Diagnostic Ratios and Directional Analysis of Air Pollutants for Source Identification: A Global Perspective with Insights from Kuwait

Identifying the sources of atmospheric pollutants is essential for effective air quality management. This study assesses the diagnostic value of SO2/NO2 and CO/NO2 ratios in distinguishing between major emission sources, including vehicular traffic, industrial activity, and biomass burning. A global literature review was conducted to establish typical ratio thresholds associated with different sources. These thresholds were then applied in a case study of Kuwait, a representative Gulf Cooperation Council country with intense vehicular traffic and industrial activity. To complement the ratio-based diagnostics, directional pollution source identification was performed using the Conditional Bivariate Probability Function (CBPF) plots, linking elevated pollutant concentrations to prevailing wind speeds/directions. Results indicate that Al-Fahaheel exhibits a distinct SO2/NO2 ratio toward the south-southeast due to industrial activities, and a pronounced CO/NO2 ratio toward the east, reflecting contributions from mixed urban and traffic-related sources. The observed ratios at the Al-Fahaheel air quality monitoring station—very low CO/NO2 and moderate to high SO2/NO2—are inconsistent with vehicular emissions and are more indicative of industrial emissions from stationary sources. Directional CBPF plots reinforce these associations by clearly linking industrial activities and vehicular traffic sources to the southeastern and western sectors, respectively.