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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Thanks for the push, Ric, I looked up what HTML wordpress allows, I think I’ve got it now:
Hg0 and Hg++ and CO2.
I seem to vaguely recall that these may cause trouble when they appear in the middle of a paragraph because they screw up line spacing Hg0 and CO2. Let me see what that does to the spacing of the lines. … Nope, seems like that’s no problem, I used the HTML instructions “sup” and “sub” for those.
Always more to learn, much appreciated.
w.
DocMartyn says:
April 2, 2012 at 5:27 pm
I do understand that, Doc. I’m just not sure what that means to you, given that we are not in a steady state. More mercury is going into the oceans than is coming out.
Overall, natural sources put thousands of tonnes of mercury into the air every year. Some comes from the deserts in the Southwest US. Some comes from volcanoes. Some comes from forests, which pull it up from the soil and add it to the air. Deserts add about 500 tonnes of mercury to the atmosphere every year. This desert and volcano mercury and the like is not recycled mercury. It is new mercury, which previously was in the ground, which is added to the air. Much of it will go into the ocean. Some of it will never (in human terms) come out.
If (as you claim) transport into the oceans equals transport out, every year we should see a huge increase in the atmospheric load. We don’t see that.
So how is that “steady state”?
Thanks,
w.
Deanster says:
April 2, 2012 at 7:39 pm
Nope. I was puzzled, as were the authors of the study I cited, as to why mercury pollution is not found downwind of power plants. For example, the very large number of power plants and industrial coal burning in the Ohio River Valley don’t have a corresponding downwind increase in mercury deposition. Turns out the mercury is added to the background circulating airborne mercury rather than being deposited out in the downwind area. Good news for Pittsburg. Bad news for me on the Pacific Coast, because that mercury comes down on me.
I hope that’s clearer.
w.
Mercury concentration of US coals is 50-130 ppb (billion), which translates into electric generating unit (EGU) stack gas concentrations of 5-13 ppb, assuming that no mercury is captured by EGU’s pollution control equipment (approx. 10 kg of stack gas is generated by burning 1 kg of coal). Mercury is vaporized in the furnace of coal-fired boilers and then recondenses as a fume as flue gas is cooled as heat is transfered from the flue gas to steam in the boiler tubes. All coal-fired EGUs are equipped with high efficiency particulate removal equipment (either electrostatic precipitators or fabric filters) which preferentially collects larger particles (because it is easier). At a minimum particulate control equpment collect 10% of the mercury. Coal fired EGU stacks (i.e. chimneys) are typically 500+ ft tall and flue gas stack exit velocities are typically a minimum of 3,000 ft/min. Given the extremely low concentrations of mercury, its sub-micron size consist, height of stacks, and high stack exit gas velocity, it shouldn’t come as a suprise that mercury ‘hot spots’ downwind of coal fired power plants are not found.
According to the EPA, US coal-fired power plants are responsible for approximately 4% of mercury deposition in the US. However, this 4% is based on mercury emissions before the $50+ billion retrofits of selective catalytic reduction (SCR) NOx control equpment and SO2 scrubbers that occurred in 2007-2010 as a result of the Clean Air Interstate Rule (CAIR). A collateral benefit of installing SCRs and SO2 scrubbers is that mercury emissions are reduced by approximately 30%, though this figure varies widely depending on the coal that the EGU is burning (the SCR catalyst converts mercury to forms that are more easily captured by the SO2 scrubber). Thus, today coal-fired power plants are probably responsible for 3%, not 4%, of US mercury deposition.
The reason there is uncertainty about the mercury species distribution in coal-fired EGU stack gases is that the relative concentrations of mercury species is affected by a number of factors, not all of which are understood. It is known that the chlorine content of coal and whether or not the EGU is equipped with an SCR affects mercury species distribution, but it appears that the variation in mercury species distribution is not explained by these two variables alone. A significant issue complicating this analysis is the accuracy of stack gas mercury concentration measurement, which is estimated to be 2 ppb +/- 1 ppb as well as the natural variability in coal mercury content.
Generally eastern US coals have higher mercury content that western coals. However, one cannot assume that coal-fired EGUs located in the East burn eastern coals as low sulfur western coal, especially coal from the Powder River Basin (located in northeastern Wyoming and southeastern Montana), is transported great distances. PRB coal has been transported to coal fired EGUs located on the east coast.
@- Willis Eschenbach says: April 2, 2012 at 8:08 pm
“Overall, natural sources put thousands of tonnes of mercury into the air every year. Some comes from the deserts in the Southwest US. Some comes from volcanoes. Some comes from forests, which pull it up from the soil and add it to the air. Deserts add about 500 tonnes of mercury to the atmosphere every year. This desert and volcano mercury and the like is not recycled mercury. It is new mercury, which previously was in the ground, which is added to the air. ”
Correct, the paper you link to that claims 5207Mg comes from ‘natural’ sources and 2320Mg new HG from anthropogenic sources.
But the 5207Mg is a combination of new HG and existing HG in oceans and biomass. The amount of new Hg from primary natural sources as opposed to natural PROCESSES that are sources of emission is probably about half the anthropogenic sources of new Hg.
Historical studies indicated that at least half of the Hg which we are exposed to at present is from anthropogenic sources. Although some of that is caused by re-emission by natural processes.
Of course all of this is highly uncertain, Mercury as the trickster God has a habit of vanishing or accumulating in unpredictable ways. As a result the error bounds for estimates of natural and anthropogenic primary sources of new Hg are around 30%.
This could mean that things are 30% better than research indicates.
Or 30% worse.
izen says:
April 2, 2012 at 11:07 pm
I’m sorry, but this “re-emission” argument strikes me as just another way that people want to load everything bad onto humans. If that “re-emission” analysis were valid, how come it’s not used for say CO2, since the ocean must be “re-emitting” carbon from humans?
For me, the question is this:
If we shut off every human emission, what would be the total amount emitted this year?
That amount, whether it is cycled or recycled, is what remains when we have turned off the human emissions. So it is the natural emissions.
Is some of this “re-emitted” by the ocean? Assuredly, just as some of the anthropogenic carbon is re-emitted by the ocean … but so what? It’s all part of the natural cycle at that point.
Again I invite you to look at FIgure 2. The overwhelming majority of the Hg in the air over the US comes from the wind blowing over the desert. Human activities in the US are responsible for almost none of that. And I’m sorry, but I’m not buying that the mercury in the desert is recycled anthropogenic mercury in any sense.
Indeed they could …
Izen, for me the issue is the slow rain of mercury coming down from the sky onto my house. By and large it comes from the ocean. It has been raining mercury here for thousands and thousand of years, since long before humans were doing anything to mercury …
w.
Willis, Izen, Deanster, et al.:
This discussion seems to have lost its focus.
The subject of the above article (and, therefore, discussion of it) is stated by Willis in the article’s first sentence that says;
“why the areas with the most power plants aren’t the areas with the worst levels of mercury pollution.”
The article and subsequent discussion make clear that the effect of those emissions is swamped by the larger variations in other emissions of mercury that are mostly natural.
Those other emission sources (and sinks) are subject of an interesting scientific discussion, but detailed consideration of them deflects attention from the reason why the article was written at this time; viz.
the intended EPA regulations to constrain mercury emissions from the power plants.
But reducing those emissions (from power plants) to zero would have no effect of any consequence because their effect is swamped by the larger variations in other emissions of mercury that are mostly natural. And that is all that matters in practical reality.
The imposition of the EPA mercury emission constraints on the power stations would be very expensive, would probably close some power stations, and would provide no benefit because the emissions have trivial effect when compared to other emission sources.
As I explained in my post at April 2, 2012 at 1:48 am, history indicates that the focus of the discussion needs to be kept because when such emission constraints are imposed the bureaucracy to impose the constraints will continuously lower the permissible limits regardless of any scientific reasoning.
Richard
From your last post on mercury, I was wondered why a state like Maine, devoid of human life forms, was so high in mercury.
EPA ruling:
Willis, perhaps you could take the ideas from this comment and whip it into a decent thread post. I do not have your ability of getting the point across unfortunately, nor the computer skills. It would be nice to put the recent EPA Final Rule into historical context with the other Presidential Executive Orders, laws, resolutions not to mention the maneuvers of NGOs and the bureaucrats in D.C.
The Intersection of Control Food and Control Energy from Henry Kissinger’s famous 1970 quote.
In the spirit of, “All animals are equal, but some animals are more equal than others,” the EPA is going to have separate emission limits for different types of boilers.
Troutman Sanders LLP was kind enough to explain what that actually means.
From those quotes and the push for Sustainable Development by the USDA, we can make the assumption that bio-mass fired boilers are going to be treated to far less stringent emission standards than coal because they are Sustainable.
This goes along with the House Concurrent Resolution 25 ~ 110th Congress, 2007–2009 A resolution that passed in the House but died in the Senate according to GovTrack.US. The resolution reads:
As usual just because the resolution failed to pass both Houses does not mean the idea died. Nor does it mean the information cannot be twisted into the following Press Release.
So now we have NGOs such as 25X25.org pushing the expanded idea.
@- Richard
“The article and subsequent discussion make clear that the effect of those emissions is swamped by the larger variations in other emissions of mercury that are mostly natural.”
Actually the emissions we are exposed to are mostly of human produced Hg. It may have been released by natural processes re-emitting historical Hg deposits. but as the links I gave indicated, Hg levels are around double pre-industrial levels because new Hg has been added to the ‘natural’ processes of emission by the ~2000Mg/yr from human sources.
You are right that emissions from US coal fied power plants are relatively small BECAUSE the FGD and other polution measures also reduce Hg emissions, but the fact that other sources which have not yet been controlled are greater contributers to the increasing total global load of Hg is hardly an arguement to relax or avoid further possible regulatory reductions where they can be made.
@-“As I explained in my post at April 2, 2012 at 1:48 am, history indicates that the focus of the discussion needs to be kept because when such emission constraints are imposed the bureaucracy to impose the constraints will continuously lower the permissible limits regardless of any scientific reasoning.”
Not quite.
The scientific reasoning is that ANY emissions of harmful material that CAN be prevented by a technological solution is worthwhile. Especially with a very persistant, bio-accumulative heavy metal poison.
So even though the US coal fied power plants are not the major sources of Hg, the fact that Hg emissions from them CAN be reduced means they should be reduced. Regulation may be required to ensure that industry does not avoid a technically possible reduction in harmfull emissions in favour of higher profitability. That idea that a little pollution was acceptable if it increased profits went out with the Victorians.
Curiousgeorge says:
April 1, 2012 at 6:33 pm
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.
____________________________
You forgot the radioactive carbon 14 in the bananas and our salads too. Oh my Gosh, run in circles scream and shout the sky is falling. (quote from Chicken Green)
stpaulchuck says:
April 1, 2012 at 8:19 pm
stpaulchuck says:
April 1, 2012 at 8:19 pm
.. JunkScience.com had a really great one about a Chinese pollution study with grunge numbers an order of magnitude higher than the new EPA danger numbers ..
….Now, is there a case for long term suspension of the mercury? could the stuff be going to Africa? In fact, some dust and pollen apparently cross the Atlantic, so I’m wondering if we’re not just shipping the stack garbage further than might be thought. Anyone got any info on that idea?
_______________________________________
I have a friend living in Alaska who complains bitterly about the smog blown into her area from China.
The dirty side of economic booms: smog knows no borders (About NOAA’s studies of cross-border air pollutants.)
Richard, I agree with your comment.
My previous post that, according to the EPA US coal fired electric generating units (EGUs) are responsible for 4% of mercury deposition is based on an EPA assumed total US mercury deposition rate of 1,000-1,100 MT/year. If the estimates of 5,207 MT/year from ‘natural’ sources and 2,320 MT/year from anthropogenic sources are correct, then US coal fired EGUs are responsible for only 0.6% of US mercury deposition. Adjusting coal fired EGU mercury emission rates for collateral mercury emission reductions associated with installing SCR NOx control and SO2 scrubbers, the contribution of US coal-fired EGUs drops to <0.5% of US mercury deposition.
izen says:
April 2, 2012 at 3:27 am
The estimated lifetime of elemental mercury in the atmosphere is around a year as another poster has noted. That means there is a global dispersion of airbourne mercury and local hotspots are due to deposition of soluble mecuric compounds from oceans/lakes more than from coal fired power plants.
Anthropogenic sources emitt around twice as much mercury (elemental and soluble) as natural surces overall. This is most notable where local industrial sources have generated Hg II compounds with beluga tusks now containting over 10x as much mercury now as they did in pre-industrial times.
It would be very hard to make a case for NOT regulating industrial mercury emissions….
____________________________________________
You are comparing Apples and Oranges. I really hate that type of scare tactics used to manipulate the public. The USA has been regulating mercury emissions for years and we are at about 10% or less compared to the unregulated times.
Mercury Study Report to Congress: Overview published in 1997
Notice how all that information is hidden in the newest version as they now go after the Coal industry.
izen:
Your post at April 3, 2012 at 6:57 am is twaddle.
Either constraining the emissions from power stations will have a discernible effect or will have no discernible effect.
THE EVIDENCE PROVES BEYOND ANY DOUBT THAT THE CONSTRAINTS WILL HAVE NO DISCERNIBLE EFFECT.
And your waffle about other things does not change that.
But one of your pieces of irrelevant twaddle is so wrong that I will bother to refute it.
You assert;
“The scientific reasoning is that ANY emissions of harmful material that CAN be prevented by a technological solution is worthwhile. Especially with a very persistant, bio-accumulative heavy metal poison.”
That is NOT “scientific reasoning”. It is stupid nonsense.
If the effect of applying the “technological solution” is net negative then it should not be applied. And applying the “technological solution” has cost, so its application uses money that could be spent on other things. So, for example, spending money on constraining Hg emissions from the power stations is net negative because the constraints would have no discernible effect but prevents use of the money for demonstrably beneficial things.
Please explain why you think such idiocy is an example of “scientific reasoning”.
Richard
izen says:
April 3, 2012 at 6:57 am
Izen, is it possible that you really believe that?
Any scientist who follows that reasoning has their head a long ways up their ivory tower.
In the real world, an intelligent person makes such a decision using a cost-benefit analysis. They don’t say EEEK, there a nano-gram of mercury, Izen says that it “CAN be prevented by a technological solution” even though the solution will cost millions, so since it CAN be prevented Izen says it’s worthwhile to prevent it …
That’s a schoolkid’s kind of reasoning. Adults realize that one always, always has to balance cost and benefit. There’s always a tradeoff.
Not only is there always a tradeoff, but as the amount of the harmful material in a waste stream decreases, the cost of removing more of it goes up very rapidly. A rule of thumb is that whatever it cost to cut the amount of unwanted material in half, it will cost double that amount to cut it in half again, and double that larger amount to cut it in half a third time.
And as anyone but a scientist in an ivory tower would know, at some point in that process, it’s no longer worth it. At some point, the costs will exceed the benefits.
And when the only justification the EPA can come up for their mercury rule is claiming that the benefit is that the IQ of fetuses whose mothers eat lots of fish will go up by two thousandths of an IQ point, they have seriously jumped the shark. This is from their Toxics Rule RIA:
Right … like they can measure or predict IQ losses to the nearest HUNDRED THOUSANDTH OF AN IQ POINT …
The goofy thing is, the analysis doesn’t even consider the effects of mercury on the population of the US. It doesn’t even consider the effects of mercury on the part of the population that eats locally caught freshwater fish in areas known to contain mercury.
Their population of interest, the ones that they are analyzing, are pregnant women who eat locally caught freshwater fish in areas known to contain mercury. That’s the population that they are trying to “protect”, Izen … wouldn’t it be cheaper to educate those women that eating fish from lakes that have contained mercury for the last million years might be a bad idea?
Because spending billions so that their children will be smarter by 2/1000 of an IQ point … well, anyone proposing that kind of madness has inhaled too much mercury in my opinion, their IQ is seriously dropping.
Izen, you seem to think I’m arguing against the regulation of mercury. I’m not. I’m against ludicrous, hugely expensive, and most important, meaningless reductions in mercury based on bogus science and inchoate fears.
w.
izen says:
April 3, 2012 at 6:57 am
Yes, and CO2 levels are heading towards double pre-industrial levels, but nobody claims that humans are exposed mostly to human generated CO2. Nobody claims that there are “re-emissions” of CO2.
SOURCE
Your assumption seems to be that mercury, once it is emitted by humans, is never removed from the atmosphere. But it is removed, and on a fairly short timescale.
As a result, the reason that mercury levels are high is that we are emitting lots of mercury NOW, about 30% of the total emissions. That’s why we have excess mercury in the atmosphere, not emissions from the gold mining days.
Are levels higher now than they were historically? Certainly. Are human emissions higher than they were historically? Well, no, they were higher fifteen years ago. Are we “re-emitting” mercury from back then? No, the levels have dropped, not stayed constant. Here’s the ice core data.
As you can see from the volcanic eruptions, the is NO long-term effect from the addition of even massive amounts of mercury to the atmospheric load. We’re not “re-emitting” mercury from Krakatoa, that was gone a few years after the eruption. Similarly, we’re not re-emitting mercury from WWII, that was sequestered long ago.
The whole concept of “re-emission” is just a way for you to try to shovel more blame onto humans. It makes no scientific sense (although I’m sure you could find “scientists” who make the same claim.
w.
@- Willis Eschenbach says: April 3, 2012 at 2:44 am
“I’m sorry, but this “re-emission” argument strikes me as just another way that people want to load everything bad onto humans. If that “re-emission” analysis were valid, how come it’s not used for say CO2, since the ocean must be “re-emitting” carbon from humans?”
Well actually…
That IS the analysis used for CO2 by Revelle in the 1950s when the objection to AGW theory was that the oceans would easily absorb any extra anthropogenic CO2. He showed that the buffering bicarbonate caused the re-emission of a large proportion of the CO2.
It is also the explanation for the long persistance of the extra anthropogenic CO2 in the carbon cycle. While the residence time for an individual CO2 molecule in the atmosphere is only a few years (or less!) the extra anthro CO2 is rapidly distributed in all the parts of the active carbon cycle, biomass, oceans and atmosphere.
The long-term geological sinks for CO2, and the primary natural sources (mainly volcanic) are somewhat smaller, and slower, than the rate of addition of anthro CO2 which is why it accumulates as shown by the Keeling curve.
I would agree that the figures for pre-industrial levels of Hg are a lot more uncertain than for CO2. Also that the rate and magnitude of the primary natural sources and sinks are approximate estimates. But within those uncertainties it is clear from the comparison with Hg levels in pre-industrial samples that there has been something like a doubling (or more) of Hg flux levels. (Mason et al 1994) The best estimates have at least twice as much Hg moving between ocean/land/atmosphere.
@-“For me, the question is this:
If we shut off every human emission, what would be the total amount emitted this year?
That amount, whether it is cycled or recycled, is what remains when we have turned off the human emissions. So it is the natural emissions.”
Well according to the Pirrone(?) and Mason paper you cite the total amount would drop by around 30% or 2320Mg in the first year.
How much it would decrease after that, and how fast is speculative. The much lower past Hg levels indicate that the natural steady state maintained by the rate of emission from natural primary sources and ocean/geological sequestration maintained a lower level than exists at present. This indicates that the rate at which anthropogenic sources add Hg is exceeding the natural sequestration rate. Your guess is as good as mine as to how fast the global Hg load would decrease if the anthropogenic sources were eliminated. It really depends on the rate of premanent removal from the system of fluxes between atmosphere/ocean/land.
As with CO2, the residence time of any additional, new, dollop of the molecule added to the natural cycle depends significantly on the rate at which the molecule is geologicaly removed from the active surface cycle.
I gather from a scan of the literature on this that there are modeling attemnpts to get a handle on these factors, using the past emission rates and historical levels to (guess)estimate the rate at which Hg is abstracted from the cycle. But given the multiple uncertainties for the rate of emission from primary natural sources, and the rate/magnitude of increase in Hg levels since industrial sources became significant I doubt that anyone would put much reliance on them.
The one unavoidable conclusion is that as with sulfur and CO2 the global levels, in the land/ocean/atmosphere cycles, have risen significantly over the last century as a result of anthropogenic sources. Any significant reduction in the emissions from those human sources would reduce the global level, any increase, or maintenance of those anthropogenic emissions will continue to raise the global levels in all parts of the cycle because in each case it is clear that present emission levels exceed the amount and rate that natural processes can sequester the molecule out of the cycle.
Willis:
At April 3, 2012 at 10:35 am you say to Izen;
“you seem to think I’m arguing against the regulation of mercury. I’m not. I’m against ludicrous, hugely expensive, and most important, meaningless reductions in mercury based on bogus science and inchoate fears.”
Excellent! Well said! Yes, that is exactly the point.
Thankyou.
Richard
@-Willis Eschenbach
Ah.
We seem to have cross-posted. I did not see your most recent replies until after my last post…
Okay, quick response, I am reassured to see the fast response time in the ice-cores after major volcanic eruptions, it seems to return to the pre-industrial level of ~5ng/L in around a decade. The rapid drop in the last few decades which is attributed to the clean air act is also a cause for optimism. Your question of how much lower your exposure to Hg would be without anthropogenic sources looks like it could return to the ‘natural level’ of 5ng/L within a decade. It is now three times that level at 15ng/L.
The large response to the Mt St Helens eruption is interesting. It probably represents the impact of a local addition and would not be reflected in a global increase as is likely from the Tambora and Krakatoa events.
This would seem to increase the value of any reduction, especially locally because the indications are the cycle would return quite rapidly to the baseline level of 5ng/L.
I guess I would not defend the idea of TOTAL elimination of human emissions, I am aware of the law of diminishing returns (grin)!
But I think the evidence does support any reduction in human sources because the payoff appears to be rapid and locally enhanced. Yes, there are arguments to be made about economic viability. But there are also good reasons if the evidence does support a rapid and significant response to reduction, to impose the costs of negative externalities on human sources.
Or perhaps you consider it cheaper to treat any negative effects on human health or biological systems that a level above the baseline may cause ?
Izen:
Your post at April 3, 2012 at 11:56 am shows you still ‘do not get it’. I will try to ‘spell it out’.
Is the atmospheric load of Hg higher than pre-industrial level?
Yes.
Will the proposed constraints on Hg emissions from the power stations make a discernible effect on the atmospheric loading of Hg?
No.
Will the proposed constraints on Hg emissions from the power stations have a significant cost?
Yes.
In the light of the above three answers, is there any point in the proposed constraints on Hg emissions from the power stations?
No, there is no point, only cost.
Do the above facts mean that significant anthropogenic sources of Hg should not be identified and possibly reduced?
No.
Would the imposition of the proposed constraints on Hg emissions from the power stations inhibit identification of anthropogenic sources of Hg that could be reduced to obtain a discernible reduction of the atmospheric loading of Hg?
Probably.
Do you ‘get it’ now?
I doubt it.
Richard
izen says:
April 3, 2012 at 11:21 am
Interesting thoughts.
Revelle showed that if you add a single large pulse of carbon to the atmosphere, when that pulse is finally re-absorbed by the natural systems including the ocean, the eventual atmospheric equilibrium CO2 level is slightly above the pre-pulse equilibrium level. I don’t find anyone describing that as “re-emission of anthropogenic carbon”.
Revelle is talking about a single specific equilibrium oceanic reaction. Are you making the argument that such a reaction exists for mercury?
Let me explain my position in another way. I find no one saying that, because CO2 levels are higher, that humans are responsible for “re-emission” of CO2. I find nothing in the literature saying that the ocean is “re-emitting” anthropogenic CO2 and that therefore humans are responsible for far greater emissions than the ~ 9 GtC we emit annually.
Because by your logic, since the mercury levels are about double what they were, humans are responsible for about half of all the mercury that is emitted by the ocean and the volcanoes and the land.
But I don’t hear a single person saying that because CO2 levels are headed towards double preindustrial levels, that humans are responsible for say 40% of all the CO2 emitted by the ocean and the volcanos and the land. That’s a bridge too far.
Look at the atmospheric response after Tambora in the figure I just posted. There’s no long-term effect. We’re responsible for part of the emissions, but the oceanic emissions are just that. They are a long-term unending source of atmospheric mercury.
Gotta run, thanks for your comments, more to follow,
w.
Nice chart. Too bad it does not go back farther. Since some of us assume that CO2 increases because of the warming since the LIA, it would be nice to see Hg charted for a few more years. Perhaps the current background has increased for the same reason as CO2.
This reference indicates that there was another anthropogenic Hg peak in the Andes around either 1500AD or 700BC, depending on the date calibration model used. Also, the volcanoes so easily visible in the USGS image don’t show up at all in the Arctic cores. Actually, since the 4 cores do not agree, it is most likely that the signal, if any, is about the same size as the noise.
Another paper clearly shows that Hg deposition peaked around 5000 BCE and is lower now than it has been for most of the last few thousand years.
Hello im in middle school and i was looking for the roman god Mercury not this random stuff i dont care about Mercury mercury in the area of states and i hate that I cant find anything about this ROMAN GOD!!!!!
What is this stuff I need information and all I get is this, like seriously, this needs A TON of work. It took me an hour to read this, and it was one hour of wasted time. Barbecue sauce!
Deb Jennie:
I have been out of contact since my last post on this thread so I have only now seen your post at April 10, 2012 at 11:32 am.
Nobody has responded to your post, and I am not surprised because it is a meaningless rant devoid of any content so there is no possible specific response. However, it is possible that you are awaiting a reply and that you did intend to make a point. Therefore, if you would care to specify
(a) the “information” you require which has not been provided by Willis and/or others,
(b) the “work” you want to see,
and
(c) what you mean by “barbecue sauce”
then I will try to provide answers.
Richard