOM composition. Preliminary data suggests that the introduction of acid drainage is responsible for the formation of a fluorophore not accounted for in the Cory and McKnight PARAFAC model. Both high concentrations of heavy metals (e.g. zinc) and the novel fluorophore are present downstream from a mining site, which indicates it as a possible source of both species. The data suggest a link between the introduction of fluorophores in acidic waters and acidophile populations at the source of the acid rock drainage.

  13. Predicting Copper Speciation in Estuarine Waters-Is Dissolved Organic Carbon a Good Proxy for the Presence of Organic Ligands?

    PubMed

    Pearson, Holly B C; Comber, Sean D W; Braungardt, Charlotte; Worsfold, Paul J

    2017-02-21

    A new generation of speciation-based aquatic environmental quality standards (EQS) for metals have been developed using models to predict the free metal ion concentration, the most ecologically relevant form, to set site-specific values. Some countries such as the U.K. have moved toward this approach by setting a new estuarine and marine water EQS for copper, based on an empirical relationship between copper toxicity to mussels (Mytilus sp.) and ambient dissolved organic carbon (DOC) concentrations. This assumes an inverse relationship between DOC and free copper ion concentration owing to complexation by predominantly organic ligands. At low DOC concentrations, the new EQS is more stringent, but above 162 μM DOC it is higher than the previous value. However, the relationship between DOC and copper speciation is poorly defined in estuarine waters. This research discusses the influence of DOC from different sources on copper speciation in estuaries and concludes that DOC is not necessarily an accurate predictor of copper speciation. Nevertheless, the determination of ligand strength and concentrations by Competitive Ligand Exchange Adsorptive Cathodic Stripping Voltammetry enabled the prediction of the free metal ion concentration within an order of magnitude for estuarine waters by using a readily available metal speciation model (Visual MINTEQ).

  14. DISSOLVED ORGANIC MATTER AND METALS: EFFECTS OF PH ON PARTITIONING NATURAL ORGANIC MATTER IN SOILS AND WATER

    EPA Science Inventory

    Eighteen Dutch soils were extracted in aqueous solutions at varying pH. Extracts were analyzed for Cd, Cu, Ni, Pb, and Zn by ICP-AES. Extract dissolved organic carbon (DOC) was fractionated into three operationally defined fractions: hydrophilic acids (Hyd), fulvic acids (FA), an...

  15. DISSOLVED ORGANIC MATTER AND METALS: EFFECTS OF PH ON PARTITIONING NATURAL ORGANIC MATTER IN SOILS AND WATER

    EPA Science Inventory

    Eighteen Dutch soils were extracted in aqueous solutions at varying pH. Extracts were analyzed for Cd, Cu, Ni, Pb, and Zn by ICP-AES. Extract dissolved organic carbon (DOC) was fractionated into three operationally defined fractions: hydrophilic acids (Hyd), fulvic acids (FA), an...

  16. Quantifying tropical peatland dissolved organic carbon (DOC) using UV-visible spectroscopy.

    PubMed

    Cook, Sarah; Peacock, Mike; Evans, Chris D; Page, Susan E; Whelan, Mick J; Gauci, Vincent; Kho, Lip Khoon

    2017-02-27

    UV-visible spectroscopy has been shown to be a useful technique for determining dissolved organic carbon (DOC) concentrations. However, at present we are unaware of any studies in the literature that have investigated the suitability of this approach for tropical DOC water samples from any tropical peatlands, although some work has been performed in other tropical environments. We used water samples from two oil palm estates in Sarawak, Malaysia to: i) investigate the suitability of both single and two-wavelength proxies for tropical DOC determination; ii) develop a calibration dataset and set of parameters to calculate DOC concentrations indirectly; iii) provide tropical researchers with guidance on the best spectrophotometric approaches to use in future analyses of DOC. Both single and two-wavelength model approaches performed well with no one model significantly outperforming the other. The predictive ability of the models suggests that UV-visible spectroscopy is both a viable and low cost method for rapidly analyzing DOC in water samples immediately post-collection, which can be important when working at remote field sites with access to only basic laboratory facilities.

  17. Biodegradation kinetics of dissolved organic matter chromatographic fractions in an intermittent river

    NASA Astrophysics Data System (ADS)

    Catalán, N.; Casas-Ruiz, J. P.; von Schiller, D.; Proia, L.; Obrador, B.; Zwirnmann, E.; Marcé, R.

    2017-01-01

    Controls on the degradation of dissolved organic matter (DOM) are complex but key to understand the role of freshwaters in the carbon cycle. Both the origin and previous degradation history have been suggested to determine DOM reactivity, but it is still a major challenge to understand the links between DOM composition and biodegradation kinetics. An appropriate context to study these links are intermittent rivers, as summer drought naturally diversifies DOM sources and sinks. Here we investigated the biodegradation kinetics of DOM in the main aquatic environments present in a temporary river. During dark incubations we traced the dynamics of bulk DOM and its main chromatographic fractions defined using LC-OCD: high molecular weight substances (HMWS), low molecular weight substances (LMWS), and humic substances and building blocks. Bulk DOM decay patterns were successfully fitted to the reactivity continuum (RC) biodegradation model. The RC parameters depicted running waters as the sites presenting a more reactive DOM, and temporary pools, enriched in leaf litter, as the ones with slowest DOM decay. The decay patterns of each DOM fraction were consistent throughout sites. LMWS and HMWS decayed in all cases and could be modeled using the RC model. Notably, the dynamics of LMWS controlled the bulk DOM kinetics. We discuss the mechanistic basis for the chromatographic fractions' kinetics during biodegradation and the implications that preconditioning and summer drought can have for DOM biodegradation in intermittent rivers.

  18. Linked changes in marine dissolved organic carbon molecular size and radiocarbon age

    NASA Astrophysics Data System (ADS)

    Walker, B. D.; Primeau, F. W.; Beaupré, S. R.; Guilderson, T. P.; Druffel, E. R. M.; McCarthy, M. D.

    2016-10-01

    Marine dissolved organic carbon (DOC) is a major global carbon reservoir, yet its cycling remains poorly understood. Previous work suggests that DOC molecular size and chemical composition can significantly affect its bioavailability. Thus, DOC size and composition may control DOC cycling and radiocarbon age (via Δ14C). Here we show that DOC molecular size is correlated to DOC Δ14C in the Pacific Ocean. Our results, based on a series of increasing molecular size fractions from three depths in the Pacific, show increasing DOC Δ14C with increasing molecular size. We use a size-age distribution model to predict the DOC and Δ14C of ultrafiltered DOC. The model predicts both large and small surface DOC with high Δ14C and a narrow range (200-500 Da) of low Δ14C DOC. Deep model offsets suggest different size distributions and/or Δ14C sources at 670-915 m. Our results suggest that molecular size and composition are linked to DOC reactivity and storage in the ocean.

  19. Heat as a tracer to estimate dissolved organic carbon flux from a restored wetland

    USGS Publications Warehouse

    Burow, K.R.; Constantz, J.; Fujii, R.

    2005-01-01

    Heat was used as a natural tracer to characterize shallow ground water flow beneath a complex wetland system. Hydrogeologic data were combined with measured vertical temperature profiles to constrain a series of two-dimensional, transient simulations of ground water flow and heat transport using the model code SUTRA (Voss 1990). The measured seasonal temperature signal reached depths of 2.7 m beneath the pond. Hydraulic conductivity was varied in each of the layers in the model in a systematic manual calibration of the two-dimensional model to obtain the best fit to the measured temperature and hydraulic head. Results of a series of representative best-fit simulations represent a range in hydraulic conductivity values that had the best agreement between simulated and observed temperatures and that resulted in simulated pond seepage values within 1 order of magnitude of pond seepage estimated from the water budget. Resulting estimates of ground water discharge to an adjacent agricultural drainage ditch were used to estimate potential dissolved organic carbon (DOC) loads resulting from the restored wetland. Estimated DOC loads ranged from 45 to 1340 g C/(m2 year), which is higher than estimated DOC loads from surface water. In spite of the complexity in characterizing ground water flow in peat soils, using heat as a tracer provided a constrained estimate of subsurface flow from the pond to the agricultural drainage ditch. Copyright ?? 2005 National Ground Water Association.

  20. Interaction of bisphenol A with dissolved organic matter in extractive and adsorptive removal processes.

    PubMed

    Zhu, Fei-Die; Choo, Kwang-Ho; Chang, Hyun-Shik; Lee, Byunghwan

    2012-05-01

    The fate of endocrine disrupting chemicals (EDCs) in natural and engineered systems is complicated due to their interactions with various water constituents. This study investigated the interaction of bisphenol A (BPA) with dissolved organic matter (DOM) and colloids present in surface water and secondary effluent as well as its adsorptive removal by powdered activated carbons. The solid phase micro-extraction (SPME) method followed by thermal desorption and gas chromatography-mass spectrometry (GC-MS) was utilized for determining the distribution of BPA molecules in water. The BPA removal by SPME decreased with the increased DOM content, where the formation of BPA-DOM complexes in an aqueous matrix was responsible for the reduced extraction of BPA. Colloidal particles in water samples sorbed BPA leading to the marked reduction of liquid phase BPA. BPA-DOM complexes had a negative impact on the adsorptive removal of BPA by powered activated carbons. The complex formation was characterized based on Fourier transform infrared (FTIR) and ultraviolet-visible (UV-Vis) spectroscopy, along with the calculation of molecular interactions between BPA and functional groups in DOM. It was found that the hydrogen bonding between DOM and BPA would be preferred over aromatic interactions. A pseudo-equilibrium molecular coordination model for the complexation between a BPA molecule and a hydroxyl group of the DOM was developed, which enabled estimation of the maximum sorption site and complex formation constant as well as prediction of organic complexes at various DOM levels. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. Diminished Stream Nitrate Concentrations Linked to Dissolved Organic Carbon Dynamics After Leaf Fall

    NASA Astrophysics Data System (ADS)

    Sebestyen, S. D.; Shanley, J. B.; Boyer, E. W.; Doctor, D. H.; Kendall, C.

    2004-05-01

    Thermodynamic coupling of the nitrogen and carbon cycles has broad implications for controls on catchment nutrient fluxes. In the northeast US, leaf fall occurs in early October and the availability of organic carbon increases as the leaves decompose. At the Sleepers River Research Watershed in northeastern Vermont (USA), we sampled stream chemistry from seven nested catchments to determine how stream dissolved organic carbon (DOC) and nitrate vary as a function of flow conditions, land-use, and basin size in response to leaf fall. Following leaf fall, nitrate concentration patterns were quantitatively different from other times of the year. Under baseflow conditions, stream and soil water DOC concentrations were higher than normal, whereas nitrate concentrations declined sharply at the five smallest catchments and more modestly at the two largest catchments. Under high flow conditions, flushing of nitrate was observed, as is typical for stormflow response at Sleepers River. Our field data suggest that in-stream processing of nitrate is likely thermodynamically and kinetically favorable under baseflow but not at higher flow conditions when expanding variable source areas make hydrological connections between nitrate source areas and streams. We are working to evaluate this hypothesis with isotopic and other monitoring data, and to model the coupled interactions of water, DOC, and nitrate fluxes in these nested catchments.

  2. The effects of dissolved organic matter and pH on sampling rates for polar organic chemical integrative samplers (POCIS).

    PubMed

    Li, Hongxia; Helm, Paul A; Paterson, Gordon; Metcalfe, Chris D

    2011-04-01

    The effect of solution pH and levels of dissolved organic matter (DOM) on the sampling rates for model pharmaceuticals and personal care products (PPCPs) and endocrine disrupting substance (EDS) by polar organic chemical integrative samplers (POCIS) was investigated in laboratory experiments. A commercially available POCIS configuration containing neutral Oasis HLB (hydrophilic-lipophilic balance) resin (i.e. pharmaceutical POCIS) and two POCIS configurations prepared in-house containing MAX and MCX anion and cation exchange resins, respectively were tested for uptake of 21 model PPCPs and EDS, including acidic, phenolic, basic and neutral compounds. Laboratory experiments were conducted with dechlorinated tap water over a pH range of 3, 7 and 9. The effects of DOM were studied using natural water from an oligotrophic lake in Ontario, Canada (i.e. Plastic Lake) spiked with different amounts of DOM (the concentration of dissolved organic carbon ranged from 3 to 5mgL(-1) in uptake experiments). In experiments with the commercial (HLB) POCIS, the MCX-POCIS and the MAX-POCIS, the sampling rates generally increased with pH for basic compounds and declined with pH for acidic compounds. However, the sampling rates were relatively constant across the pH range for phenols with high pKa values (i.e. bisphenol A, estrone, estradiol, triclosan) and for the neutral pharmaceutical, carbamazepine. Thus, uptake was greatest when the amount of the neutral species in solution was maximized relative to the ionized species. Although the solution pH affected the uptake of some model ionic compounds, the effect was by less than a factor of 3. There was no significant effect of DOM on sampling rates from Plastic Lake. However, uptake rates in different aqueous matrixes declined in the order of deionized water>Plastic Lake water>dechlorinated tap water, so other parameters must affect uptake into POCIS, although this influence will be minor. MAX-POCIS and MCX-POCIS showed little advantage

  3. Deepwater Horizon oil in Gulf of Mexico waters after 2 years: transformation into the dissolved organic matter pool.

    PubMed

    Bianchi, Thomas S; Osburn, Christopher; Shields, Michael R; Yvon-Lewis, Shari; Young, Jordan; Guo, Laodong; Zhou, Zhengzhen

    2014-08-19

    Recent work has shown the presence of anomalous dissolved organic matter (DOM), with high optical yields, in deep waters 15 months after the Deepwater Horizon (DWH) oil spill in the Gulf of Mexico (GOM). Here, we continue to use the fluorescence excitation-emission matrix (EEM) technique coupled with parallel factor analysis (PARAFAC) modeling, measurements of bulk organic carbon, dissolved inorganic carbon (DIC), oil indices, and other optical properties to examine the chemical evolution and transformation of oil components derived from the DWH in the water column of the GOM. Seawater samples were collected from the GOM during July 2012, 2 years after the oil spill. This study shows that, while dissolved organic carbon (DOC) values have decreased since just after the DWH spill, they remain higher at some stations than typical deep-water values for the GOM. Moreover, we continue to observe fluorescent DOM components in deep waters, similar to those of degraded oil observed in lab and field experiments, which suggest that oil-related fluorescence signatures, as part of the DOM pool, have persisted for 2 years in the deep waters. This supports the notion that some oil-derived chromophoric dissolved organic matter (CDOM) components could still be identified in deep waters after 2 years of degradation, which is further supported by the lower DIC and partial pressure of carbon dioxide (pCO2) associated with greater amounts of these oil-derived components in deep waters, assuming microbial activity on DOM in the current water masses is only the controlling factor of DIC and pCO2 concentrations.

  4. Isotopic analysis of dissolved organic carbon in produced water brines by wet chemical oxidation and cavity ring-down spectroscopy

    NASA Astrophysics Data System (ADS)

    Thomas, Randal; Conaway, Christopher; Saad, Nabil; Kharaka, Yousif

    2013-04-01

    Identification of fluid migration and escape from intentionally altered subsurface geologic systems, such as in hydraulic fracturing, enhanced oil recovery, and carbon sequestration activities, is an important issue for environmental regulators based on the traction that the "fracking" process is gathering across the United States. Given diverse injected fluid compositions and the potential for toxic or regulated compounds to be released, one of the most important steps in the process is accurately identifying evidence of injected fluid escape during and after injection processes. An important tool in identifying differences between the natural groundwater and injected fluid is the isotopic composition of dissolved constituents including inorganic components such as Sr and carbon isotopes of the dissolved organic compounds. Since biological processes in the mesothermal subsurface can rapidly alter the organic composition of a fluid, stable carbon isotopes of the dissolved organic compounds (DOC) are an effective means to identify differences in the origin of two fluids, especially when coupled with inorganic compound analyses. The burgeoning field of cavity ring-down spectroscopy (CRDS) for isotopic analysis presents an opportunity to obtain rapid, reliable and cost-effective isotopic measurements of DOC in potentially affected groundwater for the identification of leakage or the improvement of hydrogeochemical pathway models. Here we adapt the use of the novel hyphenated TOC-CRDS carbon isotope analyzer for the analysis of DOC in produced water by wet oxidation and describe the methods to evaluate performance and obtain useful information at higher salinities. Our methods are applied to a specific field example in a CO2-enhanced EOR field in Cranfield, Mississippi (USA) as a means to demonstrate the ability to distinguish natural and injected DOC using the stable isotopic composition of the dissolved organic carbon when employing the novel TOC-CRDS instrumentation

  5. Flushing of distal hillslopes as an alternative source of stream dissolved organic carbon in a headwater catchment

    Treesearch

    John P. Gannon; Scott W. Bailey; Kevin J. McGuire; James B. Shanley

    2015-01-01

    We investigated potential source areas of dissolved organic carbon (DOC) in headwater streams by examining DOC concentrations in lysimeter, shallow well, and stream water samples from a reference catchment at the Hubbard Brook Experimental Forest. These observations were then compared to high-frequency temporal variations in fluorescent dissolved organic matter (FDOM)...

  6. CARBON LOSS AND OPTICAL PROPERTY CHANGES DURING LONG-TERM PHOTOCHEMICAL AND BIOLOGICAL DEGRADATION OF ESTUARINE DISSOLVED ORGANIC MATTER

    EPA Science Inventory

    Terrestrially derived dissolved organic matter (DOM) impacts the optical properties of coastal seawater and affects carbon cycling on a global scale. We studied sequential long-term photochemical and biological degradation of estuarine dissolved organic matter from the
    Satilla...

  7. CARBON LOSS AND OPTICAL PROPERTY CHANGES DURING LONG-TERM PHOTOCHEMICAL AND BIOLOGICAL DEGRADATION OF ESTUARINE DISSOLVED ORGANIC MATTER

    EPA Science Inventory

    Terrestrially derived dissolved organic matter (DOM) impacts the optical properties of coastal seawater and affects carbon cycling on a global scale. We studied sequential long-term photochemical and biological degradation of estuarine dissolved organic matter from the
    Satilla...

  8. Effects of sulfate deposition on pore water dissolved organic carbon, nutrients, and microbial enzyme activities in a northern peatland

    Treesearch

    L.R. Seifert-Monson; B.H. Hill; R.K. Kolka; T.M. Jicha; L.L. Lehto; C.M. Elonen

    2014-01-01

    Export of dissolved organic carbon from lakes and streams has increased throughout Europe and North America over the past several decades. One possible cause is altered deposition chemistry; specifically, decreasing sulfate inputs leading to changes in ionic strength and dissolved organic carbon solubility. To further investigate the relationship between deposition...

  9. Organic amendments' dissolved organic carbon influences bioavailability of agricultural soil DOC

    NASA Astrophysics Data System (ADS)

    Straathof, Angela L.; Chincarini, Riccardo; Hoffland, Ellis; Comans, Rob N. J.

    2013-04-01

    Agricultural soils benefit from additions of organic amendments because they improve soil structure, are a source of plant nutrients, and increase concentrations of soil organic carbon (SOC). The latter fuels microbial processes important for plant growth, including nutrient mineralization and the suppression of plant diseases. However, these amendment additions range in quality and quantity of C and little is known about how their properties interact with native soil C and affect turnover. The dissolved pool of SOC (DOC) may be the most important C source for these processes as it is more biologically available and thus relatively easily turned over by the soil microbial biomass. Using a rapid-batch DOC fractionation procedure, we studied the composition of different organic amendments' DOC pools and measured how their additions change the quantity and turnover of soil DOC. Fractions isolated and quantified with this procedure include humic and fulvic acids, hydrophobic neutral and hydrophilic compounds. We hypothesized that these range from biologically recalcitrant to readily available, respectively. Amendments analysed included composts of different source materials and maturation stages collected from two different compost facilities in the Netherlands. Both total DOC concentrations and proportions of the aforementioned fractions ranged highly between composts. Composts cured for >10 days had a lower proportion of hydrophilic C compounds, suggesting that these are the most bioavailable and released as CO2 via microbial activity during maturation. To measure the effects of compost DOC on soil DOC, we extracted the former and added it to a sandy soil in an incubation experiment. The amendment increased soil total DOC, CO2 production from the soil, and the pools of humic and fulvic acids as a proportion of total DOC. Turnover of C from the incubated soil was measured by substrate-induced CO2 production (an indicator of microbial activity) from a 96-well

  10. Is the Composition of Dissolved Organic Carbon Changing in Upland Acidic Streams?

    NASA Astrophysics Data System (ADS)

    Dawson, J. J.; Soulsby, C.; Middlemas, S.; Tetzlaff, D.; Malcolm, I.

    2009-12-01

    The quantity and composition of dissolved organic carbon (DOC) exported from upland soils to surface waters is a key link in the global carbon cycle and economically important for treating potable waters. DOC ranges from simple hydrophilic molecules to larger hydrophobic (more recalcitrant) structures. The relationship between UV absorbance and DOC concentration is useful for assessing hydrophobic properties and biodegradability of DOC. Long-term variations in this relationship within the same watershed, may indicate fundamental changes in decomposition processes affecting composition of exported organic carbon. A significant change in the relationship between concomitantly determined absorbance (wavelength = 250nm) and DOC at 2 upland streams in Scotland, UK has been observed from 1986-2007. Statistical mixed-modeling approaches indicated that for a given DOC concentration, absorbance had decreased over the time period of the investigation. Of the potentially mechanistic variables tested, only annual non-marine sulphate loads were significant in explaining this change. However, additional environmental controls were potentially super-imposed on the long-term trend as intra or inter-annual variability within the UV absorbance-DOC relationship. Ultimately, this study suggests that although DOC concentrations may be increasing in these upland streams, the proportion that is hydrophobic has been decreasing. It is hypothesised that enhanced heterotrophic decomposition of organic matter and increased solubility of carbon compounds in soils where sulphate driven acidification is reduced are the dominant mechanisms behind the changing DOC composition. These trends will impact on carbon substrate dynamics, potentially increasing biodegradability of exported organic matter and affecting the fate of DOC during soil-water-atmosphere carbon cycling.

  11. Method development for measuring biodegradable dissolved organic nitrogen in treated wastewater.

    PubMed

    Khan, Eakalak; Awobamise, Mayo; Jones, Kimberly; Murthy, Sudhir

    2009-08-01

    A method for determining biodegradable dissolved organic nitrogen (BDON) in treated wastewater was developed. The method adopts the approaches used in the biochemical oxygen demand and biodegradable dissolved organic carbon tests to make it usable as a routine procedure at wastewater treatment plants (WWTPs). The development focused on various aspects of the procedure, including inoculum type and concentration, incubation period, and the need for sample filtration after incubation. The method was tested with filtered effluent samples from two nutrient removal WWTPs and standard organic nitrogen solutions. Accurate and precise BDON results were obtained with 2 mL of acclimated mixed-liquor suspended solids diluted to a concentration of 240 mg/L as an inoculum and an incubation period of 20 days. Sample filtration after incubation was not required.

  12. Coupled ocean-atmosphere loss of marine refractory dissolved organic carbon

    NASA Astrophysics Data System (ADS)

    Kieber, David J.; Keene, William C.; Frossard, Amanda A.; Long, Michael S.; Maben, John R.; Russell, Lynn M.; Kinsey, Joanna D.; Tyssebotn, Inger Marie B.; Quinn, Patricia K.; Bates, Timothy S.

    2016-03-01

    The oceans hold a massive quantity of organic carbon, nearly all of which is dissolved and more than 95% is refractory, cycling through the oceans several times before complete removal. The vast reservoir of refractory dissolved organic carbon (RDOC) is a critical component of the global carbon cycle that is relevant to our understanding of fundamental marine biogeochemical processes and the role of the oceans in climate change with respect to long-term storage and sequestration of atmospheric carbon dioxide. Here we show that RDOC includes surface-active organic matter that can be incorporated into primary marine aerosol produced by bursting bubbles at the sea surface. We propose that this process will deliver RDOC from the sea surface to the atmosphere wherein its photochemical oxidation corresponds to a potentially important and hitherto unknown removal mechanism for marine RDOC.

  13. 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.

  14. Artificial neural network modeling of dissolved oxygen in reservoir.

    PubMed

    Chen, Wei-Bo; Liu, Wen-Cheng

    2014-02-01

    The water quality of reservoirs is one of the key factors in the operation and water quality management of reservoirs. Dissolved oxygen (DO) in water column is essential for microorganisms and a significant indicator of the state of aquatic ecosystems. In this study, two artificial neural network (ANN) models including back propagation neural network (BPNN) and adaptive neural-based fuzzy inference system (ANFIS) approaches and multilinear regression (MLR) model were developed to estimate the DO concentration in the Feitsui Reservoir of northern Taiwan. The input variables of the neural network are determined as water temperature, pH, conductivity, turbidity, suspended solids, total hardness, total alkalinity, and ammonium nitrogen. The performance of the ANN models and MLR model was assessed through the mean absolute error, root mean square error, and correlation coefficient computed from the measured and model-simulated DO values. The results reveal that ANN estimation performances were superior to those of MLR. Comparing to the BPNN and ANFIS models through the performance criteria, the ANFIS model is better than the BPNN model for predicting the DO values. Study results show that the neural network particularly using ANFIS model is able to predict the DO concentrations with reasonable accuracy, suggesting that the neural network is a valuable tool for reservoir management in Taiwan.

  15. Advanced Residuals Analysis for Determining the Number of PARAFAC Components in Dissolved Organic Matter.

    PubMed

    Cuss, Chad W; Guéguen, Céline; Andersson, Per; Porcelli, Don; Maximov, Trofim; Kutscher, Liselott

    2016-02-01

    Parallel factor analysis (PARAFAC) has facilitated an explosion in research connecting the fluorescence properties of dissolved organic matter (DOM) to its functions and biogeochemical cycling in natural and engineered systems. However, the validation of robust PARAFAC models using split-half analysis requires an oft unrealistically large number (hundreds to thousands) of excitation-emission matrices (EEMs), and models with too few components may not adequately describe differences between DOM. This study used self-organizing maps (SOM) and comparing changes in residuals with the effects of adding components to estimate the number of PARAFAC components in DOM from two data sets: MS (110 EEMs from nine leaf leachates and headwaters) and LR (64 EEMs from the Lena River). Clustering by SOM demonstrated that peaks clearly persisted in model residuals after validation by split-half analysis. Plotting the changes to residuals was an effective method for visualizing the removal of fluorophore-like fluorescence caused by increasing the number of PARAFAC components. Extracting additional PARAFAC components via residuals analysis increased the proportion of correctly identified size-fractionated leaf leachates from 56.0 ± 0.8 to 75.2 ± 0.9%, and from 51.7 ± 1.4 to 92.9 ± 0.0% for whole leachates. Model overfitting was assessed by considering the correlations between components, and their distributions amongst samples. Advanced residuals analysis improved the ability of PARAFAC to resolve the variation in DOM fluorescence, and presents an enhanced validation approach for assessing the number of components that can be used to supplement the potentially misleading results of split-half analysis.

  16. Dissolved organic matter (DOM) in microalgal photobioreactors: a potential loss in solar energy conversion?

    PubMed

    Hulatt, Chris J; Thomas, David N

    2010-11-01

    Microalgae are considered to be a potential alternative to terrestrial crops for bio-energy production due to their relatively high productivity per unit area of land. In this work we examined the amount of dissolved organic matter exuded by algal cells cultured in photobioreactors, to examine whether a significant fraction of the photoassimilated biomass could potentially be lost from the harvestable biomass. We found that the mean maximum amount of dissolved organic carbon (DOC) released measured 6.4% and 17.3% of the total organic carbon in cultures of Chlorellavulgaris and Dunaliella tertiolecta, respectively. This DOM in turn supported a significant growth of bacterial biomass, representing a further loss of the algal assimilated carbon. The release of these levels of DOC indicates that a significant fraction of the photosynthetically fixed organic matter could be lost into the surrounding water, suggesting that the actual biomass yield per hectare for industrial purposes could be somewhat less than expected. A simple and inexpensive optical technique, based on chromophoric dissolved organic matter (CDOM) measurements, to monitor such losses in commercial PBRs is discussed.

  17. Seasonal and event-scale controls on dissolved organic carbon and nitrate flushing from catchments

    NASA Astrophysics Data System (ADS)

    Sebestyen, S. D.; Boyer, E. W.; Shanley, J. B.; Doctor, D. H.

    2005-05-01

    To explore terrestrial and aquatic linkages controlling nutrient dynamics in forested catchments, we collected high-frequency samples from 2002 to 2004 at the Sleepers River Research Watershed in northeastern Vermont USA. We measured DOC (dissolved organic carbon), SUVA (specific UV absorbance), nitrate, and major ion concentrations over a wide range of flow conditions. In addition, weekly samples since 1991 provide a longer term record of stream nutrient fluxes. During events, DOC concentrations increased with flow consistent with the flushing of a large reservoir of mobile organic carbon from forest soils. Higher concentrations of DOC and SUVA in the growing versus dormant season illustrated seasonal variation in sources, characteristics (i.e. reactivity), availability, and controls on the flushing response of organic matter from the landscape to streams. In contrast, stream nitrate concentrations increased with flow but only when catchments "wetted-up" after baseflow periods. Growing season stream nitrate responses were dependent on short-term antecedent moisture conditions indicating rapid depletion of the soil nitrate reservoir when source areas became hydrologically connected to streams. While the different response patterns emphasized variable source and biogeochemical controls in relation to flow patterns, coupled carbon and nitrogen biogeochemical processes were also important controls on stream nutrient fluxes. In particular, leaf fall was a critical time when reactive DOC from freshly decomposing litter fueled in-stream consumption of nitrate leading to sharp declines of stream nitrate concentrations. Our measurements highlight the importance of "hot spots" and "hot moments" of biogeochemical and hydrological processes that control stream responses. Furthermore, our work illustrates how carbon, nitrogen, and water cycles are coupled in catchments, and provides a conceptual model for future work aimed at modeling forest stream hydrochemistry at the

  18. Response Characteristics of Dissolved Organic Carbon Flushing in a Subarctic Alpine Catchment

    NASA Astrophysics Data System (ADS)

    Carey, S. K.

    2002-12-01

    Dissolved organic carbon (DOC) is an important part of ecosystem-scale carbon balances and in the transport of contaminants as it interacts with other dissolved substances including trace metals. It also can be used as a surrogate hydrological tracer in permafrost regions as near-surface waters are often DOC enriched due to the presence of thick organic soils. In a small subarctic alpine catchment within the Wolf Creek Research Basin, Yukon, Canada, DOC was studied in the summer of 2001 and spring of 2002 to determine the role frost (both permanent and seasonal), snowmelt and summer storms on DOC flushing. Peak DOC concentrations occurred during the snowmelt period, approximately one week prior to peak discharge. However, peak discharge took place several weeks after snow on south facing exposures had melted. Within the hillslopes, DOC concentrations were three to five times greater in wells underlain with permafrost compared with seasonal frost. Groundwater DOC concentrations declined during snowmelt, yet remained at levels above the streamflow. After peaking, streamflow DOC concentrations declined exponentially suggesting a simple flushing mechanism, however there did not appear to be a relation between DOC and topographic position. Following melt, permafrost underlain slopes had near-surface water tables and retained elevated levels of DOC, whereas slopes without permafrost had rapidly declining water tables at upslope locations with low DOC concentrations at all positions except near-stream riparian zones. The influence of summer rainstorms on DOC was monitored on three occasions. In each case DOC peaked on the ascending limb of the runoff hydrograph and declined exponentially on the receding limb and hysteretic behavior occurred between discharge and DOC during all events. Patterns of DOC within the hillslopes and streams suggest that runoff from permafrost-underlain slopes control DOC flushing within the stream during both snowmelt and summer periods. This

  19. Pan-arctic trends in terrestrial dissolved organic matter from optical measurements

    USGS Publications Warehouse

    Mann, Paul J.; Spencer, Robert G.M.; Hernes, Peter J.; Six, Johan; Aiken, George R.; Tank, Suzanne E.; McClelland, James W.; Butler, Kenna; Dyda, Rachael Y.; Holmes, Robert M.

    2016-01-01

    Climate change is causing extensive warming across Arctic regions resulting in permafrost degradation, alterations to regional hydrology and shifting amounts and composition of dissolved organic matter (DOM) transported by streams and rivers. Here, we characterize the DOM composition and optical properties of the six largest Arctic rivers draining into the Arctic Ocean to examine the ability of optical measurements to provide meaningful insights into terrigenous carbon export patterns and biogeochemical cycling. The chemical composition of aquatic DOM varied with season, spring months were typified by highest lignin phenol and dissolved organic carbon (DOC) concentrations with greater hydrophobic acid content, and lower proportions of hydrophilic compounds, relative to summer and winter months. Chromophoric DOM (CDOM) spectral slope (S275–295) tracked seasonal shifts in DOM composition across river basins. Fluorescence and parallel factor analysis identified seven components across the six Arctic rivers. The ratios of “terrestrial humic-like” vs. “marine humic-like” fluorescent components co-varied with lignin monomer ratios over summer and winter months, suggesting fluorescence may provide information on the age and degradation state of riverine DOM. CDOM absorbance (a350) proved a sensitive proxy for lignin phenol concentrations across all six river basins and over the hydrograph, enabling for the first time the development of a single pan-arctic relationship between a350 and terrigenous DOC (R2 = 0.93). Combining this lignin proxy with high-resolution monitoring of a350, pan-arctic estimates of annual lignin flux were calculated to range from 156 to 185 Gg, resulting in shorter and more constrained estimates of terrigenous DOM residence times in the Arctic Ocean (spanning 7 months to 2½ years). Furthermore, multiple linear regression models incorporating both absorbance and fluorescence variables proved capable of explaining much of the variability in

  20. Pan-arctic trends in terrestrial dissolved organic matter from optical measurements

    USGS Publications Warehouse

    Mann, Paul J.; Spencer, Robert G. M.; Hernes, Peter J.; Six, Johan; Aiken, George R.; Tank, Suzanne E.; McClelland, James W.; Butler, Kenna; Dyda, Rachael Y.; Holmes, Robert M.

    2016-01-01

    Climate change is causing extensive warming across Arctic regions resulting in permafrost degradation, alterations to regional hydrology and shifting amounts and composition of dissolved organic matter (DOM) transported by streams and rivers. Here, we characterize the DOM composition and optical properties of the six largest Arctic rivers draining into the Arctic Ocean to examine the ability of optical measurements to provide meaningful insights into terrigenous carbon export patterns and biogeochemical cycling. The chemical composition of aquatic DOM varied with season, spring months were typified by highest lignin phenol and dissolved organic carbon (DOC) concentrations with greater hydrophobic acid content, and lower proportions of hydrophilic compounds, relative to summer and winter months. Chromophoric DOM (CDOM) spectral slope (S275–295) tracked seasonal shifts in DOM composition across river basins. Fluorescence and parallel factor analysis identified seven components across the six Arctic rivers. The ratios of “terrestrial humic-like” vs. “marine humic-like” fluorescent components co-varied with lignin monomer ratios over summer and winter months, suggesting fluorescence may provide information on the age and degradation state of riverine DOM. CDOM absorbance (a350) proved a sensitive proxy for lignin phenol concentrations across all six river basins and over the hydrograph, enabling for the first time the development of a single pan-arctic relationship between a350 and terrigenous DOC (R2 = 0.93). Combining this lignin proxy with high-resolution monitoring of a350, pan-arctic estimates of annual lignin flux were calculated to range from 156 to 185 Gg, resulting in shorter and more constrained estimates of terrigenous DOM residence times in the Arctic Ocean (spanning 7 months to 2½ years). Furthermore, multiple linear regression