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Radionuclides and heavy metals
Published in Rym Salah-Tazdaït, Djaber Tazdaït, Phyto and Microbial Remediation of Heavy Metals and Radionuclides in the Environment, 2022
Rym Salah-Tazdaït, Djaber Tazdaït
Hg2+ and Hg0 can interact with carbon to form organic Hg compounds such as monomethylmercury, dimethylmercury, ethylmercury, and phenyl-mercury. Monomethylmercury (MeHg) is the most frequently encountered in the environment and can be easily accumulated in the tissues of organisms, including humans, causing severe toxic effects. MeHg can result from both abiotic and biotic processes. The biotic process is dominant in the environment and occurs by the action of soil and aquatic microorganisms, mainly in anaerobic conditions. This process consists mainly of transferring a methyl group from a donor molecule (methylcobalamin) to mercuric cation through the acetyl-coenzyme A pathway (Ma, Du, and Wang 2019, 1901). It is worth noting that Hg0 can be formed from MeHg (Lehnherr and St. Louis 2009, 5692) or Hg2+ (Amyot, Mierle, Lean, and McQueen 1994, 2366) through abiotic photoreduction, which occurs in aquatic media.
Public Health Issues Emanating from Heavy Metal Contamination of Freshwater Ecosystems and Groundwater
Published in Abhik Gupta, Heavy Metal and Metalloid Contamination of Surface and Underground Water, 2020
Mercury is a toxic metal which has no known biological function, and is ubiquitously distributed in the environment. Mercury exists in three forms in the environment, viz., metallic mercury, and inorganic and organic mercury compounds. Inorganic mercury compounds are water soluble with a bioavailability of 7–15% after ingestion. They are mostly accumulated in the kidneys, where they damage these organs. Elemental mercury in contrast mostly enters the human body through the inhalation of Hg vapor during dental amalgam restorations. Among the organic forms, methylmercury and ethylmercury are the most common. Microorganisms can methylate inorganic mercury to form methylmercury. Human exposure to methylmercury and inorganic mercury mostly occurs through seafood and other contaminated food, respectively (WHO 2005a; Park and Zheng 2012). Mining activities are also responsible.
History of Chemical Exposure Assessment
Published in Jack Daugherty, Assessment of Chemical Exposures, 2020
More than six hundred Japanese were again poisoned by methylmercury in 1964. Endrin poisoned almost seven hundred Qatari in 1967. Over sixteen hundred Japanese received polychlorinated biphenyl (PCB) doses in 1968. Eleven years after the ethylmercury episode, fifty thousand Iraqis were poisoned by methylmercury in 1971. Milk was contaminated by polybrominated biphenyls (PBB) in Michigan in 1973. Seventy-five hundred Pakistanis were dosed with malathion in 1976. The same year, a lead exposure scare rocked Kellogg, Idaho. Also, in 1976, a reactor ran away and blew up at the ICMESA plant, a Hoffmann-LaRoche subsidiary in Seveso, Italy, near Milan, spreading several pounds of dioxin (2,3,7,8-tetrachlorodibenzo-para-dioxin) over the countryside. The town was evacuated after several weeks when the truth of the incident was finally released to the press. The cleanup was completed only recently. The next year brought a 1,2-dibromo-3-chloropropane (DBCP) release in California.
Nanomaterials and nanotechnology for water treatment: recent advances
Published in Inorganic and Nano-Metal Chemistry, 2021
Alumina NPs is a good adsorbent for heavy metals, and could be prepared by sol-gel method and has been employed as solid phase extraction material for separation/pre-concentration of trace metal ions. It has been shown that chemical or physical modification of alumina NPs with certain functional groups containing some donor atoms, including oxygen, nitrogen, sulfur and phosphorus improved their sorption toward heavy metals. Fixing mercaptopropy-trimethoxysilane on the surface of alumina would improve its selectivity toward Cu, Hg, Au and Pd ions.[39,40] In one study, an alumina nanoparticle adsorbent was developed using solution combustion synthesis method and was utilized for the removal of zinc (Zn(II)) (maximum adsorption was found at pH value of 7) and color black G (CBG) (maximum adsorption was found at pH value of 2) from wastewater; the maximum adsorbent capacity of alumina NPs for the removal of Zn(II) and CBG being 1,047.83 and 263.16 mg g−1, respectively.[223] Furthermore, It was reported that by mixing gold NPs (13 nm) with Al2O3 particles (50-200 μm), Au NP-Al2O3 adsorbents were prepared[224]; these adsorbents were used for removal of mercury species [Hg2+, methylmercury (MeHg+), ethylmercury (EtHg+), and phenylmercury (PhHg+)]wherein gold NPs had a higher binding affinity for Hg2+ ions than the Al2O3 adsorbent. The Au NP-Al2O3 adsorbent provided a synergic effect and, therefore, was effective for removal of most tested metal ions and organic mercury species.[224] Additionally, an aluminum oxide-impregnated carbon nanotube membrane has been synthesized, and applied for the removal of toxic metal cadmium ions, Cd(II); membrane did not require any binder to hold the carbon nanotubes together. Instead, the Al2O3 particles impregnated on the surface of carbon nanotubes were sintered together during heating at 1400 °C and the extreme hydrophilic behavior of the developed membrane yielded a high water flux through the membrane. The filtration system removed 84% of the Cd(II) ions at pH 7 using carbon nanotubes membrane with 10% Al2O3 loading.[225]