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.