Suomen pintavesien lyijyn ja nikkelin taustapitoisuudet ja niiden biosaatavuus

Natural background concentrations of lead and nickel in Finnish surface waters are low. The average background concentration of lead is 0.30 µg L-1 and median is 0.21 µg L-1. The average background concentration of nickel is 1.17 µg L-1 and median is 0.44 µg L-1. Concentrations of metals change locally. High lead concentrations in waters are almost independent of geological conditions while high nickel concentrations in waters can be explained by features of bedrock and soil. In addition to background concentrations of lead and nickel the harmfulness of metals is estimated with bioavailability. Bioavailability of metals is determined by biotic ligand (BLM) models. Bioavailable portion of lead and nickel is estimated with amounts of free metal ions and metals ions that attach to biotic ligand. Modeling works well with lead but with nickel there remains room for further development. In the case of lead amount of free lead ions are clearly under 1 % of waters lead concentrations and amount of lead ions attach to biotic ligand are under 1 % of free lead ions. In the case of nickel bioavailable concentrations vary depending on modeling program. Free nickel ion concentrations were between permilles and 80 % of waters nickel concentrations. The material of this study is based on 1812 analytical results from Finnish surface waters. Materials are from the monitoring program of environmental database Hertta and large-scale stream water mapping of Geological Survey of Finland (GSF). Research methods that are used are statistical analysis and BLM modeling programs. Bioavailability of lead is estimated with Biotic Ligand Model version 2.2.3 and Mineql + version 4.6. Bioavailability of nickel is estimated with Mineql + version 4.6 and Visual MINTEQ version 3.0. Suitability of environmental quality standard (EQS) limits of EU water framework directive in chemical conditions of Finnish surface waters is estimated based on results of this study. According to material of this study current EQS limits which are 7.2 µg L-1 for lead and 20 µg L-1 for nickel are suitable for Finnish surface water conditions and limits are exceeded only in a small proportion of stream water analyses. Based on estimation of bioavailability of lead and nickel it is possible that EQS limits could be lowered to the proposed levels that are for inland surface waters 1.2 µg L-1 for lead and 4 µg L-1 for nickel. New limits would be concentrations, which are accumulated to organisms and then bioavailability questions would be taken into account. There should be working and reliable BLM model for nickel also if EQS limits will be tightened.