Search results

This paper aims to assess the effects of chemically accelerated leaching on the physical and mechanical properties of aerial lime–cement mortars (LCMs).

Two aerial LCMs, differencing mainly in their calcium hydroxide content, were degraded by the use of an ammonium nitrate solution as a leaching agent. The leaching effects were studied by evaluating the rate of change in physical (sorptivity and mass loss) and mechanical (flexural and compressive strength) characteristics of aerial LCMs. To quantify the evolution and kinetics of degradation, the leached depth was then characterized at different levels of degradation by means of a phenolphthalein solution.

The experimental results showed that the dissolution of binder decreases the mass, alkalinity and strength of aerial LCMs but increases their sorptivity. A linear relationship was derived by plotting the values of leached depth against the square root of immersion time in an aggressive solution. It was found that the leached depth followed diffusion-controlled kinetics.

It was found that the global loss of compressive strength of aerial LCMs because of complete dissolution of calcium hydroxide can reach up to 80 per cent.

Hydraulic conductivity is very low in saline-sodic soil, which decreases water infiltration. For saline-sodic soil, increasing infiltration water has a special meaning. Increasing infiltration water not only increases the water in the soil profile but also decreases the salinity of the soil, thus making it suitable for growing crops. This study aims to examine the effect of sand pipes on soil water and salt distribution through laboratory tests with different depths and diameters of sand pipes.

The soil water and salt distribution responses to different sand pipe depths and diameters was investigated. Treatments included sand pipes with diameters of 4 cm, 5cm, 6 cm and the same depth of 4 cm; with depths of 2cm, 6 cm and the same diameter of 5 cm, and a control with no sand pipe (with the diameter of 0 cm and the depth of 0 cm).

The results suggested that the amount of cumulative infiltration water and transport distance of the wetting front could be increased by increasing the depth and diameter of sand pipes. The soil water content in the soil profile decreased under all treatments except for the control, whereas the value of EC increased with increasing distance from the film hole center. Positive relationships were also found among the sand pipe depth, diameter and the zone of low salt content. Furthermore, salt leaching depth increased with sand pipe depth and diameter. Overall, the treatments with and without sand pipes exhibited obvious differences.

The correlation analysis proved that increasing the infiltration area through sand pipes positively affected the amount of infiltration water, wetting scope and salt leaching depth.

Major land use changes can have a significant impact on the environment, e.g. increased leaching and run‐off losses of nutrients and water contamination. Nitrate (NO₃^–) can be easily leached and, when present at high concentrations in drinking water, can be a health hazard. This paper seeks to report an easy‐to‐use computer model designed to provide predictions of possible impacts on groundwater NO₃^– concentration on a regional scale.

The model takes into account NO₃^–‐N concentrations from various land use activities, land surface recharge rates (as affected by soil water retention capacity, land management, irrigation and rainfall), and mixing of surface recharge and river recharge. Spatial information on land use and groundwater recharge sources are lumped into groundwater management zones (100‐500 km²), and vertical concentration profiles of NO₃^– in groundwater are estimated from a one‐dimensional dispersion model. The model is applied to the 2,300 km² Central Canterbury Plains of New Zealand.

A scenario analysis for the Bankside groundwater management zone showed that the NO₃^–‐N concentration at the groundwater surface could increase from 7.8 mg N L^‐1 to 11.3 mg N L^‐1 if all the land used for sheep farming is replaced by dairy farming (increasing dairy land from 21 per cent to 64 per cent of the total land area). However, the impact of such land use changes on the NO₃^–‐N concentration 50 m below the groundwater surface was relatively small, resulting in an increase of NO₃^–‐N concentration from 0.4 to 0.5 mg N L^‐1. This is because of the significant mixing of surface recharge with river recharge at this depth.

The model can serve as a useful tool for first‐order estimation of possible trends of NO₃^–‐N concentration profiles in aquifers as a result of land use changes.

The present study aims to determine the residue levels in the soil and water prior to, and after fertilization, as previous soil investigations in Kuwait indicated that different types of fertilizers are used leaving residues in the soil, in order to assist the prospective farmers in choosing environmental sound chemicals for each crop. The importance of the following is to determine the geologic conditions of the soil in such a productive farm area and the effect of the use of fertilizers.

To achieve the study purpose soil and water samples were collected over a wide area and chemical parameters (pH, electrical conductivity (ECe), cations (Ca⁺², Mg⁺²), and anions (CO₃⁻²,HCO₃⁻,Cl⁻)) were obtained via the suitable and most appropriate chemical analyses.

The soils have several levels of calcareous contents along with varying salinity and alkalinity. Before fertilization on average, soil ECe ranges from 0.93 to 4.37 mS/cm, pH from 7.4 to 7.60, cations 8.00 to 36.00 meq/l, and anions from 4.85 to 29.61 meq/l. After fertilization pH ranges from 7.09 to 7.47, ECe ranged from 3.79 to 12.85 mS/cm, cations ranges from 29.75 to 66.36 meq/l, and anions ranges from 15.18 to 63.32 meq/l; showing that ECe, cations and anions average values has increased by almost three to four orders of magnitude. Furthermore, ECe, pH, cations, and anions values have sharply increased with depth. The evidence from this study shows that vertical leaching adversely contributes to the deterioration of the groundwater quality and rate.

The output of this study is intended to be the building block or the nuclei for a data bank on the prevailed agricultural practices in different aspects, and upon which further studies on the southern area of Kuwait will depend.

The farm areas in the southern region of Kuwait state (case study: Al‐Wafrah farms) suffer from misuse and mismanagement of the agricultural lands in different aspects. This paper provides new source of information on the historical record of farm development and the nature, performance and results of the associated agricultural practices in such areas, as so to be the base or the starting point form which further studies can go forth.

An environmental impact assessment, EIA, was carried out before the final development and implementation of an irrigation project with a total area of 118,853 ha. in the Konya Plain located in Central Anatolia of Turkey, by the General Directorate of State Water Works (DSI). The objectives of the project are to supply water for irrigation and municipal demands by developing the Beysehir Lake, Suğla Lake Gembos basin and other water sources in the region, by conveying the excess water through an improved BSA channel to the Cumra‐Konya plains and to increase the irrigated agriculture. Evaluates six sub‐projects by considering construction and operation phases with respect to agricultural environmental problems, possible water quality impact, ecological changes and, finally, water budget and meteorological conditions. In order to reduce the possible adverse environmental impact of the originally considered design values, some significant changes were adopted according to results of this EIA study. Presents only the water quality aspect of the work.

The potential problems and their consequences due to fly ash disposal have been well studied around the world. Ash pond is a common available disposal facility for thermal power plants. The pond ash is subjected to weathering and the ions present in ash migrate to the soil and subsequently to the ground water over a period of time. A study has been carried out at Vijayawada Thermal Power Station (VTPS), Andhra Pradesh, India, to monitor the ground water quality in order to determine the potential impact of ash ponds. It has been found that ground water quality is deteriorated due to the presence of fly ash ions (macro and micro such as Fe, Ca, Mg etc.) which were leached out from the ash up to some extent. The contamination is likely to increase in the case of toxic and other ions with the passage of time. The presence of vegetative cover and plant growth on the down stream slope and fly ash ponds which are covered by soil may effectively control the leaching of ions.

The purpose of this paper is to apply the numerical methods to study the heap leaching process in a bed of porous and spherical ore particles. This study is performed in two stages: first, modeling the leaching process of a soluble mineral from a spherical and porous ore particle to obtain the distribution of mineral concentrations, leaching solvent concentration and dissolved mineral in the particles (the particle model), and second, modeling the heap leaching of the mineral from a porous bed consisting of spherical and porous ore particles to obtain the distribution of mineral concentrations, leaching solvent concentration and dissolved mineral in the bed (the bed model).

The governing equations are derived for the particle model, and then converted into non‐dimensional form using reference quantities. The non‐dimensional equations are discretised on a uniform spherical grid fitted to the particle using finite difference method. The resulting algebraic equations are solved using Tri‐Diagonal Matrix Algorithm, and the governing equations are derived for the bed model, and then converted into non‐dimensional form using reference quantities. The non‐dimensional equations are discretised explicitly on a one‐dimensional and uniform grid fitted to the bed. The unknown quantities are evaluated using the corresponding values at the previous time interval.

The results obtained from numerical modeling show that, when the particle has a low diffusion resistance or a high chemical resistance, the reaction takes place slowly and homogeneously throughout the ore particle. On the other hand, when the bed has a low convection resistance, the reaction takes place homogeneously throughout the bed. As the convection resistance increases, the non‐homogeneous (local) behavior predominates. It is also noticed that, when the chemical reaction resistance is high, the reaction takes place homogeneously throughout the bed.

The dynamic diffusion and movement of solution in the ore particles and ore bed are not modeled and volumetric ratio of solution in the particles and the bed and also vertical velocity of solution in the bed are assumed to be fixed constants.

This study shows that the reaction takes place homogeneously throughout the bed when the convection resistance is low, the diffusion resistance is high, the concentration resistance is low, and the chemical reaction resistance is high.

Homogeneous reaction conditions being suitable for heap leaching operations are identified. Thus, it is recommended to approach the above conditions when preparing ore heaps and designing the relevant operation.

Heavy metals play a crucial role in the economic development of any nation. Industries utilizing heavy metals, consequently, emanate a large volume of metal-containing liquid effluents. Since metals are non-renewable and finite resources, their judicious and sustainable use is the key. Hazardous metal-laden water poses threat to human health and ecology. Apart from metals, these industrial effluents also consist of toxic chemicals. Conventional physical–chemical techniques are not efficient enough as it consumes energy and are, therefore, not cost effective.

It is known that biomaterials namely microorganisms, plants, and agricultural biomass have the competence to bind metals, in some cases, selectively, from aqueous medium. This phenomenon is termed as “metal biosorption.” Biosorption has immense potential of becoming an effective alternative over conventional methods. The authors in the present chapter have used secondary data from their previous research work and attempted to develop few strategic models through their feasibility studies for metal sustainability.

Examines the relative nutrient status and public health aspects of six livestock manures when added to soil. Provides analysis of the chemical composition of soils at pig, cattle, goat, rabbit, sheep and poultry waste dump sites and shows a highly significant difference in the level of added nutrients. Draws the conclusion that the observed levels of micronutrients at all waste sites suggest that potential plant toxicity and food chain accumulation problems will be low. Highlights the effect of land application of the manure on human health.

Discusses the particulation of organic barrier layers, based on laboratory‐bench data, obtained from the exposure of painted panels in low, high or neutral pHelectrolytes. It also discusses their compatibility with the succeeding and preceding layers and the galvanic interactions at the layer substrate interfaces. Aspects like substrate effect, leaching of the micaceous iron powder, role of high temperature and hydrodynamic disturbances and distribution of ultrafine particulates have been highlighted using potential versus time plot, AAS data, and galvanic current measurements and XRD analysis. Exposure tests conducted under ambient conditions and under very strong hydrodynamic disturbances, revealed superior properties of the SiC particulated epoxy based barrier layers.