I’ve been puzzling for a while about why the areas with the most power plants aren’t the areas with the worst levels of mercury pollution. Why aren’t the areas downwind from the power plants heavily polluted? I keep running across curious statements like “There was no obvious relationship between large-mouth bass or yellow perch fish tissue mercury concentrations and their locations relative to prevailing wind patterns and the incinerators” (source). In that regard I came across a critically important paper. The paper starts with what to me is a most surprising statement.
But before I get to that, a short digression. There are a couple kinds of mercury emitted by power plants, by forest fires, and by your automobile, for that matter. Well, actually three kinds, but there’s very little particulate mercury coming from any of those sources. The two kinds are “divalent” and “elemental”.
Elemental mercury (written as “Hg0”) means what you’d think, atoms of mercury vapor. Because it doesn’t bind with much and it is insoluble, it has a fairly long atmospheric half-life, on the order of a year or so. Elemental mercury is what forms the background mercury levels that are present everywhere in the atmosphere.
Figure 1. Areas in the US where fish have high levels of mercury. White areas have not been tested. EPA threshold as safe to eat is 0.30 ppm (two lightest shades of red). From the EPA’s Mercury Maps (PDF)
The other kind of mercury, divalent mercury (written as HgII), exists in the form of compounds like mercuric chloride (HgCL2). Because these compounds are both water-soluble and chemically reactive, they come out of the atmosphere quickly through deposition by precipitation. In addition, they come out slowly as elemental mercury is slowly changed into divalent mercury in the atmosphere. And as a result of all of these kinds of atmospheric mercury, plus mercury naturally in the soils, we end up with mercury in the fish.
To summarize: elemental mercury is added to the background mercury and doesn’t settle out near the power plant. Divalent mercury is reactive and water-soluble, so it rains and precipitates out near the power plant. And the problem is that analysis of the emissions from the smokestack of coal-fired power plants show on the order of 25% more divalent mercury than elemental mercury. Which sounds like bad news for those living downwind from our power plants.
With that as prologue, here’s the opening statement that I found so surprising, from a paper called “Modeling Mercury in Power Plant Plumes”.
First, the Mercury Deposition Network (MDN) data (1) along a west-to-east transect from Minnesota to Pennsylvania show no significant spatial gradient in annual mercury (Hg) concentrations in atmospheric precipitation although the Ohio Valley includes several large Hg emission sources located, under prevailing wind conditions, upwind of Pennsylvania.
Say what? No hot spots for mercury downwind of several large power plant mercury emission sources? How come I haven’t heard of that?
So I wandered off to the Mercury Deposition Network, where I found a couple more surprising maps.
Figure 2. Total Mercury concentration in the atmosphere in 2010. Units are nanograms per litre. The red “hot spot” in the center of the US reflects the natural mercury coming from deserts and croplands, as I discussed in “The EPA’s Mercurial Madness” SOURCE
As an aside, the EPA and other scientists claim that much of the mercury in the atmosphere is “recycled” anthropogenic mercury. They say the natural emissions are in large part just man-made emissions being re-emitted. I certainly would hope that Figure 2 would put a stop to those claims. The main and overwhelming source of atmospheric mercury in the US is the natural mercury in the soils.
OK, another surprise for me. We’ve seen where the sources are and what’s in the air. Now, let’s see what gets deposited in the rain and snow. Figure 3 shows the wet deposition map for the US in 2010.
Figure 3. Mercury wet deposition rates for the US. Units are micrograms per square metre of surface. SOURCE
Note that strangely, this is kind of a weather map. Why is it a weather map? Well, for example I live on the coast not far north of San Franciso Bay. I was amazed to see that I live in an area of relatively high mercury deposition. Why?
The answer is, because when the moist air sweeps in off the Pacific and hits the coastal mountains, it rains. And when it rains, I get showered with natural mercury from the ocean. Further inland on the east side of California, you can see the western slopes of the Sierra Nevada mountains painted in red. They get the moisture that doesn’t fall on the coastal ranges. And since they are much higher, they pretty much wring the moisture (and the mercury) out of the air, leaving Nevada with little mercury deposition.
The main flow of air in the US is from west to east. As a result, the hot spot over the southwestern US precipitates out in the central US. It is aided by moist air flowing in from the Gulf of Mexico during some months. This can be seen all along the Gulf Coast. Florida, like where I live, is another victim of oceanic mercury poisoning.
Finally, to return to the surprising statement I started with, in Figure 3 the blue arrow shows the prevailing winds blowing over the power plants in the Ohio River Valley towards Pennsylvania. If it is the case that the majority of the mercury emissions are divalent mercury, then why is there no trace of them raining out along the way as we’d expect?
The authors look at several different possibilities. Their final conclusion? (emphasis mine)
A sensitivity study of the impact of the Hg dry deposition velocity shows that a difference in dry deposition alone cannot explain the disparity. Similarly, a sensitivity study of the impact of cloud chemistry on results shows that the effect of clouds on Hg chemistry has only minimal impact. Possible explanations include HgII reduction to Hg0 in the plume, rapid reduction of HgII to Hg0 on ground surfaces, and/or an overestimation of the HgII fraction in the power plant emissions.
We propose that a chemical reaction not included in current models of atmospheric mercury reduces HgII to Hg0 in coal-fired power plant plumes.
This has large implications for the regulation of power plants. All the big power plants in the Ohio River Valley aren’t increasing the mercury deposition towards Pennsylvania. The mercury is being converted into elemental mercury along the way somewhere, so it’s added to the background mercury rather than raining out near the power plants.
In fact, where I live, on the pure clean Pacific coast with lots of sea breeze, I get more mercury pollution than they get around Pennsylvania despite all the coal-burning power stations just upwind from them.
And that, dear friends, was a very big surprise … when’s the EPA gonna step in to save me?
Does this mean mercury is not a poison? By no means, mercury is a bad thing, and it’s everywhere … it just shows the story has lots of tricks and turns.
Always more to learn,
w.
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Willis said, “I certainly would hope that Figure 2 would put a stop to those claims.”
Would that be the same as the second figure one?
[Indeed it would … fixed, thanks. -w.]
Your second figure is labeled figure 1.
This is an excellent adjunct to your earlier post. Sampling density could be an issue when trying to describe the footprint of mercury fallout from coal-burning plants. If they have a tall stack then dispersion widens but I suspect the footprint is still very small relative to the regional sampling evident from your smooth-looking images (Figure 1 especially). What happens, for example, when you plot a small (200 km by 200 km) region centered on a coal plant? Is there no clear pattern or are there only one or two sample points for mercury concentration?
You will notice a very deep red patch just South of San Francisco Bay on that first map. The fish here are so contaminated with mercury in our fresh water lakes in Santa Clara County that they can not be eaten. The reason isn’t “pollution”, the reason is natural mercury in the soil. During the gold mining days there were many mercury mines in Santa Clara County. The place is just full of it. Fish in Stevens Creek Reservoir are so full of it that there are signs everywhere telling you not to eat the fish.
Mercury does occur naturally and some of these environmental commissars need to be aware of that fact.
“or an overestimation of the HgII fraction in the power plant emissions”??
With all that budget they can not measure accurately and do not know?
George says:
April 1, 2012 at 5:19 pm
Mercury does occur naturally and some of these environmental commissars need to be aware of that fact.
Fact is they don’t care. It’s not about pollution, it’s about political objectives.
Always more to learn,
w.
=================
Not enough people shouting it from their rooftops.
SO … what is this interstate basis for the recent EPA rulings again?
When’s the ocean going to be subjected to EPA Administrative Law edicts; I want to see fines levied and cease and desist orders issued to Gaia …
.
I’ve gotten the impression much of the impetus behind the assault on mercury from coal power plants was the mistaken assumption that since autism levels are high near power plants, mercury must be causing it. This is based on the false assumption that mercury causes autism (science has found no statistically significant connection between mercury preservatives in vaccines and autism rates, and this specific false assumption first connected mercury and autism.)
You are likely to see a spike in autism rates near coal fired power plants, but it is caused not by mercury, but by genetics; if the power plant is one of a rural area’s largest employers, and a significant number of engineers and technicians settle in the area, local autism rates go up, just have they have in other areas of high concentrations of engineers like Silicon Valley and Rochester Minnesota. A recent Dutch study contrasted autism rates in Dutch cities known as technology centers versus cities not known for technology and found a similar autism spike in the technology centers. My personal observation is that the highest rates of severe autism are associated with graduates of Midwest land grant colleges. Engineering majors meet Nursing majors in chemistry class, get married, and have a high incidence of severely autistic kids.
It’s called assortive mating.
obviously you are science hating racist …
Our river (Shenandoah in Virginia) has old mercury from Dupont (at least 50 years old). The mercury levels have actually increased a bit which attributed to the cleaner water which allows more plant growth. The plants get uprooted in floods and out comes the mercury.
I think metallic mercury is somewhat demonized, though I don’t have any good data other than anecdotal. Apparently Thomas Edison and his crew working on the light bulb had a little trouble with the mercury vacuum pump they used. Near as I could tell, it entailed taking a bucket/flask/container of mercury up a ladder, pouring it through glass piping and that would entrain bubbles of air to be dumped outside the apparatus.
I suspect they spilled a lot of mercury.
Then there was the time in 2nd grade where I had some mercury in a shallow dish (I think an old makeup container) that I was showing around the class for show & tell. I had a penny in it showing how the mecury wetted it. Not a very stable way to carry mercury, and some spilled on to the floor. That was 1958 or so, I think it’s evaporated by now. (Dad worked for Baily Meter, and they used mercury in manometers, so he’d bring a little home from time to time.)
It’s really a pity that the EPA would freak out these days if they heard some kid was holding a large drop of mercury in his hand, even if he got it mostly back in the container.
One of my favorite mercury stories is only ten years old. My daughter came home from school and said her science homework was to bring in five samples of different metals. I first considered if I should give her copper pipe or wire, when it dawned on me we could make a lasting impression.
In the basement, in a box labeled “heirloom chemicals” that I inherited from Dad, I had added a plastic film can that has a little glass jar that has a little mercury from a broken thermometer. Obviously, this would have to be one of the five, but given the current era, I took out the glass container with the mercury, wrote “Hg” on the top of the film container and had Hannah take the empty film can to school.
I gave her instructions to no open the can, but be sure the teacher saw the “Hg.” Worked great – teacher saw it, commanded “Hannah, give that to me right now!” and quickly figured out she’d just been pwned. Except we didn’t call it that because the word hadn’t been invented.
Eventually, I gave the teacher one of my two mercury wetted switch modules from the heirloom chemical box. Each module has about 500g of Hg and electrical contacts in a glass module. I make a point of not dropping that box….
While metallic mercury is so safe that even a child can survive exposure, organic mercury compounds are a very different story. Monomethylmercury is worth avoiding (I think that’s what’s in fish), and dimethylmercury is worth avoiding as though your life depends on it. It soaks through skin and latex gloves offer about 15 seconds of protection. Merely 400 mg will kill you, slowly.
See http://www.nejm.org/doi/full/10.1056/NEJM199806043382305 for the best documented case. It ends with “Before she lapsed into a vegetative state, the patient [Karen Wetterhahn at Dartmouth College] requested that her case be presented to the general medical community, to scientists working with mercury, and to toxicologists, in the hope of improving the recognition, treatment, and prevention of future cases of mercury poisoning.”
Willis:
This is outstanding. You have done a very good job and have scientific reasons with your analysis. Thank you Sir!
Those are merely facts. Facts are of no importance when you are establishing a Socialist state.
Might I suggest some background information about the toxicology of mercury, including it’s organic forms, ethyl- and methylmercury: http://www.nejm.org/doi/full/10.1056/NEJMra022471
After all, the health impacts depend on this.
Source http://www.naturalhub.com/natural_food_guide_seafood.htm
For years, we have probably eaten tuna and swordfish with mercury levels above FDA’s limit without harmful effects. Analysis of museum specimens of tuna caught from 1879 to 1909 reveal that they contain levels of mercury as high as those in fish being caught today. Scientists therefore conclude that mercury levels in tuna, and probably swordfish, have not changed in the past 100 years…Researchers found that some fish, including tuna, can block and reduce the toxicity of mercury in their tissues. This research may explain how we have safely eaten fish containing levels of mercury higher than allowed by FDA
Next thing you know, the greenies and the EPA will be banning banana’s because of radioactive potassium. Always a new boogie man under the bed to scare us with. Screw ’em.
Where you have rainfall, Hg2+ will dissolve and end up underground (and eventually trapped as HgS), in plant material (such as the lignin of tree rings) or carried away. Low rain fall results in very poor mobilization, so deserts will have higher surface levels of Hg0, CH3HgCl and HgCl2.
You have to examine the influx rate, airborne delivery, and efflux rates, water transport below the surface, into the sea or into plants.
Coal burning increases the airborne influx, however, if there is a lot of water, the area is scrubbed clean, and the mercury is carried away, until it gets to a lake or estuary.
here is a nice paper which covers the fluxes in the US:-
http://cdn.intechopen.com/pdfs/32914/InTech-Hydrology_and_methylmercury_availability_in_coastal_plain_streams.pdf
Gold miners would use mercury to make gold amalgams, sucking the gold out of rock. They would then heat the amalgam, vaporizing the mercury and leaving the gold behind. This introduced huge amounts of mercury into the environment.
You can examine tree ring for chronology and mercury, using X-rays spectroscopy. This is often used to track changes in local changes in mobile mercury levels.
The odd thing about this is that deposition of mercury, and other heavy metals, precedes exposure, as the metals are chelated in soft lignin, so the mercury diffuses into the rings that are in the process of hardening.
There is a large body of literature on using tree rings and X-Ray spectroscopy to monitor heavy metal toxicity. I have always suspected that the ‘divergence’ in X-Ray derived ring density temperature is due to the various clean air acts and the removal of lead from gasoline.
With regard to fish, methyl mercury is perhaps a bigger issue. MeHg is produced by bacteria, and is very soluble in water. Dimethyl mercury is produced in high pH environments and is more volatile. Mercury can be sequestered in sediments in aquatic environments and mobilized depending on various factors including dissolved oxygen, pH, and temperature. The biological implications have more to do with biology than the rather simplistic chemistry being discussed.
EW-3 says:
April 1, 2012 at 5:26 pm
George says:
April 1, 2012 at 5:19 pm
Mercury does occur naturally and some of these environmental commissars need to be aware of that fact.
===============
Fact is they don’t care. It’s not about pollution, it’s about political objectives.
Someone in Congress ought to question the EPA on this. Let everyone be aware that the EPA is purely looking for grounds to shut down baseload power generation, to ensure that the power companies are bankrupted as predicted. This is an end-run around Congress after all.
Steve from Rockwood’s comment about sample density is well taken. Willis showed where the coal stations are, but the sample stations will have uneven weight on areas in the contour maps.
Here are two maps that show 2009 sample stations:
Total Mercury:
http://nadp.sws.uiuc.edu/maplib/archive/mdn/2009/2009MDNconc.gif
Lots of green east of the Mississippi River from dozens of stations. Only S. Florida is moderately high surrounded by ocean.
But that hot spot in the SW USA, is controlled by only 5 stations: 1 on all of AZ, 1 in SLC, 1 in Durango, CO, 2 in N. Nevada (gee, I wonder what is going on there!) There are only 2 stations along 1-10 from California to East Texas.
No data for Oregon. 3 in all of California.
Wet Mercury:
http://nadp.sws.uiuc.edu/maplib/archive/mdn/2009/2009MDNdep.gif
This one cries out for examination. If those are indeed the control points, just how does one justify the hot spots in NW Nevada and SW Colorado?? Yes, Durango is at 11, but the uncontrolled, extrapolated(!) hot spot high 100 miles NE of Durango is almost double that! Likewise southern AR is extrapolated at least 50% higher than any nearby control points. This contouring algorithm stinks!
Show the control before showing the interpretation!
Just think about all the black soot from diesel truck emissions caused by moving all the garbage from New York City, Long Island, and New Jersey to Pennsylvania and West Virginia.
What caused this insane bucket brigade of 18 wheelers? Why the theoretical mercury emissions from garbage to energy incinerators which were effectively banned.
It is estimated that between 5 and 10 percent of the diesel fuel use in the CT, NY, NJ metropolitan area is consumed moving trash which could otherwise be incinerated, thereby MAKING electricity rather than buring diesel.
And, the theoretical deaths due to emission from never to be built incinerators pales in comparison to the actual deaths caused by long haul garbage truck accidents.
Errata: I mistakenly said that Willis showed the coal stations, when in fact, the dots were the sample stations. However, Figure 3 shows far higher spatial frequency than can be justified by the control points. Just look at NE Calif, n of Yosemite. Somehow, Figure 3 is some modeled interaction of control points and terrain. Both Fig 1 and Fig 3 do not show the values for the control points, so who knows what the contouring algorithm and model are doing to the real data.
It is way more complex that that too. When you get into the far north right across the continent we inf water shed hot spots what are mostly related to natural Hg from the rocks. Hg is often used as pathfinder trace element in base and precious metals exploration. That is not to say we need not be careful with how we dispose and handle it. We should be careful and prudent not paranoid. We also need to learn that just because we can measure things in concentrations of three or four decimal points does not automatically equal bad.
“And that, dear friends, was a very big surprise … when’s the EPA gonna step in to save me?”
Be careful what you wish for…..