Identification of potential regional sources of ambient criteria air pollutants at a national controlled air quality observation site in Guiyang

Abstract

Abstract Comprehensively characterising air pollutant cross-boundary transport is indispensable for determining effective control measures to further improve the air quality. Taking advantage of datasets of criteria pollutants (i.e., PM10, PM2.5, SO2, CO, NO, NO2, NOx and O3) and meteorological parameters, we comprehensively characterised the regional transport of air pollutants in Guiyang using bivariate polar plots (BPPs) and Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT-4), potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) models. The average mass concentrations of PM10, PM2.5, SO2, CO, NO2 and O3 were lower than the CNAAQ Class I standards and were much lower than those in the key air pollution control regions for the Blue Sky Protection Campaign. Decreasing trends in PM10, PM2.5, SO2, NO, NO2 and NOx and an increasing trend in O3 were observed, confirming the effectiveness of air pollution control policies and suggesting that continuous and effective emission control measures should be implemented to further improve the air quality. The BPPs revealed that all pollutants, except O3, attained higher mass concentrations when wind speeds were low, and under the high-wind speed scenario, the dependence of the air pollutant concentrations on the wind speed and wind direction varied seasonally. The high-concentration backward trajectories and PSCF and CWT analysis results demonstrated that both tailored local emission reduction and regional cooperative control, which should be implemented when suitable, are crucial for controlling multiple pollutants and hence further improving the air quality in Guiyang in the upcoming years.