Sunday, October 02, 2011

From the Ground Up

While there is much meta going on and on and on and on, even at Rabett Run, Eli came across some interesting science in Science. As previously discussed here, the oxidative capacity of the atmosphere has remained constant, a bit of a shock as with the increasing injection of methane and various dirties (as in Asian brown cloud), somebunny might think that it would have fallen, as indeed the authors of the previously discussed paper did

However, a consistent, predictive understanding of the net response of [OH] on broad scales to such perturbations is lacking. For example, a range of negative [OH] feedbacks is calculated from changes in atmospheric methane abundance (3, 57).
Which is why a new paper by Su and a list of co authors long enough for CERN, Uli Poeschl being the last but not least, is so interesting. The experiment was simple enough, they put some dirt into a tube and blew air through it, analyzing what came out. they found that nitrite (NO2-) converts to nitrous acid, HNO2, in the soil which desorbs into the atmosphere as HONO (yes atmospheric science folk pronounce it that way).

At this point Eli has to commit some chemistry. The first point, which is NOT taught in General Chemistry, or at least most GChem courses, is that molecules that you can buy are not reactive.

They are stable. In the case of organic or molecules consisting of non-metals, each atom is surrounded by a shared outer shell of eight electrons which makes them think they are noble gases, much as Chris Monckton thinks he is a Nobel prize winner, and they don't want to know different or associate with non-peers.

However there are some molecules with an odd number of electrons in the outer shell (so they can't have eight) called free radicals, and free radicals are very reactive because that odd electron is looking for a partner. In the atmosphere HO is the most important free radical and the one responsible for cleaning out all the hydrocarbons such as methane (chemistry at link).


the question being where the HO comes from.

The generic answer is in water aerosols where nitrogen dioxide has dissolved
H2O(aq) + 2 NO2(aq)= HNO3(aq) + HONO (g)
HONO is THE source of HO in the atmosphere, because it is the only one which can absorb above the ozone cut off at 306 nm which blocks deep UV from reaching the troposphere

and the HONO absorbs a photon and falls apart into HO + NO but there is not enough of this process to explain the concentration of HO in the atmosphere, without significant ear waving. Su et al have added the red arrow below the line processes.


H+(aq) + NO2-(aq) = HNO2(aq) = HONO (g)

This appears to be catalyzed at low pH (acid conditions) and we know that agriculture is increasingly acidifying and fertilizing soils which is degrading water quality and increasing eutrophication. It may also have maintained the oxidative capacity of the atmosphere, leaving us lagomorphs with the choice of dirty air or dirty water

19 comments:

Simon Donner said...

Keep committing chemistry. Your description of OH was clearer than what is in any of the atmospheric chemistry textbooks I was reviewing a few weeks ago.

David B. Benson said...

What Simon Donner wrote.

Anonymous said...

OFFs people, and Roger Jnr. I am specifically pointing at you. Do not expect every paper to get published, get over your ego and paranoia already. And look at this, those "meanie gatekeepers" at AGU blocking the truth. This is the Editor's pick for JGR-Atmospheres right now:

"Surge in North Atlantic hurricanes due to better detectors, not climate change
A spate of research has indicated there may be a link between climate change and the prevalence of North Atlantic tropical cyclones. Upon closer inspection, however, researchers have noted that the prominent upswing in tropical cyclone detections beginning in the midtwentieth century is attributable predominantly to the detection of "shorties," tropical cyclones with durations of less than 2 days. That the apparent surge in cyclone activity could be attributable to changes in the quality and quantity of detections has gained ground as a potential alternative explanation. Using a database of hurricane observations stretching back to 1878, Villarini et al. (2011) try to tease out any detectable climate signal from the records. The authors note that between 1878 and 1943 there were 0.58 shorty detections per year, and between 1944 and 2008 there were 2.58 shorty detections per year. This increase in shorties, which the authors propose may be related to the end of World War II and the dawn of air-based reconnaissance and weather tracking, was not mirrored by an increase in tropical cyclone activity for storms longer than 2 days. The authors compared the rate of shorty detections against a variety of climate parameters, including North Atlantic sea surface temperature, mean tropical sea surface temperature, the North Atlantic Oscillation, and the Southern Oscillation Index. The authors found that North Atlantic sea surface temperatures were related to tropical cyclones of longer than 2 days' duration but were not related to the rate of short detections. Additionally, for every decade after 1950s the occurrence of shorties seemed to be related to a different climate parameter. Both of these findings are highly suggestive of data quality problems for the shorties record. The researchers note that their finding does not rule out the possibility of a climate-driven increase in shorties over the twentieth century. Rather, any existing trend will be imperceptible, as it is masked by data quality issues."


The paper that those dratted gatekeepers let through is here. Actually the editor's pick got the title wrong, the paper says:

"Is the recorded increase in short-duration North Atlantic tropical storms spurious?"

This paper of course doesn't refute the findings that the frequency of strong tropical storms in the N. Atlantic is on the increase as documented elsewhere in the literature.

ML

Hank Roberts said...

> soils

How much of this chemistry also happens in the oceans?
http://rsta.royalsocietypublishing.org/content/369/1943/1980.full

hankroberts said...

(because the oceans are also acidifying)

Steve Bloom said...

Could this explain the recent flat spot in the methane trend?

rehuie said...

HONO is a source of OH in the atmosphere. THE source, however, is the photolysis of ozone and the subsequent reaction of O1D with water.

Anonymous said...

Eli,

Looks like you got a 24-carrot expert to comment! Of course, I am not familiar with the OH density vs altitude, or where the organics get oxidized (up high I imagine), vs where the ozone is, etc. If any elaboration is forthcoming, I am all bunny ears.

Rib Smokin' (compleat with nitroso-hemoglobin) Bunny

EliRabett said...

Up high

Hank Roberts said...

> photolysis of ozone

And we keep getting better at doing that:
http://www.theozonehole.com/arctic2001loss.htm
(This is about 2011, not about 2011, typo is in the link)

Hank Roberts said...

drat.

EliRabett said...

Yeah, blew that, and a buddy did the best measurements on the 306 nm tail yield of O 1D. Drat

student of baroque painings said...

just curious...why is this not taught in chemistry courses? I did some chem so this strikes me as off-centre.

rp^2 said...

To "student of baroque painings": In the past 10-20 years, research in the top tier Chemistry departments (in the US, at least) has been dominated by Chemical Biology and, more recently, by Materials and Nanoscience (especially with respect to emerging energy technologies). Traditional gas-phase physical chemistry has become something of a backwater - it's been offloaded to other disciplines, much as cutting-edge problems in acid-base and solubility equilibria were offloaded to chemical oceanography about 30 years ago.

Robert

John said...

UNEMPLOYMENT STRIKES BUNNIES

The NBC show, The Playboy Club, was just cancelled, one of the first shows of the new teevee season to be scrapped, throwing attractive young bunnies out on the street. How can honest hard-working bunnies expect to put carrots and parsnips on the table when battling the scourge of unemployment? And how will the cute bunnies fired by The Playboy Club expect to find time to study the gas-phase chemistry lessons, expounded by Eli?

EliRabett said...

They get retraining money. . . .

Anonymous said...

I'm willing to undertake their retraining.

Others wishing to help, please form an orderly queue behind me.

Cymraeg llygoden

Anonymous said...

Please add more good information that would help others in such good way.
stop snoring

owlbrudder said...

The fact that I had to look up 'lagomorph' places me in the lower percentile of posters on this thread. The fact that I DID look it up places me in the upper percentile of red-neck lounge lizards. For the benefit of those below me in the food chain: A member of the mammalian taxonomic order, Lagomorpha, which includes hares, rabbits, and pikas.

Drat! Now I have to look up 'pika'. Too hard.

Pass me another bunny, I've broken this one ..