薪柴和经济作物秸秆燃烧VOCs排放特征

薪柴及经济作物秸秆在中国农村地区仍普遍使用,其燃烧是挥发性有机物(VOCs)的重要排放源,当前对其排放特征研究仍比较薄弱.本研究选取了3种薪柴(白杨树、杉木和柑橘枝)和6种经济作物秸秆(黄豆秆、芝麻秆、玉米棒、棉花秆、花生秆和玉米秆),通过实验室模拟燃烧和稀释通道采样系统,采用Tedlar袋和Agilent 7820A/5977E气相色谱/质谱联用法采集和分析了烟气中102种VOCs组分组成,并对不同类型生物质燃烧排放VOCs的臭氧生成潜势进行分析.结果表明,不同类型的生物质燃烧排放的VOCs组分存在差异,乙烷(11.1%)、反-2-戊烯(15.4%)、乙烯(8.3%)和二氯甲烷(11.9%)是白杨树和杉木燃烧排放的主要VOCs组分;甲苯(49.8%)是柑橘枝燃烧排放的VOCs含量最丰富的物种;乙烯(11.8%～17.5%)和丙酮(9.2%～14.7%)是秸秆类燃料燃烧的主要VOCs组分.玉米秆、花生秆和柑橘枝具有相似的VOCs源成分谱,分歧系数小于0.1.本研究及已有报道中的生物质燃烧排放苯/甲苯比值范围是0.030～6.48,在开展源解析研究中,采用苯/甲苯比值大于1认定为受到生物质燃烧排放影响值得商榷.烯烃、含氧VOCs和芳香烃对生物质燃烧排放VOCs的臭氧生成潜势的贡献分别为30.6%～80.3%、 6.5%～21.0%和3.8%～56.5%,对臭氧生成潜势贡献比例超过10.0%的组分为乙烯、丙烯、反-2-戊烯、顺-2-戊烯、甲苯和丙醛.

Profile Characteristics of VOCs from Wood and Economic Crop Burning

Wood and economic crops are still widely used in rural areas of China. Although their combustion is an important source of volatile organic compounds (VOCs), study on their emission characteristics is relatively weak. In this study, three kinds of wood (poplar, cedarwood, and citrus branches) and six economic crop straws (soybean stalk, sesame stalk, corn cob, cotton stalk, peanut stalk, and corn stalk) were selected and their burning was simulated in the laboratory. A dilution tunnel system was used to dilute the smoke, and then Tedlar bags were used to collect the smoke. The compositions of 102 VOCs were analyzed by Agilent 7820A/5977E gas chromatography/mass spectrometry. The ozone formation potential (OFP) of VOCs for different types of biomass burning was analyzed. The results indicated that there are differences in the VOC compositions of different types of biomass burning emissions. Ethane (11.1%), trans-2-pentene (15.4%), ethylene (8.3%), and dichloromethane (11.9%) are the main VOCs emitted from poplar and cedarwood burning. Toluene (49.8%) is the most abundant species of VOC emitted from burning of citrus branches. Ethylene (11.8%-17.5%) and acetone (9.2%-14.7%) are the main VOCs components of straw burning. Corn stalks, peanut stalks, and citrus branches have similar VOC source profiles, with the coefficient of divergence less than 0.1. The benzene/toluene ratio for biomass burning emissions obtained in this study and in the literature is in the range of 0.030-6.48. It is arguable that a value higher than 1 indicated the impact of biomass burning. The contributions of alkenens, oxygenated VOCs, and aromatic hydrocarbons to the OFP of biomass burning were 30.6%-80.3%, 6.5%-21.0%, and 3.8%-56.5%, respectively. The components contributing more than 10.0% to the OFP are ethylene, propylene, trans-2-pentene, cis-2-pentene, toluene, and propionaldehyde.