Abstract:

This study was initiated to explore the pollution status of Lanzhou City in recent years and provide a reference for its prevention and management. The daily air quality index and mass concentrations of PM_2.5, PM₁₀, SO₂, NO₂, O₃ (8 h, the 8 h moving average of ozone), and CO from 2014 to 2021 were used to analyze the monthly, seasonal, and interannual variation characteristics of air pollution in the valley city of Lanzhou. The changes in air pollutants and the continuous characteristics of air pollution in Lanzhou were also analyzed. The results show that the number of short-term mild continuous and long-term moderate and severe continuous pollution processes peaked in winter, the number of short-term moderate and severe continuous pollution processes peaked in spring, no moderate and severe continuous pollution processes occurred in summer, and long-term mild continuous pollution processes occurred more often in fall and winter. Pollutants that play a major role in the process of continuous pollution differ because of different seasons, durations, and grades of continuous pollution. The main pollutant in the mild, moderate, and short-term severe continuous pollution processes in winter is PM_2.5, and the main pollutants in the long-term severe continuous pollution process are PM_2.5 and PM₁₀. The main pollutant in the continuous pollution process in spring is PM₁₀, the main pollutant in the mild continuous pollution process in summer is O₃ (8 h), the main pollutant in the short-term mild continuous pollution process in fall is PM₁₀, whereas the main pollutants in the long-term mild continuous pollution process are PM₁₀, PM_2.5, and NO₂.

Key words: continuous pollution process, air quality, pollutant, valley city, Lanzhou