Air Pollution: Weathering Rocks And Our Health

Air pollution is caused by solid and liquid particles and certain gases that are suspended in the air. These particles and gases are detrimental to human health and the planet as a whole. They can come from car and truck exhaust, factories, dust, pollen, mold spores, volcanoes, and wildfires. Air pollution can also cause rocks to weather. This is evident in the severe stone deterioration observed at the Cologne Cathedral, where black weathering crusts on the silicate Drachenfels trachyte contribute to the degradation of the historic building material.

Acid rain

In addition to sulphur dioxide, carbon dioxide is another significant contributor to air pollution and the formation of acid rain. Carbon dioxide is released into the atmosphere through various human activities, such as the combustion of fossil fuels, and natural processes, such as volcanic eruptions. When carbon dioxide dissolves into rainwater, it can form a mild acid, leading to carbonic acid rain. This type of acid rain also contributes to the chemical weathering of rocks, particularly those that are rich in silicon, as the carbonic acid reacts with the rock's composition.

The impact of acid rain on rock weathering is evident in the Earth's climate regulation processes. Over long periods, the weathering of rocks by acid rain helps control the planet's temperature by reducing the amount of carbon dioxide in the atmosphere. As carbon dioxide is a potent greenhouse gas, its removal through chemical weathering leads to a cooling effect on the planet. This natural thermostat mechanism, however, is not as efficient as previously believed, and the Earth's climate has experienced significant temperature variations throughout its geological history.

Industrial emissions

Particulate matter (PM), a component of industrial emissions, is of particular concern. PM is composed of fine chemicals such as sulfates, nitrates, carbon, or mineral dust, which can be inhaled deeply into the lungs, leading to serious health problems. Fine particulate matter (PM 2.5) has been linked to an increased risk of respiratory infections, asthma, and even dementia.

In addition to PM, industrial emissions also release a range of noxious gases, including carbon dioxide, carbon monoxide, nitrogen oxides (NOx), and sulfur oxides (SOx). These gases contribute to ground-level ozone, or smog, which has been associated with short-term respiratory infections and asthma, particularly in children.

The impact of industrial emissions on air quality is not limited to the immediate vicinity of industrial sites. Wind can carry pollutants over long distances, affecting air quality in downwind areas. This was evident in a study of Tehran province, Iran, where data analysis revealed significant variations in pollutant concentrations among industrial clusters. The study forecasted that concentrations of carbon monoxide, sulfur dioxide, and nitrogen dioxide would continue to increase until 2025, highlighting the need for urgent action to reduce industrial air pollution.

To mitigate the effects of industrial emissions, it is essential to transition to renewable energy sources, such as solar, wind, and hydropower, and to implement regulatory initiatives and sustainable practices in the industrial sector.

Particulate matter

Airborne particulate matter (PM) is a complex mixture of solids and aerosols composed of small droplets of liquid, dry solid fragments, and solid cores with liquid coatings. The particles vary widely in size, shape, and chemical composition and may contain inorganic ions, metallic compounds, elemental carbon, organic compounds, and compounds from the Earth's crust. For regulatory purposes, particles are defined by their diameter. Those with a diameter of 10 microns or less (PM10) are inhalable into the lungs and can induce adverse health effects. Fine particulate matter, or PM2.5, is defined as particles that are 2.5 microns or less in diameter. These particles are so small that they can be inhaled deeply into the lungs, contributing to serious health problems.

PM2.5 is associated with a wide range of adverse health effects, including premature mortality, increased hospital admissions for heart or lung causes, acute and chronic bronchitis, asthma attacks, respiratory symptoms, and restricted activity days. These effects are particularly pronounced in infants, children, and older adults with pre-existing heart or lung diseases. Long-term exposure to PM2.5 has also been linked to an increased risk of lung cancer and other chronic diseases.

Particle pollution can come from both outdoor and indoor sources. Outdoor sources include vehicle exhaust, burning wood, gas and other fuels, and fires, while indoor sources include tobacco smoke, cooking, burning candles or incense, and indoor air pollution from household cleaning products and air fresheners. Weather conditions, such as wind speed, air turbulence, and temperature inversions, can also affect the dispersion and concentration of particulate matter in the atmosphere.

Carbon dioxide and methane

Carbon dioxide (CO2) is a greenhouse gas that is released into the air by volcanoes and human activities such as the burning of fossil fuels. When CO2 dissolves into rainwater, it forms carbonic acid (H2CO3), a weak acid that can react with rocks, breaking them down through chemical weathering. This process, known as silicate weathering, results in the creation of elements like calcium and the release of carbon into rivers and oceans, where it becomes locked in carbon-containing limestone on the seafloor. The weathering of limestone by carbonic acid, on the other hand, releases CO2 into the atmosphere.

The rate of silicate rock weathering is influenced by temperature and precipitation levels. As temperatures rise, the rate of chemical weathering increases, causing more rainfall and accelerating the chemical reactions between rainwater and rock. This feedback loop leads to a warmer Earth and further enhanced weathering rates. However, the increase in CO2 levels due to human activities is far greater than what can be mitigated by silicate weathering.

Additionally, the exposure of sedimentary rocks through erosion and geological processes such as mountainous uplift can create CO2 "hot spots." The breakdown of organic carbon in these rocks releases significant amounts of CO2 into the atmosphere. This process has been observed in various mountain ranges, including the eastern Himalayas, the Rockies, and the Andes.

Methane (CH4) is another potent greenhouse gas that contributes to climate change and air pollution. While it is governed under the UNFCCC climate regime, this framework primarily addresses its impact as a "CO2 equivalent" on a 100-year time frame. Methane's role as a precursor to tropospheric ozone, a well-known air pollutant, and its alarming rise in atmospheric concentrations highlight the urgent need for accelerated mitigation of CH4 emissions globally.

Fossil fuels and wood burning

Fossil fuels, including coal, oil, and natural gas, are burned to generate energy for electricity, transportation, and industrial processes. The burning of fossil fuels releases greenhouse gases, such as carbon dioxide (CO2) and nitrous oxide (N2O), into the atmosphere, intensifying the greenhouse effect and contributing to global warming. These gases can remain in the atmosphere for extended periods, from decades to centuries. Additionally, the combustion of fossil fuels emits toxic air pollutants, such as soot, sulfur dioxide, nitrogen oxides, and ultra-fine particles, which have significant impacts on both the environment and human health.

The effects of air pollution from fossil fuel combustion are far-reaching. It contributes to climate change, leading to more frequent and severe extreme weather events, including wildfires, hurricanes, wind storms, flooding, and droughts. The release of greenhouse gases also causes global temperature rise, resulting in sea-level rise due to the melting of glaciers and land-based ice sheets. Air pollution from fossil fuels has been linked to various health issues, including respiratory and cardiovascular diseases, asthma, cancer, and premature death. It particularly affects vulnerable populations, including children, the elderly, and individuals with pre-existing health conditions.

Furthermore, fossil fuel extraction, transportation, and refining carry additional environmental risks. Oil spills, for instance, have devastating consequences for marine ecosystems, wildlife, and coastal communities. They destroy habitats, erode shorelines, and result in the closure of beaches, parks, and fisheries. Water pollution is another significant concern, as fracking fluids and oil spills can contaminate groundwater and drinking water sources with toxic substances such as arsenic, lead, chlorine, and mercury.

In addition to fossil fuels, wood burning is a significant contributor to air pollution and climate change. When wood is burned, the carbon dioxide (CO2) absorbed by the tree during its lifetime is released back into the atmosphere, contributing to the greenhouse effect and global warming. Wood burning is a notable source of black carbon emissions, which have negative impacts on climate and air quality. Additionally, the burning of wood releases methane and volatile organic compounds, further contributing to air pollution and climate change.

The wood pellet industry, which has received subsidies and support in some regions, has been associated with air pollution and explosions at manufacturing facilities. Reports from communities near biomass production sites describe thick smoke and smoldering wood piles, indicating the localized impacts of wood burning on air quality. While natural gas is often promoted as a cleaner alternative to coal and oil, it still contributes significantly to carbon emissions and climate change. Overall, the combustion of fossil fuels and wood has wide-ranging impacts on the environment, human health, and ecosystems, underscoring the urgency of transitioning to renewable and sustainable energy sources.

Frequently asked questions