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Identifying geochemical hot moments and their controls on a contaminated river floodplain system using wavelet and entropy approaches

Arora, Bhavna, Dwivedi, Dipankar, Hubbard, Susan S., Steefel, Carl I., Williams, Kenneth H.
Environmental modelling & software 2016 v.85 pp. 27-41
aquifers, computer software, entropy, environmental models, floodplains, groundwater contamination, hydrologic cycle, rivers, temporal variation, wavelet, weather
Geochemical hot moments are defined here as short periods of time that are associated with disproportionally high levels of concentrations (biogeochemically-driven or transport-related) relative to longer intervening time periods. We used entropy and wavelet techniques to identify temporal variability in geochemical constituents and their controls along three transects within a contaminated floodplain system near Rifle CO. Results indicated that transport-dominated hot moments drove overall geochemical processing in the contaminated groundwater and seep zones. These hot moments were associated with seasonal hydrologic variability (∼4 months) in the contaminated aquifer and with annual hydrologic cycle and residence times in the seep zone. Hot moments associated with a naturally reduced zone within the aquifer were found to be biogeochemically-driven, with a different dominant frequency (∼3 months) and no correlation to hydrologic or weather variations, in contrast to what is observed in other regions of the floodplain.