Sulphate source apportionment by a 10 yr-long record at Ny-Ålesund (Svalbard Islands)

Gruvebadet Observatory at Ny-Ålesund (Svalbard Islands) has been recognized as a valuable facility for long-term studies of atmospheric chemistry in the High Arctic, with particular attention to natural and anthropic aerosol sources and transport processes by using chemical tracers.A long-term study of the chemical composition of PM10 aerosol is being accomplished at Gruvebadet Observatory since 2010 by continuous collection at high resolution (1 to 2 days) and chemical analysis of major and trace ions and elements.The contribution of different sources (sea spray, crustal, biogenic and anthropogenic) to the total sulphate budget was estimated by using specific markers (namely sodium, calcium and methanesulphonate) and their characteristic marker-to-sulphate ratios in sea water, mineral dust and marine biogenic source. The obtained data set was also compared with the one derived from the Zeppelin Observatory, also located in Ny-Ålesund.The anthropogenic fraction resulted to be the dominant component, reaching the highest value in March and April during the Haze period, followed by the sea salt, biogenic and crustal ones. The comparison between the two datasets confirms the seasonal trend of these fractions although some differences in extent were observed, probably due to discrepancies in the timing and resolution of sampling campaigns as well as to different analytical procedures.The temporal profile of the anthropogenic fraction, evaluated in both sites, showed no evident continuous trend from 2010 to 2019, even though higher concentrations were observed in the 2017-19 period, with respect to the previous years. Focusing on single months, two opposite trends in the sulphate budget along 10 years were observed for March against April and September. Whereas a decrease was observed in March, April and September showed an increase in the monthly mean concentration values.Finally, the correlation between the non-sea salt non-crustal sulphate fraction and ammonium was evaluated. An increase in the ammonia neutralizing effect, eventually causing a decrease in aerosol acidity, was observed at Gruvebadet, from the 2010 to 2017, to reach fairly constant values later. Instead, a decrease in ammonia concentration was found at Zeppelin since 2015, leading to an increase of the non sea salt sulphate/ammonium ratio in the same period.