[Characteristics and Source Analysis of Atmospheric Carbonaceous Aerosols in the Cities of Hangzhou and Ningbo].

To investigate the seasonal variations and sources of carbonaceous aerosols in the cities of Hangzhou and Ningbo, field PM2.5 sampling was conducted at four representative sites (two urban, one suburban, and one rural) in this region from December 2014 to November 2015. A thermal/optical carbon analyzer was employed to analyze both organic carbon (OC) and elemental carbon (EC) contents in PM2.5 by identifying eight different carbon fractions, including OC1, OC2, OC3, OC4+OPC, EC1-OPC, EC2, and EC3. Based on these fractions, OC and EC were defined as OC1+OC2+OC3+OC4+OPC and EC1+EC2+EC3-OPC, respectively; total carbon (TC) was calculated as the sum of OC and EC; and total carbonaceous aerosols (TCAs) were quantified via the sum of organic aerosols (OAs; converted from OC) and EC. The results showed the following. ①The annual average level of TC in this region was (14.3±4.1) µg·m-3, accounting for (26.2±6.5)% of the annual average PM2.5 concentration. The annual average OC and EC concentrations were (11.3±3.4) µg·m-3 and (3.0±0.9) µg·m-3, respectively. The highest TC level was observed in winter among the four seasons. ②The annual average TCA concentration in this region was (25.6±7.5) µg·m-3, contributing (42.2±10.0)% of PM2.5. In addition, secondary organic carbon (SOC) was also estimated by the commonly applied EC method. It was found that SOC contributed (41.1±5.5)% to OC on an annual average basis. ③The sources of carbonaceous aerosols were determined using the correlation between OC and EC, OC/EC mass ratio, and different carbon fraction characteristics. The annual average OC/EC ratio in this region was 4.7±1.7, which falls in the diagnostic ratio range for vehicular emissions, coal combustion, and biomass burning, indicating these sources are probably the major contributors of the regional carbonaceous aerosols. Moreover, a higher char-EC/soot-EC ratio was observed during winter and autumn at all sites, possibly implying the enhanced biomass burning activities during these two seasons.

Temporal and spatial variation in major ion chemistry and source identification of secondary inorganic aerosols in Northern Zhejiang Province, China.

To investigate the seasonal and spatial variations of ion chemistry of fine particles in Northern Zhejiang Province (NZP), China, one year-long field sampling was conducted at four representative sites (two urban, one suburb, and one rural sites) in both cities of Hangzhou and Ningbo from December 2014 to November 2015. Twelve water soluble inorganic ions (WSII) were characterized in this comprehensive study. The annual average of PM2.5 concentration in NZP as overall was 66.2 ± 37.7 µg m-3, and urban sites in NZP were observed with more severe PM2.5 pollution than the suburban and rural sites. The annual average concentration of total WSII at four sampling sites in NZP was 29.1 ± 19.9 µg m-3, dominated by SO42- (10.3 µg m-3), and followed by NO3- (8.9 µg m-3), NH4+ (6.6 µg m-3), Cl- (1.3 µg m-3) and K+ (0.7 µg m-3). Among all cations, NH4+ was the predominant neutralizing ion with the highest neutralization factor (NF), while the remaining cations showed limited neutralization capacity. The highest and lowest sulfur oxidation ratio (SOR) values in this region were found in summer and winter, respectively; while the seasonal patterns for nitrogen oxidation ratio (NOR) were opposite to that of SOR. Principal component analysis (PCA) showed that the significant sources of WSII in NZP were industrial emissions, biomass burning, and formation of secondary inorganic aerosols. In addition, contribution from transboundary transport of polluted aerosols was also confirmed from the assessment through air mass backward trajectory analysis.