It will be interesting to see now that EPA has given its blessing to the AdBlue urea injection system that will Mercedes-Benz offer its 2.3-liter turbodiesel engine for the new C-Class sedan. Can you imagine around 170 bhp power and nearly 40 mpg fuel economy? :-)

The 208 hp, 400 lb-ft E320 BLUETEC carries a fuel economy rating of 35 mpg.

It carries a 26 mpg rating. The 35 mpg figure was the highway fuel economy under previous EPA testing standards.

@ Jack - ALL NMHC sources contribute to ambient NMHC concentrations, including all anthropogenic and natural (biogenic) sources, not just on-road sources.

Not only do NMHC contribute to ozone (smog) formation, they oxidize in the atmosphere to formaldehyde, and eventually to low vapor pressure oxidation products that "condense" into secondary particulate matter (SOA), mostly in the nanoparticle and ultrafine size modes.

SOA can account for up to 90% of organic aerosol mass in urban areas and organic aerosol typically makes up the largest mass fraction of PM2.5, much larger than elemental carbon - EC - which is supposed to be a marker for diesel particulate matter. In my opinion, more needs to be done to address this fugitive VOC emissions issue.

ALL NMHC sources contribute to ambient NMHC concentrations, including all anthropogenic and natural (biogenic) sources, not just on-road sources.

Yes, I know. This has nothing to do with you substantiating your original claim that 80% of NHMC in the air basin comes from gasoline-fueled vehicles. For that to have any relevance, one first needs to know the percentage of vehicle fuel consumed in the air basin is gasoline. It's akin to someone pointing out how big of a percentage of federal personal income tax revenues the top 1% of income earners pay without mentioning the percentage of all personal income they get.

If around 80% of the vehicle fuel consumed is gasoline, then it's not being unduly harmful to air quality with respect to that particular pollutant emission.

In my opinion, more needs to be done to address this fugitive VOC emissions issue.

What do you propose should be done?

Using this logic, we could presume anything about anyone's true beliefs and discussing anything would be meaningless.

Huge leap of logic. You have to be seriously or willfully naive to think that policy regulations are never compromises. Using this logic, it follows that Hg emissions from coal plants are perfectly acceptable; that because we don't monitor PAHs or even simple aromatics from car exhausts they're not harmful; that PM mass is much more important than PM number; that CO2 emissions are not worth tracking; that ethanol is worth subsidising. But then, it was a huge leap of logic to go from EPA regulations to assuming that EPA scientists don't actually agree with at least some of the criticisms of said regulations.

You have to be seriously or willfully naive to think that policy regulations are never compromises.

You have to be seriously and willfully dishonest to construct strawmen. Of course regulations are often compromises. It doesn't then logically mean that behind every regulation there is a polar opposite opinion in the people who make the regulation or support it. You have no way of knowing that unless you're an insider.

You're running away from the basic notion of the fact that there are regulations out there, well-defended by scientists working at these agencies, over a long period of time (so that it's not simply a partisan blip). To think that somehow that over that long period of time, under scrutiny by reputable people, that somehow massive flaws in thinking about air quality persist, particularly when the sorts of objections being raised aren't new at all, really doesn't pass the smell test. It smacks of conspiracy thinking that lacks a rational explanation of why there is a conspiracy and how it has persisted.

Yes, I know. This has nothing to do with you substantiating your original claim that 80% of NHMC in the air basin comes from gasoline-fueled vehicles.

I said (if you care to go back and look at my original post) that 80% of AMBIENT NMHC in SoCAB was attributed to gasoline vehicles. Ambient NMHC is the concentration of NMHC in the environment (boundary layer of the atmosphere). The whole point of these source apportionment studies is to try to determine how much each NMHC source contributes to the overall ambient levels of NMHC.

IIRC, the 2007 journal article I referenced apportioned 34% of the AMBIENT NMHC to evaporative gasoline emissions from gasoline distribution/storage, 20% from gasoline vehicles' exhaust, 26% from evaporative gasoline emissions from the vehicle itself, something like 15% from industrial processes like coatings or parts cleaning with hydrocarbon solvents, and 1% to biogenic VOC sources. The remaining 4% or whatever is from "all other" category.

These sources can be apportioned because different sources have different "fingerprints", i.e. there may be more abundance of a specific hydrocarbon (e.g., C6) from a certain specific source. The relative abundance of these "characteristic" hydrocarbons in the atmosphere (i.e., ambient levels) is used to determine the source and quantity from that source.

The point of my original post was that just because a gasoline vehicle is certified to meet the PZEV emission category doesn't necessarily mean that it has less of an impact on air quality than a T2B5 diesel vehicle because these "exembodied" emissions aren't taken into account in the vehicle emission regs (Tier 2/LEV II).

It doesn't then logically mean that behind every regulation there is a polar opposite opinion in the people who make the regulation or support it.

Now that is a strawman!

You're running away from the basic notion of the fact that there are regulations out there, well-defended by scientists working at these agencies, over a long period of time (so that it's not simply a partisan blip). To think that somehow that over that long period of time, under scrutiny by reputable people, that somehow massive flaws in thinking about air quality persist, particularly when the sorts of objections being raised aren't new at all, really doesn't pass the smell test. It smacks of conspiracy thinking that lacks a rational explanation of why there is a conspiracy and how it has persisted.

Science evolves, which is exactly what the reference to the Atmospheric Environment shows.

Science evolves? I didn't know that! The things one can learn here!

Carl,
If we can keep something as leaky as a tiniest molecule of H2 contained at super duper pressures of 5,000 -10,000 psi, why do you supposed that we would let a molecule as large as an octane molecule, straight or branched, or a ringed cyclohexane or aromatic, at much lower pressures of just about one or two psi's, to escape into the air to cause VOC problem?

Last nite, when I fueled my Prius on the way home from work, I had to push the spigot with a large rubber seal around it tightly into the filler receptacle of the car or it won't pump at all. I don't think that there was any gasoline vapor leaked into air using that kind of filling setup. Gone are the days that one would let the spigot hanging loosely in the car's receptacle and the gasoline vapor flying everywhere.

Carl, the gasoline VOC problem is very minor in comparison to the H2 filling infrastructure. Don't worry, amigo!

Roger - you may be right, but I don't find it real encouraging that EPA proposed a rule under their air toxics regulations about a year ago that would reduce evaporative emissions from delivery of gasoline to gas stations by less than 10%. The proposed rule was published in the Federal Register, November 9, 2006. The "press release" can be obtained here.

I haven't heard if this proposed rule has become final yet.

The concern for proper use of the aftertreatment (urea) is valid and could be assured with a change in the refueling process.
The VOC issue and incremental spills can also be addressed during refueling. The "science evolves" comment is applicable in the effect that exhaust emissions and PM are being addressed. What should be the next evolution in the dispensing process is shown as a parallel method for commercial vehicals.

http://www.r2dot.org/article.pl?sid=07/10/26/1156228