Long-term assessment of PM10 and SO2 in northwestern Türkiye: meteorology, inversions, and transboundary transport

This study provides a comprehensive long-term assessment of air quality in Balıkesir, northwestern Türkiye, focusing on the spatiotemporal variability of PM10 and SO2 during 2013-2023. The analysis integrates pollutant observations with ERA5 reanalysis meteorological data to examine seasonal and diurnal variations, long-term trends, and the role of temperature inversions and atmospheric circulation in shaping pollution episodes. Results indicate that both pollutants reach their highest concentrations in winter due to intensified domestic heating and stagnant meteorological conditions, with temperature inversions acting as a key driver of near-surface accumulation. The Theil-Sen trend analysis revealed an insignificant long-term change in PM10 but a statistically significant upward trend in SO2 (+ 0.5 µg m⁻3 year⁻1), suggesting persistent reliance on sulfur-rich fuels during the cold season. However, a short-term decline after 2020 reflected the combined effects of cleaner fuels and pandemic-related emission reductions. Correlation analysis demonstrated that PM10 and SO2 are moderately interrelated (r = 0.49) and primarily controlled by high-pressure, low-wind conditions. HYSPLIT trajectory analyses confirmed that severe winter episodes result from the combined influence of local stagnation and regional air mass transport. These findings highlight the dual importance of emission control and meteorological monitoring in managing winter pollution. Policy recommendations include stricter regulation of heating fuels, inversion-based early-warning systems, and enhanced regional cooperation to mitigate transported particulate matter.