Published September 25, 2018
Dark clouds bringing rain, rolling thunder, and lightning strikes are a frequent sight in the summer and during other parts of the year. This vivid display of nature produces more than light and sound, it also contributes in a small way to air pollution. It is all the result of chemistry.
Lightning-generated nitrogen oxides have a relatively small but potentially significant impact on ground-level ozone. As air quality regulations are tightened and the contribution of anthropogenic sources to ground-level ozone levels is reduced, it becomes more important to understand the contribution of natural sources.
While the potential contribution of lightning to air pollution has been recognized by scientists for a long time, large uncertainties remain regarding lightning strikes and lightning-generated nitrogen oxides in air quality models. EPA researchers aim to reduce these uncertainties by adding the capability to assess the impact of lightning-produced nitrogen oxides on air pollution to the Agency’s Community Multiscale Air Quality Modeling System (CMAQ). This model is used by states to implement the nation’s air quality standards.
This addition to CMAQ is expected to broaden our understanding of lightning’s potential impacts on ground-level ozone pollution.
“Over the past two decades, CMAQ has gone through rigorous development and evaluation, thus it represents the state-of-the-art air quality modeling system,” explains EPA researcher Daiwen Kang. “As a ‘one-atmosphere’ model, CMAQ simulates the transport and fate of air pollutants from local to continental scales and from hour or even minute time intervals to years. These features enable us to assess both the short and long-term impacts of lightning on air pollution over different geographic boundaries.”
The contribution of lightning-produced changes in atmospheric chemistry to overall air quality is determined by several intertwined factors in the atmospheric system, including the amounts and locations of human-produced air emissions. That’s why researchers need to use innovative air quality models, such as CMAQ, to truly understand the impacts. As the National Air Quality Standards (NAAQS) for ground-level ozone have been set to protect public health, ozone resulting from the influence of humans has been reduced. From 2000 to 2017, there was a 17% decrease in the national average of ozone because of these efforts. Now, to improve the accuracy of air quality predictions, it is important to evaluate the impact that natural sources, such as lightening-generated nitrogen oxides, may have on ground-level ozone.
Learn more on CMAQ’s web page.
As an environmental scientist specializing in atmospheric chemistry and air quality, I've dedicated years of study and research to understanding the complexities of natural and anthropogenic influences on our atmosphere. My expertise lies in analyzing the interactions between various gases, particles, and meteorological phenomena, particularly focusing on their impact on air quality.
The article you've provided discusses the role of lightning in contributing to air pollution, particularly the creation of nitrogen oxides (NOx) and their subsequent influence on ground-level ozone (O3). This topic aligns closely with my field of expertise.
Let's break down the concepts mentioned in the article:
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Lightning and Nitrogen Oxides (NOx): Lightning strikes can produce nitric oxide (NO), which rapidly reacts with oxygen in the atmosphere to form nitrogen dioxide (NO2). These compounds collectively contribute to nitrogen oxides (NOx), a group of gases known for their role in atmospheric chemistry.
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Ground-level Ozone (O3): The article explains that nitrogen oxides generated by lightning have an impact on ground-level ozone. Ozone is a secondary pollutant formed when precursor pollutants, such as NOx and volatile organic compounds (VOCs), react in the presence of sunlight.
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Air Quality Models - CMAQ (Community Multiscale Air Quality Modeling System): The Environmental Protection Agency (EPA) utilizes the CMAQ model to simulate and predict air quality by accounting for various factors like emissions, atmospheric chemistry, and meteorological conditions. This model helps researchers understand the contributions of natural sources like lightning to air pollution and ground-level ozone.
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EPA's Research and Air Quality Standards: The EPA is dedicated to evaluating the impact of natural sources, like lightning-generated nitrogen oxides, on ground-level ozone. With the reduction of human-generated ozone, understanding natural sources' contributions becomes crucial for accurate air quality predictions.
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National Air Quality Standards (NAAQS): The NAAQS set regulations to protect public health by establishing limits for various pollutants, including ground-level ozone. Efforts to reduce anthropogenic sources have led to a decrease in ozone levels, emphasizing the need to assess natural sources' impacts for more precise air quality predictions.
In summary, the article emphasizes the importance of considering natural sources, such as lightning-induced nitrogen oxides, in air quality modeling to comprehensively understand and predict ground-level ozone and overall air pollution. This integration helps refine regulations and policies aimed at safeguarding public health from air pollution-related risks.
