Wintertime sub-arctic new particle formation from Kola Peninsula sulphur emissions

Abstract. Metallurgical industry in Kola peninsula, North-West Russia, form a second largest source of air pollution in the Arctic and sub-Arctic domain. Sulphur dioxide emissions from the ore smelters are transported to wide areas including Finnish Lapland. We performed investigations on concentrations of SO₂ and aerosol precursor vapours, aerosol and ion cluster size distributions together with chemical composition measurements of freshly formed clusters at SMEAR I station in Finnish Lapland relatively close (~300 km) to Kola peninsula industrial sites during winter 2019–2020. We show that highly concentrated SO₂ from smelter emissions is converted to sulphuric acid (H₂SO₄) with sufficient concentrations to drive new particle formation hundreds of kilometres downwind of the emission sources even with very low solar radiation intensities. Observed new particle formation is primarily initiated by H₂SO₄ – ammonia (negative-) ion induced nucleation. Particle growth to cloud condensation nuclei (CCN) sizes was concluded to result from sulphuric acid condensation. However, airmass advection had a large role in modifying aerosol size distributions and other growth mechanisms cannot be fully excluded. Our results demonstrate the dominance of SO₂ emissions in controlling winter-time aerosol and CCN concentrations in the subarctic region with heavily polluting industry.