Abstract: According to the monitoring information and data of air quality over Aksu City,issued by the Ministry of Environmental Protection during the period of 2001-2010,the change of concentrations of air pollutants and its trend were quantitatively analyzed using the Daniel Spearman rank correlation coefficient test so as to determine the main air pollutants and air quality trend as well as their impacts on environment.The results showed that the monthly PM₁₀ concentration was the highest in March (0.818 mg·m^-3) and the lowest in September (0.282 mg·m^-3) during the period of 2001-2010; seasonally,the PM₁₀ concentration was high in spring (0.760 mg·m^-3) and low in fall (0.305 mg·m^-3) in recent 10 years.According to the distribution of monthly SO₂ concentration during the period of 2001-2010,the monthly SO₂ concentration was the highest in January (0.028 mg·m^-3) and the lowest in June (0.012 mg·m^-3); seasonally,the SO₂ concentration was high in winter (0.027 mg·m^-3) and low in summer (0.012 mg·m^-3) in recent 10 years.The monthly NO₂ concentration was the highest in December (0.032 mg·m^-3) and the lowest in July (0.019 mg·m^-3) during the period of 2001-2010; seasonally,the NO₂ concentrations was high in winter (0.030 mg·m^-3) and low (0.020 mg·m^-3) in summer in recent 10 years.Air pollution was more serious in heating period than that in non-heating period.Air pollutants in Aksu City were dominated by inhalable particles,and the air quality was generally good.From the view of the annual variation,SO₂ and NO₂ were in a significant increase trend,PM₁₀ was in an obvious decrease trend,and the urban air quality over Aksu was holistically improved year by year.

Key words: air quality, pollution characteristics, Daniel trend test, Spearman's rank correlation, Aksu City, Xinjiang