Pollution characteristics of ozone and atmospheric particulate matter during 2013-2017 associated with meteorological factors in Lhasa, Tibet

The paper presents the air pollutant measurements and the spatial variation of air pollutants in Lhasa to reflect the characteristics of the air pollutants in a typical high-altitude city. According to the research, five-year measurements of air pollutants at 6 sites in Lhasa, were analyzed from January 2013 to December 2017. Within this period, the average pollutant concentration was highest for O3, at about 65.24 μg/m3, followed by PM10, with an average of 58μg/m3. The lowest concentration was found for SO2, with an average of 9.258 μg/m3; additionally, the concentrations of surface ozone were higher in spring (100.73μg/m3) than in winter (49.00μg/m3). O3 concentrations are greater in the spring and summer and clearly peaked at 12 and 6 PM. The NOx concentration peaked in the winter and rise sharply between 9:00-11:00 and 22:00-01:00.Air pollutants at all the 6 sites in Lhasa generally displayed similar patterns of both diurnal and monthly variations, indicating the mixed atmospheric environment and the overall effect of the meteorological conditions in the city.The air quality in Lhasa is better than in other Chinese provincial capitals because it has lower concentrations of all air pollutants except O3. The vegetation index is also one of the key factors affecting the concentration of pollutants. The highest correlation with the vegetation index was found to be with PM10 (-0.91), followed by PM2.5 and SO2, with correlation coefficients of -0.74 and -0.68, respectively. The vegetation index has a strong impact on the pollutants in Lhasa city, and areas with sparse vegetation and a dry climate usually result in higher atmospheric ozone loads. We suggested that underscoring the need for targeted interventions to enhance green spaces and mitigate the adverse effects of climate on air quality.