Clay Media Research Articles

Shade Avoidance in Soybean Reduces Branching and Increases Plant-to-Plant Variability in Biomass and Yield Per Plant

Recent studies have suggested that soybeans express shade avoidance in response to low red : far-red (R : FR) light reflected from neighboring plants and that this response may determine the onset and outcome of crop–weed competition. We tested the hypothesis that the low R : FR ratio would trigger characteristic shade avoidance responses in soybean and that the subsequent phenotype would experience reproductive costs under non–resource-limiting conditions. Soybeans were grown in a fertigation system in field trials conducted in 2007 and 2008 under two light quality treatments: (1) high R : FR ratio (i.e., weed-free) i.e., upward reflected light from a baked clay medium (Turface MVP®), or (2) low R : FR ratio (i.e., weedy) of upward reflected light, from commercial turfgrass. Results of this study indicated that a reduction in the R : FR ratio of light reflected from the surface of turfgrass increased soybean internode elongation, reduced branching, and decreased yield per plant. Shade avoidance also increased the plant-to-plant variability in biomass and yield per plant. Per plant yield losses were, however, more closely associated with reductions in biomass accumulation than population variability as the expression of a shade avoidance response did not influence harvest index. While these results suggest that weed induced shade avoidance decreases soybean per plant yield by reducing branching, it is possible the productivity of a soybean stand as a whole may be buffered against these reduction by a similar, but opposite, expression of plasticity in branching.

Site index curves for poplar growing on former farmland in Sweden

Site index (SI) curves for H 20 (dominant height at 20 years total age) were constructed using growth data from 64 hybrid poplars (Populus spp.) growing in 33 stands planted on farmland in Sweden (Lat. 55–60°N). The mean age of the stands was 24 years (range 14–45), the mean density 993 stems ha−l (155–3493), and the mean diameter at breast height (outside bark) 24 cm (10–45). SI curves fitted for H 20 at total age were well in accordance with the SI curves presented by other studies. A number of dynamic equations for modeling top-height growth from total age were assessed. A generalized algebraic difference approach (ADA) model derived by Cieszewski performed best. The model explained 98% of the observed variation in height development and exhibited no apparent bias across the range of predicted site indices. SI was also examined in relation to soil type. Multiple samples were available for three types of soil: light clay, medium clay, and till. There were no significant differences between the soil types.

Moisture can be the dominant environmental parameter governing cadaver decomposition in soil

Forensic taphonomy involves the use of decomposition to estimate postmortem interval (PMI) or locate clandestine graves. Yet, cadaver decomposition remains poorly understood, particularly following burial in soil. Presently, we do not know how most edaphic and environmental parameters, including soil moisture, influence the breakdown of cadavers following burial and alter the processes that are used to estimate PMI and locate clandestine graves. To address this, we buried juvenile rat ( Rattus rattus) cadavers (∼18 g wet weight) in three contrasting soils from tropical savanna ecosystems located in Pallarenda (sand), Wambiana (medium clay), or Yabulu (loamy sand), Queensland, Australia. These soils were sieved (2 mm), weighed (500 g dry weight), calibrated to a matric potential of -0.01 megapascals (MPa), -0.05 MPa, or -0.3 MPa (wettest to driest) and incubated at 22 °C. Measurements of cadaver decomposition included cadaver mass loss, carbon dioxide-carbon (CO 2-C) evolution, microbial biomass carbon (MBC), protease activity, phosphodiesterase activity, ninhydrin-reactive nitrogen (NRN) and soil pH. Cadaver burial resulted in a significant increase in CO 2-C evolution, MBC, enzyme activities, NRN and soil pH. Cadaver decomposition in loamy sand and sandy soil was greater at lower matric potentials (wetter soil). However, optimal matric potential for cadaver decomposition in medium clay was exceeded, which resulted in a slower rate of cadaver decomposition in the wettest soil. Slower cadaver decomposition was also observed at high matric potential (-0.3 MPa). Furthermore, wet sandy soil was associated with greater cadaver decomposition than wet fine-textured soil. We conclude that gravesoil moisture content can modify the relationship between temperature and cadaver decomposition and that soil microorganisms can play a significant role in cadaver breakdown. We also conclude that soil NRN is a more reliable indicator of gravesoil than soil pH.

Anodic Activation of Iron Corrosion in Clay Media under Water-Saturated Conditions at 90 °C: Characterization of the Corrosion Interface

To understand the process governing iron corrosion in clay over centuries, the chemical and mineralogical properties of solids formed by free or anodically activated corrosion of iron in water-saturated clay at 90 degrees C over 4 months were probed using microscopic and spectroscopic techniques. Free corrosion led to the formation of an internal discontinuous thin (<3 microm thick) magnetite layer, an external layer of Fe-rich phyllosilicate, and a clay transformation layer containing Ca-doped siderite (Ca(0.2)Fe(0.8)CO(3)). The thickness of corroded iron equaled approximately 5-7 microm, consistent with previous studies. Anodic polarization resulted in unequally distributed corrosion, with some areas corrosion-free and others heavily corroded. Activated corrosion led to the formation of an inner magnetite layer, an intermediate Fe(2)CO(3)(OH)(2) (chukanovite) layer, an outer layer of Fe-rich 7 A-phyllosilicate, and a transformed matrix layer containing siderite (FeCO(3)). The corroded thickness was estimated to 85 microm, less than 30% of the value expected from the supplied anodic charge. The difference was accounted for by reoxidation at the anodically polarized surface of cathodically produced H(2)(g). Thus, free or anodically activated corroding conditions led to structurally similar interfaces, indicating that anodic polarization can be used to probe the long-term corrosion of iron in clay. Finally, corrosion products retained only half of Fe oxidized by anodic activation. Missing Fe probably migrated in the clay, where it could interact with radionuclides released by alteration of nuclear glass.

Confrontational ceramics: the artist as social critic

Those who associate ceramics with functional vessels or charming knick-knacks are in for a shock. Clay may start out soft, but in the right hands it can deliver a hard blow. From British Toby Jugs to Marcel Duchamp's Fountain to a wall of gruesome tiles that forms a portrait of President George W. Bush, ceramic art has the power to provoke and subvert. Confrontational Ceramics surveys the work of contemporary sculptors, potters, and mixed media artists who have turned the ancient medium of clay into an articulate vehicle for political and social commentary. Educator and curator Judith S. Schwartz gathers the works of more than two hundred artists from thirty different countries into a glossy full-color overview of the radical ceramics scene. Provocative pieces from makers such as Grayson Perry, Robert Arneson, Richard Notkin, Howard Kottler, as well as newer talents, address personal, social, and geopolitical injustices from rape to racism. In their own words, these bold artists discuss the outrage behind their outrageous works. Schwartz provides historical context for current and late twentieth-century protest in the form of ceramics. She also places the artists within thematic groupings: war and politics, the social and human condition, gender issues, the environment, and popular and material culture. Filled with subtle satire, garish jests, grotesque shock treatments, and moving testaments, Confrontational Ceramics is a radical departure from conventional coffee-table ceramics books on decorative housewares or formal abstractions. This art book will amuse, inspire, and possibly offend art historians, ceramics collectors, and anyone with an eye for the outlandish.

A Study on the Needs of Art Education to Develop Child’s Sensibility -with clay medium-

A Study on the Needs of Art Education to Develop Child’s Sensibility -with clay medium-

Penetration of rigid bodies into loose and layered media

Penetration and motion of rigid bodies in ground media attracts the researchers’ attention because of various problems arising as the technology evolves. In fact, there are two independent directions of studies in this field: (1) the problem of earth excavation when a rigid body of a definite shape slowly moves along a given trajectory in the ground; (2) an impact of a rapidly flying free rigid or deformable body against the ground. In the latter case, to which the proposed studies pertain, it is sometimes of interest to study the medium behavior and the motion of the free body, which moves in the medium after the impact owing to the kinetic energy of itself. In this field, a majority of studies deal with collision and penetration of bodies of various shapes into clay media. An extensive survey of these studies is given in [1]. After this survey appeared, numerous paper dealing with complicated collision conditions have been published [2]. Penetration in loose media has been studied much more rarely. The direct collision with fractured rock was studied in connection with the expected landing of spacecraft on other planets [3, 4]. In this case, the influence of grain dimensions and the density of the filling and vacuum on the penetration was studied for the initial velocities in the range of 1.7–10 m/s. On the other hand, in [5], the results of investigating the penetration of conic bodies in sand at entry velocities of 700–900 m/s are given; these velocities significantly exceed the speed of sound in this medium, which lies in the range of 100–200 m/s for dry sand. Analyzing the experimental results, the author came to the conclusion that it is necessary to use different representations of the drag force in the supersonic and subsonic modes. In the present paper, we do not consider the influence of the grain distribution, sand density, and filling methods on the penetration. But, as follows from the experiments whose results are described in [6] and [7], to represent the results of penetration of rigid bodies at velocities up to several hundreds of meters per second, in addition to the characteristics listed above, it is also required to describe the technology of the experiment preparation, because such media have the property of shape “memory.”

Storage and stability of organic matter and fossil carbon in a Luvisol and Phaeozem with continuous maize cropping: A synthesis

AbstractQuantitative information about the amount and stability of organic carbon (OC) in different soil organic‐matter (OM) fractions and in specific organic compounds and compound‐classes is needed to improve our understanding of organic‐matter sequestration in soils. In the present paper, we summarize and integrate results performed on two different arable soils with continuous maize cropping (a) Stagnic Luvisol with maize cropping for 24 y, b) Luvic Phaeozem with maize cropping for 39 y) to identify (1) the storage of OC in different soil organic‐matter fractions, (2) the function of these fractions with respect to soil‐OC stabilization, (3) the importance and partitioning of fossil‐C deposits, and (4) the rates of soil‐OC stabilization as assessed by compound‐specific isotope analyses. The fractionation procedures included particle‐size fractionation, density fractionation, aggregate fractionation, acid hydrolysis, different oxidation procedures, isolation of extractable lipids and phospholipid fatty acids, pyrolysis, and the determination of black C. Stability of OC was determined by 13C and 14C analyses. The main inputs of OC were plant litter (both sites) and deposition of fossil C likely from coal combustion and lignite dust (only Phaeozem).

Of storytelling and the slippery medium of clay: Babette Wainwright's Image of the Women at the Diasporic Crossroads

The paper seeks to explore the art historical dimension of Babette Wainwright's artistic preoccupation as it intersects with the emerging field of African diaspora and visual culture studies. To those unfamiliar with the visual vocabulary of Babette Wainwright's artistic preoccupation, her evocative and visually compelling imagery can be alienating. It is a scopic event of phenomenal dimension. One is either drawn by its charming and intriguing nature or one is simply repelled by it. It is an experience that compels the viewer to participate in its ‘communal visuality’, thus involving a tripartite dialogue between the gallery space, the work and the viewer. Right there in the middle of gallery, Wainwright suspended three wrecked ceramic boats in mid air, attached with the aid of a fishing string to the ceiling of the exhibition space. And on the floor, she displayed remnants of lost humanity, severed limbs, wreckages of ship and cargo, amidst the detritus of wasted lives, the gripping evidence of the white sand on the gallery floor. The entire atmosphere is very eerie and surreal. By one magical command, we are transported to the bottom of the ocean to view the evidence of man's inhumanity in its genocidal dimensions. Taken together, these material remains, represent vestiges and echoes of a bygone era. Here in poignant manner she has captured and immobilized more than three hundred years of the dispersal, enslavement, and catastrophic arrival of peoples of African descent in the Western Hemisphere.

Injuries to law enforcement officers: The backface signature injury

In today's law enforcement community, one of the most vital tools an officer can possess is personal body armor. However, a recent Department of Justice investigation has raised important questions regarding the protection actually afforded officers through the use of personal body armor, and the current test methods used to assess the armor. Test results show that most Zylon-containing vests showed deformations in excess of the 0101.04 Standard's 44 mm backface signature limit. Such increased deformation can lead to serious injuries, including backface signature injuries, which have occurred in the field. Although the vest is successful in containing the round, it is not effectively dissipating the energy enough to prevent large amounts of vest deformation at the area of impact. Therefore, open, penetrating wounds occur even though the bullet did not penetrate the vest. The objective of the current study was to further define the backface signature injury through the use of case studies and laboratory experiments. Following the case study investigation, backface signature testing was conducted using a clay medium based on the NIJ 0101.04 Standard. The final component of this research involved the use of post-mortem human specimens (PMHS) for further investigation of the backface signature injury. Although the underlying cause of backface signature injuries is unknown, energy density is likely to play a role in the mechanism. Energy density ( E/ a) is defined as the energy per unit area and has been previously used in less lethal skin penetration research. Further research into the underlying causes of backface signature injuries is necessary. In addition to armor testing, the study of law enforcement personnel who have been shot while wearing soft body armor is also a valuable tool for determining the effectiveness of certification standards. Finally, it is important for medical personnel to recognize the backface signature injury and document this as a type of injury separate from blunt trauma or penetrating trauma behind armor injuries. Detailed knowledge of the injury, including the depth of the wound, would be beneficial to the scientific community.

Estimation of clay content in soil based on resistivity modelling and laboratory measurements

ABSTRACTThe determination of clay content in near‐surface formations is crucial for geotechnical, hydrogeological and oil‐contamination studies. We have developed a technique for estimating clay content that consists of the minimization of the difference between the theoretically calculated and measured soil resistivities as a function of water salinity. To calculate the resistivity, we used a model that takes into account the electrochemical processes in the clay micropores. The experimental measurements of soil resistivity were performed on soil samples, completely saturated by brines at different concentrations of NaCl salt in the range 0.6–100 g/l, to obtain the resistivity versus salinity curve. The parameters obtained with this curve inversion are the clay content, the total porosity and the cation exchange capacity. To verify the new technique, we determined clay concentrations of artificial mixtures of calibrated sand and clay. The relative mean error in the clay content does not exceed 20% for a 5% fitting error of the resistivity versus salinity curves. Such evaluations allow the correct separation of the main lithological groups (sand, sandy loam, loam, and light, medium and heavy clay).We applied this technique to estimate the petrophysical parameters of soils (clay content, porosity and cation exchange capacity) at various sites in Mexico. The results improved the interpretation of the vertical electrical soundings, the lithological soil characterization and the delineation of oil‐contaminated areas.

Experimental Study on Aero Conductivity of Porous Media

ABSTRACT To study the variation pattern of aero conductivity of different porous media under low pressure conditions, three kinds of media are selected. These include sandy clay loam, fine sand, and medium sand, and air as fluid to conduct soil column ventilation tests. Pressure at both ends of the columns is measured under different ventilation flow rates during testing. The test results show that the aero conductivity, solved by Darcy's law, is not a constant. It is a variable, which increases first when air flow velocity is less than 0.258 7 cm/s for sandy clay loam, 0.637 3 cm/s for fine sand and then decreases when air flow velocity is bigger than that with the increase of the ventilation flow rate when the medium is determined. By analyzing various factors that influence the flow resistance, the reasons for variation in aero conductivity are found as follows: first, the change of pore structure results in better ventilation; second, the relationship between pressure head loss and air flow velocity is nonlinear, and it is beyond the condition of the laminar flow domain to which Darcy's law can be applied, when the air flow rate increases to a certain value and the flow velocity is in the transition range to turbulent flow.

Behaviour of silicon released during alteration of nuclear waste glass in compacted clay

Long term integrated in situ experiments are performed in the HADES underground research facility (Mol, Belgium) in order to study the coupled reactivity between the different components of an underground repository for vitrified high level radioactive waste (HLW): glass, compacted clay, and stainless steel containers, at 90 °C and under gamma irradiation. Studies pertaining to the behaviour of silicon, a major element released during glass alteration, are presented here. Data collected from the integrated experiment, from simplified tests, and from modelling are put together, giving complementary information. The integrated experiment is used to investigate overall reactivity, whereas diffusion experiments coupled with modelling focused on the precipitation of silica in clay media. In the integrated in situ experiment, a bentonite clay (FoCa7) mixed with 5 wt.% of powdered glass frit was put in contact with U/Th-doped SON68 reference glass specimens for 1.2 years. One of the samples was thoroughly analysed by ESEM, SEM-EDS, TEM, XRD, and FTIR. The observations showed that after combined heating and γ irradiation, the glass/clay interface is still fully reactive. At this interface, the most important process occurring is silica precipitation either as spherical flaky nodules, or in the form of coatings on the clay surface, as chalcedony and amorphous silica. In parallel, numerical modelling was used to investigate the interactions between silica and clay material in a simplified experiment using diffusion cells. A fit between calculation results and silica migration measurements in diffusion cells was performed, including sensitivity tests with regard to the diffusion coefficients and the precipitation rate of amorphous silica. A satisfactory agreement is reached with the experimental results, using a set of reasonable fitting parameters for the FoCa7 clay material. Surface area values for silica precipitation are found to be very high, i.e. 2% of the total surface area of the clayey material indicating that silica precipitation occurs on surfaces other than those of pure silica minerals.

Relationships among Coefficient of Linear Extensibility and Clay Fractions in Expansive, Stoney Soils

An expansive soil is any soil that has a potential for shrinking and swelling under changing moisture conditions. Structural damage to homes (i.e., walls and foundations) due to expansive soils is costly to repair and may be somewhat avoidable if soil properties, such as clay content and the coefficient of linear extensibility (COLE), are investigated. The objectives of this study were to examine the relationships among COLE, clay fractions, and coarse‐fragment content and determine the usefulness of COLE as an indicator of structural damage in expansive and stoney soils. Sixteen individual homeowner sites were selected for sampling in the Fayetteville area of Washington County, Arkansas based on a homeowner questionnaire and visual inspection. COLE was determined based on the rod method from the length change of a moist and oven‐dry soil‐paste rod (COLErod). Measured COLErod values were adjusted for coarse‐fragment content (COLEadj) by multiplying COLErod by the volume fraction of fine‐earth plus pores, yielding a 0.003 unit reduction (P &lt; 0.001) in COLErod, but no change in hazard‐class rating. COLErod was positively correlated (P &lt; 0.001) with total (r = 0.88), coarse (r = 0.55), and medium plus fine (r = 0.79) clay fractions. However, COLErod adjustments for coarse‐fragment content did not improve linear relationships between COLErod and clay fractions. The summation of soil profile COLErod values for a site was a reasonable predictor, while the average COLErod value for a site and COLEadj were poor predictors of home structural damage. Results demonstrate that COLErod is a reasonably reliable predictor of potential home structural damage.

Root distribution of Eucalyptus grandis and Corymbia maculata in degraded saline soils of south-eastern Australia

Planting trees, in farm forestry enterprises, to control rising watertables is an increasing practice for both economic and environmental benefits. One central biophysical issue which determines the effectiveness of trees to control groundwater is the ability of trees to grow roots through degraded soils and take up groundwater. We investigated the effect of soil properties, especially the presence of shallow watertables and site preparation practice, on the vertical and horizontal distributions of Eucalyptus grandis W. Hill ex Maiden and Corymbia maculata (Hook.) K.D. Hill and L.A.S. Johnson roots. In order to improve the reliability of root data, we measured root growth and distribution by three different methods – (i) number of roots intercepting the vertical plane of the soil profile, (ii) root length density in soil cores taken at different depths but in the horizontal plane of the profile, and (iii) root length density in soil cores in the vertical plane at different radial positions from trees and compared the results. Two experimental sites were established in flood-irrigated, farm forestry plantations on contrasting soils in the Murray Riverina region of south-eastern Australia. At one site (Norwood Park), we studied a 58-month-old stand of E. grandis growing in clay loam overlaying medium clay, saline, sodic and alkaline subsoil with a saline (11.5 dS m−1) watertable at 2.8 m depth. Here, there were few roots growing above the watertable. The Karawatha site had adjacent stands of 46-month old E. grandis and C. maculata growing in a sandy, neutral and non-saline soil with a shallow (3.1 m deep) non-saline (2.8 dS m−1) watertable. Here roots proliferated above the watertable in both species but to a much greater extent under C. maculata than under E. grandis. Root distributions in the surface soil were similar at all sites but differences in root growth in the capillary zones paralleled differences in groundwater uptake by trees. We conclude (i) that appropriate matching of species with site characteristics, especially soil and groundwater properties, will enhance tree growth and groundwater uptake and (ii) that extensive planting of C. maculata over non-saline watertables maximises the chances of achieving the multiple objectives of regional groundwater control, fast growth rates and reduced irrigation demand.

Picasso and Ceramics (review)

Reviewed by: Picasso and Ceramics Elissa Auther (bio) Paul Bourassa, curator. Picasso and Ceramics Éditions Hazan and the Gardiner Museum of Ceramic Art. xi, 288. $79.99 Picasso and Ceramics is the catalogue for the 2004 exhibition of the same title organized by the Musée National des Beaux-Arts du Québec. The book contains five engaging and informative essays chronicling Pablo Picasso' s turn to ceramics, the evolution of his prodigious body of work in the medium, and the details of his working relationship with the Atelier Madoura in the village of Vallauris, France. The book is well illustrated, containing over two hundred and fifty colour and black and white images documenting the exhibition and the evolution of Picasso's work as a ceramicist. In addition, there is a very useful, comprehensive bibliography of books, articles, and exhibition catalogues pertaining to Picasso's ceramic oeuvre. As Paul Bourassa, curator of the exhibition 'Picasso and Ceramics' and lead author of the catalogue, notes, the aim of the exhibition and its accompanying catalogue is 'to demonstrate the importance of Picasso's contribution to the history of the discipline.' Bourassa means the history of the discipline of ceramics, in which Picasso's 'discovery' or turn to clay in 1947 has always been viewed with some suspicion. I would argue that the book makes a similar case for the importance of Picasso's work in ceramics to art historical scholarship about the artist. Despite the seriousness and intensity of Picasso's engagement with the medium of clay (his ceramic oeuvre is estimated to be as large as 4500 pieces), this body of work is still often neglected and dismissed as 'decorative' or a leisure-time pursuit in Picasso scholarship. Picasso and Ceramics works both to legitimize Picasso's work in clay as an important contribution to the discipline of ceramics and to redress the ignorance and prejudice towards ceramics as a medium of art that lie at the root of its marginalization and denigration in art history's treatment of Picasso's career. Each of the essays contributes to this twin objective. Bourassa's lead essay 'Encounters with Ceramics,' demonstrates that Picasso's interest in pottery was not sudden but went back to his early encounters with and admiration for the work of Spanish and French artists such as Paco Durrio and Paul Gauguin, both of whom produced pivotal works in ceramics in the 1880s and 1890s. Under their influence Picasso produced sketches for vases in 1902 or 1903 and produced his first works in ceramics in 1906. Along with Bourassa's essay, which goes on to chronicle in detail the continuing evolution of Picasso's work in ceramics through 1969, Harald [End Page 329] Theil's essay, 'The Preliminary Drawings for Picasso's Ceramics,' makes the case that Picasso's works in clay are essentially that of a ceramist in the way they demonstrate a conscious adaptation of historical sources and the conventions of the discipline. Theil focuses on the anthropomorphic and zoomorphic works Picasso produced in the late 1940s, which were at once vessels and sculptures, to make his point. Readers interested in the history of ceramic workshop production will be delighted with Yves Peltier ' s essay, 'Madoura,' about the eponymous atelier founded by Suzanne Ramié in 1938 in the village of Vallauris, where Picasso worked from 1947 to 1971. Ramié played a central role in the revival of traditional French pottery from southern France as well as made a name for herself with innovative designs based on her reinterpretations of these traditional forms and their glazes. The repertoire of forms Picasso used for his anthropomorphic and zoomorphic works were those Ramié had revived. A related essay by Marie-Noélle Delorme discusses the posters Picasso produced for the annual exhibition of the Association Vallaurienne d'Expansion Céramique from 1948 to 1964. The final essay, 'Ceramics: Sources and Resources,' coauthored by Léopold L. Foulem and Paul Bourassa, provides a wealth of information regarding Picasso's techniques and formal appropriations that, once again, makes the case for the artist as technical master and conceptual innovator in the field of ceramics and the history of art. The aim of legitimizing...

Static dissolution tests of α-doped UO2 under repository relevant conditions: Influence of Boom Clay and α-activity on fuel dissolution rates

ABSTRACTSince reprocessing is no longer the reference policy in Belgium, studies on the direct disposal of spent fuel in a clay formation have gained increased interest in the last years. In order to determine to what extent the clay properties and the α-activity influence the dissolution kinetics of spent fuel for the long term disposal, static dissolution tests have been performed on 5 different types of α-doped UO2, representing a PWR fuel with a burn-up of 45 or 55 GWd · tHM−1 and fuel ages ranging between 150 and 90,000 years, in different Boom Clay (BC) media at room temperature and in an anoxic atmosphere for 90 to 720 days. The uranium activity in the clay fraction over time was found to be much higher than the U-activity in the leachates, which has been mainly ascribed to the high retention capacity of the BC. The average dissolution rate between 0 and 90 days obtained for the 5 types of α-doped UO2 were all found to be high and quite similar at ∼263 µg · m−2· d−1and a “longer-term” rate (181 to 720 days) ranging between zero and 15 µg · m−2· d−1. These results suggest that the activity of the fuels does not seem to have an effect on the UO2 dissolution rates under the considered test conditions. In order to study the partition/redistribution of U during UO2dissolution, sequential extraction experiments were performed. Results of the latter have provided a better mechanistic understanding of BC/spent fuel interaction processes as well as information on the role of the different minerals controlling the U-retention/immobilization.

Impacts of tree plantations on groundwater in south-eastern Australia

In some regions dependent on groundwater, such as the lower south-east of South Australia in the Green Triangle, deep-rooted, woody vegetation might have undesirable hydrological impacts by competing for finite, good-quality groundwater resources. In other regions, such as the Riverina in south-central New South Wales, where rising watertables and associated salinisation is threatening the viability of agriculture, woody vegetation might have beneficial hydrological impacts. In response to a growing need to better understand the impacts of tree plantations on groundwater, annual evapotranspiration and transpiration were measured at 21 plantation sites in the Green Triangle and the Riverina. Sources of tree water uptake from rainfall and groundwater were determined by measurements of evapotranspiration and soil water over periods of 2–5 years. In the Green Triangle, under a combination of permeable soil over groundwater of low salinity (&lt;2000 mg L–1) at 6-m depth or less, in a highly transmissive aquifer, annual evapotranspiration at eight research sites in Pinus radiata D.Don and Eucalyptus globulus Labill. plantations averaged 1090 mm year–1 (range 847–1343 mm year–1), compared with mean annual precipitation of 630 mm year–1. These plantation sites used groundwater at a mean annual rate of 435 mm year–1 (range 108–670 mm year–1). At eight other plantation sites that had greater depth to the watertable or a root-impeding layer, annual evapotranspiration was equal to, or slightly less than, annual rainfall (mean 623 mm year–1, range 540–795 mm year–1). In the Riverina, where groundwater was always present within 3 m of the surface, Eucalyptus grandis Hill ex Maiden trees at three sites with medium or heavy clay, alkaline, sodic, saline subsoils used little or no groundwater, whereas E. grandis and Corymbia maculata (Hook.) K.D.Hill and L.A.S.Johnson trees at a site with a neutral sandy soil and groundwater of low salinity used 380 and 730 mm year–1 of groundwater (respectively 41 and 53% of total annual evapotranspiration). We conclude that commonly grown Eucalyptus species and P. radiata are able to use groundwater under a combination of light- or medium-textured soil and shallow depth to a low-salinity watertable.

Leaching of Cesium and Uranium from Spent PWR fuel in the Gel-state Clays

ABSTRACTThe amounts of cesium and uranium released from crushed spent PWR fuel in the gel-state clays with a few ml of supernatant at hot cell temperature under Ar-atmosphere have been measured. The fractions of cesium dissolved from the fuel for 873 days were 0.29 and 0.25% in Boom clay/Boom-clay water and Ca-bentonite/synthetic granitic groundwater, respectively. These cesium fractions were very close to the gap inventory of cesium, which was determined to be around 0.30% in the previous experiment. The fraction of uranium released up to 193 days in the Boom clay media was 0.011% and this fraction has been retained until 873 days. Such this phenomenon was also obtained in the Ca-bentonite media even though the released fraction was higher than that in Boom clay. The increase of less than 0.001% in the dissolved uranium fraction between 193 and 873 days suggests that the long-term leach rate of uranium from spent fuel would be much less than 24 μg·m−2·day−1.

Development of an empirical model for domestic wastewater treatment by biological aerated filter

An empirical model for wastewater treatment by biological aerated filters (BAF) was developed in the study, which relates influent soluble chemical oxygen demand (sCOD) to effluent sCOD and medium bed height in order to simply engineering design and verify experimentally the suitability of this model and ascertain the relationship between the constant values calculated with the model and reactor performance. The theoretical model was based on design of contact oxidation process and conventional biofilter because these fixed-film processes show similar flow pattern. Firstly, the two parallel BAF systems packed with lava medium and expanded clay medium, respectively, were run for actual domestic wastewater at different hydraulic loading rates during the experiment. A great deal of data was then used to the empirical model, which was based on a first-order reaction, to calculate the empirical values of n (medium constant) and K (overall process constant). The experimental results show that the treatment efficiency of lava medium exceed to that of expanded clay medium, which just conform to what the model predict, the higher value of K the greater efficiency of sCOD removal, and the lower value of n the greater variation of sCOD removal indicating a poor resistance to shock loading. Next, the effect of suspended solid (SS) on model was estimated by simulated domestic wastewater to verify its feasibility.