Use of factor analysis to investigate processes controlling the chemical composition of four streams in the Adirondack Mountains, New York

Four streams were monitored intensively over a 2 year period. Factor analysis was used to identify interrelationships between dissolved species during this period, and to determine physical processes controlling their behaviour. Analysis of the full dataset identified species which varied predominantly on an episodic timescale, and species which were subject to seasonal cycles. Two-month subsets of data were defined to remove the influence of seasonal cycles, and factor analysis of individual subsets then allowed episodic behaviour to be examined for each 2 month period. Results showed that base cation dilution was a consistent cause of changes in acid neutralising capacity (ANC) in all four streams. NO3- exhibited strong seasonality in concentration and also in episode behaviour, increasing during winter-snowmelt episodes, but diluting during some summer episodes. DOC concentrations also varied seasonally, but 2 month analysis indicated episodic increases during all periods. SO42- did not exhibit consistent episodic behaviour, as it was strongly influenced by antecedent conditions. Behaviour of Ca2+ and Mg2+ was apparently influenced by a significant soil source in three of the streams.