scholarly journals Sediment geochronology and spatio-temporal and vertical distributions of radionuclides in the Upper Bonny Estuary (South Nigeria)

2014 ◽  
Vol 41 (4) ◽  
pp. 369-376 ◽  
Author(s):  
Omorotionmwan Omokheyeke ◽  
Francis Sikoki ◽  
Abdelmourhit Laissaoui ◽  
David Akpuluma ◽  
Peter Onyagbodor ◽  
...  
Keyword(s):  
Sediment Cores ◽  
Sediment Accumulation ◽  
Dry Weight ◽  
Radiometric Dating ◽  
Layer By Layer ◽  
Excess 210Pb ◽  
Radio Nuclide ◽  
Vertical Distributions ◽  
Southwest Nigeria ◽  
Spatio Temporal

Abstract Surface deposits and sediment cores were collected from the Upper Bonny Estuary, located in Southwest Nigeria, and analyzed to determine spatio-temporal and vertical distributions of radio-nuclide activities expressed in Bq·kg−1 dry weight. The results of activities of naturally occurring radionuclides of 226Ra (15 ± 2–34 ± 3 Bq·kg−1), 228Ra (32 ± 5–48 ± 6 Bq·kg−1), 40K (264 ± 29–462 ± 36 Bq·kg−1) were found to be all within the range of typical values reported for coastal regions. Ratios of 226Ra to 228Ra suggested accretion for all samples with low sediment accumulation registered during rainy months. In addition, vertical distributions at the three sampling sites were also studied with the initial aim of establishing chronologies from the decay of excess 210Pb. In two cores, excess 210Pb, estimated by subtracting 226Ra from total 210Pb on a layer-by-layer basis, exhibit relatively constant activity with discrete minima and maxima. Therefore, these cores were excluded from radiometric dating. Only the third core could be dated by the constant rate of supply model, and 137Cs was utilized to validate the 210Pb chronology.

scholarly journals Evaluating the historical sedimentation patterns in two different Mediterranean deep environments (Sardinia and Sicily Channels)

2019 ◽  
Vol 20 (3) ◽  
pp. 542 ◽  
Author(s):  
NOUR EL HOUDA HASSEN ◽  
NAFAÂ REGUIGUI ◽  
MOHAMED AMINE HELALI ◽  
NEZHA MEJJAD ◽  
ABDELMOURHIT LAISSAOUI ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Water Depth ◽  
Accumulation Rate ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Inverse Correlation ◽  
Accumulation Rates ◽  
Deep Sediment ◽  
210Pb And 137Cs ◽  
Excess 210Pb

The sediment accumulation rate in the Sardinia and Sicily channels in the central part of the Mediterranean Sea was studied by using short-lived radionuclides (210Pb and 137Cs) in two deep sediment cores. Different sedimentation regimes were identified indicating substantial differences in accumulation rates and historical patterns. The 210Pb-derived mean accumulation rate found in the Strait of Sardinia was 0.05 g.cm-2.y-1, lower than that in Sicily Channel (0.1 g.cm-2.y-1) suggesting an inverse correlation with water depth. Excess 210Pb inventories were 24 ± 1 and 6.0 ± 0.4 kBq.m-2, while the fluxes to the sediment were 745 ± 31 and 188 ± 11 Bq.m-2.y-1 in Sicily and Sardinia channels, respectively. 137Cs failed to use for the validation of the established chronologies, while its inventories found 450 Bq.m-2 and 355 Bq.m-2 in the Sicily and Sardinia channel, respectively.

scholarly journals Spatio-temporal assessment of the polychlorinated biphenyl (PCB) sediment contamination in four major French river corridors (1945–2018)

2020 ◽  
Vol 12 (2) ◽  
pp. 1153-1170 ◽  
Author(s):  
André-Marie Dendievel ◽  
Brice Mourier ◽  
Alexandra Coynel ◽  
Olivier Evrard ◽  
Pierre Labadie ◽  
...  
Keyword(s):  
Western Europe ◽  
Polychlorinated Biphenyl ◽  
Sediment Cores ◽  
Sharp Decrease ◽  
Dry Weight ◽  
Port Authorities ◽  
Suspended Particulate ◽  
Degradation Rates ◽  
Spatio Temporal ◽  
Living Organisms

Abstract. Environmental pollution by polychlorinated biphenyls (PCBs) is a key cause for concern about river quality because of their low degradation rates leading to their accumulation in sediments and living organisms. An original interdisciplinary work was conducted along the four main French rivers (Seine, Rhône, Loire and Garonne rivers), which flow into major European seas. We completed a dataset based on sediment analyses provided by monitoring agencies, port authorities and research teams on different solid matrices (sediment cores, bed and flood deposits, suspended particulate matter and dredged sediments). This dataset focused on the seven indicator PCBs and their sum (ΣPCBi) from 1945 to 2018 (nΣPCBi =1416). Special effort was put into the quality control to provide robust spatio-temporal information. Taking into account hydrological and human drivers, we outlined two main pollution trends: (1) from 1945 to 1975, a quick increase in ΣPCBi (up to 4 mg kg−1 dry weight, dw) and a sharp decrease in the 1980s on the Seine and Loire rivers and (2) increasing but moderate ΣPCBi levels (50 to 150 µg kg−1 dw) followed by a decline after the 1990s on the Rhône and Garonne rivers. In addition to these patterns, PCB emissions from urban and industrial areas or accidental events were significant in each river. Finally, when calculating specific flux, the Rhône exhibited the uppermost ΣPCBi load (up to 12 µgm-2yr-1 in 1977–1987), at least 25 % higher than those of the Seine and Loire rivers, while the Garonne showed a very low flux. In western Europe, we confirmed that the Rhône, Seine and Loire rivers contribute significantly to the PCB contamination of the seas, while French specific ΣPCBi fluxes are 2 orders of magnitude lower than those found in American or Asian rivers. The dataset is available at https://doi.org/10.1594/PANGAEA.904277 (Dendievel et al., 2019).

Pigment Preservation in Lake Sediments: A Comparison of Sedimentary Environments in Trout Lake, Wisconsin

1991 ◽  
Vol 48 (3) ◽  
pp. 472-486 ◽  
Author(s):  
James P. Hurley ◽  
David E. Armstrong
Keyword(s):  
Accumulation Rate ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Sediment Surface ◽  
Water Interface ◽  
Sedimentary Pigments ◽  
Sedimentary Environments ◽  
Trout Lake ◽  
Secondary Carotenoids ◽  
Β Carotene

Fluxes and concentrations of a phorbins and major algal carotenoids were quantified in sediment trap material and sediment cores from two basins of Trout Lake, Wisconsin (TrDH and TrAB). The basins were chosen to contrast the influence of oxygen content at the sediment–water interface (TrDH, oxic and TrAB, reducing), sediment accumulation rate, and focusing. Pigment diagenesis occurred in both basins, but transformations and destruction were more extensive in TrDH. Although untransformed chlorophyll a was the major phorbin deposited at the sediment surface of both basins (51–64 mol%), pigment destruction, coupled with transition to pheophytin, accounted for substantial losses, especially in oxic TrDH sediments. Fucoxanthin, peridinin, and diadinoxanthin, despite representing > 70% of the deposited carotenoid flux, were substantially degraded or transformed in both basins. However, preservation was relatively high for secondary carotenoids, such as diatoxanthin and β-carotene, and for a major cryptomonad pigment, alloxanthin. Residual profiles in sediments show that pigment sedimentation from the epilimnion and accumulation in the permanent sediments are not directly related and that diagenesis must be considered in interpreting sedimentary pigments.

The Toba Volcanic Event and Interstadial/Stadial Climates at the Marine Isotopic Stage 5 to 4 Transition in the Northern Indian Ocean

2002 ◽  
Vol 57 (1) ◽  
pp. 22-31 ◽  
Author(s):  
Hartmut Schulz ◽  
Kay-Christian Emeis ◽  
Helmut Erlenkeuser ◽  
Ulrich von Rad ◽  
Christian Rolf
Keyword(s):  
Arabian Sea ◽  
Water Productivity ◽  
Ice Core ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Sediment Supply ◽  
Volcanic Event ◽  
Additional Support ◽  
Marine Isotope Stage 5 ◽  
A Minor

AbstractThe Toba volcanic event, one of the largest eruptions during the Quaternary, is documented in marine sediment cores from the northeastern Arabian Sea. On the crest of the Murray Ridge and along the western Indian continental margin, we detected distinct concentration spikes and ash layers of rhyolithic volcanic shards near the marine isotope stage 5–4 boundary with the chemical composition of the “Youngest Toba Tuff.” Time series of the Uk′37-alkenone index, planktic foraminiferal species, magnetic susceptibility, and sediment accumulation rates from this interval show that the Toba event occurred between two warm periods lasting a few millennia. Using Toba as an instantaneous stratigraphic marker for correlation between the marine- and ice-core chronostratigraphies, these two Arabian Sea climatic events correspond to Greenland interstadials 20 and 19, respectively. Our data sets thus depict substantial interstadial/stadial fluctuations in sea-surface temperature and surface-water productivity. We show that variable terrigenous (eolian) sediment supply played a crucial role in transferring and preserving the productivity signal in the sediment record. Within the provided stratigraphic resolution of several decades to centennials, none of these proxies shows a particular impact of the Toba eruption. However, our results are additional support that Toba, despite its exceptional magnitude, had only a minor impact on the evolution of low-latitude monsoonal climate on centennial to millennial time scales.

scholarly journals Simulations over South Asia using the weather research and forecasting model with chemistry (WRF-Chem): chemistry evaluation and initial results

2012 ◽  
Vol 5 (1) ◽  
pp. 1-66 ◽  
Author(s):  
R. Kumar ◽  
M. Naja ◽  
G. G. Pfister ◽  
M. C. Barth ◽  
C. Wiedinmyer ◽  
...  
Keyword(s):  
South Asia ◽  
Biomass Burning ◽  
Surface Ozone ◽  
Ozone Production ◽  
Weather Research And Forecasting ◽  
Northern India ◽  
Vertical Distributions ◽  
Spatio Temporal ◽  
First Time ◽  
Vertical Ozone

Abstract. This study presents annual simulations of tropospheric ozone and related species made for the first time using the WRF-Chem model over South Asia for the year 2008. The model simulated ozone, CO, and NOx are evaluated against ground-based, balloon-borne and satellite-borne (TES, OMI and MOPITT) observations. The comparison of model results with surface ozone observations from seven sites and CO and NOx observations from three sites, indicate the model's ability in reproducing seasonal variations of ozone and CO, but show some differences in NOx. The modeled vertical ozone distribution agrees well with the ozone soundings data from two Indian sites. The vertical distributions of TES ozone and MOPITT CO are generally well reproduced, but the model underestimates TES ozone, OMI tropospheric column NO2 and MOPITT total column CO retrievals during all the months except MOPITT retrievals during August–January. Largest differences between modeled and satellite retrieved quantities are found during spring when intense biomass burning activity occurs in this region. The evaluation results indicate large uncertainties in anthropogenic and biomass burning emission estimates, especially for NOx. The model results indicate clear regional differences in the seasonality of surface ozone over South Asia with estimated net ozone production during daytime (11:30–15:30 h) over inland regions of 0–5 ppbv h−1 during all seasons and of 0–2 ppbv h−1 over marine regions during outflow periods. The model results indicate that ozone production in this region is mostly NOx-limited. This study shows that WRF-Chem model captures many important features of the observations and gives confidence to using the model for understanding the spatio-temporal variability of ozone over South Asia. However, improvements of South Asian emission inventories and simulations at finer model resolution, especially over the complex Himalayan terrain in Northern India, are also essential for accurately simulating ozone in this region.

scholarly journals Long- to short-term denudation rates in the southern Apennines: geomorphological markers and chronological constraints

2011 ◽  
Vol 62 (1) ◽  
pp. 27-41 ◽  
Author(s):  
Dario Gioia ◽  
Claudio Martino ◽  
Marcello Schiattarella
Keyword(s):  
Sediment Accumulation ◽  
Radiometric Dating ◽  
Sedimentation Rates ◽  
Southern Apennines ◽  
Short Term ◽  
Small Catchment ◽  
Fluvial Terraces ◽  
Denudation Rates ◽  
Land Surfaces

Long- to short-term denudation rates in the southern Apennines: geomorphological markers and chronological constraints Age constraints of geomorphological markers and consequent estimates of long- to short-term denudation rates from southern Italy are given here. Geomorphic analysis of the valley of the Tanagro River combined with apatite fission track data and radiometric dating provided useful information on the ages and evolution of some significant morphotectonic markers such as regional planated landscapes, erosional land surfaces and fluvial terraces. Reconstruction of paleotopography and estimation of the eroded volumes were perfomed starting from the plano-altimetric distribution of several orders of erosional land surfaces surveyed in the study area. Additional data about denudation rates related to the recent and/or active geomorphological system have been obtained by estimating the amount of suspended sediment yield at the outlet of some catchments using empirical relationships based on the hierarchical arrangement of the drainage network. Denudation rates obtained through these methods have been compared with the sedimentation rates calculated for two adjacent basins (the Pantano di San Gregorio and the Vallo di Diano), on the basis of published tephrochronological constraints. These rates have also been compared with those calculated for the historical sediment accumulation in a small catchment located to the north of the study area, with long-term exhumation data from thermochronometry, and with uplift rates from the study area. Long- and short-term denudation rates are included between 0.1 and 0.2 mm/yr, in good agreement with regional data and long-term sedimentation rates from the Vallo di Diano and the Pantano di San Gregorio Magno basins. On the other hand, higher values of exhumation rates from thermochronometry suggest the existence of past erosional processes faster than the recent and present-day exogenic dismantling. Finally, the comparison between uplift and denudation rates indicates that the fluvial erosion did not match the tectonic uplift during the Quaternary in this sector of the chain. The axial zone of the southern Apennines should therefore be regarded as a landscape in conditions of geomorphological disequilibrium.

scholarly journals 240+239Pu depositional signatures as a viable geochronological tool in the Amazon Basin

2017 ◽  
Vol 44 (1) ◽  
pp. 142-149 ◽  
Author(s):  
Luciana M Sanders ◽  
Kathryn H Taffs ◽  
Debra Stokes ◽  
Alex Enrich-Prast ◽  
Christian J Sanders
Keyword(s):  
Amazon Basin ◽  
Environmental Science ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Recent Sediment ◽  
Floodplain Lake ◽  
Accumulation Rates ◽  
Amazon Floodplain ◽  
Dating Methods ◽  
Lead 210

AbstractAnthropogenic radionuclide signatures associated with nuclear testing are increasingly utilized in environmental science to explore recent sedimentation. In this study, we assess the suitability of Pu radioisotope analysis in floodplain lake environments in the Amazon Basin to form geochronologies during the 20thcentury. The240Pu +239Pu (240+239Pu) signatures in six sediment cores indicate sediment accumulation rates in the floodplain lakes of the major rivers; Amazon (2.3 mm year-1), Tapajos (10.2 and 2.4 mm year-1) and Madeira (3.4, 4.2 and 6.2 mm year-1). The results from this study show that240+239Pu fallout activities, and the well documented (240Pu/239Pu) atomic ratios of the above ground nuclear tests which began in the 1950’s, are sufficient and well preserved in Amazon floodplain lake sediments to infer chronologies. Lead-210 dating analyses in the same sediment cores produced comparable sediment accumulation rates at three of the six sites. The differences between dating methods may be attributed to the different time scale these dating methods represent and/or in the solubility between Pb and Pu along the sediment column. The geochronologies derived from the240+239Pu and210Pb dating methods outlined in this work are of interest to identify the effects of changing sediment accumulation rates during the previous century as a result of development, including deforestation, along the Amazon Basin which increased towards the middle of the 20thcentury. This study shows that Pu dating provides a viable alternative geochronology tool for recent sediment accumulation (previous ~60 years) along the Amazon Basin.

3000-Year paleoseismological record from the region of the 1988 Saguenay, Quebec, earthquake

1998 ◽  
Vol 88 (5) ◽  
pp. 1198-1203
Author(s):  
Ronald Doig
Keyword(s):  
Active Region ◽  
Lake Sediment ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Recurrence Interval ◽  
Pattern Match ◽  
Local Origin ◽  
Organic Rich Sediment

Abstract The 1988, magnitude mb 5.9 (mbLg 6.5) Saguenay, Quebec, earthquake occurred in a region considered to be aseismic, but the epicenter was less than 100 km northwest of the seismically active region of Charlevoix. Lake sediment cores representing some 3000 yr of sediment accumulation contain abnormal silt layers attributed to seismic shaking events prior to the 1988 earthquake. The layers are formed by the relatively rapid settling of the silt portion of the seismically resuspended organic-rich sediment. Cores were obtained over a distance of 120 km, perpendicular to the Saguenay graben structure. Several silt layers are much thicker and more widely distributed than the effect of the 1988 earthquake and are comparable to those observed at Charlevoix that were produced by magnitude 6 to 7 events. The silting events do not correlate between the sampled lakes nor does the pattern match that at Charlevoix, so that the shaking events are interpreted to be of local origin. The recurrence interval for magnitude ≧6 earthquakes ranges from 350 to 1000 yr, in contrast to the roughly 75-yr historical recurrence of earthquakes of magnitude greater than 6 at Charlevoix.

scholarly journals Variation of carbon contents in eelgrass ( Zostera marina ) sediments implied from depth profiles

2019 ◽  
Vol 15 (6) ◽  
pp. 20180831 ◽  
Author(s):  
Theodor Kindeberg ◽  
Emilia Röhr ◽  
Per-Olav Moksnes ◽  
Christoffer Boström ◽  
Marianne Holmer
Keyword(s):  
Organic Carbon ◽  
Zostera Marina ◽  
Large Scale ◽  
Environmental Changes ◽  
Sediment Cores ◽  
Depth Profiles ◽  
Seagrass Meadows ◽  
Spatio Temporal ◽  
Organic Carbon Storage ◽  
Eelgrass Beds

Seagrass meadows are able to store significant amounts of organic carbon in their underlying sediment, but global estimates are uncertain partly owing to spatio-temporal heterogeneity between and within areas and species. In order to provide robust estimates, there is a need to better understand the fate of, and mechanisms behind, organic carbon storage. In this observational study, we analyse a suite of biotic and abiotic parameters in sediment cores from 47 different eelgrass ( Zostera marina ) beds spanning the distributional range of the Northern Hemisphere. Depth profiles of particulate organic carbon (POC) revealed three patterns of vertical distribution where POC either increased, decreased or showed no pattern with sediment depth. These categories exhibited distinct profiles of δ 13 C and C:N ratios, where high POC profiles had a proportionally larger storage of eelgrass-derived material whereas low POC profiles were dominated by phytoplanktonic and macroalgal material. However, high POC did not always translate into high carbon density. Nevertheless, this large-scale dataset provides evidence that the variability in organic matter source in response to natural and anthropogenic environmental changes affects the potential role of eelgrass beds as POC sinks, particularly where eelgrass decline is observed.

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