The Inorganic Geochemistry of Coal: A Scanning Electron Microscopy View

The scanning electron microscope (SEM), equipped with an energy dispersive X-ray analyzer (EDX), has been widely used to study the inorganic geochemistry of coal. This system was instrumental in establishing that the bulk of most trace elements in bituminous coals are associated with fine-grained accessory minerals. Textural evidence, as observed in the SEM, indicates that many of these minerals are embedded in relatively large organic particles. As a consequence of this association, these minerals, and the elements they contain, can be rafted up into the lighter specific gravity fractions during sink-float separation of the coal. Textural evidence also indicates the presence of two distinct mineral suites. The first suite includes kaolinite, sulfides, carbonates, and crandallite-group minerals. They occur predominantly in the pores of the inertinite macerals. These minerals commonly exhibit crystal faces and are intimately intergrown with one another. An authigenic origin is indicated for these minerals. The second suite occurs in bands of intermixed maceral fragments and angular to subrounded mineral grains that are probably of detrital origin. This suite includes quartz (some rutilated), illite, mixed-layer clays, rutile, and zircon. The perfection of ancillary techniques, such as cathodoluminescence and automated image analyses, will enhance the future value of the SEM in the study of coal geochemistry

The Future Environmental and Health Impacts of Coal

In the United States, coal consumption in the last 12 years has declined from 1,045,140 million short tons in 2007 to 539,420 million short tons in 2019, a decrease of almost 50%. During that period the number of electric power coal generators has declined from 1,470 to 738 accounting for 21% of capacity. An even more dramatic decrease in coal use has occurred in Western Europe. This significant reduction in coal use and the concomitant closure of coal mines and coal-burning power plants will result in substantially cleaner air, reductions in respiratory problems such as asthma, less heart disease, fewer hospitalizations, and other health benefits, as well as a reduction in occupational health problems such as silicosis and Coal Workers’ Pneumoconiosis (Black Lung Disease). However, in China, India, Russia and in several other Asian countries some projections indicate an increase in coal production and use. In some situations, the coal is burned in old, highly polluting power plants. In these regions the health impacts of coal use could worsen. In addition, millions of people in these regions still burn coal in their homes resulting in maximal exposure to the pollutants such as arsenic, selenium, fluorine, and mercury released from coal combustion

Medical Geology : a globally emerging discipline

Medical Geology, the study of the impacts of geologic materials and processes on animal and human health, is a dynamic emerging discipline bringing together the geoscience, biomedical, and public health communities to solve a wide range of environmental health problems. Among the Medical Geology described in this review are examples of both deficiency and toxicity of trace element exposure. Goiter is a widespread and potentially serious health problem caused by deficiency of iodine. In many locations the deficiency is attributable to low concentrations of iodine in the bedrock. Similarly, deficiency of selenium in the soil has been cited as the principal cause of juvenile cardiomyopathy and muscular abnormalities. Overexposure to arsenic is one of the most widespread Medical Geology problems affecting more than one hundred million people in Bangladesh, India, China, Europe, Africa and North and South America. The arsenic exposure is primarily due to naturally high levels in groundwater but combustion of mineralized coal has also caused arsenic poisoning. Dental and skeletal fluorosis also impacts the health of millions of people around the world and, like arsenic, is due to naturally high concentrations in drinking water and, to a lesser extent, coal combustion. Other Medical Geology issues described include geophagia, the deliberate ingestion of soil, exposure to radon, and ingestion of high concentrations of organic compounds in drinking water. Geoscience and biomedical/public health researchers are teaming to help mitigate these health problems as well as various non-traditional issues for geoscientists such as vector-borne diseases

Notes on Contributions to the Science of Rare Earth Element Enrichment in Coal and Coal Combustion Byproducts

Coal and coal combustion byproducts can have significant concentrations of lanthanides (rare earth elements). Rare earths are vital in the production of modern electronics and optics, among other uses. Enrichment in coals may have been a function of a number of processes, with contributions from volcanic ash falls being among the most significant mechanisms. In this paper, we discuss some of the important coal-based deposits in China and the US and critique classification systems used to evaluate the relative value of the rare earth concentrations and the distribution of the elements within the coals and coal combustion byproducts

Sequential solvent extraction for the modes of occurrence of selenium in coals of different ranks from the Huaibei Coalfield, China

Forms of selenium in bituminous coal, anthracite, and cokeite (natural coke) from Huaibei Coalfield, Anhui, China, have been determined by sequential solvent extraction. The selenium content in bulk samples is 4.0, 2.4, and 2.0 μg/g in bituminous coal, anthracite, and cokeite, respectively. The six forms of selenium determined by six-step solvent extraction are water-leachable, ion-exchangeable, organic matter-associated, carbonate-associated, silicate-associated, and sulfide-associated. The predominant forms of selenium in bituminous coal are organic matter-associated (39.0%), sulfide-associated (21.1%), and silicate bound (31.8%); these three forms account for 92% of the total. The organic matter bound-selenium decrease dramatically from bituminous coal (39.0%) to anthracite (11.6%) and to cokeite (0%), indicating that organic matter bound selenium is converted to other forms during metamorphism of the coal, most likely sulfide-form. The sulfide-associated form increased remarkably from bituminous coal (21.1%) to anthracite (50.4%) and cokeite (54.5%), indicating the formation of selenium sulfide, possibly in pyrite during the transformation of bituminous coal to anthracite and cokeite. The silicate-associated selenium in bituminous coal (31.8%) is much higher than that in anthracite (16.4%) and cokeite (15.8%), indicating that silicate-associated selenium is partly converted to sulfide during metamorphism

Medical Geology: Its Relevance to Mexico

Interest in medical geology issues is rapidly expanding around the world. The objective of this paper is to highlight medical geology issues in Mexico and to discuss the importance of natural resources and its relation to human and animal health. Three Mexico ́s zones are discussed; North, Central and Western. In addition, two main concerns are addressed; the arsenic and the flouride levels in ground water. These two trace elements along with others such as uranium and radon are elements that pose a serious threat to human health. The last part is dedicated to Chihuahua where arsenic, fluorine, uranium and radon coming from geogenic or anthropogenic sources present a serious threat to humans. The authors hope to encourage students and professors to participate and engage in medical geology conferences and events in order to improve their knowledge on this topic as well as to improve the health of Mexican citizens and people all over the world. Resumen El concepto y la importancia del estudio de la geología médica está creciendo alrededor del mundo. El objetivo de este trabajo es discutir la importancia de diversos aspectos de geología médica en México y señalar la relacion de los recursos naturales con la salud humana y animal. Se discuten tres grandes regiones del país: la región norte, la región central y la región oeste. Además, se analizan dos preocupaciones fundamentales: el arsénico y el flúor. Estos dos elementos, junto con otros como el uranio y radón son elementos que potencialmente representan una amenaza a la salud humana en el país. La última parte del análisis se enfoca en el estado de Chihuahua, que es el más grande de México, y donde el arsénico, flúor, uranio y radón, presentes ya sea de fuentes naturales (geogénicas) o antropogénicas, representan una seria amenaza a la salud humana. Los autores desean motivar tanto a estudiantes como profesores a participar e involucrarse en el tema de la geología médica con el fin de ahondar en sus diferentes aspectos y, como consecuencia, mejorar la salud de los habitantes de México y del mundo. Palabras clave: salud humana, amenaza, arsénico, flúor, uranio, radón

Leaching of Potential Hazardous Elements of Coal Cleaning Rejects

The geochemical characteristics of coal cleaning rejects (CCR) in Santa Catarina State, Brazil, were investigated. Around 3.5 million ton/ year of coal waste are dumped in Santa Catarina State. Coal beneficiation by froth flotation results in large amounts of CCR composed of coaly and mineral matter, the latter characterized by the occurrence of sulphide minerals and a broad array of leachable elements. The total and leachable contents of more than 60 elements were analyzed. Atmospheric exposure promotes sulphide oxidation that releases substantial sulphate loads as well as Ca2+, K+, Mg2+, Cl- and Al3+. The metals with the most severe discharges were Zn, Cu, Mn, Co, Ni and Cd. Most trace pollutants in the CCR displayed a marked pH-dependent solubility, being immobile in near-neutral samples. The results highlight the complex interactions among mineral matter solubility, pH and the leaching of potentially hazardous elements. © 2010 Springer Science+Business Media B.V