title: Testing approaches for calculating stomatal ozone fluxes from passive samplers.
abstract: Current ozone (O3) levels are high enough to negatively affect vegetation and may become worse in the future. Ozone risk assessments have recently shifted from exposure-based to flux-based metrics. Modeling stomatal O3fluxes requires hourly O3and meteorological data, which are not always available. Large datasets of O3concentrations measured with passive samplers exist worldwide, and usually provide weekly to monthly means. We tested the suitability of using aggregated data instead of hourly data for O3flux calculations with 3-year time series of O3data from 24 Spanish air quality stations. Five different approaches and three different parameterizations were tested. Ozone-averaged values in combination with hourly meteorological data provided the most robust estimates of accumulated O3fluxes (Phytotoxic Ozone Dose with no threshold, POD0), and the median of the absolute percent error (MAPE) due to aggregation came close to 5%. Aggregations from 1week to 1month yielded similar errors, which is important in the cost-efficiency terms of the chosen passive sampler exposure periodicity. One major limitation of these approaches is that they are not suitable for high POD thresholds, and that accuracy of the measurements with passive samplers has to be strictly assured in order to finally obtain acceptable errors. A combination of meteorological data and O3passive sampler measurements may be used to estimate O3fluxes at remote forest sites as a valuable risk assessment tool.
authors: Fundación CEAM, c/ Charles R. Darwin, 14, Parque Tecnológico, Paterna 46980, Spain. Electronic address: vicent@ceam.es.
authors: Vicent
authors: V
authors: Calatayud
authors: Fundación CEAM, c/ Charles R. Darwin, 14, Parque Tecnológico, Paterna 46980, Spain.
authors: José Jaime
authors: JJ
authors: Diéguez
authors: ACRI-HE, 260 route du Pin Montard, 06904 Sophia-Antipolis Cedex, France.
authors: Pierre
authors: P
authors: Sicard
authors: Swiss Federal Research Institute WSL, Zuercherstrasse 111, 8903 Birmensdorf, Switzerland.
authors: Marcus
authors: M
authors: Schaub
authors: ENEA, CR Casaccia, Via Anguillarese 301, Roma, Italy.
authors: Alessandra
authors: A
authors: De Marco
keywords: Ozone fluxes; Passive samplers; Phytotoxic Ozone Dose; Risk assessment