The air we breathe is absolutely crucial for our health, helping us stay strong and live vibrant lives. Clean air doesn’t just benefit our lungs—it supports the overall health of ecosystems and affects the quality of the soil and water that sustain life on Earth. But with the growing issue of air pollution, both humans and animals are at risk. Polluted air can disrupt ecosystems, damage health, and contribute to environmental problems. This makes understanding air pollutants and, more importantly, how to reduce them, critical for a healthy future.

Previous studies have shown that areas with more plants generally have cleaner air, with lower levels of pollutants like nitrogen dioxide (NO₂), volatile organic compounds (VOCs), and particulate matter (PM). Interestingly, it’s not just about how many plants are present—the type of plant plays an important role in determining how efficiently they can remove pollutants from the air. Motivated by these findings, my research partner and I set out to explore how the plants around our college campus might be affecting air quality. 

At the start of our research, we made an interesting observation: some common areas on our campus had high levels of air pollutants. This led us to dive deeper into whether the surrounding vegetation could be helping to reduce these pollution levels. In our experiment, we decided to measure the concentration of several key air pollutants, including nitrogen dioxide (NO₂), VOCs, PM2.5, and PM10, to see how their levels might differ in vegetated versus non-vegetated areas.

Additionally, we decided to investigate Hydroxyl (OH) free radicals. These radicals can help remove certain pollutants like sea spray, dust, or smoke from the air. However, OH radicals can also lead to the production of other harmful pollutants, such as PM2.5, PM10, and ozone (O₃), which are dangerous to both humans and the environment. We were curious to see how these different variables interacted.

Our hypothesis was straightforward: areas with more plants should have cleaner air, and areas with fewer plants should show higher levels of pollutants. To test this, we used low-cost Flow sensors from Plume Labs to measure NO₂, VOCs, PM2.5, and PM10 in real time. These sensors connect to a smartphone via Bluetooth and provide instant readings, which makes our data collection both easy and efficient.

To measure OH radicals, we used a glass bubbler with a frit attached to a vacuum pump, which allowed us to capture these reactive molecules from the air. By using both devices side by side, we could compare the levels of various pollutants and radicals at different sites on our campus.

Our experiment focused on two main areas: Strata Plaza, a heavily vegetated part of the campus, and the Loading Dock, a non-vegetated, concrete-heavy site. We expected to see higher levels of VOCs and other pollutants at the Loading Dock due to the lack of plant life. However, our findings weren’t exactly what we anticipated.

In the early stages of our study, VOC levels at the Loading Dock were over ten times higher than those at Strata Plaza. While we expected higher VOC levels at Strata Plaza, over time, VOC levels actually decreased there. On the other hand, VOC levels increased at the Loading Dock site. When it came to other pollutants like NO₂, PM2.5, and PM10, their concentrations stayed consistent at Strata Plaza but were significantly higher at the Loading Dock in week 3 compared to week 5.

We believe that several environmental factors came into play. Wind patterns, for example, could have shifted pollution toward or away from the sites at different times. Traffic patterns near campus might also have influenced the amount of pollutants in the air, especially on different days of sampling. And of course, different plant types, exposure to sunlight, and temperature all impact how effectively plants can absorb or filter pollutants.

While we couldn’t conclusively prove that vegetation alone cleans the air completely, our data supports the idea that more plants generally lead to cleaner air. However, there are many factors at play, including environmental conditions, plant types, and even human activity, like traffic. All of these variables affect the ability of plants to reduce air pollution.

In the end, while plants may not be the end all be all  for solving air pollution, they can certainly play a significant role in improving air quality. Our experiment highlighted the importance of understanding how plants interact with pollutants and how they can be part of a larger solution to reducing harmful air contaminants. So, next time you’re walking through a park or sitting under a tree, remember: those plants aren’t just pretty—they’re working hard to keep the air around you clean!

Figure 3: Average air pollutant concentrations (ppb or ug/㎥) for each site on week 3. 

Figure 4: Average air pollutant concentrations (ppb or ug/㎥) for each site on week 4. 

Figure 5: Average air pollutant concentrations (ppb or ug/㎥) between week 3 and 5. 

Sources: 

Zhai, H., et al. (2022). & quot;Study of the Effect of Vegetation on Reducing Atmospheric Pollution Particles." Remote Sensing 14(5): 1255.