Natural and anthropogenic influences on aluminium in the humic rich waters of northern Sweden
The issue of acidification of surface waters has been one of the central environmental problems in Sweden for the last four decades. Aluminium (Al) is critical to the issue of acidification because it is often the combination of depressed pH along with elevated concentrations of Al, and specifically...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
| Published: |
2006
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| Online Access: | https://pub.epsilon.slu.se/1178/ https://pub.epsilon.slu.se/1178/1/Thesis_neil_cory.pdf |
| Summary: | The issue of acidification of surface waters has been one of the central environmental problems in Sweden for the last four decades. Aluminium (Al) is critical to the issue of acidification because it is often the combination of depressed pH along with elevated concentrations of Al, and specifically inorganic Aluminium (Ali), which are implicated in the decline and disappearance of aquatic organisms. In northern Sweden where sulphate deposition has not been as high as in the south, chronic soil acidification has not taken place; instead it is episodic acidification, especially during the spring snow melt that is important. The presence of organic matter complicates the issue of acidification and Al by providing both natural acidity and abundant binding capacity that reduces the inorganic fraction of Al. This thesis addresses the issue of anthropogenic influence in northern Sweden by examining Al solubility, speciation and modelling across spatial and temporal scales that range from a hillslope or episode to a landscape and decades. At the hillslope scale Al transport and speciation were strongly influenced by the organic phase. No front of Al mobilization was seen in the mineral soil that would be indicative of chronic soil acidification. The superficial, transiently saturated flow pathways in the riparian peats had accumulated a large amount of Al, and were the major source of Al leaving a hillslope transect. At the landscape levels the influence of landcover was important for both concentration and speciation of Al. Areas draining wetlands had lower concentrations of Al than forested sites despite significantly lower pH. This was attributed to source limitation, with wetlands lacking a mineral source of Al. Forested sites showed higher concentrations of total Al and Ali, especially during snowmelt episodes. Aluminium speciation was modelled for lake and river samples from Sweden’s national survey using the Windermere Humic Aqueous Model (WHAM). The calibration proved robust, and Ali could be correctly placed ... |
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