| With rapid development of economy and urban congregation,the Yangtze River Delta(YRD)experiences serious air pollution due to the huge energy consumption and large emissions.Because of the clustered cities,flat landscape and the influence of climatic conditions,the impact of air pollution transport among cities is extremely significant.Among all the cities in the YRD region,Zhoushan islands is seriesly influenced of outside emissions with the total transport contribution rate of SO2 92%.To investigate the pollution formation and causes of island city,the MM5/CALPUFF modeling system was applied to quantificationally calculate the effects of air transportation on air quality in Zhoushan islands.Based on the year of 2011,this study was mainly according to the original data of pollution source census and some relevant national policies and regulations of the YRD region.Firstly,when making the emission inventory,the study considered the larger emission sources with high emission heights in YRD regionas point sources,and smaller emission sources with low emission heights as district-level area sources.Secondly,meteorological characteristics of study area was analyzed by the coupling system of MM5 and CALMET applied.Finally,CALPUFF model was used to simulate the concentration of pollution in Zhoushan island.Based on the results of CALPUFF output data,the study analyzed the transport contribution rate from other cities in the YRD region to Zhoushan and the process of the day with high air pollution in winter and summer.What's more,the relationship between pollution concentrations and meteorological was also discussed.It aimed at providing decision support to the pollution synergetic control and making the foundation of the long-range transport further understanding of secondary pollutants such as ozone and fine particles.The simulated results of meteorological data shows that the YRD region affected by the land high was prevailing northwest wind in winter,and air masses come from the northwest throughout Jiangsu and Shanghai arrived at Zhoushan;in summer,the southeast monsoon carries clean air from the sea and improves the air quality.Affected by the difference of the specific heat of sea and land,the air temperature above sea is higher than inland in winter,and lower in summer.The isothermal stratification of Zhoushan island decides the weak convection,which caused pollution dispersed weakly in vertical directory.The mixing height(MH)of islands,which is influenced by the different sources of airstream,is higher in autumn and winter than in spring and summer.Compared with cities inland,the average MH is lower in islands for whole year.Atmopheric stratification are uaually unstable(C)during the day time,but neutral(D)in winter night,and stability(E).According to the simulated results of pollution concentration data,Shanghai had the biggest contribution for SO2 71%?79%and NO2 72%?83%in Zhoushan,which mainly due to the transmission of pollutants in upper northwest atmosphere in winter;local atmospheric pollution had the biggest contribution for PM10 86.39%,and Shanghai is the biggest contributor to other cities.Zhejiang had dramatical influence on the condition of south wind,with SO252%?63%,NO2 49%?55%and PM10 54%?72%in summer,respectively.Heavy air pollutions were continually emerged,which considered relevant weather conditions such as frequent and high-speed northwest or northerly wind,the highest concentration of all monitoring sites were 122?194 ?g/m3 of NO2 per hour and 98%of contribution from regional transportation.A suggestion was presented that air quality improvement in Zhoushan islands should be jointed prevention and control with other cities. |
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