Abstract: Based on the annual average daily concentration of PM₁₀ by city was collected from 2002 to 2012, the statistical and GIS methods were used to study the spatio-temporal changes of concentration of PM₁₀ in ambient air of China. The results showed that during the study period, (1) annual daily average concentration of PM₁₀ in cities at or above prefecture level decreased from 0.130 mg·m^-3 to 0.076 mg·m^-3, and the proportion of cities meeting the Grade Ⅱ national air quality standard increased from 37.6% to 92%. (2) PM₁₀ had a highest monthly average concentration in December, followed by January and November; and showed a lowest monthly average concentration in August, followed by July and September. (3) Seriously PM₁₀ polluted areas decreased significantly, and the distribution type changed from centralized distribution to scattered punctuate distribution. But the spatial pattern of PM₁₀ pollution did not change obviously. Northern China, especially northwest China, north China, Shandong, Jiangsu and Hubei were still the relatively serious PM₁₀ polluted areas. (4) PM₁₀ pollution was more serious in northern China than in southern China, and this difference was mainly observed in heating season (from November to next April). (5) Mitigation of PM₁₀ pollution was mainly reflected on the decrease of seriously polluted cities, which accounted for 1/10 of all the cities, and could reduce about 1/3 of the national average concentration of PM₁₀. Different from heavily PM₁₀ polluted cities, the situation of PM₁₀ pollution in relatively clean cities showed an aggravating trend. (6) The PM₁₀ pollution in major environmental protection cities was slightly polluted, accounting for 80.4% of the total number of pollution days. The proportion of serious pollution day was higher in March and April due to the dust-sand weather. The results can provide reference for a better understanding of the situation and changing trend of atmospheric particulate matter pollution in China, and of significance to help the governments at all levels or policy makers to make targeted prevention and control on particulate matters pollution.

Key words: spatial differentiation, PM₁₀, spatio-temporal pattern, ambient air quality