Science.gov

Sample records for allochthonous dissolved organic

  1. Fate of allochthonous dissolved organic carbon in lakes: a quantitative approach.

    PubMed

    Hanson, Paul C; Hamilton, David P; Stanley, Emily H; Preston, Nicholas; Langman, Owen C; Kara, Emily L

    2011-01-01

    Inputs of dissolved organic carbon (DOC) to lakes derived from the surrounding landscape can be stored, mineralized or passed to downstream ecosystems. The balance among these OC fates depends on a suite of physical, chemical, and biological processes within the lake, as well as the degree of recalcintrance of the allochthonous DOC load. The relative importance of these processes has not been well quantified due to the complex nature of lakes, as well as challenges in scaling DOC degradation experiments under controlled conditions to the whole lake scale. We used a coupled hydrodynamic-water quality model to simulate broad ranges in lake area and DOC, two characteristics important to processing allochthonous carbon through their influences on lake temperature, mixing depth and hydrology. We calibrated the model to four lakes from the North Temperate Lakes Long Term Ecological Research site, and simulated an additional 12 'hypothetical' lakes to fill the gradients in lake size and DOC concentration. For each lake, we tested several mineralization rates (range: 0.001 d(-1) to 0.010 d(-1)) representative of the range found in the literature. We found that mineralization rates at the ecosystem scale were roughly half the values from laboratory experiments, due to relatively cool water temperatures and other lake-specific factors that influence water temperature and hydrologic residence time. Results from simulations indicated that the fate of allochthonous DOC was controlled primarily by the mineralization rate and the hydrologic residence time. Lakes with residence times <1 year exported approximately 60% of the DOC, whereas lakes with residence times >6 years mineralized approximately 60% of the DOC. DOC fate in lakes can be determined with a few relatively easily measured factors, such as lake morphometry, residence time, and temperature, assuming we know the recalcitrance of the DOC.

  2. Understanding the Photoreactivity of Dissolved Organic Carbon in Natural Waters: The Role of the Triplet Excited-State of Allochthonous and Autochthonous DOC

    NASA Astrophysics Data System (ADS)

    Cottrell, B. A.; Timko, S. A.; Robinson, A. K.; Weiden, L. M.; Cooper, W.

    2012-12-01

    The photochemical reactivity of DOC in sunlit waters is a major factor for the in situ processing of DOC itself and trace contaminants in streams, lakes and the ocean. There is an increasing interest in the use of wetlands to mitigate contaminant removal. Laser flash photolysis is used to determine the reaction rate constants of dissolved organic carbon (DOC) with emerging contaminants in natural waters. DOC, produced by the decomposition of plant and microbial material, is one of the most complex naturally occurring mixtures. DOC plays a major role in the global carbon cycle, the sequestration and transport of trace chemicals and contaminants, and the biogeochemistry of natural waters. Hydrolysis, direct photolysis and reactions with singlet oxygen and the hydroxyl radical account for up to 25% of the photo reactivity of natural organic matter. The remaining 75% is attributed to reactions with the triplet-excited state of DOC (3DOC*). In this study, 1H NMR is used to characterize DOC from the Black River (NC), the San Joaquin Wetlands (Irvine, CA), and coastal seawater (Crystal Cove, CA). These sites encompass both allochthonous and autochthonous organic matter from catchment, wetlands, and marine waters. We then determine the reaction rate constants of known triplet state reactants and pharmaceuticals with the 3DOC* in the natural waters and with the DOC isolated by solid phase extraction. Studies of 3DOC* could provide a measure of DOC reactivity, essential in the design of constructed wetlands for contaminant removal.

  3. Temporal evolution of organic carbon concentrations in Swiss lakes: trends of allochthonous and autochthonous organic carbon.

    PubMed

    Rodríguez-Murillo, J C; Filella, M

    2015-07-01

    Evaluation of time series of organic carbon (OC) concentrations in lakes is useful for monitoring some of the effects of global change on lakes and their catchments. Isolating the evolution of autochthonous and allochthonous lake OC might be a useful way to differentiate between drivers of soil and photosynthetic OC related changes. However, there are no temporal series for autochthonous and allochthonous lake OC. In this study, a new approach has been developed to construct time series of these two categories of OC from existing dissolved organic carbon (DOC) data. First, temporal series (longer than ten years) of OC have been compiled for seven big Swiss lakes and another 27 smaller ones and evaluated by using appropriate non-parametric statistical methods. Subsequently, the new approach has been applied to construct time series of autochthonous and allochthonous lake OC in the seven big lakes. Doing this was possible because long term series of DOC concentrations at different depths are available for these lakes. Organic carbon concentrations generally increase in big lakes and decrease in smaller ones, although only in some cases are these trends statistically significant. The magnitude of the observed changes is generally small in big lakes (<1% annual change) and larger in smaller lakes. Autochthonous DOC concentrations in big lakes increase or decrease depending on the lake and the station but allochthonous DOC concentrations generally increase. This pattern is consistent with an increase in the OC input from the lakes' catchments and/or an increase in the refractoriness of the OC in question, and with a temporal evolution of autochthonous DOC depending on the degree of recovery from past eutrophication of each particular lake. In small lakes, OC dynamics are mainly driven by decreasing biological productivity, which in many, but not all cases, outweighs the probable increase of allochthonous OC.

  4. Photochemical reactivities of dissolved organic matter (DOM) in a sub-alpine lake revealed by EEM-PARAFAC: An insight into the fate of allochthonous DOM in alpine lakes affected by climate change.

    PubMed

    Du, Yingxun; Zhang, Yuanyuan; Chen, Feizhou; Chang, Yuguang; Liu, Zhengwen

    2016-10-15

    Due to climate change, tree line advance is occurring in many alpine regions. Within the next 50 to 100years, alpine lake catchments are expected to develop increased vegetation cover similar to that of sub-alpine lake catchments which currently exist below the tree line. Such changes in vegetation could trigger increased allochthonous DOM inputs to alpine lakes. To understand the fate of allochthonous DOM in alpine lakes impacted by climate change, the photochemical reactivity of DOM in sub-alpine Lake Tiancai (located 200m below the tree line) was investigated by excitation emission matrix fluorescence combined with parallel factor analysis (EEM-PARAFAC) and UV-Vis spectra analysis. With photo-exposure, a decrease in apparent DOM molecular weight was observed and 32% DOM was photomineralized to CO2. Interestingly, the aromaticity of DOM increased after photodegradation, as evidenced by increases in both the specific UV absorbance at 254nm (SUVA254) and the humification index (HIX). Five EEM-PARAFAC components were identified, including four terrestrially-derived substances (C1, C2, C3 and C4; allochthonous) and one tryptophan-like substance (C5; autochthonous). Generally, allochthonous DOM represented by C2 and C3 exhibited greater photoreactivity than autochthonous DOM represented by C5. C4 was identified as a possible photoproduct with relatively high aromaticity and photorefractive tendencies and contributed to the observed increase in SUVA254 and HIX. UV light facilitated the photodegradation of DOM and had the greatest effect on the removal of C3. This study provides information on the transformation of EEM-PARAFAC components in a sub-alpine lake, which is important in understanding the fate of increased allochthonous DOM inputs to alpine lakes impacted by climate change. PMID:27300561

  5. Photochemical reactivities of dissolved organic matter (DOM) in a sub-alpine lake revealed by EEM-PARAFAC: An insight into the fate of allochthonous DOM in alpine lakes affected by climate change.

    PubMed

    Du, Yingxun; Zhang, Yuanyuan; Chen, Feizhou; Chang, Yuguang; Liu, Zhengwen

    2016-10-15

    Due to climate change, tree line advance is occurring in many alpine regions. Within the next 50 to 100years, alpine lake catchments are expected to develop increased vegetation cover similar to that of sub-alpine lake catchments which currently exist below the tree line. Such changes in vegetation could trigger increased allochthonous DOM inputs to alpine lakes. To understand the fate of allochthonous DOM in alpine lakes impacted by climate change, the photochemical reactivity of DOM in sub-alpine Lake Tiancai (located 200m below the tree line) was investigated by excitation emission matrix fluorescence combined with parallel factor analysis (EEM-PARAFAC) and UV-Vis spectra analysis. With photo-exposure, a decrease in apparent DOM molecular weight was observed and 32% DOM was photomineralized to CO2. Interestingly, the aromaticity of DOM increased after photodegradation, as evidenced by increases in both the specific UV absorbance at 254nm (SUVA254) and the humification index (HIX). Five EEM-PARAFAC components were identified, including four terrestrially-derived substances (C1, C2, C3 and C4; allochthonous) and one tryptophan-like substance (C5; autochthonous). Generally, allochthonous DOM represented by C2 and C3 exhibited greater photoreactivity than autochthonous DOM represented by C5. C4 was identified as a possible photoproduct with relatively high aromaticity and photorefractive tendencies and contributed to the observed increase in SUVA254 and HIX. UV light facilitated the photodegradation of DOM and had the greatest effect on the removal of C3. This study provides information on the transformation of EEM-PARAFAC components in a sub-alpine lake, which is important in understanding the fate of increased allochthonous DOM inputs to alpine lakes impacted by climate change.

  6. Allochthonous Addition of Meteoritic Organics to the Lunar Regolith

    NASA Technical Reports Server (NTRS)

    Thomas-Keprta, K. L.; Clemett, S.; Ross, D. K.; Le, L.; Rahman, Z.; McKay, D. S.; Gibson, E. K.; Gonzalez, C.

    2013-01-01

    Preparation of lunar samples 74220,861 was discussed in detail in [3, 4]. Our analysis sequence was as follows: optical microscopy, UV fluorescence imaging, -Raman, FESEM-EDX imaging and mapping, FETEMEDX imaging and mapping of a Focused Ion Beam (FIB) extracted section, and NanoSIMs analysis. We observed fluffytextured C-rich regions of interest (ROI) on three different volcanic glass beads. Each ROI was several m2 in size and fluoresced when exposed to UV. Using FESEM/EDX, the largest ROI measured 36 m and was located on an edge of a plateau located on the uppermost surface of the bead. The ROI was covered on one edge by a siliceous filament emanating from the plateau surface indicating it was attached to the bead while on the Moon. EDX mapping of the ROI shows it is composed primarily of heterogeneously distributed C. Embedded with the carbonaceous phase are localized concentrations of Si, Fe, Al and Ti indicating the presence of glass and/or minerals grains. -Raman showed strong D- and G-bands and their associated second order bands; intensity and location of these bands indicates the carbonaceous matter is structurally disorganized. A TEM thin section was extracted from the surface of a glass bead using FIB microscopy. High resolution TEM imaging and selected area electron diffraction demonstrate the carbonaceous layer to be amorphous; it lacked any long or short range order characteristic of micro- or nanocrystalline graphite. Additionally TEM imaging also revealed the presence of submicron mineral grains, typically < 50 nm in size, dispersed within the carbonaceous layer. NanoSIMs data will be presented and discussed at the meeting. Given the noted similarities between the carbonaceous matter present on 74220 glass beads and meteoritic kerogen, we suggest the allochthonous addition of meteoritic organics as the most probable source for the C-rich ROIs.

  7. Mineralization of allochthonous organic carbon in lake sediments, from lake to landscape scale

    NASA Astrophysics Data System (ADS)

    Gudasz, C.; Ask, J.; Tranvik, L. J.; Karlsson, J.

    2012-04-01

    Lake sediments are well-recognized sites for the processing as well as sequestration of organic carbon. In particular boreal lake sediments have been recognized as important sites for the sequestration of organic carbon, comparable to soils or living biomass. Lakes in the boreal zone import large amounts of terrestrially derived organic carbon. Part of this organic carbon reaches the sediment surface through flocculation and sedimentation. The microbial processing of organic carbon represents one of the main factors that regulate the balance between sequestration of organic carbon and emission of green house gasses in boreal lake sediments. Recently, it has been shown a strong constrained microbial processing of allochthonous organic carbon in boreal lake sediments. However, a clear picture about the extent of the allochthonous organic carbon influence on the mineralization of sediment organic carbon in lakes and its significance at a large scale is currently lacking. We conducted a study, which explored the effect of allochthonous organic carbon on sediment organic carbon mineralization along a gradient of lakes characterized by increasing terrestrial organic carbon influence. We show a strong negative effect on sediment mineralization in lakes with increasing allochthonous organic carbon influence, which applies to a large number of lakes in the boreal zone.

  8. Allochthonous subsidies of organic matter across a lake-river-fjord landscape in the Chilean Patagonia: Implications for marine zooplankton in inner fjord areas

    NASA Astrophysics Data System (ADS)

    Vargas, Cristian A.; Martinez, Rodrigo A.; San Martin, Valeska; Aguayo, Mauricio; Silva, Nelson; Torres, Rodrigo

    2011-03-01

    Ecosystems can act as both sources and sinks of allochthonous nutrients and organic matter. In this sense, fjord ecosystems are a typical interface and buffer zone between freshwater systems, glaciated continents, and the coastal ocean. In order to evaluate the potential sources and composition of organic matter across fjord ecosystems, we characterized particulate organic matter along a lake-river-fjord corridor in the Chilean Patagonia using stable isotope (δ 13C) and lipid (fatty acid composition) biomarker analyses. Furthermore, estimates of zooplankton carbon ingestion rates and measurements of δ 13C and δ 15N in zooplankton (copepods) were used to evaluate the implications of allochthonous subsidies for copepods inhabiting inner fjord areas. Our results showed that riverine freshwater flows contributed an important amount of dissolved silicon but, scarce nitrate and phosphate to the brackish surface layer of the fjord ecosystem. Isotopic signatures of particulate organic matter from lakes and rivers were distinct from their counterparts in oceanic influenced stations. Terrestrial allochthonous sources could support around 68-86% of the particulate organic carbon in the river plume and glacier melting areas, whereas fatty acid concentrations were maximal in the surface waters of the Pascua and Baker river plumes. Estimates of carbon ingestion rates and δ 13C in copepods from the river plume areas indicated that terrestrial carbon could account for a significant percentage of the copepod body carbon (20-50%) during periods of food limitation. Particulate organic matter from the Pascua River showed a greater allochthonous contribution of terrigenous/vascular plant sources. Rivers may provide fjord ecosystems with allochthonous contributions from different sources because of the distinct vegetation coverage and land use along each river's watershed. These observations have significant implications for the management of local riverine areas in the context of

  9. Microbial primary production on an Arctic glacier is insignificant in comparison with allochthonous organic carbon input.

    PubMed

    Stibal, Marek; Tranter, Martyn; Benning, Liane G; Rehák, Josef

    2008-08-01

    Cryoconite holes are unique freshwater environments on glacier surfaces, formed when solar-heated dark debris melts down into the ice. Active photoautotrophic microorganisms are abundant within the holes and fix inorganic carbon due to the availability of liquid water and solar radiation. Cryoconite holes are potentially important sources of organic carbon to the glacial ecosystem, but the relative magnitudes of autochthonous microbial primary production and wind-borne allochthonous organic matter brought are unknown. Here, we compare an estimate of annual microbial primary production in 2006 on Werenskioldbreen, a Svalbard glacier, with the organic carbon content of cryoconite debris. There is a great disparity between annual primary production (4.3 mug C g(-1) year(-1)) and the high content of organic carbon within the debris (1.7-4.5%, equivalent to 8500-22 000 mug C g(-1) debris). Long-term accumulation of autochthonous organic matter is considered unlikely due to ablation dynamics and the surface hydrology of the glacier. Rather, it is more likely that the majority of the organic matter on Werenskioldbreen is allochthonous. Hence, although glacier surfaces can be a significant source of organic carbon for glacial environments on Svalbard, they may be reservoirs rather than oases of high productivity. PMID:18430008

  10. Dissolved trace element concentrations in the East River-Long Island Sound system: relative importance of autochthonous versus allochthonous sources.

    PubMed

    Buck, Nathaniel J; Gobler, Christopher J; Sañudo-Wilhelmy, Sergio A

    2005-05-15

    Dissolved trace metal (Ag, Cd, Cu, Fe, Ni, Pb, and Zn), inorganic nutrient (NO3, NH4, PO4, H4SiO4), and DOC concentrations were measured at 43 stations during low (July 2000) and high (April 2001) river discharge conditions in surface waters of Long Island Sound (LIS). To evaluate the impact of fluvial sources to the total metal budget of the sound, samples were collected from major tributaries discharging into LIS (Thames, Quinnipiac, Housatonic, Connecticut, and East Rivers). To compare LIS with other coastal embayments, samples were also collected from five LIS coastal embayments (Manhassett Bay, Huntington Harbor, Oyster Bay, Hempstead Harbor, and Port Jefferson Harbor), which are monitored by the U.S. National Status and Trends Program. Metal and nutrient distributions identified two biogeochemical regimes within LIS: an area of relatively high nutrient and metal concentrations in the East River/Narrows region in western LIS and an area in the eastern region of the sound that had comparatively lower concentrations. Mass balance estimates indicated that, during low flow conditions, the East River was the dominant allochthonous source of most trace metals (Ag, Cd, Cu, Ni, Zn) and inorganic nutrients (NO3 and PO4); during high flow conditions, the most influential source of these constituents was the Connecticut River. Mass balance estimates also evidenced a large autochthonous source of Cu, Ni, and Zn, as their spatial distributions displayed elevated concentrations away from point sources such as the East River. Principal component analysis suggested that metal and nutrient distributions in the LIS system were influenced by different seasonal processes: remobilization from contaminated sediments, anthropogenic inputs from sewage discharges and phytoplankton scavenging during the spring freshet, and benthic remobilization during summer conditions.

  11. 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

  12. 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.

  13. 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.

  14. Dissolved organic matter processing within the Atchafalaya basin: from river to backwater swamps

    NASA Astrophysics Data System (ADS)

    Jones, C. N.; Edwards, B.; Keim, R.; Scott, D.

    2013-12-01

    Hydrologic complexity in large floodplains makes examining the fate of nutrients and carbon challenging. We used a combination of stable isotopes (δ18O-H2O, δD-H2O, δ13C-DOC, and δ13C-DIC) and carbon characterization (PARAFAC modeling, SUVA, flurescence index) to identify the fate of both allochthonous (externally produced) and autochthonous (internally produced) dissolved organic matter (DOM) in the Atchafalaya swamp. Three separate synoptic sampling campaigns were completed across an annual flood pulse (rising limb, peak, and falling limb), in which the stable isotopic content of water was used to quantify the gradient of hydrologic connectivity from river to backwater swamp. The carbon characterization and isotopic content provided insight into sources and processing of DOM along that gradient. Results reveal autochthonous and allochthonous carbon signatures across the gradient from backwater swamp to river water during the rising limb. However, as sites become hydrologically connected during the peak, DOM was dominated by allochthonous sources. Following the flood pulse, we expect to once again see stratification across the sites altering the DOM sources, composition, and bioavailability.

  15. 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.

  16. [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.

  17. High mobilization of arsenic, metals and rare earth elements in seepage waters driven by respiration of old allochthonous organic carbon.

    PubMed

    Weiske, Arndt; Schaller, Jörg; Hegewald, Tilo; Machill, Susanne; Werner, Ingo; Dudel, E Gert

    2013-12-01

    Metal and metalloid mobilization processes within seepage water are of major concern in a range of water reservoir systems. The mobilization process of arsenic and heavy metals within a dam and sediments of a drinking water reservoir was investigated. Principle component analysis (PCA) on time series data of seepage water showed a clear positive correlation of arsenic with iron and DOC (dissolved organic carbon), and a negative correlation with nitrate due to respiratory processes. A relationship of reductive metal and metalloid mobilization with respiration of old carbon was shown. The system is influenced by sediment layers as well as a recent DOC input from degraded ombrotrophic peatbogs in the catchment area. The isotopic composition ((12)C, (13)C and (14)C) of DOC is altered along the path from basin to seepage water, but no significant changes in structural parameters (LC-OCD-OND, FT-IR) could be seen. DIC (dissolved inorganic carbon) in seepage water partly originates from respiratory processes, and a higher relationship of it with sediment carbon than with the DOC inventory of infiltrating water was found. This study revealed the interaction of respiratory processes with metal and metalloid mobilization in sediment water flows. In contrast to the presumption that emerging DOC via respiratory processes mainly controls arsenic and metal mobilization it could be shown that the presence of aged carbon compounds is essential. The findings emphasize the importance of aged organic carbon for DOC, DIC, arsenic and metal turnover.

  18. Phytoplankton variation and its relation to nutrients and allochthonous organic matter in a coastal lagoon on the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Aké-Castillo, José A.; Vázquez, Gabriela

    2008-07-01

    In tropical and subtropical zones, coastal lagoons are surrounded by mangrove communities which are a source of high quantity organic matter that enters the aquatic system through litter fall. This organic matter decomposes, becoming a source of nutrients and other substances such as tannins, fulvic acids and humic acids that may affect the composition and productivity of phytoplankton communities. Sontecomapan is a coastal lagoon located in the southern Gulf of Mexico, which receives abundant litter fall from mangrove. To study the phytoplankton composition and its variation in this lagoon from October 2002 to October 2003, we evaluated the concentrations of dissolved folin phenol active substances (FPAS) as a measure of plant organic matter, salinity, temperature, pH, O 2, N-NH 4+, N-NO 3-, P-PO 43-, Si-SiO 2, and phytoplanktonic cell density in different mangrove influence zones including the three main rivers that feed the lagoon. Nutrients concentrations depended on freshwater from rivers, however these varied seasonally. Concentrations of P-PO 43-, N-NH 4+ and FPAS were the highest in the dry season, when maximum mangrove litter fall is reported. Variation of these nutrients seemed to depend on the internal biogeochemical processes of the lagoon. Blooms of diatoms ( Skeletonema spp., Cyclotella spp. and Chaetoceros holsaticus) and dinoflagellates ( Peridinium aff. quinquecorne, Prorocentrum cordatum) occurred seasonally and in the different mangrove influence zones. The high cell densities in these zones and the occurrence of certain species and its ordination along gradient of FPAS in a canonical correspondence analysis, suggest that plant organic matter (i.e. mangrove influence) may contribute to phytoplankton dynamics in Sontecomapan lagoon.

  19. Chemical and optical changes in freshwater dissolved organic matter exposed to solar radiation

    USGS Publications Warehouse

    Osburn, C.L.; Morris, D.P.; Thorn, K.A.; Moeller, R.E.

    2001-01-01

    We studied the chemical and optical changes in the dissolved organic matter (DOM) from two freshwater lakes and a Sphagnum bog after exposure to solar radiation. Stable carbon isotopes and solid-state 13C-NMR spectra of DOM were used together with optical and chemical data to interpret results from experimental exposures of DOM to sunlight and from seasonal observations of two lakes in northeastern Pennsylvania. Solar photochemical oxidation of humic-rich bog DOM to smaller LMW compounds and to DIC was inferred from losses of UV absorbance, optical indices of molecular weight and changes in DOM chemistry. Experimentally, we observed a 1.2??? enrichment in ??13C and a 47% loss in aromatic C functionality in bog DOM samples exposed to solar UVR. Similar results were observed in the surface waters of both lakes. In late summer hypolimnetic water in humic Lake Lacawac, we observed 3 to 4.5??? enrichments in ??13C and a 30% increase in aromatic C relative to early spring values during spring mixing. These changes coincided with increases in molecular weight and UV absorbance. Anaerobic conditions of the hypolimnion in Lake Lacawac suggest that microbial metabolism may be turning over allochthonous C introduced during spring mixing, as well as autochthonous C. This metabolic activity produces HMW DOM during the summer, which is photochemically labile and isotopically distinct from allochthonous DOM or autochthonous DOM. These results suggest both photooxidation of allochthonous DOM in the epilimnion and autotrophic production of DOM by bacteria in the hypolimnion cause seasonal trends in the UV absorbance of lakes.

  20. Whole watershed spectrometric and fluorometric characterization of dissolved organic matter in two large rivers in Canada with differing impact

    NASA Astrophysics Data System (ADS)

    Hutchins, R.; Schiff, S.; Elgood, R.

    2009-05-01

    Dissolved Organic Matter (DOM) is one of the largest active organic carbon pools on Earth. In aquatic systems, DOM can be derived from a terrestrial source (allochthonous) or within the aquatic system (autochthonous). These two types of DOM differ in UV absorbance and fluorescence. These methods are useful in differentiating the source and quality of DOM. Allochthonous DOM contains more humic and fulvic acids with higher absorbance at 254nm (SUVA) than autochthonous DOM. Using 3D fluorescence, the fluorescence index (FI) is higher for autochthonous than allochthonous DOM. These sources of DOM have implications on the availability to heterotrophic microorganisms, the depth of the photic zone for photosynthesis, the attenuation of damaging ultraviolet radiation, and the mobility of harmful contaminants. We investigated the changes in DOM at the watershed scale. The Grand River watershed has an area of 6800 km2 and stretches 300km through southern Ontario, Canada, flowing into Lake Erie. The primary land use in the basin is agriculture and the population is about 900,000 mostly in urban centres along the river. The largest cities Kitchener, Waterloo, and Cambridge are located in the middle of the watershed. The Burnt River in the Muskokas serves as a less impacted comparison. Changes in the spectrometric and fluorometric properties DOM along the length of the Grand River show the influence of seasons and land use, particularly agricultural and urban. The more impacted Grand River shows a generally more autochthonous signature than the less impacted Burnt River.

  1. Functional variability of dissolved organic matter from the surface water of a productive lake.

    PubMed

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

    2008-01-01

    Functional variability of dissolved organic matter (DOM) from the surface water of Esthwaite Water (N. England) was investigated using a series of 12 standardised assays, which provide quantitative information on light absorption, fluorescence, photochemical fading, pH buffering, copper binding, benzo(a)pyrene binding, hydrophilicity, and adsorption to alumina. Ten lakewater samples were collected at different times of year during 2003-2005, and DOM concentrates obtained by low-temperature rotary evaporation. Suwannee River Fulvic Acid was used as a quality control standard. For nine of the assays, variability among DOM samples was significantly (p<0.01) greater than could be explained by analytical error. Seasonal trends observed for six of the assays could be explained by a simple mixing model in which the two end-members were DOM from the catchment (allochthonous) and DOM produced within the lake (autochthonous). The fraction of autochthonous DOM predicted by the model is significantly correlated (p<0.01) with chlorophyll concentration, consistent with production from phytoplankton. Autochthonous DOM is less light-absorbing, less fluorescent, more hydrophilic, and possesses fewer proton-dissociating groups, than allochthonous material. PMID:17675206

  2. Effects of pH on Dissolved Organic Matter From Freshwater Algal Species

    NASA Astrophysics Data System (ADS)

    Kehret, Y.; Gueguen, C.

    2009-05-01

    Dissolved organic matter (DOM) is ubiquitous in all natural waters. The nature and composition of aquatic DOM depends on its origin (autochthonous vs. allochthonous) and the physical chemical conditions (pH) of the system. It is clear that autochthonous DOM of algal origin is an important contributor to the DOM pool in most aquatic systems. Little is known on its nature and composition. In this study, algal monocultures of S. acutus and F. crotonensis were grown at two different pHs (pH 7 and 5). The production of exudates was monitored over time and characterized by dissolved organic carbon content, absorbance and synchronous fluorescence. Results indicate a significant difference in the concentration of dissolved organic carbon (DOC) formed per species. The ratio of DOC to chlorophyll a is ten times greater in S. acutus than F. crotonensis. In terms of composition, the production of humic-like compounds varies between species with F. crotonensis producing up to four fold more at natural pH. At lower pH, the production of algal DOM is less but there were more proteins and humic materials generated by both species under decreasing pH, with a significant increase in the S. acutus species. Therefore, the concentration and composition of DOM depends not only on algal species but also on the physical chemical condition (pH level) indicating that water acidification would have a major impact on DOM composition.

  3. Temporal evolution of hyporheic dissolved organic carbon

    NASA Astrophysics Data System (ADS)

    Gabrielsen, P. J.

    2010-12-01

    Dissolved organic carbon (DOC) is a complex suite of organic compounds present in natural ecosystems, and is particularly studied in river systems. The hyporheic zone (HZ), a region of surface water-shallow groundwater exchange, has been identified as a hotspot of DOC processing and is generally regarded as a net sink of organic matter. More recent studies into riverine DOC have shifted to examining DOC quality rather than bulk quantity. DOC quality variability has been linked to hydrologic and climatic variability, both focuses of current climate change research. This presentation examines the effect of organic and inorganic HZ DOC processes, i.e. microbial uptake and sorption, respectively, on DOC quality as measured through molecular weight distributions (MWDs). Sediment and water samples from East Fork Jemez River in northern New Mexico are used to experimentally simulate DOC processes and observe the subsequent effect on MWD evolution. Parallel factor analysis (PARAFAC) of excitation-emission matrices (EEMs) is also used to examine fluorescent properties throughout DOC process experimentation, providing a second characterizing metric. Results from this study will be applied to a field sampling campaign in the summer of 2011 along the East Fork Jemez River to study temporal and spatial variability in organic and inorganic DOC processes.

  4. 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

  5. Climate-driven terrestrial inputs in ultraoligotrophic mountain streams of Andean Patagonia revealed through chromophoric and fluorescent dissolved organic matter.

    PubMed

    Garcia, Roberto D; Reissig, Mariana; Queimaliños, Claudia P; Garcia, Patricia E; Dieguez, Maria C

    2015-07-15

    Fluvial networks transport a substantial fraction of the terrestrial production, contributing to the global carbon cycle and being shaped by hydrologic, natural and anthropogenic factors. In this investigation, four Andean Patagonian oligotrophic streams connecting a forested catchment (~125km(2)) and draining to a double-basin large and deep lake (Lake Moreno complex, Northwestern Patagonia), were surveyed to analyze the dynamics of the allochthonous subsidy. The results of a 30month survey showed that the catchment supplies nutrients and dissolved organic matter (DOM) to the streams. The eruption of the Puyehue-Cordón Caulle at the beginning of the study overlapped with seasonal precipitation events. The largest terrestrial input was timed with precipitation which increased particulate materials, nutrients and DOM through enhanced runoff. Baseline suspended solids and nutrients were very low in all the streams (suspended solids: ~1mg/L; total nitrogen: ~0.02mg/L; total phosphorus: ~5μg/L), increasing several fold with runoff. Baseline dissolved organic carbon concentrations (DOC) ranged between 0.15 and 1mg/L peaking up to three-fold. Chromophoric and fluorescent analyses characterized the DOM as of large molecular weight and high aromaticity. Parallel factor modeling (PARAFAC) of DOM fluorescence matrices revealed three components of terrestrial origin, with certain degree of microbial processing: C1 and C2 (terrestrial humic-like compounds) and C3 (protein-like and pigment derived compounds). Seasonal changes in MOD quality represent different breakdown stages of the allochthonous DOM. Our survey allowed us to record and discuss the effects of the Puyehue-Cordón Caulle eruption, showing that due to the high slopes, high current and discharge of the streams the volcanic material was rapidly exported to the Moreno Lake complex. Overall, this survey underscores the magnitude and timing of the allochthonous input revealing the terrestrial subsidy to food webs in

  6. Atmospheric fluxes of organic matter to the Mediterranean Sea: contribution to the elemental C: N: P ratios of surface dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Djaoudi, Kahina; Barani, Aude; Hélias-Nunige, Sandra; Van Wambeke, France; Pulido-Villena, Elvira

    2016-04-01

    It has become increasingly apparent that atmospheric transport plays an important role in the supply of macro- and micro-nutrients to the surface ocean. This atmospheric input is especially important in oligotrophic regions where the vertical supply from the subsurface is low particularly during the stratification period. Compared to its inorganic counterpart, the organic fraction of atmospheric deposition and its impact on surface ocean biogeochemistry has been poorly explored. In the ocean, carbon export to depth (and therefore, its long term storage with presumed consequences on climate) occurs both through particle sedimentation and through the transfer of dissolved organic matter (DOM) via diffusion or convection. DOM export from the surface ocean represents up to 50% of total organic carbon flux to the deep ocean in oligotrophic regions such as the Mediterranean Sea. The efficiency of this C export pathway depends, among others, on the elemental C: N: P ratios of surface DOM which might be affected by the relative contribution of microbial processes and allochthonous sources. This work reports a one-year time-series (April 2015-April 2016) of simultaneous measurements of (1) total (dry + wet) atmospheric fluxes of organic carbon, organic nitrogen, and organic phosphorus and (2) concentration of dissolved organic carbon, dissolved organic nitrogen, and dissolved organic phosphate at the surface layer (0-200 m) in the NW Mediterranean Sea. Atmospheric and oceanic surveys were conducted at the Frioul and ANTARES sites, respectively, operated by the long-term observation network MOOSE (Mediterranean Oceanic Observation System for the Environment).

  7. Transient Dissolved Organic Carbon Through Soils

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    Dissolved organic carbon (DOC) is an important constituent of soil solution that plays a role in many chemical and biological processes in soils; it is also an important energy source for bacteria in the soil ecosystem. Hydrology has a significant control on the transport and fate of dissolved organic carbon in the soil but mechanisms that affect said transport are not well understood. In particular, dynamic information on DOC transport through forest soils on short time scales (one or two precipitation event) is lacking at present. DOC is a very complex mix of organic compounds. A key to quantifying DOC dynamics is to establish useful approximations for behavior of this complex mixture. Biodegradable dissolved organic carbon (BDOC) is an important part of DOC. It is reported that between 12 and 44% of DOC released from the forest floor can be decomposed in solutions by indigenous microbes. In our study, we considered how DOC, BDOC, and flow interact in soil columns. In-situ soil cores with two different lengths were installed under a mixed deciduous canopy. The effects of artificial rain on DOC and BDOC transport were examined by dripping nano pure water amended with bromide on the top of soil cores and sampling the water collected at the bottom of the cores for DOC and BDOC. We used plug-flow biofilm reactors to measure the BDOC concentration. It is likely that reduced rates of decomposition in dry soils will cause microbial products of DOC to accumulate; hence DOC concentration should be high at the first flush of rain and decline as the event proceeds. The experimental results show the expected pattern, that is, the first samples we collected always had the highest DOC and BDOC concentrations. The concentrations tend to decline through the simulated precipitation event. Application of a second “storm” forty minutes after the cessation of the first application of water resulted in effluent DOC concentration increasing a small amount initially and then

  8. 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

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  11. Sources of dissolved and particulate organic material in Loch Vale Watershed, Rocky Mountain National Park, Colorado, USA

    USGS Publications Warehouse

    Baron, J.; McKnight, D.; Denning, A.S.

    1991-01-01

    The sources of both dissolved organic carbon (DOC) and particulate organic carbon (POC) to an alpine (Sky Pond) and a subalpine lake (The Loch) in Rocky Mountain National Park were explored for four years. The importance of both autochthonous and allochthonous sources of organic matter differ, not only between alpine and subalpine locations, but also seasonally. Overall, autochthonous sources dominate the organic carbon of the alpine lake, while allochthonous sources are a more significant source of organic carbon to the subalpine lake. In the alpine lake, Sky Pond, POC makes up greater than one third of the total organic matter content of the water column, and is related to phytoplankton abundance. Dissolved organic carbon is a product of within-lake activity in Sky Pond except during spring snowmelt and early summer (May-July), when stable carbon isotope ratios suggest a terrestrial source. In the subalpine lake, The Loch, DOC is a much more important constituent of water column organic material than POC, comprising greater than 90% of the spring snowmelt organic matter, and greater than 75% of the organic matter over the rest of the year. Stable carbon isotope ratios and a very strong relation of DOC with soluble Al(tot) indicate DOC concentrations are almost entirely related to flushing of soil water from the surrounding watershed during spring snowmelt. Stable carbon isotope ratios indicate that, for both lakes, phytoplankton is an important source of DOC in the winter, while terrestrial material of plant or microbial origin contributes DOC during snowmelt and summer. ?? 1991 Kluwer Academic Publishers.

  12. Spectrophotometric discrimination of river dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Baker, Andy

    2002-11-01

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

  13. Carbon dynamics and their link to dissolved organic matter quality across contrasting stream ecosystems.

    PubMed

    Bodmer, Pascal; Heinz, Marlen; Pusch, Martin; Singer, Gabriel; Premke, Katrin

    2016-05-15

    Streams represent active components of the carbon cycle as emitters of carbon dioxide (CO2) and methane to the atmosphere at a global scale. However, the mechanisms and governing factors of these emissions are still largely unknown, especially concerning the effect of land use. We compared dissolved and gaseous carbon dynamics in streams bordered by contrasting types of land use, specifically agriculture and forest. Carbon dioxide and methane partial pressures (pCO2 and pCH4, respectively) in the water body and carbon emissions via both gases were studied for 24h during four field expeditions. pCH4 did not differ between the two system types. pCO2 was constantly oversaturated in all streams and significantly higher in agricultural streams (annual mean 4282 ppm) compared to forest streams (annual mean 2189 ppm) during all seasons. However, emissions of CO2 were not significantly different between the stream types due to significantly higher gas transfer velocity in forest compared to agricultural streams. pCO2 was significantly positively correlated to the concentrations of dissolved organic carbon, dissolved nitrogen and soluble reactive phosphorus in the water. Furthermore, pCO2 was correlated to optical parameters of dissolved organic matter (DOM) quality, e.g., it increased with indicators of molecular size and an allochthonous fluorescent component identified by Parallel Factor Analysis (PARAFAC). This study demonstrates that different forms of land use may trigger a cascade of effects on the carbon production and emission of streams linked to changes in DOM quality. PMID:26938320

  14. 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.

  15. Enhanced bacterial decomposition with increasing addition of autochthonous to allochthonous carbon without any effect on bacterial community composition

    NASA Astrophysics Data System (ADS)

    Attermeyer, K.; Hornick, T.; Kayler, Z. E.; Bahr, A.; Zwirnmann, E.; Grossart, H.-P.; Premke, K.

    2014-03-01

    Dissolved organic carbon (DOC) concentrations - mainly of terrestrial origin - are increasing worldwide in inland waters. Heterotrophic bacteria are the main consumers of DOC and thus determine DOC temporal dynamics and availability for higher trophic levels. Our aim was to study bacterial carbon (C) turnover with respect to DOC quantity and chemical quality using both allochthonous and autochthonous DOC sources. We incubated a natural bacterial community with allochthonous C (13C-labeled beech leachate) and increased concentrations and pulses (intermittent occurrence of organic matter input) of autochthonous C (phytoplankton lysate). We then determined bacterial C consumption, activities, and community composition together with the C flow through bacteria using stable C isotopes. The chemical analysis of single sources revealed differences in aromaticity and low- and high-molecular-weight substance fractions (LMWS and HMWS, respectively) between allochthonous and autochthonous C sources. Both DOC sources (allochthonous and autochthonous DOC) were metabolized at a high bacterial growth efficiency (BGE) around 50%. In treatments with mixed sources, rising concentrations of added autochthonous DOC resulted in a further, significant increase in bacterial DOC consumption of up to 68% when nutrients were not limiting. This rise was accompanied by a decrease in the humic substance (HS) fraction and an increase in bacterial biomass. Changes in DOC concentration and consumption in mixed treatments did not affect bacterial community composition (BCC), but BCC differed in single vs. mixed incubations. Our study highlights that DOC quantity affects bacterial C consumption but not BCC in nutrient-rich aquatic systems. BCC shifted when a mixture of allochthonous and autochthonous C was provided simultaneously to the bacterial community. Our results indicate that chemical quality rather than source of DOC per se (allochthonous vs. autochthonous) determines bacterial DOC turnover.

  16. Dissolved organic matter and lake metabolism. Technical progress report, 1 July 1979-30 June 1980

    SciTech Connect

    Wetzel, R.G.

    1980-01-01

    Progress in research to evaluate the impact of utilization of fossil fuels on surface water is reported. Analyses of regulatory mechanisms of growth and rates of carbon cycling center on evaluation of quantitative control interactions among the microflora of the pelagial zones of several lakes of progressively greater eutrophy, littoral photosynthetic producer-decomposer complex, and allochthonous inorganic-organic influxes and their biotic processing. The underlying thesis is that quantification of the dynamic carbon fluxes among these components and their rate control mechanisms by physical and chemical factors are fundamental to elucidation of the rate functions of lake eutrophication. A major portion of the research has been directed towards the fate and nutrient mechanisms regulating qualitative and quantitative utilization and losses of organic carbon synthesized within lakes and their drainage basins. It has become increasingly apparent that the wetland and littoral flora, and attendant epiphytic and benthic microflora, have major regulatory controls on biogeochemical cycling of whole lake systems. A major effort on factors regulating the metabolism of littoral macrophytes and attached algae has been coupled to integrated studies on their decomposition and the fate of detrital dissolved and particulate organic matter. These organic products are being coupled to influences on enzymatic activity and inorganic nutrient cycling.

  17. Dissolved Fe(II) in a river-estuary system rich in dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Hopwood, Mark J.; Statham, Peter J.; Milani, Ambra

    2014-12-01

    Reduced iron, Fe(II), accounts for a significant fraction of dissolved Fe across many natural surface waters despite its rapid oxidation under oxic conditions. Here we investigate the temporal and spatial variation in dissolved Fe redox state in a high dissolved organic matter (DOM) estuarine system, the River Beaulieu. We couple manual sample collection with the deployment of an autonomous in situ analyser, designed to simultaneously measure dissolved Fe(II) and total dissolved Fe, in order to investigate processes operating on the diurnal timescale and to evaluate the performance of the analyser in a high DOM environment. Concentrations of dissolved Fe available to the ligand ferrozine are elevated throughout the estuary (up to 21 μM in freshwater) and notably higher than those previously reported likely due to seasonal variation. Fe(II) is observed to account for a large, varying fraction of the dissolved Fe available to ferrozine (25.5 ± 12.5%) and this fraction decreases with increasing salinity. We demonstrate that the very high DOM concentration in this environment and association of this DOM with dissolved Fe, prevents the accurate measurement of dissolved Fe concentrations in situ using a sensor reliant on rapid competitive ligand exchange.

  18. Habitat management affects soil chemistry and allochthonous organic inputs mediating microbial structure and exo-enzyme activity in Wadden Sea salt-marsh soils

    NASA Astrophysics Data System (ADS)

    Mueller, Peter; Granse, Dirk; Thi Do, Hai; Weingartner, Magdalena; Nolte, Stefanie; Hoth, Stefan; Jensen, Kai

    2016-04-01

    The Wadden Sea (WS) region is Europe's largest wetland and home to approximately 20% of its salt marsh area. Mainland salt marshes of the WS are anthropogenically influenced systems and have traditionally been used for livestock grazing in wide parts. After foundation of WS National Parks in the late 1980s and early 1990s, artificial drainage has been abandoned; however, livestock grazing is still common in many areas of the National Parks and is under ongoing discussion as a habitat-management practice. While studies so far focused on effects of livestock grazing on biodiversity, little is known about how biogeochemical processes, element cycling, and particularly carbon sequestration are affected. Here, we present data from a recent field study focusing on grazing effects on soil properties, microbial exo-enzyme activity, microbial abundance and structure. Exo-enzyme activity was studied conducting digestive enzyme assays for various enzymes involved in C- and N cycling. Microbial abundance and structure was assessed measuring specific gene abundance of fungi and bacteria using quantitative PCR. Soil compaction induced by grazing led to higher bulk density and decreases in soil redox (∆ >100 mV). Soil pH was significantly lower in grazed parts. Further, the proportion of allochthonous organic matter (marine input) was significantly smaller in grazed vs. ungrazed sites, likely caused by a higher sediment trapping capacity of the taller vegetation in the ungrazed sites. Grazing induced changes in bulk density, pH and redox resulted in reduced activity of enzymes involved in microbial C acquisition; however, there was no grazing effect on enzymes involved in N acquisition. While changes in pH, bulk density or redox did not affect microbial abundance and structure, the relative amount of marine organic matter significantly reduced the relative abundance of fungi (F:B ratio). We conclude that livestock grazing directly affects microbial exo-enzyme activity, thus

  19. Method of dissolving organic filter cake

    SciTech Connect

    Hollenbeck, K.H.; Norman, L.R.

    1989-03-07

    A method of dissolving a polysaccharide-containing filter cake present in a subterranean formation is described, comprising: injecting an effective amount of a treatment fluid comprising a water soluble source of fluoride ions present in an amount sufficient to provide a molar concentration of from about 0.01 to about 0.5 and a source of hydrogen ions present in an amount sufficient to produce a pH in the treatment fluid in the range of from about 2 to about 4 into a subterranean formation wherein a filter cake is present; and maintaining the treatment fluid within the subterranean formation and in contact with the filter cake for a sufficient time to dissolve at least a portion of the filter cake.

  20. Seasonal Changes in Arctic Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  1. Dissolved Organic Matter in the Hudson River Plume

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

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

  2. 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.

  3. Chromophoric Dissolved Organic Matter across a Marine Distributed Biological Observatory in the Pacific Arctic Region

    NASA Astrophysics Data System (ADS)

    Berman, S. L.; Frey, K. E.; Shake, K. L.; Cooper, L. W.; Grebmeier, J. M.

    2014-12-01

    Dissolved organic matter (DOM) plays an important role in marine ecosystems as both a carbon source for the microbial food web (and thus a source of CO2 to the atmosphere) and as a light inhibitor in marine environments. The presence of chromophoric dissolved organic matter (CDOM; the optically active portion of total DOM) can have significant controlling effects on transmittance of sunlight through the water column and therefore on primary production as well as the heat balance of the upper ocean. However, CDOM is also susceptible to photochemical degradation, which decreases the flux of solar radiation that is absorbed. Knowledge of the current spatial and temporal distribution of CDOM in marine environments is thus critical for understanding how ongoing and future changes in climate may impact these biological, biogeochemical, and physical processes. We describe the quantity and quality of CDOM along five key productive transects across a developing Distributed Biological Observatory (DBO) in the Pacific Arctic region. The samples were collected onboard the CCGS Sir Wilfred Laurier in July 2013 and 2014. Monitoring of the variability of CDOM along transects of high productivity can provide important insights into biological and biogeochemical cycling across the region. Our analyses include overall concentrations of CDOM, as well as proxy information such as molecular weight, lability, and source (i.e., autochthonous vs. allochthonous) of organic matter. We utilize these field observations to compare with satellite-derived CDOM concentrations determined from the Aqua MODIS satellite platform, which ultimately provides a spatially and temporally continuous synoptic view of CDOM concentrations throughout the region. Examining the current relationships among CDOM, sea ice variability, biological productivity, and biogeochemical cycling in the Pacific Arctic region will likely provide key insights for how ecosystems throughout the region will respond in future

  4. Dissolved organic carbon in the deep Southern Ocean: Local versus distant controls

    NASA Astrophysics Data System (ADS)

    Bercovici, Sarah K.; Hansell, Dennis A.

    2016-02-01

    The global ocean contains a massive reservoir (662 ± 32 Pg C) of dissolved organic carbon (DOC), and its dynamics, particularly in the deepest zones, are only slowly being understood. DOC in the deep ocean is ubiquitously low in concentration (~35 to 48 µmol kg-1) and aged (4000 to 6000 years), persisting for multiple meridional overturning circulations. Deep waters relatively enriched in DOC form in the North Atlantic, migrate to the Southern Ocean to mix with waters from Antarctic shelves and the deep Pacific and Indian Oceans, in turn forming the voluminous waters of the Circumpolar Deep Water. Here we seek evidence for local (autochthonous) versus distant (allochthonous) processes in determining the distribution of DOC in the deep Southern Ocean. Prior analyses on DOC in the deep Southern Ocean have conflicted, describing both conservative and nonconservative traits: the deep DOC field has been reported as uniform in distribution, yet local inputs have been suggested as quantitatively important. We use multiple approaches (multiple linear regression, mass transport, and mass balance calculations) with data from Climate Variability and Predictability Repeat Hydrography sections to evaluate the system. We find that DOC concentrations in the deep Southern Ocean largely reflect the conservative mixing of the several deep waters entering the system from the north. Mass balance suggests that the relatively depleted DOC radiocarbon content in the deep Southern Ocean is a conserved property as well. These analyses advance our understanding of the controls on the DOC reservoir of the Southern Ocean.

  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. 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...

  7. Bacterial growth efficiency in a tropical estuary: seasonal variability subsidized by allochthonous carbon.

    PubMed

    Pradeep Ram, A S; Nair, Shanta; Chandramohan, D

    2007-05-01

    Bacterial growth efficiency (BGE) is a key factor in understanding bacterial influence on carbon flow in aquatic ecosystems. We report intra-annual variability in BGE, and bacteria-mediated carbon flow in the tropical Mandovi and Zuari estuaries (southwest India) and the adjoining coastal waters (Arabian Sea). BGE ranged from 3% to 61% and showed clear temporal variability with significantly (ANOVA, p < 0.01) higher values in the estuaries (mean, 28 +/- 14%) than coastal waters (mean, 12 +/- 6%). The greater variability of BGE in the estuaries than coastal waters suggest some systematic response to nutrient composition and the variability of dissolved organic matter pools, as BGE was governed by bacterial secondary production (BP). Monsoonal rains and its accompanied changes brought significant variability in BGE and bacterial productivity/primary productivity (BP/PP) ratio when compared to nonmonsoon seasons in the estuaries and coastal waters. High BP/PP ratio (>1) together with high carbon flux through bacteria (>100% of primary productivity) in the estuarine and coastal waters suggests that bacterioplankton consumed dissolved organic carbon in excess of the amount produced in situ by phytoplankton of this region, which led to the mismatch between primary production of carbon and amount of carbon consumed by bacteria. Despite the two systems being subsidized by allochthonous inputs, the low BGE in the coastal waters may be attributable to the nature and time interval in the supply of allochthonous carbon. PMID:17356948

  8. 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.

  9. 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...

  10. Unimodal response of fish yield to dissolved organic carbon.

    PubMed

    Finstad, Anders G; Helland, Ingeborg P; Ugedal, Ola; Hesthagen, Trygve; Hessen, Dag O

    2014-01-01

    Here, we demonstrate a contrasting effect of terrestrial coloured dissolved organic material on the secondary production of boreal nutrient poor lakes. Using fish yield from standardised brown trout gill-net catches as a proxy, we show a unimodal response of lake secondary productivity to dissolved organic carbon (DOC). This suggests a trade-off between positive and negative effects, where the initial increase may hinge upon several factors such as energy subsidising, screening of UV-radiation or P and N load being associated with organic carbon. The subsequent decline in production with further increase in DOC is likely associated with light limitations of primary production. We also show that shallow lakes switch from positive to negative effects at higher carbon loads than deeper lakes. These results underpin the major role of organic carbon for structuring productivity of boreal lake ecosystems. PMID:24165396

  11. Seasonal Variation in Dissolved Organic Matter Composition and Photoreactivity within a Small Sub-arctic Stream.

    NASA Astrophysics Data System (ADS)

    Guerard, J.; Osborne, R.

    2015-12-01

    Dissolved organic matter (DOM) is a complex heterogeneous mixture, ubiquitous to all natural surface waters, uniquely composed of source inputs specific to spatial, temporal, and ecological circumstances. In arctic and sub-arctic regions, elucidating DOM composition and reactivity is complicated by seasonal variations. These include changes in productivity and source inputs to the water column, as well as winter overflow events that may contribute allochthonous organic material. DOM from a small boreal stream in a watershed of discontinuous permafrost in the Goldstream Valley of interior Alaska was isolated by solid-phase extraction (PPL) at multiple points during the year - late spring, late summer, and in the winter during an active overflow event. Compositional characteristics of each of the isolates were characterized by SPR-W5-WATERGATE 1H NMR spectroscopy, specific UV-Vis absorbance, and excitation emission matrix (EEM) fluorescence spectroscopy and compared against end-member reference DOM isolates. Kinetics of photobleaching experiments reveal the influence of compositional differences among the isolated DOMs on their chemical reactivity, and offer insight into potential differences in their source materials and ecological function throughout the year. Photobleaching studies were conducted using a variety of reactive species quenchers or sensitizers in order to assess susceptibility of oxidative transformation mechanisms on the different DOM isolates, which were then analyzed by 1H NMR, UV-Vis degradation kinetics, and parallel factor analysis (PARAFAC) of fluorescence EEMs. Better understanding of the seasonal variations of boreal DOM character and function on a molecular level is critical to assessing alterations in its ecological role and cycling in the face of current and future ecosystem perturbations in arctic and sub-arctic regions.

  12. Analysing Submarine Groundwater Discharge (SGD)-borne Dissolved Organic Matter (DOM) in a karstic aquifer, Co. Galway, Ireland.

    NASA Astrophysics Data System (ADS)

    Kelly, Tara; Rocha, Carlos

    2014-05-01

    Submarine Groundwater Discharge (SGD) constitutes an "invisible" link between land and sea, transporting allochthonous and autochthonous dissolved organic matter (DOM), nutrients and metals to the ocean via the subterranean estuary. The latter acts as a powerful bioreactor where groundwater, in transit from land to sea, mixes with seawater leading to active modulation of both DOM content and chemical makeup of SGD. DOM in freshwater systems is a key component of the global carbon cycle. Climate change may hence increase the concentration of allochthonous carbon entering the oceans as terrestrial DOC is released from soils at higher temperatures, and transported via SGD. Presently, little is known about the effects of SGD-borne DOM on coastal carbon cycling. SGD therefore represents a dynamic reservoir and analysis is critical to forecast future environmental management programmes, both on a local and global scale. Labile DOM plays a crucial role in microbial remineralisation processes, and as it breaks down it contributes to the groundwater nutrient pool. Locally, this could add to eutrophication. However, if refractory carbon is present, it will be recalcitrant to mineralisation in transit and at the subterranean estuary. This putative additional input will thus imply the contribution of SGD to oceanic carbon storage. This study is focused on Kinvara Bay (Galway, western Ireland), the focal point for waters discharging from the Gort-Kinvara karstic aquifer. This aquifer represents the ideal study location for evaluation of SGD contribution to the coastal DOM pool, as SGD is focused in the bay, surface drainage is very limited, and groundwater travels across a large catchment area with a short residence time, minimising DOM modification in transit. DOM samples collected in the field have been analysed using Three-Dimensional Excitation Emission Matrix Fluorescence (3D-EEMF) and High Temperature Catalytic Oxidation. PARAFAC is subsequently used as a tool to

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

    PubMed

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

    2013-06-18

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

  14. Chemical composition of dissolved organic nitrogen in the ocean

    NASA Astrophysics Data System (ADS)

    McCarthy, Matthew; Pratum, Tom; Hedges, John; Benner, Ronald

    1997-11-01

    Fixed nitrogen is one of the main limiting nutrients for primary production in the ocean, where it is biologically available in the form of dissolved inorganic and organic matter. Inorganic nitrogen concentrations are consequently very low in surface waters of temperate ocean gyres, yet fixed nitrogen persists in the form of dissolved organic matter. The small, rapidly cycling organic compounds fundamental to microbial and planktonic growth (such as free amino acids, amines and urea) account for only a minor fraction of total dissolved organic nitrogen (DON). In contrast, the vast majority of DON, especially in the deep ocean, resides in the form of nitrogenous substances that are resistant to biological degradation. These substances, which represent an enormous reservoir of fixed nitrogen, are not readily identified by conventional biochemical techniques, but have been assumed to consist largely of structurally complex macromolecules resulting from the degradation and spontaneous abiotic condensation of biochemical precursors. Here we present 15N NMR measurements that contradict this view. Our results show that most higher-molecular-weight DON in the ocean exists in amide form, rather than as a collection of nitrogen heterocycles that might be indicative of spontaneous condensation products. Because these amides are unlikely to form abiotically, the bulk of the ocean's DON reservoir appears to derive directly from degradation-resistant biomolecules.

  15. Evaluating the distribution of terrestrial dissolved organic matter in a complex coastal ecosystem using fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamashita, Youhei; Boyer, Joseph N.; Jaffé, Rudolf

    2013-09-01

    The coastal zone of the Florida Keys features the only living coral reef in the continental United States and as such represents a unique regional environmental resource. Anthropogenic pressures combined with climate disturbances such as hurricanes can affect the biogeochemistry of the region and threaten the health of this unique ecosystem. As such, water quality monitoring has historically been implemented in the Florida Keys, and six spatially distinct zones have been identified. In these studies however, dissolved organic matter (DOM) has only been studied as a quantitative parameter, and DOM composition can be a valuable biogeochemical parameter in assessing environmental change in coastal regions. Here we report the first data of its kind on the application of optical properties of DOM, in particular excitation emission matrix fluorescence with parallel factor analysis (EEM-PARAFAC), throughout these six Florida Keys regions in an attempt to assess spatial differences in DOM sources. Our data suggests that while DOM in the Florida Keys can be influenced by distant terrestrial environments such as the Everglades, spatial differences in DOM distribution were also controlled in part by local surface runoff/fringe mangroves, contributions from seasgrass communities, as well as the reefs and waters from the Florida Current. Application of principal component analysis (PCA) of the relative abundance of EEM-PARAFAC components allowed for a clear distinction between the sources of DOM (allochthonous vs. autochthonous), between different autochthonous sources and/or the diagenetic status of DOM, and further clarified contribution of terrestrial DOM in zones where levels of DOM were low in abundance. The combination between EEM-PARAFAC and PCA proved to be ideally suited to discern DOM composition and source differences in coastal zones with complex hydrology and multiple DOM sources.

  16. Rates of dissolved organic carbon (DOC) production and bacterial activity in the eastern North Atlantic Subtropical Gyre during summer

    NASA Astrophysics Data System (ADS)

    Teira, E.; Pazó, M. J.; Quevedo, M.; Fuentes, M. V.; Niell, F. X.; Fernández, E.

    2003-04-01

    Rates of particulate organic carbon production, dissolved organic carbon production (DOC) and bacterial production were measured at 8 stations located in the eastern North Atlantic Subtropical Gyre during August 1998. Euphotic-depth-integrated particulate organic carbon (POC) production rate was on average 27 mg C m-2 h-1. The corresponding averaged integrated DOC production rate was 5 mg C m-2 h-1, i.e., about 20 % of total primary production. No statistically significant relationship was found between the rates of DOC and POC production, suggesting that other processes besides phytoplankton exudation, such as cell lysis or protist grazing, could substantially contribute to the release of DOC. Euphotic-depth-integrated bacterial biomass and production were, on average, 214 mg C m-2 and 1.4 mg C m-2 h-1, respectively. The lack of correlation between the rates of DOC release and bacterial activity, and a bacterial carbon demand (BCD, calculated by using an estimated bacterial growth efficiency ranging from 11 to 18%) in excess of DOC production suggest the existence of additional organic carbon sources (both allochthonous and/or autochthonous reservoirs), apart from in situ phytoplankton-derived DOC production, for the maintenance of bacterial activity in this region during summer.

  17. The Biogeochemistry of Dissolved Organic Carbon: Isotopic and Spectroscopic Insights From an Upland Mediterranean Catchment

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

    In upland catchments, allochthonous inputs of dissolved organic carbon (DOC) represent the major source of reduced energy to the aquatic ecosystem. The concentration and chemistry of this stream DOC is a primarily controlled by a complex interplay between soil biogeochemical cycling and hydrologic routing. Here we present results from an intensive field and laboratory examination of DOC fluxes and chemistry within a small headwater catchment (3 ha) in a coastal California prairie ecosystem. Over the course of 2 years, DOC in soil water samples at multiple depths and at multiple hillslope locations, as well as stream water samples were chemically characterized using both isotopic (13C and 14C) and spectroscopic (UV/VIS and 13C NMR) analyses. In upland soil profiles where vertically infiltrating throughflow dominates, we find a progressive shift in DOC age and recalcitrance as water percolates through the soil profile due to continuous exchange with native soil organic matter. Imprinted over this general trend, are two interesting patterns: 1) a seasonal shift in DOC chemistry as the annual grasses at this site become more active in the late winter/early spring; and 2) a more stochastic trend of depletion and replenishment of a readily dissolvable potential DOC source pool that depends on rainfall intensity and timing. Moving downslope, where saturated flow persists for longer periods of time following each rain event, this depletion of a potential DOC source pool is both more pronounced and more persistent. The combination of highly dynamic soil hydrology and a seasonal shift in biological activity leads to distinctive patterns in stream water DOC chemistry. A large expansion of variably saturated zones during large rain events acts to directly connect DOC-rich source regions (surface soils) to the stream network. Rapid saturated overland and subsurface flow effectively bypasses the typical removal/exchange mechanisms deeper in the mineral soil, resulting in the

  18. Monitoring dissolved organic carbon in surface and drinking waters.

    PubMed

    Volk, Christian; Wood, Larry; Johnson, Bruce; Robinson, Jeff; Zhu, Hai Wei; Kaplan, Louis

    2002-02-01

    The presence of natural organic matter (NOM) strongly impacts drinking water treatment, water quality, and water behavior during distribution. Dissolved organic carbon (DOC) concentrations were determined daily over a 22 month period in river water before and after conventional drinking water treatment using an on-line total organic carbon (TOC) analyzer. Quantitative and qualitative variations in organic matter were related to precipitation and runoff, seasons and operating conditions. Following a rainfall event, DOC levels could increase by 3.5 fold over baseflow concentrations, while color, UV absorbance values and turbidity increased by a factor of 8, 12 and 300, respectively. Treated water DOC levels were closely related to the source water quality, with an average organic matter removal of 42% after treatment.

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

    SciTech Connect

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

    2014-01-01

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

  20. 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.

  1. 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.

  2. 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.

  3. Utilizing Colored Dissolved Organic Matter to Derive Dissolved Black Carbon Export by Arctic Rivers

    NASA Astrophysics Data System (ADS)

    Stubbins, Aron; Spencer, Robert; Mann, Paul; Holmes, R.; McClelland, James; Niggemann, Jutta; Dittmar, Thorsten

    2015-10-01

    Wildfires have produced black carbon (BC) since land plants emerged. Condensed aromatic compounds, a form of BC, have accumulated to become a major component of the soil carbon pool. Condensed aromatics leach from soils into rivers, where they are termed dissolved black carbon (DBC). The transport of DBC by rivers to the sea is a major term in the global carbon and BC cycles. To estimate Arctic river DBC export, 25 samples collected from the six largest Arctic rivers (Kolyma, Lena, Mackenzie, Ob’, Yenisey and Yukon) were analyzed for dissolved organic carbon (DOC), colored dissolved organic matter (CDOM), and DBC. A simple, linear regression between DOC and DBC indicated that DBC accounted for 8.9 ± 0.3% DOC exported by Arctic rivers. To improve upon this estimate, an optical proxy for DBC was developed based upon the linear correlation between DBC concentrations and CDOM light absorption coefficients at 254 nm (a254). Relatively easy to measure a254 values were determined for 410 Arctic river samples between 2004 and 2010. Each of these a254 values was converted to a DBC concentration based upon the linear correlation, providing an extended record of DBC concentration. The extended DBC record was coupled with daily discharge data from the six rivers to estimate riverine DBC loads using the LOADEST modeling program. The six rivers studied cover 53% of the pan-Arctic watershed and exported 1.5 ± 0.1 million tons of DBC per year. Scaling up to the full area of the pan-Arctic watershed, we estimate that Arctic rivers carry 2.8 ± 0.3 million tons of DBC from land to the Arctic Ocean each year. This equates to ~8% of Arctic river DOC export, slightly less than indicated by the simpler DBC vs DOC correlation-based estimate. Riverine discharge is predicted to increase in a warmer Arctic. DBC export was positively correlated with river runoff, suggesting that the export of soil BC to the Arctic Ocean is likely to increase as the Arctic warms.

  4. 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

  5. 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.

  6. Molecular-level dynamics of refractory dissolved organic matter

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

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

    PubMed

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

    2015-04-28

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

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

    PubMed

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

    2016-06-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

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

    PubMed

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

    2015-04-28

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

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. Determining sources of dissolved organic carbon and disinfection byproduct precursors to the McKenzie River, Oregon

    USGS Publications Warehouse

    Kraus, T.E.C.; Anderson, C.A.; Morgenstern, K.; Downing, B.D.; Pellerin, B.A.; Bergamaschi, B.A.

    2010-01-01

    This study was conducted to determine the main sources of dissolved organic carbon (DOC) and disinfection byproduct (DBP) precursors to the McKenzie River, Oregon (USA). Water samples collected from the mainstem, tributaries, and reservoir outflows were analyzed for DOC concentration and DBP formation potentials (trihalomethanes [THMFPs] and haloacetic acids [HAAFPs]). In addition, optical properties (absorbance and fluorescence) of dissolved organic matter (DOM) were measured to provide insight into DOM composition and assess whether optical properties are useful proxies for DOC and DBP precursor concentrations. Optical properties indicative of composition suggest that DOM in the McKenzie River mainstem was primarily allochthonous - derived from soils and plant material in the upstream watershed. Downstream tributaries had higher DOC concentrations than mainstem sites (1.6 ?? 0.4 vs. 0.7 ?? 0.3 mg L-1) but comprised <5% of mainstem flows and had minimal effect on overall DBP precursor loads. Water exiting two large upstream reservoirs also had higher DOC concentrations than the mainstem site upstream of the reservoirs, but optical data did not support in situ algal production as a source of the added DOC during the study. Results suggest that the first major rain event in the fall contributes DOM with high DBP precursor content. Although there was interference in the absorbance spectra in downstream tributary samples, fluorescence data were strongly correlated to DOC concentration (R 2 = 0.98), THMFP (R2 = 0.98), and HAAFP (R2 = 0.96). These results highlight the value of using optical measurements for identifying the concentration and sources of DBP precursors in watersheds, which will help drinking water utilities improve source water monitoring and management programs. Copyright ?? 2010 by the American Society of Agronomy.

  19. Determining sources of dissolved organic carbon and disinfection byproduct precursors to the McKenzie River, Oregon.

    PubMed

    Kraus, Tamara E C; Anderson, Chauncey A; Morgenstern, Karl; Downing, Bryan D; Pellerin, Brian A; Bergamaschi, Brian A

    2010-01-01

    This study was conducted to determine the main sources of dissolved organic carbon (DOC) and disinfection byproduct (DBP) precursors to the McKenzie River, Oregon (USA). Water samples collected from the mainstem, tributaries, and reservoir outflows were analyzed for DOC concentration and DBP formation potentials (trihalomethanes [THMFPs] and haloacetic acids [HAAFPs]). In addition, optical properties (absorbance and fluorescence) of dissolved organic matter (DOM) were measured to provide insight into DOM composition and assess whether optical properties are useful proxies for DOC and DBP precursor concentrations. Optical properties indicative of composition suggest that DOM in the McKenzie River mainstem was primarily allochthonous--derived from soils and plant material in the upstream watershed. Downstream tributaries had higher DOC concentrations than mainstem sites (1.6 +/- 0.4 vs. 0.7 +/- 0.3 mg L(-1)) but comprised < 5% ofmainstem flows and had minimal effect on overall DBP precursor loads. Water exiting two large upstream reservoirs also had higher DOC concentrations than the mainstem site upstream of the reservoirs, but optical data did not support in situ algal production as a source of the added DOC during the study. Results suggest that the first major rain event in the fall contributes DOM with high DBP precursor content. Although there was interference in the absorbance spectra in downstream tributary samples, fluorescence data were strongly correlated to DOC concentration (R2 = 0.98), THMFP (R2 = 0.98), and HAAFP (R2 = 0.96). These results highlight the value of using optical measurements for identifying the concentration and sources of DBP precursors in watersheds, which will help drinking water utilities improve source water monitoring and management programs.

  20. Determining sources of dissolved organic carbon and disinfection byproduct precursors to the McKenzie River, Oregon.

    PubMed

    Kraus, Tamara E C; Anderson, Chauncey A; Morgenstern, Karl; Downing, Bryan D; Pellerin, Brian A; Bergamaschi, Brian A

    2010-01-01

    This study was conducted to determine the main sources of dissolved organic carbon (DOC) and disinfection byproduct (DBP) precursors to the McKenzie River, Oregon (USA). Water samples collected from the mainstem, tributaries, and reservoir outflows were analyzed for DOC concentration and DBP formation potentials (trihalomethanes [THMFPs] and haloacetic acids [HAAFPs]). In addition, optical properties (absorbance and fluorescence) of dissolved organic matter (DOM) were measured to provide insight into DOM composition and assess whether optical properties are useful proxies for DOC and DBP precursor concentrations. Optical properties indicative of composition suggest that DOM in the McKenzie River mainstem was primarily allochthonous--derived from soils and plant material in the upstream watershed. Downstream tributaries had higher DOC concentrations than mainstem sites (1.6 +/- 0.4 vs. 0.7 +/- 0.3 mg L(-1)) but comprised < 5% ofmainstem flows and had minimal effect on overall DBP precursor loads. Water exiting two large upstream reservoirs also had higher DOC concentrations than the mainstem site upstream of the reservoirs, but optical data did not support in situ algal production as a source of the added DOC during the study. Results suggest that the first major rain event in the fall contributes DOM with high DBP precursor content. Although there was interference in the absorbance spectra in downstream tributary samples, fluorescence data were strongly correlated to DOC concentration (R2 = 0.98), THMFP (R2 = 0.98), and HAAFP (R2 = 0.96). These results highlight the value of using optical measurements for identifying the concentration and sources of DBP precursors in watersheds, which will help drinking water utilities improve source water monitoring and management programs. PMID:21284308

  1. Hydrological conditions regulate dissolved organic matter quality in an intermittent headwater stream. From drought to storm analysis.

    PubMed

    Guarch-Ribot, Alba; Butturini, Andrea

    2016-11-15

    Storms and droughts are an essential driver for the dissolved organic matter (DOM) concentration in headwater streams. However, the relationship between DOM quality and discharge (Q) has not been addressed in depth and the impact of other hydro-climatic or biogeochemical drivers has not been explored. In this study DOM quality variability was explored at seasonal and storm event scales during an intensive 2.5-year-long sampling in a Mediterranean stream characterized by a severe summer drought. DOM quality was described in terms of absorbance and fluorescence properties. Most of the DOM properties were strongly related to discharge revealing the input of allochthonous, degraded, aromatic, humic and increased-molecular-size DOM under high flow conditions. However, these relationships disappeared or reversed during drying and rewetting periods. Each DOM response at the storm event scale (DOM-Q hysteresis) was outlined with two descriptors that summarised its trend (dilution/flushing/chemostasis) and shape (linear/nonlinear response). Multiple linear regression and commonality analysis showed that, in addition to the magnitude of storm episodes, antecedent hydrological conditions, namely pre-event basal flow and the magnitude of the previous storm event, played a significant role in regulating the trends and shapes of DOM-Q hysteresis. PMID:27470016

  2. Hydrological conditions regulate dissolved organic matter quality in an intermittent headwater stream. From drought to storm analysis.

    PubMed

    Guarch-Ribot, Alba; Butturini, Andrea

    2016-11-15

    Storms and droughts are an essential driver for the dissolved organic matter (DOM) concentration in headwater streams. However, the relationship between DOM quality and discharge (Q) has not been addressed in depth and the impact of other hydro-climatic or biogeochemical drivers has not been explored. In this study DOM quality variability was explored at seasonal and storm event scales during an intensive 2.5-year-long sampling in a Mediterranean stream characterized by a severe summer drought. DOM quality was described in terms of absorbance and fluorescence properties. Most of the DOM properties were strongly related to discharge revealing the input of allochthonous, degraded, aromatic, humic and increased-molecular-size DOM under high flow conditions. However, these relationships disappeared or reversed during drying and rewetting periods. Each DOM response at the storm event scale (DOM-Q hysteresis) was outlined with two descriptors that summarised its trend (dilution/flushing/chemostasis) and shape (linear/nonlinear response). Multiple linear regression and commonality analysis showed that, in addition to the magnitude of storm episodes, antecedent hydrological conditions, namely pre-event basal flow and the magnitude of the previous storm event, played a significant role in regulating the trends and shapes of DOM-Q hysteresis.

  3. [Absorption and fluorescence characteristics of dissolved organic matter (DOM) in rainwater and sources analysis in summer and winter season].

    PubMed

    Liang, Jian; Jiang, Tao; WeiI, Shi-Qiang; Lu, Song; Yan, Jin-Long; Wang, Qi-Lei; Gao, Jie

    2015-03-01

    This study aimed at evaluating the variability of the optical properties including UV-Vis and fluorescence characteristics of dissolved organic matter (DOM) from rainwater in summer and winter seasons. UV-Vis and fluorescence spectroscopy, together with Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model and fire events map, were conducted to characterize DOM and investigate its sources and contributions. The results showed that as compared with aquatic and soil DOM, rainwater DOM showed similar spectral characteristics, suggesting DOM in precipitation was also an important contributor to DOM pool in terrestrial and aquatic systems. The concentrations of DOC in rainwater were 0.88-12.80 mg x L(-1), and the CDOM concentrations were 3.17-21.11 mg x L(-1). Differences of DOM samples between summer and winter were significant (P < 0.05). In comparison to summer, DOM samples in winter had lower molecular weight and aromaticity, and also lower humification. Input of DOM in winter was predominantly derived from local and short-distance distances, while non-special scattering sources were identified as the main contributors in summer. Although absorption and fluorescence spectroscopy could be used to identify DOM composition and sources, there were obvious differences in spectra and sources analysis between rainwater DOM and the others from other sources. Thus, the classic differentiation method by "allochthonous (terrigenous) and autochthonous (authigenic)" is possibly too simple and arbitrary for characterization of DOM in rainwater.

  4. 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...

  5. 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...

  6. 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.

  7. Latitudinal Gradients in Degradation of Marine Dissolved Organic Carbon

    PubMed Central

    Arnosti, Carol; Steen, Andrew D.; Ziervogel, Kai; Ghobrial, Sherif; Jeffrey, Wade H.

    2011-01-01

    Heterotrophic microbial communities cycle nearly half of net primary productivity in the ocean, and play a particularly important role in transformations of dissolved organic carbon (DOC). The specific means by which these communities mediate the transformations of organic carbon are largely unknown, since the vast majority of marine bacteria have not been isolated in culture, and most measurements of DOC degradation rates have focused on uptake and metabolism of either bulk DOC or of simple model compounds (e.g. specific amino acids or sugars). Genomic investigations provide information about the potential capabilities of organisms and communities but not the extent to which such potential is expressed. We tested directly the capabilities of heterotrophic microbial communities in surface ocean waters at 32 stations spanning latitudes from 76°S to 79°N to hydrolyze a range of high molecular weight organic substrates and thereby initiate organic matter degradation. These data demonstrate the existence of a latitudinal gradient in the range of complex substrates available to heterotrophic microbial communities, paralleling the global gradient in bacterial species richness. As changing climate increasingly affects the marine environment, changes in the spectrum of substrates accessible by microbial communities may lead to shifts in the location and rate at which marine DOC is respired. Since the inventory of DOC in the ocean is comparable in magnitude to the atmospheric CO2 reservoir, such a change could profoundly affect the global carbon cycle. PMID:22216139

  8. Photo-oxidation of Dissolved Organic Matter in River Water and its Effect on Trace Element Speciation

    NASA Astrophysics Data System (ADS)

    Shiller, A. M.; Duan, S.; van Erp, P.; Bianchi, T.

    2004-12-01

    elements also showed decreases in their retention by an anion exchange column, likewise implying a decrease in the organically-complexed form. Our results suggest that as fluvial DOC becomes more photo-refractory upon exposure to sunlight, there will be a transfer of certain trace elements from dissolved, complexed forms to colloidal or particulate adsorbed forms. This should lead to fundamental differences in metal speciation, transport, and bioavailability between low-order streams with fresh allochthonous carbon inputs and floodplain rivers dominated by photo-refractory carbon.

  9. 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...

  10. 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. PMID:27019968

  11. 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

  12. 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.

  13. Characterization of dissolved organic matter in drinking water sources impacted by multiple tributaries.

    PubMed

    Rosario-Ortiz, Fernando L; Snyder, Shane A; Suffet, I H

    2007-10-01

    The characterization of dissolved organic matter (DOM) in drinking water sources is important as this material contributes to the formation of disinfection by-products (DBPs) and affects how water treatment unit operations are optimized. Drinking water utilities often draw water from sources impacted by multiple tributaries, with possible shifts in DOM concentrations and reactivity over time, depending on specific environmental conditions. In this study, results are presented on the characterization of DOM under varying ambient conditions from the four main tributaries of Lake Mead, a large reservoir in the southwest United States. The tributaries include the Las Vegas Wash (LVW), Muddy River (MR), Virgin River (VR) and the upper Colorado River (UCR). One additional sample was collected at the outflow of the reservoir (lower Colorado River (LCR)). The DOM was characterized by both bulk parameters (specific ultraviolet absorbance (SUVA)) and specific physicochemical properties, i.e. size, polarity and fluorescence. The analyses were performed emphasizing limited changes in its natural configuration by eliminating analytical preparation steps, excluding sample filtration (0.45 microm filter). Results indicate that each tributary had a different molecular weight distribution, as well as fluorescence properties, which helped in the identification of the relative source of DOM (allochthonous versus autochthonous). The largest apparent molecular weight distribution was observed for DOM samples collected at the MR site, which is fed mostly by groundwater seepage. The smallest apparent molecular weight was observed for DOM collected at the LCR site, suggesting that retention in the reservoir resulted in a decrease in molecular weight as a probable result of photo oxidation and microbial processes. Fluorescence analysis aided the differentiation of DOM by clearly identifying waters that were affected by microbial activity (LVW, UCR, and LCR), either by wastewater influence

  14. 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

  15. 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

    2015-01-01

    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. PMID:25704539

  16. [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.

  17. Dissolved organic carbon and dissolved organic nitrogen export from forested watersheds in Nova Scotia: Identifying controlling factors

    NASA Astrophysics Data System (ADS)

    Aitkenhead-Peterson, J. A.; Alexander, J. E.; Clair, T. A.

    2005-12-01

    Riverine nutrient export represents a transfer of terrestrial nutrients to lakes, estuaries and the near-coastal zone. In this study, we constructed regional predictive models for riverine dissolved organic carbon (DOC) and organic nitrogen (DON) exports. We used a subset of 10 watersheds to construct regional empirical models of DOC and DON export, reserving two watersheds for testing the predictive ability of each model. For the subset of 10 watersheds, mean watershed soil column C:N ratio explained 75% of the variance in DOC export and 73% of the variance in DON export (p < 0.01). Organic C:N explained 63% and 71% of the variance in DOC and DON exports, respectively. There was a stronger relationship between riverine DOC:DON ratio and mineral soil C:N (R2 = 0.77 p < 0.001) than with organic C:N (R2 = 0.49 p < 0.05), suggesting that de-coupling of DOC and DON dynamics in rivers may occur when hydrologic flow paths favor organic layers. We suggest that mean watershed soil C:N ratio is likely to be an integrator of several controls on riverine DOC export including temperature and precipitation (climatic control), soil texture and nutrient status (edaphic control), vegetative species and their associated micro-flora (biological control) and watershed topography (topographical control). Soil C:N appears to be a useful tool for predicting variability in both DOC and DON flux at a regional scale.

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

    PubMed

    Nebbioso, Antonio; Piccolo, Alessandro

    2013-01-01

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

  19. 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+)).

  20. 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. PMID:27318445

  1. 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.

  2. Estimating the Age Distribution of Oceanic Dissolved Organic Carbon

    NASA Astrophysics Data System (ADS)

    Follett, C. L.; Forney, D. C.; Repeta, D.; Rothman, D.

    2010-12-01

    Dissolved organic carbon (DOC) is a large, ubiquitous component of open ocean water at all depths and impacts atmospheric carbon dioxide levels at both short and long timescales. It is currently believed that oceanic DOC contains a multi-thousand-year-old refractory deep-water component which is mixed with a young labile component in surface waters. Unfortunately, the only evidence for this comes from a few isolated depth profiles of both DOC concentration and bulk radiocarbon. Although the profile data is consistent with a two-component mixing model, directly separating the two components has proven to be a challenge. We explore the validity of the two component mixing model by directly estimating the age distribution of oceanic DOC. The two-component model suggests that the age distribution is composed of two distinct peaks. In order to obtain an estimate of the age distribution we first record changes in both concentration and percent radiocarbon as a sample is oxidized under ultra-violet radiation [1]. We formulate a mathematical model relating the age distribution to these changes, assuming that they result from components of different radiocarbon age and UV-reactivity. This allows us to numerically invert the data and estimate the age distribution. We apply our procedure to DOC samples collected from three distinct depths (50, 500, and 2000 meters) in the north-central Pacific Ocean. [1] S.R. Beaupre, E.R.M. Druffel, and S. Griffin. A low-blank photochemical extraction system for concentration and isotopic analyses of marine dissolved organic carbon. Limnol. Oceanogr. Methods, 5:174-184, 2007.

  3. Dissolved organic carbon (DOC) in Arctic ground ice

    NASA Astrophysics Data System (ADS)

    Fritz, M.; Opel, T.; Tanski, G.; Herzschuh, U.; Meyer, H.; Eulenburg, A.; Lantuit, H.

    2015-01-01

    Thermal permafrost degradation and coastal erosion in the Arctic remobilize substantial amounts of organic carbon (OC) and nutrients which have been accumulated in late Pleistocene and Holocene unconsolidated deposits. Their vulnerability to thaw subsidence, collapsing coastlines and irreversible landscape change is largely due to the presence of large amounts of massive ground ice such as ice wedges. However, ground ice has not, until now, been considered to be a source of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and other elements, which are important for ecosystems and carbon cycling. Here we show, using geochemical data from a large number of different ice bodies throughout the Arctic, that ice wedges have the greatest potential for DOC storage with a maximum of 28.6 mg L-1 (mean: 9.6 mg L-1). Variation in DOC concentration is positively correlated with and explained by the concentrations and relative amounts of typically terrestrial cations such as Mg2+ and K+. DOC sequestration into ground ice was more effective during the late Pleistocene than during the Holocene, which can be explained by rapid sediment and OC accumulation, the prevalence of more easily degradable vegetation and immediate incorporation into permafrost. We assume that pristine snowmelt is able to leach considerable amounts of well-preserved and highly bioavailable DOC as well as other elements from surface sediments, which are rapidly stored in ground ice, especially in ice wedges, even before further degradation. In the Yedoma region ice wedges represent a significant DOC (45.2 Tg) and DIC (33.6 Tg) pool in permafrost areas and a fresh-water reservoir of 4172 km3. This study underlines the need to discriminate between particulate OC and DOC to assess the availability and vulnerability of the permafrost carbon pool for ecosystems and climate feedback upon mobilization.

  4. Dissolved organic carbon (DOC) in Arctic ground ice

    NASA Astrophysics Data System (ADS)

    Fritz, M.; Opel, T.; Tanski, G.; Herzschuh, U.; Meyer, H.; Eulenburg, A.; Lantuit, H.

    2015-04-01

    Thermal permafrost degradation and coastal erosion in the Arctic remobilize substantial amounts of organic carbon (OC) and nutrients which have accumulated in late Pleistocene and Holocene unconsolidated deposits. Permafrost vulnerability to thaw subsidence, collapsing coastlines and irreversible landscape change are largely due to the presence of large amounts of massive ground ice such as ice wedges. However, ground ice has not, until now, been considered to be a source of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and other elements which are important for ecosystems and carbon cycling. Here we show, using biogeochemical data from a large number of different ice bodies throughout the Arctic, that ice wedges have the greatest potential for DOC storage, with a maximum of 28.6 mg L-1 (mean: 9.6 mg L-1). Variation in DOC concentration is positively correlated with and explained by the concentrations and relative amounts of typically terrestrial cations such as Mg2+ and K+. DOC sequestration into ground ice was more effective during the late Pleistocene than during the Holocene, which can be explained by rapid sediment and OC accumulation, the prevalence of more easily degradable vegetation and immediate incorporation into permafrost. We assume that pristine snowmelt is able to leach considerable amounts of well-preserved and highly bioavailable DOC as well as other elements from surface sediments, which are rapidly frozen and stored in ground ice, especially in ice wedges, even before further degradation. We found that ice wedges in the Yedoma region represent a significant DOC (45.2 Tg) and DIC (33.6 Tg) pool in permafrost areas and a freshwater reservoir of 4200 km2. This study underlines the need to discriminate between particulate OC and DOC to assess the availability and vulnerability of the permafrost carbon pool for ecosystems and climate feedback upon mobilization.

  5. Elevated dissolved organic carbon biodegradability from thawing and collapsing permafrost

    NASA Astrophysics Data System (ADS)

    Abbott, Benjamin W.; Larouche, Julia R.; Jones, Jeremy B.; Bowden, William B.; Balser, Andrew W.

    2014-10-01

    As high latitudes warm, a portion of the large organic carbon pool stored in permafrost will become available for transport to aquatic ecosystems as dissolved organic carbon (DOC). If permafrost DOC is biodegradable, much will be mineralized to the atmosphere in freshwater systems before reaching the ocean, accelerating carbon transfer from permafrost to the atmosphere, whereas if recalcitrant, it will reach marine ecosystems where it may persist over long time periods. We measured biodegradable DOC (BDOC) in water flowing from collapsing permafrost (thermokarst) on the North Slope of Alaska and tested the role of DOC chemical composition and nutrient concentration in determining biodegradability. DOC from collapsing permafrost was some of the most biodegradable reported in natural systems. However, elevated BDOC only persisted during active permafrost degradation, with a return to predisturbance levels once thermokarst features stabilized. Biodegradability was correlated with background nutrient concentration, but nutrient addition did not increase overall BDOC, suggesting that chemical composition may be a more important control on DOC processing. Despite its high biodegradability, permafrost DOC showed evidence of substantial previous microbial processing, and we present four hypotheses explaining this incongruity. Because thermokarst features form preferentially on river banks and lake shores and can remain active for decades, thermokarst may be the dominant short-term mechanism delivering sediment, nutrients, and biodegradable organic matter to aquatic systems as the Arctic warms.

  6. 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

  7. Which insect species numerically respond to allochthonous inputs?

    NASA Astrophysics Data System (ADS)

    Sugiura, Shinji; Ikeda, Hiroshi

    2013-08-01

    Herons (Ardeidae) frequently breed in inland forests and provide organic material in the form of carcasses of prey (that they drop) and chicks (that die) to the forest floor. Such allochthonous inputs of organic materials are known to increase arthropod populations in forests. However, the exact species that show numerical responses to allochthonous inputs in heron breeding colonies remains unclear. Very few studies have clarified which factors determine numerical responses in individual species. We used pitfall and baited traps to compare the densities of arthropods between forest patches in heron breeding colonies (five sites) and areas outside of colonies (five sites) in central Japan. The density of all arthropods was not significantly different between colonies and non-colony areas. However, significant differences between colonies and non-colony areas were found in four arthropod groups. Earwigs (Dermaptera: Anisolabididae), hister beetles (Coleoptera: Histeridae), and carrion beetles (Coleoptera: Silphidae) were more abundant in colonies, while ants (Hymenoptera: Formicidae) were less abundant in colonies. We detected numerical responses to heron breeding in two earwig, one histerid, five silphid, and one ant species. Chick and prey carcasses from herons may have directly led to increases in consumer populations such as earwigs, histerids, and silphids in colonies, while microenvironmental changes caused by heron breeding may have reduced ant abundance. In the Silphidae, five species showed numerical responses to allochthonous inputs, and the other two species did not. Numerical responses in individual species may have been determined by life history traits such as reproductive behaviour.

  8. 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.

  9. Disentangling the interactions between photochemical and bacterial degradation of dissolved organic matter: amino acids play a central role.

    PubMed

    Amado, André M; Cotner, James B; Cory, Rose M; Edhlund, Betsy L; McNeill, Kristopher

    2015-04-01

    Photochemical and bacterial degradation are important pathways to carbon mineralization and can be coupled in dissolved organic matter (DOM) decomposition. However, details of several mechanisms of the coupled photochemical and biological processing of DOM remain too poorly understood to achieve accurate predictions of the impact of these processes on DOM fate and reactivity. The aim of this study was to evaluate how photochemical degradation of amino acids affects bacterial metabolism and whether or not photochemical degradation of DOM competes for amino acids with biological processes. We examined the interactions between photochemical and bacterial degradation dynamics using a mixture of 18 amino acids and examined their dynamics and turnover rates within a larger pool of allochthonous or autochthonous DOM. We observed that photochemical exposure of DOM containing amino acids led to delayed biomass production (even though the final biomass did not differ), most likely due to a need for upregulation of biosynthetic pathways for amino acids that were damaged by photochemically produced reactive oxygen species (ROS). This response was most pronounced in bacterial communities where the abundance of photosensitive amino acids was highest (amended treatments and autochthonous DOM) and least pronounced when the abundance of these amino acids was low (unamended and allochthonous DOM), likely because these bacteria already had these biosynthetic pathways functioning. We observed both a cost and benefit associated with photochemical exposure of DOM. We observed a cost associated with photochemically produced ROS that partially degrade key amino acids and a benefit associated with an increase in the availability of other compounds in the DOM. Bacteria growing on DOM sources that are low in labile amino acids, such as those in terrestrially influenced environments, experience more of the benefits associated with photochemical exposure, whereas bacteria growing in more amino

  10. Bioavailability, Composition and Fate of Dissolved Organic Matter in the Swan-Canning Catchment, South-Western Australia

    NASA Astrophysics Data System (ADS)

    Petrone, K. C.; Hughes, C. S.; Norris, J. R.; Grierson, P. F.

    2007-12-01

    Dissolved organic nitrogen (DON) comprises the bulk of the total nitrogen load to the N-limited Swan-Canning river and estuary that bisects Perth, WA, yet its ecological role is largely unknown. Our objective was to assess the bioavailability and composition of dissolved organic matter (DOM), particularly its DON component, and the potential of DOM to supply dissolved inorganic nitrogen (DIN) to the estuary during the summer months when algal blooms are common. We compared water samples from 10 sub-catchments of the Swan-Canning that vary in land-use: eucalypt forests on the Darling Scarp most distant from the estuary, mixed (agriculture/ residential) catchments on the metropolitan perimeter, and urban catchments on the Swan Coastal Plain near Perth CBD. We inoculated water samples with a common bacterial inoculum and measured changes in DOC, DON and DIN over time. We found that 2 to 17 per cent of DOC and 18 to 44 per cent of the DON was consumed during the experiment and DIN was produced in 8 of 10 catchments. DOC and DON consumption were linearly related to concentration across sites and were greatest in the urban catchments. However, DOC and DON consumption were not significantly related, suggesting that C and N are concentrated in different fractions of DOM. Using resin fractionation techniques, we found that DOC was concentrated in the hydrophobic fraction, followed by transphilics, and lesser amounts of charged and neutral hydrophilics. Ongoing analyses will examine the N content of resin fractions and the amino acid composition of streams to determine how N composition relates to DOM decomposition. We are currently examining organic matter leached from native plants (Corymbia, Melaleuca) in coastal plain wetlands in order to characterize allochthonous DOM. Further examination of algal- derived DOM and point sources will enable us to determine the bioavailability and composition of in-stream and anthropogenic sources. These studies provide much needed

  11. Role of dissolved organic matter in ice photochemistry.

    PubMed

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

    2014-09-16

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

  12. 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.

  13. 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...

  14. 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

  15. 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

  16. 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

  17. 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

  18. Chemical composition of dissolved organic matter draining permafrost soils

    NASA Astrophysics Data System (ADS)

    Ward, Collin P.; Cory, Rose M.

    2015-10-01

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

  19. Tracking fluorescent dissolved organic matter in multistage rivers using EEM-PARAFAC analysis: implications of the secondary tributary remediation for watershed management.

    PubMed

    Nie, Zeyu; Wu, Xiaodong; Huang, Haomin; Fang, Xiaomin; Xu, Chen; Wu, Jianyu; Liang, Xinqiang; Shi, Jiyan

    2016-05-01

    Profound understanding of behaviors of organic matter from sources to multistage rivers assists watershed management for improving water quality of river networks in rural areas. Ninety-one water samples were collected from the three orders of receiving rivers in a typical combined polluted subcatchment (diffuse agricultural pollutants and domestic sewage) located in China. Then, the fluorescent dissolved organic matter (FDOM) information for these samples was determined by the excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC). Consequently, two typical humic-like (C1 and C2) and other two protein-like (C3 and C4) components were separated. Their fluorescence peaks were located at λ ex/em = 255(360)/455, <250(320)/395, 275/335, and <250/305 nm, which resembled the traditional peaks of A + C, A + M, T, and B, respectively. In addition, C1 and C2 accounted for the dominant contributions to FDOM (>60 %). Principal component analysis (PCA) further demonstrated that, except for the autochthonous produced C4, the allochthonous components (C1 and C2) had the same terrestrial origins, but C3 might possess the separate anthropogenic and biological sources. Moreover, the spatial heterogeneity of contamination levels was noticeable in multistage rivers, and the allochthonous FDOM was gradually homogenized along the migration directions. Interestingly, the average content of the first three PARAFAC components in secondary tributaries and source pollutants had significantly higher levels than that in subsequent receiving rivers, thus suggesting that the supervision and remediation for secondary tributaries would play a prominent role in watershed management works.

  20. 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.

  1. 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.

  2. 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.

  3. [Effects of dissolved organic matter on copper absorption by ryegrass].

    PubMed

    Tang, Chao; Wang, Bin; Liu, Man-Qiang; Hu, Feng; Li, Hui-Xin; Jiao, Jia-Guo

    2012-08-01

    In this study, dissolved organic matter (DOM) was extracted from earthworm casts and from the cattle manure with which the earthworms were fed, and a water culture experiment was conducted to study the effects of the DOM on the copper (Cu2+) absorption by ryegrass in the presence of different concentration Cu2+ (0, 5 and 10 mg x L(-1)). With the increasing concentration of Cu2+ in the medium, there was a gradual decrease in the dry mass of ryegrass shoots and roots and in the root length, surface area, volume, and tip number. In the presence of medium Cu2+, DOM increased the biomass of shoots and roots and the root length, surface area, volume, and tip number significantly. DOM reduced the Cu2+ concentration in roots, promoted the Cu2+ translocation from roots to shoots, and significantly increased the Cu2+ accumulation in shoots. The DOM from earthworm casts had better effects than that from cattle manure, and high concentration DOM had better effects than low concentration DOM. PMID:23189712

  4. 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. PMID:25385632

  5. 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.

  6. The Oxidant Budget of Dissolved Organic Carbon Driven Isotope Excursions

    NASA Astrophysics Data System (ADS)

    Bristow, T. F.; Kennedy, M. J.

    2008-12-01

    Negative carbon isotope values, falling below the mantle average of about -5 per mil, in carbonate phases of Ediacaran age sedimentary rocks are widely regarded as reflecting negative excursions in the carbon isotopic composition of seawater lasting millions of years. These isotopic signals form the basis of chemostratigraphic correlations between Ediacaran aged sections in different parts of the world, and have been used to track the oxidation of the biosphere. However, these isotopic values are difficult to accommodate within limits prescribed by the current understanding of the carbon cycle, and a hypothetical Precambrian ocean dissolved organic carbon (DOC) pool 100 to 1000 times the size of the modern provides a potential source of depleted carbon not considered in Phanerozoic carbon cycle budgets. We present box model results that show the remineralization of such a DOC pool to drive an isotope excursion of the magnitude observed in the geological record exhausts global budgets of free oxygen and sulfate in 800 k.y. These results are incompatible with the estimated duration of late Ediacaran isotope excursions of more than 10 m.y., as well as geochemical and biological indicators that oceanic sulfate and oxygen levels were maintained or even increased at the same time. Therefore the carbon isotope record is probably not a useful tool for monitoring oxygen levels in the atmosphere and ocean. Covariation between the carbon and oxygen isotope records is often observed during negative excursions and is indicative of local processes or diagenetic overprinting.

  7. 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.

  8. Relationships between molecular weight and fluorescence properties for size-fractionated dissolved organic matter from fresh and aged sources.

    PubMed

    Cuss, C W; Guéguen, C

    2015-01-01

    Relationships between the molecular weight (MW) and fluorescence properties of dissolved organic matter (DOM) are important considerations for studies seeking to connect these properties to water treatment processes. Relationships between the size and fluorescence properties of nine allochthonous DOM sources (i.e. leaf leachates, grass, and headwaters) were measured using asymmetrical flow field-flow fractionation (AF4) with on-line absorbance and fluorescence detectors. Correlations between optical properties and MW were readily apparent using parallel factor analysis (PARAFAC) coupled to self-organizing maps (SOM): protein/polyphenol-like fluorescence (peaks B and T) was highest at lower molecular weights (<0.5 kDa), fulvic/humic-like fluorescence (peaks A, C, and M) was highest at mid-weights (0.5-1 kDa), and humic-like fluorescence (Peaks A + C) was highest at larger molecular weights (>1 kDa). Proportions of peaks B, T, and A + C were significantly correlated with MW (p < 0.001). The first principal component (PC1, 42% of variation in fluorescence properties) was a significant predictor of sample MW (R² = 0.63, p < 0.05), while scores on PC2 (27% of total variance) traced a source-based gradient from deciduous leachates/headwaters through to coniferous leachates/headwaters. PC3 (13% of var.) was also correlated with MW (p < 0.005). A secondary peak in peak T fluorescence was associated with larger size fractions in aged sources, and scores on PC1 also traced a path from the leachates of fresher leaves, through more humified leaves, to headwaters. Findings are consistent with the hypothesis that the structure of aged DOM arises through supramolecular assembly.

  9. The influence of dissolved organic matter (DOM) on sodium regulation and nitrogenous waste excretion in the zebrafish (Danio rerio).

    PubMed

    Al-Reasi, Hassan A; Smith, Scott D; Wood, Chris M

    2016-08-01

    Dissolved organic matter (DOM) is both ubiquitous and diverse in composition in natural waters, but its effects on the branchial physiology of aquatic organisms have received little attention relative to other variables (e.g. pH, hardness, salinity, alkalinity). Here, we investigated the effects of four chemically distinct DOM isolates (three natural, one commercial, ranging from autochthonous to highly allochthonous, all at ∼6 mg C l(-1)) on the physiology of gill ionoregulation and nitrogenous waste excretion in zebrafish acclimated to either circumneutral (7.0-8.0) or acidic pH (5.0). Overall, lower pH tended to increase net branchial ammonia excretion, net K(+) loss and [(3)H]PEG-4000 clearance rates (indicators of transcellular and paracellular permeability, respectively). However, unidirectional Na(+) efflux, urea excretion and drinking rates were unaffected. DOM sources tended to stimulate unidirectional Na(+) influx rate and exerted subtle effects on the concentration-dependent kinetics of Na(+) uptake, increasing maximum transport capacity. All DOM sources reduced passive Na(+) efflux rates regardless of pH, but exerted negligible effects on nitrogenous waste excretion, drinking rate, net K(+) loss or [(3)H]PEG-4000 clearance, so the mechanism of Na(+) loss reduction remains unclear. Overall, these actions appear beneficial to ionoregulatory homeostasis in zebrafish, and some may be related to physico-chemical properties of the DOM sources. They are very different from those seen in a recent parallel study on Daphnia magna using the same DOM isolates, indicating that DOM actions may be both species and DOM specific.

  10. The influence of dissolved organic matter (DOM) on sodium regulation and nitrogenous waste excretion in the zebrafish (Danio rerio).

    PubMed

    Al-Reasi, Hassan A; Smith, Scott D; Wood, Chris M

    2016-08-01

    Dissolved organic matter (DOM) is both ubiquitous and diverse in composition in natural waters, but its effects on the branchial physiology of aquatic organisms have received little attention relative to other variables (e.g. pH, hardness, salinity, alkalinity). Here, we investigated the effects of four chemically distinct DOM isolates (three natural, one commercial, ranging from autochthonous to highly allochthonous, all at ∼6 mg C l(-1)) on the physiology of gill ionoregulation and nitrogenous waste excretion in zebrafish acclimated to either circumneutral (7.0-8.0) or acidic pH (5.0). Overall, lower pH tended to increase net branchial ammonia excretion, net K(+) loss and [(3)H]PEG-4000 clearance rates (indicators of transcellular and paracellular permeability, respectively). However, unidirectional Na(+) efflux, urea excretion and drinking rates were unaffected. DOM sources tended to stimulate unidirectional Na(+) influx rate and exerted subtle effects on the concentration-dependent kinetics of Na(+) uptake, increasing maximum transport capacity. All DOM sources reduced passive Na(+) efflux rates regardless of pH, but exerted negligible effects on nitrogenous waste excretion, drinking rate, net K(+) loss or [(3)H]PEG-4000 clearance, so the mechanism of Na(+) loss reduction remains unclear. Overall, these actions appear beneficial to ionoregulatory homeostasis in zebrafish, and some may be related to physico-chemical properties of the DOM sources. They are very different from those seen in a recent parallel study on Daphnia magna using the same DOM isolates, indicating that DOM actions may be both species and DOM specific. PMID:27207642

  11. Relationships between molecular weight and fluorescence properties for size-fractionated dissolved organic matter from fresh and aged sources.

    PubMed

    Cuss, C W; Guéguen, C

    2015-01-01

    Relationships between the molecular weight (MW) and fluorescence properties of dissolved organic matter (DOM) are important considerations for studies seeking to connect these properties to water treatment processes. Relationships between the size and fluorescence properties of nine allochthonous DOM sources (i.e. leaf leachates, grass, and headwaters) were measured using asymmetrical flow field-flow fractionation (AF4) with on-line absorbance and fluorescence detectors. Correlations between optical properties and MW were readily apparent using parallel factor analysis (PARAFAC) coupled to self-organizing maps (SOM): protein/polyphenol-like fluorescence (peaks B and T) was highest at lower molecular weights (<0.5 kDa), fulvic/humic-like fluorescence (peaks A, C, and M) was highest at mid-weights (0.5-1 kDa), and humic-like fluorescence (Peaks A + C) was highest at larger molecular weights (>1 kDa). Proportions of peaks B, T, and A + C were significantly correlated with MW (p < 0.001). The first principal component (PC1, 42% of variation in fluorescence properties) was a significant predictor of sample MW (R² = 0.63, p < 0.05), while scores on PC2 (27% of total variance) traced a source-based gradient from deciduous leachates/headwaters through to coniferous leachates/headwaters. PC3 (13% of var.) was also correlated with MW (p < 0.005). A secondary peak in peak T fluorescence was associated with larger size fractions in aged sources, and scores on PC1 also traced a path from the leachates of fresher leaves, through more humified leaves, to headwaters. Findings are consistent with the hypothesis that the structure of aged DOM arises through supramolecular assembly. PMID:25462755

  12. Dissolved organic matter dynamics in streams of intermittent flow - linkages with ecohydrologic processes from pool to catchment in northern Australia

    NASA Astrophysics Data System (ADS)

    Grierson, Pauline; Siebers, Andre; Skrzypek, Grzegorz; Fellman, Jason; Pettit, Neil; Dogramaci, Shawan

    2015-04-01

    Changes in both the frequency and intensity of flood-drought cycles of intermittent streams, either through changing climate or anthropogenic management, may have significant impacts on stream functioning. However, little is known about how and to what extent the quantity and composition of dissolved organic matter (DOM) changes during inter-flood periods and how this relates to stream hydrology, particularly of intermittent rivers. We hypothesised that with increasing time since flooding, controls on stream biogeochemical processes transition from predominantly hydrological to more local scale environmental factors. We also argue that in strongly seasonal and oligotrophic regions, such as those of the tropical northwest of Australia, groundwater inputs of old DOC may increase the bioavailability of stream organic matter. We used δ18O and δ2H values of surface water and groundwater in the alluvium (AW) together with DOM fluorescence excitation-emission spectroscopy and radiocarbon dating to (i) characterise DOM and (ii) assess the relative importance of autochthonous versus allochthonous sources among pools according to how connected they are to groundwater. Our findings show that as streams increase in size and accumulate aromatic DOC from terrestrial plant material, percent bioavailability decreases concomitant with the modernization of the DOC pool. Therefore, rapid biotic uptake of old, bioavailable DOC originating in groundwater springs and the accumulation of modern, terrestrially derived DOC work in opposite directions affecting the dynamics of DOC along fluvial networks. The metabolism of old DOC in small streams is a direct link between terrestrial and aquatic ecosystems but also provides a biogeochemical link between non-contemporary carbon fixation and modern river productivity. Recognition of the hydrologic complexity of dryland rivers is clearly necessary for more effective catchment-scale management strategies that balance an increasing demand for

  13. 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.

  14. Dissolved Organic Carbon in Groundwater Overlain by Irrigated Sugarcane.

    PubMed

    Thayalakumaran, Thabo; Lenahan, Matthew J; Bristow, Keith L

    2015-01-01

    Elevated dissolved organic carbon (DOC) has been detected in groundwater beneath irrigated sugarcane on the Burdekin coastal plain of tropical northeast Australia. The maximum value of 82 mg/L is to our knowledge the highest DOC reported for groundwater beneath irrigated cropping systems. More than half of the groundwater sampled in January 2004 (n = 46) exhibited DOC concentrations greater than 30 mg/L. DOC was progressively lower in October 2004 and January 2005, with a total decrease greater than 90% indicating varying load(s) to the aquifer. It was hypothesized that the elevated DOC found in this groundwater system is sourced at or near the soil surface and supplied to the aquifer via vertical recharge following above average rainfall. Possible sources of DOC include organic-rich sugar mill by-products applied as fertilizer and/or sugarcane sap released during harvest. CFC-12 vertical flow rates supported the hypothesis that elevated DOC (>40 mg/L) in the groundwater results from recharge events in which annual precipitation exceeds 1500 mm/year (average = 960 mm/year). Occurrence of elevated DOC concentrations, absence of electron acceptors (O2 and NO3 (-) ) and both Fe(2+) and Mn(2+) greater than 1 mg/L in shallow groundwater suggest that the DOC compounds are chemically labile. The consequence of high concentrations of labile DOC may be positive (e.g., denitrification) or negative (e.g., enhanced metal mobility and biofouling), and highlights the need to account for a wider range of water quality parameters when considering the impacts of land use on the ecology of receiving waters and/or suitability of groundwater for irrigated agriculture.

  15. Dissolved Organic Carbon in Groundwater Overlain by Irrigated Sugarcane.

    PubMed

    Thayalakumaran, Thabo; Lenahan, Matthew J; Bristow, Keith L

    2015-01-01

    Elevated dissolved organic carbon (DOC) has been detected in groundwater beneath irrigated sugarcane on the Burdekin coastal plain of tropical northeast Australia. The maximum value of 82 mg/L is to our knowledge the highest DOC reported for groundwater beneath irrigated cropping systems. More than half of the groundwater sampled in January 2004 (n = 46) exhibited DOC concentrations greater than 30 mg/L. DOC was progressively lower in October 2004 and January 2005, with a total decrease greater than 90% indicating varying load(s) to the aquifer. It was hypothesized that the elevated DOC found in this groundwater system is sourced at or near the soil surface and supplied to the aquifer via vertical recharge following above average rainfall. Possible sources of DOC include organic-rich sugar mill by-products applied as fertilizer and/or sugarcane sap released during harvest. CFC-12 vertical flow rates supported the hypothesis that elevated DOC (>40 mg/L) in the groundwater results from recharge events in which annual precipitation exceeds 1500 mm/year (average = 960 mm/year). Occurrence of elevated DOC concentrations, absence of electron acceptors (O2 and NO3 (-) ) and both Fe(2+) and Mn(2+) greater than 1 mg/L in shallow groundwater suggest that the DOC compounds are chemically labile. The consequence of high concentrations of labile DOC may be positive (e.g., denitrification) or negative (e.g., enhanced metal mobility and biofouling), and highlights the need to account for a wider range of water quality parameters when considering the impacts of land use on the ecology of receiving waters and/or suitability of groundwater for irrigated agriculture. PMID:25213667

  16. 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.

  17. 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.

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

    PubMed

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

    2015-01-01

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

  20. Effect of bacteria and dissolved organics on mineral dissolution kinetics:

    NASA Astrophysics Data System (ADS)

    Pokrovsky, Oleg; Shirokova, Liudmila; Benezeth, Pascale; Zabelina, Svetlana

    2010-05-01

    Quantification of the effect of microorganisms and associated organic ligands on mineral dissolution rate is one among the last remaining challenges in modeling of water-rock interactions under earth surface and subsurface environments. This is especially true for deep underground settings within the context of CO2 capture, sequestration and storage. First, elevated CO2 pressures create numerous experimental difficulties for performing robust flow-through experiments at a given saturation state. Second, reactivity of main rock-forming minerals in abiotic systems at pCO2 >> 1 atm and circumneutral pH is still poorly constrained. And third, most of microbial habitats of the subsurface biosphere are not suitable for routine culturing in the laboratory, many of them are anaerobic and even strictly anaerobic, and many bacteria and archae cultures can live only in the consortium of microorganisms which is very hard to maintain at a controlled and stable biomass concentration. For experimental modeling of bio-mineral interactions in the laboratory, two other main conceptual challenges exist. Typical concentration of dissolved organic carbon that serves as a main nutrient for heterotrophic bacteria in underground waters rarely exceeds 3-5 mg/L. Typical concentration of DOC in nutrient media used for bacteria culturing is between 100 and 10,000 mg/L. Therefore, performing mineral-bacteria interactions in the laboratory under environmentally-sound conditions requires significant dilution of the nutrient media or the use of flow-through reactors. Concerning the effect of organic ligands and bacterial excudates on rock-forming mineral dissolution, at the present time, mostly empirical (phenomenological) approach can be used. Indeed, the pioneering studies of Stumm and co-workers have established a firm basis for modeling the catalyzing and inhibiting effects of ligands on metal oxide dissolution rate. This approach, very efficient for studying the interaction of organic and

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  2. 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...

  3. 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...

  4. 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

  5. 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...

  6. 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

  7. 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.

  8. 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.

  9. [Three-dimensional Fluorescence Spectral Characteristics of Different Molecular Weight Fractionations of Dissolved Organic Matter in the Water-level Fluctuation Zones of Three Gorges Reservoir Areas].

    PubMed

    Chen, Xue-shuang; Jiang, Tao; Lu, Song; Wei, Shi-qiang; Wang, Ding-yong; Yan, Jin-long

    2016-03-15

    The study of the molecular weight (MW) fractions of dissolved organic matter (DOM) in aquatic environment is of interests because the size plays an important role in deciding the biogeochemical characteristics of DOM. Thus, using ultrafiltration ( UF) technique combined with three-dimensional fluorescence spectroscopy, DOM samples from four sampling sites in typical water-level fluctuation zones of Three Gorge Reservoir areas were selected to investigate the differences of properties and sources of different DOM MW fractions. The results showed that in these areas, the distribution of MW fractions was highly dispersive, but the approximately equal contributions from colloidal (Mr 1 x 10³-0.22 µm) and true dissolved fraction (Mr < 1 x 10³) to the total DOC concentration were found. Four fluorescence signals (humic-like A and C; protein-like B and T) were observed in all MW fractions including bulk DOM, which showed the same distribution trend: true dissolved > low MW (Mr 1 x 10³-10 x 10³) > medium MW (Mr 10 x 10³-30 x 10³) > high MW (Mr 30 x 10³-0.22 µm). Additionally, with decreasing MW fraction, fluorescence index (FI) and freshness index (BIX) increased suggesting enhanced signals of autochthonous inputs, whereas humification index ( HIX) decreased indicating lowe humification degree. It strongly suggested that terrestrial input mainly affected the composition and property of higher MW fractions of DOM, as compared to lower MW and true dissolved fractions that were controlled by autochthonous sources such as microbial and alga activities, instead of allochthonous sources. Meanwhile, the riparian different land-use types also affected obviously on the characteristics of DOM. Therefore, higher diversity of land-use types, and also higher complexity of ecosystem and landscapes, induced higher heterogeneity of fluorescence components in different MW fraction of DOM. PMID:27337878

  10. [Three-dimensional Fluorescence Spectral Characteristics of Different Molecular Weight Fractionations of Dissolved Organic Matter in the Water-level Fluctuation Zones of Three Gorges Reservoir Areas].

    PubMed

    Chen, Xue-shuang; Jiang, Tao; Lu, Song; Wei, Shi-qiang; Wang, Ding-yong; Yan, Jin-long

    2016-03-15

    The study of the molecular weight (MW) fractions of dissolved organic matter (DOM) in aquatic environment is of interests because the size plays an important role in deciding the biogeochemical characteristics of DOM. Thus, using ultrafiltration ( UF) technique combined with three-dimensional fluorescence spectroscopy, DOM samples from four sampling sites in typical water-level fluctuation zones of Three Gorge Reservoir areas were selected to investigate the differences of properties and sources of different DOM MW fractions. The results showed that in these areas, the distribution of MW fractions was highly dispersive, but the approximately equal contributions from colloidal (Mr 1 x 10³-0.22 µm) and true dissolved fraction (Mr < 1 x 10³) to the total DOC concentration were found. Four fluorescence signals (humic-like A and C; protein-like B and T) were observed in all MW fractions including bulk DOM, which showed the same distribution trend: true dissolved > low MW (Mr 1 x 10³-10 x 10³) > medium MW (Mr 10 x 10³-30 x 10³) > high MW (Mr 30 x 10³-0.22 µm). Additionally, with decreasing MW fraction, fluorescence index (FI) and freshness index (BIX) increased suggesting enhanced signals of autochthonous inputs, whereas humification index ( HIX) decreased indicating lowe humification degree. It strongly suggested that terrestrial input mainly affected the composition and property of higher MW fractions of DOM, as compared to lower MW and true dissolved fractions that were controlled by autochthonous sources such as microbial and alga activities, instead of allochthonous sources. Meanwhile, the riparian different land-use types also affected obviously on the characteristics of DOM. Therefore, higher diversity of land-use types, and also higher complexity of ecosystem and landscapes, induced higher heterogeneity of fluorescence components in different MW fraction of DOM.

  11. 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. PMID:24946034

  12. Insight into dissolved organic matter fractions in Lake Wivenhoe during and after a major flood.

    PubMed

    Aryal, Rupak; Grinham, Alistair; Beecham, Simon

    2016-03-01

    Dissolved organic matter is an important component of biogeochemical processes in aquatic environments. Dissolved organic matter may consist of a myriad of different fractions and resultant processing pathways. In early January 2011, heavy rainfall occurred across South East Queensland, Australia causing significant catchment inflow into Lake Wivenhoe, which is the largest water supply reservoir for the city of Brisbane, Australia. The horizontal and vertical distributions of dissolved organic matter fractions in the lake during the flood period were investigated and then compared with stratified conditions with no catchment inflows. The results clearly demonstrate a large variation in dissolved organic matter fractions associated with inflow conditions compared with stratified conditions. During inflows, dissolved organic matter concentrations in the reservoir were fivefold lower than during stratified conditions. Within the dissolved organic matter fractions during inflow, the hydrophobic and humic acid fractions were almost half those recorded during the stratified period whilst low molecular weight neutrals were higher during the flood period compared to during the stratified period. Information on dissolved organic matter and the spatial and vertical variations in its constituents' concentrations across the lake can be very useful for catchment and lake management and for selecting appropriate water treatment processes.

  13. Insight into dissolved organic matter fractions in Lake Wivenhoe during and after a major flood.

    PubMed

    Aryal, Rupak; Grinham, Alistair; Beecham, Simon

    2016-03-01

    Dissolved organic matter is an important component of biogeochemical processes in aquatic environments. Dissolved organic matter may consist of a myriad of different fractions and resultant processing pathways. In early January 2011, heavy rainfall occurred across South East Queensland, Australia causing significant catchment inflow into Lake Wivenhoe, which is the largest water supply reservoir for the city of Brisbane, Australia. The horizontal and vertical distributions of dissolved organic matter fractions in the lake during the flood period were investigated and then compared with stratified conditions with no catchment inflows. The results clearly demonstrate a large variation in dissolved organic matter fractions associated with inflow conditions compared with stratified conditions. During inflows, dissolved organic matter concentrations in the reservoir were fivefold lower than during stratified conditions. Within the dissolved organic matter fractions during inflow, the hydrophobic and humic acid fractions were almost half those recorded during the stratified period whilst low molecular weight neutrals were higher during the flood period compared to during the stratified period. Information on dissolved organic matter and the spatial and vertical variations in its constituents' concentrations across the lake can be very useful for catchment and lake management and for selecting appropriate water treatment processes. PMID:26837382

  14. Natural versus wastewater derived dissolved organic carbon: implications for the environmental fate of organic micropollutants.

    PubMed

    Neale, Peta A; Antony, Alice; Gernjak, Wolfgang; Leslie, Greg; Escher, Beate I

    2011-08-01

    The interaction of organic micropollutants with dissolved organic carbon (DOC) can influence their transport, degradation and bioavailability. While this has been well established for natural organic carbon, very little is known regarding the influence of DOC on the fate of micropollutants during wastewater treatment and water recycling. Dissolved organic carbon-water partition coefficients (K(DOC)) for wastewater derived and reference DOC were measured for a range of micropollutants using a depletion method with polydimethylsiloxane disks. For micropollutants with an octanol-water partition coefficient (log K(OW)) greater than 4 there was a significant difference in K(DOC) between reference and wastewater derived DOC, with partitioning to wastewater derived DOC over 1000 times lower for the most hydrophobic micropollutants. The interaction of nonylphenol with wastewater derived DOC from different stages of a wastewater and advanced water treatment train was studied, but little difference in K(DOC) was observed. Organic carbon characterisation revealed that reference and wastewater derived DOC had very different properties due to their different origins. Consequently, the reduced sorption capacity of wastewater derived DOC may be related to their microbial origin which led to reduced aromaticity and lower molecular weight. This study suggests that for hydrophobic micropollutants (log K(OW) > 4) a higher concentration of freely dissolved and thus bioavailable micropollutants is expected in the presence of wastewater derived DOC than predicted using K(DOC) values quantified using reference DOC. The implication is that naturally derived DOC may not be an appropriate surrogate for wastewater derived DOC as a matrix for assessing the fate of micropollutants in engineered systems. PMID:21703657

  15. 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…

  16. 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.

  17. Trophic complexity in aqueous systems: bacterial species richness and protistan predation regulate dissolved organic carbon and dissolved total nitrogen removal.

    PubMed

    Saleem, Muhammad; Fetzer, Ingo; Harms, Hauke; Chatzinotas, Antonis

    2016-02-24

    Loading of water bodies with dissolved organic carbon (DOC) and dissolved total nitrogen (DTN) affects their integrity and functioning. Microbial interactions mitigate the negative effects of high nutrient loads in these ecosystems. Despite numerous studies on how biodiversity mediates ecosystem functions, whether and how diversity and complexity of microbial food webs (horizontal, vertical) and the underlying ecological mechanisms influence nutrient removal has barely been investigated. Using microbial microcosms accommodating systematic combinations of prey (bacteria) and predator (protists) species, we showed that increasing bacterial richness improved the extent and reliability of DOC and DTN removal. Bacterial diversity drove nutrient removal either due to species foraging physiology or functional redundancy, whereas protistan diversity affected nutrient removal through bacterial prey resource partitioning and changing nutrient balance in the system. Our results demonstrate that prey-predator diversity and trophic interactions interactively determine nutrient contents, thus implying the vital role of microbial trophic complexity as a biological buffer against DOC and DTN.

  18. Trophic complexity in aqueous systems: bacterial species richness and protistan predation regulate dissolved organic carbon and dissolved total nitrogen removal.

    PubMed

    Saleem, Muhammad; Fetzer, Ingo; Harms, Hauke; Chatzinotas, Antonis

    2016-02-24

    Loading of water bodies with dissolved organic carbon (DOC) and dissolved total nitrogen (DTN) affects their integrity and functioning. Microbial interactions mitigate the negative effects of high nutrient loads in these ecosystems. Despite numerous studies on how biodiversity mediates ecosystem functions, whether and how diversity and complexity of microbial food webs (horizontal, vertical) and the underlying ecological mechanisms influence nutrient removal has barely been investigated. Using microbial microcosms accommodating systematic combinations of prey (bacteria) and predator (protists) species, we showed that increasing bacterial richness improved the extent and reliability of DOC and DTN removal. Bacterial diversity drove nutrient removal either due to species foraging physiology or functional redundancy, whereas protistan diversity affected nutrient removal through bacterial prey resource partitioning and changing nutrient balance in the system. Our results demonstrate that prey-predator diversity and trophic interactions interactively determine nutrient contents, thus implying the vital role of microbial trophic complexity as a biological buffer against DOC and DTN. PMID:26888033

  19. 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

  20. Data on natural organic substances in dissolved, colloidal, suspended-silt and -clay, and bed-sediment phases in the Mississippi River and some of its tributaries, 1987-90

    USGS Publications Warehouse

    Leenheer, J.A.; Noyes, T.I.; Brown, P.A.

    1994-01-01

    The Mississippi River and some of its tributaries were sampled for natural organic substances dissolved in water and in suspended and bed sediments during seven sampling cruises from 1987-90. The sampling cruises were made during different seasons, in the free-flowing reaches of the river from St. Louis, Missouri, to New Orleans, Louisiana. The first three cruises were made during low-water conditions, and the last four cruises during high-water conditions. The purpose for sampling and characterizing natural organic substances in the various phases in the river was to provide an understanding of how these substances facilitate contaminant transport and transformations in the Mississippi River. Significant conclusions of this study were: (1) Natural organic substances appear to stabilize ' certain colloids against aggregation; therefore, these colloids remain in suspension and can act as transport agents that are not affected by sedimentation. Bacteria were found to be a significant fraction of organic colloids. (2) A new class of organic contaminants (polyethylene glycols) derived from nonionic surfactant residues was discovered dissolved with natural organic substances in water. These polyethylene glycols have the potential to affect both organic and inorganic contaminant transport in water. (3) The entire dissolved organic-matter component under varying hydrologic and seasonal conditions was characterized. (4) A method was developed to characterize organic matter in sediment by solid-state, 13C-nuclear magnetic resonance spectrometry. (5) The organic matter in suspended sediments was characterized by a variety of spectral and nonspectral methods. The protein component (significant in trace-metal binding) and lipid component (significant in organic-contaminant binding) were found to be major constituents in natural organic matter in suspended sediment. (6) Pools are reservoirs acting as traps of sedimentary organic matter of allochthonous origin and export

  1. 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.

  2. 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.

  3. Cosorption study of organic pollutants and dissolved organic matter in a soil.

    PubMed

    Flores-Céspedes, F; Fernández-Pérez, M; Villafranca-Sánchez, M; González-Pradas, E

    2006-08-01

    In this study we have evaluated the effects of dissolved organic matter (DOM) on sorption of imidacloprid, 3,4-dichloroaniline (3,4-DCA) and 4-bromoaniline (4-BA) on a typical calcareous soil (Luvic Xerosol) from south-eastern Spain. Two different types of DOM were used, that is to say, dissolved natural organic matter extracts from a commercial peat (DNOM) and a high-purity tannic acid (TA) solution. The experiments were carried out in a 0.01 M CaCl2 aqueous medium at 25 degrees C. The results indicated that the presence of both DNOM and TA, over a concentration range of 15-100 mg L(-1), produced an increase in the amount of 3,4-DCA and 4-BA sorbed and a decrease in the amount of imidacloprid retained on the soil studied. A modified distribution coefficient, K(doc), has been proposed as a safer parameter for soil sorption predictions of organic pollutants and it could be of help to model the fate of these in the environment.

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

    PubMed

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

    2012-10-15

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

  5. 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 ...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  7. 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.

  8. 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...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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)...

  10. 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 ...

  11. 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...

  12. 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...

  13. 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...

  14. 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.

  15. 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.

  16. Chromatographic methods for the isolation, separation and characterisation of dissolved organic matter.

    PubMed

    Sandron, Sara; Rojas, Alfonso; Wilson, Richard; Davies, Noel W; Haddad, Paul R; Shellie, Robert A; Nesterenko, Pavel N; Kelleher, Brian P; Paull, Brett

    2015-09-01

    This review presents an overview of the separation techniques applied to the complex challenge of dissolved organic matter characterisation. The review discusses methods for isolation of dissolved organic matter from natural waters, and the range of separation techniques used to further fractionate this complex material. The review covers both liquid and gas chromatographic techniques, in their various modes, and electrophoretic based approaches. For each, the challenges that the separation and fractionation of such an immensely complex sample poses is critically reviewed. PMID:26290053

  17. Chromatographic methods for the isolation, separation and characterisation of dissolved organic matter.

    PubMed

    Sandron, Sara; Rojas, Alfonso; Wilson, Richard; Davies, Noel W; Haddad, Paul R; Shellie, Robert A; Nesterenko, Pavel N; Kelleher, Brian P; Paull, Brett

    2015-09-01

    This review presents an overview of the separation techniques applied to the complex challenge of dissolved organic matter characterisation. The review discusses methods for isolation of dissolved organic matter from natural waters, and the range of separation techniques used to further fractionate this complex material. The review covers both liquid and gas chromatographic techniques, in their various modes, and electrophoretic based approaches. For each, the challenges that the separation and fractionation of such an immensely complex sample poses is critically reviewed.

  18. 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.

  19. 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 ...

  20. 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.

  1. 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

    2012-10-01

    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. PMID:22475414

  2. Tracking the monthly changes of dissolved organic matter composition in a newly constructed reservoir and its tributaries during the initial impounding period.

    PubMed

    Chen, Meilian; He, Wei; Choi, Ilhwan; Hur, Jin

    2016-01-01

    Understanding the roles of inland reservoirs becomes increasingly important with respect to global carbon cycling as well as water resource management due to the unprecedented demand for construction in recent decades. In this study, the dissolved organic matter (DOM) quantity and quality in a newly constructed dam reservoir and its tributaries were monitored monthly during the initial impounding period (July to November 2014) using a size exclusion chromatography (SEC) with online organic carbon detector (OCD). The highest values were observed in the month of August with the highest precipitation for the bulk dissolved organic carbon (DOC), specific UV absorbance (SUVA), and most of the assigned size fractions (except for biopolymers) in the tributaries, indicating that allochthonous sources of DOM were dominant in the feeding stream waters of the reservoir. The bulk DOC and high molecular weight humic substance fraction (∼1 kDa) were generally co-varied with the monthly precipitation in the tributaries, while building blocks (350-500 Da), and low molecular weight (LMW) acids and neutrals showed different trends. In a dam site, the smaller molecular fractions became more abundant during the dry season (September to November), presumably due to the in-reservoir processes such as photo- and bio-degradation. Our results also revealed that storms mobilized a large amount of highly aromatic soil-derived DOM to the reservoir. A depth profile at the dam site showed the water is well mixed up to a depth of ∼20 m. The SEC-OCD data coupled with non-metric multidimensional scaling provided a clear visualization of the spatiotemporal variations in DOM composition, which shed new light on the DOM composition formed in a newly constructed dam reservoir and also on the strategies for future water treatment options.

  3. [Photobleaching of dissolved organic matter (DOM) from confluence of two rivers under natural solar radiation: a case study of Fujiang River-Jialingjiang River].

    PubMed

    Gao, Jie; Jiang, Tao; Yan, Jin-long; Wei, Shi-qiang; Wang, Ding-yong; Lu, Song; Li, Lu-lu

    2014-09-01

    Three-dimensional fluorescence spectroscopy combined with ultraviolet-visible absorption spectra was used to investigate the photobleaching process of dissolved organic matter (DOM) sampled from Fujiang River (FJ), Jialingjiang River (JLJ) and the confluence (FJ-JLJ) under natural solar radiation. The results indicated that obvious photochemical degradation of colored dissolved organic matter (CDOM) concentration [ α(280) ] and all fluorescence peaks intensity (A, C, M and T) occurred under natural solar radiation, and the degradation degree was in order of JLJ > FJ-JLJ > FJ. Photobleaching properties of DOM samples from different locations showed significant differences, which could be partially explained by the sampling sites surroundings including various landuse types, and dilution effect of river confluence. Light-induced bleaching activity of JLJ samples, which was mainly terrestrial input from forest system, was the highest as compared to the lowest activity of FJ samples, which was predominated by urban inputs. Samples from confluence were in the middle. Additionally, the spectrum slope(S) and absorbance ratio (A250/A350) were increased, while the humification index(HIX) was decreased with increasing irradiation time, which can be used as important indicators for photobleaching properties changes during the process. More importantly, the predominantly allochthonous (terrigenous) characteristics of DOM almost showed a tendency of transferring to autochthonous (authigenic) characteristics due to photobleaching. Especially, IT/Ic firstly decreased and then increased significantly in the process. Thus the photodegradation process may exaggerate DOM autochthonous contribution, and further interfere with the assessment of anthropogenic impacted-water quality by using IT/Ic. In addition, mechanisms of light-induced DOM degradation process consistently showed by absorption and fluorescence spectrum parameters suggested the validation of analyzing DOM geochemical

  4. Algal extracellular release in river-floodplain dissolved organic matter: response of extracellular enzymatic activity during a post-flood period

    PubMed Central

    Sieczko, Anna; Maschek, Maria; Peduzzi, Peter

    2015-01-01

    River-floodplain systems are susceptible to rapid hydrological events. Changing hydrological connectivity of the floodplain generates a broad range of conditions, from lentic to lotic. This creates a mixture of allochthonously and autochthonously derived dissolved organic matter (DOM). Autochthonous DOM, including photosynthetic extracellular release (PER), is an important source supporting bacterial secondary production (BSP). Nonetheless, no details are available regarding microbial extracellular enzymatic activity (EEA) as a response to PER under variable hydrological settings in river-floodplain systems. To investigate the relationship between bacterial and phytoplankton components, we therefore used EEA as a tool to track the microbial response to non-chromophoric, but reactive and ecologically important DOM. The study was conducted in three floodplain subsystems with distinct hydrological regimes (Danube Floodplain National Park, Austria). The focus was on the post-flood period. Enhanced %PER (up to 48% of primary production) in a hydrologically isolated subsystem was strongly correlated with β-glucosidase, which was related to BSP. This shows that—in disconnected floodplain backwaters with high terrestrial input—BSP can also be driven by autochthonous carbon sources (PER). In a semi-isolated section, in the presence of fresh labile material from primary producers, enhanced activity of phenol oxidase was observed. In frequently flooded river-floodplain systems, BSP was mainly driven by enzymatic degradation of particulate primary production. Our research demonstrates that EEA measurements are an excellent tool to describe the coupling between bacteria and phytoplankton, which cannot be deciphered when focusing solely on chromophoric DOM. PMID:25741326

  5. Metabolic and physiochemical responses to a whole-lake experimental increase in dissolved organic carbon in a north-temperate lake

    USGS Publications Warehouse

    Zwart, Jacob A.; Craig, Nicola; Kelly, Patrick T.; Sebestyen, Stephen D.; Solomon, Christopher T.; Weidel, Brian C.; Jones, Stuart E.

    2016-01-01

    Over the last several decades, many lakes globally have increased in dissolved organic carbon (DOC), calling into question how lake functions may respond to increasing DOC. Unfortunately, our basis for making predictions is limited to spatial surveys, modeling, and laboratory experiments, which may not accurately capture important whole-ecosystem processes. In this article, we present data on metabolic and physiochemical responses of a multiyear experimental whole-lake increase in DOC concentration. Unexpectedly, we observed an increase in pelagic gross primary production, likely due to a small increase in phosphorus as well as a surprising lack of change in epilimnetic light climate. We also speculate on the importance of lake size modifying the relationship between light climate and elevated DOC. A larger increase in ecosystem respiration resulted in an increased heterotrophy for the treatment basin. The magnitude of the increase in heterotrophy was extremely close to the excess DOC load to the treatment basin, indicating that changes in heterotrophy may be predictable if allochthonous carbon loads are well-constrained. Elevated DOC concentration also reduced thermocline and mixed layer depth and reduced whole-lake temperature. Results from this experiment were quantitatively different, and sometimes even in the opposite direction, from expectations based on cross-system surveys and bottle experiments, emphasizing the importance of whole-ecosystem experiments in understanding ecosystem response to environmental change.

  6. 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...

  7. 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 ...

  8. Abiotic effects on effluent dissolved organic nitrogen along an estuarine transect.

    PubMed

    Funkey, Carolina P; Latour, Robert J; Bronk, Deborah A

    2015-03-01

    Biological nutrient removal is a process commonly used in water resource recovery facilities to reduce dissolved inorganic nitrogen (DIN) concentrations in effluent; this process is less effective at removing all of the effluent dissolved organic nitrogen (EDON). The goal of this study was to investigate the fate of EDON after it undergoes the disinfection process and enters receiving waters. The authors quantified the abiotic effects of effluent exposure to sunlight, increased salinity, and a combination of the two factors. Effluent dissolved organic nitrogen showed significant breakdown during the disinfection process (UV and chlorine) and when exposed to sunlight and increasing salinity. Approximately 7% of the EDON was transformed to DIN and dissolved primary amines after exposure to 9 hours of sunlight and a salinity increase from 0 to 33. The production of DIN and primary amines should be taken into account when considering sources of labile nitrogen to aquatic ecosystems.

  9. 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

  10. 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...

  11. Contribution of Allochthonous Carbon Subsidies to the Minho Estuary Lower Food Web

    EPA Science Inventory

    To study the contribution of autochthonous and allochthonous organic matter (OM) sources fuelling the lower food web in Minho River estuary (N-Portugal, Europe), we characterized the carbon (?13C) and nitrogen (?15N) stable isotope ratios of zooplankton and their potential OM sou...

  12. Contribution of Allochthonous Carbon to American Shad Production in the Mattaponi River, Virginia, Using Stable Isotopes

    EPA Science Inventory

    Our objective was to quantify the contribution of autochthonous, locally-produced phytoplankton, and allochthonous, terrestrial-derived organic matter (OM) to the production of young-of-year (YOY) American shad using stable isotopes...The results suggest an important link between...

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

    PubMed

    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.

  14. 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

  15. 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.

  16. 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.

  17. Lithotectonic units in the Golconda allochthon, Nevada

    SciTech Connect

    Tomlinson, A.J. ); Murchey, B.L. )

    1991-02-01

    The Golconda allochthon can be divided into several regional lithotectonic units. Each consists of an imbricate thrust stack of similar, but variably deformed, depositional sequences and represents a paleogeographic-depositional province of the basin(s) that existed prior to the Sonoma orogeny. At least four lithotectonic units are recognized. (1) An eastern unit consists of Upper Mississippian( ) to Middle Pennsylvanian chert, Middle Pennsylvanian to Lower Permian argillite and calcarenite turbidites, and Permian phosphatic sandstones, calcarenites, and chert. (2) The second unit consists of Middle Pennsylvanian greenstone, Middle Pennsylvanian to Lower Permian argillite and minor chert, middle Leonardian calcarenite, upper Leonardian chert and minor phosphatic, chert- and volcanic-lithic-rich sandstone, and Upper Permian sponge spicule chert turbidites. (3) The third unit consists of Lower Mississippian basalts, Upper Mississippian to Middle Pennsylvanian clastic rocks and radiolarian chert, and Lower Permian calcarenites and calcareous sandstone. (4) The fourth unit consists of Mississippian to permian volcaniclastic rock-bearing sections. Units 1, 2 and 3 have rocks indicating they were deposited within or adjacent to the continental margin. Rocks in unit 4 have a volcanic terrane affinity. In each lithotectonic unit the youngest rocks of Leonardian or Guadalupian age are involved n the deformation and are conformable or paraconformable on older rocks indicated the shortening history in the allochthon is entirely post-deposition and represents a short-lived Permian-Triassic event.

  18. 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,...

  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. Anthropogenic impacts on the optical characteristics and biodegradability of dissolved and particulate organic matter in the Han River watershed, South Korea

    NASA Astrophysics Data System (ADS)

    Shirina Begum, Most; Jin, Hyojin; Yoon, Tae Kyung; Park, Ji-Hyung

    2016-04-01

    To understand how anthropogenic perturbations such as dams and pollution modify the chemical characteristics and biological transformations of riverine organic matter during transit through urbanized watersheds, we compared the optical characteristics and biodegradability of dissolved organic matter (DOM) and particulate organic matter (POM) along different reaches and urban tributary streams of the Han River watershed during short-term incubations. Laboratory incubations were conducted for 5-7 days at 20-25 oC with filtered or unfiltered water samples collected from up-, mid-, and downstream reaches with different levels of anthropogenic perturbations and three urban streams along the downstream reach that receive effluents from waste water treatment facilities in the metropolitan Seoul. Optical parameters such as ultraviolet absorbance at 254 nm, absorption coefficients at 254 nm and 350 nm, fluorescence index, humic-like fluorescence, microbial humic-like fluorescence, and protein-like fluorescence, and spectral slope at 350-400 nm were significantly correlated with increasing concentration of biodegradable dissolved organic carbon (BDOC) in filtered and unfiltered sample along the Han River up-, mid-, down-, and urban streams. The concentrations of BDOC in the urban streams were 6-12 times higher than in the filtered and unfiltered main-stem river samples, with significantly higher values in presence of POM in the unfiltered samples than in the filtered samples. In a separate 5-day incubation experiment with the unfiltered water sample from a downstream location of the Han River and its urban tributary water in isolation or mixed , the rate of concurrent biodegradation of both DOM and POM, as measured by the cumulative rate of CO2 production, was higher in the mixture than the average rate of the separately incubated samples, indicating the priming effect of mixed organic materials on the biodegradation of allochthonous organic materials from the other site

  1. An Automated Method for the Optical Characterization of Dissolved Organic Matter in a Rapidly Suburbanizing Watershed, Southeastern New Hampshire

    NASA Astrophysics Data System (ADS)

    Gettel, G. M.; McDowell, W.; Pisani, O.

    2006-12-01

    Dissolved organic matter (DOM) is exported from watersheds to downstream ecosystems where it can contribute to eutrophication problems by enhancing microbial respiration and lowering oxygen levels. DOM quality affects microbial respiration; however, little is known about how watershed processes affect the quality of DOM export. In order to document temporal and spatial variability in DOM quality at the watershed scale, we are developing a method to automate the optical characterization of DOM in the Lamprey River watershed in southeastern New Hampshire. This method employs a refrigerated autosampler and column heater associated with a Shimadzu high-pressure liquid chromatograph (HPLC) with a photo-diode array (PDA) UV absorbance detector and an in-line Horiba Jobin Yvon Fluoromax 3 fluorometer capable of 3D excitation- emission scans (EEM). One advantage of this method is that the HPLC flow-through cell in the fluorometer reduces inner-filter effects due to its small volume. Furthermore, specific UV absorbance or SUVA can also be calculated because an in-line UV PDA is used. We found that a number of fluorescence indices are related to DOC, DON, or NO3 concentrations throughout the Lamprey River watershed. For example, Fluorescence Index (F.I.), an indicator of autochthonous sources of DOM, is positively correlated with nitrate and negatively correlated with DOC concentrations (R2=0.95; p<0.01; R2=0.86; p<0.05 respectively). The highest F.I. occurred in the highest-population density sub-basin with the highest nitrate concentrations, while the lowest F.I. occurred in the lowest-population density sub-basin with highest DOC concentrations. These results indicate that nitrate may increase within-stream generation of DOC at high- population sites while DOC from low-population, low-nitrate sites is predominately allochthonous. This allows DOM characterization to be performed in conjunction with weekly and monthly monitoring of many water quality parameters and to be

  2. Optical Characterization and Spatial Distribution of Dissolved Organic Matter (DOM) in Seven Water Bodies of Mississippi, USA

    NASA Astrophysics Data System (ADS)

    Singh, S.; Dash, P.; Moorhead, R.

    2015-12-01

    Lakes and estuaries can serve as indicators of overall health of terrestrial and aquatic ecosystems. The characteristics of dissolved organic matter (DOM) in these water bodies provide insights into the biogeochemical processes undergoing at the source, during transport and in the water bodies. Land use and land cover plays not only a significant role in controlling the quantity of the exported DOM, but also influences the quality of DOM via various biogeochemical and biodegradation processes. We investigated the characteristics and spatial distribution of DOM in five major lakes - Sardis, Enid, Grenada, Okatibbee, and Ross Barnett Reservoir (RBR), an estuary, the Lower Pearl River (LPR) Estuary, and a coastal region, Grand Bay, in the state of Mississippi, USA. Water samples from the lakes and Grand Bay were collected during the summer of 2012-2014 while samples from LPR were collected during winter 2014 and spring 2015. We employed absorption and fluorescence spectroscopy including excitation emission matrix (EEM) combined with parallel factor analysis (PARAFAC) modeling techniques to determine optical properties of DOM and its characteristics in these study sites. A site-specific PARAFAC model was developed to evaluate DOM characteristics, which resulted in five diverse DOM compositions including two terrestrial humic-like, two microbial humic-like, and one protein-like DOM. The lakes and Grand Bay region showed high concentrations of microbial humic-like or protein-like DOM fluorescence signatures while the samples from LPR Estuary and the RBR showed relatively high concentration of terrestrial humic-like DOM. Moreover, we also observed strong correlations between microbial humic-like DOM (PARAFAC derived) and DOM indices such as biological/freshness and fluorescence indices (EEM based). DOM in the lakes indicated autochthonous characteristics predominantly probably because of photochemical degradation while the LPR Estuary and the RBR samples showed mainly

  3. Seasonal Changes in Estuarine Dissolved Organic Matter Due to Variations in Discharge, Flushing Times and Wind-driven Mixing Events

    NASA Astrophysics Data System (ADS)

    Dixon, Jennifer Louise

    Estuaries are highly productive habitats that transport and transform organic matter (OM), experience large changes in ionic composition and act as a transition zone between terrestrial and marine environments (Paerl et al. 1998; Markager et al. 2011; Osburn et al. 2012). OM source and matrix effects (such as salinity and pH) influence the chemical structure of DOM in estuaries and therefore affect its bioavailability, photo-reactivity, and its overall fate in these systems (Jaffe et al. 2004; Boyd et al. 2010; Pace et al. 2012; Osburn et al. 2012; Cawley et al. 2013). Within estuaries, dissolved organic matter (DOM) is a heterogeneous mixture of aromatic and aliphatic compounds, and its composition in aquatic systems varies spatially and temporally with source (Bauer and Bianchi 2011). However, the main source of DOM in estuaries, rivers and other aquatic systems, originates from vascular plant detritus, soil humus, older fossil (i.e., petrogenic) organic carbon, black carbon, marine OM and in situ production (Hedges 2002; Houghton 2007; Bauer and Bianchi 2011). Chromophoric dissolved organic matter (CDOM), the light absorbing fraction of DOM, can be characterized using optical methods such as absorption and fluorescence spectroscopy (e.g. Coble, 1996; Stedmon and Markager, 2003). By analyzing the spatial and temporal variability of DOM and CDOM within estuaries, information pertaining to OM source and fate across the freshwater-marine continuum can be obtained. These methods offer an inexpensive, non-destructive means for obtaining sensitive measurements of a diverse group of organic compounds. By using this technology to analyze the spatial and temporal variability of CDOM within estuaries, information pertaining to OM source and fate across the freshwater-marine continuum can be obtained (Fellman et al. 2011; Osburn et al. 2012; Murphy et al. 2014). Chemical biomarkers are also routinely used to identify DOM sources in coastal waters. Examples are carbon stable

  4. Predicting dissolved organic nitrogen export from a drained loblolly pine plantation

    NASA Astrophysics Data System (ADS)

    Tian, Shiying; Youssef, Mohamed A.; Skaggs, R. Wayne; Chescheir, G. M.; Amatya, Devendra M.

    2013-04-01

    Dissolved organic nitrogen (DON) export from terrestrial ecosystems influences the ecology of receiving surface waters. The soil carbon (C) and nitrogen (N) model, DRAINMOD-N II, was modified to simulate key processes associated with DON transformations and transport in the soil profile. DON production is modeled by tracking dynamic C:N ratios of dissolved organic matter originating from various organic matter pools. The Langmuir isotherm was used to quantify the assumed instantaneous equilibrium between potentially soluble organic N in solid and aqueous phases. DON transport with soil water was simulated using a numerical solution to the advection-dispersion reaction equation. The modified model was used for simulating temporal variations of DON export from three loblolly pine (Pinus taeda L.) plantations located in eastern North Carolina. Results showed that the model can accurately predict DON export dynamics during storm events with Nash-Sutcliffe efficiency (E) of 0.5, seasonal DON losses with E above 0.6, and annual DON losses with E above 0.7. In addition to the well-recognized role of hydrological processes, reasonable quantifications of the seasonal changes in the potentially soluble soil organic matter, the DON sorption to soil particles, and the dynamic C:N ratios of dissolved organic matter were found to be essential for mechanistic representation of DON export dynamics. Specifically, adapting the dynamic C:N ratios enabled the model to reasonably describe the temporal variations of correlations between DON and dissolved organic carbon in drainage water.

  5. 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.

  6. 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.

  7. Spatial variability in chromophoric dissolved organic matter for an artificial coastal lake (Shiwha) and the upstream catchments at two different seasons.

    PubMed

    Phong, Diep Dinh; Lee, Yeonjung; Shin, Kyung-Hoon; Hur, Jin

    2014-06-01

    Selected water quality parameters and spectroscopic characteristics of dissolved organic matter (DOM) were examined during two different seasons for an artificial coastal lake (Shiwha Lake in South Korea), which are affected by seawater exchange due to the operation of a tidal power plant and external organic loadings from the upstream catchments. The coastal lake exhibited much lower concentrations of organic matter and nutrients than the upstream sources. The spectroscopic properties of the lake DOM were easily distinguished from those of the catchment sources as revealed by a lower absorption coefficient, lower degree of humification, and higher spectral slopes. The observed DOM properties suggest that the lake DOM may be dominated by smaller molecular size and less condensed structures. For the lake and the upper streams, higher absorption coefficients and fluorescence peak intensities but lower spectral slopes and humification index were found for the premonsoon versus the monsoon season. However, such seasonal differences were less pronounced for the industrial channels in the upper catchments. Three distinctive fluorophore groups including microbial humic-like, tryptophan-like, and terrestrial humic-like fluorescence were decomposed from the fluorescence excitation-emission matrix (EEM) of the DOM samples by parallel factor analysis (PARAFAC) modeling. The microbial humic-like component was the most abundant for the industrial channels, suggesting that the component may be associated with anthropogenic organic pollution. The terrestrial humic-like component was predominant for the upper streams, and its relative abundance was higher for the rainy season. Our principal component analysis (PCA) results demonstrated that exchange of seawater and seasonally variable input of allochthonous DOM plays important roles in determining the characteristics of DOM in the lake. PMID:24622988

  8. Importance of microbial soil organic matter processing in dissolved organic carbon production.

    PubMed

    Malik, Ashish; Gleixner, Gerd

    2013-10-01

    Soil dissolved organic carbon (DOC) sources and its seasonal dynamics are poorly known. We aimed to determine the contribution of plant and soil organic matter (SOM) to size classes of DOC in a field experiment with C3 to C4 vegetation change on two soil types through different seasons. Stable isotope ratios of DOC size classes were measured using size exclusion chromatography (SEC) coupled online to liquid chromatography-isotope ratio mass spectrometry (LC-IRMS). SEC resolved DOC into three size classes: very high molecular weight/vHMW (> 10 kDa), high molecular weight/HMW (0.4-10 kDa), and low molecular weight/LMW (< 0.4 kDa). HMW DOC was most abundant in all seasons, soil types, and depths. In contrast, vHMW DOC was only seen postsnowmelt in upper 20 cm and was mainly (87 ± 9%) plant-derived. Through all seasons, HMW and LMW DOC had less than 30% recent plant contribution. Similar size range and source of DOC size classes and soil chloroform fumigation extracts suggest microbial origin of DOC. Thus, microbial SOM recycling is an important process in DOC production. We suggest that DOC molecules get partitioned manifold between soil solution and the mineral matrix (chromatography), thereby getting constantly decomposed, altered, or produced anew by soil microorganisms (reactive transport).

  9. Qualitative changes of riverine dissolved organic matter at low salinities due to flocculation

    NASA Astrophysics Data System (ADS)

    Asmala, Eero; Bowers, David G.; Autio, Riitta; Kaartokallio, Hermanni; Thomas, David N.

    2014-10-01

    The flocculation of dissolved organic matter (DOM) was studied along transects through three boreal estuaries. Besides the bulk concentration parameters, a suite of DOM quality parameters were investigated, including colored DOM (CDOM), fluorescent DOM, and the molecular weight of DOM as well as associated dissolved iron concentrations. We observed significant deviations from conservative mixing at low salinities (<2) in the estuarine samples of dissolved organic carbon (DOC), UV absorption (a(CDOM254)), and humic-like fluorescence. The maximum deviation from conservative mixing for DOC concentration was -16%, at salinities between 1 and 2. An associated laboratory experiment was conducted where an artificial salinity gradient between 0 and 6 was created. The experiment confirmed the findings from the estuarine transects, since part of the DOC and dissolved iron pools were transformed to particulate fraction (>0.2 µm) and thereby removing them from the dissolved phase. We also measured flocculation of CDOM, especially in the UV region of the absorption spectrum. Protein-like fluorescence of DOM decreased, while humic-like fluorescence increased because of salt-induced flocculation. Additionally, there was a decrease in molecular weight of DOM. Consequently, the quantity and quality of the remaining DOM pool was significantly changed after influenced to flocculation. Based on these results, we constructed a mechanistic, two-component flocculation model. Our findings underline the importance of the coastal filter, where riverine organic matter is flocculated and exported to the sediments.

  10. Spatial and temporal variations of dissolved organic matter dynamics in a disturbed Sphagnum peatland after hydrological restoration

    NASA Astrophysics Data System (ADS)

    Le Moing, Franck; Guirimand-Dufour, Audrey; Jozja, Nevila; Defarge, Christian; D'Angelo, Benoît; Binet, Stéphane; Gogo, Sébastien; Laggoun, Fatima

    2015-04-01

    Peatlands contain a third of the world soil C in spite of their relatively low global area (3% of land area). They can become sources of C because of human disturbances such as drainage. The aim of this work is to assess the effect of an hydrological restoration on a disturbed Sphagnum peatland. It concerns spatial and temporal variations of dissolved organic matter (DOM) dynamics. The investigated site was La Guette peatland (France, N 47°19'44', E 2°17'04', alt. 154m), whose hydrological conditions are influenced by a road passing through its former area. The road drain accelerates drying mechanisms, favouring thus vascular plants settlement to the detriment of specific flora of peatlands (i.e. Sphagnum). Hydrological restoration was undertaken in February 2014. It consisted in building thresholds to slow down drain runoff and to promote the soil rewetting. Two transects of piezometers were settled in independent two hydrological sub-systems: Trans-up and Trans-down. Trans-down is supposed to be influenced by the hydrological restoration, while Trans-up is not. These transects cross the peatland and follow water flow direction until the outlet. Six sampling campaigns were performed before, during and after the vegetation period. Water conductivity and pH were measured on site. Water samples were collected in the piezometers. Samples were filtered in the field at 0.45 μm. Concentrations of dissolved organic carbon (DOC), cations (Na+, K+, Ca2+, Mg2+, NH4+) and anions (Cl-, SO42-, PO43-, NO2-, NO3-) were measured. Absorbance was measured by UV-VIS spectrophotometer to assess SUVA254 and aromaticity of DOM. Three-dimensional excitation-emission matrices (EEM) were undertaken to characterise fluorescent DOM (FDOM). Humification (HIX) and biological (BIX) fluorescence indices were calculated. PARAFAC algorithm was used to treat EEMs. Precipitations and water levels were measured automatically by a weather station and automatic probes, respectively. Rain water was

  11. 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.

  12. 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

  13. 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

  14. Results of the 2008 dissolved organic matter fluorescence intercalibration study

    NASA Astrophysics Data System (ADS)

    Murphy, K. R.; Butler, K.; Spencer, R. G.; Boehme, J.; Aiken, G.

    2009-12-01

    In 2008, 20 laboratories around the world participated in an intercalibration study of organic matter fluorescence measurements via Excitation-Emission Matrix Spectroscopy (EEMS). The goal was to assess the variability of fluorescence measurements obtained for identical samples (n = 5 natural samples, Suwanee River Fulvic Acid, quinine sulphate and four Starna Fluorescence Reference cells) by different laboratories, and to examine potential sources of this variability. Operator error was found to be a significant source of variability, with 6 laboratories submitting erroneous EEMs in an initial round. Uncorrected EEMs were significantly different from corrected EEMs, particularly at relatively low and relatively high excitation (λex) and emission (λem) wavelengths. When data from each lab were corrected according to a standard set of algorithms, the variability between EEMs for the same sample measured by different labs was wavelength dependent, with EEMs normalized to raman areas more similar at low λex and λem, and EEMs normalized to quinine sulphate equivalents more similar at higher wavelengths. The results confirm the importance of (1) applying spectral corrections prior to comparing fluorescence data acquired on different instruments, (2) full reporting of correction procedures and implementation according to an agreed standard protocol, and (3) strict implementation of quality assurance protocols prior to reporting EEMs.

  15. 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

  16. 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 PMID:22894106

  17. 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.

  18. Pyrolysis temperature-dependent release of dissolved organic carbon from plant, manure, and biorefinery wastes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  19. 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...

  20. Response to Comment on “Dilution limits dissolved organic carbon utilization in the deep ocean”

    NASA Astrophysics Data System (ADS)

    Arrieta, Jesús M.; Mayol, Eva; Hansman, Roberta L.; Herndl, Gerhard J.; Dittmar, Thorsten; Duarte, Carlos M.

    2015-12-01

    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.

  1. 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...

  2. 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...

  3. 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 ...

  4. Organic carbon and dissolved oxygen budgets for a commerical-size, in-pond raceway system

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  5. ESTIMATING THE POTENTIAL FOR FACILITATED TRANSPORT OF NAPROPAMIDE BY DISSOLVED ORGANIC MATTER

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dissolved organic matter (DOM) has been found to significantly affect the soil sorption/desorption of napropamide [2-(a-naphthoxy-N, N-diethylpropionamide] and to enhance its transport through soil columns. A method to qualitatively predict if DOM will enhance the transport of napropamide based on e...

  6. 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.

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. Dissolved Organic Nitrogen Hydrolysis Rates in Axenic Cultures of Aureococcus anophagefferens (Pelagophyceae): Comparison with Heterotrophic Bacteria

    PubMed Central

    Berg, Gry Mine; Repeta, Daniel J.; Laroche, Julie

    2002-01-01

    The marine autotroph Aureococcus anophagefferens (Pelagophyceae) was rendered axenic in order to investigate hydrolysis rates of peptides, chitobiose, acetamide, and urea as indicators of the ability to support growth on dissolved organic nitrogen. Specific rates of hydrolysis varied between 8 and 700% of rates observed in associated heterotrophic marine bacteria. PMID:11772651

  12. 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...

  13. 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...

  14. 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.

  15. 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

  16. 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

  17. 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.

  18. 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...

  19. Relative copper binding capacities of dissolved organic compounds in a coastal-plain estuary. [Thalassiosira pseudonana

    SciTech Connect

    Newell, A.D.; Sanders, J.G.

    1986-08-01

    Naturally occurring organics in samples taken from the mesohaline portion of a Chesapeake Bay tributary were separated into four nominal molecular weight fractions and analyzed for their ability to bind copper by using an algal bioassay. The organics exhibited a relatively high capacity for copper, with the binding capacity directly proportional to dissolved organic carbon (DOC) concentrations. The relationship between binding capacity and DOC is similar in the Chesapeake Bay and in other estuaries and marine ecosystems. Such correlation is not found in freshwater ecosystems. The strong relationship between DOC concentrations and binding capacities in marine ecosystems may be due to the autochthonous origin of marine organics. 44 references, 3 figures, 2 tables.

  20. 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

  1. Complexation of Cu with dissolved organic carbon in municipal solid waste incinerator bottom ash leachates

    SciTech Connect

    Meima, J.A.; Van Zomeren, A.; Comans, R.N.J.

    1999-05-01

    The complexation of Cu with dissolved organic carbon (DOC) in leachates from fresh and 1.5-year old municipal solid waste incinerator (MSWI) bottom ash was studied using a competitive ligands-exchange solvent extraction procedure. At least two different ligands appear to be involved in the complexation of copper with DOC. The dissolved Cu appears to be 95--100% organically bound in leachates from both the fresh and the weathered bottom ash, and geochemical modeling indicates that the leaching of Cu from these ashes is primarily controlled by the availability of the organic ligands in the bottom ash. The mechanism that binds Cu to the solid phase is likely to be tenorite in the fresh bottom ash, and sorption to amorphous Fe/Al-(hydr)-oxides in the weathered bottom ash.

  2. 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.

  3. 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.

  4. Continuous hyperspectral absorption measurements of colored dissolved organic material in aquatic systems

    NASA Astrophysics Data System (ADS)

    Kirkpatrick, Gary J.; Orrico, Cristina; Moline, Mark A.; Oliver, Matthew; Schofield, Oscar M.

    2003-11-01

    The majority of organic carbon in the oceans is present as dissolved organic matter (DOM) therefore understanding the distribution and dynamics of DOM is central to understanding global carbon cycles. Describing the time-space variability in colored dissolved organic matter (CDOM) has been difficult, as standard spectrophotometric methods for CDOM determination are laborious and susceptible to methodological biases. Previously, measurements of CDOM absorption in discrete water samples by use of a liquid-waveguide capillary cell (LWCC) compared favorably with measurements made with a benchtop spectrophotometer. Given this, we focused on automating the LWCC technique to improve our spatial and temporal sampling capabilities for CDOM. We found strong correlations between CDOM absorption spectra collected from discrete water samples using standard methods and selected corresponding CDOM spectra collected by the automated LWCC system. The near-continuous measurements by the LWCC system made it possible to map the temporal, spatial, and spectral variability of CDOM absorption along the ship track.

  5. Removal of dissolved organic carbon and nitrogen during simulated soil aquifer treatment.

    PubMed

    Essandoh, H M K; Tizaoui, C; Mohamed, M H A

    2013-07-01

    Soil aquifer treatment was simulated in 1 m laboratory soil columns containing silica sand under saturated and unsaturated soil conditions to examine the effect of travel length through the unsaturated zone on the removal of wastewater organic matter, the effect of soil type on dissolved organic carbon removal and also the type of microorganisms involved in the removal process. Dissolved organic carbon removal and nitrification did enhance when the wastewater travelled a longer length through the unsaturated zone. A similar consortium of microorganisms was found to exist in both saturated and unsaturated columns. Microbial concentrations however were lowest in the soil column containing silt and clay in addition to silica sand. The presence of silt and clay was detrimental to DOC removal efficiency under saturated soil conditions due to their negative effect on the hydraulic performance of the soil column and microbial growth.

  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. Nitrogen and dissolved organic carbon (DOC) losses from an artificially drained grassland on organic soils

    NASA Astrophysics Data System (ADS)

    Tiemeyer, B.; Kahle, P.

    2014-02-01

    Nitrate-nitrogen (NO3-N) as well as dissolved organic carbon (DOC) and nitrogen (DON) concentrations and losses were studied for three respectively two years in a small catchment dominated by a degraded peatland used as intensive grassland. Concentrations in the shallow groundwater were spatially and temporally very variable with NO3-N being the most dynamic component (7.3 ± 12.5 mg L-1). Average NO3-N concentrations of 10.3 ± 5.4 mg L-1 in the ditch draining the catchment and annual NO3-N losses of 19, 35 and 26 kg ha-1 confirmed drained peatlands as an important source of diffuse N pollution. The highest NO3-N losses occurred during the wettest year. Resulting from concentrations of 2.4 ± 0.8 mg L-1, DON added further 4.5 to 6.4 kg ha-1 to the N losses and thus formed a relevant component of the total N losses. Ditch DOC concentrations of 24.9 ± 5.9 mg L-1 resulted in DOC losses of 66 kg ha-1 in the wet year 2006/07 and 39 kg ha-1 in the dry year 2007/08. Both DOC and N concentrations were governed by hydrological conditions, but NO3-N reacted much faster and clearer on rising discharge rates than DOC which tended to be higher under dryer conditions. In the third year of the study, the superposition of a very wet summer and land use changes from grassland to arable land in a part of the catchment suggests that under re-wetting conditions with a high groundwater table in summer, NO3-N would diminish quickly, while DOC would remain on a similar level. Further intensification of the land use, on the other hand, would increase N losses to receiving water bodies.

  8. Optical signatures of dissolved organic matter from the Endeavour and Axial vent fields

    NASA Astrophysics Data System (ADS)

    Stubbins, A.; Butterfield, D.; Rossel, P. E.; Dittmar, T.

    2011-12-01

    Recent studies have revealed that hydrothermal systems in the deep ocean are both sources and processors of dissolved organic matter (DOM). Sub-floor stores of fossil organic carbon may be exported to the deep ocean directly adding fossil C to the deep ocean dissolved organic carbon (DOC) pool and altering its apparent age. Fossil methane and carbon dioxide are also exported from vents. These C sources can then be utilized by chemotrophs and later enter the DOM pool as fossil DOC. Finally, when deep ocean waters are entrained into vent systems, the resultant heating may alter the chemical and optical properties of the DOM in these deep ocean waters. Dissolved organic matter (DOM) samples were collected from vents ranging in temperature from 10 to over 300 degrees centigrade across the Endeavour and Axial fields along the Juan de Fuca ridge. Elevated DOC and protein-like fluorescence reveal the vents to fuel the chemotrophic production of organic matter either in the adjacent water column or local sediments. High DOC and increased humic-like fluorescence in the hottest vent fluids, suggests the thermal degradation of DOM either from buried fossil sources or the entrainment of local waters enriched in DOC due to chemotrophic productivity. Natural and radio-carbon analyses are underway and will provide further insight into the ultimate source of this colored, fluorescent hydrothermal DOM.

  9. Copper-binding ability of dissolved organic matter derived from anaerobically digested biosolids

    SciTech Connect

    Han, N.; Thompson, M.L.

    1999-05-01

    The fate of metals in soils where soluble organic compound are present may be strongly influenced by the degree to which they are complexed by organic ligands. The authors undertook this study to determine the combined effect of molecular weight (MW) and hydrophobicity on the Cu-binding ability of dissolved organic compounds in biosolids (i.e., sewage sludge). Dissolved organic matter (DOM) from anaerobically digested sewage biosolids was fractionated by using a combination of MW fractionation and XAD-8 resin chromatography. The Cu-binding abilities of the DOM fractions were obtained by using a Cu{sup 2+}-ion-selective electrode (Cu-ISE) technique. The Cu-binding ability of fractionated DOM decreased significantly with increasing molecular weight, indicating that low-MW DOM had more metal-binding sites than high-MW DOM. Within each MW fraction, the hydrophilic and the hydrophobic components also exhibited differences in Cu-binding ability. For the DOM with MW 500--3,500 Da, the hydrophilic fraction showed a greater Cu-binding capacity than did the hydrophobic fraction, whereas the hydrophobic acid components were most important in binding Cu for DOM with MW > 3,500 Da. The maximum Cu-binding capacities of different biosolids-derived DOM fractions, estimated by employing a Langmuir model, ranged from 1.85 to 14.3 mmol Cu mol{sup {minus}1} dissolved organic C (DOC), which is the same order of magnitude as similar measurements of DOM from other sources.

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

    PubMed

    Hopkinson, Charles S; Vallino, Joseph J

    2005-01-13

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

  11. INFLUENCE OF METHOD FOR REMOVAL OF SESTON ON THE DISSOLVED ORGANIC MATTER(1).

    PubMed

    Parker, B C

    1967-12-01

    Comparisons of various methods and method modifications for treating water samples to render them free of seston prior to analysis of dissolved organic matter have corroborated a number of suspected sources of error. Among the more important points arising from this study arc: 1. All cellulose ester filters must be washed to remove elutable carbon. 2. In some instances filtration to dryness may produce artifacts resulting from cell injury. 3. A significant difference in filter retention can result between 0.45 and 0.22 μ membranes. 4. Among the methods most satisfactory are wet filtration through 0.22 μ pre-washed Millipore membranes and continuous-flow centrifugation at ca. 10,000 x g and 100 cc/min flow rate, both of which have their inherent weaknesses and limitations. 5. Regular centrifugation does not remove some planktonic organisms which have considerable buoyancy, or organic substances may somehow be released by cells without producing morphological damage. The newly developed bio dialysis technique for dissolved organic matter collection consistently yielded lower values than continuous-flow centrifugation. In contrast, biodialysis yielded lower values for pond water and higher values for Scenedesmus cultures than the best filtration method. Evidence suggests that biodialysis will be useful as both a supplementary and, in some zuays, more accurate method in studies of dissolved organic matter. PMID:27065026

  12. Exchanges and photo-biogeochemical transformation of dissolved organic compounds in Eastern US tidal marsh ecosystems.

    NASA Astrophysics Data System (ADS)

    Tzortziou, Maria; Neale, Patrick; Megonigal, Patrick; Butterworth, Megan; Jaffe, Rudolf

    2010-05-01

    The role of tidal marshes as sources, sinks and/or transformers of biologically important nutrients, carbon and pollutants has been studied in various marsh-estuarine environments and geomorphological settings. Although there is no consensus on the magnitude and direction of marsh-estuary net (particulate and dissolved) organic fluxes, most previous studies suggest that salt marshes export dissolved organic carbon (DOC) to the surrounding estuarine waters. There has been less attention, however, to the influence of transformations on marsh-exported organic carbon composition or "quality". Yet, carbon composition affects a wide variety of estuarine processes, including microbial respiration and photochemistry. Our objectives in this study were to quantify the photo-reactivity and bio-availability of dissolved organic carbon compounds exported from tidal wetlands of the Chesapeake Bay and determine their effects on the optical properties of colored organic matter (CDOM). We quantified DOC bioavailability with two assays of microbial mineralization: the traditional batch incubation approach in which a suspension of DOM and microbial cells (1 µm filtrate) was incubated in bottles for 7 d, and a continuous-flow bioreactor approach in which DOC (0.2 µm filtrate) was passed through a microbial community that had been pre-established on glass beads from the same source water. Photochemical degradation was measured after a 10h exposure to filtered xenon irradiance simulating midday surface exposure. We measured decreases in CDOM absorption and fluorescence spectra, DOC concentrations, changes in molecular weight distribution, and increases in dissolved inorganic carbon (DIC) and CO2. Results provide important insights on the transformation, fate and cycling of marsh-exported organic compounds, and the role of tidal marsh systems as major regulators of short-scale biological, optical and biogeochemical variability in highly dynamic coastal margins and catchment areas.

  13. Application of passive sampling for measuring dissolved concentrations of organic contaminants in the water column at three marine superfund sites

    EPA Science Inventory

    At contaminated sediment sites, including U.S. EPA Superfund sites, it is critical to measure water column concentrations of freely dissolved contaminants to understand the complete exposure of aquatic organisms to hydrophobic organic contaminants (HOCs). However, historically a...

  14. 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...

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

    EPA Science Inventory

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

  16. 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. PMID:23274796

  17. Molecular weight distribution of phosphorus fraction of aquatic dissolved organic matter.

    PubMed

    Ged, Evan C; Boyer, Treavor H

    2013-05-01

    This study characterized dissolved organic phosphorus (DOP) that is discharged from the Everglades Agricultural Area as part of the larger pool of aquatic dissolved organic matter (DOM). Whole water samples collected at the Everglades stormwater treat area 1 West (STA-1 W) were fractionated using a batch ultrafiltration method to separate organic compounds based on apparent molecular weight (AMW). Each AMW fraction of DOM was characterized for phosphorus, carbon, nitrogen, UV absorbance, and fluorescence. The DOP content of the Everglades water matrix was characteristically variable constituting 4-56% of total phosphorus (TP) and demonstrated no correlation with dissolved organic carbon (DOC). Measured values for DOP exceeded 14μgL(-1) in four out of five sampling dates making phosphorus load reductions problematic for the stormwater treatment areas (STAs), which target inorganic phosphorus and have a goal of 10μgL(-1) as TP. The molecular weight distributions revealed 40% of DOP is high molecular weight, aromatic-rich DOM. The results of this research are expected to be of interest to environmental chemists, environmental engineers, and water resources managers because DOP presents a major obstacle to achieving TP levels <10μgL(-1).

  18. Cellulase activity and dissolved organic carbon release from lignocellulose macrophyte-derived in four trophic conditions.

    PubMed

    Bottino, Flávia; Cunha-Santino, Marcela Bianchessi; Bianchini, Irineu

    2016-01-01

    Considering the importance of lignocellulose macrophyte-derived for the energy flux in aquatic ecosystems and the nutrient concentrations as a function of force which influences the decomposition process, this study aims to relate the enzymatic activity and lignocellulose hydrolysis in different trophic statuses. Water samples and two macrophyte species were collected from the littoral zone of a subtropical Brazilian Reservoir. A lignocellulosic matrix was obtained using aqueous extraction of dried plant material (≈40°C). Incubations for decomposition of the lignocellulosic matrix were prepared using lignocelluloses, inoculums and filtered water simulating different trophic statuses with the same N:P ratio. The particulate organic carbon and dissolved organic carbon (POC and DOC, respectively) were quantified, the cellulase enzymatic activity was measured by releasing reducing sugars and immobilized carbon was analyzed by filtration. During the cellulose degradation indicated by the cellulase activity, the dissolved organic carbon daily rate and enzyme activity increased. It was related to a fast hydrolysable fraction of cellulose that contributed to short-term carbon immobilization (ca. 10 days). After approximately 20 days, the dissolved organic carbon and enzyme activity were inversely correlated suggesting that the respiration of microorganisms was responsible for carbon mineralization. Cellulose was an important resource in low nutrient conditions (oligotrophic). However, the detritus quality played a major role in the lignocelluloses degradation (i.e., enzyme activity) and carbon release. PMID:26991278

  19. Dynamics of Dissolved Organic Matter in Amazon Basin: Insights into Negro River Contribution

    NASA Astrophysics Data System (ADS)

    Moreira-Turcq, P.; Perez, M. P.; Benedetti, M.; Oliveira, M. A.; Lagane, C.; Seyler, P.; Oliveira, E.

    2006-12-01

    The study of global carbon cycle requires a precise knowledge of spatial and temporal distributions and exportation from continents to oceans. Organic carbon fluxes represent approximately half of the total carbon budget carried by rivers. Tropical rivers transport two third of the total organic carbon discharged into the world oceans but important gaps still exist in the knowledge of the tropical river carbon biochemistry. The Amazon River is responsible for 10% of the annual amount of organic carbon transported from rivers to oceans. The most important portion of total organic matter transported in the Amazon Basin is the dissolved fraction (between 80% and 95%). Amazonian annual flux of dissolved organic matter is directly related to hydrological variations. All rivers in the Amazon basin are characterized by monomodal hydrograms, with a low water period in october/november and a high water period in may/june. Temporal variations in Amazon dissolved organic carbon (3.0 to 9.1 mg l^{- 1}) are mainly controled by Negro River inputs. DOC and DON contributions from the Negro River can vary between 120 kgC s-1 and 520 kg C s-1, and between 5 kgN s--1 and 15 kgN s-1, during low and high water period, respectivelly. In the Negro River, during high water stages, while DOC concentrations are stable from the upstream stations to the downstream ones (about 11 mg l-1), discharge increases from 16000 to 46000 m3 s-1 and NOD can quintuple from upstream (0.071 mg l-1) to downstream (0.341 mg l-1). Then the nature of dissolved organic matter is variable (C/N ratio varied from 33 to 120 from upstream to downstream). During low water stages DOC concentrations are lower (mean DOC of 8.1 mg l-1) while DON is in the same range, discharge is about 10000 m3 s-1 at downstream stations of Negro River and the C/N ratio is lower and steadier along the River. Finaly, despite a low basin surface (12%) compared with the two other main Amazon tributaries, Solimões and Madeira Rivers, and a

  20. Influence of dissolved organic carbon on methylmercury bioavailability across Minnesota stream ecosystems.

    PubMed

    Tsui, Martin Tsz Ki; Finlay, Jacques C

    2011-07-15

    Stream ecosystems are widely contaminated by mercury (Hg) via atmospheric transport and deposition in watersheds. Dissolved organic carbon (DOC) is well-known to be the dominant ligand for aqueous methylmercury (MeHg), the bioaccumulative form of Hg in aquatic food webs. However, it is less clear if and how the concentration and character (e.g., aromaticity) of DOC influences the availability of dissolved MeHg to stream food webs. In this work, we analyzed total-Hg and/or MeHg concentrations in water, seston, and macroinvertebrates (filter-feeding hydropsychid caddisflies), and other physiochemical properties in 30 streams along a south-north geographic gradient in eastern Minnesota that corresponds to substantial changes in dominant land cover (i.e., agriculture, urban, wetland, and forest). In general, MeHg concentrations in seston and hydropsychids were higher in watersheds with more forest and wetland coverage, and increased with dissolved MeHg concentration. However, we found that the efficiency of MeHg incorporation into the stream food webs (i.e., bioconcentration factors of MeHg in both seston and hydropsychids, BCF(MeHg) = solid MeHg ÷ dissolved MeHg) decreased significantly with DOC concentration and aromaticity, suggesting that MeHg bioavailability to the base of food webs was attenuated at higher levels of terrestrial DOC. Therefore, our findings suggest that there is a dual role of DOC on MeHg cycling in streams: terrestrial DOC acts as the primary carrier ligand of dissolved MeHg for transport into surface waters, yet this aromatic DOC also attenuates dissolved MeHg uptake by aquatic food webs. Thus, consideration of MeHg bioavailability and its environmental regulation could help improve predictive models of MeHg bioaccumulation in stream ecosystems.

  1. Adsorption of dissolved organics in lake water by aluminum oxide. Effect of molecular weight

    USGS Publications Warehouse

    Davis, J.A.; Gloor, R.

    1981-01-01

    Dissolved organic compounds in a Swiss lake were fractionated into three molecular size classes by gel exclusion chromatography, and adsorption of each fraction on colloidal alumina was studied as a function of pH. Organic compounds with molecular weight (Mr) greater than 1000 formed strong complexes with the alumina surface, but low molecular weight compounds were weakly adsorbed. Electrophoretic mobility measurements indicated that alumina particles suspended in the original lake water were highly negatively charged because of adsorbed organic matter. Most of the adsorbed organic compounds were in the Mr range 1000 < Mr < 3000. Adsorption of these compounds during the treatment of drinking water by alum coagulation may be responsible for the preferential removal of trihalomethane precursors. Adsorption may also influence the molecular-weight distribution of dissolved organic material in lakes. surface, the present work will focus on the influence of molecular size and pH on the adsorption behavior of dissolved organic material of a Swiss lake. From a geochemical point of view, it is important to know the molecular-weight distribution of adsorbed organic matter so that we may better assess its reactivity with trace elements. The study also serves as a first step in quantifying the role of adsorption in the geochemical cycle of organic carbon in lacustrine environments. For water-treatment practice, we need to determine whether molecular weight fractionation occurs during adsorption by aluminum oxide. Such a fractionation could be significant in the light of recent reports that chloroform and other organochlorine compounds are preferentially produced by particular molecular-weight fractions (25-27). ?? 1981 American Chemical Society.

  2. Elevated atmospheric CO2 fuels leaching of old dissolved organic matter at the alpine treeline

    NASA Astrophysics Data System (ADS)

    Hagedorn, Frank; van Hees, Patrick A. W.; Handa, I. Tanya; HäTtenschwiler, Stephan

    2008-06-01

    Dissolved organic matter (DOM), the mobile form of soil organic matter (SOM), plays an important role in soil C cycling and in nutrient transport. We investigated the effects of 5 years of CO2 enrichment (370 versus 570 μmol CO2 mol-1) on DOM dynamics at the alpine treeline, including the analysis of fast-cycling components such as low molecular weight organic acids (LMWOAs), dissolved organic carbon (DOC) biodegradability, and the decomposition of 14C-labeled oxalate. Concentrations of DOC in canopy throughfall were 20% higher at elevated CO2, probably driven by higher carbohydrate concentrations in leaves. In the organic soil layer, 5 years of CO2 enrichment increased water-extractable organic C by 17% and soil solution DOC at 5 cm depth by 20%. The 13C tracing of recently assimilated CO2 revealed that the input of recent plant-derived C (<15% of total DOC) was smaller than the CO2-induced increase in DOC. This strongly suggests that CO2 enrichment enhanced the mobilization of native DOC, which is supported by significant increases in dissolved organic nitrogen (DON). We mainly attribute these increases to a stimulated microbial activity as indicated by higher basal and soil respiration rates (+27%). The 14C-labeled oxalate was more rapidly mineralized from high CO2 soils. The concentrations of LMWOAs, but also those of "hydrophilic" DOC and biodegradable DOC (6% of total DOC), were, however, not affected by elevated CO2, suggesting that production and consumption of "labile" DOC were in balance. In summary, our data suggest that 5 years of CO2 enrichment speeded up the cycling of "labile" DOM and SOM in a late successional treeline ecosystem and increased the mobilization of older DOM through a stimulated microbial activity. Such a "priming effect" implies that elevated CO2 can accelerate the turnover of native SOM, and thus, it may induce increasing losses of old C from thick organic layers.

  3. Comparison of optical properties of chromophoric dissolved organic matter (CDOM) in alpine lakes above or below the tree line: insights into sources of CDOM.

    PubMed

    Su, Yaling; Chen, Feizhou; Liu, Zhengwen

    2015-05-01

    Here we investigated absorption and fluorescence properties of chromophoric dissolved organic matter (CDOM) in 15 alpine lakes located below or above the tree line to determine its source and composition. The results indicate that the concentrations of CDOM in below-tree-line lakes are significantly higher than in above-tree-line lakes, as evidenced from the absorption coefficients of a250 and a365. The intensities of the protein-like and humic-like fluorescence in below-tree-line lakes are higher than in above-tree-line lakes as well. Three fluorescent components were identified using parallel factor analysis (PARAFAC) modelling. Component 1 is probably associated with biological degradation of terrestrial humic component. The terrestrial humic-like component 2 is only found in below-tree-line lakes. The protein-like or phenolic component 3 is dominant in above-tree-line lakes, which is probably more derived from autochthonous origin. In this study, (1) higher a250/a365 and S275-295 values indicate smaller molecular weights of CDOM in above-tree-line lakes than in below-tree-line lakes, and smaller molecular weights at the surface than at 2.0 m depth; (2) SUVA254 and FI255 results provide evidence of lower percent aromaticity of CDOM in above-tree-line lakes; and (3) FI310 and FI370 suggest a strong allochthonous origin at the surface in below-tree-line lakes, and more contribution from autochthonous biological and aquatic bacterial origin in above-tree-line lakes.

  4. [The qualitative analysis method of the dissolved organic matter (DOM) for ABS wastewater].

    PubMed

    Lai, Bo; Zhou, Yue-xi; Song, Yu-dong; Xi, Hong-bo; Sun, Li-dong; Chen, Jia-yun

    2011-03-01

    The dissolved organic matter (DOM) of acrylonitrile-butadiene-styrene (ABS) resin wastewater was qualitatively analysed by gas chromatography with mass spectrometry(GC-MS), Fourier transform infrared spectrometer(FTIR) and three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy. The detected results shows that the GC-MS qualitatively analysed 21 dissolved organic pollutants, such as acetophenone, styrene, alpha, alpha-dimethyl-benzenemethanol, 3,3'oxybis-propanenitrile, 3, 3'-iminobis-propanenitrile, 3,3'-thiobis-propanenitrile, 3-(dimethylamino)-propanenitrile and 2-propenenitrile. The results of Fourier transform infrared spectrometer (FTIR) and three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy could examine and certify the accuracy and integrity for the qualitative analysis of GC-MS. The results of this study provides an important guiding role for the development of wastewater treatment process.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  6. Importance of within-lake processes in affecting the dynamics of dissolved organic carbon and dissolved organic and inorganic nitrogen in an Adirondack forested lake/watershed

    NASA Astrophysics Data System (ADS)

    Kang, Phil-Goo; Mitchell, Myron J.; McHale, Patrick J.; Driscoll, Charles T.; Inamdar, Shreeram; Park, Ji-Hyung

    2016-05-01

    Lakes nested in forested watersheds play an important role in mediating the concentrations and fluxes of dissolved organic matter. We compared long-term patterns of concentrations and fluxes of dissolved organic carbon (DOC) and dissolved organic (DON) and inorganic nitrogen (DIN) in aquatic ecosystems of the Arbutus Lake watershed to evaluate how a lake nested in a forested watershed affects the sources (e.g., production) and sinks (e.g., retention) of DOC and DON in the Adirondack Mountains of New York, USA. We observed no significant long-term changes of DOC and DON in the lake outlet since 1983 and 1994, respectively. However, the temporal patterns of DOC and DON concentrations in the lake inlet showed significant seasonality such as increases during the vegetation-growing season along with notable decreases in the dormant season. A comparison of mass balances between inlet and outlet for the period from 2000 to 2009 suggested that the lake was a sink of DOC (mean of influx minus outflux: +1140 mol C ha-1 yr-1). In contrast, the difference of discharge-weighted DON concentrations (mean of inlet minus outlet: -1.0 µmol N L-1) between inlet and outlet was much smaller than the discharge-weighted DOC concentrations (average of inlet minus outlet: + 87 µmol C L-1). DON fluxes showed considerable variation among years (mean of influx minus outflux: +8 mol N ha-1 yr-1; range of differences: -15 to 27 mol N ha-1 yr-1). DON exhibited low percent retention ((influx-outflux)/influx) (mean: 6.9 %, range: -34.8 to +31.2) compared to DOC (mean: 30.1 %, range: +9.2 to +44.1). The resultant increase of DON within the lake was closely linked with a net decrease of DIN through monthly Pearson correlation analysis, suggesting the importance of biotic factors in mediating lake DON dynamics. Our results show different relative retentions of DOC compared with DON, along with a larger retention of DIN than DON, suggesting that DOC and DON might display substantially different

  7. Effects of dissolved organic carbon on sorption and mobility of imidacloprid in soil.

    PubMed

    Flores-Céspedes, F; González-Pradas, E; Fernández-Pérez, M; Villafranca-Sánchez, M; Socías-Viciana, M; Ureña-Amate, M D

    2002-01-01

    To evaluate the effects of dissolved organic carbon on sorption and mobility of the insecticide imidacloprid [1-(6-chloro-3-pyridinyl) methyl-N-nitro-2-imidazolidinimine] in soils, adsorption and column experiments were performed by using a typical calcareous soil from southeastern Spain and two different types of dissolved organic carbon, that is, dissolved organic carbon extracts from a commercial peat (DOC-PE) and high-purity tannic acid (DOC-TA). The experiments were carried out from a 0.01 M CaCl2 aqueous medium at 25 degrees C. The results obtained from the sorption experiments show that the presence of both DOC-PE and DOC-TA, over a concentration range of 15 to 100 mg L(-1), produces in all cases a decreasing amount of imidacloprid adsorbed in the soil studied. From the column experiments the retardation coefficients (RC) were calculated for imidacloprid by using either 0.01 M CaCl2 aqueous solution (RC = 2.10), 0.01 M CaCl2 DOC-PE solution (RC = 1.65), or 0.01 M CaCl2 DOC-TA solution (RC = 1.87). The results indicate that mobility of imidacloprid is increased 21.4 and 11.0% in the presence of DOC-PE and DOC-TA solutions, respectively. Dissolved organic carbon reduces imidacloprid sorption by competing with the pesticide molecules for sorption sites on the soil surface, allowing enhanced leaching of imidacloprid and potentially increasing ground water contamination.

  8. 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.

  9. Nitrogen and dissolved organic carbon (DOC) losses from an artificially drained grassland on organic soils

    NASA Astrophysics Data System (ADS)

    Tiemeyer, B.; Kahle, P.

    2014-08-01

    Nitrate-nitrogen (NO3-N) as well as dissolved organic carbon (DOC) and nitrogen (DON) concentrations and losses were studied for three and two years, respectively, in a small catchment dominated by a degraded peatland used as intensive grassland. Concentrations in the shallow groundwater were spatially and temporally very variable, with NO3-N being the most dynamic component (7.3 ± 12.5 mg L-1) and ranging from 0 to 79.4 mg L-1. Average NO3-N concentrations of 10.3 ± 5.4 mg L-1 (0 to 25.5 mg L-1) in the ditch draining the catchment and annual NO3-N losses of 19, 35 and 26 kg ha-1 confirmed drained peatlands as an important source of diffuse N pollution. The highest NO3-N losses occurred during the wettest year. Resulting from concentration of 2.4 ± 0.8 mg L-1 (0.7 to 6.2 mg L-1), DON added a further 4.5 to 6.4 kg ha-1 to the N losses and thus formed a relevant (15%) component of the total N losses. Ditch DOC concentrations of 24.9 ± 5.9 mg L-1 (13.1 to 47.7 mg L-1) resulted in DOC losses of 66 kg ha-1 in the wet year of 2006/2007 and 39 kg ha-1 in the dry year of 2007/2008. Ditch DOC concentration were lower than the groundwater DOC concentration of 50.6 ± 15.2 mg L-1 (14.9 to 88.5 mg L-1). Both DOC and N concentrations were governed by hydrological conditions, but NO3-N reacted much faster and clearer on rising discharge rates than DOC, which tended to be higher under drier conditions. In the third year of the study, the superposition of a very wet summer and land use changes from grassland to arable land in a part of the catchment suggests that, under re-wetting conditions with a high groundwater table in summer, NO3-N would diminish quickly, while DOC would remain on a similar level. Further intensification of the land use, on the other hand, would increase N losses to receiving water bodies.

  10. 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

  11. Dissolved Gases and Ice Fracturing During the Freezing of a Multicellular Organism: Lessons from Tardigrades.

    PubMed

    Kletetschka, Gunther; Hruba, Jolana

    2015-01-01

    Three issues are critical for successful cryopreservation of multicellular material: gases dissolved in liquid, thermal conductivity of the tissue, and localization of microstructures. Here we show that heat distribution is controlled by the gas amount dissolved in liquids and that when changing the liquid into solid, the dissolved gases either form bubbles due to the absence of space in the lattice of solids and/or are migrated toward the concentrated salt and sugar solution at the cost of amount of heat required to be removed to complete a solid-state transition. These factors affect the heat distribution in the organs to be cryopreserved. We show that the gas concentration issue controls fracturing of ice when freezing. There are volumetric changes not only when changing the liquid into solid (volume increases) but also reduction of the volume when reaching lower temperatures (volume decreases). We discuss these issues parallel with observations of the cryosurvivability of multicellular organisms, tardigrades, and discuss their analogy for cryopreservation of large organs. PMID:26309797

  12. The surface Arctic Ocean: A dynamic reservoir of terrigenous dissolved organic carbon

    NASA Astrophysics Data System (ADS)

    Hansell, D. A.; Letscher, R. T.

    2012-04-01

    The upper mixed layer of the Arctic Ocean is a globally important sink for dissolved organic matter mobilized from adjacent continents, which in turn are subject to substantial changes with warming of the Arctic system. Understanding the dynamics and fate of this terrigenous material has become critical for our understanding the contributions of the Arctic to the global carbon cycle. Terrigenous dissolved organic carbon (tDOC) had long been viewed as highly conserved within the Arctic Ocean, yet only a fraction of that entering from the rivers survived for export to the North Atlantic. Extensive surveys of tDOC and other tracers between the shelves and the waters overlying the deep basins indicate that a large fraction of the tDOC is subject to slow mineralization. The extent of removal within the Arctic system depends then on the time scale for water mass retention; the longer the retention, the greater the remineralization within the Arctic. Remineralization of tDOC adds to the inorganic carbon inventory and seawater pCO2, thus impacting exchange of CO2 with the atmosphere. This talk will begin with a global view of marine dissolved organic carbon (DOC), from which the context for tDOC in the Arctic Ocean will be established. The surface Arctic Ocean distribution of tDOC will be presented, along with consideration of its dynamics and export to the North Atlantic.

  13. Dissolved Gases and Ice Fracturing During the Freezing of a Multicellular Organism: Lessons from Tardigrades.

    PubMed

    Kletetschka, Gunther; Hruba, Jolana

    2015-01-01

    Three issues are critical for successful cryopreservation of multicellular material: gases dissolved in liquid, thermal conductivity of the tissue, and localization of microstructures. Here we show that heat distribution is controlled by the gas amount dissolved in liquids and that when changing the liquid into solid, the dissolved gases either form bubbles due to the absence of space in the lattice of solids and/or are migrated toward the concentrated salt and sugar solution at the cost of amount of heat required to be removed to complete a solid-state transition. These factors affect the heat distribution in the organs to be cryopreserved. We show that the gas concentration issue controls fracturing of ice when freezing. There are volumetric changes not only when changing the liquid into solid (volume increases) but also reduction of the volume when reaching lower temperatures (volume decreases). We discuss these issues parallel with observations of the cryosurvivability of multicellular organisms, tardigrades, and discuss their analogy for cryopreservation of large organs.

  14. 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.

  15. Dissolved Gases and Ice Fracturing During the Freezing of a Multicellular Organism: Lessons from Tardigrades

    PubMed Central

    Kletetschka, Gunther; Hruba, Jolana

    2015-01-01

    Abstract Three issues are critical for successful cryopreservation of multicellular material: gases dissolved in liquid, thermal conductivity of the tissue, and localization of microstructures. Here we show that heat distribution is controlled by the gas amount dissolved in liquids and that when changing the liquid into solid, the dissolved gases either form bubbles due to the absence of space in the lattice of solids and/or are migrated toward the concentrated salt and sugar solution at the cost of amount of heat required to be removed to complete a solid-state transition. These factors affect the heat distribution in the organs to be cryopreserved. We show that the gas concentration issue controls fracturing of ice when freezing. There are volumetric changes not only when changing the liquid into solid (volume increases) but also reduction of the volume when reaching lower temperatures (volume decreases). We discuss these issues parallel with observations of the cryosurvivability of multicellular organisms, tardigrades, and discuss their analogy for cryopreservation of large organs. PMID:26309797

  16. Reconciling stream dissolved organic matter with snowmelt-driven subsurface flowpaths in a montane, headwater catchment.

    NASA Astrophysics Data System (ADS)

    Barnard, H. R.; Burns, M. A.; McKnight, D. M.; Gabor, R. S.; Brooks, P. D.

    2014-12-01

    Dissolved organic matter (DOM) transport is a key biogeochemical link across the terrestrial-aquatic interface in headwater catchments, and therefore is intimately linked with the hydrologic connectivity of the catchment to the stream. This study evaluated the mobility of specific chemical constituents of DOM during snowmelt in a montane, semi-arid catchment in the Boulder Creek CZO. Dissolved organic matter quality was monitored using fluorescence spectroscopy on a daily basis from water sampled from the soil (10 - 25 cm depth) via tension lysimeters and from the stream during snowmelt and was compared to approximately bi-monthly groundwater samples (~18 m depth). In the stream, a transition occurred from fluorescent DOM (FDOM) being dominated by protein-like material to FDOM being dominated by more humic-like material. The FDOM in the interstitial water of the soils and the groundwater did not change in character. Thus, the stream transition is indicative of an engagement of DOM originating from hillslope soils during snowmelt. Dissolved organic carbon (DOC) normalization of these fluorescent loadings suggest that the peak in DOC concentration seen in the stream is mainly controlled by the non-fluorescent fraction of DOM. These results indicate that shifts in hydrologic connectivity of different watershed units to the stream are a major control on DOM export from the watershed.

  17. 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.

  18. Chemical characterization of high molecular weight dissolved organic matter in fresh and marine waters

    NASA Astrophysics Data System (ADS)

    Repeta, Daniel J.; Quan, Tracy M.; Aluwihare, Lihini I.; Accardi, AmyMarie

    2002-03-01

    The high molecular weight fraction of dissolved organic matter in a suite of lakes, rivers, seawater, and marine sediment interstitial water samples was collected by ultrafiltration and characterized by molecular level and spectroscopic techniques. Proton nuclear magnetic resonance spectra of all samples show a high degree of similarity, with major contributions from carbohydrates, bound acetate, and lipids. Molecular level analyses of neutral sugars show seven monosaccharides, rhamnose, fucose, arabinose, xylose, mannose, glucose, and galactose, to be abundant, and to occur in comparable relative amounts in each sample. Previous studies have emphasized the distinctive composition of dissolved humic substances in fresh and marine waters, and have attributed these differences to sources and transformations of organic matter unique to each environment. In contrast we find a large fraction of freshwater high molecular weight dissolved organic matter (HMWDOM; > 1kD) to be indistinguishable from marine HMWDOM in bulk and molecular-level chemical properties. Aquatic HMWDOM is similar in chemical composition to biologically derived acylated heteropolysaccharides isolated from marine algal cultures, suggesting a biological source for some fraction of persistent HMWDOM. High molecular weight DOC contributes 51 ± 26% of the total DOC, and monosaccharides 18 ± 8% of the total HMWDOC in our freshwater samples. These contributions are on average higher and more variable, but not significantly different than for surface seawater (30% and 16% respectively). Biogeochemical processes that produce, accumulate, and recycle DOM may therefore share important similarities and be broadly comparable across a range of environmental settings.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  20. Dissolved Organic Matter Quality in a Shallow Aquifer of Bangladesh: Implications for Arsenic Mobility.

    PubMed

    Mladenov, Natalie; Zheng, Yan; Simone, Bailey; Bilinski, Theresa M; McKnight, Diane M; Nemergut, Diana; Radloff, Kathleen A; Rahman, M Moshiur; Ahmed, Kazi Matin

    2015-09-15

    In some high arsenic (As) groundwater systems, correlations are observed between dissolved organic matter (DOM) and As concentrations, but in other systems, such relationships are absent. The role of labile DOM as the main driver of microbial reductive dissolution is not sufficient to explain the variation in DOM-As relationships. Other processes that may also influence As mobility include complexation of As by dissolved humic substances, and competitive sorption and electron shuttling reactions mediated by humics. To evaluate such humic DOM influences, we characterized the optical properties of filtered surface water (n = 10) and groundwater (n = 24) samples spanning an age gradient in Araihazar, Bangladesh. Further, we analyzed large volume fulvic acid (FA) isolates (n = 6) for optical properties, C and N content, and (13)C NMR spectroscopic distribution. Old groundwater (>30 years old) contained primarily sediment-derived DOM and had significantly higher (p < 0.001) dissolved As concentration than groundwater that was younger than 5 years old. Younger groundwater had DOM spectroscopic signatures similar to surface water DOM and characteristic of a sewage pollution influence. Associations between dissolved As, iron (Fe), and FA concentration and fluorescence properties of isolated FA in this field study suggest that aromatic, terrestrially derived FAs promote As-Fe-FA complexation reactions that may enhance As mobility. PMID:26192081

  1. Dissolved Organic Matter Quality in a Shallow Aquifer of Bangladesh: Implications for Arsenic Mobility.

    PubMed

    Mladenov, Natalie; Zheng, Yan; Simone, Bailey; Bilinski, Theresa M; McKnight, Diane M; Nemergut, Diana; Radloff, Kathleen A; Rahman, M Moshiur; Ahmed, Kazi Matin

    2015-09-15

    In some high arsenic (As) groundwater systems, correlations are observed between dissolved organic matter (DOM) and As concentrations, but in other systems, such relationships are absent. The role of labile DOM as the main driver of microbial reductive dissolution is not sufficient to explain the variation in DOM-As relationships. Other processes that may also influence As mobility include complexation of As by dissolved humic substances, and competitive sorption and electron shuttling reactions mediated by humics. To evaluate such humic DOM influences, we characterized the optical properties of filtered surface water (n = 10) and groundwater (n = 24) samples spanning an age gradient in Araihazar, Bangladesh. Further, we analyzed large volume fulvic acid (FA) isolates (n = 6) for optical properties, C and N content, and (13)C NMR spectroscopic distribution. Old groundwater (>30 years old) contained primarily sediment-derived DOM and had significantly higher (p < 0.001) dissolved As concentration than groundwater that was younger than 5 years old. Younger groundwater had DOM spectroscopic signatures similar to surface water DOM and characteristic of a sewage pollution influence. Associations between dissolved As, iron (Fe), and FA concentration and fluorescence properties of isolated FA in this field study suggest that aromatic, terrestrially derived FAs promote As-Fe-FA complexation reactions that may enhance As mobility.

  2. Uptake of dissolved organic carbon and trace elements by zebra mussels

    NASA Astrophysics Data System (ADS)

    Roditi, Hudson A.; Fisher, Nicholas S.; Sañudo-Wilhelmy, Sergio A.

    2000-09-01

    Zebra mussels (Dreissena polymorpha) are widespread and abundant in major freshwater ecosystems in North America, even though the phytoplankton food resources in some of these systems seem to be too low to sustain them. Because phytoplankton biomass is greatly depleted in ecosystems with large D. polymorpha populations and bacteria do not seem to be an important food source for this species, exploitation of alternative carbon sources may explain the unexpected success of D. polymorpha in such environments. Here we examine the possibility that absorption of dissolved organic carbon (DOC) from water could provide a nutritional supplement to zebra mussels. We find that mussels absorb 14C-labelled DOC produced by cultured diatoms with an efficiency of 0.23%; this indicates that DOC in natural waters could contribute up to 50% of the carbon demand of zebra mussels. We also find that zebra mussels absorb some dissolved metals that have been complexed by the DOM; although absorption of dissolved selenium was unaffected by DOC, absorption of dissolved cadmium, silver and mercury by the mussels increased 32-, 8.7- and 3.6-fold, respectively, in the presence of high-molecular-weight DOC.

  3. Uptake of dissolved organic carbon and trace elements by zebra mussels.

    PubMed

    Roditi, H A; Fisher, N S; Sañudo-Wilhelmy, S A

    2000-09-01

    Zebra mussels (Dreissena polymorpha) are widespread and abundant in major freshwater ecosystems in North America, even though the phytoplankton food resources in some of these systems seem to be too low to sustain them. Because phytoplankton biomass is greatly depleted in ecosystems with large D. polymorpha populations and bacteria do not seem to be an important food source for this species, exploitation of alternative carbon sources may explain the unexpected success of D. polymorpha in such environments. Here we examine the possibility that absorption of dissolved organic carbon (DOC) from water could provide a nutritional supplement to zebra mussels. We find that mussels absorb 14C-labelled DOC produced by cultured diatoms with an efficiency of 0.23%; this indicates that DOC in natural waters could contribute up to 50% of the carbon demand of zebra mussels. We also find that zebra mussels absorb some dissolved metals that have been complexed by the DOM; although absorption of dissolved selenium was unaffected by DOC, absorption of dissolved cadmium, silver and mercury by the mussels increased 32-, 8.7- and 3.6-fold, respectively, in the presence of high-molecular-weight DOC.

  4. Microbial metabolism mediates interactions between dissolved organic matter and clay minerals in streamwater

    PubMed Central

    Hunter, W. R.; Battin, T. J.

    2016-01-01

    Sorption of organic molecules to mineral surfaces is an important control upon the aquatic carbon (C) cycle. Organo-mineral interactions are known to regulate the transport and burial of C within inland waters, yet the mechanisms that underlie these processes are poorly constrained. Streamwater contains a complex and dynamic mix of dissolved organic compounds that coexists with a range of organic and inorganic particles and microorganisms. To test how microbial metabolism and organo-mineral complexation alter amino acid and organic carbon fluxes we experimented with 13C-labelled amino acids and two common clay minerals (kaolinite and montmorillonite). The addition of 13C-labelled amino acids stimulated increased microbial activity. Amino acids were preferentially mineralized by the microbial community, concomitant with the leaching of other (non-labelled) dissolved organic molecules that were removed from solution by clay-mediated processes. We propose that microbial processes mediate the formation of organo-mineral particles in streamwater, with potential implications for the biochemical composition of organic matter transported through and buried within fluvial environments. PMID:27481013

  5. Effect of biomass adaptation to biodegradation of dissolved organic carbon in water.

    PubMed

    Tihomirova, K; Briedis, A; Rubulis, J; Juhna, T

    2012-04-01

    In the present study the time of adaptation of fixed biomass for biodegradation of natural organic matter was investigated. The experiments were done in columns that are usually used for rapid determination of biodegradable dissolved organic carbon (BDOC). The biomass was adapted to samples with different concentrations of organic substances before measurements by pumping water to be investigated through the columns for several days. The time of adaptation was dependent on the initial concentration of the organic matter in the water sample. The adaptation time increased from 6 to 24 h with increase of concentration of acetate solution from 2 to 10 mg/l, thus adaptation rate decreased simultaneously from 0.28 to 0.11 min(-1). In natural water samples with the initial concentration in the range from 4.61-10.82 mg/l of dissolved organic carbon (DOC) the maximal adaptation time was less than 24 h. During the adaptation period the increase in reproducibility and decrease in the standard deviation was observed. The study showed that adaptation of column to the different concentration of organic matter in water sample is necessary in order to decrease the bias in BDOC measurements when using columns tests. PMID:21892664

  6. Microbial metabolism mediates interactions between dissolved organic matter and clay minerals in streamwater

    NASA Astrophysics Data System (ADS)

    Hunter, W. R.; Battin, T. J.

    2016-08-01

    Sorption of organic molecules to mineral surfaces is an important control upon the aquatic carbon (C) cycle. Organo-mineral interactions are known to regulate the transport and burial of C within inland waters, yet the mechanisms that underlie these processes are poorly constrained. Streamwater contains a complex and dynamic mix of dissolved organic compounds that coexists with a range of organic and inorganic particles and microorganisms. To test how microbial metabolism and organo-mineral complexation alter amino acid and organic carbon fluxes we experimented with 13C-labelled amino acids and two common clay minerals (kaolinite and montmorillonite). The addition of 13C-labelled amino acids stimulated increased microbial activity. Amino acids were preferentially mineralized by the microbial community, concomitant with the leaching of other (non-labelled) dissolved organic molecules that were removed from solution by clay-mediated processes. We propose that microbial processes mediate the formation of organo-mineral particles in streamwater, with potential implications for the biochemical composition of organic matter transported through and buried within fluvial environments.

  7. Microbial metabolism mediates interactions between dissolved organic matter and clay minerals in streamwater.

    PubMed

    Hunter, W R; Battin, T J

    2016-01-01

    Sorption of organic molecules to mineral surfaces is an important control upon the aquatic carbon (C) cycle. Organo-mineral interactions are known to regulate the transport and burial of C within inland waters, yet the mechanisms that underlie these processes are poorly constrained. Streamwater contains a complex and dynamic mix of dissolved organic compounds that coexists with a range of organic and inorganic particles and microorganisms. To test how microbial metabolism and organo-mineral complexation alter amino acid and organic carbon fluxes we experimented with (13)C-labelled amino acids and two common clay minerals (kaolinite and montmorillonite). The addition of (13)C-labelled amino acids stimulated increased microbial activity. Amino acids were preferentially mineralized by the microbial community, concomitant with the leaching of other (non-labelled) dissolved organic molecules that were removed from solution by clay-mediated processes. We propose that microbial processes mediate the formation of organo-mineral particles in streamwater, with potential implications for the biochemical composition of organic matter transported through and buried within fluvial environments. PMID:27481013

  8. Microbial metabolism mediates interactions between dissolved organic matter and clay minerals in streamwater.

    PubMed

    Hunter, W R; Battin, T J

    2016-01-01

    Sorption of organic molecules to mineral surfaces is an important control upon the aquatic carbon (C) cycle. Organo-mineral interactions are known to regulate the transport and burial of C within inland waters, yet the mechanisms that underlie these processes are poorly constrained. Streamwater contains a complex and dynamic mix of dissolved organic compounds that coexists with a range of organic and inorganic particles and microorganisms. To test how microbial metabolism and organo-mineral complexation alter amino acid and organic carbon fluxes we experimented with (13)C-labelled amino acids and two common clay minerals (kaolinite and montmorillonite). The addition of (13)C-labelled amino acids stimulated increased microbial activity. Amino acids were preferentially mineralized by the microbial community, concomitant with the leaching of other (non-labelled) dissolved organic molecules that were removed from solution by clay-mediated processes. We propose that microbial processes mediate the formation of organo-mineral particles in streamwater, with potential implications for the biochemical composition of organic matter transported through and buried within fluvial environments.

  9. Association of dissolved mercury with dissolved organic carbon in U.S. rivers and streams: The role of watershed soil organic carbon

    NASA Astrophysics Data System (ADS)

    Stoken, Olivia M.; Riscassi, Ami L.; Scanlon, Todd M.

    2016-04-01

    Streams and rivers are important pathways for the export of atmospherically deposited mercury (Hg) from watersheds. Dissolved Hg (HgD) is strongly associated with dissolved organic carbon (DOC) in stream water, but the ratio of HgD to DOC is highly variable between watersheds. In this study, the HgD:DOC ratios from 19 watersheds were evaluated with respect to Hg wet deposition and watershed soil organic carbon (SOC) content. On a subset of sites where data were available, DOC quality measured by specific ultra violet absorbance at 254 nm, was considered as an additional factor that may influence HgD:DOC . No significant relationship was found between Hg wet deposition and HgD:DOC, but SOC content (g m-2) was able to explain 81% of the variance in the HgD:DOC ratio (ng mg-1) following the form: HgD:DOC=17.8*SOC-0.41. The inclusion of DOC quality as a secondary predictor variable explained only an additional 1% of the variance. A mathematical framework to interpret the observed power-law relationship between HgD:DOC and SOC suggests Hg supply limitation for adsorption to soils with relatively large carbon pools. With SOC as a primary factor controlling the association of HgD with DOC, SOC data sets may be utilized to predict stream HgD:DOC ratios on a more geographically widespread basis. In watersheds where DOC data are available, estimates of HgD may be readily obtained. Future Hg emissions policies must consider soil-mediated processes that affect the transport of Hg and DOC from terrestrial watersheds to streams for accurate predictions of water quality impacts.

  10. Dissolved organic matter release and retention in ultisols in relation to land use patterns.

    PubMed

    Zhang, Qichun; Hou, Changping; Liang, Yingying; Feng, Ying

    2014-07-01

    The application of organic fertilizer to maintain soil fertility and crop yield has been practiced for thousands of years in China. This practice improves soil carbon sequestration, due to the high level of dissolved organic matter (DOM) in organic manure. In this study, batch equilibrium studies were conducted to examine the capacity of three ultisols from areas under different land use patterns to retain dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) extracted from rape cake and chicken manure. The results showed that the amount of DOM removed or released in solution by the soil was a linear function of the initial amount added to the soil-water system; therefore, analysis of sorption isotherms was best conducted using the initial mass isotherm IM method. The ultisol retained, on average, 19.9% of the total DOC and 41.7% of the total DON in solution, suggesting that ultisol has a relatively low DOC adsorption capacity. The ultisol from a bamboo forest was found to have a higher capacity than that from a pear orchard to retain DOC and DON. The adsorption affinities of DOM according to soil type were in the following order: bamboo forest (BF)>tea garden (TG)>pear orchard (PO). These results suggested that the continuous application of high doses of organic manure, particularly rape cake, may saturate the DOC adsorptive sites, thereby permitting increased leaching of DOC and the possibility of ground water contamination. Furthermore, we note that amorphous Fe and Al oxides play an important role in the adsorption capacity of both DOC and DON in ultisols. PMID:24704143

  11. Dissolved organic matter release and retention in ultisols in relation to land use patterns.

    PubMed

    Zhang, Qichun; Hou, Changping; Liang, Yingying; Feng, Ying

    2014-07-01

    The application of organic fertilizer to maintain soil fertility and crop yield has been practiced for thousands of years in China. This practice improves soil carbon sequestration, due to the high level of dissolved organic matter (DOM) in organic manure. In this study, batch equilibrium studies were conducted to examine the capacity of three ultisols from areas under different land use patterns to retain dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) extracted from rape cake and chicken manure. The results showed that the amount of DOM removed or released in solution by the soil was a linear function of the initial amount added to the soil-water system; therefore, analysis of sorption isotherms was best conducted using the initial mass isotherm IM method. The ultisol retained, on average, 19.9% of the total DOC and 41.7% of the total DON in solution, suggesting that ultisol has a relatively low DOC adsorption capacity. The ultisol from a bamboo forest was found to have a higher capacity than that from a pear orchard to retain DOC and DON. The adsorption affinities of DOM according to soil type were in the following order: bamboo forest (BF)>tea garden (TG)>pear orchard (PO). These results suggested that the continuous application of high doses of organic manure, particularly rape cake, may saturate the DOC adsorptive sites, thereby permitting increased leaching of DOC and the possibility of ground water contamination. Furthermore, we note that amorphous Fe and Al oxides play an important role in the adsorption capacity of both DOC and DON in ultisols.

  12. Abundance and Characterization of Dissolved Organic Carbon in Suburban Streams of Baltimore, Maryland, USA

    NASA Astrophysics Data System (ADS)

    Mora, G.; Fazekas, M.

    2014-12-01

    The contribution of streams and rivers to the carbon cycle is significant, transporting to the oceans ~1.4 Pg C/yr, with dissolved carbon corresponding to as much as 0.7 Pg C/yr. Changes in land use have the potential effect of modifying this flux, particularly in urban areas where impervious areas are common. To investigate the effect of urbanization on riverine carbon transport, we studied four first-order streams in Towson, a suburb of Baltimore, Maryland, USA. The watersheds from the studied streams exhibit different levels of urbanization as measured by the percentage of impervious areas. Samples from these four streams were taken weekly, and several chemical constituents were measured either in the field or in the laboratory. These constituents included nitrate, dissolved organic nitrogen, pH, dissolved organic carbon (DOC), total carbon, dissolved inorganic carbon (DIC), phosphate, the carbon isotopic compositions of DOC and DIC, and fluorescence intensity of the DOC. Results show that DOC concentrations were consistently below 5 mg C/L regardless of the level of imperviousness of the watershed. Similarly, carbon isotope ratios were consistent across the studied streams, with values centered around -26.4 per mil, thus suggesting a significant influx of soil-derived organic carbon originated from C3 plants that are common in the watersheds. Confirming this interpretation, fluorescence spectroscopy data suggest a humic-like origin for the DOC of the streams, thus pointing to the heterotrophic nature of the streams. The combined results suggest that the studied streams exhibit similar DOC concentrations, carbon isotopic values, and fluorescence spectra, despite their level of impervious surfaces in their watersheds.

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

    PubMed

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

    2016-03-15

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

  14. Linking CDOM spectral absorption to dissolved organic carbon concentrations and loadings in boreal estuaries

    NASA Astrophysics Data System (ADS)

    Asmala, Eero; Stedmon, Colin A.; Thomas, David N.

    2012-10-01

    The quantity of chromophoric dissolved organic matter (CDOM) and dissolved organic carbon (DOC) in three Finnish estuaries (Karjaanjoki, Kyrönjoki and Kiiminkijoki) was investigated, with respect to predicting DOC concentrations and loadings from spectral CDOM absorption measurements. Altogether 87 samples were collected from three estuarine transects which were studied in three seasons, covering a salinity range between 0 and 6.8, and DOC concentrations from 1572 μmol l-1 in freshwater to 222 μmol l-1 in coastal waters. CDOM absorption coefficient, aCDOM(375) values followed the trend in DOC concentrations across the salinity gradient and ranged from 1.67 to 33.4 m-1. The link between DOC and CDOM was studied using a range of wavelengths and algorithms. Wavelengths between 250 and 270 nm gave the best predictions with single linear regression. Total dissolved iron was found to influence the prediction in wavelengths above 520 nm. Despite significant seasonal and spatial differences in DOC-CDOM models, a universal relationship was tested with an independent data set and found to be robust. DOC and CDOM yields (loading/catchment area) from the catchments ranged from 1.98 to 5.44 g C m-2 yr-1, and 1.67 to 11.5 aCDOM(375) yr-1, respectively.

  15. Atmospheric pressure mass spectrometry: a new analytical chemical characterization method for dissolved organic matter in rainwater.

    PubMed

    Seitzinger, Sybil P; Styles, Renée M; Lauck, Ron; Mazurek, Monica A

    2003-01-01

    The complex mixture of organic compounds in the atmosphere influences climate, air quality, and ecosystem processes. Atmospheric pressure electrospray ionization mass spectrometry (APESI-MS) was evaluated as a potential tool for direct measurement of the total suite of individual dissolved organic matter (DOM) compounds in rainwater. The APESI-MS response was linear to all DOM compounds of atmospheric significance examined as standard solutions. Urban precipitation samples from New Brunswick, NJ (USA) were analyzed by APESI-MS over the mass-to-charge (m/z) range 50-3,000. Over 95% of the m/z ions detected were in the low m/z range (50-500). Over 300 unique m/z ions were detected across the 11 rainwater samples indicating the complexity of the mixture of DOM in rainwater. Forty percent of the organic bases (positive mode detection) and 22% of the organic acids (negative mode) occurred in at least 6 of the 11 rainwater samples. Ions corresponding to the m/z of carboxylic acids standards (nonanedioic acid; 1,4-butanedicarboxylic acid; pentanedioic acid; hydroxybutanedioic acid; and butanedioic acid) and to reduced N standards (allylurea; caffeine; imidazole; and N-2-propenylurea) occurred in at least one of the 11 rainwater samples. Total dissolved organic carbon (DOC) estimated from the APESI-MS analysis and measured by standard DOC methods were not statistically different.

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

    DOE PAGES

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

    2015-01-12

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

  17. 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

  18. Effect of algal flocculation on dissolved organic matters using cationic starch modified soils.

    PubMed

    Shi, Wenqing; Bi, Lei; Pan, Gang

    2016-07-01

    Modified soils (MSs) are being increasingly used as geo-engineering materials for the sedimentation removal of cyanobacterial blooms. Cationic starch (CS) has been tested as an effective soil modifier, but little is known about its potential impacts on the treated water. This study investigated dissolved organic matters in the bloom water after algal removal using cationic starch modified soils (CS-MSs). Results showed that the dissolved organic carbon (DOC) could be decreased by CS-MS flocculation and the use of higher charge density CS yielded a greater DOC reduction. When CS with the charge density of 0.052, 0.102 and 0.293meq/g were used, DOC was decreased from 3.4 to 3.0, 2.3 and 1.7mg/L, respectively. The excitation-emission matrix fluorescence spectroscopy and UV254 analysis indicated that CS-MS exhibits an ability to remove some soluble organics, which contributed to the DOC reduction. However, the use of low charge density CS posed a potential risk of DOC increase due to the high CS loading for effective algal removal. When CS with the charge density of 0.044meq/g was used, DOC was increased from 3.4 to 3.9mg/L. This study suggested, when CS-MS is used for cyanobacterial bloom removal, the content of dissolved organic matters in the treated water can be controlled by optimizing the charge density of CS. For the settled organic matters, other measures (e.g., capping treatments using oxygen loaded materials) should be jointly applied after algal flocculation. PMID:27372131

  19. Molecular insights into the microbial formation of marine dissolved organic matter: recalcitrant or labile?

    NASA Astrophysics Data System (ADS)

    Koch, B. P.; Kattner, G.; Witt, M.; Passow, U.

    2014-02-01

    The degradation of marine dissolved organic matter (DOM) is an important control variable in the global carbon cycle and dependent on the DOM composition. For our understanding of the kinetics of organic matter cycling in the ocean, it is therefore crucial to achieve a mechanistic and molecular understanding of its transformation processes. A long-term microbial experiment was performed to follow the production of non-labile DOM by marine bacteria. Two different glucose concentrations and dissolved algal exudates were used as substrates. We monitored the bacterial abundance, concentrations of dissolved and particulate organic carbon (DOC, POC), nutrients, amino acids, and transparent exopolymer particles (TEP) for two years. Ultrahigh resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS) allowed the molecular characterization of extracted DOM after 70 days and after ∼2 years of incubation. Although glucose was quickly degraded, a DOC background was generated in glucose incubations. Only 20% of the organic carbon from algal exudate was degraded within the 2 years of incubation. TEP, which are released by micro-organisms, were produced during glucose degradation but decreased within less than three weeks back to half of the maximum concentration and were below detection in all treatments after 2 years. The molecular analysis demonstrated that DOM generated during glucose degradation differed appreciably from DOM produced during the degradation of the algal exudates. Our results led to several conclusions: (i) Higher substrate levels result in a higher level of non-labile DOC which is an important prerequisite for carbon sequestration in the ocean; (ii) TEP are generated by bacteria but are also degraded rapidly, thus limiting their potential contribution to carbon sequestration; (iii) The molecular signatures of DOM derived from algal exudates or glucose after 70 days of incubation differed strongly from refractory DOM. After 2 years

  20. 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.

  1. [Spectral characteristics of dissolved organic matter released during the metabolic process of small medusa].

    PubMed

    Guo, Dong-Hui; Yi, Yue-Yuan; Zhao, Lei; Guo, Wei-Dong

    2012-06-01

    The metabolic processes of jellyfish can produce dissolved organic matter (DOM) which will influence the functioning of the aquatic ecosystems, yet the optical properties of DOM released by jellyfish are unknown. Here we report the absorption and fluorescence properties of DOM released by a medusa species Black fordia virginica during a 24 h incubation experiment. Compared with the control group, an obvious increase in the concentrations of dissolved organic carbon (DOC), absorption coefficient (a280) and total dissolved nitrogen (TDN) was observed in incubation group. This clearly demonstrated the release of DOM, chromophoric DOM (CDOM) and dissolved nutrients by B. virginica which feed on enough of Artemia sp. before the experiment. The increase in spectral slope ratio (SR) and decrease in humification index (HIX) indicated that the released DOM was less-humified and had relatively lower molecular weight. Parallel factor analysis (PARAFAC) decomposed the fluorescence matrices of DOM into three humic-like components (C1-C3) and one protein-like component (C4). The Fmax of two components (C2: < 250, 295/386 nm; C4: 275/334 nm) with the emission wavelength < 400 nm increased significantly during the metabolic process of B. virginica. However, the Fmax of the other two components with the emission wavelength > 400 nm showed little changes. Thus, we suggested a zooplankton index (ZIX) to trace and characterize the DOM excreted by metabolic activity of zooplankton, which is calculated as the ratio of the sum of Fmax of all fluorescence components with the emission wavelength < 400 nm to the sum of Fmax of the other components with the emission wavelength > 400 nm. PMID:22870644

  2. Bacterial Contribution to Dissolved Organic Matter in Eutrophic Lake Kasumigaura, Japan

    PubMed Central

    Komatsu, Kazuhiro; Kohzu, Ayato; Tomioka, Noriko; Shinohara, Ryuichiro; Satou, Takayuki; Watanabe, Fumiko Nara; Tada, Yuya; Hamasaki, Koji; Kushairi, M. R. M.; Imai, Akio

    2013-01-01

    Incubation experiments using filtered waters from Lake Kasumigaura were conducted to examine bacterial contribution to a dissolved organic carbon (DOC) pool. Bacterial abundance, bacterial production, concentrations of DOC, total dissolved amino acids (TDAA), and total dissolved neutral sugars (TDNS) were monitored during the experiments. Bacterial production during the first few days was very high (20 to 35 μg C liter−1 day−1), accounting for 40 to 70% of primary production. The total bacterial production accounted for 34 to 55% of the DOC loss during the experiment, indicating high bacterial activities in Lake Kasumigaura. The DOC degradation was only 12 to 15%, whereas the degradation of TDAA and TDNS ranged from 30 to 50%, suggesting the preferential usage of TDAA and TDNS. The contribution of bacterially derived carbon to a DOC pool in Lake Kasumigaura was estimated using d-amino acids as bacterial biomarkers and accounted for 30 to 50% of the lake DOC. These values were much higher than those estimated for the open ocean (20 to 30%). The ratio of bacterially derived carbon to bulk carbon increased slightly with time, suggesting that the bacterially derived carbon is more resistant to microbial degradation than bulk carbon. This is the first study to estimate the bacterial contribution to a DOC pool in freshwater environments. These results indicate that bacteria play even more important roles in carbon cycles in freshwater environments than in open oceans and also suggests that recent increases in recalcitrant DOC in various lakes could be attributed to bacterially derived carbon. The potential differences in bacterial contributions to dissolved organic matter (DOM) between freshwater and marine environments are discussed. PMID:24038686

  3. Export of Dissolved Organic Matter, Nutrients and Carbon from Himalayan River System in Central Nepal

    NASA Astrophysics Data System (ADS)

    Bhatt, M. P.

    2014-12-01

    Chemical weathering is a vital ecosystem process and plays a central role in regulation of global carbon cycles. Weathering from Himalayan landscape supply high amount of major ions, nutrients and suspended sediments to the oceans. Surface water samples were collected from sixteen stations at different altitude along the Langtnag-Narayani Himalayan river system in central Nepal on a monthly basis for one year. This study aims to investigate spatiotemporal variations of dissolved organic matter, nutrients and carbonic species and to evaluate their controlling factors within the basin. The fluxes of these species appeared several fold higher at low elevation than at mid mountains and high elevation Himalaya sites. Seasonality appeared to exert major control on concentrations and fluxes of major solutes along the drainage network. The highest export rate of chemical species corresponded to the monsoon season, followed by the ones corresponding to post-monsoon and pre-monsoon seasons. Carbonate has major control on the flux of major solutes within the basin. The export rate of dissolved organic carbon and total dissolved nitrogen were about three and seventeen times higher respectively at the Narayani basin than its headwater at Langtang basin within the high Himalaya. Nitrate and phosphate export rates in the Narayani basin were 5.07 and 0.34 tons km-2 yr-1 respectively which is several fold higher than the rates in the high Himalaya probably due to input from agricultural activities. The export of dissolved inorganic carbon from the Narayani basin was 101.87 tons km-2 yr-1 of which bicarbonate appeared to be the dominant fraction (94.9%) followed by carbonic acid (4.7%) and carbonate (0.4%). Partial pressure of carbon dioxide (pCO2) resulted under-saturated in the high elevation Himalayan basin and supersaturated at the low elevation Narayani basin. The concentration of pCO2 is considered to be an important factor for regulating weathering rates of any landscape.

  4. Dissolved Organic Carbon Mobilisation in a Groundwater System Stressed by Pumping

    PubMed Central

    Graham, P. W.; Baker, A.; Andersen, M. S.

    2015-01-01

    The concentration and flux of organic carbon in aquifers is influenced by recharge and abstraction, and surface and subsurface processing. In this study groundwater was abstracted from a shallow fractured rock aquifer and dissolved organic carbon (DOC) was measured in observation bores at different distances from the abstraction bore. Groundwater abstraction at rates exceeding the aquifers yield resulted in increased DOC concentration up to 3,500 percent of initial concentrations. Potential sources of this increased DOC were determined using optical fluorescence and absorbance analysis. Groundwater fluorescent dissolved organic material (FDOM) were found to be a combination of terrestrial-derived humic material and microbial or protein sourced material. Relative molecular weight of FDOM within four metres of the abstraction well increased during the experiment, while the relative molecular weight of FDOM between four and ten metres from the abstraction well decreased. When the aquifer is not being pumped, DOC mobilisation in the aquifer is low. We hypothesise that the physical shear stress on aquifer materials caused by intense abstraction significantly increases the temporary release of DOC from sloughing of biofilms and release of otherwise bound colloidal and sedimentary organic carbon (SOC). PMID:26691238

  5. Water solubility enhancement of some organic pollutants and pesticides by dissolved humic and fulvic acids

    USGS Publications Warehouse

    Chiou, C.T.; Malcolm, R.L.; Brinton, T.I.; Kile, D.E.

    1986-01-01

    Water solubility enhancements by dissolved humic and fulvic acids from soil and aquatic origins and by synthetic organic polymers have been determined for selected organic pollutants and pesticides (p,p???-DDT, 2,4,5,2???,5???-PCB, 2,4,4???-PCB, 1,2,3-trichlorobenzene, and lindane). Significant solubility enhancements of relatively water-insoluble solutes by dissolved organic matter (DOM) of soil and aquatic origins may be described in terms of a partition-like interaction of the the solutes with the microscopic organic environment of the high-molecular-weight DOM species; the apparent solute solubilities increase linearly with DOM concentration and show no competitive effect between solutes. With a given DOM sample, the solute partition coefficient (Kdom) increases with a decrease of solute solubility (Sw) or with an increase of the solute's octanol-water partition coefficient (Kow). The Kdom values of solutes with soil-derived humic acid are approximately 4 times greater than with soil fulvic acid and 5-7 times greater than with aquatic humic and fulvic acids. The effectiveness of DOM in enhancing solute solubility appears to be largely controlled by the DOM molecular size and polarity. The relative inability of high-molecular-weight poly(acrylic acids) to enhance solute solubility is attributed to their high polarities and extended chain structures that do not permit the formation of a sizable intramolecular nonpolar environment.

  6. Closely related phytoplankton species produce similar suites of dissolved organic matter

    PubMed Central

    Becker, Jamie W.; Berube, Paul M.; Follett, Christopher L.; Waterbury, John B.; Chisholm, Sallie W.; DeLong, Edward F.; Repeta, Daniel J.

    2014-01-01

    Production of dissolved organic matter (DOM) by marine phytoplankton supplies the majority of organic substrate consumed by heterotrophic bacterioplankton in the sea. This production and subsequent consumption converts a vast quantity of carbon, nitrogen, and phosphorus between organic and inorganic forms, directly impacting global cycles of these biologically important elements. Details regarding the chemical composition of DOM produced by marine phytoplankton are sparse, and while often assumed, it is not currently known if phylogenetically distinct groups of marine phytoplankton release characteristic suites of DOM. To investigate the relationship between specific phytoplankton groups and the DOM they release, hydrophobic phytoplankton-derived dissolved organic matter (DOMP) from eight axenic strains was analyzed using high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS). Identification of DOM features derived from Prochlorococcus, Synechococcus, Thalassiosira, and Phaeodactylum revealed DOMP to be complex and highly strain dependent. Connections between DOMP features and the phylogenetic relatedness of these strains were identified on multiple levels of phylogenetic distance, suggesting that marine phytoplankton produce DOM that in part reflects its phylogenetic origin. Chemical information regarding the size and polarity ranges of features from defined biological sources was also obtained. Our findings reveal DOMP composition to be partially conserved among related phytoplankton species, and implicate marine DOM as a potential factor influencing microbial diversity in the sea by acting as a link between autotrophic and heterotrophic microbial community structures. PMID:24748874

  7. Dissolved Organic Carbon Mobilisation in a Groundwater System Stressed by Pumping.

    PubMed

    Graham, P W; Baker, A; Andersen, M S

    2015-01-01

    The concentration and flux of organic carbon in aquifers is influenced by recharge and abstraction, and surface and subsurface processing. In this study groundwater was abstracted from a shallow fractured rock aquifer and dissolved organic carbon (DOC) was measured in observation bores at different distances from the abstraction bore. Groundwater abstraction at rates exceeding the aquifers yield resulted in increased DOC concentration up to 3,500 percent of initial concentrations. Potential sources of this increased DOC were determined using optical fluorescence and absorbance analysis. Groundwater fluorescent dissolved organic material (FDOM) were found to be a combination of terrestrial-derived humic material and microbial or protein sourced material. Relative molecular weight of FDOM within four metres of the abstraction well increased during the experiment, while the relative molecular weight of FDOM between four and ten metres from the abstraction well decreased. When the aquifer is not being pumped, DOC mobilisation in the aquifer is low. We hypothesise that the physical shear stress on aquifer materials caused by intense abstraction significantly increases the temporary release of DOC from sloughing of biofilms and release of otherwise bound colloidal and sedimentary organic carbon (SOC). PMID:26691238

  8. Bioavailability of riverine dissolved organic matter to phytoplankton in the marine coastal waters

    NASA Astrophysics Data System (ADS)

    Jurgensone, Iveta; Aigars, Juris

    2012-07-01

    Nutrient inputs from catchments with intensive agriculture are mostly dominated by inorganic nutrients, whereas the contribution of organic nutrients from catchments with natural forests can be considerable but there is a pooere understanding of this nutrient source. Consequently this study investigated spring, summer and autumn phytoplankton community responses to enrichment by riverine dissolved organic matter (DOM). Dissolved organic substances were extracted from the Daugava River, fractionated into three molecular size classes: 1) 5-100 kDa, 2) 100-1000 kDa, and 3) >1000 kDa, and added to a microcosm with natural assemblages from the Gulf of Riga. During the spring the phytoplankton community was dominated (97%) by diatoms and the species composition did not change over the course of the experiment. Specific species and functional groups of the summer and autumn phytoplankton communities responded positively to these treatments. Small-celled cyanobacteria and Monoraphidium contortum responded to almost all size fractions of DOM for the summer and autumn experiments. Oocystis spp. characteristic for the summer and Chaetoceros wighamii, Cyclotella spp., Thalassiosira baltica for the autumn responded to treatment by two and three size classes of organic substances, respectively, while Merismopedia spp. shifted from one food source to another during the summer experiment.

  9. PHOTOGENERATION OF SINGLET OXYGEN AND FREE RADICALS IN DISSOLVED ORGANIC MATTER ISOLATED FROM THE MISSISSIPPI AND ATCHAFALAYA RIVER PLUMES

    EPA Science Inventory

    The photoreactivity to UV light of ultrafiltered dissolved organic matter (DOM) collected during cruises along salinity transects in the Mississippi and Atchafalaya River plumes was examined by measuring photogenerated free radicals and singlet molecular oxygen (1O2) photosensiti...

  10. PHOTOCHEMICALLY-INDUCED ALTERATION OF STABLE CARBON ISOTOPE RATIOS (DELTA C-13) IN TERRIGENOUS DISSOLVED ORGANIC CARBON

    EPA Science Inventory

    Exposure of riverine waters to natural sunlight initiated alterations in stable carbon isotope ratios (delta C-13) of the associated dissolved organic carbon (DOC). Water samples were collected from two compositionally distinct coastal river systems in the southeastern United Sta...

  11. SPATIAL AND TEMPORAL DISTRIBUTION OF COLOURED DISSOLVED ORGANIC MATTER (CDOM) IN NARRAGANSETT BAY, RI: IMPLICATIONS FOR PHYTOPLANKTON IN COASTAL WATERS

    EPA Science Inventory

    One indicator of health in estuarine and coastal ecosystems is the ability of local waters to transmit sunlight to planktonic, macrophytic, and other submerged vegetation for photosynthesis. The concentration of coloured dissolved organic matter (CDOM) is a primary factor affecti...

  12. EFFECTS OF PHOTOCHEMICAL, MICROBIAL AND SORPTION PROCESSES ON THE OPTICAL PROPERTIES AND DEGRADATION OF DISSOLVED ORGANIC MATTER FROM COASTAL WETLANDS

    EPA Science Inventory

    The dissolved organic matter (DOM) exported from rivers and intertidal marshes to coastal oceans is rich in light-absorbing, fluorescent constituents, including humic substances and other polyphenolic moieties. Interactions between microbial and photochemical processes have impor...

  13. INTERACTIONS BETWEEN PHOTOCHEMICAL AND MICROBIAL DECOMPOSITION IN MODIFYING THE BIOLOGICAL AVAILABILITY AND OPTICAL PROPERTIES OF ESTUARINE DISSOLVED ORGANIC MATTER

    EPA Science Inventory

    Direct photodecomposition and photochemically-mediated bacterial degradation (via photochemical modification of otherwise refractory DOM into biologically labile forms) provide
    important pathways for the loss of dissolved organic matter in coastal waters. Here we report
    lab...

  14. Characterization of dissolved organic materials in surface waters within the blast zone of Mount St Helens, Washington

    USGS Publications Warehouse

    McKnight, Diane M.; Pereira, W.E.; Ceazan, M.L.; Wissmar, Robert C.

    1982-01-01

    After the May 18, 1980, eruption of Mount St Helens, the concentration of dissolved organic material in surface waters near the volcano increased significantly as a result of the destruction of the surrounding conifer forest. Low molecular weight organic compounds identified in the blast zone surface waters were derived from pyrolysis of plant and soil organic materials incorporated into pyroclastic flow, mud flow and debris avalanche deposits. A major fraction of the dissolved organic material consisted of high molecular weight, colored, organic acids that are similar in their general properties to aquatic fulvic acids found in more typical surface waters except for greater sulfur contents. The other major fraction of the dissolved organic material consisted of hydrophilic acids, which may include compounds capable of supporting heterotrophic microorganisms, and precursors in the formation of aquatic fulvic acids. The organic chemistry of blast zone surface waters will probably be greatly influenced by the May 18, 1980, eruption for many years. ?? 1982.

  15. Cu Binding to Iron Oxide-Organic Matter Coprecipitates in Solid and Dissolved Phases

    NASA Astrophysics Data System (ADS)

    Vadas, T. M.; Koenigsmark, F.

    2015-12-01

    Recent studies indicate that Cu is released from wetlands following storm events. Assymetrical field flow field fractionation (AF4) analyses as well as total and dissolved metal concentration measurements suggest iron oxide-organic matter complexes control Cu retention and release. Coprecipitation products of Fe oxide and organic matter were prepared under conditions similar to the wetland to assess Cu partitioning to and availability from solid phases that settle from solution as well as phases remaining suspended. Cu coprecipitation and sorption to organomineral precipitation solids formed at different Fe:organic carbon (OC) ratios were compared for net Cu removal and extractability. As more humic acid was present during precipitation of Fe, TEM images indicated smaller Fe oxide particles formed within an organic matrix as expected. In coprecipitation reactions, as the ratio of Fe:OC decreased, more Cu was removed from solution at pH 5.5 and below. However, in sorption reactions, there was an inhibition of Cu removal at low OC concentrations. As the pH increased from 5.5 to 7 and as solution phase OC concentration increased, more Cu remained dissolved in both coprecipitation and sorption reactions. The addition of Ca2+, glycine, histidine and citric acid or lowering the pH resulted in more extractable Cu from the coprecipitation compared with the sorption reactions. The variations in Cu extraction were likely due to a combination of a more amorphous structure in CPT products, and the relative abundance of available Fe oxide or OC binding sites. Suspended Fe oxide-organic matter coprecipitates were assessed using AF4 coupled to online TOC analysis and ICP-MS. In laboratory prepared samples, Cu was observed in a mixture of small 1-5 nm colloids of Fe oxide-organic matter precipitates, but the majority was observed in larger organic matter colloids and were not UV absorbing, suggesting more aliphatic carbon materials. In field samples, up to 60% of the dissolved Cu

  16. State factor relationships of dissolved organic carbon and nitrogen losses from unpolluted temperate forest watersheds

    USGS Publications Warehouse

    Perakis, S.S.; Hedin, L.O.

    2007-01-01

    We sampled 100 unpolluted, old-growth forested watersheds, divided among 13 separate study areas over 5 years in temperate southern Chile and Argentina, to evaluate relationships among dominant soil-forming state factors and dissolved carbon and nitrogen concentrations in watershed streams. These watersheds provide a unique opportunity to examine broad-scale controls over carbon (C) and nitrogen (N) biogeochemistry in the absence of significant human disturbance from chronic N deposition and land use change. Variations in the ratio dissolved organic carbon (DOC) to nitrogen (DON) in watershed streams differed by underlying soil parent material, with average C:N = 29 for watersheds underlain by volcanic ash and basalt versus C:N = 73 for sedimentary and metamorphic parent materials, consistent with stronger adsorption of low C:N hydrophobic materials by amorphous clays commonly associated with volcanic ash and basalt weathering. Mean annual precipitation was related positively to variations in both DOC (range: 0.2-9.7 mg C/L) and DON (range: 0.008-0.135 mg N/L) across study areas, suggesting that variations in water volume and concentration may act synergistically to influence C and N losses across dry to wet gradients in these forest ecosystems. Dominance of vegetation by broadleaf versus coniferous trees had negligible effects on organic C and N concentrations in comparison to abiotic factors. We conclude that precipitation volume and soil parent material are important controls over chemical losses of dissolved organic C and N from unpolluted temperate forest watersheds. Our results raise the possibility that biotic imprints on watershed C and N losses may be less pronounced in naturally N-poor forests than in areas impacted by land use change and chronic N deposition. Copyright 2007 by the American Geophysical Union.

  17. Effects of coral reef benthic primary producers on dissolved organic carbon and microbial activity.

    PubMed

    Haas, Andreas F; Nelson, Craig E; Wegley Kelly, Linda; Carlson, Craig A; Rohwer, Forest; Leichter, James J; Wyatt, Alex; Smith, Jennifer E

    2011-01-01

    Benthic primary producers in marine ecosystems may significantly alter biogeochemical cycling and microbial processes in their surrounding environment. To examine these interactions, we studied dissolved organic matter release by dominant benthic taxa and subsequent microbial remineralization in the lagoonal reefs of Moorea, French Polynesia. Rates of photosynthesis, respiration, and dissolved organic carbon (DOC) release were assessed for several common benthic reef organisms from the backreef habitat. We assessed microbial community response to dissolved exudates of each benthic producer by measuring bacterioplankton growth, respiration, and DOC drawdown in two-day dark dilution culture incubations. Experiments were conducted for six benthic producers: three species of macroalgae (each representing a different algal phylum: Turbinaria ornata--Ochrophyta; Amansia rhodantha--Rhodophyta; Halimeda opuntia--Chlorophyta), a mixed assemblage of turf algae, a species of crustose coralline algae (Hydrolithon reinboldii) and a dominant hermatypic coral (Porites lobata). Our results show that all five types of algae, but not the coral, exuded significant amounts of labile DOC into their surrounding environment. In general, primary producers with the highest rates of photosynthesis released the most DOC and yielded the greatest bacterioplankton growth; turf algae produced nearly twice as much DOC per unit surface area than the other benthic producers (14.0±2.8 µmol h⁻¹ dm⁻²), stimulating rapid bacterioplankton growth (0.044±0.002 log10 cells h⁻¹) and concomitant oxygen drawdown (0.16±0.05 µmol L⁻¹ h⁻¹ dm⁻²). Our results demonstrate that benthic reef algae can release a significant fraction of their photosynthetically-fixed carbon as DOC, these release rates vary by species, and this DOC is available to and consumed by reef associated microbes. These data provide compelling evidence that benthic primary producers differentially influence reef microbial

  18. [Evolution of Dissolved Organic Matter Properties in a Constructed Wetland of Xiao River, Hebei].

    PubMed

    Ma, Li-na; Zhang, Hui; Tan, Wen-bing; Yu, Min-da; Huang, Zhi-gang; Gao, Ru-tai; Xi, Bei-dou; He, Xiao-song

    2016-01-01

    The evolution of water DOC and COD, and the source, chemical structure, humification degree and redox of dissolved organic matter (DOM) in a constructed wetland of Xiao River, Hebei, was investigated by 3D excitation--emission matrix fluorescence spectroscopy coupled with ultraviolet spectroscopy and chemical reduction, in order to explore the geochemical processes and environmental effects of DOM. Although DOC contributes at least 60% to COD, its decrease in the constructed wetland is mainly caused by the more extensive degradation of elements N, H, S, and P than C in DOM, and 65% is contributed from the former. DOM is mainly consisted of microbial products based on proxies f470/520 and BIX, indicating that DOM in water is apparently affected by microbial degradation. The result based on PARAFAC model shows that DOM in the constructed wetland contains protein-like and humus-like components, and Fulvic- and humic-like components are relatively easier to degrade than protein-like components. Fulvic- and humic-like components undergo similar decomposition in the constructed wetland. A common source of chromophoric dissolved organic matter (CDOM) and fluorescent dissolved organic matter (FDOM) exists; both CDOM and FDOM are mainly composed of a humus-like material and do not exhibit selective degradation in the constructed wetland. The proxies E2 /E3, A240-400, r(A, C) and HIX in water have no changes after flowing into the constructed wetland, implying that the humification degree of DOM in water is hardly affected by wet constructed wetland. However, the constructed wetland environment is not only beneficial in forming the reduced state of DOM, but also facilitates the reduction of ferric. It can also improve the capability of DOM to function as an electron shuttle. This result may be related to the condition that the aromatic carbon of DOM can be stabilized well in the constructed wetland.

  19. Effects of Coral Reef Benthic Primary Producers on Dissolved Organic Carbon and Microbial Activity

    PubMed Central

    Haas, Andreas F.; Nelson, Craig E.; Wegley Kelly, Linda; Carlson, Craig A.; Rohwer, Forest; Leichter, James J.; Wyatt, Alex; Smith, Jennifer E.

    2011-01-01

    Benthic primary producers in marine ecosystems may significantly alter biogeochemical cycling and microbial processes in their surrounding environment. To examine these interactions, we studied dissolved organic matter release by dominant benthic taxa and subsequent microbial remineralization in the lagoonal reefs of Moorea, French Polynesia. Rates of photosynthesis, respiration, and dissolved organic carbon (DOC) release were assessed for several common benthic reef organisms from the backreef habitat. We assessed microbial community response to dissolved exudates of each benthic producer by measuring bacterioplankton growth, respiration, and DOC drawdown in two-day dark dilution culture incubations. Experiments were conducted for six benthic producers: three species of macroalgae (each representing a different algal phylum: Turbinaria ornata – Ochrophyta; Amansia rhodantha – Rhodophyta; Halimeda opuntia – Chlorophyta), a mixed assemblage of turf algae, a species of crustose coralline algae (Hydrolithon reinboldii) and a dominant hermatypic coral (Porites lobata). Our results show that all five types of algae, but not the coral, exuded significant amounts of labile DOC into their surrounding environment. In general, primary producers with the highest rates of photosynthesis released the most DOC and yielded the greatest bacterioplankton growth; turf algae produced nearly twice as much DOC per unit surface area than the other benthic producers (14.0±2.8 µmol h−1 dm−2), stimulating rapid bacterioplankton growth (0.044±0.002 log10 cells h−1) and concomitant oxygen drawdown (0.16±0.05 µmol L−1 h−1 dm−2). Our results demonstrate that benthic reef algae can release a significant fraction of their photosynthetically-fixed carbon as DOC, these release rates vary by species, and this DOC is available to and consumed by reef associated microbes. These data provide compelling evidence that benthic primary producers differentially influence reef

  20. Development of gas chromatographic system for dissolved organic carbon analysis in seawater. Annual progress report

    SciTech Connect

    Chipman, D.W.; Takahashi, T.

    1992-12-01

    During the first six months of this two-year grant, we have completed the construction of the analytical portion of a prototype gas chromatograph-based system for the analysis of dissolved organic carbon in seawater. We also have begun testing the procedures to be used to cryogenically concentrate and transfer carbon dioxide from the oxidizing atmosphere of the high-temperature furnace into the reducing hydrogen carrier gas of the gas chromatograph. During the second half of the first year, we will construct the high-temperature catalytic oxidation furnace and test the entire system on laboratory-prepared aqueous solutions of various organic compounds. Also during this period, we will take part in an initial scoping study within the Cape Hatteras field area on board the R/V Gyre. This study will involve both the collection of samples of seawater for organic and inorganic carbon analysis and the measurement of surface-water pCO{sub 2}.

  1. Development of gas chromatographic system for dissolved organic carbon analysis in seawater

    SciTech Connect

    Chipman, D.W.; Takahashi, T.

    1992-12-01

    During the first six months of this two-year grant, we have completed the construction of the analytical portion of a prototype gas chromatograph-based system for the analysis of dissolved organic carbon in seawater. We also have begun testing the procedures to be used to cryogenically concentrate and transfer carbon dioxide from the oxidizing atmosphere of the high-temperature furnace into the reducing hydrogen carrier gas of the gas chromatograph. During the second half of the first year, we will construct the high-temperature catalytic oxidation furnace and test the entire system on laboratory-prepared aqueous solutions of various organic compounds. Also during this period, we will take part in an initial scoping study within the Cape Hatteras field area on board the R/V Gyre. This study will involve both the collection of samples of seawater for organic and inorganic carbon analysis and the measurement of surface-water pCO[sub 2].

  2. Chemical and carbon isotopic composition of dissolved organic carbon in a regional confined methanogenic aquifer

    USGS Publications Warehouse

    Aravena, R.; Wassenaar, L.I.; Spiker, E. C.

    2004-01-01

    This study demonstrates the advantage of a combined use of chemical and isotopic tools to understand the dissolved organic carbon (DOC) cycle in a regional confined methanogenic aquifer. DOC concentration and carbon isotopic data demonstrate that the soil zone is a primary carbon source of groundwater DOC in areas close to recharge zones. An in-situ DOC source linked to organic rich sediments present in the aquifer matrix is controlling the DOC pool in the central part of the groundwater flow system. DOC fractions, 13C-NMR on fulvic acids and 14C data on DOC and CH4 support the hypothesis that the in-situ DOC source is a terrestrial organic matter and discard the Ordovician bedrock as a source of DOC. ?? 2004 Taylor and Francis Ltd.

  3. Dissolved and particulate organic carbon fluxes from an agricultural watershed during consecutive tropical storms

    NASA Astrophysics Data System (ADS)

    Caverly, Emma; Kaste, James M.; Hancock, Gregory S.; Chambers, Randolph M.

    2013-10-01

    Low-frequency high-magnitude hydrologic events mobilize a disproportionate amount of dissolved organic carbon (DOC) from watersheds, but few studies measure the role of extreme storms in exporting organic carbon from croplands. We use high-resolution measurements of storm runoff to quantify DOC and particulate organic carbon (POC) fluxes from an agricultural field during consecutive tropical storms that delivered 41 cm of rainfall to the Virginia Coastal Plain. Over a 2 week period, we measured exports of 22 kg DOC ha-1 and 11.3 kg POC ha-1. Ultraviolet absorbance measurements indicate that the aromatic DOC fraction systematically increased as plant-derived aliphatic carbon was depleted during the initial event. Croplands can have event-scale carbon losses that equal or exceed published estimates of annual export for perennial streams draining forested and mixed land use watersheds. We quantify aromatic DOC fractions approaching 50%, indicating that agricultural stormflow can produce a significant load of relatively photoreactive carbon.

  4. Dynamics of dissolved organic matter: A view from two dimensional correlation spectroscopy techniques

    NASA Astrophysics Data System (ADS)

    Abdulla, Hussain A. N.; Hatcher, Patrick G.

    2014-07-01

    Dissolved organic matter (DOM) is the most reactive organic carbon pool in earth. However, the heterogeneity of this organic mixture makes it difficult to investigate its dynamics under different external perturbations. In this review, we present the potential of using the two dimensional correlation spectroscopy analysis (2D correlations) as a tool to study the dynamic of DOM. We demonstrate the application of the 2D correlation analysis on high molecular weight DOM (HMW-DOM) with the salinity as perturbation parameter. We used four different chemical probes: Carbon nuclear magnetic resonance spectroscopy (13C NMR), Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR) and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS).

  5. Distribution and relationship of uranium and radium along an allochthonously dominated wetland gradient.

    PubMed

    Nassour, Mohammad; Weiske, Arndt; Schaller, Jörg; Brackhage, Carsten; Gert Dudel, E

    2015-02-01

    Uranium mining may pose a large threat for freshwater ecosystems, caused by elevated concentrations of metals/radionuclides in drainage water. Important pollutants of such waters are uranium (U) and radium (Ra), because of their impact due to both radio- as well as chemo-toxicity. Despite the comprehensive knowledge about specific element speciation as well as fixation processes, less is known about the retention of U and Ra at a higher level of complexity (within allochthonous ecosystems as predominant for low order streams). Consequently, we investigated the distribution and retention potential of allochthonous ecosystems regarding U and Ra as well as changing U/Ra ratios. We found U predominantly transported over long distances, whereas Ra mainly precipitates immediately after reaching the surface, i.e. in the spring area. Although high U accumulation in organic rich sediments is found, still high transport rates are detected. Low overall fixation of U within the allochthonously dominated wetland results in an U transport over long distances. Consequently, large areas are affected by U mining activities and its post-mining impact, with U being more relevant compared to Ra.

  6. Distribution and relationship of uranium and radium along an allochthonously dominated wetland gradient.

    PubMed

    Nassour, Mohammad; Weiske, Arndt; Schaller, Jörg; Brackhage, Carsten; Gert Dudel, E

    2015-02-01

    Uranium mining may pose a large threat for freshwater ecosystems, caused by elevated concentrations of metals/radionuclides in drainage water. Important pollutants of such waters are uranium (U) and radium (Ra), because of their impact due to both radio- as well as chemo-toxicity. Despite the comprehensive knowledge about specific element speciation as well as fixation processes, less is known about the retention of U and Ra at a higher level of complexity (within allochthonous ecosystems as predominant for low order streams). Consequently, we investigated the distribution and retention potential of allochthonous ecosystems regarding U and Ra as well as changing U/Ra ratios. We found U predominantly transported over long distances, whereas Ra mainly precipitates immediately after reaching the surface, i.e. in the spring area. Although high U accumulation in organic rich sediments is found, still high transport rates are detected. Low overall fixation of U within the allochthonously dominated wetland results in an U transport over long distances. Consequently, large areas are affected by U mining activities and its post-mining impact, with U being more relevant compared to Ra. PMID:25547685

  7. Black Carbon in Estuarine (Coastal) High-molecular-weight Dissolved Organic Matter

    NASA Technical Reports Server (NTRS)

    Mannino, Antonio; Harvey, H. Rodger

    2003-01-01

    Dissolved organic matter (DOM) in the ocean constitutes one of the largest pools of organic carbon in the biosphere, yet much of its composition is uncharacterized. Observations of black carbon (BC) particles (by-products of fossil fuel combustion and biomass burning) in the atmosphere, ice, rivers, soils and marine sediments suggest that this material is ubiquitous, yet the contribution of BC to the ocean s DOM pool remains unknown. Analysis of high-molecular-weight DOM isolated from surface waters of two estuaries in the northwest Atlantic Ocean finds that BC is a significant component of DOM, suggesting that river-estuary systems are important exporters of BC to the ocean through DOM. We show that BC comprises 4-7% of the dissolved organic carbon (DOC) at coastal ocean sites, which supports the hypothesis that the DOC pool is the intermediate reservoir in which BC ages prior to sedimentary deposition. Flux calculations suggest that BC could be as important as vascular plant-derived lignin in terms of carbon inputs to the ocean. Production of BC sequesters fossil fuel- and biomass-derived carbon into a refractory carbon pool. Hence, BC may represent a significant sink for carbon to the ocean.

  8. Characterization of Rainwater Dissolved Organic Matter by Ultrahigh Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Mead, R. N.; Podgorski, D. C.; Mullaugh, K. M.; Avery, B.; Kieber, R. J.; Willey, J. D.; Cooper, W. T.

    2011-12-01

    Rainwater is a complex, heterogeneous mixture of dissolved organic matter (DOM) that remains largely uncharacterized at the molecular level. Rainwater with dissolved organic carbon values ranging from 3 to 450 μM was collected during 40 separate rain events from 2007-2011 that included coastal and terrestrial storms based upon 36 hour back trajectories. Individual rain samples were lypholized and solvent added in preparation for analysis by negative electrospray ionization and atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). This data set is unique in that each rain event was analyzed individually and not combined allowing for unprecedented insight into rainwater DOM at the molecular level on an episodic basis. Unique elemental compositions were assigned for compounds belonging to CHO, CHOS and CHON classes. Data visualization by van Krevelen diagrams showed clear differences in coastal and terrestrial storm events with a majority of coastal storms having high H/C (1.5-2.0) relative to terrestrial storms. Further inspection of the data revealed that rainwater has relatively high O/C (1.4) and low H/C (<0.5) which suggests rainwater DOM is compositionally different than fog water, water soluble organic carbon isolated from aerosols and surface waters.

  9. Associations of free-living bacteria and dissolved organic compounds in a plume of contaminated groundwater

    USGS Publications Warehouse

    Harvey, R.W.; Barber, L.B.; ,

    1992-01-01

    Associations of free-living bacteria (FLB) and dissolved organic contaminants in a 4-km-long plume of sewage-contaminated groundwater were investigated. Abundance of FLB in the core of the plume (as delineated by maximum specific conductance) steadily decreased in the direction of flow from a point 0.25 km downgradient from the source to the toe of the plume. At 0.25 km downgradient, FLB comprised up to 31% of the total bacterial population, but constituted < 7% of the population at 2 km downgradient. Abundance of FLB correlated strongly (r = 0.80 n = 23) with total dissolved organic carbon (DOC) in contaminated groundwater between 0.64 and 2.1 km downgradient, although distributions of individual contaminants such as di-, tri- and tetrachloroethene were highly variable, and their association with FLB less clear. Numbers of FLB in the downgradient portion of the plume which is contaminated with branched-chain alkylbenzenesulfonate (ABS) surfactants were low (< 5??108/L) in spite of relatively high levels of DOC (up to 4 mg/L). However, abundance of FLB correlated strongly with non-surfactant DOC along vertical transects through the plume. The ratio of FLB to DOC and the ratio of FLB to attached bacteria generally decreased in the direction of flow and, consequently, with the age of the organic contaminants.

  10. Assessing the Influences of Urbanization On Dissolved Organic Nitrogen in Stormwater and a Receiving Stream

    NASA Astrophysics Data System (ADS)

    Lusk, M. G.; Toor, G.

    2013-12-01

    Nitrogen (N) is present in several forms in terrestrial and aquatic systems. In water bodies, N is present in inorganic (NH4, NO3) and organic (both dissolved and particulate) forms. Nitrogen carried via stormwater runoff or leaching from fertilized urban landscapes to water bodies can have detrimental effects on water quality because the inorganic N forms are readily available to phytoplankton. There is growing evidence that a part of the dissolved organic N (DON) may also be bioavailable to phytoplankton. DON in urban stormwater runoff, for example, has been shown to be highly bioavailable. The objective of this research is to characterize the sources and chemical fractionation of organic N in stormwater runoff from an urban residential neighborhood and in streamwater along an urban to rural gradient. We hypothesize that urban stormwater DON will be highly fractionated into labile low-molecular weight fractions and that streamwater DON will become increasingly bioavailable with increased urbanization because of shifts in vegetation patterns and hydrologic flowpaths. To test this hypothesis, we are collecting stormwater runoff from an urban neighborhood near Tampa, Florida and streamwater from both urban and rural sub-basins of the adjacent Alafia River.

  11. Compost impacts on dissolved organic carbon and available nitrogen and phosphorus in turfgrass soil.

    PubMed

    Wright, Alan L; Provin, Tony L; Hons, Frank M; Zuberer, David A; White, Richard H

    2008-01-01

    Compost application to turfgrass soils may increase dissolved organic C (DOC) levels which affects nutrient dynamics in soil. The objectives of this study were to investigate the influence of compost source and application rate on soil organic C (SOC), DOC, NO(3), and available P during 29 months after a one-time application to St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] turf. Compost sources had variable composition, yet resulted in few differences in SOC, DOC, and NO(3) after applied to soil. Available NO(3) rapidly decreased after compost application and was unaffected by compost source and application rate. Available P increased after compost application and exhibited cyclical seasonal patterns related to DOC. Compost application decreased soil pH relative to unamended soil, but pH increased during the course of the study due to irrigation with sodic water. Increasing the compost application rate increased SOC by 3 months, and levels remained fairly stable to 29 months. In contrast, DOC continued to increase from 3 to 29 months after application, suggesting that compost mineralization and growth of St. Augustinegrass contributed to seasonal dynamics. Dissolved organic C was 75%, 78%, and 101% greater 29 months after application of 0, 80, and 160 Mg compostha(-1), respectively, than before application. Impacts of composts on soil properties indicated that most significant effects occurred within a few months of application. Seasonal variability of SOC, DOC, and available P was likely related to St. Augustinegrass growth stages as well as precipitation, as declines occurred after precipitation events.

  12. Dissolved organic matter quality and bioavailability changes across an urbanization gradient in headwater streams.

    PubMed

    Hosen, Jacob D; McDonough, Owen T; Febria, Catherine M; Palmer, Margaret A

    2014-07-15

    Landscape urbanization broadly alters watersheds and stream ecosystems, yet the impact of nonpoint source urban inputs on the quantity, quality, and ultimate fate of dissolved organic matter (DOM) is poorly understood. We assessed DOM quality and microbial bioavailability in eight first-order Coastal Plain headwater streams along a gradient of urbanization (i.e., percent watershed impervious cover); none of the streams had point source discharges. DOM quality was measured using fluorescence excitation-emission matrices (EEMs) coupled with parallel factor analysis (PARAFAC). Bioavailability was assessed using biodegradable dissolved organic carbon (BDOC) incubations. Results showed that watershed impervious cover was significantly related to stream DOM composition: increasing impervious cover was associated with decreased amounts of natural humic-like DOM and enriched amounts of anthropogenic fulvic acid-like and protein-like DOM. Microbial bioavailability of DOM was greater in urbanized streams during spring and summer, and was related to decreasing proportions of humic-like DOM and increasing proportions of protein-like DOM. Increased bioavailability was associated with elevated extracellular enzyme activity of the initial microbial community supplied to samples during BDOC incubations. These findings indicate that changes in stream DOM quality due to watershed urbanization may impact stream ecosystem metabolism and ultimately the fate of organic carbon transported through fluvial systems.

  13. Differences in dissolved organic matter between reclaimed water source and drinking water source.

    PubMed

    Hu, Hong-Ying; Du, Ye; Wu, Qian-Yuan; Zhao, Xin; Tang, Xin; Chen, Zhuo

    2016-05-01

    Dissolved organic matter (DOM) significantly affects the quality of reclaimed water and drinking water. Reclaimed water potable reuse is an effective way to augment drinking water source and de facto reuse exists worldwide. Hence, when reclaimed water source (namely secondary effluent) is blended with drinking water source, understanding the difference in DOM between drinking water source (dDOM) and reclaimed water source (rDOM) is essential. In this study, composition, transformation, and potential risk of dDOM from drinking water source and rDOM from secondary effluent were compared. Generally, the DOC concentration of rDOM and dissolved organic nitrogen (DON) content in reclaimed water source were higher but rDOM exhibited a lower aromaticity. Besides, rDOM comprises a higher proportion of hydrophilic fractions and more low-molecular weight compounds, which are difficult to be removed during coagulation. Although dDOM exhibited higher specific disinfection byproducts formation potential (SDBPFP), rDOM formed more total disinfection byproducts (DBPs) during chlorination including halomethanes (THMs) and haloacetic acids (HAAs) due to high DOC concentration. Likewise, in consideration of DOC basis, rDOM contained more absolute assimilable organic carbon (AOC) despite showing a lower specific AOC (normalized AOC per unit of DOC). Besides, rDOM exhibited higher biotoxicity including genotoxicity and endocrine disruption. Therefore, rDOM presents a greater potential risk than dDOM does. Reclaimed water source needs to be treated carefully when it is blended with drinking water source.

  14. Dissolved organic matter and heterotrophic microneuston in the surface microlayers of the north atlantic.

    PubMed

    Sieburth, J M; Willis, P J; Johnson, K M; Burney, C M; Lavoie, D M; Hinga, K R; Caron, D A; French, F W; Johnson, P W; Davis, P G

    1976-12-24

    Dissolved organic carbon, carbohydrates, and adenosine triphosphate in the size fractions 0.2 to 3 micrometers and 3 to 1000 micrometers are significantly enriched in the upper 150-micrometer surface layer compared to subsurface water, mean enrichment factors being 1.6, 2.0, 2.5, and 3.1, respectively. When calculated as a 0.1-micrometer microlayer of wet surfactants, the mean concentration of organic matter was 2.9 grams per liter, of which carbohydrates accounted for 28 percent. The data for plant pigments and particulate adenosine triphosphate indicated that bacterioneuston was enriched at seven of nine stations while phagotrophic protists were enriched at five stations. Instances of enrichment and inhibition were verified by cultural data for bacteria and amoebas. The observations indicate that the surface microlayers are largely heterotrophic microcosms, which can be as rich as laboratory cultures, and that an appreciable part of the dissolved organic carbon is carbohydrate of phytoplankton origin, released and brought to the surface by migrating and excreting phagotrophic protists.

  15. Differences in dissolved organic matter between reclaimed water source and drinking water source.

    PubMed

    Hu, Hong-Ying; Du, Ye; Wu, Qian-Yuan; Zhao, Xin; Tang, Xin; Chen, Zhuo

    2016-05-01

    Dissolved organic matter (DOM) significantly affects the quality of reclaimed water and drinking water. Reclaimed water potable reuse is an effective way to augment drinking water source and de facto reuse exists worldwide. Hence, when reclaimed water source (namely secondary effluent) is blended with drinking water source, understanding the difference in DOM between drinking water source (dDOM) and reclaimed water source (rDOM) is essential. In this study, composition, transformation, and potential risk of dDOM from drinking water source and rDOM from secondary effluent were compared. Generally, the DOC concentration of rDOM and dissolved organic nitrogen (DON) content in reclaimed water source were higher but rDOM exhibited a lower aromaticity. Besides, rDOM comprises a higher proportion of hydrophilic fractions and more low-molecular weight compounds, which are difficult to be removed during coagulation. Although dDOM exhibited higher specific disinfection byproducts formation potential (SDBPFP), rDOM formed more total disinfection byproducts (DBPs) during chlorination including halomethanes (THMs) and haloacetic acids (HAAs) due to high DOC concentration. Likewise, in consideration of DOC basis, rDOM contained more absolute assimilable organic carbon (AOC) despite showing a lower specific AOC (normalized AOC per unit of DOC). Besides, rDOM exhibited higher biotoxicity including genotoxicity and endocrine disruption. Therefore, rDOM presents a greater potential risk than dDOM does. Reclaimed water source needs to be treated carefully when it is blended with drinking water source. PMID:26874770

  16. Relevance of dissolved organic nutrients for the Arctic Ocean nutrient budget

    NASA Astrophysics Data System (ADS)

    Torres-Valdés, Sinhué; Tsubouchi, Takamasa; Davey, Emily; Yashayaev, Igor; Bacon, Sheldon

    2016-06-01

    We ask whether dissolved organic nitrogen (DON) and phosphorus (DOP) could account for previously identified Arctic Ocean (AO) inorganic nutrient budget imbalances. We assess transports to/from the AO by calculating indicative budgets. Marked DON:DOP ratio differences between the Amerasian and Eurasian AO reflect different physical and biogeochemical pathways. DON and DOP are exported to the North Atlantic via Davis Strait potentially being enhanced in transit from Bering Strait. Fram Strait transports are balanced. Barents Sea Opening transports may provide an additional nutrient source to the Barents Sea or may be locked within the wider AO Atlantic Water circulation. Gaps in our knowledge are identified and discussed.

  17. BOREAS TGB-5 Dissolved Organic Carbon Data from NSA Beaver Ponds

    NASA Technical Reports Server (NTRS)

    Bourbonniere, Rick; Hall, Forrest G. (Editor); Conrad, Sara K. (Editor)

    2000-01-01

    The BOReal Ecosystem-Atmosphere Study Trace Gas Biogeochemistry (BOREAS TGB-5) team collected several data sets related to carbon and trace gas fluxes and concentrations in the Northern Study Area (NSA). This data set contains concentrations of dissolved organic and inorganic carbon species from water samples collected at various NSA sites. In particular, this set covers the NSA Tower Beaver Pond Site and the NSA Gillam Road Beaver Pond Site, including data from all visits to open water sampling locations during the BOREAS field campaigns from April to September 1994. The data are provided in tabular ASCII files.

  18. Modeling the removal of dissolved organic carbon by ion exchange in a completely mixed flow reactor.

    PubMed

    Boyer, Treavor H; Miller, Cass T; Singer, Philip C

    2008-04-01

    A mathematical model was developed to describe removal of dissolved organic carbon (DOC) by a macroporous, strong-base anion exchange resin in a completely mixed flow reactor with resin recycle and partial resin regeneration. The two-scale model consisted of a microscale model describing the uptake of DOC by the resin coupled with a macroscale model describing the continuous-flow process. Equilibrium and kinetic parameters were estimated from batch laboratory experiments. The model was validated using continuous-flow data from two pilot plant studies. Model predictions were found to be in good agreement with the observed pilot plant data.

  19. Dissolved Organic Carbon and Disinfection By-Product Precursor Release from Managed Peat Soils

    USGS Publications Warehouse

    Fleck, J.A.; Bossio, D.A.; Fujii, R.

    2004-01-01

    A wetland restoration demonstration project examined the effects of a permanently flooded wetland on subsidence of peat soils. The project, started in 1997, was done on Twitchell Island, in the Sacramento-San Joaquin Delta of California. Conversion of agricultural land to a wetland has changed many of the biogeochemical processes controlling dissolved organic carbon (DOC) release from the peat soils, relative to the previous land use. Dissolved organic C in delta waters is a concern because it reacts with chlorine, added as a disinfectant in municipal drinking waters, to form carcinogenic disinfection byproducts (DBPs), including trihalomethanes (THMs) and haloacetic acids (HAAs). This study explores the effects of peat soil biogeochemistry on DOC and DBP release under agricultural and wetland management. Results indicate that organic matter source, extent of soil organic matter decomposition, and decomposition pathways all are factors in THM formation. The results show that historical management practices dominate the release of DOC and THM precursors. However, within-site differences indicate that recent management decisions can contribute to changes in DOC quality and THM precursor formation. Not all aromatic forms of carbon are highly reactive and certain environmental conditions produce the specific carbon structures that form THMs. Both HAA and THM precursors are elevated in the DOC released under wetland conditions. The findings of this study emphasize the need to further investigate the roles of organic matter sources, microbial decomposition pathways, and decomposition status of soil organic matter in the release of DOC and DBP precursors from delta soils under varying land-use practices.

  20. Characteristics of dissolved organic matter following 20years of peatland restoration.

    PubMed

    Höll, Bettina S; Fiedler, Sabine; Jungkunst, Hermann F; Kalbitz, Karsten; Freibauer, Annette; Drösler, Matthias; Stahr, Karl

    2009-12-15

    The changes in the amounts and composition of dissolved organic matter (DOM) following long-term peat restoration are unknown, although this fraction of soil organic matter affects many processes in such ecosystems. We addressed this lack of knowledge by investigating a peatland in south-west Germany that was partly rewetted 20 years ago. A successfully restored site and a moderately drained site were compared, where the mean groundwater levels were close to the soil surface and around 30 cm below surface, respectively. The concentrations of dissolved organic carbon (DOC) at 4 depths were measured over one year. The specific absorbance was measured at 280 nm and the fluorescence spectra were used to describe the aromaticity and complexity of DOM. The investigations showed that 20 years of peatland restoration was able to create typical peatland conditions. The rewetted site had significantly lower DOC concentrations at different depths compared to the drained site. The specific UV absorbance showed that the rewetted site had a lower level of aromatic DOM structures. The decreasing specific UV absorbance might indicate an increasing contribution of small organic molecules to DOM. It was hypothesized that the decreasing DOC concentrations and the relative enrichment of small, readily degradable organic molecules, reflect the slower decomposition of organic matter after the re-establishment of the water table. Seasonal trends provided substantial evidence for our hypothesis that reduced DOC concentrations were caused by reduced peat decomposition. During summer, the elevated DOC values were accompanied by an increase in DOM aromaticity and complexity. Our results demonstrated a close link between C mineralization and DOC production. We concluded that long-term peatland restoration in the form of the successful re-establishment of the water table might result in reduced peat decomposition and lower DOC concentrations. The restoration of peatlands seems to have a

  1. Detrital control on the release of dissolved organic nitrogen (DON) and dissolved inorganic nitrogen (DIN) from the forest floor under chronic N deposition.

    PubMed

    Park, Ji-Hyung; Matzner, Egbert

    2006-09-01

    The role of detrital quantity and quality in forest floor N leaching was investigated in a litter manipulation experiment at a deciduous forest under chronic N deposition. Dissolved inorganic nitrogen (DIN) comprised the bulk of nitrogen leaching from the control except a short period following autumn litterfall. The dominance of DIN was strengthened by litter exclusion, whereas the addition of glucose or fresh litter led to a small increase in dissolved organic nitrogen (DON) and either a temporary or gradual reduction in NO(3)(-) release, respectively. Changes in soluble organic C and microbial C in the forest floor implied that increased availability of C sources might have enhanced microbial immobilization of DIN, either temporarily following glucose application or over the longer term following litter addition. The results suggest that detrital quantity and quality can play a crucial role in determining the balance between DIN and DON in N-enriched forest soils.

  2. Characterization of Dissolved Organic Carbon in Deep Groundwater from the Witwatersrand Basin

    NASA Astrophysics Data System (ADS)

    Pullin, M. J.; Hendrickson, S.; Simon, P.; Sherwood Lollar, B.; Wilkie, K.; Onstott, T. C.; Washton, N.; Clewett, C.

    2013-12-01

    This work describes the isolation, fractionation, and chemical analysis of dissolved organic carbon (DOC) in deep groundwater in the Witwatersrand Basin, South Africa. The groundwater was accessed through mining boreholes in gold and diamond mine shafts. Filtered water samples were collected and preserved for later analysis. In some cases, the organic carbon was also collected on DAX-8 and XAD-4 adsorption resins in situ and then transported to the surface for removal, clean-up, and lyophilization. Solid state C-13 NMR analysis of that organic carbon was conducted. Organic compounds were also isolated from the water using solid phase extraction cartridges for later analysis by GC-MS. Absorbance, fluorescence, and HPLC analyses was were used to analyze the DOC in the filtered water samples. C-14 and C-13 isotopic analysis of the organic carbon was also conducted. Identifiable components of the DOC include both organic acids and amino acids. However, initial results indicate that the majority of the subsurface DOC is a complex heterogeneous mixture with an average molecular weight of approximately 1000 Da, although this DOC is less complex than that found in soils or surface water. Finally, we will discuss possible sources of the organic carbon and its biogeochemical cycling in the subsurface.

  3. 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

    Understanding the relative importance of anthropogenic and natural landscape features that drive spatial variability in water quality is a central challenge in studying the biogeochemistry of heterogeneous landscapes. We quantified the average annual flux and concentration of dissolved inorganic nitrogen (DIN), dissolved organic nitrogen (DON), dissolved organic carbon (DOC), phosphate-P (PO4-P), sodium (Na+) and chloride (Cl-) at ~40 stream sites in three major (51 to 903 km2) NH basins. We used GIS to quantify anthropogenic (e.g. human population density, % impervious surface cover and % agriculture) and natural (e.g. % forest, % wetlands and soil C:N) landscape features for each sub-basin and then employed multiple-regression analysis to relate water quality parameters to landscape characteristics. Anthropogenic features were strong predictors of DIN flux and Na+ and Cl- concentrations, whereas wetland cover (a natural feature) was a significant, but weak predictor of DOC (r2=0.26, p<0.01) and DON (r2 = 0.14, p<0.05) flux. Anthropogenic features could not explain a significant amount of variance in DON or DOC flux. Mean PO4-P concentrations were surprisingly low (<0.015 mg P/L) when compared to the larger range in mean DIN concentrations (0.03 to 0.96 mg/L) and consequently no landscape characteristics could explain a significant amount of spatial variability in PO4-P flux or concentration. Human population density was the single best predictor of DIN flux (r2=0.76, p<0.01), and together with % impervious surface and % agriculture explained 86% (p<0.01) of the total variance. Among all sites, % road pavement was a strong predictor of stream Na+ and Cl- concentrations (r2 = 0.75 to 0.78, p<0.01) and % impervious surface was a stronger predictor (r2 = 0.86 to 0.92, p<0.01) among a subset of sites. Our results suggest that DIN and DON result from different sources in the landscape and although sources of DON and DOC are similar, DON and DOC concentrations respond

  4. Effect of dissolved organic matter on the uptake of trace metals by American oysters.

    PubMed

    Guo, L; Hunt, B J; Santschi, P H; Ray, S M

    2001-03-01

    To examine the effects of dissolved organic matter on metal bioavailability, uptake of trace metals (Cd, Co, Hg, Cr, Ag, Zn) by American oysters (Crassostrea virginica) was compared between treatments with different dissolved organic carbon (DOC) concentrations and contrasting low molecular weight (LMW, 1 kDa) and high molecular weight (HMW, 1 kDa-0.2 micron) DOC fractions, using radiotracer techniques and short-term exposure experiments. Uptake rate constants (mL g-1 h-1) of metals, in general, increased with increasing DOC concentrations, with an initial decrease at lower DOC concentrations. Oyster dry weight concentration factors (DCF, mL g-1), determined at the end of exposure experiments (8 h), also increased for Cd, Co, Cr, Ag, and Zn, but decreased for Hg, with increasing DOC concentrations. Changes of metal uptake rate constants and DCF values with DOC concentration suggest that metal uptake pathways by American oysters vary from predominantly uptake (by diffusion of neutral) of free ionic, inorganically complexed, and LMW organic ligand complexed metals at very low DOC concentration to direct ingestion and digestion of HMW or colloidally complexed metals at higher DOC concentrations. Measured partition coefficients (Kc) between dissolved and colloidal phases were comparable between metals, ranging from 10(5.12) to 10(5.75) mL g-1. However, DCF values and uptake rate constants differed considerably between metals, with the highest DCF values and uptake rate constants found for B-type metals, e.g., Ag, Hg, Zn, and Cd, and the lowest ones for several intermediate-type metals (e.g., Co, Cr). Metal types and thus the interaction of metals with organic ligands, such as strong complexation of B-type metals with S-containing organic ligands, may play an important role in the bioavailability and toxicity of metals to aquatic organisms. Differences in metal uptake in contrasting LMW and HMW DOC treatments suggest a generally depressed bioavailability of colloidally

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

    SciTech Connect

    Walsh, J.J.; Carder, K.L.; Mueller-Karger, F.E.

    1992-10-15

    Using bio-optical estimates of gelbstoff and a few platinum measurements of dissolved organic carbon (DOC{sub pt}), a budget of the meridional flux of DOC and dissolved organic nitrogen (DON) across 36{degrees}25{prime}N in the North Atlantic is constructed from previous inverse models of water and element transport. Distinct southward subsurface fluxes of dissolved organic matter (DOM) within subducted shelf water, cabelled slope water, and overturned basin water are inferred. Within two cases of a positive gradient of DOC{sub pt} between terrestrial/shelf and offshore stocks, the net equatorward exports of O{sub 2} and DOC{sub pt} from the northern North Atlantic yield molar ratios of 2.1 to 9.1, compared to the expected Redfield O{sub 2}/C ratio of 1.3. In the first case, 63% of the apparent oxygen utilization demands of the water column may be met by DOC, instead of only 14% in the second scenario, preserving a role for falling particles in the sea. With a DOC/DON ratio of 10, the larger net southward export of DON across 36{degrees}25{prime}N balances the postulated net northward input of 1.7 x 10{sup 3} kg NO{sub 3} s{sup {minus}1} of unutilized nitrate within the Gulf Stream. Without an enhanced supply of DOM from the shelves, a zero seaward gradient of DOM in the third case suggests that none of the poleward nitrate flux is returned southward as DON, but instead a net poleward flux of DON prevails as well. The authors present estimates are confounded, however, by the seasonal and multiyear variability of sinking processes in the North Atlantic. Future active and passive remote sensors, field programs, and simulation models must now discriminate between particulate and dissolved components of surface color signals to verify the importance of both continental margins and DOM in global biogeochemical cycles. 98 refs., 4 figs., 4 tabs.

  6. 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.

  7. Co-precipitation of dissolved organic matter by calcium carbonate in Pyramid Lake, Nevada

    USGS Publications Warehouse

    Leenheer, Jerry A.; Reddy, Michael M.

    2008-01-01

    Our previous research has demonstrated that dissolved organic matter (DOM) influences calcium carbonate mineral formation in surface and ground water. To better understand DOM mediation of carbonate precipitation and DOM co-precipitation and/or incorporation with carbonate minerals, we characterized the content and speciation of DOM in carbonate minerals and in the lake water of Pyramid Lake, Nevada, USA. A 400-gram block of precipitated calcium carbonate from the Pyramid Lake shore was dissolved in 8 liters of 10% acetic acid. Particulate matter not dissolved by acetic acid was removed by centrifugation. DOM from the carbonate rock was fractionated into nine portions using evaporation, dialysis, resin adsorption, and selective precipitations to remove acetic acid and inorganic constituents. The calcium carbonate rock contained 0.23% DOM by weight. This DOM was enriched in polycarboxylic proteinaceous acids and hydroxy-acids in comparison with the present lake water. DOM in lake water was composed of aliphatic, alicyclic polycarboxylic acids. These compound classes were found in previous studies to inhibit calcium carbonate precipitation. DOM fractions from the carbonate rock were 14C-age dated at about 3,100 to 3,500 years before present. The mechanism of DOM co-precipitation and/or physical incorporation in the calcium carbonate is believed to be due to formation of insoluble calcium complexes with polycarboxylic proteinaceous acids and hydroxy-acids that have moderately large stability constants at the alkaline pH of the lake. DOM co-precipitation with calcium carbonate and incorporation in precipitated carbonate minerals removes proteinaceous DOM, but nearly equivalent concentrations of neutral and acidic forms of organic nitrogen in DOM remain in solution. Calcium carbonate precipitation during lime softening pretreatment of drinking water may have practical applications for removal of proteinaceous disinfection by-product precursors.

  8. 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

    2016-04-01

    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.

  9. Photochemical Flocculation of Terrestrial Dissolved Organic Matter (tDOM) and Iron: Mechanisms and Geochemical Implications

    NASA Astrophysics Data System (ADS)

    Mopper, K.; Helms, J. R.; Mao, J.; Abdulla, H. A.; Schmidt-Rohr, K.

    2013-12-01

    Photoflocculation of DOM has received relatively little attention. No previous studies have examined the chemical composition of the flocs nor investigated the coagulation mechanisms. We observed that, after 30 days of simulated solar UV irradiation of 0.1-um filtered Great Dismal Swamp (Virginia) water, 7.1% of the DOC was converted to POC while 75% was remineralized. Approximately 87% of the iron was removed from the dissolved phase after 30 days, but iron did not flocculate until a major fraction of DOM was removed by photochemical degradation and flocculation (>10 days); thus, during the initial 10 days, there were sufficient organic ligands present and/or the pH was low enough to keep iron in solution. Although photoflocculation of iron did eventually occur, it is not clear if iron is required for the initial flocculation of DOM. Using NMR and FT-IR techniques, we found that photochemically flocculated POM was enriched in aliphatics and amide functionality relative to the residual non-flocculated DOM, while carbohydrate-like material was neither photochemical degraded nor flocculated. Based on this spectroscopic evidence, we propose several mechanisms for the formation of the flocs during irradiation. We also speculate that abiotic photochemical flocculation may remove a significant fraction of tDOM and iron from the upper water column between headwaters and the ocean, including estuaries. Fig. 1. Concentrations of dissolved (gray), particulate (black), and adsorbed (white) material as a function of irradiation time: (a) organic carbon, (b) absorption at 300 nm, (c) total iron by atomic absorption, and (d) total nitrogen. Error bars represent the combined standard deviations of the 'total,' 'dissolved,' and 'adsorbed' terms from which the 'particulate' term was calculated. Total nitrogen was not determined for the 'adsorbed' material

  10. 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.

  11. 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

  12. Formation of trihalomethanes of dissolved organic matter fractions in reservoir and canal waters.

    PubMed

    Musikavong, Charongpun; Srimuang, Kanjanee; Tachapattaworakul Suksaroj, Thunwadee; Suksaroj, Chaisri

    2016-07-28

    The formation of trihalomethanes (THMs) of hydrophobic organic fraction (HPO), transphilic organic fraction (TPI), and hydrophilic organic fraction (HPI) of reservoir and canal waters from the U-Tapao River Basin, Songkhla, Thailand was investigated. Water samples were collected three times from two reservoirs, upstream, midstream, and downstream of the U-Tapao canal. The HPO was the major dissolved organic matter (DOM) fraction in reservoir and canal waters. On average, the HPO accounted for 53 and 45% of the DOM in reservoir and canal waters, respectively. The TPI of 19 and 23% in reservoir and canal waters were determined, respectively. The HPI of 29% of the reservoir water and HPI of 32% of the canal water were detected. For the reservoir water, the highest trihalomethane formation potential (THMFP)/dissolved organic carbon (DOC) was determined for the HPI, followed by the TPI and HPO, respectively. The average values of the THMFP/DOC of the HPI, TPI, and HPO of the reservoir water were 78, 52, and 49 µg THMs/mg C, respectively. The highest THMFP/DOC of the canal water was detected for the HPI, followed by HPO and TPI, respectively. Average values of the THMFP/DOC of HPI of water at upstream and midstream locations of 58 µg THMs/mg C and downstream location of 113 µg THMs/mg C were determined. Average values of THMFP/DOC of HPO of water at upstream and midstream and downstream locations were 48 and 93 µg THMs/mg C, respectively. For the lowest THMFP/DOC fraction, the average values of THMFP/DOC of TPI of water at upstream and midstream and downstream locations were 35 and 73 µg THMs/mg C, respectively.

  13. 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. PMID:25978545

  14. 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

  15. Sources and Quantity of Dissolved Organic Matter Released From Flooding Upland Boreal Forests for Reservoir Creation

    NASA Astrophysics Data System (ADS)

    Schiff, S. L.; Venkiteswaran, J. J.; Ferguson, G. A.; Oelbermann, M.; Elgood, R. J.; Hurley, J. P.; Rolfhus, K. R.; Beaty, K. G.; Bodaly, R. A.

    2004-05-01

    Flooding of northern landscapes for the creation of hydroelectric and drinking water reservoirs results in elevated emissions of greenhouse gases and methylmercury in fish. Dissolved organic matter (DOM) is an integral component of both carbon and mercury cycling. At the Experimental Lakes Area in NW Ontario, three reservoirs were created by flooding boreal forests of differing carbon stocks with water from a nearby oligotrophic lake in the FLUDEX experiment. In the reservoirs, DOM concentrations continued to be elevated in all 5 years of flooding. DOM was the dominant form of nitrogen loss and comparable to dissolved inorganic carbon (DIC) release from all reservoirs as a result of flooding. Magnitude of DOM release did not mimic the order of carbon stores and is consistent with laboratory experiments. Changes in the quality of DOM generated throughout the experiment were followed by 13C/12C, 15N/14N and C/N ratios, spectral absorbance, and organic alkalinity. Sources of DOM and processes affecting the fate of DOM were followed in each year of flooding by determining the 13C/12C, 15N/14N and C/N ratios of vegetation, soils and periphyton, leaching experiments of flooded and unflooded soils, and constructing DOC, DON and DOC-13C/12C budgets for each reservoir in conjunction with DIC-13C/12C budgets.

  16. Environmental photoinactivation of extracellular phosphatases and the effects of dissolved organic matter.

    PubMed

    Janssen, Elisabeth M L; McNeill, Kristopher

    2015-01-20

    Alkaline phosphatases are ubiquitous extracellular enzymes in aquatic systems and play a central role in the biogeochemical cycling of phosphorus. Yet, the photochemical stability of phosphatase and effects of natural organic matter (DOM) are not completely understood. We demonstrate that phosphatase activity in natural biofilm samples decreased during sunlight exposure similar to well-defined bacterial phosphatase solutions. Direct photoinactivation was slowed by more than 50% in the presence of redox-active dissolved organic matter (DOM, 10 mgC L(–1)) or a model antioxidant (esculetin, 50 μM), even after light screening effects had been accounted for. Thus, DOM can not only inhibit enzymes (in the dark) or sensitize photodegradation by producing photochemically produced reactive intermediates but can also significantly quench direct photoinactivation of phosphatase. Our data further suggest that direct photooxidation of tryptophan residues within the protein structure are significantly involved in the photoinactivation of phosphatase because a loss of tryptophan-like fluorescence paralleled photoinactivation kinetics and because DOM acted as an antioxidant toward photoinactivation, a phenomenon recently established for the photooxidation of freely dissolved tryptophan. Thus, photoinactivation of phosphatase can be significantly slowed in the presence of naturally occurring antioxidants like DOM. The mechanistic link between tryptophan photooxidation and inactivation of phosphatase may have applicability to other extracellular enzymes but remains to be established.

  17. New nutrients exert fundamental control on dissolved organic carbon accumulation in the surface Atlantic Ocean.

    PubMed

    Romera-Castillo, Cristina; Letscher, Robert T; Hansell, Dennis A

    2016-09-20

    The inventories of carbon residing in organic matter dissolved in the ocean [dissolved organic carbon (DOC)] and in the atmosphere as CO2 are of the same order of magnitude, such that small changes in the DOC pool could have important consequences in atmospheric carbon and thus climate. DOC in the global ocean is largely formed in the sunlit euphotic zone, but identifying predictable controls on that production is an important yet unrealized goal. Here, we use a testable and causative correlation between the net production of DOC and the consumption of new nutrients in the euphotic zone of the Atlantic Ocean. We demonstrate that new nutrients introduced to the euphotic zone by upwelling in divergence zones and by winter convective overturn of the water column, and the primary production associated with those nutrients, are the ultimate driver of DOC distributions across the Atlantic basins. As new nutrient input will change with a changing climate, the role of DOC in the ocean's biological pump should likewise be impacted. PMID:27582464

  18. Experimental evidence of dust-induced shaping of surface dissolved organic matter in the oligotrophic ocean

    NASA Astrophysics Data System (ADS)

    Pulido-Villena, Elvira; Djaoudi, Kahina; Barani, Aude; Charrière, Bruno; Delmont, Anne; Hélias-Nunige, Sandra; Marc, Tedetti; Wambeke France, Van

    2016-04-01

    Recent research has shown that dust deposition may impact the functioning of the microbial loop. On one hand, it enhances bacterial mineralization of dissolved organic matter (DOM), and so may limit the carbon export. On the other hand, the interaction between heterotrophic bacteria and DOM in the surface ocean can increase the residence time of DOM, promoting its export and sequestration in the deep ocean. The main goal of this study was to experimentally assess whether the bacterial response to dust deposition is prone to have an effect on the residence time of the DOM pool by modifying its bioavailability. The bacterial degradation of DOM was followed on dust-amended and control treatments during long-term incubations. Dissolved organic carbon concentration decreased by 9 μmol L-1 over the course of the experiment in both control and dust-enriched conditions, with no significant differences between treatments. However, significant differences in DOM optical properties appeared at the latest stage of the incubations suggesting an accumulation of DOM of high molecular weight in the dust-amended treatment. At the end of the incubations, the remaining water was filtered and re-used as a new culture medium for a bacterial natural assemblage. Bacterial abundance and production was lower in the treatment previously submitted to dust enrichment, suggesting a decrease in DOM lability after a dust deposition event. These preliminary results point to a new link between dust and ocean carbon cycle through the modification of the residence time of the DOM pool.

  19. 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.

  20. Shift in the chemical composition of dissolved organic matter in the Congo River network

    NASA Astrophysics Data System (ADS)

    Lambert, Thibault; Bouillon, Steven; Darchambeau, François; Massicotte, Philippe; Borges, Alberto V.

    2016-09-01

    The processing of terrestrially derived dissolved organic matter (DOM) during downstream transport in fluvial networks is poorly understood. Here, we report a dataset of dissolved organic carbon (DOC) concentrations and DOM composition (stable carbon isotope ratios, absorption and fluorescence properties) acquired along a 1700 km transect in the middle reach of the Congo River basin. Samples were collected in the mainstem and its tributaries during high-water (HW) and falling-water (FW) periods. DOC concentrations and DOM composition along the mainstem were found to differ between the two periods because of a reduced lateral mixing between the central water masses of the Congo River and DOM-rich waters from tributaries and also likely because of a greater photodegradation during FW as water residence time (WRT) increased. Although the Cuvette Centrale wetland (one of the world's largest flooded forests) continuously releases highly aromatic DOM in streams and rivers of the Congo Basin, the downstream transport of DOM was found to result in an along-stream gradient from aromatic to aliphatic compounds. The characterization of DOM through parallel factor analysis (PARAFAC) suggests that this transition results from (1) the losses of aromatic compounds by photodegradation and (2) the production of aliphatic compounds by biological reworking of terrestrial DOM. Finally, this study highlights the critical importance of the river-floodplain connectivity in tropical rivers in controlling DOM biogeochemistry at a large spatial scale and suggests that the degree of DOM processing during downstream transport is a function of landscape characteristics and WRT.

  1. 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.

  2. Effects of compositional changes on reactivity continuum and decomposition kinetics of lake dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Mostovaya, Alina; Koehler, Birgit; Guillemette, François; Brunberg, Anna-Kristina; Tranvik, Lars J.

    2016-07-01

    To address the link between the composition and decomposition of freshwater dissolved organic matter (DOM), we manipulated the DOM from three boreal lakes using preincubations with UV light to cleave large aromatic molecules and polyvinylpyrrolidone (PVP) to remove colored phenolic compounds. Subsequently, we monitored the dissolved organic carbon (DOC) loss over 4 months of microbial degradation in the dark to assess how compositional changes in DOM affected different aspects of the reactivity continuum, including the distribution of the apparent decay coefficients. We observed profound effects on decomposition kinetics, with pronounced shifts in the relative share of rapidly and more slowly decomposing fractions of the DOM. In the UV-exposed treatment initial apparent decay coefficient k0 was almost threefold higher than in the control. Significantly higher relative DOC loss in the UV-exposed treatment was sustained for 2 months of incubation, after which decay coefficients converged with those in the control. The PVP removed compounds with absorbance and fluorescence characteristics representative of aromatic compounds, which led to slower decomposition, compared to that in the control. Our results demonstrate the reactivity continuum underlying the decomposition of DOM in freshwaters and highlight the importance of intrinsic properties of DOM in determining its decomposition kinetics.

  3. Selection of magnetic anion exchange resins for the removal of dissolved organic and inorganic matters.

    PubMed

    Wang, Qiongjie; Li, Aimin; Wang, Jinnan; Shuang, Chengdong

    2012-01-01

    Four magnetic anion exchange resins (MAERs) were used as adsorbents to purify drinking water. The effect of water quality (pH, temperature, ionic strength, etc.) on the performance of MAER for the removal of dissolved organic matter (DOM) was also investigated. Among the four studied MAERs, the strong base resin named NDMP-1 with high water content and enhanced exchange capacity exhibited the highest removal rate of dissolved organic carbon (DOC) (48.9% removal rate) and UV-absorbing substances (82.4% removal rate) with a resin dose of 10 mL/L after 30 min of contact time. The MAERs could also effectively remove inorganic matter such as sulfate, nitrate and fluoride. Because of the higher specific UV absorbance (SUVA) value, the DOM in the raw water was found to be removed more effectively than that in the clarified water by NDMP resin. The temperature showed a weak influence on the removal of DOC from 6 to 26 degrees C, while a relatively strong one at 36 degrees C. The removal of DOM by NDMP was also affected to some extent by the pH value. Moreover, increasing the sulfate concentration in the raw water could decrease the removal rates of DOC and UV-absorbing substances.

  4. Estimating dissolved organic carbon concentration in turbid coastal waters using optical remote sensing observations

    NASA Astrophysics Data System (ADS)

    Cherukuru, Nagur; Ford, Phillip W.; Matear, Richard J.; Oubelkheir, Kadija; Clementson, Lesley A.; Suber, Ken; Steven, Andrew D. L.

    2016-10-01

    Dissolved Organic Carbon (DOC) is an important component in the global carbon cycle. It also plays an important role in influencing the coastal ocean biogeochemical (BGC) cycles and light environment. Studies focussing on DOC dynamics in coastal waters are data constrained due to the high costs associated with in situ water sampling campaigns. Satellite optical remote sensing has the potential to provide continuous, cost-effective DOC estimates. In this study we used a bio-optics dataset collected in turbid coastal waters of Moreton Bay (MB), Australia, during 2011 to develop a remote sensing algorithm to estimate DOC. This dataset includes data from flood and non-flood conditions. In MB, DOC concentration varied over a wide range (20-520 μM C) and had a good correlation (R2 = 0.78) with absorption due to coloured dissolved organic matter (CDOM) and remote sensing reflectance. Using this data set we developed an empirical algorithm to derive DOC concentrations from the ratio of Rrs(412)/Rrs(488) and tested it with independent datasets. In this study, we demonstrate the ability to estimate DOC using remotely sensed optical observations in turbid coastal waters.

  5. Bioavailability of riverine dissolved organic carbon and nitrogen in the Heilongjiang watershed of northeastern China.

    PubMed

    Shi, Jianhong; Cui, Hongyang; Jia, Liming; Qiu, Linlin; Zhao, Yue; Wei, Zimin; Wu, Junqiu; Wen, Xin

    2016-02-01

    The bioavailabilities of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) were examined in eight sampling stations of the Heilongjiang watershed, located in Heilongjiang Province, northeast China. Water samples were incubated for 55 days at 20 °C, and the decreases in the DOC and DON concentrations were measured during the laboratory incubations. The experiments showed that bioavailable DOC (BDOC) accounted for 15-30% of DOC and bioavailable DON (BDON) accounted for 29-57% of DON. DOM bioavailability was higher for DON compared to DOC, suggesting that DON was more bioavailable and had a faster turnover than DOC in the Heilongjiang watershed. Furthermore, the percent of bioavailable DOC (%BDOC) was significantly related to SUVA254, not the DOC concentration, suggesting that the chemistry composition of DOM played a more important role in affecting its bioavailability compared to the DOM concentration. In addition, significant negative correlations were observed between the initial DOC/DON ratios and the percent of bioavailable DOM fractions (%BDOC and %BDON), especially for %BDON, implying that low C/N molecules or N-rich compounds may be preferentially utilized by microbes. Graphical Abstract DOC concentrations of eight sampling sites, microbial decomposition of DOC over 55 days, % bioavailable DOC of eight sampling sites, DOM chemical composition of eight sampling sites, demonstrated chemical composition influence on DOM bioavailability.

  6. The river as a chemostat: fresh perspectives on dissolved organic matter flowing down the river continuum

    USGS Publications Warehouse

    Creed, Irena F.; McKnight, Diane M.; Pellerin, Brian; Green, Mark B.; Bergamaschi, Brian; Aiken, George R.; Burns, Douglas A.; Findlay, Stuart E G; Shanley, James B.; Striegl, Rob; Aulenbach, Brent T.; Clow, David W.; Laudon, Hjalmar; McGlynn, Brian L.; McGuire, Kevin J.; Smith, Richard A.; Stackpoole, Sarah M.

    2015-01-01

    A better understanding is needed of how hydrological and biogeochemical processes control dissolved organic carbon (DOC) concentrations and dissolved organic matter (DOM) composition from headwaters downstream to large rivers. We examined a large DOM dataset from the National Water Information System of the US Geological Survey, which represents approximately 100 000 measurements of DOC concentration and DOM composition at many sites along rivers across the United States. Application of quantile regression revealed a tendency towards downstream spatial and temporal homogenization of DOC concentrations and a shift from dominance of aromatic DOM in headwaters to more aliphatic DOM downstream. The DOC concentration–discharge (C-Q) relationships at each site revealed a downstream tendency towards a slope of zero. We propose that despite complexities in river networks that have driven many revisions to the River Continuum Concept, rivers show a tendency towards chemostasis (C-Q slope of zero) because of a downstream shift from a dominance of hydrologic drivers that connect terrestrial DOM sources to streams in the headwaters towards a dominance of instream and near-stream biogeochemical processes that result in preferential losses of aromatic DOM and preferential gains of aliphatic DOM.

  7. Controls on the dynamics of dissolved organic matter in boreal lakes

    NASA Astrophysics Data System (ADS)

    Kothawala, Dolly; Kellerman, Anne; Catalan, Nuria; Tranvik, Lars

    2016-04-01

    The reactivity of dissolved organic matter (DOM) strongly influences the biogeochemical cycling of key nutrients including carbon and nitrogen. Dissolved organic nitrogen (DON) comprises a small, yet functionally important, fraction of total DOM in boreal lakes. This pool of DON can influence the fate of total DOM by catalyzing microbial degradation pathways, or alternatively being less reactive to photo-degradation. Upon mineralization, it may also constitute an important nutrient for planktonic primary producers. By examining the optical and detailed molecular characteristics of DOM from several hundred lakes spanning a 13 degree latitude gradient across Sweden, we found that the molecular composition of DOM was influenced primarily by the water residence time of lakes, followed by mean annual temperature, which spanned from -6.1 to 6.5 degrees C, from north to south, respectively. Land cover across Sweden is typical of the boreal zone, being comprised of primarily forest and wetland cover; however, at this large spatial scale, land cover did not influence the molecular composition of DOM. We discuss how these results provide insight into predicting the relative influence of climatic, hydrological and catchment characteristics on the fate of DOM under a changing climate. In particular, we explore how DON constituents play a pivotal role in the overall chemical diversity of DOM and how this diversity ultimately drives its reactivity or persistence through freshwaters.

  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. The Photodegradation of Ibuprofen and Dissolved Organic Matter in Lake Superior and St. Louis River Water

    PubMed Central

    Moynan, Angela B.

    2012-01-01

    Abstract Ibuprofen can enter bodies of water via waste water treatment. The question was what effect does photodegradation have on ibuprofen and dissolved organic matter (DOM) in Lake Superior (oligiotrophic) and St. Louis (tannic stained) River water? Ibuprofen concentrations of 15,000, 30,000, and 60,000 μg/L were made from lake, river, and distilled water, as well as additional distilled concentrations of 7,500 and 120,000 μg/L. Half of the eighty-four trial cups were placed in an ultraviolet light cabinet and half of the set were placed in a dark cabinet for three days. After the exposure period, a UV-Vis was performed to measure change in molar mass and the summed absorbance of colored dissolved organic matter (CDOM). It appears that ibuprofen decreases in molar mass after exposure to light in distilled and lake water with 15,000 μg/L of ibuprofen. Surprisingly, the molar mass of DOM in river water increases after UV exposure. Possibly, this occurred because the river water has such a high molar mass of DOM and was not filtered. Microbial biomass could also have contributed to this increase. Ibuprofen entering bodies of water via the waste water treatment system appears to be affected by UV light exposure, but in different ways. PMID:23244688

  10. The photodegradation of ibuprofen and dissolved organic matter in Lake Superior and St. Louis River water.

    PubMed

    Moynan, Angela B; Welsh, Cynthia A

    2012-12-01

    Ibuprofen can enter bodies of water via waste water treatment. The question was what effect does photodegradation have on ibuprofen and dissolved organic matter (DOM) in Lake Superior (oligiotrophic) and St. Louis (tannic stained) River water? Ibuprofen concentrations of 15,000, 30,000, and 60,000 μg/L were made from lake, river, and distilled water, as well as additional distilled concentrations of 7,500 and 120,000 μg/L. Half of the eighty-four trial cups were placed in an ultraviolet light cabinet and half of the set were placed in a dark cabinet for three days. After the exposure period, a UV-Vis was performed to measure change in molar mass and the summed absorbance of colored dissolved organic matter (CDOM). It appears that ibuprofen decreases in molar mass after exposure to light in distilled and lake water with 15,000 μg/L of ibuprofen. Surprisingly, the molar mass of DOM in river water increases after UV exposure. Possibly, this occurred because the river water has such a high molar mass of DOM and was not filtered. Microbial biomass could also have contributed to this increase. Ibuprofen entering bodies of water via the waste water treatment system appears to be affected by UV light exposure, but in different ways. PMID:23244688

  11. New nutrients exert fundamental control on dissolved organic carbon accumulation in the surface Atlantic Ocean.

    PubMed

    Romera-Castillo, Cristina; Letscher, Robert T; Hansell, Dennis A

    2016-09-20

    The inventories of carbon residing in organic matter dissolved in the ocean [dissolved organic carbon (DOC)] and in the atmosphere as CO2 are of the same order of magnitude, such that small changes in the DOC pool could have important consequences in atmospheric carbon and thus climate. DOC in the global ocean is largely formed in the sunlit euphotic zone, but identifying predictable controls on that production is an important yet unrealized goal. Here, we use a testable and causative correlation between the net production of DOC and the consumption of new nutrients in the euphotic zone of the Atlantic Ocean. We demonstrate that new nutrients introduced to the euphotic zone by upwelling in divergence zones and by winter convective overturn of the water column, and the primary production associated with those nutrients, are the ultimate driver of DOC distributions across the Atlantic basins. As new nutrient input will change with a changing climate, the role of DOC in the ocean's biological pump should likewise be impacted.

  12. Dissolved organic matter in the Florida everglades: Implications for ecosystem restoration

    USGS Publications Warehouse

    Aiken, G.R.; Gilmour, C.C.; Krabbenhoft, D.P.; Orem, W.

    2011-01-01

    Dissolved organic matter (DOM) in the Florida Everglades controls a number of environmental processes important for ecosystem function including the absorption of light, mineral dissolution/precipitation, transport of hydrophobic compounds (e.g., pesticides), and the transport and reactivity of metals, such as mercury. Proposed attempts to return the Everglades to more natural flow conditions will result in changes to the present transport of DOM from the Everglades Agricultural Area and the northern conservation areas to Florida Bay. In part, the restoration plan calls for increasing water flow throughout the Everglades by removing some of the manmade barriers to flow in place today. The land- and water-use practices associated with the plan will likely result in changes in the quality, quantity, and reactivity of DOM throughout the greater Everglades ecosystem. The authors discuss the factors controlling DOM concentrations and chemistry, present distribution of DOM throughout the Everglades, the potential effects of DOM on key water-quality issues, and the potential utility of dissolved organic matter as an indicator of success of restoration efforts. Copyright ?? 2011 Taylor & Francis Group, LLC.

  13. Dissolved Organic Matter in Arctic and Boreal Streams: Rates and Fates of Decomposition

    NASA Astrophysics Data System (ADS)

    Mutschlecner, A.; Harms, T.

    2015-12-01

    As high-latitude regions warm, new inputs of carbon from thawing permafrost may influence the carbon cycle. Some of this newly released carbon, bound up in molecules of dissolved organic matter (DOM), will be exported into streams and rivers where it may be incorporated into microbial biomass, released to the atmosphere as carbon dioxide, or exported downstream. The factors that control the fate of dissolved organic carbon (DOC) are not fully understood, nor are the seasonal and spatial dynamics of these relationships. We sampled six streams along an arctic-boreal gradient in interior Alaska, collecting water from under ice in April, during snowmelt (May), and in early summer (June). These samples were incubated in the laboratory to determine the fraction of DOC that is susceptible to microbial decomposition and the fraction released as carbon dioxide. Nitrogen and phosphorous additions were used to determine the effect of nutrient limitation on DOC processing. Percent DOC loss across sites ranged from 37-71% in April before snowmelt, 0-9% during snowmelt, and 0-53% in June. We observed no effect of nutrient addition on lability of DOC. Seasonal data are critical to predicting how the processing of DOC in streams will respond to changes in permafrost extent, as well as to changes in the timing of snowmelt and ice-off.

  14. Biodegradable dissolved organic carbon for indicating wastewater reclamation plant performance and treated wastewater quality

    SciTech Connect

    Khan, E.; Babcock, R.W. Jr.; Viriyavejakul, S.; Suffet, I.H.; Stenstrom, M.K.

    1998-07-01

    Various methods for measuring biodegradable dissolved organic carbon (BDOC) in water have been introduced in the last decade. Applications of the methods have been limited to drinking water. The measure of BDOC has been used mainly to indicate the quality of raw and finished waters and evaluate the performance of biological activated carbon (ozone/granular activated carbon) systems in water treatment plants. Recently, a modified BDOC protocol was developed for examining reclaimed and secondary-treated wastewaters. Use of the new BDOC method can be extended to the wastewater treatment and reclamation fields. Samples collected from a wastewater reuse pilot facility were tested for BDOC. The modified BDOC method was able to detect the increase in biodegradability of ozonated tertiary-treated wastewater. Good relationships among BDOC, dissolved organic carbon (DOC), and soluble biochemical oxygen demand were obtained. The modified protocol was later used to measure BDOC in secondary-effluent samples from 13 municipal wastewater treatment plants. The results show that BDOC can also be used as an indicator of secondary-effluent quality. Likewise, strong and significant correlations were found among BDOC, DOC, and soluble chemical oxygen demand in secondary effluents.

  15. Changes in the dissolved organic matter leaching from soil under severe temperature and N-deposition.

    PubMed

    Nguyen, Hang Vo-Minh; Choi, Jung Hyun

    2015-06-01

    In this study, we conducted growth chamber experiments using three types of soil (wetland, rice paddy, and forest) under the conditions of a severe increase in the temperature and N-deposition in order to investigate how extreme weather influences the characteristics of the dissolved organic matter (DOM) leaching from different soil types. This leachate controls the quantity and quality of DOM in surface water systems. After 5 months of incubation, the dissolved organic carbon (DOC) concentrations decreased in the range of 21.1 to 88.9 %, while the specific UV absorption (SUVA) values increased substantially in the range of 19.9 to 319.9 % for all of the samples. Higher increases in the SUVA values were observed at higher temperatures, whereas the opposite trend was observed for samples with N-addition. The parallel factor analysis (PARAFAC) results showed that four fluorescence components: terrestrial humic-like (component 1 (C1)), microbial humic-like (component 2 (C2)), protein-like (component 3 (C3)), and anthropogenic humic-like (component 4 (C4)) constituted the fluorescence matrices of soil samples. During the experiment, labile DOM from the soils was consumed and transformed into resistant aromatic carbon structures and less biodegradable components via microbial processes. The principle component analysis (PCA) results indicated that severe temperatures and N-deposition could enhance the contribution of the aromatic carbon compounds and humic-like components in the soil samples.

  16. Removal of fluorescence and ultraviolet absorbance of dissolved organic matter in reclaimed water by solar light.

    PubMed

    Wu, Qianyuan; Li, Chao; Wang, Wenlong; He, Tao; Hu, Hongying; Du, Ye; Wang, Ting

    2016-05-01

    Storing reclaimed water in lakes is a widely used method of accommodating changes in the consumption of reclaimed water during wastewater reclamation and reuse. Solar light serves as an important function in degrading pollutants during storage, and its effect on dissolved organic matter (DOM) was investigated in this study. Solar light significantly decreased the UV254 absorbance and fluorescence (FLU) intensity of reclaimed water. However, its effect on the dissolved organic carbon (DOC) value of reclaimed water was very limited. The decrease in the UV254 absorbance intensity and FLU excitation-emission matrix regional integration volume (FLU volume) of reclaimed water during solar light irradiation was fit with pseudo-first order reaction kinetics. The decrease of UV254 absorbance was much slower than that of the FLU volume. Ultraviolet light in solar light had a key role in decreasing the UV254 absorbance and FLU intensity during solar light irradiation. The light fluence-based removal kinetic constants of the UV254 and FLU intensity were independent of light intensity. The peaks of the UV254 absorbance and FLU intensity with an apparent molecular weight (AMW) of 100Da to 2000Da decreased after solar irradiation, whereas the DOC value of the major peaks did not significantly change.

  17. New nutrients exert fundamental control on dissolved organic carbon accumulation in the surface Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Romera-Castillo, Cristina; Letscher, Robert T.; Hansell, Dennis A.

    2016-09-01

    The inventories of carbon residing in organic matter dissolved in the ocean [dissolved organic carbon (DOC)] and in the atmosphere as CO2 are of the same order of magnitude, such that small changes in the DOC pool could have important consequences in atmospheric carbon and thus climate. DOC in the global ocean is largely formed in the sunlit euphotic zone, but identifying predictable controls on that production is an important yet unrealized goal. Here, we use a testable and causative correlation between the net production of DOC and the consumption of new nutrients in the euphotic zone of the Atlantic Ocean. We demonstrate that new nutrients introduced to the euphotic zone by upwelling in divergence zones and by winter convective overturn of the water column, and the primary production associated with those nutrients, are the ultimate driver of DOC distributions across the Atlantic basins. As new nutrient input will change with a changing climate, the role of DOC in the ocean’s biological pump should likewise be impacted.

  18. Removal of fluorescence and ultraviolet absorbance of dissolved organic matter in reclaimed water by solar light.

    PubMed

    Wu, Qianyuan; Li, Chao; Wang, Wenlong; He, Tao; Hu, Hongying; Du, Ye; Wang, Ting

    2016-05-01

    Storing reclaimed water in lakes is a widely used method of accommodating changes in the consumption of reclaimed water during wastewater reclamation and reuse. Solar light serves as an important function in degrading pollutants during storage, and its effect on dissolved organic matter (DOM) was investigated in this study. Solar light significantly decreased the UV254 absorbance and fluorescence (FLU) intensity of reclaimed water. However, its effect on the dissolved organic carbon (DOC) value of reclaimed water was very limited. The decrease in the UV254 absorbance intensity and FLU excitation-emission matrix regional integration volume (FLU volume) of reclaimed water during solar light irradiation was fit with pseudo-first order reaction kinetics. The decrease of UV254 absorbance was much slower than that of the FLU volume. Ultraviolet light in solar light had a key role in decreasing the UV254 absorbance and FLU intensity during solar light irradiation. The light fluence-based removal kinetic constants of the UV254 and FLU intensity were independent of light intensity. The peaks of the UV254 absorbance and FLU intensity with an apparent molecular weight (AMW) of 100Da to 2000Da decreased after solar irradiation, whereas the DOC value of the major peaks did not significantly change. PMID:27155416

  19. Transformation of dissolved organic matter in a novel groundwater recharge system with reclaimed water.

    PubMed

    Wu, Linlin; Zhao, Xuan; Zhang, Meng

    2011-12-01

    A novel process, enhanced direct injection-well recharge system (EnDir), can overcome the technical difficulties during the application of conventional surface spreading and has been developed to recharge groundwater with reclaimed water. In this study, removal and transformation of dissolved organic matter (DOM) in the system were investigated in laboratory-scale experiments. Results demonstrated that dissolved organic carbon and trihalomethane formation potential values could be reduced from 6.54 +/- 1.30 mg/L and 267.9 +/- 24.3 microg/L to 1.59 +/- 0.64 mg/L and 104.5 +/- 10.2 microg/L, respectively, as a result of DOM biodegradation in the aerobic short-term vadose soil treatment. Fluorescence spectra showed that aromatic protein-like substances and soluble microbial byproducts could be removed, to a great extent, in the soil system. Despite different removal efficiencies of DOM in different molecular weight fractions, the residual DOM was composed mainly of fulvic acid-like and humic acid-like substances, with molecular weights of 500 Da to 1 kDa. PMID:22368955

  20. Transformation of dissolved organic matters in swine, cow and chicken manures during composting.

    PubMed

    Wang, Ke; Li, Xiangkun; He, Chao; Chen, Chia-Lung; Bai, Jianwei; Ren, Nanqi; Wang, Jing-Yuan

    2014-09-01

    The changes of dissolved organic matters (DOMs) extracted from swine, cow and chicken manures were assessed by Fourier transform infrared, ultraviolet, gel permeation chromatography (GPC), excitation-emission-matrix fluorescence (EEM-FL), Biolog Eco and (1)H NMR during 60-day composting. Pumice was adopted to eliminate the disturbing of common organic bulking agents. The results showed chicken manure had the highest DOC, DTN (dissolved total nitrogen) and lowest DOC/DTN among the three manures; cow manure had the highest volatile solids, lowest DTN, slowest DOMs hydrolysis rate and the fastest bio-stabilization rate. (1)H NMR showed the decrease rates of OC band and saturated carbon chain were distinctly faster than that of olefinic and aromatic structures. The molecular size distribution of DOMs in the three manures was in the range of 1-10 kDa detected by GPC. Microbial carbon utilization capacity decreased in cow manure with composting time, but the contrast was observed in the chicken and swine manures. PMID:24813566

  1. Identification of Reactive and Refractory Components of Dissolved Organic Nitrogen by FT-ICR Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Cooper, W. T.; Podgorski, D. C.; Osborne, D. M.; Corbett, J.; Chanton, J.

    2010-12-01

    Dissolved organic nitrogen is an often overlooked but potentially significant bioavailable component of dissolved organic matter. Studies of bulk DON turnover have been reported, but the compositions of the reactive and refractory components of DON are largely unknown. Here we show the unique ability of atmospheric pressure photoionization (APPI) coupled to ultrahigh resolution mass spectrometry to identify the reactive and refractory components of DON. Figure 1 is an isolated 0.30 m/z window from an ultrahigh resolution APPI FT-ICR mass spectrum of DON in surface waters draining an agricultural area in South Florida. Using this optimized, negative-ion APPI strategy we have been able to identify the reactive and refractory components of DON in these nitrogen-rich waters. Similar results were observed with samples from soil porewaters in sedge-dominated fens and sphagnum-dominated bogs within the Glacial Lake Agassiz Peatlands (GLAP) of northern Minnesota. Surprisingly, microbes appear to initially use similar enzymatic pathways to degrade DON and DOC, often with little release of nitrogen. Figure 1. Isolated 0.30 m/z window at nominal mass 432 from negative-ion APPI FT-ICR mass spectrum of DOM from waters draining an agricultural area in South Florida. Peaks marked contain nitrogen.

  2. Characterisation of dissolved organic matter in stormwater using high-performance size exclusion chromatography.

    PubMed

    Huang, Huiping; Chow, Christopher W K; Jin, Bo

    2016-04-01

    Understanding the complexity of dissolved organic matter (DOM) in stormwater has drawn a lot of interest, since DOM from stormwater causes not only environmental impacts, but also worsens downstream aquatic quality associated with water supply and treatability. This study introduced and employed high-performance size exclusion chromatography (HPSEC) coupled with an ultraviolet-visible (UV-vis) diode array detector to assess changes in stormwater-associated DOM characteristics. Stormwater DOM was also analysed in relation to storm event characteristics, water quality and spectroscopic analysis. Statistical tools were used to determine the correlations within DOM and water quality measurements. Results showed that dissolved organic carbon (DOC) and UV absorbance at 254 nm (UV254) as conventional DOM parameters were found to be correlated well to the changes in stormwater quality during each of the three storm events studied. Both detector wavelengths (210 and 254 nm) and their ratio (A210/A254) were found to provide additional information on the physiochemical properties of stormwater-associated DOM. This study indicated that A210/A254 is an important parameter which could be used to estimate the DOM proportions of functional groups and conjugated carbon species. This study provided also an understanding of stormwater quality constituents through assessing variability and sensitivity for various parameters, and the additional information of rainfall characteristics on runoff quality data for a better understanding of parameter correlations and influences. PMID:27090716

  3. Combined ion exchange treatment for removal of dissolved organic matter and hardness.

    PubMed

    Apell, Jennifer N; Boyer, Treavor H

    2010-04-01

    Dissolved organic matter (DOM) and hardness cations are two common constituents of natural waters that substantially impact water treatment processes. Anion exchange treatment, and in particular magnetic ion exchange (MIEX), has been shown to effectively remove DOM from natural waters. An important advantage of the MIEX process is that it is used as a slurry in a completely mixed flow reactor at the beginning of the treatment train. Hardness ions can be removed with cation exchange resins, although typically using a fixed bed reactor at the end of a treatment train. In this research, the feasibility of combining anion and cation exchange treatment in a single completely mixed reactor for treatment of raw water was investigated. The sequence of anion and cation exchange treatment, the number of regeneration cycles, and the chemistry of the regeneration solution were systematically explored. Simultaneous removal of DOM (70% as dissolved organic carbon) and hardness (>55% as total hardness) was achieved by combined ion exchange treatment. Combined ion exchange is expected to be useful as a pre-treatment for membrane systems because both DOM and divalent cations are major foulants of membranes.

  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. Investigating extent of dissolved organic carbon stabilization by metal based coagulant in a wetland environment

    NASA Astrophysics Data System (ADS)

    Henneberry, Y.; Mourad, D.; Kraus, T.; Bachand, P.; Fujii, R.; Horwath, W.

    2008-12-01

    This study is part of a larger project designed to investigate the feasibility of using metal-based coagulants to remove dissolved organic carbon (DOC) from island drainage water in the San Joaquin Delta and subsequently retaining the metal-DOC precipitate (floc) in wetlands constructed at the foot of levees to promote levee stability. Dissolved organic carbon is a constituent of concern as some forms of DOC can be converted to carcinogenic compounds during drinking water treatment. The focus of this work is to assess floc stability over time and to determine whether floc can be permanently sequestered as part of wetland sediment. Drainage water collected seasonally from Twitchell Island was coagulated with ferric sulfate and polyaluminum chloride at optimal and 50%-optimal dosage levels. Floc was incubated in the laboratory under anaerobic conditions for six weeks under various conditions including different DOC concentrations, microbial inoculants, and addition of nutrients. Preliminary results indicate the floc is a stable system; little to no DOC was released from the floc into the water column under incubations with native microbial inoculate. In addition, floc incubated with previously coagulated water appeared to remove additional DOC from the water column. Future work will involve field and laboratory studies using 13C labeled plant material to examine the effects of fresh plant matter and the effects of peat soil DOC on floc stability, in order to elucidate mechanisms behind carbon stabilization by metal-based floc.

  6. Underwater radiant energy absorbed by phytoplankton, detritus, dissolved organic matter, and pure water

    SciTech Connect

    Kishino, M.; Booth, C.R.; Okami, N.

    1984-03-01

    The spectral irradiance distribution at five stations on lakes and at sea was measured with a portable underwater spectral irradiance meter. Chlorophyll a concentration and the absorption coefficient of the water were concurrently measured. From measured spectral irradiance distributions, radiant energy absorbed per unit volume was computed. At these stations, the effect of upward irradiance on total quanta absorbed by the water was negligibly small for all layers. The relative contributions of phytoplankton, detritus, dissolved organic matter, and pure water to the total absorbed quanta were also computed by taking into consideration the spectral dependency of each component: the contribution of quanta absorbed by the water was negligibly small for all layers. The relative contributions of phytoplankton, detritus, dissolved organic matter, and pure water to the total absorbed quanta were also computed by taking into consideration the spectral dependency of each component: the contribution of quanta absorbed by phytoplankton was about 3-10% in clear water and about 30-40% in the plankton-rich water.

  7. Quantifying and correcting the impacts of freezing samples on dissolved organic matter absorbance

    NASA Astrophysics Data System (ADS)

    Griffin, C. G.; McClelland, J. W.; Frey, K. E.; Holmes, R. M.

    2012-12-01

    The use of optical measurements as proxies for organic matter concentration and composition has become increasingly popular in recent years. Absorbance of chromophoric dissolved organic matter (CDOM) can be used to estimate concentrations of dissolved organic carbon (DOC), as a qualitative assessment of dissolved organic matter (DOM) average molecular weight and is often used to calibrate satellite remote sensing of organic matter. However, there is evidence that preservation of samples can lead to significant changes in CDOM absorbance spectra. Freezing is a popular means of preservation, but can result in flocculation of DOM when samples are thawed for analysis. We hypothesize that the particles generated as a result of a freeze/thaw cycle lead to increasing absorption in visible wavelengths (400-800 nm). Yet, absorbance in the UV spectra should remain similar to original values. These hypotheses are tested on CDOM spectra collected from two large Arctic watersheds (the Mackenzie and Yukon rivers) and four smaller Texas watersheds (the Colorado, Guadalupe, Nueces and San Antonio rivers). In addition, we experiment with additional filtering and sonication to correct for flocculation from frozen samples. Preliminary data show that short wavelengths are relatively well preserved (200-300 nm). However, CDOM absorption changes unpredictably from 350-450 nm, the wavelengths most commonly used to estimate DOC. Absorption coefficients tend to be higher in these wavelengths after a freeze/thaw cycle, but the magnitude of this increase varies. Some of these impacts can be corrected for with sonication. For instance, when comparing experimental treatments to initial absorption at 365 nm from Mackenzie River samples, R2 increases from 0.60 to 0.79 for samples undergoing one freeze/thaw cycle to those that were also sonicated. Regardless of treatment, however, no spectral slopes were well preserved after a freeze/thaw cycle. These results reinforce earlier work that it is

  8. Molecular evidence for abiotic sulfurization of dissolved organic matter in marine shallow hydrothermal systems

    NASA Astrophysics Data System (ADS)

    Gomez-Saez, Gonzalo V.; Niggemann, Jutta; Dittmar, Thorsten; Pohlabeln, Anika M.; Lang, Susan Q.; Noowong, Ann; Pichler, Thomas; Wörmer, Lars; Bühring, Solveig I.

    2016-10-01

    Shallow submarine hydrothermal systems are extreme environments with strong redox gradients at the interface of hot, reduced fluids and cold, oxygenated seawater. Hydrothermal fluids are often depleted in sulfate when compared to surrounding seawater and can contain high concentrations of hydrogen sulfide (H2S). It is well known that sulfur in its various oxidation states plays an important role in processing and transformation of organic matter. However, the formation and the reactivity of dissolved organic sulfur (DOS) in the water column at hydrothermal systems are so far not well understood. We investigated DOS dynamics and its relation to the physicochemical environment by studying the molecular composition of dissolved organic matter (DOM) in three contrasting shallow hydrothermal systems off Milos (Eastern Mediterranean), Dominica (Caribbean Sea) and Iceland (North Atlantic). We used ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) to characterize the DOM on a molecular level. The molecular information was complemented with general geochemical data, quantitative dissolved organic carbon (DOC) and DOS analyses as well as isotopic measurements (δ2H, δ18O and F14C). In contrast to the predominantly meteoric fluids from Dominica and Iceland, hydrothermal fluids from Milos were mainly fed by recirculating seawater. The hydrothermal fluids from Milos were enriched in H2S and DOS, as indicated by high DOS/DOC ratios and by the fact that >90% of all assigned DOM formulas that were exclusively present in the fluids contained sulfur. In all three systems, DOS from hydrothermal fluids had on average lower O/C ratios (0.26-0.34) than surrounding surface seawater DOS (0.45-0.52), suggesting shallow hydrothermal systems as a source of reduced DOS, which will likely get oxidized upon contact with oxygenated seawater. Evaluation of hypothetical sulfurization reactions suggests DOM reduction and sulfurization during seawater

  9. Characterization of water dissolved organic matter under woody vegetation patches in semi-arid Mediterranean soils.

    PubMed

    Cerdán, M; Sánchez-Sánchez, A; Jordá, J D; Amat, B; Cortina, J; Ruiz-Vicedo, N; El-Khattabi, M

    2016-05-15

    Woody patches in semiarid environments favor the establishment of other plants. Facilitation may be favored by an increase in soil fertility. Dissolved organic matter (DOM), is the most active fraction of soil organic matter and may contain compounds affecting plant establishment, as allelochemicals, hormone-like substances and metal carriers. However, information on DOM contents and composition in these environments is scarce. In this paper, we study the impact of woody patches on DOM in Stipa tenacissima L. steppes and discuss its implications for community dynamics. DOM under patch- and inter-patch areas, was analyzed for elemental composition, UV-Vis indices and organic acid content. Element concentration and composition in DOM, and organic acid concentration were similar in patch- and inter-patch areas. Yet, soils under patches were richer in DOC, aromatic species and organic acids (particularly fumaric acid) than soils in inter-patch areas. Dominant species affected organic matter concentration and quality in complex ways. Thus, patches dominated by Ephedra fragilis showed higher concentrations of TOC and aromatics than those dominated by other species. Rhamnus lycioides patches showed the highest accumulation of fumaric acid, which may contribute to its successful recruitment rate and expansion in the area. Our results show substantial differences in the amount and composition of DOM and specific compounds affecting soil functionality and plant dynamics. Further studies on the effects of such changes on seedling performance are needed to increase our understanding of plant-plant interactions in semiarid environments. PMID:26930307

  10. Ocean chemistry. 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

    2015-04-17

    Oceanic dissolved organic carbon (DOC) is the second largest reservoir of organic carbon in the biosphere. About 72% of the global DOC inventory is stored in deep oceanic layers for years to centuries, supporting the current view that it consists of materials resistant to microbial degradation. An alternative hypothesis is that deep-water DOC consists of many different, intrinsically labile compounds at concentrations too low to compensate for the metabolic costs associated to their utilization. Here, we present experimental evidence showing that low concentrations rather than recalcitrance preclude consumption of a substantial fraction of DOC, leading to slow microbial growth in the deep ocean. These findings demonstrate an alternative mechanism for the long-term storage of labile DOC in the deep ocean, which has been hitherto largely ignored.

  11. Changes in dissolved organic carbon of soil amendments with aging: effect on pesticide adsorption behavior.

    PubMed

    Cox, Lucia; Fernandes, M Conceicao; Zsolnay, Adam; Hermosín, M Carmen; Cornejo, Juan

    2004-09-01

    The effect of aging in the soil of three organic amendments (OAs), one liquid (LF) and two solid ones (SF and AL), has been investigated and related to changes in soil adsorption of metalaxyl and tricyclazole. LF and AL have very high dissolved organic carbon (DOC) contents with low humification index values, whereas SF has a low DOC content but the highest amounts of highly humified material. All OAs increased the adsorption of tricyclazole, whereas adsorption of metalaxyl decreased in soils amended with LF and AL, due to competition with DOC for mineral adsorption sites. With aging, DOC from SF amended soils is not significantly affected and neither is adsorption behavior. On the contrary, the great reduction of DOC from LF and AL with aging has been shown to affect adsorption of metalaxyl and tricyclazole, and this effect is dependent on the pesticide, the nature of the DOC, and the type of soil, in particular its clay mineralogy.

  12. Zeolite-fiber integrated optical chemical sensors for detection of dissolved organics in water.

    PubMed

    Zhang, Jian; Dong, Junhang; Luo, Ming; Xiao, Hai; Murad, Sohail; Normann, Randy A

    2005-09-13

    MFI zeolite coated optical fiber sensors have been developed for in situ detection of dissolved organics in water. The sensors operate by monitoring the optical reflectivity changes caused by the selective adsorption of organic molecules, i.e., 2-propanol or pentanoic acid in this study, from aqueous solutions in the zeolitic pores. Reversible and monotonic sensor signals were observed in response to the variation of 2-propanol concentration in water with fast response. However, the sensor exhibited a much slower response to pentanoic acid than to 2-propanol. It was also found that substitution of Si by Al in the MFI framework increased the adsorption of pentanoic acid that resulted in enhanced sensor responses.

  13. Significant anaerobic production of fluorescent dissolved organic matter in the deep East Sea (Sea of Japan)

    NASA Astrophysics Data System (ADS)

    Kim, Jeonghyun; Kim, Guebuem

    2016-07-01

    The distribution of fluorescent dissolved organic matter (FDOM) in the East Sea (Sea of Japan) was examined by excitation-emission matrix spectroscopy with parallel factor analysis (PARAFAC). Humic-like FDOM (FDOMH) increased with depth and was significantly correlated with Apparent Oxygen Utilization (AOU), indicating that FDOMH in the deep water is mainly produced by oxidation of organic matter. In addition, a surprisingly large excess of FDOMH relative to that expected from the observed AOU was found from 1000 m to the bottom (up to 3500 m). Based on the high-resolution geographical distribution and characteristics of FDOM in the East Sea, we conclude that this excess likely originates from anaerobic FDOMH production in subsurface bottom sediments. This FDOMH flux accounts for 8-15% of the total FDOM production in the water column. Our results suggest that anaerobic activities in subsurface sediments are an important hidden source of FDOM in the ocean.

  14. Characterization of biocoals and dissolved organic matter phases obtained upon hydrothermal carbonization of brewer's spent grain.

    PubMed

    Poerschmann, J; Weiner, B; Wedwitschka, H; Baskyr, I; Koehler, R; Kopinke, F-D

    2014-07-01

    The wet biomass brewer's spent grain was subjected to hydrothermal carbonization to produce biocoal. Mass balance considerations indicate for about two thirds of the organic carbon of the input biomass to be transferred into the biocoal. The van Krevelen plot refers to a high degree of defunctionalization with decarboxylation prevailing over dehydration. Calorific data revealed a significant energy densification of biocoals as compared to the input substrate. Sorption coefficients of organic analytes covering a wide range of hydrophobicities and polarities on biocoal were similar to those for dissolved humic acids. Data from GC/MS analysis indicated that phenols and benzenediols along with fatty acids released from bound lipids during the hydrothermal process constituted abundant products. Our findings demonstrate that the brewer's spent grain by-product is a good feedstock for hydrothermal carbonization to produce biocoal, the latter offering good prospects for energetic and soil-improving application fields.

  15. [Roles of soil dissolved organic carbon in carbon cycling of terrestrial ecosystems: a review].

    PubMed

    Li, Ling; Qiu, Shao-Jun; Liu, Jing-Tao; Liu, Qing; Lu, Zhao-Hua

    2012-05-01

    Soil dissolved organic carbon (DOC) is an active fraction of soil organic carbon pool, playing an important role in the carbon cycling of terrestrial ecosystems. In view of the importance of the carbon cycling, this paper summarized the roles of soil DOC in the soil carbon sequestration and greenhouse gases emission, and in considering of our present ecological and environmental problems such as soil acidification and climate warming, discussed the effects of soil properties, environmental factors, and human activities on the soil DOC as well as the response mechanisms of the DOC. This review could be helpful to the further understanding of the importance of soil DOC in the carbon cycling of terrestrial ecosystems and the reduction of greenhouse gases emission.

  16. Origin, transport and fate of the dissolved organic matter produced in the watershed of the Paraíba do Sul River, Brazil.

    NASA Astrophysics Data System (ADS)

    Marques da Silva Junior, Jomar; Soares Gonçalves Serafim, Tassiana; Gomes de Almeida, Marcelo; Dittmar, Thorsten; de Rezende, Carlos Eduardo

    2015-04-01

    The Paraíba do Sul River (PSR) is an important river from Southeastern Brazil that flows through the states of São Paulo, Minas Gerais and Rio de Janeiro. The PSR is responsible for the water supply of over 14 million of the habitants. Due the human occupation and anthropic pressure, only 8% of it is original forest cover remains in the form of small fragmented patches. The remaining of the basin is mostly covered by grasses, such as pasture and sugar cane. Isotopic studies allows the monitoring of ecosystem changes and promotes specific links between ecology, land use and biogeochemical processes. We investigated the isotopic composition of the dissolved organic matter (DOM) in PSR. Our objective was to identify how extensive land use changes, from forest (C3 Plants) to pasture and sugar cane (C4 Plants), have affected river biogeochemistry of organic matter transported by PSR. Water samples were collected at 24 sites along the main channel of the PSR, 14 sites samples at the tributaries and 21 sites samples in the estuarine and marine environmental until 35km of the coast. Sampling was performed in the wet season of the 2013 and the dry season of the 2013. The fluvial and estuarine samples were processed with conventional filtration and the marine samples were processed with the cross-flow filtration. The dissolved organic matter (DOM) was isolated by solid-phase extraction (SPE) with the PPL cartridges (Styrene divinyl benzene polymer). Isotope measurements, organic carbon and nitrogen concentration were performed with a isotope-ratio mass spectrometry (Thermo Finningan). The 13C and the 15N values ranged from -20.0‰ and -29.0‰, and from -0.80 to 4.59 respectively, while the (C/N)a ratio varied between 8 and 41. The 13C were depleted in 13C at the river samples from the wet season, and in the estuary and marine areas as well. The 13C average values observed during the wet season in the PSR and in the estuarine samples are close to those

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

    DOE PAGES

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

    2014-06-16

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

  18. The Influence of Regional Groundwater on the Dissolved Organic Matter in Costa Rican Streams

    NASA Astrophysics Data System (ADS)

    Barnett, E.; Osburn, C. L.; Oviedo-Vargas, D.; Genereux, D. P.; Oberbauer, S. F.; Dierick, D.

    2015-12-01

    The aim of this study was to better understand the role of regional groundwater in stream organic matter in two tropical watersheds in Costa Rica. Dissolved organic matter (DOM) concentration, stable C isotopes, absorbance, and fluorescence were used to distinguish DOM sources in two adjacent watersheds, the Arboleda and the Taconazo, which are similar in size, soils, rainfall, and vegetation, yet differ because the Arboleda receives a significant input of regional groundwater that is chemically distinct from the local groundwater, whereas the Taconazo does not. Characteristics of the DOM differed largely among the two streams. Fluorescence and isotope data suggested that more degraded DOM was predominant during dry periods in the Arboleda due to the influence of regional groundwater in that stream. During wet periods, fresher soil-derived DOM was predominant in both streams, similar to the quality of DOM in the Taconazo during base flow. DOM δ13C values of the Arboleda during baseflow ranged from -23 to -34‰, while in the Taconazo values ranged from -25 to -34‰. During storm flow the ranges were smaller and more similar. The Taconazo ranged from -23 to -29‰ and the Arboleda ranged from -23 to -31‰. These differences were more noticeable at baseflow and during the dry season (December to April), suggesting that the DOM from regional groundwater entering the Arboleda had less of an impact when heavily diluted by soil DOM mobilized by precipitation. In both streams, during periods of heavy precipitation, DOM concentrations were much higher than during base flow. Further, at baseflow the Arboleda showed generally lower concentrations of dissolved organic carbon (DOC) than the Taconazo, yet export of DOC from the Arboleda watershed was far higher than from the Taconazo due to the large contribution by regional groundwater to the Arboleda water export. Results from this research emphasize the role of regional groundwater in shaping the quality of the organic

  19. Adsorption and structural fractionation of dissolved organic matter (DOM) by soil mineral surfaces

    NASA Astrophysics Data System (ADS)

    Avneri, Shani; Polubesova, Tamara; Chefetz, Benny

    2015-04-01

    Dissolved organic matter (DOM) represents a small but highly reactive fraction of the soil organic matter (SOM). One of the important processes affecting the fate of DOM in soils is its interactions with mineral phases. Adsorptive fractionation of DOM by soils and minerals has been observed previously, however detailed changes in composition of DOM due to its interactions with mineral soils were not yet elucidated. In this research the adsorption and physico-chemical fractionation of DOM by soil poor with organic matter and rich with iron oxides and clay fraction was investigated. The changes in DOM structural composition were studied using separation with polymeric resins. The following fractions were obtained: hydrophobic acid (HoA), hydrophobic neutral (HoN), hydrophilic acid (HiA), hydrophilic base (HiB), and hydrophilic neutral (HiN). Two types of DOM were studied: DOM extracted from composted biosolids (compost DOM) and DOM from Suwanee River (SRNOM). Sorption affinity of DOM to soil mineral surfaces was source and chemistry dependent. SRNOM, which was characterized by higher content of aromatic and carboxylic groups demonstrated higher affinity to the studied soil than compost DOM. For both DOM samples preferential adsorption of HoA by soil (50-85% from adsorbed carbon) was observed. Desorption of both DOM types demonstrated significant hysteresis (up to 90-100% of dissolved organic carbon was retained by the soil after 3 cycles of desorption stages). This suggests that DOM desorption behavior was affected by HoA dominant adsorption to the soil mineral fraction, and not by DOM source. Results of this study indicate that interactions of different types of DOM with mineral soil may result in similar changes in composition and properties of DOM both in the supernatant as well as in the adsorbed phase. The change in DOM composition due to its interaction with soil minerals may influence the interactions of pollutants with DOM and soil particle surfaces.

  20. Nutrient and dissolved organic carbon removal from natural waters using industrial by-products.

    PubMed

    Wendling, Laura A; Douglas, Grant B; Coleman, Shandel; Yuan, Zheng

    2013-01-01

    Attenuation of excess nutrients in wastewater and stormwater is required to safeguard aquatic ecosystems. The use of low-cost, mineral-based industrial by-products with high Ca, Mg, Fe or Al content as a solid phase in constructed wetlands potentially offers a cost-effective wastewater treatment option in areas without centralised water treatment facilities. Our objective was to investigate use of water treatment residuals (WTRs), coal fly ash (CFA), and granular activated carbon (GAC) from biomass combustion in in-situ water treatment schemes to manage dissolved organic carbon (DOC) and nutrients. Both CaO- and CaCO(3)-based WTRs effectively attenuated inorganic N species but exhibited little capacity for organic N removal. The CaO-based WTR demonstrated effective attenuation of DOC and P in column trials, and a high capacity for P sorption in batch experiments. Granular activated carbon proved effective for DOC and dissolved organic nitrogen (DON) removal in column trials, but was ineffective for P attenuation. Only CFA demonstrated effective removal of a broad suite of inorganic and organic nutrients and DOC; however, Se concentrations in column effluents exceeded Australian and New Zealand water quality guideline values. Water treated by filtering through the CaO-based WTR exhibited nutrient ratios characteristic of potential P-limitation with no potential N- or Si-limitation respective to growth of aquatic biota, indicating that treatment of nutrient-rich water using the CaO-based WTR may result in conditions less favourable for cyanobacterial growth and more favourable for growth of diatoms. Results show that selected industrial by-products may mitigate eutrophication through targeted use in nutrient intervention schemes.

  1. 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

  2. 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

  3. 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

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

    USGS Publications Warehouse

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

    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

  5. Dissolved organic phosphorus (DOP) and its potential role for ecosystem nutrition

    NASA Astrophysics Data System (ADS)

    Brödlin, Dominik; Hagedorn, Frank; Kaiser, Klaus

    2016-04-01

    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 about the fluxes of dissolved organic phosphorus (DOP) forms and their role in the P cycle. However, there is evidence that DOP is composed of some plant-derived organic phosphorus compounds, such as phytate, which are less mobile and prone to be sorbed to mineral surfaces, whereas microbial-derived compounds like nucleic acids and simple phospho-monoester may represent more mobile forms of soil phosphorus. In our study, we estimated fluxes, composition, and bioavailability of DOP along a gradient in phosphorus availability at five sites on silicate bedrock across Germany (Bad Brückenau, Conventwald, Vessertal, Mitterfels and Lüss) and at a calcareous site in Switzerland (Schänis). Soil solution was collected at 0 down to 60 to 150 cm soil depth at different intervals. Since most solutions had very low P concentrations (<0.05 mg total dissolved P/L), soil solutions had to be concentrated by freeze-drying for the enzymatic characterization of DOP. In order to test the potential bioavailability, we used an enzyme assay distinguishing between phytate-like P (phytate), diester-like P (nucleic acids), monoester-like P (glucose-6-phosphate), and pyrophosphate of bulk molybdate unreactive phosphorus (MUP). First results from the enzymatic assay indicated that monoester-like P and diester-like P were the most prominent form of the hydrolysable DOP constituents. In leachates from the organic layer, there was a high enzymatic activity for monoester-like P, indicating high recycling efficiency and rapid hydrolysis of labile DOP constituents. DOP was the dominating P form in soil solution at some of the sites, with a greater

  6. Molecular insights into the microbial formation of marine dissolved organic matter: recalcitrant or labile?

    NASA Astrophysics Data System (ADS)

    Koch, B. P.; Kattner, G.; Witt, M.; Passow, U.

    2014-08-01

    The degradation of marine dissolved organic matter (DOM) is an important control variable in the global carbon cycle. For our understanding of the kinetics of organic matter cycling in the ocean, it is crucial to achieve a mechanistic and molecular understanding of its transformation processes. A long-term microbial experiment was performed to follow the production of non-labile DOM by marine bacteria. Two different glucose concentrations and dissolved algal exudates were used as substrates. We monitored the bacterial abundance, concentrations of dissolved and particulate organic carbon (DOC, POC), nutrients, amino acids and transparent exopolymer particles (TEP) for 2 years. The molecular characterization of extracted DOM was performed by ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) after 70 days and after ∼2 years of incubation. Although glucose quickly degraded, a non-labile DOC background (5-9% of the initial DOC) was generated in the glucose incubations. Only 20% of the organic carbon from the algal exudate degraded within the 2 years of incubation. The degradation rates for the non-labile DOC background in the different treatments varied between 1 and 11 μmol DOC L-1 year-1. Transparent exopolymer particles, which are released by microorganisms, were produced during glucose degradation but decreased back to half of the maximum concentration within less than 3 weeks (degradation rate: 25 μg xanthan gum equivalents L-1 d-1) and were below detection in all treatments after 2 years. Additional glucose was added after 2 years to test whether labile substrate can promote the degradation of background DOC (co-metabolism; priming effect). A priming effect was not observed but the glucose addition led to a slight increase of background DOC. The molecular analysis demonstrated that DOM generated during glucose degradation differed appreciably from DOM transformed during the degradation of the algal exudates. Our

  7. Litter leachate sources for streamwater dissolved organic matter in an oak woodland catchment

    NASA Astrophysics Data System (ADS)

    Dyda, R. Y.; Hernes, P. J.; Flores, S. C.; O'Geen, A. T.; Dahlgren, R. A.; Spencer, R.

    2009-12-01

    Streamwater dissolved organic matter (DOM) is derived from a variety of sources, but until recently was largely thought to originate from degraded soil organic matter (SOM) pools. However, recent investigations of dissolved organic carbon (DOC) have called into question the idea that DOM in streams is derived primarily from aged SOM. Evidence includes riverine DOC 14C ages (~5 years) that are much younger than SOM within the catchment as well as the riverine particulate organic matter (POM) pool (decades to 100’s of years). Molecular fractionation due to litter leaching in the laboratory and sorption to mineral surfaces can completely account for the degraded molecular signatures observed in dissolved lignin compositions within the DOM pool. To evaluate whether these processes hold true under environmental conditions, we conducted a leaching incubation experiment using litters and degraded “duff” litters (estimated 2-5 yrs of degradation) from four vegetation types (live and blue oak leaves, foothill pine needles, and mixed annual grasses) in an oak woodland ecosystem in the foothills of the Sierra mountains of California. Litters and duffs were placed on sieves within funnels throughout the catchment, and leachates were collected during each rainfall event from Dec. 1, 2006 through May 31, 2007. On a bulk carbon basis, duff material yielded the greatest flux of DOC and weighted average carbon normalized lignin yields and ratios of syringyl and cinnamyl phenols to vanillyl phenols were remarkably similar to that observed in the stream, indicating that processes such as sorption may not be the driving force behind the composition observed. However, elevated ratios of acid to aldehyde compounds of the syringyl and vanillyl phenols in the stream relative to the weighted average of the litter leachate as well as the litter and duff materials indicates that some modification of the lignin phenols. Areal yields of DOM are up to two orders of magnitude greater than

  8. A proteomic fingerprint of dissolved organic carbon and of soil particles.

    PubMed

    Schulze, Waltraud X; Gleixner, Gerd; Kaiser, Klaus; Guggenberger, Georg; Mann, Matthias; Schulze, Ernst-Detlef

    2005-01-01

    Mass spectrometry-based proteomics was applied to analyze proteins isolated from dissolved organic matter (DOM). The focal question was to identify the type and biological origin of proteins in DOM, and to describe diversity of protein origin at the level of higher taxonomic units, as well as to detect extracellular enzymes possibly important in the carbon cycle. Identified proteins were classified according to their phylogenetic origin and metabolic function using the National Center for Biotechnology Information (NCBI) protein and taxonomy database. Seventy-eight percent of the proteins in DOM from the lake but less than 50% in forest soil DOM originated from bacteria. In a deciduous forest, the number of identified proteins decreased from 75 to 28 with increasing soil depth and decreasing total soil organic carbon content. The number of identified proteins and taxonomic groups was 50% higher in winter than in summer. In spruce forest, number of proteins and taxonomic groups decreased by 50% on a plot where trees had been girdled a year before and carbohydrate transport to roots was terminated. After girdling, proteins from four taxonomic groups remained as compared to nine taxonomic groups in healthy forest. Enzymes involved in degradation of organic matter were not identified in free soil DOM. However, cellulases and laccases were found among proteins extracted from soil particles, indicating that degradation of soil organic matter takes place in biofilms on particle surfaces. These results demonstrate a novel application of proteomics to obtain a "proteomic fingerprint" of presence and activity of organisms in an ecosystem.

  9. The episodic acidification of a stream with elevated concentrations of dissolved organic carbon

    NASA Astrophysics Data System (ADS)

    Wellington, Brian I.; Driscoll, Charles T.

    2004-10-01

    Organic acids are generally thought to play a minor role in the episodic acidification of streams in the USA. In this study, we investigated the episodic acidification of a stream at the Hubbard Brook Experimental Forest in New Hampshire with high concentrations of dissolved organic carbon and naturally occurring organic acids. We studied three events in 2001: spring snowmelt, which occurred from 6 April to 14 May and resulted in two distinct melt events; and two rain events, one on 17 June and the other on 17 July. During snowmelt events organic acids were a minor contributor to the short-term acidification of stream water, with increases in NO3- and dilution of base cations being the dominant mechanisms. During summer rainfall events, however, increases in inputs of organic acids were the dominant mechanism of episodic acidification when soil water was the dominant contributor to stream discharge (59 to 66% of peak stream discharge). We also found that precipitation events occurring after relatively wet antecedent conditions (17 July event) resulted in more severe acid episodes than events that followed drier antecedent conditions (17 June event). The minimum acid neutralizing capacity (ANC) was only -19 μeq l-1 for the 17 June event, whereas the minimum ANC for the 17 July event was much lower (-62 μeq l-1) although the total rainfall amount was similar for the two events.

  10. Dissolved inorganic and organic nitrogen uptake in the coastal North Sea: A seasonal study

    NASA Astrophysics Data System (ADS)

    Moneta, Alessia; Veuger, Bart; van Rijswijk, Pieter; Meysman, Filip; Soetaert, Karline; Middelburg, Jack J.

    2014-06-01

    Nitrogen incorporation into total particulate suspended matter, hydrolysable amino acids and bacterial biomarker D-Alanine was assessed seasonally in the coastal North Sea using 15N-labeled ammonium, nitrate, nitrite and 15N- and 13C-labeled urea, glycine, leucine, phenylalanine, and two complex pools of dissolved organic matter (DOM) derived from algal and bacterial cultures (A-DOM, B-DOM). We investigated: 1) uptake rates for the various substrates and their contribution to total N uptake; 2) microbial preferences for the different N sources; 3) the coupling of C and N uptake from organic substrates; 4) the contribution of bacteria to the total microbial uptake of these substrates, and 5) the role of a complex pool of organic matter for plankton nutrition. Seasonality in the preferences for N substrates was observed, with A-DOM and B-DOM being preferred in autumn and winter whereas NH4+ was preferentially taken up in spring and summer. C and N uptake was coupled for all the organic substrates, except urea that was mainly used as a nitrogen source in summer and spring. Bacterial contribution to the uptake of A-DOM and B-DOM was, on an annual average, the lowest among the N-substrates. This suggests an important role for phytoplankton in the incorporation of complex organic matter and the importance of DOM for phytoplankton nutrition.

  11. Dissolved Organic Phosphorus Production during Simulated Phytoplankton Blooms in a Coastal Upwelling System

    PubMed Central

    Ruttenberg, K. C.; Dyhrman, S. T.

    2012-01-01

    Dissolved organic phosphorus (DOP) is increasingly recognized as an important phosphorus source to marine primary producers. Despite its importance, the production rate and fate of DOP is poorly understood. In this study, patterns of DOP production were evaluated by tracking the evolution of DOP during simulated phytoplankton blooms initiated with nutrient amended surface waters, relative to controls, from the Oregon (USA) coastal upwelling system. Nitrogen (N) and phosphorus (P) additions were used to decouple DOP production and hydrolysis by inducing or repressing, respectively, community alkaline phosphatase activity. In order to examine the progression of nutrient uptake and DOP production under upwelling versus relaxation conditions, two experiments were initiated with waters collected during upwelling events, and two with waters collected during relaxation events. Maximum [under (+P) conditions] and minimum [under (+N) conditions] DOP production rates were calculated and applied to in situ DOP levels to evaluate which end-member rate most closely approximates the in situ DOP production rate at the four study sites in this coastal system. Increases in DOP concentration occurred by day-5 in control treatments in all experiments. N treatments displayed increased chlorophyll a, increased alkaline phosphatase activity, and yielded lower net DOP production rates relative to controls, suggesting that DOP levels were depressed as a consequence of increased hydrolysis of bioavailable DOP substrates. Phosphorus additions resulted in a significant net production of DOP at all stations, but no increase in chlorophyll a relative to control treatments. The contrasting patterns in DOP production between treatments suggests that changes in the ambient dissolved inorganic nitrogen:dissolved inorganic phosphorus (DIN:DIP) ratio could exert profound control over DOP production rates in this system. Patterns of DOP production across the different experiments also suggest that

  12. Dissolved organic nitrogen budgets for upland, forested ecosystems in New England

    USGS Publications Warehouse

    Campbell, J.L.; Hornbeck, J.W.; McDowell, W.H.; Buso, D.C.; Shanley, J.B.; Likens, G.E.

    2000-01-01

    Relatively high deposition of nitrogen (N) in the northeastern United States has caused concern because sites could become N saturated. In the past, mass-balance studies have been used to monitor the N status of sites and to investigate the impact of increased N deposition. Typically, these efforts have focused on dissolved inorganic forms of N (DIN = NH4-N + NO3-N) and have largely ignored dissolved organic nitrogen (DON) due to difficulties in its analysis. Recent advances in the measurement of total dissolved nitrogen (TDN) have facilitated measurement of DON as the residual of TDN - DIN. We calculated DON and DIN budgets using data on precipitation and streamwater chemistry collected from 9 forested watersheds at 4 sites in New England. TDN in precipitation was composed primarily of DIN. Net retention of TDN ranged from 62 to 89% (4.7 to 10 kg ha-1 yr-1) of annual inputs. DON made up the majority of TDN in stream exports, suggesting that inclusion of DON is critical to assessing N dynamics even in areas with large anthropogenic inputs of DIN. Despite the dominance of DON in streamwater, precipitation inputs of DON were approximately equal to outputs. DON concentrations in streamwater did not appear significantly influenced by seasonal biological controls, but did increase with discharge on some watersheds. Streamwater NO3-N was the only fraction of N that exhibited a seasonal pattern, with concentrations increasing during the winter months and peaking during snowmelt runoff. Concentrations of NO3-N varied considerably among watersheds and are related to DOC:DON ratios in streamwater. Annual DIN exports were negatively correlated with streamwater DOC:DON ratios, indicating that these ratios might be a useful index of N status of upland forests.

  13. The role of dissolved organic nitrogen in a nitrate-rich agricultural stream.

    PubMed

    Oviedo-Vargas, Diana; Royer, Todd V

    2015-03-01

    Agricultural activities have heavily altered the nitrogen (N) cycle in stream ecosystems draining croplands, particularly in the midwestern United States. However, our knowledge about dissolved organic N (DON) biogeochemistry in agricultural ecosystems is limited. From January 2011 to June 2012, we investigated DON dynamics in an agricultural headwater stream in the midwestern United States. We quantified the contribution of DON to the total dissolved N (TDN) pool and examined the role of DON as a source of N for microbial metabolism. For this we measured N-acquiring enzyme activities (aminopeptidases) and whole-stream DON uptake through short-term releases of amino acids. To investigate potential coupling between the N and C cycles occurring via simultaneous uptake of these two elements during assimilation of amino acids, seven of the short-term releases were performed concurrently with acetate. We found minimal contribution of DON to the TDN pool in this stream as a result of high concentrations of nitrate. Acetate uptake suggested that C was a limiting factor for microbial metabolism in this stream. In contrast, we were not able to detect amino acid uptake during any of the 13 short-term releases we conducted, likely as a result of high availability of dissolved inorganic N. Aminopeptidase (AMP) activity did not reflect N demand. Large spatial variability in AMP was observed within and among sites, possibly as result of physicochemical characteristics of the sediments. In contrast to other human-dominated streams, DON appeared to play a minor role in microbial metabolic processes and contributed minimally to the N pool of the study stream. PMID:26023984

  14. Characterization of dissolved organic matter in fogwater by excitation-emission matrix fluorescence spectroscopy

    USGS Publications Warehouse

    Birdwell, J.E.; Valsaraj, K.T.

    2010-01-01

    Dissolved organic matter (DOM) present in fogwater samples collected in southeastern Louisiana and central-eastern China has been characterized using excitation-emission matrix fluorescence spectroscopy. The goal of the study was to illustrate the utility of fluorescence for obtaining information on the large fraction of organic carbon in fogwaters (typically >40% by weight) that defies characterization in terms of specific chemical compounds without the difficulty inherent in obtaining sufficient fogwater volume to isolate DOM for assessment using other spectroscopic and chemical analyses. Based on the findings of previous studies using other characterization methods, it was anticipated that the unidentified organic carbon fraction would have characteristic peaks associated with humic substances and fluorescent amino acids. Both humic- and protein-like fluorophores were observed in the fogwater spectra and fluorescence-derived indices for the fogwater had similar values to those of soil and sediment porewater. Greater biological character was observed in samples with higher organic carbon concentrations. Fogwaters are shown to contain a mixture of terrestrially- and microbially-derived fluorescent organic material, which is expected to be derived from an array of different sources, such as suspended soil and dust particles, biogenic emissions and organic substances generated by atmospheric processes. The fluorescence results indicate that much of the unidentified organic carbon present in fogwater can be represented by humic-like and biologically-derived substances similar to those present in other aquatic systems, though it should be noted that fluorescent signatures representative of DOM produced by atmospheric processing of organic aerosols may be contributing to or masked by humic-like fluorophores. ?? 2010.

  15. 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.

  16. Biochar amendment to soil changes dissolved organic matter content and composition.

    PubMed

    Smebye, Andreas; Alling, Vanja; Vogt, Rolf D; Gadmar, Tone C; Mulder, Jan; Cornelissen, Gerard; Hale, Sarah E

    2016-01-01

    Amendments of biochar, a product of pyrolysis of biomass, have been shown to increase fertility of acidic soils by enhancing soil properties such as pH, cation-exchange-capacity and water-holding-capacity. These parameters are important in the context of natural organic matter contained in soils, of which dissolved organic matter (DOM) is the mobile and most bioavailable fraction. The effect of biochar on the content and composition of DOM in soils has received little research attention. This study focuses on the effects of amendments of two different biochars to an acidic acrisol and a pH-neutral brown soil. A batch experiment showed that mixing biochar with the acrisols at a 10 wt.% dose increased the pH from 4.9 to 8.7, and this resulted in a 15-fold increase in the dissolved organic carbon concentration (from 4.5 to 69 mg L(-1)). The pH-increase followed the same trend as the release of DOM in the experiment, causing higher DOM solubility and desorption of DOM from mineral sites. The binding to biochar of several well-characterised reference DOM materials was also investigated and results showed a higher sorption of aliphatic DOM to biochar than aromatic DOM, with DOM-water partitioning coefficients (Kd-values) ranging from 0.2 to 590 L kg(-1). A size exclusion occurring in biochar's micropores, could result in a higher sorption of smaller aliphatic DOM molecules than larger aromatic ones. These findings indicate that biochar could increase the leaching of DOM from soil, as well as change the DOM composition towards molecules with a larger size and higher aromaticity.

  17. 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.

  18. Dissolved Organic Carbon Dynamics in Precipitation of Central Pennsylvania as Influenced by Climatic Variability

    NASA Astrophysics Data System (ADS)

    Iavorivska, L.; Boyer, E. W.; Grimm, J.; Fuentes, J. D.

    2012-12-01

    Dissolved organic carbon (DOC) is ubiquitous in atmospheric water, plays an important role in cloud formation processes, and contributes to organic acidity of precipitation. Rain and snow deposited to the landscape is a source of acidity and nutrient enrichment to ecosystems and water bodies. Despite the significance of DOC to a plethora of ecosystem processes, knowledge about its contributions via precipitation remains limited. In this research project, we are quantifying temporal variations in the sources and concentrations of organic carbon in precipitation in the central Pennsylvania. Here, we present results of a study focusing on the dynamic variability of DOC in rainwater, at multiple time scales, at two sites located in the Appalachian Plateau Region. Sequential sampling during stormflow events at the first site, the Shale Hills Critical Zone Observatory, was conducted to address event-scale variability in rainfall DOC concentrations and is explored in the context of the types and the origins of the storms. Weekly sampling over many years at the second site, the Leading Ridge Experimental watershed, was conducted to address relationships among emissions sources, seasonal variability in storm tracks, antecedent atmospheric moisture conditions, and the temporal variability in DOC responses. In addition to DOC, other chemical analyses were conducted on the rainwater samples, including dissolved inorganic carbon, forms of nitrogen, major cations and anions, trace elements, water isotopes, pH and conductivity. These ancillary data, along with meteorological back trajectory analyses, help to identify sources and origins of DOC in the rainwater of central Pennsylvania over short and long time scales.

  19. Assessing the drivers of dissolved organic matter export from two contrasting lowland catchments, U.K.

    PubMed

    Yates, Christopher A; Johnes, Penny J; Spencer, Robert G M

    2016-11-01

    Two lowland catchments in the U.K. were sampled throughout 2010-11 to investigate the dominant controls on dissolved organic matter quantity and composition. The catchments had marked differences in terms of nutrient status, land cover and contrasting lithologies resulting in differences in the dominant flow pathways (groundwater vs. surface water dominated). The Upper Wylye is a chalk stream with a baseflow index of 0.98, draining a catchment dominated by intensive agricultural production. Millersford Brook is a lowland peat catchment with a baseflow index of 0.43, draining a semi-natural catchment with heather moorland and coniferous forest. Samples were collected weekly between October 2010 and September 2011 from eleven sampling locations. Samples were analysed to determine dissolved organic carbon, nitrogen and phosphorus fractions with DOM composition evaluated via the DOC:DON ratio, DOC:DOP ratio, specific UV absorption at 254nm, absorbance ratio (a250:a365) and the spectral slope parameter between 350 and 400nm (S350-400). Significant differences were observed in all determinands between the catchments, over time, and spatially along nutrient enrichment and geoclimatic gradients. Seasonal variation in preferential flow pathways mobilising groundwater-derived DOM were identified as likely controls on the delivery of DOM in the permeable chalk dominated catchment. Steeper S350-400 values and elevated a250:a365 ratios in this catchment suggest material of a lower bulk aromatic C content and molecular weight delivered during the winter months when compared to the summer. DOC:DON ratios were markedly lower in the chalk catchment than the peatland catchment, reflecting the paucity of organic matter within the mineral soils of the chalk landscape, and higher fertiliser application rates. This manuscript highlights that DOM composition varies according to catchment landscape character and hydrological function. PMID:27422728

  20. Controls on the composition and lability of dissolved organic matter in Siberia's Kolyma River basin

    NASA Astrophysics Data System (ADS)

    Mann, P. J.; Davydova, A.; Zimov, N.; Spencer, R. G. M.; Davydov, S.; Bulygina, E.; Zimov, S.; Holmes, R. M.

    2012-03-01

    High-latitude northern rivers export globally significant quantities of dissolved organic carbon (DOC) to the Arctic Ocean. Climate change, and its associated impacts on hydrology and potential mobilization of ancient organic matter from permafrost, is likely to modify the flux, composition, and thus biogeochemical cycling and fate of exported DOC in the Arctic. This study examined DOC concentration and the composition of dissolved organic matter (DOM) across the hydrograph in Siberia's Kolyma River, with a particular focus on the spring freshet period when the majority of the annual DOC load is exported. The composition of DOM within the Kolyma basin was characterized using absorbance-derived measurements (absorbance coefficienta330, specific UV absorbance (SUVA254), and spectral slope ratio SR) and fluorescence spectroscopy (fluorescence index and excitation-emission matrices (EEMs)), including parallel factor analyses of EEMs. Increased surface runoff during the spring freshet led to DOM optical properties indicative of terrestrial soil inputs with high humic-like fluorescence, SUVA254, and low SRand fluorescence index (FI). Under-ice waters, in contrast, displayed opposing trends in optical properties representing less aromatic, lower molecular weight DOM. We demonstrate that substantial losses of DOC can occur via biological (˜30% over 28 days) and photochemical pathways (>29% over 14 days), particularly in samples collected during the spring freshet. The emerging view is therefore that of a more dynamic and labile carbon pool than previously thought, where DOM composition plays a fundamental role in controlling the fate and removal of DOC at a pan-Arctic scale.

  1. Biochar amendment to soil changes dissolved organic matter content and composition.

    PubMed

    Smebye, Andreas; Alling, Vanja; Vogt, Rolf D; Gadmar, Tone C; Mulder, Jan; Cornelissen, Gerard; Hale, Sarah E

    2016-01-01

    Amendments of biochar, a product of pyrolysis of biomass, have been shown to increase fertility of acidic soils by enhancing soil properties such as pH, cation-exchange-capacity and water-holding-capacity. These parameters are important in the context of natural organic matter contained in soils, of which dissolved organic matter (DOM) is the mobile and most bioavailable fraction. The effect of biochar on the content and composition of DOM in soils has received little research attention. This study focuses on the effects of amendments of two different biochars to an acidic acrisol and a pH-neutral brown soil. A batch experiment showed that mixing biochar with the acrisols at a 10 wt.% dose increased the pH from 4.9 to 8.7, and this resulted in a 15-fold increase in the dissolved organic carbon concentration (from 4.5 to 69 mg L(-1)). The pH-increase followed the same trend as the release of DOM in the experiment, causing higher DOM solubility and desorption of DOM from mineral sites. The binding to biochar of several well-characterised reference DOM materials was also investigated and results showed a higher sorption of aliphatic DOM to biochar than aromatic DOM, with DOM-water partitioning coefficients (Kd-values) ranging from 0.2 to 590 L kg(-1). A size exclusion occurring in biochar's micropores, could result in a higher sorption of smaller aliphatic DOM molecules than larger aromatic ones. These findings indicate that biochar could increase the leaching of DOM from soil, as well as change the DOM composition towards molecules with a larger size and higher aromaticity. PMID:25980657

  2. 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

  3. 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.

  4. Systematic removal of neutral sugars within dissolved organic matter across ocean basins

    NASA Astrophysics Data System (ADS)

    Goldberg, Stuart J.; Carlson, Craig A.; Brzezinski, Mark; Nelson, Norm B.; Siegel, David A.

    2011-09-01

    Dissolved combined neutral sugars (DCNS) support heterotrophic bacterioplankton metabolism throughout the ocean, which affects ocean carbon cycling and biogeochemistry. Variability in DCNS composition also provides information about the diagenetic state of oceanic dissolved organic matter (DOM). Here, we present results of the DCNS composition in ˜600 discrete samples from ocean basin-scale sections within the North Atlantic and South Pacific Oceans; and at the Bermuda Atlantic Time-series Study site in the Sargasso Sea. As DCNS concentrations decline with water mass age the mole percentages of glucose, mannose + xylose, and galactose change in a ratio of +2.10:-1.10:-1.00 enriching the DOM pool in glucose relative to mannose + xylose, and galactose. A new proxy is presented based on the relative change in these major sugars, diagenetic distance, which allows for comparison of the diagenetic state of DOM over broad regions of the global ocean while simultaneously quantifying progress along this pathway. In all, this inter-basin comparison suggests that there is a common diagenetic pathway for oceanic DOM.

  5. Synoptic Sampling of Dissolved Nitrogen Species and Organic Carbon in the Rio Grande Basin

    NASA Astrophysics Data System (ADS)

    Villinski, J. E.; Hogan, J. F.; Brooks, P. D.; Haas, P. A.; Mills, S. K.

    2002-12-01

    Synoptic sampling has been performed along the Rio Grande from the headwaters in Colorado to Fort Quitman, Texas, south of El Paso. Samples from August 2001 and January 2002 were analyzed for nitrate (NO3-), ammonium (NH_{4}$+), total dissolved nitrogen (TDN), and dissolved organic carbon (DOC). DOC concentrations increase slowly between Colorado and southern New Mexico and then approximately double in Texas. Large sources of N during both sampling periods were the urban areas around Albuquerque and El Paso, Texas and Ciudad Juarez, Mexico, and agricultural regions in the Rincon and Mesilla valleys of southern New Mexico. Nitrate-N concentrations remained high south of Albuquerque to Elephant Butte reservoir in the summer, presumably due to lack of primary production. Inorganic N concentrations generally are higher in the winter than in the summer. During the summer, ammonium concentrations were greater than 100 mg N/l only at the outlet of Elephant Butte Reservoir, and in Texas. However, winter concentrations were on average an order of magnitude greater, again with the largest ammonium values (5000 \\mug N/l) in Texas. These patterns are consistent with a reduction in biological nutrient demand during the non-growing season.

  6. Determination of migration pathways of DNAPL and dissolved phase volatile organic compounds in heterogeneous aquifer systems

    SciTech Connect

    Lamb, B. ); Prucha, R.

    1993-10-01

    Before an effective ground-water extraction system can be designed, it is essential to determine the distribution of chemicals of concern in ground-water and preferential pathways for chemical migration. At the study site, determining the chemical migration pathways and spatial distribution of chemicals are complicated by the presence of halogenated volatile organic compounds (VOCs) and dense nonaqueous phase liquids (DNAPL) coupled with the heterogeneous nature of the aquifer. DNAPL is denser than ground water and therefore sinks due to gravity while the dissolved components tend to be dominated by regional ground-water advective flow. The study area is a former industrial site. The aquifer is a low permeability unit with thin lenses of sandy material. Dissolved phase chemicals preferentially migrate in these sand units. To determine pathways for the migration of chemicals both laterally and horizontally, borehole lithologic data, hydraulic data, and chemical data were synthesized into a computer database and used as input for graphical illustrations using computer aided drafting (CAD). The CAD software was also used to provide the basis for 2-D and 3-D visualization to interpret field data which aided in development of a detailed conceptual site model and in construction of a numerical ground-water flow model for the site.

  7. Treatment of dissolved perchlorate, nitrate, and sulfate using zero-valent iron and organic carbon.

    PubMed

    Liu, YingYing; Ptacek, Carol J; Blowes, David W

    2014-05-01

    Waters containing ClO and dissolved NO, derived from detonated explosives and solid propellants, often also contain elevated concentrations of other dissolved constituents, including SO. Four column experiments, containing mixtures of silica sand, zero-valent Fe (ZVI) and organic C (OC) were conducted to evaluate the potential for simultaneous removal of NO, SO and ClO. Initially, the flow rate was maintained at 0.5 pore volumes (PV) d and then decreased to 0.1 PV d after 100 PV of flow. Nitrate concentrations decreased from 10.8 mg L (NO-N) to trace levels through NO reduction to NH using ZVI alone and through denitrification using OC. Observations from the mixture of ZVI and OC suggest a combination of NO reduction and denitrification. Up to 71% of input SO (24.5 ± 3.5 mg L) was removed in the column containing OC, and >99.7% of the input ClO (857 ± 63 μg L) was removed by the OC- and (ZVI + OC)-containing columns as the flow rate was maintained at 0.1 PV d. Nitrate and ClO removal followed first-order and zero-order rates, respectively. Nitrate >2 mg L (NO-N) inhibited ClO removal in the OC-containing column but not in the (ZVI + OC)-containing column. Sulfate did not inhibit ClO degradation within any of the columns.

  8. Fluorescent dissolved organic matter in the continental shelf waters of western Bay of Bengal

    NASA Astrophysics Data System (ADS)

    Chari, Nvhk; Rao, P. Sudarsana; Sarma, Nittala S.

    2013-10-01

    Fluorescent dissolved organic matter (FDOM) of southwestern Bay of Bengal surface water during southwest monsoon consisted five fluorophores, three humic-like and two protein-like. The humification index (HIX) and humic fluorophores, viz., visible (C), marine (M) and UV (A) humic-likes indicated, better than biogeochemical constituents analyzed, that the northern-half region of the study area which is closer to the head bay (less salinity) is distinctly more terrestrially influenced. Similarly, the southern-half region (less dissolved oxygen) is indicated as more in situ influenced. This region is enriched with tyrosine protein-like fluorophore (B), an indicator of bacterial metabolism in some of its samples due to upwelled water. Although chlorophyll a is less in this (southern) region, the fluorescence based biological index (BIX) which is an index of recent phytoplankton production is about the same in the two regions, and the lower chlorophyll a of southern region is attributed to greater grazing pressure. Fluorescence properties, e.g., BIX are more informative about phytoplankton production than chlorophyll a.

  9. Linking the Molecular Signature of Heteroatomic Dissolved Organic Matter to Watershed Characteristics in World Rivers.

    PubMed

    Wagner, Sasha; Riedel, Thomas; Niggemann, Jutta; Vähätalo, Anssi V; Dittmar, Thorsten; Jaffé, Rudolf

    2015-12-01

    Large world rivers are significant sources of dissolved organic matter (DOM) to the oceans. Watershed geomorphology and land use can drive the quality and reactivity of DOM. Determining the molecular composition of riverine DOM is essential for understanding its source, mobility and fate across landscapes. In this study, DOM from the main stem of 10 global rivers covering a wide climatic range and land use features was molecularly characterized via ultrahigh-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). FT-ICR mass spectral data revealed an overall similarity in molecular components among the rivers. However, when focusing specifically on the contribution of nonoxygen heteroatomic molecular formulas (CHON, CHOS, CHOP, etc.) to the bulk molecular signature, patterns relating DOM composition and watershed land use became apparent. Greater abundances of N- and S-containing molecular formulas were identified as unique to rivers influenced by anthropogenic inputs, whereas rivers with primarily forested watersheds had DOM signatures relatively depleted in heteroatomic content. A strong correlation between cropland cover and dissolved black nitrogen was established when focusing specifically on the pyrogenic class of compounds. This study demonstrated how changes in land use directly affect downstream DOM quality and could impact C and nutrient cycling on a global scale. PMID:26153846

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

    PubMed Central

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

    2016-01-01

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

  11. Enhanced Indirect Photochemical Transformation of Histidine and Histamine through Association with Chromophoric Dissolved Organic Matter.

    PubMed

    Chu, Chiheng; Lundeen, Rachel A; Remucal, Christina K; Sander, Michael; McNeill, Kristopher

    2015-05-01

    Photochemical transformations greatly affect the stability and fate of amino acids (AAs) in sunlit aquatic ecosystems. Whereas the direct phototransformation of dissolved AAs is well investigated, their indirect photolysis in the presence of chromophoric dissolved organic matter (CDOM) is poorly understood. In aquatic systems, CDOM may act both as sorbent for AAs and as photosensitizer, creating microenvironments with high concentrations of photochemically produced reactive intermediates, such as singlet oxygen (1O2). This study provides a systematic investigation of the indirect photochemical transformation of histidine (His) and histamine by 1O2 in solutions containing CDOM as a function of solution pH. Both His and histamine showed pH-dependent enhanced phototransformation in the CDOM systems as compared to systems in which model, low-molecular-weight 1O2 sensitizers were used. Enhanced reactivity resulted from sorption of His and histamine to CDOM and thus exposure to elevated 1O2 concentrations in the CDOM microenvironment. The extent of reactivity enhancement depended on solution pH via its effects on the protonation state of His, histamine, and CDOM. Sorption-enhanced reactivity was independently supported by depressed rate enhancements in the presence of a cosorbate that competitively displaced His and histamine from CDOM. Incorporating sorption and photochemical transformation processes into a reaction rate prediction model improved the description of the abiotic photochemical transformation rates of His in the presence of CDOM.

  12. Linking the Molecular Signature of Heteroatomic Dissolved Organic Matter to Watershed Characteristics in World Rivers.

    PubMed

    Wagner, Sasha; Riedel, Thomas; Niggemann, Jutta; Vähätalo, Anssi V; Dittmar, Thorsten; Jaffé, Rudolf

    2015-12-01

    Large world rivers are significant sources of dissolved organic matter (DOM) to the oceans. Watershed geomorphology and land use can drive the quality and reactivity of DOM. Determining the molecular composition of riverine DOM is essential for understanding its source, mobility and fate across landscapes. In this study, DOM from the main stem of 10 global rivers covering a wide climatic range and land use features was molecularly characterized via ultrahigh-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). FT-ICR mass spectral data revealed an overall similarity in molecular components among the rivers. However, when focusing specifically on the contribution of nonoxygen heteroatomic molecular formulas (CHON, CHOS, CHOP, etc.) to the bulk molecular signature, patterns relating DOM composition and watershed land use became apparent. Greater abundances of N- and S-containing molecular formulas were identified as unique to rivers influenced by anthropogenic inputs, whereas rivers with primarily forested watersheds had DOM signatures relatively depleted in heteroatomic content. A strong correlation between cropland cover and dissolved black nitrogen was established when focusing specifically on the pyrogenic class of compounds. This study demonstrated how changes in land use directly affect downstream DOM quality and could impact C and nutrient cycling on a global scale.

  13. The effect of drain blocking on dissolved organic carbon under the peak flow conditions

    NASA Astrophysics Data System (ADS)

    zhang, zhuoli

    2014-05-01

    There are numerous studies that have shown increasing dissolved organic carbon (DOC) concentration down stream of upland peat catchments (eg. Worrall et al., 2007; Clark et al., 2007; Gibson et al., 200). In the UK, upland peat soils are both an important water source and an important carbon store, therefore, the transportation of DOC from soil to the aquatic system remains a critical part of the impact that upland peat environments have on wider society. The majority of the DOC is delivered from the peat soil during the peak flow events (Clark et al., 2008), however, most of the storm events analysis has been developed for organo-mineral soil rather than for peat soil catchments. Worrall et al., (2007) suggested that drain blocking as a potential method for controlling DOC release from peat soil. An events analysis was conducted on the drain blocking data collected from 2008 to 2010 from Cronkley Fell (UK National grid reference NY 83800 26996). A total of 756 peak flow events were chosen to access the impact of drain blocking on DOC concentration and flux during the events. The data was analysed by the combination of principal components analysis (PCA) and end member mixing analysis (EMMA). The results showed that during the peak flow events, the effects of drain blocking was minimised by the rapid flushing of the event water: the DOC concentration on storm events increased after blocking rather than decreased; DOC flux did decrease after blocking but rather as a result of the increased volume of the event water. Worrall, F., Armstrong, A., Holden, J., 2007. Short term impact of peat drain blocking on water color, dissolved organic carbon concentration and water table depth. Journal of Hydrology 337,315-325 Clark, J.M., Lane, S.N., Chapman, P.J., Adamson, J.K., 2007. Export of dissolved organic carbon from an upland peat during storm events: Implication for flux estimates. Journal of Hydrology 347, 438-447. Aitkenhead, J.A., McDowell, W. H., 2000. Soil C: N ratio

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  15. Excitation Emission Matrix Spectra (EEMS) of Chromophoric Dissolved Organic Matter Produced during Microbial Incubation

    NASA Astrophysics Data System (ADS)

    McDonald, N.; Nelson, N. B.; Parsons, R.

    2013-12-01

    The chromophoric or light-absorbing fraction of dissolved organic matter (CDOM) is present ubiquitously in natural waters and has a significant impact on ocean biogeochemistry, affecting photosynthesis and primary production as well direct and indirect photochemical reactions (Siegel et al., 2002; Nelson et al., 2007). It has been largely researched in the past few decades, however the exact chemical composition remains unknown. Instrumental methods of analysis including simultaneous excitation-emission fluorescence spectra have allowed for further insight into source and chemical composition. While certain excitation-emission peaks have been associated with ';marine' sources, they have not been exclusively linked to bacterial production of CDOM (Coble, 1996; Zepp et al., 2004). In this study, ';grazer diluted' seawater samples (70% 0.2μm filtered water; 30% whole water) were collected at the Bermuda Atlantic Time Series (BATS) site in the Sargasso Sea (31° 41' N; 64° 10' W) and incubated with an amendment of labile dissolved organic carbon (10μM C6H12O6), ammonium (1μM NH4Cl) and phosphate (0.1μM K2HPO4) to facilitate bacterial production. These substrates and concentrations have been previously shown to facilitate optimum bacterial and CDOM production (Nelson et al., 2004). Sample depths were chosen at 1m and 200m as water at these depths has been exposed to UV light (the Subtropical Mode Water at 200m has been subducted from the surface) and therefore has low initial concentrations of CDOM. After the samples were amended, they were incubated at in-situ temperatures in the dark for 72 hours, with bacteria counts, UV-Vis absorption and EEMS measurements taken at 6-8 hour intervals. Dissolved organic carbon (DOC) measurements were collected daily. For the surface water experiment specific bacteria populations were investigated using Fluorescence In-Situ Hybridization (FISH) analysis. Results showed a clear production of bacteria and production of CDOM, which

  16. Biochemical Composition of Dissolved Organic Matter Released During Experimental Diatom Blooms

    NASA Technical Reports Server (NTRS)

    Mannino, Antonio; Harvey, H. Rodger

    2002-01-01

    An axenic culture of Skeletonema costatum was grown to late-log phase to examine the molecular weight distribution and the biochemical composition of high molecular weight dissolved organic matter released in the absence of actively growing bacteria. A second culture was grown in a 5 m(exp 3) mesocosm and placed in darkness for a period of 51 days to examine the impact of phytoplankton bloom dynamics and microbial decomposition on dissolved (DOM) and particulate organic matter (POM) composition. DOM was separated using tangential-flow ultrafiltration into three nominal size fractions: LDOM (less than 1 kDa DOM), HDOM (1-30 kDa) and VHDOM (30 kDa-0.2 micron) and characterized. Both axenic and mesocosm diatom blooms released 28-33% of net primary production as dissolved organic carbon (DOC). In the axenic culture, HDOM and LDOM each comprised about half of the diatom-released DOC with less than l% as VHDOM. Diatoms from both experiments released carbohydrate-rich high molecular weight DOM. Much of the axenic diatom-released high molecular weight DOC could be chemically characterized (61% of HDOM and 78% of VHDOM) with carbohydrates as the primary component (45% of HDOM and 55% of VHDOM). Substantial amounts of hydrolyzable amino acids (16% of HDOM and 22% of VHDOM) and small amounts of lipids (less than 1%) were also released. Proportions of recognizable biochemical components in DOM produced in the mesocosm bloom were lower compared to the axenic culture. The presence of bacterial fatty acids and peptidoglycan-derived D-amino acids within high molecular weight fractions from the mesocosm bloom revealed that bacteria contributed a variety of macromolecules to DOM during the growth and decay of the diatom bloom. Release of significant amounts of DOC by diatoms demonstrates that DOM excretion is an important component of phytoplankton primary production. Similarities in high molecular weight DOM composition in marine waters and diatom cultures highlight the importance

  17. Sources, distributions and dynamics of dissolved organic matter in the Canada and Makarov Basins

    USGS Publications Warehouse

    Shen, Yuan; Benner, Ronald; Robbins, Lisa L.; Wynn, Jonathan

    2016-01-01

    A comprehensive survey of dissolved organic carbon (DOC) and chromophoric dissolved organic matter (CDOM) was conducted in the Canada and Makarov Basins and adjacent seas during 2010–2012 to investigate the dynamics of dissolved organic matter (DOM) in the Arctic Ocean. Sources and distributions of DOM in polar surface waters were very heterogeneous and closely linked to hydrological conditions. Canada Basin surface waters had relatively low DOC concentrations (69 ± 6 μmol L−1), CDOM absorption (a325: 0.32 ± 0.07 m−1) and CDOM-derived lignin phenols (3 ± 0.4 nmol L−1), and high spectral slope values (S275–295: 31.7 ± 2.3 μm−1), indicating minor terrigenous inputs and evidence of photochemical alteration in the Beaufort Gyre. By contrast, surface waters of the Makarov Basin had elevated DOC (108 ± 9 μmol L−1) and lignin phenol concentrations (15 ± 3 nmol L−1), high a325 values (1.36 ± 0.18 m−1), and low S275–295 values (22.8 ± 0.8 μm−1), indicating pronounced Siberian river inputs associated with the Transpolar Drift and minor photochemical alteration. Observations near the Mendeleev Plain suggested limited interactions of the Transpolar Drift with Canada Basin waters, a scenario favoring export of Arctic DOM to the North Atlantic. The influence of sea-ice melt on DOM was region-dependent, resulting in an increase (Beaufort Sea), a decrease (Bering-Chukchi Seas), and negligible change (deep basins) in surface DOC concentrations and a325 values. Halocline structures differed between basins, but the Canada Basin upper halocline and Makarov Basin halocline were comparable in their average DOC (65–70 μmol L−1) and lignin phenol concentrations (3–4 nmol L−1) and S275–295 values (22.9–23.7 μm−1). Deep-water DOC concentrations decreased by 6–8 μmol L−1 with increasing depth, water mass age, nutrient concentrations, and apparent oxygen utilization. Maximal estimates of DOC degradation rates (0.036–0.039 μmol L−1

  18. Linkages between the circulation and distribution of dissolved organic matter in the White Sea, Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Pavlov, Alexey K.; Stedmon, Colin A.; Semushin, Andrey V.; Martma, Tõnu; Ivanov, Boris V.; Kowalczuk, Piotr; Granskog, Mats A.

    2016-05-01

    The White Sea is a semi-enclosed Arctic marginal sea receiving a significant loading of freshwater (225-231 km3 yr-1 equaling an annual runoff yield of 2.5 m) and dissolved organic matter (DOM) from river run-off. We report discharge weighed values of stable oxygen isotope ratios (δ18O) of -14.0‰ in Northern Dvina river for the period 10 May-12 October 2012. We found a significant linear relationship between salinity (S) and δ18O (δ18O=-17.66±0.58+0.52±0.02×S; R2=0.96, N=162), which indicates a dominant contribution of river water to the freshwater budget and little influence of sea ice formation or melt. No apparent brine additions from sea-ice formation is evident in the White Sea deep waters as seen from a joint analysis of temperature (T), S, δ18O and aCDOM(350) data, confirming previous suggestions about strong tidal induced vertical mixing in winter being the likely source of the deep waters. We investigated properties and distribution of colored dissolved organic matter (CDOM) and dissolved organic carbon (DOC) in the White Sea basin and coastal areas in summer. We found contrasting DOM properties in the inflowing Barents Sea waters and White Sea waters influenced by terrestrial runoff. Values of absorption by CDOM at 350 nm (aCDOM(350)) and DOC (exceeding 10 m-1 and 550 μmol l-1, respectively) in surface waters of the White Sea basin are higher compared to other river-influenced coastal Arctic domains. Linear relationship between S and CDOM absorption, and S and DOC (DOC=959.21±52.99-25.80±1.79×S; R2=0.85; N=154) concentrations suggests conservative mixing of DOM in the White Sea. The strongest linear correlation between CDOM absorption and DOC was found in the ultraviolet (DOC=56.31±2.76+9.13±0.15×aCDOM(254); R2=0.99; N=155), which provides an easy and robust tool to trace DOC using CDOM absorption measurements as well as remote sensing algorithms. Deviations from this linear relationship in surface waters likely indicate contribution from

  19. Dissolved pesticides, dissolved organic carbon, and water-quality characteristics in selected Idaho streams, April--December 2010

    USGS Publications Warehouse

    Reilly, Timothy J.; Smalling, Kelly L.; Wilson, Emma R.; Battaglin, William A.

    2012-01-01

    Water-quality samples were collected from April through December 2010 from four streams in Idaho and analyzed for a suite of pesticides, including fungicides, by the U.S. Geological Survey. Water samples were collected from two agricultural and two nonagricultural (control) streams approximately biweekly from the beginning of the growing season (April) through the end of the calendar year (December). Samples were analyzed for 90 pesticides using gas chromatography/mass spectrometry. Twenty-three pesticides, including 8 fungicides, 10 herbicides, 3 insecticides, and 2 pesticide degradates, were detected in 45 water samples. The most frequently detected compounds in the two agricultural streams and their detection frequencies were metolachlor, 96 percent; azoxystrobin, 79 percent; boscalid, 79 percent; atrazine, 46 percent; pendimethalin, 33 percent; and trifluralin, 33 percent. Dissolved-pesticide concentrations ranged from below instrumental limits of detection (0.5-1.0 nanograms per liter) to 771 nanograms per liter (hexazinone). The total number of pesticides detected in any given water sample ranged from 0 to 11. Only three pesticides (atrazine, fipronil, and simazine) were detected in samples from the control streams during the sampling period.

  20. 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.

  1. Transformations and Fates of Terrigenous Dissolved Organic Matter in River-influenced Ocean Margins

    NASA Astrophysics Data System (ADS)

    Fichot, Cedric G.

    Rivers contribute about 0.25 Pg of terrigenous dissolved organic carbon (tDOC) to the ocean each year. The fate and transformations of this material have important ramifications for the metabolic state of the ocean, air-sea CO2 exchange, and the global carbon cycle. Stable isotopic compositions and terrestrial biomarkers suggest tDOC must be efficiently mineralized in ocean margins. Nonetheless, the extent of tDOC mineralization in these environments remains unknown, as no quantitative estimate is available. The complex interplay of biogeochemical and physical processes in these systems compounded by the limited practicality of chemical proxies (organic biomarkers, isotopic compositions) make the quantification of tDOC mineralization in these dynamic systems particularly challenging. In this dissertation, new optical proxies were developed (Chapters 1 and 2) and facilitated the first quantitative assessment of tDOC mineralization in a dynamic river-influenced ocean margin (Chapter 3) and the monitoring of continental runoff distributions in the coastal ocean using remote sensing (Chapter 4). The optical properties of chromophoric dissolved organic matter (CDOM) were used as optical proxies for dissolved organic carbon concentration ([DOC]) and %tDOC. In both proxies, the CDOM spectral slope coefficient ( S275-295) was exploited for its informative properties on the chemical nature and composition of dissolved organic matter. In the first proxy, a strong relationship between S275-295 and the ratio of CDOM absorption to [DOC] facilitated accurate retrieval (+/- 4%) of [DOC] from CDOM. In the second proxy, the existence of a strong relationship between S275-295 and the DOC-normalized lignin yield facilitated the estimation of the %tDOC from S 275-295. Using the proxies, the tDOC concentration can be retrieved solely from CDOM absorption coefficients (lambda = 275-295 nm) in river-influenced ocean margins. The practicality of optical proxies facilitated the calculation

  2. Petroleum pollutants in surface and groundwater as indicated by the carbon-14 activity of dissolved organic carbon.

    PubMed

    Spiker, E C; Rubin, M

    1975-01-10

    The (14)C activity of dissolved organic carbon (DOC) can be used to distinguish between the fossil organic carbon due to petrochemical effluents and modern organic carbon due to domestic wastes and natural decaying organic matter. Rivers polluted by petrochemical effluents show varying amounts of depression of the DOC (14)C activity, reflecting concentrations of (14)C-deficient fossil carbon of as much as about 40 percent of the total DOC.

  3. A novel molecular approach for tracing terrigenous dissolved organic matter into the deep ocean

    NASA Astrophysics Data System (ADS)

    Medeiros, Patricia M.; Seidel, Michael; Niggemann, Jutta; Spencer, Robert G. M.; Hernes, Peter J.; Yager, Patricia L.; Miller, William L.; Dittmar, Thorsten; Hansell, Dennis A.

    2016-05-01

    Marine dissolved organic matter (DOM) contains one of the largest exchangeable organic carbon pools on Earth. Riverine input represents an important source of DOM to the oceans, yet much remains to be learned about the fate of the DOM linking terrestrial to oceanic carbon cycles through rivers at the global scale. Here we use ultrahigh-resolution mass spectrometry to identify 184 molecular formulae that are indicators of riverine inputs (referred to as t-Peaks) and to track their distribution in the deep North Atlantic and North Pacific Oceans. The t-Peaks were found to be enriched in the Amazon River, to be highly correlated with known tracers of terrigenous input, and to be observed in all samples from four different rivers characterized by vastly different landscapes and vegetation coverage spanning equatorial (Amazon and Congo), subtropical (Altamaha), and Arctic (Kolyma) regions. Their distribution reveals that terrigenous organic matter is injected into the deep ocean by the global meridional overturning circulation, indicating that a fraction of the terrigenous DOM introduced by rivers contributes to the DOM pool observed in the deep ocean and to the storage of terrigenous organic carbon. This novel molecular approach can be used to further constrain the transfer of DOM from land to sea, especially considering that Fourier transform ion cyclotron resonance mass spectrometer analysis is becoming increasingly frequent in studies characterizing the molecular composition of DOM in lakes, rivers, and the ocean.

  4. Increases in dissolved organic carbon accelerate loss of toxic Al in Adirondack lakes recovering from acidification

    USGS Publications Warehouse

    Lawrence, Gregory B.; Dukett, James E; Houck, Nathan; Snyder, Phillip; Capone, Susan B.

    2013-01-01

    Increasing pH and decreasing Al in surface waters recovering from acidification have been accompanied by increasing concentrations of dissolved organic carbon (DOC) and associated organic acids that partially offset pH increases and complicate assessments of recovery from acidification. To better understand the processes of recovery, monthly chemistry from 42 lakes in the Adirondack region, NY, collected from 1994 to 2011, were used to (1) evaluate long-term changes in DOC and associated strongly acidic organic acids and (2) use the base-cation surplus (BCS) as a chemical index to assess the effects of increasing DOC concentrations on the Al chemistry of these lakes. Over the study period, the BCS increased (p < 0.01) and concentrations of toxic inorganic monomeric Al (IMAl) decreased (p < 0.01). The decreases in IMAl were greater than expected from the increases in the BCS. Higher DOC concentrations that increased organic complexation of Al resulted in a decrease in the IMAl fraction of total monomeric Al from 57% in 1994 to 23% in 2011. Increasing DOC concentrations have accelerated recovery in terms of decreasing toxic Al beyond that directly accomplished by reducing atmospheric deposition of strong mineral acids.

  5. 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.

  6. Increases in dissolved organic carbon accelerate loss of toxic Al in Adirondack lakes recovering from acidification.

    PubMed

    Lawrence, Gregory B; Dukett, James E; Houck, Nathan; Snyder, Phil; Capone, Sue

    2013-07-01

    Increasing pH and decreasing Al in surface waters recovering from acidification have been accompanied by increasing concentrations of dissolved organic carbon (DOC) and associated organic acids that partially offset pH increases and complicate assessments of recovery from acidification. To better understand the processes of recovery, monthly chemistry from 42 lakes in the Adirondack region, NY, collected from 1994 to 2011, were used to (1) evaluate long-term changes in DOC and associated strongly acidic organic acids and (2) use the base-cation surplus (BCS) as a chemical index to assess the effects of increasing DOC concentrations on the Al chemistry of these lakes. Over the study period, the BCS increased (p < 0.01) and concentrations of toxic inorganic monomeric Al (IMAl) decreased (p < 0.01). The decreases in IMAl were greater than expected from the increases in the BCS. Higher DOC concentrations that increased organic complexation of Al resulted in a decrease in the IMAl fraction of total monomeric Al from 57% in 1994 to 23% in 2011. Increasing DOC concentrations have accelerated recovery in terms of decreasing toxic Al beyond that directly accomplished by reducing atmospheric deposition of strong mineral acids.

  7. 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. PMID:23424099

  8. Rangeomorphs, Thectardis (Porifera?) and dissolved organic carbon in the Ediacaran oceans.

    PubMed

    Sperling, E A; Peterson, K J; Laflamme, M

    2011-01-01

    The mid-Ediacaran Mistaken Point biota of Newfoundland represents the first morphologically complex organisms in the fossil record. At the classic Mistaken Point localities the biota is dominated by the enigmatic group of "fractally" branching organisms called rangeomorphs. One of the few exceptions to the rangeomorph body plan is the fossil Thectardis avalonensis, which has been reconstructed as an upright, open cone with its apex in the sediment. No biological affinity has been suggested for this fossil, but here we show that its body plan is consistent with the hydrodynamics of the sponge water-canal system. Further, given the habitat of Thectardis beneath the photic zone, and the apparent absence of an archenteron, movement, or a fractally designed body plan, we suggest that it is a sponge. The recognition of sponges in the Mistaken Point biota provides some of the earliest body fossil evidence for this group, which must have ranged through the Ediacaran based on biomarkers, molecular clocks, and their position on the metazoan tree of life, in spite of their sparse macroscopic fossil record. Should our interpretation be correct, it would imply that the paleoecology of the Mistaken Point biota was dominated by sponges and rangeomorphs, organisms that are either known or hypothesized to feed in large part on dissolved organic carbon (DOC). The biology of these two clades gives insight into the structure of the Ediacaran ocean, and indicates that a non-uniformitarian mechanism delivered labile DOC to the Mistaken Point seafloor.

  9. Increases in dissolved organic carbon accelerate loss of toxic Al in Adirondack lakes recovering from acidification.

    PubMed

    Lawrence, Gregory B; Dukett, James E; Houck, Nathan; Snyder, Phil; Capone, Sue

    2013-07-01

    Increasing pH and decreasing Al in surface waters recovering from acidification have been accompanied by increasing concentrations of dissolved organic carbon (DOC) and associated organic acids that partially offset pH increases and complicate assessments of recovery from acidification. To better understand the processes of recovery, monthly chemistry from 42 lakes in the Adirondack region, NY, collected from 1994 to 2011, were used to (1) evaluate long-term changes in DOC and associated strongly acidic organic acids and (2) use the base-cation surplus (BCS) as a chemical index to assess the effects of increasing DOC concentrations on the Al chemistry of these lakes. Over the study period, the BCS increased (p < 0.01) and concentrations of toxic inorganic monomeric Al (IMAl) decreased (p < 0.01). The decreases in IMAl were greater than expected from the increases in the BCS. Higher DOC concentrations that increased organic complexation of Al resulted in a decrease in the IMAl fraction of total monomeric Al from 57% in 1994 to 23% in 2011. Increasing DOC concentrations have accelerated recovery in terms of decreasing toxic Al beyond that directly accomplished by reducing atmospheric deposition of strong mineral acids. PMID:23751119

  10. Characterization of dissolved and particulate natural organic matter (NOM) in Neversink Reservoir, New York

    USGS Publications Warehouse

    Wershaw, Robert L.; Leenheer, Jerry A.; Cox, Larry G.

    2005-01-01

    Natural organic matter (NOM) was isolated from the water of the Neversink Reservoir, part of the New York City water supply, located in the Catskill Mountains of New York. The NOM was fractionated into the following nine different fractions by the isolation procedure: (1) coarse particulates, (2) fine-particulate organics, (3) solvent-extractable organics, (4) hydrophobic neutrals (HPON fraction), (5) dissolved colloids, (6) bases, (7) hydrophobic acids (HPOA), (8) transphilic acids + neutrals (TPI-A+N), and (9) hydrophilic acids + neutrals (HPI-A+N). Each of these fractions, with exception of the first and the third which were too small for the complete series of analyses, was characterized by elemental, carbohydrate, and amino acid analyses, and by nuclear magnetic resonance and infrared spectrometry. The data obtained from these analyses indicate (1) that the fine-particulate organics and colloids are mainly composed of peptidoglycans, and lipopolysaccharides derived from algal, bacterial, and fungal cell walls, (2) that the HPO-N fraction most likely consists of a mixture of alicyclic terpenes and carbohydrates, (3) that the HPOA fraction consists mainly of lignin components conjugated to carbohydrates, (4) that the TPI-A+N and the HPI-A+N fractions most likely represent complex mixtures of relatively low molecular weight carboxylic acids derived from terpenes, carbohydrates, and peptides, and (5) that the base fraction is composed of free amino acids, browning reaction products, and peptide fragments.

  11. Dissolved organic matter composition and photochemical transformations in the northern North Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Medeiros, Patricia. M.; Seidel, Michael; Powers, Leanne C.; Dittmar, Thorsten; Hansell, Dennis A.; Miller, William L.

    2015-02-01

    The composition and photochemical transformations of dissolved organic matter (DOM) in the northern North Pacific Ocean were investigated at the molecular level using ultrahigh resolution mass spectrometry and geochemical tracers. Analyses included vertical profiles and experiments in which deep sea DOM was exposed to sunlight and incubated in the dark. The composition of the deep sea DOM was found to be approximately uniform and enriched with highly unsaturated compounds, with highly aromatic compounds, and with polycyclic aromatics. Surface DOM had a significantly different composition, being enriched with both highly unsaturated and with unsaturated aliphatic compounds potentially due to the addition of photodegradation products and phytoplankton inputs. Deep sea DOM composition is transformed by photoreactions, becoming more similar to surface DOM. The influence of photochemistry extends beyond the photic zone, presumably because of vertical export of DOM previously modified at the surface.

  12. Radiocarbon Signatures and Cycling of Dissolved Organic Carbon in the World Ocean

    NASA Astrophysics Data System (ADS)

    Druffel, E. R.; Griffin, S.; Walker, B. D.

    2012-12-01

    Radiocarbon (Delta14C) measurements of bulk dissolved organic carbon (DOC) in the deep ocean range from -390 per mil in the North Atlantic to -550 per mil in the Northeast Pacific. We report Delta14C measurements of DOC from six sites in the South Pacific and three sites in the South Atlantic collected on Repeat Hydrography cruises P6 (2010) and A10 (2011). We compare our new results with those reported earlier for the North central Pacific, Northeast Pacific, Southern Ocean and Sargasso Sea. We find that the Delta14C results from the deep South Pacific are lower than expected, given the range between Southern Ocean DOC Delta14C values (-500 per mil) and those from the North central Pacific (-525 per mil). Implications for DOC cycling in the world ocean are presented.

  13. Photodegradation of ormetoprim in aquaculture and stream-derived dissolved organic matter.

    PubMed

    Guerard, Jennifer J; Chin, Yu-Ping

    2012-10-01

    Ormetoprim (OMP) is an antibiotic approved for use in the United States to prevent the spread of disease in freshwater aquaculture. It has been shown in the previous literature to be photochemically stable to direct photolysis, but the role of photosensitization processes in the presence of dissolved organic matter (DOM) on the rate of degradation is not well understood. The present results show that water and DOM (specifically the fulvic acid fraction) isolated from a eutrophic aquaculture catfish pond and a nearby stream (Deer Creek) at the Mississippi State University Delta Research and Extension Center facility in Stoneville, MS, significantly increased the phototransformation of OMP relative to direct photolysis. Similar results were reported for reference fulvic acids obtained from the International Humic Substances Society. Results from a combination of scavenging experiments and experiments conducted under anoxic conditions indicate the indirect photodegradation pathway occurs by hydroxyl radical, singlet oxygen attack, and reaction with triplet excited-state DOM.

  14. Fractions and biodegradability of dissolved organic matter derived from different composts.

    PubMed

    Wei, Zimin; Zhang, Xu; Wei, Yuquan; Wen, Xin; Shi, Jianhong; Wu, Junqiu; Zhao, Yue; Xi, Beidou

    2014-06-01

    An experiment was conducted to determine the fractions of molecular weights (MW) and the biodegradability of dissolved organic matter (DOM) in mature composts derived from dairy cattle manure (DCM), kitchen waste (KW), cabbage waste (CW), tomato stem waste (TSW), municipal solid waste (MSW), green waste (GW), chicken manure (CM), sludge (S), and mushroom culture waste (MCW). There were distinct differences in the concentration and MW fractions of DOM, and the two measures were correlated. Fraction MW>5kDa was the major component of DOM in all mature composts. Determined 5day biochemical oxygen demand (BOD5) of DOM was correlated to the concentration of DOM and all MW fractions except MW>5kDa, indicating that the biodegradability of DOM was a function of the content and proportion of fraction MW<5kDa. This study suggests that the amount and distribution of low MW fractions affect DOM biodegradability. PMID:24704883

  15. Phototransformation of pesticides in prairie potholes: effect of dissolved organic matter in triplet-induced oxidation.

    PubMed

    Karpuzcu, M Ekrem; McCabe, Andrew J; Arnold, William A

    2016-02-01

    Photochemical reactions involving a variety of photosensitizers contribute to the abiotic transformation of pesticides in prairie pothole lakes (PPLs). Despite the fact that triplet excited state dissolved organic matter (DOM) enhances phototransformation of pesticides by acting as a photosensitizer, it may also decrease the overall phototransformation rate through various mechanisms. In this study, the effect of DOM on the phototransformation of four commonly applied pesticides in four different PPL waters was investigated under simulated sunlight using photoexcited benzophenone-4-carboxylate as the oxidant with DOM serving as an anti-oxidant. For atrazine and mesotrione, a decrease in phototransformation rates was observed, while phototransformations of metolachlor and isoproturon were not affected by DOM inhibition. Phototransformation rates and the extent of inhibition/enhancement by DOM varied spatially and temporally across the wetlands studied. Characterization of DOM from the sites and different seasons suggested that the DOM type and variations in the DOM structure are important factors controlling phototransformation rates of pesticides in PPLs.

  16. Complexation of silver and dissolved organic matter in soil water extracts.

    PubMed

    Settimio, Lara; McLaughlin, Mike J; Kirby, Jason K; Langdon, Kate A; Janik, Les; Smith, Scott

    2015-04-01

    An important aspect of the behaviour and fate of silver (Ag) in soils is the interaction with dissolved organic matter (DOM). The complexation and strength of binding of Ag(+) with DOM in soil water extracts was examined and modelled based on a range of chemical and quality DOM measurements. Silver ion binding measured by addition of the (110m)Ag radioisotope in addition to a cation exchange resin technique were used to determine strongly complexed Ag in solutions. Silver was found to be up to 70% strongly complexed. The variability in Ag(+) binding by DOM across different soils was closely related (R(2) = 0.8) to the mid-infrared spectra of these extracts. The affinity of Ag(+) for DOM was stronger in solutions containing a greater content of humic and aromatic structures. The ability of Ag(+) to complex with DOM could result in increased mobilisation of this m