Air quality, indoor and outdoor. A study of connections between indoor and outdoor concentrations: NO2, CO2, PM10 and PM2.5

Abstract

Air pollution is a hazard to human health and especially vulnerable are those who live in urban areas. Urban areas are undergoing fast driven urbanization which often results in increased air pollution. Since different types of air pollutions have various impact on human health, the knowledge of how these air pollutants behave is important in the context of reducing air pollutant and aiming toward a sustained environment with clean air. Today, focus is often on outdoor air quality, we will with this study highlight the importance of studying indoor environment since it is showed that people in general spend 90 % of their time indoors. This study investigates how the indoor air quality is affected by outdoor concentrations of air pollutant. Further we will examine the variability of outdoor air quality depending on prevailing meteorological factors such as air pressure, air temperature, precipitation, solar radiation and wind speed. The study is based on measurements taken at Mölndal municipality building and complemented with measurement data of pollutants and meteorology from monitoring stations in the Gothenburg and Onsala area. Result showed that outdoor NO2 and PM10 concentrations at Mölndal municipally building is mainly an effect of urban sources while PM2.5 originates from both the regional background and urban sources. The indoor PM and CO2 concentrations increase with occupancy in the building which can be seen when looking at differences between weekdays/weekends and day/night concentrations. Further, when studying the indoor/outdoor (I/O) CO2 ratio the connection to activity in the building seems clear. Both NO2 and PM seems to be dependent on the activity of ventilation, during times with indoor ventilation the outdoor concentrations of the compounds is mirrored in the indoor environment but with a lag time. NO2, PM10 and PM2.5 could not be highly correlated between indoor and outdoor environment, the absence of correlation is rather a result by lag times than a lack of connection to each other. Indoor PM is shown to be dependent on both occupancy and ventilation, but to which degree ventilation and occupancy affects indoor PM is hard to determine. Inversions where found to be the main influencer on outdoor monthly mean values while outdoor concentrations of CO2, NO2, PM10 and PM2.5 generated no clear connection to the prevailing meteorology. The reason could be the dependency of interaction between meteorological parameters or because a lag time might be present. Further investigating in the topic is needed to be able to bring out indoor air quality regulations to promote healthy indoor environment. Also, to understand the outdoor variations in air pollution concentrations to a greater extent.