Sammendrag
In 2018, action-oriented monitoring was carried out in Tista and the Iddefjord on behalf of Norske Skog Saugbrugs AS, hereafter Saugbrugs. The monitoring program is approved by the Norwegian Environment Agency and designed in accordance with the Water Frame Directive. The program includes studies of biological quality elements and physical-chemical supporting parameters. The waste water from Saugbrugs contains organic matter, suspended material and nutrients, which are discharged into Tista and flows with the river water further out into the Iddefjord.
Overall, the results of the monitoring in 2018 indicate that Saugbrugs emissions have a significant effect on the ecological state of the biological quality elements examined in the river Tista, and that this trend is clearer in 2018 compared with 2015. The eutrophication index PIT for fouling algae was in ‘good condition’ upstream and ‘moderate’ downstream, heterotrophic fouling index HBI2 was in ‘very good’ condition upstream and ‘moderate’ downstream and the bottom animal index ASPT gave ‘moderate’ and ‘poor’ ecological status, respectively upstream and downstream Saugbrugs emissions. The bottom animals are the decisive quality element for the ecological state of Tista, both upstream and downstream of the disposal point. Both stations in Tista are thus in danger of not achieving the environmental goal of ‘good ecological status’ by the year 2021.
For nutrients, the overall condition was ‘good’ upstream in both years and ‘moderate’ and ‘poor’ downstream respectively in 2015 and 2018. There has thus been a deterioration of the condition downstream the discharges. For chemical oxygen consumption (COD), the condition was poor both upstream and downstream the discharges both years, but with somewhat lower nEQR values downstream the discharges.
The results for soft bottom fauna in the Iddefjord 2018 indicate that the fjord is organically loaded. There is a high content of organic carbon and nitrogen in the sediments, and the sediments from ID-1 and ID-43 smelled of H2S. On ID-1 there was almost no fauna and ‘very poor’ conditions. On ID-43, a total of 23 species were registered, but the fauna was classified as ‘poor’ due to low species diversity and high dominance of tolerant species. These two stations in the Iddefjord are thus in danger of not achieving the environmental goal of ‘good ecological status’ by the year 2021. Station R-5 had a ‘good’ condition for soft bottom fauna, but this station also had high organic carbon and nitrogen content in the sediment.
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