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The Biomethylation and Cycling of Selected Metals and Metalloids in Aquatic Sediments
Published in Renato Baudo, John P. Giesy, Herbert Muntau, Sediments:, 2020
Lead, a toxic metal, is found in all surface waters. The maximum permissible concentration allowed by the U.S. EPA under its drinking water standards is 50 µg Pb/L. Atmospheric input is the primary source of Pb to aquatic sediments (Edington & Robbins 1976, Kemp & Thomas 1976). Besides emissions from natural erosion and volcanic activity, internal combustion engines, especially in the past, have released five alkyllead compounds. These are: 1) tetramethyllead, (CH3)4Pb; 2) trimethyllead, (CH3)3Pb+; 3) dimethyldiethyllead, (CH3-CH2)2(CH3)2Pb; 4) methyltriethyllead, (CH3-CH2)3CH3Pb; and 5) tetraethyllead, (CH3-CH2)4Pb (DeJonghe & Adams 1982). However, chemical reactions in the atmosphere convert these compounds into PbCO3PbOx, (PbO)2PbCO3·PbSO4, and PbBrCl (Corrin & Natusch 1977). Thus, only small concentrations reach aquatic systems directly. Atmospheric input reaches the land and surface waters by wet and dry deposition, through precipitation and runoff.
Metals
Published in Ronald M. Scott, in the WORKPLACE, 2020
Storage batteries are the largest single use of lead. Another major use is in the production of tetramethyllead and tetraethyllead as antiknock additives in automobile fuels. This industry is being phased out due to environmental restrictions, first because lead poisons the catalytic converters required in automobiles, then later because of concerns about levels of lead in the atmosphere. Alloyed with antimony and tin, lead is used to sheath electrical cables to weatherproof them, as type metal, and in bearings. Lead is found in pigments, in solders, and in ammunition. The use of lead in shot has been vigorously and, more recently, successfully opposed by environmental groups because of long-range negative effects on wildlife.
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Published in Maurizio Cumo, Antonio Naviglio, Safety Design Criteria for Industrial Plants, 2019
Claudia Bartolomei, Sergio Paribelli
Toxicity — Tetramethyl lead is highly toxic if it is inhaled, if it comes in contact with the eyes, or if it is swallowed. It may be absorbed through skin, but in this case it is moderately toxic. Tetramethyl lead is suspected to be carcinogen. It affects the central nervous system; intoxication resembles that caused by tetraethyl lead.
The limits of lead (Pb) phytoextraction and possibilities of phytostabilization in contaminated soil: a critical review
Published in International Journal of Phytoremediation, 2020
Sara Perl Egendorf, Peter Groffman, Gerry Moore, Zhongqi Cheng
Anthropogenic sources of Pb include PbS, PbO, PbSO4, and PbO*PbSO4 from smelting, PbCrO4, Pb3O4, PbCO3 from paint, as well as Pb(C2H5)4 from tettraethyllead (TEL), and Pb(CH3)4 in tetramethyllead (TML), both gasoline additives (Table 3). Automobile exhausts contain Pb halides such as PbBr, PbBrCl, Pb(OH)Br, and (PbO)2PbBr2 (Biggins and Harrison 1979). When these compounds react with neutral and acid sulfate droplets in the atmosphere, they tend to form more stable PbSO4. Photochemical decomposition can produce Pb oxides, and exhaust particles can be converted into oxides, carbonates, and sulfates in soils (Olson and Skogerboe 1975). The subsequent behavior of each form of Pb differs in soils, depending on a variety of soil processes and properties.