Sulfur concentrations and isotope ratios in sediments from Kiel Bay, western Baltic Sea

The isotope-ratios of sulfur-components in several sedimentologically different cores of recent marine sediments from Kiel Bay (Baltic Sea) were investigated. In addition, quantitative determinations were made on total sulfur, sulfate, sulfide, chloride, organic carbon, iron and watercontent in the sediment or in the pore-water solution. The investigations gave the following results: 1. The sulfur in the sediment (about 0.3 -2 % of the dry sample) was for the most part introduced into the sediment after sedimentation. This confirms the results of Kaplan et al. (1963, doi:10.1016/0016-7037(63)90074-7). The yield of Sulfur from organic material is very small (in our samples about 5-10% of the total sulfur in the sediment). 2. The sulfur bound in the sediment is taken from the sulfate of the interstitial water. During normal sedimentation, the exchange of sulfate by diffusion significant for changes in the sulfur-content goes down to a sediment depth of 4-6 cm. In this way the sulfate consumed by reduction and formation of sulfide or pyrite is mostly replaced. The uppermost layer of the sediment is an partly open system for the sulfur. The diagenesis of the sulfur is allochemical. 3. The isotope-values of the sediment-sulfur are largely influenced by the sulfur coming into the sediment by diffusion and being bound by bacteriological reduction. Due to the prevailing reduction of 32S and reverse-diffusion of sulfate into the open sea-water, an 32S enrichment takes place in the uppermost layer of the sediment. delta34S-values in the sediment range between -15 and -35 ? while seawater-sulfate has +20 ?. No relationship could be established between sedimentological or chemical changes and isotope-ratios. In the cores, successive sandy and clayly layers showed no change in the delta-values. The sedimentation rate, however, seems to influence isotope-ratios. In one core with low sedimentationrates the delta34S-values varied between -29 and -33 ?, while cores with higher sedimentationrates showed values between -17 and -24 ?. 4. As sediment depth increases, the pore-water sulfate shows decreasing concentrations (in a depth of 30-40 cm we found between 20 and 70 % of the seawater-values), and increasing delta 34S-values (in one case reaching more than +60 ?). The concentration of sulfide in the pore-water increases with sediment-depth (reaching 80 mg S/l in one case). The (delta34S-values of the pore-water-sulfide in all cores show increases paralleling the sulfate sulfur, with a nearly constant delta-distance of 50-60 ? in all cores. This seems to confirm the genetic relationship between the two components.

Geochemistry, microbiology and phospholipid fatty acid content of ODP Site 169-1036 sediments

Phospholipid fatty acids were measured in samples of 60°-130°C sediment taken from three holes at Site 1036 (Ocean Drilling Program Leg 169) to determine microbial community structure and possible community replacement at high temperatures. Five of six samples had similar concentrations of phospholipid fatty acids (2-6 pmol/g dry weight of sediment), and biomass estimates from these measurements compare favorably with direct microscopic counts, lending support to previous microscopic measures of deep sedimentary biomass. Very long-chain phospholipid fatty acids (21 to 30 carbons) were detected in the sediment and were up to half the total phospholipid fatty acid measured; they appear to increase in abundance with temperature, but their significance is not known. Community composition from lipid analysis showed that samples contained standard eubacterial membrane lipids but no detectable archaeal lipids, though archaea would be expected to dominate the samples at high temperatures. Cluster analysis of Middle Valley phospholipid fatty acid compositions shows that lipids in Middle Valley sediment samples are similar to each other at all temperatures, with the exception of very long-chain fatty acids. The data neither support nor deny a shift to a high-temperature microbial community in hot cores, so at the present time we cannot draw conclusions about whether the microbes observed in these hot sediments are active.

Interstitial-water chemistry of ODP Leg 119 sites

Ocean Drilling Program inorganic geochemistry procedures routinely overlook more than 99% of the sediment column. Present and past biogeochemical reactions alter the sediment record; however, most of these reaction zones are bypassed by the normal methods where samples are collected every 30 m. A new approach to increase resolution was introduced during Leg 119. Ten milliliters of sediment provided interstitial-water samples for ammonia, silica, sulfate, magnesium, and calcium analyses. The new method introduced some systematic differences in concentrations, as well as some decrease in precision. A number of advantages, however, may warrant using the method in some instances. In cases where routine interstitial-water data showed anomalous results, core sections were retrieved from the storage facility and resampled. The new high-resolution procedure was used to provide water samples in cases were water contents were low and routine squeezing could not recover pore water.

Sulphur chemistry of the ODP Site 206-1256 volcanic section

Sulfide mineralogy and the contents and isotope compositions of sulfur were analyzed in a complete oceanic volcanic section from IODP Hole 1256D in the eastern Pacific, in order to investigate the role of microbes and their effect on the sulfur budget in altered upper oceanic crust. Basalts in the 800 m thick volcanic section are affected by a pervasive low-temperature background alteration and have mean sulfur contents of 530 ppm, reflecting loss of sulfur relative to fresh glass through degassing during eruption and alteration by seawater. Alteration halos along fractures average 155 ppm sulfur and are more oxidized, have high SO4/Sum S ratios (0.43), and lost sulfur through oxidation by seawater compared to host rocks. Although sulfur was lost locally, sulfur was subsequently gained through fixation of seawater-derived sulfur in secondary pyrite and marcasite in veins and in concentrations at the boundary between alteration halos and host rocks. Negative d34S[sulfide-S] values (down to -30 per mil) and low temperatures of alteration (down to ~40 °C) point to microbial reduction of seawater sulfate as the process resulting in local additions of sulfide-S. Mass balance calculations indicate that 15-20% of the sulfur in the volcanic section is microbially derived, with the bulk altered volcanic section containing 940 ppm S, and with d34S shifted to -6.0 per mil from the mantle value (0 per mil). The bulk volcanic section may have gained or lost sulfur overall. The annual flux of microbial sulfur into oceanic basement based on Hole 1256D is 3-4 * 10**10 mol S/yr, within an order of magnitude of the riverine sulfate source and the sedimentary pyrite sink. Results indicate a flux of bacterially derived sulfur that is fixed in upper ocean basement of 7-8 * 10**-8 mol/cm**-2/yr1 over 15 m.y. This is comparable to that in open ocean sediment sites, but is one to two orders of magnitude less than for ocean margin sediments. The global annual subduction of sulfur in altered oceanic basalt lavas based on Hole 1256D is 1.5-2.0 * 10**11 mol/yr, comparable to the subduction of sulfide in sediments, and could contribute to sediment-like sulfur isotope heterogeneities in the mantle.

Stable isotope composition of pore waters from ODP Site 195-1200 serpentinite mud, South Chamorrow Seamount

The South Chamorro Seamount is a serpentinite mud volcano near the southern end of the Mariana forearc. The mud volcano was sampled by drilling during Ocean Drilling Program Leg 195. Samples of pore water squeezed from serpentinite mud were analyzed for stable isotope compositions of carbon in dissolved inorganic carbon and methane, sulfur in sulfate and sulfide, and oxygen in sulfate.

Composition of sediments, hydrothermal manifestations, interstitial waters, and aeolian material from the TAG Hydrothermal Field and Central Atlantic

The book is devoted to regularities of spatial distribution, mineralogy and geochemistry of hydrothermal and hydrothermal-sedimentary manifestations of the Mid-Atlantic Ridge rift zone.

Chemical element concentrations and speciations in bottom sediments from the Ob River mouth area

According to data from Cruise 54 of R/V Akademik Mstislav Keldysh (September 2007) results of geochemical studies of redox processes in bottom sediments from the Ob River mouth area as applied to redox indicator elements (such as manganese, iron, and sulfur) are presented. Parameters of bottom sediments and distribution of these elements evidence not only a significant role of mixing processes at an geochemical profile of bottom sediments in the estuary but also a role of postsedimentation (diagenetic) processes.

Sulfur in bottom sediments and intersitial waters of the Gulf of California

The book is devoted to study of diagenetic changes of organic matter and mineral part of sediments and interstitial waters of the Pacific Ocean due to physical-chemical and microbiological processes. Microbiological studies deal with different groups of bacteria. Regularities of quantitative distribution and the role of microorganisms in geochemical processes are under consideration. Geochemical studies highlight redox processes of the early stages of sediment diagenesis, alterations of interstitial waters, regularities of variations in chemical composition of iron-manganese nodules.

Geochemistry of glass shards in the volcanic ash layers of the Izu-Bonin Arc

To examine the processes and histories of arc volcanism and of volcanism associated with backarc rifting. 130 samples containing igneous glass shards were taken from the Plioccne-Quatemai^ succession on the rift Hank (Site 788) and the Quaternary fill in the basin fill of the Sumisu Rift (Sites 790 and 791). These samples were subsequently analyzed at the University of Illinois at Chicago and Shizuoka University. The oxides determined by electron probe do not account for the total weight of the material; differences between summed oxides and 100% arise from the water contents, probably augmented by minor losses thai result from alkali vaporization during analysis. Weight losses in colorless glasses are up to 9%; those in brown glasses (dacitcs to basalts) arc no more than 4.5%; shards from the rift-flank (possibly caused by prolonged proximity to ihc scafloor) generally have higher values than those from the rift-basin fill How much of the lost water is magmatic, and how much is hydrated is uncertain; however, although the shards absorb potassium, calcium, and magnesium during hydration in the deep sea, they do so only to a minor extent that does not significantly alter their major element compositions. Therefore, the electron-probe results are useful in evaluating the magmatism recorded by the shards. Pre- and syn-rift Izu-Bonin volcanism were overwhelmingly dominated by rhyolile explosions, demonstrating that island arcs may experience significant silicic volcanism in addition to the extensive basaltic and basaltic andestic activity, documented in many arcs since the 1970s, that occurs in conjunction with the andesitic volcanism formerly thought to be dominant. Andesitic eruptions also occurred before rifting, but the andesitic component in our samples is minor. All the pre- and syn-rift rhyolites and andesites belong to the low-alkali island-arc tholeiitic suite, and contrast markedly with the alkali products of Holocene volcanism on the northernmost Mariana Arc that have been attributed to nascent rifting. The Quaternary dacites and andesites atop the rift flank and in the rift-basin fill are more potassic than those of Pliocene age, as a result of assimilation from the upper arc crust, or from variations in degrees of partial melting of the source magmas, or from metasomatic fluids. All the glass layers from the rift-flank samples belong to low-K arc-tholeiitic suites. Half of those in the Pliocene succession are exclusively rhyolitic: the others contain minor admixtures of dacite and andesite, or andesite and either basaltic andesite or basalt. In Contrast, the Quaternary (syn-rift) volcaniclastics atop the rift-flank lack basalt and basaltic andesite shards. These youngest sediments of the rift flank show close compositional affinities with five thick layers of coarse, rhyolitic pumice deposits in the basin fill, the two oldest more silicic than the younger ones. The coarse layers, and most thin ash layers that occur in hemipelagites below and intercalated between them, are low-K rhyolites and therefore probably came from sources in the arc. However, several thin rhyolitic ash beds in the hemipelagites are abnormally enriched in potassium and must have been provided by more distal sources, most likely to the west in Japan. Remarkably, the Pliocene-Pleistocene geochemistry of the volcanic front does not appear to have been influenced by the syn-rift basaltic volcanism only a few kilometers away. Rare, thin layers of basaltic ash near the bases of the rift-basin successions are not derived from the arc. They deviate strongly from trends that the arc-derived glasses display on oxide-oxide plots, and show close affinities to the basalts empted all over the Sumisu Rift during rifting. These basalts, and the basaltic ashes in the basal rift-basin fill, arc compositionally similar to those erupted from mature backarc basins elsewhere.

Sediment and porewater geochemistry of core GIK13725, Wester Baltic Sea

Based on chemical-thermodynamical balances the species distributions and mineral stabilities of the chemical compositions of the pressed pore solutions taken from a Baltic Sea mudsediment are evualuated by means of the computer program WATEQF (PLUMMER et al., 1976). According to these evaluations calcite and aragonite are to be found in supersaturation throughout the whole profile. The SiO2 concentration of the pore solutions is mainly controlled by the dissolutions of amorphous silica present in minimal undersaturation. By means of SEM pictures idiomorph quartzcrystals as well as presumptive clay minerals transformation and reformations could be proved as stable transformation phases of the dissolved SiO2 species. The stability of the solid phases containing Al-components as of feldspars and clayminerals decreases with increasing dept and is mainly controlled by AIF3 complexes higher concentrated with increasing depth.

Sulfur speciation in bottom sediments from the Peru upwelling area

Sulfur speciation in bottom sediments from the area of the Peru upwelling has been studied. Data on sulfur contents in different compounds (sulfide, elemental, sulfate, pyritic and organic), water content, Eh, and organic carbon content in the bottom sediments have been obtained. The bottom sediments from the area are characterized by high content of organic carbon and low contents of total and reactive iron; this is typical for bottom sediments from ocean upwelling areas. Intense process of sulfate reduction occurs in the bottom sediments of the area, and accumulation of reduced sulfur compounds derivated from bacterial hydrogen sulfide does not exceed previously known values for other regions of the ocean.

Barium in sediments off northwest Africa

High-resolution down-core analyses of the solid phase content of total barium (Batot) and total organic carbon (TOC) back to 25 kyr B.P. were performed on a gravity core from the upper continental slope off Cape Yubi (Morocco). The observed discrepancy between the two potential paleoproductivity proxies, Batot and TOC, initiated supplementary examinations of the pore water, the geochemistry of the clay fraction, X-ray diffraction analyses, and the application of a sequential Ba extraction method of selected samples. Additionally, we analyzed down-core samples of the planktonic foraminifera Turborotalita quinqueloba and Globorotalia inflata for their Ba/Ca ratios. These analyses, which were performed for the first time on these species, were used to reconstruct past oceanic Ba concentrations. We suggest that in the study area, which is characterized by high accumulation rates, the preserved TOC content is a valuable proxy for past primary productivity, whereas the solid phase Batot contents appear to be affected by other mechanisms and factors. Peaks of total barium content in the clay fraction and of Ba/Ca ratios in the planktonic foraminifera shells found during the Younger Dryas and the Heinrich 1 event are likely to result from increased meltwater influx into the northern North Atlantic. We suggest that Ba-enriched meltwater was transmitted by the eastern boundary current system from higher latitudes to the region of the Canary Islands. Total barium contents of the clay fraction (Batot,clay) and Ba/Ca in planktonic foraminifera shells seem to be reliable proxies for this discharge of meltwater.

Geochemistry of pore water and sediments offshore Nicaragua and Costa Rica

Four volcanic ash-bearing marine sediment cores and one ash-free reference core were examined during research cruise RV Meteor 54/2 offshore Nicaragua and Costa Rica to investigate the chemical composition of pore waters related to volcanic ash alteration. Sediments were composed of terrigenous matter derived from the adjacent continent and contained several distinct ash layers. Biogenic opal and carbonate were only minor components. The terrigenous fraction was mainly composed of smectite and other clay minerals while the pore water composition was strongly affected by the anaerobic degradation of particulate organic matter via microbial sulphate reduction. The alteration of volcanic matter showed only a minor effect on major element concentrations in pore waters. This is in contrast to prior studies based on long sediment cores taken during the DSDP, where deep sediments always showed distinct signs of volcanic ash alteration. The missing signal of ash alteration is probably caused by low reaction rates and the high background concentration of major dissolved ions in the seawater-derived pore fluids. Dissolved silica concentrations were, however, significantly enriched in ash-bearing cores and showed no relation to the low but variable contents of biogenic opal. Hence, the data suggest that silica concentrations were enhanced by ash dissolution. Thus, the dissolved silica profile measured in one of the sediment cores was used to derive the in-situ dissolution rate of volcanic glass particles in marine sediments. A non-steady state model was run over a period of 43 kyr applying a constant pH of 7.30 and a dissolved Al concentration of 0.05 ?M. The kinetic constant (AA) was varied systematically to fit the model to the measured dissolved silica-depth profile. The best fit to the data was obtained applying AA = 1.3 * 10**-U9 mol of Si/cm**2/ s. This in-situ rate of ash dissolution at the seafloor is three orders of magnitude smaller than the rate of ash dissolution determined in previous laboratory experiments. Our results therefore imply that field investigations are necessary to accurately predict natural dissolution rates of volcanic glasses in marine sediments.

Measurements of seawater and aerosol particles during POLARSTERN cruise ANT-XXVII/4

An analytical method for the determination of the alpha dicarbonyls glyoxal (GLY) and methylglyoxal (MGLY) from seawater and marine aerosol particles is presented. The method is based on derivatization with o-(2,3,4,5,6-Pentafluorobenzyl)-hydroxylamine (PFBHA) reagent, solvent extraction and GC-MS (SIM) analysis. The method showed good precision (RSD < 10%), sensitivity (detection limits in the low ng/l range), and accuracy (good agreement between external calibration and standard addition). The method was applied to determine GLY and MGLY in oceanic water sampled during the Polarstern cruise ANT XXVII/4 from Capetown to Bremerhaven in spring 2011. GLY and MGLY were determined in the sea surface microlayer (SML) of the ocean and corresponding bulk water (BW) with average concentrations of 228 ng/l (GLY) and 196 ng/l (MGLY). The results show a significant enrichment (factor of 4) of GLY and MGLY in the SML. Furthermore, marine aerosol particles (PM1) were sampled during the cruise and analyzed for GLY (average concentration 0.19 ng/m**3) and MGLY (average concentration 0.15 ng/m**3). On aerosol particles, both carbonyls show a very good correlation with oxalate, supporting the idea of a secondary formation of oxalic acid via GLY and MGLY. Concentrations of GLY and MGLY in seawater and on aerosol particles were correlated to environmental parameters such as global radiation, temperature, distance to the coastline and biological activity. There are slight hints for a photochemical production of GLY and MGLY in the SML (significant enrichment in the SML, higher enrichment at higher temperature). However, a clear connection of GLY and MGLY to global radiation as well as to biological activity cannot be concluded from the data. A slight correlation between GLY and MGLY in the SML and in aerosol particles could be a hint for interactions, in particular of GLY, between seawater and the atmosphere.

Pore water concentrations and solid phase concentrations of sediment cores from the Ligurian continental slope

In October 1979, a period of heavy rainfall along the French Riviera was followed by the collapse of the Ligurian continental slope adjacent to the airport of Nice, France. A body of slope sediments, which was shortly beforehand affected by construction work south of the airport, was mobilized and traveled hundreds of kilometers downslope into the Var submarine canyon and, eventually, into the deep Ligurian basin. As a direct consequence, the construction was destroyed, seafloor cables were torn, and a small tsunami hit Antibes shortly after the failure. Hypotheses regarding the trigger mechanism include (i) vertical loading by construction of an embankment south of the airport, (ii) failure of a layer of sensitive clay within the slope sequence, and (iii) excess pore fluid pressures from charged aquifers in the underground. Over the previous decades, both the sensitive clay layers and the permeable sand and gravel layers were sampled to detect freshened waters. In 2007, the landslide scar and adjacent slopes were revisited for high-resolution seafloor mapping and systematic sampling. Results from half a dozen gravity and push cores in the shallow slope area reveal a limited zone of freshening (i.e. groundwater influence). A 100-250 m wide zone of the margin shows pore water salinities of 5-50% SW concentration and depletion in Cl, SO4, but Cr enrichment, while cores east or west of the landslide scar show regular SW profiles. Most interestingly, the three cores inside the landslide scar hint towards a complex hydrological system with at least two sources for groundwater. The aquifer system also showed strong freshening after a period of several months without significant precipitation. This freshening implies that charged coarse-grained layers represent a permanent threat to the slope's stability, not just after periods of major rainfall such as in October 1979.