The remediation and management of old municipal solid waste (MSW) landfills are pivotal for advancing urban ecological sustainability. This study aims to systematically assess the mechanical properties, environmental behaviors, and synergistic mechanisms of remediated landfill-mined soil-like material (SLM) through advanced oxidation and stabilization processes. The results indicate that synergistic remediation with advanced oxidation and stabilization processes significantly increased the mechanical strength of stabilized SLM to over 0.6 MPa, and reduced the organic content by about 20 %, making it suitable for reuse in geotechnical engineering. The choice of oxidizing agents markedly affected the mechanical properties of stabilized SLM; for example, the application of sodium percarbonate in conjunction with stabilized materials further enhances the strength by simultaneously promoting the pozzolanic reaction. Furthermore, the heavy metal leaching behaviors of the stabilized SLM were found to be environmentally safe. The enhanced performance of stabilized SLM is primarily attributed to the synergistic effects of oxidation and pozzolanic reactions. The advanced oxidation process decreases organic matter content and increases its stability by reducing the proportion of readily decomposable O-alkyl C. Concurrently, pozzolanic reactions produce ettringite crystals and C-(A)-S-H gels, which not only fill micropores and improve particle bonding but also aid in heavy metal immobilization through surface adsorption, complexation, and physical encapsulation. These insights provide a comprehensive understanding of the remediation processes and resource recovery potential of SLM from old MSW landfills.

Field capacity (F.C.) is a crucial parameter in soil analysis, defining the limits of plant-available moisture content (M.C.). Integrating this concept into sensing technology provides valuable information for optimizing irrigation scheduling by determining the appropriate timing and quantity of irrigation, thereby preventing crop damage. This article presents a fractal-based microwave planar sensor (MPS) designed to estimate soil-moisture characteristics related to F.C. The proposed sensor utilizes a self-similar fractal (SSF) approach, operating in the ISM frequency band at 2.4 GHz, achieving high return losses of approximately -47.94 dB and enhanced sensitivity in material characterization. The sensor's performance is evaluated by varying F.C. values from 0% to 100% for similar textured soils with organic matter content (OMC) variations. The results demonstrate that variations in OMC significantly impact the dielectric properties of soil with moisture variations. Specifically, Sample-1, which has a low OMC, exhibits a lower epsilon(r) values than Sample-2 at all F.C. levels. The data suggest that the proposed sensor is sensitive to detect the impact of OMC variations on soil-moisture characteristics concerning F.C. A mathematical model has been formulated as a second-order polynomial equation, exhibiting coefficient of determination (R-2) value of 0.9771. This model has been developed specifically to evaluate F.C. values, demonstrating a strong correlation with the observed data. The performance of the proposed sensor confirms its potential application in agricultural fields for efficient irrigation scheduling and water resource conservation.

The development of soil structure, characterized by fractal geometry, improves plant-rooting development and improves water retention, drainage, and air permeability. However, due to this function to increase fertility, excessive intensive cultivation contributes to environmental load. The amount of nitrogen in rivers in agricultural watersheds is significantly related to the surplus nitrogen in the watershed, and since the nitrogen load increases with the increase in the crop field proportion, it is important to manage the surplus nitrogen in crop field. On the other hand, since wetlands have reduced the surplus nitrogen in the watershed through the purification of nitrate nitrogen in river water, it is possible to reduce the environmental load by optimizing land use. Replacing a part of chemical fertilizer application with organic fertilizer application increased soil organic carbon and contribute to the prevention of global warming without reducing crop yield. In Japanese grasslands, the annual application of 3.5tC ha-1 of compost offset greenhouse gas emissions. Furthermore, the continuous use of compost mitigated soil acidification and suppressed N2O emissions. I investigated the impact of greenhouse gas emissions associated with agricultural development on permafrost and peat soils, which are the world's soil carbon reservoirs. In eastern Siberia, disturbance of taiga forests caused permafrost melting and increased CH4 emissions. Drainage of peatland reduced CH4 emissions, but increased CO2 and N2O emissions due to peat decomposition, which was exacerbated by the application of chemical fertilizers. It was essential to keep the groundwater level at -20 cm to -40 cm to suppress greenhouse gas emissions. Environmental load means that soil health is being damaged. It is necessary to develop agricultural techniques to maintain and restore soil health. In particular, organic matter management can restore soil structure by increasing soil organic matter, and also reduce the amount of chemical fertilizer used, which has the effect of reducing greenhouse gas emissions. On the other hand, excessive continuous use of organic fertilizer can increase nitrogen loads. It has been pointed out that the relationship between cover crops and tillage is also important for organic matter management. Regional research is increasingly essential.

In order to study the strength characteristics of organic-matter-contaminated red soil and the improvement effects of different modifiers, the red soil in the Yulin area was taken as the research object, and triaxial compression tests were carried out to study the effects of different mass fractions (0%, 2%, 4%, 6%, 8%) of organic matter (sodium humate) on the strength characteristics of red soil. Unconfined compressive strength (UCS) tests and scanning electron microscopy (SEM) tests were carried out to study the improvement effects of different amounts of lignin, fly ash, and xanthan gum on organic-matter-contaminated red soil (organic matter content of 8%). The results of the tests showed that the cohesion and internal friction angle of red soil both tended to decrease with the increase in organic matter content. When the organic matter content increased from 0% to 8%, the cohesion of the red soil decreased from 60.98 kPa to 40.07 kPa, a decrease of 34.29%; and the internal friction angle decreased from 17.42 degrees to 7.28 degrees, a decrease of 58.21%. The stress-strain relationship curves of organic-matter-contaminated red soil all show a hardening type. Under different confining pressures, as the organic matter content increased, the shear strength of the red soil decreased continuously. The unconfined compressive strength of organic-matter-contaminated red soil increased with the increase in lignin content, and increased first and then decreased with the increase in fly ash content and xanthan gum content. Through comparative analysis, it was found that the fly ash with a content of 15% had the best improvement effect. The lignin-amended red soil enhanced the connection of soil particles through reinforcement, reduced pores, and improved soil strength. Fly ash improved the acidification reaction, and the hydrates filled the pores and enhanced the soil strength. Xanthan gum improved the red soil by absorbing water and promoting microbial growth, further enhancing the bonding force between soil particles. This study can provide a reference for engineering construction and red soil improvement in red soil areas.

Soil microplastics (MPs) are a substantial threat to soil health, particularly by disrupting soil aggregation. Additionally, MPs undergo aging processes in the soil, which may significantly alter their long-term impacts on soil structure. To investigate these effects, we conducted an eight-month soil incubation experiment, examining the influence of MPs and their aging on soil aggregation. The experiment utilized a factorial design with various combinations of MPs and biochar additions: 1% by weight of 1000-mesh polyethylene and polypropylene MPs, and 5-mm biochar, resulting in six treatment groups: [CK], [PE], [PP], [Biochar], [PE + biochar], and [PP + biochar]. Our findings revealed that both MPs and biochar underwent aging throughout the incubation, evidenced by the formation of oxygen-containing functional groups on their surfaces. Microplastics, particularly polyethylene, primarily affected the 0.5-1 mm and >2 mm aggregate fractions, with average reductions of 21% and 77%, respectively. These adverse effects intensified with the aging of MPs. Contrary to expectations, the addition of biochar was found to exacerbate the negative impacts of MPs on the 0.25-0.5 mm aggregates, with a decrease of 11% associated with PE MPs. The influence of biochar on mitigating the damage caused by MPs to soil aggregation is dependent on aggregate size.

Although it has been recognized that soil structure formation affects soil organic carbon (SOC) sequestration, experimental data elucidating the relation between mechanical properties of soil structure and soil organic matter (SOM) stability are lacking. This study assesses the link between aggregate stability and SOM stability in lowland and hilly land soils of Central Europe. Overall, 39 topsoil samples were taken. Besides determining basic properties and nutrient availability, stability of soil aggregates was quantified using wet sieving (WS) and rainfall simulation (RS) procedures. The samples were analyzed by thermogravimetry and differential scanning calorimetry (TG-DSC). Besides significant correlations with basic soil properties and contents of selected nutrients, the aggregate stability data were linked to thermal processes, such as water desorption and SOM degradation. The RS values were significantly correlated (r > 0.7, p < 0.001) with the rate of water desorption (T < 200 degrees C) and SOM degradation (200 - 570 degrees C). Observed correlation pattern, with multiple maxima, suggests that aggregate stability is supported by clay and several SOM fractions, each showing different thermal stability. Significant correlations observed bellow 200 degrees C indicate that properties controlling soil specific surface area (SOM and clay) are important also for the aggregate stability. The 78 % of the variance observed in aggregate stability testing was explained by multilinear regression using weight loss rates recorded at selected temperatures (80, 130, 248, 401 and 455 degrees C) as predictors. We observed different relations between exothermic energy values, soil aggregate stability and thermal stability of SOM (SOC). Exothermic heat flux normalized with respect to SOC mass (energy density) indicates presence of stable organic fraction, as it showed correlation also with clay, which has positive effect on SOC stabilization. This is in line with the positive correlation between SOC energy density and aggregate stability. On contrary, normalizing the heat with respect to SOM mass indicates the content of labile organic components, as the correlations with clay or aggregate stability were insignificant. The TG-DSC data revealed that hilly land soils are depleted in fresh organic material, which is due to their genesis and the erosion intensified by tillage.

Ongoing and amplified climate change in the Arctic is leading to glacier retreat and to the exposure of an ever-larger portion of non-glaciated permafrost-dominated landscapes. Warming will also cause more precipitation to fall as rain, further enhancing the thaw of previously frozen ground. Yet, the impact of those perturbations on the geochemistry of Arctic rivers remains a subject of debate. Here, we determined the geochemical composition of waters from various contrasting non-glacial permafrost catchments and investigated their impact on a glacially dominated river, the Zackenberg River (Northeast Greenland), during late summer (August 2019). We also studied the effect of rainfall on the geochemistry of the Zackenberg River, its non-glacial tributaries, and a nearby independent non-glacial headwater stream Gr ae nse. We analyzed water properties, quantified and characterized dissolved organic matter (DOM) using absorbance and fluorescence spectroscopy and radiocarbon isotopes, and set this alongside analyses of the major cations (Ca, Mg, Na, and K), dissolved silicon (Si), and germanium/silicon ratios (Ge/Si). The glacier-fed Zackenberg River contained low concentrations of major cations, dissolved Si and dissolved organic carbon (DOC), and a Ge/Si ratio typical of bulk rock. Glacial DOM was enriched in protein-like fluorescent DOM and displayed relatively depleted radiocarbon values (i.e., old DOM). Non-glacial streams (i.e., tributaries and Gr ae nse) had higher concentrations of major cations and DOC and DOM enriched in aromatic compounds. They showed a wide range of values for radiocarbon, Si and Ge/Si ratios associated with variable contributions of surface runoff relative to deep active layer leaching. Before the rain event, Zackenberg tributaries did not contribute notably to the solute export of the Zackenberg River, and supra-permafrost ground waters governed the supply of solutes in Zackenberg tributaries and Gr ae nse stream. After the rain event, surface runoff modified the composition of Gr ae nse stream, and non-glacial tributaries strongly increased their contribution to the Zackenberg River solute export. Our results show that summer rainfall events provide an additional source of DOM and Si-rich waters from permafrost-underlain catchments to the discharge of glacially dominated rivers. This suggests that the magnitude and composition of solute exports from Arctic rivers are modulated by permafrost thaw and summer rain events. This event-driven solute supply will likely impact the carbon cycle in rivers, estuaries, and oceans and should be included into future predictions of carbon balance in these vulnerable Arctic systems.

Rainfall can alter the hydrothermal state of permafrost, subsequently affecting organic carbon decomposition and CO2 transport. However, the mechanisms by which rainfall influences organic carbon decomposition and carbon dioxide transport processes in permafrost remain unclear. In this study, a coupled permafrost water-heatvapor-carbon model, based on the surface energy-water balance theory, is employed to explore the effects of increased precipitation on permafrost moisture, temperature, organic carbon decomposition, and carbon dioxide transport through numerical simulations. The results are as follows: (1) with increased rainfall, surface latent heat flux rises while surface sensible heat flux declines, leading to a reduction in surface heat flux. The annual mean surface heat fluxes for the three precipitation conditions of no change in precipitation (zP = 0 mm), 50 mm increase in precipitation (zP = 50 mm) and 100 mm increase in precipitation (zP = 100 mm) are -0.1 W/m2, -0.2 W/m2 and -0.4 W/m2 respectively; and (2) as rainfall increases, soil moisture content increases significantly, but the impact of rainfall on soil moisture content diminishes with increasing soil depth; and (3) increased rainfall results in a decrease in soil carbon fluxes, soil organic matter decomposition rates, and CO2 concentrations. Compared to the case of constant precipitation, the surface carbon fluxes decreased by 0.04 mu mol center dot m-2s-1 and 0.08 mu mol center dot m-2s-1 under zP = 50 mm and zP = 100 mm, respectively. Additionally, the decomposition rate of soil organic matter at 10 cm depth decreased by 3.2 E-8 mol center dot m-2s-1 and 6.3 E-8 mol center dot m-2s-1, respectively, while the soil carbon concentration decreased by 3 mu mol/mol and 5 mu mol/mol, respectively.

Soil organic carbon (SOC) rapidly accumulates during ecosystem primary succession in glacier foreland. This makes it an ideal model for studying soil carbon sequestration and stabilization, which are urgently needed to mitigate climate change. Here, we investigated SOC dynamics in the Kuoqionggangri glacier foreland on the Tibetan Plateau. The study area along a deglaciation chronosequence of 170-year comprising three ecosystem succession stages, including barren ground, herb steppe, and legume steppe. We quantified amino sugars, lignin phenols, and relative expression of genes associated with carbon degradation to assess the contributions of microbial and plant residues to SOC, and used FT-ICR mass spectroscopy to analyze the composition of dissolved organic matter. We found that herbal plant colonization increased SOC by enhancing ecosystem gross primary productivity, while subsequent legumes development decreased SOC, due to increased ecosystem respiration from labile organic carbon inputs. Plant residues were a greater contributor to SOC than microbial residues in the vegetated soils, but they were susceptible to microbial degradation compared to the more persistent and continuously accumulating microbial residues. Our findings revealed the organic carbon accumulation and stabilization process in early soil development, which provides mechanism insights into carbon sequestration during ecosystem restoration under climate change.

Microplastics (MPs) affect the carbon cycle in coastal salt marsh soils. However, studies on their effects on CHCl3 and CHBr3, which are volatile halohydrocarbons that can damage the ozone layer, are lacking. In this study, indoor simulation experiments were conducted to explore the effects of MPs invasion on the source and sink characteristics of soil CHCl3 and CHBr3. The results showed that different concentrations of polyethylene (PE)MPs promoted CHCl3 and CHBr3 emissions. Emission peaks of the two gases appeared on days 3 and 15 during the culture cycle. CHCl3 and CHBr3 fluxes were mainly affected by soil physicochemical properties and microbial communities. PE-MPs caused changes in soil properties, microorganisms, and related functional genes. Soil total organic carbon, which was significantly and positively correlated with CHCl3. Dissolved organic matter, which was one of the main factors affecting CHBr3, its relative content increased after the addition of PE-MPs. The abundances of Methylocella and Dehalococcoides, which mediate dechlorination reduction, decreased with the addition of PE-MPs. The addition of PE-MPs also significantly varied the abundance of ctrA, which controls dechlorination in soil microorganisms. The gene pceA greatly influenced CHCl3 emissions. In addition, CHBr3 flux was influenced by the interactions between sediment redox and microbial co-metabolic reactions under the control of genes such as TC.FEV.OM and soxB. This study provides theoretical and data support for the source and sink characteristics of volatile halohydrocarbons in coastal salt marshes and highlights the environmental hazards of MPs.