Granulometry Assessment of Lom Pangar Dam Sediments (East-Cameroon)

The Lom Pangar dam, the largest reservoir in Cameroon with a storage capacity of 6 km3 and a 30 MW hydropower plant, primarily regulates the hydrologic regime of the Sanaga River to maintain hydropower efficiency during dry seasons and enhance downstream hydropower plant performance. Understanding and managing sediments are crucial for the sustainability of dams, as indicated by numerous studies. This study assessed the granulometry of the sediments transported across the reservoir. For that purpose, 6 samples of fresh sediments were collected in the lacustrine and transitional sections of the reservoir using the standard method. Particles size was assessed using the laser diffusion technic after a 3 mm sieving. Various granulometric parameters were derived from the literature to analyze and characterize those sediments. Results show that silts are more than 70% of particles size and range between 2.19 - 60.26 µm. Size distribution also shows the same trend with D75 less than 51 µm. This is confirmed by the low values of Inman Skewness SkΦ (−0.168 to 0.303). The Sorting index S0 ranges from 0.31 to 0.53 µm, showing a very well-sorted sediments, aligning with low values of Krumbein index (0.906 - 1.683) that express the low heterometry of the particles. The consequence on the dam will be a quick clogging of the bottom of the reservoir. Their pH varies from 7.0 to 7.5. It also appears that the sandy fraction trend is higher in the right bank of the dam and reaches 22% on the right bank of Pangar River due to crystalline geology. Fraction greater than 3000 µm is negligible. The management of the dam has to keep attention to these results as siltation may close the safety outlet of the dam, damage turbines, and provoke recurrent technical and safety issues. Further, the clogging of the bottom of the reservoir may lead to an ecological problem with the limitation of hyporheic flow. Thus, water exchange with the underground water table and the natural purification of water reduce, while increasing sediments deposits change the biogeochemistry processes.

Sedimentological Characterization of Alluvial Gold Deposits of Betrare-Oya and Its Surroundings (Cameroon Eastern Region)

Sedimentological methods such as granulometry, morphoscopy and heavy minerals analysis have been carried out to characterize alluvial gold deposits of Betare-Oya and its surroundings, with the aim to determine their origin and conditions in which they are formed and also to determine the mineralogical content of these deposits, their nature and distribution. It came out from this study the following: The alluvial deposits studied are sand, constituting of coarse fraction (grains), medium grains in abundant and fine grains. The average values of sorting index (S0) and coefficient of asymmetry (A) are respectively 2.53 and 0.73. These values indicate that the sand is poorly arranged and poorly sorted with a better classification or arrangement in the coarse fraction (grains). These are sediments that are deposited together by high competent currents. It would therefore probably be torrential deposits and or streams from short transport. Unused grains are dominating (80.5%) which translate a proximal source of the sediments. So it would be probably from the dismantling of the surrounding landforms. The heavy minerals studied revealed the presence of the following minerals;zircon, gold, sphene, green hornblende, tourmaline, rutile, augite, hypersthene, sillimanite, glau-cophane, biotite, staurotide, and the opaque. These minerals belong to the cortege of plutonic and metamorphic rocks from a single proximal distributing province.

Age and Calcium Sources in Laying Hen Feed Affect Calcium Digestibility

The apparent calcium (Ca) digestibility coefficient (ADC) and true digestibility coefficient (TDC) of different inorganic calcium sources were determined in laying hens of different ages. Three Ca digestibility tests were carried out, each assessing 240 Lohmann Brown lineage laying hens distributed in a completely randomized design. Nine dietary treatments were arranged in a 3 × 3 factorial design consisting of three ages (40, 50 and 70 weeks) × three Ca (dicalcium phosphate (DCP) sources, fine (FL) and coarse (CL)) limestone, comprising eight replicates per treatment of six birds per experimental unit. Regarding the DCP, the ADC was higher (P < 0.05) in 40-week-old birds. The DCP ADC for 40-, 50- and 70-week-old birds was 0.889, 0.613 and 0.712, respectively. No effect (P > 0.05) of age on the ADC was noted for either FL or CL. Comparing Ca sources, DCP exhibited a higher (P < 0.05) ADC (0.889), followed by FL (0.699) and CL (0.515), in 40-week-old birds. DCP (0.712) and FL (0.652) presented (P < 0.05) higher ADC compared to CL (0.482), in 70-week-old birds. No effect of Ca sources at 50 weeks on the ADC was observed (P > 0.05). Endogenous loss values of 790, 860 and 930 mg·kg-1 of consumed dry matter were observed at 40, 50 and 70 weeks, respectively. For the TDC, no interaction (P > 0.05) was observed between Ca sources and bird age. The highest TDC value (P > 0.05) was found in birds fed DCP (0.786) followed by FL (0.637) and CL (0.534). In addition, birds at 40 weeks of age (0.714) exhibited higher TDC values (P < 0.05) compared to animals at 50 weeks of age (0.608). The findings reported herein demonstrate that the true digestibility is greater in the youngest birds and that consumed the DCP and the FL in relation to the birds that consumed the CL.

Comparative Study of Physico-Chemical Properties of Sediments from Two Sectors Close to Bandama in Northern Côte D’Ivoire (Sinematiali and Niakaramadougou)

This study aims to show the impact of successive floods on the spatial variation of the physico-chemical properties of sediments along the Bandama River in the localities of Sinématiali and Niakaramadougou because of their importance in the functioning of this ecosystem. Several samples were taken from both stations based on flood recurrence areas. The particle size analysis was done using the Robinson’s Pipette method. Traditional methods of sediment analysis have been used to measure organic carbon (O.C.), nitrogen (N), and other chemical properties including pH, organic matter (MO), and C/N ratio. Statistical analyzes were carried out to assess the differences between the physico-chemical parameters of the different sampling zones. In the area of niakamadougou, the lower values in MO were recorded in areas subject to more frequent flooding, thus close to the watercourse. In the Sinématiali area, lower M.O. values were recorded in sediments far from the stream. Total organic matter levels are higher in surface sediments with the lowest proportions of clay. The results show that the physico-chemical properties of the sediments vary at the level of the vertical distribution and according to their spatial distribution. Successive floods have a direct effect on the dynamics of the physico-chemical properties of sediments along the shore.

Physical Characterization of Batie and Bandjoun-Djione Sands(West-Cameroon),Used in the Manufacture of Concrete:Improvement of Resistance to Compression

The objective of this work, was to characterize the sands of the quarries of: Bandjoun-Djione, Djengou, Hiala and La’gou I, mainly from their mechanical strengths, the equivalent of sand and the finesse module. In order to study the compressive strength of concrete made from these sands, we determined their granularity, fineness modulus and density;the concrete was then formulated by the Dreux-Gorisse method. A total of 72 specimens were constructed with the objective of achieving an average compressive strength of 25 MPa at 28 days. But we have obtained a compressive strength at 28 days, varying from 13.14 MPa to 17.50 MPa. The correction of the modulus of fineness of these sands made it possible to improve the granularity and increase the compressive strength of these concretes by more than 70%. We have thus obtained the compression resistance of 25 MPa aimed for each of the corrected sands.

Contribution of different granulometric populations to powder reactivity

In this article, different population contributions of quartz powders to chemical reactivity in pozzolanic reaction were studied. Deconvolution software was used to show the different particle populations of each product. Reaction of quartz powder with lime in the pozzolanic reaction at 20 ℃ shows that reactivity of each powder population depends on its particle size. Adsorbed fine particles on coarse particle surfaces have a significant role in the first term of the reaction. In a second term, the micropowders react. The mesopowders react only in the last reaction terms. Until now, the reactivity of adsorbed powder has been attributed to amorphization of the particle surface.

Effects of type, level and time of sand and gravel mining on particle size distributions of suspended sediment

Monitoring the sediment transport behavior induced by different interventions, particularly sand mining from rivers, is needed to adaptively manage the watersheds. The particle size distribution of the sus-pended sediment in up and downstream of rivers is one of the main indicators to know about fate of sediments, which may be varied in different conditions. We investigated the effect of some types of sand and gravel (i.e., manual and low, semi-heavy, and heavy machinery) mining on particle size distribution of suspended sediment in the Vaz-e-Owlya, Vaz-e-Sofla and Alesh-Roud riverine mines located in Ma-zandaran Province, northern Iran. The study was conducted on a monthly basis from February, 2012 to January, 2013. Laser granulometry was used to analyze the particle size distribution of suspended se-diment samples taken from up and downstream sections of the study mines. The results revealed that the level and intensity of mining activity affected particle size distribution of suspended sediments. Further statistical assessments in up and downstream sections of the mines proved that sorting, D50, mean, D90, kurtosis, skewness and D10 of the suspended sediment were not significantly influenced by mining activities at levels of 0.09, 0.11, 0.12, 0.15 to 0.69, 0.15–0.69, 0.77, 0.87, 0.97, respectively. While it was not statistically significant, we found that the type of mine and the level of the exploitation changed the particle size distribution of the suspended sediment.