Scientific Support to Policy BRIDGE
Background cRiteria for the IDentification of Groundwater thrEsholds
Contract n° SSPI-2004-006538 Project start date : 1 January 2005 Duration of the project : 24 Months Contract signature : 23 December 2004
Deliverable : D22
Title : Application and evaluation of a proposed methodology for derivation of groundwater threshold values – a case study summary report
Due date of deliverable : October 2006 Actual submission date : December 2006
The deliverable authors are responsible for the content A
UTHOR: K. Hinsby
A
FFILIATION: GEUS
A
DDRESS: Øster Voldgade 10, 1350 Copenhagen, Denmark T
EL.: +45 3814 2780
E
MAIL:
khi@geusF
URTHERA
UTHORS: MT Condesso de Melo
Document InformationD
OCUMENTT
YPE DeliverableD
OCUMENTN
AME:
WP4 case study summaryR
EVISION: 3
R
EV.D
ATE: 22. Dec. 2006
C
LASSIFICATION: PP
2 1. Introduction
This report presents a summary of the main results of the 14 selected case studies evaluating the preliminary methodology for derivation of groundwater threshold values developed in the BRIDGE Work Package 3 (D15, Hart el al. 2006), and partly also the final methodology presented in the deliverable D18 (Müller et al.
2006). The 14 case studies were selected based on criteria presented in deliverable D19 (Hinsby et al. 2005) to represent the major part of the aquifer typologies occurring in Europe as defined in BRIDGE Work Package 2 (D9, Pauwels et al. 2006; Wendland et al. 2006) and to represent most of the regions for dependent ecosystems described in the Water Framework Directive (Directive 2000/60/EC).
2. Locaction and type of investigated groundwater bodies
The investigated groundwater bodies are located in 12 of the 25 eco-regions for rivers and lakes defined in the Water Framework Directive, and they cover most of the important aquifer typologies in Europe. Hence most of the major climatological and hydrogeological settings are represented by the suggested selection of sites. The maps on the following pages simply serve as a means of illustrating the geographical distribution of the investigated groundwater bodies, the aquifer typologies, and their location in relation to major eco- regions as defined in the water framework directive. They are not necessarily representative for the general or average conditions in the eco-region to which they belong, and not all of the investigated groundwater bodies interact significantly with an aquatic or terrestrial ecosystem.
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Figure 1. Location of the 14 groundwater bodies selected for the representative site case studies. The type of aquifer or other earlier or on-going programs in which the groundwater bodies are studied, is also indicated.
4 Figure 2. Location and aquifer typology of investigated groundwater bodies. Circles are sand and gravel aquifers, diamonds are carbonates, hexangles are sandstone, triangles are crystalline rocks and squares are volcanic rocks.
Figure 3. Ecoregions with investigated groundwater bodies for evaluation of the proposed methodology for derivation of groundwater threshold values. The base map is a modified version of the map of
“Ecoregions for rivers and lakes” developed for the EEA and included in Annex XI of the Water Framework Directive. Ecoregions with investigated groundwater bodies are marked with a red square.
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Figure 4. Map of ecoregions for transnational and coastal waters as defined in Annex XI of the Water Framework Directive. The map is slightly modified from the original as the Black Sea has been included.
Coastal ecoregions that receive discharge from river basins in which the selected groundwater bodies are located are marked with rectangles. Note that, this does not imply that the selected groundwater bodies significantly affect the coastal ecoregions, just that they are located in catchments discharging to these.
6 Table 1. List of investigated groundwater bodies (GWB’s). The ”Ecoregion for rivers and lakes”(Fig.3) in which the GWB is located, and the ”Ecoregion for coastal waters” (Fig.4) to which their associated river basin discharge is also indicated. Numbers in column 1 are used for easy reference to specific GWB’s in later tables and figures. Note that some groundwater bodies are known to interact directly with surface water systems, some lack information about possible interaction and some probably do not interact significantly with any surface water system. For further information about specific sites see Appendix 1.
No. Country Name Ecoregions for rivers and lakes
Ecoregions for coastal waters 1 Austria Südl. Wr. Becken /
(GWB-GK100024) 11.Hungarian Lowlands (partly 4. Alps)
7. Black Sea
2 Belgium Central Campine
system / (GWB- CKS_0200_GWL_1)
13. Western plains 4. North Sea
3 Bulgaria Sofia Kettle 7. Eastern Balkan 7. Black Sea 4 Denmark Odense Pilot River
Basin 14. Central plains 4-5. North Sea /
Baltic Sea 5 Estonia NE Estonia 15. Baltic province 5. Baltic Sea 6 Finland ISS - group of GWB’s 22. Fenno-Scandia 5. Baltic Sea 7a France/
Germany
Upper Rhine 8. Western highlands 4. North Sea 7b Germany Black Forest 9. Central Highlands 4. North Sea 7c Germany Swabian and
Franconian Alb 9. Central Highlands 4. North Sea 8 Greece Pinios Pilot River
Basin 6. Hellenic western
Balkan 6. Mediterranean Sea
9 Hungary Transdanubian Central Mountains
11. Hungarian Lowlands 7. Black Sea
10 Italy Tevere Pilot River
Basin
3. Italy 6. Mediterranean Sea 11 Lithuania Joniskis (LT 00102) 15. Baltic province 5. Baltic Sea
12 Netherlands NE coastal areas 14. Central plains 4. North Sea
13 Poland Kedzierzyn 10. The Carpathians 5. Baltic Sea
14 Portugal Vouga River Basin 1. Iberic region 1. Atlantic Ocean
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Selected information on investigated groundwater bodies
Examples of other projects and programs and other important information on the investigated groundwater bodies are liste below:
European Pilot River Basins (PRB’s)
Four European Pilot River Basins or parts of Pilot River Basins of the Common Implementation Strategy (CIS) are among the investigated sites. From south to north these are: Tevere PRB (Italy), Pinios PRB (Greece), Scheldt PRB (Belgium) and Odense PRB (Denmark). Scheldt is a transboundary river basin.
Groundwater bodies (GWB’s) investigated in BASELINE project
Four of the investigated groundwater bodies or systems of groundwater bodies were also studied in BASELINE project (Edmunds and Shand 2007). From south to north these are: Cretaceous-Quaternary GWB’s in the Vouga Basin/ Aveiro (Portugal), Oligocene-Pleistocene GWB’s in the Central Campino System (Belgium), Pleistocene GWB’s in the Odense PRB (Denmark) and Cambrian-Vendian GWB’s in Northern Estonia (Estonia).
Groundwater bodies in transboundary river basins:
(A) GWB’s in the French and German part of the Upper Rhine Basin. The Rhine River Basin is the largest in Western Europe, 185.000 km2, and is described by the UNEP as one of the world's most important transboundary waterways. (B) GWB’s in Austria (upstream) and Bulgaria (downstream) in the Danube River Basin, which is the largest river basin (817.000 km2) for a river rising in the EU. (C) A GWB located in the Belgian part of the Scheldt Basin (22.000 km2). (D) A GWB in the Dutch part of the Rhine-Maas (Rhine- Meuse) Basin. (E) A GWB in southern Poland, in the southern part of the Oder (Odra) River Basin, 124.000 km2. (sources: UNEP, 2005 ; WAN, 2005).
Groundwater bodies to be studied in both BRIDGE WP4 & WP5 (socio-economic studies):
GWB’s in the French and German part of the Upper Rhine Basin, small shallow GWB’s in Finland, GWB’s in the Dutch part of the Scheldt Basin, GWB’s in the Vouga Basin (Portugal).
8 3. Summary of proposed methodology for derivation of groundwater threshold values.
The developed methodology has suggested ‘groundwater itself’ as a receptor in addition to the dependent ecosystems and outlined two basic options to derive threshold values; one for groundwater itself and one for dependent aquatic ecosystems (Hart el al. 2006, b). In both cases the initial evaluation refer to the natural background level (NBL) of the investigated element or substance. Hence the first step towards the derivation of threshold values is to derive the NBL of the investigated substance. The flow diagram below illustrate the process of deriving threshold values, which may be derived for dependent ecosystems (Tier 1-4) depending on the system and the available data, or for “groundwater itself” (Tier 1-2a) based on natural background levels and relevant reference values, such as environmental quality standards, EQS, or drinking water standards, DWS, (Figure 5).
Tier 2 Is [pollutant] > QS?
Check for trends
Check for trends MONITORED DATA
Is [pollutant] > NBL?
Tier 1
Yes Set threshold= QS (or
NBL if exceeding)
Set threshold= QS/DF Status = GOOD
Status = GOOD No
No
Is [pollutant] > (QS/DF)*AF?
Set threshold= (QS/DF)*AF Is [pollutant] > (QS/DF)?
Tier 3
Tier 4
Status = GOOD
Status = POOR
Check for trends Yes
Yes No
Rules
1. Use the appropriate quality standard, QS.
If ecological risk use EQS.
If human health risk use DWS.
2. If dilution factor, DF, not known assume = 1.0 3. If attenuation factor, AF, not known assume =
1.0
4. In check for Trends use ALL triggers-consider need for trend reversal if crossing each trigger Does appropriate
Investigation show that conditions for good chemical
status are not met?
Define Objectives and Measures Yes
No Derive NBL (according to Annex I)
Derive TV (according to
Annex II) Tier 2a
Is [pollutant] > TV?
OR
Figure 5. Flow diagram illustrating the tiered approach proposed for derivation of groundwater threshold values for either dependent aquatic ecosystems (Tier 1-4) or for groundwater itself (Tier 1-2a).
The approach for deriving the natural background levels is described below and illustrated in Figure 6. If no
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national methodology exist or data does not allow for derivation of natural background levels by more advanced methods using environmental tracers, oxidation capacity or other indicators (e.g. Edmunds and Shand 2007, Hinsby et al. 2001, Hinsby et al. 2007, Passier et al. 2006) the simplified preselection approach described in D15 may be applied. By this method the natural background levels are derived as the 90th (or 97.7th ) percentiles of a preselected dataset, which are selected to approximate a natural groundwater composition of a given aquifer typology. The preselection criteria used in the BRIDGE case study evaluations corresponds to the central path in Figure 6 as described in D15 are:
1) Samples with incorrect ion balance (exceeding 10%) are discarded 2) Samples of unknown depth are discarded
3) Monitoring data not attachable to WP 1 aquifer typologies are discarded 4) Data from hydrothermal aquifers are discarded
5) Data from salty aquifers (NaCl content of more than 1000 mg / l) (coastal or influenced by evaporates) are discarded and/or evaluated separately.
6) Time series should be eliminated by median averaging (in order to guarantee that all sampling sites contribute equally to the NBL derivation).
7) Groundwater analyses with median nitrate concentrations above 10 mg/l are removed. Hence , only screens with nitrate concentrations less than or equal to 10 mg/l remains and are used as a proxy for groundwater with a natural composition.
10 The preselection described above have been used for the derivation of the natural background levels at the 90th and 97.7th percentiles in all the performed case studies in WP4 in order to be able to compare and discuss the obtained results (see next chapter).
Derivation of threshold values for groundwater itself.
It is proposed to derive groundwater threshold values based on groundwater itself as a receptor, where the groundwater body does not have a significant influence on a dependent ecosystem. In this case the groundwater threshold values may be derived at the following two tiers:
Tier 1. Comparing pollutant to NBL (is pollutant > NBL) Tier 2a.
Option 1: The TV is derived from NBL and REF values as described below
Option 2: The TV is derived from NBL and a maximum permissible addition (MPA) as described below (this approach was discarded in the final proposal)
OPTION 1.
For the derivation of TVs at Tier 2a (“groundwater itself”) the proposed methodology suggested a simple method for the estimation of threshold values, and natural background levels in case no national natural background levels have been derived as described above. The originally proposed method, which has been applied and evaluated in all 14 case studies, suggest to derive threshold values for the following three different cases (scenarios) defined on the basis of the ratio between the estimated natural background level (NBL) and a relevant reference value (REF) – e.g. a DWS or EQS:
Case 1: 1/3 < NBL/REF < 1 => TV = (NBL+REF)/2 Case 2: NBL/REF ≤ 1/3 => TV = 2 x NBL
Case 3: NBL/REF ≥ 1 => TV = NBL
Hence the threshold value is easy to derive when the natural background level and the relevant reference value are known, but consequently the final threshold value strongly depends on the right selection of NBL and REF values. NBL and REF values can be scientifically established although uncertainties always exist.
The derivation of the threshold values are illustrated graphically in Figure 7 below.
The philosophy of the method summarised above is that it is assumed that natural groundwater types generally do not harm the natural ecosystems in an area. Hence the groundwater quality should be close to the natural background level in order to assure no harm or as little harm as possible.
Further, it acknowledges the fact that the final selection of a method for derivation of threshold values will be political not scientific, and that it may be expected that the finally selected method for derivation of threshold values will derive threshold values between the natural background levels and reference values.
WP4 Case study summary report
Figure 7. Graphic illustration of the derivation of threshold values in the three defined cases.
The above three cases were defined in the preliminary proposal for derivation of groundwater threshold values (D15, Hart el al. 2006). Case two in the above figure has been removed in the final proposal for derivation of groundwater threshold values (D18, Müller et al. 2006). Hence, only case 1 and 3 remain i.e.
the threshold value (TV) is set by the two following ways: If NBL < REF then TV= (NBL+REF)/2; if NBL
≥ REF then TV = NBL in the final proposal.
The case studies have generally only evaluated the original methodology, since the final one was just recently released. However, chapter 5 in this report summarises and compares threshold values derived from both methods in tables and figures to illustrate the consequences for the derived threshold values based on the original data obtained by the preselection method and the natural background levels derived at the 90th and 97.7th percentiles.
OPTION 2.
The TV is derived from the NBL and a maximum permissible addition (MPA) i.e. TV = NBL +MPA. This option has only been evaluated by the Austrian case study (see Austrian report for further details). However,
12 Threshold values for dependent aquatic ecosystems.
The threshold for dependent aquatic ecosystems may be derived at the following four different tiers (figure 5) depending on the available information, (in the following PC = pollutant concentration):
Tier 1. PC comparison to NBL
Tier 2. PC comparison to EQS (if PC < EQS then TV = EQS or NBL) Tier 3. PC comparison EQS/DF – (if PC < EQS/DF then TV = EQS/DF)
Tier 4. PC comparison EQS/AF – (if PC < EQS/(DF*AF) then TV = EQS/(DF*AF)
Dilution and attenuation factors (DF and AF) may be applied at tier 3 and 4, when the investigated groundwater body is not the only water body or source discharging water to the dependent ecosystem or the dissolved pollutants are known to be attenuated along the flow path, at the interface between groundwater and the dependent ecosystem or in the dependent aquatic ecosystem. Basically it take into account the possible degradation etc. of pollutants in the groundwater bodies (attenuation) and/or the mixing or discharge of other water bodies with lower pollutant concentrations (dilution). These processes may be expressed as dilution and attenuation factors (DF and AF, respectively) and evaluated by different methods. Please refer to annex 4 and 5 of the BRIDGE D15 report for a detailed description of the evaluation and application of dilution and attenuation factors.
Threshold values for dependent terrestrial ecosystems.
No specific approach was proposed for this situation due to lack of scientific data on the issue. If needed the tiered approach developed for the dependent aquatic ecosystems may be applied as a first approximation until more relevant data and methods are available.
4. Summary of performed evaluations
The BRIDGE case studies cover 5 out of 8 major groundwater body typologies defined in BRIDGE. These are carbonates, volcanic rocks, crystalline rocks, sand and gravel, and sandstone. Chalk, schist and marls, evaporites and clays are not covered.
The elements and substances for which natural background levels and reference values have been derived in a minimum of two different case studies, at tier 2 or at higher tiers, are shown in Table 2.
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Table 2. Elements and inorganic substances evaluated in more than one of the 14 BRIDGE case studies. X indicate which studies have derived NBLs and TVs for the specific substance. Highlighted elements and substances are examples with results presented in further detail in the following.
Case AT BE BG DK EE FI DE/FR GR HU IT LT NL PL PT
Al x x x x x
As x x x x x x x x x
B x x x
Ba x x x
Ca x x x
Cd x x x x x x
Cl x x x x x x x x x x x x x x
Cr x x x x x
Cu x x x x x
EC x x x x x x x x Fe x x x x x x
HCO3 x x x x
Hg x x x x x x
K x x x Mg x x x Mn x x x x
Na x x x x
NH4 x x x x x x x x x x x
Ni x x x
NO3 x x x x x x x x x
NO2 x x x x x
O2 x x
pH x x x
Pb x x x x x x x x PO4 x x x x x x x
SO4 x x x x x x x x x x x x
Zn x x x x
Table 3. Organic contaminants evaluated in the 14 BRIDGE case studies
Case AT BE BG DK EE FI DE/FR GR HU IT LT NL PL PT
TCE x x x
PCE x x x
4.1 Threshold values derived for groundwater itself at Tier 2a
14
preselection method for the derivation of natural background levels suggested by BRIDGE. This evaluation is the most straightforward and requires less information about the investigated system than the analyses at Tier 3 and 4. Due to the limited time of the project, and the amount of data needed it was not possible to investigate the evaluated groundwater bodies at Tier 3 and 4 in most case studies.
Besides the general method described in BRIDGE the Austrian and Polish studies compare the results to national NBLs and other groundwater classifications.
OPTION 2.
The approach suggests a “maximum permissible addition” (MPA) to the natural background value.
However, this option was only evaluated in the Austrian case study (please refer to the Austrian case study report for more details), and since it was abandoned in the final proposal it is not evaluated further in this report.
4.2 Threshold values derived for dependent ecosystems at Tier 2, 3 and 4.
In addition to the derived groundwater threshold values for groundwater itself as a receptor a few case studies also derived groundwater threshold values based on quality standards for dependent ecosystems. The Austrian, Belgian, Danish, Hungarian and Dutch case studies derive groundwater threshold values using EQS values for surface water etc. either at Tier 2 assuming no dilution and attenuation i.e. a dilution factor of 1 (Belgium, Hungary and the Netherlands), at Tier 3 taking dilution into account (Austria) or at Tier 4 taking dilution and attenuation into account (Denmark).
A short description of the performed evaluations are given below:
Austria: Derives threshold values at tier 3 for the river Fischa at two different stations with dilution
factors of 1 and 0.3 for selected trace metals, N compounds and TCE, PCE (Schramm et al. 2006).
Belgium: Derives threshold values for a wide range of substances using drinking water as well as
different environmental quality standards for four different receptors: Groundwater itself, dependent terrestrial ecosystems, dependent aquatic ecosystems and drinking water. However, no data where available for evaluation of dilution and attenuation. Hence, dilution and attenuation factors of one are used. Different threshold values are also derived for hardness dependent reference values for selected trace elements (Coetsiers and Walraevens 2006).
Denmark:
Derives groundwater threshold values based on environmental quality standards and
estimated sustainable loads for a lake and an estuary for P and N, at tier 2 and 4, respectively. Data
allowing for the estimation of an attenuation factor was only available for N. The
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mobilisation/immobilisation mechanisms for P seems to be more complex and is not yet known in the same detail. The attenuation factor for N is obtained from integrated hydrological modelling studies of the total catchment and is primarily controlled by nitrate reduction by pyrite in the groundwater bodies, which seems to degrade (reduce) about half of the N leaching from the agricultural soils before discharging to the Odense river (Hansen JR, 2006, Hinsby et al. 2006).
Hungary: Derives threshold values for a karstic groundwater body at tier 2 or at “tier 3 and 4”, but
assumes/argues for dilution and attenuation factors of 1 (Simonffy et al. 2006).
Netherlands.
Derives threshold values for groundwater itself or dependent aquatic ecosystems at tier 2 by using the lowest reference value of either drinking water standards or surface water EQS values for the TV definition (Passier et al. 2006).
For a more detailed description of the derivation of threshold values at tier 3 and 4 please refer to the case study summary sheets for the relevant cases in appendix 1 or the complete case study reports available at the CIRCA website (www.wfd-bridge.net).
5. Summary of NBL and TV results
5.1 Examples of derived NBL and TVs at tier 2a from all investigated groundwater bodies.
The estimated natural background values and the derived threshold values derived at tier 2a for selected elements and substances highlighted in table 2 are shown in table 4 for all case studies.
Table 5 list the TVs derived by the final proposal for comparison. The EU drinking water standards (DWS) have generally been used as the REF value since these are currently the most well established REF values, and since no environmental quality standards (EQS) for groundwater itself have been established so far. However, for the Netherlands and Portugal alternative reference values for surface and irrigation waters, have been used to derive the TVs in table 4. Other case studies have also used alternative or additional reference values to derive TVs, but the results from these are not shown in Table 4 (see e.g. Belgian and Hungarian case studies and summary reports for more details). The numbers highlighted in red and green represents numbers, which are above or equal to the selected reference values or an order of magnitude lower than the reference values (<
REF/10).
The distribution of NBL90 and TV90 values in all case studies for four selected elements and
substances from Table 4 and 5are shown in the quantile (percentile) plot in figure 8. The threshold
values TV1 and TV2 represent the TV values derived by the original case 1, 2 and 3 of the
preliminary methodology described in ch. 3 (TV1) – Müller et al. (2006a), and the threshold values
16 Table 4. NBL and TV values at p90 and p97.7 for selected substances. Using the preselection method described in D15 and the three defined cases. Note that the Italian case study did not have any samples with nitrate less than 10 mg/l – therefore this criteria was not used. The Dutch study have used the lowest reference value of the DWS and an EQS to derive TVs. The Portuguese study have used EQS values for irrigation water, which e.g. will lower the TV for chloride but increase the TV for sulphate compared to the DWS derived TVs. Bold red numbers indicate where REF values are breached – green underlined numbers show where the derived TV is very low (< REF/10).
Chloride, Cl Sulphate, SO4 Nitrate, NO3 Arsenic, As Phosphate, PO4
Country NBL90 NBL97.7 TV90 TV97.7 NBL90 NBL97.7 TV90 TV97.7 TV90 NBL97.7 TV90 TV97.7 NBL90 NBL97.7 TV90 TV97.7 NBL90 NBL97.7 TV90 TV97.7 AT 41 50 82 100 164 197 207 224 0,001 0,001 0,002 0,002 0,08 0,10 0,16 0,20 BE 65 137 130 194 183 311 217 311 2,0 6,6 4,0 13 0,030 0,069 0,030 0,069 1,00 2,50 1,0 2,5
49 145 98 198 161 288 205 288 9,0 10,0 18 20 1,81 2,95 1,8 3,0
BG
45 70 90 140 123 236 187 243 8,9 10,0 18 20 1,40 2,17 1,4 2,2
83 144 166 197 114 186 182 218 1,0 4,5 2 9 0,011 0,018 0,011 0,018 0,46 0,83 0,46 0,83 DK
64 154 128 202 117 163 184 207 2,0 6,7 4,0 13 0,008 0,017 0,009 0,017 0,67 1,20 0,67 1,20
EE 287 397 287 397 34 42 68 85 0,010 0,010 0,010 0,010
FI 6 6 11 11 5 5 11 11 5,5 5,5 11,0 11,0
79 119 158 185 106 231 178 241 8,6 9,5 17 19 0,004 0,018 0,007 0,018 0,21 0,61 0,33 0,61 67 117 134 184 37 39 74 78 5,2 9,0 10 18 0,001 0,004 0,003 0,007 0,15 0,38 0,30 0,42 15 54 30 108 47 76 94 152 9,5 10,0 19 20 0,001 0,002 0,003 0,004 0,10 0,57 0,20 0,57 DE; FR
12 24 24 48 10 15 21 30 9,3 9,9 19 20 0,005 0,009 0,008 0,010 0,22 3,30 0,34 3,3
GR 21 42 43 84 29 94 59 172 9,1 9,9 18 20
HU 50 100 80 200 160 225 10 20 0,006 0,008 0,008 0,009
IT 189 227 219 238 88 101 169 176 24 37 37 44 0,047 0,069 0,047 0,069
339 547 339 547 86 226 93 226 0,011 0,033 0,011 0,033 11,09 22,61 11 23 296 548 296 548 289 590 289 590 0,047 0,082 0,047 0,082 9,58 10,73 9,6 11 NL
149 341 150 341 109 199 109 199 0,006 0,022 0,008 0,022 11,61 24,92 12 25
46 92 82 163 0,22 0,34
36 71 710 710
43 86 1582 1582
LT
45 90 579 579
PL 70 260 140 260 110 140 180 195 5,0 10 0,009 0,017 0,009 0,017
91 255 171 255 64 190 128 220 3,6 6,9 7,2 14 0,004 0,007 0,007 0,009 PT
170 216 210 233 124 244 187 247 0,02 5,4 0,04 11 0,009 0,029 0,010 0,029
N 25 20 25 20 25 21 25 21 16 14 16 14 17 17 17 17 14 13 14 13
min 6 6 11 11 5 5 11 11 0,02 5 0,04 9 0,001 0,001 0,002 0,002 0,08 0,10 0,16 0,20 max 339 548 339 548 1582 590 1582 590 24 37 37 44 0,047 0,082 0,047 0,082 12 25 12 25 mean 94 193 136 223 201 180 247 208 7 10 13 18 0,012 0,024 0,013 0,025 3 6 3 6 p10 18 40 35 80 31 39 62 78 2 5 3 11 0,001 0,003 0,003 0,006 0 0 0 0 p50 64 145 128 197 109 190 180 220 7 9 14 19 0,008 0,017 0,009 0,017 1 2 1 2 p90 248 412 260 412 463 288 463 288 10 10 20 20 0,037 0,069 0,037 0,069 11 20 11 20
WP4 Case study summary report
Table 5. NBL and TV values at p90 and p97.7 for selected substances. Using the preselection method described in D15 and the two defined cases of the final proposal for derivation of groundwater threshold values (D18). The Dutch study have used the lowest reference value of the DWS and an EQS to derive TVs. The Portuguese study have used EQS values for irrigation water, which e.g. will lower the TV for chloride but increase the TV for sulphate compared to the DWS derived TVs. Bold red numbers indicate where REF values are breached – green underlined numbers show where the derived TV is very low (< REF/10).
Chloride, Cl Sulphate, SO4 Nitrate, NO3 Arsenic, As Phosphate, PO4
Country NBL90 NBL97.7 TV90 TV97.7 NBL90 NBL97.7 TV90 TV97.7 NBL90 NBL97.7 TV90 TV97.7 NBL90 NBL97.7 TV90 TV97.7 NBL90 NBL97.7 TV90 TV97.7
AT 41 50 146 150 164 197 207 224 0,001 0,001 0,006 0,006 0,08 0,10 0,27 0,28
BE 65 137 158 194 183 311 217 311 2,0 6,6 26 28 0,030 0,069 0,030 0,069 1,0 2,5 1,0 2,5
49 146 150 198 161 288 205 288 9,0 18 30 34 1,8 3,0 1,8 3,0
BG
45 70 148 160 123 236 187 243 8,9 10 29 30 1,4 2,2 1,4 2,2
83 144 167 197 114 186 182 218 1,0 4,5 26 27 0,011 0,018 0,011 0,018 0,46 0,83 0,46 0,83 DK
64 154 157 202 117 163 184 207 2,0 6,7 26 28 0,008 0,017 0,009 0,017 0,67 1,20 0,67 1,20
EE 287 397 287 397 34 42 142 146 0,010 0,010 0,010 0,010
FI 6 6 128 128 5 5 128 128 5,5 5,5 28 28
79 119 165 185 106 231 178 241 8,6 9,5 29 30 0,004 0,018 0,007 0,018 0,21 0,61 0,33 0,61 67 117 159 184 37 39 144 145 5,2 9,0 28 30 0,001 0,004 0,006 0,007 0,15 0,38 0,30 0,42 15 54 133 152 47 76 149 163 9,5 10 30 30 0,001 0,002 0,006 0,006 0,10 0,57 0,28 0,57 DE; FR
12 24 131 137 10 15 130 133 9,3 10 30 30 0,005 0,009 0,008 0,010 0,22 3,3 0,34 3,3
GR 21 42 136 146 29 94 140 172 9,1 9,9 30 30
HU 50 150 80 200 165 225 10 30 0,006 0,008 0,008 0,009
IT 189 227 219 238 88 101 169 176 24 37 37 44 0,047 0,069 0,047 0,069
339 547 339 547 86 226 93 226 0,011 0,033 0,011 0,033 11 23 11 23
296 548 296 548 289 590 289 590 0,047 0,082 0,047 0,082 9,6 11 9,6 11
NL
149 341 150 341 109 199 109 199 0,006 0,022 0,008 0,022 12 25 12 25
46 148 82 166 0,22 0,34
36 143 710 710
43 147 1582 1582
LT
45 148 579 579
PL 70 260 160 260 110 140 180 195 5,0 28 0,009 0,017 0,009 0,017
91 255 171 255 64 190 157 220 3,6 6,9 27 28 0,004 0,007 0,007 0,009
PT
170 216 210 233 124 244 187 247 0,02 5,4 25 28 0,009 0,029 0,010 0,029
N 25 20 25 20 25 21 25 21 16 14 16 14 17 17 17 17 14 13 14 13
18
1 10 100 1000
concentration (mg/l) 0.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
CL_TV2 CL_TV1 CL_NBL
1 10 100 1000
concentration (mg/l) 0.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
SO4_TV2 SO4_TV1 SO4_NBL
0.10 1.00 10.00 100.00 1000.00 concentration (mg/l)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
NO3_TV2 NO3_TV1 NO3_NBL
0.10 1.00 10.00 100.00 1000.00 concentration (mg/l)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
AS_TV2 AS_TV1 AS_NBL
Figure 8. Percentile (quantile) plots of estimated NBLs at the 90th percentile and derived TVs for selected substances in all investigated groundwater bodies. Note that the NBL and TVs are identical when the NBL is greater than or equal to the reference value (in this case the drinking water standard / dashed red line). The data set represents samples with NO3 less than 10 mg/l as described by the proposed preselection criteria. TV1 is the threshold value estimated by originally proposed procedure with three cases: Case 1: 1/3REF < NBL < REF => TV = (NBL+REF)*0.5; Case 2: NBL ≤ 1/3REF => TV = 2*NBL; Case 3: NBL ≥ REF => TV = NBL . TV2 is derived by the method of the final proposal (D18) by only two cases: Case 1: NBL < REF => TV = (NBL+REF)*0.5; Case 2: NBL ≥ REF => TV=NBL
5.2 Summary of selected NBL and TVs for sand and gravel aquifers at tier 2a (groundwater itself).
The variation of the NBL and TV values in all investigated sand and gravel aquifers for Cl, SO4, NO3, PO4 and As are compared and illustrated in Table 6 and 7 and Figure 9-13 on the following pages. The EU drinking water standards are used as the reference value for all the presented groundwater bodies to enable direct comparison between the data of the different case studies.
Table 6 derives the TVs from the original three cases, while Table 7 derives the TVs by case one and three as described in section 5.1 and by Müller et al (2006a,b). Recall that the nitrate concentrations above 10 mg/l were discarded in the preselection procedure, and therefore are not represented in the dataset. The illustrated distribution of nitrate concentrations therefore only represent monitoring points with median nitrate concentrations less than 10 mg/l, like all other investigated elements and substances.
Figure 9-10 illustrate and compare the TVs (TV90 and TV97.7) derived from the natural background levels computed as the 90th and 97.7th percentiles (NBL90 and NBL97.7) using the EU drinking water standards as REF values and the original three cases described in chapter 3.
Figure 11-12 illustrate the same parameters, however, with TV90 and TV97.7 derived by using only
case 1 and 3 as described in the paragraph above. Finally, Figure 13 compare the TV90 values
derived by the originally proposed method with case 1, 2 and 3 with the TV90 values derived on the
same data, but with the finally proposed method using only case 1 and 3 as described above.
20
Table 6. NBL and TV values at p90 and p97.7 of selected substances in sand and gravel gwbs; using the preselection method described in D15 and the three cases defined in the preliminary proposal. The EU drinking water standards are used as reference value in all case studies to enable easy comparison. Bold red numbers indicate where REF values are breached – green underlined numbers show where the derived TV is very low (< REF/10).
Chloride, Cl Sulphate, SO4 Nitrate, NO3 Arsenic, As Phosphate, PO4 Country NBL90 NBL97 TV90 TV97 NBL90 NBL97 TV90 TV97 NBL90 NBL97 TV90 TV97 NBL90 NBL97 TV90 TV97 NBL90 NBL97 TV90 TV97 AT 41 50 82 100 164 197 207 224 9,0 9,6 18 19 0,001 0,001 0,002 0,002 0,08 0,10 0,16 0,20 BE 65 137 130 194 183 311 217 311 2,0 6,6 4,0 13 0,030 0,069 0,030 0,069 1,00 2,50 1,0 2,5
49 145 98 198 161 288 205 288 9,0 10,0 18 20 1,81 2,95 1,8 3,0 BG 45 70 90 140 123 236 187 243 8,9 10,0 18 20 1,40 2,17 1,4 2,2 83 144 166 197 114 186 182 218 1,0 4,5 2 9 0,011 0,018 0,011 0,018 0,46 0,83 0,46 0,83 DK 64 154 128 202 117 163 184 207 2,0 6,7 4,0 13 0,008 0,017 0,009 0,017 0,67 1,20 0,67 1,20
FI 6 6 11 11 5 5 11 11 5,5 5,5 11,0 11,0
79 119 158 185 106 231 178 241 8,6 9,5 17 19 0,004 0,018 0,007 0,018 0,21 0,61 0,33 0,61 DE, FR
67 117 134 184 37 39 74 78 5,2 9,0 10 18 0,001 0,004 0,003 0,007 0,15 0,38 0,30 0,42 GR 21 42 43 84 29 94 59 172 9,1 9,9 18 20
339 547 339 547 86 226 289 590 0,011 0,033 0,011 0,033 11,09 22,61 11 23 NL 149 341 150 341 109 199 109 199 0,006 0,022 0,008 0,022 11,61 24,92 12 25
LT 46 92 82 163 0,22 0,34
PL 70 260 140 260 110 140 180 195 5,0 10 0,009 0,017 0,009 0,017 PT 91 255 171 255 64 190 128 220 3,6 6,9 7,2 14 0,004 0,007 0,007 0,009 N 15 14 15 14 15 14 15 14 12 11 12 11 10 10 10 10 11 10 11 10 min 6 6 11 11 5 5 11 11 1 5 2 9 0,001 0,001 0,002 0,002 0,08 0,10 0,16 0,20 max 339 547 339 547 183 311 217 311 9 10 18 20 0,030 0,069 0,030 0,069 12 25 12 25 mean 81 171 132 207 99 179 155 205 6 8 11 16 0,008 0,021 0,010 0,021 3 6 3 6 p10 29 44 58 89 32 55 65 106 2 5 4 11 0,001 0,004 0,003 0,007 0,15 0,35 0,30 0,40 p50 65 141 130 195 109 194 180 222 5 9 11 18 0,007 0,018 0,009 0,018 0,7 1,7 0,7 1,7 p90 126 317 188 317 163 272 206 275 9 10 18 20 0 0 0 0 11 23 11 23
WP4 Case study summary report
Table 7. NBL and TV values at p90 and p97.7 of selected substances in sand and gravel gwbs; using the preselection method described in D15 and only case 1 and 3 of the three originally suggested cases as defined in the final proposal for derivation of groundwater threshold values (D18). The EU drinking water standards are used as reference value in all case studies to enable easy comparison. Bold red numbers indicate where REF values are breached – green underlined numbers show where the derived TV is very low (< REF/10).
Chloride, Cl Sulphate, SO4 Nitrate, NO3 Arsenic, As Phosphate, PO4 Country NBL90 NBL97 TV90 TV97 NBL90 NBL97 TV90 TV97 NBL90 NBL97 TV90 TV97 NBL90 NBL97 TV90 TV97 NBL90 NBL97 TV90 TV97 AT 41 50 146 150 164 197 207 224 9,0 9,6 30 30 0,001 0,001 0,006 0,006 0,08 0,10 0,27 0,28 BE 65 137 158 194 183 311 217 311 2,0 6,6 26 28 0,030 0,069 0,030 0,069 1,0 2,5 1,0 2,5
49 146 150 198 161 288 205 288 9,0 18 30 34 1,8 3,0 1,8 3,0 BG 45 70 148 160 123 236 187 243 8,9 10 29 30 1,4 2,2 1,4 2,2 83 144 167 197 114 186 182 218 1,0 4,5 26 27 0,011 0,018 0,011 0,018 0,46 0,83 0,46 0,83 DK 64 154 128 202 117 163 184 207 2,0 6,7 26 28 0,008 0,017 0,009 0,017 0,67 1,20 0,67 1,20 FI 6 6 128 128 5 5 128 128 5,5 5,5 28 28
79 119 165 185 106 231 178 241 8,6 9,5 29 30 0,004 0,018 0,007 0,018 0,21 0,61 0,33 0,61 DE, FR
67 117 159 184 37 39 144 145 5,2 9,0 28 30 0,001 0,004 0,006 0,007 0,15 0,38 0,30 0,42 GR 21 42 136 146 29 94 140 172 9,1 9,9 30 30
339 547 339 547 86 226 93 226 0,011 0,033 0,011 0,033 11 23 11 23 NL 149 341 150 341 109 199 109 199 0,006 0,022 0,008 0,022 12 25 12 25
LT 46 148 82 166 0,22 0,34
PL 70 260 160 260 110 140 180 195 5,0 28 0,009 0,017 0,009 0,017 PT 91 255 171 255 64 190 157 220 3,6 6,9 27 28 0,004 0,007 0,007 0,009 N 15 14 15 14 15 14 15 14 12 11 12 11 10 10 10 10 11 10 11 10 min 6 6 128 128 5 5 128 128 1 5 26 27 0,001 0,001 0,006 0,006 0,08 0,10 0,27 0,28 max 339 547 339 547 183 311 217 311 9 18 30 34 0,030 0,069 0,030 0,069 12 25 12 25 mean 81 171 167 225 99 179 175 218 6 9 28 29 0,008 0,021 0,010 0,021 3 6 3 6 p10 29 44 131 147 32 55 141 153 2 5 26 28 0,001 0,004 0,006 0,007 0,15 0,35 0,30 0,41 p50 65 141 158 195 109 194 180 222 5 9 28 30 0,007 0,018 0,009 0,018 0,7 1,7 0,7 1,7 p90 126 317 188 317 163 272 206 275 9 10 30 30 0 0 0 0 11 23 11 23
22
1 10 100 1000
concentration (mg/l) 0.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV90_CL NBL90_CL
1 10 100 1000
concentration (mg/l) 0.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV97_CL NBL97_CL
1 10 100 1000
concentration (mg/l) 0.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV90_SO4 NBL90_SO4
1 10 100 1000
concentration (mg/l) 0.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV97_SO4 NBL97_SO4
Figure 9. Comparison of natural background levels and threshold values for chloride and sulphate derived at the 90th and 97.7th percentiles by case 1, 2 and 3 (D15). Broken line indicate drinking water standards.
WP4 Case study summary report
0.001 0.010 0.100 concentration (mg/l)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV90_AS NBL90_AS
0.001 0.010 0.100 concentration (mg/l)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV97_AS NBL97_AS
0.10
1.00
10.00
concentration (mg/l) 0.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV90_PO4 NBL90_PO4
0.10
1.00
10.00
concentration (mg/l) 0.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV97_PO4 NBL97_PO4
Figure 10. Comparison of natural background levels and threshold values for arsenic and phosphate derived at the 90th and 97.7th percentiles by case 1, 2 and 3 (D15). Broken line indicate drinking water standards.
24
1 10 100 1000
concentration (mg/l) 0.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV90_CL NBL90_CL
1 10 100 1000
concentration (mg./l) 0.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV97_CL NBL97_CL
1 10 100 1000
concentration (mg./l) 0.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV90_SO4 NBL90_SO4
1 10 100 1000
concentration (mg./l) 0.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV97_SO4 NBL97_SO4
Figure 11. Comparison of natural background levels and threshold values for chloride and sulphate derived at the 90th and 97.7th percentiles by case 1and 3 as described in the final proposal for derivation of groundwater threshold values (D18, Müller et al., 2006).
WP4 Case study summary report
0.001 0.010 0.100 concentration (mg./l)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV90_AS NBL90_AS
0.001 0.010 0.100 concentration (mg./l)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV97_AS NBL97_AS
0.10
1.00
10.00
concentration (mg./l) 0.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV90_PO4 NBL90_PO4
0.10
1.00
10.00
concentration (mg./l) 0.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV97_PO4 NBL97_PO4
Figure 12. Comparison of natural background levels and threshold values for arsenic and phosphate derived at the 90th and 97.7th percentiles by case 1 and 3 as described in the final proposal for derivation of groundwater threshold values (D18, Müller et al., 2006).
26
1 10 100 1000
concentration (mg/l) 0.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV90_CL_123 TV90_CL_13
1 10 100 1000
concentration (mg/l) 0.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV90_SO4_123 TV90_SO4_13
0.001 0.010 0.100 concentration (mg/l)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV90_AS_123 TV90_AS_13
0.10
1.00
10.00
concentration (mg/l) 0.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fraction of Data
TV90_PO4_123 TV90_PO4_13
Figure 13. Comparison of threshold values for chloride, sulphate, arsenic and phosphate derived at the 90th percentile by case 1, 2 and 3; and by case 1 and 3 as described in the final proposal for derivation of groundwater threshold values (D18 - Müller et al., 2006).
5.3 Summary of NBL and TVs for carbonate, sandstone, volcanic and crystalline rock aquifers at tier 2a (groundwater itself).
There are too few groundwater bodies represented within these aquifer typologies to plot and illustrate the variation of data. For a summary of statistical data from these please refer to Table 4 and 5.
5.4 Summary of groundwater TVs derived based on EQS values for dependent aquatic ecosystems (tier 1-4)
Groundwater threshold values obtained by the use of EQS values for dependent ecosystems from Austria, Belgium, Denmark, Hungary and the Netherlands are compared to groundwater threshold values derived for groundwater itself at tier2a in Table 8 on the following page. It is found that the groundwater threshold values derived for groundwater itself are lower than the groundwater threshold values derived based on EQS values for dependent aquatic ecosystems in some cases (like e.g. As in the Austrian case), while it is higher in other cases (like e.g. Phosporus in the Danish case). The Dutch example list only the lowest groundwater TVs, which has been derived. Hence, the Dutch example also illustrates that the method which derives the strictest threshold values vary depending on the actual element or substance in question.
Evaluation of the groundwater threshold values at tier 3 and 4 taking dilution and attenuation
requires a considerable amount of knowledge and data from the investigated systems. Appendix 4
and 5 of the final proposal present methods to estimate the actual dilution and attenuation factors in
a given system. Unfortunately, time and data did not generally allow these evaluations to be
performed in the BRIDGE project. However, investigations and research projects on this subject
will be of great importance in the coming years in order to be able to establish proper threshold
values based on the environmental quality standards for dependent aquatic and terrestrial
ecosystems.
28 Table 8. Comparison of groundwater threshold values derived based on groundwater itself as a receptor (tier 2a) and the p90 NBL and based on reference values for dependent aquatic ecosystems for groundwater bodies in the Austrian, Belgian, Danish, Hungarian and Dutch case study areas.
Austria Belgium Denmark Hungary Netherlands
TV90_gw TV_eco TV90_gw TV_eco TV90_gw TV_eco TV90_gw TV_eco TV90_gw TV_eco
DF=1a DF=0.3b DF=1 AF=0.5
As 2 24 80 30 30 11 0.8 8 15 11
Cdc 3 1 3.3 1 0.75 0.6 0.25/1.5 ? 0.4 0.2 0.4
Cuc 2 9.3 31 16 16 1.2 10 1.5
Crc 2 9 30 8 8 1.1 2.5 8.7
Hg 1 3.3 0.5 0.4 0.006 0.01 0.3 0.06
Pb 2 11 37 10 10 2 7.2 10 4 8
NH4 0.02 0.89 3 1 1.6* 0.52 0.5 - 0.03
NO2 0.04 0.18 1 0.06 0.02
N (19) 4.1** 4** (0.5) 4 8
PO4_P 0.026 0.52 0.48*** 0.15*** 0.08*** 0.15***
TCE 5 10 33 - - 10
PCE 5 10 33 - - 10
a Haschendorf site b Fischamend site c Hardness dependent (see com(2006)397/appendix 5) and Coetsiers and Walraevens 2006)
* NH4_N ** NO3 + NO2 ***total P
6. Summary of findings and suggestions
The general conclusion from the conducted case studies is that the general concept of the developed methodology seems logical and that it is easy and practical to apply although it may be simplified in some parts (e.g. case definitions) and should be developed in further detail in other (e.g. preselection criteria for NBL derivation).
The case studies revealed the following issues, which still need clarification and development:
6.1 Comments and suggestions to the derivation of natural background levels The following issues regarding NBL derivation were raised by different partners:
1) Related to preselection of data used for derivation of NBLs a) Aerobic versus anaerobic groundwater bodies b) Fresh versus saline groundwater bodies
c) Delineation of groundwater bodies and hydrochemistry d) Deep groundwater bodies without dependent ecosystems
2) It is important to recognise the variability of the natural background concentration – the natural background is a range not a fixed value,
3) NBL selection at what percentile (90 or 97.7) ? 4) Selection of relevant reference values
5) What is a reasonable level of the TVs between the NBL and REF?
6) How to deal with increasing or decreasing trends – what part may/should be used for NBL derivation?
7) Derivation of threshold values for organic pollutants and harmful substances 8) how to treat detection limit and level of quantification in the NBL calculations
Re 1)
a) The BRIDGE pre-selection method simply suggest to select data sets with NO3 concentrations less than 10 mg/l as a natural groundwater level – all analyses from monitoring points with median NO3 concentrations above 10 mg/l are excluded. This raises the following issues:
This preselection method will include natural quality groundwaters in some areas and groundwater with human impact in others.
