【作者】 李黎；

【导师】 傅家谟； 汪午；

【作者基本信息】 上海大学 ， 环境工程， 2009， 博士

【摘要】 二次气溶胶因环境、气候、健康效应愈来愈受到人们的关注,其中,天然源二次气溶胶因其前体释放量巨大,不容忽视。本文按照纬度的不同,选择了四个典型森林地区(长白山自然保护区、崇明岛东平国家森林公园、鼎湖山自然保护区、海南尖峰岭自然保护区),作为中国寒温带、温带、亚热带、热带森林的代表,研究其二次气溶胶的化学组成和浓度水平。长白、崇明、鼎湖、海南地区PM2.5的质量浓度分别为89.2,38.8,30.4,18μg/m3;有机物和元素碳分别占PM2.5总量的22-35%和1.3-2.3%;三种主要的无机离子(SO42-,NO3-,NH4+)总和分别占PM2.5质量的44%,50%,45%,16%;水溶性有机碳占有机碳质量的35-65%。此外,重要的PM2.5组分还包括地壳类物质、海盐和水。除海南外,长白、崇明、鼎湖的PM2.5总量、有机碳、硫酸根、铵离子的浓度浓度在世界森林地区中均偏高,四个森林地区重要的PM2.5构成来自于其周边地区的污染传输,程度不同地呈现了区域污染特征。中国森林面积1.75亿公顷,异戊二烯和单萜挥发总量和整个欧洲相当。中国森林气溶胶中异戊二烯氧化产物和α-蒎烯氧化产物的浓度分别为4.8-53 ng/m3和n.d.-31 ng/m3,依次占当地OC总量的0.02-0.96%和0.01-0.23%。不同区域的测定结果显示:异戊二烯氧化产物表现了一致的昼夜变化趋势,即白天浓度高于夜晚;长白气溶胶中异戊二烯氧化产物和当地大气中SO2,O3,CO2具有明显相关性,提示大气痕量气体在异戊二烯氧化过程中发挥了重要作用。α-蒎烯氧化产物在不同地域气溶胶中表现了不一致的昼夜变化规律。除上述氧化产物之外,四个森林地区气溶胶中测定的其他天然源二次组分还有:葡萄糖、果糖、阿拉伯醇、甘露醇等,检出的天然源极性二次组分分别占当地气溶胶OC总量的1.2-4.4%。此外,论文还建立了一个针对于气溶胶中2-甲基丁四醇的稳定碳同位素分析方法,即甲基硼酸衍生物稳定碳同位素分析法。测定异戊二烯氧化产物—2-甲基丁四醇的稳定碳同位素组成,通过异戊二烯的同位素值可判断其前体物不同光合作用类型植物(C3、C4、CAM)的稳定碳同位素组成特征,还可揭示大气中异戊二烯光化学反应的稳定碳同位素变化规律。论文通过实验证实了2-甲基丁四醇甲基硼酸衍生化过程中没有同位素分馏,甲基硼酸衍生法物稳定碳同位素分析方法应用于实验室光化学反应及长白气溶胶样品中2-甲基丁四醇的稳定碳同位素测定,获得了较好的测量精密度和准确性。更多还原

【Abstract】 Secondary aerosols have been captured more and more consideration due to their impacts on environment, climate and health. Thereinto, biogenic secondary aerosols take an important position in secondary aerosol since their enormous precursors. This dissertation is objected to four typical forests along north latitude in boreal, boreal- temperate, temperate, subtropical, tropical climatic zones in eastern China. i. e. Changbai Mountain Nature Reserve (CB), Dongping National Forest Park in Chongming island (CM), Dinghu Mountain Nature Reserve (DH), Jianfengling Nature Reserve in Hainan island (HN). Chemical composition and polar tracer levels of four forest aerosols were determined, formation mechanism of isoprene andα-pinene oxidation were discussed.The 24-h average concentrations of PM2.5 were 38.8, 89.2, 30.4, 18μg/m3 at CB, CM, DH and HN, respectively. Organic matter and elemental carbon (EC) accounted for 20-31% and 1.3-2.3% of local PM2.5 mass, respectively. Sum of three dominant secondary ions (SO42-, NO3-, NH4+) accounted for 44%, 50%, 45% and 16% of local PM2.5 mass at CB, CM, DH and HN, respectively. Water soluble organic carbon (WSOC) comprised 35-65% of organic carbon (OC). Major components of PM2.5 also included crustal matter, sea salt and bound water. Except HN, CB, CM, DH all had relatively high concentrations of PM2.5, organic matter, sulfate, ammonium among forest areas in the world, the air quality at four forest areas is dominated by regional transport, attributed to be a typical regional pollution.China has total forest areas of 175, 000, 000 ha. Emission of Isoprene and monoterpene in China are comparable with in Europe. The concentrations of isoprene andα-pinene oxidation products at above four forests were ranged from 4.8 to 5.3 ng/m3 and from n.d. to 31 ng/m3, accounting for 0.02-0.96% and 0.01-0.23% of OC, respectively. A diel variation of isoprene oxidation products was found at four forest areas with highest concentrations during daytime, consistent with their photochemical reaction mechanisms. At CB, isoprene oxidation products were found have a good correlation with SO2, O3, CO2 in the atmosphere. On the other hand,α-pinene oxidation products did not show consistent diel variation between different sampling places. Beside isoprene andα-pinene oxidation products, many other biogenic marker compounds were also determined in this study, involving glucose, fructose, levglucosan, arabitol, mannitol etc. Total identified polar tracers contributed 1.2-4.4% of OC for four forest areas.Moreover, this dissertation has established a novel analytical method for stable carbon isotopic determination of 2-methyltetrols, the major marker compound of isoprene photooxidation products in the atmosphere. Methylboronic acid was used to derivatize 2-methyltetrols and the stable carbon isotope compositions of methylboronate derivatives were measured by gas chromatography/isotope ratio mass spectrometry (GC/C/IRMS). Because C3, C4, CAM plants emit isoprene with differentδ13C values, studies on the stable carbon composition of 2-methyltetrols, may provideδ13C values of isoprene, the precursor volatile organic compound, and theδ13C information of the isoprene-emitted vegetation, as well as atmospheric insight on the photochemical process from isoprene to 2-methyltetrols. Experiments illustrates that there is no isotope fractionation during methylboronic acid derivatization of tetrols and the new method acquired high accuracy and good precision when it was used in determining stable carbon isotopic composition of 2-methyltetrols from laboratory isoprene photochemical reactions and Changbai aerosol samples.更多还原