Investigation of suspended particles levels inside the stations and trains of Athens Metro

Abstract

In recent years, where Air Pollution issues are continuously growing and are receiving more attention from both worldwide health and political organisations, the issue of collecting data sustainably and efficiently for the observation and treatment of Air Pollution has been arose. A multitude of papers and studies have been conducted that dig further on the technical and economical aspects of data collecting and Air Quality monitoring with Low-Cost sensors showcasing a promising solution. Low-Cost sensors are called to solve the problem of portability, accessibility and budget friendly option for monitoring of Air Quality with a seemingly minor loss on reliability and precision. In this thesis the goal is to showcase, through a real-case scenario study, the capabilities of lowcost sensors as well as to pinpoint what are the drawbacks of using such devices. To achieve such goal the thesis was separated in two individual parts, the first part was the calibration and comparison of the Low-Cost sensor to a reference instrument of high accuracy over observatory “open field” conditions and the second part, where the sensor was used to monitor a route from a suburb area of Athens, Varkiza, to a central area of Athens, Aigaleo, through the use of public transportation and more in specific public buses and metro. The studied pollutant was particulate matters of sizes of 2.5. The thesis studied the mass concentration of particulate matter within the air (μm/m3) as well the value of the particular matter (PM) concentration in AQI (Air Quality Index). The sequence in which the monitoring took place was modelled in such way of recreating the weekly routine of a student resident or a full time working resident, simulating the average exposure of a public transportation user. In the phase of processing data for the formation of graphs and conclusions temperature, humidity and pressure were taken into consideration, provided by the Low-Cost sensor used for the monitoring of PM. The results showcase that the metro station has the highest concentration of PM in comparison of public buses and walking routes and public buses have the lowest exposure to the passengers of PMs. The Low-Cost sensor also provided data for tracking phenomenons of intense production/concentration of PM in the air, while in the metro subway (the air created during the slowing down of a metro wagon etc.). Furthermore a comparison of the concentration of PM was showcased in the suburb area (Varkiza) and central area (Aigaleo) of Athens and once again the Low-Cost sensor was able to track down the correlation between the car activity and phenomenons of PM concentration intense increase. Finally during the monitoring sessions and through the graphs provided from the data collected it seems that the density of passenger play minor role in the increase of PM concentration and instead a major factor is the intensity of the activity of the passengers (the amount of passengers boarding and disembarking the wagon), even if the total amount of passengers is relatively low.