Atmospheric Purification: Removing Pollutants From Our Air

Air pollution, caused by the release of harmful chemicals and gases into the air, poses a significant threat to human health and the planet. To combat this, it is imperative to not only reduce emissions but also actively remove pollutants from the atmosphere. This can be achieved through natural processes like absorption by vegetation, soil, stone, and water bodies, as well as chemical reactions within the atmosphere. Additionally, human interventions such as adopting clean technologies, improving waste management, transitioning to renewable energy sources, and implementing carbon removal strategies like reforestation and direct air capture play a crucial role in mitigating air pollution and its detrimental effects.

Planting trees and vegetation

Dispersion occurs when particles collide with trees and plants, causing concentrated clouds of pollutants to disperse and dilute in the air. This reduces the risk of inhalation by humans. The extent of dispersion depends on the size and structure of the vegetation, with larger canopies and leaves trapping and dispersing more particles.

Deposition involves the trapping of particulate matter on the leaves and bark of trees. The particulate matter can include toxic pollutants such as sulphur dioxide, nitrogen dioxide, and carbon monoxide. When it rains, the trapped particles are washed away and carried into the soil or dissolved in stormwater runoff.

Trees also directly remove pollutants from the air through the absorption of gaseous molecules. Tiny pores on leaf surfaces, called stomata, absorb air containing toxic pollutants. Once inside the leaf, the gases react with inner-leaf surfaces, permanently converting pollutants. Trees are particularly effective at removing ozone, a major component of smog, through this process.

In addition to these mechanisms, trees and vegetation can improve air quality by reducing air temperatures and energy consumption in buildings. Lower temperatures decrease pollution concentrations, while reduced energy consumption leads to lower emissions from power sources.

The benefits of planting trees and vegetation to improve air quality are well-documented. Urban forests in the United States, for example, remove millions of metric tons of air pollution each year, leading to significant health and ecological benefits.

Reducing vehicle usage

The burning of fossil fuels like gasoline and diesel releases carbon dioxide, a greenhouse gas, into the atmosphere. Greenhouse gas emissions from transportation account for about 28% of total US greenhouse gas emissions, making it the largest contributor of US GHG emissions. Motor vehicles are the largest source of air pollution in Washington.

To reduce vehicle usage and its associated pollutants, individuals can opt for more fuel-efficient vehicles, such as electric or hybrid models, which emit less pollution than traditional gasoline-powered cars. Newer vehicles are also generally more fuel-efficient and emit less pollution than older models. Proper maintenance, including regular oil changes and keeping tires properly inflated, can also help improve fuel efficiency and reduce pollution.

Additionally, individuals can reduce vehicle usage by opting for alternative modes of transportation, such as walking or biking to their destination, or using public transportation for longer distances. Carpooling is another option to reduce the number of vehicles on the road. For shorter distances, individuals can consider using electric or battery-powered lawn and garden equipment, which are quieter and less polluting than gas-powered alternatives.

On a broader scale, initiatives such as the US EPA's SmartWay program work with the freight transportation sector to improve supply chain efficiency, reduce greenhouse gas emissions, and save fuel costs. The EPA also provides resources like the Green Vehicle Guide and the Fuel Economy and Environment Label to help consumers choose more fuel-efficient and environmentally friendly vehicles.

By implementing a combination of individual choices and industry initiatives, it is possible to significantly reduce vehicle usage and the associated pollutants released into the atmosphere.

Using clean technologies

Clean technologies are an essential part of the fight against air pollution. The deployment of such technologies has been prompted by legislation such as the Clean Air Act in the US, which has also helped to spur their development.

One example of clean technology is direct air capture (DAC), which chemically scrubs carbon dioxide from the ambient air and then sequesters it underground or in long-lived products like concrete. DAC is an example of carbon removal, which differs from carbon capture and storage (CCS) in that it removes excess carbon that has already been emitted into the atmosphere, rather than capturing it at the source. While DAC is a costly and energy-intensive process, it has seen a significant jump in public and private investment in recent years, with companies committing to spending billions on carbon removal.

Another clean technology is the catalytic converter, which is used in vehicles to reduce the environmental and health impacts of exhaust fumes. Catalytic converters do have some downsides, such as restricting the flow of exhaust and requiring rare metals in their creation, but they are still an important tool in reducing emissions.

Wet scrubbers and dry scrubbers are also used to remove pollutants from industrial exhaust. These use a liquid, usually water, or dry reagents to absorb particles or gases from a stream of air. Scrubbers are beneficial as they do not disrupt the production process, allowing economic and industrial activity to continue without increasing air pollution.

Other clean technologies include low-emitting or VOC-free consumer products and building materials, portable air cleaners, and ultraviolet (UV) disinfection technologies, which are designed to inactivate airborne microbes rather than capture them.

In addition to these technologies, air quality monitoring plays a crucial role in the fight against air pollution, even though it does not directly reduce emissions. By monitoring air quality, policymakers and the public can be better informed about the sources of pollution and the progress of emissions reduction efforts.

Capturing methane gas

Methane removal can be achieved through oxidation, converting it into CO2 and water vapour. This process occurs naturally through hydroxyl radicals, highly reactive molecules that break down methane and other air pollutants. However, methane's low concentration in the atmosphere makes it challenging to capture. Emerging technologies, such as zeolites (crystalline materials), show promise in absorbing methane gas.

To maximize the effectiveness of methane capture, efforts should focus on regions with consistently higher methane concentrations, such as those associated with oil and gas extraction, abandoned coal mines, landfills, and agriculture. These strategic targets are considered methane mitigation rather than pure methane capture due to their focus on known sources.

While developing methane removal technologies is challenging, it is essential to recognize the potential financial gains. If carbon offset prices rise as predicted, each ton of methane removed could be worth over $2,700. This incentive highlights the importance of investing in methane removal research and development to complement carbon dioxide removal efforts.

In conclusion, capturing methane gas is a critical yet complex aspect of combating climate change. By targeting regions with high methane concentrations and leveraging emerging technologies, we can make significant strides in reducing the warming impact of this potent greenhouse gas.

Improving soil health

Soil is the foundation of the agri-food system, with about 95% of the food we eat coming directly or indirectly from crops grown in the soil. Healthy soils are critical for supporting human health and well-being. They are essential for food, biomass, and fibre production, the production of certain medicines, and retaining and filtering water. Soil also plays a critical role in capturing carbon and slowing global climate change.

Soil pollution is a serious environmental concern and a growing threat to human health. It affects soil fertility, jeopardises food security, and poses risks to human health. Soil may be polluted by heavy metals, organic chemicals such as pesticides, biological pathogens, and micro/nanoplastic particles. Pollution reduces the soil’s ability to yield food and results in food crop contamination and disease. Soil pollution can also increase the salinity of the soil, making it barren and unsuitable for growing most types of plants.

• Reduce the use of disposable products and increase the recycling and reuse of items to limit the amount of waste that ends up in landfills, which is a major source of soil contamination.
• Minimise the use of chemical fertilisers and pesticides, opting for manure and other natural fertilisers instead. While appropriate amounts of chemical fertilisers can improve soil fertility, overuse can disrupt soil pH levels, destroy beneficial microorganisms, and pollute water through runoff.
• Plant trees and other deep-rooted plants, which absorb contaminants in the soil and incorporate them into their tissues. Phytoremediation is a process where plants "breathe" volatile contaminants to the atmosphere, where they dissipate.
• Remediation processes can be used to clean up contaminated sites. In-situ remediation methods, such as air sparging, are considered more environmentally friendly as the contaminated soil does not need to be removed and no one is exposed to the contamination during the process.
• Biodegradation is a naturally occurring process where certain microorganisms in the soil feed on contaminants. Injecting zero-valent iron, or iron in its elemental form, into the soil can accelerate natural biodegradation.

Frequently asked questions