三明市大气颗粒物数浓度与粒径分布季节特征

利用颗粒物粒径谱仪对三明市城区站点不同季节的10~10 000nm粒径段内颗粒物的数浓度与粒径分布进行测量,全年颗粒物数浓度平均为15 608个·cm~(-3),季节特征表现为春季冬季夏季秋季,冬季凝结核模态粒子数浓度最高,各季节积聚模态颗粒物均占比最高.颗粒物总数浓度日变化存在早、晚高峰与中午时段的3峰特征,其中爱根核模态与积聚模态粒子均有早、晚双峰特征;凝结核模态与爱根核模态粒子则均在中午时段出现峰值.各季节颗粒物数浓度中值粒径与几何平均粒径差异较小,春夏季以爱根核模态为主,为单峰模式;秋季为双峰模式(爱根核模态+积聚模态);总体上秋冬季存在较多凝结核与爱根核模态的超细粒子.

Seasonal Characteristics of Number Concentration and Size Distribution of Atmospheric Particles over Sanming

Utilizing particle sizer instruments,number concentration and size distribution of particles with diameter ranging from 10 to 10 000 nm were measured at Sanming urban area in different seasons.The total particle number concentrations are overall averaged at 15 608 pcs · cm-3 with seasonal sequence of spring＞winter＞ summer＞ autumn.The nucleation mode particles peaked in winter while the portion of accumulation mode particles are highest among all the seasons.The diurnal variation of total number concentration behaved with triple peaks around morning/evening rush hours and noon time.Both Aitken and accumulation mode particles showed peaks at morning/evening rush hours,however,peaks of nucleation and Aitken mode particles occurred around noontime.The median and geometric mean diameters of particles are similar between different seasons.The size distribution exhibited a single peak (Aitken mode) in spring and summer.Bimodal pattern (Aitken and accumulation modes) was observed in fall.Generally,more nucleation and Aitken modes of ultra-fine particles were existed in autumn and winter.