Wang,X., Zhao,L., Liu,X., A,L. and Zhang,Y.(2013): Temperature effect on the transport of nitrate and ammonium ions in a loose-pore geothermal reservoir. Journal of Geochemical Exploration, 124, 59-66.

『ゆるい−孔隙をもつ地熱リザーバにおける硝酸塩とアンモニウムイオンの移動に対する温度の影響』


Abstract
 The concentration of NO3--N in some of the geothermal water samples collected from Kaifeng City, Henan Province, China has exceeded the World Health Organization's guideline value for drinking water (10 mg/L). The NH4+-N concentration cannot also meet the demand for quality standard for groundwater (0.2 mg/L) in China. There is a need to predict the mobility of these two ions in a geothermal reservoir. Column experiments were performed at temperatures from 15℃ to 60℃ and the computer code CXTFIT was used to fit the experimental data and to determine the transport parameters and ammonium adsorption parameters. Effects of both the flow rate and temperature on nitrate transport parameters were evaluated. The convection-dispersion equation (CDF) was used to describe the nitrate transport process at temperature from 15℃ to 60℃, where the tracer transport was dominated by advection under experimental conditions. The solute hydrodynamic dispersion and dispersivity in the simulated sandy column were enhanced with the increase of temperature. The asymmetrical shape and tailing of the ammonium breakthrough curve showed the ammonium was subject to nonequilibrium transport. The amounts of adsorbed ammonium increased significantly, while the first-order kinetic rate decreased along with the drop of temperature.

Keywords: Nitrate; Ammonium; Breakthrough curve; Loose-pore geothermal reservoir; Fine sand』

1. Introduction
2. Materials and methods
 2.1. Column material
 2.2. Ammonium and nitrate solution preparation and analysis
 2.3. Column displacement experiments
 2.4. Transport model
  2.4.1. Local equilibrium assumption (LEA)
  2.4.2. Nonequilibrium assumption
   2.4.2.1. Two-region nonequilibrium transport
   2.4.2.2. Two-site nonequilibrium transport
   2.4.2.3. Dimensionless transport equations
 2.5. Parameter estimation
3. Results and discussion
 3.1. Tracer experiments
  3.1.1. Analysis of nitrate breakthrough curves
  3.1.2. Effect of temperature on the nitrate transport
 3.2. Ammonium breakthrough curves
  3.2.1. Comparison of nitrate and ammonium breakthrough curves
  3.2.2. Effect of temperature on the ammonium transport
4. Conclusion
Acknowledgments
References


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