The electrokinetic(EK)process has been proposed for soil decontamination from heavy metals and organic matter.The advantages of the EK process include the low operating energy,suitability for fine-grained soil deconta...The electrokinetic(EK)process has been proposed for soil decontamination from heavy metals and organic matter.The advantages of the EK process include the low operating energy,suitability for fine-grained soil decontamination,and no need for excavation.During the last three decades,enhanced and hybrid EK systems were developed and tested for improving the efficiency of contaminants removal from soils.Chemically enhanced-EK processes exhibited excellent efficiency in removing contaminants by controlling the soil pH or the chemical reaction of contaminants.EK hybrid systems were tested to overcome environmental hurdles or technical drawbacks of decontamination technologies.Hybridization of the EK process with phytoremediation,bioremediation,or reactive filtermedia(RFM)improved the remediation process performance by capturing contaminants or facilitating biological agents’movement in the soil.Also,EK process coupling with solar energy was proposed to treat off-grid contaminated soils or reduce the EK energy requirements.This study reviews recent advancements in the enhancement and hybrid EK systems for soil remediation and the type of contaminants targeted by the process.The study also covered the impact of operating parameters,imperfect pollution separation,and differences in the physicochemical characteristics and microstructure of soil/sediment on the EK performance.Finally,a comparison between various remediation processes was presented to highlight the pros and cons of these technologies.展开更多
High-rise buildings form deep urban street canyons and restrict the dispersion of vehicle emissions,posing severe health risks to the public by aggravating roadside air quality.Field measurements are important for und...High-rise buildings form deep urban street canyons and restrict the dispersion of vehicle emissions,posing severe health risks to the public by aggravating roadside air quality.Field measurements are important for understanding the dispersion process of tailpipe emissions in street canyons,while a major challenge is the lack of a suitable tracer gas.Carbon dioxide(CO_(2)),which is safe to the public and inexpensive to obtain,can be reliably measured by existing gas analysers.This study investigated the suitability of using CO_(2)as a tracer gas for characterising vehicle emission dispersion in a real-world street canyon.The tracer gas was released via a line or point source,whose dispersion was characterised by a sensors network comprising low-cost air quality sensors.The results showed that the CO_(2)contained in the exhaust gas of a test vehicle itself had unmeasurable effect at roadsides.Both the line and point sources produced obvious CO_(2)level elevations at approximately 30 s after the test vehicle passed by.In addition,for both line and point sources,the CO_(2)elevations were much more distinct at the roadside next to tailpipe exit than the opposite side,and were higher at 0.8 m than 1.6 m above the ground.The present study demonstrated that using CO_(2)as a tracer gas is feasible for investigating vehicle emission dispersion in real-world street canyons.Future studies are needed to improve the gas release rate of the developed tracer gas systems for more reliable measurements and larger street canyons.展开更多
This research aims to improve erosion control practice in the Loess Plateau,by studying the surface erosion processes,including splash,sheet/interrill and rill erosion in four contrasting soils under high rainfall int...This research aims to improve erosion control practice in the Loess Plateau,by studying the surface erosion processes,including splash,sheet/interrill and rill erosion in four contrasting soils under high rainfall intensity(120 mm h^(−1))with three-scale indoor artificial experiments.Four contrasting soils as sandy loam,sandy clay loam,clay loam and loamy clay were collected from different parts of the Loess Plateau.The results showed that sediment load was significantly impacted by soil properties in all three sub-processes.Splash rate(4.0-21.6 g m^(−2∙)min^(−1))was highest in sandy loam from the north part of the Loess Plateau and showed a negative power relation with the mean weight diameter of aggregates after 20 min of rainfall duration.The average sediment load by sheet/interrill erosion(6.94-42.86 g m^(−2∙)min^(−1))was highest in clay loam from middle part of the Loess Plateau,and the stable sediment load after 20 min showed a positive power relation with the silt content in soil.The average sediment load increased dramatically by rill and interrill erosion(21.03-432.16 g m^(−2∙)min^(−1)),which was highest in loamy clay from south part of the Loess Plateau.The average sediment load after the occurrence of rill showed a positive power relation with clay content and a negative power relation with soil organic matter content.The impacts of slope gradient on the runoff rate and sediment load also changed with soil properties.The critical factors varied for different processes,which were the aggregate size for splash erosion,the content of silt particles and slope gradient for sheet/interrill erosion,and the content of clay particles,soil organic matter and slope gradient for rill erosion.Based on the results of the experiments,specific erosion control practices were proposed by targeting certain erosion processes in areas with different soil texture and different distribution of slope gradient.The findings from this study should support the improvement of erosion prediction and cropland management in different regions of the Loess Plateau.展开更多
Black carbon(BC)in ten contaminated sediments from the Song-Liao watershed,NE China,was isolated upon treatments using a combustion method at 375℃,and the isolates’sorption isotherms for phenanthrene(Phen)were deter...Black carbon(BC)in ten contaminated sediments from the Song-Liao watershed,NE China,was isolated upon treatments using a combustion method at 375℃,and the isolates’sorption isotherms for phenanthrene(Phen)were determined.All sorption isotherms were nonlinear and fitted well by the Freundlich model.A negative relation was found between Freundlich sorption nonlinearity parameter(n values)and BC/total organic carbon(TOC)content of the original sediments(r^(2)=0.687,p<0.01),indicating the dominance of BC in Phen sorption nonlinearity.The BC isolates from this industrialized region had n values of 0.342 to 0.505 and logKFOC values of 6.02 to 6.42(μg·kg^(–1)·OC^(–1))/(μg·L^(–1))n for Phen.At a given Ce,the BC had higher Koc value than the original sediments,revealing a higher sorption capacity for BC.BC was responsible for 50.0%to 87.3%of the total sorption at Ce=0.05 Sw,clearly indicating the dominance of BC particles in overall sorption of Phen by sediments.展开更多
文摘The electrokinetic(EK)process has been proposed for soil decontamination from heavy metals and organic matter.The advantages of the EK process include the low operating energy,suitability for fine-grained soil decontamination,and no need for excavation.During the last three decades,enhanced and hybrid EK systems were developed and tested for improving the efficiency of contaminants removal from soils.Chemically enhanced-EK processes exhibited excellent efficiency in removing contaminants by controlling the soil pH or the chemical reaction of contaminants.EK hybrid systems were tested to overcome environmental hurdles or technical drawbacks of decontamination technologies.Hybridization of the EK process with phytoremediation,bioremediation,or reactive filtermedia(RFM)improved the remediation process performance by capturing contaminants or facilitating biological agents’movement in the soil.Also,EK process coupling with solar energy was proposed to treat off-grid contaminated soils or reduce the EK energy requirements.This study reviews recent advancements in the enhancement and hybrid EK systems for soil remediation and the type of contaminants targeted by the process.The study also covered the impact of operating parameters,imperfect pollution separation,and differences in the physicochemical characteristics and microstructure of soil/sediment on the EK performance.Finally,a comparison between various remediation processes was presented to highlight the pros and cons of these technologies.
基金supported by the Environment and Conservation Fund(No.ECF 14/2018)of the Hong Kong SAR Government,China.
文摘High-rise buildings form deep urban street canyons and restrict the dispersion of vehicle emissions,posing severe health risks to the public by aggravating roadside air quality.Field measurements are important for understanding the dispersion process of tailpipe emissions in street canyons,while a major challenge is the lack of a suitable tracer gas.Carbon dioxide(CO_(2)),which is safe to the public and inexpensive to obtain,can be reliably measured by existing gas analysers.This study investigated the suitability of using CO_(2)as a tracer gas for characterising vehicle emission dispersion in a real-world street canyon.The tracer gas was released via a line or point source,whose dispersion was characterised by a sensors network comprising low-cost air quality sensors.The results showed that the CO_(2)contained in the exhaust gas of a test vehicle itself had unmeasurable effect at roadsides.Both the line and point sources produced obvious CO_(2)level elevations at approximately 30 s after the test vehicle passed by.In addition,for both line and point sources,the CO_(2)elevations were much more distinct at the roadside next to tailpipe exit than the opposite side,and were higher at 0.8 m than 1.6 m above the ground.The present study demonstrated that using CO_(2)as a tracer gas is feasible for investigating vehicle emission dispersion in real-world street canyons.Future studies are needed to improve the gas release rate of the developed tracer gas systems for more reliable measurements and larger street canyons.
基金Financial support was provided by the National Natural Science Foundation of China(Grant No.41977069,41771314).
文摘This research aims to improve erosion control practice in the Loess Plateau,by studying the surface erosion processes,including splash,sheet/interrill and rill erosion in four contrasting soils under high rainfall intensity(120 mm h^(−1))with three-scale indoor artificial experiments.Four contrasting soils as sandy loam,sandy clay loam,clay loam and loamy clay were collected from different parts of the Loess Plateau.The results showed that sediment load was significantly impacted by soil properties in all three sub-processes.Splash rate(4.0-21.6 g m^(−2∙)min^(−1))was highest in sandy loam from the north part of the Loess Plateau and showed a negative power relation with the mean weight diameter of aggregates after 20 min of rainfall duration.The average sediment load by sheet/interrill erosion(6.94-42.86 g m^(−2∙)min^(−1))was highest in clay loam from middle part of the Loess Plateau,and the stable sediment load after 20 min showed a positive power relation with the silt content in soil.The average sediment load increased dramatically by rill and interrill erosion(21.03-432.16 g m^(−2∙)min^(−1)),which was highest in loamy clay from south part of the Loess Plateau.The average sediment load after the occurrence of rill showed a positive power relation with clay content and a negative power relation with soil organic matter content.The impacts of slope gradient on the runoff rate and sediment load also changed with soil properties.The critical factors varied for different processes,which were the aggregate size for splash erosion,the content of silt particles and slope gradient for sheet/interrill erosion,and the content of clay particles,soil organic matter and slope gradient for rill erosion.Based on the results of the experiments,specific erosion control practices were proposed by targeting certain erosion processes in areas with different soil texture and different distribution of slope gradient.The findings from this study should support the improvement of erosion prediction and cropland management in different regions of the Loess Plateau.
基金the National Basic Research Program of China(Grant No.2004CB418502)the National Natural Science Foundation of China(Grant No.20477003).
文摘Black carbon(BC)in ten contaminated sediments from the Song-Liao watershed,NE China,was isolated upon treatments using a combustion method at 375℃,and the isolates’sorption isotherms for phenanthrene(Phen)were determined.All sorption isotherms were nonlinear and fitted well by the Freundlich model.A negative relation was found between Freundlich sorption nonlinearity parameter(n values)and BC/total organic carbon(TOC)content of the original sediments(r^(2)=0.687,p<0.01),indicating the dominance of BC in Phen sorption nonlinearity.The BC isolates from this industrialized region had n values of 0.342 to 0.505 and logKFOC values of 6.02 to 6.42(μg·kg^(–1)·OC^(–1))/(μg·L^(–1))n for Phen.At a given Ce,the BC had higher Koc value than the original sediments,revealing a higher sorption capacity for BC.BC was responsible for 50.0%to 87.3%of the total sorption at Ce=0.05 Sw,clearly indicating the dominance of BC particles in overall sorption of Phen by sediments.
