Characterization of PM 2.5 fugitive metal in the workplaces and the surrounding environment of a secondary aluminum smelter

Abstract

Fugitive metal in PM 2.5 at the blast furnace ( S 1), reverberatory furnace ( S 2), and surrounding environment ( S 0) of a secondary aluminum smelter (a secondary ALS) was studied. PM 2.5 mass concentration at the blast furnace exceeded that at the reverberatory furnace and this was especially apparent during operation, giving an early indication that the blast furnace is more important as a pollutant source. Further, PM 2.5 mass concentration levels and patterns at S 0 indicated that emissions from the blast furnace and reverberatory furnace were the major source of the observed fine particle pollution in the surrounding environment. Si and K were the main components and hence pollutants by mass in the PM 2.5 at S 1, S 2 and S 0 during both operation and non-operation. Hg was not detected in the PM 2.5 aerosol during smelter operation but was present at all three sampling locations during non-operation. This is due to the falling blast furnace and reverberatory furnace temperatures during non-operation which cause Hg vapor formed during operation to condense to form detectable Hg particles, and hence Hg contributes to the pollutant load during non-operation. Average S 1/ S 0 and S 2/ S 0 mass concentration ratios of 40.32 and 18.53, respectively, for all measured metals during operation and 7.83 and 5.73 for all measured metals during non-operation indicate that metal particulate pollution at the workplaces of secondary ALSs, particularly at the blast furnace during operation, is a serious issue. S 1/ S 0 mass concentration ratios were higher still for Pb (62.22), Ti (113.40) and Ba (248.64), while the S 2/ S 0 mass concentration ratio for Mo was 138.20. Principal component analyses produced a PC1 that explained 32.36–48.16% of the total variance during operation of the smelter and 47.86–69.Ten percent during non-operation. Their strong component loadings were mainly related to the fugitive PM 2.5 mass. Compared to atmospheric metal concentrations reported for other regions of the world, the toxic metals that have relatively higher concentrations in the secondary ALS emissions are Cr, Cd, Cu, As, Pb, Se, Al and Zn, especially during smelter operation. Concentrations of these toxic heavy metals are approximately 2–4 orders of magnitude higher than those reported for various industrial regions and metropolises with heavy traffic across the world.