Air QualityJanuary AMS Short Course on Instrumentation 1 Air Quality Monitoring Melanie A. Wetzel Desert Research Institute University of Nevada, Reno and

Air QualityJanuary AMS Short Course on Instrumentation 2 Goals ? Introduce meteorological aspects of air quality ? Summarize monitoring needs for atmospheric gases and particulates ? Describe measurement systems ? Discuss evaluation methods

Air QualityJanuary AMS Short Course on Instrumentation 3 Characteristics of Air Quality j Gas concentrations (organic and inorganic) j Aerosol number concentration j Aerosol chemical composition j Relative abundances of interacting gases and aerosol j Visibility and spectral attenuation j Abundance of water vapor (photochemistry, respiration) j Solar radiation and UV radiation distribution j Radioactive gas and particle concentration j Transport processes j In-cloud transformation and deposition j Surface-air exchange and surficial effects

Air QualityJanuary AMS Short Course on Instrumentation 4 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 QualityJanuary AMS Short Course on Instrumentation 5 Air Motions = Both horizontal and vertical velocities control the transport of pollutants = 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 QualityJanuary AMS Short Course on Instrumentation 6 Radiative Interactions Spectral nature of photodissociation Actinic fluxes Photolysis rates Effects of gas-particle mixtures Variation due to altitude, humidity NO 2 dissociation leads to reactions that form H 2 SO 4 and HNO 3

Air QualityJanuary AMS Short Course on Instrumentation 7 Deposition by Rain, Snow and Fog Frontal passage and cloud systems influence aerosol concentrations

Air QualityJanuary AMS Short Course on Instrumentation 8 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 QualityJanuary AMS Short Course on Instrumentation 9 Regulatory Guidelines National Ambient Air Quality Standards New regulations in progress Importance of locally-specific monitoring programs

Air QualityJanuary AMS Short Course on Instrumentation 10 Time Resolution of Aerosol Monitoring Grab Sampling Sequential Samplers Continuous Samplers

Air QualityJanuary AMS Short Course on Instrumentation 11 Particulate Size Distributions Health impacts are determined by size Interactions with cloud and other particles also size-dependant Deliquescence Coagulation

Air QualityJanuary AMS Short Course on Instrumentation 12 Aerosol Sensor Types Filter Sampler Dichotomous Sampler Beta Attenuation Monitor Aethalometer Differential Mobility Analyzer

Air QualityJanuary AMS Short Course on Instrumentation 13 Aerosol Chemistry Bulk sampling Size-segregated sampling Single particle analysis

Air QualityJanuary AMS Short Course on Instrumentation 14 Laboratory Analysis of Filters X-ray Diffraction Wet Chemistry Neutron Activation Weighing

Air QualityJanuary AMS Short Course on Instrumentation 15 Gas Species and Sources Nitrogen Oxides (NO x ) Ozone (O 3 ) Sulfur Dioxide (SO 2 ) Carbon Monoxide (CO) Methane (CH 4 ) Ammonia (NH 3 ) Carbon Dioxide (CO 2 ) Fluorocarbons (FC’s)

Air QualityJanuary AMS Short Course on Instrumentation 16 Gas Sampling Absorption: continuous-flow photometric techniques such as non-dispersive infrared analyzer or tunable diode absorption spectroscopy; chemical analysis from bubbler or impinger collection Adsorption: collection of molecules, then desorption and analysis such as by gas chromatography Condensation: cold trap captures condensed molecules which are then processed through chemical or photometric techniques Grab Samples: evacuated canister, flask used to capture samples for laboratory analysis

Air QualityJanuary AMS Short Course on Instrumentation 17 Gas Detection UV Absorption Spectroscopy Laser Spectroscopy Gas Chromatography Gas Correlation Radiometry Chemical Ionization Mass Spectrometry Chemiluminescence Resonance Fluorescence

Air QualityJanuary AMS Short Course on Instrumentation 18 Remote Spectroscopic Observations Solar extinction measurements Automobile exhaust sensing Lidar profiling Long-path transmissometer Development of satellite sensors

Air QualityJanuary AMS Short Course on Instrumentation 19 Airborne Sampling Techniques Aircraft Continuous Grab Samples Tetherballoon Boundary-layer sampling Sondes Ozone profiles Aerosol profiles

Air QualityJanuary AMS Short Course on Instrumentation 20 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.