Sorption of Some Fission Products and Actinides in Concrete Systems

1985 ◽  
Vol 50 ◽  
Author(s):  
S. Höglund ◽  
L. Eliasson ◽  
B. Allard ◽  
K. Andersson ◽  
B. Torstenfelt
Keyword(s):  
Pore Water ◽  
Fission Products ◽  
Exchange Capacity ◽  
Matrix Composition ◽  
Cement Matrix ◽  
Pore Waters ◽  
High Concentration ◽  
Hydro Power ◽  
Sorption Behaviour ◽  
Competing Cations

AbstractThe sorption of some actinides (Th, U, Np, Pu and Am) and fission products (I, Cs) was measured on two types of Standard Portland cements as well as on samples from old (70 years) hydro power dam constructions using a batch technique. Pore water compositions were analysed, and artificial pore water solutions were used as aqueous phases in the experiments. Measurements were also performed on five other concrete types (not reported in detail in this paper) to illustrate the effects of the cement matrix composition on the sorption behaviour of the radionuclides.The sorption of actinides in the trivalent (americium), tetravalent (thorium) pentavalent (neptunium) and hexavalent (uranium) states was high in all the studied concrete systems.Generally, the sorption of cesium was low due to the low exchange capacity of the cement and the high concentration of competing cations in the pore waters.The sorption of iodine was much higher than in most silicate minerals of geologic origin.The differences between the various concrete systems were generally minor in terms of their sorbing capacities.

scholarly journals Hydrochemistry of sediment pore water in the Bratsk reservoir (Baikal region, Russia)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
V. I. Poletaeva ◽  
E. N. Tirskikh ◽  
M. V. Pastukhov
Keyword(s):  
Pore Water ◽  
Ionic Composition ◽  
Water System ◽  
Water Reservoir ◽  
Environmental Parameters ◽  
Water Area ◽  
Pore Waters ◽  
Overlying Water ◽  
Major Ion ◽  
Bratsk Reservoir

AbstractThis study aimed to identify the factors responsible for the major ion composition of pore water from the bottom sediments of the Bratsk water reservoir, which is part of the largest freshwater Baikal-Angara water system. In the Bratsk reservoir, the overlying water was characterized as HCO3–Ca–Mg type with the mineralization ranging between 101.2 and 127.7 mg L−1 and pore water was characterized as HCO3–SO4–Ca, SO4–Cl–Ca–Mg and mixed water types, which had mineralization varying from 165.9 to 4608.1 mg L−1. The ionic composition of pore waters varied both along the sediment depth profile and across the water area. In pore water, the difference between the highest and lowest values was remarkably large: 5.1 times for K+, 13 times for Mg2+, 16 times for HCO3−, 20 times for Ca2+, 23 times for Na+, 80 times for SO42−, 105 times for Cl−. Such variability at different sites of the reservoir was due to the interrelation between major ion concentrations in the pore water and environmental parameters. The major factor responsible for pore water chemistry was the dissolution of sediment-forming material coming from various geochemical provinces. In the south part of the reservoir, Cl−, Na+ and SO42− concentrations may significantly increase in pore water due to the effect of subaqueous flow of highly mineralized groundwater.

Dissolution and recrystallization in modern shelf carbonates: evidence from pore water and solid phase chemistry

1993 ◽  
Vol 344 (1670) ◽  
pp. 27-36 ◽  
Keyword(s):  
Organic Matter ◽  
Pore Water ◽  
Solid Phase ◽  
Chemical Exchange ◽  
Isotope Composition ◽  
Geochemical Data ◽  
Carbonate Sediments ◽  
Pore Waters ◽  
Carbonate Minerals ◽  
Carbonate Production

We present an overview of geochemical data from pore waters and solid phases that clarify earliest diagenetic processes affecting modern, shallow marine carbonate sediments. Acids produced by organic matter decomposition react rapidly with metastable carbonate minerals in pore waters to produce extensive syndepositional dissolution and recrystallization. Stoichiometric relations among pore water solutes suggest that dissolution is related to oxidation of H 2 S which can accumulate in these low-Fe sediments. Sulphide oxidation likely occurs by enhanced diffusion of O 2 mediated by sulphide-oxidizing bacteria which colonize oxic/anoxic interfaces invaginating these intensely bioturbated sediments. Buffering of pore water stable isotopic compositions towards values of bulk sediment and rapid 45 Ca exchange rates during sediment incubations demonstrate that carbonate recrystallization is a significant process. Comparison of average biogenic carbonate production rates with estimated rates of dissolution and recrystallization suggests that over half the gross production is dissolved and/or recrystallized. Thus isotopic and elemental composition of carbonate minerals can experience significant alteration during earliest burial driven by chemical exchange among carbonate minerals and decomposing organic matter. Temporal shifts in palaeo-ocean carbon isotope composition inferred from bulk-rocks may be seriously compromised by facies-dependent differences in dissolution and recrystallization rates.

scholarly journals Waste Tire Particles and Gamma Radiation as Modifiers of the Mechanical Properties of Concrete

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Eduardo Sadot Herrera-Sosa ◽  
Gonzalo Martínez-Barrera ◽  
Carlos Barrera-Díaz ◽  
Epifanio Cruz-Zaragoza
Keyword(s):  
Mechanical Properties ◽  
Gamma Radiation ◽  
Chemical Properties ◽  
Plain Concrete ◽  
Cement Matrix ◽  
Portland Cement Concrete ◽  
High Concentration ◽  
Good Tool ◽  
Waste Tire ◽  
Physical And Chemical

In polymer reinforced concrete, the Young’s modulus of both polymers and cement matrix is responsible for the detrimental properties of the concrete, including compressive and tensile strength, as well as stiffness. A novel methodology for solving such problems is based on use of ionizing radiation, which has proven to be a good tool for improvement on physical and chemical properties of several materials including polymers, ceramics, and composites. In this work, particles of 0.85 mm and 2.80 mm obtained from waste tire were submitted at 250 kGy of gamma radiation in order to modify their physicochemical properties and then used as reinforcement in Portland cement concrete for improving mechanical properties. The results show diminution on mechanical properties in both kinds of concrete without (or with) irradiated tire particles with respect to plain concrete. Nevertheless such diminutions (from 2 to 16%) are compensated with the use of high concentration of waste tire particles (30%), which ensures that the concrete will not significantly increase the cost.

scholarly journals Sorption performances of TiO(OH)(H2PO4)·H2O in synthetic and mine waters

RSC Advances ◽  
2017 ◽  
Vol 7 (4) ◽  
pp. 1989-2001 ◽  
Author(s):  
Mylène Trublet ◽  
Marina V. Maslova ◽  
Daniela Rusanova ◽  
Oleg N. Antzutkin
Keyword(s):  
Exchange Capacity ◽  
Titanium Phosphate ◽  
Mine Waters ◽  
Sorption Behaviour ◽  
Fast Kinetics ◽  
First Report

The first report on sorption behaviour of a titanium phosphate sorbent containing entirely –H2PO4 groups reveals a high exchange capacity and fast kinetics.

scholarly journals Particulate organic carbon (POC) in relation to other pore water carbon fractions in drained and rewetted fens in Southern Germany

2008 ◽  
Vol 5 (6) ◽  
pp. 1615-1623 ◽  
Author(s):  
S. Fiedler ◽  
B. S. Höll ◽  
A. Freibauer ◽  
K. Stahr ◽  
M. Drösler ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Pore Water ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Relative Importance ◽  
Pore Waters ◽  
Calcareous Fens ◽  
Essential Components ◽  
The Individual

Abstract. Numerous studies have dealt with carbon (C) contents in Histosols, but there are no studies quantifying the relative importance of the individual C components in pore waters. For this study, measurements were taken of all the carbon components (particulate organic carbon, POC; dissolved organic carbon, DOC; dissolved inorganic carbon, DIC; dissolved methane, CH4) in the soil pore water of calcareous fens under three different water management regimes (re-wetted, deeply and moderately drained). Pore water was collected weekly or biweekly (April 2004 to April 2006) at depths between 10 and 150 cm. The main results obtained were: (1) DIC (94–280 mg C l−1) was the main C-component. (2) POC and DOC concentrations in the pore water (14–125 mg C l−1 vs. 41–95 mg C l−1) were pari passu. (3) Dissolved CH4 was the smallest C component (0.005–0.9 mg C l−1). Interestingly, about 30% of the POM particles were colonized by microbes indicating that they are active in the internal C turnover. Certainly, both POC and DOC fractions are essential components of the C budget of peatlands. Furthermore, dissolved CO2 in all forms of DIC appears to be an important part of peatland C-balance.

scholarly journals DOC-dynamics in a small headwater catchment as driven by redox fluctuations and hydrological flow paths – are DOC exports mediated by iron reduction/oxidation cycles?

2013 ◽  
Vol 10 (2) ◽  
pp. 891-904 ◽  
Author(s):  
K.-H. Knorr
Keyword(s):  
Ionic Strength ◽  
Pore Water ◽  
Surface Waters ◽  
Iron Reduction ◽  
Stream Water ◽  
Riparian Wetlands ◽  
Pore Waters ◽  
Flow Paths ◽  
Discharge Patterns ◽  
Iron Concentrations

Abstract. Dissolved organic carbon (DOC) exports from many catchments in Europe and North-America are steadily increasing. Several studies have sought to explain this observation. As possible causes, a decrease in acid rain or sulfate deposition, concomitant reductions in ionic strength and increasing temperatures were identified. DOC often originates from riparian wetlands; but here, despite higher DOC concentrations, ionic strength in pore waters usually exceeds that in surface waters. In the catchment under study, DOC concentrations were synchronous with dissolved iron concentrations in pore and stream water. This study aims at testing the hypothesis that DOC exports are mediated by iron reduction/oxidation cycles. Following the observed hydrographs, δ18O of water and DOC fluorescence, the wetlands were identified as the main source of DOC. Antecedent biogeochemical conditions, i.e., water table levels in the wetlands, influenced the discharge patterns of nitrate, iron and DOC during an event. The correlation of DOC with pH was positive in pore waters, but negative in surface waters; it was negative for DOC with sulfate in pore waters, but only weak in surface waters. Though, the positive correlation of DOC with iron was universal for pore and surface water. The decline of DOC and iron concentrations in transition from anoxic wetland pore water to oxic stream water suggests a flocculation of DOC with oxidising iron, leading to a drop in pH in the stream during high DOC fluxes. The pore water did not per se differ in pH. There is, thus, a need to consider processes more thoroughly of DOC mobilisation in wetlands when interpreting DOC exports from catchments. The coupling of DOC with iron fluxes suggested that increased DOC exports could at least, in part, be caused by increasing activities in iron reduction, possibly due to increases in temperature, increasing wetness of riparian wetlands, or by a shift from sulfate dominated to iron reduction dominated biogeochemical regimes.

scholarly journals Geochemistry of intertidal sediment pore waters from the industrialized Santos-Cubatão Estuarine System, SE Brazil

2012 ◽  
Vol 84 (2) ◽  
pp. 427-442 ◽  
Author(s):  
Winston F.O. Gonçalves ◽  
Wanilson Luiz-Silva ◽  
Wilson Machado ◽  
Erico C. Nizoli ◽  
Ricardo E. Santelli
Keyword(s):  
Surface Water ◽  
Pore Water ◽  
Surface Waters ◽  
Water Concentration ◽  
Point Sources ◽  
Intertidal Sediment ◽  
Estuarine System ◽  
Pore Waters ◽  
Geochemical Composition ◽  
Se Brazil

The geochemical composition of sediment pore water was investigated in comparison with the composition of sediment particles and surface water in an estuary within one of the most industrialized areas in Latin America (Santos-Cubatão estuarine system, SE Brazil). Pore and surface waters presented anomalously high levels of F-, NH4+, Fe, Mn and P due to two industrial point sources. In the summer, when SO4(2-)/Cl- ratios suggested an enhanced sulfate reduction, the higher dissolved levels observed in pore waters for some metals (e.g., Cu and Ni) were attributed to reductive dissolution of oxidized phases. Results evidenced that the risks of surface water concentration increase due to diffusion or advection from pore water are probably dependent on coupled influences of tidal pumping and groundwater inputs.

Migration of acidic pore waters at the Waite Amulet tailings site near Rouyn–Noranda, Quebec, Canada

1992 ◽  
Vol 29 (3) ◽  
pp. 466-476 ◽  
Author(s):  
Ernest K. Yanful ◽  
Luc C. St-Arnaud
Keyword(s):  
Hydraulic Conductivity ◽  
Pore Water ◽  
Mine Drainage ◽  
Geotechnical Properties ◽  
Horizontal Flow ◽  
Sulphide Mineral ◽  
Saturated Zone ◽  
Pore Waters ◽  
Dissolved Metals ◽  
Water Contents

Pore waters found in the unsaturated zone of the Waite Amulet tailings have been modified by sulphide mineral oxidation, resulting in acidic pH (near 4) and high concentrations of dissolved iron and sulphate at about 5 and 12 g/L, respectively. These pore waters have been displaced down into the shallow saturated zone of the tailings by infiltrating water. Most metals are removed from the pore water as a result of pH buffering before they reach the deeper saturated zone. However, some dissolved metals still remain in solution and are transported with the pore water through the tailings. Numerical flow modelling shows that an anisotropy in hydraulic conductivity (ratio of Kx/Ky is estimated to be 100) exists in the tailings, most likely due to the presence of horizontal fine-grained "slime" layers. The estimated horizontal pore-water velocity is almost 20 times higher than the vertical velocity. Anisotropy in hydraulic conductivity has the effect of promoting horizontal flow over vertical flow in the model. The geometry of the tailings impoundment and the assumed impermeability of the varved clay soil underlying the tailings also contribute to increased horizontal flow. To verify that a preferred horizontal flow exists and that the clay subsoil is indeed impermeable, the geotechnical properties and hydrogeochemistry of the clay are also evaluated. The results indicate that clay located beneath the tailings is slightly overconsolidated in the shallow zone but normally consolidated at greater depth by the weight of the tailings. Overconsolidation ratios reach a maximum value of 2.0. In the clay–tailings interface zone, the soil is characterized by lower in situ water contents and slightly higher undrained shear strengths Cu than the deeper clay. The water contents of the near-interface clay average about 40% and the Cu values 80 kPa, compared with an average water content of 55% and a Cu value of only 20 kPa for the clay at greater depths. These geotechnical properties confirm the presence of a desiccated oxidized upper zone identified in previous studies. It is hypothesized that fractures that could have appeared in the oxidized zone before the tailings deposition would have been closed due to consolidation by the tailings mass. Above-background sulphate concentrations observed in the clay layer at a depth of 1 m are believed to be controlled by diffusion and advection. The presence of fractures in the oxidized zone and excess pore-water pressures generated during consolidation of the clay by the tailings mass could have also influenced chemical transport. Key words : acid generation, acid mine drainage, diffusion, geotechnical, hydrogeochemistry, tailings.

Evaporative Evolution of Carbonate-Rich Brines from Synthetic Topopah Spring Tuff Pore Water, YuccaMountain, NV

2004 ◽  
Vol 824 ◽  
Author(s):  
Mark Sutton ◽  
Maureen Alai ◽  
Susan Carroll
Keyword(s):  
Pore Water ◽  
Yucca Mountain ◽  
Nuclear Waste Repository ◽  
Pore Waters ◽  
Starting Solution ◽  
Sequential Experiments ◽  
High Level Nuclear Waste ◽  
High Level ◽  
Topopah Spring Tuff

AbstractThe evaporation of a range of synthetic pore water solutions representative of the potential high-level-nuclear-waste repository at Yucca Mountain, NV is being investigated. The motivation of this work is to understand and predict the range of brine compositions that may contact the wastecontainers from evaporation of pore waters, because these brines could form corrosive thin films on the containers and impact their long-term integrity. A relatively complex synthetic Topopah Spring Tuff pore water was progressively concentrated by evaporation in a closed vessel, heated to 95°C in a series of sequential experiments. Periodic samples of the evaporating solution were taken to determine the evolving water chemistry. According to chemical divide theory at 25°C and 95°C our starting solution should evolve towards a high pH carbonate brine. Results at 95°C show that this solution evolves towardsa complex brinethat contains about 99 mol% Na+for the cations, and 71 mol% Cl-, 18 mol% ΣCO2(aq), 9 mol% SO42- for the anions. Initial modeling ofthe evaporating solution indicates precipitation of aragonite, halite, silica, sulfate and fluoride phases. The experiments have been used to benchmark the use of the EQ3/6 geochemical code in predicting the evolution of carbonate-rich brines during evaporation.

scholarly journals Benthic fluxes of dissolved organic nitrogen in the Lower St. Lawrence Estuary and implications for selective organic matter degradation

2013 ◽  
Vol 10 (5) ◽  
pp. 7917-7952
Author(s):  
M. Alkhatib ◽  
P. A. del Giorgio ◽  
Y. Gelinas ◽  
M. F. Lehmann
Keyword(s):  
Organic Matter ◽  
Pore Water ◽  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
Bottom Water ◽  
Estuarine Sediments ◽  
Pore Waters ◽  
Lower Estuary ◽  
Lawrence Estuary ◽  
St Lawrence Estuary

Abstract. The distribution of dissolved organic nitrogen (DON) and carbon (DOC) in sediment pore waters was determined at nine locations along the St. Lawrence Estuary and in the Gulf of St. Lawrence. The study area is characterized by gradients in the sedimentary particulate organic matter (POM) reactivity, bottom water oxygen concentrations, as well as benthic respiration rates. Based on pore water profiles we estimated the benthic diffusive fluxes of DON and DOC. Our results show that DON fluxed out of the sediments at significant rates (110 to 430 μmol m−2 d−1). DON fluxes were positively correlated with sedimentary POM reactivity and sediment oxygen exposure time (OET), suggesting direct links between POM quality, aerobic remineralization and the release of DON to the water column. DON fluxes were on the order of 30% to 64% of the total benthic inorganic fixed N loss due to denitrification, and often exceeded the diffusive nitrate fluxes into the sediments. Hence they represented a large fraction of the total benthic N exchange. This result is particularly important in light of the fact that DON fluxes are usually not accounted for in estuarine and coastal zone nutrient budgets. The ratio of the DON to nitrate flux increased from 0.6 in the Lower Estuary to 1.5 in the Gulf. In contrast to DON, DOC fluxes did not show any significant spatial variation along the Laurentian Channel (LC) between the Estuary and the Gulf (2100 ± 100μmol m−2 d−1), suggesting that production and consumption of labile DOC components proceed at similar rates, irrespective of the overall benthic characteristics and the reactivity of POM. As a consequence, the molar C/N ratio of dissolved organic matter (DOM) in pore water and the overlying bottom water varied significantly along the transect, with lowest C/N in the Lower Estuary (5–6) and highest C/N (> 10) in the Gulf. We observed large differences between the C/N of pore water DOM with respect to POM, and the degree of the C– versus –N element partitioning seems to be linked to POM reactivity and/or redox conditions in the sediment pore waters. Our results thus highlight the variable effects selective OM degradation and preservation can have on bulk sedimentary C/N ratios, decoupling the primary source C/N signatures from those in sedimentary archives. Our study further underscores that the role of estuarine sediments as efficient sinks of bioavailable nitrogen is strongly influenced by the release of DON during early diagenetic reactions, and that DON fluxes from continental margin sediments represent an important internal source of N to the ocean.

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