New research presented at the American Geophysical Union conference in San Francisco has determined that mercury from the ocean is most likely seeping into cloudbanks that roll in from the coast. Though mercury had previously been detected in California fog, its source was a mystery.
Though the concentration of mercury isn’t high enough to harm anyone walking through it, its presence suggests that the element is beginning to accumulate in the coast’s water cycle. Mercury also accumulates in plants and animals and could pose a threat to the ecosystem over time.
Peter Weiss-Penzias, an atmospheric chemist at the University of California, Santa Cruz, measured seawater at depths of up to 3,300 feet, finding the highest concentrations of mercury at around 660 feet, close to the surface. Further study of the air directly above the ocean is needed to conclusively determine that the mercury is seeping into the fog. "It is a bit of a mystery where [the mercury's] coming from,” says Weiss-Penzias. “But I think what we're seeing is a large-scale phenomenon that has to do with upwelling of deep ocean water along the coast."