A natural-gradient field tracer test for evaluation of pollutant-transport parameters in a porous-medium aquifer |
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| Authors: | Y Yang X Lin T Elliot R Kalin |
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| Institution: | (1) School of Civil Engineering, Queen's University of Belfast, Belfast, BT9 5AG, UK,;(2) Institute of Environmental Sciences, Beijing Normal University, Beijing, 100875, China, |
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| Abstract: | This paper describes a natural-gradient field tracer test to characterise solute-transport properties in a sand and gravel
aquifer in the Hebei Province, northern China. Some laboratory-scale column tests on aquifer material and a local-scale field
borehole-dilution test have been conducted previously, but the field test reported herein represents the only large-scale
tracer test in the aquifer, which is the sole water supply to the city of Shi Jiazhuang and which is threatened by urban pollution.
The aim of the study was to quantify the transport behaviour of nonreactive pollutants in this aquifer. Little quantitative
data are available concerning its solute-transport properties; thus, the results of the tracer test are significant and critical
for understanding pollutant transport and fate. The in-situ tracer test was carried out in the aquifer using a slug injection
of the geochemically conservative, radioactive iodine tracer 131I. The longitudinal (α
L
) and transverse (α
T
) hydrodynamic dispersivities for solute transport in the field are 1.72 and 0.0013 m, respectively. The ratio of longitudinal
dispersivity α
L
and the flow length at the field scale is 1:10. The ratio between α
L
and α
T
from the in-situ test (~1,300:1) demonstrates a dominant longitudinal dispersion in this fluvial sand and gravel aquifer.
The tracer test further indicates a relatively short transit time for the aquifer (linear velocities ~13 m/d) under natural-gradient
conditions.
Electronic Publication |
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| Keywords: | tracer tests contamination groundwater hydraulics porous medium aquifer China |
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