Trends in new particle formation in eastern Lapland, Finland: effect of decreasing sulfur emissions from Kola Peninsula

Abstract

Abstract. The smelter industry in Kola Peninsula is the largest source of anthropogenic SO 2 in the Arctic part of Europe and one of the largest within the Arctic domain. Due to socio-economic changes in Russia, the emissions have been decreasing especially since the late 1990s resulting in decreased SO 2 concentrations close to Kola in eastern Lapland, Finland. At the same time, the frequency of new particle formation days has been decreasing distinctively at SMEAR I station in eastern Lapland, especially during spring and autumn. We show that sulfur species, namely sulfur dioxide and sulfuric acid, have an important role in both new particle formation and subsequent growth and that the decrease in new particle formation days is a result of the reduction of sulfur emissions originating from Kola Peninsula. In addition to sulfur species, there are many other quantities, such as formation rate of aerosol particles, condensation sink and nucleation mode particle number concentration, which are related to the number of observed new particle formation (NPF) days and need to be addressed when linking sulfur emissions and NPF. We show that while most of these quantities exhibit statistically significant trends, the reduction in Kola sulfur emissions is the most obvious reason for the rapid decline in NPF days. Sulfuric acid explains approximately 20-50 % of the aerosol condensational growth observed at SMEAR I, and there is a large seasonal variation with highest values obtained during spring and autumn. We found that (i) particles form earlier after sunrise during late winter and early spring due to high concentrations of SO 2 and H 2 SO 4 ; (ii) several events occurred during the absence of light, and they were connected to higher than average concentrations of SO 2 ; and (iii) high SO 2 concentrations could advance the onset of nucleation by several hours. Moreover, air masses coming over Kola Peninsula seemed to favour new particle formation.

Seasonal variation of atmospheric particle number concentrations, new particle formation and atmospheric oxidation capacity at the high Arctic site Villum Research Station, Station Nord

“…It should also be noted that Asmi et al (2016) reported measuring particle diameters of 7 nm at Tiksi, whereas only those above 10 nm were reported in this study. NPF events were still observed at the subarctic stations Värriö, Pallas and Abisko during the darker months (November-February), though the fraction of event occurrence was typically much lower compared to other seasons (Kyrö et al, 2014;Asmi et al, 2011;Väänäinen et al, 2013). Notably, not a single event was observed at VRS, Station Nord, during the Arctic night in the absence of sunlight.…”

Particulate matter, air quality and climate: lessons learned and future needs

“…A negative trend in N 100 was also reported for Europe over the same period, although observations were limited to five locations . Declining SO 2 emissions have also been linked to observed negative trends in sulfur dioxide concentrations, new particle formation, total PN, N 50 , N 80 , N 100 and N 150 at a site in northern Finland (Kyrö et al, 2014). Collaud found negative trends for scattering and absorption coefficients (mean −2 % yr −1 ) for locations in North America but no trend over Europe during the period 1996-2010.…”

Atmospheric new particle formation and growth: review of field observations

“…Saha et al (2018) reported that the regional NPF event frequency decreased from about 30% during 2001−2002 to about 10% during 2016 −2017 In Pittsburg, Pensylvania, in United States, accompanied by a strong decline in the SO 2 concentration of about 90% between these two time periods. Kyrö et al (2014) observed a strong decline (−3.7% yr −1 ) in the NPF event frequency at Värriö in Northern Finland over the time period of 1998−2011, and attributed this decline to decreasing sulfur emissions from the nearby industrial sources in the Kola Peninsula. Pallas, a site about 300 km west from Värriö, however, displayed no trend in the NPF event frequency during 2000−2010 .…”