Search

To investigate the change in biochar's ability to directly immobilize Cd in soil, a successive wheat cultivation experiment was conducted. Three biochars with different Cd adsorption mechanisms were added to the soils, and a mesh bag was used to separate the soil particles (> 1 μm) from the biochar. The results showed that the ash contents and anionic contents (CO32− and PO43−) of the biochar decreased with the cultivation time, while the oxygen-containing functional group content and CEC of the biochar increased. As a result, the Cd concentration on biochar decreased, by 68.9% for WBC300, while unstable Cd species (acid soluble and reducible fraction of Cd) on biochar increased with successive cultivation, increasing from 3 to 17% for WBC300 in FS. Correspondingly, the ability of biochar to inhibit Cd accumulation in wheat decreased. The results of this study illustrated that the ability of biochar to directly immobilize Cd in soil is not permanent; it gradually decreases with aging in soil. The adsorption mechanism of Cd on biochar changed from precipitation to complexation, and ion exchange processes could be the main reason. [ABSTRACT FROM AUTHOR]

This paper reports an investigation into the effects of nano-silicon dioxide, nano-titanium dioxide and nano-aluminum oxide (nano-SiO2, nano-TiO2, and nano-Al2O3) on the water resistance and flexural properties of corn straw/polyvinyl chloride (PVC) composites under simulated soil accelerated aging conditions, and the reinforcing effect of three nano-fillers was compared. The results indicated that the addition of nano-fillers exhibited a positive effect on the water resistance and flexural resistance properties of corn straw/PVC composites, especially nano-SiO2. After 21 d of the simulated soil accelerated aging, the nano-SiO2 reinforced composites had relatively low water absorption and moisture absorption rates, and the similar enhancement effect was also found with flexural strength, flexural modulus and flexural creep resistance. The microstructure of nano-SiO2 reinforced composites showed no significant breakage or pullout of the fiber, and the voids and the micro-cracks cannot be found in SEM observation indicating stronger interfacial bonding strength, thus improving the water-resistance and flexural resistance properties. [ABSTRACT FROM AUTHOR]

Oxidation of Cr(III) by birnessite (δ-MnO2) was an important geochemical reaction determining the toxicity and mobility of dissolved Cr(III) in soils. Herein, changes of Cr speciation and fractionation were systematically studied in Cr(III)-contaminated soils with δ-MnO2 in soil aging process. The results showed that Cr(III) could be rapidly oxidized to Cr (VI) by δ-MnO2, and the coating of Fe and Al oxides on δ-MnO2 had a strong hindering effect on the oxidation of Cr(III). The Cr(III) oxidation process by δ-MnO2 followed a two-phase model of pseudo first-order kinetics. The rapid decrease of oxidation rate constant in second phase was due to the coverage of adsorbed Cr(III) and newly generated Cr(VI) and Mn(II) on the active sites of δ-MnO2. X-ray photoelectron spectroscopy analysis further confirmed that the diffusion and adsorption of Cr(III) on the electron-accepting sites were important factors affecting the Cr(III) oxidation by δ-MnO2. Compared with the soils without δ-MnO2, high contents of Cr(VI) were generated in silt (22.30 mg/kg) and sandy soil (70.95 mg/kg) with 2 wt% δ-MnO2 after the addition of Cr(III) wastewater within 2 days, and the Cr(VI) contents were above 1 mg/kg in these two soils during the whole incubation process. Moreover, the total Cr proportion of the exchangeable fraction increased by 12.8% in silt and 5.2% in sandy soil with 2 wt% δ-MnO2 after soil aging for 120 days. The presence of δ-MnO2 markedly increased the oxidation potential and mobility of exogenous Cr(III) in soils. [ABSTRACT FROM AUTHOR]

To understand the bioaccessibility of cadmium（Cd）in compound-contaminated soils containing cadmium and ciprofloxacin, uncontaminated soils were artificially polluted with cadmium and ciprofloxacin at 4 different treatment rates（CK:0mg·kg-1, CIP：I5mg·kg-1,II25mg kg-1, andIII50mg kg-1; Cd：80mg·kg-1）. A pot experiment was performed with three soil aging times to investigate the risk of Cd to human health using in vitrodigestion method and SHIME model. The results showed that there was no significant difference in the bioaccessibility of Cd among different soil aging times in compound-contaminated soils. Besides, the bioaccessibility of Cd decreased with soil aging time（D60

We examined forest and tree responses to decreasing nutrient availability with soil aging in a species-rich tropical montane rain forest on Mount Kinabalu, Borneo. Community composition and structure and tree growth rates were compared between two 1 ha plots on nutrient-rich young soil versus nutrient-deficient old soil. Myrtaceae and Fagaceae dominated both plots. With soil aging, the dominance of Lauraceae, stem density, basal area and aboveground biomass decreased, and the forest understory became brighter. Some dominant taxa on the old soil (Podocarpaceae and the genus Tristaniopsis in Myrtaceae) were virtually absent on the young soil; this was attributed to light limitation in the understory. Growth rates of understory trees were lower on the young soil, whereas those of canopy trees were lower on the old soil. This suggested that the growth of understory trees was limited by light on the young soil, whereas that of canopy trees was limited by nutrients on the old soil. Of the eight species that were abundant in both plots, the dominance of five species was considerably lower on the old soil, four of which also exhibited decreased maximum sizes and lower growth rates. The remaining three species showed similar dominance across plots without a decline in growth rates, although they exhibited decreased maximum sizes on the old soil. These analyses demonstrated divergent responses of species to the soil-age gradient. We suggest that the differential responses of species to decreasing nutrient availability with a concomitant increase in understory light levels explain floristic turnover with soil aging. [ABSTRACT FROM AUTHOR]

Data from 58 high-quality liquefaction case histories from the Darfield and Christchurch earthquakes are utilized to investigate the efficacy of current liquefaction aging correction procedures. Toward this end, liquefaction case histories are analyzed in which aging corrections are and are not applied, and the resulting predictions are compared to the actual liquefaction response of the deposits. An error-index is calculated to quantify the efficacy of aging corrections. While all the sites located in the Christchurch area are classified as Holocene, based on their geological age, their liquefaction response is influenced more by the geotechnical age of the soil deposits. Aging correction was determined to be beneficial for the liquefaction assessment of soils that experienced recurrent liquefaction (i.e., geotechnical young deposits). However, aging corrections were determined to exacerbate the liquefaction assessment of relatively old (greater than ∼62–580 years) soil deposits. [ABSTRACT FROM AUTHOR]

To estimate pesticide residue levels in succeeding crops based on those in soils, the relationship between pesticide concentrations in komatsuna (Brassica rapa var. perviridis) and the concentrations extracted sequentially from soils using water and acetone was investigated. The concentrations of many pesticides in komatsuna shoots showed higher positive correlation with water-extractable concentrations (CW) than total-extractable concentrations in soils, so that the CW was available for evaluating the phytoavailability of pesticides in the soil. As a result of examining the dissipation behavior of the CW, the dissipation of the CW was able to be predicted by considering time-dependent soil sorption, which could be estimated using the sorption coefficients (Kd) measured by a standard batch method. Furthermore, the present study showed that the properties of soil organic carbon such as black carbon content and the molecular structure of pesticides were important for estimating the Kd values more accurately. [ABSTRACT FROM AUTHOR]

Abstract The effects of wheat root exudates and the aging interactions between biochar and soil on atrazine desorption from biochar-amended soil were carefully examined. Compared with CaCl 2 solution, wheat root exudates significantly increase the desorption of atrazine from biochar, mainly by promoting the desorption of atrazine adsorbed on biochar with specific forces. Wheat root exudates were effectively separated into three components with different electrical properties, namely, anionic, neutral, and cationic components. Mainly due to the carboxyl-containing compounds, the anionic component was the main active component in the wheat root exudates that enhances the desorption of atrazine from the biochar. Additionally, wheat root exudates can increase the desorption of atrazine from biochar-amended soil. The promotion of atrazine desorption by root exudates was more obvious in soils with low organic matter contents, where atrazine was mainly adsorbed by biochar. The aging interaction between the biochar and soil increased the total desorption rate and rapid desorbing fraction of the atrazine in the soil, most likely due to the reduction of the biochar sorption capacity in the aged biochar-amended soil. Highlights • Root exudates released atrazine that was sorbed on biochar with specific forces. • Root exudates were divided into three components by electrodialysis. • Anionic component was the active component that released atrazine from biochar. • Aging interaction between biochar and soil increased atrazine desorption from soil. [ABSTRACT FROM AUTHOR]

Due to its continuous data recording capability, excellent repeatability and accuracy, relatively low cost and simplicity of operation, the cone penetration test (CPT) offers enhanced liquefaction assessment over its predecessor the standard penetration test (SPT). However, soil ageing, which influences the cyclic resistance ratio (CRR), is difficult, if not impossible, to be detected by the CPT due to disturbance during the test. This situation may lead to excessively conservative estimation of CRR values which result in conservative assessment of liquefaction potential. This paper presents and discusses liquefaction assessment using the CPT and methods for accounting for soil ageing. A field study, conducted at Gillman, South Australia, is presented and the study site is assessed for liquefaction potential. This paper also explores the influence of soil ageing on the subsequent liquefaction assessment using a magnitude earthquake of up to 7.5. [ABSTRACT FROM AUTHOR]

The bioavailability and potential uptake of heavy metals by crops is fundamentally influenced by the forms of metals in soils. Organic matter plays an important role in controlling the transformation of heavy metal fractionations in soils. However, long-term effects of organic matter on heavy metal speciation remains highly uncertain. In this study, rice straw was introduced to a subtropical Pb-contaminated soil for 2-year period so as to clarify the redistribution of Pb fractions and their correlations with soil properties. By combining sequential extraction and X-ray absorption fine structure spectroscopy, we find that lead is predominantly presented in Fe oxide-bound, surface adsorbed, and residual fractions in the soil. The incorporation of rice straw can effectively reduce the labile species of Pb by promoting the binding of Pb to iron oxides. Furthermore, aging leads to the transfer of considerable amounts of Pb to the association with Fe oxides and this transformation is enhanced by the presence of organic matter. Organic matter input and soil aging tend to shift Pb to amorphous Fe oxides than crystalline Fe oxides. The correlation analysis shows that Fe oxide fractions play vital roles in controlling the forms of Pb in soil. This study presents the first result regarding the long-term effect of organic matter on the redistribution of Pb in naturally polluted soil, which is useful for understanding the fate of Pb and developing remediation strategies for Pb-polluted soils. [ABSTRACT FROM AUTHOR]

The study is intended for geotechnical engineers who deal with the construction of deep foundations using driving piles with the implementation of seismic cross-hole technique to estimate the accompanying increase (or decrease) in soil shear strength. The study concluded that there is a direct relation between the increases in soil undrained shear strength with yield stress ratio and reverse relation with moisture water content and void ratio. The increase in undrained shear strength is observed in the clay soil layer at 3-5 m in depth with low moisture content and void ratio due to the effect of time. While at depth of 1-3 m, the reverse was noticed, this decrease is attributed to the upward displacement of the soil due to shear force from driven pile and then leading to increase the soil moisture content and void ratio. The study also concluded that an increase in undrained shear strength and yield stress ratio causing a decrease in void ratio and moisture content due to the effect of aging factor. The present results have provided good overall views of the shear strength increases and their distributions and the estimated values are also of the right sizes.

A sand blow from a paleo-earthquake was identified at Fort Dorchester, South Carolina in 2007. Geotechnical field investigations indicate the thickness of the source sand layer ranges from 1.2 to 3.1 m and the depth below the ground surface to the top of the layer ranges from 2.3 to 3.9 m. The layer is predominantly angular to subangular silty quartz sand with a fines content of 4 to 22% and the predominant mean grain diameter of 0.18-0.26 mm. The geotechnical data were used with paleoliquefaction evaluation methods and two independent relations to account for soil aging to estimate the minimum magnitude and peak ground acceleration of the prehistoric earthquake. Four regionally proper Ground Motion Prediction Equations were used in combination with the back-calculated peak ground accelerations to obtain proper estimation of a - M. For a range of site-to-source distance from 4 to 10 km, the minimum earthquake magnitude and peak ground acceleration of prehistoric earthquakes at the Fort Dorchester site ranges from 5 to 6.3 and 0.19 to 0.39 g respectively. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aging affects arsenic (As) bioaccessibility in soils. This study focuses on the influences of particle size and redox potential on As(V) aging in irrigated soils. The results showed that variation of As fractions in fine particles, except the loosely adsorbed fraction, was larger than that in coarse particles over time. Anoxic conditions decreased the change in As fractions, with the exception of the exchangeable fraction in soils over time, in comparison to the aerobic condition. The aging processes of As(V) in different particle sizes and soils at different redox potentials exhibited several stages. The only significant difference in the aging process of As(V) in different particle sizes was the longer transformation period of the water-soluble fraction into the Fe/Mn/Al oxides-bound fraction in fine particles than in coarse particles. The redox potential had a significant influence on the aging process of As(V) in soils after 10 days of incubation. In terms of As bioaccessibility, anoxic conditions shortened the aging process of As(V) in soils. During the aging process, fine particles and aerobic conditions intensified the decrease in As(V) bioaccessibility in soils in comparison to the coarse particles and anoxic condition. [ABSTRACT FROM PUBLISHER]

In this study, the minimum earthquake magnitude and peak ground acceleration required to initiate liquefaction at the time of prehistoric earthquakes that date back to 11,000 years before present at the Hollywood site located in the South Carolina Coastal Plain were computed. The soils at this site are estimated to be about 120,000 to 130,000 years old. In-situ geotechnical data, including cone penetration data with pore water pressure measurements, were used with empirical methods that account for the age of the soil deposit to back analyse the peak ground acceleration. Results were then combined with the corresponding values obtained using Ground Motion Prediction Equations (GMPEs) to obtain a proper estimation of a max -M of the prehistoric earthquakes at the Hollywood site. When the age of the earthquake was not considered, the minimum magnitude ranged from 5.8 to 6.5 and the corresponding peak ground acceleration ranged from 0.25 to 0.32 g. When the age of the earthquake was considered, the minimum magnitude was found to be 0.2 to 0.3 units lower depending on earthquake age and the GMPE model. For the most recent prehistoric earthquake with the age of 546 ± 17, the minimum magnitude ranged from 5.6 to 6.3 with corresponding acceleration ranging from 0.21 to 0.28 g. [ABSTRACT FROM AUTHOR]

Redox conditions and arsenic (As) loads may affect the aging mechanisms of As in soils. A batch experiment of one wastewater-irrigated soil under four different conditions was performed to investigate the impact of redox conditions and As loads on the aging mechanisms of As in soils in this study. The results showed that the aerobic condition substantially decreased the more labile fractions and increased the less mobilizable or immobilizable fractions in soils over time, which was likely due to the oxidation of As(III) to As(V) and the decomposition of organic matter. The redistribution of the strongly adsorbed and organically bound fraction (F4) occurred in all soils during the aging process, and both low As load and aerobic conditions accelerated this redistribution. The aging processes of As were characterized by three stages in various soils except the low As load soil with two stages within 180 days: The transformations of As fractions were from three former fractions to three later ones in all soils in the first stage (0 day–10 days), while the main transformations after 10 days were from F4 to bound to Fe and Mn/Al oxides fraction (F5) and from water soluble fraction (F1) to F5 in soils with low and high As loads, respectively; In contrast, the main transformations in the second stage were from F1 to F4 and from F1 to F5 in soils at low oxygen and aerobic conditions, respectively, and were from F4 to F5 in the third stage in both redox conditions. The bioaccessibility of As in the low As load soil decreased markedly from approximately 40% down to < 10% due to the aging and more remarkably from > 70% down to < 20% in three other soils. Both high As load and low oxygen conditions preserved higher bioaccessibility of As in soils after long aging process. In terms of As bioaccessibility, high As load and aerobic condition prolonged the aging process of arsenic in soils. [ABSTRACT FROM AUTHOR]

A suite of organisms from different taxonomical and ecological positions is needed to assess environmentally relevant soil toxicity. A new bioassay based on Dictyostelium is presented that is aimed at integrating slime molds into such a testing framework. Toxicity tests on elutriates and the solid phase developmental cycle assay were successfully applied to a soil spiked with a mixture of Zn, Cd, and diesel fuel freshly prepared (recently contaminated) and after 2 yr of aging. The elutriates of both soils provoked toxic effects, but toxicity was markedly lower in the aged soil. In the D. discoideum developmental cycle assay, both soils affected amoeba viability and aggregation, with fewer multicellular units, smaller fruiting bodies and, overall, inhibition of fruiting body formation. This assay is quick and requires small amounts of test soil, which might facilitate its incorporation into a multispecies multiple-endpoint toxicity bioassay battery suitable for environmental risk assessment in soils. Environ Toxicol Chem 2016;35:1413-1421. © 2015 SETAC [ABSTRACT FROM AUTHOR]

EDTA-based remediation is reaching maturity but little information is available on the state of chelant in remediated soil. EDTA soil retention was examined after extracting 20 soil samples from Pb contaminated areas in Slovenia, Austria, Czech Republic and USA with 120 mM kg −1 Na 2 H 2 EDTA, CaNa 2 EDTA and H 4 EDTA for 2 and 24 h. On average, 73% of Pb was removed from acidic and 71% from calcareous soils (24 h extractions). On average, 15% and up to 64% of applied EDTA was after remediation retained in acidic soils. Much less; in average 1% and up to the 22% of EDTA was retained in calcareous soils. The secondary emissions of EDTA retained in selected remediated soil increased with the acidity of the media: the TCLP (Toxicity Characteristic Leaching Procedure) solution (average pH end point 3.6) released up to 36% of EDTA applied in the soil (28.1 mmol kg −1 ). Extraction with deionised water (pH > 6.0) did not produce measurable EDTA emissions. Exposing soil to model abiotic (thawing/freezing cycles) and biotic (ingestion by earthworms Lumbricus rubellus ) ageing factors did not induce additional secondary emissions of EDTA retained in remediated soil. [ABSTRACT FROM AUTHOR]

There is a need for inexpensive, readily-available and environmentally-friendly soil washing agents to remediate polluted soils. Thus, batch washing experiments were performed to evaluate the feasibility of using a solution of humic substances (HS) extracted from compost as a washing agent for simultaneous removal of Cu, Cd, Zn, Pb and Ni from artificially contaminated soils aged for 1 month, 12 months and 24 months. The efficiency of metal removal in single and multiple washings and kinetic constants (equilibrium metal concentration q e and rate constant k from the second-order kinetic equation) were determined. On average, triple washing removed twice as much metal as that removed with a single washing. At pH 7 and a HS concentration of 2.2 g C L −1 , metal removal from all soils decreased in this order: Cd (79.1–82.6%) > Cu (51.5–71.8%) > Pb (44.8–47.6%) > Ni (35.4–46.1%) > Zn (27.9–35.8%). However, based on q e (mg kg −1 ), metal removal was in this order: Pb > Zn ≈ Cu > Ni > Cd. This difference was due to different concentrations of metals, which is typical for multi-metal contaminated soils. Regardless of washing mode, removal of Cd and Pb was not affected by soil age, whereas removal of Cu, Ni and Zn was higher in soils that had been aged for a shorter time. These results indicate that HS are suitable for remediating soil contaminated with multiple heavy metals in extremely high concentrations. [ABSTRACT FROM AUTHOR]

The relationship between pesticide concentrations in Komatsuna (Brassica rapa var. perviridis) shoots and the extractable concentrations in soils by a sequential soil-extraction method was investigated in 8 pesticides and in 4 soils. Concentrations of many pesticides in Komatsuna shoots showed higher positive correlation with water-extractable than with total-extractable soil concentrations. We also examined the effects of the soil-aging periods (SAPs) between pesticide applications and sowing on pesticide concentrations in Komatsuna shoots. Pesticide concentrations in Komatsuna shoots and soil-water extracts decreased with increasing SAPs. These results imply that estimating the pesticide concentrations in crops based on water-extractable concentrations in soil and setting the appropriate SAPs prevent contamination of crops by pesticide residues in soil. However, the correlation between pesticide concentrations in Komatsuna shoots and water extracts in soils, and the effectiveness of pesticide reduction in Komatsuna shoots by setting long SAPs differed according to the pesticide type. Hence, the applicability of the water-extraction method should be verified for each pesticide. [ABSTRACT FROM AUTHOR]

The aging phenomenon, which produces changes in material state over time, is associated with significant modification of mechanical and physical soil properties. This change should be accounted for during geotechnical design. Although soils sometimes improve with aging, the opposite effect is occasionally observed. This paper describes a study performed to investigate the effect of aging on the mechanical behavior and the permeability of a silty soil. Undrained unconsolidated triaxial shear tests and triaxial permeability tests were performed on disturbed and compacted samples. Upon conclusion of these tests, the samples were sealed from air and moisture. The results show an important increase in both the undrained shear strength and the deformation modulus caused by silt rigidification during the aging process. These changes cause an over estimation of laboratory measured shear strength. For instance, the increase in the deformation modulus and undrained cohesion can approach 100 % for an approximate 328 day storage period. Sample permeability was found to decrease with aging. This reduction can be ascribed to several causes including micro-organisms growth, secondary sample consolidation and progressive filling caused by the migration of very fine particles. These phenomena might have negated the expected increase in permeability with aging time reported in the literature. [ABSTRACT FROM AUTHOR]

ABSTRACT Temporal variations in soil erosion resistance are often the result of decreased soil cohesion due to physical disruption followed by a regain of soil strength through a process called aging, stabilization or consolidation. The goal of this study was to quantify changes in soil cohesion due to aging and subsurface hydrologic condition using a fluidized bed method. A flume experiment was also used to verify that findings from the fluidized bed experiment translated into measurable changes in soil erodibility. Tests were performed on three different soils (a Miami soil, a Cecil soil and Crosby-Miami soil complex). Changes in soil cohesion due to aging and drainage state were successfully detected by the fluidized bed technique. For all soils tested, cohesion developed in a two-stage process where an increase in cohesion with aging duration immediately after the soil was rewetted, was followed by a decrease in cohesion which often started after 24 h of aging. When soils were aged at field capacity, the resulting cohesion measured by the fluidized bed method was on average 3.13 times higher than that measured when aging was performed at saturation. Trends in soil rill erodibility Kr with aging duration measured in the flume experiment were consistent with the two-stage pattern observed in soil cohesion estimates but the legacy effect of suction applied at field capacity faded after 72 h of aging. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Arsenic (As) bioaccessibility is an important factor in estimating human health risk. Bioaccessibility of As in soils is primarily dependent on As adsorption, which varies with residence time. This study evaluated the effect of soil aging on potential lifetime cancer risk associated with chronic exposure to As contaminated soils. Four soils, chosen based on their differences in As reactivity, were amended with two arsenical pesticides – sodium arsenate, and dimethylarsinic acid (DMA) at two rates (675 and 1500mgkg−1). Rice was used as the test crop. Soil was sampled immediately after spiking, after 6 months, 1 year, and 3 years. Bioaccessible and total soil As concentrations were used to calculate lifetime excess cancer risk (ECR), which decreased significantly with soil–pesticide equilibration time. Immokalee soil, with the least As adsorption capacity, showed the highest decrease in ECR after 6 months resulting in values lower than the USEPA's cancer risk range of 1×10−4 to 1×10−6. For all other soils, the ECR was much higher than the target range even after 3 years. In the absence of significant changes in As bioaccessibility with time, the total soil As concentration more directly influenced the changes in ECR values with soil aging. [Copyright &y& Elsevier]

The finding of dieldrin (88 ng/g), DDE (52 ng/g), and heptachlor epoxide (19 ng/g) in earthworms from experimental plots after a single moderate application (9 kg/ha) 45 years earlier attests to the remarkable persistence of these compounds in soil and their continued uptake by soil organisms. Half-lives (with 95 % confidence intervals) in earthworms, estimated from exponential decay equations, were as follows: dieldrin 4.9 (4.3-5.7) years, DDE 5.3 (4.7-6.1) years, and heptachlor epoxide 4.3 (3.8-4.9) years. These half-lives were not significantly different from those estimated after 20 years. Concentration factors (dry weight earthworm tissue/dry weight soil) were initially high and decreased mainly during the first 11 years after application. By the end of the study, average concentration factors were 1.5 (dieldrin), 4.0 (DDE), and 1.8 (heptachlor epoxide), respectively. [ABSTRACT FROM AUTHOR]

Because of their isolation and geographical position, and in contrast to the multi-species tree canopies of tropical rain forests on the continents, the Hawaiian Islands have only two native dominant canopy species in their rain forests, Acacia koa and Metrosideros polymorpha. The wetter forest ecosystems are dominated by only the latter. In 1905, a dieback of lowland tropical Metrosideros rain forest was observed over a 35 km stretch on the lower east slope of Haleakalā Mountain on Maui Island. This was dubbed ‘The Maui Forest Trouble.’ Although the synchronous decline of so many trees was initially believed to be caused by an epidemic disease, a decade of research yielded no pathogen. The conclusion was that the Hawaiian flora consisted primarily of colonizer species that were unable to continue growing on aging soils. Although this made ecological sense at that time, it was a rather limited and thereby unfortunate conclusion. Further research has shown that the Maui Forest Trouble was a ‘bog-formation dieback’, a process of vegetation dynamics not only related to soil aging but more broadly to geomorphic aging and fundamental landscape change. This process is clearly a marginal-site syndrome, but a natural process of profound consequence for biological conservation. This will be further explained as a paradigm for vegetation ecology. [ABSTRACT FROM AUTHOR]

Abstract: A new methodology is proposed for the geotechnical analysis of strength of paleoseismic shaking using liquefaction effects. The proposed method provides recommendations for selection of both individual and regionally located test sites, provides techniques for validation of field data for use in back-analysis, and presents a recently developed energy-based solution to back-calculate paleoearthquake magnitude and strength of shaking. The proposed method allows investigators to qualitatively assess the influence of post-earthquake density change and aging. The proposed method also describes how the back-calculations from individual sites should be integrated into a regional assessment of paleoseismic parameters. [Copyright &y& Elsevier]

The final distribution of the CaO within Ca-treated clays was determined many years after the original treatment, i.e., when the soil-CaO reaction was completed, along with a study of evolution of the corresponding pH. The results reveal that the value of pH accepted in the literature as an indication of the end of the reaction, may not be the actual case. [ABSTRACT FROM AUTHOR]

Artificially contaminated soil is often used in laboratory experiments as a substitute for actual field contaminated soils. In the preparation and use of laboratory contaminated soils, questions remain as to how much and how long metals remain in labile form and in their oxidation state during the contamination process. Therefore, the objectives of this study were to determine if the speciation of added contaminants can be retained in the original form and to observe the change in lability of each element with aging time. In this study, natural soil was artificially polluted with five redox-sensitive toxic elements in their oxidized or reduced forms, i.e., As(III)/As(V), Sb(III)/Sb(V), Cr(III)/Cr(VI), Mo(VI), and W(V). Metal distribution was measured in progressive chemical fractionation using sequential extraction methods in contaminated soils after 3, 100, and 300 days of aging. The results indicated that the more strongly bound fraction of metals increased by day 100; whereas the fractions were not significantly different from those in the 300-day-aged soil. Among five metals, the ratio of weakly-bound fractions remained highest in As- and lowest in Cr-contaminated soils. The W(VI)-contaminated soil showed strong sorption without changes in speciation during aging. The oxidized or reduced metal species converged to occur as a single species under given soil conditions, regardless of the initial form of metal used to spike the soil. Both As and Sb existed as their oxidized form while Cr existed as its reduced form. The results of this study may provide a useful and practical guideline for artificial soil contamination. • As and Mo were relatively more mobile than Sb, Cr, and W. • Tungsten fraction did not significantly change with soil aging. • Soil aging process is closely related to Fe–Mn oxides and soil organic matter. • The oxidation state of spiked metals converged to the one dominant oxidation state in soil. [ABSTRACT FROM AUTHOR]

• Pig glue, egg and milk all experienced deterioration due to the primary and secondary structure changes. • Pig glue owned better aging resistance because of the less changes in hydrophobic amino acids, FTIR spectrum and minimum secondary structure variations. • Ultramarine accelerated the soil aging process but did not bring extra influences on the primary structure. Soil aging was the major aging form that affected great numbers of unearthed Chinese ancient artworks and would fundamentally influence the deterioration processes of the proteinaceous binders applied in polychromy artworks. The three main categories of the proteinaceous binders, pig glue, egg and milk, would present various stabilities towards soil aging due to their different characteristics, the study of which was of high importance for exploring the degradation mechanisms of polychromy artworks. In this paper, GC-MS and FTIR were applied to study the changes of the primary structure (amino acids) and secondary structure of pure pig glue, egg, milk and binder with ultramarine in a simulated anoxic, dark, microthermal, compacted stable burial environment for one year. Results illustrated that all binders experienced deterioration due to the changes in individual, different groups of amino acids and the broadening of Amide A. Comparatively, pig glue owned better aging resistance because of the less changes in hydrophobic amino acids, FTIR spectrum and minimum secondary structure variations. Moreover, ultramarine accelerated the soil aging process but did not bring extra influences on the primary structure. [ABSTRACT FROM AUTHOR]

A thorough understanding of the geochemical behavior of W in soils is crucial for environmental risk assessment. Soil pH is known as master variable of element solubility and bioavailability in soils. Here we report on effects of soil pH (modified by liming and acid – base additions) and soil aging on the environmental availability of W in soil using W solubility and chemical fractionation as indicators. Experimental soils included two naturally acidic soils with contrasting soil texture (SAND, CLAY), at native pH or limed with 2.5% CaCO 3 , and spiked with increasing concentration of W. Our results showed that W was significantly more labile in alkaline compared to acidic soils, confirming the validity of results of pure-mineral studies for more heterogeneously composed soils. While labile W was generally greater in the SAND compared to the CLAY soil, the reverse trend was observed in the limed soils at the highest W addition (5000 mg kg−1). Combining our results with previous mechanistic reports suggests that clay edge sorption sites significantly contributed to W retention in treatments with low to medium W additions, resulting in lower environmental availability for W in the CLAY soil. At high W concentrations and high pH, the stronger W retention in the SAND was attributed to continuous formation of W surface polymers on the more abundant metal (oxyhydr)oxides, a process that has been previously reported to occur even under alkaline conditions. A first comparison of various soil chemical methods (Bray & AB-DTPA extractions, soil solution centrifugation C L , diffusion-based DGT) to predict W phytoavailability in soil also revealed a strong pH dependency challenging the identification of a suitable method. This study is one of the first demonstrating the pH dependence of W in natural soils and delivers evidence for increased risk of W mobilization in W polluted, alkaline soil environments. Unlabelled Image • Soil pH and time (aging) are master variables governing bioavailability of tungsten (W) in soil. • W is significantly more labile in alkaline soils. • W polymerization plays a crucial role in determining W solubility in soils. • In acidic, high W soils, W polymer formation in the soil solution reduces W sorption. • Surface polymerization of W on (oxyhydr)oxide surfaces increases W sorption even at high pH. [ABSTRACT FROM AUTHOR]

This study examines the influence of soil aging on Standard Penetration Test (SPT) N-Vs correlations, and seismic site classification. Energy-corrected SPT-Vs correlations are developed for two regions where subsurface layering consists of soil deposits with very young geotechnical ages according to the last critical soil disturbance that occurred in the study areas. It is observed that the uncorrected correlations of the current study fall into the lower bound of the uncorrected SPT-Vs correlations existing in the literature due to soil aging effects. To better illustrate the effects of soil aging on SPT-Vs correlations, the uncorrected correlations from the literature and this study are divided into two age categories of Holocene and Pleistocene according to their geological age. Using the two age categories, the boundaries proposed in the NEHRP for different seismic site classes are divided into three zones according to their uncertainty level regarding seismic site classification. The results clearly indicate the need to consider the age of soil deposits for seismic site classification when using the SPT method to avoid incorrect seismic site classification. Additionally, it is found that the use of raw (uncorrected) SPT N values can lead to incorrect seismic site classification, with either conservative or unconservative results depending on the Energy Transfer Ratio (ETR) of the SPT hammer used for the seismic site class determination. • Two new age categories of Holocene and Pleistocene are defined for the uncorrected SPTVs correlations for sandy soils. • Energy-corrected SPT-Vs correlation should be used to avoid inconsistency between different studies caused by hammer ETR. • In the SPT method, the use of uncorrected SPT N values can lead to incorrect seismic site classification. • The age of soil needs to be considered for seismic site classification when using the SPT method. [ABSTRACT FROM AUTHOR]

This paper develops an analytical approach to estimate the long-term load-displacement behaviors of jacked piles in clayey soils. Apart from considering the effects of pile installation, subsequent re-consolidation and loading, the proposed approach properly considers the effects of soil aging on the long-term behavior of the surrounding soil so as to determine the load-displacement response of the jacked pile in the long run. An elastic-viscoplastic soil model is incorporated into the load transfer method to predict long-term soil properties. The comparison between the predictions from the presented approach and the data measured from the field pile loading test shows the validity of the proposed method. Parametric studies are conducted to illustrate the effects of the in-situ overconsolidation ratio, internal friction angle and the secondary consolidation coefficient on the long-term load-displacement behaviors of old piles. Results show that the proposed approach not only is capable of predicting the short-term set-up of jacked piles, but also could yield reasonable long-term load carrying behavior. The three parameters pertaining to the strength and stiffness of soil have significant impacts on the long-term load-displacement curve of the pile. [ABSTRACT FROM AUTHOR]