ESEM study of illite/smectite freshwater sensitivity in sandstone reservoirs

The water sensitivity of authigenic smectite- and illite-rich illite/smectites in sandstone reservoirs has been investigated using an Environmental Scanning Electron Microscope (ESEM). The ESEM enabled the illite/smectites to be directly observed in situ at high magnification during freshwater immersion, and was also particularly effective in allowing the same selected illite/smectite areas to be closely compared before and after freshwater treatments. The tendency of authigenic smectite-rich illite/smectite to swell on contact with fresh water varies greatly. Smectite-rich illite/smectite may osmotically swell to many times its original volume to form a gel which greatly reduces porosity and permeability, or may undergo only a subtle morphological change which has little or no adverse effect on reservoir quality. Authigenic illite-rich illite/smectite in sandstones does not swell when immersed in fresh water. Even after prolonged soaking in fresh water, illite-rich illite/smectite particles retain their original morphology. Accordingly, illite-rich illite/smectite in sandstones is unlikely to cause formation damage if exposed to freshwater-based fluids. © 1993.

Transmission X-ray microscopy : a new tool in clay mineral floccules characterization

Effective flocculation and dewatering of mineral processing streams containing clays are microstructure dependent in clay-water systems. Initial clay flocculation is crucial in the design and for the development of a new methodology of gas exploitation. Microstructural engineering of clay aggregates using covalent cations and Keggin macromolecules have been monitored using the new state of the art Transmission X-ray Microscope (TXM) with 60 nm tomography resolution installed in a Taiwanese synchrotron. The 3-D reconstructions from TXM images show complex aggregation structures in montmorillonite aqueous suspensions after treatment with Na+, Ca2+ and Al13 Keggin macromolecules. Na-montmorillonite displays elongated, parallel, well-orientated and closed-void cellular networks, 0.5–3 μm in diameter. After treatment by covalent cations, the coagulated structure displays much smaller, randomly orientated and openly connected cells, 300–600 nm in diameter. The average distances measured between montmorillonite sheets was around 450 nm, which is less than half of the cell dimension measured in Na-montmorillonite. The most dramatic structural changes were observed after treatment by Al13 Keggin; aggregates then became arranged in compacted domains of a 300 nm average diameter composed of thick face-to-face oriented sheets, which forms porous aggregates with larger intra-aggregate open and connected voids.

The difference of thermal stability between Fe-substituted palygorskite and Al-rich palygorskite

Sedimentary palygorskite (SP) and hydrothermal palygorskite (HP) were characterized by XRF, TG/DSC, andXRD. The total iron and dissociative iron in palygorskite were detected using spectrophotometry. The results showed that about 3.57 wt% of Fe2O3 was detected in SP in contrast with 0.4 wt% in HP. SP was a Fe-substituted palygorskite, and HP was an Al-rich palygorskite. The occurrence of Fe substitution in SP resulted in two mass loss steps of coordinated water and resulted in a larger d spacing. The SP showed greater thermal stability than the HP. It was proposed the change of (200) diffraction peak and (240) diffraction peak reflect changes of tetrahedral and octahedral structures in palygorskite.

Distribution of organic-rich sediments through the Phanerozoic

It is commonly assumed that rates of accumulation of organic-rich strata have varied through geologic time with some periods that were particularly favorable for accumulation of petroleum source rocks or coals. A rigorous analysis of the validity of such an assumption requires consideration of the basic fact that although sedimentary rocks have been lost through geologic time to erosion and metamorphism. Consequently, their present-day global abundance decreases with their geologic age. Measurements of the global abundance of coal-bearing strata suggest that conditions for coal accumulation were exceptionally favorable during the late Carboniferous. Strata of this age constitute 21% of the world's coal-bearing strata. Global rates of coal accumulation appear to have been relatively constant since the end of the Carboniferous, with the exception of the Triassic which contains only 1.75% of the world's coal-bearing strata. Estimation of the global amount of discovered oil by age of the source rock show that 58% of the world's oil has been sourced from Cretaceous or younger strata and 99% from Silurian or younger strata. Although most geologic periods were favourable for oil source-rock accumulation the mid-Permian to mid-Jurassic appears to have been particularly unfavourable accounting for less than 2% of the world's oil. Estimation of the global amount of discovered natural gas by age of the source rock show that 48% of the world's oil has been sourced from Cretaceous or younger strata and 99% from Silurian or younger strata. The Silurian and Late Carboniferous were particularly favourable for gas source-rock accumulation respectively accounting for 12.9% and 6.9% of the world's gas. By contrast, Permian and Triassic source rocks account for only 1.7% of the world's natural gas. Rather than invoking global climatic or oceanic events to explain the relative abundance of organic rich sediments through time, examination of the data suggests the more critical control is tectonic. The majority of coals are associated with foreland basins and the majority of oil-prone source rocks are associated with rifting. The relative abundance of these types of basin through time determines the abundance and location of coals and petroleum source rocks.

Discussion: Response of a plastic pipe buried in expansive clay

Response to discussion on Gallage CPK, Chan D and Kodilara J (2012) Response of a plastic pipe buried in expansive clay. Proceedings of ICE, Geotechnical Engineering, Vol 164, February 2012, Issue GE1, pages 45-57.

Transcription and expression of Plasmodium falciparum histidine-rich proteins in different stages and strains : implications for rapid diagnostic tests

Background: Although rapid diagnostic tests (RDTs) for Plasmodium falciparum infection that target histidine rich protein 2 (PfHRP2) are generally sensitive, their performance has been reported to be variable. One possible explanation for variable test performance is differences in expression level of PfHRP in different parasite isolates. Methods: Total RNA and protein were extracted from synchronised cultures of 7 P. falciparum lines over 5 time points of the life cycle, and from synchronised ring stages of 10 falciparum lines. Using quantitative real-time polymerase chain reaction, Western blot analysis and ELISA we investigated variations in the transcription and protein levels of pfhrp2, pfhrp3 and PfHRP respectively in the different parasite lines, over the parasite intraerythrocytic life cycle. Results: Transcription of pfhrp2 and pfhrp3 in different parasite lines over the parasite life cycle was observed to vary relative to the control parasite K1. In some parasite lines very low transcription of these genes was observed. The peak transcription was observed in ring-stage parasites. Pfhrp2 transcription was observed to be consistently higher than pfhrp3 transcription within parasite lines. The intraerythrocytic lifecycle stage at which the peak level of protein was present varied across strains. Total protein levels were more constant relative to total mRNA transcription, however a maximum 24 fold difference in expression at ring-stage parasites relative to the K1 strain was observed. Conclusions: The levels of transcription of pfhrp2 and pfhrp3, and protein expression of PfHRP varied between different P. falciparum strains. This variation may impact on the detection sensitivity of PfHRP2-detecting RDTs.

Practical applications for clay-derived zeolite N : an ammonium-selective ion exchanger for industry use

Over the past ten years, scaled-up utilisation of a previously under-exploited zeolite, Zeolite N1, has been demonstrated for selective ion exchange of ammonium and other ions in aqueous environments. As with many zeolite syntheses, the required source material should contain predictable levels of aluminium and silicon and, for full-scale industrial applications, kaolin and/or montmorillonite serve such a purpose. Field, pilot and commercial scale trials of kaolin-derived Zeolite N have focused on applications in agriculture and water treatment as these sectors are primary producers or users of ammonium. The format for the material – as fine powders, granules or extrudates – depends on the specific application albeit each has been evaluated.

Observation of exsolution textures within Ba-Cu-O-rich solidified melts of Y-Ba-Cu-O materials and their relationship to Y123 nucleation and texturing

Layers (about 60-100 μm thick) of almost pure BaCuO2 (BC1), as determined using X-ray diffractometry (XRD) and scanning electron microscopy (SEM), coat the surfaces of YBa2Cu3O7-x (Y123) samples partial melt processed using a single-zone vertical furnace. The actual Cu/Ba ratio of the BC1 phase is 1.2-1.3 as determined using energy dispersive X-ray spectrometry (EDS). The nominally BC1 phase displays an exsolution of BC1.5 or BC2 in the form of thin plates (about 50-100 nm thick) along {100}-type cleavage planes or facets. The exsolved phase also fills cracks within the BC1 layer that require it to be in a molten state at some stage of processing. The samples were influenced by Pt contamination from the supporting wire, which may have stabilised the BC1.5 phase. Many of the Y123 grains have the same morphology as the exsolution domains, and run nearly parallel to the thin plates of the exsolved phases, strongly indicating that Y123 nucleation took place at the interface between the BC1 and the BC1.5 or BC2 exsolved phases. The network of nearly parallel exsolved 'channels' provides a matrix and a mechanism through which a high degree of local texture can be initiated in the material.

Growing biodiverse carbon-rich forests

Regrowing forests on cleared land is a key strategy to achieve both biodiversity conservation and climate change mitigation globally. Maximizing these co-benefits, however, remains theoretically and technically challenging because of the complex relationship between carbon sequestration and biodiversity in forests, the strong influence of climate variability and landscape position on forest development, the large number of restoration strategies possible, and long time-frames needed to declare success. Through the synthesis of three decades of knowledge on forest dynamics and plant functional traits combined with decision science, we demonstrate that we cannot always maximize carbon sequestration by simply increasing the functional trait diversity of trees planted. The relationships between plant functional diversity, carbon sequestration rates above-ground and in the soil are dependent on climate and landscape positions. We show how to manage ‘identities’ and ‘complementarities’ between plant functional traits in order to achieve systematically maximal co-benefits in various climate and landscape contexts. We provide examples of optimal planting and thinning rules that satisfy this ecological strategy and guide the restoration of forests that are rich in both carbon and plant functional diversity. Our framework provides the first mechanistic approach for generating decision-making rules that can be used to manage forests for multiple objectives, and supports joined carbon credit and biodiversity conservation initiatives, such as Reducing Emissions from Deforestation and forest Degradation REDD+. The decision framework can also be linked to species distribution models and socio-economic models in order to find restoration solutions that maximize simultaneously biodiversity, carbon stocks and other ecosystem services across landscapes. Our study provides the foundation for developing and testing cost-effective and adaptable forest management rules to achieve biodiversity, carbon sequestration and other socio-economic co-benefits under global change.

Effect of palygorskite clay on pyrolysis of rape straw : an in situ catalysis study

Biomass tar restricts the wide application and development of biomass gasification technology. In the present paper, palygorskite, a natural magnesium-containing clay mineral, was investigated for catalytic pyrolysis of rape straw in situ and compared with the dolomite researched widely. The two types of natural minerals were characterized with XRD and BET. The results showed that combustible gas derived from the pyrolysis increased with an increase in gasification temperature. The Hconversion and Cconversion increased to 44.7% and 31% for the addition of palygorskite and increased to 41.3% and 31.3% for the addition of dolomite at the gasification temperature of 800 °C, compared with 15.1% and 5.6% without addition of the two types of material. It indicated that more biomass was converted into combustible gases implying the decrease in biomass tar under the function of palygorskite or dolomite and palygorskite had a slightly better efficiency than that of dolomite in the experimental conditions.

Trace-element modeling of the magmatic evolution of rare-earth-rich carbonatite from the Miaoya deposit, Central China

Carbonatites are known to contain the highest concentrations of rare-earth elements (REE) among all igneous rocks. The REE distribution of carbonatites is commonly believed to be controlled by that of the rock forming Ca minerals (i.e., calcite, dolomite, and ankerite) and apatite because of their high modal content and tolerance for the substitution of Ca by light REE (LREE). Contrary to this conjecture, calcite from the Miaoya carbonatite (China), analyzed in situ by laser-ablation inductively-coupled-plasma mass-spectrometry, is characterized by low REE contents (100–260 ppm) and relatively !at chondrite-normalized REE distribution patterns [average (La/Yb)CN=1.6]. The carbonatite contains abundant REE-rich minerals, including monazite and !uorapatite, both precipitated earlier than the REE-poor calcite, and REE-fluorocarbonates that postdated the calcite. Hydrothermal REE-bearing !uorite and barite veins are not observed at Miaoya. The textural and analytical evidence indicates that the initially high concentrations of REE and P in the carbonatitic magma facilitated early precipitation of REE-rich phosphates. Subsequent crystallization of REE-poor calcite led to enrichment of the residual liquid in REE, particularly LREE. This implies that REE are generally incompatible with respect to calcite and the calcite/melt partition coefficients for heavy REE (HREE) are significantly greater than those for LREE. Precipitation of REE-fluorocarbonates late in the evolutionary history resulted in depletion of the residual liquid in LREE, as manifested by the development of HREE-enriched late-stage calcite [(La/Yb)CN=0.7] in syenites associated with the carbonatite. The observed variations of REE distribution between calcite and whole rocks are interpreted to arise from multistage fractional crystallization (phosphates!calcite!REE-!uorocarbonates) from an initially REE-rich carbonatitic liquid.

Rich and purposeful mathematical knowledge of mothers and children in a Torres Strait Islander community

This paper focuses on a pilot study that explored the situated mathematical knowledge of mothers and children in one Torres Strait Islander community in Australia. The community encouraged parental involvement in their children’s learning and schooling. The study explored parents’ understandings of mathematics and how their children came to learn about it on the island. A funds of knowledge approach was used in the study. This approach is based on the premise that people are competent and have knowledge that has been historically and culturally accumulated into a body of knowledge and skills essential for their functioning and well-being (Moll, 1992). The participants, three adults and one child are featured in this paper. Three separate events are described with epiphanic or illuminative moments analysed to ascertain the features that enabled an understanding of the nature of the mathematical events. The study found that Indigenous ways of knowing of mathematics were deeply embedded in rich cultural practices that were tied to the community. This finding has implications for teachers of children in the early years. Where school mathematics is often presented as disembodied and isolated facts with children seeing little relevance, learning a different perspective of mathematics that is tied to the resources and practices of children’s lives and facilitated through social relationships, may go a long way to improving the engagement of children and their parents in learning and schooling.

Nanohybrids of silver particles on clay platelets delaminate Pseudomonas biofilms

Aim To evaluate the effectiveness of novel nanohybrids, composed of silver nanoparticles and nanoscale silicate platelets, to clear Pseudomonas aeruginosa biofilms. Materials & methods The nanohybrids were manufactured from an in situ reduction of silver salts in the silicate platelet dispersion, and then applied to biofilms in vitro and in vivo. Results In reference to the biocidal effects of gentamycin, the nanohybrids mitigated the spreading of the biofilms, and initiated robust cell death and exfoliation from the superficial layers of the biofilms in vitro. In vivo, the nanohybrids exhibited significant therapeutic effects by eliminating established biofilms from infected corneas and promoting the recovery of corneal integrity. Conclusion All of the evaluations indicate the high potency of the newly developed silver nanoparticle/nanoscale silicate platelet nanohybrids for eliminating biofilms.

Handmade clay balls and recycled crush glass as alternative media in water filtration

For many years materials such as quarried sand, anthracite, and granular activated carbon have been the principal media-products traditionally used in water and wastewater filtration plants. Pebble Matrix Filtration (PMF) is a novel non-chemical, sustainable pre-treatment method of protecting Slow Sand Filters (SSF) from high turbidity during heavy monsoon periods. PMF uses sand and pebbles as the filter media and the sustainability of this new technology might depend on availability and supply of pebbles and sand, both finite resources. In many countries there are two principal methods of obtaining pebbles and sand, namely dredging from rivers and beaches, and due to the scarcity of these resources in some countries the cost of pebbles is often 4-5 times higher than that of sand. In search for an alternative medium to pebbles after some preliminary laboratory tests conducted in Colombo-Sri Lanka, Poznan-Poland and Cambridge-UK, a 100-year-old brick factory near Sudbury, Suffolk, has produced hand-made clay pebbles satisfying the PMF quality requirements. As an alternative to sand, crushed recycled glass from a UK supplier was used and the PMF system was operated together with hand-made clay balls in the laboratory for high turbidity removal effectively. The results of laboratory experiments with alternative media are presented in this paper. There are potential opportunities for recycled crushed glass and clay ball manufacturing processes in some countries where they can be used as filter media.