Assessing the Impact of Urban Green Spaces on Air Quality in Metropolitan Areas

Thesis Abstract

Urban air pollution remains a critical challenge in metropolitan areas, with particulate matter and gaseous pollutants posing significant health risks and environmental degradation. Despite increasing urban green space development as a strategy to improve air quality, there is limited empirical evidence quantifying the extent of its effectiveness within densely populated cities. This study aims to assess the impact of urban green spaces on ambient air quality in metropolitan environments, with specific objectives to measure variations in air pollutant concentrations across green and non-green urban zones, identify key vegetation characteristics influencing pollutant removal, and develop predictive models of air quality improvement attributable to green spaces. The research adopts a mixed-methods approach, with a predominantly quantitative research design grounded in environmental science and urban ecology frameworks. The study population comprises residents and environmental monitoring stations within the metropolitan area of a major city, with a sample of 30 strategically selected green space sites and 15 adjacent non-green control sites, identified via stratified random sampling. Data collection involved deploying calibrated air quality sensors, such as Particulate Matter (PM2.5 and PM10), Nitrogen Dioxide (NO2), and Ozone (O3), over a six-month period covering both dry and rainy seasons to capture seasonal variability. Vegetation surveys documented species diversity, canopy cover, and green space size at each site. To supplement quantitative data, semi-structured interviews with city planners and environmental managers provided contextual insights. Data analysis proceeded in multiple stages. Descriptive statistics characterized baseline pollution levels, while inferential analyses employed multiple regression to examine relationships between green space variables and air pollutant concentrations. ANOVA tests evaluated differences in pollutant levels between green and non-green zones, and time-series analysis identified temporal pollution trends correlating with vegetation attributes. Spatial analysis utilizing Geographic Information Systems (GIS) mapped pollution dispersion and green space distribution. The theoretical underpinning draws on the Ecosystem Services Theory and the Urban Green Space Model, highlighting the role of vegetation in pollutant mitigation and urban resilience. Additionally, it incorporates the Hypothesis of Vegetative Barriers, positing that dense canopy cover reduces pollutant dispersion and concentration. Expected findings include statistically significant reductions in PM2.5, PM10, NO2, and O3 levels within green spaces compared to non-green areas, with larger, more diverse vegetation correlating strongly with improved air quality. Seasonal analysis is anticipated to reveal amplified pollutant removal during rainy seasons due to enhanced deposition mechanisms. The models developed may provide quantitative estimates of pollutant reduction attributable to green space characteristics, informing urban planning and policy formulation. The study contributes to existing knowledge by empirically validating the mitigating influence of urban green spaces on air quality, highlighting specific vegetation attributes that maximize pollution absorption. This evidence base offers a scientific foundation for integrating green infrastructure into urban environmental management strategies. The main conclusion underscores the importance of strategic green space planning to optimize air quality benefits, emphasizing the need for increased vegetation cover, species diversity, and spatial distribution across metropolitan areas. Based on the findings, recommendations include adopting urban planning policies that prioritize the expansion and maintenance of green spaces, promoting species selection based on air pollutant mitigation capacity, and integrating green infrastructure assessments into city development plans. The study also advocates for further longitudinal research to evaluate long-term impacts of green space growth and maintenance on urban air quality, alongside exploring socio-economic benefits associated with enhanced urban greenery.