Variations In Granulometry Research Articles

Effect of Freeze-Thaw on CBR in Soils with Different Gradation and Mineralogy

Freeze-thaw cycles are prevalent climatic phenomena with substantial effects on soils, leading to alterations in soil strength, stiffness, and hydraulic properties due to disruptions in the soil structure. With the ongoing climate change, weather patterns have grown progressively erratic, resulting in more frequent occurrences of extreme weather events, including heavy snowfall, intense rainfall, and windstorms, even in regions characterized typically with mild climates across the globe. The climate change can potentially threat man-made infrastructure constructed within or upon local soils, regardless of their susceptibility to freezing in temperate climates. The principal objective of this study is to assess the influence of freeze-thaw cycles on the California Bearing Ratio (CBR %) across 12 distinct soils with variations in granulometry and mineralogy. The freeze-thaw cycles resulted in a notable decrease in CBR (%) within the range of 40% to 70%. A strong inverse correlation with D50 was observed regarding the decrease in CBR (%). Nevertheless, it was discerned that the decrease in CBR (%) subsequent to freeze-thaw cycles varied among soil samples sharing identical D50 and liquid limit characteristics. The aim of this study is to enhance our comprehension of how freeze-thaw cycles can impact the bearing capacity of these soils, thereby providing essential insights for predicting their behavior and potential influence on infrastructure in the context of climate change.

Spectral analysis of soils in the lower course of the Acaraú River, Northeastern Brazil

The objective of this research was to analyze the spectral response of alluvial soils, representative of the coastal plain in the lower course of the Acaraú River, Ceará, Brazil, and to correlate with the granulometry and soil organic matter (SOM) contents, seeking to identify the best method to predict the attributes studied. In four soil profiles (n = 23 soil samples) the sand, silt, and clay and SOM contents were determined and was carried out the mineralogical characterization. Soil samples were submitted to spectral analysis using a spectroradiometer, with spectral range from visible to shortwave to near infrared (350 - 2,500 nm). It was possible to relate the soil attributes such as color, SOM contents, variation in granulometry and even mineralogy aspects, such as types of minerals in the clay fraction, with the spectral reflectance curves. Some spectral interpretations were useful in understanding aspects associated with the genesis of these soils, especially with regard to the formation environment and mineralogy. For the SOM contents, the best estimates were obtained by simple linear regression and higher correlation for the 564 nm spectrum range. Regression methods were efficient in estimating soil attributes, but the study is limited to the small sample size.

Responses of functional traits of macrobenthic communities on the presence of Polycyclic Aromatic Hydrocarbons contamination in three tropical estuaries

Estuaries are considered receptors of various contaminants released into the environment, including Polycyclic Aromatic Hydrocarbons (PAH), a ubiquitous contaminant. In this study, the response of subtidal macrofauna in the polyhaline zone of three tropical estuaries was analyzed using a taxonomic approach, multimetric indices, and functional traits, to three different levels of PAH. The estuaries presented distinct degrees of contamination, with PAH directly correlated with mud percentage and organic matter. The considerable variation in granulometry found in the three studied estuaries may indicate complex hydrodynamics, with very different sedimentary characteristics. The community structure showed typical estuarine characteristics, with low diversity and high dominance. The macrofauna was distinct among estuaries, with no shared dominant species and with several species occurring just in one site, with different compositions, although other parameters of the community structure were similar. The AMBI and functional indices performed better than taxonomic indices in separating the areas with different impacts. In the analyzed communities, the functional traits approach demonstrated consolidated patterns in the estuarine environment, such as the predominance of opportunistic species, generally of smaller size and detritivore/depositivore, under conditions of pollution by the organic load. Local characteristics, such as the predominance of suspensivore organisms and relatively more mobility in areas with higher hydrodynamics, provide insight into the community's behavior on natural and anthropogenic stressors. The multivariate taxonomic and functional analyses were complementary, emphasizing the importance of integrating them in these environments diagnosis. Stressed environments need information from the entire data set for a correct assessment of the community.

On site determination of trace metals in estuarine sediments by field-portable-XRF

A portable x-ray fluorescence (XRF) spectrometer and mobile test stand have been employed to examine the feasibility of on site measurements of trace metals in estuarine sediment. In the laboratory, the instrument was able to detect the trace metals: As, Cr, Cu, Pb, Sn and Zn; and the geochemical proxy metals: Ca, Fe, K and Rb; in both fresh and freeze-dried surficial samples from the Tamar and Tavy estuaries, southwest England, that had been emplaced in polyethylene bags over the detector window. The presence of interstitial water in fresh samples acted as both a diluent of sediment mass and an attenuator of incident and fluorescent x-rays, resulting in measured (fresh weight) metal concentrations that were significantly lower than corresponding (dry weight) concentrations derived from dry analyses. Gravimetric correction for fractional water content (fw ~ 0.2–0.6) gave rise to results that were within 20% of those derived from dry analyses with the exception of K, whose relatively low energy fluorescent x-rays were subject to significant attenuation from the aqueous medium; further x-ray attenuation was observed for both K and Ca through the sample bag, thereby limiting the usefulness of the approach for these metals. A relationship between the concentration of Rb and fw in fresh samples suggests that Rb may be used as a proxy for interstitial water content through its covariance with sediment grain size. Accordingly, on site measurements of trace metals of sufficient fluorescent x-ray energies may be corrected empirically with respect to Rb in order to simultaneously account for variations in granulometry and mass contribution of water. On this basis, results from an axial transect of the Tamar and an intertidal transect in the Tavy were able to detect variations in trace metal concentrations that were consistent with known sources and geochemical behaviours.

Forensic recovery of transient eruption parameters for the 2360 BP fall deposit, Mount Meager, British Columbia

The 2360BP eruption of Mount Meager, Canada featured an explosive subplinian onset resulting in dacitic fallout tephra and associated pumiceous pyroclastic flow deposits, followed by the effusion of dacite lava and the deposition of a thick sequence of block and ash flow deposits. Fall deposits are distributed to the NE of the vent onto a rugged, deeply incised landscape. The central axis of deposition is ~063° Az; the lateral margins of the fall deposit are massive to unbedded whereas deposits underlying the plume axis feature complex bedding relationships. We present componentry and granulometry data for eight outcroppings of the fall deposit (four on plume axis and four off plume axis). Vertical cross-sections, based on surface outcrops and drill core logs from local commercial drilling programs, are used to relate the accessory lithics to their source depth in the underlying subvolcanic basement. These combined datasets inform on the dynamics of this explosive phase of the eruption including variations in column height, eruption intensity, atmospheric conditions, and depth to fragmentation front. The lateral variations within the fall strata reflect the effects of the prevailing atmospheric conditions on the form and dispersal pattern of the subplinian plume. Vertical variations in granulometry and componentry of the fall deposits are used to track temporal changes in eruption intensity and column height and the transient influence of the jetstream on the dispersal pattern of the plume. Lastly, vertical variations in lithic componentry, combined with our knowledge of the subsurface geology, are used to quantitatively track the deepening of the fragmentation front. Our computed results show that the fragmentation front migrated from ~640m to ~1160m below the vent over the course of the 2360BP Mount Meager eruption.

Metals in soils of erosional systems in forest zone in the central part of European Russia

Small erosional landforms, despite their importance in mass transfer processes, have received insufficient attention in geochemical studies. This paper presents a case study dealing with geochemistry of two small erosional systems, typical of humid moraine landscapes of the central part of European Russia. They are considered as integrated systems comprising several units viz. slopes, bottoms, detrital fans as well as adjacent areas as sources of solid material. Chemical composition of topsoil (total concentrations of Ti, Zr, Mn, Co, Zn, Cu, Pb, Cr, V, Ni, Sn, Sr, Ba and concentrations of the acid-extractable Fe, Mn, Co, Zn, Cu, Pb, Cr, Ni) was used to explore the role of granulometry, pH, organic matter content and transport processes in geochemical differentiation of the systems. Spatial variations in granulometry across the various units indicate a progressive depletion of a finer material in the gully and comparatively invariant distribution of the same fractions within the balka. The granulometry is the main factor controlling the distribution of total and acid-extractable metal concentrations in both systems. The findings imply that the prevailing mechanism of metal migration through the studied systems is a suspension transfer in association with clay and silt particles. The young gully system operates as a transit system and shows higher geochemical differentiation than the aged balka system where some elements may accumulate in topsoil of the lower units of this system.

Understanding Holocene variations in the vegetation of Sao Joao River basin, southeastern coast of Brazil, using phytolith and carbon isotopic analyses

To understand variations in the vegetation of the southeastern coast of Brazil during the Holocene and to identify roughly when they took place, we make use of phytolith morphology and carbon stable isotope analyses coupled with 14C dating of soil profiles. The soil profile studied is located in the Sao Joao River Basin close to Cabo Frio, Rio de Janeiro State. We evaluated the soil characteristics, which showed great variations in granulometry, with larger texture in upper horizons that enabled the movement of particles to lower layers. The accumulation soil horizons revealed several palaeoclimatic aspects: higher phytolith stocks, a higher density of trees, and a lower water stress at the bottom of the profile, and a predominance of C3 grasses throughout the Holocene. Carbon stable isotopic ratios of the soil profile confirm the predominance of C3 plants, except for E/Bt horizon which was enriched in 13C. The soil organic matter mean residence time ranges from post-bomb (topsoil) to 10,245yearscal BP at the base of the profile. The results of this study are compatible with other evidence of a more humid environment in the first half of the Holocene.

A 2300-year record of environmental change from SW Anatolia, Lake Burdur, Turkey

This work deals with changes recorded by lacustrine sediments from SW Anatolia in Turkey in the context of increasing stress on the Mediterranean environment in relation to human-climate-environmental interactions. Paleolimnological investigations were carried out on Lake Burdur (Lake District geographical subregion of Turkey), which has been subject to rapid changes in its hydrological system that caused a ~10-m water-level drop in the last 30 years. Study of a 5-m-long sediment core, taken from the recently dried out part of the lake, shows significant variation in granulometry, clay mineralogy, nitrogen and organic carbon content and its isotopic composition (∂13Corg) throughout the sedimentary sequence, which represents the last 2,300 years. Chronology is based on radiocarbon dates obtained from plant fragments. The results provide a record of environmental changes, including biological productivity and erosion intensity, in relation to changes in water level and humidity of the area. The lowest previous water level, which is the same as observed today, occurred at approximately 300 BC, after which time a water-level increase led to a maximum stage between AD 200 and 1200. From AD 1200 to the present, the climate became drier accompanied by an overall lowering of water level, with periods of water-level fluctuations superimposed. The lake never dried out as is observed today at the coring site. The present drop in the lake water level is attributed to human activity rather than to climate change. This record of climate and environmental change in the Lake Burdur area appears to be stratigraphically complete. This study provides rare data for the late Holocene in Anatolia as well as information about rapid climate changes during specific periods. The influence of both the Northern hemisphere atmospheric circulation and Indian monsoon on the east Mediterranean remains unclear. Nevertheless, the North Sea—Caspian atmospheric teleconnection could be an important factor that explains local differences in climatic evolution of Anatolia during the period considered.

Historical changes in trace metals and hydrocarbons in nearshore sediments, Alaskan Beaufort Sea, prior and subsequent to petroleum-related industrial development: Part I. Trace metals

Concentrations of Fe, As, Ba, Cd, Cu, Cr, Pb, Mn, Ni, Sn, V and Zn in mud (<63μm size), and total and methyl Hg in gross sediment are reported for Arctic Alaska nearshore. Multivariate-PCA analysis discriminated seven station clusters defined by differences in metal concentrations, attributed to regional variations in granulometry and, as in Elson Lagoon, to focused atmospheric fluxes of contaminants from Eurasia. In Colville Delta-Prudhoe Bay, V increase was noted in 1985 and 1997 compared to 1977, and Ba increase from 1985 to 1997. Presumably the source of increased V is the local gas flaring plant, and the elevated Ba is due to barite accumulation from oil drilling effluents. In Prudhoe Bay, concentration spikes of metals in ∼1988 presumably reflect enhanced metals deposition following maximum oil drilling in 1980s. In summary, the Alaskan Arctic nearshore has remained generally free of metal contamination despite petroleum-related activities in past 40years.

Formulation and combustion of emulsified fuel: The changes in emission of carbonaceous residue

Burning dense, viscous combustibles such as heavy fuel-oil as a water-in-oil emulsified combustible enables to decrease the emission of solid carbonaceous residue, in comparison with raw, non-emulsified combustible. This is due to the phenomenon of micro-explosion, meaning the rapid (<0.1 ms) vaporization of the water droplets inside the emulsion, breaking up the initial emulsion droplet into numerous and faster ‘daughter-droplets’. The present work is based on a small-scale furnace (300 kW max.) feed with heavy fuel-oil mixed with 10–20% of gasoil, with and without emulsion of water. The emulsification of combustible enables to record a reproducible lowering in emission of carbonaceous residue from the combustion of emulsified fuel, in comparison with raw fuel. This is added to a variation in granulometry of carbonaceous residue, hereby considered as an indicator of second atomization. Copyright © 2009 John Wiley & Sons, Ltd.

Comparison of saponite and montmorillonite behaviour during static and stirring maturation with seawater for pelotherapy

Two different bentonites (saponite and montmorillonite) have been used for maturation with seawater. These bentonites are very rich in phyllosilicates (> 90%), with calcite, silica minerals (quartz, cristobalite) and feldspars (plagioclase) as subordinated minerals. Maduration tests have been realized both in static and stirring conditions and sampling points at 0, 15, 30, 60, 90 and 120 days have been established. Several mineralogical (XRD, SEM-EDX) chemical and physico-chemical (CEC, pH, granulometry, plasticity, conductivity) analytical techniques have been used. Results indicate no mineralogical changes during maturation process but differences in the smectite crystallinity (crystallite size) and basal spacing d (001). The last related with the variation of exchangeable cations (mainly Na + for Ca 2+) within the smectite interlayer. Variations in granulometry, plasticity index and conductivity have also been observed. Similar results are reported for static and stirring procedures, and therefore the former is preferred. Maturation time of between 60 and 90 days would be enough for the bentonite to achieve the optimum physico-chemical properties for its use as a peloid. Between the two bentonites under study, saponite is clearly better than montmorillonite for its application as peloids in pelotherapy. This fact is mainly due to differences in grain size distribution and consequently in the cationic exchange capacity, which enables in saponite a higher retention of water ions making possible their transference to patients, and therefore reaching a better influence in their health.

Compaction and movement of interstitial water in bottom sediments of the Saguenay Fjord, Quebec, Canada

Eight sediment cores were collected along the length of the Saguenay Fjord and Baie des Ha! Ha!, Québec, Canada. Profiles of the sediment water contents were determined for each core. Porosities were fitted to an exponential relation with core depth. The relation was modified to account for variations in granulometry and in organic carbon contents of the sediments. Porosities were observed to be more sensitive to variations in organic content than to variations in granulometry, and grain sorting appeared more important than grain size. Grain-size distribution of the sediments is in agreement with a sedimentation model where most of the suspended load enters the fjord from the Saguenay River and is deposited downstream with the surface current. The coarse particles are mainly found close to the head of the fjord, whereas the fine particles are carried farther downstream. Surface porosities were observed to be proportional to the sedimentation fluxes obtained from the literature whereas the compaction showed an inverse relationship. The fractional decreases in porosity due to compaction along the fjord indicate some horizontal flow of the interstitial water at both ends of the sampled part of the fjord. An average vertical interstitial pore water flow of 0.4 cm yr −1 with respect to the surface horizon is estimated from the data. This is small compared with the diffusion of the major constituents of sea water through the sediment.