Ambient Air Quality Monitoring Methods
Lydia Scheer ITEP
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What will we learn?
Reasons for monitoring ambient air quality Methods available for different pollutants
and/or parameters Considerations for air monitoring National and regional issues related to air
monitoring
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Why Monitor Air Quality? Examine and characterize airshed
Health or environmental effects Cultural reasons Political issues Economic or land-use planning
Gauge compliance with standards/regulations NAAQS attainment or non-attainment
EPA Green Book lists NA areas (www.epa.gov/airquality/greenbk/) Non-attainment: progress toward attainment What control/prevention strategies are needed? Are they
working?
Why is your tribe monitoring? Answering this question will help to determine your air
monitoring objectives
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Evaluating Impacts
Think about monitoring objectives—why are you monitoring? Consider impacts at both the receptor and the source
What is the level at source? What are downwind/upwind levels? What areas are most impacted and/or what areas are you
concerned about? (receptors) Establish baseline data representative of your area Determine maximum, average pollutant concentrations Will you be issuing health alerts or monitoring trends?
Are you meeting your objectives?
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Network Considerations
“Network” can be a single site or multiple sites Monitoring objectives Meteorology & pollutant/precursor transport Monitoring schedule Site requirements, access and security, long-term
viability NAAQS monitoring: 40 CFR Part 58 Appendix E Met monitoring: EPA-454/R-99-005 Special projects often have their own specific
requirements
Necessary to review and modify network based on objectives and changes to surrounding conditions
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Equipment Considerations
Monitors/samplers & sensors FRM or FEM or not?
Must be FRM/FEM in order to compare to NAAQS (40CFR Part 53) Collocation requirements for some types of monitoring
Ancillary equipment Dataloggers QA/QC equipment incl. flow meters, transfer standards,
calibrators, etc. Consumables
Grease/oil Filters/filter tape
Concrete pad and shelter Electricity requirements A/C or heating needs
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Regulatory Considerations
To officially compare to the NAAQS (for attainment designations or compliance) you MUST follow all requirements outlined in 40CFR Part 58
All EPA-funded projects involving data collection require approved QAPP
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Pollutants & Parameters Criteria pollutants
Particulates PM10 (particulate matter < 10 mm) PM2.5 (particulate matter < 2.5 mm)
Ozone Lead SO2 NOx CO
Air Toxics (HAPs) and/or VOCs Meteorological parameters Acid & Mercury deposition
Particle Sizes
Human Hair (~70 µm diameter)
PM2.5
(2.5 µm)PM10
(10µm)
Cross Section: (~70 µm)
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PM Filter-Based Samplers
HiVol (TSP or PM10 only), MiniVol, Partisol, others
Most HiVols & Partisols are FRM or FEM (epa.gov/ttn)
24-hour sample collected onto filter Single channel or sequential option for Partisol Filter mass weighed by lab to determine
average ambient concentration Samples can be analyzed further for
constituents (speciation)
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Filter-Based Pros & Cons
Filter-based equipment demands more resources Personnel/time Filters & other consumables Laboratory analysis is costly
Less expensive to purchase than continuous samplers
Data are not “real-time” MiniVols are more portable than larger equipment
MiniVol is not FRM or FEM MiniVol can sample PM10 or PM2.5 MiniVol data is not legally-defensible
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R&P PM2.5 Partisol FRM
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HiVol & MiniVol
14Credit: www.rpco.com
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Filters
47mm Teflon-coated Glass (PM2.5 or PM10)
47mm Quartz Fiber or pure Teflon (used for speciation)
8” x 10” Glass Fiber (PM10 HiVol) Also specialized filters for some models
See examples
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Continuous PM Monitors
Examples: TEOM, BAM, Nephelometer (some applications)
Collect samples “continuously” (readouts vary from every 5 minutes to every 1 hour)
Particles collected on filter tape or pad and weight (mass) is analyzed internally
Can be used for PM10 or PM2.5
Several models are FEM
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TEOM & BAM
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Continuous Pros & Cons
Provides data in “real-time” Continuous equipment is more
costly/fragile Automated readings and no filters means
minimized personnel time & lab costs Some consumables and maintenance Needs constantly reliable power source &
adequate shelter Requires Datalogger/DAS
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Dataloggers/DAS
Electric or electronic computing devices that record measurements from other instruments
Various programming requirements and configurations
Datalogger input connection must match sensor output connection
Helpful to understand basic electricity concepts for troubleshooting
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Datalogger Characteristics
Analog Transmits voltage reading, translated into pollutant
concentration or other parameter Typically linear relationship between outputs and
readings enables logging values anywhere within the range
“Noise” in analog connections can introduce error Digital
Transmits specific values for pollutant concentration or other parameters
Values can increase or decrease only at specific, discrete intervals and not between intervals
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Gaseous Monitoring Methods
“Passive” sampling Often a chemical reaction involved, end
sample is analyzed Spectrophotometry and UV Photometry
Measures amount of light a sample absorbs Primarily used for SO2 & Ozone
Chemiluminescence Chemical reactions gives off light of a certain
color Used for O3, NOx, SOx and H2S
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Sampling Equipment- Gaseous Pollutants
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Air Toxics/HAPs
187 Hazardous Air Pollutants (HAPs) Volatile & semi-volatile organic vapors
e.g., benzene, dioxin, formaldehyde, etc.
Heavy-metal dust, aerosols & vapors e.g., mercury, nickel, antimony, etc.
Inorganic & mineral dust, aerosols & vapors
e.g., arsenic, asbestos, etc.
Radionuclides Including radon
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Sampling Methods - HAPs
Multiple methods depending on pollutant and emission process
Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air (Method TO-1, etc.)
Compendium of Methods for the Determination of Inorganic Compounds in Ambient Air (Method IO-1, etc.)
Photo courtesy of Frank BlackCloud, Spirit Lake Tribe
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Meteorological Monitoring
Can be conducted along with ambient air monitoring Helps to identify where pollution is coming from
and/or where its impacts are greatest Some ambient air samplers & dataloggers can record
limited met data Meteorological parameters to consider
Wind speed (how far?) Wind direction (where/what direction?) Temperature (affects aerosolization of particles) Barometric pressure (impacts atmospheric conditions
affecting transport) Relative humidity (affects aerosolization of particles) Solar radiation (affects formation of ozone)
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TOWERS
WIND SENSORS
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Atmospheric Deposition
Wet Deposition (“Acid Rain”) Monitored by National Atmospheric Deposition Program
(NADP) Acid deposition occurs when pollutants (primarily SOx or
NOx) react in atmosphere with water vapor & returns to earth as precipitation (rain, snow, fog)
Measurements are made for pH and conductivity and precipitation
Dry Deposition Monitored by the Clean Air Status & Trends Network
(CASTNET) Occurs when pollutants react, but not with water Pollutants settle out of atmosphere as particles or gases
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Mercury Deposition
Mercury Deposition Network part of NADP analyzes mercury samples from wet deposition monitoring
Monitoring for elemental and inorganic mercury conducted at the source
Organic mercury (methylmercury) samples can also be collected from environmental receptors Aquatic and other wildlife Wetlands/waterways Sediments
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Typical NADP Site
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What We Just Covered
Ambient air pollution can be monitored, sampled and/or analyzed in numerous ways
Sampling types include filter-based, continuous, passive and chemical-based methods
All monitoring methods have pros and cons
Monitoring may or may not be important to meet certain needs of an air program
EPA regularly revises NAAQS standards
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