摘要
气溶胶吸湿性不仅影响颗粒物非均相化学反应过程和大气能见度,且对云凝结核形成起决定性作用.本研究运用加湿串联拆分迁移分析仪(H-TDMA)对冬季南京城市大气气溶胶吸湿性进行外场观测研究.结果表明:吸湿增长因子概率分布函数(GF-PDF)呈双峰分布,峰值分别为1.000±0.010(弱吸湿峰)和1.400±0.035(强吸湿峰);在85%相对湿度条件下,不同粒径段(40、80、110、150、200 nm)弱吸湿组粒子数目占比(NFLH)随粒径的增大从40%降低至20%,而强吸湿组粒子数目占比(NFMH)却从60%增加到80%.弱吸湿组GF-PDF离散程度(σLH)在0.04~0.05之间,而强吸湿组GF-PDF离散程度(σMH)>0.1,说明强吸湿组粒子化学成分较复杂,外混合程度较高.对比各粒径段气溶胶吸湿性日变化规律发现,平均吸湿增长因子(GFmean)和NFMH均呈双峰特征,峰值分别出现在7:00和17:00左右.受夜晚边界层降低、强吸湿性组分非均相转化生成等影响,GFmean和NFMH夜间数值整体大于白天;受降水等气象条件影响,污染时段所有粒径段气溶胶的GFmean和NFMH均高于清洁时段.
The hygroscopic properties of aerosol particles make significant impacts on aerosol heterogeneous chemical reactions,degrading visibility,and the formation of cloud condensation nuclei.A Hygroscopic Tandem Differential Mobility Analyzer（H-TDMA） was deployed to measure the hygroscopic growth factors（GF） during wintertime in urban region of Nanjing.The results show that the probability distribution of growth factor（GF-PDF） is bimodal,the peaks of which are GF=1.000±0.010（the less-hygroscopic group） and GF=1.400±0.035（the more-hygroscopic group）.At relative humidity（RH） of 85%,the number fraction of the less-hygroscopic particles（NFLH） decreases slightly from 40% to 20% as those particles＇ sizeincreased（i.e.,40 nm,80 nm,110 nm,150 nm,and 200 nm）,while the number fraction of more-hygroscopic particles（NFMH） increase from 60% to 80%.The dispersion（σLH） of GF-PDF for NFLH-group particles varies in the range 0.04-0.05,but the σMHof NFLH-group particles presents larger values（more than 0.1）,suggesting variously complex chemical compounds of NFMH-group particles being much more external mixing.Comparing with size-dependent analysis of the diurnal cycles,the mean hygroscopic growth factors（GFmean） and NFMHpresents same bimodal peaks at around 7：00 and 17：00,respectively.Overall,the GFmeanand NFMHare larger during nighttime than that during daytime,which might be due to the influence of lower atmospheric boundary layer height and heterogenous reaction process that promotes the formation of the more-hygroscopic particles under the nighttime conditions.Considering to effects of meteorological factors（e.g.,rainfall）,the GFmeanand NFMHin all particles＇ size range show higher values during polluted episodes rather than that in air clean.
出处
《环境科学学报》
CAS
CSCD
北大核心
2018年第1期32-40,共9页
Acta Scientiae Circumstantiae
基金
国家自然科学基金重大研究计划(No.D0512
91544231)
江苏省环保科研课题(No.2015017)
国家重点研发计划(No.2016YFC0200505)~~
关键词
气溶胶
吸湿性
南京
冬季
aerosol
hygroscopicity
Nanjing
wintertime
