Objective To analyze the time-spatial variation of air pollutants, i.e. SO2, NO2 and PM10, at two monitoring spots of Shanghai from 2002 to 2005.
Methods Daily average air SO2, NO2 and PM10 levels during 2002 through 2005 from two environmental monitoring spots (spot A in urban district and spot B in suburb district) of Shanghai were collected. The variation of pollutant levels by month, season and year was analyzed by Wilcoxon rank sum test and Kruskal-Wallis test, and the correlation between pollutants in the two sites was analyzed by Spearman rank correlation analysis using SPSS 11.5.
Results The monthly SO2 level in spot B was higher than that in spot A in January, February, March, May, September, and October (P < 0.01 or P < 0.05). The monthly NO2 level in spot B was higher than that in spot A in July and December (P < 0.01). Except February, March and May, the monthly PM10 level in spot B was higher than that in spot A (P < 0.01 or P < 0.05). The variation of monthly SO2, NO2 and PM10 levels from January to December showed a "V" shape fluctuation in both spots. The seasonal level of SO2 in spot B was higher than that in spot A in spring, autumn and winter (P < 0.01). The seasonal level of NO2 in spot B was higher than that in spot A in summer (P < 0.05). The seasonal level of PM10 in spot B was all higher than that in spot A (P < 0.01). Almost all air pollutant levels in the two spots were higher in winter and lower in summer. From 2002 through 2005, in spot A, air SO2 level was ascending year after year, variations of air PM10 and NO2 was not distinct. As for spot B, variations of air NO2 was not distinct, but air SO2 and PM10 levels were decreasing because of the comprehensive treatment of local government. According to Ambient Air Quality Standard, GB 3095-1996, the SO2, NO2 and PM10 levels of the two monitoring spots both exceeded limits, especially PM10 followed by SO2, whereas problems in spot B was more serious than that in spot A. There was a weak correlation among the levels of the three air pollutants, which was more stronger in spot A than in spot B, especially the correlation between NO2 and PM10.
Conclusion Generally, the air quality in the two spots was acceptable. The air pollution in site B was more serious than that in site A, and a weak correlation was observed among air pollutants SO2, NO2 and PM10.
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