【作者】 邓丛蕊；

【导师】 庄国顺；

【作者基本信息】 复旦大学 ， 环境科学， 2011， 博士

【摘要】 大气气溶胶通过影响大气辐射、大气化学及云和降水过程,改变地水气系统内部的辐射能量收支和水循环,对全球气候和环境变化产生巨大影响。气溶胶长距离输送是全球生物地球化学循环的重要途径之一。大气气溶胶与酸雨,灰霾,温室效应等气候与环境的重大问题息息相关。本研究着重于大气气溶胶生物质燃烧源的追溯及其灰霾的形成的影响,取得了以下几方面的重要成果：1.发现了生物质燃烧对城市大气污染的贡献逐年增加规律。根据上海十年来的大气常规监测指标PM、SO2、NO2、大气降尘、道路降尘、烟尘排放量等数据的变化统计分析,发现了以下三个事实：一是上海大气的能见度全年均值低10公里,整体处于灰霾水平,二是酸雨几率持续升高而降水pH值持续下降,三是细颗粒物的浓度持续升高。进一步分析细颗粒物组分,发现颗粒物中的矿物组分(Fe, Al)的浓度有明显的下降趋势,而与生物质燃烧排放直接有关的组分,例如钾离子、OC、EC和OC/EC等持续上升,证明大气中细颗粒物的增加可能来自于生物质燃烧贡献的增加。2.揭示了生物质燃烧排放颗粒物引起区域严重灰霾的形成机制。通过实验发现,生物质燃烧排放颗粒物不仅含有高浓度的钾离子,还含有高浓度的碳质组分,其OC/EC比值介于9.4-21.6,高于煤燃烧排放颗粒物中OC/EC比值,也高于大气气溶胶中的OC/EC比值；根据对秸秆燃烧排放颗粒物老化前后组分分析,发现老化后颗粒中硫酸根,硝酸根,铵根含量迅速增加,并造成氯离子的缺失；由于硫酸根,硝酸根,铵根等相应的盐具有高吸湿性,生物质燃烧排放物能够极大地改变大气光学性质,引起区域严重灰霾。3.建立了大气气溶胶中生物质燃烧的源追踪的评估方法。通过全国284个尘土样品组成分析,得到扣除钾离子的矿尘源和海洋源,以矿尘为背景的气溶胶中生物质燃烧钾离子来源贡献的计算公式：上式适于计算气溶胶中总的生物质燃烧来源钾离子的量。考虑到除海盐和矿尘外,钾离子可能有其他的一些来源,因此提出了用气溶胶中Na+/Al和K+/Al的最小值作为生物质燃烧钾离子来源计算的背景值的公式：上述公式用于定量评估生物质燃烧对大气污染物的贡献,具有普遍应用价值。4.通过卫星观测、近地面气溶胶采样以及在线监测,揭示了2009年大规模秸秆燃烧事件造成了长江三角州区域性严重灰霾的污染过程和形成机理。事件发生期间,K+、EC、OC、OC/EC比值,以及SO42-、NO3和NH4+等均有明显的增加。钾离子与PM10和PM2.5的相关系数分别为0.582和0.702,而SO2、NO2与PM2.5的相关系数分别仅为0.35和0.17,说明生物质燃烧对该期间的颗粒物污染起着主要作用,且对细颗粒物的贡献更多,而局地的污染源对颗粒物浓度贡献不大。根据气态组分、颗粒物及其组成的变化,估算了在大规模秸秆燃烧事件后期来自于生物质燃烧排放的PM2.5为42.10μg/m3,最高值达到87.24μg/m3,生物质燃烧的贡献平均高达45%,超出了矿尘(19%)以及其它来源(36%)的贡献,而在非秸秆燃烧期间,生物质燃烧对上海PM2.5的贡献仅为为7%。5.发现泰山顶部细颗粒物污染严重,甚至超过了北京和上海。泰山顶部气溶胶的PM2.5/TSP比值在2006年的夏季高达0.91,是已有所有研究的最高值。生物质燃烧在春季对泰山细颗粒物的贡献为10.2%,夏季高达33.9%,泰山顶部整个夏季都受到了严重的生物质燃烧污染。根据泰山气溶胶组分分析,揭示了区域性生物质燃烧是中国中东部边界层细颗粒严重污染以及灰霾形成的主要原因,并提出了生物质燃烧产生的气溶胶在中长距离传输中能够导致边界层卤代烃浓度的升高,可能对平流层臭氧产生破坏作用。6.对生物质燃烧产生的颗粒物(BBPM)中的重金属分析,发现了农作物秸秆排放BBPM中重金属的富集因子远远高于土壤、大气气溶胶以及树木燃烧排放颗粒物中的富集因子；且不同农作物秸秆类型燃烧排放BBPM对重金属总的富集系数接近,但不同的作物对不同金属表现出不同的富集效应。基于BBPM对重金属的富集作用,提出了生物质燃烧驱动重金属在土壤层和大气层间循环的新概念。更多还原

【Abstract】 1. Contribution from biomass burning to urban air pollution increases in recent years. Air quality seems to getting better according to general monitoring terms, such as PM1o, SO2, NO2, air precipitation, smoke emissions, which were decreasing in the past ten years due to the reduction emissions of these species in Shanghai, but the following three against:first, haze days occurred more frequently, and averaged visibility was bellowed 10km; Second, pH of the wet deposits continue to decline, and the ratios of acidic rain rose; last, the level of PM2.5 kept increasing. Further analysis of the constituents of the particulate matter showed that species related to mineral source (Al, Fe) decreased, species related to sea salt (Na+) no obvious change, while species related to biomass burning (K+, OC, EC, and OC/EC) continued to increase, which mean that the addition pollutions of PM2.5 was neither from crustal source, nor from the sea salt, but owing to the increase of biomass burning, and the increasing of PM2.5 could result in haze day and acidic precipitation.2. Particles emitted from biomass burning (BBPM) are mainly in fine mode, and the emissions factors were variable due to the change of the burning conditions. Biomass and petrified fuel both release particles of more carbon content, accounting for more than 40%of the total mass of the particles, but the quality of carbon content is very big difference between the two kind fuels:Carbon content is major of organic carbon(OC) in particles from biomass burning, with OC/EC of 9.4-21.6, while mainly elemental carbon(EC) in petrified fuel particles with OC/EC of 0.39. OC/EC get from atmospheric aerosols is about 3 in urban aerosols, from which can deduce the source of the carbon content. Cl- and K+ are the main ions in fresh BBPM. The constituents of the BBPM would change with the rapid increase of sulfate, nitrate and ammonium, while chloride decrease during aged in the atmosphere, reveal that secondary transformation is significant for fresh BBPM. Organic aerosol, sulfate, nitrate and element carbon, all as strong light absorbing species, were the major contributors to light extinction, which could change the optical character of the atmosphere, and result in the low visibility.3. New method was proposed to evaluation the contribution of biomass burning source in aerosols. Water soluble potassium (K+BB) is used as tracer by deducing the K+ originated from crustal source(K+cust) and sea salt(K+ss) from the total K+ in aerosols. (K+/Al)crust and (Na+/Al)crust were obtained from analyses of 179 soil sample from west, north and central east China. So. the K+ from biomass burning using soil as background is given as: Further, considerating that potassium may have some other sources, so aerosols with the minum value of (K+/Al)Aerosoi and (Na+/Al)Aerosol was used as background to ommiting the non-K+BBMass contribution of PM2.5 from biomass is get from K+BB and the centent of K+ in BBPM.4. By satellite, ground observation, aerosols sampling and online monitoring data monitoring, the air quality degradation and formation mechanism of haze in big cities of China was elucidated by comprehensive research of atmospheric aerosol and trace gases in Shanghai,2009. Major contributors to the aerosol in Shanghai were soluble inorganic ions, organic aerosol and mineral aerosol. SO42-, NH4+, NO3- and K+ were main species of soluble inorganic ions, which derived from photochemical reactions, in-cloud aqueous formation and biomass burning. Biomass burning. play major source of urban PM2.5 during certain period of harvest season due to the opening burning of the agriculture waste in the field. The hourly concentration of K+reaches 29.38μg/m3, while is less than 2μg/m" during normal time. Potassium correlated well to chlorine ion, PM10, and PM25 with the coefficients reach to 0.944,0.582, and 0.702, indicating the common source of these species. Average mass of PM25 attributed to biomass burning were 42.10μg/m3, the maxium value to 87.24μg/m3. The contribution from biomass burning reach 45%on average, far beyond mineral dust (19%) and other sources (36%) during opening burning season, while 7%in ordinary days. Sulfate, nitrate, and ammonium increase rapidly after K+, together with the high concentration of PM2.5 lead to serious pollution episode of regional haze event over the whole Yangtze River Delta (YRD), China. Regional biomass burning was also indicated by the satellite signal, i.e., fire spots, column carbon monoxide, and aerosol optical depth.5. Biomass burning produces even more serious impact on air quality of boundary layer in middle-eastern China. TSP is relatively seasonal stable, but PM2.5 shows obviourly season fluctuations on the summit of Mount Tai. and ratio of PM2.5/TSP reach 0.91 in summer on Mount Tai, which is the high value among the literatures, indicating that pollution from fine particle is significant in boundary layer. Concentration of PM2.5 on Mount Tai was even higher than that in Shanghai in summer,2006. High concentration of Ca2+ in Spring and K+ in Summer reveal that aerosol pollution in this site is attributed to mineral source in spring, while biomass burning in Summer. CH3Cl, CH3Br and CO, as well as secondary ions, also increased significantly in Summer. CH3Cl and CH3Br are also markers of biomass burning, and they can cause adverse impact on the ozone layer by furnishing Br and Cl into the stratosphere. Biomass burning contributes 10.22%in Spring, while 33.9%in Summer on average, and even reach 81.6% on certain day to PM2.5 on Mount Tai. Aerosols on the summit of Mount Tai represent the regional air pollution of central-east China.6. The heavy metals were found to be significant high enriched in BBPM compared to soil and aerosol samples. Vegetable can absorb heavy metals from soil, irrigation, and fertilization, and would release and further enriched in the BBPM while the vegetable are burnt, especially in the crop waste. Cd was more enriched in BBPM from rice stalks, while Pb and Zn wheat stalks. As and Cu corn stalks. Heavy metals in BBPM could be widely spread trough the long distance transport of aerosol. Heavy metals return to the ground by dry or wet precipitation. So biomass burning bridges the transport of metals between soil layer and atmospheric layer.更多还原