| One long-term campaign about new particle formation was carried out in the industrial zone of Beilun Port from January 20 to February 25,2018?winter?,March 30 to April 21,2018?spring?,and August 18 to October 19,2018?autumn?,to investigate the particle size distribution,and the formation and growth of new particles at a coastal site in eastern China.The factors that affected the variation of particle concentration and particle size distribution including marine source,industrial zone emission and atmospheric oxidation.During the observation period,the time series of particle size spectrum reflected the typical process of new particle formation and growth,indicating the contribution of new particle formation to the particle concentration.The long-distance transmission of air mass had a significant influence on the particle concentration,and the particle concentration in NPF events was relatively high under the influence of inland air mass.The average total concentration of particles at 2-750 nm in winter,spring,and autumn was 11664.67±7760.75 cm-3,16615.38±15491.18 cm-3,and 12203.42±6902.92 cm-3,respectively.In winter the diurnal pattern of the particle size distributions was affected by heavy pollution process,while in spring and autumn it was mainly dominated by new particle formation events.At Beilun Port,the new particle formation event frequency was observed at6.3%of the analyzed days with 11%in winter,5.6%in spring and 5.6%in autumn.The frequency was generally low.A higher SO2 concentration and O3 concentration together with a lower temperature,relatively humidity,PM2.5 concentration and condensation sink tended to favor the occurrence of NPF events.The particle formation rate of J2,J4,J10,J20,J30 ranged within 15.01-122.89 cm-3s-1,1.39-46.85 cm-3s-1,0.82-4.70 cm-3s-1,0.18-1.89 cm-3s-1,0.14-0.51 cm-3s-1 successively,and the corresponding particle growth rate ranged within 0.50-1.40 nm h-1,3.50-13.10 nm h-1,2.40-10.30 nm h-1,2.10-14.30 nm h-1,3.50-14.30 nm h-1 successively.The particle formation rate was positively related with RH and temperature,negatively related with SO2concentration while particle growth rate was positively related with SO2 concentration,temperature and RH.The seasonal variation of ion concentration was mainly affected by soil emission concentration,background particle concentration and seasonal transformation of boundary layer.The number concentration of the small ion was the highest in autumn,while the medium ion showed hightest tendency in winter among the observation.In each seaon,the diurnal variation characteristics of small ion were similar.It changed with the diversification of boundary layer height,which revealed that the decay of substances in boundary layer resulted in the generation of small ion.Diurnal variration of mdium ion was under impact of NPF enents.The positive?negative?ion formation rate of J2?ion?,J4?ion?respectively ranged within0.12-0.28 cm-3 s-1(0.067-0.23 cm-3 s-1),0.15-0.45 cm-3 s-1(0.13-0.37 cm-3 s-1).The formation rate of 4 nm ion was higher than that of 2 nm ion,which represented the interaction between ion-particle and ion-neutral particle.The averaged ratio between the ion formation rate and the particle formation rate at 4 nm was 0.085.As the particle formation rate increased with the decrease of particle size,the formation rate of 2 nm ion was lower than that of 4 nm ion.As a result,the ratio between the ion formation rate and the particle formation rate at 2 nm was much lower,suggesting that the ion played weak role in new particle formation. |
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