AMBIO: A Journal of the Human Environment, Dec 1, 2011
Long-term (1860-2010) catchment mass balance calculations rely on models and assumptions which ar... more Long-term (1860-2010) catchment mass balance calculations rely on models and assumptions which are sources of uncertainty in acidification assessments. In this article, we report on an application of MAGIC to model acidification at the four Swedish IM forested catchments that have been subject to differing degrees of acidification stress. Uncertainties in the modeled mass balances were mainly associated with the deposition scenario and assumptions about sulfate adsorption and soil mass. Estimated base cation (BC) release rates (weathering) varied in a relatively narrow range of 47-62 or 42-47 meq m-2 year-1 , depending on assumptions made about soil cation exchange capacity and base saturation. By varying aluminum solubility or introducing a dynamic weathering feedback that allowed BC release to increase at more acidic pHs, a systematic effect on predicted changes in acid neutralizing capacity (DANC ca. 10-41 leq l-1) and pH (ca. DpH = 0.1-0.6) at all sites was observed. More robust projections of future changes in pH and ANC are dependent on reducing uncertainties in BC release rates, the timing, and extent of natural acidification through BC uptake by plants, temporal changes in soil element pools, and fluxes of Al between compartments.
AMBIO: A Journal of the Human Environment, Nov 15, 2014
For more than 50 years, scientific insights from surface water monitoring have supported Swedish ... more For more than 50 years, scientific insights from surface water monitoring have supported Swedish evidence-based environmental management. Efforts to understand and control eutrophication in the 1960s led to construction of wastewater treatment plants with phosphorus retention, while acid rain research in the 1970s contributed to international legislation curbing emissions. By the 1990s, long-time series were being used to infer climate effects on surface water chemistry and biology. Monitoring data play a key role in implementing the EU Water Framework Directive and other legislation and have been used to show beneficial effects of agricultural management on Baltic Sea eutrophication. The Swedish experience demonstrates that well-designed and financially supported surface water monitoring can be used to understand and manage a range of stressors and societal concerns. Using scientifically sound adaptive monitoring principles to balance continuity and change has ensured long-time series and the capability to address new questions over time.
Sverige rapporterar årligen, inom FN:s ramkonvention för klimatförändringar (UNFCCC) och Kyotopro... more Sverige rapporterar årligen, inom FN:s ramkonvention för klimatförändringar (UNFCCC) och Kyotoprokollet, Sveriges samlade utsläpp av växthusgaser, (National Inventory Report - NIR). En del av denna rapportering rör utsläpp kopplade till export av löst organiskt kol (DOC) från dikad organogen mark. Hittills har denna rapportering baserats på IPCC:s vägledning där ett schablonvärde till utsläppsfaktor (12 g C/m2/år) applicerats för beräkning av utsläpp från all dikad organogen mark, dvs. att ingen hänsyn tagits till markanvändning eller geografiskt läge för den organogena dikade marken. De årliga beräknade utsläppen motsvarar omkring 0,5 miljoner ton CO2 per år. Här har syftet varit att ta fram en rumsligt upplöst modell för att bättre skatta DOC-export från dikad organogen mark vilken tar hänsyn till geografiska och hydrometeorologiska variationer. I denna studie användes totalt organiskt kol (TOC) som en proxy för DOC då studier från svenska förhållanden visar att DOC utgör >90 % av TOC över olika vattendrag och säsonger. Baserat på data från ca 900 små vattendrag (avrinningsområdesarea <5 km2) representerande stora delar av Sveriges skogs- och myrmarker gjordes urval av vattendrag med stor andel (>20 %) myrmark i avrinningsområdet. En modell för TOC-koncentration visade på stora geografiska skillnader med ökande halter längs med nord-sydlig samt väst-ostliga gradienter. Dessutom var även den genomsnittliga årliga nederbörden kopplad till TOC-koncentrationen i vattendragen. Höjd över havet var negativt relaterat till TOC-koncentrationen, men bidrog inte signifikant till den slutliga modellen. Den framtagna modellen föreslås användas tillsammans med avrinningsdata för skattning av DOC-export från dikad organogen mark i kommande växthusgasrapportering. Som jämförelse med det tidigare använda schablonvärdet till utsläppsfaktor använt i rapporteringen beräknades TOC-exporten från de i studien ingående 123 vattendrag representerande dikad organogen mark (dvs. >20% våtmark i avrinningsområdet). Denna var i median 10.7 (5,7-16,5) g C/m2/år, dvs. något lägre än schablonvärdet. Dock ska beaktas att i studien ingående vattendrag till olika stor del påverkas av mineraljord i avrinningsområdet, varför studien även belyser behovet av riktade provtagningsprogram där export av organiskt kol specifikt kvantifieras från dikad samt odikad organogen mark.Sweden reports annually, within the UN Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol, Sweden's total greenhouse gas emissions (National Inventory Report - NIR). A small part of this reporting concerns emissions linked to the export of dissolved organic carbon (DOC) from drained organic soils. To date, this reporting has been based on the IPCC's guidance and where a default emission factor (12 g C/m2/year) has been applied for all drained organic soils, i.e. land-use or geographical position have not been considered. The annual emissions related to DOC corresponds to ca 0.5 million tonnes of CO2. Here, the purpose has been to develop a spatially distributed model to better estimate DOC exports from drained organic soils, which takes into account geographical and hydrometeorological variations. In this study, total organic carbon (TOC) was used as a proxy for DOC as studies from Sweden show that DOC corresponds to >90 % of TOC across watercourses and seasons. Based on data from about 900 small watercourses (catchment area <5 km2), representing large parts of Sweden's area of forests and wetlands, a selection was made of watercourses with a large proportion (> 20 %) of organic soils in the catchment area. A model for TOC concentration showed large geographical differences with increasing concentrations along north-south and west-east gradients. In addition, mean annual long-term precipitation was linked to TOC concentration. Elevation above sea level was negatively related to TOC concentration but did not contribute significantly to the final model. The model developed is proposed to be used together with run-off data for estimating DOC exports from drained organic soils in future greenhouse gas inventories. The estimated TOC export from the 123 watercourses included in the study, and that represented drained organic soils, was on median 10.7 (5.7-16.5) g C/m2/year, i.e. slightly lower than the default emission factor currently used in the reporting. However, it should be taken into account that included watercourses are to varying degrees affected by mineral soil in the catchment area, which is why the study also highlights the need for targeted sampling programs where exports of organic carbon are specifically quantified from drained and undrained organic soils
The recovery from acidification has led to the demand for more precise criteria for classificatio... more The recovery from acidification has led to the demand for more precise criteria for classification of acidification. The Swedish Environmental Protection Agency has revised Sweden's Ecological Quality Criteria for acidification to improve the correlation between the chemical acidification criteria and biological effects. This paper summarises the most relevant findings from several of the studies commissioned for this revision. The studies included data on water chemistry in 74 reference lakes in southern Sweden with data on fish in 61 of the lakes, as well as data on littoral fauna in 48 lakes. We found that the acidity variable most strongly correlated to the biota was the median pH from the current year. Our results probably do not reflect the mechanisms behind the negative effects of acidity on the biota, but are fully relevant for evaluation of monitoring data. The biogeochemical models used for predicting acidification reference conditions generate a pre-industrial buffering capacity. In order to get an ecologically more relevant criteria for acidification based on pH, we transferred the estimated change in buffering capacity into a corresponding change in pH. A change of 0.4 units was defined as the threshold for acidification. With this criterion a considerably lower number of Swedish lakes were classified as acidified when compared with the present Ecological Quality Criteria. Keywords fish. monitoring. littoral fauna. water chemistry 1 Introduction In Sweden, a set of official Environmental Quality Criteria for surface waters (EQC) have been used for
AMBIO: A Journal of the Human Environment, Nov 15, 2014
Long-term (1987-2012) water quality monitoring in 36 acid-sensitive Swedish lakes shows slow reco... more Long-term (1987-2012) water quality monitoring in 36 acid-sensitive Swedish lakes shows slow recovery from historic acidification. Overall, strong acid anion concentrations declined, primarily as a result of declines in sulfate. Chloride is now the dominant anion in many acid-sensitive lakes. Base cation concentrations have declined less rapidly than strong acid anion concentrations, leading to an increase in charge balance acid neutralizing capacity. In many lakes, modeled organic acidity is now approximately equal to inorganic acidity. The observed trends in water chemistry suggest lakes may not return to reference conditions. Despite declines in acid deposition, many of these lakes are still acidified. Base cation concentrations continue to decline and alkalinity shows only small increases. A changing climate may further delay recovery by increasing dissolved organic carbon concentrations and sea-salt episodes. More intensive forest harvesting may also hamper recovery by reducing the supply of soil base cations. Keywords Acidification Á Recovery Á Sweden Á Base cation decline Á Acid neutralizing capacity Á Dissolved organic carbon Ó The Author(s) 2014. This article is published with open access at Springerlink.com www.kva.se/en
Wildfires are the major disturbance in boreal ecosystems, and are of great importance for the bio... more Wildfires are the major disturbance in boreal ecosystems, and are of great importance for the biogeochemical cycles of carbon (C) and nutrients. However, these fire-induced impacts are hard to quantify and rarely assessed together at an ecosystem level incorporating both aquatic and terrestrial environments. Following a wildfire in Sweden in an area with ongoing monitoring, we conducted a pre-and post-fire multi-catchment investigation of element losses (combustion and leaching), and impacts on water quality. Direct C and nitrogen (N) losses through combustion were ca. 4500 g m-2 and 100 g m-2 , respectively. Net CO2 loss associated with soil and biomass respiration was ~150 g C m-2 during the first year, but the ecosystem started to show net CO2 uptake in June three years post-fire. Aquatic C and N losses during the first 12 months were 7 g m-2 and 0.6 g m-2 , respectively. Hence, soil respiration comprised a non-negligible part of the post-fire C loss, whereas aquatic C losses were minor, and did not increase post-fire. However, other elements (e.g., Ca, S) exhibited ecologically relevant increases in fluvial export and concentration, with large peaks in the immediate post-fire period. The temporal dynamics of stream concentrations suggest the presence of faster-and slower-release nutrient pools with half-lives of around 2 weeks and 4 months, which we attribute to physicochemically and biologically mediated mobilisation processes, respectively. Three years after the fire, it appears that biogeochemical cycles have largely returned to pre-fire conditions, but there is still net release of CO2.
The near-stream zone has been identified as an important controi of runoff chemistry. In northem ... more The near-stream zone has been identified as an important controi of runoff chemistry. In northem forested areas, near-stream zones have been found to be both natural sources and sinks for acidity. The near-stream zon e can be a buffer against acidity by cation exchange and sulphate reduction. Oxidation of sulphide and leaching of organic acids are natural sources of acidity from the near-stream zone. A relatively high pH and base saturation in the near-stream zone favours nitrogen cycling processes. Hence, the near-stream zone has a potential to controi nitrogen leaching from the catchment. Nitrogen can be retained by denitrification, microbiai immobilisation and plant uptake. On the other hand, mineralisation, nitrification and leaching of organic matter can make the near-stream zone into a source for nitrogen to the stream water. The geomorphology and the hydrological flow paths are likely to be crucial for the function of the near-stream zone. This thesis reports the results from an investigation on a small forested catchment in central south Sweden, designed to c1arify the effect of processes in the near-stream zone on acidity and nitrogen chemistry in runoff. Both hydrological and water chemistry data suggested that runoff was dominated by superficial ground water, which agrees with what is common ly found in Swedish till soils. The Kindla catchment is heavily affected by acidification with a pH in the stream water between 4.4 and 4.6. Despite the severe acidification, there were no indications of forest decline at the Kindla catchment that retains nitrogen in deposition efficiently. The leaching of inorganic nitrogen was only 3% of bulk deposition. There were no indications that the near-stream zone acted as a buff er against acidity or nitrogen leaching from upiand soils. The main function of the near-stream zone at Kindla with respect to runoff chemistry was rather to serve as a source for organic acids and organic nitrogen and, to a small extent, nitrate and ammonium. The contribution of organic anions to acidity was however overshadowed by a high sulphate concentration, except during a spring flood episode when organic matter was flushed out. Indications of sulphate reduction in the ground water were found but this probably had no influence on stream water chemistry. Ammonium was almost only found during the spring flood episode, when 72% of the annual transport of ammonium in the stream too k place. Nitrate was found more frequently, but mainly at concentrations below 100 Ilg L• I. This nitrate probably origmated in the near-stream zone. The results contrasted to what was found by other authors with respect to the influence of the near-stream zone on stream water chemistry. This would imply that since the function of the near-stream zone appears to vary greatly between catchments, there is a need for further catchment studies that also account for within catchment variation in order to achieve a more general picture of the impact of near-stream zones on runoff chemistry.
Vi utvecklat en statistiskt modeller med målet att kunna prediktera sjödjup och sjövolym för alla... more Vi utvecklat en statistiskt modeller med målet att kunna prediktera sjödjup och sjövolym för alla svenska sjöar enbart utgående från kartbaserade data. Sjövolym kunde förklaras mycket väl utifrån sjöarea och den maximala lutningen i en 50 m bred buffertzon från strandlinjen (R 2 =0.92). Däremot kunde varken det maximala djupet eller medeldjupet modelleras utifrån kartbaserade data (R 2 <0.4). Trots den höga förklaringsgraden (92%) är prediktionen av volym för en enstaka sjö behäftad med en stor statistisk osäkerhet. Däremot blir det statistiska felet mycket mindre om man predikterar den genomsnittliga volymen för minst 5 sjöar åt gången. Volymmodellen kan därför användas för att prediktera den totala sjövolymen, och i förlängning vattnets uppehållstid för avrinningsområden som innehåller minst 5 sjöar.
En kvantifiering av internbelastningen av fosfor gjordes i de eutrofierade sjöarna Vansjön och No... more En kvantifiering av internbelastningen av fosfor gjordes i de eutrofierade sjöarna Vansjön och Nordsjön i Norduppland genom fysiokemisk mätning av vattnet och fraktionsanalys samt inkuberingsanalys av sediment. Mycket låga syrehalter mättes under vintern 2021 medan vattnet var övermättat på syre under våren detsamma året. Detta kan ha starka kopplingar till just övergödningsproblematiken som föreligger. Vid analys av sedimenten konstaterades det att Vansjön hade högst halter fosfor och att koncentrationerna var likvärdiga på de två provtagna platserna. I Vansjön var mängden löst fosfor mer än i Nordsjön. Nordsjön hade något lägre koncentration fosfor i sedimenten och saknade nästan helt löst fosfor. Sjön hade desto högre halter organiskt bunden fosfor, vilken blir lätt tillgänglig vid varma perioder under året i och med högre nedbrytningshastighet av det organiska materialet. För att förbättra sjöarnas status behöver åtgärder göras riktad mot både extern och intern belastning. Injek...
The near-stream zone has been identified as an important controi of runoff chemistry. In northem ... more The near-stream zone has been identified as an important controi of runoff chemistry. In northem forested areas, near-stream zones have been found to be both natural sources and sinks for acidity. The near-stream zon e can be a buffer against acidity by cation exchange and sulphate reduction. Oxidation of sulphide and leaching of organic acids are natural sources of acidity from the near-stream zone. A relatively high pH and base saturation in the near-stream zone favours nitrogen cycling processes. Hence, the near-stream zone has a potential to controi nitrogen leaching from the catchment. Nitrogen can be retained by denitrification, microbiai immobilisation and plant uptake. On the other hand, mineralisation, nitrification and leaching of organic matter can make the near-stream zone into a source for nitrogen to the stream water. The geomorphology and the hydrological flow paths are likely to be crucial for the function of the near-stream zone. This thesis reports the results from an investigation on a small forested catchment in central south Sweden, designed to c1arify the effect of processes in the near-stream zone on acidity and nitrogen chemistry in runoff. Both hydrological and water chemistry data suggested that runoff was dominated by superficial ground water, which agrees with what is common ly found in Swedish till soils. The Kindla catchment is heavily affected by acidification with a pH in the stream water between 4.4 and 4.6. Despite the severe acidification, there were no indications of forest decline at the Kindla catchment that retains nitrogen in deposition efficiently. The leaching of inorganic nitrogen was only 3% of bulk deposition. There were no indications that the near-stream zone acted as a buff er against acidity or nitrogen leaching from upiand soils. The main function of the near-stream zone at Kindla with respect to runoff chemistry was rather to serve as a source for organic acids and organic nitrogen and, to a small extent, nitrate and ammonium. The contribution of organic anions to acidity was however overshadowed by a high sulphate concentration, except during a spring flood episode when organic matter was flushed out. Indications of sulphate reduction in the ground water were found but this probably had no influence on stream water chemistry. Ammonium was almost only found during the spring flood episode, when 72% of the annual transport of ammonium in the stream too k place. Nitrate was found more frequently, but mainly at concentrations below 100 Ilg L• I. This nitrate probably origmated in the near-stream zone. The results contrasted to what was found by other authors with respect to the influence of the near-stream zone on stream water chemistry. This would imply that since the function of the near-stream zone appears to vary greatly between catchments, there is a need for further catchment studies that also account for within catchment variation in order to achieve a more general picture of the impact of near-stream zones on runoff chemistry.
AMBIO: A Journal of the Human Environment, Dec 1, 2011
Long-term (1860-2010) catchment mass balance calculations rely on models and assumptions which ar... more Long-term (1860-2010) catchment mass balance calculations rely on models and assumptions which are sources of uncertainty in acidification assessments. In this article, we report on an application of MAGIC to model acidification at the four Swedish IM forested catchments that have been subject to differing degrees of acidification stress. Uncertainties in the modeled mass balances were mainly associated with the deposition scenario and assumptions about sulfate adsorption and soil mass. Estimated base cation (BC) release rates (weathering) varied in a relatively narrow range of 47-62 or 42-47 meq m-2 year-1 , depending on assumptions made about soil cation exchange capacity and base saturation. By varying aluminum solubility or introducing a dynamic weathering feedback that allowed BC release to increase at more acidic pHs, a systematic effect on predicted changes in acid neutralizing capacity (DANC ca. 10-41 leq l-1) and pH (ca. DpH = 0.1-0.6) at all sites was observed. More robust projections of future changes in pH and ANC are dependent on reducing uncertainties in BC release rates, the timing, and extent of natural acidification through BC uptake by plants, temporal changes in soil element pools, and fluxes of Al between compartments.
AMBIO: A Journal of the Human Environment, Nov 15, 2014
For more than 50 years, scientific insights from surface water monitoring have supported Swedish ... more For more than 50 years, scientific insights from surface water monitoring have supported Swedish evidence-based environmental management. Efforts to understand and control eutrophication in the 1960s led to construction of wastewater treatment plants with phosphorus retention, while acid rain research in the 1970s contributed to international legislation curbing emissions. By the 1990s, long-time series were being used to infer climate effects on surface water chemistry and biology. Monitoring data play a key role in implementing the EU Water Framework Directive and other legislation and have been used to show beneficial effects of agricultural management on Baltic Sea eutrophication. The Swedish experience demonstrates that well-designed and financially supported surface water monitoring can be used to understand and manage a range of stressors and societal concerns. Using scientifically sound adaptive monitoring principles to balance continuity and change has ensured long-time series and the capability to address new questions over time.
Sverige rapporterar årligen, inom FN:s ramkonvention för klimatförändringar (UNFCCC) och Kyotopro... more Sverige rapporterar årligen, inom FN:s ramkonvention för klimatförändringar (UNFCCC) och Kyotoprokollet, Sveriges samlade utsläpp av växthusgaser, (National Inventory Report - NIR). En del av denna rapportering rör utsläpp kopplade till export av löst organiskt kol (DOC) från dikad organogen mark. Hittills har denna rapportering baserats på IPCC:s vägledning där ett schablonvärde till utsläppsfaktor (12 g C/m2/år) applicerats för beräkning av utsläpp från all dikad organogen mark, dvs. att ingen hänsyn tagits till markanvändning eller geografiskt läge för den organogena dikade marken. De årliga beräknade utsläppen motsvarar omkring 0,5 miljoner ton CO2 per år. Här har syftet varit att ta fram en rumsligt upplöst modell för att bättre skatta DOC-export från dikad organogen mark vilken tar hänsyn till geografiska och hydrometeorologiska variationer. I denna studie användes totalt organiskt kol (TOC) som en proxy för DOC då studier från svenska förhållanden visar att DOC utgör &gt;90 % av TOC över olika vattendrag och säsonger. Baserat på data från ca 900 små vattendrag (avrinningsområdesarea &lt;5 km2) representerande stora delar av Sveriges skogs- och myrmarker gjordes urval av vattendrag med stor andel (&gt;20 %) myrmark i avrinningsområdet. En modell för TOC-koncentration visade på stora geografiska skillnader med ökande halter längs med nord-sydlig samt väst-ostliga gradienter. Dessutom var även den genomsnittliga årliga nederbörden kopplad till TOC-koncentrationen i vattendragen. Höjd över havet var negativt relaterat till TOC-koncentrationen, men bidrog inte signifikant till den slutliga modellen. Den framtagna modellen föreslås användas tillsammans med avrinningsdata för skattning av DOC-export från dikad organogen mark i kommande växthusgasrapportering. Som jämförelse med det tidigare använda schablonvärdet till utsläppsfaktor använt i rapporteringen beräknades TOC-exporten från de i studien ingående 123 vattendrag representerande dikad organogen mark (dvs. &gt;20% våtmark i avrinningsområdet). Denna var i median 10.7 (5,7-16,5) g C/m2/år, dvs. något lägre än schablonvärdet. Dock ska beaktas att i studien ingående vattendrag till olika stor del påverkas av mineraljord i avrinningsområdet, varför studien även belyser behovet av riktade provtagningsprogram där export av organiskt kol specifikt kvantifieras från dikad samt odikad organogen mark.Sweden reports annually, within the UN Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol, Sweden's total greenhouse gas emissions (National Inventory Report - NIR). A small part of this reporting concerns emissions linked to the export of dissolved organic carbon (DOC) from drained organic soils. To date, this reporting has been based on the IPCC's guidance and where a default emission factor (12 g C/m2/year) has been applied for all drained organic soils, i.e. land-use or geographical position have not been considered. The annual emissions related to DOC corresponds to ca 0.5 million tonnes of CO2. Here, the purpose has been to develop a spatially distributed model to better estimate DOC exports from drained organic soils, which takes into account geographical and hydrometeorological variations. In this study, total organic carbon (TOC) was used as a proxy for DOC as studies from Sweden show that DOC corresponds to &gt;90 % of TOC across watercourses and seasons. Based on data from about 900 small watercourses (catchment area &lt;5 km2), representing large parts of Sweden's area of forests and wetlands, a selection was made of watercourses with a large proportion (&gt; 20 %) of organic soils in the catchment area. A model for TOC concentration showed large geographical differences with increasing concentrations along north-south and west-east gradients. In addition, mean annual long-term precipitation was linked to TOC concentration. Elevation above sea level was negatively related to TOC concentration but did not contribute significantly to the final model. The model developed is proposed to be used together with run-off data for estimating DOC exports from drained organic soils in future greenhouse gas inventories. The estimated TOC export from the 123 watercourses included in the study, and that represented drained organic soils, was on median 10.7 (5.7-16.5) g C/m2/year, i.e. slightly lower than the default emission factor currently used in the reporting. However, it should be taken into account that included watercourses are to varying degrees affected by mineral soil in the catchment area, which is why the study also highlights the need for targeted sampling programs where exports of organic carbon are specifically quantified from drained and undrained organic soils
The recovery from acidification has led to the demand for more precise criteria for classificatio... more The recovery from acidification has led to the demand for more precise criteria for classification of acidification. The Swedish Environmental Protection Agency has revised Sweden's Ecological Quality Criteria for acidification to improve the correlation between the chemical acidification criteria and biological effects. This paper summarises the most relevant findings from several of the studies commissioned for this revision. The studies included data on water chemistry in 74 reference lakes in southern Sweden with data on fish in 61 of the lakes, as well as data on littoral fauna in 48 lakes. We found that the acidity variable most strongly correlated to the biota was the median pH from the current year. Our results probably do not reflect the mechanisms behind the negative effects of acidity on the biota, but are fully relevant for evaluation of monitoring data. The biogeochemical models used for predicting acidification reference conditions generate a pre-industrial buffering capacity. In order to get an ecologically more relevant criteria for acidification based on pH, we transferred the estimated change in buffering capacity into a corresponding change in pH. A change of 0.4 units was defined as the threshold for acidification. With this criterion a considerably lower number of Swedish lakes were classified as acidified when compared with the present Ecological Quality Criteria. Keywords fish. monitoring. littoral fauna. water chemistry 1 Introduction In Sweden, a set of official Environmental Quality Criteria for surface waters (EQC) have been used for
AMBIO: A Journal of the Human Environment, Nov 15, 2014
Long-term (1987-2012) water quality monitoring in 36 acid-sensitive Swedish lakes shows slow reco... more Long-term (1987-2012) water quality monitoring in 36 acid-sensitive Swedish lakes shows slow recovery from historic acidification. Overall, strong acid anion concentrations declined, primarily as a result of declines in sulfate. Chloride is now the dominant anion in many acid-sensitive lakes. Base cation concentrations have declined less rapidly than strong acid anion concentrations, leading to an increase in charge balance acid neutralizing capacity. In many lakes, modeled organic acidity is now approximately equal to inorganic acidity. The observed trends in water chemistry suggest lakes may not return to reference conditions. Despite declines in acid deposition, many of these lakes are still acidified. Base cation concentrations continue to decline and alkalinity shows only small increases. A changing climate may further delay recovery by increasing dissolved organic carbon concentrations and sea-salt episodes. More intensive forest harvesting may also hamper recovery by reducing the supply of soil base cations. Keywords Acidification Á Recovery Á Sweden Á Base cation decline Á Acid neutralizing capacity Á Dissolved organic carbon Ó The Author(s) 2014. This article is published with open access at Springerlink.com www.kva.se/en
Wildfires are the major disturbance in boreal ecosystems, and are of great importance for the bio... more Wildfires are the major disturbance in boreal ecosystems, and are of great importance for the biogeochemical cycles of carbon (C) and nutrients. However, these fire-induced impacts are hard to quantify and rarely assessed together at an ecosystem level incorporating both aquatic and terrestrial environments. Following a wildfire in Sweden in an area with ongoing monitoring, we conducted a pre-and post-fire multi-catchment investigation of element losses (combustion and leaching), and impacts on water quality. Direct C and nitrogen (N) losses through combustion were ca. 4500 g m-2 and 100 g m-2 , respectively. Net CO2 loss associated with soil and biomass respiration was ~150 g C m-2 during the first year, but the ecosystem started to show net CO2 uptake in June three years post-fire. Aquatic C and N losses during the first 12 months were 7 g m-2 and 0.6 g m-2 , respectively. Hence, soil respiration comprised a non-negligible part of the post-fire C loss, whereas aquatic C losses were minor, and did not increase post-fire. However, other elements (e.g., Ca, S) exhibited ecologically relevant increases in fluvial export and concentration, with large peaks in the immediate post-fire period. The temporal dynamics of stream concentrations suggest the presence of faster-and slower-release nutrient pools with half-lives of around 2 weeks and 4 months, which we attribute to physicochemically and biologically mediated mobilisation processes, respectively. Three years after the fire, it appears that biogeochemical cycles have largely returned to pre-fire conditions, but there is still net release of CO2.
The near-stream zone has been identified as an important controi of runoff chemistry. In northem ... more The near-stream zone has been identified as an important controi of runoff chemistry. In northem forested areas, near-stream zones have been found to be both natural sources and sinks for acidity. The near-stream zon e can be a buffer against acidity by cation exchange and sulphate reduction. Oxidation of sulphide and leaching of organic acids are natural sources of acidity from the near-stream zone. A relatively high pH and base saturation in the near-stream zone favours nitrogen cycling processes. Hence, the near-stream zone has a potential to controi nitrogen leaching from the catchment. Nitrogen can be retained by denitrification, microbiai immobilisation and plant uptake. On the other hand, mineralisation, nitrification and leaching of organic matter can make the near-stream zone into a source for nitrogen to the stream water. The geomorphology and the hydrological flow paths are likely to be crucial for the function of the near-stream zone. This thesis reports the results from an investigation on a small forested catchment in central south Sweden, designed to c1arify the effect of processes in the near-stream zone on acidity and nitrogen chemistry in runoff. Both hydrological and water chemistry data suggested that runoff was dominated by superficial ground water, which agrees with what is common ly found in Swedish till soils. The Kindla catchment is heavily affected by acidification with a pH in the stream water between 4.4 and 4.6. Despite the severe acidification, there were no indications of forest decline at the Kindla catchment that retains nitrogen in deposition efficiently. The leaching of inorganic nitrogen was only 3% of bulk deposition. There were no indications that the near-stream zone acted as a buff er against acidity or nitrogen leaching from upiand soils. The main function of the near-stream zone at Kindla with respect to runoff chemistry was rather to serve as a source for organic acids and organic nitrogen and, to a small extent, nitrate and ammonium. The contribution of organic anions to acidity was however overshadowed by a high sulphate concentration, except during a spring flood episode when organic matter was flushed out. Indications of sulphate reduction in the ground water were found but this probably had no influence on stream water chemistry. Ammonium was almost only found during the spring flood episode, when 72% of the annual transport of ammonium in the stream too k place. Nitrate was found more frequently, but mainly at concentrations below 100 Ilg L• I. This nitrate probably origmated in the near-stream zone. The results contrasted to what was found by other authors with respect to the influence of the near-stream zone on stream water chemistry. This would imply that since the function of the near-stream zone appears to vary greatly between catchments, there is a need for further catchment studies that also account for within catchment variation in order to achieve a more general picture of the impact of near-stream zones on runoff chemistry.
Vi utvecklat en statistiskt modeller med målet att kunna prediktera sjödjup och sjövolym för alla... more Vi utvecklat en statistiskt modeller med målet att kunna prediktera sjödjup och sjövolym för alla svenska sjöar enbart utgående från kartbaserade data. Sjövolym kunde förklaras mycket väl utifrån sjöarea och den maximala lutningen i en 50 m bred buffertzon från strandlinjen (R 2 =0.92). Däremot kunde varken det maximala djupet eller medeldjupet modelleras utifrån kartbaserade data (R 2 <0.4). Trots den höga förklaringsgraden (92%) är prediktionen av volym för en enstaka sjö behäftad med en stor statistisk osäkerhet. Däremot blir det statistiska felet mycket mindre om man predikterar den genomsnittliga volymen för minst 5 sjöar åt gången. Volymmodellen kan därför användas för att prediktera den totala sjövolymen, och i förlängning vattnets uppehållstid för avrinningsområden som innehåller minst 5 sjöar.
En kvantifiering av internbelastningen av fosfor gjordes i de eutrofierade sjöarna Vansjön och No... more En kvantifiering av internbelastningen av fosfor gjordes i de eutrofierade sjöarna Vansjön och Nordsjön i Norduppland genom fysiokemisk mätning av vattnet och fraktionsanalys samt inkuberingsanalys av sediment. Mycket låga syrehalter mättes under vintern 2021 medan vattnet var övermättat på syre under våren detsamma året. Detta kan ha starka kopplingar till just övergödningsproblematiken som föreligger. Vid analys av sedimenten konstaterades det att Vansjön hade högst halter fosfor och att koncentrationerna var likvärdiga på de två provtagna platserna. I Vansjön var mängden löst fosfor mer än i Nordsjön. Nordsjön hade något lägre koncentration fosfor i sedimenten och saknade nästan helt löst fosfor. Sjön hade desto högre halter organiskt bunden fosfor, vilken blir lätt tillgänglig vid varma perioder under året i och med högre nedbrytningshastighet av det organiska materialet. För att förbättra sjöarnas status behöver åtgärder göras riktad mot både extern och intern belastning. Injek...
The near-stream zone has been identified as an important controi of runoff chemistry. In northem ... more The near-stream zone has been identified as an important controi of runoff chemistry. In northem forested areas, near-stream zones have been found to be both natural sources and sinks for acidity. The near-stream zon e can be a buffer against acidity by cation exchange and sulphate reduction. Oxidation of sulphide and leaching of organic acids are natural sources of acidity from the near-stream zone. A relatively high pH and base saturation in the near-stream zone favours nitrogen cycling processes. Hence, the near-stream zone has a potential to controi nitrogen leaching from the catchment. Nitrogen can be retained by denitrification, microbiai immobilisation and plant uptake. On the other hand, mineralisation, nitrification and leaching of organic matter can make the near-stream zone into a source for nitrogen to the stream water. The geomorphology and the hydrological flow paths are likely to be crucial for the function of the near-stream zone. This thesis reports the results from an investigation on a small forested catchment in central south Sweden, designed to c1arify the effect of processes in the near-stream zone on acidity and nitrogen chemistry in runoff. Both hydrological and water chemistry data suggested that runoff was dominated by superficial ground water, which agrees with what is common ly found in Swedish till soils. The Kindla catchment is heavily affected by acidification with a pH in the stream water between 4.4 and 4.6. Despite the severe acidification, there were no indications of forest decline at the Kindla catchment that retains nitrogen in deposition efficiently. The leaching of inorganic nitrogen was only 3% of bulk deposition. There were no indications that the near-stream zone acted as a buff er against acidity or nitrogen leaching from upiand soils. The main function of the near-stream zone at Kindla with respect to runoff chemistry was rather to serve as a source for organic acids and organic nitrogen and, to a small extent, nitrate and ammonium. The contribution of organic anions to acidity was however overshadowed by a high sulphate concentration, except during a spring flood episode when organic matter was flushed out. Indications of sulphate reduction in the ground water were found but this probably had no influence on stream water chemistry. Ammonium was almost only found during the spring flood episode, when 72% of the annual transport of ammonium in the stream too k place. Nitrate was found more frequently, but mainly at concentrations below 100 Ilg L• I. This nitrate probably origmated in the near-stream zone. The results contrasted to what was found by other authors with respect to the influence of the near-stream zone on stream water chemistry. This would imply that since the function of the near-stream zone appears to vary greatly between catchments, there is a need for further catchment studies that also account for within catchment variation in order to achieve a more general picture of the impact of near-stream zones on runoff chemistry.
Uploads
Papers by Jens Fölster