| Weekly samples of PM2.5 and PM10 were collected at two sites, Fudan and Dongtan, in Shanghai from October 2008 to November 2010. Fudan site situated in urban area and Dongtan site located in the international important wetland inside Chongming Island. The mass concentration, organic carbon (OC), element carbon (EC) and water soluble ions were determined. Chemical mass closure was calculated, and then the sources of atmospheric particles were analyzed. We also examined the charicteristics of atmospheric partcles in typical polluted periods in urban and dongtan all the year, and explored the effects of Shanghai Changjiang Tunnel-bridge on atmospheric environment in Dongtan wetland, and discussed the influence of emission control on urban atmospheric particles and regional environment during Shanghai EXPO. Besides, we investigated the partcles number concentration, chemical composition and size distribution, and discussed the characterization of atmospheric particle number and size during longterm heavy pollution, particularly focused on the particle number concentration, size distribution and chemical composition during haze and photo-chemical smog episodes in Shanghai. The purpose was to explore the features of atmospheric particles in Dongtan wetland, and reveal completely the long-range variation trend of urban atmospheric particle pollution in Shanghai, the coastal mega-cities. These results could provide forceful support for dealing with atmospheric issuses of urban agglomeration.The main results in the dissertation as bellow:1. Level and chemical properties of PM2.5 and PM10 in urban Shanghai and Dongtan wetland:(1) Average mass concentration of PM2.5 and PM10 in urban were 27.8 and 48.6 μg/m3,2.53 and 1.35 times the average value of the world cities, respectively. The average mass concentration of PM2.5 and PM10 in Dongtan were 15.8 and 22.1 μg/m3, over the first grade of the Ambient Air Quality Standard. The PM10 mass showed a strong seasonal variation in urban and Dongtan wetland, and exhibited uniform chatacters, i.e., winter>spring>autumn>summer. The urban PM2.5 mass showed seasonality similar to PM10, but the seasonal change of PM2.5 in Dongtan wetland was different from PM10. The ratio of PM2.5/PM10 in Dongtan wetland was bigger than urban, and PM2.5 in Dongtan was influenced greatly by urban. (2)The total water soluble ions were 45.8% and 56.6% of the mass concentration of PM10 and PM2.5 in urban Shanghai, respectively. The total water soluble ions were 55.1% and 65.7% of the mass concentration of PM10 and PM2.5 in Dongtan wetland, respectively. The total water soluble ions concentration of urban PM was 1.5-1.8 times that of Dongtan. The three dominated ions of SO42-, NO3- and NH4+ accounted for 88.9% and 80.9% of the total soluble ions of PM2.5 and PM10 in urban,90.6% and 85.7% in Dongtan. The concentration of Ca2+ and Cl" in PM10, Cl- and K+ in PM2.5, was higher than other minor ions at urban site, but the concentration of Na+ and K+ in PM10 and PM2.5 was higher than other minor ions at Dongtan site. It showed that the influence of ocean and biomass burning on ionic species of Dongtan wetland. Ionic size distribution was different in different seasons in urban and Dongtan. (3)The concentration of OC and EC were 16.3% and 9.6% of PM10,21.2% and 14.8% of PM2.5 in urban, respectively. The concentration of OC and EC were 15.1% and 10.8% of PM10,20.4% andl6.9% of PM2.5 in Dongtan, respectively. Carbonaceous aerosol chiefly distributed in fine particles. The content of OC was higher than EC, and the concentration of OC and EC in urban were higher than Dongtan wetland. OC and EC size distribution were different in different seasons in urban and Dongtan. The ratio of OC/EC in Dongtan wetland was smaller than urban.2. Sources of atmospheric particles in urban Shanghai and Dongtan wetland: (1)The conversion factors f of OC-to-POM (particulate organic matter) and k of Ca2+-to-dust obtained from the dataset of PM10 and PM2.5 from long-term samples. The f and k value were 0.10 and 1.3 in Fudan,0.05 and 1.4 in Dongtan, respectively. Particle chemical mass closure displayed that the highest contribution of dust (30.0%), followed by POM (19.5%) in urban PM10. The major component was POM (23.6%), followed by SO42-(22.2%) in urban PM2.5. The highest dust and SO42- contribution (22.7%) were found in Dongtan PM10. SO42 (27.5%) and POM (21.8%) were major components in Dongtan PM2.5. (2)Each proportion of five backward trajactories of air mass (L, E, S, W, N) was 12.1%,20.3%,21.6%,6.3%,39.7% during the investigated period. W and L were heavy polluted types in Dongtan wetland, secondly N, then E and S. W were highest polluted types in urban, followed by N and L alternately. The highest proportion of NH4+、NO3-、K+、Cl- appeared in L, W, L, N, respectively. The highest proportion of SO42- existed in L. The highest proportion of OC and EC was W and S in Dongtan wetland, differed from that of urban. (3)The ratio of NO3-/SO42- in Dongtan wetland was smaller than urban, dominated by stationary sources. The K+/OC value in PM2.5 of harvest time was higher, greatly influenced by biomass burning.3. The features of atmospheric particles during typical periods in urban and Dongtan wetland:(1)The mass concentration of PM2.5 and PM10 in duststorm, biomass buring, haze and fireworks events were 2 to 4 times as that of clear days. The content of Ca2+ in PM10 was highest of four polluted event, and the ratio of PM2.5/PM10 was smallest in dustsrtorm. K+ was highest in biomass buring. Total soluble ions was highest, especially SO42-, NO3- and NH4+. Cl- and NO3-/SO42- was highest in fireworks, and mainly distributed in coarse particles. Cabonaceous aerosol was highest in biomass buring and haze. (3)The Shanghai Changjiang Tunnel-bridge was opened in the periods of sampling, which greatly influenced NH4+, NO3-, SO42-and Cl- of the total soluble ions in Dongtan PM by high vehicle flow. The concentration of NH4+, NO3-, SO42- and Cl" in PM2.5 increased by 52.9%,22.3%,26.7% and 25.5%, respectively, as compared to the same period of the previous year. The contents of NH4+, NO3- and SO42- in PM10 had 24.8%,21.3% and 12.7% increased. Anthropogenic pollution had tremendous impact on the atmospheric particles in Dongtan wetland. (3)The particulate concentration of during the EXPO was lower than the corresponding period of the previous year, in which K+、NH4+、SO42- and Cl-declined remarkably in Dongtan, and K+ and Ca2+ decreased sharply. Control measures achieved satisfactory results, but regional transport still had considerable affect on particulate pollution in the condition of strict emission control strategies.4. Particle number concentration, size distribution and chemical composition in urban Shanghai:(1)Annual number concentration of atmospheric particles was 1.11 × 104 cm-3, and the concenration of nucleation, Aitken, accumulation mode were 1156, 7619, and 2388 cm-3, respevtively. The total surface and volume concentration was 443 μm2/cm3 and 40 μm3/cm3. Number, surface and volume concentration had the same seasonal change, that is the maximum in winter, and then spring and autumn, the minimum is in summer. (2)The days of continued heavy pollution accounted for 74.2% of the December of 2013, in which the greatly increase of particulate number of 100 nm-1 μm was the chief cause, with high suface and volume concentration during severe pollution. (3)Soluble ions mainly distributed in the particles within range of 0.4-2.1 μm, and peak at 0.7-1.1 pm. The two peaks of NO3- presented in partilces lager than 5.8 μm and smaller than 2.1 μm. The peaks of Ca2+ and Cl- appered in 5.8-10 μm, and K+ and Na+ scattered within diameter in a fairly equal manner.5. Particle number concentration, size distribution and chemical composition during haze and photochemical smog episodes in Shanghai:The number of haze days accounted for 42.7%, of which 32.1% was severe (visibility<2 km) and moderate (2 km≤visibility<3 km) haze, mainly distributing in winter and spring. The mean particle number concentration was 1.70 x 104 cm-3 in haze, more than 2 times that of clean days. The greatest increase of particle number concentration was in 0.5-1 μm and 1-10 μm during haze events, about 17.78 times and 8.78 times those of clean days. The largest increase of particle number concentration was within 50-100 nm and 100-200 nm during photochemical smog episodes, about 5.89 times and 4.29 times those of clean days. The particle volume concentration and surface concentration in haze, photochemical smog and clean days were 102,49,15 μm3/cm3 and 949,649,206 μm2/cm3, respectively. As haze events got more severe, the number concentration of particles smaller than 50 nm decreased, but the particles of 50-200 nm and 0.5-1 μm increased. The diurnal variation of particle number concentration showed a bimodal pattern in haze days. All soluble ions were increased during haze events, of which NH4+, SO42- and NO3- increased greatly, followed by Na+, K+, Ca2+ and Cl-. These ions were very different in size-resolved particles during haze and photo-chemical smog episodes. |
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