Boutrup, S. (ed.), Fauser, P., Thomsen, M., Dahllöff, I., Larsen M.M., Strand, J., Sortkjær, O., Ellermann, T., Rasmussen, P., Jørgensen, L.F., Pedersen, M.W. & Munk, L.M. 2009: Hazardous substances and heavy metals in the aquatic environment. State and trend, 1998-2003. National Environmental Research Institute, Aarhus University, Denmark. 44 pp. – NERI Technical Report No. 705.
Summary
The Danish Nationwide Monitoring and Assessment Programme for the Aquatic Environment (NOVA-2003) run over the period 1998-2003. The programme monitored the air, wastewater treatment plants and other point sources, agricultural catchments, the groundwater, watercourses, lakes and marine waters. The Danish monitoring programme was established in 1987 in order to follow development in the aquatic environment and record the effects of the reduction in discharges. In 1998 monitoring of hazardous substances and heavy metals was added to the programme. The monitoring results were reported yearly and the present report gives an overview of the results for the entire period.
The overall picture shows that hazardous substances and heavy metals are generally found in low concentrations and with no environmental significance. The monitoring results have further documented that some areas are impacted or the Danish permitted limits or quality criteria have been exceeded.
Pesticides found most frequently in groundwater and fresh surface water
Pesticides were found in groundwater and fresh surface water while other organic hazardous substances were hardly present. Pesticides were found more frequently in lakes than in watercourses, but concentrations were generally lower in the lakes than in the watercourses.
Accumulation in the marine environment
Among the organic hazardous substances only pesticides occurred in a few cases in watercourses and lakes. Even the substances which were found most often in outlets from wastewater treatment plants or substances discharged in large amounts were found in only a few samples from watercourses and lakes. This applies, for example, to the softener DEHP.
A number of substances were found in sediment, mussels and fish from marine areas. It was typically slowly degradable and accumulative substances such as DEHP, which were found widely in sediment in fjords and coastal areas. Some of the substances which occurred in sediment, mussels and fish are not used in Denmark any longer. DDT is one example. Some of the substances occurred in such high concentration that they may pose an environmental risk.
Heavy metals in the aquatic environment
The amount of heavy metals transported to inland areas and surface waters has been decreasing since the 1990s. In 2003 heavy metal concentrations in fresh surface waters were low compared to the Danish quality criteria, while most metals in marine areas were found in concentrations exceeding the level described by the OSPAR quality criteria as a good environmental state. Concentrations of a few naturally occurring metal in groundwater were so high that they could pose health problems, if the water is used for drinking water.
Sexual changes in snails
The effect of TBT (tributyltin) in marine waters has been investigated in supplement to the measurements of concentrations of hazardous substances. TBT has been used as antifouling agent in ship painting. The substance acts specifically on snails by causing hormone disturbances and sexual changes. The sexual changes were widespread with the highest frequencies close to harbours, where there was the largest TBT impact.
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