Operational monitoring of the Sunndalsfjord with data from 2019. Monitoring on behalf of Hydro Aluminium Sunndal

Summary

In 2019 NIVA conducted a monitoring of contaminants in blue mussels and sediments in the Sunndalsfjord on behalf of Aluminiumindustriens Miljøsekretariat (AMS). The Norwegian Environment Agency has approved that the 2019-data can be used to report operational monitoring of the Sunndalsfjord in 2020. The purpose of the operational monitoring has been to identify whether discharges from Hydro Aluminium Sunndal affects the chemical status of the fjord. Sediment samples from five stations and blue mussels from five stations were analysed for polycyclic aromatic hydrocarbons (PAHs) and metals (arsenic, lead, cadmium, copper, chromium, mercury, nickel and zinc). Blue mussels were deployed at five stations, and they were exposed for six weeks. In general, there were low concentrations of metals in the sediments, but the sediment was in Class III (“moderate condition”) for nickel. The innermost sediment station was in Class V (“very bad condition”) for eight PAH compounds and in Class IV (“bad condition”) for seven other PAHs. There were decreasing concentrations of PAHs with increasing distance from the discharge point from the smelter. The high concentrations of PAH compounds found in the sediments can cause acute and extensive toxic effects to organisms living in the sediments. In the sediments, there were exceedances of limit values for nickel and seven PAH compounds that are defined as priority substances in the Water Framework Directive. Chemical status of the sediment stations is therefore classified as "not good" for the five sediment stations. After six weeks of exposure to the water in the Sunndalsfjord, there was no increase in concentration of PAH compounds in the blue mussels. In fact, there was a reduction in concentration of PAH compounds compared to the concentrations that were in the mussels when they were deployed in the fjord. One of the mussel stations had a concentration of mercury of 20 μg per kg wet weight, which is also the limit value for mercury in biota in the Water Framework Directive. Chemical status of that station is therefore classified as "not good". There were no exceedances of limit values for priority substances at the other stations, and chemical status of the other four stations are therefore classified as "good". The sediments exceeded the limit values for the water region specific substances acenaphthene, benzo(a)anthracene, dibenzo(a,h)anthracene, phenanthrene, fluorene, chrysene and pyrene. In the event of a study of soft bottom fauna to determine ecological status, the exceedances of limit values for water region specific substances would lead to ecological status at these stations being maximally set to "moderate". There were no exceedances of limit value for the water region specific substance benzo(a)anthracene for any of the blue mussel stations. Since 2008 there has been an increase in level of PAH16 in sediment at the innermost station, and a reduction of PAH16 in the sediment at the stations farther out in the fjord.