Multiple anthropogenic drivers behind upward trends in organic carbon concentrations in boreal rivers

Increases of riverine organic carbon concentrations have been observed across the northern hemisphere over the past few decades. These increases are the result of multiple environmental drivers, but the relative importance of the drivers is still unclear. We analyzed a dataset of >10 000 observations of riverine total organic carbon (TOC) concentrations and associated water chemistry and hydrological observations from 1993 to 2017. The observations span a ~600 km north–south gradient from 30 individual river systems in Finland. Our data show significantly increasing TOC concentrations in 25 out of 30 systems, with an average increase from 12.0 to 15.1 mg l−1. The observed increase in riverine TOC concentrations led to an increase of 0.28 Mt in annual TOC load to the Baltic Sea from 1993 level to 2017 level. We analyzed the role of three putative environmental drivers of the observed TOC trends. Multiple regression analysis revealed that the most common driver was discharge, which alone explained TOC increases in 13 rivers, whereas pH and temperature were less important drivers (sole predictor in one and zero rivers, respectively). Different permutations of these three drivers were also found to be significant; the combination of discharge and pH being the most common (4 rivers). Land use was not in general linked with trends in TOC, except for the proportion of ditched land in the catchment, which was significantly correlated with increases in TOC concentration. Land use showed significant relationships with trends in discharge and pH. We also found that catchment characteristics are regulating the extent of these regional or global environmental changes causing the upward trends of riverine organic carbon.peerReviewe

Influence of EU policy on agricultural nutrient losses and the state of receiving surface waters in Finland

In Finland, the first large-scale efforts to control nutrient loading from agriculture got under way with the introduction of the EU Agri-Environmental Program in 1995. We examined whether these efforts have decreased agricultural nutrient losses and improved the quality of receiving waters. To do so we used monitoring data on fluxes of nutrients and total suspended solids in agricultural catchments in 1990–2004 and on the water quality of agriculturally loaded rivers, lakes and estuaries in 1990–2005. No clear reduction in loading or improvement in water quality was detected. Hydrological fluctuations do not seem to have eclipsed the effects of the measures taken, since there was no systematic pattern in runoff in the period studied. The apparent inefficiency of the measures taken may be due to the large nutrient reserves of the soil, which slowed down nutrient reductions within the period studied. Simultaneous changes in agricultural production (e.g. regional specialisation) and in climate may also have counteracted the effects of agri-environmental measures. The actions to reduce agricultural loading might have been more successful had they focused specifically on the areas and actions that contribute most to the current loading

Horizontal and vertical distribution of biogenic silica in coastal and profundal sediments of the Gulf of Finland (northeastern Baltic Sea)

Peer reviewe

Increases in organic carbon and nitrogen concentrations in boreal forested catchments — Changes driven by climate and deposition

Highlights • Brownification is an increasing threat to aquatic ecosystems. • Reasons behind changes in C and N concentrations in forested streams were studied. • TOC and TON concentrations increased significantly in 7–10 of 12 forested catchments in 30 yrs. • Air temperature and sulphate concentrations explained 83% of the TOC variation. • TON trends were connected to TOC and linked to climatic factors and drainage-%.Brownification, caused by increasing dissolved organic carbon (DOC) concentrations is a threat to aquatic ecosystems over large areas in Europe. The increasing concentrations of DOC in northern boreal streams and lakes have attracted considerable attention with proposed important drivers such as climate, deposition and land-use, and complex interactions between them. Changes in total organic N (TON) concentrations have received less attention, even though carbon and nitrogen losses are highly related to each other. We used long-term (1990–2019) monitoring records of 12 small data-rich headwater forested catchments in a large gradient of climate and deposition. We found that total organic carbon (TOC) concentrations were significantly increasing in almost all study catchments. The mean air temperature and change in sulphate concentrations had a strong, significant correlation to TOC change-%. Both explained, alone, more than 65% of the change in TOC concentrations, and, together, up to 83% of the variation. Sulphur deposition has already decreased to low levels, our results indicate that its importance as a driver of TOC leaching has decreased but is still clearly detected, while the impact of climate warming as a driver of TOC leaching will be even more pronounced in the future. A positive correlation was found between drainage-% and increases in TON, suggesting also importance of land management. TON trends were tightly connected to changes in TOC, but not directly linked to decreasing S deposition

Joint Polish–Finnish sampling of surface waters around the phosphogypsum waste stacks in Gdańsk and Police from 1 to 3 July 2013 – Results of the expedition

The report describes the results of the joint Polish–Finnish sampling expedition aimed at estimating the possible effects of the two Polish phosphogypsum stacks located in Wislinka (Gdańsk) and Police on the loading of the Baltic Sea and the nearby watercourses. The joint expedition was based on the agreement between the Polish and Finnish Ministers of the Environment in June 2013. The results indicate a clear effect of the phosphogypsum stack on phosphate and total phosphorus concentrations in the Martwa Wisla. The physical nature of the basin with no permanent flow into the sea weakens mixing and dilution and may cause a local enrichment of pollutants from external sources, compared with a normal river having a constant water flow into the sea. Our suggestion is that a comprehensive study should be carried out in the stack area of Wislinka, as well as in the Martwa Wisla and its catchment area, to be able to calculate water and phosphorus mass balances in the area, and the magnitude of inputs of phosphorus to the Baltic Sea caused by the stack. The role of sediments as sinks and sources of phosphorus and other pollutants in the Martwa Wisla should be studied as well. In Police the effects of the phosphogypsum stack were less obvious. This could be expected as a result of effective mixing and dilution due to the high flow in the Oder River. Additionally, measures have been implemented to prevent leakage, by means of a hydraulic barrier and by collecting runoff water and directing it to the local wastewater treatment plant (WWTP). However, the results of the present expedition and also the results of the local monitoring programme from 2008 to 2012 indicate that the effects of the phosphogypsum stack on the quality of the recipient water cannot be ruled out. In order to estimate possible leakages in Police we suggest that an intensive monitoring programme for both groundwater and surface waters would be initiated. The sampling frequency for monitoring the leakage from the phosphogypsum stack should be increased to at least 12 annual samples at both the upstream and downstream stations. In addition, the water flow of the Oder between the stack and the nearby island should be continuously monitored. This would enable a reliable estimation of the potential phosphorus load into the Baltic Sea caused by the stack

PFASs in Finnish rivers and fish and the loading of PFASs to the Baltic Sea

The concentrations of per- and polyfluoroalkyl substances (PFASs) in the Finnish aquatic environment were measured in riverine waters and in inland, coastal and open sea fish. In addition, the PFAS load to the Baltic Sea from 11 rivers was calculated. Measurements show that PFASs, including restricted perfluorooctane sulfonic acid (PFOS), are widely present in the Finnish aquatic environment. At three out of 45 sampling sites, the concentration of PFOS in fish exceeded the environmental quality standard (EQS) of the Water Framework Directive (WFD). The annual average (AA) ∑23PFAS concentration in surface waters ranged from 1.8 to 42 ng L−1 and the concentration of PFOS exceeded the AA-EQS in three out of 13 water bodies. In European perch (Perca fluviatilis) and Baltic herring (Clupea harengus membras), the ∑PFAS concentration ranged from 0.98 to 1 µg kg−1 f.w. (fresh weight) and from 0.2 to 2.4 µg kg−1 f.w., respectively. The highest concentrations in both surface water and fish were found in waters of southern Finland. The riverine export of ∑10PFAS to the Baltic Sea from individual rivers ranged from 0.4 kg yr−1 to 18 kg yr−1. PFAS concentrations in fish of point-source-polluted sites and coastal sites were higher compared to fish of open sea or diffusely polluted sites. The PFAS profiles in surface waters of background sites were different from other sites. This study shows that PFASs are widely found in the Finnish aquatic environment. Different PFAS profiles in samples from background areas and densely populated areas indicate diverse sources of PFASs. Although atmospheric deposition has a substantial influence on PFAS occurrence in remote areas, it is not the dominant source of all PFASs to the aquatic environment of Finland. Rather, wastewaters and presumably contaminated land areas are major sources of PFASs to this aquatic environment

Vesien tila 1990-2000. Vesiensuojelun tavoiteohjelman väliarviointi

Julkaisussa tarkastellaan vesiensuojelulle asetettujen tavoitteiden toteutumista 1990-luvun aikana (Valtioneuvoston periaatepäätös 19.3.1998 vesien suojelun tavoitteista vuoteen 2005). Vesiensuojelutoimenpiteiden vaikutuksia pintavesien tilan kehitykseen tarkasteltiin eräillä esimerkkialueilla. Rannikkovesistä, järvistä ja jokivesistöistä valitut esimerkkialueet edustavat pääasiassa metsäteollisuuden, yhdyskuntien, turvetuotannon, kalankasvatuksen ja maa- tai metsätalouden kuormittamia alueita. Erityistä huomiota kiinnitettiin pintavesien ravinteisiin ja niiden aiheuttamaan rehevyyteen. Lisäksi tarkasteltiin muita vesien tilaa kuvaavia tekijöitä, kuten hapen pitoisuuksia, sähkönjohtavuutta, kemiallista hapen kulutusta, väriä ja hygienian indikaattoribakteereja. Aineistona käytettiin ympäristöhallinnon pintavesien tietojärjestelmään tallennettuja veden laatutietoja. Vesiensuojelutoimenpiteiden positiiviset vaikutukset näkyivät selvimmin 1990-luvulla suurten jätevesikuormittajien alapuolisissa vesistöissä. Veden laadun paranemisesta huolimatta jätevesien haitalliset vaikutukset näkyvät kaikilla pistekuormitetuilla alueilla. Maa- ja metsätalouden kuormittamissa vesistöissä ei havaittu merkkejä rehevyyden olennaisesta vähenemisestä. Maatalouden kuormittamien järvien tila näytti jopa heikentyneen joidenkin vedenlatumuuttujien osalta. Muutamilla sisävesien havaintopaikoilla sähkönjohtavuusarvot näyttivät kohonneen 1990-luvulla. Lyhyt tarkastelujakso ja vuosien väliset vaihtelut kuormituksessa sekä sää- ja hydrologisissa oloissa vaikeuttivat luotettavien johtopäätösten tekoa veden laadun muutoksista