Lokala belastningstak (NICs) för näringstillförsel via tillflöden till Egentliga Östersjön

The Swedish commitments to reduce nutrient inputs to the Baltic Proper under HELCOM Baltic Sea Action Plan (BSAP) represent a significant challenge. The need for reductions at the local level has been examined by allocating the reduction commitments across the nationally monitored major rivers that transport nutrients from land to the sea. In addition to this load, inputs from other smaller watercourses and coastal unmonitored areas must also be addressed, as well as discharges from wastewater treatment plants and industries that release effluents directly into the sea. For nitrogen loads, reduced atmospheric deposition is also required.In summary, all calculations show that, broadly speaking, both phosphorus and nitrogen inputs from land-based sources to the Baltic Proper need to be reduced to levels close to what is estimated to be the natural background load for Sweden’s commitments under HELCOM BSAP to be met. This means that any local nutrient input ceilings for individual river mouths need to be set around the estimated natural background inputs, and in some cases even lower. For phosphorus inputs, the commitments do not appear to be achievable unless account can also be taken of the reduction credit that can be obtained from inputs to the Bothnian Sea being lower than Sweden’s commitments. For nitrogen inputs, substantial reductions in atmospheric deposition are also required if the commitments are to be achieved. Current inputs to the Bothnian Sea are too close to the input ceiling for that sea basin for any significant reduction credit to be applied. There is some scope for reductions in direct discharges to the Baltic Proper, but as the potential for measures in this area is unknown, no calculations have been carried out.The report also presents the individual nationally monitored major rivers, showing trends over time in phosphorus and nitrogen concentrations at river mouths compared with estimated background concentrations, as well as reference values and threshold values for good and moderate ecological status under the EU Water Framework Directive, and the locally estimated input ceilings developed in this work. In these cases, the local input ceilings have been converted from annual input amounts (tonnes per year) to concentrations using average water flow. This allows the ceilings to be directly comparable with the various reference concentrations and facilitates comparison with the continuous data obtained through environmental monitoring of these watercourses. The main sources of these nutrients are also presented, based on the latest national source apportionment work for Sweden’s reporting to HELCOM under PLC-8 (Pollution Load Compilation No. 8).