Biogeochemistry

Toxic sediments

Glob. Biogeochem. Cycles https://doi.org/jzh (2012)

Credit: © ISTOCKPHOTO / THINKSTOCK

The Yangtze River, which traverses some of the most populous and developed regions in China, delivers large quantities of sediments and pollutants to the East China Sea. An analysis of estuarine sediments suggests that significant quantities of polycyclic aromatic hydrocarbons — a widespread carcinogenic organic pollutant — are deposited at the mouth of the river.

Tian Lin of Fudan University, Shanghai, and colleagues measured the polycyclic aromatic hydrocarbon content of surface sediments in the mud belt that stretches from the mouth of the Yangtze River to the inner shelf of the East China Sea. According to their analysis, 152 tons of these toxic hydrocarbons are deposited on the estuarine inner shelf each year. This is equivalent to around 38% of the total annual input of these hydrocarbons into the East China Sea, and makes the inner shelf of the Yangtze estuary one of the largest terrestrial repositories of polycyclic aromatic hydrocarbons globally. The predominance of hydrocarbon compounds with low molecular weight suggests that a significant fraction is sourced from oil.

Re-suspension of the polycyclic aromatic hydrocarbons in the water column, for example by strong currents induced by monsoon winds, could constitute a significant secondary source of toxins to the East China Sea.

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Armstrong, A. Toxic sediments. Nature Geosci 6, 18 (2013). https://doi.org/10.1038/ngeo1701

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