Environmental context
Atmospheric aerosols affect the Earth’s climate system and can cause adverse effects on human health depending on their loading and chemical composition. This study presents the chemical characteristics and seasonality of inorganic ions and trace metals in atmospheric aerosols from Sapporo, northern Japan, and explores their possible sources. The work is relevant for our understanding of atmospheric composition and climate change.
Abstract
To better understand the characteristics, seasonality and sources of inorganic aerosols in North-east Asia, we studied total suspended particulate samples collected in Sapporo, northern Japan for inorganic ions and trace metals over a 1-year period. SO42– was found as the most abundant ionic species, which accounted for on average 43±15% of the measured total ionic mass followed by Cl–≈NO3–≈Na+. Among the metals determined, Ca was found as the most abundant (45±5.2% of the measured total metals) followed by Fe. Temporal variations of methanesulfonate (MS–) and SO42– showed a clear seasonal pattern with a maximum in summer followed by spring. Cl–, NO3–, NH4+ and K+ showed increasing trends from mid autumn to winter. Na+, Ca2+ and Mg2+ and crustal metals (Al, Ca, Fe, Ti and Mn) peaked in early spring. Na+ and Mg2+ and Ni, Cu and As were abundant in autumn whereas Zn was in spring. However, Cd and Pb did not show any seasonality. Based on comparisons of such seasonal trends with those of organic tracers as well as the air mass trajectories, we infer that the seasonality in inorganic aerosols in the North-east Asian atmosphere is mainly controlled by their season-specific source(s): soil dust in early spring, biogenic emissions in spring–summer, microbial activities in autumn and forest fires and biomass burning in autumn–winter. However, contributions from anthropogenic sources are significant in all seasons. This study also suggests that fungal spores partly contribute to some trace metals (i.e. Ni, Cu and As) whereas pollen contributes to Zn in aerosols.
Time-resolved variations in the distributions of inorganic ions, carbonaceous components, dicarboxylic acids and related compounds in atmospheric aerosols from Sapporo, northern Japan during summertime
