The equivalence of diffusive samplers to reference methods for monitoring O3, benzene and NO2 in ambient air

Abstract

A study of the equivalence to the reference methods of the Radiello samplers for ozone (O₃) and benzene as well as the membrane-closed Palmes tube (MCPT) for nitrogen dioxide (NO₂) is presented. These samplers benefit from new model equations capable of estimating their uptake rate. For O₃, the aim here was to demonstrate the equivalence for the reference period of 8 h and 120 µg m⁻³, the target value of the 3rd European Daughter Directive. For benzene, the demonstration of equivalence to the annual limit value of 5 µg m⁻³ of the 2nd European Daughter Directive was examined. In the case of NO₂, the equivalence to the annual limit value of the 1st European Daughter Directive (40 µg m⁻³) was considered. Results show that the radial sampler for O₃ fails to meet the Data Quality Objective (DQO) for continuous monitoring. However, with an expanded uncertainty of less than 30%, the O₃ diffusive sampler fulfils the DQO for indicative measurements. For benzene, the Radiello sampler exposed for 7 days gave satisfying results showing the ability of the sampler to meet the DQO of the reference method. Nevertheless, the field tests should be complemented by measurements for a wider range of benzene concentrations. In the case of NO₂, all the results of the laboratory and field experiments respected the requirements necessary for the demonstration of equivalence. Overall, these findings thus show that the Radiello sampler and the MCPT are equivalent to the reference methods only for assessment of benzene and NO₂, respectively.