不同生物质燃烧排放多环芳烃及糖醇类化合物的模拟研究

Simulation Study of the Emission of Polycyclic Aromatic Hydrocarbons and Sugar Alcohols from Biomass Burning

选择水稻、小麦、玉米及棉花秸秆与马尾松枝,采集模拟燃烧时排放的PM2.5,分析PM2.5中多环芳烃(PAHs)和糖醇类化合物的含量,获得PM2.5及负载的两类化合物的排放因子;采用500 W汞灯直接照射收集了PM2.5的尘膜,获得了中、高环PAHs及左旋葡聚糖的光解动力学.结果表明,PM2.5的排放因子介于(2.26±0.60)g·kg-1(马尾松枝)^(14.33±5.26)g·kg-1(玉米秸秆)之间;19种PAHs的排放因子介于(0.82±0.21)mg·kg-1(马尾松枝)^(11.14±5.69)mg·kg-1(棉花秸秆)之间,且以4环类PAHs所占比例最高,介于51%~71%之间(其中马尾松枝燃烧时惹烯的排放因子最大);9种糖醇类化合物的排放因子范围为(52.34±50.16)mg·kg-1(水稻秸秆)^(238.81±33.62)mg·kg-1(小麦秸秆),且都以左旋葡聚糖占绝对优势(72%~96%).光照模拟显示,目标化合物的光照损失都遵循拟一级动力学,其中≥4环的PAHs的光解速率常数随着尘膜中PAHs的负载量增大而减小,来源特征比值Flua/(Flua+Py)和Ip/(Ip+Bg P)相对稳定,而左旋葡聚糖的光解速率常数为0.004 5 min-1,与苯并[a]蒽的光解速率常数(0.004 1~0.005 0 min-1)接近.

To measure the emission factors of PM2. 5and its associated PAHs and sugar alcohols,Chinese red pine stick and four crop straw including rice,wheat,corn and cotton were burned in a chamber. In addition,the kinetics of certain compounds were obtained through the irradiation of the glass filters with PM2. 5loading by 500 W mercury lamp. The emission factors of PM2. 5were ranged from( 2. 26 ± 0. 60) g·kg- 1( Chinese red pine stick) to( 14. 33 ± 5. 26) g·kg- 1( corn straw). Although the emission factors of the total19 PAHs differed from( 0. 82 ± 0. 21) mg·kg- 1( Chinese red pine stick) to( 11. 14 ± 5. 69) mg·kg- 1( cotton straw),4 ring PAHs showed predominance over other PAHs accounting for 51%-71% except Chinese red pine in which retene was the predominant compound. The emission factors of 9 sugar alcohols were ranged from( 52. 34 ± 50. 16) mg·kg- 1( rice straw) to( 238. 81 ± 33. 62)mg·kg- 1( wheat straw) with levoglucosan accounting for 72%-96% of the total sugar alcohols. Both the selected PAHs and levoglucosan associated with PM2. 5followed the first order kinetics. The photolysis kinetic coefficient of PAHs( ring number≥4) was decreased with the increase of PAHs loading in filters. Two PAHs source characteristic ratios such as Flua /( Flua + Py) and IP /( IP +Bg P) were relative stable during the irradiation. The photolysis kinetic coefficient of levoglucosan( 0. 004 5 min- 1) was comparable to benzo[a]anthracene( 0. 004 1-0. 005 0 min- 1).