Mercury as an Environmental Toxicant: Analysis and Evaluation
Sources of Mercury in the Environment
Mercury is a naturally occurring heavy metal that is introduced into the environment through both
natural processes and anthropogenic activities. The following are key sources:
1. Natural Sources
Mercury is released from natural geological processes, such as volcanic eruptions, weathering of rocks,
and emissions from the ocean. These processes contribute to a baseline level of mercury in the
environment (Driscoll et al., 2013).
2. Anthropogenic Sources
Human activities have significantly increased mercury levels in the environment. Key contributors
include:
• Coal Combustion: Coal-fired power plants release mercury vapor into the atmosphere
(UNEP, 2019).
• Industrial Processes: Industries such as cement production, smelting, and chlor-alkali
manufacturing discharge mercury (Evers et al., 2011).
• Gold Mining: Artisanal and small-scale gold mining (ASGM) involves the use of mercury
to extract gold, leading to significant environmental contamination (Telmer & Veiga, 2009).
• Waste Disposal: Improper disposal of products like thermometers, fluorescent bulbs,
and batteries contributes to mercury pollution (UNEP, 2019).
Pathways of Mercury in the Environment
Mercury cycles through the environment in three main forms: elemental mercury (Hg⁰), inorganic
mercury (Hg²⁺), and organic mercury (methylmercury). These forms interact with air, water, and soil
through various pathways:
1. Atmospheric Deposition
Mercury released into the atmosphere is deposited on land and water bodies through rain or dry
deposition (Selin, 2009).
2. Aquatic Systems
In water bodies, mercury is converted by microorganisms into methylmercury, a highly toxic form that
bioaccumulates in fish and biomagnifies through the food chain (Mergler et al., 2007).
3. Soil and Sediments
Mercury in soil and sediments can persist for decades, leaching into groundwater or re-entering the
atmosphere (Driscoll et al., 2013).
Problems Associated with Mercury Contamination
1. Human Health Impacts
Mercury exposure can have severe effects on human health, particularly affecting the nervous system,
kidneys, and immune system.
• Methylmercury Toxicity: Consumption of contaminated fish and shellfish is the primary
exposure route for humans. This is particularly harmful to pregnant women, as it can impair fetal brain
development (Mergler et al., 2007).
• Elemental Mercury: Inhalation of mercury vapor affects the lungs and brain, leading to
neurological and cognitive deficits (Clarkson & Magos, 2006).
2. Ecological Impacts
Mercury contamination disrupts ecosystems by affecting the health and reproduction of aquatic and
terrestrial species.
• Bioaccumulation: Mercury accumulates in organisms, particularly top predators like fish
and birds, leading to toxic effects (Selin, 2009).
• Biodiversity Loss: Sensitive species may decline due to mercury toxicity, altering
ecosystem dynamics.
3. Economic Consequences
• Losses in fisheries and aquaculture due to mercury contamination affect livelihoods.
• Costs associated with public health interventions and ecosystem remediation are
significant (UNEP, 2019).
Practical Approaches to Treating Waste Containing Mercury
Addressing mercury contamination requires integrated strategies targeting prevention, treatment, and
remediation. The following approaches are practical and effective:
1. Source Reduction
• Policy Measures: International agreements like the Minamata Convention aim to reduce
mercury emissions globally (UNEP, 2019).
• Cleaner Technologies: Transitioning to alternative energy sources and mercury-free
industrial processes.
2. Treatment of Mercury-Containing Wastes
• Stabilization and Solidification: Mercury in waste is stabilized using sulfur-based
compounds to form insoluble mercury sulfide, reducing its mobility (USEPA, 2019).
• Thermal Desorption: This process involves heating mercury-containing waste to vaporize
mercury, which is then captured using condensation systems (Telmer & Veiga, 2009).
• Amalgamation: Mercury is mixed with other metals to form a stable alloy, preventing
further release into the environment.
3. Environmental Remediation
• Phytoremediation: Certain plants, such as Brassica juncea (Indian mustard), can absorb
mercury from contaminated soil (UNEP, 2019).
• Sediment Dredging: Contaminated sediments in water bodies are physically removed
and treated.
• In Situ Treatment: Mercury in sediments can be immobilized using binding agents like
activated carbon.
4. Waste Management Practices
• Recycling: Products containing mercury, such as fluorescent bulbs and thermometers,
should be recycled in facilities designed to safely recover mercury.
• Hazardous Waste Landfills: Proper disposal of mercury waste in secure landfills prevents
leaching into the environment (USEPA, 2019).
Conclusion
Mercury pollution is a global concern with serious health and environmental implications. Tackling this
issue requires a combination of preventive measures, innovative waste treatment technologies, and
robust policies. By reducing mercury emissions, promoting safer waste management practices, and
remediating contaminated sites, we can mitigate the risks posed by this toxicant and safeguard
environmental and public health.
References
• Clarkson, T. W., & Magos, L. (2006). The toxicology of mercury and its chemical
compounds. Critical Reviews in Toxicology, 36(8), 609-662.
• Driscoll, C. T., Mason, R. P., Chan, H. M., Jacob, D. J., & Pirrone, N. (2013). Mercury as a
global pollutant: Sources, pathways, and effects. Environmental Science & Technology, 47(10), 4967-
4983.
• Evers, D. C., Han, Y. J., Driscoll, C. T., & Kamman, N. C. (2011). Biological mercury hotspots
in the northeastern United States and southeastern Canada. Bioscience, 57(1), 29-43.
• Mergler, D., Anderson, H. A., Chan, L. H. M., Mahaffey, K. R., & Stern, A. H. (2007).
Methylmercury exposure and health effects in humans: A worldwide concern. AMBIO, 36(1), 3-11.
• Selin, N. E. (2009). Global biogeochemical cycling of mercury: A review. Annual Review of
Environment and Resources, 34, 43-63.
• Telmer, K., & Veiga, M. M. (2009). World emissions of mercury from artisanal and small-
scale gold mining. Mercury Fate and Transport in the Global Atmosphere, 131-172.
• United Nations Environment Programme (UNEP). (2019). Global Mercury Assessment
2018. Nairobi: UNEP.
• United States Environmental Protection Agency (USEPA). (2019). Mercury Treatment
Technologies.
