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  • 1
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    Nutrients, biological silica concentrations and stable silicon isotope compositions with the hydrographic parameters all year round in the Yellow River estuary and Bohai Sea (2024)
    PANGAEA
    Details
    Publikationsdatum: 2024-03-14
    Beschreibung: To study how the biogeochemical Si cycle in large river estuary and coastal areas has responded to one of the largest river regulation projects in the world, we conducted four cruises covering 33 stations across the Yellow River estuary and Bohai Sea via the RV CHUANGXINYI over four seasons, from October 2021 to August 2022. Temperature and salinity were monitored by a SeaBird-911 Conductivity-Temperature-Depth (CTD) recorder. Nutrients of phosphate, dissolved inorganic nitrogen and dissolved silica were measured by SEAL QuAAtro 39-SFA analyzer, biogenic silica was measured by alkaline digestion method, and Si isotope values of dissolved silica isotopes were measured by MC-ICP-MS. Our data reveal that the Si cycle in the Yellow River estuary and Bohai Sea is subject to high pressure of human activities and large natural variability.
    Schlagwort(e): Alkaline extraction; BB1_Autumn; BB1_Spring; BB1_Summer; BB1_Winter; BB2_Autumn; BB2_Spring; BB2_Summer; BB2_Winter; BB3_Autumn; BB3_Spring; BB3_Summer; BB3_Winter; BB4_Autumn; BB4_Spring; BB4_Summer; BB4_Winter; BB5_Autumn; BB5_Spring; BB5_Summer; BB5_Winter; BB6_Autumn; BB6_Spring; BB6_Summer; BB6_Winter; biogenic silica; Biogenic silica; China; Chlorophyll a; CTD, Sea-Bird, SBE 911; Date/Time of event; DEPTH, water; Diatoms; Event label; L1_Autumn; L1_Spring; L1_Winter; L2_Autumn; L2_Spring; L2_Summer; L2_Winter; L3_Autumn; L3_Spring; L3_Summer; L3_Winter; L4_Autumn; L4_Spring; L4_Summer; L4_Winter; L5_Autumn; L5_Spring; L5_Summer; L5_Winter; L6_Autumn; L6_Spring; L6_Summer; L6_Winter; Latitude of event; LB1_Autumn; LB1_Spring; LB1_Summer; LB1_Winter; LB2_Autumn; LB2_Spring; LB2_Summer; LB2_Winter; LB3_Autumn; LB3_Spring; LB3_Summer; LB3_Winter; LB4_Autumn; LB4_Spring; LB4_Summer; LB4_Winter; Longitude of event; M1_Autumn; M1_Spring; M1_Summer; M1_Winter; M10_Autumn; M10_Spring; M10_Summer; M10_Winter; M2_Autumn; M2_Spring; M2_Summer; M2_Winter; M3_Autumn; M3_Spring; M3_Summer; M3_Winter; M4_Autumn; M4_Spring; M4_Summer; M4_Winter; M5_Autumn; M5_Spring; M5_Summer; M5_Winter; M6_Autumn; M6_Spring; M6_Summer; M6_Winter; M7_Autumn; M7_Spring; M7_Summer; M7_Winter; M8_Autumn; M8_Spring; M8_Summer; M8_Winter; M9_Autumn; M9_Spring; M9_Summer; M9_Winter; Multi-Collector ICP-MS (MC-ICP-MS); N1_Autumn; N1_Spring; N1_Summer; N1_Winter; N2_Autumn; N2_Spring; N2_Summer; N2_Winter; N4_Autumn; N4_Spring; N4_Summer; N4_Winter; N5_Autumn; N5_Spring; N5_Summer; N5_Winter; Nitrogen, inorganic, dissolved; nutrient concentrations; Phosphorus, inorganic, dissolved; Salinity; Season; Segmented Flow Analysis (SFA), SEAL Analytical, QuAAtro39; Silica, dissolved; Silicon isotopes; Station label; Temperature, water; Water sample; WS; Y1_Autumn; Y1_Spring; Y1_Summer; Y1_Winter; Y2_Autumn; Y2_Spring; Y2_Summer; Y2_Winter; Y3_Autumn; Y3_Spring; Y3_Summer; Y3_Winter; Y4_Autumn; Y4_Spring; Y4_Summer; Y4_Winter; Y5_Autumn; Y5_Spring; Y5_Summer; Y5_Winter; Y6_Autumn; Y6_Spring; Y6_Summer; Y6_Winter; Y7_Autumn; Y7_Spring; Y7_Summer; Y7_Winter; Y8_Autumn; Y8_Spring; Y8_Summer; Y8_Winter; Y9_Autumn; Y9_Spring; Y9_Summer; Y9_Winter; Yellow River estuary and Bohai Sea; δ29Si; δ29Si, standard deviation; δ30Si; δ30Si, standard deviation
    Materialart: Dataset
    Format: text/tab-separated-values, 4516 data points
    Standort Signatur Einschränkungen Verfügbarkeit
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    DATA PANGAEA
  • 2
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    Anaerobic methane oxidation inducing carbonate precipitation at abiogenic methane seeps in the Tuscan archipelago (Italy) (2018)
    Public Library of Science
    In:  PLoS ONE, 13 (12). e0207305.
    Details
    Publikationsdatum: 2021-02-08
    Beschreibung: Seepage of methane (CH4) on land and in the sea may significantly affect Earth's biogeochemical cycles. However processes of CH4 generation and consumption, both abiotic and microbial, are not always clear. We provide new geochemical and isotope data to evaluate if a recently discovered CH4 seepage from the shallow seafloor close to the Island of Elba (Tuscany) and two small islands nearby are derived from abiogenic or biogenic sources and whether carbonate encrusted vents are the result of microbial or abiotic processes. Emission of gas bubbles (predominantly CH4) from unlithified sands was observed at seven spots in an area of 100 m(2) at Pomonte (Island of Elba), with a total rate of 234 ml m(-2) d(-1). The measured carbon isotope values of CH4 of around -18 parts per thousand (VPDB) in combination with the measured delta H-2 value of -120 parts per thousand (VSMOW) and the inverse correlation of delta C-13-value with carbon number of hydrocarbon gases are characteristic for sites of CH4 formation through abiogenic processes, specifically abiogenic formation of CH4 via reduction of CO2 by H-2. The H-2 for methanogenesis likely derives from ophiolitic host rock within the Ligurian accretionary prism. The lack of hydrothermal activity allows CH4 gas to become decoupled from the stagnant aqueous phase. Hence no hyperalkaline fluid is currently released at the vent sites. Within the seep area a decrease in porewater sulphate concentrations by ca. 5 mmol/l relative to seawater and a concomitant increase in sulphide and dissolved inorganic carbon (DIC) indicate substantial activity of sulphate-dependent anaerobic oxidation of methane (AOM). In absence of any other dissimilatory pathway, the delta C-13-values between -17 and -5 parts per thousand in dissolved inorganic carbon and aragonite cements suggest that the inorganic carbon is largely derived from CH4. The formation of seep carbonates is thus microbially induced via anaerobic oxidation of abiotic CH4.
    Materialart: Article , PeerReviewed
    Format: text
    DOI: 10.1371/journal.pone.0207305
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
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    Stable Silicon Isotopic Compositions of the Lena River and its Tributaries: Implications for Silicon Delivery to the Arctic Ocean (2018)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 241 . pp. 120-133.
    Details
    Publikationsdatum: 2021-02-08
    Beschreibung: Silicon isotope values (δ30SiDSi) of dissolved silicon (DSi) have been analyzed in the Lena River and its tributaries, one of the largest Arctic watersheds in the world. The geographical and temporal variations of δ30SiDSi range from +0.39 to +1.86‰ with DSi concentrations from 34 to 121 μM. No obvious patterns of DSi concentrations and δ30SiDSi values were observed along over 200 km of the two major tributaries, the Viliui and Aldan Rivers. In summer, the variations of DSi concentrations and δ30SiDSi values in the water are either caused by biological uptake by higher plants and phytoplankton or by mixing of water masses carrying different DSi concentrations and δ30SiDSi values. DSi in tributaries from the Verkhoyansk Mountain Range seems to be associated with secondary clay formation that increased the δ30SiDSi values, while terrestrial biological production is likely more prevalent in controlling δ30SiDSi values in Central Siberian Plateau and Lena Amganski Inter-River Area. In winter, when soils were frozen, the δ30SiDSi values in the river appeared to be controlled by weathering and clay formation in deep intrapermafrost groundwater. During the spring flood, dissolved silicate materials and phytoliths were flushed from the upper thawed soils into rivers, which reset δ30SiDSi values to the values observed prior to the biological bloom in summer. The results indicate that the Si isotope values reflect the changing processes controlling Si outputs to the Lena River and to the Arctic Ocean between seasons. The annual average δ30SiDSi value of the Lena Si flux is calculated to be +0.86±0.3‰ using measured δ30SiDSi values from each season. Combined with the estimate of +1.6±0.25‰ for the Yenisey River, an updated δ30SiDSi value of the major river Si inputs to the Arctic Ocean is estimated to be +1.3±0.3‰. This value is expected to shift towards higher values in the future because of the impacts from a variety of biological and geochemical processes and sources under global warming.
    Materialart: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.gca.2018.08.044
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  • 4
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    Assessing Sedimentary Boundary Layer Calcium Carbonate Precipitation and Dissolution Using the Calcium Isotopic Composition of Pore Fluids (2021)
    Frontiers
    Details
    Publikationsdatum: 2024-02-07
    Beschreibung: We present pore fluid geochemistry, including major ion and trace metal concentrations and the isotopic composition of pore fluid calcium and sulfate, from the uppermost meter of sediments from the Gulf of Aqaba (Northeast Red Sea) and the Iberian Margin (North Atlantic Ocean). In both the locations, we observe strong correlations among calcium, magnesium, strontium, and sulfate concentrations as well as the sulfur isotopic composition of sulfate and alkalinity, suggestive of active changes in the redox state and pH that should lead to carbonate mineral precipitation and dissolution. The calcium isotope composition of pore fluid calcium (δ 44 Ca) is, however, relatively invariant in our measured profiles, suggesting that carbonate mineral precipitation is not occurring within the boundary layer at these sites. We explore several reasons why the pore fluid δ 44 Ca might not be changing in the studied profiles, despite changes in other major ions and their isotopic composition, including mixing between the surface and deep precipitation of carbonate minerals below the boundary layer, the possibility that active iron and manganese cycling inhibits carbonate mineral precipitation, and that mineral precipitation may be slow enough to preclude calcium isotope fractionation during carbonate mineral precipitation. Our results suggest that active carbonate dissolution and precipitation, particularly in the diffusive boundary layer, may elicit a more complex response in the pore fluid δ 44 Ca than previously thought.
    Materialart: Article , PeerReviewed
    Format: text
    Format: archive
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  • 5
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    GEOTRACES Intercalibration of the Stable Silicon Isotope Composition of Dissolved Silicic Acid in Seawater (2017)
    Royal Society of Chemistry
    Details
    Publikationsdatum: 2023-01-31
    Beschreibung: The first inter-calibration study of the stable silicon isotope composition of dissolved silicic acid in seawater, δ30Si(OH)4, is presented as a contribution to the international GEOTRACES program. Eleven laboratories from seven countries analyzed two seawater samples from the north Pacific subtropical gyre (Station ALOHA) collected at 300 m and at 1000 m water depth. Sampling depths were chosen to obtain samples with a relatively low (9 μmol L-1, 300 m) and a relatively high (113 μmol L-1, 1000 m) silicic acid concentration as sample preparation differs for low- and high- concentration samples. Data for the 1000m water sample were not normally distributed so the median is used to represent the central tendency for the two samples. Median δ30Si(OH)4 values of +1.66 ‰ for the low-concentration sample and +1.25 ‰ for the high-concentration sample were obtained. Agreement among laboratories is overall considered very good; however, small but statistically significant differences among the mean isotope values obtained by different laboratories were detected likely reflecting interlaboratory differences in chemical preparation including pre-concentration and purification methods together with different volumes of seawater volume analyzed, and the use of different mass spectrometers including the Neptune MC-ICP-MS (Thermo Fisher™, Germany), the Nu Plasma MC-ICP-MS (Nu Instruments™, Wrexham, UK), and the Finnigan™ (now Thermo Fisher™, Germany) MAT 252 IRMS. Future studies analyzing δ30Si(OH)4 in seawater should also analyze and report values for these same two reference waters in order to facilitate comparison of data generated among and within laboratories over time.
    Materialart: Article , PeerReviewed
    Format: text
    Standort Signatur Einschränkungen Verfügbarkeit
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