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Composition and Sorce of Atmosphere Aerosol Water Soluble Ions over the China Coastal Seas

Author: HeYuHui
Tutor: YangGuiPeng
School: Ocean University of China
Course: Marine Chemistry
Keywords: aerosol MSA non-sea-salt-sulfate water-soluble ions China Coastal Seas Research of characteristics
CLC: X513
Type: Master's thesis
Year: 2011
Downloads: 93
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Abstract

The atmospheric aerosol is constituent by the water-soluble ions （WSI）. Aerosols plasmid affect the global climate change through direct and indirect radiative forcing. Therefore the research of WSI is significance. From the local point of view, it also plays an important role in air quality. The reason of high concentration water-soluble ions of atmospheric aerosols over China coastal seas is the input of higher natural sources in East Asia and man-made sources. At the same time, the appropriate weather conditions make these high concentrations of aerosols over the Pacific Ocean through atmosphere and then affect the ecological environment and the atmosphere chemical composition of ocean zones. Because China coastal seas act as the major tunnels through which the East Asia aerosols could be transported to the ocean areas. In this dissertation we choose the Yellow Sea, South China Sea and East China Sea as research objectives.The marine aerosol samples were collected over the Yellow Sea, the South Yellow Sea, the East China Sea and the South China Sea during spring and winter 2009, summer 2008, spring, autumn and winter 2009 and winter 2009, respectively. With the ion chromatographic method, we detected the water-soluble ions concentration in atmospheric aerosol, and the seasonal and regional variations, the sources of major WSI and the aerosol characteristics are studied. The main conclusions are draw as follows:（1）the concentration of the major WSI follow the order nss-SO₄^2-> NO₃^-> Cl^-> Na⁺> Ca²⁺> Mg²⁺> NH₄⁺> K⁺ in the total suspended particulates（TSP） during the spring cruise 2009 over Yellow Sea, while the orders of that in the summer cruise 2008 and winter cruise 2009 are nss-SO₄^2->NO₃^->Cl^->Na⁺>NH₄⁺>Ca²⁺>Mg²⁺>K⁺ and NO₃^->nss-SO₄^2->Cl^->NH₄⁺>Na⁺>Ca²⁺>Mg²⁺>K⁺, respectively.The average concentration variations of samples which were collected in the three seasons are different, but secondary ion (NO₃^-, nss-SO₄^2-, NH₄⁺) concentrations contribute over 58% of the total detected WSI mass concentration. The changes of sea salt ions (Cl^-, Na⁺, Mg²⁺) concentration are similar, while the mixed sources of K⁺ and Ca²⁺ concentration remain the same, and shares of K⁺ in the three cruises are the lowest concentration ratio, especially in summer cruise 2008（only 0.5%）.The results indicate that the chemical composition of TSP over Yellow Sea and South Yellow Sea is strongly influenced by anthropogenic emissions. The average concentration of methanesulfonic acid in the three seasons of the samples collected were 0.078±0.011μg·m^-3 in spring2009, 0.048±0.012μg·m^-3 in winter 2009 and 0.012±0.011μg·m^-3 in summer 2008, respectively. At the same time, single-factor variance analysis showed that there were significant seasonal differences.（2） The concentrations of the major WSI in the aerosols of East China Sea follow the order of NO₃^-> nss-SO₄^2-> Cl^-> Na⁺> Ca²⁺> Mg²⁺> NH₄⁺> K⁺ in aerosol samples during the spring cruise of 2009,which are similar to the Yellow Sea in spring voyage. The changes of average concentration are similar in autumn cruises and winter cruises and follow the order of nss-SO₄^2-> NO₃^-> NH₄⁺> Cl^-> Na⁺> Ca²⁺> Mg²⁺> K⁺ and nss-SO₄^2-> NO₃^-> Cl^-> NH₄⁺> Na⁺> Ca²⁺> K⁺> Mg²⁺,respectively. The concentration ratio of nss-SO₄^2- in every voyage decline to around 30%, while the proportion of NO₃^- varies slightly, indicating that the loss degrees of the secondary ions in transporting process in the atmosphere are different. The minimum value of NH₄⁺ that appears in the spring may due to special weather conditions what speed up its deposition velocity. The seasonal variations of concentration of MSA in TSP are obvious, with a mean concentration of 0.060±0.031μg·m^-3 in spring, 0.015±0.012μg·m^-3 in autumn and 0.0088±0.0048μg·m^-3 in winter. The significant seasonal variation is due to the vibrant reproduction of phytoplankton which releases a high concentration of dimethylsulfide （DMS） in surface water in the spring, and the further oxidation reaction of DMS generates MSA.（3） The significant changes of the Secondary ions in TSP of the winter cruise 2009 over the South China Sea which are significantly lower than the proportion of sea salt ions relate to the sampling area, meteorological conditions and different sources of air particles. The average concentration of the major WSI follows the order of Cl^-> nss-SO₄^2-> Na⁺> NH₄⁺> NO₃^-> Mg²⁺> K⁺> Ca²⁺. The proportion of sea salt ions reaches up to 55% which indicates the degree of air pollution in the South China Sea is relatively smaller. And the reason for the lower degree of air pollution may be the heavy losses of secondary ions during the wide-range and long-distance transportation. The concentration of MSA is only 0.0026±0.0015μg·m^-3 in the South China Sea, which is only 29.5% in the East China Sea in winter voyage.（4） Simple relationships between ion pairs are studied through cross-correlation analysis. Correlation analysis between the secondary ions indicates that they share similar source----the anthropogenic land-based sources. The significant positive correlation among Cl^-, Na⁺ and Mg²⁺ , and the closer slope of the linear regression equation between Na⁺ , Mg²⁺ and bulk seawater indicate that the three ions mainly from marine. Sources of K⁺ and Ca²⁺ are more complex because there is significant correlation between them and also correlate with other ions, so the two ions would be classified to land-based sources and influenced by marine. Correlation analysis between the WSI concentrations and the meteorological date show that the sea salt components are influenced by wind speed. The significant positive relationships between the secondary ions and the temperature / relative humidity （RH） indicate that the secondary ions tend to form better at a relatively high temperature and RH.（5） Biogenic sulfur’s contribution to non-sea-salt-sulfate(nss-SO₄^2-) is calculated based on the empirical ratio (nss-SO₄^2-/MSA=19) over the remote ocean region. Over the Yellow Sea, the biogenic sulfur’s contributions during spring and winter 2009 and summer 2008 are 16.76%, 2.97% and 9.21%, respectively; while over the East China Sea the contribution of biogenic sulfur during spring ,autumn and winter 2009 were 16.00%, 3.08% and 1.42%,respectively. The biogenic contribution over the South China Sea during winter is 0.72%. The contribution of biogenic sulfur to nss-SO₄^2- over the studied area is the highest in spring and the lowest in winter. The phenomenon can be attributed to the vigorous activity of phytoplankton in spring which can release a large number of DMS to the surface water, and affect the contribution of biogenic sulfur ultimately through a series of chemical reactions. Generally, the atmospheric nss-SO₄^2- over the sampling areas are mainly from anthropogenic emissions of land-based sources, but biogenic sulfur contribution can not be ignored.（6） The research of aerosol characteristics mainly focus on pH and form of the main combination of NH₄⁺ and SO₄^2- over the Yellow Sea in winter, the East China Sea and the South China Sea, respectively. The results indicate that the aerosols over Yellow Sea, the East China Sea and South China Sea are neutral, acid present, and weak alkaline, respectively. The main combining form of NH₄⁺ and SO₄^2-in aerosol are diverse in different seas. The main combining form in the aerosol samples which were collected from the Yellow Sea and the East China Sea is NH₄HSO₄ ,however, that over the South China Sea is （NH₄）₂SO₄.

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