Abstract
Based on ambient air quality data of the four key cities (Nanning, Liuzhou, Guilin, and Beihai) in Guangxi, China, along with an analysis of the main emission sources, topographic features, weather conditions, and backward trajectories, the variation of main air pollutants and pollution episodes in the four cities were studied. Results showed that air pollution was most serious in Liuzhou and Guilin, followed by Nanning and Beihai. PM2.5 was the dominant pollutant in each city, followed by O3, PM10, and NO2. Concentrations of SO2 and CO did not exceed their National Ambient Air Quality Standard Grade II limit values. In the cities, the concentrations of PM2.5, PM10, NO2, and SO2 were high during fall and winter and low during spring and summer, while the concentrations of O3 were high during fall and low during the other seasons. Concentrations of CO were low during summer and high during the other seasons in Nanning and Liuzhou, while they were high during spring and winter and low during summer and fall in Guilin and Beihai. In these cities, pollution episodes resulted mainly from stagnant accumulation and showed characteristics of regional pollution. However, pollution levels and durations for each city were different due to differences in main pollution sources, local geography, and weather conditions. The influences of air masses on the four cities were similar. They were mainly influenced by local emission sources in the spring, while during autumn, long-distance transportation from Hunan and Hubei was significant. In winter, air pollution in Nanning and Beihai was mostly affected by local emission sources, and that in Liuzhou and Guilin was mainly affected by long-distance transportation from the south and northeast of Guangxi.
Highlights
The annual mean was highest in Liuzhou (70 μg m−3 ), followed by Guilin (66 μg m−3 ), Nanning (57 μg m−3 ), and Beihai (46 μg m−3 )
The concentrations of SO2 were highest in Liuzhou, followed by Guilin, Nanning, and Beihai, with 24 h mean 98th percentile values of 80 μg m−3, 77 μg m−3, 52 μg m−3, and 38 μg m−3, respectively
Concentrations of PM2.5, PM10, NO2, and SO2 were low during summer and high during fall and winter
Summary
Located in the southern part of China, the Guangxi region is bordered by Guangdong to the east, Guizhou to the north, Yunnan to west, the Gulf of Beibu and Southeast Asia to the south, and Vietnam to the southwest. Its capital, Nanning, is the permanent host city for the China-ASEAN Expo and the International Folk Song Arts Festival. Guilin, and Beihai are famous tourist attractions in China and abroad. Liuzhou is an industrial city, and Beihai is the only coastal city in western China. The four cities have domestic and international influences, and their local air quality has attracted extensive attention
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