三江平原作物收获期大气颗粒物浓度特征

通过对2013年10月东北三江平原农作物收获期大气颗粒物的在线监测,结合卫星火点数据与后向轨迹模拟,分析了秸秆燃烧和作物收割等农业活动对大气颗粒物质量浓度及粒径分布的影响.结果表明:作物收获前期、中期和后期大气PM2.5的平均质量浓度分别为36.0,158.3,33.8μg/m3;现场观测表明,水稻收割(321.1μg/m3)和秸秆燃烧(2777.1μg/m3)时监测田块内PM2.5的平均浓度分别是收割前和燃烧前平均浓度的2.5倍和11.5倍;卫星火点及后向轨迹分析发现,观测期间PM2.5与该地区卫星火点数量的变化趋势比较一致,且气团轨迹经过火点较集中区域时测得较高的PM2.5浓度值;对不同粒径(1μm,1~2.5μm,2.5~10μm)大气颗粒物质量浓度的观测表明,收获中期受大面积秸秆燃烧的影响,0~1μm粒径组分明显增加,而收获后期由于降水过程对0~1μm粒径颗粒物的清除效率较低,故该粒径颗粒物仍维持较高比例.

Mass concentration of atmospheric fine particulates in crop harvesting period in Sanjiang Plain,Northeast China

Using the portable real-time particulate matter (PM) analyzer, we measured rural airborne PM2.5 concentrations in the Sanjiang Plain during the periods of crop harvest and straw burning in October 2013. Combined with satellite-based fire spot numbers and HYSPLIY backward trajectories, the relationship of PM2.5 concentration and PM size distribution and agricultural operations (i.e., residue burning and rice harvest) were discussed. The mass concentration of PM2.5 averaged to 36.0μg/m3,158.3μg/m3and 33.8μg/m3in pre-harvest, harvest and post-harvest stages, respectively. The mass concentration of PM2.5 in the field during the rice harvesting and rice straw burning were about 2.5 and 11.5 times higher than the background levels, respectively, which indicate the importance of agricultural operations. Furthermore, we found that the mass concentrations of ambient PM2.5 were closely related with the number of the fire spots. Wind speed had a negative influence on the mass concentration of PM2.5 levels due to the acceleration of diffusion. The mass concentrations of PM with different diameters (0~1μm, 1~2.5μm, 2.5~10μm) showed that the ratio of fine particles (0~1μm) increased significantly since rice straw burning.