Development of West-European PM2.5 and NO2 land use regression models incorporating satellite-derived and chemical transport modelling data

Satellite-derived (SAT) and chemical transport model (CTM) estimates of PM2.5 and NO2 are increasingly used in combination with Land Use Regression (LUR) models. We aimed to compare the contribution of SAT and CTM data to the performance of LUR PM2.5 and NO2 models for Europe. Four sets of models, all including local traffic and land use variables, were compared (LUR without SAT or CTM, with SAT only, with CTM only, and with both SAT and CTM). LUR models were developed using two monitoring data sets: PM2.5 and NO2 ground level measurements from the European Study of Cohorts for Air Pollution Effects (ESCAPE) and from the European AIRBASE network. LUR PM2.5 models including SAT and SAT+CTM explained ~60% of spatial variation in measured PM2.5 concentrations, substantially more than the LUR model without SAT and CTM (adjR(2): 0.33-0.38). For NO2 CTM improved prediction modestly (adjR(2): 0.58) compared to models without SAT and CTM (adjR(2): 0.47-0.51). Both monitoring networks are capable of producing models explaining the spatial variance over a large study area. SAT and CTM estimates of PM2.5 and NO2 significantly improved the performance of high spatial resolution LUR models at the European scale for use in large epidemiological studies

High-Resolution Gas Chromatography-Tandem Mass Spectrometry: A Sensitive Analytical Technique Suitable for the Study of Atmospheric Processes of Polychlorinated Biphenyls and Dibenzo-p-Dioxins/Furans

The trace-level environmental determination of polychlorinated biphenyls (PCBs) and 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) requires the use of delicate fractionation and analytical techniques such as high-resolution gas chromatography coupled with high-resolution mass spectrometry. The analytical requirements are even higher if atmospheric physicochemical processes of these persistent organic compounds (POPs) are to be studied in remote areas, where concentrations are very low. The optimization of a fractionation method, and of the high-resolution gas chromatography/ion trap tandem mass spectrometry system instrumental parameters enabled us to establish the optimum conditions for the determination of atmospheric PCBs and PCDD/Fs at the low pg or even fg m-3 level. By using this analytical procedure, we accomplished the reliable determination of ca. 54 PCBs and 17 PCDD/Fs individual congeners, of different chlorination level, in the gas and particulate phase of atmospheric aerosol samples collected from the Eastern Mediterranean basin. Furthermore, we were also able to study the atmospheric physicochemical and loss processes of PCBs, such as gas-particle partitioning, wet and dry deposition, and PCBs reaction with hydroxyl radicals