Air Quality Monitoring ENV 4101/5105 Elements of Air Pollution 3/3/20161 Aerosol & Particulate Research Lab XIE/ /tablesgraphs/figure3-en.htm Reading: Chap 7.1 & 7.2

Air Quality Monitoring  Monitoring Considerations Manual vs. automated (real-time, continuous) monitoring Sampling time Federal reference method (FRM) vs. equivalent method (EM)  Monitoring of Ambient Air Pollutants SO 2, NOx, CO, O 3 Hydrocarbons PM 10, PM 2.5  Source Sampling and Monitoring Sampling train Isokinetic sampling  Quality Assurance Programs Quality Assurance Quality Control  Air Quality Monitoring Network 3/3/20162 Aerosol & Particulate Research Lab What’s the use of ambient air quality monitoring data?

Monitoring Considerations Sampling location: limited number of fixed site monitors whose locations reflect objectives of air quality monitoring program Lower limit of detection (LOD): a sufficient amount of pollutant must be collected, f(sampling rate, duration) –Integrated sampling vs. real-time sampling –Area sampling vs. personal sampling Collection efficiency of the instrument: –Low flow rate for gas-phase contaminants (< 1 L/min) 3/3/2016Aerosol & Particulate Research Lab3 Examples of criteria for selecting ambient sampling locations? What are the objectives?

4 Differences in averaging times associated with real-time data 3/3/2016Aerosol & Particulate Research Lab Which duration should you use?

5 National Ambient Air Quality Standards PollutantPrimary Stds.Averaging TimesSecondary Stds. CO9 ppm (10 mg/m 3 )8-hour (1) (1) None 35 ppm (40 mg/m 3 )1-hour (1) (1) None Pb1.5 µg/m 3 Quarterly AveSame as Primary NO ppm (100 µg/m 3 )Annual (Arith. Mean)Same as Primary PM 10 Revoked (2) (2) Annual (2) (Arith. Mean) (2) 150 µg/m 3 24-hour (3) (3) PM µg/m 3 Annual (4) (Arith. Mean) (4)Same as Primary 35 µg/m 3 24-hour (5) (5) O3O ppm8-hour (6) (6) Same as Primary 0.12 ppm1-hour (7) (Applies only in limited areas) (7) Same as Primary SO ppmAnnual (Arith. Mean) ppm24-hour (1) (1) hour (1) (1) 0.5 ppm (1300 µg/m 3 ) 3/3/2016Aerosol & Particulate Research Lab Why different durations?

Federal Reference Methods for Criteria Pollutants PollutantReference Method SO 2 Spectrophotometry (pararosanilne method) NO 2 Gas-phase chemiluminescence CO Nondispersive infrared photometry O3O3 Chemiluminescence NMHCs Gas chromatography – FID (flame ionization detection) PM 10 Performance-approved product PM 2.5 Performance-approved product 3/3/20166 Aerosol & Particulate Research Lab

SO 2 FRM - Spectrophotometry (pararosanilne method) Air sample  potassium tetrachloromercurate solution  HgCl 2 SO 3 -2  react with HCHO and colorless pararosaniline hydrochloride  red-violet product  measured spectrophotometrically  SO 2 concentration EM – FT- IR Spectrometry (Absorption of IR by SO 2 in the air  SO 2 concentration) 3/3/20167 Aerosol & Particulate Research Lab

3/3/2016Aerosol & Particulate Research Lab8 SO 2 EM – UV Fluorescence 1) UV light excites SO 2 to a higher energy state SO 2 + hv 1  SO 2 * 2) Decay of the excited SO 2 *, emitting a characteristic radiation SO 2 *  SO 2 + hv 2

NO – NO 2 – NOx FRM – Gas-Phase Chemiluminescence Chemiluminescence: emission of light from electronically excited chemical species formed in chemical reactions. NO + O 3  NO 2 * + O 2 NO 2 *  NO 2 + hv Measurement of NO 2 : conversion of NO 2 to NO, and subsequent measurement by chemiluminescence. 2NO 2 + Mo  3 NO + MoO 3 Possible interference: N-containing compounds  higher measured NO 2 Can you design an instrument that can measure the concentration of both NO and NO 2 in the air? 3/3/20169 Aerosol & Particulate Research Lab EM – FT- IR Spectrometry

CO FRM – Nondispersive Infrared (NDIR) spectrometry CO strongly absorbs infrared energy at certain wavelengths. Detection device: two cylindrical cells, a sample and a reference cell. Difference in infrared energy in the two cells  concentration of CO Sample Cell Reference Cell CO ~ IR ~ Detection 3/3/ Aerosol & Particulate Research Lab

O3O3 FRM – Chemiluminescence Light emissions produced on reaction of O 3 with ethylene (C 2 H 4 ). C 2 H 4 flammable – replaced by Rhodamine B dye embedded in a disk Rhodamine B does not attain a stable baseline rapidly after exposure to O 3 EM – UV Photometry Absorption of UV light (254 nm) by O 3 and subsequent use of photometry to measure the reduction of UV energy O3O3 UV light (254 nm) Detector O3O3 What would cause an interference on a UV photometry O 3 monitor? 3/3/ Aerosol & Particulate Research Lab

NMHCs FRM – Gas Chromatography - FID Time Intensity Generate an electronic signal when a gas other than the carrier gas elutes from the column. GC-Detector: Stationary and mobile phases 3/3/ Aerosol & Particulate Research Lab

NMHC FID – Flame Ionization Detection: –Combustion of organic substances –Positive ions (+) and electrons (-) are formed when burned – change in current 3/3/2016Aerosol & Particulate Research Lab13 −Mass sensitive rather than concentration sensitive

Particulate Pollutants PM 10 sampler with size-selective inlet Impaction and filtration are the primary PM collection principles Measure the weight of exposed and clean filters High-volume sampler (Hi-Vol) Typical sampling duration – 24 h PM 10 Sampler Remove particles > 10 µm by impaction on a greased surface Particles < 10 µm collected on a quartz glass fiber filter What does the PM 10 sampler measure? Number or mass concentration of particles? Animation – PM 10 Impactor 3/3/ Aerosol & Particulate Research Lab

Dichotomous Sampler How can a Dichotomous sampler measure coarse (PM ) and fine (PM 2.5 ) particles? Animation – Virtual Impactor TEOM Series 1400ab Ambient Particulate Monitor Thermo Electron Co. Equivalent method: TEOM Measure PM 10, PM 2.5, TSP Tapered element oscillating microbalance Real-time measurement of particle mass collected on a filter 3/3/ Aerosol & Particulate Research Lab

Cascade Impactor Animation – Cascade Impactor How can we collect different sizes of particles using cascade impactor? Aerosol flow In Clean air out 3/3/ Aerosol & Particulate Research Lab

Source Sampling and Monitoring Stack Sampling of PM 1)Probe inserted into the stack 2)Temperature sensor 3)Pitot tube – gas velocity and flow rate 4)Two-module sampling unit Isokinetic Sampling 1)Particles – inertial forces 2)Samples must be collected at the same rate of low as the stack gas 3/3/ Aerosol & Particulate Research Lab What’s the use of source emission data?

Isokinetic Sampling 3/3/2016Aerosol & Particulate Research Lab18 Fig 8 -2, Aerosol Measurement, 2nd Edition, 2001

Continuous Emission Monitoring (CEM) Certain utilities and industrial sources are required to measure stack emission continuously SO 2, NO 2, opacity, CO 2, TRS, H 2 S, Hg 3/3/2016Aerosol & Particulate Research Lab19 Opacity Ringlemann chart Compare plume darkness to Ringlemann chart by trained smoke readers Averages of measurements of ¼ or ½ minute over an hour Simple, low cost, legal acceptance

Accuracy, Precision and Bias Accuracy is a combination of random (precision) & systematic (bias) errors. Which of the 3 cases has the highest accuracy? Why? 3/3/ Aerosol & Particulate Research Lab Relative Error: Coefficient of variation:  Bias  Precision

Calibration Often used for adjusting bias-type errors Measured values are compared to standard reference values (for pollutant concentration) or standard airflow measuring techniques/devices (for volume air flow) Primary vs. secondary standard for flow: traceable to the National Institute of Standards and Technology (NIST) –Primary: bubble meter –Secondary: wet or dry test meters calibrated by bubble meter Gas standards: traceable to a NIST reference material –CO, SO 2, NO 2, NO: available in cylinder gas or permeation tubes –O 3 : NIST certified O 3 generator 3/3/2016Aerosol & Particulate Research Lab21

Quality Assurance Programs Quality Assurance (QA) Setting policy and overseeing management controls Planning, review of data collection activities and data use Setting data quality objectives, assigning responsibilities, conducting reviews, and implementing corrective actions Goal: Valid and reliable air quality monitoring data Quality Control (QC) Technical aspects of data quality programs Implementation of specific QC procedures: calibrations, checks, replicate samples, routine self- assessment, and audits It is federal rule to document QA/QC efforts ! 3/3/ Aerosol & Particulate Research Lab

Air Quality Monitoring Network State and Local Air Monitoring Stations (SLAMS) Highest pollutant concentrations Representative concentrations in areas of high population density Impact of major emission sources Regional background concentrations Extent of pollutant transport among populated areas Welfare-related impacts in more rural and remote areas National Air Monitoring Stations (NAMS) Urban area, long-term air quality monitoring network Air quality comparisons and trends analysis Photochemical Assessment Monitoring Stations (PAMS) Monitor O 3 and photochemical air pollutants Clean Air Status and Trends Network (CASTNet) Primary source for rural O 3 level and dry atmospheric deposition 3/3/ Aerosol & Particulate Research Lab National Atmospheric Deposition Program (NADP) Assess the problem of atmospheric deposition and its effects on aquatic and terrestrial ecosystems (H +, NH 4 +, SO 4 2-, NO 3 -, Cl -, Ca 2+, Mg 2+, K +, Hg)

Quick Reflections  Monitoring Considerations Manual vs. automated (real-time, continuous) monitoring Sampling time Federal reference method (FRM) vs. equivalent method (EM)  Monitoring of Air Pollutants SO 2, NOx, CO, O 3 Hydrocarbons PM 10, PM 2.5  Source Sampling and Monitoring Sampling train Isokinetic sampling  Quality Assurance Programs Quality Assurance Quality Control  Air Quality Monitoring Network 3/3/ Aerosol & Particulate Research Lab