Overvåking av vassdrag i forbindelse med larvikittbrudd i Larvikområdet. Resultater fra biologiske og vannkjemiske undersøkelser i 2016.

Abstract

I henhold til tillatelsene til de ulike larvikittbruddene og -deponiene i Larvik er bedriftene pålagt å utvikle og følge fastsatte overvåkingsprogram. Formålet med dette prosjektet har vært å kartlegge effektene av utslipp fra steinindustrien i 2016 på bunndyr og zooplankton i resipientene rundt Lundhs AS’ brudd (Klåstad, Krukåsen og Tvedalen vest og deponi (Brattås) samt Saga Pearl AS’ brudd(Saga Pearl) i henhold til de respektive overvåkingsprogrammene. Dette er sett i sammenheng med vannkjemiske målinger, og de påvirkede lokalitetene er sammenliknet med utvalgte referanselokaliteter. Resultatene er sammenlignet med tidligere undersøkelser der dette er mulig, og bruken av filtrerende organismer for å se på effekter av partikkelforurensning på biota er diskutert.

The purpose of this project has been to map the effects of surface runoff from quarrying activities on macroinvertebrates and zooplankton in recipients around the quarries/landfills Klåstad/Brattås, Krukåsen, Saga Pearl and Tvedalen west in 2016. The affected localities are compared with selected reference sites, and the results are compared to previous surveys. The use of filtering organisms to quantify the effects of particulate pollution on biota are discussed.

In general, we see a greater proportion of filtering organisms in reference sites compared to affected sites, and this applies to both macroinvertebrates (streams) and zooplankton (lakes). Following the respective monitoring programs of each quarry, water sampling has been conducted only four times, and with such a sparse data set, it is difficult to document increased particulate loading through water chemistry sampling alone. For the future, it is recommended that the water sampling is conducted at different rainfall events in order to better reflect the different runoff conditions of the quarries.

It is also apparent that several other factors beyond increased particle load affects areas around quarries, and there is a high nutrient load in most areas. Sources of phosphorus seems to be agriculture and runoff from the quarries, but the bioavailability of phosphorus from the stone industry seems to be low. Sources of nitrogen appears to be agriculture, and probably also sewage in some areas, and there is no apparent connection between nitrogen and the quarries. There are also indications that some localities may be influenced by organic pollution, but our study has not looked specifically at this.