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Rare earth elements (REEs) are essential raw materials for modern industries but mining them has caused severe environmental issues, particularly the recovery of heavy REEs (HREEs) from ion-adsorption deposits (IADs). Very recently, an emerging technology, electrokinetic mining (EKM), has been proposed for the green and efficient recovery of REEs from IADs. However, the conduction mechanism of the weathering crust soil, which is also a prerequisite for EKM, remains unclear, making the EKM process unpredictable. Here, we systematically investigated the conductivity of weathering crust soil in the presence of light REEs (LREEs, i.e., La3+ and Sm3+) and HREEs (Er3+ and Y3+), respectively. Results suggested that the voltage was dynamically and spatially redistributed by the movement of REEs and water during EKM, and the conventional assumption of the linear distribution of voltage leads to an inaccurate description of soil voltage. We proposed an improved Archie's equation by coupling the mechanisms of liquid phase and solid-liquid interface conduction, which can predict soil conductivity more precisely. Moreover, the extended Archie's equation is able to recalculate the voltage distribution at distinct times and spaces well during EKM. More importantly, the water content in field-scale weathered-crust soils can be retrieved by the newly proposed Archie's equation, which helps optimize the leaching wells and improve the recovery rate of REE. This study focuses on the conduction mechanism of weathering crust soil, which provides a theoretical basis for better use of the EKM technology and promotes mining efficiency fundamentally. [ABSTRACT FROM AUTHOR]

In recent decades, agricultural sustainability has been negatively affected by the structural degradation of soils resulting from excessive land use. In this research, the impact of different irrigation methods applied for five years in a region experiencing crusting issues on the soil's physical quality was investigated. Soil samples were taken from a region where wheat is grown and four different irrigation systems [Natural rainfall (NR), linear pivot irrigation (LPI), subsurface drip irrigation (SDI), and sprinkler irrigation (SI)] are employed, at depths of 0-20 cm, from both degraded and undegraded soils. The soil's mean weight diameter (MWD), water-resistant aggregates (WRA), saturation level (Ts), field capacity (FC), wilting point, available water content (AWC), aeration capacity, modulus of rupture, plastic limit (PL), liquid limit (LL), and plasticity index (PI) were determined. The soil's WRA were found to be the lowest at 7.76% in the NR, but this result increased by 150.64% to 19.45% in the SDI. The MWD values of the soils in the NR system were found to be 0.178 mm and it has been found to increase in the SDI system, reaching 0.467 mm. In the SDI system, the highest values were obtained for Ts, FC, and AWC. While the modulus of rupture was found to be 151.56 kPA in the NR, it was found 154.4, 44.78 and 154.2 kPA in the LPI, SDI and SI areas, respectively. The PL, LL, and PI values of the soils were not affected by different irrigation systems, and values were determined as 44.57%, 21.14%, and 23.44%, on average respectively. In this direction, the necessity of monitoring the results of soil aggregate stability and water characteristics for many years and examining them in different soil types has emerged. In addition, it has been suggested that the possible effects of irrigation systems should be considered for the sustainable use of lands. [ABSTRACT FROM AUTHOR]

In order to address the problems of soil crusting and the lack of soil fertility produced by long-term planting of tobacco, an operation device integrated the functions of deep loosening, fertilizer application, and riding was proposed in this study. The agronomic requirements of tobacco planting and the ecological benefits of organic fertilizers and other advantages were considered during the design of the device. The device was consisted of the frame, deep loosening fertilizer shovel, and ridging part. ANSYS software was used to establish the finite element model of the frame and deep loosening fertilizer shovel, and the modal simulation experiment was conducted. Results show that, under the torsion and braking interaction, the stress change of the Frame is not obvious, and the stress of the shovel tip is mainly concentrated on the combination of shovel handle and shovel body, with the stress change of other areas being insignificant. The modal analysis of the Frame shows that its resonance frequency is 61.138 Hz, and the error rate between the modal simulation and the modal test is less than 10%, which verified the feasibility of the structural design. The results of this study provide technical references for the structural design of a device for improving deep soil characteristics. [ABSTRACT FROM AUTHOR]

Urban stormwater ponds (SPs) are important for flood protection strategies in areas with heavily sealed soils as they mitigate the negative effects of floods. SPs with temporary waters (TWs) are only flooded when water levels or surface runoffs are high, while SPs with permanent waters (PWs) contain a permanently flooded area. In urban areas, SPs are important secondary habitats for plants and animals as natural aquatic and semi-aquatic habitats are often destroyed during urbanization. In 2017, a large survey on vascular plant diversity of 80 SPs was conducted in the city of Hamburg (Germany). The aim of the study was to analyze plant diversity of TWs and PWs and to identify relationships between plant diversity and different urbanization parameters. In total, 30% of the plant species pool of Hamburg was found in the surveyed SPs representing 0.03% of the total area of Hamburg. We found significant differences in the number and proportion of aquatic, threatened and non-native species between the shoreline and bottom of TWs and PWs. The number and proportion of aquatic species was positively correlated with the proportion of urban green and negatively correlated with the degree of soil sealing in the direct surrounding of SPs. For the proportion of threatened species in the bottom of TWs, a positive relationship was found with the proportion of urban green in the surrounding of SPs. For the number and proportion of non-native species in the shoreline of SPs, negative relationships were found with the proportion of urban green and the number of different habitat types in the surrounding of SPs. Further, a positive relationship with the degree of soil sealing was identified. Our results highlight the nature conservation value of urban SPs for plants and showed the negative effects of urbanization on several plant species groups. • Diverse plant species assemblages were found in the stormwater ponds (SPs) in Hamburg. • 30% of the plant species of Hamburg were found on 0.03% of its total area. • No clear patterns for the influence of urbanization on plant diversity were found. • Patterns differed between the hydrological conditions and zones of SPs. [ABSTRACT FROM AUTHOR]

Soil erosion is a significant environmental issue worldwide, particularly in island regions where land resources are exceedingly scarce. Biological soil crusts play a crucial role in mitigating soil erosion, yet the precise effect and mechanism of biological soil crusts against erosion remain ambiguous. In this study, biological soil crusts at various developmental stages from a tropical coral island in the South China Sea were chosen to investigate the role of carbonic anhydrase in mitigating erosion. A cohesive strength meter, real-time quantitative PCR, and 16S rRNA gene high-throughput sequencing were employed to assess variations in soil antiscouribility as well as bacterial abundance and composition during the formation and development of biological soil crusts. Scanning electron microscopy was utilized to detect carbonates induced by bacterial carbonic anhydrase and elucidate their role in the solidification of sand particles. The findings indicate that the formation and development of biological soil crusts significantly enhance anti-scouribility. Comparison to those of bare coral sand, the shear stress increased from 0.35 to 1.11 N/m2 in the dark biocrusts. Moreover, significantly elevated carbonic anhydrase activity was observed in biological soil crusts, demonstrating a positive correlation with antiscouribility. In addition, there was a significant increase in bacterial abundance within the biological soil crusts. The enrichment of Cyanobacteriales and Chloroflexales potentially contributed to the increased carbonic anhydrase activity and antiscouribility. Furthermore, three cyanobacterial strains with carbonic anhydrase activity were isolated from biological soil crusts and subsequently confirmed to enhance sand solidification through microbial carbonate precipitation. This study presents initial evidence for the role of microbial carbonic anhydrase in enhancing the antiscouribility of biological soil crusts during their formation and development. These findings offer novel insights into the functional and mechanistic dimensions underlying the mitigation of soil erosion facilitated by biological soil crusts, which are valuable for implementing sustainable biorestoration and environmental management technologies to prevent soil erosion. [Display omitted] • Antiscourability and carbonic anhydrase activity enhanced during the formation and development of biological soil crusts. • Antiscourability was positive correlated with carbonic anhydrase activity. • Cyanobacteriales and Chloroflexales contribute to the augmentation of carbonic anhydrase activity. • Carbonic anhydrase-induced carbonates enhanced soil shear strength in biological soil crusts. [ABSTRACT FROM AUTHOR]