2011 Air Chemistry Study at the Boulder Atmospheric Observatory

“Nitrogen, Aerosol Composition and Halogens on a

Tall Tower” (NACHTT)

February 16 – March 13, 2011

Photos: Rolf Sander

Steven S. Brown NOAA Earth System Research Laboratory

Boulder, CO

Scientific Goals – January 7, 2011

1.  Understand winter halogen activation 2.  Obtain an improved inventory for chloride

3.  Improved understanding of inorganic aerosol thermodynamics and relationships to heterogeneous processes listed above

4.  Characterize wintertime heterogeneous uptake efficiency of N2O5

5.  Wintertime radical reservoirs and budgets

Post-Study Additions

6.  Aerosol composition and sources within the Denver “Brown Cloud” 7.  Emissions from the oil and gas industry

Instruments & Participants - BAO Tower Species Instrument Investigators

NO, NO2, NO3, N2O5, O3 CRDS Wagner, Young, Dubé, Brown

ClNO2, Cl2, N2O5 CIMS (I-) Riedel, Thornton (UW)

HCl, HNO3, HONO, etc. CIMS (acetate) Vandenboer, Roberts

Aerosol Composition AMS Ozturk, Bahreini, Middlebrook

Aerosol Size Distribution UHSAS Brock

Speciated VOCs Canister samples Sive (UNH / Appalachian State)

Height Data on Carriage Counter, GPC Dubé

Met Data on Carriage Sonics, RH probe, etc.

Wolfe, Williams, Wagner

Tower server, ground communication & Control

Jameson, Wagner, Dubé

PISA + BAO Tower

Instruments & Participants - Ground Site Species Instrument Investigators

HCl, HNO3, NH3, HCOOH, CH3COOH, soluble Br- (gas and particle phase)

Mist Chamber / IC Pszenny (UNH), Keene (UVA)

Size resolved aerosol ionic composition, 0.25 - 20 µm

Cascade Impactor / IC Pszenny (UNH), Keene (UVA)

HCl CRDS Yalin / Hagen (CSU)

Micrometeorology Tethered balloon Meillier (CU)

VOCs PTR TOF / GC Warneke, Gilman, Lerner, Graus de Gouw

VOCs Canister samples Sive (UNH)

OH CIMS Kim (NCAR)

Photolysis rates (NO2, O3) Filter radiometer Lerner

Ozone UV absorption Williams

Ground Site Layout

HCl CRDS + PiLS

VOC / OH Trailer

Sample Tower

UVA / UNH Container

18 m Balcony

NOx Profiles

NOx = NO + NO2

Aerosol Profiles

Note: Dry aerosol volume - substantial RH correction would skew nighttime distribution

NOx vs. Wind Direction

• Westerly (downslope) flow observed both day and night, uniformly warm • Night has: SW (warm), SE (cooler) and NE (cold) sectors

Aerosol Volume / Mass vs. Wind Direction • Day: W = Downslope flow, low aerosol E = Upslope flow, higher aerosol NE = Highest aerosol • Night: SW = Clean SE, NE = Both high aerosol Eastern plains (NE) source of high aerosol but moderate NOx. Ammonia source ?

VOC inlet

VOC trailer

~8 m

In-­‐situ  GC-­‐MS:  •     5  min  sample  acquisi6on  •     1  sample  every  30  min  •     44  species  analyzed  for  NACHTT  

•     C2  to  C12  hydrocarbons  •     C6-­‐C9  aroma6cs,  OVOCs,  etc.  

PTR-­‐MS:  1.  Quadrupole  MS  

•  1  min  6me  base  posted  •  14  masses  scanned  •  Unit  mass  resolu6on  

2.  HR  Time-­‐of-­‐flight  MS  •  Full  mass  spectra  •  High  mass  resolu6on  

VOCs in Cans

20 m

Canister  Samples:  •     Discrete  samples  once  an  hour  

VOC data courtesy of: Jessica Gilman, Carsten Warneke, Brian Lerner, Martin Graus, Joost de Gouw

2.0

1.5

1.0

0.5

0.0

Ben

zene

(ppb

v)

2/25/2011 2/27/2011 3/1/2011 3/3/2011 3/5/2011

Date and Time (MST)

PTR-MS GC-MS Canisters

0.001

0.01

0.1

1

10

100

Mix

ing

Rat

io (p

pbv)

Etha

nePr

opan

en-

Buta

nei-B

utan

en-

Pent

ane

i-Pen

tane

n-H

exan

en-

Hep

tane

Cyc

lope

ntan

en-

Oct

ane

n-N

onan

en-

Dec

ane

n-U

ndec

ane

Tolu

ene

Benz

ene

m&p

-Xyl

enes

o-Xy

lene

Benz

ene_

1eth

ylBe

nzen

e_13

5trim

ethy

lEt

hene

Prop

ene

Styr

ene

Isop

rene

Ethy

ne

Average Mixing Ratio ± St. Dev.

C2-­‐C12  Alkanes  

Aroma0cs  

Alkenes  

Average  Mixing  Ra0o  ±  Std.  Dev.    

  The  site  experienced  wind  from  all  sectors      Highest  winds  were  predominately  from  the  west  

  Lower  wind  speeds  from  12  am  to  12  pm,  higher  wind  speeds  in  the  aZernoon  

Alkane  mixing  ra6os  generally  an6-­‐correlate  with  local  wind  speeds  

Height  =  10  m  

-0.4 -0.2 0.0 0.2 0.4

Ethane

Propane

n-Butane

i-Butane

n-Pentane

i-Pentane

Cyclopentane

n-Hexane

n-Heptane

n-Octane

Benzene

n-Nonane

Toluene

m&p-Xylenes

n-Decane

n-Undecane

o-Xylene

Benzene_1ethyl

Benzene_vinyl (Styrene)

Benzene_135trimethyl

Ethene

Propene

Ethyne

•  Look  for  correla6ons  between  VOCs  in  order  to  iden6fy  a  source  signature  

•  Local  •  Ground-­‐level  •  Con6nuous  emissions  •  Primary  source  •  Enriched  in  alkanes  

     Propane:    Natural  gas  tracer          C2-­‐C9  alkanes  and  Benzene    

         Ethyne:          Urban/on-­‐road  tracer          Alkenes  and  C10+  alkanes            Toluene  and  C8,  C9  aroma6cs      

Δr  =  rpropane  -­‐  rethyne  

60

40

20

0

Num

ber o

f Occ

uran

ces

1 10 100Propane (ppbv)

Average Propane: 2006 Houston, TX 2010 Pasadena, CA 2011 Erie, CO

60

40

20

0

Num

ber o

f Occ

uran

ces

1 10 100Ethyne (ppbv)

Average Ethyne: 2006 Houston, TX 2010 Pasadena, CA 2011 Erie, CO

   Rachel  Russo,  Andrew  Hart,  Bob  Swarthout,  Yong  Zhou,  Barkley  Sive  

VOC  Measurements  from  the  Tower    

18  February  –  13  March  2011    

Hourly  samples  from  20  m  Profile  samples  throughout  campaign  (usually  2-­‐3  per  day)  

 Sample  heights  (m):    50,  100,  150,  200,  250    

All  samples  pressurized  to  ~30  psig  using  a  metal  bellows  pump  

0

5000

10000

15000

20000

25000

30000

35000

0

5000

10000

15000

20000

25000

30000

35000

N

NW

W

SW

S

SE

E

NE

ethanepropanen-butane

0

100

200

300

400

500

600

700

800

0

100

200

300

400

500

600

700

800

N

NW

W

SW

S

SE

E

NE

etheneethynetoluene

Wind  Rose  Mean  mixing  ra6os  in  45o  wind  sectors  

Oil and Gas Urban

Propane (pptv)

0 8000 16000 24000

Hei

ght (

m)

0

50

100

150

200

250

300

2-24 01:20-01:552-24 07:25-08:002-24 16:20-16:452-24 23:20-23:45

Ethene (pptv)

100 150 200 250 300 350 400 4500

50

100

150

200

250

300

Ethyne (pptv)

350 400 450 500 550 600 650 700

Hei

ght (

m)

0

50

100

150

200

250

300n-Pentane (pptv)

500 1000 1500 2000 2500 3000 35000

50

100

150

200

250

300

2-24 01:20-01:552-24 07:25-08:002-24 16:20-16:452-24 23:20-23:45

NMHC  Profiles  

Oil and Gas

Urban

Summary  

•  Ground-­‐based  measurements  can  be  “de-­‐coupled”  from  tower    –  Low  surface  winds  and  shallow  mixed  layers,  par6cularly  at  night  –  Higher  mixing  ra6os  and  greater  variability  of  VOCs  closer  to  the  surface  

•  Large  source  of  alkanes  from  local  natural  gas  opera6ons  –  Ethane  and  Propane:    Averages  over  10  ppb  with  maximums  over  100  ppb  –  Strong  correla6on  among  C2-­‐C9  alkanes  and  benzene  

•  Typical,  winter-­‐6me  “urban”  background  –  Stronger  correla6ons  among  C7-­‐C9  aroma6cs,  alkenes,  and  ethyne  

•  VOC  oxida6on  appears  to  be  minimal  –  Primary  emissions  will  have  longer  atmospheric  life6mes  –  Decreased  produc6on  of  secondary  by-­‐products  such  as  OVOCs  and  ozone