Hilary I. Inyang

Environmental issues from coal mining and their solutions

Abstract The environmental challenges from coal mining include coal mine accidents, land subsidence, damage to the water environment, mining waste disposal and air pollution. These are either environmental pollution or landscape change. A conceptual framework for solving mine environmental issues is proposed. Clean processes, or remediation measures, are designed to address environmental pollution. Restoration measures are proposed to handle landscape change. The total methane drainage from 56 Chinese high methane concentration coal mines is about 101.94 million cubic meters. Of this methane, 19.32 million, 35.58 million and 6.97 million cubic meters are utilized for electricity generation, civil fuel supplies and other industrial purposes, respectively. About 39% of the methane is emitted into the atmosphere. The production of coal mining wastes can be decreased 10% by reuse of mining wastes as underground fills, or by using the waste as fuel for power plants or for raw material to make bricks or other infrastructure materials. The proper use of mined land must be decided in terms of local physical and socio-economical conditions. In European countries more than 50% of previously mined lands are reclaimed as forest or grass lands. However, in China more than 70% of the mined lands are reclaimed for agricultural purposes because the large population and a shortage of farmlands make this necessary. Reconstruction of rural communities or native residential improvement is one environmental problem arising from mining. We suggest two ways to reconstruct a farmers house in China.

Geoenvironmental Engineering : Principles and Applications

Principles and processes soil formation and composition soil structure flow of water in solids mass transport and transfer in solids non-aqueous phase liquids (NAPLs) in solids fundamentals of contaminated site treatment introduction technical basis for treatment technique selection principles of site treatment techniques fundamentals of waste containment introduction containment system configurations elements of containment system design barrier composition and performance.

Experimental Investigation of the Desiccation Cracking Behavior of Soil Layers during Drying

Desiccation cracking in drying soil is a common natural phenomenon, and it significantly impacts the soil’s mechanical and hydraulic behavior. In this study, experimental desiccation tests were conducted on an initially saturated soil layer. Several aspects of the behavior of the soil—water evaporation, volume shrinkage, crack initiation, and propagation—were investigated. By applying image processing techniques, the geometric or morphological characteristics of the crack patterns were quantitatively described. The results show that cracking occurred during the constant evaporation rate stage, when the soil was still fully saturated at a water content of 41%. A growing crack obeys certain objective laws, and it finally splits the soil surface into relatively regular patterns: The first crack generally occurs on surface defects at the bottom of “potholes” and at the fringe of aggregates. Cracks intersect with one another at right angles, and the final crack pattern is dominated by square shapes. Most crack...

Patterns of VOC and BTEX concentration in ambient air around industrial sources in Daegu, Korea

Patterns of VOC and BTEX (Benzene, Toluene, Ethylvenzene, and Xylene) distribution at industrial emission sources, proximal residential areas of industrial estates, and ambient air were studied in Daegu, Korea. Daytime and night-time sampling was done at 12 sites and 9 emission sources to provide samples for analyses, using the TO-14 method. Measured BTEX component ratios B/T, T/EB, T/X and EB/X in ambient air were found to be 2.6 g, 11.3 g, 1.0 g and 1.2 g in the residential area; 2.2 g, 11.0 g, 1.0 g and 1.6 g in the commercial area; and 1.0 g, 14.9 g, 1.0 g and 1.3 g in the industrial area. The significant difference observed between the ratios for the residential and commercial areas implies that the two areas have different emission sources. This is also indicated by the significant differences observed between daytime and nighttime BTEX concentrations. Toluene and xylene were detected at very high concentrations, at the sampling sites. This pattern reflects the type of industrial processes and materials that are managed at the emission sources, as well as topographic/climatic factors that impact upon pollutant transport processes in the atmosphere. The BTEX distribution pattern in Daegu is observed to be similar to that of several Asian cities, particularly Hong Kong. These results are useful in the design of emission source control measures for VOCs and BTEX in Daegu.

Simplified calculation of maximum allowable contaminant concentration in waste-amended construction materials

A rational approach is often sought for relating the maximum permissible fractional replacement of traditional materials with construction-quality waste materials in constructed facilities. The development of such an approach hinges on the ability to back-calculate contaminant release rates that correspond to risk-based concentration limits in soil, groundwater or surface-water around the targeted facility. For constructed facilities in which the transport pathway is in the subsurface, the critical release mechanism for the targeted contaminant is leaching. In this paper, a simplified methodology for establishing the maximum allowable contaminant concentration in a waste material-amended concrete is developed. Contaminant leachability equations are coupled with contaminant transport factors and groundwater quality standards. Using the example of a generic contaminant contained in petroleum-contaminated soil (PCS) concrete, a methodology for back calculation of the maximum allowable concentration of the contaminant in the concrete for fixed compliance limits in a proximal well is presented.

Effects of Various Polyethylenimine Solutions on Desiccation of Na-Montmorillonite

Airborne particulates such as dust can cause human health problems and environmental damage. There is a national search for effective measures for controlling fugitive dust sources at construction sites and unsurfaced roads. In this article, results are presented on investigations of liquid loss from Na-montmorillonite, a mineral that is commonly found in fugitive dust. Cracking and dust generation are largely attributable to liquid loss from clayey soils in the presence of wind. Liquid loss from clay can be used as an index of potential cracking and dust generation. The ability of aqueous solutions of polyethylenimine (PEI) to retard liquid loss from Na-montmorillonite was investigated. Montmorillonite samples were mixed with polymer solutions of aqueous concentrations ranging from 0 g/L to 10 g/L and were tested in a specially designed desiccation chamber. Desiccation tests conducted at a temperature of 30°C and relative humidity of 40% show reduction in liquid loss with increase in polymer solution concentration. The time to reach 50% liquid loss with distilled water is 54.1 h and at 8 g/L is 79.2 h, respectively. These conclusions are valid for a drying time of 935 h. This research shows that polyethylenimine solution can retard liquid loss from montmorillonite with possible desirable effects on dust generation from exposed clayey soils that contain this mineral. Below the PEI concentration of 10 g/L, liquid loss is not very sensitive to concentration.

CATALYTIC OXIDATION OF TOLUENE IN CONTAMINANT EMISSION CONTROL SYSTEMS USING MN‐CE/γ‐AL2O3

Abstract Toluene, the alkyl benzene, is a common constituent of contaminant streams emitted by hydrocarbon fuel combustion systems. The oxidation of toluene to less toxic compounds can be enhanced through catalysis. The capacity of Mn‐Ce/γ‐Al2O3 to catalyze toluene oxidation was investigated using a fixed bed flow reactor, operating within a temperature range of 160–400°C. Mono‐metallic catalysts were prepared with the manganese and cerium contents of 1–21 wt% on γ‐Al2O3 support and bi‐metallic catalysts were prepared with cerium (0.5–21 wt%) on 18.2 wt% manganese. The results indicate that the 18.2 wt% Mn–10.0 wt% Ce catalyst combination had the best catalytic efficiency for toluene oxidation. Increase in cerium loading reduces the surface area of catalytic materials measured by BET, but increases catalytic activity. Data obtained through TGA (Thermogravimetric analysis), XRD (X‐ray diffraction) and toluene‐TPR (Temperature Programmed Reduction) measurements show that the reduction of the catalysts in the process of toluene oxidation is directly proportional to observed weight loss under hydrogen flow. From these results, it is concluded that cerium improves the catalytic role of manganese in toluene oxidation. Oxygen mobility is also promoted in a redox mechanism in which MnO2 serves as the active sites. These results are useful in the development of toluene emission control systems for hydrocarbon fuel combustion systems.

Effect of polyurethane on the stability of sand–clay mixtures

Three types of polyurethane were synthesized from mixtures of toluene diisocyanate, polyethylene glycol and polypropylene glycol for use in soil stabilization to improve the erosion resistance. The three polyurethanes were tested at different aqueous concentrations and sand:clay mixtures at weight ratios of 1:1, 1:3 and 1:5. The results of the rainfall simulation, unconfined compression and direct shear tests showed that the polyurethanes improve both strength and erosion resistance significantly. The observed improvement in soil erosion resistance is attributable to the physico-chemical interaction of the long-chain macro-molecules of polyurethane with the clay fraction of the soil.RésuméTrois types de polyuréthane ont été synthétisés à partir de mélanges de diisocyanate de toluène, de polyéthylène glycol et de polypropylène glycol pour utilisation dans la stabilisation de sols en vue d’améliorer leur résistance à l’érosion. Les trois polyuréthanes ont été testés pour différents mélanges de sable et d’argile dans les proportions 1/1, 1/3 et 1/5, avec différentes teneurs en eau. Les résultats de simulations de pluie, d’essais de compression simple et de cisaillement direct ont montré que le polyuréthane augmente à la fois la résistance mécanique et la résistance à l’érosion de façon significative. L’amélioration observée de la résistance à l’érosion est attribuable à l’interaction physico-chimique des macromolécules à longue chaîne de polyuréthane avec la fraction argileuse des sols.

GIS-Based Quantitative Analysis of Orientation Anisotropy of Contaminant Barrier Particles Using Standard Deviational Ellipse

Clayey soil is an essential component of waste containment systems. The orientation of soil particles relative to gradients of heat, hydraulic pressure and stress is a significant factor as regards the stability and hydraulic conductivity of waste containment barriers. In this paper, an analytical method called Standard Deviational Ellipse Method, which is often used for point set distribution analysis in Geographical Information System (GIS), is used to analyze particle orientation quantitatively. Through the conversion and processing of soil microstructural images, the orientation angles of soil particles are herein determined and correlated spatially across planar cross-sections. This methodology is demonstrated for a selected SEM image of a clayey soil of 0.558 porosity. The results show that the predominant orientation angle of soil particle averages is 13.445° with an anisotropic ratio of 11.49°. These results indicate that the soil sample is mostly isotropic.

Patterns of subsidence in the lower Yangtze Delta of China: the case of the Suzhou-Wuxi-Changzhou Region

Investigation indicates that the subsidence pattern in the lower Yangtze Delta area is related to groundwater extraction. Suzhou-Wuxi-Changzhou region (“Su-Xi-Chang”) belongs to the hinterland of the lower Yangtze Delta that has a total area of 12,000 km2. From 1979 to 2000, long-term pumping of groundwater at Su-Xi-Chang has caused a rapid decline in groundwater table, resulting in large-scale land subsidence. In this paper, establishment of a GPS-based monitoring system for land subsidence using 30 years of data, is presented. The data were obtained through monitoring of 184 wells. Also analyzed herein is the relationship between the observed lowering of the groundwater table and subsidence. Monitoring data indicate that the depression cone of groundwater table and the occurrence of subsidence are basically identical in time and space. The generation of both features is attributed to excessive extraction of ground water in the region. Finally, countermeasures against subsidence are proposed.