Composition Of Parent Material Research Articles

Quantifying weathering on variable rocks, an extension of geochemical mass balance: Critical zone and landscape evolution

AbstractWe present a statistical model of soil and rock weathering in deep profiles to expand the capacity to assess weathering to heterogeneous bedrock types, which are common at the Earth's surface. We developed the Weathering Trends (WT) model by extending the fractional mass change calculation (tau) of the geochemical mass balance model in two important ways. First, WT log transforms the elemental ratio data, to discern the log‐linear patterns that naturally develop from thermodynamic and kinetic laws of chemistry. Second, WT statistically fits log‐transformed element concentration ratio data – log(cj/ci), the only depth‐varying term in tau – as a function of depth to determine characteristic depths of transitions in weathering processes, along with confidence intervals. With no prior assumptions, WT estimates average parent material composition, average composition of the upper weathered zone and mean fractional mass change of each element over the entire weathering profile. WT displays the mean shape of weathering profiles of log‐transformed geochemical data bounded by calculated confidence intervals. We share the WT model code as an open‐source R package (https://github.com/fisherba/WeatheringTrends). The WT model was designed to interpret two 21 m cores from the Laurels Schist bedrock in the Christina River Basin Critical Zone Observatory in the Pennsylvania Piedmont, where our morphological and elemental data provided inconclusive estimates of bedrock depth. The WT model differentiated between rock variability and weathering to delineate the maximum extent of weathering at 12.3 m (CI 95% [9.2, 21.3]) in Ridge Well 1 and 7.2 m (CI 95% [4.3, 13.0]) in Interfluve Well 2. The water table was 5–8 m below fresh rock at Ridge Well 1, but at the same depth as fresh rock at the lower elevation interfluve. We assess statistical approaches to identify the best immobile element for use in WT and tau calculations. Copyright © 2017 John Wiley & Sons, Ltd.

Pedogenesis Dan Klasifikasi Tanah Yang Berkembang Dari Dua Formasi Geologi Dan Umur Bahan Erupsi Gunung Tangkuban Perahu

The efforts to utilize the agricultural land need a proper understanding of the soil characteristics. The soil characteristics themselves are influenced by the factors that regulate and control the soil forming and pedogenesis processes. The main soil forming factors in this study was the different ages and composition of parent materials from the eruption of Mt. Tangkuban Parahu in West Java. This research was done to comprehend the pedogenesis and to figure out the soil classifications that developed in two geological formations (Qyd and Qvu) and two ages of eruption (Holocene and Pleistocene) of Mt. Tangkuban Parahu. The study was conducted in Ciater, Subang Regency and Jatinangor, Sumedang Regency in West Java Province. The study consisted of four stages: preparation, field survey and soil sampling, laboratory analysis and presenting the report. The results showed that Pedon of Jatinangor consisted of three different stratifications of ages. The clay mineralogical composition was dominated by kaolinite, whereas mineralogical composition of the sandy fractions (heavy fractions) was augite-hypersthene. Pedon of Ciater also consists of three different stratifications of age. The clay mineralogical composition was dominated by allophane, while mineralogical compositions of the sandy fractions (heavy fractions) were green amphibole-hypersthene in the overlying horizons and amphibole-augite in the underlying horizons. The stage of soil formation on both pedon were cambic or viril. The soil classification according to Soil Taxonomy were Acrudoxic Durudands, medial over loamy-skeletal, isohyperthermic in Ciater Pedon and Fluventic Eutrudepts, fine, kaolinitic, isohyperthermic in Jatinangor Pedon.Key words: slow sand filter, activated carbon, silica sand, sand, gravel, zeolite

Seasonal fate of phosphorus in vineyard soils

Backdrop: Vineyard landscape. Inset: Volcanic (obsidian) soil. Growing premium wine grapes requires the right soil and climate. An ideal combination occurs in parts of California where the majority of the wine grapes in the United States are produced. As an agricultural system, wine grapes are a specialty crop, and there is limited research on the soils and nutrient dynamics that occur in vineyards. “There's a huge need for a better understanding of nutrient cycling and soil fertility in vineyards,” says Stewart Wilson, lead author of a recent Soil Science Society of America Journal article titled, “Seasonal Phosphorus Dynamics in a Volcanic Soil of Northern California.”1 According to Wilson, a Ph.D. candidate at the University of California–Davis (UC-Davis), research presented in the article was initiated when growers in Lake County, CA, approached scientists at UC-Davis about fertilizer use in vineyards. The study site is located on volcanic soils, which are highly weathered. “Volcanic and weathered soils are largely thought to be P fixing,” Wilson says. This is due to high-surface-area minerals and iron (Fe) and aluminum (Al) compounds that readily bind phosphate. To compensate for this, growers often fertilizer with P at levels that are well above plant requirements. Over-applying fertilizer could contribute to P runoff and pollution of local watersheds. For growers in Lake County, which has the second largest freshwater lake in the state, avoiding contributing to P runoff is important. Using organic materials as part of a fertilization regime is one way that wine growers may be able to reduce P inputs and subsequent runoff, but there is limited research on the topic. In this study, the researchers tested three different fertilizer applications. Fertilizer treatments were applied in January 2012 and included: triple superphosphate (TSP), composted steer manure, and a mix of the two. The applied phosphorus levels were equivalent across the three treatments (39 kg/ha). The researchers also established control plots to monitor background P levels in unamended vineyard soils. To evaluate the seasonal fluctuations of P, soil samples were taken in April (bud break), August (verasion, or grape ripening), and November (postharvest). The researchers measured P sorption and fractionated P. Fractionated P data were used to gauge phosphate derived from both fertilizer inputs and pedogenesis. This provides a better idea of how plant-available P changes throughout the season and could be used to improve timing and rate of fertilizer application. They also measured factors known to influence P dynamics, including microbial biomass carbon (MBC), dissolved organic carbon (DOC), and pH. Wilson discussed the two main findings from this work. The first is the effectiveness of compost fertilizer, and the second is how soil parent material can influence P dynamics. All fertilizer treatments increased labile inorganic phosphorus (Pi), Fe/Al-Pi, and total P. The authors report that for both chemical and compost fertilizers, there was high Pi availability. But when looking at additional soil characteristics, Wilson says, “Compost performs as well or better than chemical fertilizer, especially in these types of soil. [Compost] increased DOC, MBC, pH, and reduced P sorption compared with chemical treatments alone.” The authors attribute this to the addition of organic carbon in the compost, which impacts the biogeochemical cycle and improves overall soil quality, unlike chemical-based fertilizers. Showing the effectiveness of compost as a vineyard fertilizer supports some of Wilson's other research. “In another companion study in the region, in a much more strongly P-fixing soil, compost improved vine yield, berry weight, and pruning weights and increased soil C, N, and P, improving the performance of severely under-performing vines where chemical fertilizers alone had failed.” The findings about parent material were contradictory to the initial expectations of the authors. Soil at the site was weathered, and “it was known to be P deficient,” Wilson says. The assumption was that added P would get fixed, but “because this parent material was derived from rhyolite, which is a very low iron parent material … it responded well to the addition of phosphorus.” This resulted in high amounts of the applied P fertilizer being available to plants and suggests that initial parent material composition has a more significant influence on P dynamics than previously thought. Understanding these P dynamics in vineyard soils will enable vineyards to adjust fertilization for optimal grape production while limiting P runoff. And, given the limited research on nutrient cycling in vineyards, Wilson says, “I think [this] research would apply in the Pacific Northwest where you have a lot of volcanics and in other regions in California and Oregon with weathered soils in volcanic and meta-volcanic parent materials” as well as international vineyards that have similar soil types.

Application of airborne gamma-ray imagery to assist soil survey: A case study from Thailand

Airborne gamma-ray imagery (AGRI) provides coarse-resolution (approximately 400×400m pixel) spatial information on gamma-ray emitting elements, i.e. potassium (K), thorium (Th) and uranium (U), in the upper half meter of the soil. These radioelements are a potential information source for soil mapping since their abundance is related to soil geochemistry, specifically the chemical composition of parent materials and their weathering products resulting from geomorphic and pedogenic processes.The aim of this study was to evaluate the potential of AGRI for improving digital soil survey process in two phases: (1) a preliminary phase, where hypotheses of soil-landscape relationships are developed, and (2) a phase where soil map unit boundaries are placed or revised. The study also evaluated the match between AGRI and existing lithologic, geopedologic, and soil series maps. The study was conducted in a well-characterized complex soil landscape: the 560km2 upper Pa Sak watershed in Petchaboon province, Thailand. The relationship between gamma-ray data and geological units was examined with box-and-whisker plots and confirmed by rock and soil samples. Rock and soil sample classifications were compared with the gamma-ray image and to typical radioelement responses found in the literature.To interpret AGRI data in terms of regolith and soil genesis, we compared AGRI to two existing soil maps: geopedologic and soil series maps. First, the geopedologic map was split into four maps according to the geopedologic hierarchy: landscape, lithology, relief, and landform; at the latter (lowest) level, soil units are also associated. Secondly, soil series and geopedologic soil units were used to examine the distribution of radioelement response to selected soil characteristics: parent material, texture, mineralogy, and thickness. The interpretations from best correlation in both soil maps were described in terms of the radioelement changes during pedogenic and geomorphic processes, based on a review of literature and supported by soil samples.In the hypotheses-generating stage, AGRI provided useful information in three forms (single signal, ratio, and ternary images enhanced with a hill shaded DEM) by relating these to lithology, material transport, and internal pedogenetic processes. AGRI correlated well with the classes of the geopedologic map (1:50,000) at the two higher levels (landscape and lithology) but to a lesser degree at the two lower levels (relief and landform in geopedologic approach). In the mapping stage, AGRI showed deficiencies in the soil series map (1:50,000) made by conventional aerial photo analysis and limited field surveys, especially in inaccessible areas but also in low-relief terraces and flood plains, which provided a basis for future field sampling to correct these deficiencies. AGRI suggested new boundaries, differentiating topsoil properties and the presence of plinthite, despite its coarse resolution.Clustering of gamma ray and elevation data (DEM) was carried out using fuzzy logic to generate various classification layers. Final map was produced using total weighted inverse distance of all the classes in a 3 by 3 window. Class label was assigned to the one with the largest total inverse distance over the entire set of fuzzy classification bands. The result shows relatively higher classification accuracy for soil parent material differentiation (overall accuracy of 72%) as compared to the classification for soil types (67%).

THE EFFECT OF WELD POSITION ON MECHANICAL PROPERTIES OF TMT ROD JOINED BY ARC WELDING

There are various welding processes for joining the materials. Arc welding is a prominent joining process in which two steel parts are joined by heat generated due to arc. Many researches have been carried out in joining of different materials by different welding techniques. Our research has been emphasized on TMT bars. A Thermo Mechanical Treated (TMT) bar is commonly used for making reinforced roofs and column of building. They are also used in for industrial purpose such as rock bolting in underground mines etc. Most of TMT bar’s joining process took place with arc welding. In this paper a study has been made for the effect of welding position on strength of joined rods. In this study four Nos. of samples were taken having different locations of welding. They were allowed to cool under ambient condition. The chemical composition of parent material and weld zone were checked and observed that weld zone have different chemical composition compared with parent material. The variations of hardness with respect to distance were also checked using Brinell hardness testing machine and it was found that firstly hardness decreases and then increases with increase in distance from weld centre. From microstructural examination it has been seen that weld zone, HAZ and parent material all have different grain size as well as phase composition. Such change has been due to differential heating during welding. This increase and decrease in hardness has been justified with microstructural changes. Smaller grains have high hardness. Higher the pearlite phase higher is the hardness. There is decrease in hardness and strength in weld zone compared to parent zone and this was justified by lower percentage of carbon in weld zone as well as the microstructure of weld zone.

Interactions between organisms and parent materials of a constructed Technosol shape its hydrostructural properties

Abstract. There is no information on how organisms influence hydrostructural properties of constructed Technosols and how such influence will be affected by the parent-material composition factor. In a laboratory experiment, parent materials, which were excavated deep horizons of soils and green waste compost (GWC), were mixed at six levels of GWC (from 0 to 50 %). Each mixture was set up in the presence/absence of plants and/or earthworms, in a full factorial design (n = 96). After 21 weeks, hydrostructural properties of constructed Technosols were characterized by soil shrinkage curves. Organisms explained the variance of hydrostructural characteristics (19 %) a little better than parent-material composition (14 %). The interaction between the effects of organisms and parent-material composition explained the variance far better (39 %) than each single factor. To summarize, compost and plants played a positive role in increasing available water in macropores and micropores; plants were extending the positive effect of compost up to 40 and 50 % GWC. Earthworms affected the void ratio for mixtures from 0 to 30 % GWC and available water in micropores, but not in macropores. Earthworms also acted synergistically with plants by increasing their root biomass, resulting in positive effects on available water in macropores. Organisms and their interaction with parent materials positively affected the hydrostructural properties of constructed Technosols, with potential positive consequences on resistance to drought or compaction. Considering organisms when creating Technosols could be a promising approach to improve their fertility.

Geographic, environmental and biotic sources of variation in the nutrient relations of tropical montane forests

Abstract:Tropical montane forests (TMF) are associated with a widely observed suite of characteristics encompassing forest structure, plant traits and biogeochemistry. With respect to nutrient relations, montane forests are characterized by slow decomposition of organic matter, high investment in below-ground biomass and poor litter quality, relative to tropical lowland forests. However, within TMF there is considerable variation in substrate age, parent material, disturbance and species composition. Here we emphasize that many TMFs are likely to be co-limited by multiple nutrients, and that feedback among soil properties, species traits, microbial communities and environmental conditions drive forest productivity and soil carbon storage. To date, studies of the biogeochemistry of montane forests have been restricted to a few, mostly neotropical, sites and focused mainly on trees while ignoring mycorrhizas, epiphytes and microbial community structure. Incorporating the geographic, environmental and biotic variability in TMF will lead to a greater recognition of plant–soil feedbacks that are critical to understanding constraints on productivity, both under present conditions and under future climate, nitrogen-deposition and land-use scenarios.

Mechanical Behavior and Applications of Plasma Arc Welded Ceramics

Zirconium diboride and zirconium carbide‐based ceramics were joined by plasma arc welding to demonstrate the versatility of this technique. A parent material composition consisting of ZrB2 with 20 vol% ZrC was hot pressed to near full density, sectioned to produce specimens for welding, and welded together to produce billets for mechanical property studies. The four‐point flexure strength of the parent material was ~660 MPa, while the strength of the welded specimens ranged from ~140 to ~250 MPa. Microstructural analysis revealed that decreased strength in the welded specimens was caused by volume flaws, microcracking of large ZrB2 grains (up to 1 mm in length), and residual tensile stresses that developed at the surface of weld pools during cooling. The versatility of plasma arc welding was demonstrated by joining of ZrC‐based ceramics and fabricating three ZrB2–ZrC components for potential applications, including a high‐temperature electrical contact, an ultra‐high‐temperature thermocouple, and a wedge that was a notional wing leading edge. These three applications demonstrated the ability to join ceramics to a refractory metal, fabricate a chemically inert high‐temperature thermocouple, and produce complex shapes for aerospace applications.

Soil properties, micromorphology, and mineralogy of Cryosols from sorted and unsorted patterned grounds in the Hornsund area, SW Spitsbergen

Patterned grounds are probably the most interesting features produced by natural processes acting on the Earth's surface. Such features occur mainly in polar areas and in high mountains indicating that the origin of patterned grounds is related to frost action and cryoturbation. In spite of the many studies concerning the mechanism of the formation and the various forms of patterned grounds, very little attention has been paid to the qualitative and quantitative analyses of their mineral composition, and especially the mineralogy of the clay fraction. The analysis of the mineralogy of clay fraction is very important due to the finest particles (especially clay minerals) may play a crucial role in cryoturbation and cryosegregation as the particles are mainly responsible for accumulation of water and rheological properties of the ground. Thus, the main aim of the present study was to verify the hypothesis that the presence of swelling clay minerals in parent material favors the development of sorted patterned grounds. To verify the hypothesis, the physical, chemical, micromorphological, and qualitative and quantitative mineralogical properties of Cryosols from sorted and unsorted patterned grounds in the Hornsund area (SW Spitsbergen) were determined. The obtained results show that Turbic Cryosols from sorted patterned grounds featuring clear frost cracking, frost segregation, and cryoturbation are characterized by a lack of clearly developed soil horizons, loamy texture and low content of soil organic matter. Haplic Cryosols show better developed soil horizonation and contain lower amounts of the silt and clay fractions, higher content of the sand fraction and soil organic matter in comparison with Turbic Cryosols exhibiting strong cryoturbation. Micromorphological analysis of Turbic Cryosols indicates frost action manifested by a vesicular microstructure; round, oval, and deformed (mammillated) vesicles as dominant voids; vertically-oriented rock fragments; and silt and silt–clay cappings occurring on rock fragments. In addition, the occurrence of Fe–Mn nodules showing a sharp boundary indicates mixing of soil material. Micromorphology of the studied Turbic Cryosols indicates that cryoturbation prevails over cryosegregation. The soil material of the studied Cryosols is composed mainly of quartz, K-feldspar, plagioclase, dioctahedral mica (muscovite and/or illite), biotite, augite, hornblende, garnet, chlorite, swelling clays (smectite, vermiculite), goethite, and in some cases also calcite and traces of kaolinite. Majority of the minerals are most likely primary minerals inherited from parent material due to weak chemical weathering in the severe Arctic climate conditions and relatively young soils. However, weak chemical weathering of biotite and formation of vermiculite and mixed layered clay minerals also take place. Quantitative mineralogical analysis shows that besides texture and moisture, the mineral composition of soil material may also play some role in the susceptibility to cryoturbation and the formation of sorted and unsorted patterned grounds. However, the small differences in mineral content between the studied Turbic Cryosols and Haplic Cryosols indicate that the mineral composition of parent material is not a crucial characteristic responsible for the formation of sorted patterned grounds.

Soil property variability in a humid natural Mediterranean environment: La Rioja, Spain .

Estimating the spatial variability of soil properties is significant for evaluating environmental impacts. For example, many soil properties are directly used in the modelling of environmental processes such as global climate change. These aspects have not previously been studied at this level in La Rioja (a region of Spain with a humid Mediterranean environment). The intention of this study was to provide quantitative information on soil assessment and mapping methods for natural soils in a humid Mediterranean environment. The properties considered included: pH and organic matter, calcium carbonate and clay contents. For testing, samples were selected from several different soil types which, in theory, were only affected by pedogenetic processes and had developed on different parent materials. More than half of the samples did not contain any CaCO<sub>3</sub>, while the rest of the samples presented a variety of CaCO<sub>3</sub>, forms, with high percentages being present in certain cases (up to 65% on the surface). It was possible to establish two different areas: one predominantly acidic and the other principally basic. The predominately basic samples were due to the high percentage of carbonate in the parent materials. The clay content on the surface was similar to that in the subsurface layers. Finally, the organic matter contents in the uppermost layers presented average values of 3.9%,with a range of from 0.3 to 17.5%. The major variations in soils were determined by soil type (therefore by soil forming processes), parent material composition, and vegetation type. This study reveals that these methods are useful to determine the spatial distribution of some soil properties in undisturbed soils. The contour maps of soil property variability could be used to improve future sampling designs and management decisions.

Soil property variability in a humid natural Mediterranean environment: La Rioja, Spain .

Estimating the spatial variability of soil properties is significant for evaluating environmental impacts. For example, many soil properties are directly used in the modelling of environmental processes such as global climate change. These aspects have not previously been studied at this level in La Rioja (a region of Spain with a humid Mediterranean environment). The intention of this study was to provide quantitative information on soil assessment and mapping methods for natural soils in a humid Mediterranean environment. The properties considered included: pH and organic matter, calcium carbonate and clay contents. For testing, samples were selected from several different soil types which, in theory, were only affected by pedogenetic processes and had developed on different parent materials. More than half of the samples did not contain any CaCO<sub>3</sub>, while the rest of the samples presented a variety of CaCO<sub>3</sub>, forms, with high percentages being present in certain cases (up to 65% on the surface). It was possible to establish two different areas: one predominantly acidic and the other principally basic. The predominately basic samples were due to the high percentage of carbonate in the parent materials. The clay content on the surface was similar to that in the subsurface layers. Finally, the organic matter contents in the uppermost layers presented average values of 3.9%,with a range of from 0.3 to 17.5%. The major variations in soils were determined by soil type (therefore by soil forming processes), parent material composition, and vegetation type. This study reveals that these methods are useful to determine the spatial distribution of some soil properties in undisturbed soils. The contour maps of soil property variability could be used to improve future sampling designs and management decisions.

Genesis study of high abundant 17α(H)-diahopanes in Lower Cretaceous lacustrine source rocks of the Lishu Fault Depression, Songliao Basin, Northeast China

Relatively abundant 17α(H)-diahopanes have been detected in the lower cretaceous lacustrine source rocks from the Lishu Fault Depression in the Songliao Basin Northeast China. Rich long chain tricyclic terpanes (carbon number up to C35) and gammacerane have been observed in those source rocks with relatively abundant 17α(H)-diahopanes, which is rarely seen in previous reports. In this paper, the formation of 17α(H)-diahopanes has been discussed from three aspects including maturity, oxidation-reduction nature of depositional environment and parent material composition by the GC/MS analyses. The results reveal that maturity and oxidation-reduction nature of depositional environment have little effect on the formation of 17α(H)-diahopanes in the investigated area. However, the positive correlation between long-chain tricyclic terpanes and 17α(H)-diahopanes argues strongly for a common origin, and the origin is related to the algaes in saline water environment. The algaes in saline water environment may be a kind of origin of 17α(H)-diahopanes.

Mineral composition vs. soil forming processes in loess soils — A case study from Kraków (Southern Poland)

The mineral composition of soil parent material has a clear impact on: soil formation, soil properties (especially chemical properties), and mineral transformation in soil environment. Despite many studies concerning loess soils, detailed, quantitative studies on the mineral composition and transformation of clay minerals in loess soils formed during Holocene and the influence of the mineral composition of parent material on the properties of loess soils are rare. The main aims of the present study were (1) to determine the influence of loess mineral composition on soil genesis and (2) to determine layer silicate transformations and clay mineral formation in loess soils in relation to soil-forming processes using qualitative and quantitative X-ray diffraction analyses (XRD and QXRD). The obtained results show that the occurrence of carbonate minerals (i.e. calcite) and their influence on chemical properties of soil play a crucial role in the evolution of loess soils. In loess that does not contain carbonates, dispersion and translocation of clay particles (including clay minerals) down the profile occur. This leads to the formation of Luvisols and Albeluvisols. In carbonate loess, clay minerals and soil organic matter form stable humus–mineral complexes leading to the accumulation of humus and the formation of Chernozems. The transformation of mica and/or smectite and/or vermiculite to hydroxy-interlayered minerals (HIMs) is the dominant process in the studied loess soils developed in a temperate climate because intense weathering of layer silicates is possible after removal of carbonates from soil profile. This indicates that the occurrence of carbonates which maintain soil pH on a level of about 7 or higher is most likely the main factor controlling the rate of weathering of layer silicates in a loess soil environment. In carbonate loess, the dissolution and leaching of carbonates prevail over the weathering of silicates. It is highly likely that the continuous leaching of carbonates – assuming that the climate will not change – will lead to more intense weathering of layer silicates.

Factors affecting Type IV creep damage in Grade 91 steel welds

Differences in parent material heat treatment and composition apparently have remarkably little influence on the creep life of the heat affected zone (HAZ). Thus, tendency for Type IV cracking in the fine grained or intercritically heat treated regions of the HAZ does not appear to directly depend on the strength of the base steel. However, the current work indicates that the angle of the weld preparation changes the measured cross weld creep life. The results presented suggest that both development of residual stresses and the local properties of the constituent zones in the HAZ influence the tendency for Type IV damage in martensitic steels.

In-service behaviour of creep strength enhanced ferritic steels Grade 91 and Grade 92 – Part 2 weld issues

In Creep Strength Enhanced Ferritic steels control of both composition and heat treatment of the parent steel is necessary to avoid producing components which have properties below the minimum expected by applicable codes. The degree of tempering involved in manufacture will modify the material hardness. While under most conditions hardness is reduced by tempering, exceeding the AC1 temperature can lead to an increase in hardness. In this heat treatment the properties will be relatively poor even though the measured hardness may be apparently acceptable. Thus, care should be exercised in imposing an acceptance test of components based on simple hardness alone.Differences in parent material heat treatment and composition apparently have remarkably little influence on the creep life of the heat affect zone (HAZ). Thus, Type IV cracking in the fine grained or intercritically heat treated regions of the HAZ does not appear to directly depend on the strength of the base steel. This form of in-service damage is relatively difficult to detect using traditional methods of non-destructive testing. Moreover, since repeated heat treatment leads to over tempering and a degradation of properties, specific procedures for making and then lifing repair welds are required. The present paper summarizes examples of damage and discusses best option repairs.

Badlands denudation “hot spots”: The role of parent material properties on geomorphic processes in 20-years monitored sites of Southern Tuscany (Italy)

Abstract Some monitoring stations have been recording for 20 years the geomorphic processes acting on calanchi and biancane badlands located in the Tyrrhenian side of Central Italy. Field monitoring was aimed at studying the dynamics of surface processes, such as sheet, rill and gully erosion, shallow landsliding, piping and tunneling, considering their space–time variability as a consequence of both natural factors and human pressure. This paper shows the results of grain size, geochemical and mineralogical composition of parent materials from Upper Orcia Valley sites (Southern Tuscany), to further elucidate the role of their properties on processes acting on both bare and vegetated surfaces. Parent materials properties are discussed with respect to the initiation and development of different badlands processes. In particular, clay dispersivity at different depths in the sample sites is examined as a well-known controlling factor of accelerated erosion, thus providing some interesting clues for understanding the spatial variability of denudation rates in the considered badlands sites.

Soil Mineral Composition in Contrasting Climatic Regions of the Great Dyke, Zimbabwe

Ultramafic-derived soils impact agricultural productivity and environmental quality. The mineralogy of soils developed from ultramafic parent materials of the Great Dyke, Zimbabwe, at Mpinga (∼800 mm mean annual rainfall) and Bannockburn (∼500 mm) were investigated to evaluate possible mineral transformation pathways under different climatic regions and landscape positions. Mineral characterization was conducted by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Clay minerals observed at both study sites included talc, chlorite, vermiculite, Fe oxides, and Fe- and Cr-rich smectite. Serpentine occurred at the Mpinga site, but only at specific landscape positions, suggesting the influence of local transport and weathering phenomena as well as parent rock composition. Palygorskite was observed at the Bannockburn site only, in association with calcic horizons. Unique to these soils was the absence of micas, the negligible presence of feldspars and relatively smaller amounts of kaolinite. The majority of the clay minerals were inherited from the parent materials by physical and chemical weathering. Iron- and Cr-smectite and Fe oxides were formed by precipitation from saturated solutions and the hydrolytic oxidation of the Fe-rich parent materials, respectively. The occurrence and composition of the primary and secondary clay minerals of the Great Dyke reflect the composition of parent materials and the localized variations in climatic conditions. Localized differences in mineralogy point toward the importance of understanding the localized mineralogy and chemistry as an aid in developing effective site-specific agricultural and environmental management strategies.

Sand and silt mineralogy of some forest soils of Pauri district, Uttarakhand

Fine sand and silt mineralogy of selected horizons of some soils representing various landforms of Pauri district of Uttarakhand were investigated. Light minerals constituted bulk of fine sand fraction and consisted of quartz, orthoclace feldspar, plagioclase feldspar and muscovite in their abundance. Heavy minerals occurred in minute amounts and were dominated by opaque minerals, zircon, hornblende, calcite, chloritized mica, biotite, tourmaline, rutile and garnet. The study suggests that quartz, tourmaline, opaque minerals, rutile and zircon were the resistant minerals present in these soils. The most weatherable minerals include feldspar, calcite, biotite, chlorirtized mica and hornblende. In silt fraction, quartz was the dominant mineral in all the pedons. Variation in mineralogical make up were mostly associated wi9th nature and composition of parent material and degree of weathering. The soils of Pauri district, in general contained moderate to high amount of weatherable minerals indicating their juvenile to intermediate stages of weathering.

Trends of the natural evolution of chernozems on the East European Plain

A generalized chronosequence of changes in the morphometric parameters of chernozems in the past 5100 years is analyzed. It is shown that the development of chernozems in the center of the East European Plain is characterized by both long-term (interglacial, encompassing the entire Holocene) and short-term (within separate climatic periods of the Holocene) trends. The long-term trend of the evolution of ordinary chernozems developed from the loess-like calcareous loam consists of a continuous increase in the thickness of the soil humus profile and an oscillating increase in the depth of the carbonate accumulations. The Late-Holocene short-term trends of the natural evolution of chernozems are characterized by the high spatial heterogeneity related to the patterns of climatic fluctuations and to the lithological composition of parent materials. In that period, the thickness of genetic horizons in the forest-steppe chernozems was increasing faster than that in the steppe chernozems.

3D initial sediment distribution and quantification of mass balances of an artificially-created hydrological catchment based on DEMs from aerial photographs using GOCAD

The spatial distribution and properties of parent material components form the starting point for any soil and ecosystem. Initial phases of ecosystem development are predominantly characterized by the redistribution of sediment components. To improve the understanding of soil-landscape development, the initial sediments need to be quantified in space and time. This study aims at developing and testing methods for the quantification of initial sediment mass balances in the three dimensions of space and in time. The initial mass balance and composition of parent material in an artificially-created hydrological catchment were quantified from a 3D-model of the catchment’s water storage layer. Multi-date digital elevation models (DEMs) were constructed from photogrammetrically derived elevation data after the assessment and improvement of elevation data quality. Three-dimensional models of volume change were constructed from the digital elevation models. Regions of significant volume change were identified. Mass changes were calculated from the volume changes in combination with bulk density information. Based on information about the catchment’s construction, mass changes were separately analyzed in subregions of the models. Terrain attributes were computed to characterize surface structure and to examine correlations with mass change. From the 3D-model, an initial sediment volume of 122,608 m 3 was quantified. A variation of about ±12,300 m 3, due to uncertainty in DEMs from aerial photographs, was calculated. The 3D-model indicates differences in sediment properties between the western and eastern part of the catchment, which are most probably resulting from the dumping of two separate material deliveries during the construction. Models of volume and mass change are constructed for three time periods of catchment evolution. Spatial variations in volume and mass change are observed. The total mass balance reveals a considerable mismatch between the detected amounts of erosion and sedimentation, which gives reason to closely examine the quality of the DEMs. Terrain attributes of four elevation models reflect the diversification of surface structures. Correlations between volume change and surface structures show that erosion processes are dependent on initial surface structures and that these structures, in turn, are enhanced by the processes of sediment redistribution. Although there is a considerable uncertainty in the observed mass changes, the 3D-modelling approach allows a first approximation of the initial, mostly erosion-affected, surface structural dynamics of the artificial catchment. The comparison of multi-date elevation data allows a critical evaluation of the quality of models of change obtained from repeated topographical surveys.