Investigation of the cross-border movement of PM2.5 in the Terai belt of Nepal using a low-cost sensor network

Transboundary air pollution is a critical environmental and public health issue across South Asia. Nepal experiences high exposure due to its geographic location near major emission regions. A network of calibrated low-cost PM2.5 sensors across the Terai belt and two Mid-land valleys recorded a sharp rise in PM2.5 levels from December 28 to 30, 2022. Monitoring sites across the country showed elevated concentration during this period. Meteorological and atmospheric data, including aerosol optical depth, air parcel trajectories, boundary layer height, ventilation coefficients, and fire events, were used to describe the regional dynamics. The Potential Source Contribution Function model was implemented to trace air masses transporting pollutants into Nepal. Our analysis shows that south-easterly winds in the east and south-westerly winds in the west carried emissions from the Indo-Gangetic Plain toward the valleys. Fire activity in the region remained low, suggesting limited influence from biomass burning. The study confirmed the viability of low-cost sensors for identifying both local and transported pollution. The findings highlight the urgent need for regional cooperation and targeted policy measures in the southern Terai to reduce cross-border and domestic emissions.

Duke Scholars

Author Michael Howard Bergin Civil and Environmental Engineering

Author Brian G McAdoo Earth and Climate Sciences