It is well known that more than 90% of our time is spent in indoor environments, notably in homes, offices or schools. Nevertheless, more insights need to be gained in order to better understand the association between indoor air quality (IAQ) and health. With the exception of some guidelines about few gaseous contaminants of particular concern (WHO, 2010), no specific legislation has been adopted in the field of indoor air pollution. Understanding the role of particulate matter in the evaluation of IAQ is a challenging task, which requires careful data interpretation. Indeed, PM concentration in confined environments is governed by the release from indoor sources as well as by the penetration efficiency of particles generated outdoor. Furthermore, when performing the evaluation of PM chemical composition, technical problems due to the use of noisy and bulky instrumentations for filter sampling can occur. The present study aims at giving an overview of the results obtained collecting indoor and outdoor PM2.5 in several residences and schools in Italy and the Republic of Malta (Figure 1) during the last three years. Sampling sites were selected on the basis of location, to include urban (Rome, Italy and La Valletta, Malta), peri-urban (Monterotondo, Italy), industrial (Gela, Italy) and rural (40 km from Rome) sites. Daily samplings were carried out on both teflon and quartz filters in order to obtain the complete chemical characterization of PM and the mass closure. Specifically designed silent samplers operating at the flow rate of 10 l/min were employed during all the studies (Silent Sampler, FAI-Instruments, Fonte Nuova, Rome, Italy). Simultaneous samplings were performed in order to compare indoor and outdoor PM2.5 concentration and chemical composition. The indoor/outdoor (I/O) concentration ratios and the correlation between the time patterns of indoor and outdoor species were also evaluated. This strategy led to take into account the modifications in particle concentration and composition due to infiltration of particles generated outdoor. Furthermore, when several schools and homes were monitored simultaneously, a comparison between daily and average differences and between specific indoor sources could be made. In general, the organic fraction was the most abundant contributor both indoor and outdoor: it was higher in indoor environments where, during the winter, it accounted for more than 60% in homes and approximately 45% in schools, indicating the impact of domestic activities (e.g. cooking and cleaning) and of the presence of the occupants. Other components, mainly some secondary inorganics and traffic-generated species did not exhibit significant variations between indoor and outdoor environments, showing I/O ratios very close to 1 and good correlation factors. Infiltration processes could be identified for some species of combustion origin: at coastal sites a good correlation was observed for indoor and outdoor Ni and V, emitted by the ship traffic. In urban sites good correlations were found for EC, Sn, Mo, Mn, Sb, which are associated to vehicular emission. During the winter, high indoor-outdoor correlations were also found for components emitted during biomass burning episodes (K, Cs, Rb). Regarding indoor environments, higher values of Cu in homes and schools were ascribed to the use of electronic appliances (hairdryers, computers). High values of K, Cd and Tl recorded in some homes were associated to the presence of smokers and related to the number of cigarettes. In winter, the depletion of nitrate and ammonium was registered indoor, indicating that residential heating can lead to the transformation of outdoor volatile species when they infiltrate indoor. This work was partly conducted within the framework of LIFE+ EXPAH project (Population Exposure to PAH) and RESPIRA project (Air quality and Respiratory Health in Malta and Sicily, Italy-Malta Cross-Border 2007-2013 OP).
Chemical characterization of indoor PM2.5 in urban areas of the Mediterranean basin
2015
Abstract
It is well known that more than 90% of our time is spent in indoor environments, notably in homes, offices or schools. Nevertheless, more insights need to be gained in order to better understand the association between indoor air quality (IAQ) and health. With the exception of some guidelines about few gaseous contaminants of particular concern (WHO, 2010), no specific legislation has been adopted in the field of indoor air pollution. Understanding the role of particulate matter in the evaluation of IAQ is a challenging task, which requires careful data interpretation. Indeed, PM concentration in confined environments is governed by the release from indoor sources as well as by the penetration efficiency of particles generated outdoor. Furthermore, when performing the evaluation of PM chemical composition, technical problems due to the use of noisy and bulky instrumentations for filter sampling can occur. The present study aims at giving an overview of the results obtained collecting indoor and outdoor PM2.5 in several residences and schools in Italy and the Republic of Malta (Figure 1) during the last three years. Sampling sites were selected on the basis of location, to include urban (Rome, Italy and La Valletta, Malta), peri-urban (Monterotondo, Italy), industrial (Gela, Italy) and rural (40 km from Rome) sites. Daily samplings were carried out on both teflon and quartz filters in order to obtain the complete chemical characterization of PM and the mass closure. Specifically designed silent samplers operating at the flow rate of 10 l/min were employed during all the studies (Silent Sampler, FAI-Instruments, Fonte Nuova, Rome, Italy). Simultaneous samplings were performed in order to compare indoor and outdoor PM2.5 concentration and chemical composition. The indoor/outdoor (I/O) concentration ratios and the correlation between the time patterns of indoor and outdoor species were also evaluated. This strategy led to take into account the modifications in particle concentration and composition due to infiltration of particles generated outdoor. Furthermore, when several schools and homes were monitored simultaneously, a comparison between daily and average differences and between specific indoor sources could be made. In general, the organic fraction was the most abundant contributor both indoor and outdoor: it was higher in indoor environments where, during the winter, it accounted for more than 60% in homes and approximately 45% in schools, indicating the impact of domestic activities (e.g. cooking and cleaning) and of the presence of the occupants. Other components, mainly some secondary inorganics and traffic-generated species did not exhibit significant variations between indoor and outdoor environments, showing I/O ratios very close to 1 and good correlation factors. Infiltration processes could be identified for some species of combustion origin: at coastal sites a good correlation was observed for indoor and outdoor Ni and V, emitted by the ship traffic. In urban sites good correlations were found for EC, Sn, Mo, Mn, Sb, which are associated to vehicular emission. During the winter, high indoor-outdoor correlations were also found for components emitted during biomass burning episodes (K, Cs, Rb). Regarding indoor environments, higher values of Cu in homes and schools were ascribed to the use of electronic appliances (hairdryers, computers). High values of K, Cd and Tl recorded in some homes were associated to the presence of smokers and related to the number of cigarettes. In winter, the depletion of nitrate and ammonium was registered indoor, indicating that residential heating can lead to the transformation of outdoor volatile species when they infiltrate indoor. This work was partly conducted within the framework of LIFE+ EXPAH project (Population Exposure to PAH) and RESPIRA project (Air quality and Respiratory Health in Malta and Sicily, Italy-Malta Cross-Border 2007-2013 OP).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
