scholarly journals Hydrodynamic and Biochemical Impacts on the Development of Hypoxia in the Louisiana–Texas Shelf Part I: Numerical Modeling and Hypoxia Mechanisms

2022 ◽  
Author(s):  
Yanda Ou ◽  
Z. George Xue
Keyword(s):  
Dissolved Oxygen ◽  
Three Dimensional ◽  
Biogeochemical Model ◽  
The West ◽  
Frequency Distributions ◽  
In Situ Data ◽  
Hypoxic Area ◽  
Water Stratification ◽  
Do Concentration ◽  
Hypoxic Volume

Abstract. A three-dimensional coupled hydrodynamic–biogeochemical model with N, P, Si cycles and multiple phytoplankton and zooplankton functional groups was developed and applied to the Gulf of Mexico to study bottom dissolved oxygen dynamics. A 15-year hindcast was achieved covering the period of 2006–2020. Extensive model validation against in situ data demonstrates that the model is capable of reproducing vertical distributions of dissolved oxygen (DO), frequency distributions of hypoxia thickness, spatial distributions of bottom DO concentration and interannual variations of hypoxic area. The impacts of river plume and along-shore currents on bottom DO dynamics were examined based on multiyear bottom DO climatology, the corresponding long-term trends, and interannual variability. Model results suggest that mechanisms of bottom hypoxia developments are different between the west and east Louisiana–Texas Shelf waters. The mid-Atchafalaya nearshore (10–20 m) region firstly suffers from hypoxia in May, followed by the west-Mississippi nearshore region in June. Hypoxic waters expand in the following months and eventually merge in August. Sediment oxygen consumption (SOC) and water stratification (measured by potential energy anomaly, PEA) are two main factors modulating the variability of bottom DO concentration. Generalized Boosted Regression Models provide analysis of the relative importance of PEA and SOC. The analysis indicates that SOC is the main regulator in nearshore regions, and water stratification outcompetes the sedimentary biochemical processes in the offshore (20–50 m) regions. A strong quadratic relationship was found between hypoxic volume and hypoxic area, which suggests that the volume mostly results from the low DO in bottom water and can be potentially estimated based on the hypoxic area.

scholarly journals VERIFICATION OF PISCES DISSOLVED OXYGEN MODEL USING IN SITU MEASUREMENT IN BIAK, ROTE, AND TANIMBAR SEAS, INDONESIA

2017 ◽  
Vol 14 (1) ◽  
pp. 37 ◽  
Author(s):  
Armyanda Tussadiah ◽  
Joko Subandriyo ◽  
Sari Novita ◽  
Widodo Setyo Pranowo
Keyword(s):  
Standard Deviation ◽  
Linear Regression ◽  
Dissolved Oxygen ◽  
Primary Data ◽  
Biogeochemical Model ◽  
Infrastructure Development ◽  
Indonesian Seas ◽  
In Situ Data ◽  
A Minor

Dissolved oxygen (DO) is one of the most chemical primary data in supported life for marine organisms. Ministry of Marine Affairs and Fisheries Republic of Indonesia through Infrastructure Development for Space Oceanography (INDESO) Project provides dissolved oxygen data services in Indonesian Seas for 7 days backward and 10 days ahead (9,25 km x 9.25 km, 1 daily). The data based on Biogeochemical model (PISCES) coupled with hydrodynamic model (NEMO), with input data from satellite acquisition. This study investigated the performance and accuracy of dissolved oxygen from PISCES model, by comparing with the measurement in situ data in Indonesian Seas specifically in three outermost islands of Indonesia (Biak Island, Rote Island, and Tanimbar Island). Results of standard deviation values between in situ DO and model are around two (St.dev ± 2). Based on the calculation of linear regression between in situ DO with the standard deviation obtained a high determinant coefficient, greater than 0.9 (R2 ≥ 0.9). Furthermore, RMSE calculation showed a minor error, less than 0.05. These results showed that the equation of the linear regression might be used as a correction equation to gain the verified dissolved oxygen.

scholarly journals Electron generation in water induced by magnetic effect and its impact on dissolved oxygen concentration

2021 ◽  
Vol 31 (1) ◽  
Author(s):  
Augustine Chung Wei Yap ◽  
Hwang Sheng Lee ◽  
Joo Ling Loo ◽  
Nuruol Syuhadaa Mohd
Keyword(s):  
Water Quality ◽  
Hydrogen Bonding ◽  
Dissolved Oxygen ◽  
Electron Density ◽  
Water Flow ◽  
Magnetic Effect ◽  
Water Quality Control ◽  
Electron Generation ◽  
Magnetic Effects ◽  
Do Concentration

AbstractpH, oxidation-reduction potential (ORP) and dissolved oxygen (DO) concentration are important parameters in water quality surveillance and treatment. The changes of these parameters are associated with electron density in water. Several techniques including electrolysis and catalysis which require redox reactions and electron exchange are employed to improve these parameters. In recent years, studies reported that magnetic effects can impart considerable changes on the pH, ORP and DO concentration of water. However, the correlation between electron density and magnetic effects on these parameters has yet to be disclosed despite the fact that increased electron density in water could improve water’s reductive properties, heat capacity and hydrogen bonding characteristics. In this study, the magnetic effects on pH, ORP and DO concentration were investigated using different magnets arrangements and water flow rates based on reversed electric motor principle. Results showed that the improvement of pH, ORP and DO concentration from 5.40–5.42 to 5.58–5.62 (+ 3.5%), 392 to 365 mV (− 6.9%), and 7.30 to 7.71 mg L− 1 (+ 5.6%), respectively were achieved using combined variables of non-reversed polarity magnet arrangement (1000–1500 G magnetic strength) and water flow rate of 0.1–0.5 mL s− 1. Such decrement in ORP value also corresponded to 8.0 × 1013 number of electron generation in water. Furthermore, Raman analysis revealed that magnetic effect could strengthen the intermolecular hydrogen bonding of water molecules and favor formation of smaller water clusters. The findings of this study could contribute to potential applications in aquaculture, water quality control and treatment of cancer attributed to free radical induced-oxidative stress.

scholarly journals Limnology of Merbok estuary, Kedah, Malaysia

2015 ◽  
Vol 41 (1) ◽  
pp. 13-19
Author(s):  
Kaniz Fatema ◽  
Wan Maznah Wan Omar ◽  
Mansor Mat Isa
Keyword(s):  
Water Quality ◽  
Dissolved Oxygen ◽  
Suspended Solids ◽  
Total Suspended Solids ◽  
Quality Parameters ◽  
The Other ◽  
Wet Season ◽  
Hand Temperature ◽  
Do Concentration ◽  
Merbok Estuary

Water quality in three different stations of Merbok estuary was investigated limnologically from October, 2010 to September, 2011. Water temperature, transparency and total suspended solids (TSS) varied from 27.45 - 30.450C, 7.5 - 120 cm and 10 -140 mg/l, respectively. Dissolved Oxygen (DO) concentration ranged from 1.22-10.8 mg/l, while salinity ranged from 3.5-35.00 ppt. pH and conductivity ranged from 6.35 - 8.25 and 40 - 380 ?S/cm, respectively. Kruskal Wallis H test shows that water quality parameters were significantly different among the sampling months and stations (p<0.05). This study revealed that DO, salinity, conductivity and transparency were higher in wet season and TSS was higher in dry season. On the other hand, temperature and pH did not follow any seasonal trends.Bangladesh J. Zool. 41(1): 13-19, 2013

scholarly journals From east to west, can feminist legal strategies be transformative? Post-disaster to everyday times of crisis

2019 ◽  
Vol 10 (2) ◽  
pp. 247-268
Author(s):  
Jane Krishnadas
Keyword(s):  
Three Dimensional ◽  
Field Research ◽  
Community Relations ◽  
Access To Justice ◽  
The West ◽  
Legal Subject ◽  
Agents Of Change ◽  
Legal Strategies ◽  
The Uk ◽  
Post Disaster

AbstractThis article engages with a key question raised by feminist legal scholars from the east to the west: whether women should or should not engage in rights strategies? Are rights systematically exercised to reproduce patriarchal, dominant sites of justice, or do rights constitute a multiple and relational force which may transform sites of justice? The experience of women’s engagements with law in South Asia has created a diversity of critical legal knowledge and scholarship reflecting the pluralism of both women’s identities and needs based on caste, religion, class and sexuality across an array of legal spaces from the family, community and state. Women in South Asian scholarship have complicated the notion of the homogenous legal subject and the static dominant site of justice. In this article I return to my underpinning field research whilst living and working within an earthquake affected area of Maharashtra, India in the post-crisis rehabilitation period (1993–1998). This research explored how women exercised their rights to reconstruct lives at different tiers of justice: in public policy, private legislation and the non-formal sphere of community relations to deconstruct the concept of rights existing within a static framework of justice. Drawing upon feminist discourse across the east to the west, I have analysed the role of rights in post-disaster sites to understand how women move from victims to survivors, beneficiaries to contributors and objects to agents of change to inform contemporary research on how women in post-domestic violence situations may exercise rights to reconstruct their lives in times of crisis in the UK. Through this analysis I argue that rights may be empowering if one can exercise one’s right to identity as agency, resources as capacity and location as mobility, as a three dimensional strategy to transform the framework in which one is situated. Over the last decade, I have actively applied this transformative methodology to create an alternative relational, intersectional and holistic legal paradigm, to transform sites of justice, in times of every day crisis, through the CLOCK/ All India Access to Justice Strategy.

Reoxygenation Rate for Airlift Inner Circulation Reactor

2013 ◽  
Vol 726-731 ◽  
pp. 1926-1929
Author(s):  
Ke Wu Pi ◽  
Min Xia ◽  
Shi Shi ◽  
Qu Xiao
Keyword(s):  
Dissolved Oxygen ◽  
Aeration Rate ◽  
Airlift Reactor ◽  
Liquid Level ◽  
Aeration Tank ◽  
Do Concentration

Airlift inner circulation reactor (AICR) consisting of beaker and built-in aeration tank was introduced in this paper. The Dissolved oxygen recovery (RDO) was highly influenced by the ratios of the height of built-in aeration tank to the height of liquid level in reactor (Rh/H), the diameter of built-in aeration tank to the diameter of the reactor (Rd/D) and aeration rate (QN). Average RDO of 24.25 m.gm-3.s-s and DO concentration of 8.97mg.l-1 were obtained at Rd/D=0.47, Rh/H=0.68 and QN =1.0m3.m-3.min-1 for aerating 370s at 17°C. The total transferred oxygen in 4L deoxidized water reached 35.89mg, which had an increase by 11.15% than that of the traditional airlift reactor (AR). The DO concentration was 88.33-9.34mg.l-1 for AICR, but it’s only 7.71-8.58mg.l-1 for AR.

scholarly journals Challenges associated with modeling low-oxygen waters in Chesapeake Bay: a multiple model comparison

2016 ◽  
Vol 13 (7) ◽  
pp. 2011-2028 ◽  
Author(s):  
Isaac D. Irby ◽  
Marjorie A. M. Friedrichs ◽  
Carl T. Friedrichs ◽  
Aaron J. Bever ◽  
Raleigh R. Hood ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Chesapeake Bay ◽  
Mixed Layer ◽  
Model Comparison ◽  
Three Dimensional ◽  
Surface Mixed Layer ◽  
Multiple Model ◽  
Low Oxygen ◽  
Mixing Depth ◽  
Biogeochemical Models

Abstract. As three-dimensional (3-D) aquatic ecosystem models are used more frequently for operational water quality forecasts and ecological management decisions, it is important to understand the relative strengths and limitations of existing 3-D models of varying spatial resolution and biogeochemical complexity. To this end, 2-year simulations of the Chesapeake Bay from eight hydrodynamic-oxygen models have been statistically compared to each other and to historical monitoring data. Results show that although models have difficulty resolving the variables typically thought to be the main drivers of dissolved oxygen variability (stratification, nutrients, and chlorophyll), all eight models have significant skill in reproducing the mean and seasonal variability of dissolved oxygen. In addition, models with constant net respiration rates independent of nutrient supply and temperature reproduced observed dissolved oxygen concentrations about as well as much more complex, nutrient-dependent biogeochemical models. This finding has significant ramifications for short-term hypoxia forecasts in the Chesapeake Bay, which may be possible with very simple oxygen parameterizations, in contrast to the more complex full biogeochemical models required for scenario-based forecasting. However, models have difficulty simulating correct density and oxygen mixed layer depths, which are important ecologically in terms of habitat compression. Observations indicate a much stronger correlation between the depths of the top of the pycnocline and oxycline than between their maximum vertical gradients, highlighting the importance of the mixing depth in defining the region of aerobic habitat in the Chesapeake Bay when low-oxygen bottom waters are present. Improvement in hypoxia simulations will thus depend more on the ability of models to reproduce the correct mean and variability of the depth of the physically driven surface mixed layer than the precise magnitude of the vertical density gradient.

scholarly journals Electron generation in water induced by magnetic effect and its impact on dissolved oxygen concentration

2021 ◽  
Author(s):  
Augustine Chung Wei Yap ◽  
Hwang Sheng Lee ◽  
Joo Ling Loo ◽  
Nuruol Syuhadaa Mohd
Keyword(s):  
Water Quality ◽  
Hydrogen Bonding ◽  
Dissolved Oxygen ◽  
Electron Density ◽  
Water Flow ◽  
Magnetic Effect ◽  
Water Quality Control ◽  
Electron Generation ◽  
Magnetic Effects ◽  
Do Concentration

Abstract pH, oxidation-reduction potential (ORP) and dissolved oxygen (DO) concentration are important parameters in water quality surveillance and treatment. The changes of these parameters are associated with electron density in water. Several techniques including electrolysis and catalysis which require redox reactions and electron exchange are employed to improve these parameters. In recent years, studies reported that magnetic effects can impart considerable changes on the pH, ORP and DO concentration of water. However, the correlation between electron density and magnetic effects on these parameters has yet to be disclosed despite the fact that increased electron density in water could improve water’s reductive properties, heat capacity and hydrogen bonding characteristics. In this study, the magnetic effects on pH, ORP and DO concentration were investigated using different magnets arrangements and water flow rates based on reversed electric motor principle. Results showed that the improvement of pH, ORP and DO concentration from 5.40–5.42 to 5.58–5.62 (+ 3.5%), 392 to 365 mV (-6.9%), and 7.30 to 7.71 mg L− 1 (+ 5.6%), respectively were achieved using combined variables of non-reversed polarity magnet arrangement (1000–1500 G magnetic strength) and water flow rate of 0.1–0.5 mL s− 1. Such decrement in ORP value also corresponded to 8.0 × 1013 number of electron generation in water. Furthermore, Raman analysis revealed that magnetic effect could strengthen the intermolecular hydrogen bonding of water molecules and favor formation of smaller water clusters. The findings of this study could contribute to potential applications in aquaculture, water quality control and treatment of cancer attributed to free radical induced-oxidative stress.

scholarly journals Hydrodynamic Drivers of Dissolved Oxygen Variability within a Tidal Creek in Myrtle Beach, South Carolina

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1723 ◽  
Author(s):  
Douglas M. Pastore ◽  
Richard N. Peterson ◽  
Diane B. Fribance ◽  
Richard Viso ◽  
Erin E. Hackett
Keyword(s):  
Water Quality ◽  
South Carolina ◽  
Dissolved Oxygen ◽  
Tidal Creek ◽  
Water Levels ◽  
Beach Erosion ◽  
Shear Stresses ◽  
Myrtle Beach ◽  
Do Concentration ◽  
Face Morphology

Beach erosion and water quality degradation have been observed in Singleton Swash, a tidal creek that traverses the beach-face connecting land and ocean in Myrtle Beach, SC. The objective of this study in Singleton Swash is to explore relationships between water quality and hydrodynamics, where the latter are influenced by beach face morphology. We measure water velocities, water levels, and dissolved oxygen concentrations (DO) (a proxy for water quality) and apply correlation analysis to examine the relationships between physical processes and dissolved oxygen variations. Results show that larger tidal ranges are associated with higher mean levels of DO in the tidal creek. The larger tidal ranges are linked to larger magnitude currents, which increase both the DO transport via larger fluxes of oxygenated oceanic water into the swash and the magnitude of Reynolds shear stresses; due to tidal asymmetries, flood currents are stronger than ebb currents in this system. Based on these results, it is concluded that the combined transport of oxygenated waters into the tidal creek from the ocean on large flood tides and subsequent mixing due to large Reynolds shear stresses result in the observed net DO concentration increases in the creek over tidal cycles.

scholarly journals Effects of Physical Forcing on Summertime Hypoxia and Oxygen Dynamics in the Pearl River Estuary

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2080 ◽  
Author(s):  
Huang ◽  
Hu ◽  
Li ◽  
Wang ◽  
Xu ◽  
...  
Keyword(s):  
River Discharge ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
Vertical Diffusion ◽  
Physical Forcing ◽  
The Pearl River Estuary ◽  
Hypoxic Area ◽  
Water Stratification ◽  
The Pearl River

A validated hydrodynamic-biogeochemical model was applied to investigate the effects of physical forcing (i.e., river discharge, winds, and tides) on the summertime dissolved oxygen (DO) dynamics and hypoxia (DO < 3 mg L−1) in the Pearl River estuary (PRE), based on a suite of model sensitivity experiments. Compared with the base model run in 2006 (a wet year), the simulated hypoxic area in the moderate year (with 75% of river discharge of the base run) and the dry year scenario (with 50% of river discharge of the base run) was reduced by ~30% and ~60%, respectively. This is because under the lower river discharge levels, less particulate organic matter was delivered to the estuary that subsequently alleviated the oxygen demand at the water–sediment interface, and in the meantime, the water stratification strength was decreased, which facilitated the vertical diffusion of DO. Regarding the effect of winds, the highly varying and intermittent strong winds had a significant impact on the replenishment of bottom DO by disrupting water stratification and thus inhibiting the development of hypoxia. Sensitivity experiments showed that the hypoxic area and volume were both remarkably increased in the low wind scenario (with a bottom hypoxic zone extending from the Modaomen sub-estuary to the western shoal in Lingdingyang Bay), whereas hypoxia was almost absent in the strong wind scenario. The DO budget indicated that winds altered the bottom DO mostly by affecting the DO flux due to vertical diffusion and horizontal advection, and had a limited influence on the DO consumption processes. Moreover, the DO concentration exhibited remarkable fluctuations over the spring-neap tidal cycles due to the significant differences in vertical diffusion. The results of a tide-sensitivity experiment indicated that without tide forcing, most of the shallow areas (average water depth < 5 m) in the PRE experienced severe and persistent hypoxia. The tides mainly enhanced mixing in the shallow areas, which led to higher vertical diffusion and enhanced replenishment of bottom DO.

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