Air Quality January 2001 -- AMS Short Course on Instrumentation
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Air Quality Monitoring Air Quality Monitoring
Melanie A. Wetzel
Desert Research Institute
University of Nevada, Renoand
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Goals
Introduce meteorological aspects of air quality
Summarize monitoring needs for atmospheric gases and particulates
Describe measurement systems
Discuss evaluation methods
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Characteristics of Air Quality
Gas concentrations (organic and inorganic) Aerosol number concentration Aerosol chemical composition Relative abundances of interacting gases and aerosol Visibility and spectral attenuation Abundance of water vapor (photochemistry, respiration) Solar radiation and UV radiation distribution Radioactive gas and particle concentration Transport processes In-cloud transformation and deposition Surface-air exchange and surficial effects
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Role of Meteorological Processes
Diurnal nature of atmospheric heating/cooling requires monitoring of temperature, humidity and radiation profiles
Thermodynamic stability and terrain-controlled flow determines air parcel mixing and transport
Cloud formation and precipitation are critical for transformation and
removal of pollutants
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Air Motions
Both horizontal and vertical velocities control the transport ofpollutants
Velocity measurements using mechanical and sonic anemometers and wind vanes provide 2- and 3-component vector data
Particle settling speed (size, density and shape) also influences deposition
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Radiative Interactions
Spectral nature of photodissociationActinic fluxesPhotolysis ratesEffects of gas-particle mixturesVariation due to altitude, humidity
NO2 dissociation
leads to reactions
that form H2SO4
and HNO3
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Deposition by Rain, Snow and Fog
Frontal passage and cloud systems influence aerosol concentrations
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Receptor Sites and Subjects
Source and receptor measurement strategies should account for time of day and day of week preferential exposure, indoor vs. outdoor exposure, and other factors of transport and dosage
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Regulatory Guidelines
National Ambient Air Quality Standards
New regulations in progress
Importance of locally-specific monitoring programs
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Time Resolution of Aerosol Monitoring
Grab SamplingSequential SamplersContinuous Samplers
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Particulate Size Distributions
Health impacts are determined by sizeInteractions with cloud and other particles also size-dependantDeliquescenceCoagulation
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Aerosol Sensor Types
Filter SamplerDichotomous SamplerBeta Attenuation
MonitorAethalometerDifferential Mobility
Analyzer
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Aerosol Chemistry
Bulk samplingSize-segregated samplingSingle particle analysis
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Laboratory Analysis of Filters
X-ray DiffractionWet Chemistry
Neutron Activation
Weighing
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Gas Species and Sources
Nitrogen Oxides (NOx)Ozone (O3)Sulfur Dioxide (SO2) Carbon Monoxide (CO) Methane (CH4) Ammonia (NH3)Carbon Dioxide (CO2)Fluorocarbons (FC’s)
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Gas Sampling
Absorption: continuous-flow photometric techniques such as non-dispersive infrared analyzer or tunable diode absorption spectroscopy; chemical analysis from bubbler or impinger collectionAdsorption: collection of molecules, then desorption and analysis such as by gas chromatographyCondensation: cold trap captures condensed molecules which are then processed through chemical or photometric techniquesGrab Samples: evacuated canister, flask used to capture samples for laboratory analysis
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Gas Detection
UV Absorption SpectroscopyLaser SpectroscopyGas ChromatographyGas Correlation Radiometry Chemical IonizationMass SpectrometryChemiluminescenceResonance Fluorescence
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Remote Spectroscopic Observations
Solar extinction measurements
Automobile exhaust sensing
Lidar profiling
Long-path transmissometer
Development of satellite sensors
Air Quality January 2001 -- AMS Short Course on Instrumentation
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Airborne Sampling Techniques
Aircraft Continuous Grab Samples
Tetherballoon Boundary-layer sampling
Sondes Ozone profiles Aerosol profiles
Air Quality January 2001 -- AMS Short Course on Instrumentation
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References
Brasseur, G.P., J.J. Orlando and J.G. Tyndall, 1999: Atmospheric Chemistry and Global Change, Oxford Press, New York, 654 pp.
Godish, T., 1997: Air Quality. Lewis Publishers, New York, 448 pp.Reist, P., 1999: Aerosol Science and Technology, McGraw-Hill.
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