An Observational Study on Air Quality in Lanzhou China

Spatial and temporal variability of SO2, NO2, NOx, PM10 and total suspended particles (TSP) concentrations in Lanzhou, China is analyzed using the observational data collected from October 1999 to April 2001. The concentrations of SO2, NO2, NOx are within the national second-standard level of air quality in spring, summer and fall, but much worse in winter, reaching low to mid alert level of air pollution. Since 1999, the concentrations of SO2, NO2, and NOx have been decreasing. However, the concentrations of PM10 and TSP have been increasing, and become major pollutants. The mean concentration of PM10 is 2.56 mg m-3. Even in summer the air pollution due to PM10 is at low alert level. The rate of polluted-day occurrence is 71% in a year, 89% in winter, and 79% in spring. Starting from November, the air pollution due to PM10 intensifies, and reaches mid to high alert level of air pollution, and continues until April next year. The mean concentration of TSP is 5.92 mg m-3, which is higher than the air quality standard. In winter and spring, the TSP concentration is 2-10 times higher than the third-standard level of air quality. Intrinsic factors and exterior preconditions for increase of PM10 and TSP are discussed such as the propagation of dust storms.