Water Infiltration Rate Research Articles

Raised Beds for Vegetable Production in Urban Agriculture

Raised beds are commonly used in urban agriculture, but crop production benefits have not been well studied. The objective of this 2‐yr field experiment in Illinois was to determine the effects of urban production system (direct soil, raised bed with compost, or raised bed with mixed compost and soil) and fertilizer source on growing media properties, weed abundance, and vegetable crop yield. Due to the presence of compost, raised bed media had higher pH, organic matter, and nutrient concentrations. Water infiltration rate was 20× higher in raised beds with compost only compared to soil. Mixing soil with compost in raised beds reduced nutrient concentrations and water infiltration rate compared to compost‐only beds. Compost‐only raised beds required more irrigation than direct soil due to lower bulk density and greater porosity, but mixing soil with compost in raised beds reduced irrigation demand by 32% in year two. Compared to direct soil, compost‐only raised beds reduced grass and broadleaf weed abundance by as much as 97 and 93%, respectively. Radish (Raphanus sativus L.), kale (Brassica oleracea L.), and cilantro (Coriandrum sativum L.) yields were highest in raised beds, regardless of growing media composition, whereas garlic (Allium sativum L.) and pepper (Capsicum annuum L.) yields were less influenced by production system. We recommend raised beds with a mix of compost and soil for vegetable production in urban agriculture.

Reconstruction of Water Infiltration Rate Reducibility in Response to Suspended Solid Characteristics Using Singular Spectrum Analysis: An Application to the Caspian Sea Coast of Nur, Iran

Drawing a distinction between the suspended solid size and concentration impacts on physical clogging process in the Managed Aquifer Recharge (MAR) systems has been fraught with difficulties. Therefore, the current study was then aimed to statistically investigate and differentiate the impacts of clay-, silt- and sand-sized suspended solids at three concentration levels including 2, 5 and 10 g/L, compared with the clean water (0 g/L), on infiltration rate reducibility. The treatments were compared by virtue of Cohen’s d effect size measure. Furthermore, the competency of Singular Spectrum Analysis (SSA) was evaluated in reconstruction of infiltration rate. Results showed that clay-sized suspended solids were found to be the most important determining factor in physical clogging occurrence. The effect size measure highlighted that a lower concentration level of clay-sized suspended solids, that is, 2 g/L could be more important in trigging the physical clogging than a higher concentration level of silt-sized suspended solids namely 5 g/L. Also, we recognized that concentration level of clay-sized suspended sediments could non-linearly decrease the infiltrability. Also, findings revealed that SSA represented a high level of competency in reconstruction of the infiltration rate under all treatments. Hence, SSA can be quite beneficial to MAR systems for forecasting applications.

Interstitial hydrocarbons reduce the infiltration rates of coarse-textured reclamation materials from the Athabasca oil sands

In the Alberta oil sands, many soils available for reclamation contain portions of oil sand referred to as aggregated oil sand material (AOSM). The objective of this study was to determine the infiltration rates of soils and AOSM from various salvage depths and with various concentrations of interstitial petroleum hydrocarbons (PHCs). The water infiltration rates of AOSM and surrounding soil were determined using a miniaturized infiltrometer, revealing that the soil allows significantly (P < 0.05) greater infiltration than the AOSM. Furthermore, highly-weathered AOSM which originate from the near-surface, exhibit significantly lower PHC contents and greater infiltration rates than medium- and low-weathered AOSM, which are found at depth. The infiltration of 95% ethanol indicates water repellency (WR) is present in both the AOSM and surrounding soil; however, the ethanol results also suggest that the reduced water infiltration rates of AOSM in comparison to the soil, are primarily due to structural differences such as reductions in total porosity and pore connectivity resulting from interstitial PHCs. The diminished infiltration of water into AOSM indicates the ability to slow the downward flow of water and increase the residence time of water in overlying coarse-textured soils, potentially altering the soil water regime and associated ecosite.

Research on the Influence of Water Vapor Diffusion and Evaporation on Water and Heat Transfer in Frozen Soil

Considering the model that the hydrothermal coupling moving rule of the seasonal frozen soil under freezing and thawing effect, a research was made that how deep we bury and the soil texture are to effect the rule of the diffusion and evaporation of water vapor. By monitoring the moisture content and temperature of the profile of the continuous freezing and thawing soil in region named Xiaotangshan mountain in Beijing and using the hydrothermal coupling moving model, the water transferring rule of clay and sandy loam in different depth that we buried was summarized. Many long-term field experiments showed that when frozen layer buried in a deep way was in a frozen state, the interactive movement of the water in the soil was not active and evaporated slowly. The average value of the water evaporation of clay was about 0.51 mm/day approximately and the situation of the sandy loam soil was 1.24 mm/day. By qualitative analyzing and observation, the less we buried (less than 0.8 m), the ice in the frozen soil layer got more. Besides, the density of the frozen soil layer went higher but the water barely diffused. On the contrary, with the increase of the depth, the diffusion went stronger and stronger due to the contact between the soil and the groundwater. In addition, according to the different soil texture detections, the diameter of soil particle has great influence on the diffusion of the water vapor in the soil. The diffusion rate of the water vapor in the sandy loam soil was twice than that of in clay. Other field water coupling experiments showed that, the soil moisture content was greater, soil freezing period density was larger, and soil water infiltration rate was zero. Soil evaporation was gradually decreased with the increasing of groundwater depth, and the size of soil particle would have a more obvious effect on soil water vapor diffusion and evaporation. Our research results can provide scientific basis for the buried area where contains groundwater to keep moisture in the winter and the resource content of the groundwater in Beijing and the locations in the same latitude of Beijing. This paper’s purpose was to research the law of water vapor diffusion and evaporation, with different soil texture and burial depth, so it can verify the coupled model of seasonal frozen soil water and heat migration.

Effect of Harvest Timing and Soil Moisture Content on Compaction, Growth and Harvest Yield in a Miscanthus Cropping System

Harvesting Miscanthus × giganteus (J.M. Greef &amp; Deuter ex Hodkinson &amp; Renvoize) after shoot emergence is known to reduce yields in subsequent seasons. This research was conducted in Miscanthus to assess the effects on crop response and soil compaction of annually repeated traffic, applied both before new growth in the rhizomes (early harvest) and after shoot emergence (late harvest), at two different soil moisture contents. While an annual early harvest, yields more than a late harvest, because damage to new shoots is avoided, soil compaction may be increased following repeated harvests. Five treatments were tested: (a) An untrafficked control, (b) early-traffic on soil with typical soil moisture content (SMC) (early-normal), (c) early-traffic on soil with elevated SMC (early-elevated), (d) late-traffic on soil with typical SMC (late-normal) and (e) late-traffic on soil with elevated SMC (late-wet). The experiment was conducted on a Gleysol in Co. Dublin, Ireland during 2010 and 2011. Crop response effects were assessed by measuring stem numbers, stem height, trafficked zone biomass yield (November) and overall stem yield (January). Compaction effects were assessed by measuring penetration resistance, bulk density and water infiltration rate. Trafficked zone biomass yield in the early-dry and early-wet treatments was, respectively, 18% and 23% lower than in the control, but was, respectively, 39% and 31% higher than in the late-dry treatment. Overall, stem yield was significantly lower in the late-normal and late-wet treatments (10.4 and 10.1 tdm ha−1 respectively) when compared with the control (12.4 tdm ha−1), but no significant difference was recorded in overall stem yield between both early-traffic treatments and the control. Penetration resistance values were significantly higher in all trafficked treatments when compared with the control at depths of 0.15 m (≥54–61%) and 0.30 m (≥27–57%) and were significantly higher in 2011 when compared with 2010 at depths of 0.15 and 0.30 m. Baler system traffic in Miscanthus significantly reduced yields and significantly increased compaction annually. Miscanthus harvested early, on a dry soil, yielded 1.1 tdm ha−1 more than when harvested late on a dry soil. The yield advantage increased to 1.3 tdm ha−1 when early harvesting on a soil with 40–43% moisture content was compared with late harvesting on a wetter soil (51–52% moisture content). In this study, the magnitude of yield losses from compaction or other causes in early harvests was substantially lower than the yield losses, which resulted from shoot damage in late harvests. It is likely in similar climates that the results of this study would also apply to other perennial crops growing in similar soil types.

Root mass may affect soil water infiltration more strongly than the incorporated residue

Crop residue incorporation increases stable soil pores and soil water infiltration and reduces surface water runoff and soil erosion. However, few studies have examined the relationship between crop residue incorporation and water infiltration. A previous study showed that water infiltration increases depending on the quantity of applied wheat straw. In this study, we examined whether the relationship is applicable to different crop residues in a crop rotation. We grew corn, rose grass, and okra in crop rotation under plastic film houses and measured the water infiltration rate at the time of ridge making. A strong correlation was found between the quantity of applied residue and the soil water infiltration rate (r = 0.953), although there are outliers in the case of no prior crop. However, aboveground biomass of the prior crop showed a stronger correlation with water infiltration rate (r = 0.965), without outliers. Previous studies have revealed the exponential relation between plant root mass and soil erosion. Our data also show a positive relationship between resistance to erosion and root mass when assuming that aboveground biomass is proportional to the underground biomass. The result also showed that the effect of the prior crop root mass disappears within the next crop period. Our results indicate that maintaining a large root biomass is crucial for reducing soil erosion.

Development of SWAT-Paddy for Simulating Lowland Paddy Fields

The recent increase in global consumption of rice has led to increased demand for sustainable water management in paddy cultivation. In this study, we propose an enhanced paddy simulation module to be introduced to Soil and Water Assessment Tool (SWAT) to evaluate the sustainability of paddy cultivation. The enhancements added to SWAT include: (1) modification of water balance calculation for impounded fields, (2) addition of an irrigation management option for paddy fields that are characterized by flood irrigation with target water depth, and (3) addition of a puddling operation that influences the water quality and infiltration rate of the top soil layer. In a case study, the enhanced model, entitled SWAT-Paddy, was applied to an agricultural watershed in Japan. The results showed that the SWAT-Paddy successfully represented paddy cultivation, water management, and discharge processes. Simulated daily discharge rates with SWAT-Paddy (R2 = 0.8) were superior to the SWAT result (R2 = 0.002). SWAT-Paddy allows the simulation of paddy management processes realistically, and thus can enhance model accuracy in paddy-dominant agricultural watersheds.

Comparison of soil use in the infiltration of rainwater: pasture and forest

Los bosques de Itajaí/SC, Brazil han sido intensamente fragmentados en la llanura, reflejando en el predominio de asentamientos urbanos, estructuras portuarias y cultivos de arroz. Al sumarse los eventos provenientes del cambio climático a las condiciones ambientales existentes, la región se torna susceptible a las inundaciones. De esta forma, este trabajo tiene como objetivo analizar la función hídrica de los bosques de llanura en la infiltración del agua de las lluvias en Itajaí. Se utilizó el Sistema de Información Geográfica para la elaboración de un mapa de uso y ocupación del suelo y se comparó con el mapa de suelos del municipio. De estos análisis fueron seleccionadas dos áreas en la llanura en la misma clase de suelos, una con pastoreo y una cubierta por bosque. En los meses de agosto y octubre, estas áreas se muestrearon y clasificaron acorde a los siguientes criterios: granulometría, humedad, conductividad hidráulica y contenido de materia orgánica de los suelos. También en estas unidades de muestra se realizó el ensayo de velocidad de infiltración básica (VIB) mediante el método de anillos concéntricos. Se utilizó el análisis de varianza (ANOVA) para verificar el efecto entre las variables obtenidas. Los valores medios obtenidos de VIB para área de pastoreo fueron 3,45 cm h-1 y 3,60 cm h-1 para los meses de agosto y octubre, respectivamente. En el área con vegetación se obtuvieron valores medios de 19,05 cm h-1 y 8,70 cm h-1 para los meses de agosto y octubre, respectivamente. En este trabajo fue posible verificar que hay diferencias significativas en la infiltración de agua, en la parte superficial del suelo,entre las coberturas con bosque y con pastoreo, donde las condiciones edáficas son iguales. La vegetación forestal denota su papel potencial en la infiltración de agua de lluvia en la planicie de inundación del área.

Dung beetle activity improves herbaceous plant growth and soil properties on confinements simulating reclaimed mined land in South Africa

Mining activities contribute greatly to economic growth and development in South Africa. However, post-mining soils have limited land-use potential due to low fertility, deficiency in organic matter content and poor physical, chemical, and microbiological properties. Dung beetles could potentially improve several aspects of soil degradation, complementing current rehabilitation efforts. Studies in relatively undisturbed soils of agro-ecosystems have found that dung burial introduces essential nutrients in dung to the plant root zone, which would otherwise remain on the soil surface and mostly volatilize in the absence of dung beetles. Furthermore, dung beetles create tunnels under dung pats, improving water infiltration rates, bulk density, soil aeration and pasture yields. The aim of the study was to determine whether these effects could be maintained on soil simulating reclaimed mined land, where very high rates of compaction may prevent tunnelling altogether. Three experimental treatments of dung + beetles (D + B), dung only (D) and control/no dung, no dung beetles (X) were applied twice over 2 years on 1 m3 experimental confinements. Various soil and herbaceous plant properties were assessed one and six months after each application of dung and beetles. Results obtained showed that water infiltration rate and plant biomass was significantly higher for all confinements containing dung beetles. Penetration resistance (soil strength) was significantly reduced for confinements with dung beetles. Magnesium and potassium levels in the soil were significantly higher for D + B treatments when compared to D and X treatments. In conclusion, results showed that dung beetles were able to maintain their activities in soils typical of reclaimed mine land, significantly improving soil properties and herbaceous plant growth. Incorporating the application of dung beetles to the conventional approach to rehabilitation has the potential to improve the efficacy of coal mine reclamation. This biological approach may also prove to be cost-effective over time as it provides a seasonal source of bioturbation, which does not disturb plant growth and reduces the requirements for soil rejuvenating tillage practices.

Predicting hydraulic conductivity around septic tank systems using soil physico-chemical properties and determination of principal soil factors by multivariate analysis

The knowledge of soil hydraulic conductivity is essential for the study of waste water infiltration rate into the soil subsurface. This study assesses selected soil hydraulic properties of soil around septic tank systems. Twelve soil samples were collected from four different locations within Ido Local Government Area, Oyo State, Nigeria. The analyzed parameters were done based on standard procedures. The measured values of soil physico-chemical properties were used to predict Ksat using multiple linear regression analysis. The soil water content, porosity, Organic Carbon, Soil pH, bulk density, soil resistivity and saturated hydraulic conductivity (Ksat) ranged from 20.6 to 26.2%, 34.3 to 47.2%, 0.11 to 0.37%, 5.8 to 6.2, 1.40 to 1.74 g/cm3, 4.55 to 5.80 O cm and 1.34 to 10.52 mm/hr respectively. The relationship obtained from regression analysis on data (R2 = 86.8) is a new model with empirical linear equation Ksat=82.08-5.93BD-10.98RES-2.69wc-16.12O.C+9.38pH which allows a new relation to estimate Ksat from the selected parameters. Principal component analysis (PCA) identified 3 major factors accounting for 92.7% of the total variation in the soil hydraulic variables. The result of Cluster Analysis (CA) shows groups based on correlation between hydraulic parameters and topographic settings.

Theoretical bounds for the exponent in the empirical power-law advance-time curve for surface flow

A fundamental and widely applied concept used to study surface flow processes is the advance-time curve, which indicates the time at which water arrives at any given distance along a field length. The advance-time curve is typically characterized by an empirical power law with an exponent r and a numerical prefactor p (i.e., x=ptr). In the literature, different values of r have been reported for various situations and types of surface irrigation. Invoking concepts from percolation theory, a theoretical approach from statistical physics for quantifying transport properties in complex systems, we relate the exponent r to the backbone fractal dimension Db (r = 1/Db). The backbone, through which transport occurs predominantly in a system, is formed by multiply connected loops composed of several paths that bring fluid from an initial point to a final point. The backbone fractal dimension Db, characterizing the complex structure of the backbone, depends on two factors: dimensionality of the system (e.g., two or three dimensions) and percolation class (e.g., random or invasion percolation with/without trapping). We show that the theoretical bounds of Db are well in agreement with experimental ranges of r reported in the literature for two furrow and border irrigation systems. We further use the value of Db from the optimal path class of percolation theory to estimate the advance-time curves of four furrows and seven irrigation cycles (i.e., 28 experiments). The optimal path is the most energetically favorable path through a system. Excellent agreement was obtained between the estimated and observed curves. We also discuss the indirect effects of initial water content, inflow rate, surface slope, and infiltration rate (soil texture) on system dimensionality, percolation class and, consequently, the backbone fractal dimension value. More specifically, we postulate that for closely-spaced furrows with steep slopes, low infiltration rates, and relatively high inflow rates, the wetting front advance will be mostly quasi one-dimensional. Since the backbone fractal dimension in one dimension is 1, one should expect the exponent r to be near 1.

Critical Moisture Content, Bulk Density Relationships and Compaction of Cultivated and Uncultivated Soils in the Humid Tropics

Soil compaction affects soil fertility through increasing bulk density and soil strength. It also decreases infiltration rate, total porosity and amount of water stored in the root zone for crop use. In this study, we evaluated the optimum moisture contents (OMC) in relation to maximum dry density (MDD) and compaction of cultivated and uncultivated soils. The study was carried out on four land use types viz: uncultivated: Velvet tamarind (Dialium quineese), rubber plantation (Hevea brasiliensis) and cultivated: 5-year fallow and 10-year continuous cultivated soil to maize crop. Proctor test for the maximum dry density-moisture content relationship was carried out, including some hydraulic and structural properties of the soil, and their effect soil compaction. Results showed that optimum moisture content (OMC) for compaction relate to the maximum dry density (MDD). In which case, dry density increased with water content to a maximum and decrease as moisture content increased above the optimum. Soil organic matter (SOM) content and particle size distribution highly affected the MDD and OMC. The MDD and OMC were: 1.92 g cm-3 and 10.4%, 1.95 g cm-3 and 11.2%, 1.91 g cm-3 and 12.3%, and 1.87 g cm-3 and 12.8% for velvet tamarind, 5-year fallow, CC and rubber plantation soils respectively, at 0-15 cm depth. Changes in field bulk densities at similar depths were in the order of velvet tamarind &lt; rubber &lt; 5-year fallow &lt; CC. There were highly significant (p &lt; 0.01) relationships between MDD, total porosity, Ksat and SOM and negative relationships between these parameters and OMC. Thus, continuous cultivation increased MDD and reduced OMC for compaction. Two- season fallow periods with legume could improve soil hydraulic properties and maintain the MDD of sandy soils at minimum.

The Faxinal System: Forest fragmentation and soil degradation on the communal grazing land

The Brazilian faxinal is a traditional agrosilvopastoral system, which combines extensive grazing, subsistence cropping and low impact forest extraction, managed within a communal property system. Today it is at serious risk of disappearing due to increasing grazing pressure and logging activities that are leading to environmental problems such as forest fragmentation and soil degradation. The objectives of the study were to: a) evaluate soil physical degradation levels in different grazing areas within the faxinal system; and b) correlate soil degradation, fodder quantity and livestock dynamics in different pasture areas according to the household's location. Landscape mapping, vegetation surveys, and livestock grazing dynamics were assessed. In addition, soil physical parameters were evaluated for each land use (e.g., resistance, bulk density, porosity, moisture, and water infiltration rates). Results showed that livestock grazing and household locations are the main driving forces that lead to forest fragmentation. The household location creates three interrelated gradients in the communal grazing land: 1) soil physical degradation decreases from the pasture areas to araucaria forests; 2) fodder quantity decreases from pastures to araucaria forests; and 3) the livestock grazing intensity decreases from pastures to araucaria forests. In addition, some management practices to mitigate land degradation, including improvement of pastures, installation of removable troughs for drinking water in the upland areas and restriction of livestock from the riparian zone, have been proposed.

Nanostructured Three-Dimensional Percolative Channels for Separation of Oil-in-Water Emulsions

SummarySeparation of oil/water mixtures has been one of the leading green technologies for applications such as oil recovery and water purification. Conventional methods to separate oil from water are based on phase separation via physical settlement or distillation. However, challenges still remain in the effective extraction of micron-sized oil droplets dispersed in water, in which case gravity fails to work as separating force. Here, we conformably decorate porous titanium (average pore size 30 μm) with superhydrophilic nanotubes. The resulting three-dimensional superhydrophilic micro channels thus provide a driving force for oil-water separation at the nanotube/emulsion interface, enhancing significantly the water infiltration rate. The high efficiency (>99.95%, with oil droplets of average diameter 10 μm) and strong mechanical durability make the structure a reusable oil/water separator. Our findings pave the way for future applications of oil-in-water emulsion separation, which can be readily scaled up for massive demulsification.

The response of metal leaching from soils to climate change and land management in a temperate lowland catchment

Changes in soil hydrology as a result of climate change or changes in land management may affect metal release and leaching from soils. The aim of this study is to assess the cascading response of SOM and DOC levels and metal leaching to climate change in the medium-sized lowland Dommel catchment in the southern part of the Netherlands. We implemented the CENTURY model in a spatial setting to simulate SOM, DOC, and water dynamics in topsoils of the Dutch portion of the Dommel catchment under various climate and land management scenarios. These CENTURY model outputs were subsequently used to calculate changes in the topsoil concentrations, solubility, and leaching of cadmium (Cd) and zinc (Zn) for current (1991–2010) and future (2081–2100) conditions using empirical partition-relations. Since the metal leaching model could not be evaluated quantitatively against measured values, we focus mainly on the trends in the projected metal concentrations and leaching rates for the different scenarios. Our results show that under all climate and land management scenarios, the SOM contents in the topsoil of the Dommel catchment are projected to increase by about 10% and the DOC concentrations to decrease by about 20% in the period from present to 2100. These changes in SOM and DOC only have a minor influence on metal concentrations and leaching rates under the climate change scenarios. Our scenario calculations show a considerable decrease in topsoil Cd concentrations in the next century as a result of increased percolation rates. Zinc, however, shows an increase due to agricultural inputs to soil via manure application. These trends are primarily controlled by the balance between atmospheric and agricultural inputs and output via leaching. While SOM and DOC are important controls on the spatial variation in metal mobility and leaching rates, climate-induced changes in SOM and DOC only have a minor influence on metal concentrations and leaching rates. The climate-induced changes in metal concentrations in both the topsoil and the soil leachate are primarily driven by changes in precipitation and associated water percolation rates.

Simulation of a hydraulic fracturing wastewater surface spill on agricultural soil

Hydraulic fracturing wastewaters (HFWWs) contain synthetic organic components and metal ions derived from the formation waters. The risk of spills of HFWW that could impact soil quality and water resources is of great concern. The ability of synthetic components, such as surfactants, in HFWW to be transported through soil and to mobilize metals in soil was examined using column experiments. A spill of HFWW was simulated in bench scale soil column experiments that used an agricultural soil and simulated seven 10-year rain events representing a total of one year's worth of precipitation for Weld County, Colorado. Although no surfactants or their transformation products were found in leachate samples, copper, lead, and iron were mobilized at environmentally relevant concentrations. In general, after the initial spill event, metal concentrations increased until the fourth rain event before decreasing. Results from this study suggest that transport of metals was caused by the high concentrations of salts present in HFWW. This is the first study utilizing authentic HFWWs to investigate the transport of surfactants and their effect on metal mobilization. Importantly, a significant decrease in the water infiltration rate of the soil was observed, leading to the point where water was unable to percolate through due to increasing salinity, potentially having a severe impact on crop production.

Effect of potato hilling on soil temperature, soil moisture distribution and sediment yield on a sloping terrain

Soil erosion rates are exacerbated in sloping arable lands of Central Kenya due mainly to the high soil disturbance caused by potato hilling. A field study was conducted in runoff plots to quantify the effect of potato hilling on soil loss, soil moisture distribution and soil temperature. Three hilling practices; hilling performed at before crop emergence (pre-hilling), one-pass hilling (at 15 days after potato emergence), the conventional two-pass hilling (at 15 and 30 days after potato emergence), and the control (non-hilling) constituted the treatments. Root length density, vegetal cover, soil surface roughness and soil water infiltration capacity were quantified at different stages of potato growth and related with the sediment yield. Soil temperature and soil moisture contents were monitored using Onset HOBO sensor probes throughout the potato growth cycle. Compared to the conventional two-pass hilling, pre-hilling increased the soil moisture content by 6% and lowered the soil temperature by up to 3.4 °C at crop emergence, thus optimized tuber germination and growth. This ensured earlier canopy closure and reduced the cumulative sediment yield by 12 t/ha. The increased surface roughness resulting from pre-hilled ridges puddled the surface water and increased the soil water infiltration rate by 7 to 9 mm/hr compared to the non-hilled plots. Planting potatoes in pre-hilled plots has a potential to optimize the soil temperature and soil moisture conditions and can reduce the high soil erosion rates in sloping arable lands.

Effects of DLVO, hydration and osmotic forces among soil particles on water infiltration

SummarySoil water infiltration is closely associated with the transport of nutrients and contaminants in soil. The physical mechanism by which electrolyte concentration influences water infiltration is not clear, however. Recent studies have shown that interaction forces between soil particles play a crucial role in the stability of soil aggregates and pores, which further affects soil water infiltration. In this research, column experiments were used to elucidate the effects of soil particle interaction forces on water infiltration in a permanently charged and a variably charged soil using different concentrations of KNO3 solutions (0.0001, 0.001, 0.01 and 0.1 mol l−1), and some interesting results on soil water infiltration were discovered. They indicated that: (i) four forces in soil (long‐range van der Waals attractive, electrostatic repulsive, hydration and osmotic repulsive forces) co‐determined the rate of soil water infiltration for both soil types tested, (ii) at smaller soil water content (large electrolyte concentration) the osmotic repulsive force became more important in soil water infiltration, and yet with a larger water content (small electrolyte concentration) the electrostatic repulsive force became more important, and (iii) the osmotic force affected water infiltration through its effect on particle interaction forces rather than its influence on the osmotic potential of water. This paper presents a quantitative description of how particle interaction forces affect water infiltration into soil.HighlightsElucidation of physical mechanisms of effects of clay charge and electrolyte concentration on soil water infiltration. Quantified effects of interaction forces of soil particles on soil water infiltration. Electrostatic repulsive and osmotic forces play a critical role in water infiltration. DLVO, hydration and osmotic forces among soil particles co‐determined soil water infiltration rate.

Evaluation of ground water quality near Chandi Devi bridge solid waste dumping site at Hairdwar city, (Uttarakhand), India : A case study

The present study observed groundwater quality around Chandi Devi bridge open dumping site at Hardwar (Uttarakhand), India. Five experimental sites viz. sites 2,3 and 5 (hand pumps) and two sites 4,6 (tubewells) within the vicinity of the dumpsite and a reference site viz. site 1 (hand pump) (Bilkeshwar temple) as a control about 5000 meter away, were selected to ascertain the influence of solid waste dumping on groundwater quality around the area. The study showed that physicochemical parameters viz temperature, colour, turbidity, pH, hardness, BOD, COD, fluoride and heavy metals ( lead and iron) of the ground water near the dumping sites-2,3,4,5,6 were higher than their counterpart parameters of the ground water at control site. However, arsenic was not detected in any sample of all the sites. The parameters viz., colour (2.08-3.49 hazen), turbidity (3.05-5.35 NTU), odour (agreeable), pH (7.46-7.80),fluoride (0.10-0.38 ppm), lead (0.00-0.032 ppm), iron (0.01-0.03 ppm) of ground water of all experimental sites were within permissible limits while the parameters BOD (3.73-3.21 ppm), hardness (240.41-203.15 ppm) at site-2, site-3 and DO (5.38-6.28 ppm) of all experimental sites were not found within permissible limits as prescribed by Bureau of Indian standards (2012). Although water was safe for drinking which may be due to higher infiltration rate of river Ganga and Eastern Ganga Canal water but higher value of temperature (oC), colour (hazen), turbidity (ppm), hardness (ppm), BOD (ppm), COD (ppm) fluoride (ppm), iron (ppm) and lead (ppm) at site- 2 was quite alarming. The study would help in making public awareness for waste sorting, adopting green technology and to predict level of contaminants in ground water produced by land filling dumping site.

Laboratory simulation of the influence of groundwater rise and drip irrigation on the settlement of a sample of collapsible desert soil

Most types of sand have low susceptibility to settlement when in dry, dense and well-graded states but certain sands, when saturated, exhibit a decrease in suction and tensile strength hence leading to a sudden decrease in volume. Such sands are known as collapsible soils and require special consideration because their behaviour cannot be assessed using conventional settlement analysis methods. Irrigated landscapes overlying collapsible strata have caused settlement problems and infrastructure damage in Abu Dhabi area. Using borehole samples from the area, the present work simulates the settlement response of the collapsible sand when sandwiched between two other layers inside a metal mould and loaded with a constant surcharge pressure while varying water infiltration rates and static water levels. The primary goal of the research is to develop relationships for estimating settlement due to collapsible strata by taking into account layer thicknesses, groundwater table and irrigation intensity and duration.