华北平原灰霾天气下大气气溶胶的单颗粒分析

为分析灰霾期间单颗粒气溶胶化学组成和混合状态，于2014年12月9日—2015年1月10日，使用单颗粒气溶胶质谱仪（SPAMS）表征华北平原郑州市中牟县的气溶胶颗粒.结果表明:灰霾期（H1:20141213T19:00—20141215T10:00；H2:20150102T10:00—20150106T03:00）和清洁期（C1:20141215T18:00—20141217T18:00；C2:20141231T16:00—20150101T20:00）大气颗粒物种类相同，主要分为有机碳（OC）、元素碳（EC）、生物质燃烧颗粒（BB）、元素碳有机碳（ECOC）、钾二次颗粒（K-Secondary）、矿尘（Dust）以及重金属颗粒（HM）7类.C1时间段，ECOC颗粒占比最高，占总颗粒数的49.8%；其次是OC和EC颗粒物，二者分别占总颗粒数的16.5%和10.8%.H1时间段，K-Secondary颗粒的占比（31.3%）最高；其次是OC和EC颗粒，二者分别占总颗粒数的23.1%和20.2%.清洁期与灰霾期质谱差分结果表明，清洁期颗粒物中含有C₃H+、C₄H₃+、C₅H₃+等有机碳碎片峰，而灰霾期颗粒物中NO₃-、HSO₄-、NO₂-等组分的信号强度显著大于清洁期.混合状态分析表明，从清洁期到灰霾期的过程中，主要颗粒物与NO₃-和HSO₄-的混合程度显著增强.清洁期与灰霾期单颗粒化学组成与混合状态的对比分析表明，清洁期新鲜排放的含碳气溶胶在灰霾期不断老化，单颗粒中二次无机组分增加，气溶胶整体老化严重.此外，灰霾期（H2）EC颗粒占总颗粒数的比例增至18.1%，并且与NO₃-、HSO₄-二次组分的混合状态增强，使平均能见度降低为4.0 km.研究显示，郑州大气能见度主要受化学组分、颗粒物混合状态和污染物质量浓度的影响. 

Analysis of Single Particle Aerosols in the North China Plain during Haze Periods

To analyze the chemical composition and mixing state of single aerosol particles under haze pollution, a single particle aerosol mass spectrometer (SPAMS) was employed to characterize the particles in Zhongmu County, Henan Province in the North China Plain from December 9, 2014 to January 10, 2015. The results showed that the same types of particles were identified during the haze periods(H1:from 19:00 13th December to 10:00 15th December in 2014; H2:from 10:00 2nd January to 03:00 6th January in 2015) and clean periods (C1:from 18:00 15th December to 18:00 17th December in 2014;C2:from 16:00 31st December in 2014 to 20:00 1st Januaryin 2015). The particleswere classified as seven types, containing organic carbon (OC), elemental carbon (EC), biomass burning (BB), internally mixed elemental and organic carbon (ECOC), K-Secondary, dust and heavy metal (HM) particles. During clean periods, OC type particles accounted for 49.8% of total number of particles, followed by ECOC and EC type which accounted for 16.5% and 10.8%, respectively. Whereas, K-Secondary particles took the highest percentage, 31.3% of total number of particles in H1 period, followed by OC and EC particles which accounted for 23.1% and 20.2%, respectively. Mass spectral subtraction plots of the particles between hazy and clean days showed that a large number of organic carbon peaks, such as C₃H+, C₄H₃+ and C₅H₃+, were observed in the particles during clean periods, while the signals of NO₃-, HSO₄- and NO₂- in the particles during haze periods were much stronger than those during clean periods. It was noted that the mixing state of particles with HSO₄- and NO₃- significantly enhanced from the cleaning period to the haze period. The comparison of chemical composition and internal mixing state of particles between clean and haze periods demonstrated that carbonaceous aerosols freshly emitted during clean periods aged continuously during haze periods, whereas secondary inorganic component in single particles increased, suggesting serious aging of aerosols. In addition, the ratio of EC type particles reached up to 18.1% in H2 period. Furthermore, internal mixing state of the particles with NO₃- and HSO₄- enhanced, which reduced the average visibility to 4.0 km. These findings suggest that the visibility in Zhengzhou City is mainly influenced by chemical composition, mixing state andmass loading of particles.