Elemental and organic carbon in PM10: a one year ...

Elemental and organic carbon in PM10: a one year

measurement campaign within the European Monitoring

and Evaluation Programme EMEP

K. E. Yttri, W. Aas, A. Bjerke, J. N. Cape, F. Cavalli, D. Ceburnis, C. Dye,

L. Emblico, M. C. Facchini, C. Forster, et al.

To cite this version:

K. E. Yttri, W. Aas, A. Bjerke, J. N. Cape, F. Cavalli, et al.. Elemental and organic carbon in PM10: a

one year measurement campaign within the European Monitoring and Evaluation Programme EMEP.

Atmospheric Chemistry and Physics, 2007, 7 (22), pp.5711-5725. ?hal-00296378?

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Atmos. Chem. Phys., 7, 5711¨C5725, 2007

7/5711/2007/

? Author(s) 2007. This work is licensed

under a Creative Commons License.

Atmospheric

Chemistry

and Physics

Elemental and organic carbon in PM10: a one year measurement

campaign within the European Monitoring and Evaluation

Programme EMEP

K. E. Yttri1 , W. Aas1 , A. Bjerke1 , J. N. Cape7 , F. Cavalli6 , D. Ceburnis2 , C. Dye1 , L. Emblico3 , M. C. Facchini3 ,

C. Forster1 , J. E. Hanssen1 , H. C. Hansson4 , S. G. Jennings2 , W. Maenhaut5 , J. P. Putaud6 , and K. T?rseth1

1 Norwegian

Institute for Air Research, P.O. Box 100, 2027 Kjeller, Norway

of Experimental Physics, National University of Ireland, Galway, Ireland

3 CNR, Institute of Atmospheric Sciences and Climate, Via P. Gobetti 101, 40129 Bologna, Italy

4 Department of Applied Environmental Science, Stockholm University, 10691 Stockholm, Sweden

5 Department of Analytical Chemistry, Institute for Nuclear Sciences, Ghent Univ., Proeftuinstraat 86, 9000 Ghent, Belgium

6 European Commission, Joint Research Centre, Institute for Environment and Sustainability, TP 460, 21020 Ispra (VA), Italy

7 Centre for Ecology & Hydrology, Edinburgh Research Station, Bush Estate, Penicuik, Midlothian, EH260QB, UK

2 Department

Received: 8 February 2007 ¨C Published in Atmos. Chem. Phys. Discuss.: 19 March 2007

Revised: 17 September 2007 ¨C Accepted: 19 October 2007 ¨C Published: 19 November 2007

Abstract. In the present study, ambient aerosol (PM10 ) concentrations of elemental carbon (EC), organic carbon (OC),

and total carbon (TC) are reported for 12 European rural

background sites and two urban background sites following

a one-year (1 July 2002¨C1 July 2003) sampling campaign

within the European Monitoring and Evaluation Programme,

EMEP (). The purpose of the campaign

was to assess the feasibility of performing EC and OC monitoring on a regular basis and to obtain an overview of the

spatial and seasonal variability on a regional scale in Europe.

Analyses were performed using the thermal-optical transmission (TOT) instrument from Sunset Lab Inc., operating according to a NIOSH derived temperature program.

The annual mean mass concentration of EC ranged from

0.17¡À0.19 ?g m?3 (mean ¡À SD) at Birkenes (Norway) to

1.83¡À1.32 ?g m?3 at Ispra (Italy). The corresponding range

for OC was 1.20¡À1.29 ?g m?3 at Mace Head (Ireland) to

7.79¡À6.80 ?g m?3 at Ispra. On average, annual concentrations of EC, OC, and TC were three times higher for rural

background sites in Central, Eastern and Southern Europe

compared to those situated in the Northern and Western parts

of Europe. Wintertime concentrations of EC and OC were

higher than those recorded during summer for the majority of the sites. Moderate to high Pearson correlation coefficients (rp ) (0.50¨C0.94) were observed for EC versus OC

Correspondence to: K. E. Yttri

(key@nilu.no)

for the sites investigated. The lowest correlation coefficients

were noted for the three Scandinavian sites: Aspvreten (SE),

Birkenes (NO), and Virolahti (FI), and the Slovakian site

Stara Lesna, and are suggested to reflect biogenic sources,

wild and prescribed fires. This suggestion is supported by

the fact that higher concentrations of OC are observed for

summer compared to winter for these sites.

For the rural background sites, total carbonaceous material

accounted for 30¡À9% of PM10 , of which 27¡À9% could be

attributed to organic matter (OM) and 3.4¡À1.0% to elemental

matter (EM). OM was found to be more abundant than SO2?

4

for sites reporting both parameters.

1

Introduction

The environmental relevance of the carbonaceous aerosol

comprises a number of important topics, such as direct and

indirect climate forcing, and air quality. The high number of organic species reported to be associated with ambient fine aerosols have a wide range of different physical

and chemical properties, of which impact on human health

and cloud formation largely remains unknown. Furthermore,

black carbon is the principal light absorbing species in the

atmosphere, significantly affecting the Earth¡¯s radiative balance (Ramanathan et al., 2001).

Published by Copernicus Publications on behalf of the European Geosciences Union.

5712

K. E. Yttri et al.: Elemental and organic carbon in PM10 : a one year measurement

Quantification of the carbonaceous content of the ambient

aerosol on the basis of single species is an insurmountable

task due to their sheer number, their various chemical and

physical properties and the complex aerosol matrix. Thus,

operational definitions of bulk carbonaceous material, such

as elemental carbon (EC) and organic carbon (OC), have

been established.

Long-term monitoring data of EC and OC is not yet available on a regional scale in Europe, although the importance of such data has been emphasized by e.g. Kahnert et

al. (2004). Monitoring of EC and OC needs to rely on both

robust and cost-efficient techniques, but at the same time a

satisfactory quality of the data must be maintained. This

poses particular challenges due to artefacts associated with

sampling of particulate OC. It is well known that quartz fibre filters adsorb organic gases (Kirchstetter et al., 2001),

and that a shift in the equilibrium between the filter, the organic constituents collected on the filter, and gaseous organic

compounds may lead to both positive and negative artefacts

during prolonged sampling. Positive artefacts arise from adsorption of gaseous organic compounds on the filter, while

negative artefacts result from evaporation of gaseous organic

material from particles collected on the filter. However, the

exact magnitude of the artefacts is difficult to address or measure by simple methods.

Significant differences have been reported for levels of

EC and OC when comparing various analytical techniques

(Schmid et al., 2001). Whereas the total carbon (TC) content corresponds well between the most commonly used analytical approaches, the recommendation made by Schmid et

al. (2001) is that only methods that account for charring during analysis should be applied when analysing for the sample content of EC and OC. Thus, methods such as thermaloptical reflectance (TOR) and thermal-optical transmittance

(TOT) should be applied. Still, differences of a factor of two

have been reported for EC when comparing the two most

commonly applied analytical protocols, NIOSH (National

Institute of Occupational Safety and Health) method 5040

and IMPROVE (Interagency Monitoring of Protected Visual

Environments) (Schmid et al., 2001; Chow et al., 2001).

Thus, in order to provide EC/OC data of high quality within

a monitoring network, a standardized protocol needs to be

established both for analysis and sampling of these carbonaceous fractions.

To assess the feasibility of performing EC and OC monitoring on a regular basis, and to obtain an overview of the

spatial and seasonal variability of EC and OC on a regional

scale in Europe, a one-year campaign was conducted at 12

rural background sites and two urban background sites in 13

European countries. The dataset benefits from the fact that

one instrument, a thermal-optical transmission instrument,

which corrects for charred organic carbon during analysis,

has been used to quantify the sample content of EC and OC.

It is our belief that the present dataset will contribute in a

positive way to the understanding of concentrations of carAtmos. Chem. Phys., 7, 5711¨C5725, 2007

bonaceous aerosols in the European rural background environment, and that it will be useful for the validation of the

EMEP model performance, in particular. Below, we present

a descriptive overview of the campaign and the major findings obtained.

2

Experimental work

2.1 Aerosol sampling

The EMEP EC/OC campaign was conducted during the period 1 July 2002 to 1 July 2003. Table 1 provides an overview

of the 14 sampling sites included in the campaign and the

sampling equipment used, whereas the spatial distribution of

the sites is shown in Fig. 1. 11 of the 14 sites are established

EMEP sites, which fulfils the criteria of a regional background site stated by EMEP (

ccc/manual/index.html). The Penicuick (UK) site is also a

rural background site, but not an EMEP site, whereas Ghent

(BE) and San Pietro Capofiume (S.P.C.) (IT) are both urban

background sites. Aerosol sampling was performed using

CEN (European Committee for Standardization) approved

or equivalent PM10 gravimetric samplers, collecting one 24h sample every week (starting Tuesday mornings 7 AM).

Aerosols were collected on pre-heated (850? C, 3.5 h) quartz

fibre filters; 47-mm and 8 inch¡Á10 inch quartz fibre filters

were purchased from Whatman (QM-A), whereas 150-mm

quartz fibre filters were purchased from Munktell (MK 360).

To minimize differences in the adsorptive capacity, filters

were picked from the same batch number. The quartz fibre

filters were conditioned at 20¡À1? C and 50¡À5% RH (relative

humidity) for 48 h before and after exposure and weighed

for obtaining PM10 mass concentration. The 47-mm filters

were transported back and forth in petri slides, whereas the

8 inch¡Á10 inch and the 150-mm quartz fibre filters were enclosed in sealed aluminium foil. All quartz fibre filters were

stored at 4? C before being analysed.

Field blanks were assigned to each fourth day of sampling,

and treated in exactly the same manner regarding preparation, handling, transport and storage as the filters being exposed.

All filter preparations, pre-heating, conditioning and

weighing, were performed at the Norwegian Institute for Air

Research (NILU) (EMEP - Chemical Coordinating Centre).

2.2 Thermal-optical transmission analysis

The samples (n=684) content of EC, OC, and TC, were

quantified using the thermal-optical transmittance (TOT) instrument from Sunset laboratories Inc, operating according

to a NIOSH derived temperature programme (Table 2). The

¡°8785 Air Particulate Matter On Filter Media¡± reference material from The National Institute of Standards and Technology (NIST) (Klouda et al., 2005) was used to test the

7/5711/2007/

K. E. Yttri et al.: Elemental and organic carbon in PM10 : a one year measurement

5713

Table 1. Sampling sites and operational parameters of the sampling equipment used at the various sites. The sites are ordered from south to

north by latitude.

Sampling sites

(EMEP code)

Country

Site category

Aerosol

sampler

Braganza (PT01)

Ispra (JRC) (IT04)

Illmitz (AT02)

Stara Lesna (SK04)

Kos?etice (CZ03)

Langenbru?gge (DE02)

Kollumerwaard (NL09)

Mace Head (IR31)

Penicuik (GB46)

Birkenes (NO01)

Aspvreten (SE12)

Virolahti (FI17)

Portugal

Italy

Austria

Slovakia

The Czech republic

Germany

Holland

Ireland

Great Britain

Norway

Sweden

Finland

Rural background

Rural background

Rural background

Rural background

Rural background

Rural background

Rural background

Rural background

Rural background

Rural background

Rural background

Rural background

San Pietro Capofiume

(S.P.C.) (IT08)

Ghent (BE02)

Italy

Belgium

10

Kollumerwaard (NL)

Filter face

velocity (cm s?1 )

Hi-Vol (Sierra)

KFG

Partisol

Partisol

FH 95 SEQ

Hi-Vol (Digitel)

KFG

KFG

Partisol

KFG

Gent Filter Unit

KFG

8¡±¡Á10¡±

47

47

47

47

150

47

47

47

47

47

47

1133

38

16.7

16.7

38

500

38

38

16.7

38

17

38

46

48

24

22

53

54

53

48

23

46

23

50

Urban background

Gent Filter Unit

47

17

23

Urban background

Gent Filter Unit

47

17

24

10

Birkenes (NO)

4

2

?g m-3

6

6

4

0

TC

OC

10

OC

4

TC

EC

10

Ghent (BE)

?g m-3

?g m-3

6

4

EC

Langenbr¨¹gge (DE)

6

4

2

0

0

TC

10

OC

TC

EC

10

Penicuik (GB)

8

OC

EC

Stara Lesna (SK)

8

?g m-3

?g m-3

OC

8

2

6

4

2

6

4

2

0

0

TC

10

OC

EC

TC

OC

10

Mace Head (IE)

8

EC

Illmitz (AT)

8

?g m-3

?g m-3

4

0

OC

8

6

4

2

6

4

2

0

0

10

OC

EC

TC

Ispra (IT)

10

Braganza (PT)

10

8

6

4

6

4

2

2

TC

OC

EC

10

6

4

OC

EC

EC

Ko?etice (CZ)

6

4

2

0

TC

OC

8

2

0

0

San Pietro Capofiume (IT)

8

?g m-3

?g m-3

8

?g m-3

TC

?g m-3

6

2

TC

EC

Virolahti (FI)

8

6

0

TC

EC

10

2

2

0

Aspvreten (SE)

8

8

?g m-3

?g m-3

8

Flow rate

(l min?1 )

?g m-3

10

Filter size

(d)(mm)

0

TC

OC

EC

TC

OC

EC

Fig. 1. Spatial distribution of the sampling sites participating in the campaign and their annual mean concentration of EC, OC and TC

(?g m?3 ) for the period 1 July 2002¨C1 July 2003.

7/5711/2007/

Atmos. Chem. Phys., 7, 5711¨C5725, 2007

5714

K. E. Yttri et al.: Elemental and organic carbon in PM10 : a one year measurement

Table 2. Quartz parameter temperature program.

MODE

MODE 1

Step 1

Step 2

Step 3

Step 4

MODE 2

Step 1

Step 2

Step 3

Step 4

Step 5

Step 6

Step 7

Carrier gas

Temperature (? C)

Time (s)

100% He

100% He

100% He

100% He

220

360

525

850

60

60

60

90

98% He/2% O2

98% He/2% O2

98% He/2% O2

98% He/2% O2

98% He/2% O2

98% He/2% O2

98% He/2% O2

550

650

720

790

820

860

890

30

30

30

40

30

20

40

performance of the temperature programme. The result is

presented in Sect. 3.1.

2.2.1 WSOC analysis

A total of 71 samples were subjected to WSOC (Watersoluble organic carbon) analysis. Before analysis, parts of

each filter were soaked in Milli-Q water (7 ml for low volume

filters and 20 ml for high volume filters) and subjected to sonication (30 min) for extraction of the WSOC. The water extracts were filtered using PTFE-membrane single-use syringe

filters (Sartorius Minisart SRP 15). The dissolved organic

material was then quantified using a Shimadzu TOC liquid analyzer (model TC5000A). This instrument also allows

for determination of inorganic (carbonate) carbon following

acidification. The inorganic carbon was subtracted from the

dissolved organic carbon in order to obtain the WSOC fraction. However, the concentrations of inorganic carbon were

negligible most of the time. The water-insoluble organic carbon (WINSOC) was quantified by subtracting WSOC from

OC. The WSOC analysis was performed at the Institute of

Atmospheric Sciences and Climate of the Italian National

Research Council (ISAC-CNR).

3

Results and discussion

3.1 Uncertainties in EC/OC measurements

The precision and the detection limits of the TOT instrument

were determined by the variability of the EC and OC concentrations on exposed filters and on filter blanks, respectively.

The precision was found to be satisfactory with a relative

standard deviation below 5%.

The level of EC on the filed blanks was negligible, whereas

the OC concentration ranged from 0.41¨C1.94 ?g cm?2

(Fig. 2). When converting ?g cm?2 to ?g m?3 , the range

Atmos. Chem. Phys., 7, 5711¨C5725, 2007

for OC was 0.1¨C1.0 ?g m?3 ; however, the concentration was

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