Aerosol composition at a rural site southeast of London measured by high resolution mass spectrometry

Lu Xu

ClearfLo (Clean Air for London) Project

• collaborative multidisciplinary project to study boundary layer pollution across London

detling

Data collection

• Good data: 1/18/2012 to 2/14/2102 (27 days)• Bypass and Thermal Denuder

Thermal Denuder

valveinlet AMS

AMS

Bypass data: time series

16

14

12

10

8

6

4

2

0

µg

/m3

1/21/2012 1/25/2012 1/29/2012 2/2/2012 2/6/2012 2/10/2012 2/14/2012Date and Time

From East(highest loading,very high nitrate)

From ocean (cleanest air mass)

Average loading:4.88 mg/m3

Bypass data: Average mass spectra

1.5

1.0

0.5

0.0Nit

rate

eq

uiv

alen

t m

ass

(µg

m-3

)

100908070605040302010m/z

MSSD Org +1.5586 MSSD NO3 +1.7910 MSSD SO4 +0.7878 MSSD NH4 +0.8409 MSSD Chl +0.1129

0.25

0.20

0.15

0.10

0.05

0.00Nit

rate

eq

uiv

ale

nt

mas

s (

µg

m-3

)

100908070605040302010m/z

MSSD Org +1.5586

Org44/Org = 0.12(O/C = 0.54, Aiken et al, 2008)

NH+(16)NH+(17)

NO+(30) NO2+(46)

CO+(28) CO2+(44)

COOH→CO+ and CO2+BBOA: 0.3 – 0.4HOA: 0.06 – 0.1

Deconvolution of organics spectraT

ime

= + +

x

Con

trib

utio

n (u

g/m

3 ), S

ourc

e 1

Mass Spectrum,Source 1

x

Con

trib

utio

n (u

g/m

3 ), S

ourc

e 2

Mass Spectrum,Source 2

x

Con

trib

utio

n (u

g/m

3 ), S

ourc

e 3

Mass Spectrum,Source 3

Mass Spectrum

+ …. . .

Positive Matrix Factorization (PMF) (Lanz et al., 2007; Ulbrich et al., 2009)

0.5 0.4 0.2 0.99+ + =

Characteristic nose and eye

Characteristic ear Characteristic mouse

UMR three factor solution

OOA: correlates better with nitrateHOA: correlates with COBBOA: fresh OA, correlates with CH3CN

21% 37%

42%

Oxygenated organic aerosol (OOA)

Biomass burning orangic aerosol (BBOA)

Hydrocarbon-like organic aerosol (HOA)

C2H4O2+(60) C3H5O2+(73)

OOA

HOA

BBOA

SOABiomass burning

POA

OOA is surrogate for SOAHOA is surrogate for POA

Bypass vs. denuded data

86420

1/21/2012 1/25/2012 1/29/2012 2/2/2012 2/6/2012 2/10/2012 2/14/2012dat

1612

840543210

Load

ing

(g/

m3)

6

4

2

0

1.5

1.0

0.5

0.0

Org

NO3

SO4

NH4

Chl

Different TD temperature

Summary

• Cleanest air mass comes from the ocean• Air mass from the East : characterized by high

loadings, especially high nitrate• PMF resolved three factors: HOA, OOA, BBOA• Nitrate and ammonia are more volatile

Future work

• High resolution analysis • Thermal denuder data• Comparison with other measurements at the

Detling site as well as other sites (especially London site)

AcknowledgementKn

owle

dge

age

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