Set Of Sediment Cores Research Articles

Assessing the chemical anthropocene – Development of the legacy pollution fingerprint in the North Sea during the last century

The North Sea and its coastal zones are heavily impacted by anthropogenic activities, which has resulted in significant chemical pollution ever since the beginning of the industrialization in Europe during the 19th century. In order to assess the chemical Anthropocene, natural archives, such as sediment cores, can serve as a valuable data source to reconstruct historical emission trends and to verify the effectiveness of changing environmental legislation. In this study, we investigated 90 contaminants covering inorganic and organic pollutant groups analyzed in a set of sediment cores taken in the North Seas' main sedimentation area (Skagerrak). We thereby develop a chemical pollution fingerprint that records the constant input of pollutants over time and illustrates their continued great relevance for the present. Additionally, samples were radiometrically dated and PAH and PCB levels in porewater were determined using equilibrium passive sampling. Furthermore, we elucidated the origin of lead (Pb) contamination utilizing non-traditional stable isotopic analysis. Our results reveal three main findings: 1. for all organic contaminant groups covered (PAHs, OCPs, PCBs, PBDEs and PFASs) as well as the elements lead (Pb) and titanium (Ti), determined concentrations decreased towards more recent deposited sediment. These decreasing trends could be linked to the time of introductions of restrictions and bans and therefor our results confirm, amongst possible other factors, the effectiveness of environmental legislation by revealing a successive change in contamination levels over the decades. 2. concentration trends for ΣPAH and ΣPCB measured in porewater correspond well with the ones found in sediment which suggests that this method can be a useful expansion to traditional bulk sediment analysis to determine the biologically available pollutant fraction. 3. Arsenic (As) concentrations were higher in younger sediment layers, potentially caused by emissions of corroded warfare material disposed in the study area after WW II.

Extreme wave events recorded in sedimentary archives of the Geropotamos River (north-central Crete, Greece)

Recent tsunami events have shown that tsunamis may propagate far inland by entering rivers mouths and may cause massive damage along the river banks. However, so far, only a few studies have been conducted such a search for studying tsunami signals in incised valley systems along the Mediterranean coasts although the tsunami hazard is high. The island of Crete is known to have been affected several times by strong tsunamis, e. g., by the AD 365 and the Late Bronze Age (LBA) Santorini tsunamis. The narrow Geropotamos River valley, distinctly incised into local bedrock and located at the northern coast of Crete and fully exposed to the Cretan Sea, was selected as a promising natural setting to search for palaeotsunami signatures in fluvial sedimentary archives. Based on a multi-electrode geoelectrical survey and a set of sediment cores, we investigated the event-geochronostratigraphic record of both the Geropotamos River mouth area and the river valley ca. 1 km upstream by means of sedimentological, geo-chemical, geochronological, geomorphological, and micropalaeontological methods. The sedimentary environment towards the present-day river mouth is dominated by (fluvio-)lagoonal muds since the mid- Holocene. These lagoonal sediments are intersected by six coarse-grained sand layers each representing an extreme wave event (EWE). EWE layers are up to several decimetres thick and are characterized by an allochthonous foraminiferal assemblage comprising shallow marine to open marine species. Also ca. 1 km further upstream, the sedimentary record revealed grain size and microfossil evidence of two high-energy events showing a clear marine imprint. Based on this, we suggest inundation from the seaside that reached minimum 1 km inland and left EWE signatures in a presently inactive external bank position of the Geropotamos River. Considering the sedimentary characteristics, the local wind and wave climate of the Cretan Sea, and the overall geomorphological setting, we interpret these EWE layers as tsunami- related. A major hiatus identified in the Geropotamos River mouth sediments seems to be related to the LBA Santorini tsunami as can be inferred based on local age-depth relations. The LBA tsunami is known to have severely hit the northern coast of Crete. However, the hiatus may also reflect changes in the subsidence rate and the local accommodation space architecture. The youngest EWE signal in the Geropotamos River archive appears to have been caused by the AD 365 tsunami event. Candidate deposits for both tsunami deposits were identified ca. 1 km further inland. Evidence of EWE impact documents channelling and acceleration effects of intruding water masses caused by the narrow and steeply incised Geropotamos River valley in an upstream direction. Further geochronological studies based on OSL dating are necessary for a reliable age control of these EWE candidate layers.

Spatial and temporal patterns of metallic pollution in Québec City, Canada: Sources and hazard assessment from reservoir sediment records

Québec City (QC, Canada) is an important urban center developed along the Saint-Charles River, at the confluence with the Saint-Lawrence River. Here, environmental issues related to pollution have been recently raised for sediments trapped upstream a dam built in the early 1970s. The major concern is about downstream transport of sediments and contaminants toward the Saint-Lawrence Estuary, a protected marine area of high socioeconomic value.This article deals with metallic contaminants in reservoir sediments collected along a longitudinal transect in the Saint-Charles River. The spatial and temporal patterns of metallic pollution have been assessed by the calculation of enrichment factors, geoaccumulation indexes, and metallic pollution index on 68 samples from a set of sediment cores and surface sediment samples. Severe to extreme pollutions are recorded with respect to silver (Ag), chromium (Cr), copper (Cu), mercury (Hg), and lead (Pb). Spatial analyses show contaminated samples are trapped in the downstream section of the river, where several point (industries, mall, harbor) and diffuse (dense urban habitat, road network) sources of pollution were evidenced using historical documents and multivariate statistics such as PCA/FA.A 50-yr sedimentary record indicates these metals were mainly delivered to the river system by the accumulation of fine-grained, organic-rich sediments during the 1970s and the 1980s. Since then, the commissioning of wastewater treatment plants in the city and environmental regulations likely played a key role to reduce the metallic yield in the Saint-Charles River. More recently, the river flow management within the reservoir favored the accumulation of much less contaminated sediments, burying the contamination. Yet, a significant environmental hazard remains if this sandy layer is removed by erosion, allowing for the remobilization and transport of contaminated sediments downstream toward the Saint-Lawrence River.

Holocene Carbon Burial in Lakes of the Uinta Mountains, Utah, USA

Recent research suggests that organic matter sequestered in lake sediment comprises a larger component of the global carbon cycle than once thought, yet little is known about carbon storage in mountain lakes. Here, we used a set of sediment cores collected from lakes in the Uinta Mountains (Utah, USA) to inform a series of calculations and extrapolations leading to estimates of carbon accumulation rates and total lacustrine carbon storage in this mountain range. Holocene rates of carbon accumulation in Uinta lakes are between 0.1 and 20.5 g/m2/yr, with an average of 5.4 g/m2/yr. These rates are similar to those reported for lakes in Greenland and Finland and are substantially lower than estimates for lakes in Alberta and Minnesota. The carbon content of modern sediments of seven lakes is notably elevated above long-term Holocene values, suggesting recent changes in productivity. The lakes of the Uintas have accumulated from 6 to 10×105 Mt of carbon over the Holocene. This is roughly equivalent to the annual carbon emissions from Salt Lake City, Utah. Based on their long-term Holocene rates, lakes in the Uintas annually sequester an amount of carbon equivalent to the emissions of <20 average Americans.

Microbial diversity of a closed salt lagoon in the Puertecitos area, Upper Gulf of California

Located 20 km south of Puertecitos on the Baja California Peninsula, Mexico, is a salt-crusted lagoon with a surface area of approximately 265,000 m2 that is isolated from the adjacent Upper Gulf of California by a 50-m wide berm. The berm rises 2 m above mean sea level extending for 530 m across the lagoon’s seaward front to bar replenishment by normal seawater except possibly by seepage. On another side of the lagoon an extinct Pliocene volcano, Volcán Prieto, marks an equally abrupt boundary delineated by basalt flows. The lagoon’s well-constrained physical geography represents a high-salinity environment under conditions of extreme aridity, flooded only during rare events associated with subtropical storms. The Volcán Prieto Lagoon (so named herein) formed through distinct stages in developmental geomorphology outlined in this study. A duplicate set of sediment cores (17 cm in length) were retrieved from the lagoon and sampled for biological associations that record high-diversity colonization and stratification of microbial mats dominated by bacteria. Small subunit ribosomal RNA gene sequencing of different horizons revealed at least 25 major named bacterial phyla and 8 major named archaeal phyla as well as several unnamed candidate taxa from miscellaneous groups. Lipid biomarker analyses of the same horizons revealed that cyanobacteria contributed significantly to biomass production only at shallow depth, whereas the lipids of anoxygenic phototrophic bacteria persisted to a depth of 15 cm, although with decreasing contents. The lipid patterns also showed that sulfate-reducing bacteria became more abundant with depth, whereas the contents of archaeal lipids increased from 1 to 5 cm depth but remained relatively constant below. Closed lagoons on the Gulf of California are widely distributed over the length of the Baja California Peninsula, but detailed taxonomic studies regarding the diverse microbial communities that colonized these extreme habitats have only begun to shed light on complex colonization patterns.
 Key words: coastal processes, closed lagoons, Gulf of California, microbial assemblages, lipid biomarkers.

Warming in Greenland's past

Climate Change To project how much sea level will rise in response to ongoing climate warming, one of the things we need to know is how sensitive the rate of Greenland Ice Sheet melting is to rising temperatures. McFarlin et al. present results from a set of sediment cores from a small nonglacial lake in the highlands of northwest Greenland, which contain deposits from the Holocene and the Last Interglacial (LIG). They found midge assemblages indicating peak July temperatures that were 4.0° to 7.0°C warmer than modern temperatures during the early Holocene and at least 5.5° to 8.5°C warmer during the LIG. This perspective of extreme warming suggests that even larger changes than predicted for this region over the coming century may be in store. Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1720420115 (2018).

Metals in Sediment Cores from Nine Coastal Lagoons in Central Vietnam

Problem statement: After being dramatically hit by war events, Vietnam is presently experiencing a huge economical and social development. However, very few data, relative to pollution levels and trends, are available for the correct management of critical areas such as coastal lagoons, where many economical activities are linked to high value environmental features. Approach: A set of sediment cores from nine coastal lagoons of central Vietnam (Lang Co, Truong Giang, An Khe, Nuoc Man, Nuoc Ngot, Thi Nai, O Loan, Thuy Trieu and Dam Nai) were sampled in 2008 and analyzed to assess metal and (Al, Cd, Cr, Cu, Fe, Hg, Li, Mn, Ni, Pb, V, U and Zn) and As levels and historical trends. Results: Concentrations are generally low, with the exception of As, which often exceeds ERL guidelines and Ni that does the same at O Loan. In some cases, concentrations-depth profiles account for recent increasing trends but surficial values are still low when compared to both international guidelines and polluted sediments all around the world. Sediment grain size seems to affect the depth distribution of a number of metals and when normalized to the content of silt and clay, values are particularly high at Dam Nai and Thi Nai, due to the very coarse composition of surficial sediments. Conclusion: Metal concentrations in lagoon sediments derive from the composition of rocks and soils in the watersheds. However, recent increasing trends need for further monitoring.

Late-Holocene climate variability in the Adriatic Sea (Central Mediterranean)

Planktic and benthic foraminifera assemblages from a set of sediment cores, collected on the Adriatic shelf and the Southern Adriatic deep basin, provide compelling evidence of submillennial-scale environmental changes during the last 6000 years. Repeated peaks in Globigerinoides sacculifer represent warm-dry intervals, including the `Mediaeval Warm Period', the `Roman Age', the late `Bronze Age' and the `Copper Age'. The Last Occurrence (LO) of G. sacculifer (550 years BP) approximates the base of the `Little Ice Age' (LIA). Significant turnovers in the structure of the water column reflect changes in the rate of formation and depth of flow of the North Adriatic Dense Water (NAdDW) and the Levantine Intermediate Water (LIW). About 7500 years BP the benthic oxygen isotope records mark the timing when the NAdDW formation intensified on the slope and shifted to its modern route. About 5500 years BP, when sea level reached its modern high stand, oxygen isotope records of intermediate planktic dwellers indicate a northward intrusion of the LIW on the slope. The oscillating isotope trends during the last five millennia document a discontinuous invasion of LIW into the Central Adriatic, possibly reflecting short-term climate changes with weakened LIW production during colder and wetter intervals.

Petroleum-related hydrocarbon seep age in a Recent North Sea sediment

In the summer of 1985, UNOCAL carried out a 55-day surface geochemical survey in the Norwegian Sector of the North Sea. The program was set up to include a variety of geochemical techniques to aid evaluation of their effectiveness for detecting hydrocarbon seepages in the marine environment. The ship was equipped with both bottom-water and bottom-sediment sampling devices and an analytical laboratory and computer network so that “onboard” measurements and “real time” data interpretation could be made. During the survey, >4100 line-kilometers of bottom-water data (∼11,000 sites) and 320 sediment cores were obtained. A major hydrocarbon gas anomaly was defined during part of the bottom-water sampling program. A set of sediment cores was taken in the vicinity of this anomaly. The data from these cores are used to illustrate the fate of hydrocarbon migration through unconsolidated marine sediment. Migration by bubble ebullition transports hydrocarbons through the near-surface sediment and produces gas plumes in the bottom water. Trapping of bubbles in the sediment will produce patchy, temporal hydrocarbon “anomalies” in the sediment. However, extensive sediment anomalies, such as those proposed to be developed by microseepage, can only be formed at depth in the sediment below the level where sulfate is depleted from the pore water. These anomalies result because vertical migration by molecular diffusion creates a steady-state hydrocarbon oxidation zone (sulfate reduction zone) at depth in the sediment which efficiently eliminates hydrocarbon transport further to the surface.