|M.Sc Student||Yacobi Tamar|
|Subject||Development and Utilization of New Methods for Urban Air|
|Department||Department of Civil and Environmental Engineering||Supervisors||Professor Barak Fishbain|
|Dr. Yael Etzion Cohen|
|Full Thesis text|
Continuous air pollution monitoring is fundamental for exposure assessment and management. Traditionally, air quality is measured by standard air quality monitoring (AQM) stations characterized by accuracy and reliability. However, these stations are expensive and bulky to setup, thus sparsely distributed. This research aims to assess the potential of complementary air monitoring methods, in order to improve monitoring spatial resolution.
The research is composed of two parts. The first part focuses on a new generation of air pollutants monitoring sensors - micro sensing units (MSU). Those are cheap, and their small size enables spatially dense deployment. The study examined the sensing capabilities within the meter scale, of different types of MSUs. For this purpose, bus stop shelters were chosen as an urban micro-environment, characterized with an ambient air pollution due to road proximity. Simultaneous measurements were carried out at three bus stops on Moria Boulevard, Haifa, Israel. Measurements took place simultaneously inside and outside the shelters of the bus stops for comparison of air-pollutants concentrations. The results show the great potential of these MSU in measuring pollution levels even in the meter scale. Moreover, the experiment showed that different types of shelters, different types of pollutants, and different days of measuring - are all affecting on the differences of air pollution levels, between inside and outside the shelter. Therefore, these results raise doubt on previous studies conclusions, which were based on short time periods and on sequential (I.e., not simultaneous) measurements at the examined bus stops.
The second part of the research focuses on the development of a new low-cost and portable method for estimating particulate matter (PM) levels, using digital cameras. Differing from traditional aerosol remote sensing, the proposed method aims to monitor horizontal near-ground atmosphere layers, thus seeking to better resolve spatial variations in ambient PM concentrations. For this purpose, five long-term campaigns were carried out: three in Haifa, Israel, and two in Brisbane, Australia. Overall, 67,000 daylight images were acquired at a rate of 5 minutes, using digital reflex camera (DSLR). For each image, various metrics were computed, including color content and blurriness. These metrics were analyzed with respect to simultaneously measured PM levels and meteorological conditions obtained by AQMs along or close to the lines of sight. The results demonstrate an existing linkage between ambient PM concentrations and image quality. Yet, this linkage is affected by meteorological conditions. The most apparent effect was higher significance of the linkage during times of high solar radiation flux. Thus, the solar radiation is a limiting factor of this PM estimation method. Moreover, it is evident that in order to quantify the linkage between ambient PM concentrations and image quality, a long-term experiment during different meteorological conditions is needed. In addition, a long open path between the camera and the image view is required. The results show that while DSLR imagery may be used as a gauge for PM levels, these limitations suggest that further research should be done so that the method would be applicable for PM estimations.