Soil Material Research Articles

Light grazing alleviates aeolian erosion–deposition effects on microbial communities in a semi-arid grassland

BackgroundSoil erosion affects the stability of terrestrial ecosystems and ecosystem services by directly or indirectly impacting the cycling of soil materials and energy and reducing the fertility of grassland soils. However, research on microbial adaptation to grazing and soil erosion is limited, particularly in relation to grassland ecosystem restoration. Here, we assess microbial communities subjected to simulated soil erosion and grazing in a semi-arid grassland of Inner Mongolia, China.ResultsNo significant change was observed in soil variables. However, the structure of the soil microbial community underwent significant changes as a result of soil erosion and soil erosion plus grazing, leading to a significant increase in the relative abundance of Cyanobacteria (116.80% vs 116.38%). Wind erosion and deposition contributed to an increase in the network complexity of soil bacterial and fungal communities. However, much of this effect was alleviated by grazing. Simultaneously, aeolian processes and grazing regulate soil microbial community assembly, leading to inconsistent patterns of change in bacterial and fungal communities. Under wind erosion and deposition, the relative contribution of deterministic processes (4.44% vs 31.11%) in bacterial communities increased, while the relative contribution of stochastic processes (2.23% vs 20%) in fungal communities reduced. Grazing resulted in a decrease in the relative contribution of deterministic processes (8.89%) in the bacterial community and an increase in the relative contribution of stochastic processes (8.89%) in the fungal community.ConclusionThis study presents a comprehensive investigation of the response of soil microbial communities to aeolian erosion–deposition and grazing in a semi-arid grassland. Our findings indicate that microbial communities in the semi-arid grassland show resistance to external disturbances and that light grazing mitigates the effects of aeolian erosion–deposition on microbial communities, which is essential for maintaining the stability and biodiversity of grassland ecosystems.

Characterization of refractory aerosol particles collected in the tropical upper troposphere–lower stratosphere (UTLS) within the Asian tropopause aerosol layer (ATAL)

Abstract. Aerosol particles with diameters larger than 40 nm were collected during the flight campaign StratoClim 2017 within the Asian tropopause aerosol layer (ATAL) of the 2017 monsoon anticyclone above the Indian subcontinent. A multi-impactor system was installed on board the aircraft M-55 Geophysica, which was operated from Kathmandu, Nepal. The size and chemical composition of more than 5000 refractory particles/inclusions of 17 selected particle samples from seven different flights were analyzed by use of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) combined with energy dispersive X-ray (EDX) microanalysis. Based on chemical composition and morphology, the refractory particles were assigned to the following particle groups: extraterrestrial, silicates, Fe-rich, Al-rich, Hg-rich, other metals, C-rich, soot, Cl-rich, and Ca-rich. Most abundant particle groups within the refractory particles are silicates and C-rich (non-volatile organics). In samples taken above the tropopause, extraterrestrial particles are becoming increasingly important with rising altitude. The most frequent particle sources for the small (maximum in size distribution DP-max=120 nm) refractory particles carried into the ATAL are combustion processes at the ground (burning of fossil fuels/biomass burning) and the agitation of soil material. The refractory particles in the ATAL represent only a very small fraction (< 2 % by number for particles > 40 nm) of the total aerosol particles, which are dominated by species like ammonium, sulfate, nitrate, and volatile organics. During one flight, a large number of very small (DP-max=25 nm) cinnabar particles (HgS) were detected, which are supposed to originate from a ground source such as coal combustion or underground coal fires.

Historical charcoal production as a factor in soil cover heterogeneity in a fluvioglacial landscape − A case study from northern Poland

Although in situ wood thermal processing, as a common practice in European forests in historical times, has been confirmed in many studies, the environmental implications of that process remain poorly explored. In this study, we focused on evaluating the impact of that process on forest vegetation and soil cover heterogeneity in a fluvioglacial landscape dominated by Brunic Arenosols. This study covered three 70–95-year-old stands of Scots pine in northern Poland. Three soil profiles, including from the relict charcoal hearth (RCH), from the surrounding ditch and a control, were examined from each stand, as well as associated vegetation. The studies showed that 19th century charcoal production platforms were overgrown with 20–60% fewer plant species than control stands. The effect on soils varied according to their characteristics. The presence of anthropogenic horizons consisting of a mixture of burnt soil material, ashes, charcoal particles, and other products of wood pyrolysis was the most distinguishing feature of RCH soils classified as Spolic Technosols (Arenic, Dystric, Pyric, Protospodic, Transportic). Typically, these horizons were characterised by lower bulk density, and higher porosity, as well as higher contents of total organic carbon, nitrogen, and exchange cations than the control soils. The differences between the RCH and control soils were highlighted by a comparison between the pools of the components in a soil column (pedon). Clear tendencies were not recorded for pH, the phosphorus content and stocks, the forms of iron and aluminium, the saturation of the soil sorption complex with bases or the trophic index. This may be due to the long-term neutralising effect of forest vegetation, dominated by Scots pine. Moreover, the results of our study may indicate the problem of toxicity of the RCH soils, which should be undertaken, considering the utilitarian importance of the issue.

Dissolved phosphate decreases the stability of amorphous ferric arsenate and nano-crystalline yukonite

Extensive research has been conducted on the competitive adsorption of arsenate (AsO43-) and phosphate (PO43-) to mineral surfaces, but the stability of ferric arsenate mineral(oid)s under elevated phosphate levels remains poorly understood. Therefore, we investigated the impact of dissolved phosphate (0, 0.5, 50 mM) on the stability of amorphous ferric arsenate (AFA; FeAsO4·nH2O) and nano-crystalline yukonite [Ca2Fe3(AsO4)3(OH)4·4H2O], both synthetic and contained in natural As-contaminated soil (∼16 g/kg As) and mine-waste material (∼39 g/kg As) for up to one year. Substantial amounts of As (∼45% of total As) were released into solution from AFA and yukonite at high phosphate concentrations due to incongruent dissolution of the solids and substitution of arsenate by phosphate in both mineral(oids). After one year, both solids sequestered ∼8 wt% P with approximately 20–30% accounting for adsorbed and precipitated species. This P increase was also observed in the soil and mine-waste samples, where AFA and yukonite comprised up to 4.3 and 4.9 wt% P, respectively. The high reactivity of ferric arsenates with aqueous phosphate may lead to a substantial overestimation of adsorbed As determined by sequential As extractions of materials containing these phases and requires increased caution when applying phosphate to stabilize polymetallic mine wastes. Furthermore, long-term phosphate additions via fertilization of As-contaminated soil or renaturalized mine tailings containing amorphous or nano-crystalline ferric arsenates should be reduced to limit the export of As(V) into surface streams and groundwater.

Damage assessment of Siverek Castle during the Kahramanmaraş Earthquakes (Mw 7.7 and Mw 7.6) on 06 February 2023: Remediation and strengthening proposals

On February 6, 2023, two significant earthquakes with magnitudes (Mw) of 7.7 and 7.6 struck Turkey, occurring nine hours apart. In addition to the tragic loss of over 50,000 lives in the earthquakes centered in Kahramanmaraş, hundreds of thousands of engineering structures, such as residences, schools, hospitals, historical landmarks, highways, and more, were severely damaged. This study assesses the damages and risk scenario following the Kahramanmaraş earthquakes concerning Siverek Castle. In addition, remediation and strengthening proposals, required to eliminate the damage and the possible risk, have been developed. The initial stage involved observational damage assessments on the castle and surrounding slopes as part of field studies, identifying five different types of damage and potential risks. Subsequently, a precise 3D digital model of the damaged castle and its slopes was generated using the digital photogrammetry method. Additionally, geological and geophysical studies were conducted in the field to determine the characteristics of the mound structure, historical castle walls, soil and rock on the slope. Non-destructive, geophysical methods consisting Vertical Electrical Sounding (VES), Seismic Refraction Method (SRM) and Multichannel Analysis of Surface Waves (MASW) measurements were specifically employed in the area with historical remnants. To verify the obtained data, five boreholes were drilled in the lower parts of the slope, and experimental studies were conducted to determine the soil and rock material properties of the slope. In the numerical studies, a total of 54 2D stability analyses were performed under static, long-term static, and dynamic conditions. Additionally, 1000 different probabilistic rockfall analyses were conducted, both in 2D and 3D, to calculate the run-out distance, bounce height, velocity, and kinetic energies of the blocks that fell or were about to fall during the earthquake. In the final stage of the study, remediation and strengthening recommendations were prepared for the strengthening of the fortification walls and slopes where failures occurred, and stability analyses were conducted. Consequently, a design proposal recommending five distinct approaches to remediate and strengthen the castle and slopes impacted by the Kahramanmaraş earthquakes was endorsed by the relevant authorities, and construction has commenced. When the remediation and strengthening works are completed, the security of the cultural heritage will be ensured, and it is planned to be opened to visitors.

Application of computer technology to numerical simulation of hydrothermal variation of subgrade enhanced by seepage drainage geoglage under freeze-thaw cycle

In seasonal frozen soil areas, engineering problems are common due to the high water content of subgrade soil. In view of this phenomenon, a new type of percolating drainage geogrid (SDG) is proposed for cooling and drainage. The changes of soil temperature and moisture at different time points were analyzed through computer simulation laboratory model test, and the changes and distribution of soil temperature and moisture under freeze-thaw conditions were obtained. The temperature and moisture changes and their distribution obtained by computer modeling agree with the experimental results. By optimizing the soil materials of the model samples, the changes of temperature and moisture with time under freeze-thaw conditions were more significant. Therefore, it can be inferred that, without changing the configuration of the percolation drain grid, the cooling drainage performance of the percolation drain grid can be improved under the same conditions by changing the heat transfer coefficient or the macroporous filling material. It provides theoretical support and data guarantee for the reinforcement of subgrade percolation and drainage grid in cold area.

EFFECT OF USING LIME AND FLY ASH AS A CEMENT SUBSTITUTE FOR SOIL STABILITY

Subgrade is the lowest layer that receives the load on it if it does not have carrying capacity that is allowed then need for soil stabilization. Chemical soil stabilization is often done with the addition of cement but the use of cement material will cost quite high, it is necessary to alternate other materials for the substitution of cement to reduce the implementation costs incurred. Cement will be replaced as a stabilizing material in this research with additional materials like lime and fly ash. In this research, soil material was taken from the Sentul – Karawang Toll Road Project STA 24+300, with fly ash from PT PUSRI as the stabilization material, and lime material obtained from the market in Yogyakarta. The stabilization material will be used with a fixed lime percentage of 4.2% of the dry weight of the soil, and fly ash at 1.4%, 2.1%, 2.8%, 3.5%, and 4.2% of the dry weight of the soil. The soil samples were tested for physical and mechanical properties, including Standard Proctor and California Bearing Ratio (CBR). All test results were compared to select one variation, which was then designated as the Optimum Mix Design (OMD) sample. The test results of the soil sample + 4.2% lime + 2.1% fly ash yielded a CBR value of 15.52%, indicating an increase of 1078.02% from the initial 1.44%, and were formally designated as an OMD sample. The CBR value satisfies the subgrade requirements, namely >6%.

Isolation and identification of Podospora flexuosa (syn. Cladorrhinum flexuosum), a potential biocontrol agent detected in sugar beet cultivation areas in Türkiye

Sugar beet (Beta vulgaris L.) is widely cultivated in Konya province of Türkiye and about one third of Türkiye’s sugar beet production is obtained from this province. As a result of the isolations made from plants showing severe root rot and desiccation symptoms in sugar beet fields in the region in 2015-2017, a new endophytic fungal isolate was obtained from leaves along with soil and foliar disease agents belonging to different fungal species. The fungal isolate has dull yellow, light olive to light brown, fast growing colony-like, flexible conidiophores and septate branched hyphae. The representative fungal isolate did not cause disease symptoms on host plant leaves. Molecular identification of the fungal isolate was carried out using primers specific to the ITS gene region, and it was identified as Podospora flexuosa (syn. Cladorrhinum flexuosum) based on morphological and molecular characteristics. Since P. flexuosa is reported to be a biological control agent living as a saprophyte in soil and plant materials, it is thought that the fungal isolate obtained in our study can be used as a potential biocontrol agent in the biological control of plant disease agents in the future. To the best of our knowledge, this fungal species is reported for the first time for Türkiye.

Novel enhancement of interfacial interaction and properties in biodegradable polymer composites using green chemically treated spent coffee ground microfiller

This study investigates the potential of utilizing green chemically treated spent coffee grounds (SCGs) as micro biofiller reinforcement in Poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) biopolymer composites. The aim is to assess the impact of varying SCG concentrations (1 %, 3 %, 5 %, and 7 %) on the functional, thermal, mechanical properties and biodegradability of the resulting composites with a PHBV matrix. The samples were produced through melt compounding using a twin-screw extruder and compression molding. The findings indicate successful dispersion and distribution of SCGs microfiller into PHBV. Chemical treatment of SCG microfiller enhanced the interfacial bonding between the SCG and PHBV, evidenced by higher water contact angles of the biopolymer composites. Field Emission Scanning Electron Microscopy (FE-SEM) confirmed the successful interaction of treated SCG microfiller, contributing to enhanced mechanical characteristics. A two-way ANOVA was conducted for statistical analysis. Mass losses observed after burying the materials in natural soil indicated that the composites degraded faster than the pure PHBV polymer suggesting that both composites are biodegradable, particularly at high levels of spent coffee grounds (SCG). Despite the possibility of agglomeration at higher concentrations, SCG incorporation resulted in improved functional properties, positioning the green biopolymer composite as a promising material for sustainable packaging and diverse applications.

A new yield criterion based constitutive model for porous materials

In the present work, a new explicit expression of macroscopic yield criterion is derived for porous materials, such as soil, rock and cement-based materials. To consider the asymmetric behavior between tensile and compression loading, the matrix is assumed to obey to a Drucker–Prager local criterion. The influence of porosity and the effect of matrix properties are well taken into account by this criterion. By using the stress variational approach with a suitable statically admissible stress field, a new more accurate estimation with a simple expression has been obtained for the case of purely deviatoric loading. The exact solutions can be retrieved by this criterion in the case of hydrostatic loading. It also resolves the problem of discontinuity between tension and compression. The weaknesses of the main existing criteria have been overcome by this new yield criterion. By comparing with the finite element numerical results with a wide range values of porosity and frictional parameter of the matrix, the proposed macroscopic yield criterion has a great accuracy and improves the existing ones. Based on this yield criterion, a complete constitutive model is constructed and implemented. This micro-mechanics based model is then applied to describe the mechanical behavior of porous sandstone, and validated by the comparisons with experimental results at different confining pressures.

Rehydration of degraded wetlands: Understanding drivers of vegetation community trajectories

AbstractDegradation of wetland ecosystems results from loss of hydrologic connectivity, nutrient enrichment, and altered fire regimes, among other factors. It is uncertain how drivers of wetland ecosystem processes and wetland vegetation communities interact in reversing the ecological trajectory from degraded to restored conditions. We analyzed biogeochemical and vegetation data collected in wetlands of the Florida Everglades at the start of (2015) and during (2018 and 2021) the initial stages of rehydration. Our objectives were to analyze the allocation of carbon and nutrients among ecosystem compartments and correlated trajectories of vegetation community change following rehydration, to identify the drivers of change, including fire, and analyze macrophyte species‐specific responses to drivers. We expected to see changes in vegetation toward more hydric communities that would differ based on wetland baseline conditions and the magnitude of the hydrologic change. During the study period, both length of inundation and surface water depth increased throughout wetlands in the region, and four fires occurred, which affected 51% of the sampling locations. We observed biogeochemical shifts in the wetland landscape, driven by both hydrology and fire. Total phosphorus concentrations in soil and flocculent detrital material decreased, while soil carbon:phosphorus and nitrogen:phosphorus mass ratios increased at sites further away from water management infrastructure. Transitions in vegetation communities were driven by an increase in hydroperiods and by the distinct changes in nutrient concentrations or soil stoichiometric ratios in each subregion. The abundance of macrophyte species typical of short‐hydroperiod prairies strongly decreased, while dominant long‐hydroperiod species, such as Eleocharis cellulosa, expanded. Fire facilitated the expansion of thickly vegetated plumes of invasive Typha at sites close to the water inflow sources. Overall, restored hydrology shifted vegetation community composition toward higher abundance of long‐hydroperiod species within six years. In contrast, removal of invasive vegetation controlled by soil phosphorus concentrations will likely require long‐term and interactive restoration strategies.

HYSTERESIS OF IMPLICIT EQUATIONS IN HYPOPLASTICITY FOR SOIL MATERIALS WITH GRANULAR HARDNESS DEGRADATION

We study a hypoplastic model for soil and granular materials stemming from geomechanical engineering which further incorporates effects of degradation of the granular hardness, therefore allowing for the description of environmental weathering. The governing system is described by a nonlinear system of transcendental-differential equations for stress and strain rate, which is investigated with respect to its long-time dynamic. Under deviatoric stress control, two different solutions of the underlying, implicit differential equations are constructed analytically. The spherical components of stress and strain rate converge asymptotically to an attractor and lead to the sparsification of material states. Whereas under cyclic loading-unloading carried out in a numerical simulation, finite ratcheting of the deviatoric strain rate is observed in the form of a square spiral.

First report of Root-Knot Nematode Meloidogyne enterolobii infecting coriander in Shaanxi, Northern China.

Coriander (Coriandrum sativum), which can be used for its root, stem, and leaf as both food and medicine (Prachayasittikul et al. 2018), is widely cultivated in China. The coriander cultivation area of Guanzhong region, including Xi' an, Xianyang, and Weinan, is 20 million m2, which accounts for 85.7% of the total cultivation area in Shaanxi. In September 2022, obvious galls were observed on the roots of coriander plants (cv. Xiaoye) growing in a field in Huyi District, Xi' an City (34°1'26.4"N, 108°31'58.8"E). The diseased plants did not show obvious above-ground symptoms. To identify the species, second-stage juveniles (J2s) and males were collected from soil in the root zone, and adult females were isolated from galls of diseased roots. The perineal patterns of adult females (n = 20) were round to oval, with high dorsal arches and no obvious lateral lines were observed. Morphological measurements of females (n = 20) included body length (L) = 682 ± 56 (554 to 780) μm, body width (BW) = 522 ± 45 (420 to 597) μm, stylet = 14.9 ± 0.9 (13.4 to 16.3) μm, dorsal pharyngeal gland orifice to stylet base (DGO) = 5.3 ± 0.5 (4.3 to 6.3) μm, vulval slit length = 26 ± 2.8 (20 to 32) μm, vulval slit to anus distance = 21 ± 1.7 (18.5 to 26) μm. Measurements of males (n = 8) were L = 1398 ± 57 (1308 to 1450) μm, BW = 28 ± 2.9 (23 to 32) μm, stylet = 16.1 ± 0.8 (15.3 to 17.3) μm, DGO = 4.5 ± 0.5 (3.5 to 4.9) μm, spicules = 27 ± 1.1 (26 to 29) μm. Measurements of J2s (n = 20) were as follows: L = 434 ± 16.8 (391 to 477) μm, BW = 15.6 ± 0.9 (13.7 to 17.3) μm, stylet = 12.6 ± 0.6 (11.3 to 13.6) μm, DGO = 3.9 ± 0.3 (3.4 to 4.5) μm, tail = 52 ± 4.0 (47 to 60) μm, hyaline tail length = 15.6 ± 1.3 (13.6 to 18.6) μm. These morphological characteristics were consistent with those described for Meloidogyne enterolobii (Yang and Eisenback 1983). Ten females were put in 10 tubes for DNA extraction following Htay et al. (2016). The ITS-rDNA sequence was amplified using the primers 18S/26S (Vrain et al. 1992). A 765 bp fragment was obtained and the sequence (GenBank OR789453) was 99.87% identical to sequences of M. enterolobii (MT406251 and MT067559). The mtDNA CoxII-16S sequence was amplified using primers C2F3/1108 (Powers and Harris, 1993). The sequence was 705 bp (OR795028) and 100% identical to sequences of M. enterolobii (MK455870 and MZ643270). A single 236 bp fragment was amplified using species-specific primers Me-F/Me-R, confirming the species as M. enterolobii (Long et al. 2006). The infection test was conducted in a greenhouse at 27 ± 2℃. Eight 2-week-old coriander plants (cv. Xiaoye) were individually grown in pots filled with sterilizer soil and inoculated with 800 J2s hatched from collected M. enterolobii egg masses. Forty-five days after nematode inoculation, the inoculated plants had galled roots like those observed in the field. The reproduction factor (final population density/initial population density) was 11.9 ± 2.0, indicating coriander was a suitable host for M. enterolobii. No symptoms were observed in controls. To our knowledge, this is the first known natural infection of coriander with M. enterolobii in China. M. enterolobii has been reported on various crops in southern provinces of China (EPPO, 2023). Considering the high level of agricultural trade between different regions, there is a high risk of M. enterolobii transmission to Guanzhong region through infested soil and susceptible plant materials. Further monitoring and research on effective control strategies are needed to prevent the spread of this nematode.

Analysis Sequential Excavation Method For Large Span

Modern tunnel design mandates the careful selection of appropriate techniques and technologies for all tunnel projects. The pivotal factor for success in tunnel construction lies in choosing the right excavation methods for extensive-span tunnel projects in soft soil materials. The choice of excavation methods during tunnel construction significantly impacts both the project timeline and associated costs. This study specifically concentrates on the selection of excavation techniques, sequencing, and temporary supports employed during the excavation phase for tunnels located in soft soil environments. Given the considerable diameter of the tunnel, exceeding 200 m2, and the presence of soft soil, traditional methods like the Full-face method and the Central Diaphragm (CD) and Side wall Drift (SD) approach are not feasible. Therefore, this study suggests the application of a Sequential Excavation Method (SEM) for the tunnel construction.

Experimental determination of the parameters of the methodology for investigating the frost strength bond of soil and foundation material

Experimental determination of the parameters of the methodology for investigating the frost strength bond of soil and foundation material

HYGIENIC RISK ASSESSMENT OF ETOFENPROX-BASED INSECTICIDES USAGE FOR HUMANS BY TOXICITY PARAMETERS

Background. As of 2023, 135 pyrethroid-based insecticides have been registered in Ukraine. The Ukrainian pesticide market offers products based on the new active ingredient etofenprox. According to the current legislation, the acceptable daily intake (ADI) of the new active ingredient etofenprox must be substantiated at the pre-registration stage.
 Aim: hygienic assessment of the toxic properties of the third-generation pyrethroid substance etofenprox and justification of the ADI of etofenprox, the active ingredient of the insecticide Trebon. Potential risk assessment for the workers and the general population. Determining the necessity of monitoring on environmental objects.
 Materials and methods. In the course of the work expert analysis, toxicological and hygienic research methods have been used.
 Results. It has been proven that etofenprox, in accordance with Sanitary Rules and Standards (SanPiN) 8.8.1.002-98, is of low danger – for oral and percutaneous ingestion and for allergenic effects, dangerous – for inhalation, moderately dangerous – for irritating effects on the skin and mucous membranes of the eyes. Integral hazard class - II (Limitation criteria - inhalation toxicity).
 The value of the ADI was estimated at the level of 0.003 mg/kg, based on toxicity data for mice in a chronic experiment and hazard class III for reproductive toxicity, embryotoxicity, teratogenicity (3.1 mg/kg is the lowest dose), factor of safety 1000 has also been considered.
 Conclusion. There has been established the necessity to consider the toxicity data of etofenprox when deciding on the need to perform monitoring studies of the content of etofenprox in water, soil, air, and agricultural raw materials.

Bioavailability of Metals in the Biosphere

In some areas, soil, sediment, water, and organic materials may exhibit elevated concentrations of various metals. Under certain conditions, these metals can take on most bioavailable forms. To assess the impacts and potential risks associated with elevated element concentrations, understanding the fraction of whole elements in water, sediment, and soil which are bioavailable is very important. The study aims to examine these conditions to accurately assess potential environmental impacts. For the study, searches were carried out using the keywords "bioavailability", "metal" and "environment" in various combinations in English. The search was limited to articles published open access in NCBI or PubMed, Scopus, and Google Scholar. The language of the manuscript was not restricted. The complex interactions of these diverse factors highlight the difficulty of assessing and understanding the bioavailability of metals in different environmental matrices. The study identified key factors affecting the bioavailability of the metal. These factors can change over time and among different microorganisms, plants, and animals. Research involving field and laboratory studies conducted at specific locations in soil, sediment, and flora using selective chemical extraction techniques is critical to a detailed understanding of the complex ecological processes associated with the bioavailability of metals to organisms.

Bank erosion and erosion processes from dendrogeomorphology in southern U.S. prairie streams

AbstractStreambank erosion processes influence the amount of soil material contributed to rivers and sedimentation rates in receiving reservoirs. However, the amount of data on bank erosion rates is limited both in range and extent affecting planning for mitigation and watershed management. Dendrogeomorphology is used to determine the date of wood anatomy changes in annual growth increments of roots exposed by erosion of stream banks that when coupled with measurement of the distance of roots to the channel side can be used to calculate the bank retreat rate. Erosion rates derived from dendrogeomorphology are important because these provide erosion data over longer time scales (decades). Here, we use this method to quantify erosion for three different sized watersheds (4 to 3781 km2) located in the water‐scarce southern U.S. prairies that are heavily reliant on surface water and reservoir storage. From 49 roots from the two smaller drainages, erosion ranged from 1.5 to 25.4. For 19 roots collected from the larger subbasin erosion rates were larger ranging from 7.4 to 325.0 cm/years with the larger values and variance associated with two high‐flow events that occurred a year before sampling. We also found differences in straight and meandering portions of the streams where the distance to bank was strongly and positively correlated with the years since root exposure in straight sections. In contrast, meandering bends also showed a positive but low correlation for root exposure date and distance collected. We attribute this difference to erosional processes (i.e., scour and mass wasting) occurring at these channel locations. When compared with other erosion studies across the southern U.S. prairie, our values were similar in magnitude but with low correlation to drainage area indicating site specificity of erosion mechanisms, and watershed landcover influence for different drainages, despite being in the same ecological region.

Quantitative analysis of iodine and bromine in soil using an energy-dispersive X-ray fluorescence spectrometer with three-dimensional polarized optics.

A nondestructive and simple method for the determination of bromine and iodine in soil was investigated using an energy-dispersive X-ray fluorescence spectrometer equipped with three-dimensional polarized optics. Using a gadolinium X-ray tube and Mo and Al2O3 as optimal secondary target materials, K-lines were detected for bromine and iodine. The minimum detection limits for bromine and iodine were calculated using JSAC0411, a certified reference material of soil for metal composition analysis, and were 0.77mg/kg for bromine and 2.3mg/kg for iodine at a measurement time of 600s. The results of the determination of bromine and iodine in soil samples by the standard addition method were 256 ± 8mg/kg for iodine and 67.9 ± 1.3mg/kg for bromine with JSAC0411, which were in close agreement with the results measured by inductively coupled plasma mass spectrometry (ICP-MS) after alkaline extraction with tetramethylammonium hydroxide (TMAH) solution. The method developed in this study is an excellent technique for direct analysis of soil by X-ray fluorescence analysis without any pretreatment such as alkaline extraction. It is expected to be a practical analytical method for elucidating the dynamics of bromine and iodine in agricultural land and soil.

Первичное почвообразование на субстратах разного гранулометрического состава в посттехногенных экосистемах таёжной зоны

The paper focuses on the primary soil formation under automorphic conditions in the middle taiga sub-zone of the European North-East of Russia (Komi Republic) on the post-technogenic territories (quarries for the extraction of minerals (construction sand)) with different soil materials (ancient alluvial sands; fluvioglacial sands and sandy loams, moraine loams). In the quarries, the processes of soil formation and vegetation cover development are interdependent and are affected by the properties of soil-forming rocks. Along with the improvement of soil properties (from sandy loam to loam), the biometric parameters of pine stands increase; in the ground cover, dominating lichens are replaced by mosses, and then by grasses. The biogenic accumulation rates of organic matter increase along with the transition of soil material to fine-textured. In automorphic conditions, the accumulation rate of Corg. in soil of sandy quarry under sparse young lichen pine forest reaches 0.1, in sandy loam under young forb-moss pine forest – 0.3, in loam under young grass-forb pine forest – 0.6 t/ha/year. Already in the first succession decades, every study soil demonstrates weakly expressed processes of eluviation and illuviation (the beginning of podzolization). These processes are evidenced by morphological signs (the appearance of bleached quartz grains and whitish patches under organic horizon and in its lower part), redistribution of silicon, iron, and aluminum compounds, as well as of silty particles proportion.