By Gary Thomas
Harvard environmental scientists have found that the accumulation of a toxic element, mercury in the Arctic has resulted due to circumpolar river flow as well as atmospheric forces carrying the element north into the Arctic Ocean. The atmospheric source was discovered previously, however it has been discovered only now that twice as much mercury comes from the rivers.
This shows that toxin concentrations may increase further as climatic changes modify the hydrological cycle of the region and mercury is released from warming Arctic soils. The study was conducted jointly by Harvard School of Public Health (HSPH) and Harvard School of Engineering and Applied Sciences (SEAS) and results published in the Nature Geoscience Journal on May 20.
Mercury is considered as a bioaccumulative, persistent toxin as it does not break down, travels the complete food chain from fish to plankton, to marine mammals and human beings and becomes more hazardous and concentrated. The study was led by Sunderland with Daniel Jacob, Vasco McCoy Family Professor of Atmospheric Chemistry and Environmental Engineering at SEAS, where Sunderland is also an associate.
Study conducted previously showed that mercury levels in the lower atmosphere of the Arctic fluctuated over a year with a sharp increase from spring to summer. Sunderland, Jacob and their team used an advanced model of Arctic Ocean conditions to study if variables such as interaction with microbes, melting ice or sunlight can cause the difference.
The Harvard team adapted the GEOS-Chem model which is capable of quantifying the complicated nuances of the ocean-ice-atmosphere environment. This model clarified that incorporating a circumpolar river source to the Arctic ocean alone explained the rise in summertime concentrations.
According to Jacob, climatic changes play a major role in mercury entering the rivers. Also, it is possible that mercury, gold and silver mines in Siberia are polluting the nearby water. The flowing of the contaminated water into the Arctic ocean causes the ocean surface layer to get supersaturated resulting in an evasion of mercury from ocean to the lower atmosphere.
The National Science Foundation's Arctic System Science Program supported this work