for Journals by Title or ISSN for Articles by Keywords help

Publisher: Springer-Verlag (Total: 2352 journals)

 Aquatic GeochemistryJournal Prestige (SJR): 0.591 Citation Impact (citeScore): 1Number of Followers: 4      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1573-1421 - ISSN (Online) 1380-6165 Published by Springer-Verlag  [2352 journals]
• Reduction of Manganese Oxides: Thermodynamic, Kinetic and Mechanistic
Considerations for One- Versus Two-Electron Transfer Steps
• Authors: George W. Luther; Aubin Thibault de Chanvalon; Véronique E. Oldham; Emily R. Estes; Bradley M. Tebo; Andrew S. Madison
Pages: 257 - 277
Abstract: Manganese oxides, typically similar to δ-MnO2, form in the aquatic environment at near neutral pH via bacterially promoted oxidation of Mn(II) species by O2, as the reaction of [Mn(H2O)6]2+ with O2 alone is not thermodynamically favorable below pH of ~ 9. As manganese oxide species are reduced by the triphenylmethane compound leucoberbelein blue (LBB) to form the colored oxidized form of LBB (λmax = 623 nm), their concentration in the aquatic environment can be determined in aqueous environmental samples (e.g., across the oxic–anoxic interface of the Chesapeake Bay, the hemipelagic St. Lawrence Estuary and the Broadkill River estuary surrounded by salt marsh wetlands), and their reaction progress can be followed in kinetic studies. The LBB reaction with oxidized Mn solids can occur via a hydrogen atom transfer (HAT) reaction, which is a one-electron transfer process, but is unfavorable with oxidized Fe solids. HAT thermodynamics are also favorable for nitrite with LBB and MnO2 with ammonia (NH3). Reactions are unfavorable for NH4+ and sulfide with oxidized Fe and Mn solids, and NH3 with oxidized Fe solids. In laboratory studies and aquatic environments, the reduction of manganese oxides leads to the formation of Mn(III)-ligand complexes [Mn(III)L] at significant concentrations even when two-electron reductants react with MnO2. Key reductants are hydrogen sulfide, Fe(II) and organic ligands, including the siderophore desferioxamine-B. We present laboratory data on the reaction of colloidal MnO2 solutions (λmax ~ 370 nm) with these reductants. In marine waters, colloidal forms of Mn oxides (< 0.2 µm) have not been detected as Mn oxides are quantitatively trapped on 0.2-µm filters. Thus, the reactivity of Mn oxides with reductants depends on surface reactions and possible surface defects. In the case of MnO2, Mn(IV) is an inert cation in octahedral coordination; thus, an inner-sphere process is likely for electrons to go into the empty e g * conduction band of its orbitals. Using frontier molecular orbital theory and band theory, we discuss aspects of these surface reactions and possible surface defects that may promote MnO2 reduction using laboratory and field data for the reaction of MnO2 with hydrogen sulfide and other reductants.
PubDate: 2018-08-01
DOI: 10.1007/s10498-018-9342-1
Issue No: Vol. 24, No. 4 (2018)

• Uranium and Multi-element Release from Orthogneiss and Granite (Austria):
Experimental Approach Versus Groundwater Composition
• Authors: Daniel Elster; Edith Haslinger; Martin Dietzel; Heinz Fröschl; Gerhard Schubert
Pages: 279 - 306
Abstract: In this study, the release of elements and in particular U from five Austrian orthogneiss and granite samples into a CO2-bearing solution was investigated to describe the initial phase (24 h) of leaching focusing on the impact of ferrous (hydro)oxide formation. Experiments were conducted at ambient temperature by flushing CO2:N2 gas through the reactive solution (pHinitial ~ 4.3) at a liquid:solid ratio of 10:1 with and without a reducing agent. The chemical evolution of the leaching solution was dominated by incongruent dissolution of silicates showing a parabolic kinetic behavior due to protective surface formation most likely caused by precipitation of amorphous FeIII/Al hydroxides. However, the relative distribution of Ca, Mg and Sr in the leaching solution excellently traced the individual bulk rock composition. The mobilization of U was highly prevented under oxidizing conditions by sorption onto ferrous (hydro)oxides, which were precipitating through ongoing silicate leaching. Therefore, the leaching behavior of individual U-bearing minerals was less relevant for U release. At reducing conditions, the above elements were accumulated in the solution, although an oversaturation regarding UIVO2 was calculated. This indicates its inhibited formation within the experimental run time. The composition of experimental leaching solutions did not reflect analyzed groundwater compositions from investigated local rock-type aquifers indicating that reaction rate constants of siliceous rocks significantly differ between values found in nature and in the laboratory. Change in active mineral surface areas with ongoing weathering, accumulation of secondary precipitates, leached layer formation and given reaction time are key factors for distinct elemental release.
PubDate: 2018-08-01
DOI: 10.1007/s10498-018-9344-z
Issue No: Vol. 24, No. 4 (2018)

• Potential Influence of Ocean Acidification on Deep-Sea Fe–Mn Nodules and
Pelagic Clays: An Improved Assessment by Using Artificial Seawater
• Authors: Quan Wang; Hodaka Kawahata; Kyoko Yamaoka; Atsushi Suzuki
Pages: 307 - 322
Abstract: In order to assess the potential risk of metal release from deep-sea sediments in response to pH decrease in seawater, the mobility of elements from ferromanganese (Fe–Mn) nodules and pelagic clays was examined. Two geochemical reference samples (JMn-1 and JMS-2) were reacted with the pH-controlled artificial seawater (ASW) using a CO2-induced pH regulation system. Our experiments demonstrated that deep-sea sediments have weak buffer capacities by acid–base dissociation of surface hydroxyl groups on metal oxides/oxyhydroxides and silicate minerals. Element concentrations in the ASW were mainly controlled by elemental speciation in the solid phase and sorption–desorption reaction between the charged solid surface and ion species in the ASW. These results indicated that the release of heavy metals such as Mn, Cu, Zn and Cd should be taken into consideration when assessing the influence of ocean acidification on deep-sea environment.
PubDate: 2018-08-01
DOI: 10.1007/s10498-018-9345-y
Issue No: Vol. 24, No. 4 (2018)

• Correction to: A Tribute to Rick and Debbie Jahnke: From Deep Sea Pore
Water to Coastal Permeable Sediments-Contributions that Cover the Oceans
• Authors: Timothy J. Shaw; Steve Emerson; Herbert L. Windom
Pages: 323 - 323
Abstract: In the original publication of the article, the third author affiliation was incorrectly published.
PubDate: 2018-08-01
DOI: 10.1007/s10498-018-9343-0
Issue No: Vol. 24, No. 4 (2018)

• Oxygen Consumption in Permeable and Cohesive Sediments of the Gulf of
Aqaba
• Authors: Valeria Boyko; Adi Torfstein; Alexey Kamyshny
Pages: 165 - 193
Abstract: Oxygen profiles were measured in the sediments of the Gulf of Aqaba (Red Sea), an oligotrophic marine system affected by episodic seasonal flash floods and intense aeolian dry deposition. Sediment cores were retrieved from shallow (15–45 m), intermediate (250–561 m) and deep (700 m) water sites of south–north and east–west transects. Dissolved oxygen concentrations were measured simultaneously by using microelectrodes and microoptodes immediately after sampling and after transportation. Oxygen penetration depths were found to increase from 2 to 5 mm at the shallow water sites with sandy permeable sediments to 10–21 mm at the deeper sites with cohesive muddy sediments. This increase corresponds to decrease in oxygen diffusive fluxes at the sediment–water interface and oxygen consumption rates with depth. Oxygen consumption rates exhibit local maxima at the oxic–anoxic sediment boundary, which may be attributed to oxygen reduction coupled to oxidation of dissolved Fe(II) and Mn(II) at deep and intermediate water sites and of hydrogen sulfide at shallow water sites. Microelectrodes and microoptodes measurements of cohesive sediments from deep and intermediate water sites yielded similar results. By comparison, the microoptodes displayed more robust measurements than microelectrodes in sandy near-shore sediments. This was attributed to their flexible fiber structure that is less likely to break or to abruptly displace sand particles. After transportation of sediment cores from Eilat to Beer Sheva followed by ≤ 24-h storage, no changes in oxygen fluxes and consumption rates were detected.
PubDate: 2018-06-01
DOI: 10.1007/s10498-018-9338-x
Issue No: Vol. 24, No. 3 (2018)

• Fluorescence Quenching and Energy Transfer Phenomena Associated with the
Interactions of Terbium Ion and Humic Acid
• Authors: Mingquan Yan; Gregory V. Korshin; Marc F. Benedetti; Chi-Wang Li
Pages: 195 - 207
Abstract: Fluorescence of the hydrophobic acid fraction (HPOA) of Suwannee River natural organic matter and Tb3+ excitation spectra were measured in tandem using the instantaneous and time-resolved emission modes. The intensity of HPOA fluorescence decreased in the presence of Tb3+, while the intensity of the emission from Tb3+ cations bound by HPOA increased by up to several orders of magnitude due to energy transfer (ET) from HPOA to Tb3+ ions. To determine intrinsic ET and fluorescence quenching (FQ) coefficients, NICA–Donnan modeling was carried. It showed that phenolic groups in HPOA dominated both the ET and FQ processes and that the binding of Tb3+ by HPOA could be described using the non-ideality parameter nTb, median binding constant log $$\tilde{K}_{\text{Tb}}$$ for the phenolic sites and intrinsic ET and FQ coefficients (denoted as ηTbΦ and αTbΦ), and were 0.48, 8.5, 1385 and 0.12, respectively. The high value of the energy transfer coefficient of Tb3+ ions bound by the phenolic groups in HPOA is indicative of both the match between the electronic levels of the donor and acceptor, and the short distance between them. The deviation of the data of Nica–Donnan modeling of the ET and FQ dependence of versus [Tb]total for a 1.0 M ionic strength highlights the need to quantify the distribution of donor–acceptor distances in HPOA molecules in more detail.
PubDate: 2018-06-01
DOI: 10.1007/s10498-018-9339-9
Issue No: Vol. 24, No. 3 (2018)

• Salt Crystallization Sequences of Nonmarine Brine and Their Application
for the Formation of Potassium Deposits
• Authors: Chuanyong Ye; Jianye Mao; Yaqiong Ren; Yingping Li; Yongjie Lin; Ian M. Power; Yangbing Luo
Pages: 209 - 229
Abstract: The salt assemblages precipitated during evaporation of concentrated brine collected from Gasikule Salt Lake (GSL) were studied to better understand the formation of potassium deposits in the Qaidam Basin. The study included isothermal evaporation at 25 °C in the laboratory and solar evaporation in the ponds at GSL field. Brines increased in density and became moderately acidic (pH ≈ 5.30) while major ion geochemistry and precipitate mineralogy all showed broad agreement between both systems. Four salt assemblages were identified in the isothermal evaporation experiment: halite → halite + hexahydrite → halite + bischofite + carnallite → bischofite. Alternately, three salt assemblages were recognized in the solar evaporation: halite → halite + epsomite + carnallite → halite + carnallite + bischofite. The key difference in salt assemblages between the two systems is attributed to differences in relative humidity and temperature conditions. Although the GSL has deep spring inflow recharge, the high abundance of MgSO4 salts demonstrates that the salt assemblages are similar to normal seawater evaporation. Thus, different proportions of deep spring inflow and river water could form both MgSO4-deficient potassium evaporite and normal seawater potassium evaporites. Therefore, nonmarine water may form diverse potassium evaporite deposits in continental basins when the geological structure as well as hydrogeological and climatic conditions is appropriate.
PubDate: 2018-06-01
DOI: 10.1007/s10498-018-9340-3
Issue No: Vol. 24, No. 3 (2018)

• Integration of In Situ Experiments and Numerical Simulations to Reveal the
Physicochemical Circumstances of Organic and Inorganic Precipitation at a
Thermal Spring
• Authors: Petra Kovács-Bodor; Dóra Anda; Laura Jurecska; Mihály Óvári; Ákos Horváth; Judit Makk; Vincent Post; Imre Müller; Judit Mádl-Szőnyi
Pages: 231 - 255
Abstract: Organic and inorganic precipitates are both characteristic in the active hypogenic karst area of Buda Thermal Karst in Hungary. As an active system, it is a good natural laboratory to study ongoing precipitation processes. Because of anthropogenic influence and the complexity of spring environments, it is challenging to reveal all the governing factors in the process of precipitation. In situ experiments, i.e. artificially controlled natural systems simplify the complexity by adding, excluding or stabilizing influencing parameters during the experiment. CO2 degassing drives changes in the physicochemical parameters of spring waters from the discharge along their flow path. The rate and spatial extension of these changes depend on local hydrogeological, geological, climatic, topographical etc. factors, affecting precipitation processes. In this study, two one-day-long in situ experiments were executed to examine the physicochemical parameter changes of thermal water in a tunnel. The integration of the results with reactive transport models revealed the physicochemical processes of ingassing and degassing and predicted CaCO3 precipitation along the flow path. Small-scale roughness of the channel surface seemed to further influence pH and concentration of HCO3−. After 6 weeks of thermal water flowing, organic precipitate (biofilm) formed close to the discharge and then, with a sharp change, inorganic precipitate (calcite) dominates a bit further from the discharge. In situ experiments and connected numerical simulations revealed the role of CO2 degassing and calcite precipitation in the changes of physicochemical parameters, but organic precipitates also have to be considered near the discharge.
PubDate: 2018-06-01
DOI: 10.1007/s10498-018-9341-2
Issue No: Vol. 24, No. 3 (2018)

• Galena Non-oxidative Dissolution Kinetics in Seawater
• Authors: Rodrigo F. Embile; Ingar Walder
Pages: 107 - 119
Abstract: The rate of non-oxidative galena dissolution in seawater compositions over the pH range of 2–4.5 was determined from batch reactor experiments. The derivative at zero time of a polynomial fit of the Pb concentration versus time data for the first 30 min was used to determine the rate. A plot of RGn (rate of galena dissolution) versus pH for data from six experiments is linear (R2 = 0.96), with a slope of 0.5. The rate equation describing the rate of galena dissolution as a function of hydrogen ion activity is $$R_{\text{Gn}} = - \,10^{ - 10.72} \left( {a_{{{\text{H}}^{ + } }} } \right)^{0.50}$$ Varying the concentration of dissolved oxygen produced no significant effect on the measured rates. The activation energy, based on four experiments carried out over the temperature range of 7–30 °C, is 61.1 kJ/mol.
PubDate: 2018-04-01
DOI: 10.1007/s10498-018-9335-0
Issue No: Vol. 24, No. 2 (2018)

• Variation of the Chemistry of the Dead Sea Brine as Consequence of the
Decreasing Water Level
• Authors: Jamal Abu-Qubu; Broder Merkel; Volkmar Dunger; Omar Rimawi
Pages: 121 - 135
Abstract: For many years, the Dead Sea suffers from an annual inflow deficiency of about one billion cubic meters, flood and baseflow. The water level changes are related to the majority of surface water inflows diverted for irrigation purposes, in addition to intensive loss of water by the high rate of evaporation and industrial water use. This causes the Dead Sea water level to decline about 35 m within the last 50 years for a long-term average of about 0.79 m per year. The changes in the hydrochemical composition were simulated experimentally to determine the changes that take place as a function of brine water evaporation level and its density. The Total Dissolved Solids (TDS) and the density of the Dead Sea water varies as a function of its water evaporation level changes. It was found that the density variation is not following a linear function with respect to water volume changes. But it follows the total amount of precipitate that occurred at different water levels. The electrical conductivity (EC) changes with respect to time and the prevailing temperature. There was no formula to calculate the high salinity of brine water above the normal ocean water. Consequently, the EC measurements were adopted to represent the Dead Sea water salinity. But in this research a converging factor (0.80971) has been found to convert the TDS values into salinity values. On contrary, the pH values revealed an inverse relationship with respect to the evaporation levels.
PubDate: 2018-04-01
DOI: 10.1007/s10498-018-9336-z
Issue No: Vol. 24, No. 2 (2018)

• The Origin and MgCl 2 –NaCl Variations in an Athalassic Sag Pond:
Insights from Chemical and Isotopic Data
• Authors: Tiziano Boschetti; Salih Muhammad Awadh; Emma Salvioli-Mariani
Pages: 137 - 162
Abstract: The examination of past and new chemical–isotopic data (2H/1H–18O/16O, 11B/10B and 87Sr/86Sr ratios) shows the meteoric origin of the Sawa Lake (Muthanna Governorate, Iraq) and its connection with the local aquifers, which feed the lake via the groundwater emerging from its floor through fault systems. The chemical and isotopic evaporation models are traced by geochemical computer codes by using a different composition of some potential inflows to the lake (e.g., the Euphrates River and Dammam aquifer). The main product of the chemical evaporation models is gypsum, as confirmed by the mineralogical examination of the sediment and the surrounding outcrops. A strong 18O–2H enrichment is a consequence of the evaporation effect in arid regions; δ18O–Cl models and δ11B = + 23.4‰ exclude the contribution of any seawater-derived fluids. This latter value along with 87Sr/86Sr = 0.707989 suggests a mixed origin from the Eocene–Miocene aquifers. The isotope and chemical evaporation paths from the meteorically recharged sources match the lake composition. However, compositional switches from NaCl toward MgCl2 occurred in the last decade and are related to post-drought periods, showing that the interaction of the recharging waters with the local soils (Na–Mg exchange and/or the leaching of the top layer salts) have a role in the chemical composition. This demonstrates that the lake is significantly influenced by climatic variations.
PubDate: 2018-04-01
DOI: 10.1007/s10498-018-9337-y
Issue No: Vol. 24, No. 2 (2018)

• Correction to: The Iodide and Iodate Distribution in the Seto Inland Sea,
Japan
• Authors: Kazuhiko Takeda; Kengo Yamane; Yuuta Horioka; Kazuaki Ito
Pages: 163 - 164
Abstract: In the original publication of the article, Figs. 3 and 4 were interchanged. Now the correct figures have been provided in this erratum.
PubDate: 2018-04-01
DOI: 10.1007/s10498-018-9334-1
Issue No: Vol. 24, No. 2 (2018)

• Passing the Editorial Baton
• Authors: George W. Luther
Pages: 1 - 2
PubDate: 2018-02-01
DOI: 10.1007/s10498-018-9331-4
Issue No: Vol. 24, No. 1 (2018)

• Editorial
• Authors: Marc F. Benedetti
Pages: 3 - 4
PubDate: 2018-02-01
DOI: 10.1007/s10498-018-9332-3
Issue No: Vol. 24, No. 1 (2018)

• Factors Controlling the Fractionation and Seasonal Mobility Variations of
Ga and In in Systems Impacted by Acidic Thermal Waters: Effects of
Thermodynamics and Bacterial Activity
• Authors: Yasumasa Ogawa; Daizo Ishiyama; Naotatsu Shikazono; Koichi Suto; Chihiro Inoue; Noriyoshi Tsuchiya; Bernhardt Saini-Eidukat; Scott A. Wood
Pages: 5 - 25
Abstract: This work assessed both the fractionation and the seasonal mobility variations of Ga and In in systems impacted by acidic thermal waters. This was accomplished by performing thermodynamic calculations using the PHREEQC algorithm and by assessing the activity of acidophilic iron-oxidizing bacteria. The pH of the Kusatsu thermal waters in Gunma Prefecture, central Japan, is rapidly increased following the addition of a lime suspension. After an abrupt pH increase, under which conditions free ions of Ga and In and their complexes with Cl− and SO42− exist only in negligible quantities, the majority of dissolved Ga and In is removed by sorption onto suspended hydrous ferric oxides (HFOs). These HFOs are then transported to an artificial lake without significant sedimentation along the river. Subsequently, the suspended HFOs settle out and are added to sediments without significant fractionation between Ga and In. The Tamagawa thermal waters in Akita Prefecture, northeast Japan, are also treated with lime. However, complete neutralization requires mixing with some tributary streams, leading to a gradual downstream increase in pH. Dissolved Ga is, in general, sorbed by HFOs in upstream areas, leading to wide dispersal of Ga across the entire watershed. In comparison, In is transported to the lake inlet predominantly as a Cl− complex species without significant removal along the river, with the majority being precipitated in an artificial lake, where Cl− concentrations are too low to form stable complex species with In, and thus, dissolved In is sorbed by HFOs. As a result, In is effectively concentrated within downstream lakebed sediments, whereas Ga is dispersed along the river. Seasonal variations in Ga mobility within the Tamagawa field between snowmelt and low-flow seasons are primarily controlled by pH, because hydrolysis reactions of these metals, which are related to sorption reactions, tend to occur in the upstream regions in the snowmelt season. However, under warmer conditions, HFO formation preferably occurs due to the activity of acidophilic iron-oxidizing bacteria. Thus, under similar pH variations, dissolved Ga is more effectively removed by HFOs during warmer seasons. On the contrary, because HFOs are abundantly formed in low-flow season, even under colder conditions, before In hydrolysis reaction starts to occur, In mobility is less affected by water temperature and then bacterial activity.
PubDate: 2018-02-01
DOI: 10.1007/s10498-018-9328-z
Issue No: Vol. 24, No. 1 (2018)

• Characterizing Major Controls on Spatial and Seasonal Variations in
Chemical Composition of Surface and Pore Brine of Maharlu Lake, Southern
Iran
• Authors: Roghyeh Khosravi; Mehdi Zarei; Moritz Bigalke
Pages: 27 - 54
Abstract: Maharlu Lake with Na–Cl water type is the terminal point of a closed basin in southern Iran. A total of 10 water samples from two rivers discharging to the lake and 78 water samples of surface and pore brine of Maharlu Lake have been collected from different depths (surface, 20, 50 and 100 cm) of four sampling stations along the lake during a period of lake water-level fluctuation (November 2014–July 2015). To investigate chemical interaction between lake surface water and shallow pore water and to understand the major factors governing chemical composition of Maharlu brine, concentrations of major and minor (boron, bromide and lithium) solutes, pH and total dissolved solids have been measured in collected water samples. Saturation indices of evaporite minerals in collected water samples have been also calculated. The chemical behavior of dissolved solutes and evaporative evolution of the lake brine during a hydrological period have been simulated using PHREEQC. The results of our investigations indicated that chemical composition of lake surface water and pore brine of Maharlu Lake are mainly connected with lake water-level fluctuations and distance from input rivers (and depth), respectively. Hydrochemical investigations and statistical analysis showed that the brines chemistry of Maharlu is mainly controlled by three processes: brine evaporative evolution, dissolution–precipitation and diagenetic evolution of secondary carbonates.
PubDate: 2018-02-01
DOI: 10.1007/s10498-018-9329-y
Issue No: Vol. 24, No. 1 (2018)

• Source and Biogeochemical Distribution of Organic Matter in Surface
Sediment in the Deep Oligotrophic Lake Fuxian, China
• Authors: Xiangchao Chen; Muhua Feng; Fan Ke; Jizheng Pan; Fan Fan; Yarui Wang; Wenchao Li
Pages: 55 - 77
Abstract: The source, quantity and quality of sedimentary organic matter (SOM) were investigated in the surface sediments of Lake Fuxian, a deep oligotrophic lacustrine system in China. Granulometry, biochemical organic composition, bulk organic proxies and their stable isotopes were determined in the surface sediments (0–4 cm). The values of δ13C, δ15N and atomic ratio of total organic carbon to total nitrogen (TOC/TN) indicated that the sediments in the large partial lake were influenced by autochthonous organic matter. The concentrations of TOC, protein (PRT) and total hydrolysable amino acids may be mainly modulated by phytodetritus sinking from euphotic zones since they correlated significantly with chlorins. Otherwise, the lack of correlation between chlorins concentrations and carbohydrate (CHO) and lipid (LIP) indicated that the latter may have an additional terrestrial source. The highest sediment quantity was found in the deepest station NC owing to its fine sediment. Stations near northwestern shore accumulated more SOM than other littoral stations, which was in accordance with sewage discharge strength. Degradation quality indices, such as chlorin index, degradation index, PRT/CHO, and LIP/CHO, were in general agreement in showing the degraded status of SOM in Lake Fuxian. No clear spatial patterns were found in sediment degradation quality, which may be influenced by bottom oxygen concentration in the deep stations.
PubDate: 2018-02-01
DOI: 10.1007/s10498-018-9330-5
Issue No: Vol. 24, No. 1 (2018)

• Seasonal Variability of Mineral Formation in Microbial Mats Subjected to
Drying and Wetting Cycles in Alkaline and Hypersaline Sedimentary
Environments
• Authors: Ó. Cabestrero; M. E. Sanz-Montero; L. Arregui; S. Serrano; P. T. Visscher
Pages: 79 - 105
Abstract: Interactions of the microbial mat community with the sedimentary environment were evaluated in two shallow, ephemeral lakes with markedly different hydrochemistry and mineralogy. The characterization of growing and decaying microbial mats by light microscopy observations and fluorescence in situ hybridization was complemented with biogeochemical and mineralogical measurements. The lakes studied were Eras and Altillo Chica, both located in Central Spain and representing poly-extreme environments. Lake Eras is a highly alkaline, brackish to saline lake containing a high concentration of chloride, and in which the carbonate concentration exceeds the sulfate concentration. The presence of magnesium is crucial for the precipitation of hydromagnesite in microbialites of this lake. Altillo Chica is a mesosaline to hypersaline playa lake with high concentrations of sulfate and chloride, favoring the formation of gypsum microbialites. Differences in the microbial community composition and mineralogy of the microbialites between the two lakes were primarily controlled by alkalinity and salinity. Lake Eras was dominated by the cyanobacterial genus Oscillatoria, as well as Alphaproteobacteria, Gammaproteobacteria and Firmicutes. When the mat decayed, Alphaproteobacteria and Deltaproteobacteria increased and became the dominant heterotrophs, as opposed to Firmicutes. In contrast, Deltaproteobacteria was the most abundant group in Lake Altillo Chica, where desiccation led to mats decay during evaporite formation. In addition to Deltaproteobacteria, Cyanobacteria, Actinobacteria, Alphaproteobacteria and Gammaproteobacteria were found in Altillo Chica, mostly during microbial mats growth. At both sites, microbial mats favored the precipitation of sulfate and carbonate minerals. The precipitation of carbonate is higher in the soda lake due to a stronger alkalinity engine and probably a higher degradation rate of exopolymeric substances. Our findings clarify the distribution patterns of microbial community composition in ephemeral lakes at the levels of whole communities, which were subjected to environmental conditions similar to those that may have existed during early Earth.
PubDate: 2018-02-01
DOI: 10.1007/s10498-018-9333-2
Issue No: Vol. 24, No. 1 (2018)

• Hydrogeochemical Processes in a Small Eastern Mediterranean Karst
Watershed (Nahr Ibrahim, Lebanon)
• Authors: N. Hanna; B. Lartiges; V. Kazpard; E. Maatouk; N. Amacha; S. Sassine; A. El Samrani
Abstract: Watersheds located in semiarid areas such as the eastern Mediterranean are particularly sensitive to the impact of climate change. To gain knowledge on the hydrogeochemical processes occurring in the Nahr Ibrahim watershed, a Critical Zone Observatory in Lebanon, we analyze the isotopic composition of the river water as well as the concentrations of the major ions exported (Ca2+, Mg2+, HCO3−, Na+, Cl−, K+, SO42−). Sampling campaigns were conducted from March 2014 to August 2016 to capture contrasting hydrological conditions. The results indicate that the carbonate lithology of the watershed is the predominant source of Ca2+, Mg2+ and HCO3−, whereas the low contents of Na+, Cl−, K+, SO42− mainly originate from sea spray. Except in the headwaters, the Nahr Ibrahim River is oversaturated with respect to calcite and dolomite. During wet seasons, calcite weathering and dolomite weathering contribute in an equivalent manner to the solute budget, whereas during dry seasons, calcite precipitates in the river. The isotopic composition of the river water reveals little seasonal dependency, the groundwater recharge by snowmelt infiltration leading to spring waters depleted in heavier isotopes during the dry seasons. A carbonate weathering rate of about 176 t/km2/year was determined at the outlet of the Nahr Ibrahim watershed. The calculated values of CO2 partial pressure, on average twice the atmospheric pressure, suggest that the river is a significant source of CO2 to the atmosphere (111 t/year).
PubDate: 2018-12-14
DOI: 10.1007/s10498-018-9346-x

• Impact of Cyanobacterial Associate and Heterotrophic Bacteria on Dissolved
Organic Carbon and Metal in Moss and Peat Leachate: Application to
Permafrost Thaw in Aquatic Environments
• Authors: Liudmila S. Shirokova; Joachim Labouret; Melissa Gurge; Emmanuelle Gérard; Irina S. Ivanova; Svetlana A. Zabelina; Oleg S. Pokrovsky
Pages: 331 - 358
Abstract: In the boreal and subarctic zone, the moss and peat interactions with rainwater and snowmelt water in shallow surface ponds control the delivery of dissolved organic matter (DOM) and metal to the rivers and further to the Arctic Ocean. The transformation of peat and moss leachate by common aquatic microorganisms and the effect of temperature on DOM mineralization by heterotrophs remain poorly known that does not allow predicting the response of boreal aquatic system to ongoing climate change. We used experimental approach to quantify the impact of boreal aquatic bacteria P. reactans, and two culturable bacteria extracted from a thaw lake of the permafrost zone (Bolshezemelskaya tundra, NE Europe): Iodobacter sp. and cyanobacterial associate dominated by order Chroococcales (Synechococcus sp). The interaction of these bacterial cultures with nutrient-free peat and moss leachate was performed in order to (1) quantify the impact of temperature (4, 25 and 45 °C) on peat leachate processing by heterotrophs; (2) compare the effect of heterotrophic bacteria and cyanobacterial associate on moss and peat leachate chemical composition, and (3) quantify the DOC and metal concentration change during cyanobacterial growth on leachate from frozen and thawed peat horizon and moss biomass. The efficiency of peat DOM processing by two heterotrophs was not modified by temperature rise from 4 to 45 °C. The DOC concentration decreased by a factor of 1.6 during 3 days of moss leachate reaction with Iodobacters sp. or cyanobacterial associate at 25 °C. The SUVA245 increased twofold suggesting an uptake of non-aromatic DOM by both microorganisms. The growth of cyanobacteria was absent on peat leachate but highly pronounced on moss leachate. This growth produced tenfold decrease in P concentration, a factor of 1.5–2.0 decrease in DOC, a factor of 4 and 100 decrease in Fe and Mn concentration, respectively. Adsorption of organic and organo-mineral colloids on bacterial cell surface was more important factor of element removal from organic leachates compared to intracellular assimilation and/or Fe oxyhydroxide precipitation. Overall, we demonstrate highly conservative behavior of peat leachate compared to moss leachate in the presence of culturable aquatic bacteria, a lack of any impact of heterotrophs on peat leachate and their weak impact on moss leachate. A very weak temperature impact on DOM processing by heterotrophs and lack of difference in the biodegradability of DOM from thawed and frozen peat horizons contradict the current paradigm that the warming of frozen OM and its leaching to inland waters will greatly affect microbial production and C cycle. Strong decrease in concentration of P, Fe and Mn in the moss leachate in the presence of cyanobacterial associate has straightforward application for understanding the development of thermokarst lakes and suggests that, in addition to P, Fe and Mn may become limiting micronutrients for phytoplankton bloom in thermokarst lakes.
PubDate: 2017-12-01
DOI: 10.1007/s10498-017-9325-7
Issue No: Vol. 23, No. 5-6 (2017)

JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327

Home (Search)
Subjects A-Z
Publishers A-Z
Customise
APIs