title: Adsorption and transformation of ammonium ion in a loose-pore geothermal reservoir: Batch and column experiments.
abstract: Adsorption kinetics and transformation process of ammonium ion (NH4(+)) were investigated to advance the understanding of N cycle in a low-temperature loose-pore geothermal reservoir. Firstly, batch experiments were performed in order to determine the sorption capacity and the kinetic mechanism of NH4(+) onto a loose-pore geothermal reservoir matrix. Then column experiments were carried out at temperatures from 20°C to 60°C in order to determine the transport parameters and transformation mechanism of NH4(+) in the studied matrix. The results showed that the adsorption process of NH4(+) onto the porous media well followed the pseudo-second-order model. No obvious variation of hydrodynamic dispersion coefficient (D) and retardation factor (R) was observed at different transport distances at a Darcy's flux of 2.27cm/h, at which nitrification could be neglected. The simulated D obtained by the CDE model in CXTFIT2.1 increased with temperature while R decreased with temperature, indicating that the adsorption capacity of NH4(+) onto the matrix decreased with the increasing of temperature. When the Darcy's flux was decreased to 0.014cm/h, only a little part of NH4(+) could be transformed to nitrate, suggesting that low density of nitrifiers existed in the simulated loose-pore geothermal reservoir. Although nitrification rate increased with temperature in the range of 20°C to 60°C, it was extremely low and no accumulation of nitrite was observed under the simulated low-temperature geothermal conditions without addition of biomass and oxygen.
authors.affiliation: Institute of Resources and Environment, Henan Polytechnic University, Jiaozuo 454000, China; Collaborative Innovation Center of Coalbed Methane and Shale Gas for Central Plains Economic Region, Henan Province, Jiaozuo 454000, China. Electronic address: zhaoli@hpu.edu.cn.
authors.forename: Li
authors.initials: L
authors.lastname: Zhao
authors.affiliation: Institute of Resources and Environment, Henan Polytechnic University, Jiaozuo 454000, China.
authors.forename: Yanli
authors.initials: Y
authors.lastname: Li
authors.affiliation: Xi'an Research Institute of China Coal Technology & Engineering group, Xi'an 710054, China.
authors.forename: Shidong
authors.initials: S
authors.lastname: Wang
authors.affiliation: Institute of Resources and Environment, Henan Polytechnic University, Jiaozuo 454000, China.
authors.forename: Xinyi
authors.initials: X
authors.lastname: Wang
authors.affiliation: Institute of Resources and Environment, Henan Polytechnic University, Jiaozuo 454000, China.
authors.forename: Hongqi
authors.initials: H
authors.lastname: Meng
authors.affiliation: Institute of Resources and Environment, Henan Polytechnic University, Jiaozuo 454000, China.
authors.forename: Shaohe
authors.initials: S
authors.lastname: Luo
mesh_terms: D000327:Adsorption; D000641:Ammonia / Q000737:chemistry*; D018533:Biomass; D045482:Hot Springs / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D062070:Hydrology / Q000379:methods*; D007700:Kinetics; D009566:Nitrates / Q000737:chemistry; D058465:Nitrification; D013696:Temperature
chemical_list: D009566:Nitrates; D000641:Ammonia
keywords: Adsorption; Ammonium ion; Loose-pore geothermal reservoir; Nitrate; Nitrification