Sediment oxygen demand(SOD)is a major contributor to hypolimnetic oxygen depletion and the release of internal nutrient loading.By measuring the SOD in experimental chambers using in both dissolved oxygen(DO)depletion...Sediment oxygen demand(SOD)is a major contributor to hypolimnetic oxygen depletion and the release of internal nutrient loading.By measuring the SOD in experimental chambers using in both dissolved oxygen(DO)depletion and diffusional oxygen transfer methods,a model of SOD for a sediment bed with water current-induced turbulence was presented.An experimental study was also performed using near-sediment vertical DO profiles and correlated hydraulic parameters stimulated using a computational fluid dynamics model to determine how turbulences and DO concentrations in the overlying water affects SOD and diffusive boundary layer thickness.The dependence of the oxygen transfer coefficient and diffusive boundary layer on hydraulic parameters was quantified,and the SOD was expressed as a function of the shear velocity and the bulk DO concentrations.Theoretical predictions were validated using microelectrode measurements in a series of laboratory experiments.This study found that flow over the sediment surface caused an increase in SOD,attributed to enhanced sediment oxygen uptake and reduced substances fluxes,i.e.,for a constant maximum biological oxygen consumption rate,an increased current over the sediment could increase the SOD by 4.5 times compared to stagnant water.These results highlight the importance of considering current-induced SOD increases when designing and implementing aeration/artificial mixing strategies.展开更多
This paper presents a method for in situ determining sediment oxygen demand (SOD) in cultivation pond. This method based on sediment surface structure, temperature, and other determining conditions like those in shrim...This paper presents a method for in situ determining sediment oxygen demand (SOD) in cultivation pond. This method based on sediment surface structure, temperature, and other determining conditions like those in shrimp cultivation environments, overcomes defects of old methods and provides more accurate estimation of SOD’s effect on dissolved oxygen in culture waters. Our experiment shows that the sediment surface structure and temperature had important effect on SOD in culture water. Different SOD values were derived from different parts of oxygen consumption curves of sediment, because the curves were not linear. According to the oxygen consumption curves of sediment and saturated DO in culture water, it was thought more suitable to calculate SOD with dissolved oxygen reduction from 5.0 to 2.0 mg/l. This method to determine the SOD of shrimp ponds yielded satisfactory results.展开更多
Various water quality parameters of a leachate pond at an offshore municipal solid waste disposal site were monitored. The pH, dissolved oxygen (DO), and water temperature at the bottom of the leachate pond were measu...Various water quality parameters of a leachate pond at an offshore municipal solid waste disposal site were monitored. The pH, dissolved oxygen (DO), and water temperature at the bottom of the leachate pond were measured during Sep. (the 1st period) and Nov.-Dec. (the 2nd period) of 2011. The results suggested that the stratification of water temperature in the pond had gradually broken down due to convection occurring between the end of the 1st period and the 2nd period. The pH was almost constant at 10 - 11 during the 1st period and was approximately 11.5 during the 2nd period. The DO was almost zero during both periods. An anaerobic batch experiment with sampled sediment was undertaken to elucidate the mechanism of material leaching from the sediment. DO decreased under all experimental conditions. With respect to oxidation reduction potential (ORP) and total sulfide in addition to DO, the condition most closely mimicking that of the site became the most anaerobic. The average sediment oxygen demand, SODave, was calculated using a brief numerical model based on batch experiment data. The SODave was 1114.7 mg/m2/d, indicating that at least 434 g/d of oxygen must be supplied to the leachate pond to maintain the DO.展开更多
Nitrobenzene is an important raw material and product, which presents a heavy threat to the ecosystem. The potential impacts of nitrobenzene on sediment oxygen demand （SOD） were studied in lake sediment simulating r...Nitrobenzene is an important raw material and product, which presents a heavy threat to the ecosystem. The potential impacts of nitrobenzene on sediment oxygen demand （SOD） were studied in lake sediment simulating reactors receiving relatively low inputs of nitrobenzene. Oxygen microprofiles were measured in these sediment reactors using microelectrodes. After an initial microprofile measurement as a control, nitrobenzene was added to the overlying water resulting in concentrations of 0, 50, 100, and 150 μg/L. Microprofiles were measured on day 1, 2, 4 and 7 following the addition of nitrobenzene. SODs were determined from the microprofiles using a reaction-diffusion model. Results showed that the SODs increased relative to the initial values measured in the pre-treatment period in reactors exposed to all nitrobenzene concentrations on day 1. However, the values decreased gradually on the following days, which eventually resulted in a 50% loss in SODs after 7 days of exposure to nitrobenzene in all reactors. In addition, the inhibition effect of nitrobenzene on SOD exhibited a weak relationship with its concentration. The microscopic observation and count of algae in the sediment showed that the exposure to nitrobenzene did not change the composition of algae greatly, however, it decreased the number of dominant algae species sharply after 7 days of exposure. These results suggested that nitrobenzene could significantly alter SOD in lakes, which could ultimately affect the pollutant recovery in aquatic-sediment systems.展开更多
Sediment is a sink for organic materials, nutrients and heavy metals and sediment condition affects the overlying water Though Serin River is a source of drinking water, agricultural and waste disposal activities in t...Sediment is a sink for organic materials, nutrients and heavy metals and sediment condition affects the overlying water Though Serin River is a source of drinking water, agricultural and waste disposal activities in the watershed may impact the sediment of the river. Therefore, the objective of this study was to investigate the organic matter, nutrients and heavy metals in the sediment of the Serin River. Five stations were selected for sediment sample collection. Results of the study show that organic matter （OM） ranged from 0.7% to 5.9%, TP was 100 -366 （mg/kg）, TAN was 16-141 （mg/kg）, TON was 550-3019（mg/kg）, and TKN was 566-3160 （mg/kg）. Sediment oxygen demand （SOD20） ranged from 5.6 to 14.2 （g O2/m^2/d）. Among the five stations OM, TKN, and SOD of the sediment were second highest at the two stations downstream of animal （fish, chicken and pig） farming. TP and TAN were the second highest at the station downstream of fish farming and third highest at the station downstream of pig farming. Zn, Cu and Cd ranged from 132-357 （mg/kg）, 26.7-96.7 （mg/kg） and 4.0-19.3（mg/kg）. According to USEPA guideline, sediments at four stations were heavily polluted with Zn, Cu and Cd whereas the station that was farthest upstream, near a village, was slightly polluted with Zn and Cu. This study indicates that animal farming has an impact on the organic matter content, nutrients （N and P）, oxygen demand and heavy metals of the sediment. Motor vehicles and discarded e-waste also contributed to the heavy metals in the sediment. Farm effluents and storm water should be treated and e-waste recycled to protect the water quality of the river for its designated use.展开更多
Water-level reduction frequently occurs in deep reservoirs,but its effect on dissolved oxygen concentration is not well understood.In this study we used a well-established water qual-itymodel to illustrate effects of ...Water-level reduction frequently occurs in deep reservoirs,but its effect on dissolved oxygen concentration is not well understood.In this study we used a well-established water qual-itymodel to illustrate effects of water level dynamics on oxygen concentration in Rappbode Reservoir,Germany.We then systematically elucidated the potential of selectivewithdrawal to control hypoxia under changing water levels.Our results documented a gradual decrease of hypolimnetic oxygen concentration under decreasing water level,and hypoxia occurred when the initial level was lower than 410 m a.s.l(71 m relative to the reservoir bottom).We also suggested that changes of hypoxic region,under increasing hypolimnetic withdrawal discharge,followed a unimodal trajectory with themaximum hypoxic area projected under the discharge between 3 m^(3)/sec and 4 m^(3)/sec.Besides,our results illustrated the extent of hypoxia was most effectively inhibited if the withdrawal strategy was applied at the end of stratification with the outlet elevation at the deepest part of the reservoir.Moreover,hy-poxia can be totally avoided under a hybrid elevation withdrawal strategy using surface withdrawal during early and mid stratification,and deep withdrawal at the end of strat-ification.We further confirmed the decisive role of thermal structure in the formation of hypoxia under water-level reduction and withdrawal strategies.We believe the conclusions from this study can be applied to many deep waters in the temperate zone,and the results should guide stakeholders to mitigate negative impacts of hypoxia on aquatic ecosystems.展开更多
基金supported by the Natural Science Foundation of China(No.51979217)。
文摘Sediment oxygen demand(SOD)is a major contributor to hypolimnetic oxygen depletion and the release of internal nutrient loading.By measuring the SOD in experimental chambers using in both dissolved oxygen(DO)depletion and diffusional oxygen transfer methods,a model of SOD for a sediment bed with water current-induced turbulence was presented.An experimental study was also performed using near-sediment vertical DO profiles and correlated hydraulic parameters stimulated using a computational fluid dynamics model to determine how turbulences and DO concentrations in the overlying water affects SOD and diffusive boundary layer thickness.The dependence of the oxygen transfer coefficient and diffusive boundary layer on hydraulic parameters was quantified,and the SOD was expressed as a function of the shear velocity and the bulk DO concentrations.Theoretical predictions were validated using microelectrode measurements in a series of laboratory experiments.This study found that flow over the sediment surface caused an increase in SOD,attributed to enhanced sediment oxygen uptake and reduced substances fluxes,i.e.,for a constant maximum biological oxygen consumption rate,an increased current over the sediment could increase the SOD by 4.5 times compared to stagnant water.These results highlight the importance of considering current-induced SOD increases when designing and implementing aeration/artificial mixing strategies.
文摘This paper presents a method for in situ determining sediment oxygen demand (SOD) in cultivation pond. This method based on sediment surface structure, temperature, and other determining conditions like those in shrimp cultivation environments, overcomes defects of old methods and provides more accurate estimation of SOD’s effect on dissolved oxygen in culture waters. Our experiment shows that the sediment surface structure and temperature had important effect on SOD in culture water. Different SOD values were derived from different parts of oxygen consumption curves of sediment, because the curves were not linear. According to the oxygen consumption curves of sediment and saturated DO in culture water, it was thought more suitable to calculate SOD with dissolved oxygen reduction from 5.0 to 2.0 mg/l. This method to determine the SOD of shrimp ponds yielded satisfactory results.
文摘Various water quality parameters of a leachate pond at an offshore municipal solid waste disposal site were monitored. The pH, dissolved oxygen (DO), and water temperature at the bottom of the leachate pond were measured during Sep. (the 1st period) and Nov.-Dec. (the 2nd period) of 2011. The results suggested that the stratification of water temperature in the pond had gradually broken down due to convection occurring between the end of the 1st period and the 2nd period. The pH was almost constant at 10 - 11 during the 1st period and was approximately 11.5 during the 2nd period. The DO was almost zero during both periods. An anaerobic batch experiment with sampled sediment was undertaken to elucidate the mechanism of material leaching from the sediment. DO decreased under all experimental conditions. With respect to oxidation reduction potential (ORP) and total sulfide in addition to DO, the condition most closely mimicking that of the site became the most anaerobic. The average sediment oxygen demand, SODave, was calculated using a brief numerical model based on batch experiment data. The SODave was 1114.7 mg/m2/d, indicating that at least 434 g/d of oxygen must be supplied to the leachate pond to maintain the DO.
基金supported by the China Postdoctoral Science Foundation Funded Project (No. 20080430046, 200801093)
文摘Nitrobenzene is an important raw material and product, which presents a heavy threat to the ecosystem. The potential impacts of nitrobenzene on sediment oxygen demand （SOD） were studied in lake sediment simulating reactors receiving relatively low inputs of nitrobenzene. Oxygen microprofiles were measured in these sediment reactors using microelectrodes. After an initial microprofile measurement as a control, nitrobenzene was added to the overlying water resulting in concentrations of 0, 50, 100, and 150 μg/L. Microprofiles were measured on day 1, 2, 4 and 7 following the addition of nitrobenzene. SODs were determined from the microprofiles using a reaction-diffusion model. Results showed that the SODs increased relative to the initial values measured in the pre-treatment period in reactors exposed to all nitrobenzene concentrations on day 1. However, the values decreased gradually on the following days, which eventually resulted in a 50% loss in SODs after 7 days of exposure to nitrobenzene in all reactors. In addition, the inhibition effect of nitrobenzene on SOD exhibited a weak relationship with its concentration. The microscopic observation and count of algae in the sediment showed that the exposure to nitrobenzene did not change the composition of algae greatly, however, it decreased the number of dominant algae species sharply after 7 days of exposure. These results suggested that nitrobenzene could significantly alter SOD in lakes, which could ultimately affect the pollutant recovery in aquatic-sediment systems.
文摘Sediment is a sink for organic materials, nutrients and heavy metals and sediment condition affects the overlying water Though Serin River is a source of drinking water, agricultural and waste disposal activities in the watershed may impact the sediment of the river. Therefore, the objective of this study was to investigate the organic matter, nutrients and heavy metals in the sediment of the Serin River. Five stations were selected for sediment sample collection. Results of the study show that organic matter （OM） ranged from 0.7% to 5.9%, TP was 100 -366 （mg/kg）, TAN was 16-141 （mg/kg）, TON was 550-3019（mg/kg）, and TKN was 566-3160 （mg/kg）. Sediment oxygen demand （SOD20） ranged from 5.6 to 14.2 （g O2/m^2/d）. Among the five stations OM, TKN, and SOD of the sediment were second highest at the two stations downstream of animal （fish, chicken and pig） farming. TP and TAN were the second highest at the station downstream of fish farming and third highest at the station downstream of pig farming. Zn, Cu and Cd ranged from 132-357 （mg/kg）, 26.7-96.7 （mg/kg） and 4.0-19.3（mg/kg）. According to USEPA guideline, sediments at four stations were heavily polluted with Zn, Cu and Cd whereas the station that was farthest upstream, near a village, was slightly polluted with Zn and Cu. This study indicates that animal farming has an impact on the organic matter content, nutrients （N and P）, oxygen demand and heavy metals of the sediment. Motor vehicles and discarded e-waste also contributed to the heavy metals in the sediment. Farm effluents and storm water should be treated and e-waste recycled to protect the water quality of the river for its designated use.
基金supported by the German Research Founda-tion(DFG,grant RI 2040/4-1)the InventWater ITN(Inventive forecasting tools for adapting water quality management to a new climate)through the European Union’s Horizon 2020 research,innovation program under the Marie Skłodowska-Curie grant agreement No.956623 and UFZ Program Integra-tion Budget+3 种基金Chenxi Mi acknowledges the financial support from the National Natural Science Foundation of China(No.42107060)Liaoning Provincial Doctoral Research Startup Fund Project(No.2022-BS-174)supported by the“Xingliao Talents Plan”science and technology in-novation leading talents project of Liaoning Province(No.XLYC2002054)the National Key Research and Develop-ment Program of China(NO.2022YFF1301000-4).
文摘Water-level reduction frequently occurs in deep reservoirs,but its effect on dissolved oxygen concentration is not well understood.In this study we used a well-established water qual-itymodel to illustrate effects of water level dynamics on oxygen concentration in Rappbode Reservoir,Germany.We then systematically elucidated the potential of selectivewithdrawal to control hypoxia under changing water levels.Our results documented a gradual decrease of hypolimnetic oxygen concentration under decreasing water level,and hypoxia occurred when the initial level was lower than 410 m a.s.l(71 m relative to the reservoir bottom).We also suggested that changes of hypoxic region,under increasing hypolimnetic withdrawal discharge,followed a unimodal trajectory with themaximum hypoxic area projected under the discharge between 3 m^(3)/sec and 4 m^(3)/sec.Besides,our results illustrated the extent of hypoxia was most effectively inhibited if the withdrawal strategy was applied at the end of stratification with the outlet elevation at the deepest part of the reservoir.Moreover,hy-poxia can be totally avoided under a hybrid elevation withdrawal strategy using surface withdrawal during early and mid stratification,and deep withdrawal at the end of strat-ification.We further confirmed the decisive role of thermal structure in the formation of hypoxia under water-level reduction and withdrawal strategies.We believe the conclusions from this study can be applied to many deep waters in the temperate zone,and the results should guide stakeholders to mitigate negative impacts of hypoxia on aquatic ecosystems.
