Welcome to PriusChat

We'd love to have you join our community and participate in the conversation! Sign up for FREE today.

Sign Up

The NOx Disbenefit

Discussion in 'Environmental Discussion' started by Trollbait, Aug 24, 2011.

Social Buttons

  1. Trollbait

    Trollbait It's a D&D thing

    Joined:
    Feb 7, 2006
    Messages:
    4,191
    Likes Received:
    775
    Location:
    eastern Pennsylvania
    Your Vehicle Year:
    Other Non-Hybrid
    Model:
    N/A
    When it comes to reducing ozone, and thus smog, focusing on NOx emissions may do no good or even hurt efforts for improving air quality. Studies have been done looking at ozone (O3) precursors (nitric oxide [NO], nitrogen oxides [NOx], carbon monoxide [CO], and volatile organic compounds [VOCs])concentrations on weekdays and weekends. Despite reductions in the precursors, mostly NOx, on the weekend, ozone levels remained unchanged.

    Journal Abstract

    VOCs are the least changed between weekdays and weekends. Decreasing NOx without decreasing them may lead to increases in ozone.
  2. austingreen

    austingreen Senior Member

    Joined:
    Nov 3, 2009
    Messages:
    9,209
    Likes Received:
    1,554
    Location:
    Austin, TX, USA
    Your Vehicle Year:
    2010 Prius
    Model:
    II


    While I agree we need to reduce VOC especially in the Houston MSA, where refining produces a great deal, I am not sure about the science of this study. It is assuming precursors only impact ozone on the day they are produced. I don't think this is a good assumption, but would like more information if anyone knows. NOx is also harmful to human health all by itself. I doubt that these cities have already reduced this to "safe" levels.
  3. GrumpyCabbie

    GrumpyCabbie Senior Member

    Joined:
    Dec 14, 2009
    Messages:
    5,907
    Likes Received:
    1,598
    Location:
    North Yorkshire, UK
    Your Vehicle Year:
    2010 Prius
    Model:
    N/A


    Hmmm. Tell that to the residents of London or Paris.
  4. wxman

    wxman Member

    Joined:
    Nov 25, 2008
    Messages:
    362
    Likes Received:
    94
    Location:
    Tennessee
    Your Vehicle Year:
    Other Non-Hybrid
    Model:
    N/A
    Actually, this is something that has been known for quite a while (since at least the early 1990s), when it was demonstrated that ozone ("smog") levels in Southern California were significantly higher on weekends than weekdays, in spite of a reduction in ozone precursors (NOx, VOC, CO), with greater NOx reductions than VOC or CO.

    There are at least 13 peer-reviewed studies (including the OP reference) which have concluded that reducing NOx emissions more than VOC and/or CO emissions result in the same or higher ozone levels in areas that are “VOC limited†with respect to ozone formation. As the referenced study suggests, all large metropolitan areas studied in the U.S. are “VOC limitedâ€.

    Here’s a list of the studies (without the study referenced in the OP)…


    Heuss, J. M. et al. "Weekday/Weekend Ozone Differences: What Can We Learn from Them," Journal of the Air & Waste Management Association, 53, pp. 772-788 (2003).

    Lawson, D. R. "The Weekend Effect--the Weekly Ambient Emissions Control Experiment." Environmental Manager, pp. 17-25 (July 2003).

    Fujita, E. M. et al. "Evolution of the Magnitude and Spatial Extent of the Weekend Ozone Effect in California's South Coast Air Basin 1981-2000," Journal of the Air & Waste Management Association, 53, pp. 864-875 (2003).

    Blanchard, C.L.; Tanenbaum, S.J. “Differences between Weekday and Weekend Air Pollutant Levels in Southern California.†J. Air & Waste Manage. Assoc. 2003, 53 (7), 816-828.

    Chinkin, L.R.; Coe, D.L.; Funk, T.H.; Hafner, H.H.; Roberts, P.T.; Ryan, P.A.; Lawson, D.R. “Weekday versus Weekend Activity Patterns for Ozone Precursor Emissions in California’s South Coast Air Basin.†J. Air & Waste Manage. Assoc. 2003, 53 (7), 829-843.

    Yarwood, G. et al. "Modeling Weekday/Weekend Ozone Differences in the Los Angeles Region for 1997," Journal of the Air & Waste Management Association, 53, pp. 864-875 (2003).

    Marr, L. C. & Harley, R. A. "Spectral Analysis of Weekday-Weekend Differences in Ambient Ozone, Nitrogen Oxide, and Non-Methane Hydrocarbon Time Series in California," Atmospheric Environment, 36, pp. 2327-2335 (2002).

    Marr, L. C. & Harley, R. A. "Modeling the Effect of Weekday-Weekend Differences in Motor Vehicle Emissions on Photochemical Air Pollution in Central California," Environmental Science & Technology, 36, pp. 4099-4106 (2002).

    Pun, B. K. & Seigneur, C. "Day-of-Week Behavior of Atmospheric Ozone in Three U.S. Cities," Journal of the Air & Waste Management Association, 53, pp. 789-801 (2003).

    Donald Stedman, PhD, “Photochemical Ozone Formation, Simpliedâ€, Environ. Chem., 2004, 1, 65-66.

    J. G. Murphy, D. A. Day, P. A. Cleary, P. J. Wooldridge, D. B. Millet, A. H. Goldstein, and R. C. Cohen, “The weekend effect within and downwind of Sacramento: Part 1. Observations of ozone, nitrogen oxides, and VOC reactivity.†Atmos. Chem. Phys., 6, 11427–11464, 2006

    Shaheen R. Tonse, Nancy J. Brown, Robert A. Harley and Ling Jin, “A process-analysis based study of the ozone weekend effect.†Atmospheric Environment, Volume 42, Issue 33, October 2008, Pages 7728-7736

    Here’s a fairly good “synopsis†of the study findings…


    http://findarticles.com/p/articles/mi_m0CYH/is_20_6/ai_92585832/


    By the way, none of these studies suggest that NOx isn't a pollutant, just that greater focus on VOC emissions need to be taken by the regulators.
  5. wxman

    wxman Member

    Joined:
    Nov 25, 2008
    Messages:
    362
    Likes Received:
    94
    Location:
    Tennessee
    Your Vehicle Year:
    Other Non-Hybrid
    Model:
    N/A
    It should be noted that EPA acknowledged the "NOx disbenefit" and expected increases in ambient ozone levels in urban areas based on "Regulatory Impact Analysis" documents (RIA) of their regulations of NOx emissions reductions from diesel engines. Some of these Rules and RIAs pre-dated these weekend ozone effect studies.

    For example, EPA specifically acknowledges that "…It should be noted, however, that the potential exists for a few localized areas to actually experience slight increases in ozone concentrations as a result of NOx emission reductions...." (EPA Final Regulatory Impact Analysis: Control of Emissions of Air Pollution from Highway Heavy-Duty Engines, http://www.epa.gov/otaq/regs/hd-hwy/1997frm/hwy-ria.pdf , page 119). In another RIA, EPA actually projects that one county (Bronx County in New York) which was not in violation of the ozone NAAQS, would violate the standard by 2020 as a result of its regulation (EPA Final Regulatory Impact Analysis: Control of Emissions from Nonroad Diesel Engines, http://epa.gov/nonroad-diesel/2004fr/420r04007c.pdf , page 2-114). On page 2-36 of another RIA (EPA Regulatory Impact Analysis: Control of Emissions of Air Pollution from Locomotive Engines and Marine Compression Ignition Engines Less than 30 Liters Per Cylinder, http://www.epa.gov/otaq/regs/nonroad/420r08001a.pdf), EPA states that their modeling indicated that 5 counties would experience increases in ambient ozone levels as a result of that specific rule, and that one county (Orange County, California) would experience a 5.5 ppb increase in ozone levels because of the NOx disbenefit in those areas. One can only imagine what the net effect of all of these regulations will eventually have on the ambient ozone levels in urban cores.

    It should be pointed out that EPA specifically states that VOC reductions in "NOx-limited" areas have virtually no effect, i.e., there's no "VOC disbenefit" in rural areas (normally expected to be NOx-limited). Thus there doesn't appear to be any valid scientific reason for EPA to focus on NOx emission reductions while doing little to further reduce VOC emissions, and its recent emission reduction strategies and priorities are perplexing.
  6. wjtracy

    wjtracy Senior Member

    Joined:
    Sep 19, 2006
    Messages:
    4,554
    Likes Received:
    734
    Location:
    NOVA
    Your Vehicle Year:
    2006 Prius
    Model:
    N/A


    A big thumbs up :thumb: for the Prius Gen II bladder gas tank which minimizes VOC escape during refueling. Hope the Gen-III+ have equally green gas tanks!

    We really do not have much ozone in Wash DC so I am wondering if the study is designed correctly. I wish they included South Jersey, now that's where we saw some O3 smog when we were getting the air from Eastern PA (hint hint TrollB). I gotta feel if Jersey were getting less NOx from PA, we would have seen less O3 excedance days. Per AG's list, NOx is probably bad for acid rain too.
  7. wxman

    wxman Member

    Joined:
    Nov 25, 2008
    Messages:
    362
    Likes Received:
    94
    Location:
    Tennessee
    Your Vehicle Year:
    Other Non-Hybrid
    Model:
    N/A


    It is to a certain degree, but the removal process for NOx is oxidization of NO2 to nitrate (NO3). Most NO3 reacts with ammonia in the atmosphere to form ammonium nitrate, which is a common fertilizer, and not to HNO3 (nitric acid).

    Ambient SOx levels generally have a much better correlation to acid rain.
    1 person likes this.
  8. austingreen

    austingreen Senior Member

    Joined:
    Nov 3, 2009
    Messages:
    9,209
    Likes Received:
    1,554
    Location:
    Austin, TX, USA
    Your Vehicle Year:
    2010 Prius
    Model:
    II


    Thanks, that seems to demonstrate we need a change in regulation.



    The gen III is very good when it comes to VOCs. We do have ozone action days here, and when it is high the city bus is free to encourage ridership. One big source is refueling vehicles, and the guidelines here say to do it at night. The prius can't do anything about the VOCs until after the gas gets into the tank.
  9. GrumpyCabbie

    GrumpyCabbie Senior Member

    Joined:
    Dec 14, 2009
    Messages:
    5,907
    Likes Received:
    1,598
    Location:
    North Yorkshire, UK
    Your Vehicle Year:
    2010 Prius
    Model:
    N/A


    We don't have vapour recovery systems on our petrol pumps.

    Do they make a difference? Is it worth the extra expense? I know when I fuel up there are always a few drops of petrol that dribbles out of the pump nozzle onto the floor. Does the vapour actually cause much harm?

    Appreciate comments as I feel an email to my MP coming on! :eek:
  10. ItsNotAboutTheMoney

    ItsNotAboutTheMoney EditProfOptInfoCustomUser Title

    Joined:
    Jul 18, 2009
    Messages:
    2,283
    Likes Received:
    442
    Location:
    Maine
    Your Vehicle Year:
    2010 Prius
    Model:
    II
    I hate the word disbenefit. :mad: It is such an ungood word. I think malfit or malefit would be unbadder.

    Hopefully this issue will be raised more and the EPA will finally attack VOCs as the next problem. Of course, since VOCs are an issue with so many chemicals, tackling them would be much more difficult politically.
  11. ItsNotAboutTheMoney

    ItsNotAboutTheMoney EditProfOptInfoCustomUser Title

    Joined:
    Jul 18, 2009
    Messages:
    2,283
    Likes Received:
    442
    Location:
    Maine
    Your Vehicle Year:
    2010 Prius
    Model:
    II


    You're paying for that dribble. I try and get my dribbles into the car.
  12. wjtracy

    wjtracy Senior Member

    Joined:
    Sep 19, 2006
    Messages:
    4,554
    Likes Received:
    734
    Location:
    NOVA
    Your Vehicle Year:
    2006 Prius
    Model:
    N/A


    Grump- I do not have the numbers, but if you ask me it should make a difference. Gasoline pump design here in USA apparently varies by state regulation. New Jersey has the most fancy vapor recovery hose system I am aware of. NJ needs it to control ozone (being at the end of the pipe re: downstream winds from other states). Everywhere else I go the states seem pretty lax about it.

    I should mention NJ is one of the few states where we do NOT have self-serve gasoline. Couple weeks ago I forgot and went to fill up myself. I made a minor mess when the liquids came out the hose. Maybe there is a technique, and maybe that is why you do not see this more.
  13. Trollbait

    Trollbait It's a D&D thing

    Joined:
    Feb 7, 2006
    Messages:
    4,191
    Likes Received:
    775
    Location:
    eastern Pennsylvania
    Your Vehicle Year:
    Other Non-Hybrid
    Model:
    N/A


    Actually, we are both getting hosed by Ohio. They are one of four states that did not agree to smokestack height limits. I grew up in NJ and know its reputation, but now most of its air pollution comes from much farther downwind.

    Going from memory here, one of the advantages of butanol as a gasoline replacement is its lower volatility, or evaporation rate. Same goes for biodiesel.
  14. austingreen

    austingreen Senior Member

    Joined:
    Nov 3, 2009
    Messages:
    9,209
    Likes Received:
    1,554
    Location:
    Austin, TX, USA
    Your Vehicle Year:
    2010 Prius
    Model:
    II


    This seems to indicate they aren't needed
    EPA says outdated gas vapor recovery nozzles no longer required

    But it is contradicted by our local instructions. It may be that the high temperatures here cause more problems, or one of the agencies is just wrong. We just broke the record of 70 100 degree (38 C) or higher days set in 1925, and we expect 10 more.

    Definitely don't top off your tank, that is why you are getting the dripping I think. Vapor recover nozzles won't prevent that.
    1 person likes this.
  15. cyclopathic

    cyclopathic Senior Member

    Joined:
    Apr 15, 2011
    Messages:
    1,560
    Likes Received:
    186
    Location:
    suburbia
    Your Vehicle Year:
    2010 Prius
    Model:
    II


    even more so the CO2 levels
  16. wjtracy

    wjtracy Senior Member

    Joined:
    Sep 19, 2006
    Messages:
    4,554
    Likes Received:
    734
    Location:
    NOVA
    Your Vehicle Year:
    2006 Prius
    Model:
    N/A


    Interesting AG, I guess that explains why Prius no longer has bladder tank due to this alternate vapor reduction technology?
  17. wjtracy

    wjtracy Senior Member

    Joined:
    Sep 19, 2006
    Messages:
    4,554
    Likes Received:
    734
    Location:
    NOVA
    Your Vehicle Year:
    2006 Prius
    Model:
    N/A


    OK TB I agree its OHIO's fault...was just kidding you.
    I was opposite of you, grew up PA moved to NJ then elsewhere.
    Well, re butanol, it is heavier then ethanol, so that may be what you are thinking. Believe there is a vapor pressure EPA regulation so it does not really matter whats in there as long as the fuel meets the spec. Possibly ethanol blends get some relief on the EPA VOC spec, not sure.
  18. F8L

    F8L Protecting Habitat & AG Lands

    Joined:
    Aug 14, 2006
    Messages:
    18,800
    Likes Received:
    3,787
    Location:
    Sacramento, CA.
    Your Vehicle Year:
    2013 Chevy Volt
    Model:
    N/A
    Just as a side note, NOx emissions are harmful to the environment in general, especially where grasslands and other non-crop native vegetation is concerned. There have been studies showing that increased nitrogen dervided from traffic has a negative effect on native plant species here in California, particularly on serpentine soils, and in some cases benefits non-native and invasive species. Invasives cost billions of dollars in productivity losses and controls.

    I realize this has nothing to do with air quality for humans but it is still a very important component of NOx regulations. On the otherhand, if it promotes the growth of such invasives as Lolium multiflorum (Italian wildrye) then this is an air quality problem because Lolium is one of the main contributors to allergy problems which translates into health care costs.

    Links:

    Nitrogen deposition in endemic-rich California serpentine grasslands


    Integrated nitrogen input systems in Denmark

    Cumulative nitrogen input drives species loss in terrestrial ecosystems
  19. Trollbait

    Trollbait It's a D&D thing

    Joined:
    Feb 7, 2006
    Messages:
    4,191
    Likes Received:
    775
    Location:
    eastern Pennsylvania
    Your Vehicle Year:
    Other Non-Hybrid
    Model:
    N/A
    I don't think anyone has claimed they aren't harmful. The issue is over just focusing on the NOx and not the others. When the increased costs of doing so will not make an improvement in the stated goal of the regulations.

    As for the native plants, we'd likely see a bigger improvement targeting the NOx emissions of lawn equipment and off road vehicles, than the diesel trucks in the city.