Identification Of Biomass Burning Source In Aerosols And The Formation Mechanism Of Haze

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 29.38?g/m3, while is less than 2?g/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 42.10?g/m3, the maxium value to 87.24?g/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.