Evaluation of sulphide oxidation rates: a laboratory study comparing oxygen fluxes and rates of oxidation product release

1994 ◽  
Vol 31 (3) ◽  
pp. 375-383 ◽  
Author(s):  
B. Elberling ◽  
R.V. Nicholson ◽  
E.J. Reardon ◽  
R Tibble
Keyword(s):  
Water Table ◽  
Oxidation Rate ◽  
Water Saturation ◽  
Temporal Trends ◽  
High Water ◽  
Sulphide Oxidation ◽  
Oxidation Rates ◽  
Mapping Tool ◽  
Fine Grain ◽  
The Impact

A series of column experiments were conducted to evaluate three methods to determine sulphide oxidation rates in mine tailings. Measurements were made of (i) the flux of oxygen across the surface of the tailings, (ii) the oxygen consumption rates at the tailings surface, and (iii) the total sulphate produced in the pore water over time. Two columns were prepared with a mixture of quartz sand and pyrrhotite and overlain with varying thicknesses and grain sizes of a nonreactive layer. The impact of nonreactive layers with varying water-table depths on the overall oxidation rate was also evaluated. Modelling was applied to verify the importance of diffusion and kinetic control of the different column configurations. The results indicate that the overall rate of oxidation is reduced when fine-grain layers are applied. This is due to the high water saturation conditions generated by the fine material regardless of the depth to the water table. The consistency and precision of the methods used to measure relative oxidation rates were noted and a new practical field mapping tool is recommended. The new method provides rapid measurements of relative oxidation rates that can be applied to existing tailings rehabilitation with soil-type covers to show spatial and temporal trends. Key words : sulphide oxidation, tailings, laboratory experiment, oxidation rate methods, water saturation, cover materials.

UK landfill methane emissions: Use of mobile plume measurements and carbon isotopic characterisation to reassess oxidation rates for open and closed sites 

2021 ◽  
Author(s):  
Semra Bakkaloglu ◽  
Dave Lowry ◽  
Rebecca Fisher ◽  
James France ◽  
Euan Nisbet
Keyword(s):  
Methane Oxidation ◽  
Mole Fraction ◽  
Oxidation Rate ◽  
Methane Emissions ◽  
Isotopic Signature ◽  
Oxidation Rates ◽  
Landfill Cover ◽  
Carbon Isotopic ◽  
Landfill Sites ◽  
The Impact

<p>Biological methane oxidation in landfill cover material can be characterised using stable isotopes. Methane oxidation fraction is calculated from the carbon isotopic signature of emitted CH<sub>4</sub>, with enhanced microbial consumption of methane in the aerobic portion of the landfill cover indicated by a shift to less depleted isotopic values in the residual methane emitted to air. This study was performed at four southwest England landfill sites. Mobile mole fraction measurement at the four sites was coupled with Flexfoil bag sampling of air for high-precision isotope analysis. Gas well samples collected from the pipeline systems and downwind plume air samples were utilized to estimate methane oxidation rate for whole sites. This work was designed to assess the impact on carbon isotopic signature and oxidation rate as UK landfill practice and waste streams have changed in recent years.</p><p>The landfill status such as closed and active, seasonal variation, cap stripping and site closure impact on landfill isotopic signature and oxidation rate were evaluated. The isotopic signature of <sup>13</sup>C-CH<sub>4</sub> values of emissions varied between -60 and -54‰, with an averaged value of -57 +- 2‰ for methane from closed and active landfill sites. Methane emissions from older, closed landfill sites were typically more enriched in <sup>13</sup>C than emissions from active sites. This study found that the isotopic signature of <sup>13</sup>C-CH<sub>4</sub> of fugitive methane did not show a seasonal trend, and there was no plume observed from a partial cap stripping process to assess changes in <sup>13</sup>C-CH<sub>4</sub>  isotopic signatures of emitted methane. Also, the closure of an active landfill cell caused a significant decrease in mole fraction of measured CH<sub>4</sub>, which was less depleted <sup>13</sup>C in the emitted plume due to a higher oxidation rate. Methane oxidation, estimated from the isotope fractionation, ranged from 3 to 27%, with mean values of 7% and 15% for active and closed landfills, respectively. These results indicate that the oxidation rate is highly site specific.</p><p> </p>

Effects of different quinoid redox mediators on the simultaneous removal of p-cresol and sulphide in a denitrifying process

2009 ◽  
Vol 59 (10) ◽  
pp. 1945-1950 ◽  
Author(s):  
Edna R. Meza-Escalante ◽  
Anne-Claire Texier ◽  
Flor Cuervo-López ◽  
Jorge Gómez ◽  
Francisco J. Cervantes
Keyword(s):  
Oxidation Rate ◽  
Simultaneous Removal ◽  
Redox Mediators ◽  
Batch Studies ◽  
Sulphide Oxidation ◽  
Degree Of Mineralization ◽  
Heterogeneous Effects ◽  
The Impact ◽  
Catalytic Effects

The catalytic effects of different quinoid redox mediators (RM) on the simultaneous removal of sulphide and p-cresol in a denitrifying process were evaluated in batch studies. 2-Hydroxy-1,4-naphthoquinone (LAW) and anthraquinone-2,6-disulphonate (AQDS) did not significantly affect the sulphide oxidation rate, which, in contrast, was increased 14% in the presence of 1,2-naphthoquinone-4-sulphonate (NQS). The input of NQS on the oxidation of sulphide was also favourably reflected in a 13% higher sulphate production. All RM promoted a higher (up to 34% compared to the control lacking RM) degree of mineralization of p-cresol. LAW also supported a 47% higher denitrifying yield (YN2), compared to the control lacking quinones. Nevertheless, AQDS and NQS decreased the YN2 by 12–13%. Our results suggest that a proper scrutiny should be conducted before deciding the sort of quinone to be applied in denitrifying processes. The heterogeneous effects observed also advise to consider both the respiratory rates and the yields as important parameters for deciphering the impact of RM on denitrifying processes.

SOIL DRAINAGE CLASSES AND SOIL WATER TABLE RELATIONS IN MEDIUM AND COARSE TEXTURED SOILS IN SOUTHERN ONTARIO

1978 ◽  
Vol 58 (3) ◽  
pp. 287-301 ◽  
Author(s):  
E. E. MACKINTOSH ◽  
J. VAN DER HULST
Keyword(s):  
Water Table ◽  
Water Saturation ◽  
Free Water ◽  
High Water ◽  
Tile Drainage ◽  
Septic Tank ◽  
Soil Morphology ◽  
Soil Drainage ◽  
Significant Difference ◽  
Poorly Drained Soils

Water table levels were recorded for up to 5 yr on five soil catenas, each containing a well, imperfectly, poorly and very poorly drained member. Water table measurements in combination with soil morphology were used to establish the zone of free water saturation and from this, periods of saturation were recorded at pre-determined depths or, alternatively, mean high water table and mean low water table levels were calculated for the periods 1 Jan.–31 Dec. and 1 May–31 Oct. Periods of saturation for well/imperfectly and imperfectly/very poorly drained soils were significantly different at the.2 level of probability, but there was no significant difference between the imperfectly/poorly or poorly/very poorly drained members. At the.05 level of probability, only two drainage classes were significantly different. The large within -class variability raises some conern over relying on soil morphology to determine water table characteristics and as well, questions the usefulness of soil drainage classes as currently defined. The significance of the data is discussed in relation to soil mapping, tile drainage and septic tank disposal of wastes.

scholarly journals Temporal water table changes in soil toposequence of the Poznań Lakeland (western Poland)

2017 ◽  
Vol 68 (4) ◽  
pp. 167-173
Author(s):  
Michał Kozłowski ◽  
Jolanta Komisarek
Keyword(s):  
Regression Analysis ◽  
Linear Regression ◽  
Water Table ◽  
Root Zone ◽  
Linear Regression Analysis ◽  
Temporal Trends ◽  
Water Table Depth ◽  
The Mean ◽  
The Impact

Abstract The paper presents results of determination of temporal changes in water table depths in the toposequence of Retisols/Luvisols and Phaeozems/Gleysols. Assessment of temporal trends in the water table depth was made with the use of the linear regression analysis. The results obtained indicate that the mean water table depth and mean high and low water table depths were deeper in the soil at the upper part of the slope in comparison with soil located at the footslope. A higher amplitude of water table was observed in Retisols than in Gleysols but the highest variability of water table level was noted in the soils at the footslope compared to those at the slope summit. In Retisols, with each month of observation from 1993 to 2012, the water table showed a tendency to increase. These trends were the highest from January to April, which may be related to the tendency of increasing monthly sums of precipitation in December, January and February. In the Gleysol at the footslope, in the period 1993–2012 and in the vegetation season, the water table depth showed a tendency to decrease. This trend may be due to the impact of water table on the soil water content at the root zone, which is used in the process of evapotranspiration.

scholarly journals Field Evaluation of Sulphide Oxidation Rates

1993 ◽  
Vol 24 (5) ◽  
pp. 323-338 ◽  
Author(s):  
B. Elberling ◽  
R.V. Nicholson ◽  
D.J. David
Keyword(s):  
Mine Tailings ◽  
Oxidation Rate ◽  
Relative Rate ◽  
Ground Surface ◽  
Field Evaluation ◽  
High Water ◽  
Oxygen Flux ◽  
Degree Of Saturation ◽  
Dissolved Metals ◽  
Oxidation Rates

The generation of acidic waters and the release of dissolved metals from inactive sulphide mine-tailings disposal is a well-known environmental problem. The flux of oxygen across the surface of the tailings was determined under different physically-controlled environmental conditions and related to the oxidation rate of pyrrhotite mine-tailings. This work was conducted to verify, i) the consistency in oxygen flux rate measurements in the field within small areas and, ii) the importance of moist layers near the ground surface in the control of the oxygen flux. The flux of oxygen across the surface is related to a relative oxidation rate of the tailings, and it can be concluded from the study that differences in the degree of saturation as a result of fine-grain layers, hardpan formation or a general high water table can control the overall rate of oxygen flux into tailings and reduce the relative rate of tailings oxidation by more than three orders of magnitudes. The oxygen flux method used in the study is shown to be a useful field mapping tool for distribution of relative oxidation rates in field settings.

Fructose-maltodextrin ratio in a carbohydrate-electrolyte solution differentially affects exogenous carbohydrate oxidation rate, gut comfort, and performance

2011 ◽  
Vol 300 (1) ◽  
pp. G181-G189 ◽  
Author(s):  
Wendy J. O'Brien ◽  
David S. Rowlands
Keyword(s):  
Oxidation Rate ◽  
Peak Power ◽  
Ingestion Rate ◽  
Carbohydrate Oxidation ◽  
Confidence Limits ◽  
Carbohydrate Ingestion ◽  
Oxidation Rates ◽  
Enhanced Absorption ◽  
And Performance ◽  
The Impact

Solutions containing multiple carbohydrates utilizing different intestinal transporters (glucose and fructose) show enhanced absorption, oxidation, and performance compared with single-carbohydrate solutions, but the impact of the ratio of these carbohydrates on outcomes is unknown. In a randomized double-blind crossover, 10 cyclists rode 150 min at 50% peak power, then performed an incremental test to exhaustion, while ingesting artificially sweetened water or one of three carbohydrate-salt solutions comprising fructose and maltodextrin in the respective following concentrations: 4.5 and 9% (0.5-Ratio), 6 and 7.5% (0.8-Ratio), and 7.5 and 6% (1.25-Ratio). The carbohydrates were ingested at 1.8 g/min and naturally 13C-enriched to permit evaluation of oxidation rate by mass spectrometry and indirect calorimetry. Mean exogenous carbohydrate oxidation rates were 1.04, 1.14, and 1.05 g/min (coefficient of variation 20%) in 0.5-, 0.8-, and 1.25-Ratios, respectively, representing likely small increases in 0.8-Ratio of 11% (90% confidence limits; ±4%) and 10% (±4%) relative to 0.5- and 1.25-Ratios, respectively. Comparisons of fat and total and endogenous carbohydrate oxidation rates between solutions were unclear. Relative to 0.5-Ratio, there were moderate improvements to peak power with 0.8- (3.6%; 99% confidence limits ± 3.5%) and 1.25-Ratio (3.0%; ±3.7%) but unclear with water (0.4%; ±4.4%). Increases in stomach fullness, abdominal cramping, and nausea were lowest with the 0.8- followed by the 1.25-Ratio solution. At high carbohydrate-ingestion rate, greater benefits to endurance performance may result from ingestion of 0.8- to 1.25-Ratio fructose-maltodextrin solutions. Small perceptible improvements in gut comfort favor the 0.8-Ratio and provide a clearer suggestion of mechanism than the relationship with exogenous carbohydrate oxidation.

scholarly journals The impact of a declining water table on observed carbon fluxes at a northern temperate wetland

2009 ◽  
Vol 6 (1) ◽  
pp. 2659-2696 ◽  
Author(s):  
B. N. Sulman ◽  
A. R. Desai ◽  
B. D. Cook ◽  
N. Saliendra ◽  
D. S. Mackay
Keyword(s):  
Water Table ◽  
Climate Models ◽  
Ecosystem Respiration ◽  
Net Ecosystem Exchange ◽  
High Water ◽  
Carbon Dioxide Exchange ◽  
Yearly Average ◽  
Ecosystem Water Use Efficiency ◽  
Wetland Biogeochemistry ◽  
The Impact

Abstract. Wetland biogeochemistry is strongly influenced by water and temperature dynamics, and these interactions are currently poorly represented in ecosystem and climate models. A decline in water table of approximately 6 cm/year was observed at a wetland in northern Wisconsin, USA over a period from 2001–2007. Eddy covariance measurements of carbon dioxide exchange in conjunction with the declining water table revealed an increase in ecosystem respiration of over 20% as water table depth fell through a range between 5 and 35 cm below the surface. Ecosystem respiration was not correlated with water table outside of this range. The limits of the range were dependent on temperature, with the effect of water table penetrating deeper at higher temperatures. Yearly average ecosystem production was approximately 20% higher in years with low water table than in years with high water table. As the water table declined, evapotranspiration decreased and ecosystem water use efficiency increased. Wetland net ecosystem exchange was not correlated with water table, but in 2007, a year with an exceptionally dry growing season, the wetland site was a net carbon source. These results suggest that changes in hydrology may not have a large impact on wetland carbon flux over inter-annual time scales due to opposing responses in both ecosystem respiration and productivity. However, this balance appears to be sensitive to changes in the seasonal distribution of precipitation.

scholarly journals Energy Economy Hampers Body Weight Loss after Gastric Bypass

2000 ◽  
Vol 85 (12) ◽  
pp. 4695-4700 ◽  
Author(s):  
E. Bobbioni-Harsch ◽  
P. Morel ◽  
O. Huber ◽  
F. Assimacopoulos-Jeannet ◽  
G. Chassot ◽  
...  
Keyword(s):  
Weight Loss ◽  
Gastric Bypass ◽  
Body Weight ◽  
Energy Intake ◽  
Oxidation Rate ◽  
Linear Regression Analysis ◽  
Body Weight Loss ◽  
Oxidation Rates ◽  
Energy Economy ◽  
The Impact

The impact of energy economy on body weight loss was investigated in 20 obese women, submitted to Roux-en-Y gastric bypass. Resting energy expenditure (REE), substrate oxidation rates, plasma glucose, free fatty acid, and insulin and leptin levels were measured before and 3, 6, and 12 months after surgery. Predicted REE was obtained from linear regression analysis of REE and fat free mass, in a group of 85 women, whose body mass index ranged between 20 and 60 kg/m2. The deviation from predicted REE, calculated as area under the curve (AUC) over the 12-month period for each patient, was considered as the expression of energy economy. Energy economy AUC was significantly (P < 0.005) negatively related to the weight lost during 12 months after surgery. Energy intake, calculated from self-reported food consumption, was also expressed as AUC. Energy intake AUC showed a significant (P < 0.002) positive correlation with weight loss. Lipid oxidation rate, also calculated as AUC, significantly correlated, negatively, with energy economy (P < 0.001) and, positively, with energy intake (P < 0.002). Preoperative leptin values were significantly (P < 0.01) linked to individual energy economy capacity. In conclusion, after Roux-en-Y gastric bypass, energy economy hampers the weight loss process, probably through a low fat oxidation rate.

scholarly journals Structure, Diversity, and Environmental Determinants of High-Latitude Threatened Conifer Forests

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 775
Author(s):  
Carlos Esse ◽  
Francisco Correa-Araneda ◽  
Cristian Acuña ◽  
Rodrigo Santander-Massa ◽  
Patricio De Los Ríos-Escalante ◽  
...  
Keyword(s):  
Water Table ◽  
Environmental Variables ◽  
National Park ◽  
High Water ◽  
Forest Communities ◽  
Competitive Effect ◽  
Forest Patches ◽  
Last Glaciation ◽  
The World ◽  
Local Topography

Pilgerodendron uviferum (D. Don) Florin is an endemic, threatened conifer that grows in South America. In the sub-Antarctic territory, one of the most isolated places in the world, some forest patches remain untouched since the last glaciation. In this study, we analyze the tree structure and tree diversity and characterize the environmental conditions where P. uviferum-dominated stands develop within the Magellanic islands in Kawésqar National Park, Chile. An environmental matrix using the databases WorldClim and SoilGrids and local topography variables was used to identify the main environmental variables that explain the P. uviferum-dominated stands. PCA was used to reduce the environmental variables, and PERMANOVA and nMDS were used to evaluate differences among forest communities. The results show that two forest communities are present within the Magellanic islands. Both forest communities share the fact that they can persist over time due to the high water table that limits the competitive effect from other tree species less tolerant to high soil water table and organic matter. Our results contribute to knowledge of the species’ environmental preference and design conservation programs.

scholarly journals Cellulose Nanofibrils/Xyloglucan Bio-Based Aerogels with Shape Recovery

Gels ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 5
Author(s):  
Samuel Mandin ◽  
Samuel Moreau ◽  
Malika Talantikite ◽  
Bruno Novalès ◽  
Jean-Eudes Maigret ◽  
...  
Keyword(s):  
Water Absorption ◽  
Shape Recovery ◽  
Cellulose Nanofibrils ◽  
High Water ◽  
Absorption Capacity ◽  
Absorption Properties ◽  
High Affinity ◽  
High Water Absorption ◽  
Freezing Procedure ◽  
The Impact

Bio-based aerogels containing cellulose nanofibrils (CNFs) are promising materials due to the inherent physical properties of CNF. The high affinity of cellulose to plant hemicelluloses (xyloglucan, xylan, pectin) is also an opportunity to develop biomaterials with new properties. Here, we prepared aerogels from gelled dispersions of CNFs and xyloglucan (XG) at different ratios by using a freeze-casting procedure in unidirectional (UD) and non-directional (ND) manners. As showed by rheology analysis, CNF and CNF/XG dispersions behave as true gels. We investigated the impact of the freezing procedure and the gel’s composition on the microstructure and the water absorption properties. The introduction of XG greatly affects the microstructure of the aerogel from lamellar to cellular morphology. Bio-based aerogels showed high water absorption capacity with shape recovery after compression. The relation between morphology and aerogel compositions is discussed.

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