Graduation Year


Document Type

Open Access Senior Thesis

Degree Name

Bachelor of Arts


Environmental Analysis

Reader 1

Kathleen Purvis-Roberts

Reader 2

Franck Fu

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© 2023 Ellen Ben Yin Hu


Densely populated regions around the United States exhibit varying concentrations of air pollutants that can impact the health of urban populations and surrounding ecosystems. Understanding why these differences exist can be important in addressing health issues as the human population continues to increase and communities across the globe move to accommodate these trends. To investigate the impact of natural processes and anthropogenic sources on pollutant concentrations, EPA daily fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone (O3) pollutant concentrations from seven metropolitan regions across the US for 2018-2022 were used. A Spearman Rank-Order correlation test was conducted utilizing NOAA's daily weather data, including precipitation, wind speed, and average temperature. It was found that while precipitation is weakly correlated with all pollutants, a strong positive correlation between O3 and temperature in addition to a strong negative correlation between wind speed and NO2 was observed for all regions. Many outliers were observed for PM2.5 concentrations in San Francisco, possibly the result of wildfire burning in California during the fall months. Further inquiry into the impact of anthropogenic sources utilized vehicle miles traveled (VMT) data acquired from Streetlight Data LLC for a portion of 2020 in California. A Spearman Rank-Order test found a relatively strong positive correlation with NO2 for San Francisco, but generally weak or nonsignificant correlations between vehicle travel and pollutants in Los Angeles. Overall, low r-values for all correlations indicate that other factors may be contributing to differences in pollutant concentrations between metropolitan regions.