| During the past decades,Yangtze River delta is the region with fastest sped of economic development, industrialization and urbanization in China; and therefore the atmospheric pollution is becoming more and more serious, especially in urban areas. Atmospheric aerosol could bring a lot of absolutely negative effects towards climate, environment and human body; where the water soluble ions played a very significant role. As a result, to study about the water soluble ions, such as its seasonal or spectral distributions and its origins, is very important to reach a higher level of understanding and provide preventive measures.This paper mainly concentrates on four typical cities (Hangzhou, Suzhou, Lin’an, Nanjing) in Yangtze River delta, of which the samples are collected by Andersen cascade impactors from those cities during October 2012 to July 2013. In this work, ion chromatograph is used for the analysis of water soluble inorganic ions while ICP-MS is applied for the evaluation of tantalums.The result shows:for the water soluble ions, the mass concentrations in fine particle size is far larger than that in coarse particle size. The seasonal distribution of mass concentration of water soluble ions (pWSls) in fine particles complies:winter> autumn> spring> summer; while the regional pWSIs complies Nanjing> Suzhou> Hangzhou> Lin’an. There observed that in all the sampling stations, the secondary ions (SAN) of SO42-、NO3- and NH4+ weighted most of pWSIs, in both find and coarse size; and on the other hand, the mass concentration of secondary ions (pSAN) complies Winter> Autumn> Spring> Summer. Additionally, pSAN of fine modal is dominantly weighted inpWSIs, where the percentage is 91.6% in Nanjing,90.2% in Suzhou, 90.6% in Lin’an and 85.2% in Hangzhou. Here, such four cities share several similar features in particle size distribution:firstly, fine modal NH4+ ion peak appears at 0.43～ 0.65μm; secondly, crude modal ion Ca2+, Mg2+ peak at 4.7～5.8μm; thirdly, bimodal ion Cl-, SO42-, NO3- peak at 0.43～1.1μm and 4.7～5.8μm; and finally, Three modal ions Na+,K+ peak at 0.43～0.65μm,2.1～3.3μm and 4.7～5.8μm. All the four cities have observed modal shift process for SAN of SO42-, NO3- and NH4+; in other words, the pea of SAN transformed from 0.43～0.65μm in Spring and Summer to 0.65～1.1μm in Winter; which indicated the SAN experienced a modal shift tendency from condensation modal to droplets modal.Humidity is supposed to be the main reason of such modal shift process; however,in winter the droplets of sulfate, nitrate has a higher weight in atmospheric particles, which could also lead to similar results. In winter, the sulfate and nitrate is mainly brought by Northern China, and a long-distance resulted in hygroscopic growth of droplets. From principle component analysis (PCA), several conclusions could be explored. Firstly, for Hangzhou, the primary pollutants in spring are secondary pollutants, reflecting a mix of anthropogenic sources of combustion sources; while in winter, biomass combustion and urban dust emissions become the main pollutants. Secondly, for Suzhou, its main pollutants in spring related to industrial and coal-based emissions,however the pollution in summer is Inconspicuous; in autumn, the pollutants are combined with soil dust, combustion sources and secondary ions; and the pollutions in winter is a mixture of anthropogenic and combustion sources. Furthermore, for Nanjing, the main pollutants in spring are secondary ion transformation and vehicle emissions, while in summer the distribution of SAN is notably influence by sea salt. In autumn, straw burning impacts greatly to the air quality and in winter the primary pollutants are biomass burning and soil dust. |
PDF Full Text Request