| Atmospheric aerosol is the general name of all kinds of solid and liquid particles suspended in the atmosphere.Atmospheric aerosols can affect atmospheric chemical process,atmospheric radiation budget,cloud precipitation process and atmospheric visibility.The climatic effects of atmospheric aerosols are influenced by their physical and chemical properties such as particle size,shape,chemical composition,etc.The physical and chemical properties of aerosols change with the emission source,transport process and meteorological conditions.In order to study aerosol more accurately,it is necessary to detect aerosol in real time on the scale of single particle.Mt.Huang is located in the famous scenic spot of huangshan city,anhui province,which is a representative alpine background area in east China.Based on the observation data obtained by the single-particle aerosol mass spectrometer(SPAMS)in Yungu Hotel(890 meters above sea level)from September to October,2012,this study analyzed the mass spectral characteristics,particle size distribution and quantity of various single-particle aerosols.Based on the data of automatic meteorological station,the relationship between the physical and chemical characteristics of single particle aerosol and meteorological factors was discussed.Based on the backward trajectory mode HYSPLIT of air mass,the similarities and differences of physical and chemical properties of various single-particle aerosols under the control of different air masses were studied.The influence of aerosol chemical composition on CCN(Cloud Condensation Nuclei)was analyzed with the data of cloud condensation nucleus scounter(CCNC).The main results are as follows:1.There are nine types of aerosols in the huangshan region.Heavy metal HM respectively(4.9%),Aged-EC with no obvious nitrate signal(43.4%),and elements carbon EC with obvious nitrate signal(5%),organic carbon OC with obvious nitrate signal(6.3%),mixture of elements carbon and organic carbon ECOC with no obvious nitrate signal(9.1%),mixture of elements carbon and heavy metals ECHM with nitric acid signal(0.4%),and mixture of potassium and sodium Na K with obvious signal of nitrate(5.6%),rich potassium(25%),Minerals(0.3%).Aged-EC,ECOC and ECHM were all mixed with sulfate after a series of chemical reactions in the atmosphere.The high proportion of secondary aerosols indicated that the aging degree of aerosols in huangshan area was serious.Aged-EC,ECOC and OC were concentrated in the accumulation mode(0.2~1.4?m),while HM,Na K and Minerals were concentrated in the coarse particle mode(>1.4?m).As the gaseous precursors of nitrate react inhomogeneous with the coarse particles,nitrate signals appear in HM,Na K and Minerals mass spectrograms.2.The particle sizes of all kinds of aerosols show single peak distribution at different wind speed and relative humidity.Higher wind speed(1.6-3.3m/s)is beneficial to the diffusion of aerosol particles.EC,HM,Na K and OC are more likely to accumulate at wind speed from 0.3 to 1.5 m/s,while ECHM and ECOC are more abundant at wind speed from 1.6 to 3.3m/s.AgedEC and EC are more likely to grow into large particles when relative humidity is 60~80%.Under high humidity,ECHM and HM with larger particle size were consumed and cleared,K moisture absorption increased and experienced collision action,the particle size increased and the quantity decreased,and Minerals were wet cleared,the particle size and proportion decreased simultaneously.During the observation period,the huangshan area was mainly controlled by a long-range air mass(34%)from the northwest,an east China sea air mass(42%)passing through the Yangtze river delta and a local air mass(24%).The distant air mass transported the most aerosols to huangshan,followed by the Yangtze river delta.K,ECOC,HM,Na K and OC particles are mainly transported over long distances,and primary EC particles are mainly contributed by local sources.Aged-EC mainly comes from local sources and industrial sources in the Yangtze river delta region,both of which are characteristic aerosols in the huangshan region.3.Aged-EC,K and ECOC were the top three single-particle aerosols in daytime and night.The proportion of Aged-EC increased at night,while the proportion of ECOC decreased,and the proportion of K changed little.Aged-EC of 0.7~0.8?m contributes the most to CCN concentration in the afternoon.As two types of characteristic particulate matter in huangshan area,Aged-EC and K contribute more to CCN number concentration,especially after 9 am.ECOC has a certain contribution to CCN number concentration during the day,mainly in 0.75~0.8?m particle size segment,and its contribution is relatively smaller at night.EC made a greater contribution to CCN number concentration from afternoon to early morning,especially from 12:00 to 16:00,which was 0.75~0.8?m.The diameter range of the high number concentration of Na K is wider than that of most single-particle aerosols,so the contribution proportion of Na K increases in the larger size range(0.8~0.9?m).4.In precipitation and cloudy weather,all kinds of single-particle aerosols were largely cleared and the particle size segment became narrow.Aged-EC is an important component of CCN in different weather,mainly distributed in 0.6~1?m.In precipitation and cloudy weather,the particle size segment of K becomes narrower,and the particle size shifts to the larger particle size segment after the cloud disperses.There are very few K particles with small particle size(0.4~0.6?m),and the number concentration of K rises more slowly than that of Aged-EC after cloudy days,resulting in a further decrease in contribution to CCN compared with AgedEC.The clearing effect of precipitation and humidity on ECOC is less than that of other singleparticle aerosols,which makes the contribution of ECOC to CCN increase in precipitation and cloudy day.The OC in the huangshan area is not easy to gather.After the concentration of OC is reduced due to the interference of weather factors,the original level cannot be restored in a short time. |
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