Sedimentation Rates Research Articles

Evaluating TLR4 Gene Expression to Monitor Disease Progression in Iraqi Patients with Rheumatoid Arthritis

Background: Toll-like receptors (TLRs) play a significant role in the activation of adaptive immunity and may have an essential role in the development of rheumatoid arthritis (RA). Objectives: To assess the gene expression of TLR4 in individuals with RA compared to healthy individuals. Methods: From July to December 2022. A total of 100 individuals were encompassed in the study, consisting of 50 individuals diagnosed with RA, of whom 42 were females and 8 were males, with an average age of 45.22 years. Additionally, there were 50 healthy control participants, 40 of whom were females and 10 were males, with an average age of 45.64 years. To assess the TLR4 transcript levels, blood samples were collected from each participant, and RNA extraction was performed. cDNA synthesis was carried out, and real-time PCR was utilized for the analysis. The researchers also assessed the clinicopathological characteristics of the patients. Results: The serum TLR4 gene was significantly overexpressed in RA patients (fold change 2.59) compared to the controls (fold change 1.07). The expression level of the TLR4 gene was correlated with the clinicopathological characteristics of the patients, including erythrocyte sedimentation rates (ESR), RF, anti-CCP antibody, and DAS28. Conclusion: TLR4 was overexpressed in RA patients and was correlated with disease activity. It might be a therapeutic target and may contribute to the pathogenesis of RA.

Identification of modern meteoric water, glacial meteoric water, and fossil seawater in a deep borehole at the coastal area of Horonobe, north Japan, using groundwater dating and paleoclimatic proxy methods

Groundwater flow in deep areas of coastal regions has attracted significant attention for geological radioactive waste disposal or geological CO2 storage. To investigate groundwater flow in coastal areas, groundwater dating methods with the potential to assess slow groundwater flow were used at depths of up to 1200 m at Hamasato, Horonobe, northern Japan. Multiple groundwater dating methods were applied using pore water in drilling core and pumping groundwater. This study shows that modern meteoric water, glacial meteoric water, and fossil seawater are distributed in sand and silt layers at 300–360 and 90–300 m in depth and in silt and mud layers below 800 m in depth, respectively. Modern meteoric water infiltrated after and glacial meteoric water infiltrated during the latest glacial period were identified using δD and δ18O values, estimated recharge temperature from noble gas concentrations, and 14C concentrations. The estimated recharge temperatures of modern and glacial meteoric waters were 8.1 ± 2.0 and 2.1 ± 2.0 °C, respectively, whereas the δD and δ18O values were −68 ± 3‰ and −10.3 ± 0.2‰, −81 ± 2‰ and −11.4 ± 0.3‰, respectively. The 14C age of modern meteoric water was 10–16 ka. However, the 14C age of glacial meteoric water could not be estimated because it was highly diluted by 14C-free CO2 from methanogenesis and marine carbonate dissolution. Fossil seawater was identified using δD, δ18O, 36Cl, and 4He. δD and δ18O values underwent water-rock interaction and approached inland fossil seawater with increasing depth. 36Cl/Cl values did not reach secular equilibrium in situ in the Yuchi Formation due to its relatively short geological age and consolidation-induced porosity changes. However, the Yuchi Formation seawater is considered extremely old because its 36Cl/Cl ratio is higher than that of modern seawater as a result of 36Cl production, which also explains the observed 36Cl/Cl increases with depth toward the secular equilibrium ratio (36Cl/Clse). 4He concentrations were in the order of 10−6 ccSTP/gw, corresponding to an in situ accumulation age of 1–2 Ma, neglecting the external flux. The contribution of external flux could be negligible for the short geological age and rapid sedimentation rates. 4He ages were equivalent to the geological age of the Yuchi Formation. Core investigations can interpolate groundwater investigations because cores, particularly those from low-hydraulic conductivity layers, can be collected continuously. In addition, stable and radioactive isotopes and noble gases can help identify modern meteoric water, glacial meteoric water, and fossil seawater, assisting in understanding the groundwater flow velocity.

Carbon stocks in the mud areas of the Chinese marginal seas

Continental marginal seas are key systems in the global carbon cycle. Carbon stocks represent the ability to store carbon, thus quantifying the carbon stocks in marine sediments would help to better understand their importance in the carbon cycle. In this study, 17 sediment cores in the mud areas of the South Yellow Sea and the East China Sea were measured for total organic carbon (TOC) and its stable isotope (δ13C), and dry bulk density; and from which the carbon stocks and carbon stock accumulation rate as well as marine/terrestrial carbon stocks/carbon stock accumulation rate were calculated. The carbon stocks in the mud area of the South Yellow Sea showed a decreasing trend during 1855 to 1950 caused by the relocation of the Yellow River Estuary in 1855, but increased after 1950s due to increased sediment input via the enhancement of South Shandong Coastal Current. In the Min-Zhe belt of the East China Sea, carbon stocks showed an overall high marine proportion due to the phytoplankton bloom induced by high nutrient level, but the decreased carbon stocks in recent decades were mainly caused by the construction of reservoirs in the Yangtze River that reduced sediment transports. The average carbon stocks in 1 m sediments from the South Yellow Sea (45.2 t ha-1) and Min-Zhe belt (52.8 t ha-1) were low compared to that of global marine sediments (66.6 t ha-1), while the carbon stock accumulation rate showed much higher values (0.1 t ha-1 yr-1 in South Yellow Sea and 0.31 t ha-1 yr-1 in the Min-Zhe belt) because of higher sedimentation rates. Although carbon stocks of Chinese marginal seas were also lower than that of the tidal flats (70.7 t ha-1) and wetland (123.6 t ha-1) in China, their much larger area could store 0.75 Pg C in marine sediments. Our temporal records suggest that anthropogenic activities have reduced carbon stocks in the marginal seas since 1950, causing carbon to re-enter the atmosphere to impact climate changes.

Morphological Response of a Highly Engineered Estuary to Altering Channel Depth and Restoring Wetlands

Estuaries are continuously adapting to anthropogenic pressure. Because of sea-level rise and reduced fluvial sediment supply, they are at risk of sediment starvation. Contrarily, some estuaries require frequent dredging after artificially deepening the channel to maintain port operations. To optimize current estuarine functions and make estuaries more resilient to future threats, improved understanding of estuarine development after system changes is essential. This paper investigates the estuarine response related to two large-scale human interventions: (1) altering channel depth, following global trends of channel deepening for port navigability; and (2) creating or restoring wetlands, a nature-based solution increasingly explored for its ecosystem services. A schematized 2D-morphological model is set up using Delft3D-FM reflecting a highly engineered estuary in a micro-tidal and wave-dominant environment. Results demonstrate how channel deepening (from 13 m to 17 m, without wetland presence) increased sedimentation in the channel by +31%. Sedimentation rates in the wetland were mostly unaffected by channel depth. After restoring the wetland area (wetland width from 0 km to 1 km, constant channel depth of 15 m), sedimentation within the channel was reduced by −72%. The wetland area not only served as sediment sink, but also increased the tidal flow, diminishing sedimentation throughout the estuarine channel. Further analysis showed that restoring wetland areas along a specific segment mostly affected channel sedimentation locally (i.e., at the channel segment along the restored wetland). As such, to alleviate dredging operations at critical locations in the navigation channel, strategic restoration of wetlands can be considered which can provide a sustainable alternative to dredging within highly engineered estuaries.

Study on the Design and Implementation of BPPT-lock Armored Groin for Sediment Control Structure in Front of Sea Water Intake

High rate accumulation of sediment materials in front of the sea water intake (SWI) of a petrochemical factory cooling water system has caused high maintenance dredging costs. A study was conducted to identify the pattern and rate of sedimentation and to find an engineering solution that enables controlling sedimentation rate reduction. Based on numerical simulation, it is identified that the existing total rate of sedimentation around the channel in front of the SWI is 50cm/year. Further numerical simulation series revealed an optimum mitigation scenario by the construction of a pair of groin along both sides of the channel in front of the SWI as a sediment control structure. Under this scenario, the average bed level change becomes 0.10 cm/year and the maximum value of the bed level change is around 24.96 cm/year. A BPPT-lock armored rubble mound-type structure was designed for this sediment control groin by considering its feasibility, ease of construction, and local availability of structure materials. BPPT-lock is selected due to its high hydraulic stability (KD) of 17 for the trunk application and 13 for the head application. It is found that about twenty-five percent more armor unit numbers were required at the final stage of construction compared to the designed one. The actual method of armor unit placement and arrangement during construction is considered the main cause of this difference. In this case, the calculation was designed for random placement, but the actual construction was in uniform placement. To provide economical insight, a calculation was made to compare the construction budget requirement between this constructed groin armored with BPPT-lock and if the same structure armored with tetrapod. The calculation result shows that BPPT-lock armor units required 64% less budget compared to the tetrapod.

Characteristics and environmental significance of organic carbon deposition in Baiyangdian Lake, China, 1969–2020

Lake sediments provide a basis for ecological information that can reconstruct the history of a lake ecosystem and clarify the carbon sink process. We combined chronological information relating to sediment cores in Baiyangdian Lake with the history of human activities, to examine the influence of the natural environment and human activities on the humification of organic carbon. This analysis revealed the evolution of the ecological environment in the lake over the past 50 years. The results showed the average deposition rate of sediments to be 0.957 cm/a; with the total organic carbon and total nitrogen contents of sediments ranging from 14.32 to 333.19 g/kg and from 0.95 to 26.90 g/kg, respectively. The δ13C values ranged from −13.04 ‰ to −29.07 ‰, while the δ15N values ranged from −1.43 ‰ to 8.37 ‰. The fulvic acid carbon (FAC) content ranged from 0.52 g/kg to 14.21 g/kg, and the humic acid carbon (HAC) content ranged from 1.67 g/kg to 23.82 g/kg. The HAC/FAC value gradually increased as the sediment deepend. The results of each index in the sedimentary column, combined with the dating information, allowed us to conclude that, from 1969 to 1985, human activities had little effect on the lake, and the source of organic carbon and the humification process remained stable. During this period, the water purification function of the lake continued to improve. From 1985 to 2014, the surrounding economy developed rapidly, resulting in significant changes in the lake's ecological structure and the distribution of lake plants. Serious eutrophication occurred, leading to increased pollution Between 2014 and 2020, the lake protection measures implemented achieved initial positive results. During the period, the source of organic carbon and the humification process stabilized, eutrophication was alleviated, and the burial and fixation of organic carbon gradually reached a healthier state.

Phosphorus cycling during the Hirnantian glaciation

Unlike other mass extinctions of the Phanerozoic, the Late Ordovician mass extinction took place during an icehouse interval, accompanied by the glaciation of Gondwana. Ice sheets reached their maximum during the Hirnantian and global sea-level dropped substantially. Consequently, the shallow tropical shelf environments of Laurentia and Baltica became subaerially exposed or remaining submerged shelves were characterized by very shallow water-depths. Redox proxies suggest that most shallow shelf settings were well oxygenated to that time, while the global extent of anoxic environments increased, implying that deoxygenation was confined to the open ocean. We speculate that the burial rate of the nutrient phosphorus (P) on shelves was minimal during the Hirnantian glacial maximum (HGM) due to bypass of the shelves in respect to the incoming riverine dissolved load. Hence, a large excess of bioavailable P entering the open ocean would have stimulated phytoplankton production which lowered oxygen concentrations by aerobic respiration.In order to test this hypothesis, we determined reactive P (Preact) contents in two low-latitude carbonate successions (Anticosti Island and Estonia) spanning the HGM. Moreover, we measured total organic carbon (C) concentrations and calculated C/P ratios to evaluate the burial efficiency of P. Samples from both sites are characterized by overall low Preact contents. We observe a decreasing trend in Preact towards the HGM, reaching a minimum during the initial transgression thereafter. C/P ratios suggest efficient P-burial throughout the study interval and, hence, Preact contents are assumed to be a direct measure of primary productivity, P-availability, and P-burial. Using the Preact concentrations, we modeled shelf P-burial fluxes with estimates for global shelf area and sedimentation rates. The model suggests that shelf P-burial fluxes around the HGM were approximately halved due to a reduced shelf area and minimum Preact contents. With the assumption of a constant P-input to the ocean, the proposed scenario serves as a plausible explanation for the observed redox gradients.

Depositional phases of Neogene rocks based on palynofacies and inorganic geochemical analyses in Nile Delta, Egypt: A focus on organic matter accumulation

The depositional phases of the Nile Delta are investigated based on the palynofacies and geochemical analyses in samples from two studied wells Baltim-1 and NDOB-1 wells. These depositional phases determine the ability to produce and preserve the organic carbon. The Nile Delta's hydrocarbon system is based mainly on the Neogene rocks, particularly those ranging from the Late Miocene to the Pleistocene, where environmental conditions governed organic matter accumulation. The depositional history in this region is related to the activity of sediment input by the different phases of the Nile River and their ability to transfer the sediments and terrigenous organic matter. Multivariate statistical analyses of the palynofacies revealed four types, namely distal-high oxic type A, proximal-suboxic type B, proximal-dysoxic type C, and distal-oxic type D. In addition, proximal-distal and oxygen depletion trends were identified based on the values of the principal components analysis (axis 1). The characterization of the palynofacies types incorporated inorganic geochemical analysis of trace elements to determine environmental gradients, were compared to the values of organic matter (0.27–1.18 wt% TOC). Organic matter concentrations were low during most depositional phases despite the active influx of the terrigenous organic matter and the productivity of marine organic matter. These results can be attributed to the Nile Delta region's depositional phases identified from the palynofacies types and major element oxides. It is inferred that the Nile River delivered a high rate of sediments into the basin, in addition to nutritious material that increased the sea surface paleoproductivity of marine organic matter. However, the high sedimentation rate during the different depositional phases did not attain the optimum threshold to preserve organic carbon in high concentrations.

Impact of magnesium on the flocculation, sedimentation and consolidation of clay-rich tailings in lime-treated seawater

The sustainability of the mining industry in times of climate change, especially in arid regions, rests on seawater. However, now more than ever, it is necessary to optimize processes regarding water consumption and increase recovery and recirculation, including water trapped in tailings dams. Seawater also offers challenges, for example, the condition in which it must be used. This study examines the effects of raw seawater (SW) and lime-treated seawater to reduce Mg content (TSW) under strong alkaline conditions (pH 11) on the flocculation, sedimentation, and consolidation of flocculated quartz-kaolin suspensions using a high molecular weight anionic polyacrylamide as a flocculant. The presence of magnesium precipitates in SW, mainly magnesium hydroxide, leads to sedimentation rates of flocculated quartz-kaolin suspensions considerably lower than in TSW because the aggregates in SW are smaller than in TSW, according to chord size analyses. The precipitates interfere in the flocculant-particle interaction, limiting the adsorption of the flocculant and its ability to form bridges of any kind, polymeric or salt, with the tailings particles. However, Mg precipitates act as short-range and limited extension binders compared to flocculants increasing the resistance of the aggregates much more in SW than in TSW in processes without and with flocculant, whether it is measured as yield stress, elastic moduli, or compressive yield stress. Thus, the new result is that Mg precipitates are responsible for most of the resistance to consolidation of quartz-kaolin suspensions and, therefore, should be avoided. Therefore, TSW should be the choice to facilitate water clarification in thickeners and water recovery from the consolidation of deformable tailings aggregates.

Investigating the mineralogical and geochemical composition of fluvial sediments of Watari river system, Kano, Nigeria

A key objective of this research is to conduct a mineralogical and geochemical screening of the fluvial sediments in Watari river. Data collected from this study can be used to further enhance scientific understanding of the fluvial processes in the Watari basin as well as the larger Hadejia-Jama' are basin. The geological data can also be used as input information for the prediction of sedimentation rates in the Watari dam, Kano. An intensive field was conducted to explore thebedforms (sand bars, ripples, and sand filled channel or dunes) of the proximal channel environments, platform geometry and sinuosity.X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses were used to study the mineralogy and chemical composition of the collected samples, respectively. The Watari river can be considered as braided due to the presence of smaller multi-threaded channels, braid or channel bars. The lithology of exposures observed at the river bank show a series of depositional cycles that comprise mudrocks (light and dark), sandstone, conglomerate and a basal quartzitic gravel deposit. The wacke and sub-litheranite rocks were sourced from mafic and intermediate igneous rocks. The relatively high La and Ce in the mudrocks can be attributed mainly to the adsorption of Ce onto Fe-oxides which are abundant in the fluvial sediments eroded from lateritic soils. From the bivariate plot of Al2O3/SiO2 against Fe2O3+MgO, the sandstone facies fall under the passive continental margin, while the quartzite and conglomerate facies are grouped under the foreland basin, and the light mudrock facies is classified under the continental island arc. In addition, the plot of Al2O3/(CaO + Na2O) against Fe2O3+MgO shows the sandstone and quartzite facies fall under the foreland basin. The relatively high concentration of feldspar and muscovite mica in the siliciclastic facies is indicative of close proximity to parent material, and low degree of weathering and diagenesis. The variability in the mineral composition points toward different cycles of fluvial sedimentation, diverse provenance, and wide range of source materials.The geochemical data further buttresses the variability in provenance, wider geographic area of the sediments or re-deposition and reworking by fluvial actions.

Holocene hydroclimate stability in three lake sediment records from the southeastern United States

Many Holocene paleoclimate records from the southeastern United States (SE US) have limited chronological constraints and/or low sedimentation rates and consequently low resolution; this presents challenges in discerning the relative importance of synoptic–scale drivers of past hydroclimate. In this study we summarize three lake sediment records that are uniquely located to test hypotheses regarding the importance of the Pacific North American (PNA) pattern and the North Atlantic Oscillation (NAO) over the last 5000 years. At Pigeon Marsh, Buck Pond, and Halls Pond, we used sedimentological (radiocarbon dating of transect cores), physical (grain size), geochemical (carbon and nitrogen ratios and isotopes), and biological (palynomorphs) proxies to reconstruct lake level and lake environment. Moderate lake and environmental changes occur around 2000 cal yr BP at Buck and Halls Pond, which is regionally consistent with other paleorecords and may suggest that the NAO was an important control. However, our results generally indicate fairly stable hydroclimate conditions up until historical European settlement when land clearance caused vegetational and lake hydrologic balance changes that were unprecedented in both magnitude and rate compared to the middle/late Holocene.

Consolidation analyses of PVD-improved marine clay considering long-term natural sedimentation

An analytical solution is derived to calculation the consolidation of marine clay improved by vertical drains under long-term natural sedimentation conditions based on Gibson's one-dimensional consolidation theory and Barron's free-strain theory. The model tests are conducted to verify the accuracy of the proposed theoretical model. Fair agreements between the results from laboratory tests and proposed theory verified it accuracy. Parametric studies are also conducted to investigate the effects of the clay deposition properties and time-dependent sedimentation rates on the consolidation of the marine clay. Under the selected parameter conditions in this article, for the deposition rate of clay deposition layer, k/(2Ch)=1, the maximum of excess pore water pressure keeps stable and is close to 6 kPa. The maximum difference in excess pore water pressure at the bottom of clay deposition layer is approximately 40.1 kPa under two conditions of deposition rate of 0.5 and 10. The average degree of consolidation U of the soil layer after 100 and 200 days of sedimentations are 86 % and 97 %, respectively.

Quantitative analysis of the Martian atmospheric dust cycle: Transported mass, surface dust lifting and sedimentation rates

The atmospheric dust cycle on Mars plays a dominant role in the planetary radiative balance, atmospheric photochemistry escape, and redistribution of materials on the surface. Although this planetary dust cycle has been extensively modelled and characterized with both orbital and in situ observations, to date little is known about the total mass of dust that is circulated, the actual dust lifting and settling rates, and the main dust sources and sinks. Using orbital global and seasonal measurements of atmospheric dust opacity, a data reduction methodology that can describe the annual dust redistribution cycle on a planetary scale with 95% accuracy is presented. The method was applied to the 9.3 μm infrared observations of the Thermal Emission Spectrometer (TES) aboard the Mars Global Surveyor (MGS) during two full Martian Years (MY) 25 and 26, and partly MY 24 and MY 27, disregarding the global dust storm that occurred in MY 25. By comparison with terrestrial observations, a mass-to-extinction conversion factor of 1.9 ± 0.3 g m−2 is proposed, assuming a dust density of 2.6 g cm−3. The analysis shows an estimation of 400 1012 g of dust transported globally in the atmosphere for a typical Mars year, which is comparable to the minimum total annual mass of dust transported on Earth. The methodology proposed here is based on remote sensing and cannot disentangle completely local surface lifting and sedimentation rates from dust advection. However, this analysis provides upper bounds which can be compared with in-situ observations. The analysis of the dust sedimentation cycle suggests that the annual cycle might produce a dust layer of about 50–100 μm on the surface of some particular zones, as Valle Marineris or Meridiani Planum. This estimation agrees with in-situ observations of rovers on Mars. The potential dust sources are mainly located from latitudes of 20°S to 60°S. Our results find the 70% of the sources previously identified by the existing planetary circulation models. This kind of large-scale analysis can be applied to other remote sensing observations to refine these calculations and study the annual and geographical variability of the dust-mass transport on Mars.

Numerical modeling of vadose zone electrical resistivity to evaluate its hydraulic parameters

Studying and determining the physical properties and hydraulic parameters of vadose zone sediments is an important key to evaluate the infiltration rate into them and assessing the extent to which aquifer sediments benefit from rainwater harvesting in arid and semi-arid areas. Due to the lack of sufficient data on the characteristics of this zone depths, a numerical modeling was used to simulate the electrical resistivity of these sediments by applying the electrical resistivity method, because it is the most affected by the physical properties of dry and wet sediments. This study was applied as a proposal for application in northwestern KSA to calculate the vertical hydraulic conductivity and transmissivity for the vadose zone. This was implemented by assuming a three-layer model using COMSOL Multiphysics model with different electrical resistivity values depending on some in situ electrical resistivity measurements for shallow depths. Hence, the infiltration rate of sediments in this area can be predicted with depth and its effect on aquifer recharge. The focus was on calculating the vertical hydraulic parameters of the most widespread surface sediments with depth and comparing the results of calculating these parameters for some sediments laboratory-wise to ensure their accuracy. Then, their infiltration rate was inferred separately with depth, predicting their ability to aquifer recharge and make the most of rainwater harvesting. Finally, this study can be considered as a preliminary study to determine the expected forward model of electrical resistivity and hydraulic parameters values for the vadose zone sediments with depth along the area and in any other areas, and then apply them accurately in situ to estimate the extent of its usefulness in rainwater harvesting, especially aquifer recharge.

Salt sheet extrusion and emplacement within the South-Central Pyrenean fold-and-thrust belt: the Les Avellanes Diapir case-of-study

ABSTRACT A detailed geological map of the Les Avellanes salt Diapir (South-Central Pyrenees, Spain) that includes both the diapir body and adjacent areas is presented to understand the diapir evolution and geometry. Structural, stratigraphical, and sedimentary data north and south of the diapir is used to infer the timing of its emplacement. The northern diapir boundary is characterized by a set of extensional faults oblique to the main Pyrenean trend, while the southern boundary is an extrusive salt sheet that overlays the late Eocene-early Oligocene sequence in three adjacent sub-basins. Salt extrusion occurred due to synorogenic folding. The topography created as salt extruded trapped the arrival of external sediments from the north, blocking the transport pathways southward. Low sedimentation rates southwards allowed for the lateral salt extrusion, advancing southwards from the feeder. The salt sheet emplacement was postdated by Oligocene conglomerates, indicating that the salt extrusion was a relatively quick event.

Concentration gradient inversion via sedimentation of coffee grounds in full immersion brewing

In full immersion brewing methods, the coffee grounds are fully submerged in water during the brew and then filtered out prior to consumption. If the brew is not agitated, most of the coffee grounds quickly float to the surface, but then eventually sediment to the bottom as they de-gas and become less buoyant. Although this behavior is readily observed, little research has investigated the impact of the transient sedimentation process on the concentration profile of total dissolved solids (TDS) within the brew. Here, we report that unagitated full immersion brews undergo a concentration gradient inversion midway through the brewing process and that the time scale of the inversion depends sensitively on the roast level of the coffee grounds. Systematic measurements of the TDS versus both depth and time reveal that the brew contains a region of nearly twice the concentration near the top air/liquid interface at the beginning of the brew, but then the higher concentration region inverts to the bottom of the container as the brew progresses. Time-lapse photography observations indicate that the time scale of the gradient inversion is consistent with the average rate of sedimentation, which occurs up to a factor of three slower for darker roasts. A key implication of our results is that sensory evaluations obtained via the traditional “cupping” method used widely in the coffee industry might be confounded by differences in TDS for different roast levels.

Reassessment of Reservoir Sedimentation Rates under a Monsoon Climate with Combined Optical and Microwave Remote Sensing: A Case Study of Three Reservoirs in the Upper Godavari Basin, India

Reassessment of Reservoir Sedimentation Rates under a Monsoon Climate with Combined Optical and Microwave Remote Sensing: A Case Study of Three Reservoirs in the Upper Godavari Basin, India

Using Cs-137 measurements and RUSLE model to explore the effect of land use changes on soil erosion and deposition rates in a mid-sized catchment in southern Italy

In some areas of southern Italy, the change in land use over the last 4–5 decades has increased pressure on land and water resources and caused different forms of soil degradation. In order to mitigate the magnitude of soil erosion, different strategies that include construction of flood control structures and reforestation programs have been done in several areas. However, quantifying the effectiveness of these strategies is difficult in absence of direct measurements of soil erosion. To cover this information gap, the use of distributed numerical models coupled with measurements of the radionuclide cesium-137 (137Cs) offers a good alternative to the classic experimental sites (plot, catchments) that, on the contrary, require long term datasets to produce reliable estimates of soil loss. In this paper, measurements of 137Cs in a floodplain area are firstly described for a representative Calabrian catchment as an example to reconstruct the trend of soil deposition rates during the last six decades. These measurements have been integrated with estimates of soil loss obtained with the Revised Universal Soil Loss Equation (RUSLE) model for which land use maps of different periods are available. The final comparison between estimates of soil erosion provided by the RUSLE at catchment scale and sedimentation rates derived from 137Cs measurements on depositional areas allowed interesting information on the trend of soil erosion and deposition rates in these areas to be obtained.

Application of 137Cs tracer technique in floodplain deposition research in mesoscale river basins

Floodplain deposition can provide important historical information about river systems. 137Cs tracer measurement is the most widely used technique for studying floodplain deposition. One-time sampling is normally used to date or estimate erosion and deposition rates, while time-interval sampling has rarely been applied. Northeast China is an important grain production area characterized by intense erosion and a low sediment transport ratio. Most studies of the region have focused on slope sedimentation, while floodplain sedimentation has received little attention. In this study, two-time steps of cross-sectional sediment core sample collection were performed to examine the floodplain sedimentation in the river basin of the Laolai River, a tributary of the Songhua River. The potential for using 137Cs to estimate the sediment deposition rate for a given time-interval was also investigated. A total of 18 cross-sections were acquired, and three repeated cross-sections were selected for double sampling. Significant differences were observed between the results obtained from the samples collected in separate rounds, suggesting the presence of internal heterogeneity during floodplain sedimentation and a significant influence of sampling positions on the analysis results. In the basin examined, sedimentation often occurs midstream, upstream, and at the outlet, and was mainly affected by topography, reservoir construction, and land use. Sedimentation occurs easily at wide, flat outlets or river intersections in braided water systems. It was observed that downstream floodplain sedimentation was increased by sediment interception by upstream reservoirs, but reduced by forests near floodplains. Sedimentation rates were significantly different between the 1954 and 1963 time markers, and we found that using rates from 1954 alone would lead to underestimation. When 137Cs sedimentation and floodplain distribution are used to determine flooding occurrence, variations in 137Cs content and particle size distribution should be considered. River bank erosion in this region should be taken into account, and riparian protection is required to reduce erosion and floodplain deposition. Since 137Cs is absent in fine particles when the sediment is predominantly sand, 137Cs measurement may underestimate the sediment deposition rate.

The SEDIMENTOLOGICAL ANALYSIS, DEPOSITIONAL ENVIRONMENT AND SEQUENCE STRATIGRAPHIC STUDY OF IDA 4, 5, 6 WELLS NIGER DELTA BASIN, NIGERIA

Sequence stratigraphic study divides sedimentary successions into unconformity or maximum flooding surface bounded units (sequence) that form during a single, major cycle of sea-level change. Detailed sedimentological and sequence stratigraphic studies of the strata penetrated by Ida-4, 5, and 6 wells were carried out to deduce the depositional environment and correlate the stratigraphic units. The wells are located in the coastal swamp depobelt of the Eastern Niger Delta. Studied samples were dry-sieved for sedimentological analyses. Each fraction was studied under reflected light microscope. The lithology consists of an alternation of shale and sandstone units. The grain size of the sandstone units consists of fine to medium grains, occasionally coarse to granule-sized grains. Dominant accessories minerals are ferruginous materials, shell fragments, carbonaceous detritus, and few records, of mica flakes, glauconite, and pyrite. Regular sand and shale intercalation pattern on the Gamma Ray log permitted easy recognition of sub-cycles (autocycles) of sedimentation in an extensively developed paralic sequence. Paleoenvironmental reconstruction using accessories minerals recognizes shallow water settings with intermittent deeper water conditions. Rapid sedimentation rates are inferred in the studied area based on the observed alternation of thick sandstone, shale, and mudstone units. The MFS and SB were dated 9.5 Ma and 10.35 Ma respectively. Lithologic and system tracts correlations show lateral continuity of sandstone units (potential reservoirs) depicted in the lithofacies subcycles correlation. This is useful in the determination of reservoir geometry, areal coverage, and calculation of the volume of accumulated hydrocarbon, and directing well trajectory during the drilling operation.