Simulation and Estimation of the Inter-Source Category and/or Inter-Pollutant Emission Offset Ratios for a Heavy Industry City

Abstract

Kao-Ping Air Basin (KPAB) is a heavy industrial area, and also the first and only air quality total quantity control district in Taiwan. Pollutant emission offsetting is an important tool to reduce pollution source emissions and improve air quality in the total quantity control district. In this study, an air quality model was employed to evaluate the sensitivity of SOX, NOX, and primary PM2.5 emissions from point, mobile, and fugitive sources on PM2.5 concentrations in KPAB. The findings show that the emission offset ratios of mobile PM2.5-to-point PM2.5 and fugitive PM2.5-to-point PM2.5 were both greater than one in urban areas (1.3 and 2.0, respectively) and both less than one in non-urban areas. The offset ratios of point SOX-to-point PM2.5 and point NOX-to-point PM2.5 were significantly greater than one, especially those in urban areas (20 and 60, respectively) were higher than those in non-urban areas by more than 2–4 times. No matter whether in urban or non-urban areas, the offset ratio of mobile NOX-to-point NOX was close to one, and the offset ratios of point NOX-to-point PM2.5 and mobile NOX-to-point PM2.5 were similar. The above findings were closely related to the proximity of point sources to densely populated urban areas in KPAB.