title: Validation and modelling of a novel diffusive sampler for determining concentrations of volatile organic compounds in air.
abstract: A novel diffusive sampler that combines radial and axial diffusion has been developed that improves upon existing commercially available designs. The POcket Diffusive (POD) sampler has been validated under laboratory and field conditions for the measurements of VOCs in ambient air. Laboratory tests varied sampling conditions of temperature (-30-40 C), humidity (10-80%), wind velocity (0.1-4 m s(-1)), and concentration (0.5-50 μg m(-3)) for a number of specific VOCs. An overall uncertainty of circa 9% for the measurement of benzene is calculated for the validation tests, in compliance with the data quality objectives of the EU air quality directive 2008/50/EC. A semi-empirical diffusion model has been developed to estimate sampling rates for compounds that were not tested, and for conditions outside of tested ranges during validation. The diffusion model (and validation tests) shows a low influence of environmental conditions on the sampling rate for the POD sampler. Average reproducibility values of circa 3% are reported with overall sampling uncertainties ranging from 9% to 15%, for the whole range of tested conditions, depending on the compound. The adsorbent cartridge is compatible with existing thermal desorption systems in the market. The diffusive sampler can modify the sampling rate by changing the diffusive body within a range of different porosities. Field tests, conducted in parallel with independent quality controlled canister sampling, confirmed the ease of use and quality of VOC measurements with the POD sampler, for compounds that were, and were not, evaluated during laboratory tests.
authors.affiliation: European Commission, Joint Research Centre, Institute for Environment and Sustainability, Air and Climate Unit, I-21027, Ispra, VA, Italy. Electronic address: pascual.ballesta@jrc.ec.europa.eu.
authors.forename: Pascual Pérez
authors.initials: PP
authors.lastname: Ballesta
authors.affiliation: European Commission, Joint Research Centre, Institute for Environment and Sustainability, Air and Climate Unit, I-21027, Ispra, VA, Italy.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Grandesso
authors.affiliation: Department of Atmospheric Science, University of Wyoming, 1000 E. University Ave., Laramie, WY, 82071, USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Field
authors.affiliation: European Commission, Joint Research Centre, Institute for Environment and Sustainability, Air and Climate Unit, I-21027, Ispra, VA, Italy.
authors.forename: Ana
authors.initials: A
authors.lastname: Cabrerizo
keywords: Benzene; Diffusion model; Diffusive sampler; Thermal desorption; Validation tests; Volatile organic compounds