During a recent research meeting with the American Geophysical Union on Dec 16 2015, an announcement was made regarding the increasing amount of coastal fog coupled with increased amount of monomethylmercury being found in the fog which has caused a lot of concern among the scientists. A lot of fog is acidic and it converts some of the gaseous mercury that escapes during ocean upwelling, commonly seen in Northern California’s coastal waters, into a more solid form of mercury, called monomethylmercury. The fog rolling in then brings it onshore. The amount of monomethylmercury is being seen at levels 19 times higher in fog than in rain. Research has found that concentrations of mercury in fog are 20 times higher than they are in rain, and they estimate plants and animals in foggy areas have 10 times more mercury than those in other areas.
How does the mercury enter the fog?
Mercury is naturally found in the environment. An increase in human activity especially industrialization has largely contributed to the increase in mercury levels in the environment. Smokestack emissions, power plants and mining operations have released diverse chemicals into the environment including mercury. The effects of mercury include damages to the nervous, digestive and immune systems as well as being toxic to humans and have been known to impair reproductive function according to the World Health Organization. The Food and Drug Administration says that mercury exposure is a particularly of concern to pregnant women as they are most susceptible to adverse mercury effects and are thus asked to refrain from consuming some types of fish due to mercury levels. A huge chunk of the emitted mercury ends up in the ocean where it causes damage on marine ecosystems. Although California industry emits relatively little mercury these days, its coastal communities may be immensely impacted based purely on geography.
Oceanographer Kenneth Coales is quoted as saying that while the mercury being seen might not be a human public health issue currently, in the long run it will be an ecosystem health issue that has its root from human activities. Coales further reports that scientists have also found mercury in the whiskers of mountain lions, and it’s even been found in wolf spiders beyond FDA limits on mercury consumption of 3 parts per million, if you were to actually eat one.
Each summer, fog covers the coast of central California hydrating the region’s majestic redwood trees and chilling beachgoers. A past research from the University of California, Santa Cruz did show that the moist air also did carry methyl mercury, which is far more toxic form of the heavy metal mercury.
It’s noteworthy to point out that it’s not dangerous to breathe the fog as the mercury levels are at very low. This was asserted by Peter Weiss-Penzias, a chemist and the lead author of the study, published in the latest issue of the journal Geophysical Research Letters.
In the long run, the researchers’ analysis suggested that during the rainless summer months, adequate levels of methylmercury could be deposited along the coastline with almost all of it from fog. In a telephone interview, Dr. Weiss-Penzias pointed out that methylmercury was basically “raining down” in a place where redwood forests, for example, were seen to collect a lot of fog precipitation. Micro-organisms which include bacteria in soil and sediments act on mercury and change it into methylmercury, which is both organic and soluble in water giving rise to a potent combination. Dr. Weiss-Penzias said that methylmercury could be found in water and consumed by organisms, stored in fatty tissues and could potentially cross the blood-brain barrier which has been found to prevent most other toxins from crossing into the brain.
How Mercury find its way into Organisms
After animals higher up in the food chain consume smaller organisms particularly from the ocean, they consume methylmercury, too. Moving up the food chain, methylmercury concentrations increase, in a process known as bioaccumulation. How mercury from fog might move through a terrestrial ecosystem still remains a mystery. However, it’s evident that mercury is being accumulated into the food web. Take an example of trees collecting the fog water that is dripping down to the forest floor and putting it into the soil, where it can be taken up by organisms and plan, going up the food chain would result in higher levels of methyl mercury.
The study team sought to find out methylmercury and total mercury levels in eight fog water samples that were collected around Monterey Bay, Calif., and in five samples of rainwater. (The researchers discarded 17 fog water samples deemed unusable due to low volumes.) In fog, methylmercury concentrations ranged between 1.5 parts per trillion to 10 parts per trillion, with an average of 3.4 parts per trillion — about five times higher than the highest levels previously recorded in rainwater.
When compared, the upper limit level in fish considered safe for consumption is 0.3 parts per million. What the researchers found in fog was way higher than that.
Dr. Weiss-Penzias puts it that, “the big scientific question” was how the methylmercury find its way into the fog. An initial investigation of the data suggested that the ocean was one source, with methylmercury from sediments brought to the surface by upwelling, which was being driven by strong winds. With the winds scaling down and the air cooling, this enhances the concentration of methylmercury into fog and what remains is the understanding of how, and how much, and when.
Studies on the role of fog in coastal ecosystems could become vital as climate change unfolds.