Spatio-Temporal Assessment of Air Quality and AQI in Former Khanh Hoa Province, Vietnam (2021-2024)

Abstract

Air pollution has become an increasingly important environmental and public health concern, particularly in rapidly urbanizing coastal provinces. This study aimed to evaluate the spatio-temporal variation characteristics of key air quality parameters (TSP, SO₂, NO₂, and CO) and the Air Quality Index (AQI) in former Khanh Hoa Province during the period 2021-2024. Periodic monitoring data collected from 28 monitoring sites across four functional zones (North, South, West, and Central) were analyzed using descriptive statistics, seasonal comparison, Pearson correlation analysis, AQI calculation, and GIS-based spatial interpolation (IDW). The results showed that SO₂ and CO concentrations significantly decreased by 62% and 22%, respectively (p<0.05), while NO₂ remained relatively stable and TSP showed signs of increasing, particularly in 2024. TSP was identified as the dominant pollutant, accounting for more than 95% of AQI deterioration and frequently exceeding the annual average standard in the Central region. Overall air quality was generally classified as “Good” and “Moderate”; however, localized pollution hotspots and short-term unhealthy AQI events were observed, especially during the dry season in urbanized areas with high traffic density and intensive construction activities. Pearson correlation analysis revealed that humidity and wind speed played important roles in pollutant dispersion and washout effects, while noise levels showed significant positive correlations with TSP, NO₂, and CO, indicating the strong influence of transportation-related emissions. These findings suggest that air quality management should prioritize TSP source control, particularly in the Central region, and strengthen seasonal monitoring strategies to support sustainable environmental management in rapidly developing coastal provinces of Vietnam.