Aerosol Measurements and Analysis

University essay from Lunds universitet/Fysiska institutionen

Abstract: Abstract The greatest source of hazardous airborne particles in an urban environment comes from traffic exhaust. Air pollution has a great impact on human health; estimated to cause 1.3 million deaths worldwide per year. About half of all mortality caused by air pollution can be linked to motorized traffic. There are several other sources that contribute to our polluted environment; from both natural and anthropogenic origin. The aim of this bachelor thesis is to determine the size distribution of aerosol particles, study variations in particle size and concentration over time and study diurnal variation and other trends, caused by meteorological conditions. This thesis analysis is made on the data from an Exposure study in Copenhagen, which was collaboration between the Health Department in Copenhagen and Ergonomics- and Aerosol Technology, Lund University. Our analysis of the measurement data was made from 20/12/2011-2/2/2012. Since the period is over New Year’s Eve, this specifically will be studied. The technique of trajectories is used to track the particles and try to determine where the air parcel comes from. From the SMPS data we can see different trends in the size distribution and particle number depending on meteorology and diurnal variations. New Year’s Eve shows a very different particle size distribution in comparison with other nights, the size of the particles is much larger this night and the number of particles shows a significant peak between 24.00-01.00. We can see that the average particle number distribution does not differ so much between the three months, even though we have two peaks over 40,000 particles in December. In the end of January the volume increases and we can see a correlation with decreasing temperature and winds coming from East. We can observe larger amount of particles every time the wind changes direction. The highest concentration of particles is in the range between 10-100 nm, which corresponds well with the theory. The particles in this range are the most hazardous to human health since they are small and deposit in the deep lung. This is favorable when doing human exposure studies. The diurnal pattern in concentration due to traffic is not as distinct as we thought during rush hours; instead we have an increase in concentration during daytime. This can be due to road works and the local topography with the open street space and the four lakes, which contribute to a large mixing volume. When we see an increase of particles during night time it can be correlated to change in wind directions. When the wind blows from the east we can see an increase in larger particles which is correlated to long range transport, likely explained by observations made of a lot of industries with strong emissions located in Poland, Germany and other locations where the wind has travelled over.

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