Soil Pollution: Atmospheric Deposition's Impact On Earth's Health

Atmospheric deposition is the process by which particles and substances from the atmosphere are deposited onto the Earth's surface. Atmospheric deposition can occur in the form of dry deposition or wet scavenging. Dry deposition refers to when pollutants are deposited onto surfaces, while wet deposition occurs when pollutants are washed out of the atmosphere by rain or snowfall. The sources of these pollutants include industrial facilities, agricultural processes, and the burning of fossil fuels. These pollutants can have detrimental effects on both human health and the environment. For instance, acid rain, formed when sulfur dioxide and nitrogen oxides are emitted from industrial plants burning fossil fuels, can cause harm or death to fish and other aquatic organisms, as well as damage to forests. Furthermore, atmospheric deposition of nitrogen can lead to eutrophication of water bodies, resulting in harmful algal blooms and contaminated drinking water.

Acid rain

Additionally, acid rain contributes to the corrosion of water pipes, leading to the leaching of heavy metals like iron, lead, and copper into drinking water. It also damages buildings, statues, and monuments, causing paint to peel and stone to deteriorate.

The effects of acid rain on human health are primarily related to respiratory issues. The pollutants that cause acid rain can create tiny particles that, when inhaled, can lead to respiratory diseases or exacerbate existing conditions. Nitrogen oxides, a component of acid rain, contribute to ground-level ozone, which is responsible for respiratory problems like pneumonia and bronchitis and can cause permanent lung damage.

To address the issues caused by acid rain, it is crucial to focus on reducing the emission of nitrogen and sulphur compounds. This can be achieved by transitioning to alternative energy sources, such as solar, wind, nuclear, hydro, and geothermal power, which produce fewer emissions and help mitigate the formation of acid rain.

Eutrophication of water bodies

Atmospheric deposition is the process by which particles and substances from the atmosphere are deposited onto the Earth's surface. It is a primary source of pollutants, such as gases, particles, metals, and nutrients, for both terrestrial and aquatic environments.

One of the adverse effects of atmospheric deposition is eutrophication, which is the addition of 'excess' nutrients to a water body. Eutrophication is a widespread environmental problem, and human activities have accelerated the rate at which it occurs. It is characterised by excessive plant and algal growth due to the increased availability of limiting growth factors, such as nitrogen and phosphorus, which are essential for photosynthesis.

When water bodies are overly enriched with nutrients, the growth of algae, plankton, and other simple plant life is favoured over the growth of more complex plant life. This greatly decreases the biodiversity of the ecosystem by killing off several desirable species. The excessive growth of algae in eutrophic waters is accompanied by the generation of a large biomass of dead algae, which sink to the bottom of the water body and are broken down by bacteria, which consume oxygen in the process. This overconsumption of oxygen leads to hypoxic conditions, which can cause the suffocation and death of larger life forms such as fish. Eutrophication can eventually turn water bodies into "dead zones" that are incapable of supporting life.

The deposition of sulfur and nutrients from atmospheric deposition may contribute to the eutrophication of various water bodies. Ammonia (NH3) and ammonium (NH4) are often emitted from fossil fuel combustion emission controls and are precursors of secondary PM2.5. They contribute to the eutrophication of water bodies, leading to harmful algal blooms and contaminated drinking water.

There are a range of techniques for preventing eutrophication, including the use of chemical coagulants such as lime, magnesium sulphate, and ferric sulphate, which have been reported to remove more than 95% of nitrate and phosphate. Biological techniques such as wetland treatment have also been effective, exhibiting high removal efficiencies for various pollutants.

Deposition of heavy metals

Atmospheric deposition of heavy metals is a serious issue, as these metals can be toxic to both humans and the ecosystem. Heavy metals are inorganic chemical hazards that are not degraded by microbial or chemical processes, so they persist in the soil for a long time. They can be deposited onto the Earth's surface through dry or wet deposition.

Heavy metals enter the soil through various sources, including atmospheric deposition, animal manure, mineral fertilisers, and pesticides. Atmospheric deposition is considered the predominant contributor to agricultural soils, especially in industrialised countries. Sources of atmospheric deposition include industrial facilities, which discharge pollutants through smokestacks, and vehicles, which emit metals such as lead and mercury through fuel combustion.

Soil heavy metal pollution poses significant threats to the eco-environment, agricultural development, and human health. Heavy metals can be absorbed by plant roots and translocated to their edible parts, leading to health risks for consumers. They can also be directly ingested or come into contact with contaminated soil.

To reduce the health risks associated with heavy metal pollution, it is essential to implement effective remediation strategies. These strategies include low-metal cultivar selection/breeding, physiological blocking, water management, soil amendment, and phytoremediation. Soil amendments, such as lime, phosphate minerals, and biochar, can immobilise heavy metals in the soil by increasing soil pH, electrostatic interaction, and adsorption. Phytoremediation, which utilises hyperaccumulator plant species, is an eco-friendly and sustainable approach to restoring contaminated land.

Dry deposition

The environmental consequences of dry deposition can be harmful or beneficial. On the one hand, it can be a cleansing process for the air and a way to transport additional nutrients to plants. On the other hand, the deposition of sulfur and nutrients may contribute to the acidification and eutrophication of various ecosystems.

Wet deposition

The effects of wet deposition vary depending on the specific substances being deposited and the local environmental conditions. For example, the deposition of oxidized and reduced forms of nitrogen can cause eutrophication of water bodies, leading to harmful algal blooms and contaminated drinking water. Additionally, the deposition of radioactive substances after nuclear accidents can accumulate in soils, sediments, and flora and fauna, posing risks to human health and the environment.

Overall, wet deposition is a complex process that plays a significant role in the Earth's biogeochemical cycling of chemicals and has important implications for the health of ecosystems and human populations.

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