River Thames
Mercury levels

Mercury (Hg) is an environmentally persistent heavy metal which can be toxic to marine life and humans. Sixty sediment cores of 1 metre (3.3 ft) depth, spanning the entire tidal River Thames between Brentford and the Isle of Grain, have been analysed for total Hg. The sediment records show a clear rise and fall of Hg pollution through history. Mercury concentrations in the River Thames decrease downstream from London to the outer Estuary, with the total Hg levels ranging from 0.01 to 12.07 mg/kg, giving a mean of 2.10 mg/kg which is higher than many other UK and European river estuaries.

The most sedimentary-hosted Hg pollution in the Thames estuary occurs in the central London area between Vauxhall Bridge and Woolwich. The majority of sediment cores show a clear decrease in Hg concentrations close to the surface, which is attributed to an overall reduction in polluting activities as well as improved effectiveness of recent environmental legalisation and river management (e.g. Oslo-Paris convention).
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