Spatial and temporal variations in criteria air pollutants in three typical terrain regions in Shaanxi, China, during 2015

Abstract

Numerous studies have investigated air pollution in severely polluted plains, but the characteristics of pollutants are not well understood in other terrain regions. In this study, air pollution characteristics were analyzed in three typical terrain regions (plateau, plain, and mountain regions) in Shaanxi, based on hourly ambient monitoring of particulate matter with diameter less than 2.5 μm (PM_2.5) and less than 10 μm (PM₁₀), CO, SO₂, NO₂, and O₃ in 2015. PM_2.5 and PM₁₀ were the dominant pollutants in three regions, and their annual concentrations exceeded the Grade II standards by 9.4–68.6 and 6.0–73.9%, respectively. PM_2.5, PM₁₀, CO, SO₂, and NO₂ concentrations had similar seasonal trends with highest values in winter and lowest values in summer, whereas O₃ concentrations exhibited the opposite trend. Guanzhong Plain had higher PM_2.5, PM₁₀, NO₂, and SO₂ concentrations but lower CO, 1-h peak O₃, and 8-h peak O₃ (8 h-O₃) compared to other regions. PM_2.5, PM₁₀, and 8 h-O₃ were the three main dominant pollutants. The nonattainment rate was highest in winter and lowest in summer or autumn. Pollution also exhibited synergy, especially in the plateau region and Guanzhong Plain. PM_2.5 was significantly correlated with PM₁₀. NO₂ and SO₂ were positively correlated with PM_2.5 and PM₁₀, while 8 h-O₃ generally had significant negative correlations with other pollutants, especially in the winter. These results provide a comprehensive understanding of pollution status in the three typical terrain regions in Shaanxi and are helpful for improving air quality.

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