Investigation Of New Particle Formation In Jinan And At The Summit Of Mt.Tai

After the reform and openness,Chinese has been experiencing the serious environmental pollution because of the immoderate pursuit of rapid economic development.Atmospheric aerosols play a critical role in affecting global climate,radiation balance,atmospheric chemical processes and human health.Previous studies have showed that new particle formation(NPF)is one of the largest sources of atmospheric aerosol particles,and field observations have exhibited that NPF typically increase the particle number concentration by a factor of several times.Based on the field observations in Jinan and at summit of Mt.Tai,the study simultaneously measured the particle size distributions,gas species,meteorological conditions,mass concentration and chemical composition of PM2.5,to investigate their general characteristics and influence factors of the NPF events.An in-depth study of the process of NPF in above two sites is of great importance for atmospheric environment in Shandong province.In this study,three campaigns were performed at the summit of Mt.Tai from 25 July to 24 August 2014(I).21 September to 9 December 2014(?).and 16 June to 7 August 2015(?).The NPF events were identified based on particle size distributions,and 66 such events were observed in a period of 164 days-corresponding to an occurrence frequency of' 40%.We carried out the measurement in Jinan from 1 September to 31 October 2015,and 20 NPF events were observed during the 49 valid days-corresponding to its frequency of 41%.Overall.Jinan and Mt.Tai showed the the approximate frequency in this study.The formation rates of nucleation mode particles in Jinan and at summit of Mt.Tai were 20.21 ± 10.59 cm-3 s-1 and 16.61 ± 13.90cm-3 s-1.respectively.The observed formation rate on Mt.Tai was smaller than that in Jinan,but larger than the results in some rural/suburban environments.Reason for the former might he the rich prcecursoirs in Jinan,and the latter was likely related to the intensive precursor transport in eastern China and enhanced photochemical activities on Mt.Tai.The growth rate at summit of Mt.Tai(1.98±1.27 nm h-1)was a little larger than that in Jinan(1.09±0.44 nm h-1),which might be attributed to the slower further growth in Jinan.The condensation sink on NPF days at summit of Mt.Tai was 1.4±0.5×10-2 s-1,significantly smaller than 2.3±0.6×10-2 s-1 in Jinan.Favorable condition for NPF varies a lot in Jinan and at summit of Mt.Tai.The NPF events were in favor to occur in lower condensation sink,higher SO2 concentration,lower O3 environment,lower temperature and lower relative humidity conditions at summit of Mt.Tai,whereas the favorable conditions in Jinan were lower condensation sink,higher sulfuric acid concentration,higher SO2 concentration,lower temperature and lower relative humidity.Without consideration the errors of sulfuric acid proxy,the sulfuric acid concentration might not be the major limiting factor for the onset of NPF on Mt.Tai.In addition,the difference values of O3 concentration between NPF days and non-NPF days in Jinan were nearly zero during the daytime.and the effect of 03 on the NPF in Jinan could be neglected.The air mass backward trajectories in Jinan and at summit of Mt.Tai could be classified into three categories:continental air masses,local air masses and maritime air masses.Both majorities of transport pathways on NPF days were continental air masses,which mainly came from the northwest direction and largely passed over Mongolia,Inner Mongolia.Shanxi Province.Hebei Province,and Beijing with the long movements.