Variation Of Dissolved Oxygen Concentration Research Articles

Longitudinal dissolved oxygen patterns in Atlantic salmon aquaculture sites in British Columbia, Canada

Dissolved oxygen (DO), an important water-quality parameter required to support aquatic life, is a critical factor for determining the general biological health of the aquatic ecosystem, and the concentration of DO is a critical factor in determining salmon growth and welfare. This study used longitudinal DO concentration, recorded hourly from 21 aquaculture sites, each with loggers in three separate cages, in four areas in British Columbia, Canada, between 2015 and 2017. The measurements were evaluated based on the recommended DO concentrations for protection of salmonids from hypoxia. Using a two-stage time-series analysis, we described variations in DO concentrations measured over the study period and their associations with environmental factors. Based on the water quality criteria for DO concentration, 42.3, 56.5, and 1.2% of the hourly DO data from the overall 21 aquaculture sites were classified as ‘optimal’, ‘sub-optimal’, and ‘stressed’, respectively. The frequency of hypoxic episodes differed substantially among seasons, aquaculture sites and even among cages within sites. The effects of environmental variables on DO concentration had markedly different patterns depending on the season. Significant associations with DO concentrations were observed for temperatures in the summer and winter months, and both wind direction and remotely-sensed estimated absorption from phytoplankton [aph(443)] in the winter months. The time-series regression model results showed overall (year-round) associations of temperature, wind speed, and aph(443) with DO concentrations. Describing DO measurements at these aquaculture sites provided an understanding of how much they deviated from the recommended DO concentrations, as well as provide baseline information for future water resource planning, including continued and improved water quality monitoring in aquaculture areas.

Under‐Ice Dissolved Oxygen and Metabolism Dynamics in a Shallow Lake: The Critical Role of Ice and Snow

AbstractInteraction of under‐ice physical, chemical, and biological processes with lake ice/snow cover is examined to better understand how changing winter climate may affect lake ecosystems. We derived under‐ice dissolved oxygen (DO) dynamics from high‐frequency observations and modified a widely used lake metabolism model by including the effect of freezing and thawing on DO concentration. Estimates were produced for the production and respiration in a shallow lake on the Mongolian Plateau in three winters. Diel, synoptic, and seasonal variations in DO concentration were detected as responses to solar radiation, episodic snowfall events, and occasional convective mixing. Based on the observations and a radiative transfer model, incident solar radiation was partitioned into reflectance, absorbance, and transmittance by the snow and ice cover. For bare ice, the contributions of these three parts were 35%, 39%, and 26%, respectively, while under a new 4.5 cm thick snow cover, the corresponding values were 79%, 17%, and 3%. This points out the critical role of snow and ice on under‐ice light conditions, which is the primary forcing for the temperature and the rate of photosynthesis under ice. The results showed three principal factors, which influenced under‐ice DO and metabolism: (1) thickness and optical properties of ice and snow, which affected the light transfer and depth of the euphotic zone, (2) mediated radiation and ice‐water heat transfer which controlled water temperature, and (3) DO exclusion during freezing and dilution by melt water. This study highlights the ecosystem characteristics in shallow ice‐covered lakes in arid temperate regions and promotes our understanding of the response of the cold aquatic environment to climate change.

Seasonal Variation of Dissolved Oxygen in the Southeast of the Pearl River Estuary

Dissolved oxygen (DO) concentration in estuaries is highly variable at different spatial and temporal scales, which is affected by physical, chemical and biological processes. This study analyzed the spatial–temporal distributions of dissolved oxygen concentration and bottom hypoxia in the southeast of the Pearl River Estuary (PRE) using monthly water quality monitoring and hydrographic data covering the period 2000–2017. The seasonal spatial–temporal variation of DO concentration was studied using various methods, such as rotated empirical orthogonal functions, harmonic analysis, and correlation analysis. The results showed that DO stratification was significant in summer, but it was not distinct in winter, during which DO concentration peaked. DO stratification exhibited a significantly positive correlation with water stratification. In the south and west of Hong Kong (SHK and WHK, respectively), DO concentration fields exhibited distinct seasonal changes in the recent 18 years. In SHK, the main periods of the surface DO variation were 24, 12, and 6 months, whereas the main period was 12 months in WHK. The main period of the bottom DO variation was 12 months in both SHK and WHK. In SHK, the spatial–temporal variations in surface and bottom DO were highly related to the variations of salinity, dissolved inorganic nitrogen (DIN), and active phosphorus, and the variation of surface DO was also connected to the variation of temperature and chlorophyll a. In WHK, the variations in surface and bottom DO were highly related to the variations of salinity and temperature, and the variation of surface DO was also connected to the variation of DIN. The river discharge and wind had a different important influence on the temporal variability of DO in WHK and SHK. These findings suggested that the variations of DO may be controlled by coupled physical and biochemical processes in the southeast of PRE. From 2000 to 2017, bottom hypoxia in the southeast of PRE occurred in the summers of 7 years. SHK appeared to be more vulnerable to hypoxia than WHK.

Spatial and temporal variability in dissolved oxygen content of Asoro stream, in south western Nigeria

This study examined the spatial and temporal variation of dissolved oxygen (DO) concentration in Asoro stream, the self-recovery ability of the stream of the effluent discharges with a view to providing a baseline information on quality of water in Asoro stream. DO is a measure of the ability of water to sustain aquatic life, it is important in water pollution control and waste water treatment process control. Samples were collected from fifteen sampling points along the Asoro stream at 500 m intervals over a 5000 m stretch for twelve-months. The DO, Biochemical Oxygen Demand and some other physico-chemical parameters of water were determined using standard methods. The hydrographic characteristics of the stream were; width (0.8 to 5.8 m), depth (0.1 to 0.55 m), discharge (0.30 to 0.52 ms -1 ), flow rate 0.07 to 0.0.73 m 3 /s. The temporal variation in DO concentration in Asoro stream fluctuated from the first week of sampling to 25th week after with a peak range of concentration (7.46 mg/L to 10.12 mg/L) between 27th week and 39th week of sampling suggesting high level of organic pollution. The mean spatial distribution of DO at each station changed slightly between the point of brewery effluent discharge and 5000 m away. Regression analysis showed that there was no significant relationship (P≥ 0.05) between time (weeks) and DO concentration along Asoro stream. The study concluded that release of organic matter from industrial effluent affects the DO and BOD concentrations of Asoro stream. Keywords: Dissolved oxygen, Temporal, Spatial, Asoro stream, self- recovery

Modelling of sequencing batch reactor operating at various aeration modes

The presented study involved designing a computer model of a sequencing batch reactor (SBR) at laboratory scale. The data pertaining to the technical aspects of the bioreactor and quality indicators of wastewater constituted the input for the employed simulation tool, i.e. GPS-X software package. The results of a simulation involving a 12-hour operation cycle are presented in this work; each cycle included 6 phases: filling, mixing, aeration, settling, decantation and idling (wasting of excess sludge). The simulations were carried out using two different modes of aeration. Concentration of dissolved oxygen (DO) was maintained at constant level of 2 mgO2/L using the PID controller in the first case. On the other hand, variation of DO concentration was employed in the aeration stage of the second variant, which was achieved using appropriately elaborated set point of oxygen concentration, considering the specific intervals in oxygen supply. The changes observed in DO concentration varied from 0.5 to 2.5 mgO2/L. This research proved that the second variant, involving variation of DO concentration, was characterised by reduced levels of pollution indicators in treated sewage, as well as lower consumption of electricity, both of which contributed towards improving the effluent quality and resulted in significant degree of dephosphatation.

The sinking of the phytoplankton community and its contribution to seasonal hypoxia in the Changjiang (Yangtze River) estuary and its adjacent waters

The phytoplankton sinking rates and the annual variations of dissolved oxygen (DO) were studied as part of a multi-disciplinary investigation in the Changjiang (Yangtze River) Estuary (CE) and its adjacent waters from February 2015 to January 2016. The sinking rates of phytoplankton ranged from 0.02 to 3.49 m d−1, determined with the homogeneous sample method SETCOL. There was clear correlation between sinking rate and the phytoplankton composition. The diatom-dominated community had higher sinking rates than the dinoflagellate-dominated community, and the variation in DO concentration indicated a close relationship with the blooming and senescence of phytoplankton. Low DO (<3 mg L−1) or hypoxic (<2 mg L−1) zones were observed in near-bottom waters between July and October. Hypoxia reached its maximum in October, with a low DO zone covering approximately 4500 km2 of the survey area. The zones of lowest DO in near-bottom water were closely associated with zones of the highest chlorophyll a (Chl a) and the highest phytoplankton sinking rates in the upper layer. The present study presents straightforward evidence on the formation of low DO and hypoxia in near-bottom waters and its correlation with sinking of the phytoplankton community, and provides useful insight to reveal the formation mechanism of seasonal hypoxia in the CE and its adjacent waters.

Model extension, calibration and validation of partial nitritation–anammox process in moving bed biofilm reactor (MBBR) for reject and mainstream wastewater

ABSTRACTIn the paper, the extension of mathematical model of partial nitritation–anammox process in a moving bed biofilm reactor (MBBR) is presented. The model was calibrated with a set of kinetic, stoichiometric and biofilm parameters, whose values were taken from the literature and batch tests. The model was validated with data obtained from: laboratory batch experiments, pilot-scale MBBR for a reject water deammonification operated at Himmerfjärden wastewater treatment and pilot-scale MBBR for mainstream wastewater deammonification at Hammarby Sjöstadsverk research facility, Sweden. Simulations were conducted in AQUASIM software. The proposed, extended model proved to be useful for simulating of partial nitritation/anammox process in biofilm reactor both for reject water and mainstream wastewater at variable substrate concentrations (influent total ammonium–nitrogen concentration of 530 ± 68; 45 ± 2.6 and 38 ± 3 gN/m3 – for reject water – and two cases of mainstream wastewater treatment, respectively), temperature (24 ± 2.8; 15 ± 1.1 and 18 ± 0.5°C), pH (7.8 ± 0.2; 7.3 ± 0.1 and 7.4 ± 0.1) and aeration patterns (continuous aeration and intermittent aeration with variable dissolved oxygen concentrations and length of aerated and anoxic phases). The model can be utilized for optimizing and testing different operational strategies of deammonification process in biofilm systems.

A Comparison of Main and Side Channel Physical and Water Quality Metrics and Habitat Complexity in the Middle Mississippi River

AbstractWorldwide large rivers have been severely modified by human intervention. Many modifications result in disconnection of the river from floodplain and off‐channel habitats generally characterized by lower velocities and Copyright © 2016 John Wiley &amp; Sons, Ltd. shallower depths relative to the main channel, conditions vital to many organisms. Extensive levees on the Middle Mississippi River (MMR) have cut off backwater systems and disconnected the river from 80% of its floodplain. However, the system is characterized by large side channels associated with islands. We examined a long term data set for differences in physical (e.g. depth and velocity) and water quality metrics (e.g. temperature, suspended solids, dissolved oxygen, chlorophyll, % organic matter) between the main and side channels of a 128‐km reach of the MMR. We compared variability between main and side channels using the coefficient of variation (COV). All metrics differed between habitats. Side channels were shallower with lower velocities and had greater mean and COV of % organic matter and more variable dissolved oxygen concentrations. Velocity, temperature, and suspended solids were similar in the spring. COVs were lowest in both habitats during the spring for all metrics except temperature and DO. Resource management in the MMR tends to focus on maintaining existing side channels because of the difficulty of working in the heavily used navigation channel. This study shows that these actions protect areas that function differently than the main channel for most of the year. However, our results also highlight the need for restoration activities aimed at restoring floodplain connectivity, especially during the spring. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Deoxygenation andReaeration Coupled hybridMixing cells Based Pollutant Transport Model to Assess water Quality Status of a River

Prediction of spatial and temporal variation of water quality is vital for managing pollutantsdisposal into the rivers. Depletion of dissolved oxygen (DO) takes place due to the consumption of oxygen bymicrobes to digest bio-degradable pollutants which enter a water course. Reaeration takes place in a specificrate depending on DO deficit. Many investigators have formulated models as an alternative to the FickianModel for the advection dispersion pollutant transport. Since Streeter-Phelps research on BOD-DO modeling,many researchers have studied fate of pollutant considering first order reaction along with only advection. TheStreeter-Phelps dispersion model includes deoxygenation and reaeration along with advection and dispersionand which has been solved by defining an axillary variable relating DO deficit and BOD concentration. Thusthis paper considered first order decay and reaeration along with advection and dispersion to simulate spatialand temporal variation of DO concentration using a hybrid mixing cells model. The proposed model has beensuccessfully applied for a hypothetical flow conditions and the River Brahmani, India. River flow requirementand regulation for pollutant disposal with pre-treatment were optimized using the responses of proposedmodel for this River. This research analyzed the selected river reach using proposed model having a particularflow and channel characteristics and found that release of 1180m3/s from Rengali Dam is required to avoidpollution problem. However, in absence of this flow at least 50% of pretreatment pollutants are requiredbefore released into river Tikira.

Contributions of wind and river effects on DO concentration in Tokyo Bay

This paper proposes a method of evaluating the occurrence of hypoxia or anoxia in bottom water of Tokyo Bay, which is typical of enclosed bays in Japan. In Tokyo Bay, the exchange of seawater with the ocean has previously been found to be dominantly controlled by estuarine circulation. Thus, one would expect the concentrations of dissolved oxygen (DO) in the bay head to be influenced mainly by estuarine circulation, which changes according to wind strength and river discharges. We investigated the effects of wind and river discharge on DO concentration around the bay head using a three-dimensional ecological model. To evaluate the occurrence of hypoxic or anoxic water, we developed a conceptual DO model, which was verified through the good agreement with the results from a three-dimensional ecological model. We conclude that the conceptual DO model has good potential for evaluating the factors leading to hypoxic or anoxic water around the bay head. Modeling suggested that, on average, wind effects were the dominant factor in the variation of bottom DO concentrations. However, we found that the contribution of extreme events, such as floods and strong winds exceeding 10 m s−1, was 50% or more. This suggests that extreme events play an important role in controlling the variation in DO concentration at the bottom of Tokyo Bay.

Identifying dissolved oxygen variability and stress in tidal freshwater streams of northern New Zealand

Tidal streams are ecologically important components of lotic network, and we identify dissolved oxygen (DO) depletion as a potentially important stressor in freshwater tidal streams of northern New Zealand. Other studies have examined temporal DO variability within rivers and we build on this by examining variability between streams as a basis for regional-scale predictors of risk for DO stress. Diel DO variability in these streams was driven by: (1) photosynthesis by aquatic plants and community respiration which produced DO maxima in the afternoon and minima early morning (range, 0.6-4.7 g/m(3)) as a product of the solar cycle and (2) tidal variability as a product of the lunar cycle, including saline intrusions with variable DO concentrations plus a small residual effect on freshwater DO for low-velocity streams. The lowest DO concentrations were observed during March (early autumn) when water temperatures and macrophyte biomass were high. Spatial comparisons indicated that low-gradient tidal streams were at greater risk of DO depletions harmful to aquatic life. Tidal influence was stronger in low-gradient streams, which typically drain more developed catchments, have lower reaeration potential and offer conditions more suitable for aquatic plant proliferation. Combined, these characteristics supported a simple method based on the extent of low-gradient channel for identifying coastal streams at risk of DO depletion. High-risk streams can then be targeted for riparian planting, nutrient limits and water allocation controls to reduce potential ecological stress.

Kinetics of chalcopyrite dissolution at pH 3

The management of mine wastes and the quantitative forecast of Acid Rock Drainage ( ARD ) generation have aroused widespread interest. In order to be coupled with gas and water flux models, chalcopyrite dissolution kinetics at pH 3, at temperatures from 25 to 70 °C and at variable dissolved oxygen concentrations was studied in flow-through experiments. In the range of conditions under study, the rate of chalcopyrite dissolution is independent of the concentration of dissolved oxygen. This enables chalcopyrite to dissolve throughout the whole waste piles. The rise in temperature from 25 to 70 °C produces an increase of one order of magnitude in the chalcopyrite dissolution rate. As a result of this study, the following expression for chalcopyrite dissolution rate was obtained: \[\mathit{R_{chalcopyrite}} = 10^{{-}5.52{\pm}0.07}\mathit{e}^{\frac{{-}32{\pm}5}{\mathit{RT}}}\] where R chalcopyrite is the chalcopyrite dissolution rate (molm −2 s −1 ), R is the gas constant (kJmol −1 uK −1 ) and T is the temperature (K). In line with earlier studies carried out under different conditions, iron was released to solution preferentially over copper in all the experiments carried out. XPS examination of the samples showed that reacted surfaces were formed by phases enriched in sulfur and copper (relative to iron) compared with the initial, pristine chalcopyrite surface. However, these surface layers allow the progress of dissolution with out passivating the chalcopyrite surface. According to the apparent activation energy obtained (32±5 kJ mol − 1 ) and to the lack of rate variation with stirring, the chalcopyrite dissolution rate seems to be controlled by surface reactions and is independent of the non-stoichiometric surface layer.

Modeling industry-wide sediment oxygen demand and estimation of the contribution of sediment to total respiration in commercial channel catfish ponds

Data collected from 45 commercial channel catfish, Ictalurus punctatus, ponds were used to develop empirical models predicting sediment oxygen demand (SOD). Seven acceptable models were combined with a Monte-Carlo sampling distribution to predict industry-wide sediment oxygen demand (SODi). The SODi values obtained from the best equation were used in simulations to assess the effect of diurnally varying water column dissolved oxygen (DO) concentrations on SOD and the effect of pond water depth on the contribution of SOD to overall pond respiration. Estimated SODi ranged from 62 to 962mgm−2h−1, with a mean of 478mgm−2h−1. There was a 95% probability of mean SODi being ≥700mgm−2h−1. The effects of diurnal variation in DO concentration in the water column on expression of SOD was modeled by combining maximum SODi, an empirical relationship between DO and SOD, and simulated pond DO concentrations. At DO concentrations >15mgl−1, diel SOD in catfish ponds exceeded 20g O2 m−2day−1. But when average diel DO was <4mgl−1 and the range of DO concentration was 6–8mgl−1, SOD decreased to 13g O2 m−2day−1 because DO availability limited the full expression of potential SOD. Respiration totals for sediment (average SODi), plankton, and fish respiration were calculated for pond water depths ranging from 0.25 to 4m. Although whole-pond respiration increases as pond depth increases, the proportion of total respiration represented by sediment decreased from 48 to 10% by increasing water depth over this range. The results of these studies show that SOD is a major component of total pond respiration and that certain management practices can affect the impact of SOD on pond oxygen budgets. Mixing ponds during daylight hours, either mechanically or by orienting ponds for maximum wind fetch, will increase oxygen supply to sediments, thereby allowing maximum expression of SOD and maximum mineralization of sediment organic matter. Given a mixed condition caused by wind or other artificial means, the construction of deeper ponds increases the total mass of DO available for all respiration, causing nighttime DO concentrations to decline at a slower rate, reducing the need for supplemental aeration. Because a pond’s water volume decreases over time from sediment accumulation, annual aeration costs will increase with pond age. Constructing ponds with greater initial depth will therefore reduce long-term cost of aeration, allow more flexible management of pond water budget, and reduce the long-term expense associated with pond reconstruction.

Dynamics of dissolved oxygen (DO) in ponded water of a paddy field

The transfer of heat and dissolved oxygen (DO) through water is important to understand the phenomenon of ponded water in a paddy soil. The heat from solar radiation is absorbed at the soil surface and transferred into the ponded water by convection. This study clarified the dynamics of DO, as well as the role of convection in water in DO transfer in the ponded water of a paddy field. DO concentration in the ponded water of a paddy field was measured in situ in the daytime and during the night. The results were confirmed in lab-scale model experiments. The DO concentration and temperature profiles in the ponded water of a lab-scale paddy field model were investigated under convective and non-convective conditions using solar radiation and infrared radiation, respectively. Under the ponded condition, solar radiation was absorbed at the soil surface whereas infrared radiation was absorbed at the water surface and thereby convective and non-convective conditions were generated, respectively. The diurnal variation in DO concentration was closely related to the intensity of solar radiation. Oxygen generation by micro-algae and its subsequent circulation by convection resulted in uniform DO concentration profiles, with super-saturated values in the ponded water in the daytime. Eventually oxygen was released to the atmosphere by deaeration until DO in water was depleted to the saturated level. During the night the oxygen moved from the atmosphere into the water surface by reaeration which depends on the oxygen deficit related to saturation. The oxygen deficit is caused by the respiration of microorganisms. The oxygen, that moved from the atmosphere to the water surface, was transferred to the soil surface by convection in the water layer. Thus convection plays an important role in the DO transfer in the ponded water of a paddy field. The DO dynamics is correlated with biological processes in the ponded paddy soil.

Structured model for Saccharomyces cerevisiae

A structured, nonsegragated model of Saccharomyces cerevisiae has been constructed. The model predicts batch growth of the yeast on a variety of nitrogen sources and at variable dissolved oxygen concentrations, and the slowing of growth through the combined effects of nutrient exhaustion and product inhibition in the later stages of the fermentation. The model has been designed to be readily amenable to the addition of aspects of yeast physiology not currently included.

Dynamic Changes in Populations of the Activated Sludge Community: Effects of Dissolved Oxygen Variations

A simple dynamic mathematical model was developed to describe a microbial system composed of two populations: filamentous and floc-forming bacteria. Growth rates of both microorganisms depend on the concentration of a single organic substrate and on the dissolved oxygen (DO) concentration. Biokinetic parameters were estimated from the experimental data reported in the literature. Using these parameters population changes were examined under variable DO concentrations. The comparison of the numerical simulations and experimental data indicated a possibility of controlling population composition within a desired range through periodic changes in DO concentration. The existence of a single common trajectory on phase plane guarantees the stability of the designed cycle.

Precise Radiotracer Measurement of the Rate of Sediment Reworking by Stylodrilus Heringianus and the Effects of Variable Dissolved Oxygen Concentrations

A radiotracer method is used to determine the rate of sediment reworking by the worm, Stylodrilus heringianus, an organism common in profundal sediments of the Great Lakes. A submillimeter layer of sediment labeled with gamma-emitting cesium-137 is added to the surface of worm-inoculated sediments contained in cells of rectangular cross-section placed in an insulated aquarium (10° C). This layer, progressively buried by the conveyor belt feeding action of the worms, is located by scanning the cell with a well-collimated detector mounted on a hydraulically actuated elevator. Precision in locating the marked layer is greatly enhanced by Gaussian profile analysis developed in this study. Relative uncertainties in location of less than 0.01 cm allow reworking rates as low as 10 −3cm/hr to be determined in 1 to 2 days. The effect of variable dissolved oxygen (D.O.) concentrations on sediment reworking rates was determined by adjusting the relative proportions of N 2 and O 2 introduced into the aquarium through a continuous bubbler system. In a cell subject to gradual reductions in D.O. (about 1 mg/L every 50 hours) from saturation concentration (10.6 mg/L), sediment reworking rates remained virtually constant down to 1 mg/L. Below this value, the rate decreased, approaching zero at 0.2 mg/L. On increasing D. O. values above about 4 mg/L, reworking returned to the initial rate. Gradual decreases in D.O. induced a reversible dormant mode in these organisms. In cells subject to coarse D.O. changes (3.7 to 8.8 mg/L per step), reworking stopped at around 4 to 5 mg/L and did not resume following reinstatement of saturation values for up to 18 days. In all cases more than 70% of worms were alive at the end of the experiment. This study illustrates the potential of the gamma scan system for quantitative behavioral bioassay of the interactions of zoobenthos with altered sedimentary environments.

Lack of in vitro oxidation of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the presence of laccase from Polyporus versicolor fungus

An investigation has been carried out to assess whether Polyporus versicolor laccase could catalyze in vitro transformation of 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD) under a number of different experimental conditions of incubation including homogeneous or heterogeneous phase, variable durations, addition of phenol, variable dissolved oxygen concentrations and TCDD/laccase ratios. No significant degradation of TCDD was detected.