Rainwater composition and acid deposition in the vicinity of fossil fuel-fired power plants in southern Australia

Daily wet-only rainwater composition was determined at four sites in the Latrobe Valley, Victoria, between February 1990 and February 1992. The Latrobe Valley sits on vast resources of easily mined brown coal which at the time of the study fuelled five coal buming power plants of 5150 MW total installed capacity. A sixth gas-fired station of 400 MW capacity is also located in the Valley. Strong preference for down-valley westerly winds on raindays coupled with location of the four rainwater samplers along the central line of the Valley provided an ideal gradation in source-receptor relationships : from the westerly location of Site 1, upwind of all power stations, to Site 2 in the centre of the Valley, upwind of half the emissions sources, to Sites 3 and 4 at the eastern end of the Valley, downwind of all the power plants. Despite the ideal geographic layout the two years of wet deposition data exhibited no clear signal attributable to the power station emissions of sulfur and nitrogen, apparently because raindays in the Latrobe Valley are mast often the product of frontal activity accompanied by high wind speeds, leading to high ventilation rates. The resultant wet deposition rates for sulfate and nitrate were in the ranges 7.0 to 14.5 and 3.1 to 4.7 meg m(-2) y(-1), values that are low in comparison with values observed in populated mid-latitude regions of the northern hemisphere.