Experimental Study on In-situ Leaching and Electrokinetic Remediation of Composite Heavy Metal-contaminated Soil

[Objectives] This study was conducted to investigate in-situ leaching and electrokinetic combined remediation of composite heavy metal-contaminated soil.[Methods] Leaching and electrokientic combined remediation was applied to remediate artificially-simulated composite Cd,Cu,Pb,and Zn-contaminated soil.The electrokinentic remediation of the soil was carried out using EDTA and acetic acid as the eluents with electrodes placed on the top and bottom of the soil,to investigate the effects of different types and concentrations of eluents,reaction time and energization methods on the remediation.[Results]Applying electrodynamic force to the leaching remediation process achieved good removal effects of Cd,Cu,Pb,and Zn in the soil.Compared with pure leaching,the leaching and electrokinetic combined remediation saved 23.8% of EDTA consumption.EDTA showed the ability to complex heavy metals better than acetic acid,and after 10 d of reaction,the 0.1 mol/L EDTA achieved very good removal effects on Cd,Cu,Pb,and Zn from the upper and middle layers of the soil column,exhibiting removal rates of 94.4%,93.3%,91.4% and 92.8% in the upper layer and 87.2%,88.2%,83.3% and 84.6%,respectively.Compared with the conventional experiments,the intermittent energization method and the voltage-increasing method improved the removal rates of Cd,Cu,Pb and Zn by 6.3%,6.1%,5.9%and 6%,and 0.6%,0.9%,0.5% and 0.4%,respectively,and saved 46.8% and 10.3% of energy consumption,respectively.[Conclusions]The study provides reference for the remediation of composite heavy metal-contaminated soil.

Air pollutant emissions from the asphalt industry in Beijing,China

Improving our understanding of air pollutant emissions fromthe asphalt industry is critical for the development and implementation of pollution control policies.In this study,the spatial distribution of potential maximum emissions of volatile organic compounds(VOCs)in the complete life cycle of asphaltmixtures,as well as the particulate matter(PM),asphalt fume,nonmethane hydrocarbons(NMHCs),VOCs,and benzoapyrene(BaP)emissions from typical processes(e.g.,asphalt and concrete mixing stations,asphalt heating boilers,and asphalt storage tanks)in asphalt mixing plants,were determined in Beijing in 2017.The results indicated that the potential maximum emissions of VOCs in the complete life cycle of asphalt mixtures were 18,001 ton,with a large contribution from the districts of Daxing,Changping,and Tongzhou.The total emissions of PM,asphalt fume,NMHC,VOCs,and BaP from asphalt mixing plants were 3.1,12.6,3.1,23.5,and 1.9×10^(−3)ton,respectively.The emissions of PMfromasphalt and concretemixing stations contributed themost to the total emissions.The asphalt storage tankwas the dominant emission source of VOCs,accounting for 96.1%of the total VOCs emissions in asphalt mixing plants,followed by asphalt heating boilers.The districts of Daxing,Changping,and Shunyi were the dominant regions for the emissions of PM,asphalt fume,NMHC,and BaP,while the districts of Shunyi,Tongzhou,and Changping contributed the most emissions of VOCs.