Current Status of Aerosol in the Northern Key Economic Zone of Vietnam and Identification of Region Affecting Hanoi's Air Quality

Abstract

The Northern Key Economic Zone (NKEZ) of Vietnam, a critical region for national development, experiences significant particulate matter pollution. This study investigates aerosol pollution and its transboundary effects across the NKEZ by integrating the Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) dataset and the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. The results reveal: (1) Anthropogenic aerosols exhibit statistically significant upward trends (p < 0.05), with sulfate concentrations ranging from 7.59 to 9.29 μg.m⁻³ and organic carbon from 4.79 to 10.87 μg.m⁻³; (2) MERRA-2 captures PM_2.5 seasonal trends, with correlation coefficients (p < 0.01) of 0.83 in spring and 0.71 in winter, though it significantly underestimates PM_2.5 level in winter in Hanoi; (3) combined analyses of trajectory frequency and pollution concentration correlations delineate five levels of impact (level 1–5, from minimal to very high) on Hanoi’s air quality and identify key black carbon (BC) source regions. These include coal-fired power plants in Thai Binh, Thanh Hoa (levels 3–4, in spring), biomass burning in east-northern mountainous region of Vietnam (levels 4–5, in autumn), biomass burning in central-southern Laos (levels 2–3, peak Fire Detection Counts in March–April) and transboundary contributions from central-southern China (levels 2–3, in autumn). The integration of MERRA-2 and HYSPLIT establishes a robust methodology for classifying pollution sources affecting Hanoi, providing a technical framework for future regional air quality investigations.