Biogeochemical carbon transformations in a drained coastal peatland of the southern Baltic Sea: An isotope and trace element perspective

2021 ◽  
Author(s):  
Anna-Kathrina Jenner ◽  
Iris Schmiedinger ◽  
Jens Kallmeyer ◽  
Cordula Gutekunst ◽  
Gerald Jurasinski ◽  
...  
Keyword(s):  
Organic Matter ◽  
Trace Metals ◽  
Baltic Sea ◽  
Pore Water ◽  
Research Training ◽  
Isotope Composition ◽  
Carbon Mineralization ◽  
Training Group ◽  
Iron Cycling ◽  
Coast Line

<p>Peatlands serve as important ecosystems since they store a substantial fraction of global soil carbon. Through draining the internal biogeochemical processes may be changed impacting the transformation of stored carbon and plant material. Pristine peatlands are primarily associated with methanogenic and iron-cycling conditions, however, minor sulfur cycling may contribute to carbon mineralization in these ecosystems depending on the amount of atmospheric sulfur deposition and accumulation. In near coastal peatlands the element budget may be altered through natural or artificial flooding by brackish/marine waters. When introducing sulfate-bearing solutions, the concentrations of electron acceptors for anaerobic mineralization or organic matter increase when compared to fresh water conditions. The investigated area is planned to be flooded by Baltic Sea coastal waters in the near future.</p><p>Here we present results from a study from a drained peatland located in the southern part of the Baltic Sea. In the past the area was agriculturally used as grassland. Soil cores were retrieved along a transect perpendicular to the coast line for (isotope) biogeochemical analyses of pore water and solid phases. Analyses included the CNS composition of soils, and dissolved major elements, nutrients, sulphide, trace metals and stable isotopes of water, DIC, and sulfate (H, O, C, S). Furthermore, acid-extractions of metals were carried out to identify zones of dissolution and formation of authigenic phases. For quantification of microbial sulphate reduction rates (SRR) additional cores were retrieved and SRR were measured in whole-core incubations.<span> </span></p><p>The pore water isotopic composition is close to the local meteoric water line at the German Baltic Seas coast line. Concentration and stable isotope composition of DIC indicate mineralization of C3 type organic matter. Pore water trace metals content indicates the importance of anaerobic mineralization for release of metals into the pore and surface waters.</p><p> </p><p>Acknowledgement: This study is supported by the DFG research training group BALTIC TRANSCOAST and Leibniz IOW.</p>

Dynamics in the isotope biogeochemistry of a SGD-impacted coastal aquifer after a storm event

2020 ◽  
Author(s):  
Anna-Kathrina Jenner ◽  
Julia Westphal ◽  
Bo Liu ◽  
Iris Schmiedinger ◽  
Michael Böttcher
Keyword(s):  
Baltic Sea ◽  
Pore Water ◽  
Sea Water ◽  
Dissolved Inorganic Carbon ◽  
Research Training ◽  
Isotope Composition ◽  
Coastal Sediments ◽  
Considerable Proportion ◽  
Storm Event ◽  
Strong Control

<p>The interface of land and sea is of particular interest regarding the exchange of elements, like nutrients, carbon and sulfur. Submarine groundwater discharge (SGD) is an important pathway for element exchange from the terrestrial to the marine environment and vice versa. The discharging water can not only consist of fresh ground water but also of a considerable proportion of recirculated often brackish seawater.</p><p>Here, we followed the water and element exchange and associated biogeochemical transformation processes in front of a rewetted peatland at the southern Baltic Sea. Vertical pore water profiles were retrieved via up to 5 m long multi-port pore water samplers on a seasonal base. An extrodinary storm event in early 2019 not only led to the partial flooding of an associated coastal peatland with brackish water but also pushed Baltic Sea water into the coastal aquifers allowing to investigate the time-dependent return to previous subterrestrial ‚normal‘ conditions via SGD-induced freshening. Weekly sampling was carried out to follow the changes after the storm event in the sediments in front of a coastal peatland. Here we present new results of the pre- and after storm event pore water profiles. A focus was set on the investigation of tracers for concentration gradients of major and redox-sensitive trace elements, nutrients and the stable isotope composition (H, C, S, O) of water, dissolved inorganic carbon (DIC) and sulfate to understand the mixing processes and superimposing biogeochemical transformation reactions.</p><p>We found evidence for a strong control of the bottom-pore water exchange by lithology and a high activity of dissimilatory sulfate-reducing microorganisms in the coastal sediments leading to the accumulation of substantial DIC superimposed by corrosion of sedimentary carbonates.</p><p> </p><p>Acknowledgement: This study is supported by the DFG research training group Baltic TRANSCOAST and the Leibniz IOW.</p>

Dissolution and recrystallization in modern shelf carbonates: evidence from pore water and solid phase chemistry

1993 ◽  
Vol 344 (1670) ◽  
pp. 27-36 ◽  
Keyword(s):  
Organic Matter ◽  
Pore Water ◽  
Solid Phase ◽  
Chemical Exchange ◽  
Isotope Composition ◽  
Geochemical Data ◽  
Carbonate Sediments ◽  
Pore Waters ◽  
Carbonate Minerals ◽  
Carbonate Production

We present an overview of geochemical data from pore waters and solid phases that clarify earliest diagenetic processes affecting modern, shallow marine carbonate sediments. Acids produced by organic matter decomposition react rapidly with metastable carbonate minerals in pore waters to produce extensive syndepositional dissolution and recrystallization. Stoichiometric relations among pore water solutes suggest that dissolution is related to oxidation of H 2 S which can accumulate in these low-Fe sediments. Sulphide oxidation likely occurs by enhanced diffusion of O 2 mediated by sulphide-oxidizing bacteria which colonize oxic/anoxic interfaces invaginating these intensely bioturbated sediments. Buffering of pore water stable isotopic compositions towards values of bulk sediment and rapid 45 Ca exchange rates during sediment incubations demonstrate that carbonate recrystallization is a significant process. Comparison of average biogenic carbonate production rates with estimated rates of dissolution and recrystallization suggests that over half the gross production is dissolved and/or recrystallized. Thus isotopic and elemental composition of carbonate minerals can experience significant alteration during earliest burial driven by chemical exchange among carbonate minerals and decomposing organic matter. Temporal shifts in palaeo-ocean carbon isotope composition inferred from bulk-rocks may be seriously compromised by facies-dependent differences in dissolution and recrystallization rates.

scholarly journals Enrichment of trace metals from acid sulfate soils in sediments of the Kvarken Archipelago, eastern Gulf of Bothnia, Baltic Sea

2020 ◽  
Vol 17 (23) ◽  
pp. 6097-6113
Author(s):  
Joonas J. Virtasalo ◽  
Peter Österholm ◽  
Aarno T. Kotilainen ◽  
Mats E. Åström
Keyword(s):  
Organic Matter ◽  
Trace Metals ◽  
Baltic Sea ◽  
Metal Transport ◽  
Acid Sulfate Soils ◽  
Acid Sulfate ◽  
Gulf Of Bothnia ◽  
Coastal Sea ◽  
Sulfate Soils ◽  
River Mouths

Abstract. Rivers draining the acid sulfate soils of western Finland are known to deliver large amounts of trace metals with detrimental environmental consequences to the recipient estuaries in the eastern Gulf of Bothnia, northern Baltic Sea. However, the distribution of these metals in the coastal sea area and the relevant metal transport mechanisms have been less studied. This study investigates the spatial and temporal distribution of metals in sediments at nine sites in the Kvarken Archipelago, which is the recipient system of Laihianjoki and Sulvanjoki rivers that are impacted by acid sulfate soils. The contents of Cd, Co, Cu, La, Mn, Ni, and Zn increased in the cores during the 1960s and 1970s as a consequence of intensive artificial drainage of the acid sulfate soil landscape. Metal deposition has remained at high levels since the 1980s. The metal enrichment in sea floor sediments is currently visible at least 25 km seaward from the river mouths. Comparison with sediment quality guidelines shows that the metal contents are very likely to cause detrimental effects on marine biota more than 12 km out from the river mouths. The dynamic sedimentary environment of the shallow archipelago makes these sediments potential future sources of metals to the ecosystem. Finally, the strong association of metals and nutrients in the same sediment grain size class of 2–6 µm suggests that the transformation of dissolved organic matter and metals to metal–organic aggregates at the river mouths is the key mechanism of seaward trace metal transport, in addition to co-precipitation with Mn oxyhydroxides identified in previous studies. The large share of terrestrial organic carbon in the total organic C in these sediments (interquartile range – 39 %–48 %) highlights the importance of riverine organic matter supply. These findings are important for the estimation of environmental risks and the management of biologically sensitive coastal sea ecosystems.

scholarly journals Spatial Variations of Trace Metals and Their Complexation Behavior with DOM in the Water of Dianchi Lake, China

2019 ◽  
Vol 16 (24) ◽  
pp. 4919
Author(s):  
Yuanbi Yi ◽  
Min Xiao ◽  
Khan M. G. Mostofa ◽  
Sen Xu ◽  
Zhongliang Wang
Keyword(s):  
Water Quality ◽  
Organic Matter ◽  
Trace Metals ◽  
Pore Water ◽  
Natural Waters ◽  
Specific Binding ◽  
Dianchi Lake ◽  
Water Compartments ◽  
High Dynamics ◽  
Lake Systems

The dynamics of trace metals and the complexation behavior related to organic matter in the interface between water and sediment would influence water quality and evolution in the lake system. This study characterized the distribution of trace metals and the optical properties of dissolved organic matter (DOM) on the surface, and the underlying and pore water of Dianchi Lake (DC) to understand the origin of metals and complexation mechanisms to DOM. Some species of trace metals were detected and Al, Ti, Fe, Zn, Sr and Ba were found to be the main types of metals in the aquatic environment of DC. Ti, Fe, Sr and Ba predominated in water above the depositional layer. Al, Ti, Fe and Sr were the most abundant metallic types in pore water. Mn and Zn were the main type found at the southern lake site, reflecting the contribution of pollution from an inflowing river. The correlations between DOM and metals suggested that both originated from the major source as particulate organic matter (POM), associated with weathering of Ca-, Mg-carbonate detritus and Fe- or Mn-bearing minerals. High dynamics of DOM and hydrochemical conditions would change most metal contents and speciation in different water compartments. Proportions of trace metals in dissolved organic carbon (DOC) in natural waters were correlated with both DOM molecular weight and structure, different metals were regulated by different organic properties, and the same metal also had specific binding characteristic with DOM in various water compartments. This study highlighted the interrelation of DOM and metals, as well as the pivotal role that organic matter and nutrients played during input, migrations and transformations of metals, thereby reflecting water quality evolution in the lake systems.

Biogeochemical cycling of nutrients and trace metals in anoxic freshwater sediments of the Neckar River, Germany

1995 ◽  
Vol 46 (1) ◽  
pp. 237 ◽  
Author(s):  
Y Song ◽  
G Muller
Keyword(s):  
Organic Matter ◽  
Trace Metals ◽  
Pore Water ◽  
Sediment Cores ◽  
Sharp Decrease ◽  
Metal Sulfides ◽  
Pore Waters ◽  
Overlying Water ◽  
Mineralization Of Organic Matter ◽  
Cycling Of Nutrients

Pore-water components (SO42-, Fe2+, Mn2+), including nutrients (NH4+:, NO3-, PO43-), alkalinity and pH were determined at three sites in the Neckar River. Sequential extraction procedures and trace metals in both pore waters and sediments are reported in order to evaluate the mobility of trace metals in contaminated sediments. The results show that the mineralization of organic matter plays an important role in the cycling of nutrients and trace metals. Pore-water profiles (Zn, Cu, Pb, Cd) suggest that the element maximums at the sediment-water interface are caused by the decomposition of biomass. Low concentrations of dissolved Zn, Cu, Pb and Cd in the anoxic sediments can be explained by a sharp decrease of SO42- in pore water concomitant with HS- production. This leads to the formation of highly insoluble metal sulfides. Solubility calculations show that the sediments act as a sink for trace metals with respect to trace metal sulfides. The organic/sulfidic-bound fraction accounts for 64-81% of Cd in the sediment cores, 36-67% of Pb and 51-69% of Cu. In contrast, Cr in pore water increases with depth because of its release from Fe/Mn oxides. NH4+ and PO43- are also released into the pore water owing to the mineralization of organic matter. No significant fluxes of NH4+ and PO43- into overlying water were found because of the existence of an oxic surface layer.

A multi-tracer study of submarine groundwater discharge into Wismar Bay, southern Baltic Sea

2020 ◽  
Author(s):  
Catia Milene Ehlert von Ahn ◽  
Jan Scholten ◽  
Iris Schmiedinger ◽  
Bo Liu ◽  
Michael Böttcher
Keyword(s):  
Baltic Sea ◽  
Pore Water ◽  
Surface Waters ◽  
Submarine Groundwater Discharge ◽  
Isotope Composition ◽  
Groundwater Discharge ◽  
Pore Waters ◽  
Southern Baltic Sea ◽  
Submarine Groundwater ◽  
Southern Baltic

<p>Submarine groundwater discharge (SGD) is considered as an important route for water and dissolved material exchange between land and coastal seas. Both freshwater and (recirculated) seawater are referred to as SGD and may impact the composition and biogeochemical processes in coastal waters. The present study focuses on the identification and the spatial variability of SGD into the Wismar Bay, in the southern Baltic Sea. On across-shore transects covering Wismar Bay waters were sampled for analysis of Radium (Ra) isotopes, stable isotopes (H, O, C, S), dissolved inorganic carbon (DIC), nutrients and major cations. In addition, sediment cores were retrieved from several stations. The detection of short-living radium isotopes (<sup>223</sup>Ra and<sup>224</sup>Ra) in surface waters of the bay indicate benthic-pelagic coupling via pore water exchange with the water column that may be an indication for SGD. Moreover, enhanced concentration of dissolved manganese and barium, resulted from anoxic pore waters, were found in areas with higher Ra activity. Pore water profiles of salinity and major ions highlight the presence of freshwater about 50 cmbsf in sediments in the central part of the bay, probably related to the presence of a coastal aquifer. In contrast, other sediments demonstrate relatively constant pore water salinity distribution with increasing depth. Slight salinity maxima in almost all core at around 6 to 12 cmbsf seems to be relict from changing bottom water salinity in the past. The water isotope composition (δ<sup>18</sup>O, δ<sup>2</sup>H) of the low saline pore water is plot close to the local meteoric water line established for Warnemünde. Saline pore waters, in contrast, have water isotope composition aligned with southern Baltic Sea surface waters. The DIC concentrations increased with depths suggesting the mineralization of organic matter within the 50 cm sediments depth at all sides. Moreover, the values of DIC even exceeding the concentration found on the percolating fresh ground water. Thus, the overall contribution of elements to the coastal ecosystem is a function of the transport processes regulating element flux across the sediment-water interface.</p><p>The investigation is supported by the DFG research training school Baltic TRANSCOAST, DAAD, and Leibniz IOW.</p>

scholarly journals Enrichment of trace metals from acid sulphate soils in sediments of the Kvarken Archipelago, eastern Gulf of Bothnia, Baltic Sea

2020 ◽  
Author(s):  
Joonas J. Virtasalo ◽  
Peter Österholm ◽  
Aarno T. Kotilainen ◽  
Mats E. Åström
Keyword(s):  
Organic Matter ◽  
Trace Metals ◽  
Baltic Sea ◽  
Metal Transport ◽  
Organic C ◽  
Acid Sulphate ◽  
Acid Sulphate Soils ◽  
Gulf Of Bothnia ◽  
Coastal Sea ◽  
River Mouths

Abstract. Rivers draining the acid sulphate soils of western Finland are known to deliver large amounts of trace metals with detrimental environmental consequences to the recipient estuaries in the eastern Gulf of Bothnia, northern Baltic Sea. However, the distribution of these metals in the coastal sea area, and the relevant metal transport mechanisms have been less studied. This study investigates the spatial and temporal distribution of metals in 9 sediment cores, collected from the Kvarken Archipelago, which is the recipient of Laihianjoki and Sulvanjoki Rivers that are impacted by acid sulphate soils. The contents of Cd, Co, Cu, La, Mn, Ni and Zn increase in the cores during the 1960s and 1970s as a consequence of intensive artificial drainage of the acid sulphate soil landscape. The metal deposition has remained at the high level since the 1980s. The metal enrichment in seafloor sediments is currently visible at least 25 km seaward from the river mouths. Comparison to sediment quality guidelines shows that the metal contents are very likely to cause detrimental effects on marine biota more than 12 km out from the river mouths. The dynamic sedimentary environment of the shallow archipelago makes these sediments potential future sources of metals to the ecosystem. Finally, the strong association of metals and nutrients to the same sediment grain size class of 2–6 µm indicates that the transformation of dissolved organic matter and metals to metal-organic aggregates at the river mouths is the key mechanism of seaward trace metal transport, in addition to co-precipitation with Mn-oxyhydroxides identified in previous studies. The large share of terrestrial organic carbon of the total organic C in these sediments (interquartile range = 39–48 %) highlights the importance of riverine organic matter supply. These findings are important for the estimation of environmental risks and the management of biologically-sensitive coastal sea ecosystems.

scholarly journals Spectral Characterization of Dissolved Organic Matter in Seawater and Sediment Pore Water from the Arctic Fjords (West Svalbard) in Summer

Water ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 202
Author(s):  
Meilian Chen ◽  
Ji-Hoon Kim ◽  
Sungwook Hong ◽  
Yun Kyung Lee ◽  
Moo Hee Kang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Pore Water ◽  
Phytoplankton Bloom ◽  
Ocean Surface ◽  
The Arctic ◽  
Sediment Pore Water ◽  
Ice Edge ◽  
Accumulation Trend ◽  
Arctic Fjords

Fjords in the high Arctic, as aquatic critical zones at the interface of land-ocean continuum, are undergoing rapid changes due to glacier retreat and climate warming. Yet, little is known about the biogeochemical processes in the Arctic fjords. We measured the nutrients and the optical properties of dissolved organic matter (DOM) in both seawater and sediment pore water, along with the remote sensing data of the ocean surface, from three West Svalbard fjords. A cross-fjord comparison of fluorescence fingerprints together with downcore trends of salinity, Cl−, and PO43− revealed higher impact of terrestrial inputs (fluorescence index: ~1.2–1.5 in seawaters) and glaciofluvial runoffs (salinity: ~31.4 ± 2.4 psu in pore waters) to the southern fjord of Hornsund as compared to the northern fjords of Isfjorden and Van Mijenfjorden, tallying with heavier annual runoff to the southern fjord of Hornsund. Extremely high levels of protein-like fluorescence (up to ~4.5 RU) were observed at the partially sea ice-covered fjords in summer, in line with near-ubiquity ice-edge blooms observed in the Arctic. The results reflect an ongoing or post-phytoplankton bloom, which is also supported by the higher levels of chlorophyll a fluorescence at the ocean surface, the very high apparent oxygen utilization through the water column, and the nutrient drawdown at the ocean surface. Meanwhile, a characteristic elongated fluorescence fingerprint was observed in the fjords, presumably produced by ice-edge blooms in the Arctic ecosystems. Furthermore, alkalinity and the humic-like peaks showed a general downcore accumulation trend, which implies the production of humic-like DOM via a biological pathway also in the glaciomarine sediments from the Arctic fjords.

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