title: Insights into the subsurface transport of As(V) and Se(VI) in produced water from hydraulic fracturing using soil samples from Qingshankou Formation, Songliao Basin, China.
abstract: Produced water is a type of wastewater generated from hydraulic fracturing, which may pose a risk to the environment and humans due to its high ionic strength and the presence of elevated concentrations of metals/metalloids that exceed maximum contamination levels. The mobilization of As(V) and Se(VI) in produced water and selected soils from Qingshankou Formation in the Songliao Basin in China were investigated using column experiments and synthetic produced water whose quality was representative of waters arising at different times after well creation. Temporal effects of produced water on metal/metalloid transport and sorption/desorption were investigated by using HYDRUS-1D transport modelling. Rapid breakthrough and long tailings of As(V) and Se(VI) transport were observed in Day 1 and Day 14 solutions, but were reduced in Day 90 solution probably due to the elevated ionic strength. The influence of produced water on the hydrogeological conditions (i.e., change between equilibrium and non-equilibrium transport) was evidenced by the change of tracer breakthrough curves before and after the leaching of produced water. This possibly resulted from the sorption of polyacrylamide (PAM (-CH2CHCONH2-)n) onto soil surfaces, through its use as a friction reducer in fracturing solutions. The sorption was found to be reversible in this study. Minimal amounts of sorbed As(V) were desorbed whereas the majority of sorbed Se(VI) was readily leached out, to an extent which varied with the composition of the produced water. These results showed that the mobilization of As(V) and Se(VI) in soil largely depended on the solution pH and ionic strength. Understanding the differences in metal/metalloid transport in produced water is important for proper risk management.
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
authors.forename: Season S
authors.initials: SS
authors.lastname: Chen
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China; State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China.
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China. Electronic address: dan.tsang@polyu.edu.hk.
authors.forename: Daniel C W
authors.initials: DCW
authors.lastname: Tsang
authors.affiliation: Environmental and Water Resources Engineering, Department of Civil and Environmental Engineering, Imperial College London, South Kensington, London SW7 2AZ, UK.
authors.forename: Nigel J D
authors.initials: NJD
authors.lastname: Graham
authors.affiliation: Korea Biochar Research Center & School of Natural Resources and Environmental Science, Kangwon National University, Chuncheon 24341, North Korea.
authors.forename: Yong Sik
authors.initials: YS
authors.lastname: Ok
authors.affiliation: State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China. Electronic address: yujief@hit.edu.cn.
authors.forename: Yujie
authors.initials: Y
authors.lastname: Feng
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
authors.forename: Xiang-Dong
authors.initials: XD
authors.lastname: Li
mesh_terms: D000327:Adsorption; D001151:Arsenic / Q000032:analysis*; D002681:China; D000067071:Hydraulic Fracking; D006863:Hydrogen-Ion Concentration; D009994:Osmolar Concentration; D012643:Selenium / Q000032:analysis*; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis*; D064091:Waste Disposal Facilities; D062065:Wastewater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D001151:Arsenic; D012643:Selenium; D012987:Soil; D012989:Soil Pollutants; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Arsenic; Hydraulic fracturing; Non-equilibrium transport; Produced water; Selenium; Solution chemistry