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PROGRESS IN OC/EC MEASUREMENTS WITHIN EMEP Fabrizia Cavalli, J.-P. Putaud and the EUSAAR community PowerPoint Presentation
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PROGRESS IN OC/EC MEASUREMENTS WITHIN EMEP Fabrizia Cavalli, J.-P. Putaud and the EUSAAR community. The goal of EUSAAR / NA2 is to define a standardized artifact-free procedure for

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slide1

PROGRESS IN OC/EC MEASUREMENTS

WITHIN EMEP

Fabrizia Cavalli, J.-P. Putaud and the EUSAAR community

slide2

The goal of EUSAAR / NA2 is to define a standardized artifact-free procedure for

determining particulate organic and elemental carbon, validated for all kinds of regional background sites Europe.

EUSAAR Standard Operating Procedure

for the sampling and thermal – optical analysis

of atmospheric particulate organic and elemental carbon

  • Successful achievement of 5 years work within EUSAAR
  • EMEP community represents our main customer
  • SOP submitted to CCC for check and approval
  • Detailed description available: www.eusaar.net
slide3

EUSAAR SOP: Sampling atmospheric particulate OC and EC

1. BEST AFFORDABLE SAMPLING TRAIN:

1.1 Positive artifact mitigation

1.2 Denuder penetration efficiency and lifetime

1.3 Negative artifact assessment

slide4

1.1 Positive artifact mitigation

Without denuder: 14 – 70 %

slide5

1.1 Positive artifact mitigation

Denuder efficiency: 43 – 93 %

slide6

1.1 Positive artifact determination

With denuder: 1 -21 %

Contribution of positive artifacts remains the largest at sites where the concentration of TC is the lowest

slide7

1.3 Negative Artifacts assessment

- Activated carbon impregnated glass fiber filters: no more manufactured

- Activated carbon impregnated cellulose fiber filters: cannot be tested

- ZORFLEX: lead to problems with the Carbon analyser

- XAD impregnated quartz fiber filters: not suitable for monitoring

- Annealed quartz fiber filters:

- the only possibility

- theory says semi-volatile OCs should condense

- used at the SEARCH network

slide8

1.3 Negative Artifacts assessment

TESTS: IT04 in springtime

  • Denuder’s effect on negative artifacts: use of the denuder does not magnify negative artifacts
  • Annealed quartz fiber back up filter efficiency: 49 ± 12%
  • Range (upper limit) negative artifact: 0.9% - 4.5%

2.2% - 7.6%, if we account for quartz filter efficiency

Being further investigated in SE11

slide9

EUSAAR SOP

2. Thermal – optical analysis

of atmospheric particulate organic and elemental carbon

  • EUSAAR_2 optimised protocol for determining OC and EC defined and published

(Cavalli et al., 2010)

  • EUSAAR_2 protocol in use in a large number of laboratories in Europe

(8 EUSAAR partners and, at least, 5 National Reference Laboratories)

  • EUSAAR_2 is recognised as one of the major protocols for OC + EC analyses
  • (considered by CEN as a potential reference method together with IMPROVE and NIOSH)
slide10

2.1 EUSAAR_2 protocol & Carbonate Carbon interference

Natural calcite: 15 μg CC

Cavalli et al., 2010

Jankosky et al., 2008

▪ Carbonate carbon evolves in the He-mode of the EUSAAR_2 analysis (at 650°C)

even for concentrations expected during severe dust outbreaks

(Jankosky, 2008; Cavalli 2010; and Karanasiou et al., 2011 submitted)

▪ if present, CC would interfere with OC

slide11

needle

septum

cap

He or N

to CO2 detection chain

of the OCEC analyser

2

carrier gas

filter punch

H

PO

3

4

conc.

2.1 Carbonate Carbon determination

Proposed set-up for carbonate determination

  • CC recovery is 99% over the range 1.8 – 12 µg CC
  • Applied for CC determination in samples from Athens and Barcelona (Karanasiou et al., 2011)
  • measured CC substracted to OC (EUSAAR_2 protocol)
slide12

2.2 Intercomparison IMPROVE, EnvCan, and EUSAAR protocols

for the particulate OC and EC analysis

▪ 27 ambient PM1 aerosol samples from rural/semi-urban sites in Canada

▪EUSAAR_2 (650°C max temp in He) vs. IMPROVE_A (580°C max temp in He)

▪ Reproducibility in TC determination better than 10% among “expert” labs

EUSAAR TOR OR TOT EC conc. (μg/m3)

IMPROVE TOR EC conc. (μg/m3)

▪ Systematic difference EC_EUSAAR_2 (TOT) vs. EC_IMPROVE_A (TOR) = 0.57 (R2 = 0.72)

▪ mainly due to optical correction (transmittance vs. reflectance) than to the thermal protocol

slide13

EUSAAR Standard Operating Procedure

for the sampling and thermal – optical analysis

of atmospheric particulate organic and elemental carbon

EUSAAR_2 protocol

- minimises biases inherent to TOA

- validated for regional background sites in Europe

Positive artifact mitigation

Negative artifact assessment

slide14

3.2 Comparability for OC /EC/TC measurement within the network (2010)

- 18 participants among which 15 EMEP laboratories

- 8 samples collected at four sites (Ispra, Birkenes, K-Pustza and Montseny)

slide15

3.2 OC / EC / TC intercomparison

3.2.1 TC amounts (µg / cm²)

TC μg C / cm2

slide16

3.2 OC / EC / TC intercomparison

3.2.1 TC relative to average outliers excluded

TC_ ratio to average outliers excluded

13 among 15 EMEP laboratories determine TC within ±13% on average

slide17

3.2 OC / EC / TC intercomparison

3.2.2 EC/TC ratios

EC / TC ratio

Difference range: a factor of 3 to 12 (all participants using thermal-optical analysis)

slide18

3.2 OC / EC / TC intercomparison

EC/TC ratios relative to average all outliers excluded

9 among 15 EMEP laboratories determine EC/TC within ±20% on average

slide19

FUTURE INTERCOMPARISONS

  • TC / OC / EC intercomparison: every year in collaboration with ACTRIS and CCC
  • Mandatory participation for EMEP laboratories reporting OCEC data
  • EMEP/CCC report
  • NEXT INTERCOMPARISON:
  • Materials: natural aerosol and reference material (e.g. BC RM by Olga Popovicheva)
  • Samples (2 high volume samples in 4 sites) to be collected 15th June
  • 4 volunteers needed to collected samples
  • Results to be delivered by 1st November