Silt Clay Research Articles

Effects of vegetation cover on sediment particle size distribution and transport processes in natural rainfall conditions on post-fire hillslope plots in South Korea

Sediments were collected from four slow vegetation recovery plots, six fast vegetation recovery plots and five unburned plots at a post-fire site on a rainfall event basis and sorted for size distribution. The aim was to evaluate the effects of vegetation cover, soil aggregate stability, slope and rainfall intensity on sediment size distribution, transport selectivity and erosion processes between the burned and unburned treatment plots. Sediment detachment and transport mechanisms and the particle size transport selectivity of the eroded sediment were assessed based on enrichment ratios (ER) and mean weighted diameter (MWD) methods. The most eroded particle size class in all treatment plots was the 125–250μm class and, generally, the percentage of eroded particle sizes did not increase with slope and rainfall intensity. Higher MWD of the eroded sediment was related to a higher percentage of bare soil exposed and gravel content associated with high soil burn severity and soil disaggregation in the slow vegetation recovery plots. The enrichment of finer clay silt particle sizes increased with varying maximum 30-min rainfall intensity (I30) in the slow vegetation recovery plots, and reflected increased aggregate breakdown and transport selectivity, whereas no good relationship was found in the fast vegetation recovery and unburned plots with varying I30. A minimum I30 of <3.56mmh–1 and a maximum of 10.9mmh–1 were found to be the threshold rainfall intensity values necessary for aggregate breakdown and transport of finer particles by both rainsplash and rainflow in the slow vegetation recovery plots, whereas the response was weak in the fast vegetation recovery and unburned plots following varying I30 dominated only by rainsplash transport closer to the plot sediment collector. The results show that higher vegetation cover in the fast vegetation recovery and unburned plots reduces erosive rainfall energy by 5.6- and 17.7-fold respectively, and runoff energy by 6.3- and 21.3-fold respectively, limiting aggregate breakdown and transport selectivity of finer particles compared with the slow vegetation recovery plots.

Intertidal assemblage variation across a subtropical estuarine gradient: How good conceptual and empirical models are?

Variation of intertidal macrobenthic structure at multiple spatial scales is still poorly known in tropical and subtropical estuaries. We have assessed the structural responses of intertidal benthic assemblages, expressed by variation in number of species, abundance and assemblage composition, to key environmental drivers in a subtropical estuary from southern Brazil. We have applied a hierarchical sampling design to assess benthic variation at each of several spatial scales, from meters to kilometers, along a marked estuarine gradient. The hypothesis that many benthic variables vary at the largest spatial scale, corresponding to the salinity gradient, was refuted for number of species but not for total abundance and species composition. However, physiological stress to salinity variation, an important environmental driver in estuaries, could not explain by itself macrobenthic distribution along local intertidal flats. Nutrient, organic matter, photosynthetic pigments contents, pH, grain size, silt–clay content and the redox discontinuity layer also varied at the largest spatial scale acting as confounding factors. Thus, overall distribution patterns of intertidal benthic assemblages resulted from a complex interaction among environmental drivers, including salinity.

Growth and yield of corn grown on two alluvial soils of Louisiana applied with different phosphorus rates

ABSTRACTThe influence of soil properties on phosphorus (P) availability of Louisiana alluvial soils is not fully understood. A pot experiment was conducted in 2011 to evaluate the effect of different P fertilizer rate (0, 34, 67, 101 and 134 kg P2O5 ha−1) on corn growth and development on Perry clay and Commerce silt loam (sil) soils and relate Mehlich-3 and Bray-2 soil test P values with yield, total biomass, and P uptake of corn. The Bray-2 P values were six times higher than Mehlich-3 P values for Commerce sil while they were similar for Perry clay. Bray-2 and Mehlich-3 extractable-P of both soils increased with increasing P rate but only corn grown on Perry clay responded to P rate (P < 0.05). Implementation of appropriate testing procedure for estimating plant-available P in soil is an important component of effective P fertilization guidelines for corn.

Ciliated protists from the nepheloid layer and water column of sites affected by the Deepwater Horizon oil spill in the Northeastern Gulf of Mexico

Benthic marine protists have been well documented from shallow marine benthic habitats but remain understudied in deeper habitats on continental shelves and slopes, particularly in the Northeastern Gulf of Mexico (NEGOM). This region was affected by a deep water oil well failure (BP-Deepwater Horizon, 2010). The combination of a lack of information on deep sea microbenthic communities and the potential for benthic microbial petroleum mineralization prompted this investigation. Water column and nepheloid layer samples were obtained via Niskin bottles and a multicorer respectively at stations across the NEGOM to: (1) determine whether nepheloid and water column communities are distinct and (2) assess benthic species richness relative to sediment PAH contamination. Phylum specific 18S rRNA gene amplification was used to construct clone libraries of ciliate assemblages. BLAST searches in the NCBI database indicated that a majority (~75%) of the clone sequences corresponded (94–100% similarity) with listed, yet unclassified sequences. Several putative species were common at most site locations and depths. Many known benthic ciliates, such as Uronychia transfuga, Uronychia setigera, and Spirotrachelostyla tani, were common in the nepheloid layer samples and not recovered in water column samples. Ciliated protist species richness increased with PAH levels found in surface sediments, suggesting a positive microbial response to petroleum enrichment of the benthos. The presence of previously unknown microbenthic communites in the nephaloid layer over oceanic clay–silt muds alters our view of microbial processes in the deep sea and merits investigation of the microbial processes and rates of microbial mineralization and biomass production important to global biogeochemistry.

Comment on: “Earthquake geology of Kashmir Basin and its implications for future large earthquakes” by Shah (2013); “Kashmir Basin Fault and its tectonic significance in NW Himalaya, Jammu and Kashmir, India” by Shah (2015)

(KBF) without any additional structural, kinematic, geologic or geomorphic data in support. Therefore, this comment aims to clarify the confusions created by Shah (2013, 2015a), and it is in this context; we provide a review of the BF. No active faults/out-of-sequence thrusts/tectonic discontinuities were known north of MBT or MCT in the Kashmir basin, except a few NW–SE suspected fault segments with the collective length of ~45 km along NW Quaternary deposits, mapped from aerial photographs and CORONA satellite images (Nakata et al. 1991), and a south-facing scarp delineated as a possible active fault using Landsat satellite images (Yeats et al. 1992). Subsequent investigations revealed that the southwest-facing scarp (Yeats et al. 1992) is a high-angle thrust fault (reverse) with an average northeast 60° dip and NW–SE strike length of ~40 km (Ahmad 2010; Madden et al. 2010, 2011; Ahmad and Bhat 2012) (Figs. 1, 2, 3). The structure was named as BF because of its exposure on the left bank of Rambiara river (tributary of Jhelum river) at Balapur village (N 33° 75′ E 74° 83′) in Shupiyan district of Jammu and Kashmir state, India (Ahmad 2010; Ahmad and Bhat 2012). With an unknown depth, the BF cuts across (NW–SE) unconsolidated Karewa deposits (Plio-Pleistocene soft sediments), devoid of gouge and breccia; however, rotated gravels at the fault contact have been marked (Ahmad and Bhat 2012). Stratigraphic relations show that the fault has uplifted the Lower Pleistocene Methawoin Member (sand, sandy clay, clay silt and lignite bands) of the Lower Karewa and juxtaposed it to the Middle Pleistocene Shupiyan Member (gravels mostly composed of Panjal Trap fragments of the Upper Karewa (Bhatt 1989). Subsequently, the BF was firmly established by paleoseismic investigation and field data (Madden et al. 2010, 2011; Ahmad et al. 2013; Ahmad 2014). An optically stimulated luminescence (OSL) sample collected from fluvial deposits a few meters above the lower strath gives Comment

Estimating Earthen Tertiary Water Channel Seepage Losses as a Function of Soil Texture

Estimation of seepage losses is important in the management of an irrigation scheme because such losses significantly affect the efficiency of water usage. An attempt was made to determine seepage losses as a function of soil texture. Losses were measured three times, with the inflow-outflow method, for each of the 30 channels made of sandy loam, clay, clay loam, silt clay, and silt loam (six channels for each soil texture), and the soil-specific losses were determined. The soil-specific values were validated in terms of computing outflows. The maximum seepage of 294 mm day−1 was found for sandy loam, followed by 200, 185, 144, and 96 mm day−1 for silt loam, silty clay, clay loam, and clay material channels, respectively. Two empirical equations requiring soil type constants were also evaluated—namely, the Moritz formula and the Molesworth and Yennidunia formula. Investigation using these two equations for seepage estimation showed either underestimation or overestimation for the soil textures investigated. Therefore, these equations should be used after calibration, in accordance with channel conditions.

Rare earth elements and neodymium isotopes in world river sediments revisited

Over the past decades, rare earth elements (REE) and their radioactive isotopes have received tremendous attention in sedimentary geochemistry, as tracers for the geological history of the continental crust and provenance studies. In this study, we report on elemental concentrations and neodymium (Nd) isotopic compositions for a large number of sediments collected near the mouth of rivers worldwide, including some of the world’s major rivers. Sediments were leached for removal of non-detrital components, and both clay and silt fractions were retained for separate geochemical analyses. Our aim was to re-examine, at the scale of a large systematic survey, whether or not REE and Nd isotopes could be fractionated during Earth surface processes.Our results confirmed earlier assumptions that river sediments do not generally exhibit any significant grain-size dependent Nd isotopic variability. Most sediments from rivers draining old cratonic areas, sedimentary systems and volcanic provinces displayed similar Nd isotopic signatures in both clay and silt fractions, with ΔεNd(clay–silt)<|1|. A subtle decoupling of Nd isotopes between clays and silts was identified however in a few major river systems (e.g. Nile, Mississippi, Fraser), with clays being systematically shifted towards more radiogenic values. This observation suggests that preferential weathering of volcanic and/or sedimentary rocks relative to more resistant lithologies may occur in river basins, possibly leading locally to Nd isotopic decoupling between different size fractions. Except for volcanogenic sediments, silt fractions generally displayed homogeneous REE concentrations, exhibiting relatively flat shale-normalized patterns. However, clay fractions were almost systematically characterized by a progressive enrichment from the heavy to the light REE and a positive europium (Eu) anomaly. In agreement with results from previous soil investigations, the observed REE fractionation between clays and silts is probably best explained by preferential alteration of feldspars and/or accessory mineral phases. Importantly, this finding clearly indicates that silicate weathering can lead to decoupling of REE between different grain-size fractions, with implications for sediment provenance studies.Finally, we propose a set of values for a World River Average Clay (WRAC) and Average Silt (WRAS), which provide new estimates for the average composition of the weathered and eroded upper continental crust, respectively, and could be used for future comparison purposes.

Spatial and temporal variation in fish assemblages in three small unpolluted estuarine rivers and associated lagoons in Kouchibouguac National Park, southern Gulf of St. Lawrence, Canada

Estuaries have among the highest primary production rates of ocean waters and provide essential habitat for many organisms. Recognition of the need to conserve these critical habitats is coupled with the need for baseline data to allow assessment of ecosystem changes. This study compares natural variations in, and correlations between, the composition of fish assemblages and environmental factors at several sites over two years in three rivers emptying into estuaries in the southern Gulf of St. Lawrence, Canada. Fish diversity and abundance were determined by beach seining and related to water temperature, salinity, substrate, and vegetation. From May to September 2000 (14 sites) and May to August 2001 (15 sites), 20 fish species were collected, seven of which accounted for 98% of the total catch. The dominant species, Mummichog (Fundulus heteroclitus), represented 44% of the catch. Its abundance and that of the other dominant species — Threespine Stickleback (Gasterosteus aculeatus) 16%, Blackspotted Stickleback (G. wheatlandi) 13%, Banded Killifish (F. diaphanus) 12%, Fourspine Stickleback (Apeltes quadracus) 7%, Atlantic Silverside (Menidia menidia) 4%, and Ninespine Stickleback (Pungitius pungitius) 2% — differed significantly both spatially and temporally. Multidimensional scaling analysis showed a spatial gradient in abundance from upstream to lagoon sites and a temporal gradient from spring to fall. Upstream sites were low in salinity and had a higher organic content and a higher proportion of silt–clay in the sediment. Variation within fish populations was related to site and seasonal changes in environmental conditions and species’ tolerance of water temperature, salinity, vegetation coverage, and fine sediments.

Consequences of using different soil texture determination methodologies for soil physical quality and unsaturated zone time lag estimates

Elucidation of when the loss of pollutants, below the rooting zone in agricultural landscapes, affects water quality is important when assessing the efficacy of mitigation measures. Investigation of this inherent time lag (tT) is divided into unsaturated (tu) and saturated (ts) components. The duration of these components relative to each other differs depending on soil characteristics and the landscape position. The present field study focuses on tu estimation in a scenario where the saturated zone is likely to constitute a higher proportion of tT. In such instances, or where only initial breakthrough (IBT) or centre of mass (COM) is of interest, utilisation of site and depth specific “simple” textural class or actual sand–silt–clay percentages to generate soil water characteristic curves with associated soil hydraulic parameters is acceptable. With the same data it is also possible to estimate a soil physical quality (S) parameter for each soil layer which can be used to infer many other physical, chemical and biological quality indicators. In this study, hand texturing in the field was used to determine textural classes of a soil profile. Laboratory methods, including hydrometer, pipette and laser diffraction methods were used to determine actual sand–silt–clay percentages of sections of the same soil profile. Results showed that in terms of S, hand texturing resulted in a lower index value (inferring a degraded soil) than that of pipette, hydrometer and laser equivalents. There was no difference between S index values determined using the pipette, hydrometer and laser diffraction methods. The difference between the three laboratory methods on both the IBT and COM stages of tu were negligible, and in this instance were unlikely to affect either groundwater monitoring decisions, or to be of consequence from a policy perspective. When tu estimates are made over the full depth of the vadose zone, which may extend to several metres, errors resulting from the use of hydraulic parameters generated from hand texture data will be resultantly greater, and may lead to flawed predictions regarding the achievability of water policy targets. For this reason laboratory analysis, regardless of method, should be preferred to simple field assessments.

Palaeoenvironmental research at Rexidora Cave: New evidence of cold and dry conditions in NW Iberia during MIS 3

The Rexidora Cave (Asturias, NW Spain), discovered in 2012, provided a remarkable large mammal assemblage of MIS 3 age. The ongoing excavation works yielded 445 fossil remains including cold-adapted elements as woolly rhinoceros (Coelodonta antiquitatis) and reindeer (Rangifer tarandus), two species of special interest since they are poorly represented in the Iberian Pleistocene. The woolly rhinoceros assemblage comprises numerous unusually well preserved elements as one mandible, one femur and one partially preserved skull. The steppe bison (Bison priscus) is the dominant species in the assemblage, providing an outstanding collection of well-preserved elements that comprises two skulls and numerous limb bones. Carnivores are represented by a partial skeleton (including a complete skull) of spotted hyena (Crocuta crocuta).Radiocarbon AMS analyses of the fossil assemblage yielded two dates of 44.5 and 37.6 Cal ka BP, corresponding to MIS 3, a phase of climatic instability characterized by fast climate changes, from extreme cold to temperate conditions. These dates are coeval with the maximum registered expansion of the mammoth fauna in the Iberian Peninsula and with the onset of glacier retreat in the Cantabrian Mountain Range, after the last local glacial maximum.Geomorphological and sedimentological evidence suggests that bone accumulation took place as the result of gravity processes in a collapse doline, filled by a chaotic accumulation of calcareous boulders, pebbles and bone fragments, embedded in a silt–clay matrix, which points to a possible natural-trap origin of this fossil assemblage. The exceptional well preservation of the fossils, as well as the lack of any evidence of human or carnivore activity, supports this idea.Palynological analyses suggest an open landscape under variable climatic conditions, responsible for the fluctuating presence/absence of the arboreal taxa. The predominance of steppe and, to a lesser extent, xeric herbaceous plants indicate very dry conditions, whereas presence of mesophilous forest taxa implies the existence of a refuge area at distance. This open and dry landscape, developed in a karst area with a relative smooth relief, is consistent with the occurrence of the large mammal species steppe bison, woolly rhinoceros and reindeer. Faunal and pollen analyses, hence, provides a new evidence for the development of cold and dry steppe-like environments in NW Iberia during MIS 3.

Distribution and formation of tephric-loess dunes in northern and eastern Japan

We studied the genesis of the Esashi, Shiriyazaki, Isozaki-Ajigaura, and Takamagahara dunes and associated blowouts. These dunes are located at the top of coastal cliffs, and they are composed of marine sediments (sand and gravel), which are covered with layers of Japanese loam. We examined pH(NaF) and pH(H2O) of samples from all dunes, and the grain size distributions, total carbon contents, humic properties, and colors (CIE-L*a*b*) of samples from the Esashi and Shiriyazaki dunes. In most samples, pH(NaF), an indicator of active aluminum, was ≥9.5. The grain size distribution in the Esashi and Shiriyazaki dunes was bimodal (with sand and silt–clay peaks), and their color, after removal of organic matter with H2O2, was similar to that of the loam. These findings show that the dunes are composed of marine sediments and loam eroded and reworked by the prevailing winds. Japanese loam is regarded as a kind of tephric loess. Thus, these dunes can be referred the tephric-loess dunes. The physicochemical properties of these tephric-loess dunes are similar to those of Kuroboku soil in that humus accumulation has been enhanced by the presence of active aluminum derived from the admixture of tephric materials.

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.

Combination of Kriging methods and multi-fractal analysis for estimating spatial distribution of geotechnical parameters

Spatial variability (randomness, correlation, and singularity) within the geotechnical parameters of complicated geological movements influences the estimation quality that depends on how well mathematical tools can account for variability through limited observations of a spatial field. Classical statistical methods depict randomness well, but cannot account for the problems associated with spatial correlations. Geostatistical methods such as ordinary Kriging (OK), universal Kriging (UK), and co-Kriging (CK) can produce predictions based on spatial auto-correlation and cross-correlation, but are always accompanied by average smoothing effects; a local singularity created by nonlinear geo-processes, therefore, requires special methods to be properly evaluated. In this study, a shallow load-bearing stratum of silt clay (length = 525 m, width = 80 m) at the former 2010 Expo Park in Shanghai was explored by performing 42 borehole laboratory experiments, which provided the key geotechnical parameters: the cohesion coefficient (\( C \), in kPa), the friction angle (\( \varphi \), in o), and the compression modulus (\( E_{\text{S}} \), in MPa). First, Kriging methods such as OK, UK, and CK estimated these geotechnical parameters, then a multi-fractal analysis was employed to measure the local singularity. Cross-validation illustrates that multi-fractal analysis has the ability to depict a local anomaly, and further that the auxiliary information utilized in CK improves spatial estimation accuracy.

Substratum as Determining Factor for the Distribution of Benthic Macroinvertebrate Fauna in a River Ecosystem

Present study was focused on the Ken river for determination of the distribution of benthic macroinvertebrate fauna with respect to substrate variation. The invertebrate samples were collected during December 2003 to March 2004 at four different stations by lifting of stones and sieving of clay–silt substratum from 0.09 m2 area. The collected samples were preserved in 5 % formalin and identified at family level. The count data was used to determine the density and composition of benthic macroinvertebrate fauna. Total mean density decreased from station S1 to S3 but increased at S4 and differed significantly among the stations. The maximum density was found in the stony substratum (boulder and cobble) as compared to small particle size (pebble, gravel and sand). The fauna was predominated by insects at stations S1 (84 %), S2 (90 %) and S3 (93 %), while reduced at S4 (48 %). Neoephemeridae and Caenidae were abundant taxa in boulder–cobble and cobble–pebble substrate, respectively. Leptophlebiidae, Baetidae and Hydropsychidae were abundant at pebble–gravel substrate and Thiaridae–Chironomidae–Nephthydae were abundant in silt–clay substrate. Principal component analysis also indicated the above observation. Canonical correspondence analysis at each station indicated that substratum (abiotic and biotic) was responsible for the distribution of benthic macroinvertebrate fauna in the Ken. Functionally, the collector insects dominate the fauna, at all the four stations because of substratum as well as the continuous source of particulate organic matter in the river.

Compaction Properties of Silty Soils in Relation to Soil Texture, Moisture Content and Organic Matter

Soil compaction is recognized as an increasingly challenging problem with regard to root growth and yield reduction in agricultural production in Thailand. The aim of this research was to study the effect of soil texture, moisture content and organic matter on the compaction properties of silty soils. Three soils with different silt contents were studied-loam, silty clay loam and silt loam. The study showed that compacting silt loam soil using the modified Proctor test resulted in a higher bulk density than from the oedometer test at 200 kPa. Statistical analysis showed that soil type and the moisture content significantly affected both the bulk density and penetration resistance. However, organic matter showed a significant effect only on the bulk density. The bulk density increased with increased moisture content. The bulk densities of compacted soils were higher in the order of loam, silt loam and silty clay loam. The penetration resistance seemed to increase with increased silt content. The differences in the bulk density and penetration resistance among these three soils decreased as the moisture content increased. Adding organic matter at 5% by weight to soils resulted in lower bulk densities of the soil using the oedometer test, with reductions of 3.9, 3.8 and 7.7% for loam, silty clay loam and silt loam, respectively. In order to avoid effects on root growth, it is recommended that machines with 200 kPa of tire contact pressure should only work in fields with a moisture content not exceeding 20.27, 18.74 and 17.88% for loam, silt loam and silty clay loam, respectively.

Effects of natural rainfall on soil and nutrient erosion on sloping cropland in a small watershed of the Dan River, China

Soil erosion and nutrient loss are two important aspects influencing crop production and water quality in the Dan River. In this study, a field experiment was conducted in the Yingwugou Watershed. A corn field of slope 23° with an area of 243 m2 was selected to study the spatial variability of soil properties for cropland and to determine the loss amounts of soil total nitrogen (STN), soil total phosphorus (STP), soil organic carbon (SOC) and silt–clay under natural rainfall. Geostatistical analysis indicated that generally STN, STP, SOC and silt–clay had strong spatial dependence (with nugget ratio <25%) primarily induced by structural factors. Kriging successfully interpolated the studied soil properties. There were some intrinsic relationships among STN, STP, SOC and silt–clay. The effect of rainfall on the spatial autocorrelation for STN and STP was more significant than that for SOC and silt–clay. Natural rainfall had a weak effect on SOC. The total loss of STN, STP and silt–clay in the sloping corn field decreased by 348.7g, 2640.4g, and 0.47% during the study period, respectively. The results provide useful information for understanding the nutrient loss and soil erosion on sloping cropland.

Pedogenetic processes and pedostratigraphy of the Quaternary on the Balearic Islands and in the Granada Basin, Spain

Sediment-soil-sequences are suitable geoarchives and may contribute to resolving palaeoclimate conditions and reconstructing the according stratigraphy. We highlight the characteristics of Holocene soils, Pleistocene palaeosols, aeolianites, loess, slope debris and calcretes on the Balearic Islands at 17 new locations on Mallorca, Ibiza, and Menorca. Their stratigraphy is correlated with sedimentary and pedogenetic processes, and compared to sequences in the Granada Basin (Southern Spain).On the Balearic Islands, surface soils are mainly brunified and loamy, while underlying palaeosols have different features due to clay illuviation, iron weathering and intense reddening, as emphasized by higher iron indices [FeIndex = (% Fed − % Feo)/(% Fet/% clay)] and their close correlation to redness. Intermediate sediments appear as aeolianites, silty loess, calcretes and silt–clay dominated slope debris, and may reflect rather dry-cool climates and scarce vegetation. The increase of palaeosol redness with depth underlines a successive development in respect of polygenesis. While the palaeoclimate is humid Mediterranean, the declined pedogenetic intensity refers to gradual transition to less pronounced humidity and lower temperatures.The palaeosols of the Granada Basin are comparatively less developed. Surface soils are brunified and loamy, and underlying palaeosols show features connected to clay-illuviation and reddening, while a distinctly smaller FeIndex is evidence of less intense weathering. Soil properties indicate declined pedogenetic intensity upon time. Soil formation is influenced by distinct sea level oscillations and a seasonal humid climate. Close correlations between FeIndex and RRvisual (R2 = 0.89) highlight hematite formation as particularly intense in the Early Pleistocene. It followed a more arid Late Pliocene with intense erosion and sedimentation, as underlined by distinctly lower values of both FeIndex and RRvisual during this time. Quaternary processes of pedogenesis and sedimentation therefore not only substantiate a distinct climatic cyclicity in the Western Mediterranean, but also reflect advanced development of palaeosols with depth and thus with time.

Experimental Heat Transfer Study on Green Roofs in a Semiarid Climate during Summer

An experimental study was conducted on green roofs under the semiarid summer climatic conditions of West Texas to investigate the effect of soil type, moisture content, and the presence of a top soil grass layer on the conductive heat transfer through the roof. Two soil types were investigated: uniform sand and local silt clay. Tests were also conducted on a control roof. A dual-needle heat-pulse sensor was used to conduct thermal property tests on the soils. The tests reveal that unlike sand, the thermal conductivity of silt clay did not increase continuously with soil moisture. Better heat transfer conditions were achieved when the sand and silt clay roofs were watered to a water depth of 10 mm per day rather than double the amount of 20 mm per day. The roof with silt clay soil had the lowest fluctuation in inner temperature between daytime and nighttime. Green roofs with silt clay soil required more than twice the amount of soil moisture than green roofs with sand to achieve similar roof heat transfer rates. The best net heat flux gains for vegetated green roofs were 4.7 W/m2 for the sand roof and 7.8 W/m2 for the silt clay roof.

High-resolution stratigraphy of the Lower Badenian deposits in selected cores of the Carpathian Foredeep

Drill cores from IK-1 Ivaň and LOM-1 Lomnice u Tisnova (Lower Badenian) was evaluated by several various proxy methods (X-ray fluorescence spektrometry XRF, gammaspectrometry, grain size analysis, RTG diffraction and chemical analysis) in order to obtain data about paleoclimatic and paleogeographic conditions of sedimentation as well as to veryficate applications of these methods on monitored Neogenous sediments. Both wells are situated in the southern part of the Karpathian Foredeep in the Czech Republic. IK-1 is situated in the central area of the basin while LOM-1 lies on the western border of it. According to the biostratigraphic data, both of the observed wells belong to the NN5 zone (Tomanova Petrova & Svabenicka 2007). Facial and litologic studies (Nehyba et al. 2007) point to similar sedimentary conditions (shallow-sea sediments of inner and outer shelf) and similar source of clastic material settling in the basin. Results from the X-ray fluorescence spectrometry were used as proxy date for grain size, weathering, oxide-reductive ratios and changes of high of sea-level. For the study, chemical elements were used, especially those which has been confirmed as reliable for given methods, specifically Al, Si, S, K, Ti, Mn, Fe, Rb and Zr. On the other hand, elements showing higher deviations during measuring were excluded, for example Cr, V, T or Ni. According to the results of grain analysis, the sediments can be classified as clay silts and, in only a fraction of cases, silt clays. Medium size of Mz grain (Folk & Ward 1957) was counted and was used to confirm grain proxies. Chosen ratios Si/Al, Ti/Al and Zr/Al (Ver Straeten et al. 2011) were used as grain proxies. Mutual correlations were insignificant, only in case of LOM-1 higher correlation between Mz and Ti/Al was proved. Therefore, the grain proxies cannot be considered reliable. Proxies for weathering show the effects of chemical weathering, which is also proved by high values of the CIA index. For surface-level changes, we used proxy Fe/Al (Clarkson et al. 2014). In IK‑1, the results were compared with ratio of plankton and bentos (Nehyba et al. 2007) and stronger similarity of trends was established. To sum it up, proxy data of studied sediments can be considered partially reliable.

Prediction of sonic velocities in shale from porosity and clay fraction obtained from logs — A North Sea well case study

Prediction of sonic velocities in shales from well logs is important for seismic to log ties if the sonic log is absent for a shaly section, for pore pressure anomaly detection, and for data quality control. An anisotropic differential effective medium (DEM) was used to simulate elastic properties of shales from elastic properties and volume fractions of silt and wet clay (a hypothetical composite material that includes all clay minerals and water). Anisotropic elastic coefficients of the wet clay were assumed as a first-order approximation to be linearly dependent on wet clay porosity (WCP). Here, by WCP we mean a ratio of a pore volume occupied by water to a total volume of the wet clay. Effects of silt inclusions on elastic coefficients of shales were taken into account by using the anisotropic differential effective medium model. Silt inclusions were modeled as spherical quartz particles. Simulated elastic coefficients of shales were used to calculate compressional and shear velocities, and these were in a good agreement with the sonic velocities observed on a test data set from an offshore Mid-Norway well penetrating a 500-m vertical section of shale. To further study the elastic properties of wet clays, elastic coefficients calculated from compressional and sonic velocities measured in shales were inverted for vertical profiles of wet clay elastic coefficients. Analysis of these coefficients found that in the well considered, the increase in elastic coefficients of shales was controlled by the increase of silt fraction with depth. Elastic coefficients of wet clay found no increase with depth. The inverted elastic moduli of wet clay found much stronger correlation with WCP than do the moduli of shale. This confirmed the hypothesis that silt fraction is one of the key parameters for the modeling of elastic properties of shale.