Clay-sized Material Research Articles

GEOLOGI DAN ANALISIS KUALITAS AIR SUMUR BERDASARKAN TOTAL DISSOLVED SOLID (TDS) DAN DERAJAT KEASAMAN (pH) DAERAH ALUVIAL MANGGAR, KOTA BALIKPAPAN

The need for clean water in the Manggar area is increasing yearly. However, the condition of cloudy, smelly, and colored water is a problem faced by people in this area. This study aimed to analyze the water quality of community wells based on the value of Total Dissolved Solids (TDS) and acidity (pH) in the alluvial plains of Manggar. Based on the research results, the value of Total Dissolved Solids (TDS) ranging from 27 ppm - to 338 ppm is classified as freshwater, while the Power of Hydrogen (pH) value ranging from 7.1 to 8.3 is alkaline. The results of the research on water quality in alluvial plains of Manggar based on these two parameters meet the requirements according to the threshold from the Ministry of Health of the Republic of Indonesia (Kemenkes RI). However, their smell and color are not suitable for consumption. The reason is that the rock units in the alluvial plains of Manggar area are still in the form of unconsolidated material, still in the form of loose clay-sized material, which can affect the quality of healthy water in the area.

The Study of Soil Permeability Test for Landfill of Slag and FABA in The Area of Location 2 LB3 in The Regency of Central Halmahera

One of the feasibility methods for landfill of nickel slag and FABA is the soil permeability test. Data of interpolation results from all areas consisted of 7 sampling points in location 2 LB3. The results of testing of Borehole on 7 points showed domination of sand-sized material with 74.40 – 86.10% (first meter) and 82.04 – 91.77% (second meter) compared to the clay and gravel materials. Interpolation results of permeability class in the area of Location 2 LB3 ranged from "slightly fast" to "fast" from a layer depth of 0-2 meters. Furthermore, the permeability class classification based on the Verruijt classification showed that the overall observed areas for location 2 LB3 were in the Medium Permeability class. This result was determined by the presence of sand-sized material which is more dominantly concentrated than gravel and clay-sized material.

The lithium isotope response to the variable weathering of soils in Iceland

This study has analysed Li isotopes ratios from well-studied soil and pore water profiles from Iceland that have the same parent material but have experienced different degrees of chemical weathering. Thus, from least to most weathered, we have analysed vitrosols (V), gleyic andosols (GA), brown andosols (BA), Histosols (H) and Histic Andosols (HA). Although the most weathered H and HA soils have the highest content in clay-sized material, they have the least fractionated δ7Lipore water values. In contrast, the least weathered GA and BA pore waters are most fractionated for Li isotopes. Given that Li isotope ratios are fractionated by clay mineral formation, this appears counter-intuitive. A single trend for all samples of δ7Li as a function of Li/Na ratios suggests that they are all controlled by a process with a single fractionation factor, in this case likely the formation of poorly-crystalline allophane, which dominates in the “least weathered” soils. This rapidly forming secondary mineral dominates Li isotope fractionation over more slowly-forming crystalline clays. The fractionation along a single path shows that the key process here in controlling the Li isotope ratio of surface waters is the degree of Li uptake by secondary minerals. This does not necessarily correspond to the amount of clay minerals present in the soil, but to the amount of clay minerals that are being newly formed in a single passage of the pore water through the soil, or are in equilibrium with soil solutions at the time of sampling.

Provenance of loess deposits and stepwise expansion of the desert environment in NE China since ~1.2 Ma: Evidence from Nd-Sr isotopic composition and grain-size record

The Quaternary wind-blown Chinese loess-paleosol sequence, which developed as a product of the intensification of Northern Hemisphere glacial-interglacial cycles, is a major source of information on aridification of the Asian interior. In northeastern (NE) China, extensive loess deposits occur that have great potential for reconstructing the long-term paleoclimatic evolution of the region. Despite existing geochemical data indicate that the probable major source areas for these loess deposits were the nearby Horqin and Otindag deserts, it is still unclear that whether there was a long-term change in the detrital source of these loess deposits. In addition, the aridity history and long-term desert evolution of NE China are currently poorly understood. In the present study, we measured the silicate Nd and Sr isotopic composition of the 28–45 μm grain-size fraction from multiple loess sections (NYZG, SBH, and TDJZ). The results show that the loess deposits of the three sites were dominantly sourced from the Otindag sandy desert and that this source remained constant for the past 1.2 Ma. Notably, the 87Sr/86Sr ratios are influenced mainly by variations in the content of clay-sized material present in the form of aggregates or adhering to the surface of coarser particles. Therefore, caution is needed in the use of 87Sr/86Sr ratios of the 28–45 μm fraction as a tracer of eolian dust, when the clay minerals are not completely removed during the pretreatment process. The grain-size variability of the three sections indicates that stepwise enhancement of aridification in the Otindag sandy desert occurred at 1.2 Ma, 0.9 Ma, and 0.7 Ma, which coincided respectively with the beginning of the Mid-Pleistocene transition (MPT), an extremely cold event at ~0.9 Ma within the MPT, and the establishment of a full glacial climate at the termination of the MPT. This finding supports the hypothesis that the growth of high-latitude ice sheets was the major driver of the long-term aridification of Asian dust source areas.

Composition of Smectite from Maastrichtian Sediment of the Afikpo Basin, southeast Nigeria

The sand, silt, shale and clay fractions soils derived from Maastrichtian sediments in the Afikpo Basin, southeastern Nigeria exhibit unusually high cation-exchange capacities. Smectite was identified by X-ray diffraction in all sample fractions and was selectively dissolved by treatment with 1HCl and 0.5 NaOH. Structural formulae, based on chemical analysis of the dissolved material, suggest that the smectite is intermediate in composition between a di- and a trioctahedral mineral and that the octahedral cation occupancy, together with the number of Mg and Fe atoms per unit cell, decreases with decrease in particle size of the soil fraction examined. The mean formula for the smectite in the clay separate is: [(M + = 0.40, Si = 3.33, Al = 0.67), (Al = 1.07, Fe 2+ = 0.09, Fe 3+ = 0.41, Mg = 0.82)] O 10 (OH) 2 . Similar analysis of smectite present in clay-size material separate from weathered granitic rock taken from the bases of the soilprofiles showed that it had close to the full trioctahedral inherited from the weathered granites.The clay mineralogy of the soils was affected by inherited smectite, probably of hydrothermal of deuteric origin. This mineral is unstable in the soil environment and, although its alteration products are fairly uniform in composition. Keywords: Dissolution, Granitic, Octahedral, Smectite, Soil

TRIASSIC CARBONATE AND EVAPORITE SEDIMENTATION IN THE IONIAN ZONE (WESTERN GREECE): PALAEOGEOGRAPHIC AND PALAEOCLIMATIC IMPLICATION

The Triassic is considered a crucial interval because during that time huge areas in our planet suffered an intense, long lasting, period of aridity, which favored the formation of worldwide evaporitic bodies. During the Triassic, great volumes of evaporites were formed in the Ionian basin (Western Greece). On the surface chaotically textured gypsum, surrounded by dolomitic breccias of solution-collapse origin, appears. Sedimentological and diagenetical data proposed that these salt bodies were formed in an intertidal to supratidal environment. Although halite suggests precipitation under long-term arid conditions, clay film intercalations reveal intervals of short term humid conditions. During arid periods sabkhas prevailed and brines were of marine origin. Instead, during humid intervals brines were modified by meteoric water and stormy episodes could be responsible for the transportation of clay-sized material, from the low relief surrounding terrains, into the evaporative basin. Death and burial of cyanobactehal population during storm events could be responsible for the enrichment of clayey layers in carbonaceous material. The co-existence of halite and clays in the Ionian evaporitic sequence imposes a complicated climate, possibly periodically and seasonally controlled. The impact of the precession of the equinoxes plus the palaeogeographical position dominates the local climate. The insolation over the Triassic Ionian basin and nearby sea and land areas is a crucial factor. Climate responses to gradual insolation forcing with an ocean land atmosphere feedback mechanism. The desert / monsoonal dominated climatic model seems to be most proper for the explanation of the existing lithologigal record.

Dust activity and surface sediment characteristics of the dustiest river in southern Africa: the Kuiseb River, Central Namib

Previous remote sensing studies (2005–2008) have identified Namibia’s Kuiseb as the dustiest river in southern Africa. The purpose of this study was to extend the dust event record through to 2014, and to examine the nature of the surfaces from which this satellite imagery indicates these dust plumes originate. The new 10-year record confirms the delta as the dustiest geomorphological unit (54% of plumes), followed by the gravel plain (28%) and then the river (8%). No dust originated from the Namib Sand Sea dunes or interdunes. Field observations provided detail about the geomorphological and sedimentological setting of the landscape components. The laboratory analysis focused on the size characteristics of 153 surface sediment samples collected from the Kuiseb main channel, its terraces, delta, gravel plain surfaces and tributaries, dunes and interdune. This study has identified that surface sediments suitable for dust production increase towards the coast with particular ‘dusty’ floodplain surfaces between Swartbank and Rooibank and the Kuiseb delta. We suggest that silt crusts formed as the flood water dissipate, provide a main source of potentially entrainable material for emission. The crusts consist entirely of silt- and clay-sized materials, with a maximum of 97% <63 μm, 39% <10 μm and 6% <2 μm. Anthropogenic disturbances of the surfaces are potentially playing a role in the production of dust, with the area undergoing significant development.

Timescales of carbon turnover in soils with mixed crystalline mineralogies

Abstract. Organic matter–mineral associations stabilize much of the carbon (C) stored globally in soils. Metastable short-range-order (SRO) minerals such as allophane and ferrihydrite provide one mechanism for long-term stabilization of organic matter in young soil. However, in soils with few SRO minerals and a predominance of crystalline aluminosilicate or Fe (and Al) oxyhydroxide, C turnover should be governed by chemisorption with those minerals. Here, we correlate mineral composition from soils containing small amounts of SRO minerals with mean turnover time (TT) of C estimated from radiocarbon (14C) in bulk soil, free light fraction and mineral-associated organic matter. We varied the mineral amount and composition by sampling ancient soils formed on different lithologies in arid to subhumid climates in Kruger National Park (KNP), South Africa. Mineral contents in bulk soils were assessed using chemical extractions to quantify Fe oxyhydroxides and SRO minerals. Because of our interest in the role of silicate clay mineralogy, particularly smectite (2 : 1) and kaolinite (1 : 1), we separately quantified the mineralogy of the clay-sized fraction using X-ray diffraction (XRD) and measured 14C on the same fraction. Density separation demonstrated that mineral associated C accounted for 40–70 % of bulk soil organic C in A and B1 horizons for granite, nephelinite and arid-zone gabbro soils, and &gt; 80 % in other soils. Organic matter strongly associated with the isolated clay-sized fraction represented only 9–47 % of the bulk soil C. The mean TT of C strongly associated with the clay-sized fraction increased with the amount of smectite (2 : 1 clays); in samples with &gt; 40 % smectite it averaged 1020 ± 460 years. The C not strongly associated with clay-sized minerals, including a combination of low-density C, the C associated with minerals of sizes between 2 µm and 2 cm (including Fe oxyhydroxides as coatings), and C removed from clay-sized material by 2 % hydrogen peroxide had TTs averaging 190 ± 190 years in surface horizons. Summed over the bulk soil profile, we found that smectite content correlated with the mean TT of bulk soil C across varied lithologies. The SRO mineral content in KNP soils was generally very low, except for the soils developed on gabbros under more humid climate that also had very high Fe and C contents with a surprisingly short, mean C TTs. In younger landscapes, SRO minerals are metastable and sequester C for long timescales. We hypothesize that in the KNP, SRO minerals represent a transient stage of mineral evolution and therefore lock up C for a shorter time. Overall, we found crystalline Fe-oxyhydroxides (determined as the difference between Fe in dithionate citrate and oxalate extractions) to be the strongest predictor for soil C content, while the mean TT of soil C was best predicted from the amount of smectite, which was also related to more easily measured bulk properties such as cation exchange capacity or pH. Combined with previous research on C turnover times in 2 : 1 vs. 1 : 1 clays, our results hold promise for predicting C inventory and persistence based on intrinsic timescales of specific carbon–mineral interactions.

Sediment trap efficiency of paddy fields at the watershed scale in a mountainous catchment in northwest Vietnam

Abstract. Composite agricultural systems with permanent maize cultivation in the uplands and irrigated rice in the valleys are very common in mountainous southeast Asia. The soil loss and fertility decline of the upland fields is well documented, but little is known about reallocation of these sediments within the landscape. In this study, a turbidity-based linear mixed model was used to quantify sediment inputs, from surface reservoir irrigation water and from direct overland flow, into a paddy area of 13 ha. Simultaneously, the sediment load exported from the rice fields was determined. Mid-infrared spectroscopy was applied to analyze sediment particle size. Our results showed that per year, 64 Mg ha−1 of sediments were imported into paddy fields, of which around 75 % were delivered by irrigation water and the remainder by direct overland flow during rainfall events. Overland flow contributed one-third of the received sandy fraction, while irrigated sediments were predominantly silty. Overall, rice fields were a net sink for sediments, trapping 28 Mg ha−1 a−1 or almost half of total sediment inputs. As paddy outflow consisted almost exclusively of silt- and clay-sized material, 24 Mg ha−1 a−1 of the trapped amount of sediment was estimated to be sandy. Under continued intensive upland maize cultivation, such a sustained input of coarse material could jeopardize paddy soil fertility, puddling capacity and ultimately food security of the inhabitants of these mountainous areas. Preventing direct overland flow from entering the paddy fields, however, could reduce sand inputs by up to 34 %.

Permo-carboniferous paleoclimate of the Congo Basin: Evidence from lithostratigraphy, clay mineralogy, and stable isotope geochemistry

Approximately 1000m of strata in the Upper Paleozoic Lukuga Formation in the Dekese core in the central Congo Basin provide lithostratigraphic, mineralogical, and isotopic evidence for substantial climatic variation within a long-lived lacustrine basin. Lithostratigraphic indicators of cold climate include polymictic strata (dropstone deposits) and coupled laminations of fine clay-size material and coarse silt (glacial varves). Dropstones are concentrated in three stratigraphic zones in the lower ~425m of the Lukuga Formation, and varved strata occur in two broad stratigraphic zones in the lower ~700m of the formation. These sedimentological indicators suggest that the lower ~2/3 of the Lukuga Formation was strongly influenced by frigid conditions and glacial-like processes.The clay-size fraction of 97 samples is dominated by detrital minerals, including quartz, feldspar, chlorite, illite, and poorly ordered expansible 2:1 phyllosilicates. Based on variation in the mineralogy of these samples, the Lukuga Formation is divisible into three Clay Mineral Zones (CMZs), numbered in ascending stratigraphic order. CMZ 1 and CMZ 3 include several horizons of expansible 2:1 phyllosilicates that represent warmer/wetter intervals. Intervening CMZ 2 is a long (~500m) zone of chlorite and illite with no expansible phyllosilicates and is interpreted as a continuous cold/frigid interval.There are numerous calcite-cemented layers, including spar-filled veins that cross depositional bedding and represent postburial alteration, radiaxial fibrous cements that displace detrital grains, and micrite that crystallized near the time of deposition. Eighty-two stable isotope analyses of micrite yield δ13C values that range from –44.6‰ to –4.1‰ and δ18O values that range from –20.0‰ to 5.0‰ (VPDB). The carbon isotope data likely reflect a range of local carbon sources derived from bacterial activity and are unrelated to paleoclimatic conditions. In contrast, stratigraphic patterns in the oxygen isotope data suggest five or six intervals of frigid conditions conducive to glacial processes.

Effects Of Drying Techniques On Grain-Size Analyses of Fine-Grained Sediment

Abstract To assess the effects of drying on subsequent grain-size analyses, a variety of drying approaches, including drying in ambient air, oven drying, and freeze drying, were applied to sediment collected from modern fluvial, lacustrine, and paludal settings, containing a wide range of clay-size fraction (16–61%). Samples were subsequently rehydrated and subjected to grain-size analysis in a laser particle-size analyzer, and histograms compared with those from control samples never subjected to drying. Results indicate that drying techniques induced no effect on grain-size distribution for samples containing 39% clay-size material, only freeze drying produced reproducible results statistically identical to the control samples.

BIOLOGICAL EFFECTS ON THE SOURCE OF GEONEUTRINOS

Detection of antineutrinos from U and Th series decay within the Earth (geoneutrinos) constrains the absolute abundance of these elements. Marine detectors will measure the ratio over the mantle beneath the site and provide spatial averaging. The measured mantle Th/U may well be significantly below its bulk earth value of ~4; Pb isotope measurements on mantle-derived rocks yield low Th/U values, effectively averaged over geological time. The physics of the modern biological process is complicated, but the net effect is that much of the U in the mantle comes from subducted marine sediments and subducted upper oceanic crust. That is, U subducts preferentially relative to Th. Oxygen ultimately from photosynthesis oxidizes U(IV) to U(VI), which is soluble during weathering and sediment transport. Dissolved U(VI) reacts with FeO in the oceanic crust and organic carbon within sediments to become immobile U(IV). These deep marine rocks are preferentially subducted relative to Th(IV)-bearing continental margin rocks. Ferric iron from anoxygenic photosynthesis and oxygen in local oases likely mobilized some U during the Archean Era when there was very little O2in the air. Conversely, these elements behave similarly in the absence of life, where the elements occur as U(IV) and Th(IV), which do not significantly fractionate during igneous processes. Neither do they fractionate during weathering, as they are essentially insoluble in water in surface environments. Th(IV) and U(IV) remain in solid clay-sized material. Overall, geoneutrino data constrain the masses of mantle chemical and isotopic domains recognized by studies of mantle-derived rocks and show the extent of recycling into the mantle over geological time.

Experiments Examine Shear-Enhanced Two-Phase Flow in Athabasca Sands

This article, written by Editorial Manager Adam Wilson, contains highlights of paper SPE 160092, ’Shear-Enhanced Two-Phase-Flow Properties in Athabasca Sands,’ by Syed M. Farrukh Hamza, SPE, Jon E. Olson, SPE, and Jon Holder, The University of Texas at Austin, prepared for the 2012 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 8-10 October. The paper has not been peer reviewed. Field results in steam assisted gravity drainage (SAGD) heavy-oil operations suggest formation permeability changes during production operations. This process was investigated using samples constructed from loose Athabasca sand. Results indicate that permeability changes and endpoint oil- and water-saturation variation are a function of loading boundary conditions. Overall, laboratory experiment results support increased permeability from steam injection in heavy oil; and, more importantly, the observed reduction in residual oil saturation implies that SAGD-induced deformation should improve recovery factors. Introduction Athabasca Oil Sands Properties. The Athabasca oil sands are relatively shallow deposits containing quartz sand, silt, clay, water, and bitumen. Most of the oil-rich sands are fine-to-medium grained with some silt- and clay-sized material. The quartz grains are water-wet. The porosity estimates range from 32 to 46%. Oil sands are loose sands, held together by bitumen. However, bitumen does not act as a cementing agent because it is a Newtonian fluid and, hence, provides no shear resistance at a zero shear rate. As a consequence, it cannot contribute to the static mechanical strength of the material, provided that the deformation does not proceed very rapidly. SAGD. During SAGD, steam is injected into the Athabasca oil sands reservoir at high temperature and pressure. The changes in pressure and temperature cause changes in stress and deformations, which result in formation shearing and permeability changes. The deformation response of Athabasca oil sands is stress-path dependent. The thermal expansion of the reservoir from the injected steam causes thermal stresses in the horizontal direction because the reservoir is bounded laterally by the surrounding rock formations. The vertical stress from the over-burden remains constant because, at shallow depths, the Earth’s surface is a free surface. Study Objective. The aim of this work was to study the deformation and associated multiphase-flow properties of the Athabasca oil sands using stress paths representative of the SAGD process. Experimental results document permeability and endpoint saturation change from SAGD stress paths that can lead to a better understanding of coupled geomechanical and fluid-flow processes, the implementation of which could lead to improved recovery from heavy-oil reservoirs.

Effect of changes in fine‐grained matrix on bedload sediment transport in a gravel‐bed river

ABSTRACTWhile clay and silt matrices of gravel‐bed rivers have received attention from ecologists concerned variously with the deteriorating environments of benthic and hyporheic organisms, their impact on sediment entrainment and transport has been explored less. A recent increase of such a matrix in the bed of Nahal Eshtemoa, an ephemeral river of the northern Negev, has more than doubled the boundary shear stress needed to initiate bedload, from 7 N m‐2 (τ* = 0.027) during the flash floods of 1991–2001 to 15 N m‐2 (τ* = 0.059) during those of 2008–2009. The relation between bedload flux and boundary shear stress continues to be well‐defined, but it is displaced. The matrix now contains a significant amount of silt and clay size material. The reasons for the increased entrainment threshold of bedload are explored. Large‐scale laser scanning of the dry bed reveals a reduction in grain‐scale morphological roughness, while artificial in situ tests of matrix integrity indicate considerable cohesion. The implications for adopting bed material sampling strategies that account for matrix development are assessed. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Effects of extreme cold and aridity on soils and habitability: McMurdo Dry Valleys as an analogue for the Mars Phoenix landing site

AbstractThe McMurdo Dry Valleys are among the driest, coldest environments on Earth and are excellent analogues for the Martian northern plains. In preparation for the 2008 Phoenix Mars mission, we conducted an interdisciplinary investigation comparing the biological, mineralogical, chemical, and physical properties of wetter lower Taylor Valley (TV) soils to colder, drier University Valley (UV) soils. Our analyses were performed for each horizon from the surface to the ice table. In TV, clay-sized particle distribution and less abundant soluble salts both suggested vertical and possible horizontal transport by water, and microbial biomass was higher. Alteration of mica to short-order phyllosilicates suggested aqueous weathering. In UV, salts, clay-sized materials, and biomass were more abundant near the surface, suggesting minimal downward translocation by water. The presence of microorganisms in each horizon was established for the first time in an ultraxerous zone. Higher biomass numbers were seen near the surface and ice table, perhaps representing locally more clement environments. Currently, water activity is too low to support metabolism at the Phoenix site, but obliquity changes may produce higher temperatures and sufficient water activity to permit microbial growth, if the populations could survive long dormancy periods (∼106years).

Clay Movement in Sand Columns and its Pedological Ramifications

Movement of clay particles and other colloids through soil profi les has been investigated extensively during the past few decades. The pathway of movement is generally accepted as being predominantly downward. This study investigated the hypothesis that clay and colloids can move upward by capillarity, and is concomitant with water movement. To test this hypothesis, two experiments were conducted. The fi rst experiment used an empty transparent plastic column standing in a 500-mL glass beaker and packed with dry sand. A reddish clay suspension was used with a concentration of 24.2 g L−1, a pH of 7.1, and an electrical conductivity (EC) of 0.05 S m−1. The clay suspension was added to the beaker so that it could move upward within the sand column by capillarity. The second transparent plastic column was placed empty in a 500-mL glass beaker and was packed with a 30-cm layer of dry sand overlain by a 5-cm layer of sandy loam, which was then overlain by a 20-cm layer of dry sand. A water table was established to test the likelihood of clay particles moving upward via capillarity. In each experiment, the movements of the clay-sized materials were visually tracked using a digital camera. The results of the fi rst experiment showed that clay particles moved 25 cm upward and even accumulated at the surface. Clay particles moved upward in the second experiment and formed some clay bands in the sand layer overlying the sandy loam layer. Peer Reviewed Papers

Permeability–porosity relationships of subduction zone sediments

Permeability–porosity relationships for sediments from the northern Barbados, Costa Rica, Nankai, and Peru subduction zones were examined based on sediment type, grain size distribution, and general mechanical and chemical compaction history. Greater correlation was observed between permeability and porosity in siliciclastic sediments, diatom oozes, and nannofossil chalks than in nannofossil oozes. For siliciclastic sediments, grouping of sediments by percentage of clay-sized material yields relationships that are generally consistent with results from other marine settings and suggests decreasing permeability as percentage of clay-sized material increases. Correction of measured porosities for smectite content improved the correlation of permeability–porosity relationships for siliciclastic sediments and diatom oozes. The relationship between permeability and porosity for diatom oozes is very similar to the relationship in siliciclastic sediments, and permeabilities of both sediment types are related to the amount of clay-size particles. In contrast, nannofossil oozes have higher permeability values by 1.5 orders of magnitude than siliciclastic sediments of the same porosity and show poor correlation between permeability and porosity. More indurated calcareous sediments, nannofossil chalks, overlap siliciclastic permeabilities at the lower end of their measured permeability range, suggesting similar consolidation patterns at depth. Thus, the lack of correlation between permeability and porosity for nannofossil oozes is likely related to variations in mechanical and chemical compaction at shallow depths. This study provides the foundation for a much-needed global database with fundamental properties that relate to permeability in marine settings. Further progress in delineating controls on permeability requires additional carefully documented permeability measurements on well-characterized samples.

Anthropogenic affects on lake sedimentation process: a case study from Lake Sapanca, NW Turkey

Lake Sapanca in NW Turkey is a fault originated freshwater basin fed by seasonally variable flows of 15 streams. Considerations of lake–river interaction, supported by statistical measures of 47 bottom samples, suggest that sediment transport and deposition within the lake is controlled by two types of human constructed structures in addition to natural factors: (1) the dykes constructed in the front of streams, which feed the lake by strong flows, to prevent the filling of lakebed by coarse-grained sediments; (2) the constructed regulator on the outflowing Carksuyu stream results in a higher sedimentation rate of clay-sized material on the NE corner of the lake, which is extraordinary in the shelf environment.

Using a global VNIR soil-spectral library for local soil characterization and landscape modeling in a 2nd-order Uganda watershed

Combining global soil-spectral libraries with local calibration samples has the potential to provide improved visible and near-infrared (VNIR, 400–2500 nm) diffuse reflectance spectroscopy (DRS) soil characterization predictions than with either global or local calibrations alone. In this study, a geographically diverse “global” soil-spectral library with 4184 samples was augmented with up to 418 “local” calibration soil samples distributed across a 2nd-order Ugandan watershed to predict the amount of clay-size material (CLAY), soil organic carbon (SOC) and proportion of expansible 2:1 clays (termed “montmorillonite” or MT in the global library). Stochastic gradient boosted regression trees (BRT) were employed for model construction, with a variety of calibration and validation schemes tested. Using the global library combined with 13- and 14-fold cross-validation by local profile for CLAY and SOC, respectively, yielded dambo/upland RMSD values of 89/68 g kg − 1 for CLAY ( N = 429/410) and 4.2/2.6 g kg − 1 for SOC ( N = 272/105). These results were obtained despite the challenge of combining spectral libraries constructed using different spectroradiometers and laboratory reference measurements (total combustion vs. Walkley–Black, hydrometer vs. pipette). Using only the global library, a VNIR-derived index of MT content was significantly correlated with the square root of X-ray diffraction (XRD) MT peak intensity for local dambo soils ( r 2 = 0.52, N = 59, p < 0.0001), an acceptable result given the semi-quantitative nature of the reference XRD method. Though VNIR predictions did not approach laboratory precision, for soil-landscape modeling VNIR characterization worked remarkably well for clay mineralogy, was adequate for mapping dambo “depth to 35% clay”, and was insufficiently accurate for SOC mapping.

Reservoir Sedimentation and Environmental Degradation

Sediments impounded within flood control reservoirs are potentially important archives of environmental and geomorphic processes occurring within drainage basins. The concentrations of select sediment-associated trace elements were assessed within the impoundment of Grenada Lake, a relatively large flood control reservoir in Mississippi with a history of contaminant bioaccumulation in fish. The post-construction sediments (after 1954) are discriminated from the pre-construction sediments (before 1954) based on depth variations in sediment texture and 137Cs emissions. The concentrations of select trace elements of the post-1954 sediments all are statistically greater than the pre-1954 sediments, and these same sediments also are enriched in clay. Once these concentrations are normalized by clay content, all trace elements in the post-1954 sediments are lower in concentration than the pre-1954 normalized sediments. Moreover, the trace elements when normalized by clay or Al content show virtually no change vertically (over time) within the reservoir impoundment. This suggests that the sources of these sediment-associated trace elements within Grenada Lake, whether natural or anthropogenic, have not changed appreciably over the lifespan of the reservoir and that the degradation of sedimentologic and ecologic indices within the lake are due to the sequestration of clay or clay-sized materials.