Study On The City Ambient Air Quality And The Assessment Methods

Environmental quality assessment is a scientific method of realization and research the environmental quality. Ambient air quality assessment is one of the important branches of the environmental quality assessment. In this paper, the rationale and the methods of city ambient air quality assessment was summarized. Probability statistics method, Air pollution index (API), Fuzzy mathematics integration judge, distance distinguish method and matter element analysis method were used in this paper to estimate the air quality of Lanzhou in 2003. The characteristics of these methods were contrasted.API was used in air quality daily, the result was definitude. But in the process of choose the max value;the information of other pollutants was leaved out. Wanli-Cheng etc advanced RAQI colligated all the pollutants' impact;Zhihua-Tao etc suggested RAPI take other pollutants into account. The estimate result was more reasonable. Fuzzy comprehensive valuing and distance distinguish method considered the fuzzy character of environmental quality assessment, based on the nearness degree of pollutants consistence to judge the pollution level. The assessment results of these two methods were close. Matter element analysis method and distance distinguish method can estimate the concretely level of the pollutants, the information was reflected comprehensively. The result of matter element analysis method was low in some days;it was induced by the weight of the serious pollutant. The assessment results of fuzzy mathematics integration judge, distance distinguish method and matter element analysis method was the level of air quality;the results were clear.In this paper, spatial and temporal distribution characteristics of city ambient air pollution in China were summarized based on API data 2001-2005 that were published by SEPA. The results indicated that, in China, the chief pollutant in city ambient air is PM₁₀, spatial and temporal distribution characteristics of city ambient air pollution is distinct, the pollution is more serious in winter and spring than summer and autumn while more serious in north cities than south cities. From 2001 to 2005, the city ambient air quality of the north China had been improved evidently.Review the influence of dust-sand weather indicated that the city ambient air quality in the north China especially in the northwest China was seriously influenced. In March and April when the dust-sand weather frequently happen, API standard deviation has peak value in these days;the air quality was instability. The influence of dust-sand weather had regional features. The cities influenced by the dust-sand weather were in the north China. Lanzhou, Xi'ning, Yinchuan, Urumchi etc. were influenced seriously by the dust-sand weather. If the dust-sand weather was severe, air quality in Zhengzbou, Chongqing, Nantong, Dalian, Yantai, Qingdao, Shanghai etc which were in the central China, north China and east China coastal cities was influenced too.