title: Blocking effect of colloids on arsenate adsorption during co-transport through saturated sand columns.
abstract: Transport of environmental pollutants through porous media is influenced by colloids. Co-transport of As(V) and soil colloids at different pH were systematically investigated by monitoring breakthrough curves (BTCs) in saturated sand columns. A solute transport model was applied to characterize transport and retention sites of As(V) in saturated sand in the presence of soil colloids. A colloid transport model and the DLVO theory were used to reveal the mechanism and hypothesis of soil colloid-promoted As(V) transport in the columns. Results showed that rapid transport of soil colloids, regulated by pH and ionic strength, promoted As(V) transport by blocking As(V) adsorption onto sand, although soil colloids had low adsorption for As(V). The promoted transport was more significant at higher concentrations of soil colloids (between 25 mg L(-1) and 150 mg L(-1)) due to greater blocking effect on As(V) adsorption onto the sand surfaces. The blocking effect of colloids was explained by the decreases in both instantaneous (equilibrium) As adsorption and first-order kinetic As adsorption on the sand surface sites. The discovery of this blocking effect improves our understanding of colloid-promoted As transport in saturated porous media, which provides new insights into role of colloids, especially colloids with low As adsorption capacity, in As transport and mobilization in soil-groundwater systems.
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, PR China; School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, PR China; Center for Environmental Remediation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China.
authors.forename: Jie
authors.initials: J
authors.lastname: Ma
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, PR China; School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, PR China. Electronic address: hmguo@cugb.edu.cn.
authors.forename: Huaming
authors.initials: H
authors.lastname: Guo
authors.affiliation: Center for Environmental Remediation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China.
authors.forename: Mei
authors.initials: M
authors.lastname: Lei
authors.affiliation: Center for Environmental Remediation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Wan
authors.affiliation: Shenyang Academy of Environmental Sciences, Shenyang 110016, PR China.
authors.forename: Hanzhi
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Center for Environmental Remediation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Feng
authors.affiliation: Center for Environmental Remediation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China.
authors.forename: Rongfei
authors.initials: R
authors.lastname: Wei
authors.affiliation: Center for Environmental Remediation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China.
authors.forename: Liyan
authors.initials: L
authors.lastname: Tian
authors.affiliation: Center for Environmental Remediation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China.
authors.forename: Xiaokun
authors.initials: X
authors.lastname: Han
mesh_terms: D000327:Adsorption; D001149:Arsenates / Q000032:analysis*; D003102:Colloids / Q000737:chemistry*; D060587:Groundwater / Q000032:analysis; D008962:Models, Theoretical; D012822:Silicon Dioxide / Q000737:chemistry*; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis*; D012996:Solutions
chemical_list: D001149:Arsenates; D003102:Colloids; D012987:Soil; D012989:Soil Pollutants; D012996:Solutions; D012822:Silicon Dioxide
keywords: Arsenate; Blocking effect; Co-transport; Low adsorption; Soil colloids; Strong repulsion