Assessment of the use of fluorescent tracers in a contaminated Chalk aquifer

Conceptualization of flow and transport in a limestone aquifer by multiple dedicated hydraulic and tracer tests

“…reworked limestone mixed with till and sand, 59 crushed or fractured limestone units (Jakobsen and Klitten, 1999), while deeper parts comprise intact 60 geological units with a low fracture density (Jakobsen et al, 1993). Fractured units of limestone aquifers 61 often exhibit a dual-continuum nature (Hartmann et al, 2007;Price et al, 1993): fast flow in a network of 62 fractures dominates the advective transport in the aquifer, while the long-term fate of solutes is strongly 63 influenced by matrix diffusion, sorption and degradation processes (Bottrell et al, 2010;Jardine et al, 1999;64 Witthuser et al, 2003). 65…”

“…Tracer tests have been commonly used to determine parameters characterizing the transport behavior 80 (porosity, matrix diffusion, dispersion) and connectivity in limestone aquifers (Bottrell et al, 2010;81 Hartmann et al, 2007) and other fractured aquifers. These tests can be performed as single-well or multiple-82 wells tests, and with chemical species or heat as tracer (Doro et have the advantage that the tracer breakthrough happens much faster than for natural gradient tracer tests.…”

“…They also provide a well-defined flow field and tracer recovery is usually high. A well-defined flow field is 92 particularly useful for fractured limestone aquifers, as it helps to reduce tracer loss and tracer occurrence at 93 unexpected locations (Bottrell et al, 2010 performed a comprehensive forced-gradient tracer test study in a fractured limestone aquifer, using single 100 fluorescent tracers for each injection. They mention the occurrence of a weathered, 'putty' chalk layer, in 101 which the boreholes were cased.…”

Performance evaluation of different horizontal subsurface flow wetland types by characterization of flow behavior, mass removal and depth-dependent contaminant load

“…We choose fluorescein as a tracer since it is (i) detectable at 10 À3 mg L À1 level (Goldscheider et al, 2008), thus can be applied at low concentrations which precludes the occurrence of density effects, (ii) toxicologically safe unlike e.g. rhodamine (Behrens et al, 2001), (iii) resistant to biodegradation (Bottrell et al, 2010), (iv) not known to be taken up by plants unlike e.g. bromide (Kung, 1990;Xu et al, 2004), (v) frequently used to trace surface-(EPA, 2003) and subsurface waters, e.g.…”

Multitracer Field Fluorometry: Accounting for Temperature and Turbidity Variability During Stream Tracer Tests

“…Fluorescent dyes have been used extensively as artificial tracers to investigate hydrological processes in both surface water and groundwater environments (Flury & Wai, ; Leibundgut et al, ). Typical applications include determining pathways and residence times of water in aquifers (Massei et al, ), identifying subglacial drainage networks (Chandler et al, ), characterizing flow velocities and storage processes (Hensley & Cohen, ; Schmadel et al, ), and tracking contaminant transport (Bottrell et al, ; Malaguerra et al, ). Commonly used fluorescent dyes (e.g., Uranine, Rhodamine WT, Eosine) are highly soluble in water, nontoxic, relatively inexpensive, and are readily detectable at concentrations as low as parts per trillion (Flury & Wai, ; Smart & Laidlaw, ); attributes that make them highly suitable for application as hydrological tracers.…”