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EAS 4/8803: Experimental Methods in AQ. Week 11: Air Quality Management (AQM) Clean Air Act (History, Objectives, NAAQS) Emissions and Atmospheric Trends (Links) Principal Measurement Techniques (NOx, CO, SO 2 ) Measurement of CO (Exp 5)

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Eas 4 8803 experimental methods in aq
EAS 4/8803: Experimental Methods in AQ

Week 11:

Air Quality Management (AQM)

Clean Air Act (History, Objectives, NAAQS)

Emissions and Atmospheric Trends (Links)

Principal Measurement Techniques (NOx, CO, SO2)

Measurement of CO (Exp 5)

NDIR Method (Interferences, Stability, DL, Precision, Accuracy)

Controlling O3 and PM2.5

Principal Measurement Techniques (O3, PM2.5)

Atmospheric Transport & Photochemistry (NOx vs VOC, SOA)

Controlling O3, Emissions and Trends (GA)

Measurement of O3 (Exp 6)

UV Absorption (Interferences, Stability, DL, Precision, Accuracy)

EAS 4/8803






Eas 4 8803 experimental methods in aq

Can we expect recent cool & wet summers to continue?

Nonattain

“Bad”

NAAQS

Attain

“Good”

EAS 4/8803


Eas 4 8803 experimental methods in aq

If we can’t depend on theweather, then what canwe control?

Volatile Organic

Compounds (VOCs)

+

Nitrogen

Oxides (NOx)

Ozone (O3)

Smog

Combustion

Processes

Fuels, Paints,

Solvents, &

Vegetation

EAS 4/8803


Photochemical processes leading to o 3 and pm
Photochemical Processes Leading to O3 and PM

An Assessment of Tropospheric Ozone Pollution, A North American Perspective, NARSTO, National Acad. Press, 2000.

NOz

SOA

EAS 4/8803


Eas 4 8803 experimental methods in aq

VOC Sources in Columbus MSA (2000)

Total: 385 tons per day

  • Anthropogenic Sources:

  • Gasoline Vehicles

  • Solvents (Paints, Automotive Products, Adhesives, etc.)

  • Carbon Black

  • Lawn & Garden

  • Bakeries

EAS 4/8803


Eas 4 8803 experimental methods in aq

Ozone Isopleths

Area of effective VOC control (most often highly populated areas)

Constant [O3]

NOx control effective(areas with high biogenics)

Nitrogen Oxides (NOx)

High [O3]

Low [O3]

Volatile Organic Compounds (VOC)

EAS 4/8803


Eas 4 8803 experimental methods in aq

Total: 42 tons per day

NOx Sources in Columbus MSA (2000)

EAS 4/8803


Implementation of nox controls since 2000 full implementation expected by 2007
Implementation of NOx Controls Since 2000,Full Implementation Expected by 2007

  • Annual, stricter vehicle emissions inspections

  • Open burning ban in 45 counties

  • Georgia Power phasing in NOx controls

  • 30 ppm sulfur gasoline in 45 counties

  • GA Power plants achieve NOx reduction in 45 counties

  • Stricter peaking generator rule

  • Large industrial source NOx reductions

EAS 4/8803


Eas 4 8803 experimental methods in aq

2007 NOx Emissions in GA by Region and Source

If Fully Implemented

Georgia Total: 1480 tons/day

Alabama Total (not shown): 998 tons/day

EAS 4/8803


Eas 4 8803 experimental methods in aq
Significant improvements in regional air quality by 2007with no additional controls (current SIP fully implemented)

EAS 4/8803


Eas 4 8803 experimental methods in aq

But will these existing controls be enough?

Region Maximum Daily Peak 8-hour Ozone

Observed / Simulated 2000  2007

Estimated Change in Regional Peak 8-hour Surface Ozone from August 17th, 2000 to 2007 under the Existing Federal Control Strategies (ppbv)

EAS 4/8803


Eas 4 8803 experimental methods in aq

Nonattain

“Bad”

NAAQS

Attain

“Good”

EAS 4/8803


Eas 4 8803 experimental methods in aq

Nonattain

“Bad”

NAAQS

Attain

“Good”

Reality

Goal

Theory

EAS 4/8803


Clarification co accuracy assessment

COspan4

5 V

COspan3

COspan2

D[COnom]4

CO Analyzer Signal (V)

D[COnom]3

zero-mode

zero-mode

COspan1

D[COnom]2

D[COnom]1

COZA

COZA

Zero-air

COspan1,0

COspan4,0

Zero-air/Zero-mode = baseline

CO0

CO0

Time (minutes)

Clarification CO Accuracy Assessment

COsensi (ppb/V) = D[COnomi] / DCOspani

ZTeffi = (COspani – COspani,0) / (COspani – CO0) > 0.9!!

COnet (V) = COraw – CO0ipol  CO (ppb) = COnet * COsens

DL (ppb) = t * STD(CO0*) * COsens

P (%) = t * STD(COsens) / AVG(COsens) *100

A1 (%) = (slope{D[COnomi] / DCOspani} -1000)/1000 *100

Rel. diff. of slope to nom. detector sens = 1000 ppb/V

A2 (%) = {S[(s(Xj))2 (dCOsens/dXj)2]}1/2

…from error propagation analysis.

EAS 4/8803


O 3 method uv absorption
O3 Method: UV Absorption

I = I0 e-e c l

e = 308 cm-1(@STP: 0oC, 760Torr)

l = 38 cm

254 nm

EAS 4/8803


O 3 primary standard calibrator

To analyzer under cal

internal vent

[O3]nomC

capped

Zero Air

254 nm

O3 Primary Standard Calibrator

I = I0 e-e c l

e = 308 cm-1(@STP: 0oC, 760Torr)

l = 38 cm

EAS 4/8803


Goals
Goals

  • Basic Functionality Test

  • Determine Analyzer Performance

    (DL, sensitivity, precision and accuracy)

  • Determine the NO2 Photolysis Rate from PSS assumptions and discuss

  • Discuss differences in O3 measured between outdoor and indoor air

EAS 4/8803


1 functionality tests
1. Functionality Tests

  • Detectors Performance check

  • System Leaks and Pump check

  • Ozone scrubber efficiency check

EAS 4/8803


2 analyzer performance

O3span1

10 V

O3span2

O3span3

D[O3nom]1

O3 Analyzer Signal (V)

D[O3nom]2

O3span4

D[O3nom]3

D[O3nom]4

O30

O30

Zero-air

Time (minutes)

2. Analyzer Performance

O3sensi (ppb/V) = D[O3nomi] / DO3spani

O3 (ppb) = O3raw * O3sens

DL1 (ppb) = t * STD(O30) * O3sens

DL2 (ppb) = i-cept{D[O3nomi] / DO3spani}

P (%) = t * STD(O3sensi) / AVG(O3sensi) *100

A1 (%) = (slope{D[O3nomi] / DO3spani} -20)/20 *100

Rel. diff. of slope to nom. detector sens = 20 ppb/V

A2 (%) = {S[(s(Xj))2 (dO3sens/dXj)2]}1/2

…from error propagation analysis.

Groups look for their individual “O3raw__.xls” data file on http://arec.gatech.edu/teaching

EAS 4/8803


3 1 determine j no2 from pss
3.1 Determine jNO2 from PSS

Assuming ambient O3 in photochemical steady-state (PSS) with NO and NO2, calculate jNO2 and discuss by comparing with literature values.

NO2 + hv (jNO2) NO + O (R1)

O + O2 + M  O3 + M (fast, not rate-limiting) (R2)

O3 + NO (k3) NO2 + O2 (R3)

Assuming first-order homogeneous reaction (R3),and

d[NO2]/dt = k3 [O3][NO] - jNO2 [NO2] = 0

yielding

jNO2 = k3 [NO] [O3] / [NO2] in s-1

EAS 4/8803


3 2 discuss j no2 diurnal profile
3.2 Discuss jNO2 Diurnal Profile

The photolysis rate coefficients (jNO2) provided here exemplarily, were calculated using a radiative transfer model (Zeng et al., 1996), which is based upon the Stamnes discrete ordinates model modified to solve the radiative transfer equation in pseudo-spherical coordinates. The discrete ordinates code was run with eight streams. The surface albedo was assumed to be 5%, and the total aerosol optical depth was parameterized in terms of visual range. The model assumes a constant visual range of 25 km for the lowest 2 km, a logarithmically decreasing aerosol optical depth above this, as well as a single scattering albedo of 0.99 and an asymmetry parameter of 0.61, which are both wavelength-independent. The jNO2 values were then scaled linearly by the flat-plate Eppley-UV (290-385 nm) measurements and by their ratio to the radiative transfer model clear-sky irradiance to account for the actual cloud and aerosol effects on jNO2. This scaling helps to correct for any errors made by the visual range assumptions.

Consult references Volz et al., 1996, and Zeng et al., 1996.

Retrieve above sample data as “jNO2sampleday.xls” from

http://arec.gatech.edu/teaching

EAS 4/8803


4 discuss o 3 indoor vs outdoor differences
4. Discuss O3 indoor vs outdoor differences

  • Determine indoor and outdoor O3 mixing ratios for a sample data set.

  • Evaluate diurnal profiles of both individually and as difference.

  • Discuss observed differences.

Look for “O3inoutday.xls”

At http://arec.gatech.edu/teaching

EAS 4/8803