Another look at NOx world wide

This was the topic of iplug's thread here last December. Now the article is published in JGR Atmospheres.

NOx is a few steps before nitrogen deposition. The actual global pattern for that is very different from a >10-year old publication that everyone in the business is still citing. That deserves correction because for forests and grasslands (not receiving fertilizer inputs), nitrogen really increases plant growth. In many instances it slows decomposition. Together these mean that nitrogen has a lot of leverage on 'natural biological' carbon cycling, which remains 6 (or more) times larger than burning.

 

The USA slide map is nifty.

Poor NJ really gets nailed with NOx/Ozone as the end-of-pipe ...I do not think anything going on in NJ itself causes that. PA is big elec power exporter so NJ/NY gets the NOx etc.

I like the way NOX stays out of Northern Virginia but creeps up just over the state line in MD.

Houston looks too low in NOx.

 

If your interest is urban NOx and its connection to ozone, the satellite pixels may be too large. Ground level measurements are commonly done. The equipment is not cheap but I think it is all made in USA so 'your money stays home'. Even China buys from USA - and more than a few.

If your interest is in regional nitrogen deposition (like me and maybe few others), there is a lot of downwind motion and other N sources including agriculture. NADP operates a high-quality rain chemistry network in USA, Canada has, Europe has, but that's it. Most of global land surface is poorly sampled. This Asian country makes an effort but I am sorry to say they are not yet up to snuff.

So, the global N deposition picture is not well defined, and it has leverage on the carbon cycle. Global satellite could really help with that. I keep whining about a 2004 article, which was already been, well, um, trashed by more recent regional studies even before this new work.

The picture is dynamic as well. Below are USA wet deposition maps from 1986 and 2014 (2015 not yet available). The northeastern sector has been 'cleaned' and I think it is well known how that happened.

OK I can't attach these two pdfs - maybe too large. If somebody is curious but can't be bothered to go to the actual NADP website (where many other wonders reside as well) I will shrink them into accommodation with PC attachment rules.

 

why would Iowa be so high in 2014?

 

Agricultural success is nitrogen, as a reasonable first approximation. Information about addition rates through time should not be difficult to find. Actually, little fertilizer N 'goes up'. Most of excess moves along by water, and river outfall 'dead zones' follow.

Don't know how much N farmers there put down, but 100 kg/ha is possible. That 10 returns via rain is not a surprise.

If it helps, lots of forests do biological N fixation @ 6 kg/ha. Grasslands, sorry, don't know if they are less. All at need have ways to hold N tightly against water export. N in (and newly supplied to) 'unfertilized' systems strongly leverages carbon cycling there. We don't have than map yet, and lack is my pain.

 

I've heard much of the pollution in NJ and Eastern Pa comes from Ohio, which is/was one of four states that didn't sign an agreement on limiting plant smoke stack height.

 

Ohio pretty bad years past I know from flying in to say Cincinnati.
Looks like getting a little better. We lived in south NJ so I know we had a lot of ozone days.

 

Apparently, there are high biogenic sources of NOx (agriculture) in Southern California. May explain the high satellite depiction of NOx in Bob's reference.

Oikawa, P. Y. et al. “Unusually high soil nitrogen oxide emissions influence air quality in a high-temperature agricultural region.” Nat. Commun. 6:8753 doi: 10.1038/ncomms9753 (2015), Unusually high soil nitrogen oxide emissions influence air quality in a high-temperature agricultural region

 

So I guess farming say in Iowa for corn could be increasing NOx emissions in say summer. Whether or nor this is significant downstream impact I do not know...if I gather from Trollbait, the higher smokestacks in Ohio carry the NOx over to Jersey. So presumably farmland NOx is closer to the ground.

 

Reference cited @9, please see Figure 6. Imperial Valley agriculture is still small compared to LA basin.

In the future we may be growing some crops at higher temperatures (where water is sufficient). It is interesting to know if fertilizer N will become more frisky.

 

Yes, I saw that. Looks like SoCAB has about as high of biogenic NOx emission rate as the Imperial Valley though.

NO2 itself isn't really a significant air quality issue in SoCAB any longer as it has effectively been in attainment with the annual NO2 NAAQS since the early 1990s (officially 1998).




Nitrogen Dioxide Concentrations, Trends, Air Quality Analysis | Pacific Southwest | US EPA


Ground-level ozone is the major air quality issue in SoCAB. It is still VOC-limited, and NOx reductions exceeding 90% (2008 baseline) are required to bring it into attainment with the ozone according to this recent study. That means ambient NO2 levels would have to decrease to around 8 ppb or lower, which may be a challenge if there's significant biogenic NOx being produced there, even if all anthropogenic sources of NOx are eliminated.

 

Can you take that a step further and say where the CA VOC is coming from? And of course the kicker question: do we really need plug-in mandate to improve things now that autos like Prius are so much cleaner?

 

Appears it's still primarily coming from gasoline exhaust - Pang et al., “Trends in selected ambient volatile organic compound (VOC) concentrations and a comparison to mobile source emission trends in California's South Coast Air Basin.” Atmospheric Environment, Volume 122, December 2015, Pages 686–695, Trends in selected ambient volatile organic compound (VOC) concentrations and a comparison to mobile source emission trends in California's South Coast Air Basin .

 

It's been known for decades that ambient ground-level ozone levels tend to increase on weekends, when ozone precursor emissions decrease, relative to weekdays, which is counter-intuitive. It's been generally concluded that larger reductions in NOx emissions (mostly due to far fewer diesel trucks on the road on weekends) than VOC emissions was the reason for the increase in ambient O3. NOx destroys O3 in the conditions found in SoCAB.

A good article on the phenomenon is available at http://pubs.awma.org/gsearch/em/2003/7/lawson.pdf .

 

We are in the midst of a local like-storm.

Plus, the US leads the world in air-pollution reduction, monitoring technology, and mechanistic understanding. PriusChat structure does not permit me to 'like' that. But it is a thing. Of all those gazillions of $$$ going into Earth System Science, more than a few go right here. And we have folks hating that. Hating the idea that USA is leading us into a cleaner and more sustainable 21st century.

Things that folks hate can be just as baffling as things that folks like...