Deposition of acidic species at a rural location in New South Wales, Australia

Abstract

Wet-only rainwater composition on a daily basis, and atmospheric SO₂ and NO₂ concentrations on a monthly basis have been measured over a two year period at four sites ∼100 km to the west of Sydney. Bulk aerosol composition on a monthly basis was also measured at one site. The study region is predominantly rural in character, but contains two coal-fired thermal power stations with a total installed capacity of 2320 MW, as well as several min or population centres, including a small city, with a total population of about 21,000. The measurement sites were located roughly on the perimeter of a circle of about 20 km radius having the power stations at its centre. Three of the sites were situated in rural settings, while the fourth was located on the outskirts of the small city of Lithgow. Atmospheric acid loadings at all sites were low by the standards usually associated with industrialised regions of Europe and North America, with about one third of rainwater total acidity provided by organic acids (formic, acetic and oxalic). At the three rural sites, total inorganic acid deposition, comprising measured wet deposition plus inferred dry deposition of acidic S and N species, averaged about 30 meq m⁻² y⁻¹, a low figure by most standards. At the site located near the city of Lithgow total deposition of acidic S and N species averaged about 80 meq m⁻² y⁻¹.