Study of the Processes of the Biogeochemical Cycle of Sulfur in Bottom Sediments of the Estuary Region of the Northern Dvina River

Significance of δ34S and evaluation of its imprint on sedimentary organic matter: I. The role of reduced sulfur species in the diagenetic stage: A conceptual review

Understanding the geochemical cycling of sulfur in sediments is important because it can have implications for both modern environments (e.g., deterioration of water quality) and interpretation of the ancient past (e.g., sediment C/S ratios can be used as indicators of palaeodepositional environment). This study investigates the geochemical characteristics of sulfur, iron, and organic carbon in fluvial and coastal surface sediments of the Laizhou Bay region, China. A total of 63 sediment samples were taken across the whole Laizhou Bay marine region and the 14 major tidal rivers draining into it. Acid volatile sulfur, chromium (II)-reducible sulfur and elemental sulfur, total organic carbon, and total nitrogen were present in higher concentrations in the fluvial sediment than in the marine sediment of Laizhou Bay. The composition of reduced inorganic sulfur in surface sediments was dominated by acid volatile sulfur and chromium (II)-reducible sulfur. In fluvial sediments, sulfate reduction and formation of reduced inorganic sulfur were controlled by TOC and reactive iron synchronously. High C/S ratios in the marine sediments indicate that the diagenetic processes in Laizhou Bay have been affected by rapid deposition of sediment from the Yellow River in recent decades.

Coupling of dissolved organic carbon, sulfur and iron cycling in Black Sea sediments over the Holocene and the late Pleistocene: Insights from an empirical dynamic model

Role of sulfur biogeochemical cycle in mercury methylation in estuarine sediments: A review

The sulfur biogeochemical cycle integrates the metabolic activity of multiple microbial pathways (e.g., sulfate reduction, disproportionation, and sulfide oxidation) along with abiotic reactions and geological processes that cycle sulfur through various reservoirs. The sulfur cycle impacts the global carbon cycle and climate primarily through the remineralization of organic carbon. Over geological timescales, cycling of sulfur is closely tied to the redox state of Earth's exosphere through the burial of oxidized (sulfate) and reduced (sulfide) sulfur species in marine sediments. Biological sulfur cycling is associated with isotopic fractionations that can be used to trace the fluxes through various metabolic pathways. The resulting isotopic data provide insights into sulfur cycling in both modern and ancient environments via isotopic signatures in sedimentary sulfate and sulfide phases. Here, we review the deep-time δ34S record of marine sulfates and sulfides in light of recent advances in understanding how isotopic signatures are generated by microbial activity, how these signatures are encoded in marine sediments, and how they may be altered following deposition. The resulting picture shows a sulfur cycle intimately coupled to ambient carbon cycling, where sulfur isotopic records preserved in sedimentary rocks are critically dependent on sedimentological and geochemical conditions (e.g., iron availability) during deposition.

Aiming to uncover the effects of tidewater and crab burrowing on sulfur cycling of Spartina alterniflora marsh, a field experiment was carried out at Jiangsu Yancheng Wetland National Nature Reserve. H2S flux, plant sulfur storage and total sulfur of sediments in S. alterniflora marsh were measured under different tidewater and crab burrows treatments. Results showed that crab burrows significantly increased H2S emission from S. alterniflora marsh, while no significant effect on H2S emission by tidewater was detected. Both tidewater and crab burrows had no significant effects on plant sulfur storage except that the crab burrows significantly decreased it in the seeding season. Tidewater only significantly impacted total sulfur in sediments of 0–30 cm depth, while those in soil of 0–20 and 40–50 cm depths were significantly affected by crab burrows. Total sulfur in sediments affected by tidewater and crab burrows exhibited a seasonal variation. The findings of this study indicated that both tidewater and crab burrowing were key disturbing factors affecting sulfur cycling in S. alterniflora marsh but in different aspects.

The geochemical cycles of iron and sulphur in marine sediments are strongly intertwined and give rise to a complex network of redox and precipitation reactions. Bioturbation refers to all modes of transport of particles and solutes induced by larger organisms, and in the present-day seafloor, bioturbation is one of the most important factors controlling the biogeochemical cycling of iron and sulphur. To better understand how bioturbation controls Fe and S cycling, we developed reactive transport model of a coastal sediment impacted by faunal activity. Subsequently, we performed a model sensitivity analysis, separately investigating the two different transport modes of bioturbation, i.e. bio-mixing (solid particle transport) and bio-irrigation (enhanced solute transport). This analysis reveals that bio-mixing and bio-irrigation have distinct—and largely opposing effects on both the iron and sulphur cycles. Bio-mixing enhances transport between the oxic and suboxic zones, thus promoting the reduction of oxidised species (e.g. iron oxyhydroxides) and the oxidation of reduced species (e.g. iron sulphides). Through the re-oxidation of iron sulphides, bio-mixing strongly enhances the recycling of Fe and S between their reduced and oxidised states. Bio-irrigation on the other hand removes reduced solutes, i.e. ferrous iron and free sulphide, from the sediment pore water. These reduced species are then reoxidised in the overlying water and not recycled within the sediment column, which leads to a decrease in Fe and S recycling. Overall, our results demonstrate that the ecology of the macrofauna (inducing bio-mixing or bio-irrigation, or both) matters when assessing their impact on sediment geochemistry. This finding seems particularly relevant for sedimentary cycling across Cambrian transition, when benthic fauna started colonizing and reworking the seafloor.

Iron-controlled oxidative sulfur cycling recorded in the distribution and isotopic composition of sulfur species in glacially influenced fjord sediments of west Svalbard

Copper sulphate (CuSO4) is commonly added to lakes and reservoirs to manage nuisance and exotic species. Several studies have previously reported that CuSO4 is very useful for this purpose, and that the copper is ultimately stored in lake sediments. In contrast, there has been little study on the fate of the sulphate from CuSO4 additions. The purpose of this study was to elucidate the effects of CuSO4 additions on sedimentary sulphur. Concentrations, isotopes, and fluxes of total and reduced sulphur in sediment cores from four Michigan lakes were compared, including two reference lakes that have never received CuSO4 additions, and two treatment lakes that have received CuSO4 additions by lake managers totalling 1–3 kg sulphate ha−1 year−1 since 1940. The results of this study confirm that sediments do not consistently provide records of sulphate loading across lakes. Isotopic evidence indicates this inconsistency is caused, in part, by lakes with well‐mixed sediments, in which sulphate is reduced to sulphide, but then subsequently reoxidized to sulphate and remobilized to the overlying water column. One of the treatment lakes, however, exhibited a clear correlation between CuSO4 additions and an increased sulphur flux to the sediment. During any given year, however, the sulphate added from CuSO4 additions amounted to no more than 10% of the sulphate added from wet deposition. Based on this seemingly insignificant quantity of sulphate, ascribing any effect of CuSO4 additions on sedimentary sulphur is tenuous at best. One possibility is that the addition of CuSO4 at rates that do not overwhelm the natural sulphur cycle of a lake or reservoir is a reasonable management tool for nuisance and exotic species.

Benthic sulfate reduction and sediment pools of sulfur and iron were examined during January 1992 at 3 stations in the Ao Nam Bor mangrove, Phuket, Thailand. Patterns of sulfate reduction rates (0–53 cm) reflected differences in physical and biological conditions at the 3 stations, and highest rates were found at the vegetated site within the mangrove (Rhizophora apiculata) forest. Due to extended oxidation of mangrove sediments, a large portion of the added35S-label was recovered in the chromium reducible pools (FeS2 and S0) (41–91% of the reduced sulfur). Pyrite was the most important inorganic sulfur component, attaining pool sizes 50–100 times higher than acid volatile pools (FeS). HCl-extractable (0.5 M HCl) iron pools, including Fe(II)HCl and Fe(III)HCl, were generally low and Fe(III)HCl was only present in the upper surface layers (0–5 cm). Maximum concentrations of dissolved Fe2+ (35–285 μM) occurred just about the depth where dissolved ΣH2S accumulated. Furthermore Fe2+ and ΣH2S coexisted only where concentrations of both were low. There was an accumulation of organic sulfur in the deep sediment at 2 stations in the inner part of the mangrove. The reoxidation of reduced sulfides was rapid, and storage of sulfur was minor in the upper sediment layers, where factors like bioturbation, the presence of roots, or tidal mixing enhance oxidation processes.

10.1016/0967-0653(95)94220-k

The dissimilatory reduction of sulfate is an ancient metabolic process central to today's biogeochemical cycling of sulfur and carbon in marine sediments. Until now its polyphyletic distribution was most parsimoniously explained by multiple horizontal transfers of single genes rather than by a not-yet-identified "metabolic island." Here we provide evidence that the horizontal transfer of a gene cluster may indeed be responsible for the patchy distribution of sulfate-reducing prokaryotes (SRP) in the phylogenetic tree. We isolated three DNA fragments (32 to 41 kb) from uncultured, closely related SRP from DNA directly extracted from two distinct marine sediments. Fosmid ws39f7, and partially also fosmids ws7f8 and hr42c9, harbored a core set of essential genes for the dissimilatory reduction of sulfate, including enzymes for the reduction of sulfur intermediates and synthesis of the prosthetic group of the dissimilatory sulfite reductase. Genome comparisons suggest that encoded membrane proteins universally present among SRP are critical for electron transfer to cytoplasmic enzymes. In addition, novel, conserved hypothetical proteins that are likely involved in dissimilatory sulfate reduction were identified. Based on comparative genomics and previously published experimental evidence, a more comprehensive model of dissimilatory sulfate reduction is presented. The observed clustering of genes involved in dissimilatory sulfate reduction has not been previously found. These findings strongly support the hypothesis that genes responsible for dissimilatory sulfate reduction were concomitantly transferred in a single event among prokaryotes. The acquisition of an optimized gene set would enormously facilitate a successful implementation of a novel pathway.

Towards a classification of organic enrichment in marine sediments based on biogeochemical indicators

Dynamic characteristics of sulfur, iron and phosphorus in coastal polluted sediments, north China

Characteristics of microbial community composition and its relationship with carbon, nitrogen and sulfur in sediments