Pub Date : 2021-02-17DOI: 10.1007/s10498-021-09392-4
Noémie Janot, Jan E. Groenenberg, Alba Otero-Fariña, José Paulo Pinheiro
The aim of this study was to develop an analytical method to determine free concentrations of Europium (Eu(III)) in natural waters. Europium(III) in solution was detected using cathodic stripping voltammetry after complexation with N-nitroso-N-phenylhydroxylamine (cupferron). Optimization of analytical parameters allowed us to detect nanomolar levels of Eu(III) in solution. Free Eu(III) in solution was measured using the Donnan membrane technique in which a natural solution (the “donor”, containing various ligands) is separated from a ligand-free solution (the “acceptor”) by a cation-exchange membrane. This membrane allows only non-colloidal cationic species to pass through it, and after an adequate time equilibrium is reached between both compartments. Total Eu(III) concentration can then be quantified in the acceptor solution and related to free Eu(III) in the natural sample. Due to its high valency, free Eu(III) tends to adsorb strongly to the cation-exchange membrane. In order to determine the physicochemical conditions minimizing this adsorption, we analyzed solutions of different Eu(III) and Ca(II) (as background ion) concentrations. Results showed that 100 mM of Ca(II) were necessary to make adsorption of Eu(III) onto the membrane negligible. The optimized setup was then used to quantify Eu(III) complexation in a Eu(III)-dissolved organic matter solution.
{"title":"Free Eu(III) Determination by Donnan Membrane Technique with Electrochemical Detection: Implementation and Evaluation","authors":"Noémie Janot, Jan E. Groenenberg, Alba Otero-Fariña, José Paulo Pinheiro","doi":"10.1007/s10498-021-09392-4","DOIUrl":"10.1007/s10498-021-09392-4","url":null,"abstract":"<div><p>The aim of this study was to develop an analytical method to determine free concentrations of Europium (Eu(III)) in natural waters. Europium(III) in solution was detected using cathodic stripping voltammetry after complexation with <i>N</i>-nitroso-<i>N</i>-phenylhydroxylamine (cupferron). Optimization of analytical parameters allowed us to detect nanomolar levels of Eu(III) in solution. Free Eu(III) in solution was measured using the Donnan membrane technique in which a natural solution (the “donor”, containing various ligands) is separated from a ligand-free solution (the “acceptor”) by a cation-exchange membrane. This membrane allows only non-colloidal cationic species to pass through it, and after an adequate time equilibrium is reached between both compartments. Total Eu(III) concentration can then be quantified in the acceptor solution and related to free Eu(III) in the natural sample. Due to its high valency, free Eu(III) tends to adsorb strongly to the cation-exchange membrane. In order to determine the physicochemical conditions minimizing this adsorption, we analyzed solutions of different Eu(III) and Ca(II) (as background ion) concentrations. Results showed that 100 mM of Ca(II) were necessary to make adsorption of Eu(III) onto the membrane negligible. The optimized setup was then used to quantify Eu(III) complexation in a Eu(III)-dissolved organic matter solution.</p></div>","PeriodicalId":8102,"journal":{"name":"Aquatic Geochemistry","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2021-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/s10498-021-09392-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4675067","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-03DOI: 10.1007/s10498-020-09390-y
C. G. E. M. van Beek, D. G. Cirkel, M. J. de Jonge, N. Hartog
Iron(II) concentrations in fresh groundwater in Dutch aquifers range from absent up to 50?mg/l. Evaluation of extensive chemical data sets learned that the maximum logarithmic concentration of iron(II) in aquifers, between?±?6.5?<?pH?<??±?8, is a linear function of pH, governed by Siderite. It is a broad relation due to oversaturation with respect to Siderite and to variation in alkalinity. Iron(II) is continuously supplied to groundwater by reduction of hydrous ferric oxides (HFO), until becoming saturated with respect to Siderite, and from then on, HFO reduction and Siderite precipitation occur simultaneously. In Dutch aquifers, the electron supply rate (equivalent to the organic matter oxidation rate) apparently exceeds the HFO electron uptake rate (equivalent to the HFO reduction rate) and the excess supply is taken up by sulfate (equivalent to the sulfate reduction rate): HFO reduction, sulfate reduction and FeS precipitation occurring simultaneously, where the presence of Siderite prevents a dip in the iron(II) concentration. After sulfate becomes exhausted, the excess electron supply is transferred to methane production: HFO reduction and methane production occurring simultaneously. This evaluation also demonstrated that the organic matter oxidation rate and the HFO reduction rate decrease over time. The results of this study are also relevant for the behavior of As and of Co, Ni and Zn in groundwater, as HFO, Pyrite and Siderite may contain variable contents of these elements.
{"title":"Concentration of Iron(II) in Fresh Groundwater Controlled by Siderite, Field Evidence","authors":"C. G. E. M. van Beek, D. G. Cirkel, M. J. de Jonge, N. Hartog","doi":"10.1007/s10498-020-09390-y","DOIUrl":"https://doi.org/10.1007/s10498-020-09390-y","url":null,"abstract":"<p>Iron(II) concentrations in fresh groundwater in Dutch aquifers range from absent up to 50?mg/l. Evaluation of extensive chemical data sets learned that the maximum logarithmic concentration of iron(II) in aquifers, between?±?6.5?<?pH?<??±?8, is a linear function of pH, governed by Siderite. It is a broad relation due to oversaturation with respect to Siderite and to variation in alkalinity. Iron(II) is continuously supplied to groundwater by reduction of hydrous ferric oxides (HFO), until becoming saturated with respect to Siderite, and from then on, HFO reduction and Siderite precipitation occur simultaneously. In Dutch aquifers, the electron supply rate (equivalent to the organic matter oxidation rate) apparently exceeds the HFO electron uptake rate (equivalent to the HFO reduction rate) and the excess supply is taken up by sulfate (equivalent to the sulfate reduction rate): HFO reduction, sulfate reduction and FeS precipitation occurring simultaneously, where the presence of Siderite prevents a dip in the iron(II) concentration. After sulfate becomes exhausted, the excess electron supply is transferred to methane production: HFO reduction and methane production occurring simultaneously. This evaluation also demonstrated that the organic matter oxidation rate and the HFO reduction rate decrease over time. The results of this study are also relevant for the behavior of As and of Co, Ni and Zn in groundwater, as HFO, Pyrite and Siderite may contain variable contents of these elements.</p>","PeriodicalId":8102,"journal":{"name":"Aquatic Geochemistry","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2021-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/s10498-020-09390-y","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4120119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-09-11DOI: 10.1007/s10498-020-09389-5
Santosh Chikkamath, Madhuri A. Patel, Aishwarya S. Kar, Vaibhavi V. Raut, Bhupendra. S. Tomar, J. Manjanna
Fe type clay minerals, Fe–montmorillonite, are expected to form in the nuclear waste repositories over a span of few years owing to the interaction of corrosion products from overpack and/or canister with bentonite consisting of montmorillonite (Mt) as the major clay mineral. Therefore, it is important to understand the properties of altered clay minerals, Fe–Mt. In the present study, the sorption behaviour of 133Ba(II), one of the high-yield fission products of uranium-based fuels and analogue of 90Sr (t1/2?=?28.5 y), on Fe(II)–Mt and Fe(III)–Mt has been investigated. Retention behavior of Ba(II) on Fe–Mt has been studied at varying pH (3–9), ionic strength (0.001?M–1?M) and Ba(II) concentration (10?9–10?3 M) by batch sorption method. The distribution coefficient (Kd) of Ba(II) on Fe–Mt was found to be nearly independent of pH while it decreased with increasing ionic strength indicating ion exchange as the dominant Ba(II) sorption mode on Fe–Mt. Adsorption isotherm of Ba(II) exhibited linearity in the entire Ba(II) concentration range. A comparison of Ba(II) sorption behavior on Fe–Mt and Na–Mt has been made. The Fe released from both Fe(III)–Mt and Fe(II)–Mt was measured in all the sorption experiments and was found to be much less in the case of Fe(III)–Mt (≤?1.7?ppm) when compared to Fe(II)–Mt (~?25?ppm). The modeling of Ba(II) sorption profiles on Fe–Mt and Na–Mt has been carried out using FITEQL 4.0.
{"title":"Experimental and Modeling Studies on Sorption Behaviour of 133Ba(II) on Fe–Montmorillonite Clay Minerals","authors":"Santosh Chikkamath, Madhuri A. Patel, Aishwarya S. Kar, Vaibhavi V. Raut, Bhupendra. S. Tomar, J. Manjanna","doi":"10.1007/s10498-020-09389-5","DOIUrl":"https://doi.org/10.1007/s10498-020-09389-5","url":null,"abstract":"<p>Fe type clay minerals, Fe–montmorillonite, are expected to form in the nuclear waste repositories over a span of few years owing to the interaction of corrosion products from overpack and/or canister with bentonite consisting of montmorillonite (Mt) as the major clay mineral. Therefore, it is important to understand the properties of altered clay minerals, Fe–Mt. In the present study, the sorption behaviour of <sup>133</sup>Ba(II), one of the high-yield fission products of uranium-based fuels and analogue of <sup>90</sup>Sr (<i>t</i><sub>1/2</sub>?=?28.5 y), on Fe(II)–Mt and Fe(III)–Mt has been investigated. Retention behavior of Ba(II) on Fe–Mt has been studied at varying pH (3–9), ionic strength (0.001?M–1?M) and Ba(II) concentration (10<sup>?9</sup>–10<sup>?3</sup> M) by batch sorption method. The distribution coefficient (<i>K</i><sub>d</sub>) of Ba(II) on Fe–Mt was found to be nearly independent of pH while it decreased with increasing ionic strength indicating ion exchange as the dominant Ba(II) sorption mode on Fe–Mt. Adsorption isotherm of Ba(II) exhibited linearity in the entire Ba(II) concentration range. A comparison of Ba(II) sorption behavior on Fe–Mt and Na–Mt has been made. The Fe released from both Fe(III)–Mt and Fe(II)–Mt was measured in all the sorption experiments and was found to be much less in the case of Fe(III)–Mt (≤?1.7?ppm) when compared to Fe(II)–Mt (~?25?ppm). The modeling of Ba(II) sorption profiles on Fe–Mt and Na–Mt has been carried out using FITEQL 4.0.</p>","PeriodicalId":8102,"journal":{"name":"Aquatic Geochemistry","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2020-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/s10498-020-09389-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4481781","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-08-18DOI: 10.1007/s10498-020-09388-6
Sandra M. Steingruber, Stefano M. Bernasconi, Giorgio Valenti
Mountains are among the most sensitive ecosystems to climate change, and one of the most evident signs of climate-related effect is the continuous net loss of ice from the cryosphere. Several studies showed that meltwater from glaciated and perennially frozen areas can profoundly affect alpine aquatic ecosystems. Here, we present the impressive temporal increase in solutes in Lake Leit, a mountain lake in the Central Alps that is impacted by an active rock glacier. During the last 30 years, concentrations of sulfate and base cations increased by factors of 4 and 3, respectively. Atmospheric deposition, the only catchment external source, could be excluded as possible cause. The inlets have sulfate and base cations concentrations that were up to double the concentrations of the lake outlet confirming the presence of catchment internal sources. The highest concentrations were measured in the springs at the bottom of the rock glacier. Ground surface temperatures of the rock glacier indicated a high probability of permafrost occurrence, while the annual mean air temperature after the mid-1980s showed continuously positive deviations from the long-term average values (period 1961–1990) with increasing values after 2010. δ34S of sulfate in the inlets and the outflow indicated that sulfate in Lake Leit mainly derived from dissolution of gypsum/anhydrite even if its presence is not confirmed by the Geologic Atlas of Switzerland. Because of these results, we postulate the presence of subsurface traces of sulfate-bearing evaporites, probably associated with Triassic metasediments. These deposits are very common in the closer surroundings. We further hypothesize that the thawing of permafrost affects the flow path of water enabling its contact with fresh highly weatherable minerals increasing the overall weathering rate and shifting the relative ionic composition in the discharge toward the ions that originate from the most soluble minerals. This study shows that increased permafrost thawing in the future can influence water quality in high-alpine settings.
{"title":"Climate Change-Induced Changes in the Chemistry of a High-Altitude Mountain Lake in the Central Alps","authors":"Sandra M. Steingruber, Stefano M. Bernasconi, Giorgio Valenti","doi":"10.1007/s10498-020-09388-6","DOIUrl":"10.1007/s10498-020-09388-6","url":null,"abstract":"<div><p>Mountains are among the most sensitive ecosystems to climate change, and one of the most evident signs of climate-related effect is the continuous net loss of ice from the cryosphere. Several studies showed that meltwater from glaciated and perennially frozen areas can profoundly affect alpine aquatic ecosystems. Here, we present the impressive temporal increase in solutes in Lake Leit, a mountain lake in the Central Alps that is impacted by an active rock glacier. During the last 30 years, concentrations of sulfate and base cations increased by factors of 4 and 3, respectively. Atmospheric deposition, the only catchment external source, could be excluded as possible cause. The inlets have sulfate and base cations concentrations that were up to double the concentrations of the lake outlet confirming the presence of catchment internal sources. The highest concentrations were measured in the springs at the bottom of the rock glacier. Ground surface temperatures of the rock glacier indicated a high probability of permafrost occurrence, while the annual mean air temperature after the mid-1980s showed continuously positive deviations from the long-term average values (period 1961–1990) with increasing values after 2010. δ<sup>34</sup>S of sulfate in the inlets and the outflow indicated that sulfate in Lake Leit mainly derived from dissolution of gypsum/anhydrite even if its presence is not confirmed by the Geologic Atlas of Switzerland. Because of these results, we postulate the presence of subsurface traces of sulfate-bearing evaporites, probably associated with Triassic metasediments. These deposits are very common in the closer surroundings. We further hypothesize that the thawing of permafrost affects the flow path of water enabling its contact with fresh highly weatherable minerals increasing the overall weathering rate and shifting the relative ionic composition in the discharge toward the ions that originate from the most soluble minerals. This study shows that increased permafrost thawing in the future can influence water quality in high-alpine settings.</p></div>","PeriodicalId":8102,"journal":{"name":"Aquatic Geochemistry","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2020-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/s10498-020-09388-6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4711122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-28DOI: 10.1007/s10498-020-09382-y
Michael G. Babechuk, Edel M. O’Sullivan, Cora A. McKenna, Carolina Rosca, Thomas F. Nägler, Ronny Schoenberg, Balz S. Kamber
{"title":"Correction to: Ultra-trace Element Characterization of the Central Ottawa River Basin Using a Rapid, Flexible, and Low-Volume ICP-MS Method","authors":"Michael G. Babechuk, Edel M. O’Sullivan, Cora A. McKenna, Carolina Rosca, Thomas F. Nägler, Ronny Schoenberg, Balz S. Kamber","doi":"10.1007/s10498-020-09382-y","DOIUrl":"https://doi.org/10.1007/s10498-020-09382-y","url":null,"abstract":"","PeriodicalId":8102,"journal":{"name":"Aquatic Geochemistry","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2020-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/s10498-020-09382-y","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5084414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-17DOI: 10.1007/s10498-020-09387-7
Larissa Costa, Nicolai Mirlean, Guilherme Quintana, Segun Adebayo, Karen Johannesson
Arsenic (As), iron (Fe), and manganese (Mn) contents were measured in sediment nodules and associated pore waters obtained from sediment cores collected from a salt marsh on Pólvora Island (southern Brazil). Sediment cores were obtained when brackish water dominated the estuary, at two different environments: an unvegetated mudflat colonized by crabs (Neohelice granulata), and a low intertidal stand vegetated by Spartina alterniflora. We determined the percentage of nodules in each depth interval of the cores, along with redox potential, and As, Fe, and Mn contents of the nodules. The mineralogy of the nodules was investigated, and results showed they are mainly composed by quartz, phyllosilicates, and amorphous Fe–Mn oxides/oxyhydroxides. Pore water results showed that bioturbation by local crabs supports oxygen penetration to depths of ca. 25 cm below the salt marsh surface, with lower Fe contents in pore water associated with the brackish period. However, S. alterniflora growth appears to have a greater impact on sediment geochemistry of Fe, Mn, and possibly As due to sulfate reduction and the associated decrease in pore water pH. Higher Fe concentrations were observed in the pore waters during the period of brackish water dominance, which also corresponded to the S. alterniflora growth season. The study demonstrates that differences in geochemical conditions (e.g., Fe content) that can develop in salt marsh sediments owing to different types of bioirrigation processes (i.e., bioirrigation driven by crabs versus that related to the growth of S. alterniflora) play important roles in the biogeochemical cycling of As.
{"title":"Effects of Bioirrigation and Salinity on Arsenic Distributions in Ferruginous Concretions from Salt Marsh Sediment Cores (Southern Brazil)","authors":"Larissa Costa, Nicolai Mirlean, Guilherme Quintana, Segun Adebayo, Karen Johannesson","doi":"10.1007/s10498-020-09387-7","DOIUrl":"10.1007/s10498-020-09387-7","url":null,"abstract":"<div><p>Arsenic (As), iron (Fe), and manganese (Mn) contents were measured in sediment nodules and associated pore waters obtained from sediment cores collected from a salt marsh on Pólvora Island (southern Brazil). Sediment cores were obtained when brackish water dominated the estuary, at two different environments: an unvegetated mudflat colonized by crabs (<i>Neohelice granulata</i>), and a low intertidal stand vegetated by <i>Spartina alterniflora</i>. We determined the percentage of nodules in each depth interval of the cores, along with redox potential, and As, Fe, and Mn contents of the nodules. The mineralogy of the nodules was investigated, and results showed they are mainly composed by quartz, phyllosilicates, and amorphous Fe–Mn oxides/oxyhydroxides. Pore water results showed that bioturbation by local crabs supports oxygen penetration to depths of ca. 25 cm below the salt marsh surface, with lower Fe contents in pore water associated with the brackish period. However, <i>S. alterniflora</i> growth appears to have a greater impact on sediment geochemistry of Fe, Mn, and possibly As due to sulfate reduction and the associated decrease in pore water pH. Higher Fe concentrations were observed in the pore waters during the period of brackish water dominance, which also corresponded to the <i>S. alterniflora</i> growth season. The study demonstrates that differences in geochemical conditions (e.g., Fe content) that can develop in salt marsh sediments owing to different types of bioirrigation processes (i.e., bioirrigation driven by crabs versus that related to the growth of <i>S. alterniflora</i>) play important roles in the biogeochemical cycling of As.</p></div>","PeriodicalId":8102,"journal":{"name":"Aquatic Geochemistry","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2020-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/s10498-020-09387-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4682946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-10DOI: 10.1007/s10498-020-09381-z
Cheryl A. Kelley, Brad M. Bebout, Jeffrey P. Chanton, Angela M. Detweiler, Adrienne Frisbee, Brooke E. Nicholson, Jennifer Poole, Amanda Tazaz, Claire Winkler
{"title":"Correction to: The Effect of Bacterial Sulfate Reduction Inhibition on the Production and Stable Isotopic Composition of Methane in Hypersaline Environments","authors":"Cheryl A. Kelley, Brad M. Bebout, Jeffrey P. Chanton, Angela M. Detweiler, Adrienne Frisbee, Brooke E. Nicholson, Jennifer Poole, Amanda Tazaz, Claire Winkler","doi":"10.1007/s10498-020-09381-z","DOIUrl":"https://doi.org/10.1007/s10498-020-09381-z","url":null,"abstract":"","PeriodicalId":8102,"journal":{"name":"Aquatic Geochemistry","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2020-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/s10498-020-09381-z","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4423239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-01DOI: 10.1007/s10498-020-09386-8
Gustave Raoul Nkoue Ndondo, J.-L. Probst, J. Ndjama, Jules Remy Ndam Ngoupayou, J.-L. Boeglin, G. E. Takem, F. Brunet, J. Mortatti, F. Gauthier-Lafaye, J.-J. Braun, G. E. Ekodeck
Stream carbon fluxes are one of the major components in the global C cycle, yet the discrimination of the various sources of stream carbon remains to a large extent unclear and less is known about the biogeochemical transformations that accompany the transfer of C from soils to streams. Here, we used patterns in stream water and groundwater δ13C values in a small forested tropical headwater catchment to investigate the source and contribution from the soil carbon pools to stream organic and inorganic carbon behavior over seasonal scales. Stream organic carbon (DOC and POC) comes mainly from the upper rich soil organic carbon horizons and derived from total organic carbon (TOC) of biogenic source. The isotopic compositions δ13CTOC, δ13CDOC and δ13CPOC of these carbon species were very close (??30‰ to ??26‰) and typical of the forested C3 vegetation. The relationship observed between DOC and log pCO2 and δ13CDIC indicated that besides the considerable CO2 evasion that occurs as DIC is transported from soils to streams, there were also other processes affecting the stream DIC pool. In-stream mineralization of DOC and mixing of atmospheric carbon had a significant influence on the δ13CDIC values. These processes which varied seasonally with hydrological changes represent the main control on DOC and DIC cycling in the wet tropical milieu. The rapid turnover of carbon on hillside soils, the transformation of TOC to DOC in wetland soils and further mineralization of stream DOC to DIC favor the evasion of C, making the zone a source of carbon to the atmosphere.
{"title":"Stable Carbon Isotopes δ13C as a Proxy for Characterizing Carbon Sources and Processes in a Small Tropical Headwater Catchment: Nsimi, Cameroon","authors":"Gustave Raoul Nkoue Ndondo, J.-L. Probst, J. Ndjama, Jules Remy Ndam Ngoupayou, J.-L. Boeglin, G. E. Takem, F. Brunet, J. Mortatti, F. Gauthier-Lafaye, J.-J. Braun, G. E. Ekodeck","doi":"10.1007/s10498-020-09386-8","DOIUrl":"https://doi.org/10.1007/s10498-020-09386-8","url":null,"abstract":"<p>Stream carbon fluxes are one of the major components in the global C cycle, yet the discrimination of the various sources of stream carbon remains to a large extent unclear and less is known about the biogeochemical transformations that accompany the transfer of C from soils to streams. Here, we used patterns in stream water and groundwater δ<sup>13</sup>C values in a small forested tropical headwater catchment to investigate the source and contribution from the soil carbon pools to stream organic and inorganic carbon behavior over seasonal scales. Stream organic carbon (DOC and POC) comes mainly from the upper rich soil organic carbon horizons and derived from total organic carbon (TOC) of biogenic source. The isotopic compositions δ<sup>13</sup>C<sub>TOC</sub>, δ<sup>13</sup>C<sub>DOC</sub> and δ<sup>13</sup>C<sub>POC</sub> of these carbon species were very close (??30‰ to ??26‰) and typical of the forested C3 vegetation. The relationship observed between DOC and log pCO<sub>2</sub> and δ<sup>13</sup>C<sub>DIC</sub> indicated that besides the considerable CO<sub>2</sub> evasion that occurs as DIC is transported from soils to streams, there were also other processes affecting the stream DIC pool. In-stream mineralization of DOC and mixing of atmospheric carbon had a significant influence on the δ<sup>13</sup>C<sub>DIC</sub> values. These processes which varied seasonally with hydrological changes represent the main control on DOC and DIC cycling in the wet tropical milieu. The rapid turnover of carbon on hillside soils, the transformation of TOC to DOC in wetland soils and further mineralization of stream DOC to DIC favor the evasion of C, making the zone a source of carbon to the atmosphere.</p>","PeriodicalId":8102,"journal":{"name":"Aquatic Geochemistry","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/s10498-020-09386-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4031170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-06-29DOI: 10.1007/s10498-020-09385-9
Irina Kurashova, Alexey Kamyshny Jr.
In aquatic systems a reaction between tetrathionate and cyanide results in the formation of thiocyanate. We have studied kinetics of the reactions of tetrathionate with free cyanide and two cyanide complexes, hexacyanoferrate(II) and hexacyanoferrate(III), at the environmentally relevant conditions. For the reaction between tetrathionate and free cyanide, the rate constant and the activation energy, but not the reaction order, strongly depend on pH. Our observations allow to propose the following pathways of thiocyanate formation by the reactions of free cyanide with tetrathionate: (1) tetrathionate reacts relatively slow with hydrogen cyanide at acidic and neutral conditions; and (2) tetrathionate reacts relatively fast with cyanide anion under highly alkaline conditions. Depending on environmental conditions, the half-lives of the reaction between free cyanide and tetrathionate will be in the ranges of hours to several years. Reactions of tetrathionate with hexacyanoferrate(II) and hexacyanoferrate(III) have no environmental significance as they are slower than the decomposition of tetrathionate. Strategy for improvement of analytical protocols for analysis of tetrathionate and cyanide is proposed based on the detected kinetics parameters.
{"title":"Kinetics of Thiocyanate Formation by Reaction of Cyanide with Tetrathionate","authors":"Irina Kurashova, Alexey Kamyshny Jr.","doi":"10.1007/s10498-020-09385-9","DOIUrl":"https://doi.org/10.1007/s10498-020-09385-9","url":null,"abstract":"<p>In aquatic systems a reaction between tetrathionate and cyanide results in the formation of thiocyanate. We have studied kinetics of the reactions of tetrathionate with free cyanide and two cyanide complexes, hexacyanoferrate(II) and hexacyanoferrate(III), at the environmentally relevant conditions. For the reaction between tetrathionate and free cyanide, the rate constant and the activation energy, but not the reaction order, strongly depend on pH. Our observations allow to propose the following pathways of thiocyanate formation by the reactions of free cyanide with tetrathionate: (1) tetrathionate reacts relatively slow with hydrogen cyanide at acidic and neutral conditions; and (2) tetrathionate reacts relatively fast with cyanide anion under highly alkaline conditions. Depending on environmental conditions, the half-lives of the reaction between free cyanide and tetrathionate will be in the ranges of hours to several years. Reactions of tetrathionate with hexacyanoferrate(II) and hexacyanoferrate(III) have no environmental significance as they are slower than the decomposition of tetrathionate. Strategy for improvement of analytical protocols for analysis of tetrathionate and cyanide is proposed based on the detected kinetics parameters.</p>","PeriodicalId":8102,"journal":{"name":"Aquatic Geochemistry","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2020-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/s10498-020-09385-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5120758","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}