The Atmospheric Degradation of

Naphthalene

Yang Chen

3rd Year Ph.D. Student

University College Cork

Introduction

0.1-1 µg m-3 (0.02 – 0.2

ppbV) in European Cities

Secondary Organic

Aerosol(SOA)

Research in Context • The EPA states: “The biggest threat now facing our air quality is emissions from road traffic” •Naphthalene is a primary pollutant emitted by road traffic which can undergo further degradation in the atmosphere to produce a range of secondary pollutants such as NO2, O3 and SOA. • Laboratory studies of the atmospheric degradation process can yield information on type of reaction products, mechanism and aerosol formation potential. • This, in turn, allows us to predict the impact of naphthalene emissions on air quality.

Objectives of our study •Determine SOA yields from degradation of naphthalene and the effect of reaction conditions on yield •Investigate chemical composition of SOA •Improve knowledge of secondary chemistry: Photolysis of oxidation products using natural sunlight • Generate chemical reaction data (kinetic and mechanistic parameters) suitable for inclusion in models used to predict the effect of emissions on air quality.

Atmospheric Simulation Chamber at UCC

• FEP foil (6500 litres) • Dry purified air • Atmospheric P and T • Humidity control

• on-line GC • NOx and O3 analysers • denuder – filter, GC-MS • Particle Sizer and counter

SOA Formation

SOA Yields

1. SOA yields 11-20%, depending on reaction conditions.

2. Higher Naphthalene/ NOx ratio gives a higher yield of SOA.

3. Higher relative humidity leads to higher yield.

4. Lower NO concentration results in more rapid formation of SOA.

5. SOA yields higher than most mono-aromatics.

Naphthalene is a significant source of SOA in urban areas

Identification of Degradation Products

Derivatization agents used to aid identification of carbonyls, acids, phenols, quinones by Gas chromatography–mass spectrometry(GC-MS)

Degradation Products

Particle Phase

Gas Phase

Degradation Products

All products identified in both gas and particle phase

Genotoxic and mutagenic !!!

Oxidation Mechanism

1% 7% 56% Calvert et al., 2002

5%

OH/hn

Photolysis of Naphthalene Photooxidation Products

European PhotoReactor (EUPHORE) Valencia, Spain

• Long path length Fourier transform infrared (FT-IR) spectroscopy • Ozone and NOx analysers • Gas chromatography–mass spectrometry (GC-MS) • Relative humidity and temperature detectors • Spectroradiometer (jNO2) • Particle sizer and counter

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Ph

thal

dia

ldeh

yde

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nce

ntr

atio

n (

pp

bv)

Time (hh:mm)

Phthalic anhydride

Phthaldialdehyde

Phthalide

SOA Mass Concentration(ug/m3)

SOA

Mas

s C

on

cen

trat

ion

(u

g/m

3)

Chamber open Chamber close

Major photolysis products:

Photolysis of Phthaldialdehyde

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ln([

Ph

thal

dia

lde

hyd

e] t

/[P

hth

ald

iald

eh

yde

] 0

j =0.0002 s-1

Lifetime≈ 83 min Photolysis is the major loss process SOA yield is up to 6%

Photolysis of Phthaldialdehyde

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10:04 11:04 12:04 13:04 14:04 15:04 16:04

SOA

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s C

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1-N

itro

nap

hth

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Time (hh:mm)

1-NitroNaphthalene

SOA Total MassConcentration(ug/m3) corrected

Photolysis of 1-nitronapthalene

Major photolysis product:

Photolysis of 1-nitronapthalene

j= 0.0012 s-1

Lifetime is about 14 min Photolysis in the atmosphere is the major loss process SOA yield is up to 52%

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ln([

1-n

itro

nap

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]0/[

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itro

nap

hth

ale

ne

]t)

Time (s)

• Atmospheric degradation of naphthalene produces SOA with a yield of 11%-20% . Naphthalene is a significant source of SOA in urban areas. • Numerous sas and particle phase products, some of which are genotoxic and mutagenic; naphthols, nitronaphthalenes, naphthoquinones, glyoxal. •Photolysis of phthaldialdehyde and 1-nitronaphtalene is the major loss process in the atmosphere , which also contributes to SOA formation.

Conclusions

3 research papers planned: • Effect of relative humidity and NOx on the yield of SOA from the

photooxidation of naphthalene • Atmospheric photolysis of phthaldialdehyde • Atmospheric photolysis of 1-nitronaphthalene

Research Products

• This study shows that naphthalene is major source of SOA – respirable nanoparticles that can damage human health and also affect Earth’s climate. • Road traffic emissions contain many other PAHs that could also contribute to SOA. •Improvements in Irish air quality are only likely if emissions from road traffic are reduced. • Solutions: zero (low) emission vehicles, less road traffic, improved public transport.

Research For A Sustainable Future

Acknowledgements

Shouming Zhou, Robert Healy, John Wenger

Monica, Esther, Mila, Amalia

STRIVE Programme (2008-PhD-AQ-1)

Expt.

RH

(%)

HC0 a

(ppbV)

NOx b

(ppbV)

HC0/NOx

ΔHC c

(μg/m3)

M0 d

(μg/m3)

SOA yield e

(%)

RH0_1 0.2 1070 520 1.95 2198 285.5 13.0

RH0_2 0.6 1040 240 4.35 1807 330.1 18.3

RH0_3 0.8 1084 250 4.34 2118 379.6 17.9

RH0_4 0.7 1081 510 2.13 2135 237.3 11.1

RH0_5 0.8 830 690 1.20 1310 136 10.3

RH0_6 0.8 602 145 4.15 1470 248.5 16.9

RH0_7 1.9 508 500 1.02 954 63.4 6.64

RH0_8 1.3 611 202 3.02 1444 230.8 16.0

RH25_1 25.1 585 470 1.24 1022 118.6 11.6

RH25_2 25.3 593 540 1.01 926 103.8 11.2

RH25_3 25.1 532 520 1.02 1055 97.2 9.23

RH25_4 25.5 611 344 1.78 1408 229.4 15.5

RH25_5 25.6 626 517 1.21 1168 155 13.3

RH25_6 25.3 699 556 1.26 1745 271.3 15.5

RH50_1 50.3 629 590 1.07 1276 218.5 17.1

RH50_2 49.2 514 496 1.04 1061 159.4 15.0

RH50_3 50.6 602 370 1.63 1287 206.9 16.1

RH50_4 51.0 705 410 1.72 1651 309.7 18.8

Supporting Information

Date 1st July 2009 2nd July 2009 03rd July 20091 10th July 20092

Initial Concentration(ppbV) 255.23 165.02 419.21 405.86

Irradiation Time 2 h 41 min 2 h 10 min 2 h 50 min 2 h 55 min

j(NO2)average(s-1) 8.26×10-3 8.22×10-3 5.07×10-3 8.03×10-3

kphthaldialdehyde(s-1) 2.07×10-4 1.87×10-4 1.00×10-4 1.47×10-4

kSF6(s-1) 5.51×10-6 7.00×10-6 5.7×10-5 5.1×10-5

kwall(s-1) 1.55×10-5 2.30×10-5 1.93×10-5 1.0×10-5

jphthaldialdehyde/jNO2 0.025±0.005 0.023±0.004 0.020±0.004 0.018±0.003

SOA yield (g/m3) 24.138 9.992 85.36 65.31

SOA yield (%) 2.10 1.56 6.70 4.51

Phthalide(ppbV) 57.22 45.79 136.08 115.66

Phthalide(%) 27.86 32.66 48.42 49.59

Phthalic anhydride(ppbV) 108.13 53.93 102.47 86.65

Phthalic anhydride(%) 44.11 48.13 34.62 21.76

Life Time (min) 80.5 89.1 166.6 113.3

1 In this experiment, 1, 3, 5-trimethylbenzene (400 ppbV) was as an OH radical tracer. 2 In this experiment CO (500 ppmV) used as an OH radical scavenger Both Phthalide and phthalic anhydride conc. are corrected by wall loss rate of 2.71×10-5 s -1 and 2.64×10-5 s -1 respectively

Supporting Information

Date 06th July 2009 07th July 2009 1 13rd July 20092 14th July 2009

Initial Conc.(ppbV) 268.98 137.34 166.41 199.13

Irradiation Time 2 h 38 min 1 h 31 min 45 Min 2 h

j(NO2)average(s-1) 8.42E-03 9.10E-03 7.43E-03 7.60E-03

K1-nitronaphthalene(s-1) 1.2E-03 0.90 E-03 0.70E-03 1.1E-03

kSF6(s-1) 7.2E-6 7.0E-6 9.0E-6 8.9E-6

kwall(s-1) 6.6E-5 2.0E-5 2.0E-5 3.0E-5

J1-nitronaphthalene/jNO2 0.142 0.098 0.094 0.1447

SOA (µg/m3) 890.41 345.86 832.87 588.21

SOA yield (%) 51.69 39.24 51.42 40.37

Life Time (min) 13.8 18.5 23.8 15.5

Supporting Information

•Aging and evolution of SOA from naphthalene photooxidation could be investigated on-line aerosol time of flight mass spectrometry. •The available data could be used to develop a chemical model of the atmospheric degradation of naphthalene using the Master Chemical Mechanism.

Future work