Mercury & compounds: Environmental effects
Description
Both mercury and its compounds have high acute (short-term) and have high chronic (long-term) toxicity on aquatic life. Eating fish contaminated with mercury has caused poisoning in humans; birds and land animals exposed in the same manner could also be subject to the same effects. There is not sufficient data to determine the acute toxicity of mercury and its compounds on plants, birds or land animals. Mercury and its compounds are highly persistent in water and the environment and will bioaccumulate or concentrate in the tissues of fish. These concentrations will be considerably higher than the water from which the fish is taken.
Entering the environment
Mercury chloride will act as a particle, following wind patterns, and being deposited by rain. Elemental mercury may be a gas in the atmosphere. Emissions of mercury and or mercury compounds can produce elevated, but still low-level concentrations in the atmosphere around the source. Elemental mercury can evaporate from both soil and water into the atmosphere.
Where it ends up
When mercury enters the environment from emissions in the air, water or soil, it oxidises into other compounds of mercury. These other forms of mercury form methyl mercury, through either chemical or biological (bacteria) processes. Methyl mercury builds up in the tissues of fish and shellfish. In areas of mercury contamination, larger and older fish tend to have higher levels of mercury. Mercury emitted to the environment will remain for years.
Environmental guidelines
Australian Water Quality Guidelines for Fresh and Marine Waters: (ANZECC, 1992):
Maximum of 0.0001 mg/L (i.e. 0.0000001 g/L)
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