Saturated hydraulic conductivity (Ks) is a critical parameter for assessing water-induced loess collapsibility, erosion, and landslides. However, accurately determining Ks has long been a challenge in geological and geotechnical engineering due to the complexity and inherent spatial variability of loess-paleosol sequences. To address this issue, this study conducted shaft sampling and laboratory experiments to measure the Ks of loess with a deposition time (T) of up to 880 ka. By leveraging the well-defined deposition time scale and global relevance of loess, a predictive model incorporating Ks variability was developed with T as a variable. This paper provides a detailed discussion of the physical significance of the model's parameters, their determination methods, and verifies its applicability. Pore distribution and scanning electron microscope (SEM) images were used to reveal the three-stage evolution of Ks over time, as well as the underlying microstructural mechanisms. Additionally, this paper explores the impact of commonly used merging layer methods on Ks variability in engineering practice. The model effectively captures the long-term evolution of Ks in loess and can predict the Ks of loess-paleosol sequences, along with their expected variability, at a lower cost. This provides more reliable parameters for geological hazard assessments and hydrological engineering design.

Granular materials usually copossess inherent and stress-induced anisotropy that significantly influences their mechanical behaviors. This paper presents a series of true-triaxial tests on aeolian sands to consider the inherent and stress-induced anisotropy in terms of soil deposition angles and intermediate principal stress coefficients, respectively. These results show that the deposition angle primarily affected the elastic-plastic stage under axisymmetric conditions. Otherwise, the deposition angle affects all deformation processes after the elastic stage when the intermediate principal stress coefficient changes. Moreover, the critical state is not unique but depends on the combined effect of the deposition angle and the intermediate principal stress coefficient, which indicates that the strength, stress-strain response, and dilatancy behavior of sands are affected by both inherent and stress-induced anisotropy.

Terrestrial ecosystems, account for approximately 31% of the global land area and play a significant role in the biogeochemical cycling of toxic elements. Previous studies have explored the spatial patterns, effects, and drivers of toxic elements along urban gradients, agricultural lands, grasslands, and mining sites. However, the elevational patterns of toxic elements in montane ecosystems and the underlying drivers remain largely unknown. Atmospheric deposition is a crucial pathway through which toxic elements accumulate along terrestrial elevational gradients. The accumulation of toxic elements exhibited seasonal variability along elevational gradients, with higher deposition occurring in summer and winter. Approximately 46.77% of toxic elements (e.g. Hg) exhibited increasing trends with elevation, while 22.58% demonstrated decreasing patterns (Ba, Co). Furthermore, 8.06% displayed hump-shaped distributions (Ag), and 22.58% showed no distinct patterns (As and Zn). The accumulation of these elements is influenced by several key factors, including atmospheric deposition (26.56%), anthropogenic activities (14.11%), and precipitation (10.37%) primarily via wet deposition of atmospheric pollutants. The accumulation of toxic elements threatens terrestrial biodiversity by disrupting food chains, altering community structures, and causing individual mortality. These disruptions also pose risks to human health through contaminated food sources and food webs, potentially leading to health issues like cancer, organ damage, and reproductive challenges. This review offers key insights into the factors affecting the accumulation and distribution of toxic elements along elevation gradients. It also lays the groundwork for further study on how toxic elements impact ecosystem functions, which is crucial for protecting biodiversity under climate change.

Wet scavenging of black carbon (BC) is essential for evaluating their atmospheric lifetime and radiative forcing. However, it is crucial to differentiate atmospheric BC into char and soot subgroups, given their significant disparities in physicochemical properties and potential impacts. We first conducted a comparative study of char/soot in PM10 and rainwater, collected over a year in urban Guangzhou, China. The mean char/soot ratio in PM10 (similar to 2.5) is obviously higher than that in rainwater (similar to 0.8), corresponding to higher wet scavenging efficiency of soot. Through sequence rainwater sampling during individual rainfall events, we further distinguished the contributions of in-cloud and below-cloud scavenging, with in-cloud scavenging predominantly contributed to the distinct difference between char and soot. Such a distinct wet scavenging behavior of char and soot would have substantial implications for the atmospheric behavior of BC, which should be considered in future models for accurate evaluation of its lifetime and climate impact.

Gaining insights into landslide deposits form can help achieve a better understanding of the overall landslide dynamics. Previous studies have focused on understanding global characteristics of the runout process and final deposit, without attempting to comprehend the deposition process and the underlying mechanisms. Here, we employed a combination of flume experiments and numerical simulations based on the material point method (MPM) to investigate the influence of friction on the characteristics of rock avalanche deposits and gain a deeper understanding of the mechanisms involved. MPM simulations have generally relied on simple soil constitutive models, which cannot capture the rate-, pressure-, and size-dependent characteristics of geomaterials. Thus, we adopted a viscoplastic non-local mu(I) rheology model, which has been proven to be able to reproduce depositional characteristics with high accuracy. We identified two stages during deposition, namely a translational stage, primarily influenced by the basal frictional resistance, and a subsequent impact shear stage, governed by the internal frictional resistance.

The impact of four distinct calcium sources on the microbial solidification of sand in the Kashi Desert, Xinjiang, was investigated. A wind tunnel test over a 60-day period revealed the cracking behavior of four different complex calcium nutrient solutions. By comparing the bearing capacity and the results from dry-wet cycling and freeze-thaw cycle tests, it was concluded that the sample treated with calcium gluconate exhibited superior sand fixation performance, whereas the sample treated with calcium acetate showed weaker sand fixation effects. The microstructure of the treated sand samples was analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Elemental analysis was conducted via energy dispersive spectroscopy (EDS), and functional groups were identified through Fourier transform infrared spectroscopy (FTIR). These experimental findings hold significant implications for soil remediation, pollutant removal in soil, enhancement of soil fertility, and desert soil stabilization.

Atmospheric ammonia (NH3) has multiple impacts on the environment, climate change, and human health. China is the largest emitter of NH3 globally, with the dynamic inventory of NH3 emissions remaining uncertain. Here, we use the second national agricultural pollution source censuses, integrated satellite data, 15N isotope source apportionment, and multiple models to better understand those key features of NH3 emissions and its environmental impacts in China. Our results show that the total NH3 emissions were estimated to be 11.2 +/- 1.1 million tonnes in 2020, with three emission peaks in April, June, and October, primarily driven by agricultural sources, which contributed 74% of the total emissions. Furthermore, employing a series of quantitative analyses, we estimated the contribution of NH3 emissions to ecosystem impacts. The NH3 emissions have contributed approximately 22% to secondary PM2.5 formation and a 16.6% increase in nitrogen loading of surface waters, while ammonium deposition led to a decrease in soil pH by 0.0032 units and an increase in the terrestrial carbon sink by 44.6 million tonnes in 2020. Reducing agricultural NH3 emissions in China would contribute to the mitigation of air and water pollution challenges, saving damage costs estimated at around 22 billion US dollars due to avoided human and ecosystem health impacts.

Airborne pesticide drift poses a substantial environmental threat in agriculture, affecting ecosystems far from the application sites. This process, in which up to 25% of applied pesticides are carried by air currents, can transport chemicals over hundreds or even thousands of kilometers. Drift rates peak during the summer months, reaching as high as 60%, and are influenced by various factors, including wind speed, temperature, humidity, and soil type. Pesticide volatilization is a significant concern, occurring 25 times more frequently than surface runoff. Under certain conditions, it can result in chemical losses of compounds like metolachlor and atrazine that are up to 150 times higher. These drifting pesticides have profound impacts on biodiversity, harming non-target plants, insects, fungi, and other organisms both near application sites and in distant ecosystems. Pesticide drift has been linked to over 50% reductions in wild plant diversity within 500 m of fields, reducing floral resources for pollinators. Despite growing evidence of these effects, the long-term consequences of airborne pesticides on biodiversity remain poorly understood, especially in complex field conditions with multiple pesticide applications. Addressing this requires urgent measures, such as improved meteorological tracking during applications, adoption of biopesticides, and integrated pest management strategies. This review highlights the pressing need for research to quantify airborne pesticides' ecological impacts, advocating for sustainable practices to mitigate environmental damage.

The escalating global crisis of plastic waste necessitates innovative and sustainable approaches to its management. This study explores a novel method; the transformation of discarded plastic materials into high quality 3D printing filaments, offering a promising solution to this pervasive environmental challenge. This review paper delves into the prospects of leveraging plastic waste recycling for the production of 3D printing filaments, thereby advancing the cause of sustainable additive manufacturing. The investigation encompasses a comprehensive examination of the recycling process, encompassing waste collection, sorting, and filament extrusion. The outcomes of this study underscore the substantial potential of recycling plastic waste for 3D printing filaments as a sustainable alternative to conventional manufacturing. This review also delves into the polymer degradation phenomenon, assessment of properties of recycled polymers, and environmental impact assessment, conducting a comparative analysis with traditional filament production methods. This paper advances the application of recycling plastic waste for 3D printing filaments, offering a tangible and immediate response to the global plastic waste crisis.

The impacts of natural boulders carried by debris flows pose serious risks to the safety and reliability of structures and buildings. Natural boulders can be highly random and unpredictable. Consequently, boulder control during debris flows is crucial but difficult. Herein, an eco-friendly control system featuring anchoring natural boulders (NBs) with (negative Poisson's ratio) NPR anchor cables is proposed to form an NB-NPR baffle. A series of flume experiments are conducted to verify the effect of NB-NPR baffles on controlling debris flow impact. The deployment of NB-NPR baffles substantially influences the kinematic behavior of a debris flow, primarily in the form of changes in the depositional properties and impact intensities. The results show that the NB-NPR baffle matrix successfully controls boulder mobility and exhibits positive feedback on solid particle deposition. The NB-NPR baffle group exhibits a reduction in peak impact force ranging from 29% to 79% compared to that of the control group in the basic experiment. The NPR anchor cables play a significant role in the NB-NPR baffle by demonstrating particular characteristics, including consistent resistance, large deformation, and substantial energy absorption. The NB-NPR baffle innovatively utilizes the natural boulders in a debris flow gully by converting destructive boulders into constructive boulders. Overall, this research serves as a basis for future field experiments and applications. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).