Measurement Of Atmospheric Aerosol Water Content And Fluorescent Biocomponents

Among the grand variety of components of atmospheric aerosol, liquid water is one of the most important. It plays a fundamental part in determining total ambient particulate matter mass concentration, and has an impact on light scattering and the extinction coefficient, therefore, in visual range, aerosol optical depth, and affects aerosol lifetime.It is also considered extremely important for acting as a site for both heterogenous and homogenous condense-phase reactions, having an important impact on local atmospheric chemistry. The frequent haze events occurring in China have proved the importance of the aerosol liquid water content by the enhancement effect that it has on the rapid build up of the PM2.5, being closely correlated. On the other hand, variated and abundant microbial populations have been measured in the atmospheric particulate matter, with implications no only on human health but also on the atmospheric chemistry. Observations in typical urban areas have found increased abundance of pathogenic microorganisms with increases in concentrations of atmospheric aerosol. The aerosol water content may contribute to microbial survivability and growth. Currently, there is a lack of direct measurements of aerosol water and abundance of bioaerosol at atmospheric conditions. In this thesis we developed an improved instrument for the rapid and continuous measurement of liquid water content at atmospheric conditions. Simultaneously, employing the latest technological instrumentation in detection of biological fluorescent particles we evaluated the abundance of viable microorganisms in a urban atmosphere. For this, we had to develop a software to minimise influence on non-biological aerosol, which is of great concern in this kind of studies. During winter season in Beijing, under polluted and clean days, we carried out field observations to analyse the factors influencing the aerosol water content and abundance of atmospheric bioaerosol. Our results include an useful alternative for the rapid determination of aerosol water content at atmospheric conditions and contributes to the understanding of the complex interaction of atmospheric chemistry and atmospheric bioaerosol.We designed, constructed and operated an improved version of a Dry Ambient Aerosol Size Spectrometer, in combination with the development of its operational and data processing software for evaluation of aerosol water content. Measurements of growth factors for laboratory generated Sodium Chloride particles using the developed instrument and theoretical estimations of particle growth are in good agreement. From its operation in Beijing we found that the local aerosol presented an efflorescence point at approx.50% RH. The amount of liquid water on the aerosol was low, with a maximum detected concentration of 1.3 ?gm-3, and was markedly dependent on aerosol chemistry and meteorological conditions. From the performed analysis between aerosol chemistry and aerosol water content during clean and polluted days, we conclude that the abundant organic fraction has a weaker influence on the water uptake during the polluted days. This is, the inorganic fraction of the aerosol is the main driver for the increase in water content in heavily polluted days. This is particularly important in the case of nitrate, which has become the main inorganic component in the urban aerosol chemistry not only in China but worldwide. The alkalinity that the urban aerosol continuously presents (mean acidity ratio =1.3) reduces the uptake of water.We evaluated abundance of fluorescent bioaerosol particles in the urban area of Bei-jing using the Waveband Integrated Bioaerosol Sampler. We developed a computational program for the processing of the WIBS-4a data, which we believe, reduced interference of non-biological aerosol, enabling the determination of the urban fluorescent bioaerosol particles (maximum concentration detected = 67.78 L-1). Differentiation in particle size distribution, particle shape (AF) and particle daily trend, give confidence on an appro-priated differentiation of biological and non-biological particles. Although, FBAP is a low-estimation of total primary bioaerosol particles, we found that the number of total viable bioaerosol particles do not increase with increases in particle matter concentration as it was expected. But a dependence of aerosol chemical composition was found, being possible to determine an apparent maximum tolerance concentration of pollutant before a diminishment of microbial viability was seen, based on individual polynomial regres-sions. Regarding the influence of RH and aerosol water content to microbial viability both showed to be positive correlated.