Modeling of atmospheric dispersion of NOx from coal-fired power plants in Japan

The Air Quality Management Division of Ministry of the Environment in Japan selected the maximum level of daily average air quality standard for NOx, which is 0.04-0.06 ppm. The yearly average atmospheric emissions of NOx from a point source, background concentrations of NOx in the atmosphere and meteorological data have been used to predict the ambient concentration of NOx at ground level by atmospheric dispersion modeling. To estimate the NOx concentration in the air of the local area, two different models have been used. The first, is the fully coupled WRF/Chem (Weather Research and Forecasting/Chemistry) model that estimates regional atmospheric distribution of NOx concentration. The second is METI-LIS (Ministry of Economy, Trade and Industry-Low-Rise Industrial Source Dispersion Model of Japan) model that estimates the atmospheric distribution of NOx concentration in the vicinity of industrial facilities. The atmospheric concentration distribution of NOx was calculated for the central Honshu Island of Japan using the WRF/Chem model, which served as a background data for the METI-LIS model to calculate the atmospheric NOx concentration in the vicinity of industrial facilities. Concentrations of particulate matters derived from the Regional acid Deposition Model (RADM2) chemical mechanism and Secondary Organic Aerosol Model (MADE/SORGAM) with aqueous reaction were used to deduce the corresponding aerosol fluxes for input to the WRF/Chem. The model was firstly integrated for 96 hours continuously starting from 00:00 UTC on 14 March 2010 to evaluate NOx concentrations and other precursor pollutants were analyzed. WPS meteorological data were used for the simulation of the WRF/Chem model in this study. Then the WRF-ARW model was integrated for 96 hours continuously starting from 00:00 UTC on 14 March 2010 to evaluate the meteorological condition in the vicinity of a hypothetical coal-fired power plant in Japan. Finally, The yearly average atmospheric emissions of NOx from an elevated industrial point source located in the coastal area of Japan with a background concentration of NOx calculated by WRF/Chem and 4 days high resolution meteorological data calculated by WRF-ARW, have been superposed in METI-LIS model for computing the ground level concentrations of NOx in the vicinity of the hypothetical coal-fired power plants. In this study, atmospheric concentrations of NOx in the vicinity of the hypothetical coal-fired power plant was calculated to be 20-30 that was lower than the Japanese daily average air quality standard for NOx.

Keywords: Dispersion modeling, Atmospheric NOx concentration, METI-LIS, WRF/Chem, NOx emissions