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Evidence of hydrological control of Sr behavior in stream water (Strengbach catchment, Vosges mountains, France)

Aubert , Dominique and Probst, Anne and Stille, Peter and Viville, Daniel Evidence of hydrological control of Sr behavior in stream water (Strengbach catchment, Vosges mountains, France). (2002) Applied Geochemistry, Vol. 1 (n° 3). pp. 285-300 . ISSN 0883-2927

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Official URL: http://dx.doi.org/10.1016/S0883-2927(01)00080-4

Abstract

Strontium and particularly 87Sr/86Sr ratios in stream water have often been used to calculate weathering rates in catchments. Nevertheless, in the literature, discharge variation effects on the geochemical behavior of Sr are often omitted or considered as negligible. A regular survey of both Sr concentrations and Sr isotope ratios of the Strengbach stream water draining a granite (Vosges mountains, France) has been performed during one year. The results indicate that during low water flow periods, waters contain lower Sr concentrations and less radiogenic Sr isotope ratios (Sr=11.6 ppb and 87Sr/86Sr=0.7246 as an average, respectively) than during high water flow periods (Sr= 13 ppb and 87Sr/86Sr=0.7252 as an average, respectively). This is contrary to expected dilution processes by meteoric waters which have comparatively lower Sr isotopic ratios and lower Sr concentrations. Furthermore, 87Sr/86Sr ratios in stream water behave in 3 different ways depending on moisture and on hydrological conditions prevailing in the catchment. During low water flow periods (discharge < 9 l/s), a positive linear relationship exists between Sr isotope ratio and discharge, indicating the influence of radiogenic waters draining the saturated area during storm events. During high water flow conditions, rising discharges are characterized by significantly less radiogenic waters than the recession stages of discharge. This suggests a large contribution of radiogenic waters draining the deep layers of the hillslopes during the recession stages, particularly those from the more radiogenic north-facing slopes. These results allow one to confirm the negligible instantaneous incidence of rainwater on stream water chemistry during flood events, as well as the existence in the catchment of distinct contributive areas and reservoirs. The influence of these areas or reservoirs on the fluctuations of Sr concentrations and on Sr isotopic variations in stream water depends on both moisture and hydrological conditions. Hence, on a same bedrock type, 87Sr/86Sr ratios in surface waters can be related to flow rate. Consequently, discharge variations must be considered as a pre-requisite when using Sr isotopes for calculating weathering rates in catchments, particularly to define the range of variations of the end-members.

Item Type:Article
Additional Information:Thanks to Elsevier editor. The definitive version is available at http://www.sciencedirect.com The original PDF of the article can be found at Applied Geochemistry: http://www.sciencedirect.com/science/journal/08832927
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Institut de Recherche pour le Développement - IRD
Université de Toulouse > Université Paul Sabatier-Toulouse III - UPS
Other partners > Université Louis Pasteur-Strasbourg I - ULP (FRANCE)
French research institutions > Centre National de la Recherche Scientifique - CNRS
Laboratory name:
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Deposited By: Florence Amor
Deposited On:02 Apr 2010 14:14

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