Tiltaksorientert vannovervåking i Holmestrandsfjorden. Overvåking for NOAH Langøya 2016

Concentrations of contaminants in blue mussels (Mytilus edulis), environmental condition in sediments by Sediment Profile Imagery (SPI), littoral zone communities and radionuclides in seawater, sediments and blue mussels were investigated by NIVA in 2016. The investigation is part of a monitoring programme in the marine recipient near a plant receiving industrial waste on the island of Langøya in the Oslofjord. NOAH AS owns the plant. A brief inspection of the area was performed by NIVA in 1994, and monitoring has been done annually since 1996. Results from the investigations performed in 2016 are presented in this report. Environmental index (BHQ) calculated from analyses of SPI pictures showed “moderate” conditions of the sediment and soft bottom fauna at one station, “very good” conditions at one station and "good" condition at 19 stations. Analyses of river basin specific pollutants (PFOA, triphenyltin, benzo (a) antracen, arsenic, copper, chromium, zinc) in sediment showed no values above EQS-value (threshold value). Analyses of priority substances in blue mussels showed “not good” condition (mercury values above the EQS-value) at the five stations on Langøya, but “good” condition (values below the EQS-value) on the reference station at Mølen. Of the priority substancens, only mercury had values above the EQS-value, while the antracen, benzo (a) pyrene, fluoranthene, naftalene, TBT, lead, cadmium and nickel had values below the EQSvalue. The operation at Langøya can contribute to some of the elevated concentrations of pollutants that were recorded. But the level of contamination is generally low, making it difficult to identify other possible sources. Analyses of radionuclides in seawater, sediment and blue mussels showed values considered to be normal radioactivity content. There is little / no indication that nitrogen discharges from NOAH has led to increased incidence of fastgrowing algae. Surveys of species composition in the littoral showed no major changes from previous surveys.