| 1. |
- Baresel, Christian, et al.
(författare)
-
Uncertainty-Accounting Environmental Policy and Management of Water Systems
- 2007
-
Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 41:10, s. 3653–3659-
-
Tidskriftsartikel (refereegranskat)abstract
- Environmental policies for water quality and ecosystemmanagement do not commonly require explicit stochasticaccounts of uncertainty and risk associated with thequantification and prediction of waterborne pollutant loadsand abatement effects. In this study, we formulate andinvestigate a possible environmental policy that does requirean explicit stochastic uncertainty account. We compareboth the environmental and economic resource allocationperformance of such an uncertainty-accounting environmentalpolicy with that of deterministic, risk-prone and riskaverseenvironmental policies under a range of differenthypothetical, yet still possible, scenarios. The comparisonindicates that a stochastic uncertainty-accountingpolicy may perform better than deterministic policies overa range of different scenarios. Even in the absence ofreliable site-specific data, reported literature values appearto be useful for such a stochastic account of uncertainty.
|
|
| 2. |
- Routh, Joyanto, 1968-, et al.
(författare)
-
Sedimentary geochemical record of humanï¿œinduced environmental changes in the Lake Brunnsviken watershed, Sweden
- 2004
-
Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 49:5, s. 1560-1569
-
Tidskriftsartikel (refereegranskat)abstract
- Environmental changes in Lake Brunnsviken, its watershed, and the greater Stockholm region since the middle of the nineteenth century have left interpretable geochemical imprints in the bottom sediments. These human-induced perturbations within the lakeï¿œs watershed included agriculture, urbanization, sewage and industrial disposal, and water column aeration. Smaller d15Ntotal values, high organic carbon mass accumulation rates, low C:N ratios, and larger d13Corg values identify periods of increased nutrient delivery and elevated primary productivity in the lake. C: S ratios that change from high to low trace the transition from an oxic hypolimnion to an anoxic one during the periods of high productivity. Accumulations of redox-sensitive trace elements increase during the anoxic period and are further magnified during a time of industrial waste discharge into the lake. A recent decrease in black carbon concentrations in sediments reflects the conversion from wood and coal to cleaner forms of energy.
|
|
| 3. |
- Konn, Cécile, 1981-
(författare)
-
Origin of organic compounds in fluids from ultramafic-hosted hydrothermal vents of the Mid-Atlantic Ridge
- 2009
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Natural gas, primarily methane (CH4), is produced in substantial amounts in ultramafic-hosted hydrothermal systems. These systems could also generate oil (heavier hydrocarbons) and the first building blocks of life (prebiotic molecules). In the presence of iron bearing minerals, serpentinisation reactions generate H2. Subsequently, CH4 could be synthesised by Fischer-Tropsch Type (FTT) reaction (4H2 + CO2 → CH4 + 2H2O) which is an abiotic process. This has lead to the idea of abiotic formation of larger organic molecules. Both thermodynamics and laboratory work support this idea, yet field data have been lacking. This study focuses on determining the organic content of fluids from ultramafic-hosted hydrothermal systems from the Mid-Atlantic Ridge (MAR) and the origin of the compounds. Fluids were collected from the Lost City, Rainbow, Ashadze and Logatchev vent fields during the EXOMAR (2005), SERPENTINE (2007), MoMARDREAMnaut (2007) and MOMAR08-Leg2 (2008) cruises conducted by IFREMER, France. A SBSE-TD-GC-MS technique was developed and used to extract, concentrate, separate and identify compounds in the fluids. Hydrothermally derived compounds appeared to consist mainly of hydrocarbons and O-bearing molecules. In addition, some amino acids were detected in the fluids by ULPC-ESI-QToF-MS but their origin will need to be determined. The organic content of the Rainbow fluids did not show intra field variability unlike differences could be noted over the years. In order to address the question of the source of the molecules, compound specific carbon isotopic analyses were carried out and completed with a bacterial (Pyrococcus abyssi) hydrothermal degradation experiment. The δ13C data fall in the range of -40 to -30‰ (vs. V-PDB), but individual δ13C values preclude the identification of a biogenic or abiogenic origin of the compounds. The degradation experiment, however, suggests an abiogenic origin of a portion of saturated hydrocarbons whereas carboxylic acids would be biogenic, and aromatic compounds would be thermogenic.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Lindgren, Georg A., et al.
(författare)
-
Inland subsurface water system role for coastal nitrogen load dynamics and abatement responses
- 2007
-
Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 41:7, s. 2159-2164
-
Tidskriftsartikel (refereegranskat)abstract
- We simulate and analyze long-term dynamics of coastalnitrogen (N) loading and the inland source changes andprocesses that may have determined its development overthe past 60-year period and may govern its possiblefuture responses to variousNsource management scenarios.With regard to processes, the results show that averagebasin-scale N delivery fractions to the coast may not berepresentative of the coastal impacts of either diffuse orpoint inland sources. The effects of inland source changesmay be greatly redistributed in space-time and delayedby slow N transport and mass transfer processes in thesubsurface water system of coastal catchments. Extrapolationof current N transport-attenuation conditionsfor quantification of future abatement effects may thereforebe misleading if the extrapolation models do not realisticallyrepresent delayed long-term influences of slow subsurfaceprocesses. With regard to policy, the results show that andwhy national Swedish and international Baltic Searegion policies for coastal N load abatement may bedifficult or impossible to achieve by inland source abatementonly. Large mitigation of both point and diffuse sourcesmay be necessary to achieve targeted coastal N loadreductions fast and maintain them also in the long term.
|
|
| 8. |
- Gustafsson, Jon Petter, et al.
(författare)
-
Towards a consistent geochemical model for prediction of uranium(VI) removal from groundwater by ferrihydrite
- 2009
-
Ingår i: Applied Geochemistry. - Oxford : Pergamon Press. - 0883-2927 .- 1872-9134. ; 24:3, s. 454-462
-
Tidskriftsartikel (refereegranskat)abstract
- Uranium(VI), which is often elevated in granitoidic groundwaters, is known to adsorb strongly to Fe (hydr)oxides under certain conditions. This process can be used in water treatment to remove U(VI). To develop a consistent geochemical model for U(VI) adsorption to ferrihydrite, batch experiments were performed and previous data sets reviewed to optimize a set of surface complexation constants using the 3-plane CD-MUSIC model. To consider the effect of dissolved organic matter (DOM) on U(VI) speciation, new parameters for the Stockholm Humic Model (SHM) were optimized using previously published data. The model, which was constrained from available X-ray absorption fine structure (EXAFS) spectroscopy evidence, fitted the data well when the surface sites were divided into low- and high-affinity binding sites. Application of the model concept to other published data sets revealed differences in the reactivity of different ferrihydrites towards U(VI). Use of the optimized SHM parameters for U(VI)-DOM complexation showed that this process is important for U(VI) speciation at low pH. However in neutral to alkaline waters with substantial carbonate present, Ca–U–CO3 complexes predominate. The calibrated geochemical model was used to simulate U(VI) adsorption to ferrihydrite for a hypothetical groundwater in the presence of several competitive ions. The results showed that U(VI) adsorption was strong between pH 5 and 8. Also near the calcite saturation limit, where U(VI) adsorption was weakest according to the model, the adsorption percentage was predicted to be >80%. Hence U(VI) adsorption to ferrihydrite-containing sorbents may be used as a method to bring down U(VI) concentrations to acceptable levels in groundwater.
|
|
| 9. |
- Routh, Joyanto, 1968-, et al.
(författare)
-
Characterization and Origin of Dissolved Organic Carbon in Yegua Ground Water in Brazos County, Texas
- 2005
-
Ingår i: Groundwater. - : John Wiley & Sons. - 1745-6584. ; 39:5, s. 760-767
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract Dissolved organic carbon (DOC) concentrations in five shallow (< 20 m) and three deeper wells (27 to 30 m) in the Eocene Yegua Formation (Brazos County in east-central Texas) ranged from 92 to 500 ￜm. Characterization of high, intermediate, and low molecular weight DOC fractions (HMW > 3000 amu, IMW 1000 to 3000 amu, and LMW 500 to 1000 amu) and combined neutral sugar analyses provide information on organic matter sources in the Yegua aquifers. Combined neutral sugars ranged in concentration from 0.6 to 2.7 ￜmol/L and comprised 0.8% to 6.7% of DOC in ground water. Glucose was the most abundant neutral sugar, followed by xylose and galactose, arabinose, mannose, rhamnose, and fucose. These combined neutral sugars were more diagenetically altered in shallow, oxic ground water as indicated by high mole % fucose + rhamnose and low neutral sugar yield. The precursors for neutral sugars are most probably angiosperm leaves, which show a similar distribution pattern of neutral sugars. Ground water DOC was depleted in 13C relative to soil-zone organic matter (OM) (-16ￜ to -19ￜ). The d13C values of bulk DOC and HMW DOC ranged from -24ￜ to ￜ32ￜ, whereas LMW and IMW DOC ranged from -32ￜ to -34ￜ and ￜ16ￜ to ￜ28ￜ, respectively. This variability in d13C values is probably related to microbial processes and selective preservation of OM. Carbon isotope analyses in bulk and different molecular weight DOC fractions imply a predominantly C3 OM source and a low contribution of soil-zone OM to DOC.
|
|
| 10. |
- Brüchert, Volker, et al.
(författare)
-
Hydrogen sulphide and methane emissions on the central Namibian shelf
- 2009
-
Ingår i: Progress in Oceanography. - : Elsevier. - 0079-6611 .- 1873-4472. ; 83:1-4, s. 169-179
-
Tidskriftsartikel (refereegranskat)abstract
- Hydrogen sulphide occurs frequently in the waters of the inner shelf coastal upwelling area off central Namibia. The area affected coincides with hatching grounds of commercially important pelagic fish, whose recruitment may be severely affected by recurring toxic sulphidic episodes. Both episodic biogenic methane gas-driven advective and molecular diffusive flux of hydrogen sulphide have been implicated as transport mechanisms from the underlying organic-matter-rich diatomaceous mud. To test hypotheses on the controls of hydrogen sulphide transport from the sediments on the inner Namibian shelf, water column and sediment data were acquired from four stations between 27 and 72 m water depth over a 3 year long period. On 14 cruises, temperature, salinity, dissolved oxygen, nitrate, methane, and total dissolved sulphide were determined from water column samples, and pore water dissolved methane, total dissolved sulphide, biomass of benthic sulphide-oxidising bacteria Beggiatoa and Thiomargarita, and bacterial sulphate reduction rates were determined from sediment cores. Superimposed on a trend of synchronous changes in water column oxygen and nutrient concentrations controlled by regional hydrographic conditions were asynchronous small-scale variations at the in-shore stations that attest to localized controls on water column chemistry. Small temporal variations in sulphate reduction rates determined with 35S-labeled sulphate do not support the interpretation that variable emissions of sulphide and methane from sediments are driven by temporal changes in the degradation rates of freshly deposited organic matter. The large temporal changes in the concentrations of hydrogen sulphide and the co-occurrence of pore water sulphate and methane support an interpretation of episodic advection of methane and hydrogen sulphide from deeper sediment depths – possibly due to gas bubble transport. Effective fluxes of hydrogen sulphide and methane to the water column, and methane and sulphide concentrations in the bottom waters were decoupled, likely due to the activity of sulphide-oxidising bacteria. While the causal mechanism for the episodic fluctuations in methane and dissolved sulphide concentrations remains unclear, this data set points to the importance of alternating advective and diffusive transport of methane and hydrogen sulphide to the water column.
|
|
