Descriptive Model of PM Pollution

in Baltimoreas derived from

Analysis of Components of Discrete Episodes at

the Ponca St. Supersite

John Ondov

Department of Chemistry and Biochemistry

University of Maryland, College Park, MD 20742

jondov@umd.edu; 301 405 1859

www.chem.umd.edu/supersite

Baltimore Supersite Study Area

C u r t is C r e e k C lu s te r

A t o c h e m

R e n d e r in g p a n t C o a s t G u a r d

Typical MidAtlantic Seaport CityPopulous, heavy industry, So. BaltimoreComplex meteorology

Major N.-S. transportation corridor

End member Washington - Boston Megalopolis

Variable Aerosol agelocal, 50 km, 100’s km source regionsAppalachian Cloud-processed sulfate

Environmental JusticeDowntown, weakly influencedSo. Baltimore 10-X PAH, Metals

1.7-X deaths via pulmonary disease

Interpretive Context25 yrs receptor modeling in regionEPA and AEOLOS studies in BaltimoreIMPROVE site, Shennandoah Nat. Park

Health Effects StudiesJHU & UMAB

Strategically located to assess urban,

industrial, and traffic influences

Industrial Sector

30o

Measurements

– Primary Site: Ponca St., East Baltimore9.5 months: March – November, 2003

– Maximum temporal, size, compositional resolution• PM2.5, EC,OC, Nitrate, Sulfate,

• Metals, Organic compounds

• PAMS VOC, CO, NOx, NO, NO2, O3

• LIDAR, Single Particle MS

• SMPS + APS size distributions 10 nm to 20 µm

– Measurement resolution 5 min, 10 min, 30 min, 1 hr, 3 hr,plus 24 Hr FRM mass and speciation

Interpretive Context

• PM air pollution may be viewed as occurring in a series of

discrete meteorologically driven discrete episodes

• Transients often caused by one or two components

• Local vs. distant sources indicated by

– Temporal behavior of constituents and marker species

– Size distribution parameters

– Detailed Analysis of episodes

Outline

• PM2.5 Episodes in 2002 (30 min data)

• Summary of major features of 6 worst

• Detailed description of highly time resolved data

for worst summer and cool weather episodes

• Features of major components

Mar Mar Apr Apr Apr

PM2.5, µg/m3

0

20

4060

80

100

Aug Aug Sep Sep Sep

PM2.5, µg/m3

0

20

40

6080

100

Oct Oct Nov Nov Dec Dec Dec

PM2.5, µg/m3

0

20

4060

80

100

May May Jun Jun Jul Jul Jul

PM2.5, µg/m3

020

40

60

80

100

30-minPM2.5 Concentrations: 2002show: series of discrete episodes of hours to 2 or 3 days duration

reconstructedA B C

D

EF

Canadian

Smoke

PM2.5 Statistics: 9.5 months, 2002

w/Canadian w/o Canadian

Smoke Smoke*

Daily means: 3.5 to 85.6 3.5 to 64

Annual mean 16.9 15.8±13

No. daily exceedences 2 ~1

No. daily means > 30 µg/m3 29

(i.e., 16.9 + 13)

*Episode B; M\maximum 30 min concentration was 198 µg/m3

6 worst episodes described in Park et al., 2005

2 will be described in this talk

Ozone (ppb) Ambient temp (°C) Relative humidity (%)Maxima NOx and CO,

ppb

Episode Date Type Avg. Range Avg. Range Avg. Range NOx CO

A June 24-25 Regional Haze 84 26-132 29.8 23.7-35.4 57.5 32-77 110 800

B July 6-8 Canadian Smoke - - 25.6 19.7-33.8 45.4 28-70 155 1600

C July 18-19 Regional Haze 70 14-91 29 23.2-34.0 57.9 38-81 130 800

D Aug.12-14Reg Haze + Local

Traffic 76 22-122 29.2 21.6-35.6 53.8 35-79 300 1800

E Oct. 2-5 Regional Haze 35 1-57 24.8 17.5-30.4 69.2 36-91 180 1300

F Nov. 20-21 Local Traffic 2 0-6 8.4 3.1-14.5 83.2 48-98 780 2800

Ozone mixing ratios represent measurements made between 10:00 and 20:00 hours.1

1

Characteristics of Six Worst PM2.5 Episodes

Baltimore Supersite, Ponca St., 2002

Episode durations: 2 to 4 days

Summer haze: high O3, hot, low NOx & CO

Fall local sources: low O3, cool, high NOx & CO

Concentrations

Table 2. Concentrations of PM2.5 mass and major chemical species for 6 pollution episodes.

PM2.5, µg/m³ Constituent expressed as indicated, µg/m³

Episode Interval TEOM Reconstructed (NH4)2SO4 OM EC NH4NO3

A Episode Avg.¹ N/A 55¹, 62² 36 16 1.2 1.7

Regional Haze Episode Range¹ 43 - 77 28 - 60 11 - 22 0.6 - 2.8 0.6 - 5.2

Bkgnd³ N/A 24 8.3 12 1.1 0.65

Bkgnd Range 22 - 27 5.8 - 10 11 - 14 0.6 - 2.3 0.6 - 0.7

B Episode Avg. 57¹, 86² 55¹, 82² 6.9 54 1.9 2.1

Canadian Smoke Episode Range¹ 20 - 180 20 - 174 3.7 - 13 14 - 161 0.5 - 3.7 0.25 - 5.4

Bkgnd³ 19 18 4.6 12.6 0.5 0.27

Bkgnd Range 15 - 17 17 - 19 2.7 - 6.2 10 - 15 0.4 - 0.5 0.2 - 0.3

C Episode Avg.¹ 49¹, 52² 48¹, 52² 34 11 1.0 1.0

Regional Haze Episode Range¹ 24 - 72 27 - 65 12.5 - 49 7.1 - 15.6 0.4 - 2.7 0.6 - 2.2

Bkgnd³ 23 23.5 10.4 10.7 1.0 1.4

Bkgnd Range 12 - 37 14 - 33 3.5 - 16.5 6.4 - 15 0.5-3.1 0.4 - 1.2

D Episode Avg.¹ 42¹, 57² 39¹, 53² 20 16 1.5 1.6Reg Haze +

Local Traffic Episode Range¹ 36 - 73 14 - 68 3.4 - 42 8 - 29 0.6 - 6.4 0.4 - 5.2

Bkgnd³ 11 13 4.6 7.5 0.7 0.7

Bkgnd Range 9.8 - 12.5 12.9 - 14 3.2 - 6 7.1 - 8 0.7 - 0.9 0.4 - 1.1

E Episode Avg.¹ 35¹, 35² 32¹, 35² 21 9.1 2.0 1.9

Regional Haze Episode Range¹ 8.9 - 52 11 - 47 14 - 28 6.9 - 15 1.1 - 3.3 0.5 - 6.0

Bkgnd³ 12 14 5.7 6.2 1.0 0.9

Bkgnd Range 6.5 - 22 8.1 - 22 3.5 - 7.5 3.8 - 11 0.4 - 2.5 0.3 - 2.4

F Episode Avg.¹ 32¹, 32² 34¹, 32² 7 14 3.3 8.9

Local Traffic Episode Range¹ 9.1 - 87 14.5 - 83 4.4 - 11 5.2 - 55 1.2 - 12 3.6 - 15

Bkgnd³ 9.6 14 4.7 4.8 1 3.2

Bkgnd Range 7,8 - 12 13 - 14 4.2 - 5.0 4.7 - 5.1 0.8 - 1.1 2.5 - 4.3

¹Average concentration during period of elevation

²Highest midnight to midnight (24-hr) average during episode

³Average before and after episode

Estimated, see text.4

4

PM2.5, µg/m3

bkgnd mean

* Summer ~20 ~60

Fall ~ 14 ~34

•Summer more sulfate

Fall comparable OM

more EC, nitrate

Table 3. Relative Composition of PM2.5

Table 3, continued.

PM Episode A

June 24-26, 2002

Summer Haze Episode, dominated by Sulfate,OM

Influence of Local sources evident

Type A

Measurement period

06/24/02 06/25/02 06/26/02

Win

d s

pee

d (

m/s

ec)

0

1

2

3

4

5

6

7

8

Win

d d

irec

tion

(d

eg)

0

40

80

120

160

200

240

280

320

360

400

Wind speed

Wind direction

Episode A: June 24-25: Sulfate Haze Event

T y p e A

M e a s u r e m e n t p e r i o d

0 6 / 2 4 / 0 2 0 6 / 2 5 / 0 2 0 6 / 2 6 / 0 2

Recon

stru

cte

d P

M2

.5 m

ass

(µµ µµ

g/m

3)

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

9 0

1 0 0

Su

lfate

an

d O

C c

on

c (µµ µµ

g/m

3)

0

5

1 0

1 5

2 0

2 5

3 0

3 5

4 0

4 5

5 0

P M 2 .5 m a s s

S u l f a t e

O r g a n i c c a r b o n

Worst Episode in 9.5 month study (except Canadian Smoke)

Aged Local, regional, fresh local components

•1.5 hrs after local

winds shift to 170o

at 3m/s = 16.2 km

•Local power plant 15

km plumes raise sulfate

concs. ∆∆∆∆15 µg/m3

Local power plants 44 - 31 = 13 µg/m3

B

Inter-regional transport 31 - 6 = 25 µg/m3

A

Aged Local, 24 - 6 = 18 µg/m3P

M2.5mass, µg/m

3

Episode A

Particle diameter (nm)

10 100 1000 10000

dN/dlogDp (x104 #/cm

3)

0.0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

3.0

June 25 (24 h avg)

1800 EST June 25

Fresh power plant accumulation mode

Aged secondary accumulation mode

18:00 06/25

24-hr avg

Bkgnd, 6 µg/m3

Bkgnd

Background A Stagnation

B Transport

Event Done

Some important points

• Arguably, sources in the local region contributed

substantial amounts of sulfate on day1

• Arrival of polluted air mass increases sulfate 7x

relative to background on day 2

• OC increase only 1.5x over background, to 10

µg/m3.

Whereas for Episode F, local (traffic) induces 3x

increase in OC!

Influence of Traffic

revealed by

characteristic size spectra, diurnal profiles

show

EC, OC, Nitrate from traffic emissions heavily influence

PM2.5 in cool, moist, low-mixing height periods

i.e., Fall, Winter, Night time

LA: Size Distributions for motor vehicle traffic3 narrow modes in ultrafine size range

Evolution w/distance

Size distribution indistinguishable

from upwind at 300 m downwind

30 m downwind - trimodal

Fresh automobile aerosol Peaks

Modal diameter changes with distance

due to evaporation/condensation of

volatiles

Source: LA Supersite/PM center, Sioutas

Baltimore: Ultrafine particles indicate traffic in AM

Any day, most any wind direction!Less pronounced in afternoon, longer rush hour, greater mixing height and wind speeds

-

Tuesday

Sunday

Sunday

Monday

Feb 18

Tuesday

Feb 19

Wednesday

Feb 20

Thursday

Feb 21

Monday morning

Holiday

FridayFeb 22

Leaving work

early

0:00 06:00 12:00 18:00 24:00

10:00 PM

10

100

0:00 06:00 12:00 18:00 24:00

10

100

Size, nm

Size, nm

06:00 12:00 18:00 06:00 12:00 18:00 06:00 12:00 18:00

W h o le p e r io d

T im e o f t h e d a y ( h r )

- 1 0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4

OC (µg C/m

3)

2 .0

2 .5

3 .0

3 .5

4 .0

4 .5

5 .0

5 .5

6 .0

6 .5

7 .0

7 .5

8 .0

EC (µg C/m

3) or CO(x2 ppm)

0 .4

0 .6

0 .8

1 .0

1 .2

1 .4

1 .6

1 .8

2 .0

2 .2

O C

E C

C O

O C -E C

M e a s u r e m e n t p e r io d

0 8 /1 1 /0 2 0 8 /1 2 /0 2 0 8 /1 3 /0 2 0 8 /1 4 /0 2 0 8 /1 5 /0 2

OC

(µµ µµ

g C

/m3

)

0

2

4

6

8

1 0

1 2

1 4

1 6

1 8

2 0

EC

(µµ µµ

g C

/m3

)

0 .0

0 .7

1 .4

2 .1

2 .8

3 .5

4 .2

4 .9

5 .6

6 .3

7 .0

O C

E C

Baltimore Ponca St: EC – Strong Diurnal CyclesPeaks correspond to morning Traffic

Average daily profile

(9.5 months)

Even in August

OC

EC

COOC:EC ratio increases

evenings & early AM

Night-time chemistry?

5:1

5:1

3:1

Baltimore Air is Heavily influenced by Traffic(Especially in Fall/Winter/Spring months)

Ultrafine particles

peak at morning

rush hour (6:00 –

9:00 AM)

E-SE winds

4hr average data

Sampling date

04/16/02 04/17/02 04/18/02

% o

f (S

O4 +

NO

3 +

EC

+ O

M) in

PM

2.5

0

10

20

30

40

50

60

70

80

90

100

SO4%(4h)

NO3%(4h)

EC%(4h)

OC%(4h)

Sampling period

04/16/02 04/17/02 04/18/02

TEO

M m

ass c

onc (ug/m

3)

0

10

20

30

40

50

60

70

80

Org

anic

carb

on c

onc (ug/m

3)

0

2

4

6

8

10

12

14

16

TEOM

Organic C

OC highly correlated w/TEOM

Sampling period

04/16/02 04/17/02 04/18/02

SM

PS #

conc (#/c

m3)

2e+4

4e+4

6e+4

8e+4

1e+5

Ele

menta

l carb

on c

onc (ug/m

3)

0

1

2

3

4

5

6

7

8

9

SMPS

Elemental C

OC & EC highly correlated

w/morning traffic peak

OC a substantial fraction of PM2.5

15 nm -

Nitrate is more complicated

NOx converted to nitrate 10x faster than SO2 to sulfate,

therefore local sources much more important for nitrate

NH4NO3 dissociation equilibrium favors nitrate at low

T, high RH

Night time radical chemistry forms nitric acid from NO2

when temperatures are typically cooler and RH higher

Monthly trend of Nitrate concentration at Ponca

Sampling period (month)

EntireFeb Mar April MayJune July Aug Sep Oct Nov

Nitra

te c

onc (ug/m

3)

0

1

2

3

4

5

Monthly data

Lower concentrations in summer when ammonium nitrate more volatile

#concentration (“pure nitrate”

50~90nm particle)

May 5 peak May 6 morning

peak

May 3-8, 2002

R&P 8400N

“Pure” Nitrate particles correlate with PM2.5 Nitrate peaks:

occur at high RH, low temperatures

RSMSIII

Tolocka et al., Submitted

These data suggest

that much of the

nitrate is formed by

nucleation of new

particles!

1 3 5 7 9 11 13 15 17 19 21 23

1280

770

440

230

140

110

90

50

45

Percentage of Total Spectra

Time (hr)

Aerodynamic Diameter (nm)

Nitrate Class April 16th, 2002

10.0%-11.0%

9.0%-10.0%

8.0%-9.0%

7.0%-8.0%

6.0%-7.0%

5.0%-6.0%

4.0%-5.0%

3.0%-4.0%

2.0%-3.0%

1.0%-2.0%

0.0%-1.0%

Fraction of Particles in Nitrate Class vs. Size / Time of DayBut other times – much forms on “droplet” mode

Weekend patterns

Saturday

Feb. 23

Sunday

Feb. 24

Saturday night

entertainment traffic or

Night time chemistry?

Bars close 2:00 AM

W in d d ir e c t io n (d e g )

0 3 0 6 0 9 0 1 2 0 1 5 0 1 8 0 2 1 0 2 4 0 2 7 0 3 0 0 3 3 0 3 6 0

Nitra

te c

onc (ug/m

3)

0

2

4

6

8

1 0

1 2

1 4

1 6

1 8

W in d s p e e d (m /s e c )

0 1 2 3 4 5 6 7 8

W in d d ire c t io n

W in d s p e e d

I-895N/I-95N

Locally Produced Nitrate concentrations frequently

observed at 30o and at wind speeds 0 to 1 m/s

30o

Example: March 23 – 25 data

Park et al., Atmos. Environ. 39:2011, 2005:

32% of Nitrate transients were > 1 µg/m3

64% w high/NOx between 5 – 8 AM

26% between 10 PM – 2 AM

E p iso d e F

M easu rem en t p e riod

1 1 /1 9 /02 11 /20 /02 1 1 /21 /02

Ambient temp (oC)

0

2

4

6

8

10

12

14

16

18

20

Relative humidity (%)

2 0

3 0

4 0

50

60

70

80

90

100

Am b ien t tem p

RH

Episode F: November 20, 21Cool Temperatures, Morning RH >90%

Winds light, variable on 20th,

Winds light, 30o, very high RH, on 21st

E pisode F

Measurement period

11/19 /02 11 /20/02 11 /21 /02

Wind speed (m/sec)

0

1

2

3

4

5

6

7

8

Wind direction (deg)

0

40

80

120

160

200

240

280

320

360

400

Wind speed

W ind dir

90%

RH

Power

Plant

30o

E pisode F

Measurement period

11/19 /02 11 /20/02 11 /21 /02

Wind speed (m/sec)

0

1

2

3

4

5

6

7

8

Wind direction (deg)

0

40

80

120

160

200

240

280

320

360

400

Wind speed

W ind dir

Episode F: November 20, 21E p isode F

Measurement period

11 /19 /02 11/20/02 11/21 /02

PM

2.5 m

ass and OC conc ( µg/m

3)

0

10

20

30

40

50

60

70

80

90

100

EC and nitrate conc ( µg/m

3)

0

2

4

6

8

10

12

14

PM2.5 mass

O rganic carbon

E lemental carbon

N itrate

E pisode F

Measurement period

11/19 /02 11 /20/02 11 /21/02

Hourly NOx conc (ppb)

0

100

200

300

400

500

600

700

800

900

1000

Hourly CO conc (ppm)

0 .0

0 .3

0 .6

0 .9

1 .2

1 .5

1 .8

2 .1

2 .4

2 .7

3 .0

NOx

CO

Episode F: November 20, 21Cool Temperatures, Stagnation, High RH, morning traffic peak;

Nitrate deposits on wet particles;

Winds from 30o all day on 21st Nitrate (lags NOx)

Highest

PM2.5 max

No obvious

power plant

influence;

mixing hgt

too low

Episode F : well correlated EC, OC, PM2.5 (Local traffic): Max conc

Episode 4 (Nov 20)

Measurement period

11/19/02 11/20/02

TEO

M P

M2.5 m

ass c

onc (ug/m

3)

0

12

24

36

48

60

72

84

96

108

120

TEOM time series (30 min)

3 hr running avg

Episode F

Measurement period

11/19/02 11/20/02

Ele

menta

l carb

on c

onc (ugC

/m3)

0

1

2

3

4

5

6

7

8

9

10

Org

anic

carb

on c

onc (ugC

/m3)

0

4

8

12

16

20

24

28

32

36

EC (1hr)

OC (1hr)0

12

24

36

48

60

72

84

96

108

120

11/2

0/02

0:0

0

11/2

0/02

1:0

0

11/2

0/02

2:0

0

11/2

0/02

3:0

0

11/2

0/02

4:0

0

11/2

0/02

5:0

0

11/2

0/02

6:0

0

11/2

0/02

7:0

0

11/2

0/02

8:0

0

11/2

0/02

9:0

0

11/2

0/02

10:

00

11/2

0/02

11:

00

11/2

0/02

12:

00

11/2

0/02

13:

00

11/2

0/02

14:

00

11/2

0/02

15:

00

11/2

0/02

16:

00

11/2

0/02

17:

00

11/2

0/02

18:

00

11/2

0/02

19:

00

11/2

0/02

20:

00

11/2

0/02

21:

00

11/2

0/02

22:

00

11/2

0/02

23:

00

Measurement period

PM

2.5 m

ass contribution (ug/m

3) Undetermined

OrganicsEC(NH4)2SO4NH4NO3

Episode F

Winter stagnation

(OC +EC)

TEOM (µg/m3) = 2.57 OC (µg/m3) + 10.53 R2=0.88

TEOM (µg/m3) = 7.39 EC (µg/m3) + 13.92 R2=0.85

Summary

• 24-hr PM2.5 standard rarely exceeded during 2002 at Ponca st. –Episode A, max 24-hr PM2.5 was ~65 ug/m3

• 9.5-month 30-min average barely exceeded annual PM2.5 standard.

• Episodes occur during periods of stability/stagnationSummer episodes caused by stationary fronts; end by break by passage of cold fronts

• Local sources – traffic; So. Baltimore industry; and local regional sources contribute substantially, to EC, OC, Nitrate, especially in fall, winter, spring

• Major summer haze events; dominated by sulfate & OC – worst event after air stagnant over Ohio Valley arrived in Baltimore w/local wind direction from So. Baltimore; but Local So. Baltimore sources contributed ≥5% of PM2.5 – enough to trip standard

• Urban traffic corridor creates PM “hot spots.”