Preliminary Study On The Transmittance And The Content Of Atmospheric Aerosol

With improvement of living standards, the environmental awareness of the public is gradually increased. Particulate matter (PM10) has become the primary pollutant of our city and the monitoring data of PM2.5have begun to the public. This is mainly caused by the impact of inhalable particulate matter on human health and the urban visual quality. Inhalable particulate matter on human health effects depends on the particle size and the corresponding component. It absorbs and scatters lots of solar radiation and reduces air quality.This paper had surveyed the different size of inhalable particle content and its transmittance at Nanjing northern suburb of living area in winter,2011. First, FA-3impingement sampler was used to measure aerosol particle size distribution to collect the information of the atmospheric particles and the weight method was adopted to measure its content. Results showed that the average mass concentration reading was228.65μg/m3, which was about2.28times for the national two standard value (100μg/m3). On average83.03%of urban mass concentration of the inhalable particle was<5.8μm,59.88%below approximately2.1μm, and12.26%of PM10was<0.43μm, suggested that fine particle was serious in air pollution. Particulate matter less than10μm can enter the nasal cavity, less than7μm particles can enter the throat, less than3μm up to bronchial, less than1μm had the highest deposition rate in the alveoli, suggested that long-term residents have serious health effects. There existed double peaks,0.65-1.1μm and5.8-9.0μm respectively, and reached a maximum between0.65-1.1μm. The reason was that the sub-micron particle had higher number concentration and that the volume of coarse particle was proportional to the cube of the scale, which leaded to higher mass concentration. Good correlation between PM10、PM2.1and PM1.0.The transmittance of different size of inhalable particle was conducted by the laboratory assembly of the optical measurement system. Results showed that fine particles (particle size r<2.1μm) had smaller value than the coarse particles (2.1<r<10μm), and in particularly at <0.43μm, which indicated that fine particulate had higher contribution on the atmospheric optical properties. The mass concentrations of particulate matter and its transmittance had a negative correlation, and fine particulates had a good fitting effect than coarse particulates.The laboratory-based assembly with FLA4000+Miniature Fiber Optic Spectrometer was used to measure the transmittance of the coarse particulates, and estimated its extinction coefficient. Results showed that the greater of the coarse particulates, variation amplitude of its transmittance with the wavelength was smaller, that means the larger particle size on the wavelength selectivity lower. The magnitude of its extinction coefficient was between10－5-10-4, which was lower than the generally value between10-4-10-3, this was also explained the roles of extinction of the coarse particle aerosol weakly.