CONFERÊNCIA: Promises of fluorescent tracers techniques in contaminant hydrogeology

XIX Congresso Brasileiro de Águas Subterrâneas1
Promises of fluorescent tracers
techniques in contaminant
hydrogeology
Dr Sc. Ph. Meus
European Water Tracing Services Sprl
XIX Congresso Brasileiro de Águas Subterrâneas
Campinas, SP, Brasil, 20-23 Sept 2016

• A brief history of tracing techniques
• Tracer tests as a tool for understanding groundwater
• Diversity of applications, performance and limits
• Why fluorescent tracers? Principles, tracers, material
and methods
• Use of tracer tests for groundwater protection
• Promises in contaminant hydrogeology
• Questions?
Content

      
History Tracer tests Applications Principles Protection Contaminants Questions
History
1845 Discovery of fluorescence by JFW. Herschel, then works of Stokes
1871 First synthesis of fluorescein by Adolf von Baeyer, under the name of resorcinphtalein
1877 1st quantitative tracer test with NaCl and fluorescein in the swallow holes of the Danube, reaching Aach
spring (KNOP inKÄSS, 1992)
1904 Birth of a Belgian Committee for Fluorescein by E. Van den Broeck (VAN DEN BROECK, MARTEL, RAHIR,
1910)
1930-59 Works of A. Jablonski and first fluorescence spectrophotometers
1964 First use of active charcoals detectors (GAC) (LALLEMAND & PALOC, 1964)
1980’ First partionning tracer tests
1970-1990 Development of tracers, increasing number of reports dealing with tracer tests in karst areas (mainly
linked to speleological research)
1988 Publication of the first guidelines for artificial tracer tests in hydrology (PARRIAUX et al., 1988)
1990’ Progress in fluorescence spectroscopy (LAKOWICZ, 1983), numerous theses on tracing experiments
1992 First monography on tracing techniques (KÄSS, 1992)
1992 First optical fibers spectrophotometers (BARCZEWSKI & MARSCHALL, 1992)
1996 First field fluorometers for continuous in-situ monitoring (BARCZEWSKI et al., 1996, MEUS et al, 1997,
SCHNEGG & DOERFLIGER, 1997, GOUZE et al., 2000)

JFW Herschel discovers the fluorescence
      

      
History
1910)

The speleologist EA Martel spreads the use of fluorescein
      

Works of Stokes and Jablonski (1930)
      

      
History
1910)

      
Parallel progress in spectroscopy and tracing techniques in the
late 80’s - early 90’s

      
History
1910)

« Tracer: a population (in a statistic
meaning) of a detectable or quantifiable
substance which is naturally or artificially
associated with the population of a
process, so that it can provide
informations about this process »
After Guizerix et Margrita, 1990
Principle of tracer and tracing
      

      
Parabolic profile of
velocities
Heterogeneity of flow
Changes of velocity
between pores
Micro dispersion
Macro dispersion
After Klinka, 2015
1. Molecular diffusion -> Fick’s law
Scale effect on
dispersivity
Transport processes
2. Dispersion
3. Adsorption, decay,
degradation…

      
Porous aquifer/ continuous
Fissured aquifer / discontinuous
Karstic aquifer/ discontinuous and
predominantly heterogeneous
Large scale
regional
Macro scale
local
Darcy
Grain scale
Micro/pore scale
Navier-Stokes
Particle/interface
scale
After Klinka, 2015
« Tracing-systems » and not the whole aquifer!
The processes and laws differ according to the
hydrogeological medium

Example of karst
After GombertConsider input-output of tracers!
      

      
After C. C. Smart, 2010
Classification of tracer tests according to the level of information
For each class consider the reliability!

 Delineation of basins/water divides, water catchments
 Delineation of protection zones based on transit time
 Flow and transport parameters, calibration of models
 Residence/renewal time studies, simulation of spills
 Vulnerability and risk assessments
 Discharge, mixing studies of surface water
 Impacts of contaminated sites or wastes
 Remediation studies
 Surface water/groundwater interactions
 Geothermal applications
 Wells studies
 Mine/quarry dewatering
 Reservoir studies
 Leakages (pipes, liners, civil engineering works…)
 Landslides
 Transboundary studies
Applications of tracer tests
      

      
Type Advantages Disadvantages
Fluorescents Very low LOD, direct
analysis
Interferences,
background
Salts(Cl, I, Li…) Simple analysis Background, toxicity
Spores, bacteria Specificity, possibility
of staining
Size, poor sensitivity,
complicate analysis
Microspheres Specificity, possibility
of staining with
fluorescent dyes, size,
neutrality
Size, poor sensitivity,
complicate analysis
Virus, phages Specificity, multi-
tracing
Storage, complicate
analysis, expensive
DNA particles Specificity, multi-
tracing
Storage, complicate
analysis, expensive
Tracers

Naphthionate Amino-G acid
Fluorescent tracers
      

Jablonski diagram
      
Principle of fluorescence

Fixed wavelengths
Emission, excitation or
synchronous scan spectra
Total spectra (EEM)
      

Fluorescent
tracer
Limit of
detection (ppb)
Uranine 0.002
Sulforhodamine B 0.006
Eosine 0.01
Tinopal 0.01
Amino G acid 0.02
Pyranine 0.02
Naphthionate 0.05
Photine 1
Instrumental limits
      
Performance of uranine
1 g of uranine instead of
50 kg of salt!

XANTHENIC TRACERS (UR,
SUB, RH, EOS)
TRACEURS
UV (NAP-
AGA)
HYDROCARBURES
Excitation/Emission wavelength
Fluorescencesignal
Increasinglimitof
discrimination
Solvent (water)
Water + NOM
Water + NOM + particles
+ organic pollutants
« Someone else’s tracer »
« Searched tracer »
Excitation/Emission wavelength
Fluorescencesignal
Increasinglimitof
discrimination
Solvent (water)
Water + NOM
+ organic pollutants
« Someone else’s tracer »
« Searched tracer »
      
Experimentally the background is a strong limitation

After C.C. Smart, 2005
      
Up to 3 sampling techniques can be used complementarily

      
Each method (sampling + analysis) is more or less sensible
to errors
Blanks are critical!

      
Positive results
Negative results
After Jozja et al., 2012
Scale of reliability

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      
27

0.1
1
10
100
0 5 10 15 20 25 30 35 40 45
Minutes
Concentration(mg/l)
Uranine
Rhodamine
Tinopal
LED 365 nm
LED 316 nm
      
Separation of tracers for multi-tracing
Uranine + éosine
Naphthionate +
amino G acid

Model for borehole
(50 mm, 100 m length,
70 m depth).
Field fluorometers
      
Pros Cons
Compacity Lower limit of detection
Time resolution Lower selectivity
Freeze proof Clogging of optical window
On line results and alarms Interferences not totally
solved
No contamination nor storage
problem
Electronic device
Turbidity correction
Correction of interferences
between tracers
Additional parameters :
conductivity
No head limit
Autonomy (several months,
thousands of data)3 fluorescence channels + turbidity
LEDs (nm)
280 -> HC
316 -> NAP
365 -> AGA, TIN
470 -> UR, EOS
525 -> RWT, SUB, SUG

      
Surface model
Warnings SMS
Borehole
model
Application of telemetry

      
Our data are
available quasi
instantaneously
(a simple clic!)

      
Peak of uranine 500 nm
 Robust and practical method even if poorly
selective and hampered by the background
 Spectral identification needed!
Active charcoal method (GAC)

      
Groundwater protection
Method applied
almost everywhere
in the EU for
drinking water
protection
Wallonia
Luxembourg
France

Example: Luxembourg sandstone (lower Lias) aquifer
      
Karstification

      
 93 waterworks studied
 87 injections (mainly
fluorescent tracers)
 176 relations checked
 70 % for injections through
boreholes/wells
 Mean mass of fluorescent
tracers = 1246 g (total 106
kg)
 Mean distance = 453 m
(max. 1900 m)

      
Transport processes along fissures

      
After P. Pessoa & al., 2014
Rain controlled injector

      
How tracer tests can help in contaminant hydrogeology
Typically, contaminated sites characterization and remediation are facing this :
 High heterogeneity (aquifer usually not « porous equivalent »)
 Uncertainties on the source itself and its infiltration
 Insufficient knowledge of the real flow pattern
 Complex behaviour of contaminants
 Models insufficiently calibrated
 Poor evaluation of the risk and its evolution based on concentrations (need
for fluxes and discharges)
Properly designed tracer tests may help in solving these questions!
But such tracer tests may be longer, more sophisticated and more expensive
than classical ones…

After N. Kresic, Amec Foster Wheeler
      
Heterogeneity of subsurface

Heterogeneity of source penetration at local scale
After N. Kresic, Amec Foster Wheeler
      

      
 Complex processes
 Involving more than 3 phases
 Retardation
 Immobile water effects

      
The model must reflect the reality

      
Control panels based on mass flux-discharge assessment
rather than concentrations
After Annable, 2016
After Brouyère, 2015
Needs a more precise
assessment of filtration
velocities (Darcy velocities)
and their variations
Allows for a better site management

      
Mass discharge must also take layering into account
After E. Lanna, 2015

      
Breakthrough curves contain a lot of information about the
aquifer and the potential behaviour of contaminants
 Natural or forced gradient tests
 Radial convergent
 Single well
 Specifically designed well network
-> Tracer results can be used for fitting
analytical solutions or numerical
models

      
TRAC software (BRGM)
After Klinka, 2015

      
Hydrodynamical parameters: dispersivities and effective porosity
After Frippiat et al. 2015
Decomposition of individual layer
contributions thanks to the high
resolution of the fluorometer during a
forced gradient tracer test:

      
Partitionning tracers
After Annable, 2016

      
Intelligent tracers
Resazurine + e-  Resorufine
Reduction due to microbiological activity

      
The Finite Volume Point Dilution Method (FVPDM): a smart single well
method for measuring filtration velocities
After Brouyère, 2015
• The method works well if Qinj < Qcritical
• It allows for variations of water fluxes

      
FVPDM can be combined with integrating methods such as passive
sampling
After Lanna and Brouyère, 2015

      
Passive sampling of contaminants are improving and they can be
combined with tracer techniques: passive flux meters (PFM)
After Annable, 2016
Improved meter for
fractured media

      
PFM used in different aquifer settings depending on fluxes
characteristics
After Annable, 2016

      
Another example of passive sampling of contaminants: the
CHLOROKARST project
Chlorinated hydrocarbons in
Switzerland
TCE and PCE

      
Detection of gasoil in water by fluorescence
PAH

      
Field test – detection of gasoil in water
System calibrated with amino G acid
with varying discharge
Times series of fluorescences
Substraction
HC signature

      
Downhole fluorometer for layered aquifers
D’après Flynn et al. 2005

      
Tracer tests in LNAPL
Spectra showing the breakthrough of
the UV tracer at 370 nm
Laboratory tests
• Background of the product
• Response of the tracer

      
Tests of interference between gasoline and uranine

      
Fluorescence can also be used to characterize leachates from wastes
or effluents
Tryptophan

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CONFERÊNCIA: Promises of fluorescent tracers techniques in contaminant hydrogeology