Dam Sediments Research Articles

PENGARUH SEDIMENTASI TERHADAP KAPASITAS TAMPUNGAN PADA AKHIR UMUR EFEKTIF (T50) WADUK KARIAN

Karian Reservoir is one of The National Strategic Projects. Located in Lebak Regency, Banten Province, Karian Reservoir has 207.48 Mm 3 effective storage, 46.4 Mm 3 dead storage and 50 years lifetime. In the dam management, one of the problems that often occurs is sedimentation. To overcome this problem, we need to know the sedimentation rate and distribution pattern of Karian Reservoir for optimalizing the reservoir management. To predict the distribution pattern of the reservoir we use Empirical Area Reduction Methods. The findings of the study show that the sediment volume of the reservoir throughout its effective life is 86.50 Mm 3 , the new zero elevation is +37.2 m, the remaining dead storage is 7.62 Mm 3 and the remaining effective storage is 167.19 Mm 3 . This indicates that theoretically the reservoir will work well up to its effective life but the dam sedimentation management must be planned because sediment not only deposit on the dead storage but also on effectife storage.

Numerical simulation of mechanical characteristics of concrete face rockfill dam under complicated geological conditions

In order to control the deformation of concrete face rockfill dams and improve the safety and stability of concrete face rockfill dams, this study uses the finite element analysis method, statistical analysis method, and numerical calculation to systematically study the stress and deformation characteristics of concrete face rockfill dam and its anti-seepage wall under complex geological conditions. The numerical simulation of the secondary development platform based on finite element software shows that the deformation caused by the foundation compression deformation, rheological deformation, and hydraulic coupling effect is the main cause of the large deformation of the overburden dam on the overburden layer. Among them, the foundation compression deformation is the main source of foundation deformation, and the deformation caused by rheological deformation and hydraulic coupling effect is the main source of secular deformation. Rockfill compression deformation is the main source of dam deformation, and the contribution of rheological deformation to dam deformation is greater than that caused by hydraulic coupling effect. In this study, the stress deformation and leakage characteristics of concrete face rockfill dam are analyzed, and the statistical laws of mechanical properties of concrete face rockfill dam are revealed. The sedimentation of the dam crest of most concrete rockfill dams is less than or equal to 0.40% H (H is the height of the face rockfill dam), and the sedimentation of most dams during the completion period is less than 1.0% H. After water storage, the panel deflection is close to the dam crest sedimentation value. Most of the dam’s panel deflection is less than 0.40% H, of which more than half is less than 0.2% H. Large rockfill deformation is the main cause of panel tensile stress, as well cracking and crushing damage.

Hydraulic - Electrical Flow Units and Water Saturation Calculation: Dam Formation, South Western Qatar, Arabian Gulf

Hydraulic-electric flow units represent two different concepts with different measuring units. They are frequently used to confirm each other’s for distinguishing the different reservoir flow zones but sometimes give undesirable results. 60 limestone samples were collected from the upper part of the Dam Formation exposed in the Al-Nakhsh area, Southwestern Qatar Peninsula. These samples represent the Upper Dam sediments which are considered as an important aquifer for underground water in its subsurface occurrences in Qatar and nearby areas. Porosity, gas permeability and electrical resistivity were laboratory measured for the collected samples. Saturation exponent (n), cementation exponent(m) and pore throat radius (r35) were calculated for each sample. The vertical profile of gas permeability and pore throat radius (R35) is accomplished. Also, gas-permeability versus porosity is performed. Numerous useful and applicable relationships have been found. The obtained reservoir flow units which are distinguished according to hydraulic flow indicators (RQI and Øz) are only three units. However, the hydraulic-electric cross-plots (i.e. n-R35 and n-FZI) indicate three and four reservoir flow units respectively. In conclusion, the obtained number of reservoir flow units in the study area ranges from 3-4. It means that the hybrid hydraulic-electric combination sometimes shows flow units in concordance with the single type parameter, but occasionally give dissimilar results. An innovative nomograph is constructed according to an empirical equation related to the Dam Formation [1] to estimate the water saturation (SW) in oolitic carbonate facies. The present nomograph is verified by carbonate facies, deltaic distributary channel and barrier bar sandstone. The obtained values of water saturation from the proposed model are acceptable in case of both resistivity ratio ( Rt/Rw) and porosity (Ø) are available.

Identifying sedimentation processes in the Coata River, Altiplano of the Puno department, Peru, by the 210Pb method

The rivers, lakes and dam sediment analyses are able to predict the back conditions of these ecosystems and determine how the environment changed as a result of anthropogenic activities. In this way they can be used as important management tools of water resources. The activity and distribution of the 210Pb in the sedimentary record resulted in a study that sought to evaluate the sedimentation rate chronology in three sedimentary profiles in the Coata River, Southern Peru, in order to follow historical changes in the past 100–150 years. Beside this, the geochemical distribution of the trace metals Ba, Zn, Cu, Cr, Ni and Co was evaluated in the sediments, allowing investigation of their potential contamination and impact over the river. The research involved the determination of some specific aspects of the sediments such as the main oxides, organic matter and granulometry, as well the physicochemical analysis of the surface waters, with the objective of assisting the interpretation of the results obtained in the sediments. The dating process was based on the 210Pb method and the Constant Flux: Constant Sedimentation Model—CF: CS was adequate. It allowed determination of distinct sedimentation rates in each profile, between 0.36 and 0.74 g/cm2 year, corresponding to linear sedimentation rates of 0.28–0.66 cm/year. The evaluation of the excess/unsupported 210Pb data permitted characterizing sediments with maximum ages between 36 and 96 years. This geochemical study showed that the recorded metals in the sediments may be a consequence of more recent anthropogenic activities in the environment and that the 210Pb is a useful method to evaluate the sedimentation history.

Assessment of reservoir sedimentation of irrigation dams in northern Ghana

Adongo TA, Kyei-Baffour N, Abagale FK, Agyare WA. 2019. Assessment of reservoir sedimentation of irrigation dams in northern Ghana. Lake Reserv Manage. 36:87–105.Sedimentation in reservoirs of irrigation dams is a serious issue that threatens their functionalities. Since information on this phenomenon in irrigation dams in northern Ghana is almost nonexistent, a study was necessary. The study used bathymetric survey integrated with geographic information systems (GIS) tools to assess reservoir sedimentation of 9 irrigation dams in 3 northern regions of Ghana. The bathymetric survey was conducted during August–October 2017 using a hand-held Hondex digital depth meter. Reservoir depths at full supply level were found to range from 0.10 to 14.70 m. The volumetric storage capacity loss in the reservoirs ranged from 0.1 to 7.94 Mm3, while the percentage storage capacity loss ranged from 8.54 to 34.12%. The reservoirs were found to be losing volume by 0.26–0.91%/yr. The water surface area of the reservoirs lost due to sedimentation ranged from 5.53 to 24.10%. Estimated mean annual sediment load and sediment inflows into the reservoirs ranged from 3159 to 12,850 mg/L and from 1594 to 355,017 m3/yr, respectively. Estimated useful life of the reservoirs ranged from 22 to 160 yr. All the reservoirs except Bontanga and Tono had a well-formed delta and slightly formed tapering deposits. Major causes of the sedimentation were observed to be mainly human activities within the reservoir catchments. Enactment and enforcement of bylaws to restrict farming, burning, and sand/gravel mining activities in the buffer zones of the reservoirs are necessary to reduce the rate of sedimentation. Improved catchment management practices, construction of check dams, installation of hydrosuction sediment-removal systems, and periodic desilting are also recommended.

Physico-chemical characteristics and heavy metal concentrations of copper mine wastes in Zambia: implications for pollution risk and restoration

Soil characterization is a vital activity to develop appropriate and effective restoration protocols for mine wastelands while insights into the total content of heavy metals in the soil is an important step in estimating the hazards that the metals may pose to the vital roles of soil in the ecosystem. This study addressed the following research questions: (1) To what extent do the physico-chemical characteristics vary between mine waste sediments and the nearby forest soil? (2) Are the concentrations of heavy metals high enough to be considered as toxic? and (3) Are heavy metals present in mine waste sediments potential sources of pollution? We hypothesized that the physico-chemical characteristics of mine waste sediments are less favorably for plant establishment and growth while the concentrations of heavy metals are very high, thus restricting the success of revegetation of mine waste lands. Mine waste sediments were sampled following a diagonal transect across tailings dams, overburden dump sites and the local forest soil from the top layer (0–20 cm) using a closed auger. Samples were analyzed for arsenic, barium, lead, cadmium, cobalt, copper, chromium, nickel, vanadium, and zinc as well as for soil physico-chemical properties. The mine waste sediments were dominated by silt whilst the forest soil by sand particles, with significantly high bulk density in the former. Both the forest soil and overburden sediments were acidic than the alkaline tailings dam sediment. Total organic carbon and nitrogen contents were significantly low in mine wasteland substrates but the concentration of Ca and Mg were significantly higher in tailings dam substrate than the forest soil. The concentrations of available P, K and Na were similar across sites. The mean concentrations of heavy metals were significantly (p < 0.01) higher in mine waste sediments than the forest soil; except for cadmium (p = 0.213). The order of contamination by heavy metals on the tailings was Cu > Co > Ba > Ni > As > Zn > Pb > Cr > V > Cd, and that on the overburdens was Cu > Co > Ba > Ni > Zn > Cr > Pb > V > As > Cd. The pollution load index (PLI) was nearly twice higher for the tailings dam (8.97) than the overburden (5.84). The findings show that the copper mine wastes (the tailings dams and overburden waste rock sites) are highly contaminated by heavy metals; which, in turn, might pose serious hazards to human health and agricultural productivity. In addition, poor macro-nutrient availability, substrate compaction and soil acidity (particularly on overburden sites) coupled with toxic level of heavy metals would be the main challenges for successful phytostabilization of copper mine wastelands.

Valorization of dredging sediments of dam BOUHNIFIA in ceramic

The main objective of this paper is the valorization of the dredging sediments of the BOUHNIFIA dam of the region of Mascara (western Algeria) in ceramic. The physical and the chemical analyses show that the characteristics of sediments of dam BOUHNIFIA are similar to the characteristics of clays used in the ceramic industry. The mechanical tests carried out at CERAL plant show the valorization percentage of up to 12% without any change in the manufacturing process. The study also showed that particle size and mineralogy of sediments are decisive factors influencing the quality of the ceramic tiles produced. For this reason, it is necessary to use these sediments in the field of ceramics in order to preserve the environment.

Indirect Assessment of Sedimentation in Hydropower Dams Using MODIS Remote Sensing Images

In this study, we used moderate resolution imaging spectroradiometer (MODIS) satellite images to quantify the sedimentation processes in a cascade of six hydropower dams along a 700-km transect in the Paranapanema River in Brazil. Turbidity field measurement acquired over 10 years were used to calibrate a turbidity retrieval algorithm based on MODIS surface reflectance products. An independent field dataset was used to validate the remote sensing estimates showing fine accuracy (RMSE of 9.5 NTU, r = 0.75, N = 138). By processing 13 years of MODIS images since 2000, we showed that satellite data can provide robust turbidity monitoring over the entire transect and can identify extreme sediment discharge events occurring on daily to annual scales. We retrieved the decrease in the water turbidity as a function of distance within each reservoir that is related to sedimentation processes. The remote sensing-retrieved turbidity decrease within the reservoirs ranged from 2 to 62% making possible to infer the reservoir type and operation (storage versus run-of-river reservoirs). The reduction in turbidity assessed from space presented a good relationship with conventional sediment trapping efficiency calculations, demonstrating the potential use of this technology for monitoring the intensity of sedimentation processes within reservoirs and at large scale.

Some examples of mineral eco-materials

Eco-materials are materials which can minimize environmental impacts, can be manufactured from recycled materials, or are beneficial for human wellbeing. This paper will illustrate these three aspects on mineral-based eco-materials through research that has been developed in our ceramic institute: preparation of dense tapes of cementitious materials at room temperature by tape casting, valorization of dam sediments as raw materials for synthesis of Portland clinker, monitoring the microstructure of plaster boards for improving the acoustical insulation in houses.

Farm dam siltation and sediment source tracing in the Zeerust - Swartruggens area in the North-West of South Africa

Soil erosion and dam siltation are two serious environmental problems facing farmers in South Africa. The study aimed to assess farmers' perceptions on dam siltation and strategies employed to address it, and to assess the potential of sediment source tracing in a farming area in the north-west region of South Africa. Most of the dams in the study area were severely affected by siltation and the most important strategy used to address the problem was regular mechanical removal of the accumulated sediment. In relation to sediment tracing, lead-210 (210Pb) was found to be a more effective tracer than caesium-137 (137Cs) for distinguishing between surface and subsurface sediment sources. On the other hand, magnetic susceptibility offered better distinction of the sediment sources than magnetic remanence. Mass balance modelling indicated that 100% of the sampled sediment dam 1 originated from surface sources. The results reflect the complexity of sediment mobilisation processes influenced by the nature and spatial distribution of rainfall and runoff connectivity in the catchments.

Farm dam siltation and sediment source tracing in the Zeerust Swartruggens area in the north-west of South Africa

Soil erosion and dam siltation are two serious environmental problems facing farmers in South Africa. The study aimed to assess farmers' perceptions on dam siltation and strategies employed to address it, and to assess the potential of sediment source tracing in a farming area in the north-west region of South Africa. Most of the dams in the study area were severely affected by siltation and the most important strategy used to address the problem was regular mechanical removal of the accumulated sediment. In relation to sediment tracing, lead-210 (210Pb) was found to be a more effective tracer than caesium-137 (137Cs) for distinguishing between surface and subsurface sediment sources. On the other hand, magnetic susceptibility offered better distinction of the sediment sources than magnetic remanence. Mass balance modelling indicated that 100% of the sampled sediment dam 1 originated from surface sources. The results reflect the complexity of sediment mobilisation processes influenced by the nature and spatial distribution of rainfall and runoff connectivity in the catchments.

Assessing the effects of Awba dam sediment (Nigeria) on the steroidogenesis of H295R cells using different extraction methods

In the present study, H295R human cells were used to investigate the endocrine disruptor potential of three different sediments extracts taken from a Nigerian tropical freshwater dam (Awba Dam), using three extraction methods that allowed a selective consideration of contaminants based on their binding affinity, which is mainly driven by polarity, to sediment particles. After exposure to different concentration of each extract, H295R cells were evaluated for the expression profiles of 10 steroidogenic enzyme genes and estradiol (E2) and testosterone (T) levels. Our results showed a comparable concentrated-related increase in the expression of 17β-hsd1, 3β-hsd2 and cyp21 in cells treated with the polar and non-polar extracts. The star, hmgr, cyp11b2 and 17β-hsd4 were slightly decreased, in an apparent concentration-specific manner, after treatment with the polar extract and decreased in the non-polar treatment. The cyp11a and cyp17 showed an opposite trend in the polar and non-polar treatments. E2 was significantly higher in cell treated with the non-polar extract. Elutriate exposure produced less pronounced variation in mRNA and hormones levels. Overall the extract with non-polar compounds produced the most severe effects in H295R cells. Thus, direct ingestion of detritus and mud from fishes and other benthonic organisms represent possible transfer of contaminants in the trophic web, and mainly account for alteration of the endocrine system previously observed in fish from the same study site.

The role of Eurasian beaver (Castor fiber) in the storage, emission and deposition of carbon in lakes and rivers of the River Ob flood plain, western Siberia

Several studies have reported significant emission of greenhouse gasses (GHG) from beaver dams, suggesting that ponds created by beavers are a net source of CO2 and CH4. However, most evidence come from studies conducted in North America (on Castor canadensis) without a parallel comparison with the Eurasian beaver's (Castor fiber) impacts and a critical consideration of the importance of the carbon deposition in dam sediments. The most abundant population of the Eurasian beaver lives in Russia, notably within the River Ob watershed in Western Siberia which is the second largest floodplain on Earth. Consequently, we assessed the holistic impact of Eurasian beavers on the multiple carbon pools in water and on other related biogeochemical parameters of the Ob's floodplain streams. We compared dammed and flowing streams in a floodplain of the middle course of the river. We found that beavers in western Siberia increase the stream emission of methane by about 15 times by building their dams. This is similar to what has been documented in North America. A new finding from the present study is that Siberian beavers facilitate 1) nutrient recycling by speeding up the nutrient release from particulate organic matter; and 2) carbon sequestration by increasing the amount of dissolved organic carbon. This carbon becomes in part recalcitrant when buried in sediments and is, therefore, removed from the short-term carbon cycle. These new results should be taken into consideration in river management and provide a further reason for the conservation and management of Eurasian Beavers.

Fertility of Technosols constructed with dam sediments for urban greening and land reclamation

Fine sediment accumulates upstream of hydroelectric dams. To ensure that dams can operate properly, part of the sediment has to be dredged and land managed. In parallel, using topsoil from agricultural parcels for urban greening or land restoration is currently controversial because arable surface areas are decreasing. An alternative idea for protecting these natural resources consists in reusing fine dredged sediment to construct multifunctional soils. This agronomic use is only possible if sediment can provide acceptable physical and chemical properties for plant growth. Four dredged sediments with contrasted initial agronomic properties and one control soil were mixed or not with green waste compost (40% v/v) and used to construct triplicate 30-cm depth soils in lysimetric containers (1.11 × 0.71 m). The 30 constructed soils were exposed to the in situ conditions and sown with ryegrass (Lolium perenne). The evolution of soil chemical and physical properties and plant development were studied every 6 months for 18 months. Above- and below-ground biomass production of the constructed soils contrasted according to the sediment properties and to compost addition. A statistical approach identified eight soil parameters linked to biomass production. Among these parameters, soil structure, quantified from aggregate stability, played a fundamental role. A focus on physical properties confirmed that some sediments were only partially adapted to ryegrass support. Compost addition improved sediment physical properties over time, but caused temporary N deficiency during the first months after installation which limited shoot biomass production. Exogenous plant species developed on the constructed Technosols, especially on the soils where the lack of structure and N deficiency had the strongest effect. All sediments were suitable for plant growth over the 18 months of the study. A few soil properties emerged as markers of the fertility of sediment-made Technosols. Among them, the soil structure was one of the most determining parameters. It can be assessed by measuring aggregate stability, macroporosity, the crustability index, and bulk density, while available nutrients (N, P, K) and pH seem sufficient to assess chemical fertility. The balance between the properties of the sediment-made Technosols and the needs of the plants seems to be an essential lever for the establishment of functional soil-plant systems for urban greening or for ecological restoration.

Comparative Studies between Urbanization and Dam Settlement Processes

The city of Viamao is located in the metropolitan region of Porto Alegre, in the Rio Grande Sul State, southern Brazil. The Mae d'Agua dam was built in 1962 and, due to the lack of urban planning during the last forty years, received large discharges of sediments and contaminants (organic and/or inorganic). This study aimed to use the geochronology technique using the lead element 210 (210Pb) through the cores of sediments sampled from the Mae D'agua dam and to establish the chronology of the sedimentary layers over the last four decades, in addition to the characterization of the sedimentation processes in the Mae D'Agua reservoir and to size the sediment volumes silted in the reservoir in the current scenario, year 2014 (year of sampling) and thus, to present the total sediment concentrations during the 40-year silting. The sediment column, bathymetry, bibliographical references and GIS resources were used to infer the process of urbanization and sedimentation process of the dam, and representative samples were collected in June 2014, using sediment cores distributed in the dam area. The sediment cores were extracted through the Piston core sampler. With the results obtained, graphs and tables were generated to create the mathematical models and later the sedimentation maps, establishing correlations with the sedimentation geochronology studies during the last four decades (layers of sedimentation generated in each of these periods). There were periods with high sedimentation rates, mainly during the acceleration of the process of urbanization of the basin resulting in a total sediment volume of 44% of the useful volume of the project, which drastically reduces the capacity of the Mae d'Agua dam. Keywords: Urban dams, Sediments, Sedimentation of dams.

Biodegradation of ethylthionocarbamates by a mixed culture of iron-reducing bacteria enriched from tailings dam sediments

Ethylthionocarbamates (ETC), which is the most widely used as collectors in the flotation of sulfide, is known to cause serious pollution to soil and groundwater. The potential biodegradation of ETC was evaluated by applying a mixed culture of iron-reducing bacteria (IRB) enriched from tailings dam sediments. The results showed that ETC can be degraded by IRB coupled to Fe(III) reduction, both of which can be increased in the presence of anthraquinone-2,6-disulfonate (AQDS). Moreover, Fe(III)-EDTA was found to be a more favorable terminal electron acceptor compared to α-Fe2O3, e.g., within 30 d, 72% of ETC was degraded when α-Fe2O3+AQDS was applied, while it is 82.67% when Fe(III)-EDTA+AQDS is added. The dynamic models indicated that the kETC degradation was decreased in the order of Fe(III)-EDTA+AQDS>α-Fe2O3+AQDS>Fe(III)-EDTA>α-Fe2O3, with the corresponding maximum biodegradation rates being 2.6, 2.45, 2.4 and 2.0 mg/(L.d), respectively, and positive parallel correlations could be observed between kFe(III) and kETC. These findings demonstrate that IRB has a good application prospect in flotation wastewater.

Aggregate stability and associated organic carbon and nitrogen as affected by soil erosion and vegetation rehabilitation on the Loess Plateau

Although soil erosion and land use change have long been focuses in carbon research, the combined influence of soil erosion and vegetation rehabilitation on aggregate stability and the associated soil organic carbon (SOC) and total nitrogen (TN) remains unclear. The current study evaluated the effects of soil erosion on aggregate stability and the associated SOC and TN dynamics in relation to vegetation rehabilitation after the implementation of the “Grain-for-Green” project in the hilly Loess region. A check dam sediment sequence was dated using 137Cs activity and erosive rainfall events. The SOC and TN in the bulk soil and aggregate fractions were measured in soils from rehabilitated grasslands and sloping croplands and in sediments retained by the check dam. The results showed that vegetation rehabilitation led to 78%, 27% and 9% average increases in the macroaggregate amount, mean weight diameter (MWD) and mean geometric diameter (MGD), respectively. In addition, rehabilitation resulted in the highest SOC and TN concentrations and contents in macroaggregates among all the aggregate size fractions. Soil erosion facilitated the modification of the aggregate size distributions along with soil mineralization and induced the incorporation of deeper SOC-poor soils during transport. These processes resulted in the aggregate-associated SOC and TN concentrations and contents in the sediments being significantly lower than those in the eroding sloping cropland soils. The highest reductions were found in microaggregates, which exhibited decreases of 48% and 44% for SOC and TN, respectively. Moreover, reaggregation and gully soils incorporated during soil erosion led to higher values of macroaggregate amount and aggregate stability at depositional sites than those at eroding sloping cropland sites in this study. Our study contributes to the understanding of the effects of soil erosion and vegetation rehabilitation on SOC and TN dynamics, which is crucial for understanding the restoration efficiency in soil erosion control and ecosystem security evaluation.

Heavy metals' contamination in sediments of Wadi Al-Aqiq water reservoir dam at Al-Baha region, KSA: Their identification and assessment

ABSTRACTSediments are the ultimate sump for heavy metal pollutants. The main purpose was to investigate the ecological and health risk assessment of heavy metals in the sediments of Wadi Al-Aqiq water reservoir. The metals detected were arranged in decreasing order Fe > Mn > Cr > Cu > Zn > Ni > Co > Pb. Pearson correlation analysis indicated strong positive association and significant linear relation between various pairs of metals. Different evaluation indices used indicated that source of contamination from lithogenic sources and sediments can be classified as low polluted quality. A comparison of the concentrations of metals with International Sediment Quality Guidelines criteria showed that only Cu and Ni concentrations above the ERL and below the ERM guideline values suggest possible adverse effects. On comparing with US Environmental Protection Agency prepared sediment quality criteria it indicated that Pb and Zn have concentrations below the non-polluted criteria, Fe, Mn, and Ni lies in the range of moderately polluted criteria, and Co and Cu are within the heavily polluted criteria. Non-carcinogenic risk quantification indicated health concern from ingestion route and no health effects for dermal exposure. On considering additive effect, the dermal exposure may cause health harm. The carcinogenic risk assessment for lead and chromium showed an acceptable risk to human health.

Al-kut Dam Sediments Content of Some Heavy Metals and Its Relationship with Pollution

&#x0D; &#x0D; &#x0D; &#x0D; This study has been carried out in Alkut city the center of Wasit province which is located about 180 km south of the capital Baghdad on one from the most important dams constructed on theriverTigris called Alkut Dam .Four pedons have been selected in this study, two pedons (A,B) are located in the lower part of dam and the other two pedons (C ,D) are located in the upper part of dam , sediments samples analysis for particle size distribution and total &amp; available heavy metals concentration (Ni ، Cd ، Zn ، Pb ،Fe) in the water and sediments.&#x0D; Results show that the total concentration of nickel ranges between(104.2 - 178.4) mg.kg-1and the higher value has been found in the second depth (156-126)cm for pedon A and the lower value has been found in the second depth (50-30) for pedon D , while total cadmium concentration ranges between (6.1-2.2)mg.kg-1and the higher value has been found in the second depth (35-20) for pedon A at the lower part of dam and the lower value has been found in the sixth depth (73-93cm)for the same pedon , the values for total Zinc concentration ranges between (108-69) mg.kg-1 and the higher value has been found in the fifth depth (73-55)cm for pedon A at the lower part of dam and the lower value has been found in the last depth (120-100cm) for pedonD in the upper part of dam, the results of total lead concentration ranges between (24.2-11.35) mg.kg-1 and the higher value has been found in the first depth (0-20cm)cm for pedon A at the lower part of dam and the lower value has been found in the third depth (60-50cm) for pedonD in the upper part of dam , while the total concentration for iron (Fe) which ranges between (4595-2988) mg.kg-1 the higher value has been found in the second depth (20-50cm) for pedon A at the lower part of dam and the lower value has been found in the seventh depth (111-93cm) for the same pedon .As compared with critical limits , results show that total concentration of heavy metals for Cd, Pb, Zn and Ni in Sediments samples all has exceed the critical limits values except in some depths.&#x0D; The results for the available heavy metal concentrations show that the available nickel concentration ranges between(33.2-107.4)mg.kg-1 and the higher value has been found in the second depth (20-35)cm for pedon A at the lower part of dam and the lower value has been found in the second depth (30-50) for pedonD in the upper part of dam,while total cadmium concentration ranges between (0.21-0.48)mg.kg-1and the higher value has been found in the first depth (0-20)cm for pedon B at the lower part of dam and the lower value has been found in the sixth depth (73-93cm)for the pedon A at the lower part of dam , the values for the available Zinc concentration ranges between (56-111) mg.kg-1 and the higher value has been found in the tenth depth (191-231)cm for pedon A at the lower part of dam and the lower value has been found in the last depth (120-100cm) for pedonD in the upper part of dam, the results of available lead (pb) concentration ranges between (6.7-20.2) mg.kg-1 and the higher value has been found in the first depth (0-20cm)cm for pedon A at the lower part of dam and the lower value has been found in the third depth (60-50cm) for pedonD in the upper part of dam , while the available concentration for iron (Fe) which ranges between (39-74)mg.kg-1 the higher value has been found in the second depth (20-50cm) for pedon A at the lower part of dam and the lower value has been found in the eighth depth(111-126) for the same pedon,at the comparison of results for the available concentrations of the studied heavy metals it can be seenthat all values have exceeded the critical limits values according to Nunes etal 2014. in the other hand the results show that there is significant correlation between the total and available concentration for same heavy metalspairs of the correlation (r2) between the available and total concentration was 0.90 , 0.74 , 0.99, 0.99 and 0.58 for Ni , Cd , Zn , Pb and Fe respectively , in the other hand, the results show that the water concentration for heavy metals are 1.7 , 0.03 ,15 , 0.07 and 27 mg.l-1for Ni , Cd , Zn , Pb and Fe respectively , which indicate that all values have exceeded the critical limits according to Iraqi standards and FAW.&#x0D; &#x0D; &#x0D; &#x0D;

Early structural stability of fine dam sediment in soil construction

PURPOSE: Fine sediments accumulate upstream of hydroelectric dams. To ensure that dams can operate properly, most sediments are returned downstream reaches, but a portion of them have to be dredged and land managed. In parallel, using topsoil from agricultural parcels for urban greening is currently controversial because arable surface areas are decreasing. An alternative idea for protecting these natural resources consists in reusing fine dredged sediment to construct functional soils. The agronomical use of fine dredged sediment raises the question of its ability to provide acceptable physical properties for plant growth. MATERIALS AND METHODS: Six dredged sediments with contrasted initial agronomical properties were mixed or not with green waste compost and submitted or not to drying-wetting cycles in a 105-day-long experiment under greenhouse conditions. The sediments were analyzed for their capacity to generate stable aggregates. We measured the proportion of macro aggregates > 2 mm with dry-sieved aggregate (DSA) fraction and the > 0.25 mm water-stable aggregate (WSA) fraction for each treatment over time. We also assessed the main sediment physicochemical properties, microbial biomass carbon, and carbon mineralization potential. RESULTS AND DISCUSSION: Compost addition (40% in volume) enhanced the WSA fraction of the low-organic-matter-content sediments (< 30 g kg⁻¹), whereas it had a non-significant effect in the other sediments. Multiple linear regressions highlighted a determining role of organic matter in the WSA fraction. At this scale of aggregation, organic matter seemed to mainly interact with clay in an acidic context. Compost addition had either no significant effect or a negative effect on the DSA fraction. Multiple linear regressions suggested that organic matter was not clearly involved in DSA formation in the sediment, whereas macro-porosity was. The first drying-wetting cycles enhanced the DSA proportion of the sediments, but the following cycles had a negative effect. We suggest that disaggregating mechanisms gradually predominated over aggregating mechanisms over time. CONCLUSIONS: All sediments showed acceptable physicochemical properties for plant growth. WSA formation in low-organic-matter-content sediments was improved by adding compost. Drying-wetting cycles had a controversial effect on DSA formation, and only the very first cycles had a beneficial effect on macro-aggregation. The mechanisms involved in aggregation and aggregate stability in soil constructed from sediments seem to be similar to those involved in natural soils. That is why we propose that the soil hierarchical aggregation model initially developed for natural and cultivated soils could be adapted to sediments.