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Groundwater extracted from coal seams may be a resource for irrigation of land in areas with low rainfall, but the effect of this water on soil properties needs to be established. A lysimeter study was conducted using intact soil cores (0.75 m diameter, 1.4 m deep) of four different soil types (Sodic Vertisol, Calcic Solonetz, Haplic Solonetz and Xanthic Lixisol) from southern Queensland, Australia, to study changes in soil physical and chemical properties under accelerated rates of irrigation with coal seam (CS) water (electrical conductivity (ECw) of 3 dS/m, pH of 8.8, and a sodium adsorption ratio (SAR) of 100). Cores were also alternately irrigated with deionised water to simulate rainfall, and either lucerne (Medicago sativa L) or Rhodes grass (Chloris gayana Kunth.) where grown in the lysimeters. The soil surface was treated with stoichiometric rates of elemental sulfur (1.4 t/ha) and gypsum (2.5 t/ha) prior to every 450 mm CS water irrigation to minimise changes in SAR and pH. Three of the soils (Vertisol, both Solonetz) had low leaching fractions (≤ 0.1 %) due to their clay texture and were initially saline in the subsoil (ECse 1.4–4.4 dS/m). Irrigation with CS water resulted in a gradual increase in salt content (EC) and SAR throughout the soil profile, but pH was not increased due to surface-applied elemental sulfur. The Lixisol had a higher hydraulic conductivity and leaching fraction (6.7 %) due to is loamy texture – in this soil, accumulated salts could be leached and no increase in salinity or pH were measured. Despite an increase in SAR for this loamy soil, no structural degradation was observed, and it could be sustainably irrigated with up to 3200 mm CS water (with cumulative irrigation volume of 5400 mm). Hence, leaching fractions rather than soil chemistry are good indicators to identify soils suitable for irrigation with CS water that is saline, alkaline, and sodic.

Karst ecosystems offer a wealth of ecosystem services, but their protection is increasingly challenging due to degradation and land-use conversion, including limestone mining. This study investigates the water provision service derived from karst ecosystems threatened by limestone mining in the Watuputih groundwater basin, Central Java, Indonesia. Water supply was quantified by measuring water discharge rates from major springs around the basin. Water usage was quantified for household consumption, agriculture, and recreation. This study also measured water infiltration rates in mining and non-mining areas to indicate the effects of limestone mining to hydrological processes. This study identified three primary springs around the basin: Sumber Seribu spring, Brubulan spring, and Kalutan spring, with discharge rates of 1080 L per second, 85 L per second, and 0.76 L per second, respectively. A local water company extracts water from Sumber Seribu spring at a rate of 80 L per second to supply approximately 57,600 individuals. The water supply from the three springs can irrigate approximately 1594 ha of rice fields. Water from Sumber Seribu spring also supports recreational activities in Sumber Semen recreation park, attracting an average of 19,173 visitors per year. This study revealed a complete impairment of soil's water infiltration capacity in limestone mining areas. These findings underscore the pressing need to safeguard the Watuputih groundwater basin and to mitigate the detrimental effects of limestone mining on hydrological processes. This involves designating the Watuputih karst ecosystem as a protected area, implementing Payment for Ecosystem Services (PES) programs, and restoring degraded post-mining sites.

Field monitoring was conducted to investigate and quantify the long-term effects of peanut shell biochar on soil-grass interaction over three years. Three 10 m × 5 m grassed plots were constructed in completely decomposed granitic soil. Two of them were amended, respectively, with 5% and 10% biochar contents (m3/m3) for grass growth, while the third was without biochar amendment. During the three-year monitoring, plant characteristics, saturated water permeability (ks) of grassed soil and soil suction were measured. The monitored results show that the grass leaf area index (LAI) and root length density (RLD) with biochar amendment were improved by 38% and 200%, respectively. In the grassed plot without biochar, a threshold RLD existed with a value of 1.7 cm/cm3, beyond which ks raised pronouncedly. The threshold RLD increased by 52% when biochar content increased from 0% to 10%. This implies that biochar may restrict the increase in ks of grassed soil due to the rise in the threshold RLD. The presence of biochar and grass can retain over 100% higher suction after heavy rainfalls, while 54% lower peak suction under evapotranspiration (ET) compared with the non-amended plot. Biochar can alleviate the negative effects on hydraulic properties caused by plant growth and reduce ET-induced excessive water loss. A 5% peanut shell biochar content is recommended for the long-term management of vegetated earthen infrastructures.

Extreme rainfall significantly threatens the safety of the landfill cover system, especially under humid climates. This study aims to provide design recommendations for a sustainable landfill cover system consisting of a low-permeability soil layer underlying a two-layer capillary barrier for humid climates. First, the numerical back-analysis was conducted for verification against a series of flume model tests. Then, a parametric study was performed to investigate the effects of inclination angle, particle size and layer thickness on the lateral diversion length (DL) of the three-layer cover system under the 100-year return period rainfall of humid climates. The results show that the water lateral DL of the cover system can be greatly enhanced by increasing the inclination angle from 3° to 18°. Moreover, the bottom layer of the cover system with a coarser d10 was more susceptible to the impact of the heavy rainfall, while this can be alleviated by increasing the thickness of the bottom layer. A dimensionless number, defined as the ratio of thickness and d10 of the bottom layer, is proposed for designing lateral diversion of the three-layer cover system under humid climates. To preserve the maximum DL, it is suggested that the proposed dimensionless number should be larger than 95 and 110 for the design of rainfall events with 50-year and 100-year return periods for humid climates, respectively.

Agricultural soils face severe challenges, including water scarcity and heavy metal contamination. Optimizing soil remediation efficiency while minimizing inputs is essential. This study assessed the water retention and heavy metal adsorption properties of L-PH hydrogel through aqueous experiments. Fourier Transform Infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS) elucidated the adsorption mechanisms. The results showed that L-PH hydrogel exhibited high water absorption efficiency, with Zn 2+ removed via electrostatic interactions and cation exchange, and Cd 2+ and Cu 2+ adsorbed through coordination complexation. Soil experiments tested water retention and heavy metal leaching under various application methods (M1 = 0-10 cm mixed, M2 = 10-20 cm mixed, T1 = 5-10 cm layered, T2 = 10-15 cm layered) and rates (NL = 0 %, L1 = 0.1 %, L2 = 0.2 %, L3 = 0.5 %). L-PH reduced water infiltration, enhanced soil water retention, and decreased heavy metal mobility across all treatments. The highest water retention was observed in the M1 method. Under M1L1, cumulative leaching of Cd 2+ , Cu 2+ , and Zn 2+ decreased by 68.84 %, 33.44 %, and 83.60 %, respectively. Two-way ANOVA revealed that application rate had a greater effect on leaching than the method. FTIR and XRD analyses showed that at low concentrations (L1, L2), L-PH formed coordination bonds with Cd 2+ and Cu 2+ , creating Cd(HCOO) 2 ·2(NH 2 ) 2 CO and Cu(HCOO)(OH) in the soil. Zn 2+ was stabilized through adsorption and precipitation, forming Zn(OH) 2 , thereby reducing leaching. Higher concentrations of L-PH may have further interacted with Zn, leading to dissolution and adsorption/precipitation processes. Redundancy analysis (RDA) analysis suggests that an increase in organic carbon and moisture content in soil aggregates larger than 2 mm, along with a decrease in bioavailable heavy metals, may enhance heavy metal stabilization, reducing their movement and leaching. This study offers valuable insights into addressing the twin challenges of water scarcity and heavy metal pollution., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Biochar, has recently, been widely used as a potential soil additive to improve the quality of cultivated land. However, the effect of biochar on irrigation water use efficiency (IWUE) remains unclear in the Qinghai-Tibet Plateau (QTP). Therefore, the purpose of this study was to explore the effects of biochar on the soil properties, water infiltration, and irrigation water efficiency of QTP cultivated land. A column experiment with four biochar application levels (0, 3, 6, and 9 kg·m -2 denoted CK, BC1, BC2, and BC3, respectively) was conducted to explore the biochar effect on the soil water infiltration process. The soil bulk density (γ), saturated water content (θs), soil water retention curve (SWRC), specific water capacity C(h), and saturated hydraulic conductivity (Ks) were measured after the trial. The effects of biochar application level, biochar application depth, irrigation water depth, and initial soil moisture on water loss and IWUE were then simulated by HYDRUS-2D. The results showed that biochar slowed the process of soil water infiltration by changing the soil physical properties and hydraulic properties, reducing the water loss by 5%-15.02%, effectively alleviating the waste of irrigation water, and therefore increasing IWUE by 2%-9.43%. Water loss and IWUE were significantly associated with the biochar application depth and level. Additionally, a biochar level of 6 kg·m -2 showed the best effect for ameliorating the QTP's cultivated soil. These results provide a novel approach for reducing water loss and enhancing the irrigation water use efficiency of QTP cultivated soil., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Understanding linkages between heterogeneous soil structures and non-uniform flow is fundamental for interpreting infiltration processes and improving hydrological simulations. Here, we utilized ground-penetrating radar (GPR) as a non-invasive technique to investigate those linkages and to complement current traditional methods that are labor-intensive, invasive, and non-repeatable. We combined time-lapse GPR surveys with different types of infiltration experiments to create three-dimensional (3D) diagrams of the wetting dynamics. We carried out the GPR surveys and validated them with in situ observations, independent measurements and field excavations at two experimental sites. Those sites were selected to represent different mechanisms that generate non-uniform flow: (1) preferential water infiltration initiated by tree trunk and root systems; and (2) lateral subsurface flow due to soil layering. Results revealed links between different types of soil heterogeneity and non-uniform flow. The first experimental site provided evidence of root-induced preferential flow paths along coarse roots, emphasizing the important role of coarse roots in facilitating preferential water movement through the subsurface. The second experimental site showed that water infiltrated through the restrictive layer mainly following the plant root system. The presented approach offers a non-invasive, repeatable and accurate way to detect non-uniform flow., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The development of a cover for inclined acid-generating areas, such as the external face of dykes and the slope of waste rock piles, is undoubtedly one of the biggest technical reclamation challenges at several mine sites. The LaRonde mine site, owned and operated by Agnico Eagle Mines (Quebec, Canada) is currently engaged to identify an optimal reclamation scenario for the Dyke 1 of its acid-generating tailings storage facilities. One of the promising reclamation options for controlling water infiltration in the acid-generating waste rock on the Dyke 1 is the use of an inclined cover built with available mine waste materials. An instrumented inclined cell with an inclination angle of 18.3 degrees was built on a slope of this dyke to validate if low sulfide tailings and non potentially acid-generating waste rock can be used as cover material to reclaim the Dyke 1. The instrumented inclined cell was monitored for 3 years (2017 to 2019) using volumetric lysimeters, suction sensors, and volumetric water content sensors. The monitoring was done under natural climatic conditions and artificial wetting events. Under natural conditions, less than 1% (5 mm) of incident rainfall percolated in the volumetric lysimeters installed along the slope of the inclined cell. Under controlled conditions associated with artificial wetting events of 6.4 mm/h over a period of 12 h, net percolation values between 1 and 9% (4 to 60 mm) of the sum of incident precipitation were measured. The distance between the top of the cell and the Down Dip Limit (DDL) point was greater than the slope length of the cover under natural conditions and the DDL point moved from the bottom toward the top to reach values between 12 and 20 m from the top of the slope when the wetting events were applied on the cover. These results confirmed the suitability of mining materials as an inclined cover material to control water infiltration in reactive mine waste rocks., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The hydrological response of forest soil in the Mediterranean environment is characterised by high runoff and erosion rates, mainly due to low infiltration and high repellency of soils. However, little literature exists about the effects of forest ages on soil water repellency (SWR) and hydraulic conductivity (SHC). This study evaluates these hydrological parameters in five Pinus nigra Arn ssp. Salzmannii stands of different ages in Central-Eastern Spain; one of these stands, unmanaged, was chosen as reference system. SWR (measured in terms of water drop penetration time, WDPT) and SHC as well as the main physico-chemical properties and surface characteristics of soils were surveyed in forty-five plots. Water infiltration was higher in the older stands (including the older and unmanaged forest) and lower (by over 60%) in the more recent pine forests. Four of the studied stands did not show water repellency; only the more recent plantation showed a slight SWR. The differences in SHC among the forest ages were mainly driven by the organic matter (OM) and nutrient contents of the soils as well as by the bulk density and quantity of dead wood. SWR was similar among the plots (despite significantly differences in WDPTs), although having variable OM contents. Considering these differences in soil properties, SHC and SWR were simply predicted for each forest stand using on dbRDA models and the following soil properties: (i) OM and total nitrogen contents of soil (for SHC and SWR); (ii) dead wood and bulk density (for SHC); and (iii) clay content and the percentage of bare soil (for SWR). Overall, this study has showed that, when a new forest stand is planted, decreases in water infiltration, with subsequent increases in runoff generation capacity) of the soils, can be expected. Conversely, no water repellency is likely to affect new pine plantations., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The objective of this paper was to identify the incidence and extent of preferential flow at two experimental areas located in Lyon, France. We used time-lapse ground-penetrating radar (GPR) surveys in conjunction with automatized single-ring infiltration experiments to create three-dimensional (3D) representations of infiltrated water. In total we established three 100 cm × 100 cm GPR grids and used differenced radargrams from pre- and post-infiltration surveys to detect wetting patterns. The analyzed time-lapse GPR surveys revealed the linkage between nonuniform flow and heterogeneous soil structures and plant roots. At the first experimental area, subsurface coarse gravels acted as capillary barriers that concentrated flow into narrow pathways via funneled flow. At the second experimental area, the interpolated 3D patterns closely matched direct observation of dyed patterns, thereby validating the applied protocol. They also highlighted the important role of plant roots in facilitating preferential water movement through the subsurface. The protocol presented in this study represents a valuable tool for improving the hydraulic characterization of highly heterogeneous soils, while also alleviating some of the excessive experimental efforts currently needed to detect preferential flow pathways in the field., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

A dune forest in SW France composed of maritime pines was irrigated with treated wastewater for a decade in an experiment (including irrigated plots versus control plots) to evaluate the environmental impact of applying wastewater on the water table, soil properties, and plants. The amount of treated wastewater (1921 mm yr -1 ) applied was twice the annual precipitation. Nutrient inputs were also very high, particularly nitrogen (N: 539 kg-N ha -1  yr -1 ), phosphorus (P: 102 kg-P ha -1  yr -1 ), and calcium (Ca: 577 kg-Ca ha -1  yr -1 ). Irrigation caused a rise in the water table, and increased its sodium (Na), NO 3 - , potassium (K), and calcium concentrations. Soil properties were affected by irrigation at least down to a depth of 1.2 m. After eight years of irrigation, soil pH had increased by 1.4 units, and soil available P content (P Olsen ) increased nearly 8-fold. In the short-term (i.e. 1-3 years), irrigation with treated wastewater improved growth, standing biomass, and the nutritional status of the vegetation. But tree dieback started in the fourth year of irrigation and worsened until the end of the monitoring period when almost all the irrigated trees were dead or moribund. The understory composition was drastically modified by irrigation, with an increase in α-biodiversity and in the biomass of herbaceous species, and a reduction in woody species abundance. The factor that best explained tree dieback was manganese nutrition (Mn): (i) the Mn content of the tree foliage was negatively affected by irrigation and below the deficiency values reported for pine species, and (ii) soil available Mn (CaCl 2 extraction) decreased by half in the topsoil layer. Manganese deficiency was probably the consequence of the increase in soil pH, which in turn reduced soil Mn availability. Tree dieback was not related to either to a macronutrient deficiency or to toxicity caused by a trace element., (Copyright © 2018 Elsevier B.V. All rights reserved.)