Vanadium (V) is a greyish metal that occurs in the form of two natural isotopes 50V and 51V. It forms oxidation states of -1, 0, +2, +3, +4, and +5, the oxidation states +3, +4, and +5 being the most common. Oxidation state +4 is the most stable.

Metallic vanadium does not occur in nature. Over 70 vanadium minerals are known, carnatite and vanadinite being the most important from the point of view of mining. Vanadium is mainly (75 - 85%) used in ferrous metallurgy as an alloy additive in various types of steel. Its use in non-ferrous metals is important for the atomic energy industry, aircraft construction, and space technology. Vanadium is also widely used as a catalyst in the chemical industry, where vanadium pentoxide and metavanadates are especially important for the production of sulfuric acid and plastics. Small quantities of vanadium are used in a variety of other applications (WHO 1988).

Power- and heat-producing plants using fossil fuels (petroleum, coal, oil) cause the most widespread discharge of vanadium into the environment. Burning of coal wastes or dumps of coal dust in mining areas are other sources of vanadium discharge into the atmosphere. In the distillation and purification of crude oil, most of the vanadium remains in the residues. Burning of distilled petroleum fuels contributes less vanadium to the atmosphere (WHO 1988).

Vanadium is not commonly monitored for in UK marine waters and was not included in the National Monitoring Programme (MPMMG 1998). Grimwood and Dixon (1997) reported some values for total vanadium at two sites in the North East region of the Environment Agency (ranging from an annual average of 1mg l^-1 to <20mg l^-1).

Most of the vanadium entering sea water is in suspension or adsorbed on colloids. It does not react chemically with sea water but passes mechanically through it. This is reflected in its distribution on the sea bed in the form of silt. Only about 10% of the vanadium is present in a soluble form. The very low concentrations of vanadium in sea water indicate that vanadium is continuously removed from sea water, but the actual mechanisms are largely unknown. Vanadium that accumulates in ascidians, holothurians, and in marine algae will end up in the silt (WHO 1988).

An exhaustive literature review on the toxicity of vanadium to marine organisms has not been carried out for the purposes of this profile. The information provided in this section is taken from existing review documents (Mance et al 1984 and Grimwood and Dixon 1997). The most sensitive groups of organisms have been identified.

The current EQS adopted in UK legislation (HMSO 1989) is a value of 100 mg l^-1, expressed as a total annual average concentration which Mance et al proposed in 1988. They found few data and these only related to acute toxicity. Too few data were available to assess which group of organisms exhibited greatest sensitivity. The EQS was derived by applying a safety factor of 100 to the lowest, most reliable LC50 of 10,000 mg l^-1, reported for the annelid Nereis diversicolor following 9 days exposure. It was recommended that the EQS should be reviewed once a larger dataset became available.

More recently, Grimwood and Dixon (1997) reviewed data on the saltwater toxicity of vanadium since the report by Mance et al (1984). They found no reliable toxicity data that indicated higher sensitivity of saltwater organisms had been reported for vanadium. They recommended that the EQS of 100 mg l^-1 (total annual average) was appropriate for the protection of all saltwater life, although where there was concern that the health of communities in sites of nature conservation importance may be compromised as a result of the presence of particularly sensitive species, a lower value may be used as a guideline. However, in the absence of any new toxicity data, it was not possible to make any recommendations on such a value.

Mance et al (1988) reviewed the limited information on the bioaccumulation of vanadium and reported the majority of BCFs below 100, indicating that bioaccumulation of vanadium is not likely to be a problem.

Potential effects include:

• acute toxic effects on marine organisms at concentrations above the EQS of 100 mg l^-1 (annual average) of dissolved vanadium in the water column.

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