Development of a source-meteorology-receptor (SMR) approach using fine particulate intermittent monitored concentration data for urban areas in Ohio.

摘要

This study presents a comprehensive source-meteorology-receptor (SMR) approach to understand the fine particulate (PM2.5, particles less than 2.5 mum in diameter) problem in three major cities of Ohio viz., Cleveland, Columbus, and Cincinnati. The work emphasizes a three pronged combined approach using the available receptor, meteorology and source data to analyze the PM 2.5 concentrations to identify, establish and quantify the PM2.5 behavior, the effect of meteorology and responsible factors, and the relative source contributions to the pollutant in the three urban areas under consideration. The different analyses are directed towards better understanding PM2.5 by characterizing the pollutant, studying the behavior, establishing the effect of meteorology, and delineating specific major sources and their relative contributions to the problem. Every step of the SMR approach helps in better understanding the pollutant by revealing the trend and the seasonal variations, by establishing favorable conditions for higher concentrations, and by identifying the problem-causing sources. Review of the literature indicates that such an approach has not been developed for urban areas where only intermittent concentration data are available and meteorology plays a minor role in fine particulate pollution problem.; The trend study revealed that all three cities exhibited a seasonal PM 2.5 concentration pattern with higher concentrations in summer and lower in winter. PM2.5 and its species both showed seasonal and spatial variations. In all the three cities, ammonium sulfate and organic carbon (OC) comprised the largest fraction of PM2.5 followed closely by ammonium nitrate concentrations. The three major components ammonium sulfate, organic carbon, and ammonium nitrate accounted for about 37-46%, 20-22%, and 15-20% of the total PM2.5 in the three cities. Sulfates dominated the summer-time PM2.5, and nitrates contributed to the winter concentrations in all the areas under study. Seasonal differences in the sulfate concentration ranged from 3-7 mug/m3 from one season to another in each of the cities. The average summer sulfate concentrations were approximately 45% more than the winter time concentrations. The nitrate concentrations were generally higher in winter than in summer, probably due to a combination of lower temperatures and meteorology. Crustal components did not show much seasonal variation for Cincinnati and Columbus, but a summer high was observed for Cleveland. The correlation analysis revealed strong component to component associations at all the sites. Total PM2.5 was found to be strongly correlated with sulfate, ammonium, and OC. Ammonium was correlated better with sulfate than nitrate; organic carbon and elemental carbon (EC) were strongly correlated with each other suggesting similar emission sources. The OC/EC ratio was consistently higher in summer and winter showing similar strengths of the pollutant emissions during both the seasons. The annual average nitrate/sulfate mass ratios for the three cities were consistently below 1 suggesting stationary source emissions as the dominant sources in the three cities studied. In addition, an evaluation of episode days when PM2.5 concentrations were over 35 mug/m3 identified summer episodes characterized by high sulfate concentrations and winter episodes with high nitrates. OC concentrations were similar during both of the seasonal episodes in all the three cities suggesting the local emissions of OC.; The meteorological effect and contribution study revealed wind speed to be the most significant meteorological variable for the three cities.; This study has developed a three pronged SMR approach to systematically analyze the fine particulate problem and the approach was successfully applied to the three major cities in Ohio. The approach incorporates both basic and advanced analyses to fully capture the PM2.5 problem in its entirety and can be applied for major urban areas in the