Comment on "Analysis of groundwater contamination using concentration-time series recorded during an integral pumping test: Bias introduced by strong concentration gradients within the plume" by Allelign Zeru and Gerhard Schäfer.
We consider the results of a recent paper in this journal [Zeru, A. and Schäfer, G., 2005. Analysis of groundwater contamination using concentration-time series recorded during an integral pumping test: Bias introduced by strong concentration gradients within the plume. Journal of Contaminant Hydrology 81 (2005) 106-124], which addresses the field-scale characterisation of contaminant plumes in groundwater. There, it is concluded that contaminant concentration gradients can bias Integral Pumping Test (IPT) interpretations considerably, in particular if IPTs are conducted in advective fronts of contaminant plumes. We discuss implications of this setting and also argue that the longitudinal and transverse dispersivities used in the examples of Zeru and Schäfer (2005) of up to 30 m and 3 m, respectively, are generally very high for the here relevant capture zone scale (<20 m). However, regardless of both longitudinal and transverse concentration gradients, we further show through a counter-example that IPT results are unbiased as long as the concentration attenuation along the flow direction is linear over the capture zone extent.
Bayer-Raich
Martí
M
Centre for Environmental Research, UFZ- Leipzig-Halle GmbH, Permosserstr. 15, 04318 Leipzig, Germany. marti.bayer@ufz.de
Jarsjö
Jerker
J
Teutsch
Georg
G
D015982:Bias; D004784:Environmental Monitoring; D008962:Models, Theoretical; D014872:Water Movements; D014873:Water Pollutants / Q000032:analysis*; D014881:Water Supply
D014873:Water Pollutants