Ching Ho Lin

A method for locating influential pollution sources and estimating their contributions

This work develops a source-oriented approach to locate the influential pollution sources and estimate their contributions to pollutant concentrations observed at a receptor site. The domain containing possible influential pollution sources is divided into systematic grid cells, and the influential grid sources are determined based on the locations of the segment endpoints of air trajectories arriving at the receptors. The contribution of each grid source is initially calculated using a formula derived from a Lagrangian box model and including the effects of source emissions, atmospheric dilution, and chemical transformation and deposition. The formula is described in detail in this study. Finally, the average contribution of each grid source is determined based on numerous analyzed events. The proposed approach was used to locate influential pollution sources and determine their contributions to a rural monitoring station during periods of high SO2 pollution in southern Taiwan. The contributions of sources in various 2 km by 2 km grid cells, five districts, three source categories, 8 industrial areas, and a power plant were evaluated. The results show that the major influential sources were in the northwestern region of south Taiwan, and belonged to three district and point sources. Furthermore, two industrial areas close to the evaluated stations were also very significant, and contributed about 30% of the total pollution.

Semi-statistical model for evaluating the effects of source emissions and meteorological effects on daily average NOx concentrations in South Taiwan

Abstract This study developed a new semi-statistical model based on a Lagrangian approach. The overall effects on the observed pollutant levels at a receptor site were divided into two groups, one including the effects of emissions from various upwind sources and the other including all other effects (including the overall effects of atmospheric dilution, chemical transformation, and wet and dry depositions). The former effects were directly accounted for by a new parameter, an emission factor, defined as the accumulated emission uptake along the air trajectory toward the analyzed receptor site. All other effects were represented by a pollutant transfer coefficient. Meteorological parameters, excluding wind direction, were suggested to simulate this coefficient. The model was used to simulate variations in daily average NOx concentrations at a receptor site in south Taiwan during 1995–1999. Four meteorological factors, temperature, humidity, wind speed and pressure, were used to simulate the pollutant transfer coefficient. The full model successfully explained 61% of the analyzed concentration variations. The emission factor was the single most important factor in the model. When this factor was omitted, the determination coefficient of the model decreased from 61% to 48%. However, the pollutant transfer coefficient still dominated the analyzed variations of concentration.