| More than 70% area of Earth covered by oceans, marine aerosol is an important type of atmospheric aerosols. Also marine aerosol is critical cloud condensation nucleus, playing an important role on the formation of clouds and rain. Ocean is an open system, especially adjent sea, greatly affected by continent. During every period from October to next April, Asian dust with the air mass movement toward the Pacific Ocean will be transported to rich marine life of N, P, Fe and other nutrients. Meanwhile, the pollutants along the way will be transported to the downwind area. Mineral aerosols and its carrying pollutants will be mixed on the way and transformed. After they reached coastal region, they may further mix with sea salt, so the atmosphere of physical and chemical characteristics will change. In addition, the aerosol would affect the marine primary productivity through wet and dry deposition. As people have been paying more attentation on the environmental problems of Red Tide, acid rain and global warming, atmospheric aerosols of adjent sea has become one focus of domestic and foreign research.A total of 210 samples were sampled from Mar.20,2008 to Feb.18,2009 on the surface land of Xiaoyangshan Island on East China Sea, analyzing their mass concentration, water soluble ions and elements. Meanwhile, it was simultaneously sampled in neighboring city—Shanghai and analyzed black carbon. The main contents of this research were:the seasonal distribution of atmospheric aerosol of adjent sea and its physical and chemical characteristics represented by Xiaoyangshan Isle; estimating the contributions of mineral aerosols and its main continental source; analyzing the sources of sulfate, nitrate, black carbon and the level of elemental pollution; discussing the mixing mechanism of continental aerosol with sea salt and the change of physical and chemical characteristics under the influence of terrene;and calculating the dry deposition flux of main compounds in aerosols. The research will help control regional environmental quality and resvole the problems of acid rain and global warming. The results were as follows:The aerosol concentration of Xiaoyangshan Isle on East China Sea is in a high level over the world. The annual average concentrations of PM2.5 and TSP were 72.5μg m-3 and 119.2μg m-3 respectively. The value of PM2.s was about as three times as the annual standard of World Health Organization--25μg m-3.Also more than 90% of sampling days, the mass concentration of PM2.5 were more than the daily standard of WHO--35μg m-3.It showed a significant seasonal variation of aerosol and its composition and size distribution.In PM2.5, the seasonal average concentration of TWSI,BC, SO42-, NO3-, NH4+ and elements Al,K, Mn, Sr, Ti, P, Co, Ni, V, Cr, Cu, Pb, S was highest in winter; in TSP, that value of TWSI, SO42-, NO3- and element Al, Fe, Mg, Na, V, As, S, Zn was maximum in spring. In winter, about 76% of the aerosol in TSP were fine particules; while more than 50% of aerosol in TSP was coarse mode in spring. The annual average concentration of total water-soluble ions (TWSI) in PM25 and TSP was 17.1μg m-3 and 33.3μg m-3, which contributed about 25% and 29% to mass concentration. Major ions were:SO42-, NH4+, NO3-, Cl-, Na+ and Ca2+,the sum concentration of them accounted 79% and 80% for the TWSI in PM2.5 and TSP respectively. The existence of these ions may form as:NH4HSO4 and (NH4) 2SO4, NH4NO3, CaSO4, Ca (NO3)2,CaCl2, MgCl2, NaCl, KNO3 and K2SO4. In spring, there was NaNO3 resulting from clorine deplacing reaction.The analysis of pH and C/A showed that, generally, there was acidic pollution of atmospheric environment in the region of Xiaoyangshan Isle on the East China Sea in all of the year. This may be resulted from the pollution of SO2 and NOx transformed to SO42-and NO3- through heterogeneous reaction on the surface of mineral aerosol, such as CaCO3.These productions will further react with NaCl in sea salt, which leaded to chlorine deficiency. This region had been influenced by fossil fuel combustion emissions transporated from Yangtze River Delta area as the correlation coefficients of nss-SO42- and BC were above 0.55 other than summer, while the slope was close to 0.07.excess K/BC showed that the biomass burning contribution to K and BC was greater than that of fossil fuel for PM2.5. The correlation coefficients of BC in TSP between Shanghai and Xiaoyangshan Isle in spring and winter were 0.66 and 0.83,indicating that the influence of costal city was significant there under the condition of air mass movement from continent. With Al as reference, element enrichment factor (EF) analysis showed that the pollution of elements on Xiaoyangshan Isle of East China Sea was similar to that of urban, which further reflected the continental characteristics of atmospheric aerosl there.The analysis of source released that the total contribution of crust and sea salt to PM25 and TSP was only 9% and 19.4%, while the average concentration of mass concentration, the major ions and elements in aerosol were maximum under the wind direction of WNW or NW. That illustrated the continental source and human activity may be more important sources for atmospheric aerosols in this area. And during the sampling period,74% days were affected by air mass from continent and the concentration of particle was highest on this condition in any season. Atmospheric aerosols may impact on the coastal ecosystems and regional climate through dry deposition. |
PDF Full Text Request