Erosion and seepage control is a prime concern for embankments, dams, and other hydraulic structures constructed with alluvial sandy soil due to its highly porous characteristics. Permeation grouting has been a popular solution for controlling seepage situations in such structures. In this study, unconfined compression tests and triaxial tests were performed to determine the strength properties of grouted alluvial sandy soil located in the Ganges-Brahmaputra-Meghna delta. A simple method was devised to prepare cylindrical grouted samples with water-cement ratios (W/C) of 2:1, 3:1, 4:1, and 5:1. Here, unconfined compressive strength test results revealed that the highest compressive strength of the grouted sandy soil samples was achieved at the 2:1 W/C ratio at all curing ages. Different failure patterns are observed for different W/C samples during unconfined compressive tests. Furthermore, triaxial tests were conducted on the grouted samples prepared at the 2:1 W/C ratio under consolidated undrained conditions. Dilation occurred during the volume change, and the pore pressure decreased with increasing confining stress. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy were conducted to discern the microstructural behavioral changes and the chemical characteristics of the grouted sandy samples, respectively. Here, SEM images revealed a reduction in porosity with decreasing W/C ratio and increasing curing age. Permeation grouting leads to a reduction in permeability without disturbing the soil microstructure. Therefore, permeation grouting is a very effective technique for improving the mechanical behavior of grouted alluvial sand.

Integral bridges with longer spans experience an increased cyclic interaction with their granular backfills, particularly due to seasonal thermal fluctuations. To accurately model this interaction behaviour under cyclic loading, it is crucial to employ appropriate constitutive models and meticulously calibrate and test them. For this purpose, in this paper two advanced elastoplastic (DeltaSand, Sanisand-MS) and two hypoplastic (Hypo+IGS, Hypo+ISA) constitutive models with focus on small strain and cyclic behaviour are investigated. The soil models are calibrated based on a comprehensive laboratory programme of a representative highly compacted gravel backfill material for bridges. The calibration procedure is shown in detail and the model capabilities and limitations are discussed on the element test level. Additional triaxial tests with repeated un- and reloading reveal significant over- and undershooting effects for the majority of the investigated material models. Finally, cyclic finite element analyses on the soil-structure interaction of an integral bridge are conducted to compare the performance of the soil models. Qualitatively similar cyclic evolution of earth pressures are detected for the soil models at various bridge lengths and test settings. However, a substantially different cyclic settlement behaviour is observed. Additionally, the investigation highlights severe overshooting effects associated with the tested hypoplastic soil models. This phenomenon is studied in detail using a single integration point analysis. Supplementary studies reveal that the foot point deformation of the abutment significantly influences the lateral passive stress mobilisation and the amount of its increase with growing seasonal cycles.

Urgent action is needed in the Amazon to halt deforestation, repair agricultural damage, and restore forests to revive ecosystemic functions such as carbon (C) storage and soil health. A critical and demanding challenge, especially in sandy soils, is ceasing the slash-and-burn in smallholder farming livelihoods to preserve ecosystem services of primary and secondary forests. Here, we examined (i) the recovery of secondary forests in structure, litter layer, and soil health, as well as C storage post-agricultural abandonment of extremely sandy Amazonian soils (> 89 % sand), and (ii) the extent of loss of these gains when a secondary forest is burned for agricultural reconversion. We tracked secondary forests at 2, 5, 10, and 20 years, including slash-and-burning the 20-year-old forest. Our methods included analyzing C stocks in soil, litter, and plants, forest vegetation ecological indexes, litter quality assessed through nitrogen (N), C, and lignocellulose contents, delta C-13 to indicate organic matter origin, and seven additional soil health indicators. Soil delta C-13 ranged from-27.1 to-28.8 parts per thousand across the sites, indicating a negligible influence of tropical grasses on the soil's organic matter and suggesting that pastures were not previously cultivated in these areas. Secondary forest growth accumulated 0.24 and 2.97 Mg C ha(- 1 )y(- 1 ) in litter and trees, respectively. Yet, soil C stocks did not show significant changes during 20 years of forest regeneration. Over 18 years, the forest increased the vegetation diversity fourfold and litter N by 41 %, improving forest structure and litter quality. This progress in organic matter aboveground contributed to improved soil biological activity and nutrient storage, facilitating soil health and multifunctionality regeneration as the forest aged. However, slash-and-burn resulted in a 67.6 Mg C ha(- 1 ) loss, reverting levels below those of the 2-year-old forest. Returning to agriculture also depleted soil cation exchange capacity, bulk density, and fauna activity, degrading soil's chemical, physical, and biological functions to levels comparable to or worse than those in the youngest forest. We conclude that Amazonian lands abandoned after long-term agriculture still offer potential for ecological restoration, with secondary forests capable of regenerating multiple ecosystem functions, even in sandy soils. However, a single slash-and-burn reverses 20 years of progress and degrades soil health further. Recognizing smallholder farmers' poverty and reliance on slash-and-burn, we advocate for educational and socioeconomic support to stop fires and encourage sustainable agriculture, including bioeconomy incentives and environmental compensation to sustain the perpetuation and benefits of secondary forests in the Amazon.

Coastal agriculture faces escalating threats from seawater intrusion (SWI), jeopardizing global food security through freshwater scarcity, soil salinization and crop damage. However, research on SWI often fails to consider its impact on coastal agriculture. Linking georeferenced SWI data with cropland presence, this review examines SWI's global distribution and primary drivers. Major attested hotspots include the Mediterranean, South and South-East Asia, and the Bohai Sea region in China. Approximately 87 Mha of cropland globally are vulnerable due to low elevation and coastal proximity, including regions where little to no literature has documented SWI. Main drivers include sea-level rise (SLR), drought, groundwater depletion, river modifications, tidal flooding and subsidence. Projections of SLR indicate cropland of North America, the Indian Subcontinent, and South-East Asia as high-risk for SWI. Additionally, regions like South-East Asia and the Indian Subcontinent are expected to experience significant demographic growth in coastal areas. Understanding present and future SWI dynamics is crucial for designing effective mitigation and adaptation strategies in coastal agriculture to support food supply.

Soil salinity typically exhibits non-uniform distribution in the natural environment. However, how vertically non-uniform distribution of soil salinity in the root zone (VNDSR) regulated plant nitrogen metabolism is still largely elusive. This study aimed to investigate the impact of VNDSR on leaf Malondialdehyde (MDA) content, upper and lower root activity, leaf Na+/Ca2+ and Na+/K+, various tomato organs' nitrogen concentration (%) and natural abundance of nitrogen isotopes (delta N-15,parts per thousand), and nitrogen utilization efficiency of tomato plants. Four treatments were established, including the upper layer of the root zone having soil salinity levels of 1 parts per thousand, 1 parts per thousand, 2 parts per thousand, and 3 parts per thousand, while the corresponding lower layer of the root zone had soil salinity levels of 1 parts per thousand, 5 parts per thousand, 4 parts per thousand, and 3 parts per thousand, respectively, denoted as T-1:1, T-1:5, T-2:4, and T-3:3. The results showed that under the same average soil salinity conditions and compared to the treatment with uniform soil salinity distribution in the root zone (T-3:3), the VNDSR treatment (T-1:5) significantly reduced leaf MDA content (p < 0.01), Na+/Ca2+ (p < 0.01) and Na+/K+ (p < 0.01), and stem delta N-15 values (p < 0.05). Moreover, the VNDSR treatment (T-1:5) significantly increased the ratio of upper and lower root biomass-weighted root activity (p < 0.01), tomato fruit yield (p < 0.01), and nitrogen partial factor productivity (PFP, gg(-1), p < 0.01) compared to uniform salt distribution treatment (T-3:3). There were significant positive correlations (p < 0.05) between leaf delta N-15 values and Nitrogen Absorption Ratio (NAR, %, p < 0.05) and PFP (p < 0.05), indicating that under VNDSR, delta N-15 values can serve as an indicator that comprehensively reflects the information of plant nitrogen utilization efficiency. In conclusion, the VNDSR could mitigate the damage of salt stress to tomatoes, enhance plant nitrogen uptake and utilization efficiency, and promote the growth and development of tomatoes.

Wave-induced liquefaction is a geological hazard under the action of cyclic wave load on seabed. Liquefaction influences the suspended sediment concentration (SSC), which is essential for sediment dynamics and marine water quality. Till now, the identification of liquefaction state and the effect of liquefaction on SSC have not been sufficiently accounted for in the sediment model. In this study, we introduced a method for simulating the liquefaction-induced resuspension flux into an ocean model. We then simulated a storm north of the Yellow River Delta, China, and validated the results using observational data, including significant wave heights, water levels, excess pore water pressures, and SSCs. The liquefaction areas were mainly distributed in coastal zones with water depths less than 12 m, and the simulated maximum potential soil liquefaction depth was 1.39 m. The liquefaction-induced SSC was separated from the total SSC of both liquefaction- and shear-induced SSCs by the model, yielding a maximum liquefaction-induced SSC of 1.07 kg center dot m(-3). The simulated maximum proportion of liquefaction-induced SSC was 26.2% in regions with water depths of 6-12 m, with a maximum significant wave height of 3.4 m along the 12 m depth contour. The erosion zone at water depths of 8-12 m was reproduced by the model. Within 52.5 h of the storm, the maximum erosion thickness along the 10 m depth contour was enhanced by 33.9%. The model is applicable in the prediction of liquefaction, and provides a new method to simulate the SSC and seabed erosion influenced by liquefaction. Model results show that liquefaction has significant effects on SSC and seabed erosion in the coastal area with depth of 6-12 m. The validity of this method is confined to certain conditions, including a fully saturated seabed exhibiting homogeneity and isotropic properties, small liquefaction depth, residual liquefaction dominating the development of pore pressures, no influence by structures, and the sediment composed of silt and mud that experiences frequent wave-induced liquefaction.

In Australia, trifluralin is one of the commonly used herbicides to manage annual grasses and some broadleaf weeds. However, it may have some ecosystem impacts such as high toxicity to terrestrial and aquatic life, so it is vital to monitor the degradation of trifluralin for a considerable period for environmental safety. For risk assessment purposes, it is necessary to estimate the half-life of trifluralin, which is often evaluated using derived mathematical dissipation models. In the literature, bi-exponential (BEXP) and gamma models were suggested for modelling the dissipation of trifluralin in soil. Both models provide the half-life estimate without discussing the uncertainty of the estimate, which is a shortcoming in the literature. In this paper, we used simulation to illustrate the importance of estimate's uncertainty (standard error) and demonstrated a method to compute the standard error for the half-life estimate mathematically for kinetic dissipation models. Later, we evaluated the performance of the two suggested models using statistical indices. The computation of the half-life and the standard error of the half-life estimate were discussed. This allows us to describe the inference of the half-life parameter and determine whether the half-life estimates are significantly different against the co-variate (moisture) levels. We demonstrated the method to calculate the standard error of the half-life of trifluralin, which allows us to determine the statistical difference between the estimates. In this study, we found that the half-life of trifluralin in soil tends to increase with increasing moisture levels, and the half-life of trifluralin in soil with 100% moisture level is significantly greater than 40% and 70% moisture levels. Our findings suggest that soil moisture levels should be carefully considered before trifluralin application to minimize the non-target environmental damage.

Carbonaceous aerosols play an important role in radiative forcing in the remote and climate-sensitive Tibetan Plateau (TP). However, the sources of carbonaceous aerosols to the TP remain poorly defined, in part due to the lack of regionally relevant data about the sources of carbonaceous aerosols. To address this knowledge gap, we present the first comprehensive analysis of the delta C-13 signatures of carbonaceous aerosol endmembers local to the TP, encompassing total carbon, water-insoluble particle carbon, and elemental carbon originating from fossil fuel combustion, biomass combustion, and topsoil. The delta C-13 signatures of these local carbonaceous endmembers differ from components collected in other regions of the world. For instance, fossil fuel-derived aerosols from the TP were C-13-depleted relative to fossil fuel-derived aerosols reported in other regions, while biomass fuel-derived aerosols from the TP were C-13-enriched relative to biomass fuel-derived aerosols reported in other regions. The delta C-13 values of fine-particle topsoil in the TP were related to regional variations in vegetation type. These findings enhance our understanding of the unique features of carbonaceous aerosols in the TP and aid in accurate source apportionment and environmental assessments of carbonaceous aerosols in this climate-sensitive region.

Rainfall variability, waterlogging and frequent natural hazards are the major obstacles for cropping system intensification in heavy textured soils of the coastal areas of Bangladesh. While earlier monsoon rice harvesting by introducing short duration varieties created opportunities for cultivating low water demanding non-rice crops in the dry season, such crops failed in many instances because of heavy rainfall and waterlogging. To address such issue, we have analysed dry season (Nov-Apr) rainfall patterns of six meteorological stations of coastal Bangladesh for studying the feasibility of growing irrigated rice and non-rice crops that can be harvested by April. Very heavy rainfall (>20 mm) occurred in 18-23% of the studied years and heavy rainfall (>10 mm) in 42-43% of cases creating the risk of water stagnation and damage to non-rice crops. The return intervals between occurrences of heavy rainfall and very heavy rainfall in November to December were 1.3-1.4 years and 1.5-2.5 years, respectively. These rainfall events generally delay establishment of non-rice crops. Similarly, in March and April, the return periods for heavy and very heavy rainfall were 1.3-1.5 years and 1.6-2.1 years, respectively. These rainfall events had a detrimental impact on non-rice crops, especially during their ripening stages. Such rainfall events during field experiments at the study locations were found in three years out of four cropping seasons that reduced sunflower and maize yields by 50-64% and sweet gourd and watermelon yields by 55-84% compared to their absence. The probability of high yield of non-rice crops was <25% and the yield variability was very high (40-75%) compared to general rice yield variability (5-6%). Risk factor analysis also revealed that dry season rice is less risky compared to other non-rice crops. To enhance risk management, intensification of cropping systems can be achieved by promoting cultivation of dry season irrigated rice where there is sufficient stored water for irrigation and encouraging farmers to grow pre-monsoon rice.

Extreme precipitation events (EPEs) are projected to become more frequent and intense due to global warming. Understanding how coastal groundwater levels respond to and recover from these severe events is important for estuarine ecosystems to adapt to global change. Numerical model and non-EPE scenario simulation were used to examine groundwater level recovery time (RT) after Super Typhoon Lekima, which triggered EPEs that resulted in groundwater rise and widespread flooding in the Yellow River Delta (YRD). The three-day rainfall during Lekima totaled 290.9 mm, equivalent to 50 % of the annual rainfall for 2019 (581.5 mm), leading to a general rise in groundwater levels. Groundwater recovery to EPE can be divided into two types: inland and coastal. The RT of groundwater levels in monitoring wells in inland areas ranged from 12 to 89 days, with an average of 56.2 days, and there was spatial variation. However, groundwater levels in monitoring wells close to the coast may not recover. Differences in recovery are reflected in the land-sea gradient, with RT gradually increasing from inland highlands to coastal depressions and lowlands. The results showed that inland aquifers were more resistant to EPEs, while coastal aquifers were less resistant. In addition, EPE can cause groundwater flooding, and areas at lower altitude and close to the sea are more sensitive to flooding. Estuarine groundwater and the ecological processes on which it depends are profoundly affected by the direct and legacy effects of EPEs, including salt contamination, widespread flooding, crop damage, and reduced biodiversity. The study of this event provides case support for the response of estuarine groundwater to EPEs, while highlighting the importance of continuous monitoring.