Air Pollutants: Damaging Our Crops And Health

Nitrogen oxides (NOx) are a group of gases that include nitrogen dioxide, which is a primary pollutant emitted by vehicles, power plants, and industrial processes. While scientists have long understood the potential for nitrogen oxides to cause harm, the specific impacts of these pollutants on agricultural productivity have been less clear due to challenges in ground-based analysis. However, recent research utilizing satellite measurements has revealed that areas with high levels of nitrogen oxides pollution experience significant declines in crop yields, demonstrating that reducing these emissions is crucial not only for the climate and human health but also for global food security.

Nitrogen oxides (NOx) are a group of gases that include nitrogen dioxide, which is harmful to crops

Nitrogen oxides (NOx) are a group of highly emitted gases that include nitrogen dioxide (NO2) and are harmful to crops. They are among the most widely emitted pollutants globally, with the potential to directly damage crop cells and negatively impact agricultural productivity.

NOx gases are phytotoxins, which means they can directly harm plants and reduce yields. They can also interfere with photosynthesis, a process vital to plant growth, by reducing access to photosynthetically active radiation. This interference leads to lower crop yields and stunted growth. In addition, NOx gases can react with other compounds in the atmosphere, forming additional pollutants that further contribute to crop damage.

One of the primary ways NOx gases harm crops is through their role as precursors to the formation of ozone (O3), a potent airborne toxin. Ozone is not directly emitted into the atmosphere but is created through the interaction of sunlight, heat, NOx, and volatile organic compounds (VOCs). Ozone is a significant air pollutant that affects agricultural production by reducing crop yields. The formation of ozone from NOx gases thus indirectly affects crop health and productivity.

Furthermore, NOx is a precursor to particulate matter aerosols. In agricultural regions, where ammonia is often present due to the use of nitrogenous fertilizers, NOx can lead to increased concentrations of ammonium nitrate aerosols. These aerosols can reflect and scatter sunlight, altering the radiation environment experienced by crops and further hindering their growth.

Recent advances in satellite observations, such as the TROPOspheric Monitoring Instrument (TROPOMI), have enabled better monitoring of tropospheric nitrogen dioxide levels. These improvements in global air pollution monitoring help in understanding the impacts of NOx on crop growth and provide valuable data for assessing the potential benefits of air quality improvements. By reducing NOx levels, it is estimated that crop yields could be significantly increased, contributing to sustainable development goals such as reducing hunger.

NOx is emitted from car exhaust, industrial emissions, and agricultural activities

NOx refers to nitrogen oxides, specifically nitric oxide (NO) and nitrogen dioxide (NO2). These gases are formed during the combustion of fuels, particularly at high temperatures, such as in car engines. As a result, car exhaust is a significant source of NOx emissions.

Vehicle exhaust gases, including those from cars, are a major source of NOx pollution. The combustion of fuels, especially at high temperatures, leads to the oxidation of nitrogen in the air, resulting in the formation of NOx gases. Diesel engines, in particular, contribute to NOx emissions due to their higher combustion temperature. Efforts have been made to reduce NOx emissions from car exhaust, such as lowering the combustion temperature through Exhaust Gas Recirculation (EGR) and Selective Catalytic Reduction (SCR) techniques.

Industrial emissions also play a significant role in NOx pollution. Industrial activities that involve the use of nitric acid, nitrates, or nitrites release NOx gases. Additionally, the combustion of oil and coal contributes to NOx emissions. Electrical power plants are a specific example of industrial sources of NOx.

Agricultural activities, particularly the excessive use of fertilizers, have been identified as a significant and underreported source of NOx emissions. Nitrogen-based fertilizers release nitrogen oxides into the atmosphere, contributing to air pollution. Research in California, one of the most prosperous agricultural regions, revealed that farmland soil can account for a significant portion of NOx pollution in the state. Similar findings were reported by a University of California, Berkeley study that analyzed air samples from Antarctica and Tasmania.

It is important to note that NOx emissions have detrimental effects on air quality and human health. They contribute to the formation of smog, acid rain, and the depletion of ozone. Additionally, NOx interacts with volatile organic compounds (VOCs) and hydrocarbons from industrial activities, leading to increased ozone and peroxide compounds, which pose risks to children, individuals with lung diseases, and those who work or exercise outside.

Satellite measurements show that areas with high NOx pollution experience significant declines in crop yields

Ozone (O3) is the primary air pollutant that damages crops, including cotton, by interfering with photosynthesis and reducing crop yields. However, ozone is not emitted directly into the atmosphere but is formed through the interaction of sunlight, heat, oxides of nitrogen (NOx), and volatile organic compounds (VOCs). Nitrogen oxides (NOx) are among the most widely emitted pollutants globally and can directly damage crop cells. They also indirectly affect crops through their role as precursors to the formation of ozone, an airborne toxin known to reduce crop yields.

Lobell and his colleagues combined satellite measures of crop greenness and nitrogen dioxide levels for 2018–2020. The TROPOspheric Monitoring Instrument (TROPOMI), launched in late 2017, is particularly effective at monitoring tropospheric nitrogen dioxide levels at a daily frequency. The study found that reducing NOx emissions by about half in each region would improve yields by approximately:

• 25% for winter crops and 15% for summer crops in China
• Nearly 10% for both winter and summer crops in Western Europe
• 8% for summer crops and 6% for winter crops in India

The study's co-author, Jennifer Burney, an associate professor of environmental science at the University of California, San Diego, noted that the actions to reduce NOx emissions, such as vehicle electrification, align with the energy transformations needed to slow climate change and improve local air quality. The agricultural benefits of these actions could be significant, helping to address the challenge of feeding a growing global population.

Reducing NOx emissions improves crop yields, with the greatest benefits in China and Western Europe

Nitrogen oxides, or NOx, are among the most widely emitted pollutants in the world. These gases can directly damage crop cells and are precursors to the formation of ozone, an airborne toxin that interferes with photosynthesis and reduces crop yields.

A Stanford University-led study found that reducing NOx emissions by about half in each region would improve yields by about 25% for winter crops and 15% for summer crops in China, nearly 10% for both winter and summer crops in Western Europe, and roughly 8% for summer crops and 6% for winter crops in India. North and South America generally had the lowest NOx exposures.

The study, published in Science Advances, used satellite images to reveal how nitrogen oxides affect crop productivity. Nitrogen oxides are invisible to humans, but new satellites have been able to map them with high precision, allowing scientists to measure crop production from space. This improved knowledge of how these gases affect agriculture in different regions.

According to the study's lead author, David Lobell, the findings have important implications for increasing agricultural output and analyzing climate change mitigation costs and benefits worldwide. Lobell is the Gloria and Richard Kushel Director of Stanford's Center on Food Security and the Environment.

The co-author of the study, Stefania Di Tommaso, a research data analyst at Stanford's Center on Food Security and the Environment, added that it was exciting how many different things could be measured from satellites, thanks to new European satellites. The research was funded by NASA and the National Science Foundation.

Other air pollutants, like sulfur dioxide and ammonia, also affect crops, and their interactions with NOx are complex

Ozone (O3) is the primary air pollutant that damages crops, including cotton crops in Arizona. It is not emitted directly but is formed through the interaction of sunlight, heat, oxides of nitrogen (NOx), and volatile organic compounds (VOCs). This process results in the interference of photosynthesis and reduced crop yields.

Ammonia emissions are a significant concern in agriculture, especially in the United States and Canada, where agricultural practices contribute to over three-fourths of ammonia emissions. The main source of ammonia is the breakdown of excess nitrogen in animal waste and fertilizers. Weather conditions also play a role in ammonia emissions, as seen in Colorado, where certain weather patterns increase the likelihood of ammonia emissions traveling toward the Rocky Mountains.

Sulfur dioxide, another air pollutant, interacts with ammonia and NOx in the atmosphere. While the direct effects of sulfur dioxide on crops are not explicitly mentioned in the sources, it likely contributes to crop damage through the formation of secondary pollutants. These interactions between sulfur dioxide, ammonia, and NOx lead to the creation of harmful particles and compounds that can have indirect effects on crop health and overall air quality.

Regulations and voluntary actions are in place to mitigate the impact of these pollutants. The Clean Air Act in the United States has helped decrease levels of sulfur dioxide, nitrogen dioxide, and ozone. Additionally, early warning systems, like the one in Colorado, provide valuable information to stakeholders, enabling them to take voluntary actions to reduce emissions and protect both the environment and public health.

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