metrology in support of long-term assessment of oceanic observables daniela stoica and paola...
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Metrology in support of long-term assessment of oceanic observables
Daniela Stoica and Paola Fisicaro (LNE)
Florence Salvetat (IFREMER), Steffen Seitz (PTB)
Michela Sega and Simona Lago (INRIM)
Challenges in the carbonate system measurements
INTRODUCTION
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• WFD• Marine Strategy
directive• Other EU directives
We cannot manage what we don’t measure!
Continue to improve the quality of analytical measurements
Needs of physico-chemical standards and reference materials for oceanic measurements
pH
Temperature
PressureSalinity/density
MetalsDissolved Oxygen
CO2Conductivity
NutrientsMonitoring Innovation
New technologies opening new measurement possibilities
MONITORING
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• Ensure geographical consistency: harmonisation of methods among countries sharing seawater areas
• Ensure support to other public programs, with both economic and environmental impact:
• Common Fisheries Policy
• Movement of marine life follows speed and direction of climate change with “climate speed”
• Acidification process largely contributes to this situation.
Anticipate problems with fish stocks similar to those encountered by Denmark, Norway or Island with mackerel stocks.
• Energy Policy
E.g. offshore wind power that provides a valuable source of renewable energy but there is still much that is unknown about the effects on the environment.
INNOVATION
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Innovative technologies
Measurement of different parameters in marine environment require the use of simple and reliable instruments.
The possibility to decrease the size while maintaining or even increasing the performances lead to the development of multiparameter sensor.
Automated analysisRemote controlReduced costs
…
MULTIPARAMETER DETECTION
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SEAOS program equipped 24 elephant seals with beacons representing miniaturized CTD devices (T, p and S sensors).
Measures in Austral Ocean during winter season, at depths between 700-1500 m.
Qualification of new technologies performances?Innovative sensor calibration?
METROLOGICAL TRACEABILITY ISSUES
Multiparameter micro-sensor allowing ions quantification in solution (Na+, K+, Ca++, Mg++) and pH. System based on the technology initially developed for pH measurements in blood by CEA Grenoble (Fr)
Some examples
IMPROVE QUALITY OF RESULTS
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Three pillars of metrology
Metrological traceability of
results
Validated measurement
procedures
Uncertainty of results
- Definition of measurand- Certified calibration standards- Calibrated instruments- Primary methods- Certified Reference Materials (CRM)
- Interlaboratory comparisons (ILC)- Method comparison
IMPROVE QUALITY OF RESULTS
The “weather” goal Defined as measurements of quality sufficient to identify relative spatial patterns and short-term variations
Supporting mechanistic response to and impact on local, immediate ocean acidification dynamics.
Objectives of uncertainty of ~ 0.02 in pH; of ~ 10 μmol kg−1 in measurements of AT and CT; a relative uncertainty of ~ 2.5% in p(CO2).
The “climate” goal Defined as measurements of quality sufficient to assess long-term trends with a defined level of confidence
Supporting detection of the long-term anthropogenically driven changes in hydrographic conditions and carbon chemistry over multi-decadal time scales.
Objectives of uncertainty of ~ 0.003 in pH; of ~ 2 μmol kg−1 in measurements of AT and CT; a relative uncertainty of about 0.5% in p(CO2).
Define the final goal
Quality of analytical measurements in oceanography *
* E. Bockmon, A. Dickson, Limnol. Oceanogr.: Methods, 2014
SEAWATER ACIDITY
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Comparability of oceanographic data
Ensure trueness of results
Need of small uncertainty
Different measurand
Realistic uncertainty determination is missing
PotentiometrypH
SpectrophotometrypHT
Calculations from associated thermodynamics
No SI traceability
Consistency problems for S <19 and T< 2°C
Low uncertainties
CHAL
ENG
ESPR
OBL
EMES
11% of global surfaces area and 42 % of its global volume
Routine measurementsPotentiometryGlass electrode
Routine measurementsUV-VIS Spectrophotometry
Secondary method (SS)Potentiometry
Secondary method (SS)UV-VIS Spectrophotometry
Primary method (PS)
Harned cell
Primary method (PS)Harned cell
pmHpaH
SI
SEAWATER ACIDITY
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Development of a primary measurement method allowing to characterise a buffer solution (ENV05)
Choice of artificial matrix (ASW) Composition + buffer (ENV05)
Find the relation between pH and pHT
Traceability to SI for pHT by spectrophotometric measurements (determination of dye dissociation constant as a function of T and S)
Consensus on the terminology (ENV05)
Current traceability
NIST, USA
NMIJ, Japan
SCRIPPS (A. Dickson)JCS (R. Pawlowicz)
Supporting JRP partnersFFCUL, Portugal
SEAWATER SALINITY
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Comparability of oceanographic data
Ensure trueness of the results
Need of small uncertainty
Different measurandPractical Salinity
SP
Absolute SalinitySA
High uncertainties
CHAL
ENG
ESPR
OBL
EMES
Density Refractive index
No direct SI traceability
Difficulties for high pressures measurements
Conductivity ratio (K15)
Calibration conditions deviate from application conditions in deep sea
Inconsistencies at salinities > 35
SEAWATER SALINITY
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Development of a novel primary sensor for p < 200 bar and 5 < T < 40 °C (ENV05)
Establishment of a link between the conductivity based “Practical Salinity” and the SI through an empirical conductivity ratio–density relationship (ENV05)
Improved model Salinity-Density for explaining the discontinuity observed at SP>35
Comparison with present sensor calibration procedure for validation of high pressure salinity measurements
Improvement of primary setup (integration of commercial high pressure conductance sensor in high pressure salinity setup developed in ENV05)
0
5
10
15
20
25
30
35
40
45
0 5 10 15 20 25 30 35 40 45
dens
ity d
iffer
ence
r T
EOS
-rm
easu
red
in
g/m
³
Practical Salinity SP(OSIL)
15 � C to 35 � C
Deviation in g/m³ ≈ 1 ppm
dens
ity d
evia
tion
from
equ
atio
n of
sta
te
g/m
3
Practical Salinity
DETERMINATION OF CO2 IN SEAWATER
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Mode of equilibration
discrete continuous continuous continuous
Equilibration of CO2 in water with CO2 in
air air air A pH-sensitive indicator solution
Equilibration achieved
In a sample flask In an equilibrator through a membrane
Through a membrane
Detection of CO2 by
GC,IR GC,IR spectrophotometry spectrophotometry
Platforms used Commercial shipResearch ship
Commercial shipResearch ship
Moorings, gliders, buoys
Moorings, gliders, buoys
Advantages: fCO2 calculation together with dissociation constant of the dye, dissociation constant of carbonic acid in seawater, the solubility coefficient, alkalinity and concentration of the dye.
Method preferred by oceanographers owing the small sample sizerequires the control and measurement of temperature of the seawater sample to ±0.05◦C, pressure measurement to ±0.5 mbar, several standard gases, and CO2-free carrier gas (for GC analysis)
U. Schuster, Ocean Sci., 2009
Focussed on open issues related to measurements of some physico-chemical parameters in seawater:
pH Salinity/Density CO2
NEXT ENVIRONMENT CALL 2016
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Potential collaborations:
WEAMEC (West Atlantic Marine Energy Center) – Nantes, FROGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale – Trieste, IT)NIST – USANMIJ – JAPANAFNOR – French Standardisation Body - FRCEA (Centre d’Energie Atomique) – Grenoble, FRCNAM (Conservatoire National des Art et Métiers) – Paris, FRSHOM (Service hydrographique et océanographique de la Marine) – FRIOW (Institute for Baltic Sea research Warnemünde) – DEOSIL (Ocean Sientific Internaltiol Ltd.) - UK
To support on site applications for oceanographic community
