Description:    Calcium concentration and calcite supersaturation (Ω) needed for calcium carbonate nucleation and crystal growth in Pyramid Lake (PL) surface water were determined during August of 1997, 2000, and 2001. PL surface water has Ω values of 10–16. Notwithstanding high Ω, calcium carbonate growth did not occur on aragonite single crystals suspended PL surface water for several months. However, calcium solution addition to PL surface-water samples caused reproducible calcium carbonate mineral nucleation and crystal growth. Mean PL surface-water calcium concentration at nucleation was 2.33 mM ( n  = 10), a value about nine times higher than the ambient PL surface-water calcium concentration (0.26 mM); mean Ω at nucleation (109 with a standard deviation of 8) is about eight times the PL surface-water Ω. Calcium concentration and Ω regulated the calcium carbonate formation in PL nucleation experiments and surface water. Unfiltered samples nucleated at lower Ω than filtered samples. Calcium concentration and Ω at nucleation for experiments in the presence of added particles were within one standard deviation of the mean for all samples. Calcium carbonate formation rates followed a simple rate expression of the form, rate (mM/min) =  A (Ω) +  B . The best fit rate equation “Rate (Δ mM/Δ min) = −0.0026 Ω + 0.0175 ( r  = 0.904, n  = 10)” was statistically significant at greater than the 0.01 confidence level and gives, after rearrangement, Ω at zero rate of 6.7. Nucleation in PL surface water and morphology of calcium carbonate particles formed in PL nucleation experiments and in PL surface-water samples suggest crystal growth inhibition by multiple substances present in PL surface water mediates PL calcium carbonate formation, but there is insufficient information to determine the chemical nature of all inhibitors. Content Type Journal Article Category Original Paper Pages 1-19 DOI 10.1007/s10498-011-9150-3 Authors Michael M. Reddy, US Geological Survey (USGS), National Research Program (NRP), Central Branch (CB), Denver Federal Center, P.O. Box 25046, MS 403, Lakewood, CO 80225, USA Anthony Hoch, US Geological Survey (USGS), National Research Program (NRP), Central Branch (CB), Denver Federal Center, P.O. Box 25046, MS 403, Lakewood, CO 80225, USA Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165

Description:    Between 1990 and 2007, twenty-nine box cores were recovered within the Arctic Ocean spanning shelf, slope and basin locations, and analyzed for aluminum (Al), manganese (Mn), other inorganic components and organic carbon (C Org ). Using these core data together with literature values, we have constructed budgets for Al and Mn in the Arctic Ocean. Most of the Al and Mn entering the Arctic comes from rivers or coastal erosion, and almost all of these two elements is trapped within the Arctic. Total Mn distributions in sediments reflect the recycling and loss of much of the Mn from shelf sediments with ultimate burial over the slopes and in basins. Mn enrichments observed as bands in long cores from the basins appear to co-occur with inter-glacial periods. Our Mn budget suggests that change in sea level associated with the accumulation and melting of glaciers is a likely cause for the banding. The Arctic Ocean, which presently contains as much as 50% shelf area, loses most of that when global sea level falls by ~120 m during glacial maxima. With lower sea level, Mn input from rivers and coastal erosion declines, and inputs become stored in permafrost on the sub-aerial shelves or at the shelf margin. Sea-level rise re-establishes coastal erosion and large riverine inputs at the margin and initiates the remobilization of Mn stored on shelves by turning on algal productivity, which provides the C Org required to reduce sedimentary Mn oxyhydroxides. Content Type Journal Article Category Original Paper Pages 1-27 DOI 10.1007/s10498-011-9149-9 Authors Robie W. Macdonald, Department of Fisheries and Oceans, Institute of Ocean Sciences, PO Box 6000, Sidney, BC V8L 4B2, Canada Charles Gobeil, INRS-ETE, Université du Québec, 490 de la Couronne, Quebec, QC G1K 9A9, Canada Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165

Description:    A geochemical model was incorporated into a stratification model for lakes to create the model package: DYCD-CORE, a numerical code that couples the thermal and hydrodynamic capabilities of DYRESM and the geochemical capabilities of the reactive transport model CORE 2 D V4. Based on the chemical composition of solutes calculated in each node for each time step, density was computed using specific partial molal volumes of all considered solutes and fed back into the stratification module of the program package. The density calculated each time step leads to a strong coupling of hydrodynamics and hydrogeochemistry and reflects the complex interaction as it is present in all lakes. To demonstrate the functionality of the numerical approach, an example of an iron-meromictic lake was chosen, where the reactivity of the dissolved iron kept the water body perennially stratified. To critically validate the model results, temperatures were continously measured at high vertical and temporal resolution in a field investigation of Waldsee (near Döbern, Germany). Multiparameterprobe profiles and water samples confirmed the continous chemical stratification and served as initial and boundary conditions for the simulation period. The model package DYCD-CORE could reproduce the permanent stratification as it were in the lake. A demonstration run using the standard UNESCO equation for density, and hence assuming non-reactive solutes, failed entirely. Hence, stratification models using salinity for density are not suited for simulating density created by lake-internal geochemical transformation of solutes. However, density can be based directly on the simultaneous numerical simulation of lake geochemistry. Predictive modeling of changing lake circulation in a variable climate or considering change of use will require a proper inclusion of the geochemistry as demonstrated in this paper. Content Type Journal Article Category Original Paper Pages 265-280 DOI 10.1007/s10498-011-9133-4 Authors Santiago Moreira, Department Lake Research, UFZ Helmholtz-Centre for Environmental Research, Brueckstrasse 3a, 39114 Magdeburg, Germany Bertram Boehrer, Department Lake Research, UFZ Helmholtz-Centre for Environmental Research, Brueckstrasse 3a, 39114 Magdeburg, Germany Martin Schultze, Department Lake Research, UFZ Helmholtz-Centre for Environmental Research, Brueckstrasse 3a, 39114 Magdeburg, Germany Severine Dietz, Department of Freshwater Conservation, Brandenburg University of Technology, P.O. Box 101344, 03013 Cottbus, Germany Javier Samper, Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos, Universidad de A Coruña, Campus de Elviña, s/n, 15071 A Coruña, Spain Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165 Journal Volume Volume 17 Journal Issue Volume 17, Number 3

Description:    The interacting effect of pH, phosphate and time on the release of arsenic (As) from As-rich river bed sediments was studied. Arsenic release edges and kinetic release experiments (pH range 3–10), in the absence and presence of phosphate, coupled with sequential extraction procedures, SEM/EDX analyses and geochemical calculations, were carried out to evaluate As remobilisation and to elucidate the mechanisms involved. The results showed that As release underwent pronounced kinetic effects, which were strongly influenced by pH and phosphate. Remobilisation of As after 24 h was low (between ~1 and 5%) and varied slightly with pH, whereas alkaline conditions generally promoted As remobilisation after 168 h, with up to 12–21% of total As released. The results showed that depending on the pH and sediment considered, the release of As increased dramatically after ~48–72 h, suggesting that different processes are involved at different reaction periods. The addition of phosphate (1 mM) increased both the amount of As released (between 2 and 8 times) and the rate of As release from the sediments within the entire pH range (3–10) and period (168 h) studied. Moreover, in some cases, it also affected the shape of the As release edges and kinetic profiles. The similarities in the release profiles and the positive correlations between As and some sediment components, especially Fe and Al hydroxides, and organic matter—which appears to play a key role at high pH—suggest that As release from the studied sediments may be associated with solid phase dissolution processes under both acid and alkaline pH, whereas desorption plays a key role in the short term and at natural pH conditions, especially in the presence of phosphate, which acts as an As-displacing ligand. Evaluation of As mobility based on short-time leaching experiments may seriously underestimate the mobilisation of As from sediments. Content Type Journal Article Category Original Paper Pages 281-306 DOI 10.1007/s10498-011-9135-2 Authors David A. Rubinos, Departamento de Edafoloxía e Química Agrícola, Facultade de Farmacia, Universidade de Santiago de Compostela, Campus Sur, 15782 Santiago de Compostela, Spain Luz Iglesias, Departamento de Edafoloxía e Química Agrícola, Facultade de Farmacia, Universidade de Santiago de Compostela, Campus Sur, 15782 Santiago de Compostela, Spain Francisco Díaz-Fierros, Departamento de Edafoloxía e Química Agrícola, Facultade de Farmacia, Universidade de Santiago de Compostela, Campus Sur, 15782 Santiago de Compostela, Spain María Teresa Barral, Departamento de Edafoloxía e Química Agrícola, Facultade de Farmacia, Universidade de Santiago de Compostela, Campus Sur, 15782 Santiago de Compostela, Spain Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165 Journal Volume Volume 17 Journal Issue Volume 17, Number 3

Description:    Volcanic islands, being characterized by highly porous basaltic/andesitic lava flows and pyroclastic deposits, are subject to important chemical weathering by subsurface waters. Moreover, such subsurface weathering is impacted by hydrothermal springs in both active and non-active volcanic areas, thus increasing dissolved load concentrations. Here, we focus on the subsurface water chemistry in the volcanic islands of the Lesser Antilles and Réunion and on the origin of these subsurface flows. We are able, through the use of various isotopic tools (C, Sr, U–Th), to identify hydrothermal influences in river water. For example, Li concentrations show a positive correlation with temperature of hot and cold springs and also a relationship with δ 13 C; from this, we can show that several sources of hydrothermal activity influence the rivers of the Lesser Antilles and that some rivers also reveal an important organic influence. As much as 20% of the subsurface hydrothermal springs go to feed the rivers. The increasing temperatures result in more dissolved elements being mobilized and an increase in chemical weathering rates. In addition, using the ( 230 Th/ 238 U) isochron for the well and river dissolved loads in Martinique, Guadeloupe and Réunion, we can evaluate residence times in the river water, i.e. the average residence time in the water along the circulation path to the sampling point. Alteration takes longer when the water circulates through thick soil, for example, 400–5,000 years when circulating under an ash profile and 1,200–15,000 years when circulating through a collapse zone. It would appear that waters circulation is globally three times longer for subsurface water than for surficial water. The weathering regime in tropical volcanic environments seems to be controlled mainly by such subsurface circulation with high chemical concentration from hydrothermal inputs. The origin of these compositions is varied and not controlled by a single hydrothermal spring. Consequently, it is subsurface circulation that determines the weathering regime in tropical volcanic islands with the main controlling parameters being temperature and residence time. Content Type Journal Article Category Original Paper Pages 221-241 DOI 10.1007/s10498-011-9122-7 Authors Sétareh Rad, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, 75238 Paris Cedex 05, France Karine Rivé, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, 75238 Paris Cedex 05, France Claude Jean Allègre, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, 75238 Paris Cedex 05, France Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165 Journal Volume Volume 17 Journal Issue Volume 17, Number 3

Description:    Lake Kitagata, Uganda, is a hypersaline crater lake with Na–SO 4 –Cl–HCO 3 –CO 3 chemistry, high pH and relatively small amounts of SiO 2 . EQL/EVP, a brine evaporation equilibrium model (Risacher and Clement 2001 ), was used to model the major ion chemistry of the evolving brine and the order and masses of chemically precipitated sediments. Chemical sediments in a 1.6-m-long sediment core from Lake Kitagata occur as primary chemical mud (calcite, magadiite [NaSi 7 O 13 (OH) 3 ·3H 2 O], burkeite [Na 6 (CO 3 )(SO 4 ) 2 ]) and as diagenetic intrasediment growths (mirabilite (Na 2 SO 4 ·10H 2 O)). Predicted mineral assemblages formed by evaporative concentration were compared with those observed in salt crusts along the shoreline and in the core from the lake center. Most simulations match closely with observed natural assemblages. The dominant inflow water, groundwater, plays a significant role in driving the chemical evolution of Lake Kitagata water and mineral precipitation sequences. Simulated evaporation of Lake Kitagata waters cannot, however, explain the large masses of magadiite found in cores and the formation of burkeite earlier in the evaporation sequence than predicted. The masses and timing of formation of magadiite and burkeite may be explained by past groundwater inflow with higher alkalinity and SiO 2 concentrations than exist today. Content Type Journal Article Category Original Paper Pages 129-140 DOI 10.1007/s10498-010-9108-x Authors Lichun Ma, Institute of Mineral Resources, Chinese Academy of Geological Sciences, 100037 Beijing, China Tim K. Lowenstein, Department of Geological Sciences, State University of New York, Binghamton, NY 13902, USA James M. Russell, Department of Geological Sciences, Brown University, Box 1846, Providence, RI 02912, USA Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165 Journal Volume Volume 17 Journal Issue Volume 17, Number 2

Description:    The sorption behavior and solid-phase associations of phosphorus (P) in fine-grained sediments (〈63 μm) from two upstream tributaries and one downstream main stem site of the Spoon River in west-central Illinois were characterized to better understand phosphorus bioavailability in this agriculturally dominated watershed. The P sorption affinities, as indicated by linear distribution coefficients ( K d ), of all sediments were 330–5,150 L/kg, and negatively correlated with equilibrium phosphorus concentration (EPC o ) values, which ranged between 0.2 and 2.2 μM. pH values measured at the conclusion of the sorption experiments varied only slightly (7.45–8.10) but were nonetheless strongly positively correlated to EPC o values, and negatively correlated to K d values, suggesting the importance of pH to the observed sorption behavior. K d values were generally lower and EPC o values higher at the main stem site than at the upstream tributary sites, suggesting dissolved reactive P (DRP) bioavailability (specifically orthophosphate) increased downstream. The solid phase associations of P were operationally assessed with the streamlined SEDEX (sedimentary extraction) procedure, and most sediment P (≥50%) was released during the step designed to determine iron oxide–associated P. On average, 70–90% of the total sediment P pool was potentially bioavailable, as estimated by the sum of the iron oxide-, authigenic carbonate-, and organic-associated P fractions. Considerable calcium was also extracted from some sediments during the step designed to specifically remove iron oxide–associated P. It is hypothesized that the severe drought conditions that persisted between April and October, 2005 allowed authigenic carbonates (perhaps partly amorphous) to accumulate, and that these carbonates dissolved during the iron oxide extraction step. The extensive benthic algal populations also present may have aided carbonate precipitation, which under more normal hydrologic conditions would be periodically flushed downstream and replaced by fresh sediment. This suggests antecedent hydrologic conditions played a dominant role in the P sorption and solid phase associations identified. Content Type Journal Article Category Original Paper Pages 639-662 DOI 10.1007/s10498-010-9103-2 Authors Michael L. Machesky, Institute of Natural Resource Sustainability, Illinois State Water Survey Division, University of Illinois, 2204 Griffith Drive, Champaign, IL 61820, USA Thomas R. Holm, Institute of Natural Resource Sustainability, Illinois State Water Survey Division, University of Illinois, 2204 Griffith Drive, Champaign, IL 61820, USA James A. Slowikowski, Institute of Natural Resource Sustainability, Illinois State Water Survey Division, University of Illinois, 2204 Griffith Drive, Champaign, IL 61820, USA Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165 Journal Volume Volume 16 Journal Issue Volume 16, Number 4

Description:    Thermodynamic properties for aqueous alkyl sulfides have been compiled and/or estimated through established methods. These properties are used to investigate reactions among various sulfur compounds in a variety of geological environments, ranging from sea floor hydrothermal systems to organic-rich sludge. Using thermodynamic data and the revised Helgeson-Kirkham-Flowers (HKF) equations of state, along with geochemical constraints imposed by the environment, it is possible to estimate the abiotic production of this class of organic sulfur compounds. For example, in hydrothermal systems in which H 2 and H 2 S concentrations are buffered by the pyrite–pyrrhotite–magnetite (PPM) mineral assemblage, calculated equilibrium activities of dimethyl sulfide (DMS) are as high as 10 −3 through formation reactions in which the environment contains millimolal concentrations of CO 2 . Higher activities are obtained when DMS formation from CO is considered and when more reducing mineral assemblages are present. Content Type Journal Article Category Original Paper Pages 621-637 DOI 10.1007/s10498-010-9102-3 Authors Mitch Schulte, Department of Geological Sciences, University of Missouri, 101 Geology Building, Columbia, MO 65211, USA Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165 Journal Volume Volume 16 Journal Issue Volume 16, Number 4

Description:    In the present work, we evaluated the origin of organic matter in the tropical estuarine-lagoon system of Mundaú–Manguaba, NE Brazil, by considering the bulk (organic carbon and chlorophyll- a ) and lipidic (n-alcohols and sterols) composition of suspended particles. Water samples were collected in August 2006 from 24 stations covering the salinity gradient from the rivers down to the sea outlet. Chlorophyll- a (Chl- a ) varied from 22.7 to 134.1 μg L −1 in the lagoons, indicating eutrophic to hypertrophic conditions at the time of sampling. The high correlation between Chl- a and phytol together with the molar C:N ratio indicated the presence of fresh and recently produced autochthonous particulate organic matter throughout the system, except for the river samples. The elevated concentrations of short-chain n-alcohols and phytosterols, mainly 24-methylcholesta-5,24(28)-dien-3β-ol, also corroborated the predominance of autochthonous organic matter in the lagoons but were generated by distinct sources: cianobacteria in the freshwater Manguaba lagoon and diatoms in the brackish Mundaú lagoon compartments. Input of terrestrial organic matter was only detected in the rivers themselves or at the upper river–lagoon interfaces. Coprostanol indicated contamination by sewage in Mundaú lagoon and in some rivers, but at lower levels when compared to other Brazilian coastal lagoons and estuaries. Content Type Journal Article Category Original Paper Pages 1-19 DOI 10.1007/s10498-010-9104-1 Authors Talitha L. F. Costa, Laboratório de Geoquímica Orgânica Marinha (LAGOM), Faculdade de Oceanografia, Universidade do Estado do Rio de Janeiro. R. São Francisco Xavier, n.524, Rio de Janeiro, 20550-013 Brazil Michelle P. Araújo, Laboratório de Geoquímica Orgânica Marinha (LAGOM), Faculdade de Oceanografia, Universidade do Estado do Rio de Janeiro. R. São Francisco Xavier, n.524, Rio de Janeiro, 20550-013 Brazil Bastiaan A. Knoppers, Departamento de Geoquímica, Universidade Federal Fluminense, Outeiro de São João Batista s/n, Niterói, RJ 24020-141, Brazil Renato S. Carreira, Laboratório de Geoquímica Orgânica Marinha (LAGOM), Faculdade de Oceanografia, Universidade do Estado do Rio de Janeiro. R. São Francisco Xavier, n.524, Rio de Janeiro, 20550-013 Brazil Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165 Journal Volume Volume 17 Journal Issue Volume 17, Number 1

Description:    Lead chloride formation constants at 25°C were derived from analysis of previous spectrophotometrically generated observations of lead speciation in a variety of aqueous solutions (HClO 4 –HCl and NaCl–NaClO 4 mixtures, and solutions of MgCl 2 and CaCl 2 ). Specific interaction theory analysis of these formation constants produced coherent estimates of (a) PbCl + , \text PbCl 2 0 , and PbCl 3 − formation constants at zero ionic strength, and (b) well-defined depictions of the dependence of these formation constants on ionic strength. Accompanying examination of a recent IUPAC critical assessment of lead formation constants, in conjunction with the spectrophotometrically generated formation constants presented in this study, revealed significant differences among various subsets of the IUPAC critically selected data. It was found that these differences could be substantially reduced through reanalysis of the formation constant data of one of the subsets. The resulting revised lead chloride formation constants are in good agreement with the formation constants derived from the earlier spectrophotometrically generated data. Combining these data sets provides an improved characterization of lead chloride complexation over a wide range of ionic strengths: log  \text Cl b 1 = 1. 4 9 1 - 2.0 4  I 1/ 2 ( 1+ 1. 5  I 1/ 2 ) - 1 + 0. 2 3 8  I log  \text Cl b 2 = 2.0 6 2 - 3.0 6  I 1/ 2 ( 1+ 1. 5  I 1/ 2 ) - 1 + 0. 3 6 9  I log  \text Cl b 3 = 1. 8 9 9 - 3.0 6  I 1/ 2 ( 1+ 1. 5  I 1/ 2 ) - 1 + 0. 4 3 9  I . Content Type Journal Article Category Original Paper Pages 325-335 DOI 10.1007/s10498-010-9101-4 Authors Robert H. Byrne, University of South Florida College of Marine Science 140 7th Ave. South, St Petersburg FL 33701 USA Wensheng Yao, University of South Florida College of Marine Science 140 7th Ave. South, St Petersburg FL 33701 USA Yanxin Luo, Pall Corporation 25 Harbor Park Dr. Port Washington NY 11050 USA Frank J. Millero, University of Miami Rosenstiel School of Marine and Atmospheric Science 4600 Rickenbacker Causeway Miami FL 33149 USA Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165 Journal Volume Volume 16 Journal Issue Volume 16, Number 3