Criteria Air Pollutants and Ambient Air Monitoring
Criteria Air Pollutants
and Ambient Air Monitoring
Topics for Discussion
• Air pollutants regulated by the EPA
• Ozone – sources, chemistry, standard,
sampling, air monitor works
• How data is collected/stored
• Locating a monitor
• Documentation/Analysis of data
Nitrogen Oxides (NO, NO2)
Particulate Matter (PM10)/Particulate Matter (PM2.5)
Note: covered under 40CFR part 50
National Ambient Air Quality
Brief comment: Ozone
• Stratospheric ozone
protects us from the
UV rays of the sun.
• Ground level ozone
respiratory tract and
damage plant life in
How is O3 created?
Chemistry of Ozone
VOCs + NOx + Sunlight + Heat = Ozone
Night Time O3 Chemistry
Ambient Air Standard-Ozone
To attain the ozone NAAQS, the 3-year average of the annual 4thhighest daily maximum 8-hour ozone concentration must be less
than or equal to 0.075 PPM (or 75 ppb).
The old ozone threshold value for a 1-hour standard is 0.12 parts
per million (PPM), measured as a 1-hour average concentration.
8 Hour Average
4th Highest 8-hr
4th Highest 8-hr
The 4th highest
This would average to 88
Schematic Diagram Ozone Monitor
Rack mount with ozone
transfer standard instrument
and ozone monitor.
Instruments for other Pollutants
• Criteria pollutants: Ozone, SO2, NOx, CO
• Other pollutants: NH3, H2S, CO2, NOy, Total
• VOC (volatile organic compounds)
• Laser/IR systems also used.
Air Monitor – Basic Principles
• UV flourescence
• Beer’s law
The chemiluminescence reaction of NO to NO2:
NO + O3 ==> NO2+ O2 + hv
Variations of chemiluminescence have been used to
perfom measurements of Ammonia (NH3):
NH3 + O2 ==> NO + H2O
4NH3 + 5O2 = 4NO + 6H2O
4NO + 4O3 -------->4NO2+4O2 + 4hv
Schematic of a reaction chamber under vacuum and a
Photomultiplier tube (PMT) for detection.
Principle - UV fluorescence
Principle - UV fluorescence
The UV fluorescence method operates on the principle that when the SO2 molecules contained in the sample gas
are excited by ultraviolet radiation they emit a characteristic fluorescence in the range of 220- 240 nm. This
fluorescence is measured and the SO2 concentration is obtained from changes in the intensity of the
The reactive mechanism is:
(1)SO2 + hv1 ¤ SO2*
(2)SO2* ¤SO + (O)
(3)SO2* ¤ SO2 + hv2
(4)SO2*+ M ¤ SO2 + M
Here, (1) shows the excited state of the SO2 molecules that have absorbed the amount of energy hv1 by
(2) shows the amount of energy, hv2 emitted by the excited molecules as they return to the ground state. (3)
shows the decomposition by the light emitted from the excited molecules. (4) shows the quenching, i.e., the
energy lost by the excited molecules colliding with other molecules.
Many compounds absorb ultraviolet (UV) or visible (Vis.) light. The diagram below shows a beam of monochromatic
radiation of radiant power P0, directed at a sample solution. Absorption takes place and the beam of radiation
leaving the sample has radiant power P.
The amount of radiation absorbed may be measured in a number of ways: Transmittance, T = P /
% Transmittance, %T = 100 T Absorbance, A = log10 P0 / P
A = log10 1 / T
A = log10 100 / %T
A = 2 - log10 %T
Calibration of a
NOx Monitor. Zero
Air machine, NOx,
Y = mx + b
Find the calibration
curve, use this to
calculate final value for
Wind Speed/Wind Direction
Air Temperature/Relative Humidity
• UV-A radiation refers to atmospheric radiation from 320
nm-400 nm (that's 0.320-0.400 m m). UV-A is very
important to photosynthesis and plant studies.
• UV-B is the shortest wavelength atmospheric radiation
that actually reaches the ground, and covers from 280-320
nm (that's 0.280-0.320 nm). However, it is UV-B that
causes skin cancer over prolonged exposure.
• UV-C is "extraterrestrial" solar radiation, and includes light
with wavelengths between 100-280 nm.
• Reference: http://www.yesinc.com/products/data/FAQuvrad/faq4.html
• Quality Assurance Project Plan (QAPP)
– Calibration of instrumentation, how data is processed
• Site Operations Procedures (SOP)
– Calibration of instruments
– How to troubleshoot equipment
– Setting up a site
• Logbook for each site
• Logbook for each instrument
• Atmospheric Research & Analysis Inc.:
TCEQ Sites for Ambient Air Monitoring
Ozone Precursors/Air Toxics
Air Toxics - There are currently 188 hazardous air pollutants (HAPS), or air toxics, regulated under the Clean
Air Act (CAA) that have been associated with a wide variety of adverse health effects. A subset of the 188
toxics thought to have the greatest impact on the public and the environment in urban areas has been identified
as the Urban Air Toxics Strategy compounds of interest. This subset of 33 compounds includes volatile
organics, semivolatile organics, and metals. Two of the six compounds identified as the risk drivers in the
strategy, benzene and 1,3-butadiene, are volatile organics which are amenable to AutoGC analysis. Data for
these two target compounds as well as all other target compounds from this analysis are forwarded to TCEQ
Toxicology Section to identify any potential health impacts that might be associated with exposure to the
measured concentrations. Ref: http://www.tceq.texas.gov/airquality/monops/agc/agc_support.html#why
GC-MS Analytical System
COLLECTION OF DATA
Automated Data Collection
The first source is the state.
EPA keeps an extensive database of monitoring sites.
Free data available for meteorology, terrain. NOAA,
NASA, many others.
Ozone Concentrations vs Wind
Time Series Graph
September 29, 2004
• Average, median, frequency analysis.
• Box-whisker plots.
• Trend analysis.
• Can be used for
common direction of
• Useful for ozone, PM,
Direction of Sources
Non parametric regression
Positive Matrix Factorization
Conditional Probability Function
Can be used for:
– Particulate Matter
• Not appropriate for ozone
Air Parcel Trajectories
Criteria Pollutants: http://www.epa.gov/air/criteria.html
Air Monitoring SOP’s: http://www.atmospheric-research.com/
Zeno Datalogger Manual
Quality Assurance Handbook for Air Pollution Measurement Systems
Volume II Ambient Air Quality Monitoring Program