What question did this study set out to answer?

This research aims to evaluate the concentration levels and sources of PAHs and eBC in indoor and outdoor environments in Barcelona's urban landscape.

April 13, 2026Open Access

Atmospheric Polycyclic Aromatic Hydrocarbon and Black Carbon concentrations and sources in primary schools and homes in a changing Mediterranean urban environment

Key Points

This research aims to evaluate the concentration levels and sources of PAHs and eBC in indoor and outdoor environments in Barcelona's urban landscape.
Conducted air sampling in five primary schools and seven homes during varying seasons.
Utilized low-volume samplers for PAH analysis via GC-MS/MS and collected PM2.5 filter samples.
Monitored continuous eBC concentrations using portable aethalometers.
Indoor PAH concentrations averaged 12.8 ng/m3, significantly higher than outdoor levels of 6.9 ng/m3.
Less volatile and hazardous PAHs were found to be strongly correlated with eBC levels.
Traffic was identified as the primary source of indoor eBC in urban sites, while biomass burning was dominant in the rural area.

Abstract

Indoor air quality at schools and homes is a concern for children’s health. This study assessed the concentrations of polycyclic aromatic hydrocarbons (PAHs) and equivalent black carbon (eBC) in indoor and outdoor environments and investigated their possible sources. Samplings were conducted at five primary schools and seven homes in urban Barcelona (Spain) during cold and warm seasons, along with a rural school located 130 km from the city. Air gas and particles were collected in SPE cartridges connected to low-volume samplers for PAH analysis by GC-MS/MS. PM 2.5 filter samples were also collected for organic carbon and organic molecular tracer analysis, and continuous eBC concentrations were monitored with portable aethalometers. Time integrated samples showed higher total PAH levels indoors (12.8 ± 7.9 ng/m 3 ) than outdoors (6.9 ± 2.9 ng/m 3 ), largely due to volatile PAHs from indoor activities at homes. In contrast, the less volatile and more hazardous PAHs were strongly correlated with eBC. The average eBC indoor-outdoor concentration ratio of 1.1 ± 0.4 indicated traffic as dominant contributor to indoor eBC and less volatile PAHs in the urban areas, whereas biomass burning was a major source at the rural site. These sources contributed largely to PAHs, eBC and organic matter identified in indoor samples, followed by dust inputs and cooking activities. The PAH and eBC levels observed in this study are lower than those reported in Barcelona a decade ago, suggesting a positive impact of the city's traffic-related air pollution mitigation measures, which may have improved outdoor air and benefited indoor environments. • LMW-PAH concentration significantly higher indoors due to indoor activities. • HMW-PAHs strongly correlated with eBC, indicating shared combustion-related sources. • Traffic emissions majorly contributing to eBC and PAH concentrations in urban sites. • Biomass burning is the main PAH source at the rural site. • Reduced PAH concentrations in Barcelona can be related to mitigation measures.

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