Long term fine aerosols at the Cape Grim global baseline station: 1998 to 2016

Publication date: October 2017
Source:Atmospheric Environment, Volume 166
Author(s): Jagoda Crawford, David D. Cohen, Eduard Stelcer, Armand J. Atanacio
Fine aerosol measurements have been undertaken at the Cape Grim global baseline station since 1992. Ion beam analysis techniques were then used to determine the elemental composition of the samples from which source fingerprints can be determined. In this study six source fingerprints were identified to contribute to the measurements of PM2.5 at Cape Grim (from 1998 to 2016); fresh sea salt (57%), secondary sulfate and nitrates (14%), smoke (13%), aged sea salt (the product of NaCl reactions with SO2; 12%), soil dust (2.4%) and industrial metals (1.5%). Back trajectory analysis showed that local Tasmanian sources of soil dust contributed to the high soil dust measurements. High measurements of secondary aerosols were recorded when air masses were arriving from the Australian mainland, in the direction of the Victorian power stations.When air masses were arriving from the baseline sector, the maximum concentration of aged sea salt was 1.3 μg/m³, compared to overall maximum of 4.9 μg/m³. For secondary sulfates and nitrates the maximum concentrations were 2.5 and 7.5 μg/m³ from the baseline sector and overall, respectively. While measurements at Cape Grim can be affected from long range transport from mainland Australia and some local Tasmanian sources, the average concentrations of anthropogenic sources are still considerably lower than those measured at more populated areas. For example, at Lucas Heights (located south-west of the Sydney central business district, with little local sources) the average concentrations of secondary sulfates/nitrates and aged sea air were 1.4 and 1.0 μg/m³, respectively; compared to average concentrations of 0.8 and 0.6 μg/m³, at Cape Grim. The average concentrations of smoke were compatible at the two sites. The impact of primary aerosols from vehicle exhaust at Cape Grim was limited and no corresponding fingerprint was resolved.



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