| Atmospheric aerosol is one of the major pollutants in the atmosphere, having significant effects on air quality and human health. Carbonaceous aerosols are known to contribute significantly to the atmospheric fine particles, and not only have crucial impacts on human health and environment, but also play important roles on climate change, radiation balance, greenhouse effect, and visibility. Due to the large energy consumption and emission, the North China is among the areas with the highest aerosol concentrations in the world. Thus, the study on physical and chemical characteristics of carbonaceous aerosols, and understanding of the sources and formation mechanism of carbonaceous aerosols in this region is therefore needed, which clould further promote the control strategy of government.In this work, representative areas were chosen to conduct measurement campaigns on atmospheric carbonaceous aerosols. The measurement studies were performed at four urban sites (Jinan, Qingdao, Zibo, Zaozhuang), one suburban site, and one mountain site (Mount Tai). In the present study, we report the concentrations and temporal variations of fine particles and carbonaceous species in urban cities and in the planetary boundary layer (PBL), investigate the sources and processes that affect the variation of carbonaceous aerosols, examine the cloud scavenging of carbonaceous aerosols and SVOC formation through aqueous-phase reactions in clouds. We also study the cloud condensation nuclei (CCN) activity of both inorganic and organic aerosols, and quantitatively determine the dynamic shaper factor of NaCl nanoparticles.The results showed that the concentrations of PM2.5, OC and EC in Jinan, Qingdao, Zibo and Zaozhuang were much higher than other urban cities in the world, and the concentrations at Mt. Tai were also higher than other background and mountain sites in the world, suggesting the serious atmospheric pollution in this region. The concentrations of PM2.5 and carbonaceous species exhibited clear seasonal variation, with higher concentration in winter and spring but lowest concentration in summer. The semi-volatile organic carbon (SVOC) was measured at Mt. Tai for the first time, and its concentration accounted for 51% and 72% of total OC in spring and summer, respectively, suggesting the predominance of semi-volatile species in organic aerosol in this region. The contribution of organic aerosol to PM2.5 mass in six sites ranged from 19.9% to 66.0%, indicating the large emission and serious pollution of carbonaceous aerosols. The long-term observation in Jinan also indicated that the concentrations of PM2.5 and carbonaceous species all exhibited a slightly increasing trend, highlighting the significance of aerosol pollution control in this region.The diurnal variation of carbonaceous species suggested that the BC concentration in urban area was related to the human activities, traffic emission and meterological parameters, whereas the carbonaceous concentrations at Mt. Tai were dominated by transport and secondary formation. The results suggested the combined sources for the transported aerosols at Mt. Tai, including coal combustion, traffic exhaust, biomass burning and photochemical production. Source analysis based on PCA and HCA indicated that high carbonaceous concentrations were dominated by transport of PBL pollutions in both seasons, and clean air masses from the free troposphere provided the general background condition with 2.13±1.05μg m-3 of NVOC,0.43±0.29μg m-3 of EC and 2.40 to 6.80μg m-3 of SVOC in the study area. Besides the biomass burning in north China, the influence of emission from Korea was observed during the campaigns, and was thought to partially contribute to the regional carbonaceous aerosol budget. Increased SVOC was associated with both cloud processing and photochemical production.The constrained EC-tracer and multiple regression method were used to estimate SOC formation at urban areas and Mt. Tai. The average concentration of SOC at four cities ranged from 8.25 to 23.46μg m-3, accounting for 40.13% to 58.19% of total OC. The average total SOC concentrations at Mt. Tai were 8.19 and 13.26 ug m-3 in spring and summer, respectively, accounting for 57.3% and 71.2% of TOC. The contributions of semi-volatile secondary organic carbon (SV-SOC) to SOC were 60.4% and 74.9% in spring and summer, respectively. The results indicated strong SOA formation during campaigns and high SOA loading in the PBL of the North China Plain. An examination of SOC with photochemical age reveals different relationships of non-volatile and semi-volatile SOC with age and also a different seasonal dependence. NV-SOC increased with photochemical age in spring, while SV-SOC exhibited a mono-peak pattern. These results indicated continuing formation of NV-SOC and SV-SOC being determined by the dynamic equilibrium between formation from gas-phase precursors and conversion to the non-volatile phase in spring. This dependence was not significant in more aged air masses observed in summer, revealing that the aerosol had been fully processed before being transported to Mt. Tai. The clear scavenging of NVOC and EC by clouds was observed at Mt. Tai, and the scavenging efficiencies of NVOC and EC were in the range of 0.33-0.93 and 0.62-0.94, respectively. In contrast to the non-volatile species, SVOC concentration showed increasing trend during clouds, with net increase ranged from 3.67 to 19.04μg m-3 for all cloud events, suggesting in-cloud formation of semi-volatile organic species. A mass balance model was proposed to quantify the scavenging coefficients for NVOC, EC and formation rate of SVOC during clouds. The derived scavenging coefficient constant for NVOC (KNVOC) varied from 0.07 to 0.55 h-1, with averages of 0.16 and 0.11 h-1 in spring and summer, respectively. The scavenging coefficient constant of EC (KEC) ranged from 0.11 to 0.90 h-1, and was higher than that of NVOC, implying internal mixing of EC with more hygroscopic species. The formation rate constant (JSVOC) and sink constant (SSVOC) of SVOC ranged from 0.09 to 1.39 h-1 and 0.001 to 1.07 h-1, respectively. The results suggest that the SVOC growth rate in cloud processing depends on both pre-existing aerosol concentration and sink mechanism, and the growth curve is determined by the competing formation and sink processes.The CCN activity of NaCl and (NH4)2SO4 particles was studied by using CCNC, and the results showed that the critical diameter of NaCl was much smaller than that of (NH4)2SO4 under the same supersaturation. The CCN activity of particles depends on both size distribution and chemical composition of particles. The SOA formed from a-pinene and isoprene in Environmental Chamber was studied, and the CCN activity was remarkably altered by SOA formed on seed particles (i.e., (NH4)2SO4). The SOA formed from a-pinene increased the CCN activity of particles more significantly than that of isoprene, suggesting that the impacts of SOA on CCN property of particles were related to its source and composition. The results also indicated that the critical supersaturation was increased for greater SOA volume fraction. The dynamic shape factor x of NaCl nanoparticles was investigated with a Flow tube-DMA-CCNC system. The drying rate at efflorescence RH was quantified and varied from 5.5±0.9 to 101±3 RH s-1, and the derived x ranged from 1.02 to 1.26. The dynamic shape factors of NaCl particles depended on both particle size and drying rate. For fixed particle diameter, theχvalue decreased with increasing drying rate. For fixed drying rate, a maximum occurred in x between 35-and 40-nm diameter, with a lower x from both smaller and larger particles. The dependence of x on particle size and drying rate could be attributed to the competing effects of the dominant characteristic time of particle-phase diffusion of water and diffusive movement of NaCl monomers, coupled to system size.
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