| The long-range transport of atmospheric aerosol from continents to the oceans has important implications for ocean ecosystems, climate and atmospheric chemistry. Nutrients from continental aerosols fertilize the ocean water by stimulating phytoplankton growth and thus influence marine geochemical cycle. Serious atmospheric pollutions have been observed along the coastal cities and ports because of rapid economic increase. The major three regions of haze pollution in China are Pearl River Delta, Yangtze River Delta and the Bohai region. The rapid deterioration of air quality in Yangtze River Delta has brought significant challenges. As the economic center of the Yangtze River Delta and the holder of the World Expo 2010, the air pollution control in shangahi has been the hot topic.The number concentration and size distribution of the atmospheric particle varies with different photochemical processes, air mass characteristics and emission types. To know about the size distribution and sources of particles in different size bins can help us have a deeper understanding about the effects of atmospheric aerosols on the atmospheric radiation balance, chemical process and even climate change. The data collected and the results got in this study would provide valuable information for the policies of the fine particle control.In this study, Total Suspended Particulates (TSP) samples were collected over the Atlantic Ocean and the Pacific Ocean during two cruises in September-December 2007 (CruiseⅠ) and March-April 2008 (CruiseⅡ) aboard the M/V OceanicⅡ. Data were analyzed and interpreted with the aid of back trajectory, principal component, and multiple linear regression analyses. We first report the overall concentrations of inorganic ions, Elemental Carbon (EC), and Organic Carbon (OC) in five regions, compare the results with those from previous studies, and then examine the contribution of continental aerosols to the marine environment and the chemical interactions between marine and continental aerosols. Secondly, we finished the TSP aerosol sampling in 11 ports over the world to find out the common chemical features for coastal cities and the effects of ship emissions. Thirdly, we focused on the seasonal and diurnal variations of particle size distribution in urban Shanghai, and the different formation mechanisms for different pollution types also have been investigated.The major results got from this study are as follows:1. Chemial Characterization of marine aerosols over the world oceans: Compared with the results over the South Pacific from two decades ago, the non-sea-salt sulfate (NSS-SO42-) concentrations over the South Pacific have increased by a factor of～1.5, while the NO3- concentration has remained constant. Assuming that the nitrate values measured in South Pacific (0.12±0.15μg·m-3) are representative of oceanic "background" and that these values are applicable to the oceans in the Northern Hemisphere, the continental sources appear to account for 82% (the Northern Atlantic Ocean Part during CruiseⅠ),89%(Southern Atlantic Ocean), 91%(the Northern Atlantic Ocean Part during CruiseⅡ), and 87%(the Mediterranean Sea) of the total nitrate concentration during the observation periods. On average, NSS-SO42- accounted for 30%-52% of the total SO42- during the two cruises. Chloride deficit was observed in all samples, with NSS-SO42- being the preferred species for acid displacement over the South Pacific and the Mediterranean Sea. Persistent clean marine air masses were only observed over the Northern Atlantic and South Pacific during CruiseⅠ, while more frequent impacts of continental air (dust, biomass burning, and industrial plumes) were observed during cruiseⅡ. Combined with the NAAPS aerosol maps, these results indicate that during cruiseⅡ:(1) Southern Atlantic was influenced by Southern Africa and the inter-hemisphere transport of biomass burning plumes in Central Africa; (2) Northern Atlantic was under the combined pollution plumes of Sahara dust intrusion and biomass burning; and (3) the Mediterranean Sea was affected by the mixed pollution from biomass burning and industrial contamination, as well as Saharan dust.2. The chemical characteristics in 11 ports over the world:Large ratios of OC and EC were found except Tahiti Islands, which were in the range of 11.1%-46.9% and 1.9%-16.8%, respectively. For the TSP mass concentration, the order is: Shanghai> Cape Verde Islands> Barcelona> Istanbul> Lisbon> Cape Town> Tahiti> Auckland> Sydney> Guayaguil> Panama. Relatively high ratio of OC has been shown in Barcelona, Istanbul and Cape Verde Islands, and Lisbon with high ratio of NO3-, Panama with high ratio of MSA, Guayaguil, Auckland and Sydney showed high ratio of SO42-. Shanghai is the most polluted port with much higher ratios of secondary inorganic ions:such as SO42-, NO3- and NH4+3. Seasonal and diurnal variations of particle number concentration and size distributions in Shanghai:Not only high number concentration, but also the higher percentage of ultrafine particles has been observed in Shanghai than in Europe and North America sites. It was found that the number concentration is dominated by Aitken mode particles with obvious seasonal and diurnal variations. Three types of diurnal variations have been observed:Single peak (atmospheric photochemical formation of particles and the role in promoting the growth process); Twin Peaks (source emissions from traffic and vehicles), Three peaks (combined effects from photochemical process and traffic emissions).4. Characterization of particle size distributions of different pollution events: The different formation mechanisms of pollution episodes are investigated during 10 months observation period in Shanghai. Three types of haze, i.e., secondary inorganic pollution, dust, and biomass burning were confirmed by using the particle size distribution, air mass backward trajectory, meteorological parameters and chemical components analysis. (1) Secondary Inorganic Pollution:generally last for 3-5 days; particle number is dominated in the size range of 20-200 nm without obvious particle formation and growth process; number concentration can be as high as 30000-80000 cm-3; (2) Dust:generally last for several hours to one day with high wind speed and low RH; particle number is dominated in the size range of 20-100 nm with the increasing of 20-100 nm percentage and total volume concentration; Concentration of Mg2+ and Ca2+ are higher than usual while secondary inorganic ions, such as SO42-、NO3-、NH4+ are "diluted" by the dust effect; (3) Biomass burning:no obvious change of total number concentration with the dominated size range of 10-100 nm; obvious increasing of number concentration in the size range of 500-1000 nm contribute to the increase of mass concentration was observed.5. Physical Characterization of Aerosol particle number size distributions during the Chinese New Year’s firework event:Particles concentrations during the peak hour of firework celebrations were approximately 3 times higher than the day before, with a clear shift of particles from nucleation and Aitken mode to small accumulation mode particles. Coagulation sinks for all particle sizes were greatly enhanced during the firework celebration due to high concentrations of accumulation mode particles. The maximum coagulation sink values for 1 and 100 nm particles were 0.146 s-1 and 6.98×10-5 s-1 during the peak hour, respectively. Thus, lifetimes of 1 and 100 nm particles were in the order of seconds and hours, respectively, resulting in reduction and disappearance of smaller particles. Daily averaged particle density was calculated as high as 2.7 g cm-3, which would be one of the parameters that directly control particle deposition in lungs by inertial and sedimentation processes. The results demonstrate that primary emissions from firework celebrations significantly alter the modal structure of particle size distributions and particle density. Both these properties are likely to influence particle radiative properties and toxicological effects. |
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