A new study by the University of Basel has revealed that the majority of mercury in the oceans comes from gas exchange, rather than contaminated rain as previously thought. Biogeochemist Martin Jiskra discovered this by examining the sources of mercury using isotopes. The study, published in the journal Nature, found that only 42% of mercury in the Mediterranean and North Atlantic oceans comes from rain, with the remaining 58% coming from gas exchange. The researchers estimate that the input of mercury from rain and gas exchange is roughly equal globally.
The discrepancy between the new study and previous assumptions is due to the difficulty of quantifying the input of mercury from rain, as there are no collection stations over the ocean. Human activities, such as mining and coal-fired power plants, have tripled the amount of mercury in the upper layers of the oceans since the beginning of the Industrial Revolution. A reduction in emissions could lead to a faster decline in mercury in the atmosphere and oceans than previously thought.
Jiskra explained that a low input of mercury from rain means that it must be deposited elsewhere, likely in plants, which would then deposit it on land. This would mean that anthropogenic mercury emissions would be bound in soil and no longer part of the global cycle. The study highlights the importance of gas exchange in the transport of mercury and the need for further research in this area.
In conclusion, the new study challenges previous assumptions about the sources of mercury in the oceans and emphasizes the importance of gas exchange. It also suggests that a reduction in emissions could lead to a faster decline in mercury in the atmosphere and oceans than previously thought.
