The efforts to reduce vehicle emissions in California have shown promising results over the years, but recent research indicates that there is a new source of pollution to contend with – ‘secondary sources’ originating from trees and shrubs in our urban landscapes. A team of US researchers embarked on a study over Los Angeles in June 2021 to directly measure the volatile organic compounds (VOCs) emitted by plants, shedding light on the role of botanical sources in the formation of secondary organic aerosols and ozone pollution.
Unlike previous methods that relied on estimates or models, the researchers used an airborne approach equipped with a mass spectrometer to measure over 400 types of emissions with unprecedented detail. The study revealed that botanical sources of VOCs, such as isoprene, monoterpenes, and sesquiterpenes, accounted for a significant portion of the potential formation of secondary organic aerosols. With the rise in temperature and drought conditions, these botanical emissions are expected to increase, posing a greater challenge as the summer progresses.
Ambient air pollution remains a pressing health concern globally, with fine particulate matter and ozone pollution linked to various health issues including respiratory illnesses and cardiovascular diseases. VOCs play a crucial role in the formation of these harmful pollutants, making it essential to identify and mitigate sources of VOC emissions in urban areas. With millions of premature deaths attributed to airborne pollution annually, there is a growing urgency to address the impact of VOCs on air quality and public health.
While industrial sources have long been recognized for their contribution to VOC emissions, the study highlights the significant role of green spaces in generating VOCs through the release of terpenoids. The analysis revealed that these biogenic emissions accounted for a substantial portion of the total VOC mass flux, emphasizing the need to consider the impact of botanical sources alongside industrial sources. As temperatures rise, the exponential increase in emissions from plants raises questions about the balance between green spaces and air quality.
Despite their role in VOC emissions, green spaces offer a host of environmental benefits, such as reducing urban heat islands and improving overall health and well-being. Certain plant species can even filter out VOCs from the air, underscoring the importance of maintaining green infrastructure in cities. However, understanding the factors that influence biogenic VOC emissions, such as drought conditions and plant species, is crucial for mitigating the negative impact of botanical sources on air quality.
As global temperatures continue to rise, the interactions between plant emissions and air quality will become increasingly complex. Identifying low-emission plant species and implementing sustainable landscaping practices can help mitigate the impact of botanical sources on urban air quality. By striking a balance between environmental benefits and pollution concerns, cities can create healthier and more sustainable living environments for their residents.
The study highlights the need to reassess the environmental impact of urban landscaping and the hidden sources of pollution in our green spaces. By addressing the challenges posed by botanical emissions and integrating strategies to reduce VOC emissions from plants, cities can achieve a more sustainable and healthy urban environment for all.
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