| Due to the increasing influence of human behavior such as more burning of fossil fuels, more and more greenhouse gases and atmospheric pollutants were produced. On one hand, it may increase the greenhouse effect. On the other hand, a series of environment problems may occur due to the climate change, and both of which may pose threats to ecosystem and human health eventually. Aerosol and greenhouse gas make a directly effect on the global climate by absorption and scattering solar radiation and long-wave radiation from the ground. Climate change plays an important role on the distribution, transport and transform of atmospheric pollutants. Under the background of climate change, it is important to understand characteristics of bioaerosols, greenhouse gas and the pollutants in the atmosphere, which is significant to understand and study the climate change and the potential impact of climate change on human and ecosystem. The air over the ocean is less influenced by the human behavior and could be sensitive to climate change. But it’s still poorly understand the variations of aerosol, greenhouse gases and atmospheric pollutants over oceans especially for the remote oceans. According to the4th Chinese National Arctic Research Expedition (CHINARE2010) and the5th Chinese National Arctic Research Expedition (CHINARE2012), we take an example of methane, bioaerosol and atmospheric mercury to discuss their temporal and spatial distributions and potentially influencing factors. The major contents and results in this dissertation are listed below.(1) The variations of methane and the influencing factorsDuring the5th China Arctic Research Expedition (CHINARE2012), we describe new shipboard determinations of atmospheric CH4concentrations and δ13C-CH4measurements conducted from offshore China to the central Arctic Ocean, covering the latitudes and longitudes of31.1°N-87.4°N and22.8°W-90°E-166.4°W. This study is the first to report the temporal and spatial distributions of atmospheric CH4concentrations from Offshore China to the central Arctic Ocean. The average value of CH4(1.88±0.12ppm) was in agreement with the current background value; however, CH4concentrations and δ13C-CH4displayed obviously temporal and spatial variations ranging from1.65to2.63ppm, and from-50.34%o to-44.94%o (average value:-48.55±0.84‰), respectively. The variation of were influenced by atmospheric oxidation, human source and microorganisms, etc. The latitudinal loss of CH4due to chemical oxidation by both OH and Cl radicals was outweighed by source contributions over the remote oceans. Changes in δ13C-CH4versus changes in mixing ratio and the air sources revealed that human sources play an important role in regional variations. By the light contrast experiment, there were no significant difference of CH4and δ13C-CH4between sunlight and dark along the cruise. However, the flux experiment showed more methane can be produced in sunlight. The flux experiments further confirmed that CH4over the central Arctic Ocean were influenced by microbes. It indicated that microbes may make up sinks of chemical oxadation.(2) The variations of bioaerosol and the influencing factorsFungi aerosols are thought to be one of important bioaerosols. During the4th Chinese National Arctic Research Expedition (CHINARE2010) from July to September,2010, the concentrations and size distributions of airborne fungi in the marine boundary layer were investigated. The concentrations of airborne fungi varied considerably with a range of0to320.4CFU/m3. The fungal concentrations in the marine boundary layer were significantly lower than those in most continental ecosystems. The mean concentrations of airborne fungi in the region of the China offshore, the western North Pacific Ocean, the Chukchi Sea, the Canada Basin, and the central Arctic Ocean were172.2±158.4,73.8±104.4,13.3±16.2,16.5±8.0, and1.2±1.0CFU/m3, respectively. Airborne fungi over oceans roughly displayed a decreasing trend with increasing latitudes.Airborne fungi has a large size distribution pattern. In most areas expect for the Arctic Ocean, airborne fungi showed a unimodal size distribution pattern, with the maximum proportion (about36.2%) in the range of2.1-3.3μm and the minimum proportion (about3.5%) in the range of0.65-1.1μm, and63.1%occurred on the range of1.1-3.3μm.Potential factors influencing airborne fungal concentrations and size distributions, including the origin of air mass, meteorological conditions, and sea ice conditions. Among these factors, temperature was the main factor. The suitable temperature and foggy condition contributed to the growth of fungi. Besides, with temperature increasing, the process of sea ice melting will be accelerated, so microorganisms or nutrient substances in the sea ice will probably be released to the atmosphere and increase the concentration of airborne fungi.(3) The variations of atmospheric mercury in the Arctic Ocean and the influencing factorsDuring the5th China Arctic Research Expedition (CHINARE2012) the Chinese vessel Xuelong first passed through the Northeast Passage and the central Arctic Ocean. High resolution data were measured by Mercury analyzer (2537B). Here we combined the data in the Arctic Ocean during CHINARE2010to report the characteristics of total gaseous mercury (TGM) concentrations through the central Arctic Ocean from July to September,2012. The TGM concentrations varied considerably (from0.15ng/m3to4.58ng/m3), with an average of1.23±0.61ng/m3. The highest frequency range was1.0-1.5ng/m3, lower than previously reported background value in the Northern Hemisphere. Inhomogeneous distributions were observed over the Arctic Ocean due to the effect of sea ice melt and/or runoff. A lower level of TGM was found in July than in September, potentially because ocean emission was outweighed by chemical loss. It indicated that more mercury enter into the Arctic Ocean due to the atmospheric chemistry, which may enhance the threat on the ecosystem in the arctic.(4) The variations of atmospheric mercury over the Northwestern-pacific volcanic belt and around Iceland region and the influencing factorsDuring the5th China Arctic Research Expedition (CHINARE2012) we reported the spatial distribution of TGM over Northwestern-pacific volcanic belt and around Iceland region outside the Arctic Ocean. The TGM concentration ranged from0.17to9.03ng/m3with an average of1.86±1.21ng/m3(median:1.55ng/m3). We divided the entire cruise into5legs based on the close volcanic or geochemical regions. The TGM average in legl and Ieg4close to Japan were1.99±0.71ng/m and2.56±1.39ng/m, respectively. The peaks in the two legs were due to the ocean emission. In leg2and leg3near to the Kamchatka peninsula TGM were1.23±0.55ng/m3and2.78±1.42ng/m3, respectively. The peaks in the Ieg3was due to the volcanic activity based on the SO2information and the air mass of volcanic ash. The peak in leg2was due to the air mass from the higher concentrations over the North Pacific Ocean. In leg5around Iceland TGM was1.39±1.02ng/m3with a peak value in Reykjavik harbor (average:1.91±1.27ng/m3) due to the role of geothermal activities. Our study focus on the effect of natural sources on the atmospheric mercury, which provides the supplement data for the global mercury and as reference data for quantitative evaluation of atmospheric mercury flux.The observation and analyze on atmospheric methane, bioaerosol and atmospheric mercury in the paper were across a large range of space, especially in the Arcitc Occean. The data update and make up the existing data and contribute to improving model research and accurate assessment of the climate effect. The discussion of the influencing factors update our knowledge of atmospheric change. Thus, it can effectively evaluate influence of the oceans on the atmosphere and the potential effects of climate. |
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