Soil Components Research Articles

Scheffe's Polynomial Optimisation of Laterite Concrete Incorporating Periwinkle Shells and Coir

Recent emphases on minimising the carbon footprint of concrete have focused on the use of non-conventional materials for the production of low-cost concrete. Such materials include laterite, periwinkle shells and coir which have been reported as suitable for use as fine and coarse aggregate replacements in specified proportions. However, the use of two or more unconventional materials in a concrete mix would require significant experimental effort that is time- and resource-consuming and usually performed by trial and error to determine the optimum mix design. A popular optimisation technique used for concrete mix design is Scheffe's second-degree polynomial modelling. However, the application of a more accurate Scheffe's third-degree polynomial optimisation technique in designing cementitious composites incorporating unconventional aggregates is rare. This study, therefore, presents the use of Scheffe's third-degree model to determine the optimum proportions of coir, laterite and periwinkle shell aggregates in a concrete mix in order to obtain the best mechanical properties of the hardened concrete. The constituents of the concrete were optimised for seven components of water, cement, fine-aggregate, laterite soil, coarse aggregate, periwinkle shell and coir on an N(7, 3) Sheffe's factor space. The optimal mix ratio for compressive and flexural strengths of 11.33 and 1.20 MPa, respectively, was 0.5149, 1.044, 3.009, 0.126, 3.934, 0.054, and 0.0046 for pseudo-components Xi: {∀i = 1, 2 3, 4, 4, 6, 7}. The coefficients of determination (R2) were 98.74% and 98.53% for the compressive and flexural response models, respectively, while the p-values obtained for the response coefficient fit parameters βi, βij, βijk for (i = 1, 2, 3, 4, 5, 6, 7) were 96.77% and 91.49% for the compressive and flexural strength models, respectively. The optimised Low-Performance Concrete (LPC) is about 4% cheaper than LPC made from conventional aggregates and is adequate for patio slabs, pedestrian footpaths, kerbs, and floorings in residential buildings. The use of Sheffe's third-degree model eliminates the significant experimental efforts needed in the design of concrete mixes incorporating unconventional aggregates.

Research on irregular plane mid story isolation structures in castor earthquake prone areas considering SSI effect

The rock composition of karst area is mainly limestone, which is easy to be eroded and dissolved by water, forming a complex and fragile tectonics. Under the action of earthquake, the instability of stratum is aggravated. The mid story isolation structure is a new type of isolation structure developed from the basic isolation structure, and irregular mid story isolation buildings are highly susceptible to adverse seismic conditions. Previous studies have mostly adopted the assumption of rigid foundations, neglecting the influence of soil on irregular structures. In order to study the seismic response of isolated structures in irregular planes in karst earthquake prone areas considering soil structure interaction, a finite element model of isolated structures in irregular planes considering soil component interaction was established, and the seismic response of the structure under rigid foundation was calculated. Soft and hard soil foundations were studied, and compared with structures without considering SSI effect. Research shows that when considering the SSI effect, the seismic response of the structure increases and the damage to the structure intensifies; When considering SSI, the seismic response of soft soil is greater than that of hard soil, and the softer the soil, the more obvious it becomes; After considering the SSI effect, the torsional effect caused by the irregularity of the plane increases; The design of building structures should fully consider the adverse effects of soil layers on the seismic response of structures under plane interlayer seismic irregularities. In the design of building structures, it is necessary to fully consider the adverse effects of irregular planes on the seismic response of the structure. This consideration is particularly important in the design of soft soil high-rise buildings in karst earthquake areas to prevent unsafe designs and consider the SSI effect in actual seismic resistance.

Response of soil oxides in complex terrain region to environment revealed by hyperspectral observations

Soil oxides are important diagnostic indicators for soil quality assessment, and their content has a positive effect on adsorption of heavy metals, remediation of pollution, and enhancement of organic matter enrichment. Moreover, soil oxides are affected by multiple environmental factors such as soil pH, geomorphological, and elevation, and their distribution is highly regional. In this study, 421 ground soil samples and 2 hyperspectral satellite data were collected. The content distribution of 8 main oxides in soil, including SiO2, Al2O3, Fe2O3, MgO, CaO, Na2O, K2O, and Corg. were obtained according to the process of data preprocessing, spectral transformation, feature extraction, band combination, and model establishment. The results indicated that the homogenization spectral transformation method is the most suitable; The calculation accuracy of complex spectral characteristic parameters is inferior to that of characteristic bands; The difference model is more suitable for the extraction of soil oxide content in this study area; The average content of SiO2 and CaO shows a decreasing trend with the elevation increasing; The average content of SiO2 and Fe2O3 shows an upward trend with the increase of slope; East is the main geomorphic direction of soil oxide enrichment. SiO2, Al2O3, and MgO are the three soil oxides with the highest correlation. The response relationship between soil oxides, topography and pH is discussed, and the distribution rule of soil oxides and environmental determinants are obtained, which provides a set of technical schemes for digital soil research. This study can extract the content of soil components in a large area, analyze the causes, and provide a new technical scheme for soil investigation and treatment.

Carbon Sequestration Strategies in Soil Using Biochar: Advances, Challenges, and Opportunities.

Biochar, a carbon (C)-rich material obtained from the thermochemical conversion of biomass under oxygen-limited environments, has been proposed as one of the most promising materials for C sequestration and climate mitigation in soil. The C sequestration contribution of biochar hinges not only on its fused aromatic structure but also on its abiotic and biotic reactions with soil components across its entire life cycle in the environment. For instance, minerals and microorganisms can deeply participate in the mineralization or complexation of the labile (soluble and easily decomposable) and even recalcitrant fractions of biochar, thereby profoundly affecting C cycling and sequestration in soil. Here we identify five key issues closely related to the application of biochar for C sequestration in soil and review its outstanding advances. Specifically, the terms use of biochar, pyrochar, and hydrochar, the stability of biochar in soil, the effect of biochar on the flux and speciation changes of C in soil, the emission of nitrogen-containing greenhouse gases induced by biochar production and soil application, and the application barriers of biochar in soil are expounded. By elaborating on these critical issues, we discuss the challenges and knowledge gaps that hinder our understanding and application of biochar for C sequestration in soil and provide outlooks for future research directions. We suggest that combining the mechanistic understanding of biochar-to-soil interactions and long-term field studies, while considering the influence of multiple factors and processes, is essential to bridge these knowledge gaps. Further, the standards for biochar production and soil application should be widely implemented, and the threshold values of biochar application in soil should be urgently developed. Also needed are comprehensive and prospective life cycle assessments that are not restricted to soil C sequestration and account for the contributions of contamination remediation, soil quality improvement, and vegetation C sequestration to accurately reflect the total benefits of biochar on C sequestration in soil.

Ciprofloxacin sorption to purple soil: Potential mechanisms and factors influencing sorption

Understanding ciprofloxacin (CIP) sorption behavior onto purple soil is essential to minimize the associated environmental risks. However, CIP sorption onto the different components of purple soil and its underlying mechanisms are poorly understood. We performed a sorption experiment using original purple soils (Dayi soil (DORI) and Ya'an soil (YORI)), soils without dissolved organic matter (DOM) (DIOM and YIOM: insoluble organic matter remaining), and soils without organic matter (OM) (DM and YM: minerals remaining) to explore the CIP sorption behavior. Compared with DORI and YORI, the CIP sorption capacity of DM and YM decreased by 67.1% and 75.7%, indicating that the CIP sorption capacity was mainly contributed by OM. Compared with DORI and YORI, the CIP sorption capacity of DIOM and YIOM increased by 17.1% and 12.6%, suggesting that DOM in soil affected CIP sorption in purple soil. Redshifts and blueshifts confirmed that H-bonds and π-π interaction dominated the CIP sorption onto OM. CIP sorption was fitted by the Langmuir model, indicating monomolecular sorption. Compared with DORI and YORI, the KL of DM and YM was higher, implying that CIP sorption was faster and easier on minerals than on OM. Compared with K+, Ca2+ had a stronger hydration capacity but lower CIP sorption capacity in DM, suggesting that the stronger hydration capacity of cations was not conducive to CIP adsorption onto minerals and proving that the hydrophobic effect drove CIP adsorption. These mechanistic insights have important implications for understanding CIP sorption in purple soil.

Effects of Nature-Based Multisensory Stimulation on Pain Mechanisms in Women with Fibromyalgia Syndrome: A Randomized Double-Blind Placebo-Controlled Trial

BackgroundThe term “nature-based sensory stimuli” refers to the sensory information produced by biotic and abiotic agents from natural environments. The literature has reported the beneficial effects of these agents on various pain dimensions in non-clinical populations. AimsTo evaluate the potential analgesic effects of nature-based multisensory stimulation in women with fibromyalgia syndrome. MethodsA randomized, double-blind, placebo-controlled, parallel-group trial with a 1:1 allocation ratio was conducted. Forty-two women with fibromyalgia syndrome interacted with either different plant species with flowers, stones, and soil organic matter or their synthetic imitations for 30 minutes. Outcome measurements were performed before and after the intervention, including clinical pain intensity using the Numeric Rating Scale, cold pain thresholds using the Cold Pressor Test, mechanical hyperalgesia and wind-up using a monofilament, and pressure pain thresholds using a pressure algometer. ResultsAnalyses revealed group × time interactions for clinical pain intensity (F = 7.915, p = .008), cold-water immersion time (F = 7.271, p = .010), mechanical hyperalgesia (F = 4.701, p = .036), and pressure pain threshold (p ≤ .017). Between-group differences were found in clinical pain intensity (p = .012), cold pain thresholds (p = .002), and pressure pain thresholds (p < .05). The experimental group exhibited reduced clinical pain intensity (p = .001) and increased pressure pain thresholds (p ≤ .034). ConclusionsWomen with fibromyalgia syndrome may benefit from multisensory stimulation using biotic and abiotic agents from natural environments for 30 minutes. Interacting with flowering plants and soil components appears to induce analgesic effects.

The features of Cs sorption onto peaty-podzolic-gleyic soil

This article studies sorption regularities and estimates the strength of 137Cs fixation by various soil horizons in peaty-podzolic-gleyic soils under a model experiment. The interaction time varied from 1 week to 3 months while Cs concentration varied from trace to micromolar concentrations. To understand the interaction mechanisms of cesium with individual soil components, we used the method of sequential removal of organic matter and non-silicate iron compounds from the soil before the sorption experiment.Illite and vermiculite were found to be the main soil components for radiocesium sorption in the mineral soil horizons. The highly selective positions (FES – frayed edge sites) of the abovementioned minerals fixed radiocesium so strongly that even strong acid solutions could not extract it from soil. Organic matter significantly contributed to the fixation of radiocesium in the soil only in the ELih horizon which contained 4.71% Corg. In the ELg horizon, a small amount of organic matter was able to inhibit sorption by blocking highly selective to radiocesium FES. The Tessier sequential extraction method of radiocesium revealed that all the studied soil samples could strongly fix the radionuclide. Increasing the interaction period up to three months under periodic wetting and drying contributed to the increased proportion of strongly bound 137Cs. The results of sorption experiments carried out before and after the removal of non-silicate iron compounds from the soil indicate that 137Cs has little or no sorption on the surface of iron hydroxides.

A novel semi-empirical soil multi-factor radiative transfer model for soil organic matter estimation based on hyperspectral imagery

Soil organic matter (SOM) concentration is an important factor affecting soil quality, and rapid and wide-scale monitoring of SOM concentration is a key step toward sustainable agriculture. Hyperspectral technology is widely used in soil composition monitoring, due to its rich spectral information. The complex imaging environment of hyperspectral imagery and the mixed pixel problem have led to the current applications of soil condition estimation mostly using data-driven methods. However, the estimation process based on data-driven methods cannot be explained by radiative transfer theory. Therefore, in this paper, a semi-empirical soil multi-factor radiative transfer (SESMRT) model combining a soil radiative transfer model and data-driven model is proposed for SOM estimation based on hyperspectral imagery. The radiative transfer model in the SESMRT model fully considers the soil components, such as SOM, soil moisture, soil iron oxides, and particle size distribution, and achieves high-precision simulation of soil spectra by resolving the mechanism of the influence of soil components on spectra. The SOM spectra calculated by the radiative transfer model are then used to estimate the SOM concentration based on a data-driven model. The SOM spectra eliminate the interference of other factors in the spectrum and significantly enhance the correlation between the spectrum and SOM. Thus, the SOM concentration can be estimated with a high degree of accuracy (R2 = 0.660 ± 0.034, RMSE = 3.923 ± 0.236, RPIQ = 2.003 ± 0.118 for GF5 and R2 = 0.685 ± 0.030, RMSE = 3.543 ± 0.311, RPIQ = 2.309 ± 0.207 for HyMap). Finally, the comparison of the estimated results for 2017 and 2019 shows that the SOM concentration of the cultivated soils in the study area increased, while the opposite is observed for the soils around the mining areas.

Theoretical calculation model for the thermal conductivity of scrap tire rubber–sand mixtures based on soil components

Theoretical calculation model for the thermal conductivity of scrap tire rubber–sand mixtures based on soil components

Spatiotemporal Variability in Soil Properties and Composition in Mangrove Forests in Baía de Todos os Santos (NE Brazil)

Soil properties and components in mangrove ecosystems influence their geochemical processes and services. Despite the extensive mangrove areas present in Brazil, few studies focusing on these themes are under development. In this sense, this work aimed to investigate the spatial variability in soil attributes and composition, the geochemistry of Fe, and the isotopic characteristics of organic matter in mangroves in Baía de Todos os Santos (Cacha Prego, Ponta Grossa, Ilha de Maré, Pitinga), which constitutes Brazil’s second largest bay. The soils investigated showed spatial and temporal changes affecting their properties (pH, Eh) and composition (TOC, Fe fractions), as well as clear spatial changes in the redox potential values (+30–+188 mV), with higher values in PT. Soil textures ranged from predominantly sandy (CP, PT, PG: sand, &gt;70%) to a finer granulometry (IM: sand, 33–64%). These characteristics influenced Fe partitioning and organic matter content, with higher TOC and pyrite values observed in IM (FeS2: 2720–9233 mg kg−1; TOC: 4.4–6.6%) and lower sulfide values found in PT, mainly in the dry season (FeS2: 85–235 mg kg−1). The soil δ13C and N/C ratios seem to suggest a mixed origin of organic matter.

Fecal antibiotic resistance genes were transferred through the distribution of soil-lettuce-snail food chain.

Massive antibiotic resistance genes (ARG) were detected in the soil modified by manure, which may affect human life safety through the food chain. However, the transmission of ARGs through the soil-plant-animal food chain is still unclear. Therefore, this study used high-throughput quantitative PCR technology to explore the effects of pig manure application on ARGs and bacterial communities in soil, lettuce phyllosphere, and snail excrement. The results showed that a total of 384 ARGs and 48 MEGs were detected in all samples after 75days of incubation. The diversity of ARGs and MGEs in soil components increased significantly by 87.04% and 40% with the addition of pig manure. The absolute abundance of ARGs in the phyllosphere of lettuce was significantly higher than that of the control group, with a growth rate of 212.5%. Six common ARGs were detected between the three components of the fertilization group, indicating that there was internal transmission of fecal ARGs between the trophic levels of the food chain. Firmicutes and Proteobacteria were identified as the dominant host bacteria in the food chain system, which were more likely to be used as carriers of ARGs to promote the spread of resistance in the food chain. The results were used to assess the potential ecological risks of livestock and poultry manure. It provides theoretical basis and scientific support for the formulation of ARG prevention and control policies.

Phenylalanine-mediated changes in the soil bacterial community promote nitrogen cycling and plant growth

Soil amino acids (AAs) are the most active components of soil N, which can be mineralized or absorbed by bacteria as N and C sources. We hypothesized that exogenous AAs could regulate the bacterial community and affect soil N cycling, and the effect sizes could vary depending on individual AAs. Here, we applied feather (keratin)-based compost rich in AAs to Poncirus trifoliata (L.) to evaluate the regulation of bacterial community by AAs; furthermore, we applied six individual AAs to test their effects. The compost significantly increased soil hydrolysable AA content, ammonia monooxygenase gene abundance, and plant growth and changed bacterial community structure. Redundancy analysis revealed that the effects of AAs on the bacterial community composition were greater than those of soil chemical properties, and phenylalanine (Phe) was the most effective among thirteen individual AAs. When applied individually, Phe caused the greatest increase in N cycling-related enzyme activity and plant growth and most significantly altered the bacterial community structure among the six exogenous AAs. Notably, Phe significantly increased the relative abundances of Burkholderia-Caballeronia-Paraburkholderia, Azospirillum, Cupriavidus, and Achromobacter, whose abundances were significantly positively correlated with plant biomass, and significantly reduced the relative abundances of Arachidicoccus, Pseudopedobacter, Sphingobacterium, and Paenibacillus, whose abundances were significantly negatively correlated with plant biomass. We demonstrate that soil AAs strongly shape the bacterial community. Particularly, Phe enhances N cycling and plant growth by increasing the potentially beneficial bacterial taxa and inhibiting the potentially harmful bacterial taxa, which needs further validation.

Mineral-organic interactions drive the aging and stabilization of exogenous Pb in soils

The interactions of soil components have profound impacts on the speciation, bioavailability and transformation of heavy metals. However, these interactions have not been well included in multi-surface model (MSM) as most of the models adopt component additive method. Here, an incubation experiment was conducted with three contrasting soils spiked with 200 mg/kg Pb and rice straw to investigate the impact of mineral-organic interactions on Pb speciation and to validate the MSM for Pb in soils. With the aid of chemical extraction and instrumental analysis (XANES and SEM-EDS), the results show that metal oxides and soil organic matter are the main scavengers for Pb, accounting for the stabilization of exogenous Pb by ∼ 40% − 80% and ∼ 13% − 30%, respectively. The accumulation of the most stable residual Pb was driven by Fe/Al oxides, which was fostered by organic matter through the formation of amorphous Fe/Al oxides. Unexpectedly, the introduction of straw promoted the activation of metal oxides and the competition from Fe/Al/Ca ions reduced the binding of Pb by soil organic matter. Simulation of organic-Fe/Al/Ca interactions largely improved the accuracy of the MSM model results for the prediction of Pb speciation distribution. Overall, this study highlights that mineral-organic interactions play important role in the stabilization of exogenous Pb in soils, while incorporate of these interactions into MSM is recommended in future heavy metal studies.

The Physicochemical Properties and Microbial Populations of Nicosulfuron Treated Soil in Yola, Adamawa State, Nigeria

The use of herbicides in the modern system of farming has really help in boosting crop production, this way meeting up with the ever increasing demand for food by the always increasing human population. However, these herbicides have different mode of actions and effect on soil components; and their continued usage has affected the soil microbial communities and other soil components most of which are the non-target. This study, therefore, was focused on evaluating the physicochemical properties and microbial population of nicosulfuron treated soils of Yola, Adamawa State, Nigeria. The study was carried out in both 2021 and 2022 in the Research Farm of the Department of Plant Science, Modibbo Adama University, Yola. The samples of the soil treated with the different concentrations of nicosulfuron were obtained at 0, 2, 4 and 6 Weeks after Treatment (WAT) at the depth between 0-12 cm. The physicochemical properties and the bacterial and fungal populations of the collected soil samples were determined using standard laboratory procedures. The results revealed that the soils treated with the 50, 100, 150 and 200 g/ha concentrations of nicosulfuron had a comparable values for physicochemical (except percentage moisture content, organic carbon and matter and total nitrogen) properties that include: pH, electrical conductivity, Calcium, magnesium and potassium ions, total exchangeable acidity, total exchangeable base, effective cation exchange capacity, percentage base saturation. On the basis of duration of application, however, the nicosulfuron had significant effect on the physicochemical properties with 6 WAT having the highest values for the physicochemical properties compared to other sampling durations. On the bacterial (except the fungal) population, the nicosulfuron also had a significant effect with the treated soils having the lowest populations of both bacteria and fungi. The study therefore, concluded that the duration of application of nicosulfuron have significant effect on physicochemical properties of soil in Yola. On the bacterial and fungal populations of the soil, nicosulfuron also had significant effect.

Interfacial interactions controlling adsorption of metal cations on montmorillonite

Abstract Montmorillonite (Mt) is a ubiquitous swelling clay mineral and major component of soft rocks, sediments, and soils with an inherent capability to sorb metal cations. This unique feature renders Mt important for the enrichment and mobilization of environmentally important metal cations, retardation of heavy metals and radionuclide ions, the evolution of clay mineral itself, soils and sediments, and other geological processes. Understanding the interfacial interactions of Mt with metal cations at the molecular level is of fundamental importance in all these processes, but still remains elusive, due to the chemical and structural complexity of Mt surfaces and the diverse chemistries of metal cations. In this Review, we aim to provide the reader with a comprehensive overview of the adsorption modes of metal cations on basal and edge surfaces of Mt, local chemical environments of the cation binding sites, the driving forces for metal sorption, and factors influencing the dynamics of cation uptake onto Mt surfaces. Various surface complexation models [i.e., nonelectrostatic model (NEM), constant capacitance model (CCM), diffuse layer model (DLM), and triple-layer model (TLM)], advanced spectroscopic techniques (i.e., NEM, CCM, DLM, and TLM), and atomistic simulation methods (i.e., MD, DFT, and FPMD) have been used in conjunction with macroscopic adsorption experiments to gain detailed insights into the interfacial interactions of metal cations on Mt. Mt adsorbs metal cations via three independent pathways: (1) cation exchange; (2) surface complexation; and (3) nucleation and surface precipitation. The principal driving force for cation exchange is electrostatic interaction, while chemical bonding governs the two other mechanisms that depend on the basal and edge surface properties of Mt. The siloxane cavities on the tetrahedral basal plane exhibit the strongest adsorption sites for cation exchange and are greatly affected by the the degree of Al3+/Si4+ tetrahedral substitutions. At the amphoteric edge surfaces bearing hydroxyl groups, metal cations could form mono/multiden-tate surface complexes on Mt [010] and [110] edges. Ionic strength, pH, the presence of competing cations, temperature, and layer charge have been shown to affect the adsorption mechanisms and quantity of adsorbed cations. The updated information on the interfacial interactions of metal cations with Mt basal and edge surfaces presented in this review provides an improved understanding of the enrichment of metals, formation of metal ores, and natural biogeochemical cycles, as well as may promote technological and engineering applications of this important clay mineral in environmental remediation, geological repository, petroleum exploration and extraction, and extraterrestrial research.

Modeling the Genetic Components of the Water and Chemical Runoff of Heavy Metals in the Basin of the Nizhnekamskoe Reservoir

A semi-distributed physical-mathematical model ECOMAG-HM is used to simulate the genetic structure of water and chemical runoff of copper, zinc, and manganese in a large river basin of the Nizhnekamsk Reservoir. The model was tested against long-term data of hydrological and hydrochemical monitoring of water bodies. The contributions of the surface, soil, and subsoil components of the water and chemical runoff of metals are estimated for different segments of river network. It was found that, in the major portion of the catchment, river pollution by metals is mostly due to their diffuse washout from the soil layer. The effect of the genetic structure of water and chemical runoff on the year-to-year and seasonal variations of metal concentrations in the river network is demonstrated.

Laterite soil stabilization using cellulose biopolymer

Laterite soil stabilization is a promising technique that aims to enhance the engineering properties of this naturally occurring soil, Cellulose are one of the potential bio-polymer stabilizers that have been widely employed. The effectiveness of Cellulose (CL) biopolymer in stabilizing laterite soil is shown in this study. In various proportions of 0%, 1%, 2%, 3%, and 4% by dry soil mass, cellulose biopolymer is treated with laterite soil. The engineering parameters of soils treated with cellulose biopolymer were determined using modified proctor tests, direct shear tests, and CBR tests. The treated soil's dry density increases slightly up to 3% cellulose content, but the optimum moisture content decreases. The addition of cellulose biopolymer greatly increased the strength and cohesiveness of laterite soil mixtures. The CBR value increases with increasing the cellulose dose up to 3%; however, with addition of dose, the CBR value decreases slightly in both soaked and unsoaked conditions. The examination of the microstructure through field emission scanning electron microscopy (FESEM) examinations revealed the emergence of novel cementitious substances as a consequence of chemical interactions between cellulose and laterite soil components at the microscopic scale. These reactions led to the enhancement of soil composition by fusing soil particles and occupying the voids within the soil framework. The use of cellulose as a material for the stabilization of laterite soil is therefore a solution for an environmentally benign soil stabilizing material.

Advances in research on the use of Brevundimonas spp. to improve crop and soil fertility and for soil bioremediation

Biofertilizers or biological fertilizers maintain soil fertility by fixing atmospheric nitrogen, solubilizing P and K, producing plant growth substances and antibiotics as well as biodegradation of organic matter in the soil that enriches the root rhizosphere. Microbial biofertilizers are eco-friendly and less expensive alternatives to chemical fertilizers. The key components of healthy soil are populations of plant growth promoting rhizobacteria (PGPR) which play multiple beneficial and ecological roles in the rhizosphere soil. PGPR colonizes rhizosphere or plant roots, resulting in phytostimulation, biofertilization and biocontrol either directly and/or indirectly. Another important role of PGPR is its ability to decontaminate soils through a process called soil bioremediation. Recently, the known rhizobacteria environmentally friendly biofertilizers for sustainable agriculture are those belonging to Brevundimonas spp., which play a significant role in improving crop production and soil health

Experiments and geochemical modelling of arsenic interaction with clay-dominated soil from Rupnagar district of Punjab, India

The present study investigates the interaction of the soil in Garhbaga village, located in the Rupnagar district of Punjab, India for As(V) adsorption under the influence of pH, contact time and varying arsenic concentrations. To understand the geochemical controls of arsenic mobilization in the region, batch sorption experiments were performed using soil obtained from arsenic contaminated district of Punjab. This study presents a novel approach by employing surface complexation models (SCMs) to investigate arsenic adsorption onto natural soils in the Punjab region, which has not been explored in previous literature. Furthermore, a comparison between Fe-based models, assuming ferrihydrite binding, and general composite (GC) approach, assuming adsorption on soil component surfaces, has not been conducted before, adding to the originality of this research. The adsorption kinetic experiment indicates about 70% adsorption of As(V) in about 4 h. The results of batch isotherm experiment shows that As(V) adsorption saturation onto the soil is reached at an aqueous concentration of about 0.89 mgL−1. The results of the pH edges study shows a maximum As(V) adsorption of 93.88% at a pH of 4. The Langmuir’s isotherm was the best fitted because the value of linear regression coefficient (R2 = 0.997) which verifies the monolayer adsorption of As(V). It was observed that the pseudo first order model best fitted for explaining the kinetic of As(V) adsorption onto the soil because it showed higher value of linear regression coefficient (R2 = 0.995). Further, three different diffused layer models under varied assumptions were used to capture the batch experimental results. The surface complexation model with general-composite (GC) approach fairly predicted the experimental results when compared to Fe-oxide based models. The GC model was able to capture the observed experimental results for adsorption isotherm and pH edges for the soil within reasonable RMSE of 6.22 % and 7.97 %, respectively.

Chemical Stoichiometry and Enzyme Activity Changes during Mixed Decomposition of Camellia sinensis Pruning Residues and Companion Tree Species Litter

(1) Background: In managing ecological tea gardens, litter composed of pruned and fallen tea leaves from companion tree species is an important component of tea garden soil. The decomposition of litter plays a crucial role in regulating nutrient cycling in tea garden ecosystems. (2) Methods: This study employed the litterbag method to investigate chemical stoichiometry characteristics and enzyme activity changes during the decomposition process of pruned and fallen Camellia sinensis leaves from companion tree species in an ecological tea garden located in central Guizhou Province. (3) Results: With decomposition duration, the general trend of changes in the C/N and C/P ratios showed a decrease in the activity of UE (urease), AP (acid phosphatase), and PPO (polyphenol oxidase) followed by an increase, while CAT (catalase) and CEL (cellulase) activity decreased, then increased, and then decreased again. On the other hand, the N/P and the activity of SC (sucrase) first increased and then decreased. The C/N and the activities of UE, PPO, and AP generally reached their maximum values during the late decomposition stage (366–428 d), while the N/P and the CAT activity peaked during the mid-decomposition stage (305 d). In contrast, the activity of SC and CEL reached its maximum value during the early decomposition stage (123 d). The N/P ratios were significantly higher than those of the CS (C. sinensis) litter in the mixed treatment, while C/N and C/P ratios were significantly lower than those in the CS during decomposition for 184–366 days. The UE, CAT, AP, and SC activities of CBL (C. sinensis + B. luminifera) litter were significantly higher than those of the CS litter during decomposition. During the experiment, antagonistic effects were observed in the C/N and C/P ratios of the different litter types. Most mixed litter exhibited additive effects on enzyme activity, while a few showed nonadditive effects. For the nonadditive effects, most were antagonistic effects, mainly in the CPM (C. sinensis + C. glanduliferum) litter. A small portion, mainly observed in the CBL and CCG (C. sinensis + C. glanduliferum) litter, showed synergistic effects. (4) Conclusions: Selecting B. luminifera and C. glanduliferum to be part of the tree species composition in ecological tea gardens can produce positive mixed effects on enzyme activity during litter decomposition, increase nutrient return capacity, maintain tea garden fertility, and achieve the ecological development of tea gardens.