Finnish Environment Institute | Suomen ympäristökeskus | Finlands miljöcentral

sykefi header valkoinen

Are the Biotic Ligand Models (BLM) suitable for assessing the ecological risk of metals in Nordic freshwaters?

+ Show information

Basic project information


Ecological risk assessment of surface waters requires monitoring of the presence of metals and toxic elements. The European Union Water Framework Directive (WFD) guides acceptable levels for priority substances, and therefore, sets environmental quality standards (EQS). These standards also affect the classification of water bodies and may induce mitigation actions.

Environmental Quality Standards (EQS) in the EU have up to now been measured as total or dissolved metal concentrations. This is because the dissolved metal concentration has previously been thought to be a better estimate of the bioavailable, hazardous fraction of a metal. However, other water chemistry factors strongly affect bioavailability of metals. Moreover, the EQS values are based on laboratory toxicity tests performed with fully dissociated inorganic metal salts. Under such test conditions, most of the metal is present as free ions and, thus most likely overestimate the test metal`s toxicity. In order to improve metal risk assessment, Biotic Ligand Models (BLMs) that connect metal toxicity, critical metal accumulation and bioavailability into a single concept have been developed.

The implementation of EU water framework directive has reached a critical turning point. Valid from the end of 2015 (e.g. Finland) the new directive amendment requires that the annual average concentrations for nickel Ni and Pb be reported as the bioavailable rather than dissolved concentration. The EU guide suggests applying the “user-friendly” BLMs to estimate the bioavailable fractions and local EQS values for Ni, Cu and Zn. Unfortunately, a significant fraction of investigated Nordic freshwaters had Ca2+ (75%), alkalinity (29%) and pH (22%) levels outside the calibration range of recommended BLMs. Nordic countries therefore need to decide which metals and which methods they will apply for the updated monitoring work. This may also need adjustment of the current EU models. It is important to note that the problem and solution do not only concern targets in Finland, Norway and Sweden but all soft and sour water bodies.

Objective and end results

The results from the project will help the Nordic countries to decide how to react to the requirements of the new Directive (2013/39/EU). The project will test current BLM models ability to assess Nordic waters in compliance with the new EU guidelines and result model adjustments/revisions if needed.


  1. The Nordic countries has a scientifically sound method to assess bioavailability based Environmental Quality Standards in soft and acidic surface waters.
  2. The implementation of the bioavailability based EQS is clear and well guided at all levels of end users.


Toxicity testing

The Environmental Quality Standards are based on toxicity tests performed with species at all levels of aquatic food web. Also, Biotic Ligand Models are adjusted with the toxicity data but the problem is that data with soft and acidic waters is scarce. This project will produce data performed with chronic, long lasting (days-weeks) toxicity tests with invertebrates and algae. Low pH and hardness will put test species close to their tolerance limits and native species will be applied. SYKE will concentrate on Daphnia longispina (water flea) and Lymnaea stagnalis (mollusc) and ACES on Daphnia longispina and Pseudokirchneriella subcapitata (algae). The tested heavy metals will be copper (in ACES), nickel and zinc (in SYKE).

The test waters will cover typical qualities in the Nordic countries. One set of sample waters concentrate on the hardness range (Ca ≤ 1 to 11 mg/L) and other set for pH and associated DOC (pH 4 -7; DOC 2 – 40 mg/L).


Our associated partners have developed the “user-friendly” models and coordinate the work internationally. They will use “full” BLMs to estimate exposure concentrations and once the data is collected, test the fit of models and perform adjustments if needed.


The practical work in the implementation of the EU and derived national legislation and in the use of BLMs requires that local authorities have knowledge and guidance. The final workshop will deal with the questions like: What are the consequences of the project results and how to use BLM models in the Nordic countries. What are the end users needs and how to support them? The purpose is also to initiate discussion between model developers and end users. At least the following stakeholders are invited; Finland (Ministry of Environment, Centres for the Economic Development, Transport and the Environment, Finnish Water Utilities Association, Regional State Administrative Agencies, Federation of the Finnish Water Protection Societies, Finnish Forest Industries, The Finnish Mining Association and consultants e.g. Pöyry Ltd, Ahma Ympäristö Ltd, Ramboll Finland); Sweden (Swedish Agency for Marine and Water Management, Swedish EPA); Norway (Norwegian Environment Agency, Norsk Industri).

Additional information

Project manager Matti Leppänen, Finnish Environment Institute SYKE

Published 2016-06-03 at 14:30, updated 2016-06-03 at 15:07

Target group: