生物质露天焚烧及家庭燃用的多环芳烃排放特征研究

农村地区生物质燃烧排放是大气多环芳烃(PAHs)的重要来源之一.本研究利用建立的烟尘罩稀释通道采样系统,对我国典型的生物质燃烧方式—水稻、玉米、花生、大豆秸秆的家庭炉灶燃烧,并对水稻、玉米、花生秸秆以及荔枝树、大叶榕、小叶榕等落叶的露天焚烧进行实验室模拟,实测了秸秆野外焚烧、落叶野外焚烧、秸秆炉灶燃烧等3种典型生物质燃烧类型排放的气相及颗粒相PAHs的排放因子.结果表明,本研究生物质露天焚烧PAHs排放因子高于大部分已有实验结果,秸秆炉灶燃烧PAHs排放因子亦高于大部分排放清单采用值.3类燃料燃烧排放PAHs的谱分布相近,均以中低环PAHs为主,中高环(4~6环)PAHs比例为22.2%~28.8%.采用某单一数值作为某类源PAHs特征比的取值,并将其运用于大气PAHs的来源解析可能会造成偏差.

Emission characteristics of PAHs from open and residential biomass burning

Biomass burning are typical combustion sources of PAHs in rural China. In this study, emissions of gaseous and particulate PAHs from typical biomass burning types were measured by laboratory simulations using a self-designed dilution chamber system under real combustion conditions. Rice straw, corn stalk, peanut stem and soybean stalk were burned in a cook stove to simulate water boiling tests. Rice straw, corn stalk, peanut stem, litchi leaves, and leaves from Ficus virens and Ficus microcarpa were burned in an open platform to simulate field burning activities. Emission factors of three typical burning types, including crop residues open burning, foliage open burning and indoor crop residue combustion were higher than previously reported values, respectively. Spectral distributions of emitted PAHs from above burning types were similar. Medium to high-ring PAHs accounted for 22.2% to 28.8% of total PAHs emitted from biomass burning. PAHs diagnostic ratios as indicators of certain pollutants sources may introduce significant uncertainty, when they were adopted in source apportionments of atmospheric PAHs.