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Carbon dioxide determination in atmosphere by non dispersive infrared spectroscopy: A possible approach towards the comparability with seawater CO 2 measurement results
Get PDFThe rising levels of carbon dioxide in the atmosphere are responsible for fundamental changes occurring in seawater carbonate chemistry. The partial pressure of oceanic CO2 (pCO2) is one of the four measurable parameters defining the marine carbon system. For this reason, the pressing need of assuring metrological traceability of pCO2 measurement results has been recognized and pointed out by the oceanographic community. In order to achieve this fundamental goal, the lack of suitable reference materials has been identified as one of the most limiting factors. At INRIM several activities are carried out to establish the metrological traceability for carbon dioxide measurement results. The present paper describes two primary methods, the gravimetry and the dynamic dilution, used for the preparation of gaseous reference standards for composition which are fundamental to calibrate sensors and analytical instrumentation for carbon dioxide determination in atmosphere. Suitable procedures for the calibration and use of Non Dispersive Infrared Analysers (NDIR) are also presented and discussed. At present, feasibility studies are ongoing at INRIM to extend the use of these metrologically traceable mixtures to the calibration of sensors used for pCO2 determination in seawater. An extensive work was carried out on a non-dispersive infrared analyser employed in air monitoring, to assess its robustness and stability, which are the major starting points to set up a calibration procedure to obtain comparable results in the atmospheric and marine compartments
Nitrogen oxides analysis: INRiM activity
No full textThe monitoring of nitrogen oxides (NOX) is
prescribed by European directives by means of
chemiluminescence. This paper presents the activity carried out
at INRiM for the preparation and analysis of NOX mixtures,
with the aim of establishing metrological traceability. Together
with the use of chemiluminescence, the application of Fourier
Transform Infrared (FTIR) spectroscopy is also under
investigation as it can allow the identification of some
impurities occurring in the gas mixtures which cannot be
discriminated by chemiluminescence
Metrological traceability for the analysis of environmental pollutants in the atmosphere
Get PDFThe importance of carrying out accurate and reliable measurements is a fundamental topic in many different fields, in particular for
the safeguard of the environment and the climatic conditions of the planet. This is the basis for the planning of correct actions to
prevent environmental damages and potential harmful effects for the health of the human beings. The application of metrology to
chemical monitoring can assure the reliability of measurement results.
At the Istituto Nazionale di Ricerca Metrologica (INRiM), the Italian Metrology Institute, different activities are carried out for the
analysis of gaseous and organic pollutants in the atmosphere. This paper deals with some examples of such activities.
For gaseous pollutants primary gravimetric mixtures are produced for the calibration of the instrumentation devoted to the analysis of
carbon dioxide (CO2) and nitrogen oxides (NOx), with the aim of assuring traceability to the measurements of CO2 at ambient level and
at the vehicles emission level, and of NOx at ambient level. On the other hand, research is carried out in the field of organic
micropollutants, in particular regarding the establishment of metrological traceability for the atmospheric concentrations of Polycyclic
Aromatic Hydrocarbons (PAHs) adsorbed on particulate matter (PM)
Marine Metrology and Oceanographic Measurements 2020
Get PDFThe measurement of oceanic parameters, and the consequent monitoring of their evolution in space and time, represent the basis for environmental information services that support a wide range of societal and commercial applications [...
Stable carbon isotope signatures in atmosphere and seawater as a basis for climate change studies
No full textCarbon dioxide is the major anthropogenic greenhouse gas and its concentration in atmosphere has increased at a rate of (2.0 ± 0.1 ppm/yr) in the period 2002-2011. The ocean is a major sink of atmospheric CO2, absorbing about the 30 % of the emitted anthropogenic CO2 giving a contribution in the moderation of the climate change effects of these emissions. The accurate measurement of the stable carbon isotopes ratio ( 13 C/ 12 C), expressed as δ 13 C according to the convention of reporting stable isotope ratios in terms of a deviation from an international standard (δ-values), is a useful tracer of CO2 derived from fossil fuel and deforestation sources. In this paper, an overview of the importance of the measurement of δ 13 C both in atmosphere and in seawater, is given, with a particular focus on the use of these δ-values as isotopic signatures to support climate change studies. The importance of carrying out accurate and precise measurements and the need of reliable stable isotopes reference standards is also highlighted
Uncertainty Evaluation for Quantification of Low Amount of Benzo[a]Pyrene: Law of Propagation of Uncertainty and Monte Carlo Method for Propagation of Distributions
No full textLaw of Propagation of Uncertainty (LPU) and Monte Carlo (MC) method for propagation of probability distributions were used for uncertainty evaluation of low amount of benzo[a]pyrene (BaP). BaP is usually chosen as a marker of Polycyclic Aromatic Hydrocarbons, which are a class of persistent organic micropollutants particularly dangerous for their toxicity and ubiquity.
Following the procedure developed at INRiM [4], glass fiber filters, commonly used for the sampling of airborne particulate matter, were spiked with a suitable certified reference material. The spiked filters were then extracted twice by Soxhlet in order to obtain two samples each having different mass fractions of BaP. Such mass fractions were quantified by means of a gas-chromatograph coupled with a mass spectrometer by using perdeuterated BaP as internal standard.
In order to investigate the difference in the uncertainties evaluated by LPU and MC methods at the limit of quantification (LOQ) of the analytical procedure, a hypothetical value of BaP mass fraction much lower than the experimental ones was also considered. The results outlined that the two methods applied to the sample containing the highest amount of BaP gave very similar coverage intervals. Instead, at the lower mass, LPU tended to provide larger uncertainty than the MC method. For the case close to LOQ, LPU led to an unphysical coverage interval (spreading over negative values), whereas MC method still produced reliable results
Metrological traceability of Polycyclic Aromatic Hydrocarbons (PAHs) measurements in green tea and mate
Get PDFThe development of suitable analytical methods to obtain metrologically traceable results in the determination of toxicants in food matrices is an important issue, as food represents the main way of assumption of many contaminants, among which the Polycyclic Aromatic Hydrocarbons (PAHs). The present work deals with the set up and internal validation of an analytical method carried out at INRiM for the quantification by gascromatography coupled with mass spectrometry (GC–MS) of some priority PAHs in green tea (Camellia sinensis) and yerba mate (Ilex paraguariensis), in order to obtain metrologically traceable results. Two approaches for the quantification were applied: an external calibration, for determining the GC–MS calibration curves by means of standard reference solutions and an internal calibration by using perdeuterated standards. For the external calibration, Weighted (WLS) and Weighted Total (WTLS) Least Squares fitting procedures were applied. The measurement uncertainty evaluation was carried out by applying the Law of Propagation of Uncertainty
Uncertainty evaluation for the quantification of low masses of benzo[a]pyrene: Comparison between the Law of Propagation of Uncertainty and the Monte Carlo method
Get PDFA proper evaluation of the uncertainty associated to the quantification of micropollutants in the environment,
like Polycyclic Aromatic Hydrocarbons (PAHs), is crucial for the reliability of the measurement
results. The present work describes a comparison between the uncertainty evaluation carried out according
to the GUM uncertainty framework and the Monte Carlo (MC) method. This comparison was
carried out starting from real data sets obtained from the quantification of benzo[a]pyrene (BaP), spiked
on filters commonly used for airborne particulate matter sampling. BaP was chosen as target analyte as it
is listed in the current European legislation as marker of the carcinogenic risk for the whole class of
PAHs.
MC method, being useful for nonlinear models and when the resulting output distribution for the
measurand is non-symmetric, can particularly fit the cases in which the results of intrinsically positive
quantities are very small and the lower limit of a desired coverage interval, obtained according to the
GUM uncertainty framework, can be dramatically close to zero, if not even negative.
In the case under study, it was observed that the two approaches for the uncertainty evaluation
provide different results for BaP masses in samples containing different masses of the analyte, MC
method giving larger coverage intervals. In addition, in cases of analyte masses close to zero, the GUM
uncertainty framework would give even negative lower limit of uncertainty coverage interval for the
measurand, an unphysical result which is avoided when using MC method. MC simulations, indeed, can
be configured in a way that only positive values are generated thus obtaining a coverage interval for the
measurand that is always positive
Use of FTIR spectroscopy for the measurement of CO2 carbon stable isotope ratios
Get PDFCarbon dioxide (CO2) is one of the most important long-lived
anthropogenic greenhouse gases. Ocean, land and biosphere contribute to
take up CO2 emissions, but approximately half of fossil fuel CO2
accumulates in the atmosphere. The study of isotopic composition of CO2
can give useful information for assessing and quantifying the uptake of CO2
in the environmental compartments, as well as for distinguishing natural
from anthropogenic carbon in the atmosphere. In this work, an activity for
the development of a Fourier Transform Infrared spectroscopy (FTIR) based
method for δ13C-CO2 determination in CO2 in air mixtures is presented. The
FTIR can be calibrated by a classical approach based on primary calibration
gas standards, but an alternative calibration can be based on the generation
of synthetic spectra, by means of radiative transfer calculation codes such as
the Multiple Atmospheric Layer Transmission (MALT - University of
Wollongong, Australia). Another software (B-FOS) developed at the Bureau
International des Poids et Mesures (BIPM) allows to interface MALT and
the FTIR management software. This calibration approach is fast and
reliable and can be used when the classical calibration based on reference
gas mixtures might be demanding. The uncertainty obtained for δ13C-CO2
measurements is around 0.1 ‰, at a nominal CO2 mole fraction of 400 μmol
mol-1 in air
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