Download Lect 4b

No matter how sophisticated you may be, a huge granite
mountain cannot be denied--it speaks in silence to the
very core of your being. Ansel Adams
Art completes what nature cannot bring to finish.
Aristotle
Art is lies that tell the truth. Picasso
Science has not yet taught us if madness is or is not the
sublimity of the intelligence. Edgar Allan Poe
Atmospheric Chemistry - Take 2
Energy equation in the atmosphere:
E = hC/l
Where l is radiation wavelength
N2 + h  2N (l < 126 nm) DHo = 945 kJ mol-1
O2 + h  2O (l < 240 nm) DHo = 498 kJ mol-1
N2 (g) + O2 (g)  2NO (g) DGo = +173 kJ mol-1
Does not occur at ambient T but does at high T
(engine combustion ~ 2500C)
The reverse reaction is favored thermodynamically but too
slow at ambient T (kinetics!)  other reactions
Atmospheric Chemistry - Tropospheric ozone
2NO + O2  2NO2
NO + O3  NO2 + O2
Atmospheric Chemistry - Tropospheric ozone
The second partner needed in the ozone formation cycle are
organic peroxides and free radicals (Organic molecules are emitted
from forests and other plants but also from human sources - e.g.
solvents or fuel at filling stations)
 H + CO2
CH4 + OH  CH3 + H2O
CH3 + OH  CH2 + H2O
ROOH + OH  ROO + H2O
CO + OH
Atmospheric Chemistry - Tropospheric ozone
NO2 (h, l<400 nm)
O + O2 + M
 NO + O
 O3
 RO + NO2
NO + O3  NO2 + O2
ROO + NO
Atmospheric Chemistry - Tropospheric ozone
• If no nitrogen oxides are available, the reaction cycle cannot take place.
• If too much nitrogen oxides are available the excess of nitrogen oxide NO
reacts not only with the peroxy-radicals but removes the ozone again.
• If no sunlight is available NO cannot be recycled again and the formation of
peroxy-radicals is not sufficient.
Atmospheric Chemistry - Tropospheric ozone
Urban traffic is not the only source of ozone  They can come
from other combustion processes: vegetations fires.
NASA Earth Probe Total Ozone Mapping Spectrometer (TOMS) - Indonesian (Oct 1997)
Atmospheric Chemistry - Take 1
Sources of CO and NOx Emissions in Europe
• In Europe, in 2001, 30 679 Gg of CO was emitted. The main source of
anthropogenic CO in the air was transportation (60%), and the industry
contributed to 36% of the total emission. Waste management and
agriculture were of marginal importance;
• Transportation was also the main source of NOx as it delivered 63% of
the total emission which amounted 10 056 Gg in 2001. Industry
contributed to 35% of the total emission. Again, emissions from waste
management and agriculture were of marginal importance.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Atmospheric Chemistry - Take 2
Sources of HC and NOx Emissions in New England
• Large industry such as chemical manufacturers, and combustion sources
such as power plants burning fossil fuels;
• Small industry such as gasoline-dispensing facilities, autobody paint
shops, and print shops;
• On-road automobiles, trucks and buses;
• Off-road engines such as aircraft, locomotives, construction equipment
and gasoline-powered lawn and garden equipment.
Atmospheric Chemistry - Take 2
Sequence of of chemical species appearing during a photochemical
smog event.
Ozone formation and atmospheric conditions
10AM
Source: USEPA - Region 1 (New England)
Ozone formation and atmospheric conditions
11AM
Ozone formation and atmospheric conditions
12PM
Ozone formation and atmospheric conditions
2PM
Ozone formation and atmospheric conditions
3PM
Ozone formation and atmospheric conditions
5PM
Ozone formation and atmospheric conditions
7PM
Ozone formation and atmospheric conditions
10PM
Change in regulation of ozone
In July 1997, based on information that the 1-hour ground-level ozone
standard did not adequately protect public health, EPA established the 8hour ozone standard. Scientific information shows that concentrations of
ozone in the air can affect human health at low levels and over longer
exposure periods concentrations to 0.08 ppm, averaged over eight hours.
The 1-hour standard limits ozone concentrations to 0.12 parts per million
(ppm), measured in hourly readings. Much of New England was previously
designated nonattainment under the the 1-hour standard.
Ozone formation and climate change
Climate change can influence the concentration and
distribution of air pollutants through a variety of direct
and indirect processes:
 modification of biogenic emissions
 change of chemical reaction rates
 mixed-layer heights that affect vertical mixing of
pollutants, and
 modifications of synoptic flow patterns that govern
pollutant transport.
For example, warmer temperatures can result in increased
concentrations of photochemical oxidants and increased
rate of O3 production.
Ozone formation and climate change
 The frequency and duration of extreme ozone events is predicted to increase
under the climate scenarios for future decades.
Regional climate change was found to
cause significant increases in the
simulated 4th-highest 8-hr O3
concentration in summertime of future
years.
 consider the effects of a changing
climate when planning for the future
attainment of regional-scale air quality
standards such as the U.S. NAAQS
(4th-highest annual daily maximum 8hr O3 concentration).
Ozone formation and Reformulated Gasoline
How should regulatory agencies determine if one RFG blend using a
particular oxygenate is preferable to another?
In attempting to mitigate ozone pollution, the USEPA currently addresses
such questions by estimating the mass of VOC emissions resulting from the
use of an individual RFG blend. If the estimated mass of emissions exceeds
a specified amount, that fuel blend is disallowed. Although certain fuel
blends, such as those using ethanol, might result in greater amounts of
emissions in terms of mass (because of the volatility of ethanol), it is argued
that those emissions have a lower ozone-forming potential compared with
emissions from other fuel blends.
 Therefore should EPA's assessment of RFG blends be based not only
upon mass of emissions, but also upon their reactivity (i.e., ozone-forming
potential)?
Ozone formation and Reformulated Gasoline
How should regulatory agencies determine if one RFG blend using a
particular oxygenate is preferable to another?
Peak ozone concentrations in 41 metropolitan areas in the United States
decreased by about 10% overall from 1986 to 1997 despite growing fuel
usage. Nevertheless, in 1997, about 48 million people lived in areas of the
United States that were classified as ozone "nonattainment" areas, and
promulgation of the new 8-hr National Ambient Air Quality Standard
(NAAQS) of 0.08 parts per million (ppm) for ozone is projected to triple the
number of counties in nonattainment and to result in extensive
nonattainment in rural areas of the eastern United States. The persistence
of ozone pollution has sparked a need for innovative approaches to
mitigation, and the RFG program is one such attempt.
Ozone formation and Reformulated Gasoline
Air-quality models suggest that implementation of the RFG
program reduces peak ozone concentrations by only a few
percent. Even if the relative contribution of motor vehicles to
the current inventory of ozone precursor emissions from all
sources has been underestimated (which, historically, has often
been the case), the reduction in peak ozone from the RFG
program would still likely be less than 10% at most. Although
long-term trends in peak ozone in the United States appear to
be downward, it is not certain that any part of these trends can
be significantly attributed to the use of RFG.
Source: National Academy of Science
Limit and Alarm Values
 For nitrogen dioxide (NO2), sulphur dioxide (SO2), lead (Pb) and
particulate matter of the diameter up to 10 µm (PM10), the limit values
are given as mean annual concentration. .
 For ozone (O3) and carbon monoxide (CO), the limit values are given as
mean 8-hour concentration.
 For NO2, SO2 and O3, apart from limit values, there are also alarm
values established. Those are mean 1-hour concentrations.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Source: Max Plank institute
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
This afternoon
 Lab #3: Lead in Urban Regions: A temporal analysis.