Sammendrag
Norwegian Institute for Water Research (NIVA) has carried out operational monitoring outside DuPont Nutrition Norge AS in the Karmsund strait in accordance to the Water Framework Directive (WFD). The Norwegian Environment Agency approved the monitoring program. The 2018 program was conducted according to the compounds present in the plant’s discharge to the WFD water body “Karmsundet-Kopervik”. The plant has permission, granted on 9.2.2007 and last modified on 8.5.2019 for a limited discharge of organic material (KOF), suspended solids, rock dust, formaldehyde, total Nitrogen (N-tot), total phosphorus (P-tot), cadmium (Cd), chromium (Cr), arsenic (As), dimetylarsenic acid (DMA) and monomethylarsenic acid (MMA) to seawater recipient.
In 2018, samples were collected of blue mussel from two stations, and surficial bottom sediments and softbottom fauna from three stations. The stations are sufficiently representative to assess the distribution and impact of the discharges from DuPont Nutrition Norge AS, and provide at the same time an opportunity to assess a more comprehensive picture of the recipient water body. The stations near the points of discharge, function as discharge control sites as well as being used to show the impact of the effluent. These stations are not considered representative for the water body status and are not used to classify the water body. The classification stations are placed farther from the points of discharges and are considered more representative for the water body. The reference station is located where the impact of discharges from DuPont Nutrition Norge AS is assumed to be negligible but is also classified along with the classification stations.
The purpose of the investigation was to document the ecological status of the softbottom fauna stations and to identify contamination of priority substances (cadmium) and river basin specific substances (arsenic and chromium) in sediment and blue mussel. Of all parameters analysed in this study, the Norwegian guidance document for the implementation of the Water Framework Directive, Guidance 02:2018 (Directorate Group Water Directive 2018), only defines the Environmental Quality Standards (EQS-values) for sediments and not for biota. Hence, only the chemical status of the water body can be assessed using EQS-value for cadmium in sediments. Whereas the assessment of arsenic and chromium is used to help evaluate the ecological status of the water body.
Lacking EQS-values for the remaining contaminants, concentrations of arsenic, cadmium and chromium in blue mussel were compared to Provisional High Reference Concentration (PROREF) according to Green et al. (2018).
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