Elements In Soils Research Articles

Warming affects leaf light use efficiency and functional traits in alpine plants: evidence from a 4-year in-situ field experiment.

Light use efficiency (LUE) is a crucial determinant of plant productivity, while leaf functional traits directly affect ecosystem functions. However, it remains unclear how climate warming affects LUE and leaf functional traits of dominant species in alpine meadows. We conducted a 4-year in-situ field warming experiment to investigate the eco-physiological characteristics for a dominant species (Elymus nutans) and a common species (Potentilla anserina) on the Tibetan Plateau. The leaf traits, photosynthesis and fluorescence characteristics were measured, along with the soil physical-chemical properties associated with the two species. Experimental warming increased the leaf LUE, maximum photochemical efficiency, non-photochemical quenching, relative water content and specific leaf area for both species. However, there was a decrease in leaf and soil element content. Different species exhibit varying adaptability to warming. Increasing temperature significantly increased the photosynthetic rate, stomatal conductance, transpiration rate, total water content, and specific leaf volume of E. nutans; however, all these traits exhibited an opposite trend in P. anserina. Warming has a direct negative impact on leaf LUE and an indirectly enhances LUE through its effects on leaf traits. The impact of warming on plant photosynthetic capacity is primarily mediated by soil nutrients and leaf traits. These results indicate that the two different species employ distinct adaptive strategies in response to climate change, which are related to their species-specific variations. Such changes can confer an adaptive advantage for plant to cope with environmental change and potentially lead to alterations to ecosystem structure and functioning.

Metal concentrations in invasive Ailanthus altissima vs native Fraxinus ornus on ultramafic soils: Evidence for higher efficiency in Ni exclusion and adjustments to Mg and Ca imbalance

AbstractAilanthus altissima is one of the major invasive trees at a global scale. Despite numerous reports about its invasiveness in different habitats, so far it was not observed on harsh ultramafic soils and to colonize the vegetation of these outcrops. In this paper we show that the species can also spread in these habitats in the Mediterranean region and is able to cope with the severe anomalies of ultramafic soils. We sampled A. altissima in four ultramafic outcrops of central Italy and in control sites to unravel the behavior of this species toward the typically high soil concentrations of trace metals, such as Ni, Cr and Co, as well the imbalance of the Ca:Mg quotient. A similar sampling was performed for the native Fraxinus ornus that occurs naturally on a broad range of soils, including those from ultramafic rocks. Trace metal concentrations in leaves of both species were below toxicity thresholds, but A. altissima showed lower translocation and bioaccumulation factors (TF and BF, respectively) for Ni. Compared with F. ornus, the invasive species displayed higher leaf concentrations of Mg, thus suggesting a higher tolerance of potentially toxic levels of this element. Moreover, the higher TF and BF values for Ca in both control and serpentine populations suggested that A. altissima was more able to extract and accumulate this macronutrient in leaves in respect to F. ornus. Given the inherent deficiency of this element in ultramafic soils, efficient use of Ca could be a key trait contributing to the invasiveness of A. altissima on these soils.

Mechanisms of cadmium mitigation in tomato plants under orthophosphate and polyphosphate fertilization regimes

Cadmium (Cd) is one of the most toxic elements in soil, affecting morphological, physiological, and biochemical processes in plants. Mineral plant nutrition was tested as an effective approach to mitigate Cd stress in several crop species. In this regard, the present study aimed to elucidate how different phosphorus (P) fertilization regimes can improve some bio-physiological processes in tomato plants exposed to Cd stress. In a hydroponic experiment, the impact of two phosphorus fertilizer forms (Polyphosphate (poly-P): condensed P-form with 100% polymerization rate and orthophosphate (ortho-P): from orthophosphoric acid) on the photosynthetic activity, plant growth, and nutrient uptake was assessed under three levels of Cd stress (0, 12, and 25 µM of CdCl2). The obtained results confirmed the negative effects of Cd stress on the chlorophyll content and the efficiency of the photosynthesis machinery. The application of poly-P fertilizer significantly improved the chlorophyll stability index (82%) under medium Cd stress (Cd12), as compared to the ortho-P form (55%). The analysis of the chlorophyll α fluorescence transient curve revealed that the amplitude of Cd effect on the different steps of electron transfer between PSII and PSI was significantly reduced under the poly-P fertilization regime compared to ortho-P, especially under Cd12. The evaluation of the RE0/RC parameter showed that the electron flux reducing end electron acceptors at the PSI acceptor side per reaction center was significantly improved in the poly-P treatment by 42% under Cd12 compared to the ortho-P treatment. Moreover, the use of poly-P fertilizer enhanced iron uptake and its stoichiometric homeostasis in the shoot tissue which maintained an adequate absorption of iron under Cd stress conditions. Findings from this study revealed for the first time that inorganic polyphosphate fertilizers can reduce Cd toxicity in tomato plants by enhancing photosynthesis activity, nutrient uptake, plant growth, and biomass accumulation despite the high level of cadmium accumulation in shoot tissues.

Reductive soil disinfestation by mixing carbon nanotubes and mushroom residues to mitigate the continuous cropping obstacles for Lilium Brownii

Reductive soil disinfestation can effectively alleviate continuous cropping obstacles. The effects of mixing mushroom residues and carbon nanotubes on the structure and function of soil microbial communities and self-toxic substances in Lilium brownii var are still unclear. We evaluated the nature of different soil treatments on soil physicochemical properties, microbial community structural response, and the impact of self-toxic substances. Compared with the compound fertilizer treatment, both organic fertilizer and mushroom residues treatments improved soil pH to 7.06 and 6.57, respectively. Carbon nanotubes treatment increased the relative abundance of Acidobacteriota by approximately 3.96%, although it could not significantly affect the soil pH. The mushroom residues flooded cover film treatment increased the soil pH to 6.75, replenished soil elements, and increased the relative abundance of Verrucomicrobiota and Campylobacterota by 1.62% and 1.79%, respectively. Carbon nanotubes and mushroom residues flooded cover film treatment significantly increased the diversity of the bacterial community. The relative abundances of Acidobacteriota, Verrucomicrobiota, Actinobacteria, and Chloroflexi increased by 2.4%, 1.39%, 0.80%, and 0.53%, respectively. Additionally, the minimum number of self-toxic substances was detected through GC–MS analysis. The results of this study showed that mushroom residues flooded cover film treatment could directly improve the soil microbial community structure by changing the physicochemical properties of the soil, and mixed carbon nanotubes further adsorbed the self-toxic substances. The species composition of fungal communities in the soil had been altered in a way by the different treatments, but the fungal diversity didn't change significantly. This research provides a theoretical basis for revealing the mechanism of continuous cropping obstacles in lily and offering better guidance for sustainable development in lily.

Size-resolved distribution of trace elements in lysimeter soil solutions under contrasting long-term agricultural management to assess their bioavailability

The chemical species of trace elements (TEs) in agricultural soils is highly variable under diverse conditions, requiring tools with clear resolution and minimal disturbance for exploration. A novel surgical (316L) stainless steel (SS) lysimeter with a 5 μm pore size was developed to collect field soil solutions. The size-resolved distribution of TEs were characterized into total (nitric acid digestion), particulate (0.45–5 μm), dissolved (<0.45 μm), colloidal (1 kDa to 0.45 μm), and mainly ionic (<1 kDa) fractions in the lysimeter soil solutions. Total concentrations of TEs (dry weight basis) in acid digested Gray Luvisolic soils were analyzed. Most TEs in lysimeter soil solutions were present in particulate phases, relevant to their geochemical affinities and occurrences in soil minerals. Among dissolved fractions, As, Ba, Co, Li, Mn, Tl, and V existed as mainly ionic species in the soil solutions. Copper, Pb, Al, Th, and U showed variable associations with dissolved organic matter (DOM) and/or inorganic colloids among agricultural treatments. Inorganic NPKS or NKS fertilizer applications with lower pH (5.25–5.74) enhanced mobility and potential bioavailability of Ba, Co, Li, Mn, and Pb present in mainly ionic species, compared with other locations (pH 5.82–6.37). Manure application exhibited a dual effect, potentially increasing bioavailability for As, Tl, and V due to probably enhanced cation exchange capacity (CEC), while also facilitating specific adsorption of Cu and U on DOM, potentially reducing their bioavailability depending on DOM molecular weight. Colloidal and ionic Al and Th concentrations were higher in forest soils than agricultural soils, with extremely low potential bioavailability of Th attributed to strong precipitation with inorganic colloids and adsorption on DOM. The lysimeter sampling and size fractionation method provided a clear insight into agricultural effects on TE distributions and enhancing understanding of agricultural soil health in terms of TE bioavailability in situ.

Remediation of soda-saline-alkali soil through soil amendments: Microbially mediated carbon and nitrogen cycles and remediation mechanisms

Due to the high salt content and pH value, the structure of saline-sodic soil was deteriorated, resulting in decreased soil fertility and inhibited soil element cycling. This, in turn, caused significant negative impacts on crop growth, posing a major challenge to global agriculture and food security. Despite numerous studies aimed at reducing the loss of plant productivity in saline-sodic soils, the knowledge regarding shifts in soil microbial communities and carbon/nitrogen cycling during saline-sodic soil improvement remains incomplete. Consequently, we developed a composite soil amendment to explore its potential to alleviate salt stress and enhance soil quality. Our findings demonstrated that the application of this composite soil amendment effectively enhanced microbial salinity resistance, promotes soil carbon fixation and nitrogen cycling, thereby reducing HCO3− concentration and greenhouse gas emissions while improving physicochemical properties and enzyme activity in the soil. Additionally, the presence of CaSO4 contributed to a decrease in water-soluble Na+ content, resulting in reduced soil ESP and pH by 14.64 % and 7.42, respectively. Our research presents an innovative approach to rehabilitate saline-sodic soil and promote ecological restoration through the perspective of elements cycles.

Assessment of the potential of microbial consortium for the reclamation of mine tailings containing potentially toxic elements

Bioremediation using microorganisms is an emerging green technology for the remediation of potentially toxic elements (PTEs) in soils and sediments. However, such technology can differently impact PTEs dynamics (e.g., immobilization and mobilization), ultimately affecting the efficiency of the remediation programs. In this study, we aimed to assess different microbial remediation mechanisms triggered by a microbial consortium to bioremediate Fe-rich mining tailings. The tailings were incubated in a mesocosm system for 35 days with increasing colony-forming units (CFU) of a specific microbial consortium (Azospirillum sp., Pseudomonas sp., Saccharomyces sp., and Rhizobium sp.). At the end of the experiment, we determined the geochemical fractionation of Fe and PTEs in the solid phase to assess the effect of treatments on PTE’s bioavailability. Increasing the CFU resulted in higher Fe (15%) and Mn (37%) reductive dissolution compared to the control. As a result, the Fe and Mn concentrations in water increased by 9-fold. In addition, microbial consortium decreased the contents of Fe and Mn associated with oxides (-59% and −79%, respectively) and increased the more bioavailable solid fractions. The microbial consortium also efficiently decreased PTEs pseudo total contents in the mine tailings (Cr: −85%, Cd: −61%, Pb: −55%, and Cu: −49%). In addition, lower CFUs increased PTEs dissolved in the drainage water, indicating a potential for assisting other remediation strategies. Lower CFU also induced high Cr biomineralization (94%). In conclusion, our work provides novel evidence of a microbial consortium for remediating Fe mine tailings through different strategies (biodissolution and biomineralization). In view of the effects of the microbial consortium over Fe and Mn oxyhydroxide dissolution rates, further research should test it on microbially assisted phytoremediation protocols.

Spartina alterniflora invasion decouples multiple elements in coastal wetland soils

Deciphering the biogeochemical coupling of multiple elements in soils could better mechanistic understanding of ecosystem stability response to the alien invasion. The coupling of 45 elements in soils from wetlands covered by Spartina alterniflora (Sa) was compared with that in soils covered by native Phragmites australis (Pa) in coastal regions of China. Results showed that S. alterniflora invasion not only significantly reshaped geochemical enrichment and dispersion states, but also decoupled the coupling of multiple elements in soils compared with Pa. Atomic mass emerged as the primary factor governing the coupling of multiple elements, of which a significantly positive correlation exhibited between atomic mass with elemental coupling in Pa, but no such relation was observed in SaThe coupling of lighter elements was more susceptible to and generally enhanced by the invasion of S. alterniflora compared to the heavier, of which carbon, iron (Fe), and cadmium (Cd) had the highest susceptibility. Besides atomic mass, biological processes (represented by soil organic carbon, nitrogen, phosphorus, and sulfur), interactions between sea and land (represented by salinity and pH), and their combination explained 17 %, 10 %, and 13 % variation in the coupling of multiple elements, respectively. The present work confirmed that S. alterniflora invasion was the important factor driving soil multi-element cycling and covariation in coastal wetlands.

Mediterranean Wildfires’ Effect on Soil Quality and Properties: A Case from Northern Euboea, Greece

Mediterranean Wildfires’ Effect on Soil Quality and Properties: A Case from Northern Euboea, Greece

Colloids facilitate transport of cadmium and uranium in arable soils, which is undetected by suction cups in the field

AbstractColloids can facilitate the transport of trace elements in soil, but earlier studies fell short either because of sampling artefacts or because no contrasting soils were used; both factors hamper a better understanding of where this occurs. Here, leaching in undisturbed and unsaturated soil columns was observed to identify colloidal transport of cadmium (Cd) and uranium (U) in soils with contrasting properties. Crucially, it was examined how such column data relate to more traditional in situ data obtained with porous suction cups. Soils were collected from three agricultural fields in Switzerland (soil pH 5.1–7.3), leached during 36 days (0.6 pore volumes, ~1.6 mm day−1), and elements trapped in the PTFE suction plates were recovered and were ascribed to colloids. Of the total mobile mass (sum percolate and plate), 18%–53% (Cd) or 8–89% (U) was retained by plates, the range depending on the field where soil was sampled and that fraction depends on soil pH and for U also on dissolved inorganic carbon. The total mobile Cd or U mass divided by the percolated volume indicates the metal concentration in the average leachate and was logically highest for Cd in the most acidic soil and for U in the most alkaline soil. The concentrations of Cd and U in these column leachates were &gt;10‐fold higher than corresponding concentrations in the suction cups in the field for those soils and elements where colloids dominated leaching. In contrast, they were within a factor of two where colloids are &lt;20% of the mobile mass. Flow Field‐Flow Fractionation (FlFFF) analyses showed an association of colloidal U with oxyhydroxides, clays and organic matter and, for colloidal Cd, an association with organic matter. These data show that suction cups or filtered percolates can underestimate the leaching of Cd and U by up to an order of magnitude.

WITHDRAWN: Trace metals translocation from soil to plants: Health risk assessment via consumption of vegetables in the urban sprawl of a developing country

The study was conducted at 15 locations around the thermal power plant of Patuakhali district at the coastal area of Bangladesh to determine trace elements in vegetable and assess risk of toxicity. Eight vegetables, namely, tomato (Solanum lycopersicum L.), radish (Raphanus raphanistrum L.), bean (Phaseolus vulgaris L.), brinjal (Solanum melongena L.), bottle gourd (Lagenaria siceraria L.), red amaranth (Amaranthus cruentus L.), arum (Arum maculatum L.) and lady's finger (Abelmoschus esculentus L.) were analyzed for nine trace metals (Cr, Ni, Cu, As, Cd, Pb, Fe, Mn and Zn) to assess contamination load of trace elements in agricultural soil, and health risks posed from vegetable consumption. The mean concentrations of Cr, Cr, Ni, Cu, As, Cd, Pb, Fe, Mn, and Zn in soil were 16.6, 14.8, 5.8, 1.3, 0.72, 9.7, 55261, 456.1, and 105.8 mg/kg, respectively. Average concentrations of As, Cd, and Pb in vegetable species were higher than the maximum allowable concentration (MAC), indicating vegetables species were contaminated by these elements and may pose potential risk to human. Fe, Mn, Zn, Cr, Cu, Pb, and As in soil and vegetables of the study area may arise from anthropogenic activities. The present study suggests that surface soil used for vegetables production should be continuously monitored to check the transfer of toxic metals into the vegetables to minimize the adverse health impacts on consumers and potential threats to food safety.

Zinc toxicity and tolerance-related responses in Inga marginata and Allophylus edulis seedlings

Although zinc (Zn) is a micronutrient, excessive amounts in the soil can have toxic effects on plants. Fertilizers, limestone materials, pesticides, and fungicides added with Zn have contributed to increasing the concentration of this element in agricultural soils. Accordingly, it is necessary to find Zn-tolerant plant species to be properly used in degraded soil restoration programs. Thus, the current study aims to investigate the influence of different Zn concentrations on photosynthetic variables, antioxidant activity, and growth of I. marginata and A. edulisseedlings to determine their potential to be used as phytoremediation species. The experiment was installed in a 2×5 factorial scheme, with the first factor being two species (Allophylus edulis and Inga marginata), and the second factor: five concentrations of Zn (2, 75, 150, 225, and 300 μM), with three replications per treatment. Each sampling unit consisted of a pot with five plants. Photosynthetic, morphological variables of the shoot and root systems, chlorophyll a fluorescence, photosynthetic pigments, antioxidant enzyme activity, lipid peroxidation, hydrogen peroxide concentration, and Zn accumulated in the roots and shoot were evaluated. Zn stress has activated an efficient antioxidant system, which reduced oxidative damage in the leaves of both species; consequently, it did not decrease shoot biomass production in Inga marginata and Allophylus edulis seedlings. High Zn accumulation in plant tissues and lack of negative effects on Inga marginata and Allophylus edulis shoot have suggested that these plant species are tolerant to Zn and may be indicated for Zn-polluted soil phytoremediation purposes.

Assessment of the Relationship Between Humic Acid Contents and Trace Elements of Some Agricultural Soils in Diyarbakır Region by Multivariate Statistical Methods

There are important relationships between humic acid (HA) and the bioavailability, reactions and mobility of trace elements in the soil. For this reason, soils are tried to be improved chemically, biologically and physically with HA applications. In this study, the relationship of humic acid contents of 118 agricultural soil samples from Diyarbakır region with some trace elements (Al, As, Ba, Be, Cd, Fe, Mn, Pb, Sb, Sn, Se, V and P) was evaluated by multivariate statistical analysis. After the soil samples were solubilized by the microwave wet digestion method, the element contents were determined with the ICP OES (Inductively Coupled Plasma Optical Emission Spectrometer) device. SRM NIST 2586 was used as SRM (Standard Reference Material) for the accuracy of the method. Recovery values were found between 91.6% and 105.9% as a result of the analysis. Humic acid was extracted from soils by the International Society for Humic Substances (IHSS) method and determined using a shaker and centrifuge device. For the accuracy of the method, it was tested with Humic Acid Sodium Salt (HA-Na). Pearson correlation and partial correlation analysis were applied to the obtained data set. In addition, multivariate statistical analyses such as multiple regression HCA (Hierarchical Cluster Analysis) and PCA (Principal Component Analysis) were applied. Multiple regression analysis was performed according to the Step-wise method. Manganese and P (p&lt; 0.01) were significant when HA was taken as the dependent variable. According to the Pearson correlation coefficient, the correlation between HA and As (r = -0.282**) in soil was negative and significant, while Fe (r = 0.185*), Mn (r = 0.273**)), Sn (r = 0.242*), Se (r = 0.325**) and P (r = 0.315**) were determined as positive and significant. In clustering and PCA analysis, HA, P Mn and Fe were found to be in the same group. The analyses have shown that HA has a positive effect on the plant nutrients in the soil.

Source analysis and contamination evaluation of potentially toxic elements in soil in typical high geological background areas at the county scale in northeastern Yunnan, China

The pollution risk of potentially toxic elements (PTEs) in soil is a common concern in the fields of environmental science and agriculture. The spatial distribution characteristics, pollution risk assessment and genetic sources of PTEs in soil in high geological background areas are crucial to the safe use of land. Based on the data for five PTEs in 921 surface soil samples from typical high geological background areas in SW China, we discuss their spatial distribution characteristics using geostatistics, the semivariance function and its model. We carry out pollution risk assessment using the influence index of comprehensive quality (IICQ) and analyse their genetic sources using the UNMIX receptor model. The spatial distribution of element content has a high spatial coupling with the stratigraphic spread, which is affected by external random factors, resulting in a weakened autocorrelation. The IICQ indicates that soil is dominated by mild and moderate pollution, accounting for 42.24 and 44.95%, respectively, with cadmium contributing up to 63.00% to the IICQ. Chromium and cadmium are controlled by natural sources, accounting for 83.98 and 69.39%, respectively. Arsenic and mercury have anthropogenic sources, accounting for 68.7 and 44.0%, respectively. Lead is controlled by both lead–zinc mining and geological background, accounting for 47.7 and 36.4%, respectively. The UNMIX model demonstrates that the spatial variability of PTEs is influenced by anthropogenic factors, such as coal combustion emissions, which account for 30.1% of the pollution sources. Soil parent material sources contribute 49.4%, followed by lead–zinc mining and smelting activities at 20.5%.

Risk Assessment of Toxic Elements in Surface Soils Collected Near and Far from a Deactivated Lead Smelter in Bahia, Brazil

Twenty-eight surface soil samples were collected in Santo Amaro, Brazil, to evaluate the current environmental impact caused by a lead smelter that operated in this city from 1960 to 1993. The smelter was deactivated after causing deaths and irreversible adverse effects on the health of the population due to contamination by lead and other elements. In this context, lead, cadmium, arsenic, chromium, copper, and zinc, six of the seven elements recommended by Hakanson in 1980 for ecological risk assessment, were determined using inductively coupled plasma – optical emission spectrometry (ICP OES). The contamination factor (CF), ecological risk index (Er), pollution load index (PLI), degree of contamination (mCdeg), and potential ecological risk index (PERI) were used to investigate the level of contamination and the ecological risk of the samples. The CF index demonstrated that the samples collected inside the smelter showed high contamination for lead, cadmium, and zinc, low contamination for chromium, and low to moderate contamination for arsenic and copper. In addition, the integrated PLI index demonstrated that all samples collected inside the foundry showed high pollution; however, of the other twenty-two samples investigated, only two showed pollution. The ecological risk index showed that the soil samples collected inside residences near the foundry denoted ecological risk due to cadmium contamination. The PERI demonstrated that samples collected on the city’s access road and samples collected on streets close to the foundry denoted low ecological risk. The results obtained by applying the principal component analysis (PCA) and hierarchical cluster analysis (HCA) to data relating to the levels of chemical elements in the soil samples fully corroborate the results found using toxicological assessment indices.

Effects of plant growth-promoting rhizobacteria on blueberry growth and rhizosphere soil microenvironment.

Plant growth-promoting rhizobacteria (PGPR) have a specific symbiotic relationship with plants and rhizosphere soil. The purpose of this study was to evaluate the effects of PGPR on blueberry plant growth, rhizospheric soil nutrients and the microbial community. In this study, nine PGPR strains, belonging to the genera Pseudomonas and Buttiauxella, were selected and added into the soil in which the blueberry cuttings were planted. All the physiological indexes of the cuttings and all rhizospheric soil element contents were determined on day 6 after the quartic root irrigation experiments were completed. The microbial diversity in the soil was determined using high-throughput amplicon sequencing technology. The correlations between phosphorus solubilization, the auxin production of PGPR strains, and the physiological indexes of blueberry plants, and the correlation between rhizospheric microbial diversity and soil element contents were determined using the Pearson's correlation, Kendall's tau correlation and Spearman's rank correlation analysis methods. The branch number, leaf number, chlorophyllcontentand plant height of the treated blueberry group were significantly higher than those of the control group. The rhizospheric soil element contents also increased after PGPR root irrigation. The rhizospheric microbial community structure changed significantly under the PGPR of root irrigation. The dominant phyla, except Actinomycetota, in the soil samples had the greatest correlation with phosphorus solubilization and the auxin production of PGPR strains. The branch number, leaf number, and chlorophyllcontent had a positive correlation with the phosphorus solubilization and auxin production of PGPR strains and soil element contents. In conclusion, plant growth could be promoted by the root irrigation of PGPR to improve rhizospheric soil nutrients and the microenvironment, with modification of the rhizospheric soil microbial community. Plant growth could be promoted by the root irrigation of PGPR to improve rhizospheric soil nutrients and the microenvironment, with the modification of the rhizospheric soil microbial community. These data may help us to better understand the positive effects of PGPR on blueberry growth and the rhizosphere soil microenvironment, as well as provide a research basis for the subsequent development of a rhizosphere-promoting microbial fertilizer.

Estimating the Heavy Metal Contents in Entisols from a Mining Area Based on Improved Spectral Indices and Catboost.

In the study of the inversion of soil multi-species heavy metal element concentrations using hyperspectral techniques, the selection of feature bands is very important. However, interactions among soil elements can lead to redundancy and instability of spectral features. In this study, heavy metal elements (Pb, Zn, Mn, and As) in entisols around a mining area in Harbin, Heilongjiang Province, China, were studied. To optimise the combination of spectral indices and their weights, radar plots of characteristic-band Pearson coefficients (RCBP) were used to screen three-band spectral index combinations of Pb, Zn, Mn, and As elements, while the Catboost algorithm was used to invert the concentrations of each element. The correlations of Fe with the four heavy metals were analysed from both concentration and characteristic band perspectives, while the effect of spectral inversion was further evaluated via spatial analysis. It was found that the regression model for the inversion of the Zn elemental concentration based on the optimised spectral index combinations had the best fit, with R2 = 0.8786 for the test set, followed by Mn (R2 = 0.8576), As (R2 = 0.7916), and Pb (R2 = 0.6022). As far as the characteristic bands are concerned, the best correlations of Fe with the Pb, Zn, Mn and As elements were 0.837, 0.711, 0.542 and 0.303, respectively. The spatial distribution and correlation of the spectral inversion concentrations of the As and Mn elements with the measured concentrations were consistent, and there were some differences in the results for Zn and Pb. Therefore, hyperspectral techniques and analysis of Fe elements have potential applications in the inversion of entisols heavy metal concentrations and can improve the quality monitoring efficiency of these soils.

Macro-microscopic mechanical behavior of geogrid reinforced calcareous sand subjected to triaxial loads: Effects of aperture size and tensile resistance

Reinforcing calcareous sands with geogrids is a potentially effective method for large-scale geotechnical constructions in coastal lands. The breakable nature of polygonal calcareous sands determines the complex particle-geogrid interactions. A three-dimensional numerical model of geogrid reinforced calcareous sand (GRCS) was established to investigate the potential mechanical laws based on the discrete element method (DEM), and the reasonableness of the numerical model was verified by comparing with the indoor triaxial test. It follows that the macro-microscopic mechanical behavior of GRCS under the influence of aperture size and tensile resistance of geogrids was further investigated via effective DEM simulations. The presented results show that the decreased aperture size and increased tensile resistance are beneficial to enhance the macro-mechanical properties of GRCS, including strength, internal friction angle and pseudo cohesion. Particle crushing is mainly affected by shear strain and confining pressure. The bulging deformation of GRCS is partially suppressed due to the confining effect of geogrids. Besides, the source of strength enhancement of GRCS is revealed based on the microscopic particle-geogrid interactions, and the calculation method of horizontal and vertical additional stresses in the reinforced soil element considering the effects of tensile resistance and aperture size is further established.

Temporal effective stress response of soil elements below the base of an excavation in sensitive clay

Investigations into the temporally evolving stress state below the base of excavations and underground structures are very scarce, in contrast to studies of horizontal earth pressures during the construction stage. Therefore in this work, the measured temporal response in terms of vertical and horizontal effective stresses and displacements below a tunnel slab at the base of an excavation located in a deep sensitive clay deposit is reported. In addition to the measured unloading response over time, the completeness of the site description and complementary measurements enables future benchmarking of numerical models at boundary and element level. Instrument clusters of earth pressure cells and piezometers were installed at three locations in one cross-section. The monitoring data allows the interpretation of effective stress paths and stress ratios, &lt;i&gt;K&lt;/i&gt;=σ'&lt;sub&gt;h&lt;/sub&gt;/σ'&lt;sub&gt;v&lt;/sub&gt;, at soil element level covering the construction and the serviceability stages. The in situ stress ratios enable a unique comparison to prior laboratory studies of &lt;i&gt;K&lt;/i&gt; during unloading. The data presented herein on the evolution of &lt;i&gt;K&lt;/i&gt; corroborate, although approximately, previous studies at laboratory scale. Furthermore, at system level, the monitoring data reveal the intricate interplay between deformations resulting from excavation and pile driving.

Risk Assessment and Attribution Analysis of Potentially Toxic Elements in Soil of Dongdagou, Baiyin, Gansu Province, China

Analyzing the cause is crucial for recognizing the risks associated with potentially harmful substances found in soil, such as toxic elements. These substances can have adverse effects on both the ecological environment and human health, as they can migrate and transform within food chain networks. Therefore, it is imperative to address and prioritize the risks associated with these elements. Dongdagou, Baiyin City, Gansu Province, is a typical area of potentially toxic element pollution in farmland soil, which has attracted much attention and urgently needs to be controlled. Therefore, the main objective of this investigation is to analyze the concentrations of As, Cd, Pb, Hg, Cu, and Zn in the agricultural soil found in Dongdagou. Using statistical analysis, ecological and human health risk, principal component analysis, and the PMF model, we found that (1) there are varying degrees of accumulation in the soil in the study area, with Cu being the main component. (2) The soil in the study area has high and extremely high concentrations of Cd, posing significant risks. On the other hand, Hg presents mild and medium risks. However, there are no risks associated with As, Pb, Cu, and Zn. Overall, the ecological risks in the study area’s soil due to potentially toxic elements are predominantly extremely high (49.65%) and high (38.25%). A small proportion of the soil exhibits low risks (2.76%) and medium risks (9.33%). (3) As has a moderate acceptable carcinogenic risk for local residents, Cd has a moderate acceptable carcinogenic risk for local children, and other potentially toxic elements do not have carcinogenic or non-carcinogenic risks. (4) The source analysis shows that Cd in the soil in the study area mainly comes from agricultural activities and sewage irrigation, As mainly comes from industrial production, and Zn, Cu, Pb, and Hg are multiple sources. We recommend adopting targeted and differentiated safety utilization and control measures based on the pollution level and potential risks of potentially toxic elements in the research area, combined with the sources of potentially toxic elements.