Water Sulfide Research Articles

Oxidation of Chemical Warfare Agents in Supercritical Water

Oxidation of chemical warfare agents (CWAs) such as Sulfur Oxidation of chemical warfare agents (CWAs) such as Sulfur Mustard (HD) and Soman (GD) and their simulants 2-chloroethyl ethyl sulfide (2-CEES) and dimethyl methylphosphonate (DMMP) in supercritical water were studied by a batch reactor. Results showed that HD, GD and their simulants 2-CEES and DMMP could be effectively destroyed into their corresponding mineral compounds by supercritical water oxidation (SCWO). The mineral ratio was a function of reaction temperature, reaction time and oxidant concentration. But reaction temperature seemed to have more important effect on the mineral ratio than other two factors. Sulfur compounds 2-CEES and HD could easily be mineralized under 475°C and the inorganic products were mainly SO32- and SO42- , while complete oxidation of organic phosphorus reactants GD and DMMP needed a high temperature of >600°C. And under relatively low temperature, DMMP tended to form a white organic phosphorus polymer with P-C and P-O-P bonds. Results also indicated that P-F bond was more easily broken than P-C bond.

One-pot synthesis of lead sulfide nanoparticles

A convenient and effective one-pot three-component synthesis of the lead sulfide nanoparticles was developed on the basis of the exchange reaction between the lead acetate and sodium sulfide in water at the ambient conditions. A possibility was shown of the direct reaction between the lead Pb2+ and sulfide S2− ions in an aqueous solution, resulting in a solid phase which contained PbS nanoparticles only, avoiding the hydrolysis stage.

Protist diversity in suboxic and sulfidic waters of the Black Sea

The oxic-anoxic transition zone of the Black Sea comprises a large suboxic zone as well as anoxic and sulfidic waters. While the prokaryotes and biogeochemical cycles that characterize this zone have been frequently studied, little is known about the diversity or ecology of its microbial eukaryotes. Here, we present the first broad qualitative report of the protist species composition in the Black Sea redoxcline using molecular tools. Fingerprint analysis from the whole redoxcline revealed a complex community structure of metabolically active protists with distinct shifts along the redox gradient. Additionally, 18S rRNA gene clone libraries were used to compare protist species composition of suboxic and sulfidic water layers. Among the ciliates, sequences related to Pleuronema and Strombidium were dominant in both water layers whereas sequences affiliated with anaerobic plagiopylids and Cyclidium were detected only in the sulfidic zone. Among the flagellates, mainly stramenopiles (mostly bicosoecids and chrysophytes) occurred throughout the redoxcline. In the sulfidic zone we found stramenopile sequences but also euglenozoans, jakobids and choanoflagellates that were related to clonal sequences from other anoxic marine habitats, thus indicating the existence of globally distributed groups of anoxic flagellates. Higher species diversity in the sulfidic zone and about twice as many novel sequence types of ciliates and stramenopiles compared with the suboxic layer emphasizes the importance of anoxic, sulfidic waters as habitat for high protist diversity although the function of these organisms is yet unknown.

Estimating the timing of early eukaryotic diversification with multigene molecular clocks

Although macroscopic plants, animals, and fungi are the most familiar eukaryotes, the bulk of eukaryotic diversity is microbial. Elucidating the timing of diversification among the more than 70 lineages is key to understanding the evolution of eukaryotes. Here, we use taxon-rich multigene data combined with diverse fossils and a relaxed molecular clock framework to estimate the timing of the last common ancestor of extant eukaryotes and the divergence of major clades. Overall, these analyses suggest that the last common ancestor lived between 1866 and 1679 Ma, consistent with the earliest microfossils interpreted with confidence as eukaryotic. During this interval, the Earth's surface differed markedly from today; for example, the oceans were incompletely ventilated, with ferruginous and, after about 1800 Ma, sulfidic water masses commonly lying beneath moderately oxygenated surface waters. Our time estimates also indicate that the major clades of eukaryotes diverged before 1000 Ma, with most or all probably diverging before 1200 Ma. Fossils, however, suggest that diversity within major extant clades expanded later, beginning about 800 Ma, when the oceans began their transition to a more modern chemical state. In combination, paleontological and molecular approaches indicate that long stems preceded diversification in the major eukaryotic lineages.

Nanocrystalline Zinc Indium Vanadate: A Novel Photocatalyst for Hydrogen Generation

Hydrogen is a future fuel and hence production of cheap hydrogen is an important area of research. Recently, the photocatalysts were used to generate hydrogen from water and hydrogen sulfide splitting under solar light. Hence, we designed Zinc Indium Vanadate, a novel visible light active photocatalyst and used for the generation of hydrogen by using solar light. We have demonstrated the synthesis of ZnIn2V2O9 (ZIV) catalyst by sonochemical route using NH4VO3, In (NO3)3 and Zn(CH3COO)2 as a precursors and PVP as a capping agent. The obtained product was further characterized by XRD, UV-DRS and FESEM. The XRD pattern reveals the existence of monoclinic crystal structure and broader peaks indicating the nanocrystalline nature of the material. The particle size was observed in the range of 50-70 nm. The optical study showed the absorption edge cut off at 520 nm with estimated band gap about 2.3 eV. Considering the band gap in visible range, ZnIn2V2O9 was used as a photocatalyst for photodecomposition of H2S under visible light irradiation to produce hydrogen. We observed excellent photocatalytic activity for the hydrogen generation by using this photocatalyst.

On-Site Measurement of Trace-Level Sulfide in Natural Waters by Vapor Generation and Microchannel Collection

Aqueous sulfide plays an important role in the environment even at low concentrations. However, it is unstable, which means field samples cannot be transported to the laboratory for analysis without fixation. In this work, a novel method was developed to determine trace levels of sulfide on site. This method is based on vapor generation and collection in a special microchannel device followed by fluorescence measurement (VG-μGAS). The microchannel scrubber gave a high enrichment factor, and a high sensitivity was achieved, which allowed measurement of nanomolar (nM) levels of sulfide. The theoretical approach to vapor generation for several compounds is discussed to evaluate the applicability of the method to these analytes, and compounds having a low Henry's law constant (<1 M atm(-1)) are suitable to measure by VG-μGAS. Under optimized conditions, concentrations of 1.0-100 nM of sulfide could be measured. The sulfide contents of hot spring, aquarium, pond, and seawater were successfully measured by this method. Nanomolar levels of sulfide could be measured on site without loss of analyte, and results were obtained instantly in the field, both of which are advantageous for effective field surveys. The method was also applied to field measurements of aqueous sulfide in the Ariake Sea and Lake Baikal.

Niche differentiation among mat-forming, sulfide-oxidizing bacteria at cold seeps of the Nile Deep Sea Fan (Eastern Mediterranean Sea)

Sulfidic muds of cold seeps on the Nile Deep Sea Fan (NDSF) are populated by different types of mat-forming sulfide-oxidizing bacteria. The predominant sulfide oxidizers of three different mats were identified by microscopic and phylogenetic analyses as (i) Arcobacter species producing cotton-ball-like sulfur precipitates, (ii) large filamentous sulfur bacteria including Beggiatoa species, and (iii) single, spherical Thiomargarita species. High resolution in situ microprofiles revealed different geochemical settings selecting for the different mat types. Arcobacter mats occurred where oxygen and sulfide overlapped above the seafloor in the bottom water interface. Filamentous sulfide oxidizers were associated with steep gradients of oxygen and sulfide in the sediment. A dense population of Thiomargarita was favored by temporarily changing supplies of oxygen and sulfide in the bottom water. These results indicate that the decisive factors in selecting for different mat-forming bacteria within one deep-sea province are spatial or temporal variations in energy supply. Furthermore, the occurrence of Arcobacter spp.-related 16S rRNA genes in the sediments below all three types of mats, as well as on top of brine lakes of the NDSF, indicates that this group of sulfide oxidizers can switch between different life modes depending on the geobiochemical habitat setting.

Dissolution modeling and potentiometric measurements of the SrS–H2O–gas system at normal pressure and temperature at salt concentrations of 0.125–2.924 mM

The SrS–H2O–gas system was studied to determine the concentrations of formed particles at equilibrium state after the dissolution of strontium sulfide in distilled water at 25 °C. The solubility of SrS was experimentally measured at a salt concentration range of 0.125–2.924 mM, and the determined pH was at a range of 10.0–11.6. The concentrations of different sulfide forms were determined spectrometrically, potentiometrically and by iodometric titration. The solubility of SrS was evaluated to be 1.671 mM (200 mg/l) and the value of the calculated solubility product (Ksp) was 2.143×10−6 (mol/l)2 according to the measured pH value of 11.18 and the calculated concentration of formed particles at equilibrium state in a closed oxygen-free test system. The average measured gaseous hydrosulfide (H2S)g bonding rate by alkaline (0.5 M NaOH) solution was 0.827 u g/h cm2.

Modelling long term corrosion behaviour of copper canisters in KBS-3 repository

The well known KBS-3 repository design involves the disposal of spent fuel in copper canisters in a deep geological repository sealed with clay based buffer and backfill materials. A one-dimensional reactive transport model has been developed to predict the evolution of the general corrosion behaviour of the copper canisters by the initially trapped O2 and by sulphide ions. Various sources of sulphide are considered, including the microbial reduction of sulphate, the dissolution of pyrite impurities and the ground water itself. The model has been used to simulate the evolution of the canister corrosion behaviour for various scenarios, including both the Olkiluoto and Forsmark proposed repository locations, the vertical and horizontal KBS-3 design variants, increased ground water sulphide or chloride concentrations, different microbial scenarios, different rates of repository saturation, and with and without the dissolution of pyrite. Following a brief description of the model, the results of these and other simulations are described.

New model for molybdenum behavior in euxinic waters

Rogoznica Lake, on the Adriatic coast of Croatia, undergoes vertical mixing in autumn, but quickly restratifies and becomes intensely sulfidic during the succeeding 11 months. Autumn's vertically homogeneous dissolved Mo concentrations quickly revert to a summer profile in which Mo concentrations are lower by an order of magnitude in the sulfidic layer than in the oxic layer. Other redox sensitive elements (As, U and V) are much less affected on this time scale. Below the depth where sulfidic waters become saturated with iron monosulfide, Mo concentrations become nearly constant. A similar pattern can be recognized in other euxinic basins and seems inconsistent with Mo removal by sorption on sinking particles. Precipitation of a previously unrecognized, probably nanoscale Fe(II)–Mo(VI) sulfide mineral is postulated to explain this phenomenon. By fitting the Rogoznica data, a provisional composition and solubility product constant for this material are derived. The mineral's formula approximates Fe 5Mo 3S 14. Its Mo content is similar to that of a synthetic precipitate previously shown by X-ray spectroscopy to resemble molybdenum's host phase in black shales. Assuming saturation with this mineral, dissolved Mo in the deep water column of a number of other euxinic basins can be predicted in most cases to within a factor of three. The model has important implications for Mo behavior in euxinic basins. For example, the model attributes the near-total Mo removal from deep Black Sea waters to a serendipitous combination of pH and H 2S concentration, implying that such removal would not be a general property of euxinic basins. This is a key point with regard to Mo isotope systematics. Contrary to previous views, the model assigns a critical role to pH in controlling the efficiency of Mo removal from euxinic basins.

Conditions required for oceanic anoxia/euxinia: Constraints from a one-dimensional ocean biogeochemical cycle model

Widespread black shale depositional intervals termed oceanic anoxic events (OAEs) occurred repeatedly during the Phanerozoic Eon. Here we developed a new vertical one-dimensional ocean biogeochemical cycle model that involves several chemical reactions in an oxic–anoxic–sulfidic water column. To explore the theoretical constraints for global oceanic anoxia/euxinia quantitatively and systematically, we conducted sensitivity analyses of the proposed causal mechanisms, including elevated rates of riverine phosphorus (P) input, ocean stagnation, and lowered oxygen solubility due to climate warming. We gave special attention to the vertical chemical structure of the ocean and also to the characteristic behaviors of the marine P cycle under anoxic conditions, because the relationship between the depth of anoxia and the benthic phosphorus flux could be important for the occurrence of oceanic anoxia/euxinia. Steady-state simulations indicated that (1) a decrease in ocean stagnation or oxygen solubility is not enough by itself to achieve widespread anoxia with the present reactive P river input rate, and (2) shallow water anoxia followed by massive P liberation from surface sediments can lead to widespread eutrophication and anoxia/euxinia. We conclude that elevated riverine flux of reactive P is the most important factor for triggering global anoxic events via a positive feedback loop among ocean anoxia, phosphorus regeneration, and surface biological productivity.

Reassessing the role of sulfur geochemistry on arsenic speciation in reducing environments

Recent evidence suggests that the oxidation of arsenite by zero-valent sulfur (S(0)) may produce stable aqueous arsenate species under highly reducing conditions. The speciation of arsenic (As) in reducing soils, sediments and aquifers may therefore be far more complex than previously thought. We illustrate this by presenting updated E h –pH diagrams of As speciation in sulfidic waters that include the most recently reported formation constants for sulfide complexes of As(III) and As(V). The results show that the stability fields of As(III) and As(V) (oxy)thioanions cover a large pH range, from pH 5 to 10. In particular, As(V)–S(–II) complexes significantly enhance the predicted solubility of As under reducing conditions. Equilibrium calculations further show that, under conditions representative of sulfidic pore waters and in the presence of solid-phase elemental sulfur, the S 0 (aq)/HS − couple yields a redox potential ( E h ) ∼ 0.1 V higher than the SO 4 2−/HS − couple. S(0) may thus help stabilize aqueous As(V) not only by providing an electron acceptor for As(III) but also by contributing to a more oxidizing redox state.

Late Archean euxinic conditions before the rise of atmospheric oxygen

Life on Earth is thought to have coevolved with the chemistry of the oceans and atmosphere, and the shift from an anoxic to an oxic world across the Archean-Proterozoic boundary represents a fundamental step in this process. In order to understand the relative influence of biological and geological factors on this transition, we must constrain key variables in seawater chemistry before the Great Oxidation Event (ca. 2500 Ma). We present a multielement (C-S-Fe-Mo) biogeochemical study of ca. 2662 Ma shales from the Hamersley Province in Western Australia. Our data reveal a sustained episode of Fe-limited pyrite formation under an anoxic and sulfidic (euxinic) water column. This is the oldest known occurrence of euxinia in Earth9s history and challenges the paradigm of persistently Fe-rich Archean oceans. Bulk trace metal chemistry and preservation of strong mass-independent S isotope fractionations in sedimentary pyrites indicate that ocean euxinia was possible prior to oxidative weathering, suggesting that sulfidic waters may have been common throughout the Archean Eon. C-S-Fe systematics suggest that oxygenic photosynthesis was the primary source of organic carbon in the basin, and the absence of Mo enrichments highlights a potential link between inefficient nitrogen fixation and the delayed arrival of the Great Oxidation Event.

Controlling Odour in Waste Water Collection Systems with Dissolved Sulphide Monitoring

High concentrations of sulphides in waste water can cause corrosive damage to concrete structures as well as septic and malodorous conditions. As a result, treatment facilities need effective methods to help them prevent sulphide formation in order to protect their waste water systems and eliminate odour problems. Sulphides can be removed by adding oxidants to the waste water, however, this is an expensive process and over-compensation can be costly, making the monitoring of dissolved sulphides necessary. Traditional techniques for monitoring the concentration of dissolved sulphides are expensive and require frequent maintenance, to overcome these issues new technology has been developed. This article discusses the challenges facing the waste water industry in measuring dissolved sulphides, the conventional monitoring methods, application examples and a new technology which surpasses traditional methods.

SiO2-supported RuCl3/3-(dichloroiodo)benzoic acid: green catalytic system for the oxidation of alcohols and sulfides in water

A green, recyclable and efficient catalytic oxidative system based on SiO2-supported RuCl3 and 3-(dichloroiodo)benzoic acid for the oxidation of alcohols and sulfides in water is developed. This catalytic oxidative system effects clean and efficient oxidation of a wide range of alcohols to the corresponding aldehydes and ketones, or sulfides to sulfoxides in high conversions with excellent chemoselectivity, under mild conditions and with an easy-work-up procedure. Furthermore, the SiO2–RuCl3 catalyst can be recovered by simple filtration and recycled in up to six consecutive runs without significant loss of activity. The reduced form of 3-(dichloroiodo)benzoic acid, 3-iodobenzoic acid, can be easily separated from reaction mixtures and converted back to 3-(dichloroiodo)benzoic acid by treatment with bleach and aqueous HCl in about 90% overall yield.

Arsenic Speciation in Sulfidic Waters: Reconciling Contradictory Spectroscopic and Chromatographic Evidence

In recent years, analytical methods have been developed that have demonstrated that soluble arsenic-sulfur species constitute a major fraction of dissolved arsenic in sulfidic waters. However, an intense debate is going on about the exact chemical nature of these compounds, since X-ray absorption spectroscopy (XAS) data generated at higher (mmol/L) concentrations suggest the presence of (oxy)thioarsenites in such waters, while ion chromatographic (IC) and mass spectroscopic data at lower (μmol/L to nmol/L) concentrations indicate the presence of (oxy)thioarsenates. In this contribution, we connect and explain these two apparently different types of results. We show by XAS that thioarsenites are the primary reaction products of arsenite and sulfide in geochemical model experiments in the complete absence of oxygen. However, thioarsenites are extremely unstable toward oxidation, and convert rapidly into thioarsenates when exposed to atmospheric oxygen, e.g., while waiting for analysis on the chromatographic autosampler. This problem can only be eliminated when the entire chromatographic process is conducted inside a glovebox. We also show that thioarsenites are unstable toward sample dilution, which is commonly employed prior to chromatographic analysis when ultrasensitive detectors like ICP-MS are used. This instability has two main reasons: if pH changes during dilution, then equilibria between individual arsenic-sulfur species rearrange rapidly due to their different stability regions within the pH range, and if pH is kept constant during dilution, then this changes the ratio between OH(-) and SH(-) in solution, which in turn shifts the underlying speciation equilibria. This problem is avoided by analyzing samples undiluted. Our studies show that thioarsenites appear as thioarsenates in IC analyses if oxygen is not excluded completely, and as arsenite if samples are diluted in alkaline anoxic medium. This also points out that thioarsenites are necessary intermediates in the formation of thioarsenates.

Phase Equilibria of Mixtures Containing Organic Sulfur Species (OSS) and Water/Hydrocarbons: VLE Measurements and Modeling Using the Cubic-Plus-Association Equation of State

We report new vapor−liquid equilibrium (VLE) data for dimethyl sulfide (DMS) in pure water, performed at three temperatures (303, 330, and 362 K) in the 1−8 MPa pressure range. The total system pressure was maintained introducing CH4. The inlet mole fraction of DMS was the same in all experiments, around 1.5 × 10−3 in the liquid phase. A “static-analytic” method was used for performing all of the measurements. The objective is to provide experimental VLE data for the dimethyl sulfide + CH4 + water system, for which no data are available in the open literature. These data will allow industry to model sulfur emissions. The new VLE data as well as the VLE data of some binary systems from the literature containing organic sulfur species + hydrocarbon, organic sulfur species + water, and some ternary systems containing organic sulfur species in hydrocarbons and water have been modeled successfully with the cubic-plus-association (CPA) equation of state. Useful remarks are presented about the application of Henry’s constant values to estimate binary interaction parameters of the CPA EoS for the description of whole vapor−liquid equilibria. The results using CPA EoS show that the cross association interactions in the methyl mercaptan + water system and ethyl mercaptan + water system should be considered. In aqueous mixtures of higher mercaptans, the consideration of such interactions does not improve the calculations, indicating that they are rather weak.

Limestone Corrosion by Neutrophilic Sulfur-Oxidizing Bacteria: A Coupled Microbe-Mineral System

Subsurface karst aquifers receiving sulfidic water can host complex chemolithotrophic microbial communities that are capable of dissolving limestone, forming new karstic habitat. Neutrophilic sulfur-oxidizing bacteria use reduced sulfur compounds as energy rich substrate, potentially producing sulfuric acid as a geochemically reactive byproduct. The physicochemical relationship between a biofilm forming on a limestone surface and the extent of microbial influence on dissolution rate, however, are unknown. We investigated the rate of Madison limestone dissolution by sulfur-oxidizers both in the field at Lower Kane Cave, WY (LKC), and in the laboratory using continuous flow culture reactors and microbial mat collected from LKC. In the field, a microbial consortium rapidly colonized limestone chips forming a thick biofilm, with deep etching of mineral surfaces underneath. In the laboratory we found that a microbial biofilm oxidizing thiosulfate on the limestone surface accelerated dissolution rate up to 7 times faster than the abiotic baseline rate. In contrast, experiments done with H2S or a mixture of H2S and thiosulfate had no effect on dissolution rate. We hypothesize that the laboratory mat community dominated by Thiothrix sp. oxidizes thiosulfate to sulfate and H+, while H2S is partially oxidized to S°. When all sulfur substrate is withheld, the community oxidizes stored intracellular sulfur, briefly accelerating limestone dissolution even in the absence of external supplied substrate. Accelerated corrosion occurs only in the reactive micro-environment under the biofilm, disconnected from the bulk reactor solution. When experiments are repeated where the microbial population is separated from the limestone by a dialysis membrane barrier, measured pH drop is greater, but there is only slight enhancement of rate. This work confirms our working hypothesis that neutrophilic sulfur-oxidizers colonize and rapidly dissolve limestone surfaces, possibly to buffer the production of excess acidity.

Particulate sulfur species in the water column of the Cariaco Basin

The biogeochemistry of iron sulfide minerals in the water column of the Cariaco Basin was investigated in November 2007 (non-upwelling season) and May 2008 (upwelling season) as part of the on-going CARIACO (CArbon Retention In A Colored Ocean) time series project. The concentrations of particulate sulfur species, specifically acid volatile sulfur (AVS), greigite, pyrite, and particulate elemental sulfur, were determined at high resolution near the O 2/H 2S interface. In November 2007, AVS was low throughout the water column, with the highest concentration at the depth where sulfide was first detected (260 m) and with a second peak at 500 m. Greigite, pyrite, and particulate elemental sulfur showed distinct concentration maxima near the interface. In May 2008, AVS was not detected in the water column. Maxima for greigite, pyrite, and particulate elemental sulfur were again observed near the interface. We also studied the iron sulfide flux using sediment trap materials collected at the Cariaco station. Pyrite comprised 0.2–0.4% of the total particulate flux in the anoxic water column, with a flux of 0.5–1.6 mg S m −2 d −1. Consistent with the water column concentration profiles for iron sulfide minerals, the sulfur isotope composition of particulate sulfur found in deep anoxic traps was similar to that of dissolved sulfide near the O 2/H 2S interface. We conclude that pyrite is formed mainly within the redoxcline where sulfur cycling imparts a distinct isotopic signature compared to dissolved sulfide in the deep anoxic water. This conclusion is consistent with our previous study of sulfur species and chemoautotrophic production, which suggests that reaction of sulfide with reactive iron is an important pathway for sulfide oxidation and sulfur intermediate formation near the interface. Pyrite and elemental sulfur distributions favor a pathway of pyrite formation via the reaction of FeS with polysulfides or particulate elemental sulfur near the interface. A comparison of thermodynamic predictions with actual concentration profiles for iron sulfides leads us to argue that microbes may mediate this precipitation.

A new particulate Mn–Fe–P-shuttle at the redoxcline of anoxic basins

Pelagic redoxclines of anoxic basins and deeps form the suboxic transition between oxygenated surface and anoxic or even sulfidic bottom waters. Intense element cycling, favoured by elevated microbial activity, causes steep gradients of physico-chemical parameters, nutrients and redox-sensitive trace metals. This study presents a conceptual model for authigenic particle formation at pelagic redoxclines, which is based on the tight coupling of Mn, Fe, and P cycles. Besides the well-known occurrence of Mn-oxides, textural (SEM-EDX) and geochemical (ICP-OES, ICP-MS) analyses of particles from the redoxclines of the Black Sea and the Baltic Sea (Gotland Basin, Landsort Deep) evidence the existence of earlier postulated Fe-oxyhydroxo-phosphates and emphasize mixed phases consisting of Mn-oxides and Fe-oxyhydroxo-phosphates as a new solid species. Most of the analyzed particles are star-shaped, of about 5 μm in size, and occur as single particles or aggregates without any morphological differences between Mn-oxides, Fe-oxyhydroxo-phosphates, and mixed phases. Throughout the redoxcline, these minerals show a general succession with maximum abundance of Mn-oxides above the redoxcline followed by mixed phases and almost pure Fe-phosphates within and below the redoxcline, respectively. Molar Fe/P ratios of single particles argue against the formation of known pure Fe-phosphates like vivianite or strengite at the lower end of the redox transition zone, but are consistent with recent experimental findings for colloidal P-bearing hydrous ferric oxides. Moreover, morphological similarities suggest the formation of irregular Fe-oxyhydroxo coatings due to oxidation of upward diffusing Fe 2+ by oxygen and stepwise replacement of Mn(IV) by Fe(III) on sinking MnO x particles followed by immediate adsorption or even co-precipitation of phosphate. Batch-type experiments using biogenic MnO x particles demonstrate the efficient potential of Fe 2+ oxidation by sinking MnO x particles. When entering sulfidic waters MnO x particles are progressively reduced leading to an increasing relative abundance of Fe- and P-rich particles. In deeper parts of the water column these particles are also reductively dissolved, thereby releasing Fe 2+ and phosphate to the water column. This Mn–Fe–P-shuttle likely affects phosphate transport throughout the water column and thus impacts primary production at least over longer time scales. Furthermore, the particulate Mn–Fe–P-shuttle must have played an important role for the cycling of P and certain trace metals in ancient ocean basins, e.g., during certain periods of Cretaceous black shale formation and should be considered in future mass balances and modeling approaches dealing with oxic/anoxic interfaces of aquatic ecosystems.