Characterizing Air Pollution and Its Association with Emission Sources in Lahore: A Guide to Adaptation Action Plans to Control Pollution and Smog

Featured Application Low-cost surveillance of emission sources for eminent pollutants to combat smog in cities using remote sensing. Lahore, the home of 11 million people, is one of the most polluted cities in the world. Pollution causes deaths, birth defects, and years of life lost. This study's real-time data analysis of the air quality index (AQI) showed that air pollution remained "unhealthy for everyone" for 54% of the time, and "unhealthy for sensitive groups" for 88% of the time, during the last three years (June 2019-September 2021). The air quality index (AQI) value in Lahore reached 175 mu g/m(3) in 2021. This alarmingly hazardous air situation was analyzed by selecting fourteen sites based on the provenance of industrialization and tailpipe emissions. An analysis of remote sensing data for these sites was performed, in addition to field surveys, to identify the relationship between pollutant concentration and on-ground current practices. The key primary and secondary air pollutants selected for analysis were carbon monoxide (CO), nitrogen dioxide (NO2), sulphur dioxide (SO2), aerosol optical depth (AOD), methane (CH4), and formaldehyde (HCHO). The assessment was carried out for the study period of July 2018 to April 2021. The real-time AQI was plotted against each pollutant's monthly concentration, which showed a significant positive correlation of AQI with SO2, NO2, and CO. A plotting of the percentage contribution of each pollutant with its emission sources highlighted the main pollutant to take action to reduce, as a priority on those particular sites. The pollutant hotspot within each economic activity was also determined. Assessments showed that the AQI value was higher on weekends than on weekdays. These findings can help to develop smart adaptation action plans for immediate implementation, to dilute the current environmental risks in the city.