Kväve på File hajdar : En undersökning av kvävehalter och modellering av kvävetransport i ytvatten på File hajdar, Gotland

Sammanfattning

On the northeast coast of Gotland in Slite lies one of Heidelberg Materials' limestone quarries. Today, the factory has permission to extract limestone until 2027, and an application for extended quarrying operations for the next 30 years is in process. The new quarrying activity will involve removing a part of a catchment area. This catchment area supplies water to several Natura 2000 areas south of the quarry. With the removal of land, there will be water losses, and as a protective measure, the factory intends to infiltrate water back into surface and groundwater. The water to be used for this purpose is drainage water from the quarry. Due to nitrogen-based explosives, this water has higher nitrogen levels than the natural levels in the area. The purpose of this study was to investigate how nitrogen levels in the area are affected by the protective measure using INCA-N, a software for simulating nutrient transport in rivers. According to the model, the future infiltration will not affect the water balance as the volumes added are relatively small. However, the infiltration will affect nitrate levels in the area where it is infiltrated. Downstream along the river, nitrogen levels will not be affected by the infiltration. INCA-N is a surface water model, and the groundwater situation in the limestone bedrock of Gotland is complex. Therefore, this model comes with many uncertainties regarding the interaction between surface and groundwater at the site.