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Soil splash is the first step of water erosion, therefore a good understanding of it is important in order to describe this multifaceted phenomenon. One of the methods describing this process is the use of splash cups, which allow us to determine the mass of soil material ejected by the impact of water drops. The aim of this study was to determine the mass ratio of splashed particles during raindrop splash on the soil surface, including their division into a splashed liquid phase and a solid phase. The investigation was carried out using three types of soil with different particle size distributions. In the first stage of the experiment, three initial moisture contents were applied (pressure head equal to 0.1 kPa, 1.0 kPa and 3.16 kPa) and the second stage measurements were based on the soil with the highest splash efficiency in the case of the different kinetic energy of the impacting drop. It was found that: (i) the texture of soil sample had a significant effect on the mass of splashed material; (ii) the lower the initial moisture content of the sample, the lower the mass of splashed material; (iii) the highest values of the mass of splashed material (both the liquid phase and solid phase) were obtained for soil with the highest sand fraction; (iv) for all types of soils, the mass of the splashed water was significantly larger than the collected mass of splashed soil; (v) the ratio of splashed masses (the proportions) was dependent on initial moisture content for soil with a higher amount of finer fractions. The obtained results are important for the physical description of the splash erosion. For instance, the knowledge of the masses of solid (soil) and water parts of the ejected material and their ejection kinetic energy will allow the estimation of the total energy needed for the displacement of splashed material. Moreover, the investigation of the water phase in the splash phenomenon is significant because of the transport processes of pollutants and pathogenic microorganisms.

The impact of a spherical intruder on a bedding of spherical particles and the behaviour of particles during the splashing phenomenon were studied experimentally and via discrete element method (DEM) simulations. The objective of this study was to gain deeper insight into the physical mechanisms governing the behaviour of the particle bedding during low-velocity impact. The experiments were performed using a high-speed camera to capture the splash of the particles. A piezoelectric ceramic pressure sensor located at the bottom of the container was employed to measure the pressure impulse generated by the intruder impact. We obtained good agreement between the DEM simulations and experimental results for all the considered parameters of the impact process. The study allowed a better understanding of the interactions in a granular bedding during impact at micro-scale. The results indicated that the dynamics of the intruder-particles, particle-particle, and particles-bottom interactions were similar, having a nonlinear increase that accompanied an increase in the impact velocity. This was caused by a local increase in the effective stiffness of the bedding resulting from simultaneous multi-collisions. The coefficient of particle-particle friction significantly affected all the measures considered: speed of the compression wave, amplitude of the impact force, amount of kinetic energy transferred from the intruder to the particles, depth of penetration and crater diameter, and number of ejected particles and their kinetic energy.

Splash is the first step of the water erosion process initiated when raindrops hit the earth’s surface and eject particles of soil. The ability to physically describe this phenomenon is important in order to counteract it. One of the research aspects of splash is energy dissipation of the impacting drop where the ejection of particles is significant part. Therefore, the main aim of this work is the presentation of an improved method for calculation of the kinetic energy of two-phase splashed material (water/solid soil particles). Measurements were carried out on Haplic Luvisol soil surface and single drop impact. Different methodologies allowed for obtaining key parameters that influence particles’ energy, including measuring the number of ejected particles, their mass, and their ejection velocity. High-speed cameras registered the phenomenon, identified particles, and reconstructed their flight trajectories. Based on the analysis of particle trajectories, it was possible to determine the distribution of particles’ ejection velocity with the average value equal 2.60 m·s−1. Splash cup measurements provided data on the total mass of splashed material, including its division into the solid phase (soil) and the liquid phase (water), and calculation of the average density of ejected particles (1.31 g·cm−3). An alternative method for particles’ mass calculation, the 2D image analysis method, was calibrated with the results obtained with the splash cup. Based on the input data, three variants of kinetic energy calculation of the splashed material were tested. The variants differed in assumptions and approximations, and it was difficult to determine which was preferable. Taking into account the results from all variants, however, it can be stated that the total kinetic energy of splashed particles in relation to the kinetic energy of a water drop hitting the soil surface ranged between 4.6% and 7.4%. To the best of the authors’ knowledge, this study is the first report of kinetic energy calculation which takes into account the two-phase nature of splashed material.

Soil splash is the first step of water erosion. There are many methods for splash investigations however the use of high-speed cameras is becoming increasingly popular. This study describes the methodological aspects of using high-speed cameras and a PTV (Particle Tracking Velocimetry) system to investigate the soil splash phenomenon. The purpose of the research was to examine the impact of image processing and the choice of settings for particle tracking software on the effectiveness of detecting and identifying splashed/ejected particles (with their flight trajectories). Experiments were carried out on moisturized Haplic Luvisol soil samples and the impact of single water-drop onto the surface was recorded by three calibrated Phantom Miro M310 high-speed cameras. Registered frames were subjected to image processing in Dantec DynamicStudio software, where the selection of the optimal set of parameters/settings was validated, in the context of maximum detection of the splashed particles. The resulted images provided the input data for the Volumetric 3D PTV module (DynamicStudio) to identify/track the ejected particles and then determine their trajectories. The study presents the use of different settings (variants) of tracking modules, enabling the most efficient identification and description of the particles’ trajectories (76%). The incomplete trajectories detected (excluding starting and landing fragments), were subjected to a reconstruction process based on mathematical extrapolation. The analyze of the registered images and reconstructed trajectories of splashed particles gave the possibility to determine the following parameters describing soil splash phenomenon: a) number of splashed particles, b) ejection angle (for each particle), c) ejection velocity, d) displacement range, e) altitude (the maximal height reached by the particle).

The phenomenon of splash is connected with soil erosion, occurs commonly, and has a complex nature. The study presents the results of research in which glass beads (dry and saturated beds) with a diameter size range of 0.425–0.6 mm were used as a soil model. Patterns and layers of glass particles (beads), distinguished by their colour were placed on the surface of the samples. Displacements of the marked beads were used for the analysis of movement caused by splash. The measurements were supplemented with recordings made with high-speed cameras and photographs from an X-ray microtomograph. Three types of displacement for dry bed elements were distinguished: (i) displacement inside the surface area wetted with a falling drop of water, (ii) ejection and (iii) placement on the crater rim, as well as two types of displacement for elements from saturated beds: (i) displacement inside the deformation and (ii) ejection. The distance travelled by the beads was related to the specificity their displacement, which was associated with the initial location of the beads on the sample surface. In the case of dry beds, glass beads with an initial location equal to 14 mm or more from the centre of the drop impact were not moved. In the case of saturated beds, this distance was about 10 mm. More than 95% of the beads ejected from dry beds came from the surface layer of the sample. All the measurement methods applied show that the deformations of the dry bed surfaces were greater and more diversified than those of the saturated beds. The results presented in the study are important for understanding the mechanisms of transport of bacteria, fungi, and pollutants transferred with ejected soil particles during splash. The results can also be used for a physical description of the phenomenon for the computer modelling of both splash and water erosion.

Knowledge about splash of water drops on leaf surfaces is required inter alia in studies of rainfall modification by plant canopies, the spread of plant diseases, and washing out and transportation of pollutants and plant protection products that have settled on leaves. Splash drop generation is a complex process that cannot yet be precisely predicted theoretically, and it is dependent on surface properties. Hypothesizing that water drop splash on leaves will be dependent on surface wettability, we aimed to describe this effect quantitatively using leaves from N. nucifera and B. oleracea (highly non-wettable); E. aureum (non-wettable); A. macrorrhizos (wettable); N. lutea, A. glutinosa, N. alba and H. tuberosus (highly wettable); and R. makoyana (super-hydrophilic). Leaf wettability was defined by the contact angle value, measured using the sessile drop method. Surface leaf structures were described based on photographs from a scanning electron microscope. Splashes were caused by single water drops (4.2 mm) falling freely from 1.5 m. The phenomena were recorded by a set of high-speed cameras. It can be concluded that falling water drop behaviour is closely related to both wettability and surface structure, particularly the presence of trichomes. Greater hydrophobicity causes this at the moment of impact; the water drop propagates faster and expands to a larger surface area. The effect of the presence of trichomes is more pronounced when there is a relation between the average number and velocity of ejected droplets and the equivalent diameter of the largest residual droplet remaining on the leaf versus contact angle. The presence of trichomes on the leaf surface causes resistance, which leads to energy losses from the hitting drop and disturbs the process of water spreading over the leaf surface.

The laser diffraction method (LDM) is a relatively new technique that is increasingly used in measurements of the particle size distribution (PSD) of soil and sediments. It has significant advantages (high precision, simple and rapid measurement) but the PSDs obtained by LDM often differ from those obtained with previously used sieve-sedimentation methods (SSMs). The main factors influencing the measurements that use LDM (among others: soil pretreatment, construction of the device settings of the operator, specificity of soil material, and the problem of fulfilling the assumptions of the method) are presented and the problem of comparability with SSM. New areas of investigations using LDM are also discussed. The work concludes with a set of postulates that should be taken into account to standardize LDM and increase the comparability of results, not only with SSMs but also with the PSDs obtained in other laboratories, including the diffractometers deriving from other producers.

The splashing of water drops on a soil surface is the first step of water erosion. There have been many investigations into splashing–most are based on recording and analysing images taken with high-speed cameras, or measuring the mass of the soil moved by splashing. Here, we present a new aspect of the splash phenomenon’s characterization the measurement of the sound pressure level and the sound energy of the wave that propagates in the air. The measurements were carried out for 10 consecutive water drop impacts on the soil surface. Three soils were tested (Endogleyic Umbrisol, Fluvic Endogleyic Cambisol and Haplic Chernozem) with four initial moisture levels (pressure heads: 0.1 kPa, 1 kPa, 3.16 kPa and 16 kPa). We found that the values of the sound pressure and sound wave energy were dependent on the particle size distribution of the soil, less dependent on the initial pressure head, and practically the same for subsequent water drops (from the first to the tenth drop). The highest sound pressure level (and the greatest variability) was for Endogleyic Umbrisol, which had the highest sand fraction content. The sound pressure for this soil increased from 29 dB to 42 dB with the next incidence of drops falling on the sample The smallest (and the lowest variability) was for Fluvic Endogleyic Cambisol which had the highest clay fraction. For all experiments the sound pressure level ranged from ~27 to ~42 dB and the energy emitted in the form of sound waves was within the range of 0.14 μJ to 5.26 μJ. This was from 0.03 to 1.07% of the energy of the incident drops.

A new practical and precise method for determining soil aggregate stability is described. Four air-dry aggregate fractions (d50) particle-size distribution decrease (interpolated with a logarithmic function) was assumed to be the measure of soil aggregate stability. In order to show the applicability of the new method, the results obtained (for selected and diverse soils) were compared with those from the wet sieving standard method. The main conclusion is that the proposed method is convenient and can be successfully used for the estimation of soil aggregate stability. Moreover, it has wider application because standard sieving methods are restricted to aggregates >0.25 mm whereas, with the use of the laser diffraction method, smaller aggregates can be measured. The energy delivered to the aggregates in the process of aggregate disintegration is more reproducible in the method described here. The method also provides an opportunity to verify that the soil aggregates are completely destroyed (lack of the changes of the median value shows the end of soil aggregate disintegration).

The splash phenomenon is being increasingly explored with the use of modern measurement tools, including the high-speed cameras. Recording images at a rate of several thousand frames per second facilitates parameterization and description of the dynamics of splash phases. This paper describes the impact of a single drop of a liquid falling on the surface of the same liquid. Three single-phase liquid systems, i.e., water, petrol, and diesel fuel, were examined. The falling drops were characterized by different kinetic energy values depending on the height of the fall, which ranged from 0.1 to 7.0 m. Four forms, i.e., waves, crowns, semi-closed domes, and domes, were distinguished depending on the drop energy. The analysis of the recorded images facilitated determination of the static and dynamic parameters of each form, e.g., the maximum height of each splash form, the width of the splash form at its maximum height, and the rate of growth of the splash form. We, Re, Fr, and K numbers were determined for al...