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Gao L.,CAS Institute of Atmospheric Physics | Zhang R.,CAS Institute of Atmospheric Physics | Han Z.,CAS Institute of Atmospheric Physics | Fu C.,Nanjing University | And 4 more authors.
Aerosol and Air Quality Research | Year: 2014

A PM2.5 pollution episode over Hangzhou, China during 8 to 16 December 2011 was simulated using the Models-3 Community Multiscale Air Quality (CMAQ). Relative contributions from local and regional emission sources to the pollution event were also investigated through numerical sensitivity tests. Comparisons between simulations and measurements at six meteorological sites over the Yangtze River Delta Region (YRDR) and four air monitoring stations at Hangzhou were satisfactory. The temporal mean of the PM2.5 mass concentration in Hangzhou was lower than those at most areas of Jiangsu province and Shanghai during the episode. Process analysis of the four air monitoring stations at Hangzhou shows that emissions and aerosol processes contributed to the primary and secondary PM2.5 concentrations, with the mean accumulated rates of 1.2-25.5 μg/m3/hr and 0.5-1.2 μg/m3/hr, respectively. The process of advection also increased the PM2.5 mass concentration (1.2-3.4 μg/m3/hr). Diffusion was the dominant removal process at most air monitoring stations, with the removal rates of 4.1-20.7 μg/m3/hr. The dry (-3.0 to -3.6 μg/m3/hr) and wet deposition and heterogeneous processes (-0.4 to -1.8 μg/m3/hr) contributed to the loss of PM2.5. Process analysis also indicates that the maximum concentrations of PM2.5 that occurred during 13-14 December were mainly due to ineffective removal through diffusion. Results of the sensitivity tests suggest that non-Hangzhou pollutants made significant contributions to the PM2.5 pollution in Hangzhou, reaching up to 70% during the focal episode. Under certain meteorological conditions, pollutants transported from outside of Hangzhou not only increased the PM2.5 concentration, but also extended the pollution episode period in Hangzhou by one day. Nevertheless Hangzhou's local emissions were not negligible, because they had important impacts on PM2.5 peak values. © Taiwan Association for Aerosol Research.

Wu L.,Nankai University | Shen J.-D.,Environmental Monitoring Center Station of Hangzhou City | Feng Y.-C.,Nankai University | Bi X.-H.,Nankai University | And 2 more authors.
Research of Environmental Sciences | Year: 2014

During hazy and non-hazy episodes in 2011, the size-segregated particulate matters were sampled in four sites using Anderson particulate cascade impactor in Hangzhou City urban area. The mass concentrations of PM in different size bins and their chemical species had been analyzed. The receptor and source profiles had been constructed, and the size-segregated source apportionment of PM had been done by using the chemical mass balance (CMB) receptor model. Modeled results revealed that there was a significant difference of source contributions between hazy and non-hazy days. In hazy days, the main source of PM mass concentrations were secondary particles, contributing by 60.4%, 62.2%, 54.8% and 46.5% respectively to PM in different size bins (≤1.1, >1.1-3.3, >3.3-5.8 and >5.8-10 μm). Among the main pollution sources, vehicle emission was an important contribution source to the fine PM less than 1.1 μm and between >1.1-3.3 μm, contributing 13.8% and 12.2% respectively. Re-suspended dust and cement dust were important sources to PM in >3.3-5.8 and >5.8-10 μm size bins respectively, contributing 16.0% and 14.2%, respectively. In non-hazy days, with the increase of the particulate size, the contribution of secondary particles decreased sharply, contributing to the fine PM (≤1.1 μm) of 42.7% and to coarse PM (>5.8-10 μm) of only 15.5%. Vehicle emission was the major source, contributing over 20% to the measured PM mass in each size bin. Coal combustion dust was also an important source to fine PM (≤3.3 μm) with 22.0% contribution rate, while re-suspended dust was the important source to intermediate size particles (>3.3-5.8 μm) and cement dust was the important source to coarse PM in >5.8-10 μm size bin.

Wang Q.,Nankai University | Bi X.-H.,Nankai University | Zhang Y.-F.,Nankai University | Yang C.-J.,Environmental Monitoring Center Station of Hangzhou City | And 3 more authors.
Zhongguo Huanjing Kexue/China Environmental Science | Year: 2012

Samples of atmospheric particles were collected in August at four monitoring stations (Yunqi, Zhaohui, Hanggang, Xiasha) in Hangzhou City. Size distributions of the main extinction components were quantified, including SO 4 2-, NO 3 -, NH 4 +, OC and EC. Meanwhile, a wide range of gaseous pollutants and meteorological elements were observed simultaneously on Zhaohui station in order to assess the influence factors of visibility degradation. PM 2.5, RH, SO 2 and NO 2were negatively correlated with visibility. The peaks of particles concentration appeared in the size of 0.4~0.7 μm and 9.0~10 μm. SO 4 2-, NO 3 -, NH 4 + and OC exhibited the single modal. The peaks of SO 4 2- and NH 4 + were in the size of 0.4~1.1 μm, while the peak of NO 3 - appeared in the size of 5.8~10 μm and the peak of OC was in 0.4~0.7 μm. EC exhibited the bi-modal and the peaks were in 0.4~0.7 μm and 2.1~3.3 μm. In order to solve the visibility problem of Hangzhou, the fine particles, especially the size that less than 1.1 μm should be reduced primarily. EC was the dominant extinction component in this study and the pollution sources of EC, such as vehicle exhausts should be primarily controlled in Hangzhou to improve the visibility and reduce the haze days.

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