Requirements for new measurements of ozone absorption...

Bureau International des Poids et Mesures

WMO Ozone Theme meeting

Geneva, 11-13 May 2009


Requirements for new measurements of ozone

absorption cross-sections for the accurate

determination of ozone concentration

J. Viallon, P. Moussay, M. Petersen and R.I. Wielgosz,


WMO Ozone Theme meeting, Geneva, 11-13 May 2009

Outline

The CIPM, the BIPM, the chemistry section

International comparisons of ozone standards

Scientific programme (1) : biases in the reference standard

Scientific programme (2) : biases in the reference method

Future programme : new measurements of the ozone absorption

cross-section


BUREAU INTERNATIONAL DES POIDS ET MESURES

The BIPM

It has headquarters near Paris, France. It is financedjointly by the Member States and Associates, and operates under the exclusive supervision of the CIPM.

Its mandate is to provide the basis for a single, coherent system of measurements throughout the world, traceable to the International System of Units (SI). This task takes many forms, from direct dissemination of units (as in the case of mass and time) to coordination through international comparisons of national measurement standards (as in length, electricity and ionizing radiation).

It maintains scientific laboratories in areas of: mass, time, frequency and gravimetry, electricity,ionizing radiation, and chemistry.

It has an international staff of over 70 and its statusvis-à-vis the French Government is similar to that ofother intergovernmental organizations.

Its budget is over eleven million euros.


COMITÉ INTERNATIONAL DES POIDS ET MESURES

The CIPM

Is made up of eighteen individuals, each from a different State. Its principal task

is to promote worldwide uniformity in units of measurement by direct action

or by submitting draft resolutions to the CGPM.

Meets annually and, its duties include:

consideration of the work of the BIPM;

consideration of reports presented to it by its Consultative Committees;

consideration of metrological work that Member Statesdecide to do in common and sets up and coordinatesactivities between specialists in metrology;

making appropriate Recommendations;

issuing an Annual Report on the administrative andfinancial position of the BIPM to the Member States;

commissioning reports in preparation for CGPMs, andothers such as the SI Brochure.

CIPM 1894

CIPM 2007


Chemical metrology is important in national measurement infrastructures

to improve industrial competitiveness, facilitate trade, implement

regulations, ensure the safety of products, protect the environment and

enhance the quality of life.

The BIPM organizes international comparisons of:

gas standards for air quality and greenhouse gas monitoring;

and of primary calibrators for laboratory medicine, food analysis and forensics.

The BIPM maintains a central O3 reference standard comparison facility,

facilities for NO and NO2 gas standard comparisons, and is developing

facilities for CH4 and CH2O gas standard comparisons.

The BIPM is coordinating comparisons on the purity of monitored therapeutic drugs and steroid hormones to underpin reference

measurement systems for clinical analytes. Future comparisons will

underpin systems for contaminants and residues in food as well as

forensic applications.

The BIPM maintains the database of the Joint Committee on Traceability in Laboratory Medicine, which lists certified

reference materials and methods of higher order which have been

reviewed by the Committee against ISO standards.

CHEMISTRY


Gas Metrology Programme (2005-2008)

1000 1100 1600 1700 1800 1900

0.000

0.005

0.010

GPT Products

wavenumber / cm-1

0.000

0.005

0.010

fitted spectrum

(HITRAN/MALT/CLS)

measured spectrum

(p, T ambient, 1 cm-1, 6.4 m cell)GPT Reactants

Absorb

ance

NO21.0 µmol mol-1

O31.0 µmol mol-1

NO2.6 µmol mol-1

Ozone reference standard

comparison facility

NO2 primary facility (dynamic preparation)

NO standard comparison facilityCCQM-P28

BIPM.QM-K1

Ozone (2-1000) nmol/mol

Method development

and validation at

10 µmol/mol

CCQM-P73

NO (30-70) µmol/mol

Gas Phase Titration

NO + O3 →→→→ NO2 + O2

Laser based SRP


1000 1100 1600 1700 1800 1900

0.000

0.005

0.010

GPT Products

wavenumber / cm-1

0.000

0.005

0.010

fitted spectrum

(HITRAN/MALT/CLS)

measured spectrum

(p, T ambient, 1 cm-1

, 6.4 m cell)GPT Reactants

Ab

so

rba

nce

Gas Metrology Programme (2009-2012)

Ozone reference standard

comparison facility BIPM.QM-K1Ozone (2-1000)

nmol/mol

Gas Phase Titration CCQM-P110

NO2 /N2 10 µmol/mol

O3 absorption cross section

240 245 250 255 260 265 270

80

90

100

110

120

Arg

on laser

Arg

on laser

Arg

on laser

YA

G laser

cro

ss-s

ectio

n /

10

-19 c

m2 .m

ole

cu

les

-1

λ / nm

294K, Hearn 61

298K, Daumont 92

295K, Bass &Paur 81

295K, Yoshino & al. 93

250K, Bass 81

298K, Molina 86

αO3

Core ComparisonCH4 / air

Analytical Challenge Comparison

CH2O 10 µmol/mol

Green House Gas comparison facility

Formaldehyde (ozone precursor)

facility


Outline






cross-section


The reference method for ozone at ambient level:UV photometry

BIPM – SRP27

OZONE SAMPLEOZONE SAMPLE

LIGHT

INTENSITY I0

ATTENUATED LIGHT

INTENSITY I

Light Path length 2l

σσσσ Ozone absorption cross-section at 253.64 nm under standard conditions of temperature and pressure

T Temperature in the cells

P Pressure in the cells

R Gas constant

NA Avogadro constant

D Product of transmittance of the two

cellsLopt light path length

1ln( )

2 opt A

T Rx D

L P Nσ

−=

x mole fraction of ozone in dry air (nmol/mol)


Scheme for international comparisons

BIPM-SRP27

National standardWMO/GAW World Calibration

Centre (EMPA)Regional networks calibration centre

National station WMO/GAW station Regional station

Stations around the world monitoring ozone at ambient level….

Chain of regular calibrations

Regular comparisons (or calibrations)


SRP27 (reference)

SRP28 SRP31

Comparisons at the BIPM

Triad of Triad of SRPsSRPs maintained at the BIPM maintained at the BIPM

One comparison = 2 ozone standards measuring different O3 concentration from the

same source

range : 0 to 1000 nmol/mol

One common reference standard : SRP27

Place for the guest ozone standard


NISTNIST

Environment CanadaEnvironment Canada

KRISSKRISS NIESNIES

CSIRCSIR--NMLNML

+ WMO + WMO -- EMPAEMPA

Reference : BIPMReference : BIPM--SRP27SRP27

+ BIPM + BIPM -- GPTGPT

Europe

ISCIIIISCIII

LNELNE

INRIMINRIM

UBAUBA

UBAUBA

NPLNPL

METASMETAS

VNIIMVNIIMFMIFMI

CHMICHMI

SPSP

NILUNILU

+ ERLAP (EC+ ERLAP (EC--JRC)JRC)

IEMIEM--DEPDEP

NMINMI--VSLVSL

Comparison CCQM-P28, 23 participants, 18 months

METROLOGY institutesMETROLOGY institutes

METEOROLOGY / Environmental METEOROLOGY / Environmental studies institutesstudies institutes


NIS

T

ISC

III

ER

LAP

Env

iron

men

t Can

ada

ME

TA

S S

RP

18

ME

TA

S S

RP

14

KR

ISS

LNE

VN

IIM FMI

WM

O/W

CC

-EM

PA

UB

A (A

)

SP

NP

L

ND

EN

W

UB

A (D

)

NIE

S

CH

MI

CS

IR-N

ML(

1)

NE

RI

NIL

U

NM

i-VS

L

IMG

C

CS

IR-N

ML

(2)

BIP

M G

PT

NIE

S G

PT-20

-15

-10

-5

0

5

10

15

20

Degre

e o

f equiv

ale

nce (

nm

ol/m

ol)

(k=2)

Comparison CCQM-P28 Final results - Di at 420 nmol/mol

NIST-SRPs i LABi BIPMD x x= −


Outline






cross-section


Biases in the SRPs

1ln( )

2 opt A

R Tx D

αL N P

−=

Gas temperature gradient

Temperature not uniform

Optical path Lopt > Lc

lampcell : Lc = 90 cm

Optical path ≠ cell length

Viallon, J., P. Moussay, J.E. Norris, F.R. Guenther, and R.I. Wielgosz, A study of systematic biases and measurement uncertainties in ozone

mole fraction measurements with the NIST Standard Reference Photometer. Metrologia, 2006. 43: 441-450.

1ln( )

2 opt A

R Tx D

αL N P

−=

Solution : avoid the heating

Partial solution : avoid multiple

reflections with tilted windows


Improved comparability

Upgraded SRPs (biases reduced) + Revised uncertainty budget

= improved comparability among National Metrology Institutes

0.98

0.99

1.00

1.01

1.02

Slo

pe

ver

sus

BIP

M-S

RP

27

second comparison 2007-2008

First comparison 2003-2004


Outline






cross-section


NIS

T

ISC

III

ER

LAP

Env

iron

men

t Can

ada

ME

TA

S S

RP

18

ME

TA

S S

RP

14

KR

ISS

LNE

VN

IIM FMI

WM

O/W

CC

-EM

PA

UB

A (A

)

SP

NP

L

ND

EN

W

UB

A (D

)

NIE

S

CH

MI

CS

IR-N

ML(

1)

NE

RI

NIL

U

NM

i-VS

L

IMG

C

CS

IR-N

ML

(2)

BIP

M G

PT

NIE

S G

PT-20

-15

-10

-5

0

5

10

15

20

Degre

e o

f equiv

ale

nce (

nm

ol/m

ol)

(k=2)

Pilot study CCQM-P28 Final results - Di at 420 nmol/mol

Gas Phase Titration

i LABi BIPMD x x= −


UV photometry and GPT traceability chains

0

1σ λ

= −

⋅ ( ln)

opt c

I

L I

( )σ λ

NO + O3 →→→→ NO2 + O2

NO

sta

nd

ard

NOx

Chemiluminscence NOxanalyser calibrated by

gravimetric NO standard

GPT stochiometric

reaction

Pure ozone concentration c

assessed by pressure measurements

I0 I

Calibration of any O3 analyser

Primary UV photometer

I0 I

0

1

σ λ

= −

⋅ l

(n'

)opt

cI

L I

O3

Calibration by comparison of measurement results c’ on an

unknown sample


1040

1080

1120

1160

1200

1240In

n '5

3H

earn

'61

De

Mor

e '6

4G

riggs

'68

Mol

ina

'86

Mau

ersb

. '86

Mau

ersb

. '87

aM

auer

sb. '

87b

Yos

hino

'88

Yos

hino

'93

Mal

icet

'89

Brio

n '9

3 B

urro

ws

'99

NIS

T-S

RP

Orp

hal '

01

GP

T '0

5

(k=2)

cro

ss s

ection / (

10

-20 c

m2/m

ole

cule

)

GPT results put the question mark on the cross-section

Independent measurements Reviews


Harmonisation issue solved

Inn 5

3

Hearn

61

De M

ore

63

Griggs 6

8

Mauers

b. 85

Molin

a 8

6

Mauers

b. 86

Yoshin

o 8

7

Mauers

b. 87

Malic

et 89

Yoshin

o 9

3

Brion 9

31000

1050

1100

1150

1200

1250

1300

(k=2)

cro

ss s

ectio

n

σ/1

0-2

0cm

2/m

ole

cu

le

Up to now : conventional value used in all ozone photometers, with a relative standard uncertainty equals to:

0.58% (NIST/NASA)0.75% (ISO standard)1% (some institutes)

2.12Expanded relative uncertainty (k=2) (%)

1.06Combined relative uncertainty (%)

0.81McLeod gauge (%)

0.54Tube length (%)

0.43Standard deviation of the mean (%)

2009 : NMIs adopt a conventional

uncertainty for the cross-section based

on Hearn uncertainty budget with GUM1

principles

1 BIPM, CEI, FICC, ISO, OIML, UICPA, and UIPPA, Guide to the Expression of

Uncertainty in Measurement. 1995, Geneva: International Organization for

Standardization. 101.


Outline






cross-section


The laser-based SRP - a potential new primary standard

Frequency doubled Argon ion laser

Wave m

ete

rSRP32 (lamp-based)

Las

er-b

ased

SR

P33


240 245 250 255 260 265 270

80

90

100

110

120

Arg

on laser

Arg

on laser

Arg

on laser

YA

G laser

cro

ss-s

ection / 1

0-1

9cm

2 .mole

cule

s-1

λ / nm

294K, Hearn 61

298K, Daumont 92

295K, Bass &Paur 81

295K, Yoshino & al. 93

250K, Bass 81

298K, Molina 86

Ozone cross-section to be measured again in the Hartley band

Actual conventional value

Three laser lines close to the ozone absorption cross-section maximum


Conclusion

The BIPM provides the basis for a single, coherent system of

measurements throughout the world, traceable to the International System

of Units (SI).

For ozone at ambient level, comparability is insured through International

comparisons of ozone standard instruments (UV photometers)

Traceability to the SI is under question as two reference methods do not

agree

To resolve this issue, new (more accurate) measurements of the ozone

absorption cross-section in the Hartley band are undertaken


www.bipm.orgwww.bipm.org

www.metrologyinfo.orgwww.metrologyinfo.org

THANK YOU

Requirements for new measurements of ozone absorption...

Documents

Transcript of Requirements for new measurements of ozone absorption...