Initial Stage Of Weathering Research Articles

Space Weathering of Genesis Mission Solar-wind Collectors with Inferences for Weathering on Airless Bodies

Samples from the Genesis Solar Wind Sample Return (NASA Discovery 5) are a unique opportunity to study the initial stages of space weathering, i.e., the physical and chemical effects of solar-wind irradiation. Arrays of collectors containing multiple materials were each exposed to a different solar-wind regime (fast, slow, bulk, or coronal mass ejection) at the L1 point for long durations (years). Materials exposed to the solar wind included metals, semiconductors, and insulators. Although the time of exposure was obviously short relative to samples having extraterrestrial origins, optical properties, surface chemical properties, and matrix structure have changed in many collectors due to exposure to solar wind. The thickness of amorphous zones, where present, appears to correspond with the depth of the peak of the solar-wind H distribution in each regime. Damage from high-energy particles was negligible because the collectors were 700 μm or less in thickness and shielded from the back by the spacecraft. Micrometeorite impacts and sputtering were also negligible because of the short exposure times. Our current results are preliminary: We hope future workers will extend this study both to support Genesis characterization efforts and to further understand space-weathering processes on a geologic timescale.

The Development of Limestone Weathering Rind in a Proglacial Environment of the Hallstätter Glacier

The contemporary retreat of glaciers results in the development of glacial forelands which constitute excellent areas for studies on the initial stages of weathering. This research concentrates on weathering rinds developed on glacially abraded Dachstein limestone surfaces (Eastern Alps) liberated from glacial ice since LIA (mid-19th century). We performed measurements of rock surface micro-roughness and strength (Schmidt hammer), spectral reflectance, and petrographic and microbiological analyses in SEM. There was a time-dependent increase in micro-roughness, decrease in rock strength and decrease in spectral reflectivity, but only within visual light. Rock surfaces on older sites reflected infrared radiation significantly better than younger ones. SEM analysis revealed that angular micro-structures inherited from glacial abrasion dominated in younger sites, eventually giving way to more rounded micro-structures. The structure of rock (micrite versus spar, phlogopite veinlets, etc.) plays a significant role. On older sites, microorganisms were detected within the studied weathering rinds, which probably results in better infrared reflectivity. We advocate the potential role of microorganisms (mainly heterotrophic) in the dissolution of limestone, and the role of cyanobacteria in the formation of the secondary porous limestone layer (extracellular biomineralization).

Mobilization and fractionation of rare earth elements during experimental bio-weathering of granites

Weathering of parent granite is pivotal in the formation of regolith-hosted rare earth elements (REE) deposits, which provide over 90 % of global heavy rare earth elements (HREE) demand. Microbes have been recognized to control the fates of REE during weathering jointly with other geochemical factors, but the specific mechanisms of how microbes affect REE mobilization and fractionation remain poorly understood. In this study, bio-weathering experiments at room temperature were conducted with four native bacterial isolates from the Dabu regolith-hosted HREE deposit to investigate the microbial effects on REE mobilization from the parent granite. The presence of these isolates remarkably enhanced the liberation of REE by a factor of 4–21 at the end of the 30-day experiments. Concomitantly, microbes could immobilize REE through extracellular metabolites-induced precipitation and, to a lesser extent, by cell sorption, resulting in 25 %–82 % underestimations of the REE release efficiencies. The synergy of acidolysis and complexation was found to be a crucial bio-weathering mechanism, and complexation with organic acid ligands was more efficient in mobilizing REE at weakly acidic to near-neutral pH. REE fractionation during bio-weathering was mainly controlled by the properties of the host minerals but also influenced by microbes. Specifically, the preferential dissolution of synchysite-Y and parisite-Ce at the initial stage of granite weathering resulted in relatively higher release efficiencies of light rare earth elements (LREE) and middle rare earth elements (MREE). In addition, the secretion of ample organic acids, malic and tartaric acids, in particular, accounted for the preferential release of MREE and HREE mediated by the two isolates from the Bacillus genus. Our results showcase high potential microbial effects on the mobilization and fractionation of REE during granite weathering, posing new sights into the biogeochemical process during the formation of regolith-hosted REE deposits.

Clay mineral evolution and formation of intermediate phases during pedogenesis on picrite basalt bedrock under temperate conditions (Yunnan, southwestern China)

In order to better understanding clay mineral evolution coupled with geochemical changes during weathering of igneous rocks under temperate conditions, the picrite basalt-derived soil in Dali (South China) was investigated using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope (SEM), and high-resolution transmission electron microscopy (HRTEM) methods. Our results show that smectite and mixed-layer clays occur throughout the weathered soil profile, while discrete kaolinite and illite phases are absent in the soil. From saprolite to topsoil, smectite decreases sharply, while mixed-layer kaolinite/smectite (K/S) and illite/smectite (I/S) clays increase markedly. Clay minerals in the saprolite consist of both dioctahedral and trioctahedral species, while those of the middle to upper profile display a uniform dioctahedral structure. I/S phases are characterized by interstratification of 12-Å smectite and 10-Å illite layers, and K/S phases by interstratification of 12-Å smectite and 7-Å kaolinite layers, with I/S/K clays containing all three layer types. Kaolinization of smectite occurs at the initial stage of weathering, earlier than that of smectite illitization. Desilication and K-fixation of smectite take place simultaneously during advanced weathering, resulting in formation of illitic and kaolinitic phases continuously throughout the developmental history of the soil. Notably high K concentrations in the weathering profile may be related to K-fixing in the interlayer of illite due to smectite illitization in response to more advanced weathering and pedogenic processes, while the increasing K content in the topsoil may be ascribed to fertilizer in land use and uptake of K by plants from deeper soil horizons. Fe2O3 and TiO2 accumulation in the topsoil is probably mediated by microorganisms.

Geochemical characterization of major elements in Gurbantunggut Desert sediments, northwestern China and their regional variations

• Mineralogical maturity increased from the piedmont to the desert center. • Provenance controls the regional differences in major element compositions. • Transport, sorting, recycling, and chemical weathering affect the sand compositions. • River sands constitute a significant source of sands in this desert. • Extensive vegetation coverage contributes to the regional differences in this desert. Identifying the geochemical composition of desert sands in the Gurbantunggut Desert is essential for understanding the formation of desert dunes in the mid-latitudes. In this study, we collected samples of desert sands (125–250 μm), fluvial sands, and lacustrine sands across the Gurbantunggut Desert and calculated the sand drift potential at four meteorological stations. The sand samples from the Gurbantunggut Desert were mostly enriched in SiO 2 , while the other major elements were depleted compared to those of the Upper Continental Crust (UCC). The chemical weathering indices (α Al E, CIA, and WIP) indicate that the sand-sized sediments in the Gurbantunggut Desert are in the initial stage of continental chemical weathering. SiO 2 and K 2 O contents as well as mineralogical maturity of the desert sands increased from the piedmont to the desert center. UCC-normalized distribution patterns were also consistent along this transect due to the homogenization of desert sand composition, whereas the concentrations of other major elements (except for TiO 2 and MnO) decreased. We conclude that (1) regional variations in the composition of the Gurbantunggut Desert sands primarily reflect differences in provenance, transport, sorting, recycling of the sediments, and vegetation cover as well as the chemical weathering; and (2) differences in indices describing the major element composition of the sands reflect regional variations in provenance from the mountains to the depositional basin. Sands within piedmont rivers possess major element characteristics similar to those of dune sands in the region, suggesting that rivers represent a significant source of sands in the desert.

Weathering and pedogenesis of the late Pleistocene and Holocene aeolian loess-paleosol sections in the Yellow River source area, NE Tibetan Plateau

The aeolian loess-paleosol sections on the northeast Tibetan Plateau (NETP) are a valuable source of paleoclimatic information because of their geographical location. In this study, two late Pleistocene–Holocene aeolian loess-paleosol sections were identified based on detailed field investigations in the Maqu reach in the Yellow River source area on the NETP. A robust chronostratigraphic framework for these two sections was established using AMS 14C dating, optically stimulated luminescence (OSL) dating, Bacon age-depth modelling and stratigraphic correlation. Measurements of magnetic susceptibility, hygroscopic water, loss-on-ignition, grain-size, micromorphology, and chemical element analysis suggest that most stratigraphic units in these aeolian loess-paleosol sections are in weak weathering and pedogenesis, whereas the mid-Holocene paleosol approaches to the moderate weathering and pedogenesis, and the sediments are in initial weathering stage of Na+ and Ca2+ leaching is dominated by plagioclase weathering. The main pedogenesis in the mid-Holocene paleosol is calcification process. In terms of intensity of weathering and pedogenesis, the stratigraphic units can be ordered as follows: paleosol > modern soil > transitional loess > aeolian loess. Multi-index comparison shows that the local climatic evolution during the late Pleistocene–Holocene was closely related to the evolution of the East Asian summer monsoon (EASM) and the Westerlies. Overall, the results provide a foundation for further exploration of the pedogenic and paleoclimatic evolution on the NETP.

Песчаные почвы лесных ландшафтов Амуро-Зейской равнины

Historically, soils of the Cambisol group have been recognized as zonal soils of the Upper Amur Basin Region. However, the wide distribution in the territory of the Amur-Zeya Plain of forest soils of light granulometric composition that were formed on loose sedimentary deposits makes it possible to identify an area of Arenosols and Podzols, for the first time described within the study area. The common features in the researched soils are a well-structured thin humus horizon and quartzfeldsparic mineralogical composition causing low intensity of the processes of weathering and metamorphism of mineral substance. The initial stages of biochemical weathering of mineral matter are diagnosed in soils of the Humic Arenosol subgroup. The most intensive processes of weathering and metamorphism of mineral matter are diagnosed in the middle horizons of the Rubic Arenosol group, which is associated with the formation of seasonal frost and the associated cycles of freezing-thawing of the soil profile. In the soils of the Entic Podzol subgroup, the process of iron illuviation is diagnosed, with formation of the maximum accumulation in the lower part of the soil profile at the boundary with the soil-forming rock. Keywords: FOREST SOILS, NEOGENIC SANDS, SOIL MORPHOLOGY, THE UPPER AMUR BASIN REGION

Precambrian paleosols on the Great Unconformity of the East European Craton: An 800 million year record of Baltica’s climatic conditions

Meso- and Neoproterozoic paleosols, collected from different areas of the East European Craton: Belarus, Estonia, Lithuania, and Ukraine, offer a chance to examine continental weathering sequences from early to advanced stages of weathering on a variety of different parent materials such as gneisses, granites, gabbros and amphibolites. They were studied using quantitative XRD of the bulk rock, XRD and Mössbauer of the clay fractions, microscopic, geochemical, carbonate stable isotopes and carbonate U-Pb geochronology methods. These paleosol profiles are on average 10 m thick, reddish coloured, and many of them are characterized by a well-developed and well-defined alteration sequence with uppermost horizons approaching the lateritic stage, as indicated by the Chemical Index of Alteration values reaching 90. The dominant type of weathering leads towards kaolinite and a Fe-oxide/hydroxide mineral assemblage through a smectitic intermediate stage. In the paleosol profiles developed on mafic parent materials, dioctahedral smectite is the first weathering product at the base, it dominates in the middle-upper horizons and it later becomes unstable and alters into kaolinite; whereas in paleosols developed on felsic parent materials kaolinite forms already at the initial stage of weathering, as a result of Na-plagioclase dissolution. Kaolinite content in the uppermost horizons reaches 34 wt% in the best developed profile, and Fe-minerals (hematite and goethite) show a clear increasing trend towards the top, reaching 12 wt%. It is likely that uppermost kaolinite-dominated horizons, which are lacking in some profiles, have been eroded. Such paleosol composition and ferric composition of smectites indicate oxidative weathering and are interpreted to represent a warm and humid climate, which seems to have prevailed on the EEC over the Meso- and Neoproterozoic, except well-documented glacial periods. The δ13C signatures of the pedogenic carbonates document microbial processes in the paleosols, which is also indicated by the elevated U/Th values in their top layers. One paleosol was dated with in situ pedogenic calcite U-Pb geochronology at 655 ± 45 Ma (2σ), confirming the estimate based on its stratigraphic position. The Proterozoic paleosol profiles, and dioctahedral smectite in particular, remained unaltered for over 900 Ma until the Paleozoic, when they were affected by low-temperature (<110 °C) diagenesis, evidenced by the presence of K-Ar dated illite–smectite and aluminoceladonite. The maximum and the most common degree of the dioctahedral smectite illitization is 26% S; the %S zonation indicates that the illitizing fluids invaded paleosols from the overlying sediments.

Clay mineralogy of soils from lower atrai basin of Bangladesh

The lower Atrai basin, the study area, lies in the Agroecological Zone-5 (AEZ-5) of Bangladesh. This study reveals the clay mineral composition of top soils of seven different soil series viz. Binsara, Taras, Jaonia, Hasnabad, Laskara, Manda and Mainam developed in the basin. X-ray diffraction (XRD) technique was employed to identify and quantify the minerals. Results show that mica (41 to 59%) was the most dominant mineral among all soils except Laskara. In Laskara soils, the interstratified mica-vermiculite-smectite (41%) was the predominant mineral. Next to mica, kaolinite (10 to 12%) was found to be present in the Binsara, Taras 1, Jaonia, and Taras 2 soils. Chlorite (7 to 17%) was identified in all the soils and was found to be the second dominant mineral in the Manda and Mainam soils. In contrast, the interstratified mica-vermiculitesmectite (33%) was found to be the second dominant mineral in the Hasnabad soils. Small amounts of vermiculite mineral (1 to 13%) were identified in almost all the soils except Binsara. All the soils have interstratified mica-chlorite minerals (2 to 7%). A tiny amount of smectite (1%) was identified in Taras 1 soil. As far as the clay mineralogical composition is concerned, most studied soils were found at the initial stage of weathering, indicating the high potential to sustain low input subsistence agriculture.&#x0D; Dhaka Univ. J. Biol. Sci. 30(2): 293-306, 2021 (July)

Nanopore Formation and Structural Changes in Black Shale During the Initial Weathering Stage: A Longmaxi Formation Profile in Northwestern Hunan, China.

Understanding the controls on composition changes and porosity evolution in the critical zone of shale remains a major challenge. The aim of the present study is to develop a model of the changes in mineral compositions, chemical compositions and nanopore formation in shale during the initial weathering stage. To understand these processes, we selected a Silurian shale profile rich in pyrite and organic matter located in South China. Based on X-ray diffraction (XRD) and bulk elemental data, the variations in mineralogical and chemical compositions with depth were studied. To characterize the full pore size spectrum and to gain insight into the nature of secondary pores and their relationship with weathering, nuclear magnetic resonance (NMR) measurements and petrographic observations were combined with scanning electron microscopy (SEM) imaging. The results show that Al and K are enriched slightly, while Ca and Na are depleted in the upper part of the weathering profile. Si, Mn and Ti are relatively stable from the bottom to the top of the profile. Quartz, feldspar, mica, illite and chlorite are the main minerals in the parent rock, and they are relatively stable along the profile. The rock density gradually decreases from 2.6 g/cm³ to 2.1 g/cm³ from the bottom to the top, and the color of the shales changes from black to grayish yellow, but no secondary minerals are detected. The chemical weathering of black shale is dominated by the oxidation of pyrite and organic matter, giving rise to color variation and nanopore formation. The increase in interparticle pores at the nanometer-micron scale is initiated by the dissolution of easily weathered components such as organic matter and pyrite. The removal of clay minerals and tiny particles by groundwater seepage may be the main cause of porosity enhancement during the initial weathering stage. This study suggests that nanoporosity may play an important role in the process of fluid-rock interaction within black shale during the initial weathering stage.

Characteristics of major and trace elements in surface sediments of the Makran Accretionary Prism, Pakistan and their implications for natural gas hydrates

To accurately identify the natural gas hydrates (NGH) in the sea area of the Makran Accretionary Prism, Pakistan, this paper presents the testing and analysis of major and trace elements in sediment samples taken from two stations (S2 and S3) in the area by the China Geological Survey. As shown by testing results, all major elements are slightly different in content between the two stations except SiO2 and CaO. This also applies to the trace elements that include Sr and Ba primarily and Cr, Ni and Zn secondarily. It can be concluded in this study that the tectonic setting of the Makran Accretionary Prism is dominated by oceanic island arc and that provenance of the Makran Accretionary Prism is dominated by felsic igneous provenance, which is at the initial weathering stage and mainly consists of granodiorite. Besides terrigenous detritus, there are sediments possibly originating from Makran-Bela Ophiolite from the northwestern part and Murray Ridge igneous rocks from the southeastern part. The V/Cr, Ni/Co, and V/(V+Ni) ratios indicate that sediments of the two stations are in an oxidation-suboxidation environment. However, the authors infer that the sedimentary environment of the sediments 3.0 m below the seafloor tends to be gradually transformed into a reduction environment by comparison with the Qiongdongnan Basin in the South China Sea where NGH has been discovered. The sediments in the Makran Accretionary Prism are rich in organic matter, with total organic carbon (TOC) content greater than 1%. According to comprehensive research, the organic matter in the sediments mainly originates from marine algae and has high TOC content, which is favorable for the formation of NGH.

Hydrobiogeochemical evolution along the regional groundwater flow systems in volcanic aquifers in Kumamoto, Japan

Kumamoto is known as the largest groundwater city in Japan. Geochemical modeling (saturation indices and mineral stability diagram) was applied in this area for better understanding a hydrogeochemical evolution in volcanic aquifers in regional scale with additional constraint from stable isotopic dataset. Geochemical evolutionary model was interpreted along the water flow dynamics. In total 136 water samples were collected from wells, springs, and rivers in and around the major groundwater flow lines for geochemical analyses. Our results indicated that plagioclase is the major weathering reactant in aquifers with secondary important weathering minerals of pyroxenes. These reactions facilitate current hydrochemical signatures and produce secondary minerals of kaolinite or halloysite and smectite in later stage. Observed hydrogeochemical processes can be distinguished into two distinct criteria along flow regime. The first processes are material loads from the surface (mixing of contaminants and river waters) and initial stage of silicate weathering, resulting in the formation of Ca-HCO3, Ca-NO3–HCO3, and Ca–Mg–Na-HCO3 type waters. These processes prevail in aquifers at the recharge to lateral flow zones with relatively shorter residence time of 55 years. Microbiological reduction reactions dominate over these areas and salinization occurs at the coast that changes aquifer waters to be Na-Cl type. Proposed models and approach shown in this study may be useful and applicable in interpreting systems in other volcanic aquifer systems at similar climate conditions and for sustainable water resources management.

Weathering mechanism of arenite sandstone with sparse calcite cement content

We conducted a multifaceted analysis of the weathering zones of arenite, containing a minute amount of calcite cement, based on mineralogical, chemical, and physical properties. The survey targeted sandstone with mudstone interbeds belonging to the Cretaceous Izumi Group. The survey revealed that the weathering mechanism is a chain reaction; the most important process is the pore opening between the grains caused by the dissolution of calcite cement in the initial stage of weathering. Subsequently, the pores between the grains connect and widen, separating the sand grains within the sandstone. This primary weathering action may be a major difference from wacke. During calcite dissolution in the initial stage, sulfuric acid generated by pyrite oxidation in sandstone plays an important role. Chlorite breaks down as calcite dissolves; however, iron resulting from the breakdown disappears only after the pore water has been replaced by acidic water.Sandstones with advanced diagenesis are dense and hard, and it was previously assumed that thick weathering zones could not develop because they were less susceptible to weathering. However, we discovered that weathering caused arenite with a minute amount of calcite cement to disintegrate into grains down to a depth of 30 m. The surface layer of the weathered arenite lost fine particle fraction and crept to form a fragile soil layer susceptible to landslides.

Micro-weathering of limestone surfaces in a foreland of Hallstätter Glacier (Dachstein, Austria)

ABSTRACTSince the end of LIA climatic amelioration results in retreat of glaciers worldwide and the development of glacial forelands with freshly abraded rock surfaces undergoing weathering. When the timing of glacier retreat is known, glacier forelands are highly valuable study sites to investigate initial and short-term weathering processes. The aim of this study is to quantify limestone surface decay in the foreland of Hallstätter Glacier in Dachtein massif, Austria, based on the measurement of surface micro-roughness and weathering rind characteristics. By establishing a post-LIA chronosequence we seek to gain insight into initial stages of weathering in a cold alpine environment. Micro-roughness was measured with a use of Handysurf E-35B electronic profilometer, and weathering rind characteristics were determined based on SEM equipped with a microprobe. The micro-roughness increases from locations close to the glacier front towards the LIA moraine. The greatest measured increase occurs within the first 50 years since deglaciation. Weathering rinds are manifested as zones of micro-cracks and micro-pits, and accumulation of mineral grains at the rock surface and along the micro-voids. Increasing rounding of the grains and their development along micro-fissures is attributed to limestone dissolution, which is probably responsible for the development of micro-pits, best observed after c. 100 years since deglaciation. No protecting shield in a form of a weathering coating was observed. Instead, the weathering rind thinning is attributed to the weathering rind erosion. Results obtained provide further insight into initial stages of limestone weathering in a cold alpine environment.

Synergies in elemental mobility during weathering of tetrahedrite [(Cu,Fe,Zn)12(Sb,As)4S13]: Field observations, electron microscopy, isotopes of Cu, C, O, radiometric dating, and water geochemistry

Tetrahedrite [(Cu,Fe,Zn)12(Sb,As)4S13] is commonly present in many ore deposits and may be transferred to mining waste. Here, we describe the behavior of all elements in tetrahedrite during oxidative dissolution in a natural oxidation zone at Piesky (Slovakia), this being a long-term analogue of weathering of tetrahedrite-rich mining wastes. Electron microprobe work identified initial, early, advanced, and mature stages of weathering. The initial stages include formation of secondary covellite and chalcocite, the following stages only oxidic products, divided into greenish masses and brown veinlets. Both of them are nanocrystalline mixtures of minerals. The masses are Cu-Sb-As-rich and consist of a nanocrystalline pyrochlore phase. The veinlets are Fe-Sb-As rich and contain tripuhyite, goethite, and pyrochlores. Quantitative elemental budgets show that some elements (Zn, S, Ni, Co) are rapidly lost whereas others (especially Cu and As) are retained and form copper arsenates in the mature stages of weathering. About 10% As and almost 50% of Sb are lost during weathering, likely released into water; some Sb is stored in secondary minerals such as camérolaite, cualstibite, or tripuhyite. Light carbon isotopic composition (δ13C down to −11.1‰) document significant biological contribution for C in the secondary minerals. Copper isotopes become progressively heavier during weathering (from initial δ65Cu of −2.45‰ in tetrahedrite up to 4.3‰ in some azurite samples but −6.3‰ in covellite and chalcocite), documenting cyclic removal of light copper isotopes into covellite and chalcocite. The observation of elemental synergies during weathering of tetrahedrite shows that the solubility and mobility of As is controlled by copper arsenates, not by iron oxides, in an environment rich in tetrahedrite but poor in pyrite. Antimony, another element of environmental concern, is mostly released into water and creates low-concentration anomalies in stream sediments and soils.

A non-equilibrium approach to modelling the weathering of stored Liquefied Natural Gas (LNG)

A model is proposed to predict the weathering of LNG stored in containment tanks. It dispenses with a standard approximation where the temperature of the generated vapour within the tank is assumed to be the same as that of the stored LNG. Instead, it treats the heat influx from the surroundings into the vapour and liquid phases separately and allows for the heat transfer between the two phases. The model was validated only by comparing with the compositional data, as no reliable measurements of vapour temperature are available.The simulation results indicate that the temperature of the vapour phase will be higher than that of the LNG, by approximately 8 °C over a period of one year, providing the heat transfer from the vapour is by conduction only; thus supporting circumstantial industrial findings. The effect on the Boil-off Gas (BOG) is considerable and the results indicate that the BOG rate will decrease by as much as 25% for particular scenarios. This has important consequences for weathering models used in industry, which currently assume isothermal conditions within the containment tanks.In the initial stages of weathering, the nitrogen content of LNG will have a marked effect on the rate of BOG generation. The lowest BOG rate is observed when the LNG contains approximately 1.4–1.5% of nitrogen.

Classification of Weathered Kerosene and Diesel Fuel using Passive Headspace Concentration with Activated Charcoal Strip and Statistical Analysis Technique

Ignitable liquids are present in trace amounts in samples collected from arson scenes therefore their chemical composition often differs from their original composition. This is due to partial evaporation, burning and contamination by pyrolysis products at the scenes. The research was done using two techniques, passive headspace concentration with activated charcoal strip and statistical Analysis, to classify weathered kerosene and diesel fuel. The passive headspace used GC-FID chromatogram pattern to visually identify both weathered ignitable liquids while statistical analysis used cluster formation to group them based on unique characteristics of their hydrocarbons and materials used in the samples. Four case studies were done which consisted of forty-two experiments carried out on twenty-six weathered and unweathered samples that were analyzed under various conditions which included various time of burning, weathering and oven temperature. The Petroleum based ignitable liquids, kerosene and diesel, were used on different types of materials for analysis under various atmospheric conditions. The result showed visual distinction between weathered kerosene and diesel fuel at the initial stage of weathering but it was more difficult to distinguish as samples became weathered over time. Hence, this is one of the reasons why the chromatogram alone cannot be used to visually distinguish between these weathered samples. Therefore, the combination of the chromatographic pattern and statistical method were applied in this research. It was possible to distinguish between the weathered kerosene and diesel fuel using statistical analysis based on n-alkane data derived from Gas Chromatography- Flame Ionization Detector (GC-FID) method.

Application of copper monoethanolamine solutions as primers for semitransparent exterior wood stains

The effects of copper monoethanolamine (CuA) treatment of wood surfaces on the surface weathering and durability of a semitransparent penetrating stain were compared with those of chromic acid (CrA) treatment which is known as a photoprotective primer, using artificial weathering trials. Chemical changes in chemically treated and untreated wood surfaces during artificial weathering were investigated using Fourier transform infrared (FTIR) spectroscopy. Surface roughness, water contact angle measurements and scanning electron microscopy observations were performed to assess stain durability. Results of FTIR analyses indicated that lignin losses following CuA and CrA treatment were less than those of the untreated wood surfaces during the initial stage of artificial weathering. CuA pretreatment prior to staining also retarded the increase in the average surface roughness compared with that observed for the CrA-pretreated surface and untreated control (only stained) during artificial weathering. Furthermore, CuA pretreatment retarded the decrease in the contact angle compared with that observed for the untreated control, although the use of a highly concentrated CuA solution led to a decrease in the water repellency of the stained wood surface. These results indicated that CuA solution could be used for the pretreatment of wood surfaces to enhance the durability of semitransparent penetrating stains, as long as excessive CuA concentrations are avoided.

Rapid weathering processes of a 120-year-old chronosequence in the Hailuogou Glacier foreland, Mt. Gongga, SW China

Increasing numbers of ‘young’ soil chronosequences have become exposed in global alpine areas as glaciers have retreated due to climate warming since the Industrial Revolution. However, knowledge on the initial stages of weathering at the decadal time scale is limited. Our aim is to reveal the weathering processes and influential factors in a 120-year-old chronosequence on Mt. Gongga in southwest China. Sixty-nine soil samples and 17 water samples were collected from 6 sites with different exposure ages (0, 30, 40, 52, 80 and 120 years). Mineral compositions were determined using X-ray diffractometry, and four mineral pools, i.e., (1) exchangeable cations, (2) carbonates and apatite, (3) biotite and hornblende and (4) refractory minerals, were separated using a sequential extraction method. The results reveal that the soil particle sizes of < 2 μm (clay) in the A horizons increased and the particle sizes of 20 – 2000 μm (sand) decreased significantly with time. The soil organic carbon accumulation rate was up to 14 g/m2·yr, which is relatively high compared with other chronosequences of similar age. The weathering can be generally divided into two stages: the first stage was dominated by the weathering of carbonates and was present at sites with an exposure age of ≤ 52 years; the second stage was characterized by the intense weathering of biotite, hornblende and apatite and was present at the 80- and 120-year-old sites, where coniferous trees were the dominant plants. The rapid weathering was a result of the interactions of the lithology, rapid vegetation succession and climate in the Hailuogou Chronosequence. Fine silt was produced in large quantities by the strong glacial abrasion and freeze-thaw cycles, providing rich materials for the subsequent chemical and biogeochemical weathering. The decarbonation and the rapid establishment of the conifer forest due to relatively high temperatures and precipitation promote mineral weathering by decreasing soil pH from 8.5 (0 years) to 4.8 (120 years). The high permeability of the soil horizons due to the high content of rock fragments and abundant precipitation allows water and organic acids to infiltrate and dissolve mineral soils above the impervious bedrock. This study highlights the importance of carbonate weathering in alpine biogeochemical cycling during the initial stage of weathering in granitoid rock areas. Furthermore, our results indicate that the weathering intensity increases with exposure age due to vegetation succession in the early stages of weathering.

Mineralogical Composition of Some Selected Paddy Soils of Bangladesh

Soil mineralogy, which largely affects the productivity of soil in low input agriculture, was determined for 28 widely distributed paddy soils from different agroecological regions (AEZs) of Bangladesh. In addition, particle-size distribution was analyzed through fractionation of soil particles into five groups viz. <2, 2-20, 20-53, 53-200 and 200-2000 μm fractions. They represented 3-45, 6-59, 6-41, 3-41 and 0-49% of soil particles, respectively. The 2-20 μm silt fraction appeared to be the dominant fraction for most of our studied soils (17 out of 28 soils). The XRD patterns of the <2um clay fraction indicated the presence of five layer silicate (mica, smectite, chlorite, vermiculite and kaolinite) and four complex minerals (quartz, feldspar, goethite and lepidocrocite) and two interstratified minerals (vermiculite-chlorite and mica-chlorite). Mica (20-50%) was the most predominant mineral identified in all the studied soils. Next to mica, chlorite (5-20%) and kaolinite (2-37%) were present in all the soils. Vermiculite (2-16%) was identified in 20 soils while smectite (1-11%) was identified in only 5 soils. In addition, vermiculite-chlorite intergrade (1-11%) and interstratified mica-chlorite (1-13%) was detected both in 11 soils. Other than layer silicates, quartz (4-21%) was the predominant non-silicate mineral identified in all the studied soils. Next to quartz, feldspars was identified in 26 soils with an approximate relative percentage ranges between 3 and 12%. Very small amount of goethite (1-2%) and lepidocrocite (1-3%) were identified only in 4 and 5 soils, respectively. According to the clay mineralogical composition, most of the studied soils were found at the initial stage of weathering, indicating the high potential to sustain low input subsistence agriculture.