One of the main issues in environmental hydraulics is pollutant release from sediments.For instance,the strong affinity between phosphorus and sediment permits most of the phosphorus to be adsorbed on the surface of t...One of the main issues in environmental hydraulics is pollutant release from sediments.For instance,the strong affinity between phosphorus and sediment permits most of the phosphorus to be adsorbed on the surface of the sediment particles in rivers or lakes.Post sediment resuspension,phosphorus is desorbed from the sediment to the overlying water.The release of phosphorus from the resuspended sediment is an important process in the secondary pollution of water.Herein,a coupled mechanical model of the overlying water,sediment,and pollutant was established based on the experimentally gathered data.Two types of sediment with different adsorption and desorption characteristics were selected to simulate the process of sediment resuspension and phosphorus release under different hydrodynamic conditions.The simulation results were subsequently used to analyze the relationship between the flow field characteristics and phosphorus concentration,from which the relationships between velocity,particle volume fraction,turbulent kinetic energy,total phosphorus concentration,desorbed phosphorus concentration,and time were elucidated.Based on the results,phosphorus is rapidly released into the overlying water from the resuspended sediment,and it reaches a peak value in a short duration.Unlike the release process of non-adsorption pollutants,hydrodynamic conditions and sediment properties play a crucial role in the phosphorus release process.The turbulent kinetic energy rapidly increases with the flow velocity,whereas the desorbed phosphorus concentration exhibits a certain relationship with the particle volume fraction and turbulent kinetic energy.In particular,the turbulent kinetic energy increases the desorbed phosphorus concentration per unit time.Additionally,the time taken by the total phosphorus concentration to attain its peak value is closely related to the characteristics of the flow field,whereas the amount of phosphorus is closely related to sediment properties.Post sediment resuspension,the release of phosphorus shows the characteristics of a centralized and massive release,which suggests that the total phosphorus concentration in the overlying water would change in a short duration and cause secondary pollution in the water environment.展开更多
Sediment layers containing contaminants play a significant role in environmental hydrodynamics. Experiments were conducted in order to characterize the relative roles of resuspended particles and pore water under diff...Sediment layers containing contaminants play a significant role in environmental hydrodynamics. Experiments were conducted in order to characterize the relative roles of resuspended particles and pore water under different flow and sediment conditions. A conservative tracer （NaC1） and a reactive tracer （phosphate） were used as contaminants in the bottom sediment in a laboratory flume. The mixing between the overlying water and pore water occurred over a short time while the desorption of contaminants from fine-grained resuspended particles lasted a relatively long time. The effects of resuspended particles and pore water on the variations of release flux and concentration of contaminants in water with time under different hydrodynamic conditions were quantified. The results show that pore water dominated the initial release flux, which could be several orders of magnitude greater than the flux due to molecular diffusion. Flux contribution of desorption from sediment particles in the latter release could be equal to what was seen from pore water in the initial stage.展开更多
Photochemical reactions can alter the transformation of sedimentary organic matter into dissolved organic matter(DOM)and affect its ultimate fate in water ecosystems.In the present study,the photorelease of DOM and Fe...Photochemical reactions can alter the transformation of sedimentary organic matter into dissolved organic matter(DOM)and affect its ultimate fate in water ecosystems.In the present study,the photorelease of DOM and Fe from resuspended lake sediments was investigated under different O_(2)and NO_(3)-concentration conditions to study the mechanisms of DOM and Fe photorelease.The amount of photoreleased Fe,which ranged from 0.22 to 0.70μmol/L,was significantly linearly correlated with the amount of photoreleased DOM.O_(2)and NO_(3)-could promote the photochemical release of DOM and Fe,especially during the initial 4 h irradiation.In general,the order of the photorelease rates of DOM and Fe under different conditions was as follows:NO_(3)-/aerobic>aerobic≈NO_(3)-/anaerobic>anaerobic.The photorelease rates of DOM and Fe were higher for the initial 4 hr irradiation than these for the subsequent 8 hr irradiation.The photorelease of DOM and Fe is thought to proceed via direct photodissolution and indirect processes.The relative contributions of indirect processes(>60%)was much greater than that of direct photodissolution(<40%).The photoproduced H 2 O_(2)under aerobic and anaerobic conditions indicated that hydroxyl radicals(·OH)are involved in the photorelease of DOM.Using·OH scavengers,it was found that 38.7%,53.7%,and 77.6%of photoreleased DOM was attributed to·OH under anaerobic,aerobic,and NO_(3)-/aerobic conditions,respectively.Our findings provide insights for understanding the mechanisms and the important role of·OH in the DOM and Fe photorelease from resuspended sediments.展开更多
Particulate matter(PM)in outdoor air pollution is one of the most critical factors that cause serious health problems and even deaths.One significant source of these particles are nonexhaust emissions,which refer to p...Particulate matter(PM)in outdoor air pollution is one of the most critical factors that cause serious health problems and even deaths.One significant source of these particles are nonexhaust emissions,which refer to pollutants that come from sources,like brake,tire,and road wear other than a vehicle's exhaust system.This review focuses on the presence of non-exhaust particles on pavement,encompassing their classification,composition,evaluation,and mitigation.Based on extensive literature,it can be concluded that the quantity of non-exhaust emissions is affected by a combination of complex factors,such as vehicle speed,tire type,and pavement material.Non-exhaust particles can be classified into organic,inorganic,and metal matter,each requiring a distinct analysis and detection method.The effective approaches to managing non-exhaust emissions include water cleaning,utilizing functional pavement materials,and applying chemical reagents to alleviate emission capacity.Finally,this review recommends future research directions such as combining tire-road simulation with environmental monitoring equipment,in the hope that this article will have a positive impact on the mitigation of non-exhaust emissions.展开更多
基金This work was financially supported by the Strategic Priority Research Program of the National Key R&D Program of China(Grants 2018YFC1505500 and 2018YFC1505504)the Chinese Academy of Science(Grant XDB10030303)and the National Natural Science Foundation of China(NSFC)(Grants 11802313 and 11872117).
文摘One of the main issues in environmental hydraulics is pollutant release from sediments.For instance,the strong affinity between phosphorus and sediment permits most of the phosphorus to be adsorbed on the surface of the sediment particles in rivers or lakes.Post sediment resuspension,phosphorus is desorbed from the sediment to the overlying water.The release of phosphorus from the resuspended sediment is an important process in the secondary pollution of water.Herein,a coupled mechanical model of the overlying water,sediment,and pollutant was established based on the experimentally gathered data.Two types of sediment with different adsorption and desorption characteristics were selected to simulate the process of sediment resuspension and phosphorus release under different hydrodynamic conditions.The simulation results were subsequently used to analyze the relationship between the flow field characteristics and phosphorus concentration,from which the relationships between velocity,particle volume fraction,turbulent kinetic energy,total phosphorus concentration,desorbed phosphorus concentration,and time were elucidated.Based on the results,phosphorus is rapidly released into the overlying water from the resuspended sediment,and it reaches a peak value in a short duration.Unlike the release process of non-adsorption pollutants,hydrodynamic conditions and sediment properties play a crucial role in the phosphorus release process.The turbulent kinetic energy rapidly increases with the flow velocity,whereas the desorbed phosphorus concentration exhibits a certain relationship with the particle volume fraction and turbulent kinetic energy.In particular,the turbulent kinetic energy increases the desorbed phosphorus concentration per unit time.Additionally,the time taken by the total phosphorus concentration to attain its peak value is closely related to the characteristics of the flow field,whereas the amount of phosphorus is closely related to sediment properties.Post sediment resuspension,the release of phosphorus shows the characteristics of a centralized and massive release,which suggests that the total phosphorus concentration in the overlying water would change in a short duration and cause secondary pollution in the water environment.
基金supported by the National Natural Science Foundation of China(Grants No.10972134 and 11032007)
文摘Sediment layers containing contaminants play a significant role in environmental hydrodynamics. Experiments were conducted in order to characterize the relative roles of resuspended particles and pore water under different flow and sediment conditions. A conservative tracer （NaC1） and a reactive tracer （phosphate） were used as contaminants in the bottom sediment in a laboratory flume. The mixing between the overlying water and pore water occurred over a short time while the desorption of contaminants from fine-grained resuspended particles lasted a relatively long time. The effects of resuspended particles and pore water on the variations of release flux and concentration of contaminants in water with time under different hydrodynamic conditions were quantified. The results show that pore water dominated the initial release flux, which could be several orders of magnitude greater than the flux due to molecular diffusion. Flux contribution of desorption from sediment particles in the latter release could be equal to what was seen from pore water in the initial stage.
基金supported by the National Science Funds for Creative Research Groups of China(No.51421006)the Fundamental Research Funds for the Central Universities(Nos.B200204033 and B2018B08414)+1 种基金the National Key Plan for Research and Development of China(No.2016 YFC0401703)the National Natural Science Foundation of China(No.51579073)。
文摘Photochemical reactions can alter the transformation of sedimentary organic matter into dissolved organic matter(DOM)and affect its ultimate fate in water ecosystems.In the present study,the photorelease of DOM and Fe from resuspended lake sediments was investigated under different O_(2)and NO_(3)-concentration conditions to study the mechanisms of DOM and Fe photorelease.The amount of photoreleased Fe,which ranged from 0.22 to 0.70μmol/L,was significantly linearly correlated with the amount of photoreleased DOM.O_(2)and NO_(3)-could promote the photochemical release of DOM and Fe,especially during the initial 4 h irradiation.In general,the order of the photorelease rates of DOM and Fe under different conditions was as follows:NO_(3)-/aerobic>aerobic≈NO_(3)-/anaerobic>anaerobic.The photorelease rates of DOM and Fe were higher for the initial 4 hr irradiation than these for the subsequent 8 hr irradiation.The photorelease of DOM and Fe is thought to proceed via direct photodissolution and indirect processes.The relative contributions of indirect processes(>60%)was much greater than that of direct photodissolution(<40%).The photoproduced H 2 O_(2)under aerobic and anaerobic conditions indicated that hydroxyl radicals(·OH)are involved in the photorelease of DOM.Using·OH scavengers,it was found that 38.7%,53.7%,and 77.6%of photoreleased DOM was attributed to·OH under anaerobic,aerobic,and NO_(3)-/aerobic conditions,respectively.Our findings provide insights for understanding the mechanisms and the important role of·OH in the DOM and Fe photorelease from resuspended sediments.
基金supported by the National Natural Science Foundation of China(Grant Nos.52311530081,52122809).
文摘Particulate matter(PM)in outdoor air pollution is one of the most critical factors that cause serious health problems and even deaths.One significant source of these particles are nonexhaust emissions,which refer to pollutants that come from sources,like brake,tire,and road wear other than a vehicle's exhaust system.This review focuses on the presence of non-exhaust particles on pavement,encompassing their classification,composition,evaluation,and mitigation.Based on extensive literature,it can be concluded that the quantity of non-exhaust emissions is affected by a combination of complex factors,such as vehicle speed,tire type,and pavement material.Non-exhaust particles can be classified into organic,inorganic,and metal matter,each requiring a distinct analysis and detection method.The effective approaches to managing non-exhaust emissions include water cleaning,utilizing functional pavement materials,and applying chemical reagents to alleviate emission capacity.Finally,this review recommends future research directions such as combining tire-road simulation with environmental monitoring equipment,in the hope that this article will have a positive impact on the mitigation of non-exhaust emissions.
