The mobility and bioavailability of arsenic (As) are strongly controlled by adsorption/precipitat... more The mobility and bioavailability of arsenic (As) are strongly controlled by adsorption/precipitation processes involving metal oxides. However, the organic matter present in the environment, in combination with these oxides, can also play an important role in the cycle of arsenic. This work concerns the interaction between As and two samples of aquatic humic substances (AHS) from tropical rivers. The AHS were extracted as proposed by IHSS, and were characterized by 13 C NMR. The experiments were conducted with the AHS in natura and enriched with metal cations, with different concentrations of As, and complexation capacity was evaluated at three different pH levels (5.0, 7.0, and 9.0). The AHS samples showed similar chemical compositions. The results suggested that there was no interaction between As(III) and AHS in natura or enriched with Al. Low concentrations of As(V) were bound to AHS in natura. For As(III), the complexation capacity of the AHS enriched with Fe was approximately 48 μmol per g of C, while the values for As(V) were in the range 69–80 μmol per grams of C. Fluorescence spectra showed that changes in Eh affected the complexation reactions of As(V) species with AHS.
The trend of increasing dissolved organic carbon (DOC) in surface waters motivated us to gain a m... more The trend of increasing dissolved organic carbon (DOC) in surface waters motivated us to gain a mecha-nistic understanding of DOC exchange at the sediment water interface in lakes. We quantified seasonal DOC and solute fluxes under different redox conditions, in a small drinking water reservoir using sediment core incubations. Processes governing benthic DOC exchange were microbial production of DOC and interaction with mineral surfaces. Mobilization of DOC in anoxic sediments seemed to be closely linked to reductive dissolution of ferric minerals as shown by the strong positive correlation (r 2 5 0.99) between DOC and Fe fluxes. Oxidized surface sediments were an efficient DOC trap where DOC was bound to ferric minerals. Redox conditions appeared to be the primary regulator of the DOC exchange, resulting in sedimentary uptake of DOC (21.8 mmol m 22 d 21) only under oxic conditions. DOC production was regulated by temperature, leading to higher DOC fluxes (up to 2.4 mmol m 22 d 21) in summer. The sediment was a net sink of DOC (20.2 tonnes yr 21) but this was small compared with the annual DOC load (15 tonnes yr 21) of the reservoir. However, the benthic DOC flux was about 10–20% of the dissolved carbon flux at the sediment–water interface, making it a significant process in the lake internal carbon cycle. Climate change is supposed to promote reducing conditions at the bottom of lakes, which might increase benthic DOC production in the future.
The distribution of metals and metalloids among particulate, dissolved, colloidal, free, and labi... more The distribution of metals and metalloids among particulate, dissolved, colloidal, free, and labile forms in natural waters is of great environmental concern since it determines their transportation behaviour and bioavailability. Organic matter can have an important role for this distribution process, since it is an important complexing agent and ubiquitous in the aquatic environment. We studied the distribution, mobility and bioavailability of Al, As and Fe in natural waters of a mining area (Quadril atero Ferrífero, Brazil) and the influence of organic matter in these processes. Water samples were taken from 12 points during the dry and rainy seasons, filtrated at 0.45 mm and ultrafiltrated (<1 kDa) to separate the particulate , colloidal and free fractions. Diffusive gradients in thin films (DGT) were deployed at 5 sampling points to study the labile part of the elements. Total and dissolved organic carbon and the physico-chemical parameters were measured along with the sampling. The results of ultrafiltration (UF) and DGT were compared. The relationship among the variables was studied through multivariate analysis (Kohonen neural network), which showed that the seasonality did not impact most of the samples. Fe and Al occurred mainly in the particulate fraction whereas As appeared more in the free fraction. Most of the dissolved Fe and Al were inert (colloidal form) while As was more labile and bioavailable. The results
Molecular formula assignment is one of the key challenges in processing high-field Fourier transf... more Molecular formula assignment is one of the key challenges in processing high-field Fourier transform ion cy-clotron resonance mass spectrometric (FT-ICR-MS) datasets. The number of potential solutions for an elemental formula increases exponentially with increasing molecular mass, especially when non-oxygen heteroatoms like N, S or P are included. A method was developed from the chemical perspective and validated using a Suwannee River Fulvic Acid (SRFA) dataset which is dominated by components consisting exclusively of C, H and O (78 % CHO). In order to get information on the application range and robustness of this method, we investigated a FT-ICR-MS dataset which was merged from 18 mine pit lake pore waters and 3 river floodplain soil waters. This dataset contained 50 % CHO and 18 % CHOS on average , whereas the former SRFA dataset contained only 1.5 % CHOS. The mass calculator was configured to allow up to five nitrogen atoms and up to one sulphur atom in assigning formulas to mass peaks. More than 50 % multiple-formula assignments were found for peaks with masses > 650 Da. Based on DBE − O frequency diagrams, many CHO, CHOS 1 , CHON 1 and CHON 1 S 1 molecular series were ultimately assigned to many m/z and considered to be reliable solutions. The unequivocal data pool could thus be enlarged by 523 (6.8 %) CHOS 1 components. In contrast to the method validation with CHO-rich SRFA, validation with sulphur-rich pit lake samples showed that formulas with a higher number of non-oxygen heteroatoms can be more reliable assignments in many cases. As an example: CHOS molecular series were reliable and the CHO classes were unreliable amongst other molecular classes in many multiple-formula assignments from the sulphur-rich pit lake samples.
This article provides an overview about the Bode River catchment that was selected as the hydrolo... more This article provides an overview about the Bode River catchment that was selected as the hydrological observatory and main region for hydro-ecological research within the TERrestrial ENvironmental Observatories Harz/ Central German Lowland Observatory. It first provides information about the general characteristics of the catchment including climate, geology, soils, land use, water quality and aquatic ecology, followed by the description of the interdisciplinary research framework and the monitoring concept with the main components of the multi-scale and multi-temporal monitoring infrastructure. It also shows examples of interdisciplinary research projects aiming to advance the understanding of complex hydrological processes under natural and anthropogenic forcings and their interactions in a catchment context. The overview is complemented with research work conducted at a number of intensive research sites, each focusing on a particular functional zone or specific components and processes of the hydro-ecological system.
The aim of this study was to identify sources of carbon turnover using stable isotope mass balanc... more The aim of this study was to identify sources of carbon turnover using stable isotope mass balances. For this purpose, two prereservoirs in the Harz Mountains (Germany) were investigated for their dissolved and particulate carbon contents (dissolved inorganic carbon (DIC), dissolved organic carbon, particulate organic carbon) together with their stable carbon isotope ratios. DIC concentration depth profiles from March 2012 had an average of 0.33 mmol L -1 . Increases in DIC concentrations later on in the year often corresponded with decreases in its carbon isotope composition (δ 13 C DIC ) with the most negative value of -18.4 ‰ in September. This led to a carbon isotope mass balance with carbon isotope inputs of −28.5 ‰ from DOC and −23.4, −31.8 and −30.7 ‰ from algae, terrestrial and sedimentary matter, respectively. Best matches between calculated and measured DIC gains were achieved when using the isotope composition of algae. This shows that this type of organic material is most likely responsible for carbon additions to the DIC pool when its concentrations and δ 13 C DIC values correlate negatively. The presented isotope mass balance is transferable to other surface water and groundwater systems for quantification of organic matter turnover.
Peatlands can be a potential source of dissolved organic matter (DOM) in fresh water catchment ar... more Peatlands can be a potential source of dissolved organic matter (DOM) in fresh water catchment areas. The quantity and quality of DOM can differ between pristine, degraded and rewetted peatlands. Due to the large scale and continuing losses of peatlands, their conservation and restoration has been increasingly emphasized. Mostly rewetting measures are required to improve the hydrology of damaged peatlands, which is a precondition for the resettlement of peat-forming plant species. Thus, in term of DOM, there is a special need to understand how rewetting measures affect DOM characteristics and concentrations. To estimate the potential leaching of humic substances from rewetted areas two natural sites were compared with four artificially rewetted sites in a peatland area of the Harz Mountains National Park, Germany. This was done with regards to DOM quality by combining the results from Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS, measured at one time in Spring) and excitation-emission-matrix fluorescence spectroscopy (EEMF, measured monthly for the period of one year). The DOM quality was significantly less variable in the pristine peatland soil water compared to the rewetted peatland soil waters, from both a spatial and a seasonal perspective. The soil water from the rewetted peatland sites showed a higher degree of humification compared to pristine peatland. DOC concentration was mostly consistent in the pristine peatland over the year. The rewetted peatlands showed higher DOC levels in Summer months and lower DOC in Winter months compared to the pristine peatland. It can be concluded that the rewetting of peatlands is coupled with high concentrations of DOC in soil water and its quality is highly aromatic (as reflected by the observed values from the humification index) during times with
Forest burning for pasture installation in tropical areas represents an important component on bi... more Forest burning for pasture installation in tropical areas represents an important component on biogeochemical cycles. In order to get information about modifications within the element composition after forest burning, in this local study the attempt has been undertaken to provide a first overview about the total contents of a larger set of elements (29) and their distribution patterns in topsoils when forest is shifted for pasture use. The work was carried out in 1999 in Rondônia state (Brazilian
Fernando Pedrozo1, Liam Kelly2, Mónica Diaz1, Pedro Temporetti1, Gustavo Baffico1, Robert Kringel... more Fernando Pedrozo1, Liam Kelly2, Mónica Diaz1, Pedro Temporetti1, Gustavo Baffico1, Robert Kringel5, Kurt Friese6, Margarete Mages3, Walter Geller3 & Stefan Woelfl4 1CONICET-Universidad Nacional del Comahue, Quintral 1250, (8400) Bariloche, Argentina Fax: +2944-422111. ...
Gaia: Okologische Perspektiven in Natur-, Geistes- und Wirtschaftswissenschaften
The formation of lakes after sudden termination of opencast lignite mining in eastern Germany is ... more The formation of lakes after sudden termination of opencast lignite mining in eastern Germany is influenced by massive hydrological problems in the mining area. In spite of restricted surface water availability flooding from external sources is preferable to slow re-ascension of ground-water for geochemical, technological and socio-economical reasons. However, the water quality of the newly formed lakes poses subsequent problems which include eutrophication, salinization, contamination by toxic substances and predominantly acidification. The geological situation in the eastern German mining areas promotes acidification by pyrite oxidation. As a result, biological colonisation of the lakes is poor and use for fishery and recreation is restricted or impossible. Strategies for abatement of acidification include limitation of further pyrite oxidation, restriction of acidity inflow into lake water and neutralisation of already existent lakes by chemical or biotechnological processes. The...
Two samples of residues from iron mining plants have been investigated for their retention capaci... more Two samples of residues from iron mining plants have been investigated for their retention capacity of As, Cu, Cr, and Pb. The sample with the higher content of iron oxides showed the highest capacity to retain metals. The adsorption affinity series changes from Pb>Cu>Cr»As to As>Pb>Cu>Cr or As>Cu>Cr>Pb, depending on the material and the concentration of the initial solution. In the competitive environment, the Pb adsorption decreases and the As, Cu and Cr adsorption increases. Sequential extraction procedures, carried out after adsorption batch experiments, showed that the most important adsorption process occurs in the oxide fraction and that the major part of the absorbed metal is remobilized from exchangeable and oxide fractions.
In August 2002 the Elbe river has seen the worst flood in more than 100 years. Flooding and destr... more In August 2002 the Elbe river has seen the worst flood in more than 100 years. Flooding and destruction of settlements has led to widespread erosion and relocation of soils and river sediments. In order to assess the pollutants entering the water phase, surveys of dissolved constituents and particulate matter (SPM) were carried out daily during the 2002 flood. Samples were taken at a monitoring site of the International Commission for the Protection of the Elbe (ICPE) near Magdeburg. Results were compared to findings from investigation on floods in the past using the same sampling strategy. At very high expected discharge, a by-pass channel upstream of Magdeburg is flooded to protect the towns of Schoenebeck and Magdeburg. In order to be able to compare measurements from August 2002 with results from past floods, only data from floods with flooded by-pass channel were used in the analysis. This paper presents results of dry weight and particle size distributions of SPM, of selected ...
The mobility and bioavailability of arsenic (As) are strongly controlled by adsorption/precipitat... more The mobility and bioavailability of arsenic (As) are strongly controlled by adsorption/precipitation processes involving metal oxides. However, the organic matter present in the environment, in combination with these oxides, can also play an important role in the cycle of arsenic. This work concerns the interaction between As and two samples of aquatic humic substances (AHS) from tropical rivers. The AHS were extracted as proposed by IHSS, and were characterized by 13 C NMR. The experiments were conducted with the AHS in natura and enriched with metal cations, with different concentrations of As, and complexation capacity was evaluated at three different pH levels (5.0, 7.0, and 9.0). The AHS samples showed similar chemical compositions. The results suggested that there was no interaction between As(III) and AHS in natura or enriched with Al. Low concentrations of As(V) were bound to AHS in natura. For As(III), the complexation capacity of the AHS enriched with Fe was approximately 48 μmol per g of C, while the values for As(V) were in the range 69–80 μmol per grams of C. Fluorescence spectra showed that changes in Eh affected the complexation reactions of As(V) species with AHS.
The trend of increasing dissolved organic carbon (DOC) in surface waters motivated us to gain a m... more The trend of increasing dissolved organic carbon (DOC) in surface waters motivated us to gain a mecha-nistic understanding of DOC exchange at the sediment water interface in lakes. We quantified seasonal DOC and solute fluxes under different redox conditions, in a small drinking water reservoir using sediment core incubations. Processes governing benthic DOC exchange were microbial production of DOC and interaction with mineral surfaces. Mobilization of DOC in anoxic sediments seemed to be closely linked to reductive dissolution of ferric minerals as shown by the strong positive correlation (r 2 5 0.99) between DOC and Fe fluxes. Oxidized surface sediments were an efficient DOC trap where DOC was bound to ferric minerals. Redox conditions appeared to be the primary regulator of the DOC exchange, resulting in sedimentary uptake of DOC (21.8 mmol m 22 d 21) only under oxic conditions. DOC production was regulated by temperature, leading to higher DOC fluxes (up to 2.4 mmol m 22 d 21) in summer. The sediment was a net sink of DOC (20.2 tonnes yr 21) but this was small compared with the annual DOC load (15 tonnes yr 21) of the reservoir. However, the benthic DOC flux was about 10–20% of the dissolved carbon flux at the sediment–water interface, making it a significant process in the lake internal carbon cycle. Climate change is supposed to promote reducing conditions at the bottom of lakes, which might increase benthic DOC production in the future.
The distribution of metals and metalloids among particulate, dissolved, colloidal, free, and labi... more The distribution of metals and metalloids among particulate, dissolved, colloidal, free, and labile forms in natural waters is of great environmental concern since it determines their transportation behaviour and bioavailability. Organic matter can have an important role for this distribution process, since it is an important complexing agent and ubiquitous in the aquatic environment. We studied the distribution, mobility and bioavailability of Al, As and Fe in natural waters of a mining area (Quadril atero Ferrífero, Brazil) and the influence of organic matter in these processes. Water samples were taken from 12 points during the dry and rainy seasons, filtrated at 0.45 mm and ultrafiltrated (<1 kDa) to separate the particulate , colloidal and free fractions. Diffusive gradients in thin films (DGT) were deployed at 5 sampling points to study the labile part of the elements. Total and dissolved organic carbon and the physico-chemical parameters were measured along with the sampling. The results of ultrafiltration (UF) and DGT were compared. The relationship among the variables was studied through multivariate analysis (Kohonen neural network), which showed that the seasonality did not impact most of the samples. Fe and Al occurred mainly in the particulate fraction whereas As appeared more in the free fraction. Most of the dissolved Fe and Al were inert (colloidal form) while As was more labile and bioavailable. The results
Molecular formula assignment is one of the key challenges in processing high-field Fourier transf... more Molecular formula assignment is one of the key challenges in processing high-field Fourier transform ion cy-clotron resonance mass spectrometric (FT-ICR-MS) datasets. The number of potential solutions for an elemental formula increases exponentially with increasing molecular mass, especially when non-oxygen heteroatoms like N, S or P are included. A method was developed from the chemical perspective and validated using a Suwannee River Fulvic Acid (SRFA) dataset which is dominated by components consisting exclusively of C, H and O (78 % CHO). In order to get information on the application range and robustness of this method, we investigated a FT-ICR-MS dataset which was merged from 18 mine pit lake pore waters and 3 river floodplain soil waters. This dataset contained 50 % CHO and 18 % CHOS on average , whereas the former SRFA dataset contained only 1.5 % CHOS. The mass calculator was configured to allow up to five nitrogen atoms and up to one sulphur atom in assigning formulas to mass peaks. More than 50 % multiple-formula assignments were found for peaks with masses > 650 Da. Based on DBE − O frequency diagrams, many CHO, CHOS 1 , CHON 1 and CHON 1 S 1 molecular series were ultimately assigned to many m/z and considered to be reliable solutions. The unequivocal data pool could thus be enlarged by 523 (6.8 %) CHOS 1 components. In contrast to the method validation with CHO-rich SRFA, validation with sulphur-rich pit lake samples showed that formulas with a higher number of non-oxygen heteroatoms can be more reliable assignments in many cases. As an example: CHOS molecular series were reliable and the CHO classes were unreliable amongst other molecular classes in many multiple-formula assignments from the sulphur-rich pit lake samples.
This article provides an overview about the Bode River catchment that was selected as the hydrolo... more This article provides an overview about the Bode River catchment that was selected as the hydrological observatory and main region for hydro-ecological research within the TERrestrial ENvironmental Observatories Harz/ Central German Lowland Observatory. It first provides information about the general characteristics of the catchment including climate, geology, soils, land use, water quality and aquatic ecology, followed by the description of the interdisciplinary research framework and the monitoring concept with the main components of the multi-scale and multi-temporal monitoring infrastructure. It also shows examples of interdisciplinary research projects aiming to advance the understanding of complex hydrological processes under natural and anthropogenic forcings and their interactions in a catchment context. The overview is complemented with research work conducted at a number of intensive research sites, each focusing on a particular functional zone or specific components and processes of the hydro-ecological system.
The aim of this study was to identify sources of carbon turnover using stable isotope mass balanc... more The aim of this study was to identify sources of carbon turnover using stable isotope mass balances. For this purpose, two prereservoirs in the Harz Mountains (Germany) were investigated for their dissolved and particulate carbon contents (dissolved inorganic carbon (DIC), dissolved organic carbon, particulate organic carbon) together with their stable carbon isotope ratios. DIC concentration depth profiles from March 2012 had an average of 0.33 mmol L -1 . Increases in DIC concentrations later on in the year often corresponded with decreases in its carbon isotope composition (δ 13 C DIC ) with the most negative value of -18.4 ‰ in September. This led to a carbon isotope mass balance with carbon isotope inputs of −28.5 ‰ from DOC and −23.4, −31.8 and −30.7 ‰ from algae, terrestrial and sedimentary matter, respectively. Best matches between calculated and measured DIC gains were achieved when using the isotope composition of algae. This shows that this type of organic material is most likely responsible for carbon additions to the DIC pool when its concentrations and δ 13 C DIC values correlate negatively. The presented isotope mass balance is transferable to other surface water and groundwater systems for quantification of organic matter turnover.
Peatlands can be a potential source of dissolved organic matter (DOM) in fresh water catchment ar... more Peatlands can be a potential source of dissolved organic matter (DOM) in fresh water catchment areas. The quantity and quality of DOM can differ between pristine, degraded and rewetted peatlands. Due to the large scale and continuing losses of peatlands, their conservation and restoration has been increasingly emphasized. Mostly rewetting measures are required to improve the hydrology of damaged peatlands, which is a precondition for the resettlement of peat-forming plant species. Thus, in term of DOM, there is a special need to understand how rewetting measures affect DOM characteristics and concentrations. To estimate the potential leaching of humic substances from rewetted areas two natural sites were compared with four artificially rewetted sites in a peatland area of the Harz Mountains National Park, Germany. This was done with regards to DOM quality by combining the results from Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS, measured at one time in Spring) and excitation-emission-matrix fluorescence spectroscopy (EEMF, measured monthly for the period of one year). The DOM quality was significantly less variable in the pristine peatland soil water compared to the rewetted peatland soil waters, from both a spatial and a seasonal perspective. The soil water from the rewetted peatland sites showed a higher degree of humification compared to pristine peatland. DOC concentration was mostly consistent in the pristine peatland over the year. The rewetted peatlands showed higher DOC levels in Summer months and lower DOC in Winter months compared to the pristine peatland. It can be concluded that the rewetting of peatlands is coupled with high concentrations of DOC in soil water and its quality is highly aromatic (as reflected by the observed values from the humification index) during times with
Forest burning for pasture installation in tropical areas represents an important component on bi... more Forest burning for pasture installation in tropical areas represents an important component on biogeochemical cycles. In order to get information about modifications within the element composition after forest burning, in this local study the attempt has been undertaken to provide a first overview about the total contents of a larger set of elements (29) and their distribution patterns in topsoils when forest is shifted for pasture use. The work was carried out in 1999 in Rondônia state (Brazilian
Fernando Pedrozo1, Liam Kelly2, Mónica Diaz1, Pedro Temporetti1, Gustavo Baffico1, Robert Kringel... more Fernando Pedrozo1, Liam Kelly2, Mónica Diaz1, Pedro Temporetti1, Gustavo Baffico1, Robert Kringel5, Kurt Friese6, Margarete Mages3, Walter Geller3 & Stefan Woelfl4 1CONICET-Universidad Nacional del Comahue, Quintral 1250, (8400) Bariloche, Argentina Fax: +2944-422111. ...
Gaia: Okologische Perspektiven in Natur-, Geistes- und Wirtschaftswissenschaften
The formation of lakes after sudden termination of opencast lignite mining in eastern Germany is ... more The formation of lakes after sudden termination of opencast lignite mining in eastern Germany is influenced by massive hydrological problems in the mining area. In spite of restricted surface water availability flooding from external sources is preferable to slow re-ascension of ground-water for geochemical, technological and socio-economical reasons. However, the water quality of the newly formed lakes poses subsequent problems which include eutrophication, salinization, contamination by toxic substances and predominantly acidification. The geological situation in the eastern German mining areas promotes acidification by pyrite oxidation. As a result, biological colonisation of the lakes is poor and use for fishery and recreation is restricted or impossible. Strategies for abatement of acidification include limitation of further pyrite oxidation, restriction of acidity inflow into lake water and neutralisation of already existent lakes by chemical or biotechnological processes. The...
Two samples of residues from iron mining plants have been investigated for their retention capaci... more Two samples of residues from iron mining plants have been investigated for their retention capacity of As, Cu, Cr, and Pb. The sample with the higher content of iron oxides showed the highest capacity to retain metals. The adsorption affinity series changes from Pb>Cu>Cr»As to As>Pb>Cu>Cr or As>Cu>Cr>Pb, depending on the material and the concentration of the initial solution. In the competitive environment, the Pb adsorption decreases and the As, Cu and Cr adsorption increases. Sequential extraction procedures, carried out after adsorption batch experiments, showed that the most important adsorption process occurs in the oxide fraction and that the major part of the absorbed metal is remobilized from exchangeable and oxide fractions.
In August 2002 the Elbe river has seen the worst flood in more than 100 years. Flooding and destr... more In August 2002 the Elbe river has seen the worst flood in more than 100 years. Flooding and destruction of settlements has led to widespread erosion and relocation of soils and river sediments. In order to assess the pollutants entering the water phase, surveys of dissolved constituents and particulate matter (SPM) were carried out daily during the 2002 flood. Samples were taken at a monitoring site of the International Commission for the Protection of the Elbe (ICPE) near Magdeburg. Results were compared to findings from investigation on floods in the past using the same sampling strategy. At very high expected discharge, a by-pass channel upstream of Magdeburg is flooded to protect the towns of Schoenebeck and Magdeburg. In order to be able to compare measurements from August 2002 with results from past floods, only data from floods with flooded by-pass channel were used in the analysis. This paper presents results of dry weight and particle size distributions of SPM, of selected ...
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