title: Using natural Chinese zeolite to remove ammonium from rainfall runoff following urea fertilization of a paddy rice field.
abstract: The potential of natural Chinese zeolite to remove ammonium from rainfall runoff following urea applications to a paddy rice field is assessed in this study. Laboratory batch kinetic and isotherm experiments were carried out first to investigate the ammonium adsorption capacity of the natural zeolite. Field experiments using zeolite adsorption barriers installed at drain outlets in a paddy rice field were also carried out during natural rainfall events to evaluate the barrier's dynamic removal capacity of ammonium. The results demonstrate that the adsorption kinetics are accurately described by the Elovich model, with a coefficient of determination (R (2)) ranging from 0.9705 to 0.9709, whereas the adsorption isotherm results indicate that the Langmuir-Freundlich model provides the best fit (R (2) = 0.992) for the equilibrium data. The field experiments show that both the flow rate and the barrier volume are important controls on ammonium removal from rainfall runoff. A low flow rate leads to a higher ammonium removal efficiency at the beginning of the tests, while a high flow rate leads to a higher quantity of ammonium adsorbed over the entire runoff process.
authors.affiliation: State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University, Tianjin, 300072, China. wangxl@tju.edu.cn.
authors.forename: Xiao-Ling
authors.initials: XL
authors.lastname: Wang
authors.affiliation: School of Environment Science and Engineering, Tianjin University, Tianjin, 300072, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Qiao
authors.affiliation: State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University, Tianjin, 300072, China.
authors.forename: Song-Min
authors.initials: SM
authors.lastname: Li
authors.affiliation: School of Environment Science and Engineering, Tianjin University, Tianjin, 300072, China.
authors.forename: Jian-Sheng
authors.initials: JS
authors.lastname: Li
mesh_terms: D000327:Adsorption; D064751:Ammonium Compounds / Q000302:isolation & purification*; D005308:Fertilizers; D007700:Kinetics; D012275:Oryza; D000644:Quaternary Ammonium Compounds; D012989:Soil Pollutants / Q000302:isolation & purification; D014508:Urea; D018508:Water Purification / Q000379:methods*; D017641:Zeolites / Q000737:chemistry*
chemical_list: D064751:Ammonium Compounds; D005308:Fertilizers; D000644:Quaternary Ammonium Compounds; D012989:Soil Pollutants; D017641:Zeolites; D014508:Urea
keywords: Adsorption; Adsorption barrier; Ammonium removal; Natural zeolite; Paddy rice field; Rainfall runoff