Download BRIDGE 2006-12-15 10-00 Pauwels WP2

Hydro-geological and geochemical
characterisation for determination of thresholds
values in groundwater - Typology of aquifers
Hélène Pauwels, Jan Hookey, Wolfram Kloppmann, Ralf Kunkel
Synthesis of contributions to WP2 from BRGM, BME, EA, Fz-Jülich,
LAGH-UGENT, IGME, ULG, HLUG, Uni-Aveiro, EAA, UT, TNO, GEUS,
UBA-D, NAGREF, ABTEVERE, DHWP/AGH
Bridge: final meeting
Friday, 15th December 2006
Establishment of threshold value :
Groundwater characteristics
> Context : TV should be established
•
•
for GW shown to be at risk and also for SW and GWTDE at risk and
fed by groundwater;
by taking account of behaviour of pollutants (origin, dispersion
tendency, persistency potential).
> Objective
To highlight common features of European aquifers- relevant to the
fate and transport of pollutants:
• To provide basic knowledge for the methodology;
• To provide recommendations for development of conceptual
models of GWB.
Recommendations and Research Needs
>
Proposed typology
>
Response lag time of aquifers
>
Interaction between groundwater and its associated
surface waters and terrestrial ecosystems
>
Attenuation
>
Possible controversy on pollutants origin
TYPOLOGY for hydro-geochemical
characterisation of groundwater
Justification of the typology : High hydro-geochemical heterogeneity
within GWBs
More common classification criteria applied for delineation of GWB
• Water abstraction classification
• Hydrogeological based classification
Primary parameters that relate to the origin of compounds
Lithology
Saline influence
Secondary parameters that related to processes
Hydrodynamics
Redox conditions
Particular occurrences ( organic matter, oxides, sulphides minerals)
Geological age
TYPOLOGY: Primary parameters
Grouped
Ten basic units
Carbonates
Limestone (Karstic/non
karstic)
group
Chalk
Unconsolidated
Sands and gravels
group
Marls and clays
Sandstones
Sandstones
Hard-rock
Crystalline basement
group
Schists
Volcanic rocks
Evaporites
Saline influence
Detailed
Karstic carbon. rocks, Paleozoic
Carbon rock, carbon rocks and
interbedded silicatic carb. Rock,…
Sands and clays, Glacial sand and
gravel deposits, Fluviatil deposits,
….
Trias. sandstones., sandstone
/silicastic alternating sequences
Map based on typology: - application to the first aquifer
compartment
Residence time of GW
Units
1d
1y
10 y
100 y
1000 y
Limestone (Karstic/non
karstic)
Chalk
Sands and gravels
Marls and clays
Sandstones
Crystalline basement
Schists
Volcanic rocks
Clear need of anticipation of any further spread of pollution
Taking response time lag into account for
threshold derivation
Recent GW must be involved within the process of TV derivation/
application.
At monitoring level:
Location of monitoring network must be representative of land use
For characterization phase:
-Appropriate characterisation of recharge conditions
-Application of environmental tracers (3H, 3H/3He, CFC, SF6, δD, δ18O)
may be helpful
Gap: Transfer time (+ Stocks of pollutants) in the vadoze zone less
known than in the groundwater
Interactions between groundwater and its associated
surface waters and terrestrial ecosystems
Baseflow estimation methods
Tier 1
 Little data
 Age/tracer//low flow survey
 Provides relative importance of groundwater input
Tier 2
 more data
 hydrograph separation with regional modelling
 gives better understanding of relative importance of
groundwater input and spatial understanding within catchment
Tier 3
 large data requirement
 deterministic modelling
gives predictive understanding of groundwater input under
different conditions within catchement
Increasing effort, cost, complexity
and reliability of results
The baseflow : a key parameter in potential dilution of pollutants
Gap: simple modelling tools for considering the links between GWB
and SW / GWDTE
Attenuation- Main parameters
x
Sorption
x
x
Cations exchange
x
x
x
x
x
x
x
Volatilization
Biotic/abiotic degradation
Salinity
x
pH
Precipitation
Sulfides
min.
Organic
matter
Oxides,
clays
Attenuation processes
Carbonates
Driving Parameters
Solid/aqueous phase
x
x
x
x
x
Aquifer’s capabilities of attenuation
Oxides,
clays
Organic
matter
Sulfides
minerals
Carbonates
Limestone
(Karstic/non karstic)
Chalk
xx
x
x
x
basic
xx
x
x
x
basic
Sands and gravels
x
xx
xx
x
variab
le
x
x
variabl
e
x
acid
x
acid
x
variabl
e
pH
Marls and clays
Sandstones
x
Crystalline basement
x
Schists
x
Volcanic rocks
x
x
Taking attenuation into account for threshold
determination
Monitoring point
for TV determination
M
Attenuation along flowpath
M
Receptor
Attenuation along flowpath
R
R
Receptor
- If attenuation occurs downstream of monitoring point, it allow
determination of less restrictive TV- but:
- Longevity and sustainability of attenuation must be verified
Other gaps:
- Local studies of attenuation within riparian / hyporheic zones have been
carried out: difficulty lies in the scale up to the catchment sacle ;
- Particular conditions of that may result in pollutant remobilization
Possible controversy on pollutant origin
Do not confuse geogenic and natural ( NBL) origin;
> Denitrification is very common within European Aquifers
•
>
>
>
NO3 reactivity induces leaching of metals from sulphides minerals and adsorbed
on Organic matter
Irrigation
•
Salinisation induces leaching of some trace elements ( B, Se, Mo, As, F..)
GW withdrawal from coastal area
•
TDS induces  of [Ca] by cation-exchange and of metals by complexes
formation
GW abstraction from confined/unconfined aquifer
•
•
Mixing through leakage/drainage between aquifers,
Mobilisation of some metals from sulphides minerals, Fe-hydroxides, Clay….
Concluding Remarks
Understanding the chemical composition of groundwater (origin,
fate and transport of substances) is a key challenge in TV
derivation.
> Proposed aquifer typology provides a general framework for
such an understanding, but must be completed by information
on transfer time;
> Heterogeneity of GWB : a key point as GWD provides for
appropriate investigation if TV is exceeded at one or more
monitoring point ;
> Scientific gaps have been identified – but GWD provides for TV
amendment if appropriate.