Uncertainty models and influence of the calibration span on ambient air measurements of NO2 by chemiluminescence

An assessment of uncertainty in the hourly and annual limit values of NO2 measurements by molybdenum NO2-to-NO conversion followed by chemiluminescence detection was carried out at 3 different span concentrations (100, 300 and 700 nmol/mol). The uncertainty of the linearity term was calculated for each span concentration by considering (i) a zero-and-span calibration and (ii) a multipoint calibration. Two uncertainty models were applied for the overall uncertainty estimation: (i) the Standard EN 14211, and (ii) a mechanistic model that considers the NO2 reduction in the converter. The main difference between these models stems from considering or not the possible covariances derived from interactions between NOx and NO concentrations and the converter’s efficiency. For both models, the span determined the possibility of meeting or not the quality objective requested by the EU Air Quality Directives in the annual limit value when no linearity corrections were performed in environments with NOz/NO2 ratios  0.04. In environments with significant amounts of NOz species (NOz/NO2 ≥ 0.12), the expanded uncertainty can be easily higher than the data quality objective if bias’ corrections are not or cannot be applied.

DOVAL MIÑARRO Marta;  PEREZ BALLESTA Pascual;  BARBERA RICO Jonathan;  GONZALEZ FERRADAS Enrique; 

2014-09-19

ROYAL SOC CHEMISTRY

JRC76676

2050-7887,   

http://pubs.rsc.org/en/Content/ArticleLanding/2013/EM/C2EM30395G#!divAbstract,    https://publications.jrc.ec.europa.eu/repository/handle/JRC76676,   

10.1039/c2em30395g,