Mercury on Earth: The Heavy Metal Problem
See more: http://theurbn.com/category/feature/conservation-conversation/
Power plants release many harmful chemicals into the air, which ultimately end up in the surrounding environment, creating problems and resulting in negative effects for nearby ecosystems. Source: flickr.com/photos/mandj98/2468396121/.
Whether cooking, showering, reading, or at work, anyone reading this article has likely turned on a light, television, or computer at some point today. But have you ever thought about where that magical luminescence we call light comes from? What exactly does turning on a light entail? Well, the answer to the first question is relatively simple and straightforward – power plants – but what does this mean for humans, and, just as importantly, aquatic life?
The cycling of mercury in an aquatic habitat. Source: pnas.org/content/104/42/16394/F1.expansion.html.
It certainly wouldn’t be a surprise if I told you that power plants pollute the environment, but what is it that is so detrimental to the surrounding habitats – specifically aquatic ecosystems? Well, the bulk of pollution from these industrial power houses can be summed up into two simple words; heavy metals. Heavy metals are chemical elements (which can be found directly on the periodic table) which exhibit metallic properties. These include such elements as iron (Fe), zinc (Zn), copper (Cu), nickel (Ni), cadmium (Cd), and one of the most harmful, mercury (Hg), all of which are emitted from most power plants (Klein & Russell, 1973). What happens is that these heavy metals are released in the plant’s emissions (“smoke”) and are able to settle out around the power plant, often quite a distance from the plant itself. As such, surrounding environments become burdened with accumulations of these potentially toxic elements which can result in negative consequences for proximate (and slightly distant) ecosystems.
One of the most threatening of these elements, as previously mentioned, is mercury. Mercury, also known as quicksilver, is the only metal know today that comes in liquid form under STP conditions; the substance found in thermometers, barometers and the like. Mercury (along with other heavy metals) accumulates in the water and sediment of lakes and surrounding water bodies (as well as terrestrial ecosystems, but I will focus on aquatic ones) and is absorbed by benthic organisms and plankton, a great meal for various fish (Jackson, 2011). When ingested by fish, the mercury from these smaller organisms gets transferred and can result in altered behaviour in the fish, potentially making them more vulnerable to predators (Webber & Haines, 2002). Moreover, when humans eat these fish, the mercury again gets passed on. The subsequent result of high levels of mercury in humans is brain damage, severely impairing speech (Pierce et al., 1972). Disturbingly, these effects are most pronounced in children. As expecting mothers ingest the mercury-contaminated fish, the mercury gets absorbed by the developing fetus, resulting in the aforementioned health problems in newborn children. In a recent interview with NPR, Lynn Goldman of George Washington University stated that hundreds of thousands of babies are born each year with unsafe mercury levels.
Through ingesting plankton and various benthic invertebrates such as clams, fish can ultimately succomb to mercury poisoning, altering their behaviour and causing harful effects in humans. Source: eggplantemily.wordpress.com/2010/10/30/theres-something-in-the-water/.).
Ultimately, it is not in our best interest to avoid eating fish all together and it definitely isn’t in our interest to continue to poison our children with mercury, so what can we do? Fortunately, steps are already being taken in the right direction. By this Friday, the EPA will have implemented harsher standards for power plants, requiring many of them to cut mercury emissions by more than 90% over the next 3 years. While many companies are trying to avoid this by insisting power costs will rise, jobs will be lost, and that this is not a feasible goal over the next 3 years, others suggest that jobs will be created and that it can be done well within the allotted time, many of these companies already having implemented the protocols to meet the new standards. This will drastically reduce the amount of mercury that is accumulated and transported through major food webs, ultimately ending up in humans, inevitably reducing the severity and prevalence of the negative health effects we are seeing today.
So the next time you leave the house, remember to turn off your lights, television, or computer – you aren’t only contributing to the sustainability of the environment, but you will be contributing to the future health of our species.
References
Jackson, T.A. 2001. Accumulation of mercury by plankton and benthic invertebrates in riverine lakes in northern Manitoba (Canada): Importance of regionally and seasonally varying environmental factors. Canadian Journal of Fisheries and Aquatic Sciences 45: 1744-1757.
Klein, D.H. and Russell, P. 1973. Heavy metals: Fallout around a power plant. Environmental Science and Technology 7: 357-358.
Pierce, P.E.,Thompson, J.F., Likosky, W.H., Nickey, L.N., Barthel, W.F. and Hinman, A.R. 1972. Alkyl mercury poisoning in humans. Journal of the American Medical Association 220: 1439-1442.
Shogren, P. 2011. EPA to unveil stricter rules for power plants. NPR. Retrieved 13 Dec 2011 from www.nrp.org.
Webber, H.M. and Haines, T.A. 2002. Mercury effects on predator avoidance behaviour of a forage fish, golden shiner (Notemigonus crysoleucas). Environmental Toxicology and Chemistry 22: 1556-1561.
Oh, and need I say: great article Jeff!
...and thank you!
So forgive me for sounding naive; when women are pregnant and they are told not to eat raw fish like salmon etc. because of the high mercury levels in it does that mean these mercury levels are totally induced by man?
Not necessarily Stephanie. Although women are told not to do these things, some still do. As I mentioned in the article, Lynn Goldman says hundreds of thousand of Americans are affected by mercury each year. I suspect that if precautions were not taken, this number would be significantly higher. With that being said, women still tend to ignore the warnings if they enjoy the fish enough and there are other potential ways in which they may be exposed to the mercury other than in the fish (eg., garden vegetables, personal livestock, etc.). I think that these new guidelines enforced by the EPA will be of great benefit!
okay thanks, so is the presence of mercury in fish totally due to pollution from these power plants aforementioned? i.e. would fish have a high mercury content if it weren't for us?
No they would not. Although all natural elements are present in the environment in small concentrations, they are not abundant enough to cause serious human health problems and behavioural changes in fish. This is true for mercury. Additionally, a study conducted by Thomas Grieb and colleagues back in 1990 found that mercury accumulation in fish can vary with varying environmental factors such as pH, acid neutralizing capacity (ANC), calcium, conductivity, aluminum, total phosphorus, dissolved organic carbon, color, sulfate, lake area, lake depth, watershed area, Secchi depth and elevation. Many things can increase or decrease mercury accumulation in fish and ultimately in humans, but the truth is that without human activity, these heavy metals would not be present in sufficient amounts to cause the problems we are seeing today.
Also to clarify, Stephanie, power plants are not the only source of mercury. With increases in eutrophication (terrestrial runoff) from clearing land and methylation from crops, humans are contributing to increased mercury levels in many different ways. With that being said, power plants are a huge source and are without a doubt a problem that has to be dealt with.
thanks for the further explanation. feel well-informed!
My pleasure!
A correction Stephanie. In some areas known as mercury hotspots, levels of mercury above the consumption standards have been reported in individual fish despite a lack of anthropogenic activity in these areas. These levels are not consistent like they are in lakes near heavily industrialized areas, however, they do occur. With that said, this does not assume that these levels are high everywhere. Areas in northeastern North America are subject to these hotspots, however, they are relatively few and far between for the rest of the continent. I am not sure of the prevalence of these areas globally, but if you'd like I could research this a bit further.
awesome, thanks Jeff. It's just interesting to know if these high levels can even be a natural phenomenon? Is there any particular reason why they'd be so high in areas which are not heavily industrialized?
There absolutely is! In these hotspots, mercury seeps into the environment from below the earth's crust. It accumulates in these areas most often from cracks in the earth releasing chemicals from below the surface. These are the only areas to see high concentrations of "natural" mercury. With that being said, one of the largest and most problematic mercury hotspots in the world is right here in Atlantic Canada. Kejimkujik National Park in southern Nova Scotia is known to have some of the world's highest concentrations of mercury despite very little urbanization and human activity. Some colleagues of mine here at UNB have been studying the transport of mercury through food webs in this area and have informed me that only some individual fish have accumulated these high concentrations (as compared to whole populations having high mercury concentrations in lakes near heavily industrialized areas, particularly with coal-burning power plants). I hope this helps!
it does! Thanks!
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