Abstract
In Italy, children spend up to 30% of their time in school institutions; for this reason, the evaluation of indoor air quality in schools constitutes a necessary step forward in the direction of child health protection. In this study, we investigated the chemical composition of PM2.5 collected simultaneously indoor and outdoor in three primary schools in Rome. Seasonal variations between winter and spring/summer were evaluated, as well as the role of the main macro-sources of PM (soil, sea, traffic, secondary inorganics and organics). During winter periods, characterized by strong atmospheric stability, the main contributors were organics and combustion products, which accounted for more than 70% of the total mass both indoor and outdoor. Spring/summer period was characterized by very low outdoor concentrations (12 μg/m3 on average) and by a more balanced contribution of organic, traffic and secondary inorganic components. Indoor, the contribution of soil-related species from re-suspension of settled dust and secondary inorganic species from outdoor photochemical reactions became significant. Given that several indoor exceedances of the international air quality standards for PM2.5 were recorded during the most polluted days, the infiltration of outdoor air, due to the inadequate construction characteristics of the buildings and the absence of automated air filtration systems, seemed to be the main causes of the high PM concentrations measured indoor.
Highlights
The World Health Organization (WHO) has included air pollution among the key determinants of health [1]
The reconstructed mass was obtained by adding elements, ions, carbonate, organic matter and elemental carbon concentrations: elements (Al, Si, Fe, Mg, K, non-soluble Na and Ca,) were calculated as oxides, multiplying each term by a correction factor for oxygen [30]; carbonate was calculated as the sum of magnesium and calcium multiplied by 2.5 and 1.5, respectively; organic matter was obtained multiplying organic carbon by a factor α that takes into account non carbon atoms in organic molecules
Traffic is calculated as the sum of elemental carbon plus an equivalent amount of organic carbon, to consider the contribution of primary organic matter to this source [33]; organics is considered as the remaining organic matter contribution, which includes both secondary organic species produced by gas/particle conversion of volatile compounds and primary components, including bio-aerosol
Summary
The World Health Organization (WHO) has included air pollution among the key determinants of health [1]. It is generally possible to obtain the mass closure, which is the correspondence between the gravimetric mass and the sum of the main components, and to estimate the main source contributions to PM mass This method has been applied successfully in outdoor air quality studies [22] and is appropriate for indoor studies [23]. The impact of the main PM macro-sources (soil, sea, secondary inorganics, traffic, and organics) on indoor and outdoor PM concentrations was investigated. To our knowledge, this was the first time that an overall assessment of fine PM components was performed simultaneously in three Italian schools
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