An Evaluation of CO2, Measurements as an Indicator of Air Pollution

Measurements of ambient carbon dioxide (CO₂), made at the Continuous Air Monitoring Program station in downtown Cincinnati, Ohio, and at a rural location near Cincinnati are presented and evaluated to determine the significance of CO₂ data in urban air quality monitoring programs. Through analysis of rural CO₂ data and evaluation of combustion-sources by means of a diffusion model, it is demonstrated that the variation of urban CO₂ concentrations around the prevailing atmosphere background level results from combustion-and noncombustion {natural) sources. The concentration from natural sources can be substantial and in fact override the combustion sources. Because it is not yet practical to predict the contribution of natural sources to urban CO₂ concentrations, data obtained for-this gas have only limited utility as an index of air quality. Significant statistical relationships between CO₂ data and air quality measurements for summer months are shown to result from similar meteorological effects rather than similar sources. A seasonal and spatial variation of ih-ese relationships is postulated and subsequently demonstrated by analysis of CO₂ and air quality measurements from New Orleans, Louisiana, and SU Louis, Missouri.