Measuring Concentration of Ice Nucleating Particles in the Atmosphere, Particulate Matters and Gaseous Pollutants in Museums: Insight from Models and Elemental Analysis.

Abera, Dereje (2017) Measuring Concentration of Ice Nucleating Particles in the Atmosphere, Particulate Matters and Gaseous Pollutants in Museums: Insight from Models and Elemental Analysis. PhD thesis, Addis Ababa University.

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Ice nucleation in clouds affects the optical thickness and lifetime of mixed-phase clouds and is responsible for a significant proportion of precipitation formed globally and ultimately indirectly affect climate. In mixed-phase clouds, where temperatures range from −370C and 00C, ice crystals can only form on certain aerosol particles. Ice nucleating particles (INPs) constitute such aerosols with reduce energy barrier of ice nucleation. Despite significant advancement in the fundamental understanding of different ice formation processes in the last decades, the ice phase in clouds still contributes major uncertainties in climate model prediction of radiative forcing. This is partly due to a limited understanding of the behaviour of aerosol particles to act as INPs and paucity of observational data in the atmosphere quantifying INP distributions. Therefore, the first part of this employed Micro-liter Nucleation by Immersed Particle Instrument (µ-NIPI) to cool down droplets containing ice-nucleating material at a controlled rate and to monitor their freezing temperatures. The experiments reveal that aerosol droplets started to freeze at −140C down to -250C;while, the concentration evolved from 0.1 to 10−3 cm−3. The average temperature in which 50% of the droplets froze occurred at −200C with a concentration of 10−3 cm−3. The experimnets have shown that the type of aerosol species that make INPs in Leeds, UK, were dominantly feldspar from mineral dust. Moreover, meteorological factors such as wind speed, temperature and relative humidity affected INPs’ concentrations. In addition to the aforementioned aerosol radiative forcing (climate forcing), aerosol has significant impact on the environment (e.g., air and water pollution). In fact, pollution is not a phenomenon just of modern time; it is intimately connected with the dawn of the industrial age in which the effects of particulate matter and gaseous pollutants on precious cultural assets become obvious. The high atmospheric load caused strong soiling as well as corrosion outdoors and indoors. The increasing attraction on indoor pollutants in the museums environment and associated investigation contribute to the understanding of basic mechanisms. Particulate matter and gaseous pollutants are involved in deterioration processes and aging mechanism was not realized until macroscopic observable damages occurred which gave the starting point for scientific investigation. Therefore, in the second part of this work, particulate matter samples were collected on Teflon membrane filters using Harvard-type Impactor collector, Aethalometry and diffusive sampler are to measure black carbon and gaseous pollutants respectively. It was observed that the daily PM10 average mass concentrations inside and outside the Magritte and Reserve OB museums-varied between 2.71 and 5.25 µg/m3 with an average concentration of 4.10 µg/m3 and 0.36 and 7.75 µg/m3 with an average concentration of 2.20 µg/m3 respectively. The concentrations were usually lower when the museum was closed and there were no tourist activities around. Inside the museums, mass concentrations were much less than outside with daily variations, which were due to wind speed, wind direction, human activity and traffic activities outside of the museums. The average mass concentrations of indoor PMs were always lower than that of the outdoor ones that as reflected in low indoor/outdoor ratios indicating that the sources of pollutants were from outside the museums. Particle number concentrations in all sizes (i.e., PM1, PM2.5 and PM10) remained at high levels during morning time which are correlated directly with temperature and inversely with relative humidity. Furthermore, the concentrations of gaseous pollutants (NO2, SO2 and O3) were lower inside the museums than the outside with some of them at undetectable levels; in addition, the levels of these gases inside the two museums were lower and below the recommended level when compared to that of other museums. Bulk aerosol samples of different sizes were analyzed by means of energy-dispersive X-ray fluorescence analysis (EDXRF) to determine their composition. The analysis led to identification of 11 elements (Al, Si, P, S, Cl, K, Ca, Mn, Fe, Cu and Zn). The levels of concentrations of these elements were found to be 27.45 and 281.85 ng/m3 at Magritte and 16.16 and 154.26 ng/m3 at Reserve OB inside and outside of the museums on average respectively; their sources were predominantly anthropogenic from traffic activities and industries. It was observed that air mass with trajectories emanating from maritime and continental sources severely affected the concentrations pollutants in the museums.

Item Type: Thesis (PhD)
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Q Science > Q Science (General)
Q Science > QC Physics
Divisions: Africana
Depositing User: Selom Ghislain
Date Deposited: 02 Oct 2018 11:12
Last Modified: 02 Oct 2018 11:12

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