Variation of Air Pollutants and Their Relation with Meteorological Conditions in Hangzhou

Based on the monitoring data of air pollutants from 2002 to 2007 over Hangzhou,according to ambient air quality every day in surrounding cities of Hangzhou,combined with different types of pollution and meteorological data,the characteristics of air pollutants and its relationship with weather conditions are analyzed.The results show that the frequency of pollution days in air quality is decreased year by year, and the air quality has been improved step by step,because the concentrations of PM_(10) that is the primary pollutant are decreased by degrees.The day of heavier level pollution in large-scale continual pollution is half more than that of other two types of pollution,and the highest concentration of PM_(10) appears in largescale continual pollution,and lowest in the individual pollution,there are 0.253 mg·m~(-3) and 0.177 mg·m~(-3),respectively.The different types of pollution are affected by various weather situations,their pollution level is also changed.The rates of different pollution types have an obvious seasonal variation,which is highest in winter,lowest in summer,there are 25.6%and 3.6%,respectively.Among the different types of pollution,the rates of individual pollution and local continual pollution are 40.7%and 29.9%,respectively. The rates of different pollution types in four seasons are very obvious,showing a higher rate of local pollution type in winter,that of individual pollution in spring,and that of the large-scale continuous pollution in autumn.The air quality in summer,that appears to be few of local pollution days,is the best in four seasons.The levels of different pollution are different,presenting the grades ofⅢ1(level of slight pollution) is mainly the type of local pollution,the grades ofⅢ2(lightly pollution) andⅣ1(moderat pollution) are mainly the large-scale continual pollution type,the grades ofⅣ2(moderat heavier pollution level) andⅤ(heavy pollution level) are mostly the individual pollution type that affected by the duststorm or firework in the Spring Festival.