Landscape Control of Stream Water Aluminum in a Boreal Catchment during Spring Flood

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• 作者：Neil Cory ; Ishi Buffam ; Hjalmar Laudon ; Stephan K&ouml ; hler ; and Kevin Bishop
• 刊名：Environmental Science & Technology
• 出版年：2006
• 出版时间：June 1, 2006
• 年：2006
• 卷：40
• 期：11
• 页码：3494 - 3500
• 全文大小：399K
• 年卷期：v.40,no.11(June 1, 2006)
• ISSN：1520-5851

文摘

Inorganic aluminum (Al) concentrations are critical fordefining the biological effects of acidification. The landscape'srole in controlling the spatial variability of Al and itsspeciation has received only limited attention. We analyzedthe speciation of stream Al at 14 sites within a 68 km²boreal catchment during spring snowmelt, a period of episodicacidity. Three factors that influenced Al at these siteswere landscape type (specifically the proportion of wetlandareas), stream pH, and dissolved organic carbon (DOC).Forested catchment sites underlain by mineral soils hadhigher total Al concentrations and greater inorganicAl proportions than catchments with larger wetland areas,despite significantly higher pH. We suggest that thisdifference results from source limitation of Al in the peatwetlands. The control of Al solubility was dominated by organiccomplexes, with the organic carrying capacity exceedingAl in the majority of samples. When assessing theinorganic phase, only four percent of the samples wereoversaturated with regards to commonly forming secondaryAl minerals, with no samples showing supersaturationhigher than 10 times with respect to any given solid phase.Inorganic Al rarely exceeded biological thresholds,except for short periods during peak flow in forestedareas, despite two-thirds of the streams having minimumpH values below 4.9. Streams with a high percentage ofwetland area were associated with lower Al:DOC ratios.The Al:DOC ratios were quite stable in each stream before,during, and after snowmelt, with the exception of isolatedspikes in the Al:DOC ratio associated with particulateAl at a downstream site during high flow.