Soil Pore Research Articles

Sustainable Stabilization of Cadmium (Cd)-Contaminated Soil with Biochar-Cement: Evaluation of Strength, Leachability, Microstructural Characteristics, and Stabilization Mechanism

ABSTRACT To facilitate the solid waste reuse of cadmium (Cd)-contaminated soil and biochar and reduce the high emission of cement materials, we employed biochar-cement composite stabilizer to remedy Cd-contaminated soil. We assessed the effects of the biochar-cement composite stabilizer dosage and curing time on stabilized soil strength by using unconfined compressive strength (UCS) tests, leaching concentration and stabilization rate in Cd-contaminated soil stabilized by biochar-cement by using toxicity characteristic leaching procedure, and mechanism of change in strength and leaching characteristics by using scanning electron microscopy and X-ray diffraction. The research results demonstrate that biochar addition to cement-stabilized soil promoted cement hydration reaction and increased particle agglomeration. A low dosage of biochar improved stabilization effects. The optimal biochar dosage was 5%, which enhanced the early growth speed of the UCS. More cement improved the stabilized soil’s UCS. At a 5% cement dosage, adding biochar significantly reduced Cd leaching concentration, and improved the stabilization rate. At a 10% cement dosage, the biochar-cement composite stabilized soil’s stabilization rate was >99.8%. Calcium silicate hydrate, calcium aluminate hydrate, and ettringite were the main products of biochar-cement stabilized soil that filled soil and biochar pores; these substances encapsulated, adsorbed, or exchanged ions of Cd2+, achieving stabilization effects.

Model Modification of the Soil–Water Characteristic Curve of Unsaturated Weak Expansive Soil

This study evaluates the impact of compaction on the soil–water characteristic curve of unsaturated remodeled weakly expansive soils by assessing changes in soil pore structure resulting from variations in compaction. The remodeled weakly expansive soil in the Xinjiang Hami area is taken as the research subject to investigate how compaction affects microscopic pore structure using mercury intrusion testing. Subsequently, mercury intrusion porosimetry is employed to examine pore structure and distribution patterns at different dry densities. Based on the capillary principle and experimental methods (filter paper method and pressure plate method test), modified soil–water characteristic curves are obtained by fitting them with a three-parameter model law. The results indicate that higher dry density leads to an increased air intake value and significantly reduces the total volume of large pores within samples. Both the Fredlund and Xing model and the three-parameter model effectively capture the influence of initial dry density on the development pattern of the soil–water characteristic curve.

Soil organic carbon turnover is controlled by soil pore space O2 concentration in brown forest soil

Soil organic carbon turnover is controlled by soil pore space O2 concentration in brown forest soil

Electrodeposition of calcareous cement from seawater in marine silica sands

The erosion of marine sediments is a pressing issue for coastal areas worldwide. Established methods to mitigate coastal erosion fail to provide lasting and sustainable solutions to protect marine ecosystems. Here we demonstrate the application of mild electrical stimulations to precipitate calcareous mineral binders from seawater in the pores of marine soils via electrodeposition, an alternative approach to mitigating coastal erosion. Results of electrochemical laboratory experiments unveil that the polymorphs, precipitation sites, intrusion mechanisms, and effects of electrodeposited minerals in marine sands vary as a function of the magnitude and duration of applied voltage, soil relative density, and electrolyte ionic concentration. Surprisingly, in addition to the precipitation of calcium carbonate and magnesium hydroxide, the formation of hydromagnesite is also observed due to electrically driven fluctuations in the local pH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${pH}$$\\end{document}. These electrodeposits lead to enhanced mechanical and hydraulic properties of the marine sands, indicating that electrodeposition routes could be developed to reinforce marine soils in coastal areas that more closely mimic natural systems.

Revealing the mechanisms of water permeability enhancement of urban loess subgrades due to vibration application

Urban loess subgrades are affected by considerable vibrations from traffic, especially when the underground pipelines leak, and seepage under vibrations often causes road damage. However, the influence of vibrations on the water permeability of loess subgrades remains elusive. Here we address this issue by performing vibration-assisted permeability tests and scanning electron microscopy, mercury intrusion porosimetry, and suction–nuclear magnetic resonance measurements. This allowed the evolution of the saturated hydraulic conductivity (Ks), water-air migration, soil microstructure, and pore water forms to be evaluated. The water permeability of the loess subgrade is promoted by vibrations due to the increase in Ks, the acceleration of wet front migration, and the escape of entrapped air. Moreover, the value of Ks under vibration is 3–14 times greater than that without vibration, and the maximum increase occurs at a vibration frequency near the natural frequency of the loess. Furthermore, a theoretical framework of loess vibration permeability is proposed, and the mechanisms by which vibration accelerates the permeability behavior of the loess subgrade are revealed. Vibration promotes the expansion of soil pores, a decrease in the binding capacity of pore water, the mobilization of fine particles, and the formation of local low-permeability layer. Moreover, it accelerates the opening of entrapped air bubbles and the displacement of water-air, the reduction in seepage resistance. Thus, seepage water flows rapidly along infiltration channels. These findings are highly important for the road safety performance and the sustainable development of the traffic environment in loess regions.

In situ and on-line monitoring of cadmium in soil pore water using an automatic sampling integrated electrochemical sensor

In situ and on-line monitoring of cadmium in soil pore water using an automatic sampling integrated electrochemical sensor

Polyvinyl chloride nanoplastics transport inhibited in natural sandy soil by iron-modified biochar.

The small particle size of nanoplastics allows them to migrate through soil and make them highly bioavailable, posing a potential threat to groundwater. Measures are urgently needed to reduce the migration of nanoplastics in soil. However, there is limited research available on this topic. In this study, two types of iron-modified biochar (magnetic corncob biochar (MCCBC) and magnetic walnut shell biochar (MWSBC)) were selected and their effects on the transport of polyvinyl chloride nanoplastics (PVC-NPs) in natural sandy soil columns under different ionic types and strengths were investigated. The results show that the transport of PVC-NPs in single sandy soil columns was rapid and efficient, with the estimated breakthrough rate of 85.10%. However, the presence of MCCBC and MWSBC (0.5%, w/w) significantly inhibited the transport of PVC-NPs in sandy soil columns (p < 0.05), and MCCBC had a stronger inhibitory effect on the transport of PVC-NPs than MWSBC. This can be attributed to the fact that the adsorption of PVC-NPs on adsorbents followed the order as: MCCBC > MWSBC > sandy soil. The retention of PVC-NPs by MCCBC and MWSBC is determined by ionic type and ionic strength. The presence of coexisting ions enhanced the inhibitory effect of iron-modified biochar on the transport of PVC-NPs, with the following order: Ca2+ > SO2- 4 > Cl- > NO- 3. The inhibitory effect of MCCBC and MWSBC on the transport of PVC-NPs in soil columns increased with increasing ionic strengths. Furthermore, MCCBC and MWSBC inhibited the migration of PVC-NPs in a rainwater-soil system. The mechanisms by which MCCBC and MWSBC affect the transport of PVC-NPs in soil columns were considered to enhancing adsorption and decreasing soil pore volume. The results provide new insights into the management of soil nanoplastic pollution.

Reducing nitrogen fertilizer applications mitigates N2O emissions and maintains sugarcane yields in South China

Fertilizer N application combined with crop residue retention and a warm and humid climate increases nitrous oxide (N2O) emissions from sugarcane systems. However, the effects of high fertilizer N application rates on N2O emissions from sugarcane fields in China and the N2O reduction potential are still unclear. This study measured N2O emissions, the δ15N values for N2O and soil mineral N (NH4+ and NO3–), and yields during three continuous growing seasons in a sugarcane field in subtropical South China when four fertilizer N application rates: 0 (N0), 300 (N300), 400 (N400), and the local conventional rate of 500 kg N ha–1 (N500), were applied. The results showed that N2O emissions peaked in the first 4 weeks after fertilizer N application and the peak amplitude was highest after applying the N500 rate. The greatest soil N2O fluxes occurred when soil NH4+ and NO3– contents were high, the soil pore spaces contained large amounts of water (around 60 %), and there was a high soil surface temperature (around 35°C). The cumulative N2O emissions over the whole season (1.3–64.8 kg N ha–1) and emission factor values (2.6–11.1 %) both strongly increased with fertilizer N rate. The δ15N values for N2O and soil NH4+ and NO3– indicated that N2O production after N fertilization was dominated by denitrification and the microbial types varied with time and N fertilization rate. The principal component analysis showed that the factors associated with denitrification and nitrification explained 53.53 % and 30.53 % of the variation in N2O fluxes, respectively. Sugarcane yields, N uptake, and sugar contents were not affected by the reduced fertilizer N rates (N400 and N300) compared to that of N500. A reasonable N fertilizer rate of around 340 kg N ha–1 could reduce N2O emissions by more than 65 % compared to the conventional N500 rates while maintaining sugarcane yields. This study quantified the N2O emissions induced by different fertilizer N rates in a sugarcane system in China and highlighted the considerable potential for reducing N2O emissions through optimization of the fertilizer N application rate.

Improved stabilization of loess soil using magnesium oxysulfate cement-based ecological composite binder

The technology of loess solidification plays a crucial role in addressing issues such as soil erosion, with the key material in this process being the loess stabilizer. To tackle the high energy consumption problem associated with traditional loess stabilizers primarily composed of Portland cement, this study employed a more ecological sustainable alternative by incorporating solid waste coal gangue and magnesium oxysulfate (MOS) cement as a binding agent for consolidating loess. The alterations in bulk density, porosity, mineral structure, and microstructure of the consolidated soil with different MOS content were systematically investigated and validated. The pore size of MOS-solidified loess decreased significantly to a range of 0.04–3.60 μm compared to 0.80–3.88 μm for pure loess. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and thermogravimetric (TG/DTG) analysis revealed that the addition of MOS binder generated hydrated magnesium silicate (M-S-H), Mg(OH)2, and a small amount of 5Mg(OH)2·MgSO4·7H2O phase which filled the gaps between soil particles and bonded them together effectively. When the proportion of MOS binder added reached 11 %, the compressive strength of stabilized loess after curing for 28 days increased up to 9.4 MPa. After immersion in water for 24 h, the strength only decreased by 5.3 %, with a softening coefficient of 94.7 %. The test results consistently indicate that the enhancement in mechanical properties can be attributed to the binding effect facilitated by MOS. The ecological composite binder based on coal gangue and MOS demonstrates great potential in the field of soil stabilization.

Variation of soil pore structure and predication of the related functions following land‐use conversion identified by multi‐scale X‐ray tomography

AbstractLand‐use conversion profoundly influences the soil pore structure, consequently modifying the soil functions. Investigating the variation of multiscale soil pore structure and their associated functions following land‐use change is critical for evaluating land management strategies. However, this topic has not yet been extensively explored in recent studies. In this study, the pore structure of soil following land‐use conversion was quantitatively investigated by multiscale X‐ray tomography. Intact soil aggregates and undisturbed soil cores were collected from paddy fields (PF) and from vegetable fields were converted from paddy fields for 5 years (VF‐5), 13 years (VF‐13), and 20 years (VF‐20), respectively. Results revealed that the connected porosity of both aggregates and soil cores was significantly increased after land‐use conversion. The isolated porosity of soil aggregates increased, while, conversely, it decreased for soil cores. The variance in pore structure was attributed to the development of new pores, including channels created by vegetable roots, fissures, earthworm holes, and packing pores resulting from the decomposition of soil organic matter and the rearrangement of soil particles. The altered pore structure influenced the soil exchangeability and reservation ability. For aggregates, the isolated porosity of PF and VF‐5 accounted for over 70% of the total imaged porosity. These aggregates displayed a larger water and carbon reservation ability, but limited exchangeability of air, water, and nutrients. The isolated porosity of VF‐13 and VF‐20 aggregates accounted for approximately 50% of the total imaged porosity, suggesting they could effectively balance the exchange and storage of air, water, and nutrients. As for soil cores, isolated pores became negligible (&lt;0.2%) following land‐use conversion, leading to the emergence of a drainable pore system suitable for vegetable plantation. These findings offer insights into the development of pore structures and the prediction of soil function variations at multiple scales, both of which are crucial for optimizing soil management protocols.

Benchmarking soil organic carbon (SOC) concentration provides more robust soil health assessment than the SOC/clay ratio at European scale

Increasing soil organic carbon (SOC) confers benefits to soil health, biodiversity, underpins carbon sequestration and ameliorates land degradation. One recommendation is to increase SOC such that the SOC to clay ratio (SOC/clay) exceeds 1/13, yet normalising SOC levels based on clay alone gives misleading indications of soil structure and the potential to store additional carbon. Building on work by Poeplau & Don (2023) to benchmark observed against predicted SOC, we advance an alternative indicator: the ratio between observed and “typical” SOC (O/T SOC) for pan-European application. Here, “typical” SOC is the average concentration in different pedo-climate zones, PCZs (which, unlike existing SOC indicators, incorporate land cover and climate, alongside soil texture) across Europe, determined from mineral (<20 % organic matter) topsoils (0–20 cm) sampled during 2009–2018 in LUCAS, Europe's largest soil monitoring scheme (n = 19,855). Regression tree modelling derived 12 PCZs, with typical SOC values ranging 5.99–39.65 g kg−1. New index classes for comparison with SOC/clay grades were established from the quartiles of each PCZ's O/T SOC distribution; these were termed: “Low” (below the 25th percentile), “Intermediate” (between the 25th and 50th percentiles), “High” (between the 50th and 75th percentiles), and “Very high” (above the 75th percentile). Compared with SOC/clay, O/T SOC was less sensitive to clay content, land cover, and climate, less geographically skewed, and better reflected differences in soil porosity and SOC stock, supporting 2 EU Soil Health Mission objectives (consolidating SOC stocks; improving soil structure for crops and biota). These patterns held for 2 independent datasets, and O/T SOC grades were sensitive enough to reflect land management differences across several long-term field experiments. O/T SOC used in conjunction with several other physical, chemical and biological soil health indicators can help support the EU Soil Monitoring Law and achieve several United Nations Sustainable Development Goals.

Optimal Mapping of Soil Erodibility in a Plateau Lake Watershed: Empirical Models Empowered by Machine Learning

Soil erodibility (K) refers to the inherent ability of soil to withstand erosion. Accurate estimation and spatial prediction of K values are vital for assessing soil erosion and managing land resources. However, as most K-value estimation models are empirical, they suffer from significant extrapolation uncertainty, and traditional studies on spatial prediction focusing on individual empirical K values have neglected to explore the spatial pattern differences between various empirical models. This work proposed a universal framework for selecting an optimal soil-erodibility map using empirical models enhanced by machine learning. Specifically, three empirical models, namely, the erosion-productivity impact calculator model (K_EPIC), the Shirazi model (K_Shirazi), and the Torri model (K_Torri) were used to estimate K values. Random Forest (RF) and Gradient-Boosting Decision Tree (GBDT) algorithms were employed to develop prediction models, which led to the creation of three K-value maps. The spatial distribution of K values and associated environmental covariates were also investigated across varying empirical models. Results showed that RF achieved the highest accuracy, with R2 of K_EPIC, K_Shirazi, and K_Torri increasing by 46%, 34%, and 22%, respectively, compared to GBDT. And distinctions among environmental variables that shape the spatial patterns of empirical models have been identified. The K_EPIC and K_Shirazi are influenced by soil porosity and soil moisture. The K_Torri is more sensitive to soil moisture conditions and terrain location. More importantly, our study has highlighted disparities in the spatial patterns across the three K-value maps. Considering the data distribution, spatial distribution, and measured K values, the K_Torri model outperformed others in estimating soil erodibility in the plateau lake watershed. This study proposed a framework that aimed to create optimal soil-erodibility maps and offered a scientific and accurate K-value estimation method for the assessment of soil erosion.

Technology Development with Zero Tillage and Stubble Residue Management for Sustainable Soil Health and System Productivity in Wheat-maize Cropping Pattern

Conventional farm operations comprising traditional soil tillage and burning stubble residues become the cause of concern for soil sickness threatening sustainable system productivity. Wheat and maize constituting one of the predominant cropping systems strive with the commitment of substantial contribution to the world food security front. A better understanding of these alarming issues insisted on us to explore ‘Conservation Agriculture’ practices designing a field experiment with tillage and crop residue management. The study from 2019 to 2022 derived phenomenal achievement with Zero Tillage (ZT) and Minimal Tillage (MT) in compliance with crop residue retention (+ R); while, the eventuality of stubble burning (- R) deteriorated soil health, especially with Conventional Tillage (CT). Results illustrated significantly higher system productivity (11.60 - 12.0 t ha-1) in terms of wheat equivalent yield at (ZT+R) stands followed by those (11.34-11.64 t ha-1) at (MT + R), significantly higher than those (10.52 - 10.59 t ha-1) at conventional (CT-R) stands and those (10.63-10.78 t ha-1) at (CT+R) stands. Soil health also significantly improved at (ZT + R) stands accounting for higher soil porosity (39.45%), pH (7.64), electrical conductivity (0.370 dS m-1), hydraulic conductivity (10.56 mm h-1), soil organic carbon (0.458%), and N, P and K contents (272.5, 18.36 and 254.8 kg ha-1) than at conventional (CT -R) stands. Therefore, the study could develop a viable cutting-edge agro-technology fostering sustainable maize-wheat production in a system perspective mode. Nonetheless, the stewardship of zero tillage along with stubble residues could also be envisaged for the mitigation of soil sickness, too.

Links between soil pore structure, water flow and solute transport in the topsoil of an arable field: Does soil organic carbon matter?

An improved understanding of preferential solute transport in soil macropores would enable more reliable predictions of the fate of agrochemicals and the protection of water quality in agricultural landscapes. The objective of this study was to investigate how soil organic carbon (SOC) and soil texture shape soil pore structure and thereby determine the susceptibility to preferential transport under steady-state near-saturated flow conditions. To do so, we took intact topsoil samples from an arable field that has large variations in SOC content (1.1–2.7%) and clay content (8–42%). Soil pore structure was quantified by X-ray tomography and soil water retention measurements. Non-reactive solute transport experiments under steady-state near-saturated conditions were carried out at irrigation rates of 2 and 5 mm h−1 to quantify the degree of preferential transport. Near-saturated hydraulic conductivities at pressure heads of −1.3 and −6 cm were also measured using a tension disc infiltrometer. The results showed that larger abundances of small macropores (240–720 µm diameter) and mesopores (5–100 µm diameter) resulted in weaker preferential transport, due to larger hydraulic conductivities in the soil matrix that prevented the activation of water flow and solute transport in large macropores. In particular, the degree of preferential transport was most strongly and negatively correlated with the mesoporosity in the 30–100 µm diameter class. In contrast, the degree of preferential transport was not correlated with connectivity measures (e.g. the percolating fraction and critical pore diameter for the macropore network), probably because i.) the pore space of almost all samples was highly connected, being dominated by one percolating cluster, and ii.) only a part of this percolating macroporosity was active under the near-saturated conditions of the experiment. We also found that the degree of preferential transport was strongly and negatively correlated with clay content, whilst the effects of SOC were not significant. Nevertheless, macroporosity in the 240–720 µm diameter class and mesoporosity were positively correlated with SOC content in our soils and in some previous studies. Therefore, SOC sequestration in arable soils may potentially reduce the risk of preferential transport under near-saturated flow conditions through better developed networks of small macropores and mesopores.

Comparing mini-disk infiltrometer, BEST method and soil core estimates of hydraulic conductivity of a sandy-loam soil

Saturated, Ks, and near-saturated, K, soil hydraulic conductivity control many hydrological processes but they are difficult to measure. Comparing methods to determine Ks and K is a means to establish how and why these soil hydrodynamic properties vary with the applied method. A comparison was established between the Ks and K values of a sandy-loam soil obtained, in the field, with the BEST (Beerkan Estimation of Soil Transfer parameters) method of soil hydraulic characterization and an unconfined MDI (mini-disk infiltrometer) experiment and, in the laboratory, with a confined MDI experiment and the CHP (constant-head permeameter) method. Using for the BEST calculations the soil porosity instead of the saturated soil water content yielded 1.4–1.1 times higher estimates of Ks and K, depending on the pressure head, and differences decreased in more unsaturated soil conditions. The confined MDI experiment yielded 22 % - 77 % higher K values than the unconfined MDI experiment, depending on the established pressure head, h0, and differences were not significant for h0 = −1 cm. In the close to saturation region, the soil hydraulic conductivity function predicted with BEST did not generally agree well with the Ks and K values obtained in the laboratory by a direct application of the Darcy’s law. In particular, BEST yielded a 5.6 times smaller Ks value than the CHP method and up to an 8.1 times higher K value than the MDI. Overall, i) the two application methods of the MDI yielded relatively similar results, especially close to saturation, and ii) there was not a satisfactory agreement between the field (BEST) and the laboratory (MDI plus CHP) determination of soil hydraulic conductivity close to saturation, unless a comparison was made with the same soil water content. The detected differences were probably attributable to soil spatial variability, overestimation of Ks in the laboratory due to preferential flow phenomena, underestimation of Ks in the field due to air entrapment in the soil and infiltration surface disturbance, inability of BEST to describe the actual soil hydraulic conductivity function at the sampled field site. Testing BEST predictions of Ks and K in other soils appears advisable and combining the MDI and CHP methods appears a rather simple means to make these checks. These additional investigations could improve interpretation of the differences between methods, which is an important step for properly selecting a method yielding Ks and K data appropriate for an intended use.

Investigation of Particle Gradation Effect on Soil-Rock Mixture Using Direct Shear Test

Soil-rock mixture (SRM) is a special geomaterial that is composed of soil and a certain percentage of rock blocks with various sizes and strengths. It has high structural strength and renewable resources that are used as filler in subgrade, construction material and embankment dams. However, the mechanical properties of the soil-rock mixture are sophisticated owing to the complicated interaction between soil and rock particles. Previously, many experimental investigations were conducted to focus on shear behaviours and the influencing factors of SRM. Yet, limited w ork has been done to underline the effect of particle size distribution towards SRM shear strength parameters. Thus, this study conducted an SRM shear test with three different kinds of gradation and rock block percentages. Various soil densities, porosities and different framework structures have resulted from different rock particle concentrations. From the results, the well-graded SRM shows a non-linear trend of cohesion value while uniformly graded and gap-graded SRMs shows contradicting trend respectively. The result and analysis in this study are especially useful in analysing its influence on the shear strength parameters of SRM with different rock block percentages.

Enhancing Soil Resilience and Sugar Beet (Beta vulgaris L.) Yield: Mid‐Term Effects of Compost and Glauconite Integration

ABSTRACTSugar beet (Beta vulgaris L.) is a globally significant crop, valued for its economic importance in sugar production. Saline‐sodic soil environments negatively impact sugar beet productivity. This study investigates the effects of using compost, glauconite enriched‐K and their combinations in mitigating the saline‐sodic soil environment, sugar beet productivity and extracted sugar quality. A two‐season field experiment in split‐plot design with the main plots is three doses of compost: control (C0), recommended (100%) dose (C1) and 150% recommended dose (C2). Each group divided into four subplots of glauconite treatments arranged according to the recommended dose of potassium (K) as follows: G0 (no glauconite), G1 (50% K), G2 (100% K, 480 Kg glauconite Fed−1) and G3 (150% K). The results showed that compost and glauconite mitigated adverse soil effects caused by salinity and sodicity. The C2G3 treatment reduced electrical conductivity (EC) and exchangeable sodium percentage (ESP), improved organic matter and enhanced soil bulk density, porosity and penetration resistance. This combination also increased soil nutrients (N, K, Fe, Mn, Zn and Cu). Regarding the sugar beet yield, C2G3 improved root yield, top yield, sugar yield and extracted sugar. The application of glauconite increased root diameter by 20% and root length by 23%, enhanced sugar quality with minimal sugar losses to molasses (2.43%), and reduced impurities of K, α‐amino N and Na. Principal component analysis showed positive correlations between root yield and soil potassium, organic matter, cation exchange capacity and soil porosity, with negative correlations to bulk density, EC, pH and ESP. Two‐way analysis of main (ANOM) illustrated significant effects of compost and glauconite on soil–plant interactions. Multivariate analysis indicated that higher glauconite doses significantly enhanced root yield. The Gag run charts confirmed that compost (100%) and G3 levels explored more homogeneity reducing the ESP%, increasing sugar beet root yield, sugar yield and quality.

Pore-Scale Formation Characteristics of Impermeable Frozen Walls for Shallow Groundwater Contamination Remediation

Impermeability and water blocking are crucial for remediating shallow groundwater contamination. Traditional methods often employ curtain-grouting technology to create impermeable layers. However, cement slurry curing is irreversible, leading to permanent closure of underground aquifers and secondary pollution. This study employs an innovative approach by fabricating cylindrical models that simulate actual strata and utilizing a high-temperature and high-pressure displacement device. It systematically analyzes the variations in soil pore structure, distribution, porosity, and permeability under different temperatures, pressures, and freezing durations. The microscopic characteristics of the freezing process in water-bearing soils were studied. Results demonstrate that longer freezing time improves the effectiveness of soil freezing, reaching complete freezing at temperatures as low as −4 °C for samples with low water content. For water-saturated samples, freezing below −6 °C results in nearly zero porosity. Increased pressure at a certain freezing temperature significantly reduces permeability. When freezing temperature falls below −4 °C, water permeability in saturated samples after freezing reaches near-zero levels, while unsaturated samples experience complete freezing. These findings provide a theoretical foundation for constructing freezing curtains in remediating shallow groundwater pollution.

Soil Development and Land Suitability for Cacao on Sandstone and Pumice Breccia in the Semilir Formation in Ponjong District, Gunungkidul Regency, Indonesia

The parent material of the Semilir Formation, which consists of breccia pumice and sandstone, was located in the villages of Sawahan and Umbulrejo, Ponjong district, and it influences the genesis and soil types. This study utilized survey and laboratory analysis methods. Two soil profiles were studied: the first profile was located in Sawahan Village with breccia pumice as the parent material, while the second profile was in Umbulrejo Village with sandstone as the parent material. The research results indicated that soils developed from breccia pumice had diagnostic horizons of umbric epipedon and argillic endopedon with an advanced soil development stage. Soils developed from sandstone had diagnostic horizons of umbric epipedon and cambic endopedon with a young soil development stage. This affects the chemical properties of the soil. Soils formed from pumice breccia tend to have base saturation of less than 50% with low exchangeable bases, while soils formed from sandstone have base saturation of &gt;50% with high exchangeable bases. Soils developed from breccia pumice and sandstone have soil classification as Typic Paleudults and Typic Dystrudepts. These soil types are suitable for cocoa plant cultivation; however, they require mechanical conservation through terrace construction and improved drainage by incorporating organic materials or compost into the soil, which can significantly enhance soil porosity, enabling better water retention and drainage.

Soil Development and Land Suitability for Cacao on Sandstone and Pumice Breccia in the Semilir Formation in Ponjong District, Gunungkidul Regency, Indonesia

The parent material of the Semilir Formation, which consists of breccia pumice and sandstone, was located in the villages of Sawahan and Umbulrejo, Ponjong district, and it influences the genesis and soil types. This study utilized survey and laboratory analysis methods. Two soil profiles were studied: the first profile was located in Sawahan Village with breccia pumice as the parent material, while the second profile was in Umbulrejo Village with sandstone as the parent material. The research results indicated that soils developed from breccia pumice had diagnostic horizons of umbric epipedon and argillic endopedon with an advanced soil development stage. Soils developed from sandstone had diagnostic horizons of umbric epipedon and cambic endopedon with a young soil development stage. This affects the chemical properties of the soil. Soils formed from pumice breccia tend to have base saturation of less than 50% with low exchangeable bases, while soils formed from sandstone have base saturation of &gt;50% with high exchangeable bases. Soils developed from breccia pumice and sandstone have soil classification as Typic Paleudults and Typic Dystrudepts. These soil types are suitable for cocoa plant cultivation; however, they require mechanical conservation through terrace construction and improved drainage by incorporating organic materials or compost into the soil, which can significantly enhance soil porosity, enabling better water retention and drainage.