Aluminum levels in the O-horizon of soils near Sundsvall, Sweden : Are levels of Al elevated due to smelter emission?

Sammanfattning: Aluminum (Al) is a potentially toxic element for humans, animals, and plants. Al emitted from smelter plants is one source of Al that may be responsible for increased exposure to humans and the environment. In this study I investigated whether the Kubikenborg aluminum smelter (Kubal AB) emitted Al to such extent that it can be detected above regional background concentrations in soils and plants. The study was conducted by analyzing O- horizon cores and Scots’ pine (Pinus sylvestris) needles along two transects using X-ray fluorescence spectrometry (XRF). In the O-horizon cores, Al concentrations along the two transects (mean conc. 5250 mg kg-1 in T1 and 3472 mg kg-1 in T2) did not decrease with distance from the smelter. In Scots’ pine needles, Al concentrations (mean conc. 491 mg kg-1 in T1 and 590 mg kg-1 in T2) decreased significantly with distance along transect T2. Aluminum showed high negative co-variance with soil organic matter content (R2 = 0.47) and positive with silicon (Si) and titanium (Ti) in the soil (R = 0.84 and R = 0.86 respectively), suggesting that mineral dust is the main source of Al. However, the Al/Si ratio of the soil decreased with increasing distance from the smelter along T1, indicating a possible additional source of Al besides that of soil dust that may originate from smelter emission. Nevertheless, I found no strong support for detectable Al emissions in humus and Scots’ pine needles near the Kubal AB smelter.