Rate of Cd2+ Release from Dissolved Fulvic Acid and Natural Dissolved Organic Carbon as a Function of UVB Dose

2006 ◽  
Vol 3 (6) ◽  
pp. 433 ◽  
Author(s):  
R. Néron ◽  
J. C. Auclair ◽  
C. Fortin
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Fulvic Acid ◽  
Surface Waters ◽  
Iron Concentration ◽  
Fulvic Acids ◽  
Ion Concentration ◽  
Uvb Radiation ◽  
Free Ion ◽  
Uv Dose

Environmental Context. Atmospheric ozone depletion results in an increase of UVB radiation impinging on the surface waters of aquatic ecosystems. Radiative absorption by dissolved humic substances results in bleaching and photochemical decomposition to smaller molecular weight dissolved components. With respect to the lake biota, this can reduce the effectiveness of a natural absorptive protective UV screen, as well as enrich the surface waters with microbial substrates and previously bound biologically unavailable trace metals. In controlled experiments using low-level Cd-contaminated dissolved fulvic acids and natural lakewater dissolved organic carbon, we examine the relationship between increasing UV dose and cadmium free-ion (Cd2+) concentrations. Abstract. Using controlled UVB exposures in a laboratory incubator, the photolytic release of bound cadmium from cadmium-contaminated dissolved fulvic acid and cadmium-amended natural lakewater dissolved organic carbon was examined using an ion-exchange technique, developed to measure the cadmium free-ion concentration (Cd2+). In the fulvic acid experiments, with increasing UVB dose, the increasing cadmium free-ion concentration followed an exponential saturation function, whereas the decrease in dissolved organic carbon was linear. Experiments using natural lakewaters did not reveal any increase in Cd2+, even at high UVB exposures. Given the much greater dissolved iron concentration in humic natural lakewaters, relative to the fulvic acid medium, iron photoreduction and reoxidation produces fresh amorphous iron oxide surfaces. We hypothesize that these bind the cadmium free-ion, thus reducing its aqueous concentration. Depending on Cd2+ affinity to biological surfaces, this mechanism might thus competitively further protect the biota from trace metal toxicity.

Bioavailability of dissolved organic carbon and fulvic acid from an Australian floodplain river and billabong

2007 ◽  
Vol 58 (2) ◽  
pp. 222 ◽  
Author(s):  
Suzanne McDonald ◽  
Jennifer M. Pringle ◽  
Paul D. Prenzler ◽  
Andrea G. Bishop ◽  
Kevin Robards
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Fulvic Acid ◽  
Heterotrophic Bacteria ◽  
Fulvic Acids ◽  
Lag Phase ◽  
Floodplain Ecosystems ◽  
Vital Resource ◽  
Number Of Bacteria

Dissolved organic carbon (DOC) is a vital resource for heterotrophic bacteria in aquatic ecosystems. The bioavailability of fulvic acid, which comprises the majority of aquatic DOC, is not well understood. The present study examined the bioavailability of bulk DOC and fulvic acid from two contrasting but inter-related water bodies: the Murrumbidgee River and adjacent Berry Jerry Lagoon. Bacteria utilised fulvic acids; however, bulk DOC was more bioavailable. Bacteria were able to utilise Murrumbidgee River DOC and fulvic acid more readily than Berry Jerry Lagoon DOC and fulvic acid, suggesting that the quality of carbon may be an important factor to consider when evaluating lateral exchange of nutrients between the main channel and floodplain. Chemical characteristics of fulvic acids appeared to explain some of the variation in fulvic acid bioavailability. The higher the molecular weight and complexity of the fulvic acid, the longer it took for bacteria to utilise the substrate (lag phase), but the larger the number of bacteria that grew on the substrate. The present study calls attention to the need for further multidisciplinary studies to address the quality of carbon in riverine-floodplain ecosystems.

Humic Colloid Generation of Transuranic Elements in Groundwater and Their Migration Behaviour

1986 ◽  
Vol 84 ◽  
Author(s):  
J.I. Kim ◽  
G. Buckau ◽  
W. Zhuang
Keyword(s):  
Heavy Metal ◽  
Humic Acid ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Metal Ions ◽  
Fulvic Acid ◽  
Photoacoustic Spectroscopy ◽  
Heavy Metal Ions ◽  
Colloidal Form ◽  
Doc Concentration

AbstractThe generation of humic colloids of Am(III) has been investigated in Gorleben groundwaters containing different amounts of humic substances. Dissolved organic carbon (DOC) in these groundwaters consists mainly of humic acid and fulvic acid, which is present in a colloidal form through aggregation with trace heavy metal ions of groundwater constituents. Concentrations of these heavy metal ions are proportional to the DOC concentration. The generation of Am(III) pseudocolloids through geochemical interactions with humic colloids in different groundwaters is quantified by ultrafiltration as well as ultracentrifugation by the aid of radiometric concentration measurements. The speciation of dissolved Am(III) species in groundwaters is carried out by laser induced photoacoustic spectroscopy (LPAS).

Monitoring advanced oxidation of Suwannee River fulvic acid

2010 ◽  
Vol 7 (3) ◽  
pp. 225 ◽  
Author(s):  
Janey V. Camp ◽  
Dennis B. George ◽  
Martha J. M. Wells ◽  
Pedro E. Arce
Keyword(s):  
Organic Carbon ◽  
Fluorescence Spectroscopy ◽  
Fulvic Acid ◽  
Electrical Discharge ◽  
Fulvic Acids ◽  
Pilot Scale ◽  
Suwannee River ◽  
Suwannee River Fulvic Acid ◽  
Pulsed Electrical Discharge ◽  
By Products

Environmental context.Potentially toxic disinfection by-products form when water containing humic and fulvic acids is chlorinated to destroy pathogenic microorganisms. A pulsed electrical discharge was examined for its ability to destroy an aquatic fulvic acid by oxidation. Spectroscopically, changes in the organic structures were observed, but carbon content and disinfection by-products were not reduced. Abstract.A pilot-scale pulsed electrical discharge (PED) system was used to treat Suwannee River fulvic acid (SRFA) as a representative precursor material for the formation of disinfection by-products (DBPs), specifically trihalomethane compounds. Ultraviolet-visible and fluorescence spectroscopy, dissolved organic carbon (DOC), and the trihalomethane formation potential (THMFP) were used as analytical parameters to monitor the effects of treatment on the substrate. The potential for SRFA degradation (5 mg L–1 DOC) was examined over 60 min at each of four operational configurations, varying pulse energy and frequency (0.15 J and 60 Hz, 0.15 J and 120 Hz, 0.4 J and 60 Hz, and 0.4 J and 120 Hz) in a factorial design. Statistically significant changes occurred for UV254, EX254EM460, and EX328EM460 under selected conditions; however, concomitant changes in DOC and THMFP were not observed. The composition of SRFA changed, but organic carbon was not mineralised to carbon dioxide. In addition to showing degradation by PED, the significance of the preliminary findings of this research was to demonstrate that spectroscopic monitoring of precursor degradation alone can be misleading, and that whereas ultraviolet-visible and fluorescence spectroscopy indicated degradation of precursor compounds, DOC and THMFP measurements were unchanged and did not support the occurrence of mineralisation in this system.

scholarly journals Distribution and bacterial availability of dissolved neutral sugars in the South East Pacific

2008 ◽  
Vol 5 (4) ◽  
pp. 1165-1173 ◽  
Author(s):  
R. Sempéré ◽  
M. Tedetti ◽  
C. Panagiotopoulos ◽  
B. Charrière ◽  
F. Van Wambeke
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Surface Waters ◽  
Detectable Effect ◽  
Neutral Sugar ◽  
The South ◽  
East Pacific ◽  
Significant Stimulation ◽  
Order Of Magnitude ◽  
Neutral Sugars

Abstract. The distribution and bacterial availability of dissolved neutral sugars were studied in the South East Pacific from October to December 2004 during the BIOSOPE cruise. Four contrasting stations were investigated: Marquesas Islands (MAR), the hyper-oligotrophic South Pacific Gyre (GYR), the eastern part of the Gyre (EGY), and the coastal waters associated to the upwelling area off Chile (UPW). Total (free and combined) dissolved neutral sugar (TDNS) concentrations were in the same order of magnitude at MAR (387±293 nM), GYR (206±107 nM), EGY (269±175 nM), and UPW (231±73 nM), with the highest and lowest concentrations found at MAR (30 m, 890 nM) and EGY (250 m, 58 nM), respectively. Their contribution to dissolved organic carbon (TDNS-C×DOC−1%) was generally low for all sites varying from 0.4% to 6.7% indicating that South East Pacific surface waters were relatively poor in neutral sugars. Free dissolved neutral sugar (FDNS; e.g. sugars analyzed without hydrolysis) concentrations were very low within the detection limit of our method (5–10 nM) accounting for <5% of the TDNS. In general, the predominant sugars within the TDNS pool were glucose, xylose, arabinose, and galactose, while in the FDNS pool only glucose was present. TDNS stock to bacterial production ratios (integrated values from the surface to the deep chlorophyll maximum) were high at GYR with respect to the low primary production, whereas the opposite trend was observed in the highly productive area of UPW. Intermediate situations were observed for MAR and EGY. Bioavailability of dissolved organic matter (DOM) exposed to natural solar radiation was also experimentally studied and compared to dark treatments. Our results showed no or little detectable effect of sunlight on DOM bacterial assimilation in surface waters of UPW and GYR, while a significant stimulation was found in MAR and EGY. The overall results clearly suggest that DOM is less labile at GYR compared to UPW, which is consistent with the observed accumulation of dissolved organic carbon and the elevated C/N ratios reported by Raimbault et al. (2008).

scholarly journals Sources and fate of terrestrial dissolved organic carbon in lakes of a Boreal Plains region recently affected by wildfire

2013 ◽  
Vol 10 (4) ◽  
pp. 6093-6141 ◽  
Author(s):  
D. Olefeldt ◽  
K. J. Devito ◽  
M. R. Turetsky
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Primary Productivity ◽  
Fulvic Acids ◽  
Lake Morphometry ◽  
Humic And Fulvic Acids ◽  
Study Region ◽  
Boreal Plains ◽  
Peat Pore Water ◽  
Surface Geology

Abstract. Downstream mineralization and sedimentation of terrestrial dissolved organic carbon (DOC) render lakes important for landscape carbon cycling in the boreal region, with regulating processes potentially sensitive to perturbations associated with climate change including increased occurrence of wildfire. In this study we assessed chemical composition and reactivity (during both dark and UV incubations) of DOC from lakes and terrestrial sources within a peatland-rich western boreal plains region partially affected by a recent wildfire. While wildfire was found to increase aromaticity of DOC in peat pore-water above the water table, it had no effect on concentrations or composition of DOC from peatland wells and neither affected mineral well or lake DOC characteristics. Lake DOC composition reflected a mixing of peatland and mineral groundwater, with a greater influence of mineral sources to lakes in coarse- than fine-textured settings. Peatland DOC was less biodegradable than mineral DOC, but both mineralization and sedimentation of peatland DOC increased substantially during UV incubations through selective removal of aromatic humic and fulvic acids. DOC composition in lakes with longer residence times had characteristics consistent with increased UV-mediated processing. We estimate that about half of terrestrial DOC inputs had been lost within lakes, mostly due to UV-mediated processes. The importance of within-lake losses of aromatic DOC from peatland sources through UV-mediated processes indicate that terrestrial-aquatic C linkages in the study region are largely disconnected from recent terrestrial primary productivity. Together, our results suggest that characteristics of the study region (climate, surface geology and lake morphometry) render linkages between terrestrial and aquatic C cycling insensitive to the effects of wildfire by determining dominant terrestrial sources and within-lake processes of DOC removal.

scholarly journals New possibility for characterization of dissociation behaviour of supramolecular electrolytes: results obtained for the International Humic Substances Society standard and reference samples by coulometry

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Martina Klučáková
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Humic Substances ◽  
Functional Groups ◽  
Dissociation Constants ◽  
Fulvic Acids ◽  
Molecular Organization ◽  
Humic And Fulvic Acids ◽  
Acid Base ◽  
Reference Samples

Abstract Background Humic substances can be considered as polyelectrolytes with supramolecular character and complicated behaviour in water environment. The fractions of humic substances dissolved in water are the most active ones and determinative for their functioning in nature, where the proton-binding and dissociation ability play a crucial role. The dissociation behaviour of humic and fulvic acids can be affected by different circumstances including their concentration which is directly connected with the molecular organization of humic particles in solution and the accessibility of their ionizable functional groups. This study is focused just on these active fractions and their dissociation behaviour in the dependence on their content in studied system. Results Standards and reference samples of International Humic Substances Society were used. Flow-through coulometry was used to determine the total content of acidic functional groups in fulvic solutions and humic leachates. The amount of dissociated acidic groups was determined on the basis of potentiometry. Several differences between the behaviour of humic and fulvic acids were found. While whole samples of fulvic acids including the weakest functional groups were analysed, only the active dissolved humic fractions containing stronger acidic functional groups were characterized. The fractions containing higher amounts of the weakest functional groups remained insoluble. The dissociation degree of fulvic acids decreased with their increasing content, but a maximum on its concentration dependence obtained for humic acids was observed. Conclusions Two different values of dissociation constants were determined for each sample. The first was determined on the basis of the extrapolation of infinite dilution, second was determined as their average value in the region of high concentrations in which it was constant. Obtained values characterize the functioning of dissolved humic substances from point of view of their dissociation ability. The results obtained by this approach can help to predict the acid–base behaviour of dissolved organic carbon in soil and generally in nature. The acid–base behaviour of dissolved organic carbon depends on its ratio to water. It behaves differently in soil which is dry and in soil which is wet or saturated by water.

Influence of catchment topography on water chemistry in southeastern Québec Shield lakes

1997 ◽  
Vol 54 (10) ◽  
pp. 2215-2227 ◽  
Author(s):  
Pierre D'Arcy ◽  
Richard Carignan
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Water Chemistry ◽  
Surface Waters ◽  
Overland Flow ◽  
Canadian Shield ◽  
Chl A ◽  
Lake Water Chemistry ◽  
High Runoff ◽  
Shield Lakes

For 30 Canadian Shield lakes of southeastern Quebec, catchment slope and lake morphometry account for 50-70% of the variability of chlorophyll a (Chl a), dissolved organic carbon (DOC), total phosphorus (TP), NO3- , and NH4+ . Dissolved organic carbon, TP, Chl a, Ca, and Mg are negatively related to catchment slope, whereas NO3- and NH4+ increase with increasing slope. Concentrations of more conservative constituents (SO42-, Na, K) increase with decreasing elevation as a result of higher evapotranspiration and lower precipitation at low elevations. Catchment variables (slope, drainage area, percent wetlands) are as good predictors of Chl a (r2 = 0.7) as are water chemistry variables (TP, Ca, Mg, and pH). Dominant vegetation (deciduous vs. coniferous) has little or no influence on lake water chemistry. Hydrogeological data for the Canadian Shield suggest that, during periods of high runoff, the development of waterlogged areas and the importance of overland flow on saturated soils are inversely proportional to catchment slope. We propose that the strong influence of catchment slope on water quality is due to slope-dependent seasonal waterlogging, which determines the fate (retention or export to surface waters) of dissolved substances produced within and moving through the forest floor.

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