Contribution of Seasalt and its Degraded Products to Particulate Loadings at Inland Sites in the Hunter Valley
A year long study in the Hunter at two near-mine rural sites and at two rural town sites has examined possible sources for measured particulate emissions. The sites sampled are in areas believed to be impacted by emissions from open-cut coal mining operations. As well as measuring particulate concentrations a series of 443 filter samples were collected and chemically analysed by ANSTO using a multi-element ion beam analytical (IBA) technique. Filter samples were also examined using scanning electron microscopy (SEM) and individual particulates chemically analysed with electron dispersive spectroscopy (EDS).
Although all sampling sites are a significant distance from the Australian East Coast the data show evidence of a substantial contribution of seasalt and its degraded products to the atmospheric particulate loading. The presence of seasalt particles in the Muswellbrook region has previously been noted and they are believed to have originated not only from the eastern seaboard but also from the Great Australian Bight some 1500 km away.
The Na and Cl content of both the fine and coarse particles were found to be strongly related (as might be expected), although there is a significant Cl deficit when compared with the seawater from which the seasalt evolved. Chloride deficient salts have been observed previously and are linked to the availability of strong sulfur-acidity in the aerosol. This linkage is strongly supported by the results of the present study. SEM and chemical analysis of individual particles allows mechanisms for the de-chlorination process to be further described.