John L. Daniels

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.

Development of a Wireless Sensor Network for Monitoring a Bioreactor Landfill

Recent studies of aerobic bioreactors have demonstrated their success in expediting stabilization of municipa l solid waste (MSW), reducing or eliminating treatment and disposal costs of leachate, and increasing landfill capacity. Such aerobic decomposition is highly dependent on maintaining optimum distribution of moisture and air throughout the highly heterogene ous waste for the duration of the stabilization process. This requires distributed monitoring of the temperature and moisture in the bioreactor. This work presents the development and implementation of an autonomous monitoring system using an array of wire less sensors (motes). Each mote is equipped with embedded microprocessor, flash memory, and a wireless transceiver. Networked data collection along with 3D interactive visualization tools are developed for efficient assessment of the conditions in the bior eactor.

A Comparative Analysis of Contaminant Migration Models Using Barrier Material Data

Waste containment facilities are often composed of barriers such as liners, grout curtains, and slurry walls. The primary design objective for such systems is to mitigate against the release and transport of contaminants. It is often necessary to quantify barrier effectiveness in order to conduct risk and exposure assessments. The extent to which a barrier material is effective can be assessed using analytical methods, laboratory testing, and field monitoring. Obviously, there is a great deal of time and expense associated with both laboratory and field monitoring, making modeling an attractive first alternative. There are, however, numerous solutions to the well-known advection-dispersion equation that vary in accuracy and applicability, depending on initial and boundary conditions. Moreover, most of the equations formulated for transport through porous media were developed for use in aquifer rather than barrier material. Prudent model selection involves matching the conditions to be analyzed with the appropriate mathematical description. In this article, five transport equations are analyzed and compared with laboratory results and projected field conditions for the migration of Pb2+ through soil-bentonite. After 30 days of continuous source injection, measurable concentrations of lead were only detected in the first 0.5 cm of a column of soil-bentonite. All five solutions predicted approximately the same level of penetration for the column tests; however, significant differences emerged after extrapolation to field conditions. For barrier design purposes, the only equations recommended are Equation 3 (the complete solution from Ogata and Banks [1961]) and Equation 6 (Cranks [1956] solution to Ficks Second Law).

Spatio-temporal variation of vegetation in an arid and vulnerable coal mining region

Environmental assessment in an arid coal mining area requires an understanding of the influences of coal mining, the arid climate and ecological remediation. To that end, we selected vegetation as the key environmental factor to observe. Remote sensing approaches to monitoring the spatio-temporal variation of vegetation caused by mining activities, the arid climate and ecological remediation in the Shengdong coal mining area are described. Over a large regional scale it was found that the vegetation was improved as a result of ecological remediation activities. At the local scale, however, the vegetation coverage and soil moisture in the mined areas were slightly lower than those in un-mined areas due to mining subsidence. These differences are partly attributed to ground fissures that injure root systems and increase the depletion of soil moisture. It is recommended that fissures be reduced and filled to lessen their adverse effects on the environment.

Improved spatial resolution in soil moisture retrieval at arid mining area using apparent thermal inertia

Abstract A surface soil moisture model with improved spatial resolution was developed using remotely sensed apparent thermal inertia (ATI). The model integrates the surface temperature derived from TM/ETM+ image and the mean surface temperature from MODIS images to improve the spatial resolution of soil temperature difference based on the heat conduction equation, which is necessary to calculate the ATI. Consequently, the spatial resolution of ATI and SMC can be enhanced from 1 km to 120 m (TM) or 60 m (ETM+). Moreover, the enhanced ATI has a much stronger correlation coefficient ( R 2 ) with SMC (0.789) than the surface reflectance (0.108) or the ATI derived only from MODIS images (0.264). Based on the regression statistics of the field SMC measurement and enhanced ATI, a linear regression model with an RMS error of 1.90% was found.

Cold Weather Subgrade Stabilization

This paper describes an approach to cold-weather subgrade stabilization. Background information was derived from the open literature, ongoing research and discussions with stakeholders in industry, academia and the government. Traditional subgrade stabilization in road construction is defined herein as the use of unmodified lime, cement or fly ash in soil to improve the strength and overall performance of a pavement system. Many of the non-traditional additives currently on the market have been evaluated in recent years. Broadly, these may be categorized as asphalts, polymers, electrolytes, biochemical additives, FGD gypsum and lime/cement additives. Careful evaluation of each category in turn reveals that the most promising alternative to unmodified lime and cement is modified lime and cement. Specifically, rapidly maturing research in the field of cold weather concreting has demonstrated the ability for cementitious reactions to occur at low and sub-freezing temperatures when modified appropriately. Cementitious reactions are the same principle by which conventional lime and cement impart strength on subgrade soils. Naturally, straightforward research is required to transfer concreting technology to soil stabilization. To that end, an experimental campaign has been conducted. In particular, three chemical additives were selected and procured from the W.R. Grace Company, namely Polarset, Gilco and Daraccel. As a preliminary metric of performance, unconfined compression strength testing was conducted on mixtures with and without the chemical additives. At the levels tested, the range of additives increase the cost of conventional stabilization from approximately 10 to 50%, although subsequent research may lower those values still. The control (unmodified) mixture of soil and cement resulted in an average 1-day strength of 487.1 kPa (70.6 psi) when cured at 2 °C (35.6 °F). For the same mixture at the same curing temperature, the average 1-day strength increased to 1286.9, 1394.5 and 1079.2 kPa (186.5, 202.1 and 156.4 psi) for the Polarset, Gilco and Daraccel additives, respectively. These increased strengths at 2 °C are also approximately double that of the unmodified samples cured at 20 °C. These results are unique in that they represent the first application of cold-weather concreting technology to soil stabilization. While more work remains, these results suggest that the additives are promising.

Soil Improvement with Organo-Silane

This manuscript provides insight into a new approach to chemically-based soil improvement with organosilanes (OS). In particular, OS creates a hydrophobic surface on virtually any silica-based material through covalent bonding. In contrast to ion exchange techniques, grafting OS on soils results in near permanent modification. As an illustration, laboratory testing was conducted to evaluate the influence of OS modification on the compaction, strength, swell, erosive and hydraulic properties of several soils. OS modification resulted in modest changes to strength and swell potential and a dramatic reduction in infiltration capacity. Likewise, use of OS on a 2H:1V slope reduced the mass of eroded soil by a factor of nearly 50. Overall, these results suggest that OS modification may have wide application in geotechnical and geoenvironmental engineering.

Practical Leachability and Sorption Considerations for Ash Management

The objective of this work was to determine, through site-specific laboratory testing and modeling, whether a liner system (i.e., geomembrane / compacted clay liner) was required for an ash landfill to ensure that groundwater quality standards would be met. To that end, several tasks were carried out, namely: (1) use of hydrologic modeling for infiltration prediction, (2) assessment of leaching via column and sequential leaching, (3) assessment of attenuation via both batch and column tests, and (4) groundwater and solute transport modeling. The results indicate that if a method for controlling infiltration is employed, then a liner system is not necessary for this particular site. Groundwater protection is predicted using the highest leachable concentrations with the lowest distribution coefficients. The controlling factor is the reduction in infiltration after construction. This reduction in infiltration, coupled with the attenuation capacity of the vadose zone in the interim period of operation, prevents significant contaminant migration.

Field Scale Characterization of Fly Ash Stabilized with Lime and FGD Gypsum

The use of lime and FGD gypsum material to stabilize coal combustion fly ash was evaluated. Five test pads were constructed at a scale that allowed use of field equipment, measuring approximately 15 m in length, 5 m in width and 0.6 m in height. The primary objective of the test pads was to evaluate the influence of lime and FGD gypsum on fly ash leachability. Secondary considerations included permeability, durability, strength and constructability. Measurements were made in the field and also with remolded laboratory specimens. Results suggest that lime influences fly ash leachability, although this varies according to mixing condition, as well as the contaminant of concern. Lime amendment reduced the mobility of cadmium, however, arsenic, chromium and selenium were all present at increased concentrations relative to the test pad constructed of fly ash alone. The hydraulic conductivity of all mixtures tested fell within the 10 -4 - 10 -3 cm/s range. Quality control over field mixing is an important concern. This is particularly sensitive when trying to use the least amount of lime to achieve solidification. Small localized variations in lime or moisture may lead to mixed results.

Coastal Pollution Mitigation with Lime and Zero Valent Iron

The Taiwan Strait region has many miles of coastline, and the Taiwan Straits Tunnel (TST) project faces many potential pollution problems as construction proceeds through sensitive areas. Conventional approaches for pollution mitigation require further examination. The recent development of nanoscale particle technology has shown distinct advantages for contaminant attenuation and ground improvement. This paper is focused on trace metals and is part of the overall effort to develop the nanoscale particle technology. Trace metals in ground and surface waters represent a continued threat to human and ecological health. One of the difficulties in removing toxic concentrations of trace metals from solution is the variable oxidation state and amphoteric nature of multiple constituents. In particular, while cationic metals (e.g., Pb2+, Cd2+, Ni2+) may be rendered less mobile under high pH conditions, anionic metals (e.g., AsO4 3−, CrO4 2−, SeO4 2−)may become more mobile. The objective of this research was to evaluate the sorption of both cationic and anionic trace elements, including arsenic (As), cadmium (Cd), chromium (Cr) and selenium (Se) under batch conditions. Mixtures of a local residual soil were tested alone and in combination with lime and zero valent iron. It was hypothesized that lime would raise the pH and precipitate positively charged metals while zero valent iron would create reducing conditions favorable to the immobilization of negatively charged metals. Results indicate that the use of lime and/or zero valent iron can increase the sorption capacity of soil. Compared to the baseline soil, sorption capacity increased with addition of lime for arsenic and cadmium while it decreased for chromium and selenium. In the case of zero valent iron addition, sorption capacity increased for cadmium, chromium and selenium, while showing no change for arsenic. When both lime and zero valent iron were used, the sorption capacity increased for all metals tested. These results suggest that the combined use of lime and zero valent iron may serve as an alternative treatment technology for removing trace metals from contaminated water systems.