Assessment of ambient particulate matter and trace gases in Istanbul: Insights from long-term and multi-monitoring stations

In this study, the long-term spatio-temporal variation, trends, and source increments of particulate matter (PM10 and PM2.5) and gaseous pollutants (SO2, NO, NO2, CO, O-3) measured from 2015 to 2021 across 37 air quality monitoring stations in the European and Asian sides of Istanbul were investigated. The average PM10 concentration on the European side is higher than the Asian side. However, the average PM2.5 in both regions showed the same values. The results show that the industries near urban sites mainly affect PM10 concentrations in Istanbul. Ship emissions (from the Istanbul Strait) make the largest incremental contribution to SO2 and CO (211% and 139%, respectively) among other pollutants. PM10, PM2.5, SO2, and NO2 concentrations show significant (p < 0.01) negative temporal trends of 6.02%, 6.97%, 5.38%, and 3.28%, respectively, most notable in the winter season. However, the CO and O-3 concentration trends are stable and increasing. According to the correlation coefficient (R) and the coefficient of divergence (COD) analysis, there is a heterogeneous distribution of pollutants at the intra-urban scale. PM2.5 concentrations are dominated by diverse pollution sources such as traffic, shipping and regional sources.