Effect Of Natural Weathering Research Articles

Release and speciation of uranium in low-ionic-strength groundwaters at an abandoned uranium mine in Val Vedello (Orobic Alp—Italy) by adsorptive cathodic stripping voltammetry

Adsorptive cathodic stripping voltammetry (AdCSV) with HDME and a chloranilic acid ligand was used in the trace analysis of uranyl ions at pH = 2 in low-ionic-strength groundwaters around mining areas. Upon optimization, the limit of detection around 0.10 µg L−1 was found with linearity up to 10 µg L−1. In the abandoned mining area of Val Vedello (Orobic Alps, Italy), measured uranium concentrations in water ranged from 0.3 µg L−1 above the uranium mineralization levels to 145 µg L−1 in groundwaters percolating from mine galleries. Such uranium concentrations are related to natural weathering effects of CO2 and/or hydrogen carbonate ion on uranium mineralizations under oxic conditions. A marked seasonal dependence was then found, in agreement with literature data on a pre-operational survey dating back to 1980–1981. No significant chemical impact of the abandoned mining activity on groundwater quality could be found. Accordingly, no significant increase in contaminants derived from the heat-burn of explosives, such as chloride and nitrate, in groundwaters from mine galleries was found.

Natural weathering effects on some properties of CPVC pipe material

Polyvinyl chloride (PVC) and more recently chlorinated-PVC (CPVC) pipes are extensively used for water distribution, wastewater and in limited applications for gas distribution. More and more cities are using CPVC pipes and pipefittings in their water distribution networks. Chlorinated-PVC is a material designed to withstand higher service pressures and temperatures than PVC. Its utilization in harsh environmental conditions, such as those of the Arabian Peninsula requires understanding of weathering effects, including UV, moisture and high ambient temperature on its mechanical properties. In this work, tensile and single-edge-notch bending (SENB) specimens prepared from locally manufactured CPVC commercial pipes have been naturally weathered for different periods (1–9 months) in harsh Saudi weather conditions. Standard tensile and SEN fracture toughness tests were performed after natural exposure periods of 1, 2, 3, 6 and 9 months. The tensile test results show that exposure for periods up to 9 months, including summer season, had limited effects on the tensile strength and modulus of elasticity of the material. This was expected given that the damage due weathering is mainly a surface phenomenon. However, the deterioration of the ultimate elongation is noticeable for exposure periods as low as 1 month. Analysis of fracture toughness results reveals a general trend that indicates a deterioration of this property at the beginning of the exposure time.

The effect of natural weathering on the mechanical, morphological and thermal properties of high impact polystyrene (HIPS)

The effect of natural weathering on the mechanical, morphological and thermal properties on the high impact polystyrene (HIPS) and cold drawn HIPS are investigated. After natural weathering period of 8760 h, under known meteorological parameters, the changes in mechanical properties are investigated by using tensile, instrumented impact and hardness tests. Thermo-mechanical properties are characterized by using thermomechanical analysis (TMA) and melt flow index (MFI). Fractured surfaces of the materials are investigated by scanning electron microscope (SEM). Natural weathering effects on fracture mechanisms are discussed by means of fractographical analysis. Remarkable morphological changes were observed especially at the surface of the material. This results in dramatic loss in mechanical properties.

Natural weathering effects on the mechanical and surface properties of polyphenylene sulphide (PPS) composites

In this paper, Natural weathering effects on the mechanical and surface properties of polyphenylene sulphide (PPS) composites were studied. Injection moulded short glass fibre and short glass fibre/calcium carbonate particle filled (hybrid) PPS composites were investigated. These specimens were subjected to natural weathering in İzmit, Turkey for 3216 h. Instrumented charpy impact tests were performed on a charpy pendulum type tester. The surfaces of the samples were examined by scanning electron microscopy (SEM). It is demonstrated that particle reinforcement (additional to the random oriented short glass fibre) reduces the impact performance of composite material but the material becomes more resistant to weathering. Percentage decrease in the impact strength after natural weathering of fibre/particle filled PPS composite is smaller compared to short fibre filled PPS composite. On the other hand, surface morphology of CaCO 3 particle reinforced PPS composite is affected less from natural weathering and this material should be considered for outdoor applications.

Weathering of vegetable fibre-clinker free cement composites

Ground iron blast-furnace slag (BFS) activated by a mixture of gypsum and hydrated lime was examined as an alternative binder for fibre-cement mortars produced by a low energy consumption method. Brazilian fibrous wastes from sisal and banana crops and also from a eucalyptus pulp mill were chosen for reinforcement. The composite preparation followed conventional mixing, ordinary vibration and wet chamber curing for the seven initial days. The composites achieved a modulus of rupture of up to 3.92 MPa at an age of 28 days. Flexural toughness was at least 40% superior to that of the non-reinforced matrix. Microstructure analyses presented additional information on the understanding of fibre-matrix interaction and its correlation with composites macrostructural behaviour. The effects of natural weathering on the performance of fibre-cement composites were investigated in comparison with accelerated ageing tests. Sixteen months of exposure in tropical climate conditions caused the severest decay in the loading capacity and composite embrittlement, in spite of the absence of superficial darkening or visible cracks. The reduction of the mechanical properties was attributed to a combination of different processes, such as matrix carbonation, fibre mineralization and transition zone degeneration.

LDPE/EPDM Multilayer Films Containing Recycled LDPE for Greenhouse Applications

In this paper the reuse of recycled LDPE in combination with the incorporation of EPDM modifier in the production of greenhouse films has been investigated. A three-layer film (60-100-40 micron thickness) containing recycled LDPE in the middle layer and a high UV-stabilized 40-micron outer layer was developed and proven to be commercially successful. Films with 25% and 50% recycled material content were produced. The effect of natural weathering on the film properties over a period of 15 months has been observed. Changes in physical and mechanical property were determined. The addition of EPDM to the raw resin was found to improve the extrudability of the compound and improve the weather resistivity of the film. The EPDM-modified films containing 25% to 50% recycled material retained approximately 95% and 75%, respectively, of their original extensibility after 9 months' exposure to natural weathering. Optimization of EPDM and UV stabilizer concentration was carried out to develop a balanced film with excellent mechanical and physical properties and resistance to weathering conditions. The use of UV stabilizer concentrations slightly higher than commercial practice in the outer layer of the multilayer film can be justified by the cost reduction by the incorporation of recycled LDPE materials.

Effect of geological processes on coal quality and utilization potential: review with examples from western Canada

This review article compares the elemental and radionuclide concentrations in coals from western Canada, the vast majority of which are used for power generation in Alberta. The coals range in age from lower Cretaceous to middle Eocene, and in rank from subbituminous to high volatile bituminous. Some of the coals were deposited in deltaic lagoonal to marine settings while others formed under lacustrine conditions in intermontane graben settings or in alluvial plains. The role of source rock (provenance), depositional environment, tectonic regime and hydrologic conditions on elemental concentration and distribution will be discussed, with specific examples from western Canada. In addition, the effect of natural weathering, igneous intrusion and self-burning (spontaneous combustion) on the enrichment and/or depletion of elements will be presented. The emphasis throughout this review article will be on the fate of elements of environmental concern and interest (e.g. As, Ba, B, Cl, Co, Cr, Cu, Mn, Mo, Se, Th, U, V and Zn) and of radionuclides of the U and Th series upon coal utilization. This article is also intended for those not familiar with the geological or environmental sciences, particularly as related to fossil fuel utilization.

99/01819 Effect of natural weathering of two medium-volatile coking coals on coke quality: Casal, M. D. et al. Rev. Metal. (Madrid), 1998, 34, (1), 3–10. (In Spanish)

99/01819 Effect of natural weathering of two medium-volatile coking coals on coke quality: Casal, M. D. et al. Rev. Metal. (Madrid), 1998, 34, (1), 3–10. (In Spanish)

Selection of Consolidants for Use on the Tower of Belem / Auswahl eines Steinfestigers für den Turm von Belem

Abstract During the exterior conservation project of the Tower of Belem, Lisbon, it was noticed that although most of the Lioz limestone used in its construction was in good condition, some specific areas presented severe powdering and flaking deterioration patterns. These are mainly due to the effect of natural weathering, including anthropogenic air-pollution, on poorer quality Lioz limestone. Since the deterioration affects mainly the immediate surface and subsurface of the stone blocks, the application of stone consolidants was considered as the most appropriate solution for this problem. This paper describes the difficulties encountered in the evaluation of the tested consolidants-an ethyl silicate ester, an acrylic resin and an epoxy resin-applied in situ. The laboratory and on-site testing used in the final selection are described as well as the actual approach to consolidating the different areas that required this treatment.

The effect of natural weathering on dissolution rates

Surface area measurements and dissolution experiments were performed on a naturally weathered mineral assemblage rich in quartz and feldspar. The surface areas of unfractured (612 μm) and ground samples were measured at different levels of surface detail, using a dissecting microscope, SEM, and the BET-krypton method. Roughness factors of the freshly created surfaces by grinding were 2.1 (SEM at 10,000× magnification) and 4.8 (BET), respectively. Roughness factors of the naturally weathered surfaces were 2.8 (SEM at 10,000×, including effects from etch pitting) and 34 (BET), respectively. These data indicate that (1) a large amount of BET surface area was created during natural weathering, and (2) etch pits did not contribute significantly to the BET surface area created during natural weathering. Comparison with data from the literature further suggests that the surface roughness factor of naturally weathered feldspar grains decreases with decreasing grain diameter. Also, most BET surface area additionally created during natural weathering appeared to be nonreactive. At pH 3 and pH 5 HCl, steady-state dissolution rates of Na, K, Ca, Al, and Si (mol·cm −2 of BET surface·s −1) were determined for the unfractured sample and for four ground samples of increasingly smaller average grain diameter. The data from the ground samples were used to extrapolate the dissolution rate of hypothetical fresh-surface grains to the average diameter of the unfractured, naturally weathered sample material. The results showed that, at 612 μm, freshly created BET surfaces would dissolve approximately one order of magnitude faster than their naturally weathered counterparts. Comparison with literature data suggests that this discrepancy in dissolution rate, at equal diameters of freshly created and naturally weathered grains, increases with increasing grain diameter. Dissolution rates of freshly created feldspar surfaces in the laboratory are frequently up to several orders of magnitude higher than those of naturally weathered feldspar surfaces in actual field situations. The findings from this research partly explain such discrepancies. However, other factors (such as imperfect contact between solution and solids, the presence of organic ligands, etc.) should also be considered in explaining the discrepancies.

Effects of natural weathering and low-temperature oxidation on some aspects of the combustion behaviour of bituminous coals

The influence of natural weathering ( in situ) and low-temperature laboratory oxidation on the combustion behaviour of bituminous coals was investigated. Five sets of coals, each comprising a fresh and crop coal from the same seam, were used. One selected fresh coal sample was oxidized in the laboratory at 200 °C for 2 and 72 h to elucidate the effect of low-temperature oxidation (simulated weathering) on the subsequent combustion behaviour. The combustion behaviour of the coals was evaluated using char reactivity and burning profiles obtained in a thermogravimetric analyser (TGA) and combustion efficiency determined in a drop-tube reactor (DTR). The reactivities of the chars produced from the crop and laboratory-oxidized coals were higher than those for the chars from the corresponding fresh coals. The reactivities of the crop coal chars were higher than those of the laboratory-oxidized coals due to the presence of inorganic species (cations) in the former which could be removed by acid washing. Reactivity changes due to such inorganic species changes did not occur upon laboratory oxidation. The combustion efficiencies of the weathered coals were higher than those of the corresponding fresh coals. A correlation was obtained between the difference in combustion efficiency between a crop coal and its fresh counterpart and oxygen uptake during natural weathering. There was an inverse relationship between the combustion efficiencies determined in the DTR and the ‘initial temperature’ in the TGA burning profiles.

Comparative Mössbauer study of the effects of natural weathering and artificial oxidation on iron minerals present in coal

Fresh and naturally weathered coal samples from the same seam as well as the former one submitted to artificial oxidation treatments were studied by Mössbauer spectroscopy to examine the effect of coal oxidation conditions on the transformations of iron minerals. It was found that illite, pyrite and siderite are converted into jarosite and goethite in a natural environment, whereas only a small fraction of Fe 2+ from pyrite was oxidized to Fe 3+ under laboratory conditions, even after heating in air to 468 K. It is concluded that artificial oxidation experiments hardly reproduce the conditions met by coal when submitted to natural weathering.

Effect of weathering on UV-stabilized low density polyethylene films (LDPE) for a multilayer greenhouse cover

Multilayer films for greenhouses is a current trend in industry. LDPE films for the top layer, stabilized with different concentrations (0·1, 1·0 and 2·5%) of a nickel quencher, were produced in the laboratory by blow extrusion. The effect of natural weathering on the film properties was investigated over a period of 12 months. Significant changes in the mechanical properties were observed in the later stages of degradation. Films stabilized with 0·1% stabilizer crumbled after 12 months of natural weathering whereas films with higher concentrations retained their mechanical properties. We believe that inclusion of the UV stabilizer interferes with the crystallization process and the stabilizer particles accumulate in the amorphous matrix. Degradation of the imperfect crystalline region with its low oxygen permeability, proceeds via cross linking whereas chain scission predominates in the amorphous region with excess of oxygen. Films stabilized with 2·5% nickel quencher form a barrier against the transmission of UV radiation and the bottom layers are least affected by UV radiation. Recycled material can, therefore, be incorporated at high concentrations into these layers.

Rock Moisture Content and Frost Weathering under Natural and Experimental Conditions: A Comparative Discussion

Frost weathering simulation studies provide a useful means of gaining insights into the nature of frost-weathering phenomena. If such studies are to be of value, however, experimental conditions should approximate those in nature. Experimental moisture regimes tend to promote degrees of saturation which exceed those likely to be attained naturally. The possibility therefore exists that experiments may exaggerate natural weathering effects. Acquisition of data on moisture contents of rocks in cold environments as a basis for freeze-thaw experiments is necessary.

The detection of weathering in coal by petrographic, rheologic and chemical methods

This study examines petrographic, rheologic, proximate and ultimate analyses techniques, to investigate the effects of natural weathering on coal. The applicability of such tests to both the detection of weathering and to the prediction of the properties of a fresh coal, based upon analyses of a weathered sample, is discussed. Rheologic parameters and a petrographic staining technique showed the most sensitive response to weathering. The latter test is considered the most suitable of these for the detection of weathering, as it is independent of prior knowledge of the properties of the fresh coal and of the petrographic composition. A petrographic approach is also considered most suitable for estimation of fresh coal characteristics from weathered samples. Rank may be closely approximated and petrographic type determined microscopically, even on highly weathered samples, and these two parameters may be used to estimate properties such as volatile matter, calorific value and dilatation. Minor modification should be made to vitrinite reflectance measurements, according to the degree of weathering as revealed by selective staining.

The effect of natural weathering on the chemical and isotopic compositions of biotites

The effect of progressive natural weathering on the isotopic (Rb-Sr, K-Ar, δD, δ 18 O) and chemical (REE, H 2O +) compositions of biotite has been studied on a suite of migmatitic biotites from the Chad Republic. During the early stages of weathering the Rb-Sr system is strongly affected, the hydrogen and oxygen isotope compositions change markedly, the minerals are depleted in light REE, the water content increases by a factor of two, and the K-Ar system is relatively little disturbed. During intensive weathering the K-Ar system is more strongly disturbed than the Rb-Sr system. Most of the isotopic and chemical modifications take place under nonequilibrium conditions and occur before newly formed kaolinite and/or smectite can be detected. These observations suggest that 1. (a) “protominerals” may form within the biotite structure during the initial period of weathering, and 2. (b) only when chemical equilibrium is approached in the weathering profile are new minerals able to form.

A study of degradation of low density polyethylene under natural weathering conditions

The effects of natural weathering on mechanical properties and chemical structure of low density polyethylene have been studied. It is found that no simple correlation exists between the development of carbonyl groups and mechanical properties such as stress or strain at break or elastic modulus. It appears that there is recovery in the mechanical properties during the winter months.

A study of the effect of natural weathering on the creep behaviour of glass fibre-reinforced polyester laminates

Glass fibre-reinforced polyester laminates having different compositions, typical of those used in commercial building panels were exposed to natural weathering at stress levels varying between 7 and 35% of the composites' short-term flexural strength. The creep curves show considerable dependence of the creep rate and the deformation on weathering. Increase in the percent strain for all nine types of laminates subjected to study has been observed to be less than 1% in 15 000 hours of exposure. The trends shown by this work indicate that grp structures may be suitable for outside use provided that good quality laminates are used.

The thermal decomposition of miscellaneous crocidolites

SummarySixteen samples of crocidolite asbestos from weathered zones in mines in Cape Province, Transvaal, Western Australia, and Bolivia have been studied by thermal analysis methods and their characteristics are compared with those of fresh crocidolite from Koegas-Westerberg given by Hodgson, Freeman, and Taylor (1965). New chemical analyses of these samples are reported.The effect of natural weathering on crocidolite tends to a removal of ¼ of the OH groups and an adjustment of the Fe2+/Fe3+ ratio to unity, but there are only minor changes in the physical characteristics of the fibre. The d.t.a. pattern of decomposition is not affected by weathering, but the endothermic peak corresponding to final decomposition is moved to higher temperatures as the Mg content of crocidolite increases. Mg-blocking of this decomposition is considered to be more important than Mg-blocking of the oxidation reaction at 400–450° C, suggested by Addison et al. (1962).D.t.a. and other evidence shows that the Transvaal crocidolite contains intergrown amosite fibres, and suggests that the Bolivian crocidolite is admixed with anthophyllite.