| In recent years, there are many researches related to the water-soluble organic compounds in the atmosphere, but most of them are on the land and on the fixed sampling points over the sea. However, researches on the distribution in time and space of water-soluble organic matter in the atmosphere of China's offshore area are still relatively less. The East China Sea and the South China Sea are the important areas where the atmosphere from Asian continent is transported to Oceans.Forits close proximity to the continental margin and largely influenced by human activities, the study of samples collected in the voyage of the East China Sea and the South Sea are mainly concentrated on ions or small molecules,while there are few studies on Water-soluble organics. Water-soluble organic matters will emit fluorescence excited by ultraviolet or visible light, so the fluorescent characteristics can be used to track the hydrolytic organic matter of aerosol.The study collected the samples of marine aerosol from the South China Sea in 2013 and 2014, and the samples of marine aerosol from the East China Sea in 2014.The organic carbon,elemental carbon,water-soluble carbon of the samples are analyzed through three-dimensional fluorescence spectra and PARAFAC, as well as the sources,temporal and spatial variations are studied.Main conclusions I got are listed as follows:1. In our study the concentration value of OC and WSOC in TSP samples that are collected in day time from the navigation in the East China Sea, and it turns out that the concentration value is higher than the samples that are collected in the night. Because of strong daylight in daytime, secondary organic aerosols can be generated in daytime easier. Owing to the effect of photochemical oxidation, the contribution of first and second organic carbon in the daytime is greater than nighttime.2. WSOC concentration in the air of the East China Sea shows a periodic change at different stages in the time series plots, and one period lasts for about six days. It could be caused by the straw burning in mainland China, and the transportation of continental air mass.3. There are significant Peak A, Peak M and Peak B in the WSOC in the air of the East China Sea. Peak A and peak M has significant correlation, which means they have similar sources. Because of stronger sunlight and longer daytime in summer, Peak B has higher degradation degree than Peak T, so Peak T in this study is not obvious. The humic-like peak decreases in the night, and protein-like peak increases gradually when it turns to the nighttime from daytime, but when the dawn comes, the emergence of the sun affects the microbial activities of marine algae, which leads to the concentration decrease of protein-like peak.4. After comparing the concentration of protein-like substance and humic-like substance in the east and south sea, as well as the spatial distribution of Peak A and Peak B, the similar consistency is found, that is, continental source> mix source> ocean source, and it has a tendency that the farther it is from the land, the lower concentration is. Besides, the concentration of humic-like substance is higher than protein-like substance, while the concentration of Peak A is the main one in concentration of the humic-like substance.5. From the three-dimensional photofluorogram of the South China Sea, only two significant peaks, Peak A and Peak M are found. With PARAFAC analysis, it can be seen the samples that are collected in 2013 and 2014 consist of three components. The excitation wavelength/emission wavelength of component C1 are 260/400-460nm and 320-360/420-460nm respectively, which can be recognized as Peak A of UVC humic acid and Peak M of UVA ocean humic acid; component C2 is a protein-like component with a Ex/Em that equals to 240/400nm; corresponding Ex/Em of component C3 are 280/460nm and 360/460nm, which can be regonized as humic-like peak. |
PDF Full Text Request