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Biotic Ligand model: A tool for risk assessment of metals in Scandinavian fresh waters?
Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Products from iron and copper mining are among Sweden’s top exports. However, as the metals are excavated, they often end up in the aquatic environment where they can cause toxicity. To implement the Water Framework Directive (WFD) within the European Union, all member states must classify their waters and set local environmental quality standards (EQS). These EQS are used to set the maximum concentration of a metal allowed in water and can be set both by the Swedish EPA and EU. The WFD EQS are to be based on the bioavailable metal fraction, as compared to the total metal concentration as have been used previously. As a tool in setting EQS, bioavailability models, like the biotic ligand model (BLM), have been proposed. BLMs can calculate toxicity endpoints based on water chemistry and organismal response and these predictions can be used for regional EQS values.

However, BLMs are often calibrated toward hard waters with neutral or high pH, containing low concentrations of natural organic material (NOM), a water chemistry most commonly found in the central and southern parts of Europe. The overarching aim of this doctoral thesis was, therefore, to assess the regulatory applicability of Cu BLMs for Swedish conditions.

Results from Paper I and II show that for at least 50% of Fennoscandinavian (Sweden, Finland and Norway) freshwater bodies, the models are not fully applicable. This due to crucial model input parameters being outside of the current calibration range of the Cu BLM. Papers II and III further showed that BLM calculated results differed from measured Cu toxicity to daphnids and algae, indicating that model-based EQS will not be protective for these organisms. Moreover, Paper III showed that Al had an impact on Cu speciation and, hence, toxicity. In conclusion, the present thesis shows that several available Cu BLMs are not yet fully applicable for Swedish or Scandinavian freshwater bodies due to incomplete parameterisation of the models.  To improve the applicability of the models, there is a need to calibrate the models for soft freshwater bodies and include Al and NOM properties as input parameters.

Abstract [sv]

Produkter från metallindustrin är bland Sveriges viktigaste exportprodukter. Metallutvinning leder dock till utsläpp som kan hamna i den akvatiska miljön och där orsaka toxicitet. Europeiska Unionens Vattendirektiv syftar till att alla medlemsstater ska klassificera sina vatten och ta fram miljökvalitetsnormer. Dessa normer ska baseras på den biotillgängliga fasen av metaller istället för den totala som tidigare. Biotiska ligand modeller (BLM) har förts fram som verktyg i denna process.

BLM kan beräkna utsläppsnivåer för sötvatten baserat på rådande vattenkemi samt vattenorganismers känslighet och ger användaren en specifikt anpassad rekommendation (LC/EC50, NOEC, PNEC o.s.v.).

Dock är dessa modeller ofta kalibrerade för en vattenkemi gällande i de centrala och södra delarna av Europa. I Sverige är det vanligt med sura mjuka vatten, vilka har en högre koncentration av biotillgängliga metaller vilka kan orsaka toxicitet. Det övergripande syftet med denna doktorsavhandling var att undersöka hur dagens BLM för koppar (Cu) fungerar för svenska sötvatten.

Resultaten från Artikel I och II visar att en stor del av de Fennoskandinaviska vatten som testats faller utanför kalibreringsintervallet för BLM.

Vidare visar Artikel III och IV att de testade modellerna inte på ett korrekt sätt kunde uppskatta toxicitet för alger och vattenloppor, vilket innebär att de inte räknar ut skyddande rekommendationer för dessa arter. Det var även tydligt i Artikel IV att aluminium (Al) påverkar kopparspecieringen och genom detta även koppars toxicitet. Sammanfattningsvis visar denna avhandling att flera tillgängliga BLM inte är helt applicerbara i mjuka vatten, ofta p.g.a. opassande intervall för de kemiska parametrarna. För att förbättra tillämpbarheten av BLMs i Sverige krävs det att modellerna dels kalibreras för den rådande vattenkemin och dels att Al och NOMs egenskaper inkluderas.

Place, publisher, year, edition, pages
Stockholm: Department of Environmental Science and Analytical Chemistry, Stockholm University , 2016. , 40 p.
Keyword [en]
BLM, Soft freshwaters, Sweden, Cu
National Category
Environmental Sciences
Research subject
Applied Environmental Science
URN: urn:nbn:se:su:diva-124330ISBN: 978-91-7649-301-4 (print)OAI: diva2:892644
Public defence
2016-02-19, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 10:00 (English)
Swedish Research Council Formas, 2006-638
Available from: 2016-01-27 Created: 2015-12-17 Last updated: 2017-02-17Bibliographically approved
List of papers
1. Evaluation of current copper bioavailability tools for soft freshwaters in Sweden
Open this publication in new window or tab >>Evaluation of current copper bioavailability tools for soft freshwaters in Sweden
2015 (English)In: Ecotoxicology and Environmental Safety, ISSN 0147-6513, E-ISSN 1090-2414, Vol. 114, 143-149 p.Article in journal (Refereed) Published
Abstract [en]

The Water Framework Directive (WFD) in Europe calls for an improved aquatic ecological status. Biotic ligand models (ELM) have been suggested as a possible tool assisting in the regulatory process. The aim of this study was therefore to investigate the applicability of ELM under the WFD to set environmental quality standards (EQS), in particular regarding copper in Swedish freshwaters of which many are softer than those used for model calibration. Three different BLMs, one acute and two chronic, were applied to water chemistry data from 926 lakes and 51 rivers (1530 data entries) and evaluated with respect to their calibration range for input parameters. In addition, the predicted no-effect concentration (PNEC) for copper was calculated. From the 1530 data entries, 750 ended up outside of the BLM calibration range, when looking at the chemical parameters Ca2+, alkalinity, pH and DOC, primarily due to low carbonate alkalinity. Furthermore, the calculated Cu PNECs were higher than the suggested Swedish limit for Cu (4 mu g L-1) in surface waters for 98% and 99% of the cases concerning lakes and rivers, respectively. To conclude, our findings show that water chemical characteristics outside of the calibration ranges are quite common in Sweden and that the investigated models differ in how they calculate toxicity concerning Cu under these conditions. As a consequence, additional work is required to validate the BLMs by use of bioassays with representative species of soft waters. Such results will show if these models can be used outside of their calibration ranges and also which of the models that gives the most reliable results.

Bioavailability tools, BLM, Sweden, Soft freshwater, Copper
National Category
Earth and Related Environmental Sciences
Research subject
Applied Environmental Science
urn:nbn:se:su:diva-116780 (URN)10.1016/j.ecoenv.2015.01.023 (DOI)000350928800019 ()25637749 (PubMedID)


Available from: 2015-04-27 Created: 2015-04-27 Last updated: 2017-12-04Bibliographically approved
2. Soft and sour: The challenge of setting environmental quality standards for bioavailable metal concentration in Fennoscandinavian freshwaters
Open this publication in new window or tab >>Soft and sour: The challenge of setting environmental quality standards for bioavailable metal concentration in Fennoscandinavian freshwaters
Show others...
2015 (English)In: Environmental Science and Policy, ISSN 1462-9011, E-ISSN 1873-6416, Vol. 54, 210-217 p.Article in journal (Refereed) Published
Abstract [en]

The European Union Water Framework Directive (WFD) requires member states to ensure that all inland and coastal waters achieve 'good' water quality status. To this end, the WFD has set environmental quality standards (EQS) or Water quality criteria (WQC) for priority pollutants that include the four metals Cd, Ni, Pb and Hg. Many states have also chosen to set EQS for Cu and Zn. The use of bioavailability models to set EQS, paves the way for accepting higher local metal concentrations in waters where metal bioavailability is deemed low. The Biotic Ligand Model (BLM) concept has been proposed as a tool for estimating metal bioavailability and for calculating local EQS in the EU guidance document. The BLM estimates metal bioavailability based on the dissolved metal concentration and key ancillary water chemistry parameters (acidity, hardness and organic carbon content). The BLMs developed so far, have only been validated for water chemistry input parameters typical of Central Europe. However, the pH, alkalinity and dissolved organic carbon levels of a significant fraction of Fennoscandinavian (Finland, Norway and Sweden) freshwaters are outside the calibration range of currently available BLMs. The levels of Ca2+, alkalinity and pH in 75%, 29% and 22%, respectively, of the ca. 2500 Fennoscandinavian freshwater bodies investigated in this survey were outside the calibration range of tested BLMs. Moreover, a comparison of the ability of the tested BLMs to predict the acute and chronic copper toxicity to Daphnia magma and Rainbow trout indicated that the BLMs should be used with caution outside their current validation range. We conclude that more work is needed to extend the application of BLMs in the practical risk assessment to encompass a broader range of European freshwater bodies.

Bioavailability tools, BLM, Fennoscandinavian, Soft freshwater, Copper, Zinc, Nickel, EQS
National Category
Earth and Related Environmental Sciences
Research subject
Applied Environmental Science
urn:nbn:se:su:diva-122908 (URN)10.1016/j.envsci.2015.07.007 (DOI)000362603400022 ()
Available from: 2015-11-17 Created: 2015-11-11 Last updated: 2017-12-01Bibliographically approved
3. Predictions of Cu toxicity in three aquatic species using bioavailability tools in four Swedish soft freshwaters
Open this publication in new window or tab >>Predictions of Cu toxicity in three aquatic species using bioavailability tools in four Swedish soft freshwaters
2015 (English)In: Environmental Sciences Europe, ISSN 2190-4715, E-ISSN 2190-4715, Vol. 27, no 25Article in journal (Refereed) Published
Abstract [en]


The EU member countries are currently implementing the Water Framework Directive to promote better water quality and overview of their waters. The directive recommends the usage of bioavailability tools, such as biotic ligand models (BLM), for setting environmental quality standards (EQS) for metals. These models are mainly calibrated towards a water chemistry found in the south central parts of Europe. However, freshwater chemistry in Scandinavia often has higher levels of DOC (dissolved organic carbon), Fe and Al combined with low pH compared to the central parts of Europe. In this study, copper (Cu) toxicities derived by two different BLM software were compared to bioassay-derived toxicity for Pseudokirchneriella subcapitata, Daphnia magna and D. pulex in four Swedish soft water lakes.


A significant under- and over prediction between measured and BLM calculated toxicity was found; for P. subcapitata in three of the four lakes and for the daphnids in two of the four lakes. The bioassay toxicity showed the strongest relationship with Fe concentrations and DOC. Furthermore, DOC was the best predictor of BLM results, manifested as positive relationships with calculated LC50 and NOEC for P. subcapitata and D. magna, respectively.


Results from this study indicate that the two investigated BLM softwares have difficulties calculating Cu toxicity, foremost concerning the algae. The analyses made suggest that there are different chemical properties affecting the calculated toxicity as compared to the measured toxicity. We recommend that tests including Al, Fe and DOC properties as BLM input parameters should be conducted. This to observe if a better consensus between calculated and measured toxicity can be established.

National Category
Earth and Related Environmental Sciences
Research subject
Applied Environmental Science
urn:nbn:se:su:diva-125493 (URN)10.1186/s12302-015-0058-1 (DOI)
Available from: 2016-01-12 Created: 2016-01-12 Last updated: 2017-11-30Bibliographically approved
4. Can natural levels of Al influence Cu speciation and toxicity to Daphnia magna in a Swedish soft water lake?
Open this publication in new window or tab >>Can natural levels of Al influence Cu speciation and toxicity to Daphnia magna in a Swedish soft water lake?
2015 (English)In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 138, 205-210 p.Article in journal (Refereed) Published
Abstract [en]

It is well known that chemical parameters, such as natural organic matter (NOM), cation content and pH may influence speciation and toxicity of metals in freshwaters. Advanced bioavailability models, e.g. Biotic Ligand Models (BLMs), can use these and other chemical parameters to calculate site specific recommendations for metals in the aquatic environment. However, since Al is not an input parameter in the BLM v.2.2.3, used in this study, there could be a discrepancy between calculated and measured results in Al rich waters. The aim of this study was to evaluate if the presence of Al in a circumneutral (pH similar to 6) soft humic freshwater, Lake St. Envattern, will affect the Cu speciation and thereby the toxicity to the cladoceran Daphnia magna. The results show a statistically significant increase in the free Cu2+ concentration with Al additions and that measured levels of Cu2+ significantly differed from BLM calculated levels of Cu2+. Furthermore, there was also a statistically significant elevated acute toxic response to D. magna at low additions of Al (10 mu g/L). However, since the large difference between calculated and measured Cu2+ resulted in a significant but minor (factor of 2.3) difference between calculated and measured toxicity, further studies should be conducted in Al rich soft waters to evaluate the importance of adding Al as an input parameter into the BLM software.

Bioavailability tools, BLM, Sweden, Freshwater, Copper, Al
National Category
Earth and Related Environmental Sciences
Research subject
Applied Environmental Science
urn:nbn:se:su:diva-122242 (URN)10.1016/j.chemosphere.2015.05.099 (DOI)000361772800028 ()
Available from: 2015-11-02 Created: 2015-10-28 Last updated: 2017-12-01Bibliographically approved

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