Mercury Gas in Neptune Grass

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Science  15 Mar 2013:
Vol. 339, Issue 6125, pp. 1255
DOI: 10.1126/science.339.6125.1255-a

Not far off the coast of the Mediterranean Sea, meadows of the flowering seagrass Posidonia oceanica, or Neptune grass, cover the seafloor. The vast network of ancient mat deposits in the sediments in and below the root layer preserve a rich record of the water chemistry over thousands of years. Serrano et al. show that a Neptune grass mat deposit in a bay off the northeast coast of the Iberian Peninsula—a region with a complex legacy of mercury (Hg) mining activities—preserves a ∼2500-year record of anthropogenic Hg pollution. In coastal zones, Hg present in run-off from local rivers is added to the water column in addition to the more common dissolved gaseous Hg that was originated in remote regions and was deposited from the atmosphere. Variable mat Hg concentrations, which reflect uptake and bioaccumulation into plant tissues during growth, correspond to known mining and metalworking activities in European history, including Roman mining, metallurgy in the Late Middle Ages, and modern industrial practices. Moreover, Hg concentrations decreased or leveled off after periods when drastic economic changes halted mining activities, such as the fall of the Roman Empire and the spread of the plague across Europe in the 14th century.

Global Biogeochem. Cycles 27, 10.1029/2012GB004296 (2013).

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