Edeboviken and outlying water
Holmen Paper's Hallsta Paper Mill annually monitors Edeboviken and the outlying waters as receiving bodies of water. In addition to emissions of treated wastewater from the mill, the inlet is also fed by various watercourses and subject to emissions from a municipal wastewater treatment plant, surface water from the Hallstavik community, ship traffic to and from the mill, and a marina.
The ecological status of Edeboviken and the outlying waters is determined primarily by biological variables such as phytoplankton, bottom fauna and rooted vegetation. The nutrient levels, visible depth and oxygen conditions of the water are used to help assess the status of the water according to applicable regulations (HVMFS 2013:19). An overall assessment shows a poor status for Edeboviken and an unsatisfactory status for Galtfjärden and moderate status for Singöfjärden. The assessment remains unchanged compared with the previous year.
Oxygen conditions and chemical oxygen demand
Measurements taken during the period 2015–2017 show generally good oxygen conditions and a high status in both Edeboviken and the outlying waters. During stratified conditions over the summer of 2015, low but not critical oxygen conditions were recorded in the deep water of Edeboviken and Galtfjärden. Oxygen conditions in the bottom water were good throughout 2016 and 2017, including during stratified conditions. As in previous years (2015–2016), low oxygen levels were measured in the surface water in inner Edeboviken. Hallsta is the source of around 39 per cent of the chemical oxygen demand (COD) in Edeboviken, which is the same as in the previous year.
The highest levels of phosphorus and nitrogen are normally recorded in Skeboån, with levels declining away from the inner part of Edeboviken. In terms of nutrients, Edeboviken appears to be the most impacted sea area included in the current monitoring of receiving waters. The bay is characterised by high levels of nitrogen during the winter (unsatisfactory status) and high levels of phosphorous in the summer (poor status). Singöfjärden is the least affected sea area. Taken together Edeboviken and Galtfjärden are judged to have unsatisfactory status regarding nutrients. Singöfjärden is judged to have moderate status.
For the period 1990–2017, a trend towards rising phosphorus levels can be discerned for Edeboviken. The outlying waters showed rising phosphorus levels up until 2013. Looking at the whole period, rising nitrogen levels have been observed for Edeboviken and the outlying waters. In the past decade (2008–2017), the outlying waters have seen falling phosphorus levels, with no other discernible trends. Decreasing phosphorus levels have been observed over the whole period for Skeboån, the largest watercourse draining into the inner part of Edeboviken, with no other discernible trends.
In terms of total emissions of phosphorus and nitrogen to Edeboviken, Hallsta accounts for around 38 per cent and 22 per cent respectively, which is somewhat lower than in the previous year.
Bottom fauna and rooted vegetation
An assessment of the environmental status of the bottom fauna indicates a poor status in Edeboviken, an unsatisfactory status in Galtfjärden and a moderate status in Singöfjärden. The situation remains unchanged compared with the previous year.
A survey of rooted vegetation takes place every three years, with the most recent conducted in 2017. The survey indicates poor to moderate status at the three stations visited in Edeboviken, moderate to good status in Galtfjärden and good to high status in Singöfjärden. Compared with the last survey (2014), the situation is judged to remain unchanged.
A survey of metals and extractive substances in sediment is carried out every three years, with the most recent conducted in 2017. In an analysis of metal levels in sediment, a third of the samples showed significantly lower levels and ten per cent had much higher levels compared with the results of the previous survey (2014). For the remaining samples, the levels were largely unchanged. Lead levels in inner Edeboviken and Singöfjärden were at a level that meant good chemical status could not be achieved. Metals that showed a substantial deviation from comparative values (pre-industrial levels) were lead, copper, cadmium, chromium, mercury and zinc in inner Edeboviken, copper and chromium in central and outer Edeboviken respectively, chromium in Galtfjärden and lead, chromium and copper in Singöfjärden. The levels of what are known as extractive substances were much higher at all the stations compared with the previous years surveyed (2006, 2011, 2014). The levels were lowest in inner Edeboviken and Singöfjärden, and highest in the outer part of Edeboviken.
A survey of fish health is carried out every five years. The most recent survey, conducted in 2013, showed an improvement in the health status of fish in Edeboviken compared with their status in the previous surveys (2003, 2008). The next survey is due in 2018.