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
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
Biological activities of marine benthos such as burrowing and feeding may change sediment characteristics.We conducted three experiments to examine the potential of using juveniles of a spoon worm Urechis unicinctus t...Biological activities of marine benthos such as burrowing and feeding may change sediment characteristics.We conducted three experiments to examine the potential of using juveniles of a spoon worm Urechis unicinctus to improve the quality of organically contaminated coastal sediment.Sediment samples were collected from a site that was heavily contaminated with organic matter (Seonso) and two sites that were clean (Myo-do,Dolsan-do).Urechis juveniles,obtained by artificial fertilization and cultured in the laboratory,were introduced to the sediment (weight 3 kg,depth 10 cm) at a density of 500 individuals per aquarium (length 50 cm,width 35 cm,height 30 cm) (Experiment 1),or at densities ranging from 100 to 900 individuals per beaker (Experiment 2).To examine how sediment contamination can be modified by the effects of Urechis,500 individuals (per aquarium) were exposed to the Seonso contaminated sediment that had been mixed with 0-100% clean sand (Experiment 3).Each experiment lasted two months and sediment samples were collected every 15 d to determine the several indexes of sediment quality,which included acid volatile sulfide (AVS),chemical oxygen demand (COD) and total ignition loss (TIL).In Experiment 1,the existence of Urechis did not result in significant changes in quality indexes in the sediments collected from Myo-do,Dolsan-do.However,AVS,COD and TIL of the Seonso sediment all decreased significantly after co-incubation with Urechis juveniles for 30 to 45 d.Experiment 2 showed that a density of at least 300 juveniles per beaker was necessary to significantly reduce all three quality indexes,and the magnitude of reduction was positively correlated with juvenile density.Experiment 3 revealed that Urechis juveniles were effective in reducing the AVS,COD and TIL of the Seonso sediment that had been mixed with 60%,80%,and 80% of clean sand,respectively.The results of the present study therefore indicated that juveniles of this spoon worm have the potential to be used to improve the quality of organically contaminated sediment in coastal waters.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
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 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Biological activities of marine benthos such as burrowing and feeding may change sediment characteristics.We conducted three experiments to examine the potential of using juveniles of a spoon worm Urechis unicinctus to improve the quality of organically contaminated coastal sediment.Sediment samples were collected from a site that was heavily contaminated with organic matter (Seonso) and two sites that were clean (Myo-do,Dolsan-do).Urechis juveniles,obtained by artificial fertilization and cultured in the laboratory,were introduced to the sediment (weight 3 kg,depth 10 cm) at a density of 500 individuals per aquarium (length 50 cm,width 35 cm,height 30 cm) (Experiment 1),or at densities ranging from 100 to 900 individuals per beaker (Experiment 2).To examine how sediment contamination can be modified by the effects of Urechis,500 individuals (per aquarium) were exposed to the Seonso contaminated sediment that had been mixed with 0-100% clean sand (Experiment 3).Each experiment lasted two months and sediment samples were collected every 15 d to determine the several indexes of sediment quality,which included acid volatile sulfide (AVS),chemical oxygen demand (COD) and total ignition loss (TIL).In Experiment 1,the existence of Urechis did not result in significant changes in quality indexes in the sediments collected from Myo-do,Dolsan-do.However,AVS,COD and TIL of the Seonso sediment all decreased significantly after co-incubation with Urechis juveniles for 30 to 45 d.Experiment 2 showed that a density of at least 300 juveniles per beaker was necessary to significantly reduce all three quality indexes,and the magnitude of reduction was positively correlated with juvenile density.Experiment 3 revealed that Urechis juveniles were effective in reducing the AVS,COD and TIL of the Seonso sediment that had been mixed with 60%,80%,and 80% of clean sand,respectively.The results of the present study therefore indicated that juveniles of this spoon worm have the potential to be used to improve the quality of organically contaminated sediment in coastal waters.
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.
