Physicochemical Characteristics Of Atmospheric Particle At Mountain Wudang

To study the Physicochemical characteristics of atmospheric particles in the middle and upper part of the atmospheric boundary layer,the atmospheric particles and gas meteorological elements were observed in June 2018 at Mt.Wudang.This paper analyzed the number concentration and size distribution characteristics of particles in the range of14.6-660 nm and discussed the effect of regional transport.The diurnal variation characteristics of new particle formation events and their influencing factors were studied;The characteristics of ions,carbon,and elemental components in PM2.5 were analyzed and the pollution sources and potential pollution areas were also analyzed.The analysis of the particle number size spectrum showed that the atmospheric particles at Mt.Wudang were dominated by Aitken mode,followed by accumulation mode.During the observation period,there were eastern air masses,northwest air masses,local air masses,and south-southwest air masses.Under their influence,the number concentration spectrum showed a single-peak distribution,and peaked at about 100 nm.The potential source analysis showed that the major source areas were Shiyan City and Xiangyang City.PMF indicated five contribution factors of particle number concentration and they were mixed source,secondary aerosol,aging aerosol,background aerosol and traffic source respectively.During the whole observation period,4 days of new particle formation(NPF)events were observed.The formation rates of J14.6 were in range of 0.38-3.44cm-3s-1,the growth rates were 2.17-9.71nm/h,and the shrinkage rate was-22.69nm/h.The average value of coagulation sink was 7.45 × 10-5s-1,and the variation range of the condensate sink was(1.87-2.69)× 10-2 s-1.the sulfuric acid formed by photochemical reaction of SO2 and organic matter produced by VOCs and O3 participated in the formation and growth progress of new particles;The NPF events could occur even on dusty days when there were higher precursor and stronger solar radiation,which may related to heterogeneous photocatalytic reaction;The conditions of high temperature,low humidity,high wind speed and strong solar radiation were conducive to the generation of new particles.The average concentration of PM2.5 in summer at Mt.Wudang was 16.49μg/m3,and the variation range was 5.0-33.65μg/m3.The daily average concentrations of POC and SOC were respectively 1.06 ± 0.53μg/m3 and 0.89 ± 0.43μg/m3.The concentration of inorganic elements ranged between 1.23-5.81μg/m3,and the average value was 2.07μg/m3.The concentration of SO42-,NH4 +,NO3-and K + had the highest values among all ions,and they were mainly affected by local air masses.The potential analysis found that the potential source areas were located at southeast of Mt.Wudang,and they were Nanzhang county,Yicheng city and the northern of Jingmen.The ions of Cl-,Ca2+,Mg2+,and Na+had the highest concentration under the influence of the fifth type of northwest air mass,which was related to the slightly higher dust content in the northwest air.Based on the principal component analysis of ions,carbons and elements,the PM2.5 pollution sources at Mt.Wudang mainly included vehicular emission sources,coal-fired sources,soil /sand dust sources,and secondary sources.