Mercury ion toxicity

The mercury ion is capable of causing local or systemic toxicity. For local irritation, they are combined with theophylline in an attempt to diminish the irritative toxicity at the site of injection. IV administration may lead to ventricular arrhythmias. They cause hepatocellular damage and even precipitate hepatic failure. They can also lead to low salt syndrome, hypochloraemic alkalosis and potassium depletion. 

Although these cations and anions are indispensable, excessive amounts of them are toxic, so that it is important that their concentrations are regulated, either by mechanisms existing in the animal or by externally imposed controls. There are also several kinds of metal ions found in Nature which do not appear to serve any useful biological function but which are highly toxic if they are absorbed into the body. These include arsenic and the environmental pollutants lead, cadmium and mercury ions. Most of the remaining metals occur as inert species such as the aluminosilicates and titanium dioxide that are poorly absorbed, if at all, by plants and animals, or are present in only trace amounts and have little physiological effect. 

If mercury ions in solution are reduced to the free element, and a current of air or inert gas is passed through the solution, mercury vapour, which is monatomic, will be swept out of the solution into the gas phase. This provides a very sensitive basis for the determination of this toxic element.1 The apparatus required is illustrated in Figure 1. The flame is replaced by a glass tube atom cell with silica end windows in atomic absorption. Usually, for convenience, the atom cell is clamped to the top of a conventional AAS burner head. If atomic fluorescence is... 

Although mercury has been used medicinally, the element and its compounds are generally very toxic (see Metal Ion Toxicity). For reasons of economy, conservation, and public health, mercury use is gradually falling back to instances where no substitute can be found and recovery efforts are becoming more scrupulous. 

Alloys Anunonia N-donor Ligands Hard Soft Acids and Bases Mercury Qrganometallic Chemistry Metal Ion Toxicity S-donor Ligands Semiconductor Interfaces Superconductivity Water O-donor Ligands Zeolites. 

Precautions have always been practiced to contain the mercury (Table 8.3) of the operating mercury cells, primarily for the value of the metal itself. The steel flasks of the metal are also covered with a layer of water to reduce mercury vapor loss during shipping and storage. However, in 1970, it was demonstrated that mercury ions and the free metal could be converted by natural processes to the far more toxic forms of mercury, methylmercury salts and dimethyl mercury even under water [23, 24]. Industrialists, toxicologists, and legislators alike were alarmed by this discovery, which led to the rapid installation of control measures to drastically reduce mercury loss rates in Europe, Japan, and North America [25] (Table 8.4). 

The toxicity and bioavailability of metals in natural waters depends on the aqueous speciation or complexation of those metals. The toxicities to aquatic life of Cu +, Cd, Zn, Ni, Hg ", and Pb are a function of the activities of the metal ions and their complexes, not of total metal concentrations (cf. Morel and Hering 1993 Manahan 1994). For example, monomethyl mercury ion (CH3Hg ) and Cu are toxic to fish, but some other Hg and Cu complexes (such as CuCO ) are far less so. The bioavailability of essential metals such as Fe, Mn, Zn, and Cu to plants is also a function of their metal speciation (Morel and Hering 1993). Until recently the U.S. Environmental Protection Agency did not recognize the importance of metal speciation in its water quality assessments (cf. Hall and Raider 1993). Metal toxicity is considered briefly near the end of this chapter. 

Keywords Mercury Acute toxicity Subacute toxicity Pila globosa Lamellidens marginalis Accumulation Ions ATPases Glycolysis Oxidative metabolism... 

Reactions of mercury (I) ions A solution of mercury(I) nitrate (0.05m) can be used for the study of these reactions. AU compounds of mercury are toxic ... 

Mercury toxicity is related to the induction of oxidative stress, as revealed by the decrease in antioxidant enzymes as glutathione S-transferase (Reddy et al. 1981). Examining interactions of purified Mn-superoxide dismutase (1 fM) with HgCl2 indicated that mercury ions suppressed Mn-superoxide dismutase activity by reduction of the native form (Shimojo et al. 2002). Due to the minimal hepatic accumulation of inorganic mercury after the subcutaneous application of HgCl2 (0.25-3 mg/kg) to mice the hepatic Mn-superoxide dismutase might be unaffected while the renal enzyme due to a 34-75 times higher accumulation of mercury in the kidney was decreased in a dose-dependent manner. 

According to the results of Clarkson et al. (1980) the divalent cation should be seen as the effective form of metallic mercury, especially because metallic mercury cannot form a chemical bond. Metallic mercury is non-polar and soluble in lipids. Particularly in vapour form it dissolves readily in membrane lipids so that it penetrates the alveolar membranes quickly and efficiently when inhaled, and is diffused into the blood. There it is partially absorbed by the erythrocytes and oxidised to the divalent ion which reacts with SH groups. Inspite of the efficient diffusion into the erythrocyte, sufficient quantities of the metallic mercury dissolved in the blood can be transported to the brain, where they are also reduced to the mercury ion (Magos, 1967 Magos et al., 1973). As far as the toxicity of mercury is concerned, its oxidation produces different effects in the... 

Waste water from certain industrial chemical processes contains aqueous Hg2 ions. Since the mercury ion is toxic, it is removed from the waste water by reaction with aqueous sodium sulfide. The products of the reaction are solid mercury(l) sulfide and aqueous sodium ions. Write a balanced equation for this reaction. 

Many things stick to metallothionein s sulfurs, so they serve as all-purpose cleaners for the cell. They have been caught mopping up extra lead and mercury ions, for example, which are also toxic and sticky. In fact, the metals are toxic because they are sticky. They jumble the chemical order of the cell. 

So hrst let us explore how some microorganisms might cope with mercury. As mentioned above, the toxic form of mercury is Hg(II) which has at least one binding site left open. Let us make this chemistry a little clearer. The mercury ion (Hg(ll)) can bind two entities under ordinary circumstances. So if it is bound strongly with two entities, it cannot bind another and hence cannot exert the toxic effects. Therefore, dimethyl mercury (CH3)2Hg where two methyl groups are bound strongly with Hg(II) is chemically nontoxic, and the common toxic forms are free Hg(II) ion and monomethyl mercury ion CHjHg or similar entities such as C H Hg. It is also to be remembered that mercury metal (the shiny liquid used in thermometer for example) itself is not chemically toxic. It shows some toxicity, only because it can be converted to Hg(II) by some means in your body. 

In this chapter we have defined the key factors for the development of receptors as indicator dyes , and surface-confined nanomaterials as carriers , for the creation of optical chemical sensors capable of selectively discriminating trace levels of toxic analytes. Our aim was to widen the knowledge base with regards to the causes of- and solutions to - metal-ion toxicity. A key factor when designing optical nanosensors to sense mercury, cadmium, lead and antimony is the stable immo-... 

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