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Ecological and Health Implications of Heavy Metals Contamination in the Environment and Their Bioremediation Approaches
Published in Ram Naresh Bharagava, Sandhya Mishra, Ganesh Dattatraya Saratale, Rijuta Ganesh Saratale, Luiz Fernando Romanholo Ferreira, Bioremediation, 2022
Methylmercury (MeHg) is an organic form of mercury and is neurotoxic in nature. Methylmercury accumulates in food chain and reaches higher concentration by biomagnification. The International Agency for Research on Cancer (IARC) has classified methylmercury as ‘possibly carcinogenic to humans’ (Group 2B). Methylmercury’s toxicity was highlighted in the 1950s in Minamata (Japan) when wastes from the chemical factory were discharged into the local bay (Yokoyama 2018). Mercury can cause mental retardation, urological defects, hearing loss, developmental defects, blindness, dysarthria and even death. Mercury causes fetotoxicity by low birth weight, spontaneous abortion, miscarriage and stillbirth. Mercury can easily cross the placental barrier and inhibit the development of foetal brain, resulting in psychomotor retardation and cerebral palsy. Children are more sensitive to MeHg, and exposure during pregnancy period can lead to delay in development, low IQ (intelligence quotient) and ADHD (attention deficit hyperactivity disorder) (WHO 2011).
Water Reuse and Recycling
Published in Maulin P. Shah, Removal of Refractory Pollutants from Wastewater Treatment Plants, 2021
Khushboo Dasauni, Divya, Tapan K. Nailwal
Another major source of industrial water pollution is mining. Unless proper precautions are taken, such as the use of sedimentation tanks, the grinding of ore and subsequent water treatment can cause toxic metal fines to be discharged into waterways. Lead and zinc ores usually contain less toxic cadmium. If cadmium is not recycled, it will cause serious water pollution. From 1940–1950, mining was the main source of cadmium poisoning (itai-itai disease) in Japan (Kjellstrom, 1986). Mercury can enter waterways from mining and industrial sites. Another source of environmental pollution by mercury is the incineration of medical waste containing damaged medical equipment. Because metallic mercury is highly volatile, it is also easily transferred into the atmosphere. Sulfate-reducing bacteria and other microorganisms in the underwater sediments of lakes, rivers, or coastal waters can methylate mercury, thereby increasing its toxicity. The accumulation and concentration of methylmercury in the food chain can cause serious neurological diseases or more subtle functional damage to the nervous system (Murata et al., 2004). Due to the local pollution of fish or shellfish, coastal seawater pollution may cause health hazards. For example, in 1956, a water disease broke out in Japan resulting in the mercury pollution of fish (WHO, 1976). Pollution of seawater by persistent chemicals (such as polychlorinated biphenyls [PCB] and dioxins) can also pose a major health hazard, even at very low concentrations (Yassi et al., 2001).
Adsorption of Mercuric Chloride Vapours from Incinerator Flue Gases on Calcium Hydroxide Particles
Published in Maria da Graça Carvalho, Woodrow A. Fiveland, F. C. Lockwood, Christos Papadopoulos, Combustion Technologies for a Clean Environment, 2021
A. Lancia, D. Musmarra, F. Pepe, G. Volpicelli
The toxicity and the relatively high concentration of mercury in the flue gas can result in severe environmental damage. In the lakes surrounding the mercury emission sources, elevated levels of this pollutant have been found, probably as a consequence of deposition from the air. High concentrations of methylmercury have been found in tissues of some kinds of comestible lake fishes, making them unsuitable for consumption, since the methylmercury is highly poisonous to man and higher animals (Roberts, 1981).
Making Mercury’s Histories: Mercury in Gold Mining’s Past and Present
Published in Ambix, 2023
Moreover, once mercury vapour or liquid mercury enters an aquatic environment, it is converted by water-dwelling bacteria into methylmercury, a relatively stable metal-organic cation [CH3Hg]+ that can persist in environments for centuries after mercury has been introduced and converted. Methylmercury is also highly toxic.2 The presence of methylmercury is a constant threat to the overall health of biota in local ecosystems. Methylmercury biomagnifies, accumulating up food chains, so it is especially dangerous to apex predators, including humans.3 Though pure methylmercury salts will form crystalline solids, these are not encountered outside of laboratories. In the natural environment, methylmercury is effectively formless. (Notably, an internet search employing the term “methylmercury” reveals no portraits of it as a substance, only schematic diagrams of its atomic structure.) Methylmercury only exists vicariously in the public consciousness, evident through the bizarre behaviour and startling appearance of humans and animals that have ingested toxic doses.4
Environmental Alchemy: Mercury-Gold Amalgamation Mining and the Transformation of the Earth
Published in Ambix, 2023
The process of mercury-gold amalgamation, whether as a mining or an artisanal process, triggers a series of reactions on multiple levels and scales that have profound consequences for people and the planet. When the mercury-gold amalgam is heated, mercury escapes its chemical bond with gold and immediately begins to transform into different, pervasive forms that go on to penetrate bodies and the biosphere. Mercury vapour simultaneously toxifies the person performing the process and releases mercury into the environment. Because it is an element and cannot break down further, mercury will condense and settle into soils and waterways where bacteria transform it into methylmercury. Organic mercuric compounds like methylmercury are particularly troublesome since they bioaccumulate up aquatic food chains, causing harm to larger fresh- and salt-water predators such as walleye, albacore tuna, and swordfish, and eventually to the people that consume these fish. Mercury also ascends into the atmosphere and precipitates planet-wide in rain and snow. Gold moves through culture and time in physical form, but mercury charts different pathways through the world.
Seasonal patterns of methylmercury production, release, and degradation in profundal sediment of a hypereutrophic reservoir
Published in Lake and Reservoir Management, 2021
Byran Fuhrmann, Marc Beutel, Priya Ganguli, Liying Zhao, Sarah Brower, Andrew Funk, Jeffrey Pasek
In the process of mercury methylation, iHg is transformed into organic methylmercury (MeHg) by anaerobic bacteria (Bigham et al. 2017). The anaerobic bacteria specifically implicated in the production of MeHg include sulfate-reducing bacteria (SRB), iron(III)-reducing bacteria (IRB), methanogens, and a small number of fermenters (Podar et al. 2015). Although not all anaerobic bacteria are capable of mercury methylation, no known aerobic bacteria have been identified, and MeHg typically accumulates in bottom waters under anaerobic conditions (Podar et al. 2015). MeHg can be converted back into either iHg or Hg0 by a process known as demethylation. MeHg demethylation can occur due to abiotic or biotic processes (Bigham et al. 2017). Abiotic demethylation primarily occurs in the surface water of lakes and reservoirs when MeHg is exposed to ultraviolet (UV) light (Paranjape and Hall 2017). Biotic demethylation has been demonstrated by a variety of microorganisms and multiple pathways have been identified (Ullrich et al. 2001). Although aerobic organisms have generally been found to express a greater ability to demethylate MeHg, there is a growing body of evidence that anaerobic organisms such as SRB and methanogens are prominent demethylators in freshwater sediments (Korthals and Winfrey 1987, Pak and Bartha 1998, Ullrich et al. 2001, Kronberg et al. 2018, Beutel et al. 2020). It is important to consider that both iHg methylation and MeHg demethylation play important roles in regulating the net pool of MeHg in aquatic environments.