Decomposition of Seston in the Hyolimnion

1987 ◽  
Vol 44 (1) ◽  
pp. 146-151 ◽  
Author(s):  
R. J. Cornett ◽  
F. H. Rigler
Keyword(s):  
Oxygen Consumption ◽  
Water Temperature ◽  
Water Column ◽  
Chlorophyll A ◽  
Significant Fraction ◽  
Oxygen Deficit ◽  
Total Oxygen ◽  
Respiration Rates ◽  
Hypolimnetic Oxygen

In 12 lakes a significant fraction of the hypolimnetic oxygen deficit was produced by the respiration of seston in the hypolimnetic water column. Mean summer seston respiration rates ranged between 4 and 80 mg O2∙m−3∙d−1. Rates of seston respiration were proportional to the in situ water temperature and to the concentration of Chlorophyll a. The amount of oxygen consumed in the water column and the fraction of the total oxygen deficit produced by sestonic respiration were correlated with the amount of phosphorus sedimented from the epilimnion. Fifteen to 66% of the total oxygen consumption occurred in the water column of the hypolimnion. Seston respiration was a larger proportion of the total respiration in the hypolimnion of lakes with a thick hypolimnion than in lakes with a shallow hypolimnetic water column.

Effect of Ambient Oxygen Concentration on Measurements of Sediment Oxygen Consumption

1986 ◽  
Vol 43 (7) ◽  
pp. 1340-1349 ◽  
Author(s):  
P. J. Campbell ◽  
F. H. Rigler
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Concentration ◽  
Oxygen Depletion ◽  
Continuous Mixing ◽  
Ambient Oxygen ◽  
Hypolimnetic Oxygen ◽  
Sediment Oxygen Consumption ◽  
The Mean ◽  
Gas Tight

The disparity between hypolimnetic oxygen depletion in situ (HOD; independent of the ambient oxygen concentration), used to calculate sediment oxygen consumption (SOC) in one lake in southern Quebec, and measurements of SOC (dependent on the oxygen concentration) was minimal when experimental factors were controlled. Using gas-tight methods, SOC at 7–5 mg∙L−1 decreased by 75% when the oxygen concentration in respirometers fell to 3–1 mg∙L−1. With continuous mixing, the comparable decrease in SOC was 50%. Finally, the decrease was less than 30% and obvious only below 2 mg∙L−1 when the oxygen concentration was held constant in continuous flow respirometers. SOC results using the last procedure were within 10% of the mean SOC calculated indirectly from hypolimnetic oxygen budgets for the two previous years. Thus, mixing and a constant or slowly changing ambient oxygen concentration are required for realistic SOC measurements. In another experiment, oxygen uptake in water overlying the sediment accounted for a large and variable portion of the SOC, often more than 50%. Therefore, it may be impossible to separate the influence of the water and sediment on the HOD.

Factors Affecting Winter Respiration in Ontario Lakes

1976 ◽  
Vol 33 (8) ◽  
pp. 1809-1815 ◽  
Author(s):  
H. E. Welch ◽  
P. J. Dillon ◽  
A. Sreedharan
Keyword(s):  
Oxygen Consumption ◽  
Chlorophyll A ◽  
Secchi Depth ◽  
Factors Affecting ◽  
Respiration Rates ◽  
Morphological Variables

Winter oxygen consumption was measured in 16 Ontario lakes. Whole lake respiration ranged from 0.08 to 0.39 g O2 m−2 day−1 and was positively correlated with mean depth, phosphorus m−2 at spring overturn, and summer chlorophyll a m−2. Morphological variables plus Secchi depth were explained over 80% of the variability in respiration rates.

Nitrification: A Significant Cause of Oxygen Depletion Under Winter Ice

1987 ◽  
Vol 44 (4) ◽  
pp. 743-749 ◽  
Author(s):  
Roger Knowles ◽  
David R. S. Lean
Keyword(s):  
Oxygen Consumption ◽  
Water Temperature ◽  
Water Column ◽  
Average Rate ◽  
Oxygen Depletion ◽  
Nitrifying Bacteria ◽  
Nitrification Activity ◽  
Mesotrophic Lake ◽  
Nitrite Nitrate

Changes in concentrations of ammonium, nitrite, nitrate, and oxygen suggested the occurrence of significant nitrification throughout the water column of mesotrophic Lake St. George, Ontario, during the winter months from 1976 to 1984. The existence of nitrapyrin- and acetylene-sensitive 14C-bicarbonate incorporation confirmed that bacterial nitrification occurred. During late January to early March (water temperature 2–3 °C), nitrification occurred at an average rate of about 13 μg N∙L−1∙d−1 for the years studied. Numbers of detectable nitrifying bacteria appeared too low (by 2 to 4 orders of magnitude) to account for the observed activity. The nitrification activity observed would result in average oxygen consumption amounting to 71% of the observed oxygen depletion. This shows that winter nitrification can be an important factor in promoting oxygen depletion and possibly winter-kill of fish.

Application of Gypsum Granule as a Capping Material to Reduce Phosphorus Release from Sediment of Lake Paldang

2007 ◽  
Vol 544-545 ◽  
pp. 521-524 ◽  
Author(s):  
Yong Jin Park ◽  
Jae Jung Ko ◽  
Young Im Kim ◽  
Sang Leen Yun ◽  
So Jung Kim ◽  
...  
Keyword(s):  
Water Column ◽  
Chlorophyll A ◽  
Nutrient Concentration ◽  
Phosphorus Release ◽  
Experimental Results ◽  
Chlorophyll A Concentration ◽  
P Concentration ◽  
In Situ Experiments ◽  
Calcium Cation

In this study, the capping effects of granular gypsum (Ca2SO4·2H2O) and sand on sediment and water column were evaluated in in-situ experiments in Lake Paldang. The results indicate that capping treatment is very effective for the restoration of eutrophied lake. It was demonstrated that phosphorus, T-N and T-P concentration in the water column of treated basin was relatively lower than control basin. As a consequence of reduction of nutrient concentration by capping treatment, chlorophyll-a concentration in treated basin was considerably lower than control basin. The chlorophyll-a concentration in water column could be reduced to 52% and 25% as compared to control basin, respectively, by the capping treatment with gypsum and sand. From the experimental results, it was concluded that gypsum was more effective capping material than sand for controlling of nutrients and chlorophyll-a. In addition, capping with gypsum bring calcium cation into sediment, which offer more site for phosphorus to bind. In case of the capping with gypsum, apatite P composition, mainly consist of Ca boun P, in the sediment increased from 24% to 43% for the two month of operation.

The Carbon:²³⁴Thorium ratios of sinking particles in the California Current Ecosystem 2: Examination of a thorium sorption, desorption, and particle transport model

2019 ◽  
Author(s):  
Michael Stukel ◽  
Thomas Kelly
Keyword(s):  
Organic Carbon ◽  
Water Column ◽  
Particulate Organic Carbon ◽  
Transport Model ◽  
California Current ◽  
In Situ Measurements ◽  
Power Law Distribution ◽  
Sinking Particles ◽  
Organic Carbon Concentration

Thorium-234 (234Th) is a powerful tracer of particle dynamics and the biological pump in the surface ocean; however, variability in carbon:thorium ratios of sinking particles adds substantial uncertainty to estimates of organic carbon export. We coupled a mechanistic thorium sorption and desorption model to a one-dimensional particle sinking model that uses realistic particle settling velocity spectra. The model generates estimates of 238U-234Th disequilibrium, particulate organic carbon concentration, and the C:234Th ratio of sinking particles, which are then compared to in situ measurements from quasi-Lagrangian studies conducted on six cruises in the California Current Ecosystem. Broad patterns observed in in situ measurements, including decreasing C:234Th ratios with depth and a strong correlation between sinking C:234Th and the ratio of vertically-integrated particulate organic carbon (POC) to vertically-integrated total water column 234Th, were accurately recovered by models assuming either a power law distribution of sinking speeds or a double log normal distribution of sinking speeds. Simulations suggested that the observed decrease in C:234Th with depth may be driven by preferential remineralization of carbon by particle-attached microbes. However, an alternate model structure featuring complete consumption and/or disaggregation of particles by mesozooplankton (e.g. no preferential remineralization of carbon) was also able to simulate decreasing C:234Th with depth (although the decrease was weaker), driven by 234Th adsorption onto slowly sinking particles. Model results also suggest that during bloom decays C:234Th ratios of sinking particles should be higher than expected (based on contemporaneous water column POC), because high settling velocities minimize carbon remineralization during sinking.

The Nature of Chemisorbed CO2 in Zeolite A

2019 ◽  
Author(s):  
Przemyslaw Rzepka ◽  
Zoltán Bacsik ◽  
Andrew J. Pell ◽  
Niklas Hedin ◽  
Aleksander Jaworski
Keyword(s):  
Solid State ◽  
Ir Spectroscopy ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Surface Coverage ◽  
Gas Mixtures ◽  
Mas Nmr ◽  
Significant Fraction ◽  
Zeolite A

Formation of CO<sub>3</sub><sup>2-</sup> and HCO<sub>3</sub><sup>-</sup> species without participation of the framework oxygen atoms upon chemisorption of CO<sub>2</sub> in zeolite |Na<sub>12</sub>|-A is revealed. The transfer of O and H atoms is very likely to have proceeded via the involvement of residual H<sub>2</sub>O or acid groups. A combined study by solid-state <sup>13</sup>C MAS NMR, quantum chemical calculations, and <i>in situ</i> IR spectroscopy showed that the chemisorption mainly occurred by the formation of HCO<sub>3</sub><sup>-</sup>. However, at a low surface coverage of physisorbed and acidic CO<sub>2</sub>, a significant fraction of the HCO<sub>3</sub><sup>-</sup> was deprotonated and transformed into CO<sub>3</sub><sup>2-</sup>. We expect that similar chemisorption of CO<sub>2</sub> would occur for low-silica zeolites and other basic silicates of interest for the capture of CO<sub>2</sub> from gas mixtures.

scholarly journals Performance of a Handheld Chlorophyll-a Fluorometer: Potential Use for Rapid Algae Monitoring

Water ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1409
Author(s):  
Hamdhani Hamdhani ◽  
Drew E. Eppehimer ◽  
David Walker ◽  
Michael T. Bogan
Keyword(s):  
Chlorophyll A ◽  
Surface Waters ◽  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Water Quality Monitoring ◽  
Ambient Light ◽  
Calibration Equation ◽  
Field Samples ◽  
Potential Use

Chlorophyll-a measurements are an important factor in the water quality monitoring of surface waters, especially for determining the trophic status and ecosystem management. However, a collection of field samples for extractive analysis in a laboratory may not fully represent the field conditions. Handheld fluorometers that can measure chlorophyll-a in situ are available, but their performance in waters with a variety of potential light-interfering substances has not yet been tested. We tested a handheld fluorometer for sensitivity to ambient light and turbidity and compared these findings with EPA Method 445.0 using water samples obtained from two urban lakes in Tucson, Arizona, USA. Our results suggested that the probe was not sensitive to ambient light and performed well at low chlorophyll-a concentrations (<25 µg/L) across a range of turbidity levels (50–70 NTU). However, the performance was lower when the chlorophyll-a concentrations were >25 µg/L and turbidity levels were <50 NTU. To account for this discrepancy, we developed a calibration equation to use for this handheld fluorometer when field monitoring for potential harmful algal blooms in water bodies.

Myocardial and Total Oxygen Consumption with Halothane

1967 ◽  
Vol 28 (6) ◽  
pp. 1042-1047 ◽  
Author(s):  
Richard A. Theye
Keyword(s):  
Oxygen Consumption ◽  
Total Oxygen
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