Changes in airborne lead particulate in port pirie, South Australia, 1986-1996

Port Pirie is 230 km north of Adelaide, the capital of South Australia. The major industry in the city is a lead smelter owned by Pasminco. Fume, dust, and fugitive emissions from the smelter have been deposited in and around Port Pirie over the past 100 years. The results presented in this paper are from an air monitoring station situated at the southeast entrance of the smelter, approximately 600 m from the blast furnace. Measurements include total suspended particulate (TSP) and total suspended particulate lead (TSPL) reported as concentrations (microgram/m3). Data are available from 1986 to 1996 and consist of 548 measurements. Analysis of geometric mean concentration levels by wind direction showed that while for TSP there was little relationship with wind direction, TSPL increased substantially as the wind came from the direction of the smelter. An analysis of geometric mean concentration levels by wind speed showed that TSP was significantly correlated with wind speed for all wind sectors apart from winds coming from the smelter production area. The lack of correlation between TSP and wind speed when the wind blows from the direction of the smelter is probably due to the dilution effect of particulate from a point source as wind speed increases. TSPL was significantly correlated with wind speed for all wind sectors apart from winds coming from the city. As expected, both TSP and TSPL concentrations were significantly lower on days when rain fell. Both mean geometric TSP and TSPL concentrations were lower in the period 1993-1996 than in 1986-1992. Multiple linear regression analysis was used to demonstrate that this decline was statistically significant after adjusting for weather conditions. Wind directions were divided into four sectors: winds from the smelter production area; winds from the smelter nonproduction area; winds from the zinc wharf and east of the city; and winds from the city. Structural equation models for each sector were used to demonstrate that the decline in geometric mean TSPL concentrations over the two periods were of a similar order of magnitude for all four sectors. The relevance of this to the lead abatement programs that have been undertaken both within the city of Port Pirie and inside the smelter itself is discussed.