Integrated modeling assessments of the population exposure in Finland to primary PM2.5 from traffic and domestic wood combustion on the resolutions of 1 and 10 km

This study assesses population exposure caused by the emissions of primary fine particulate matter (PM2.5) originated from road traffic and domestic wood combustion in Finland in 2000 and 2020. The evaluations were performed using source-receptor matrices (SRMs) based on the computations using a local and a regional scale atmospheric dispersion model, on two different grid resolutions: 1 and 10 km. Road traffic and domestic wood combustion are nationally the most important emission source categories of primary PM2.5; they were projected to contribute to 42% of the Finnish total emissions in 2020. Although traffic exhaust emissions were projected to decrease considerably in the future, by 91% from 2000 to 2020, non-exhaust emissions were predicted to increase. Traffic emissions were found to cause on the average considerably higher population-weighted concentration (PWC) to primary PM2.5, compared with domestic wood combustion emissions. Based on the computation with 1-km resolution SRMs, the exhaust and non-exhaust traffic emissions were projected to cause 5.5% and 62% of the PWC, respectively, of the total combined PWC caused by traffic and domestic combustion in Finland in 2020. Regarding the sub-categories of domestic wood combustion, supplementary wood heating was found to cause relatively high PWC, 22% in 2020. The modeling of traffic emissions and dispersion using the regional scale model on a resolution of 10 km resulted in PWC that is more than an order of magnitude smaller, compared with the corresponding computations using a local scale model on a resolution of 1 km. The general implication of this study is that the PWC values evaluated using integrated assessment models can be sensitive to the methodology, especially these can substantially increase with an increasing spatial resolution.