Influence of coupling of sorption and photosynthetic processes on trace element cycles in natural waters

Nature
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Abstract

Chemical and biological processes have important roles in the transport and cycling of trace elements in natural waters, but their complex interactions are often not well understood. Trace-element concentrations may, for example, be controlled by adsorption-desorption reactions at mineral surfaces, with the equilibrium strongly influenced by pH. Variations in pH due to photosynthetic activity should result in concentration fluctuations as the adsorption-desorption equilibrium shifts with pH. To investigate these interactions, we have studied the effect of diurnal cycling of pH on dissolved arsenate in a perennial stream contaminated with arsenic. As expected, a diurnal cycle in arsenate concentration was observed, but surprisingly, the arsenate cycle lags several hours behind the pH cycle. Laboratory experiments show that the lag results from a slow approach to sorption equilibrium. Our observations demonstrate that the coupling of photosynthesis and sorption processes may have an important influence on the cycling of many trace elements and emphasize the importance of understanding sorption kinetics in modelling these processes.
Publication type Article
Publication Subtype Journal Article
Title Influence of coupling of sorption and photosynthetic processes on trace element cycles in natural waters
Series title Nature
DOI 10.1038/340052a0
Volume 340
Issue 6228
Year Published 1989
Language English
Publisher Nature
Contributing office(s) Toxic Substances Hydrology Program
Description 6 p.
First page 52
Last page 57
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