b'18Changes of organic carbon concentrations in correlation with climate and land use changes - Analysis of river catchments in Northern Finland Cano Bernal JE1, Rankinen K1 and Thielking S2 1Finnish Environment Institute, Helsinki, Finland 2Leibniz Universitt Hannover, Germany Total Organic Carbon (TOC) has lately shown an increasing trend in boreal regions. The interest in TOC has raised due to the currently observed changes in the climate patterns worldwide. TOC is mostly stored in sediments on the oceans bottom and in northern latitudes, where the soil may endurance long frozen periods. The disturbances created by the changes in the climate are provoking that these TOC storages gradually become sources of TOC instead. There are only a few studies on water quality in rivers in northern Finland. TOC concentration in Finland has been observed to be increasing (Lepist et al., 2008) as well as the estimated annual load in catchments characterized by organic soils (Arvola et al., 2004). A rivers carbon content is dependent on hydrological conditions, climate and land use properties of the catchment(Mattsson et al., 2005). Changes in TOC may affect the water chemistry which can haveconsiderable consequences for the aquatic biota (Jarvie, 1991). In this study, we have investigated river catchments in northern Finland between 2000 and 2018 to find changes in TOC concentrations as well as its link with the alterations of temperature and precipitation patterns. This relationship agrees with our results as we found increasing trends in TOC concentration as well as an increase in temperature and discharge. To try to get a deeper understanding, we have also considered and studied changes in land use in this area and the potential connection with TOC concentration as the northern catchments are sparsely populated and not heavily impacted by agriculture or industrial activities. References:Arvola L, Rike A, Kortelainen P, Jrvinen M. The effect of climate and landuse on TOCconcentrations and loads in Finnish rivers. Boreal Environment Research 2004; 9: 381-387. Jarvie DM. Total organic carbon (TOC) analysis: Chapter 11: geochemical methods andexploration. 1991. Lepist A, Kortelainen P, Mattsson T. Increased organic C and N leaching in a northern borealriver basin in Finland. Global Biogeochemical Cycles 2008; 22. Mattsson T, Kortelainen P, Rike A. Export of DOM from boreal catchments: impacts of land use cover and climate. Biogeochemistry 2005; 76: 373-394.62'