| Black carbon aerosols have a great impact on climate, environment and health. Black carbon can also be transported long distance, and hence affecting the regional environment. Therefore, there is growing interest on black carbon related research. With the rapid economic development, industrialization and urbanization, Chengdu, as the central city in western China, has huge black carbon emission, which greatly deteriorates the atmospheric environment. It is known that both the concentration and chemical composition of the Black carbon aerosol will affect the air quality. However, there is only handful study on black carbon in Chengdu area. In order to understand every aspect of the characteristics of the black carbon particles in Chengdu, it needs research on both macro and micro levels.In this work, the Seven bands Aethalometer and single particle aerosol mass spectrometry (SPAMS) were used to monitor changes in black carbon. SPAMS is one of the widely used, leading edge technics in atmospheric research. Along with other monitoring instruments, we have studied the characteristics of the black carbon in Chengdu in the period from December 2013 to November 2015. We focused on black carbon concentration variation, chemical composition, and their influencing factors and mixed state, etc. We also analyzed the characteristics of black carbon in a specific period when biomass burning occurred.It is found that black carbon concentration was the highest in winter, followed by spring and autumn, and finally the lowest in summer, with concentrations of 11.25μg/m3,5.69μg/m3, 6.24μg/m3,4.28μg/m3, respectively. The average daily variation of black carbon concentration in winter and summer is the bimodal distribution, but single peak distribution in spring and autumn. and the maximum frequency of black carbon concentration was 3.77μg/m3. Monthly changes of carbon black was influenced by precipitation. From December to January, the contamination level of carbon black is higher, followed by that from October to November, then from February to March, and finally from April to September. Meteorological conditions were important factors that affect the black carbon concentration. It showed that there is inverse correlation between black carbon concentration and visibility, and the absolute value of the coefficient reaches maximum when relative humidity was between 60% and 80%.We used SPAMS to analyze the chemical composition of black carbon particles. There were seven categories of elemental carbon-Containing particles found in Chengdu. They were EC-Fresh, ECOC, EC-NOx, EC-SOx, EC-NH4, ECK, ECCa. The size of elemental carbon-Containing particles is mainly in the range of 0.2μm～1.8μm, the maximum diameter in summer is the lowest, which is around 0.48μm. For other seasons, the sizes are between 0.62μm and 0.68μm. All kinds of elemental carbon-containing particles showed their own laws with the changing of time, while the diurnal variation characteristics of ECOC particles in the four seasons were similar. It showed that ECOC particles have the same mechanism in the four seasons.In May Chengdu suffers from the impacts from the biomass burning. The contribution of the biomass burning around Chengdu to the city’s carbon black can not be ignored, especially the Ziyang-Meishan area. During the monitoring period, the daily average concentration of carbon black increased from the normal period of 2.98μg/m3 to 5.63μg/m3. There was also an increase in CO, the correlation is 0.88. |
PDF Full Text Request