Chemical speciation of elements in stack-collected, respirable-size, coal fly ash

Association between Arsenic Level, Gene Expression in Asian Population, and In Vitro Carcinogenic Bladder Tumor

The IARC classified arsenic (As) as "carcinogenic to humans." Despite the health consequences of arsenic exposure, there is no molecular signature available yet that can predict when exposure may lead to the development of disease. To understand the molecular processes underlying arsenic exposure and the risk of disease development, this study investigated the functional relationship between high arsenic exposure and disease risk using gene expression derived from human exposure. In this study, a three step analysis was employed: (1) the gene expression profiles obtained from two diverse arsenic-exposed Asian populations were utilized to identify differentially expressed genes associated with arsenic exposure in human subjects, (2) the gene expression profiles induced by arsenic exposure in four different myeloma cancer cell lines were used to define common genes and pathways altered by arsenic exposure, and (3) the genetic profiles of two publicly available human bladder cancer studies were used to test the significance of the common association of genes, identified in step 1 and step 2, to develop and validate a predictive model of primary bladder cancer risk associated with arsenic exposure. Our analysis shows that arsenic exposure to humans is mainly associated with organismal injury and abnormalities, immunological disease, inflammatory disease, gastrointestinal disease, and increased rates of a wide variety of cancers. In addition, arsenic exerts its toxicity by generating reactive oxygen species (ROS) and increasing ROS production causing the imbalance that leads to cell and tissue damage (oxidative stress). Oxidative stress activates inflammatory pathways leading to transformation of a normal cell to tumor cell specifically; there is significant evidence of the advancing changes in oxidative/nitrative stress during the progression of bladder cancer. Therefore, we examined the relation of differentially expressed genes due to exposure of arsenic in human and bladder cancer and developed a bladder cancer risk prediction model. In this study, integrin-linked kinase (ILK) was one of the most significant pathways identified between both arsenic exposed population which plays a key role in eliciting a protective response to oxidative damage in epidermal cells. On the other hand, several studies showed that arsenic trioxide (ATO) is useful for anticancer therapy although the mechanisms underlying its paradoxical effects are still not well understood. ATO has shown remarkable efficacy for the treatment of multiple myeloma; therefore, it will be helpful to understand the underlying cancer biology by which ATO exerts its inhibitory effect on the myeloma cells. Our study found that MAPK is one of the most active network between arsenic gene and ATO cell line which is involved in indicative of oxidative/nitrosative damage and well associated with the development of bladder cancer. The study identified a unique set of 147 genes associated with arsenic exposure and linked to molecular mechanisms of cancer. The risk prediction model shows the highest prediction ability for recurrent bladder tumors based on a very small subset (NKIRAS2, AKTIP, and HLA-DQA1) of the 147 genes resulting in AUC of 0.94 (95% CI: 0.744-0.995) and 0.75 (95% CI: 0.343-0.933) on training and validation data, respectively.

Progressive utilisation prospects of coal fly ash: A review

The rapid surge in global energy needs has paved way for the development of various alternatives to natural resources every now and then. However, dependence on coal-based energy has not reduced greatly. Thus, massive quantities of coal fly ash (CFA) are generated worldwide, which is a serious threat to ecology owing to constraints associated with its storage and disposal. There exists a pressing and ongoing need to develop new, and green product streams from CFA to reduce the threat to the environment. The present review begins with an emphasis on the generation, physicochemical properties, and potential dangers of CFA. Then, it focuses on impending applications such as synthesis of geopolymers (alternative to cement), silica aerogels (insulating materials), carbon nanotubes (carbon allotropes) for electronic devices, and the separation of radioactive isotopes as well as rare earth elements from CFA. Furthermore, the review analyses factors restraining the motive for effective management strategies that drives utilisation of CFA (either in raw and processed state) for new product streams. Finally, the review elucidates the role of CFA as an emerging input in delivering eco-friendly amenities and future derivatives.

Radiative forcing by light-absorbing aerosols of pyrogenetic iron oxides

Iron (Fe) oxides in aerosols are known to absorb sun light and heat the atmosphere. However, the radiative forcing (RF) of light-absorbing aerosols of pyrogenetic Fe oxides is ignored in climate models. For the first time, we use a global chemical transport model and a radiative transfer model to estimate the RF by light-absorbing aerosols of pyrogenetic Fe oxides. The model results suggest that strongly absorbing Fe oxides (magnetite) contribute a RF that is about 10% of the RF due to black carbon (BC) over East Asia. The seasonal average of the RF due to dark Fe-rich mineral particles over East Asia (0.4–1.0 W m⁻²) is comparable to that over major biomass burning regions. This additional warming effect is amplified over polluted regions where the iron and steel industries have been recently developed. These findings may have important implications for the projection of the climate change, due to the rapid growth in energy consumption of the heavy industry in newly developing countries.

Abatement of organic pollutants using fly ash based adsorbents

The presence of organic pollutants in the environment is of major concern because of their toxicity, bio-accumulating tendency, threat to human life and the environment. It is a well-known fact that, these pollutants can damage nerves, liver, and bones and could also block functional groups of essential enzymes. Conventional methods for removing dissolved pollutants include chemical precipitation, chemical oxidation or reduction, filtration, ion-exchange, electrochemical treatment, application of membrane technology, evaporation recovery and biological treatment. Although all the pollutant treatment techniques can be employed, they have their inherent advantages and limitations. Among all these methods, adsorption process is considered better than other methods because of convenience, easy operation and simplicity of design. A fundamentally important characteristic of good adsorbents is their high porosity and consequent larger surface area with more specific adsorption sites. This paper presents a review of adsorption of different pollutants using activated carbon prepared from fly ash sources and the attendant environmental implications. Also, the ways of overcoming barriers to fly ash utilization together with regeneration studies are also discussed.

Coal fly ash as a source of iron in atmospheric dust

Anthropogenic coal fly ash (FA) aerosol may represent a significant source of bioavailable iron in the open ocean. Few measurements have been made that compare the solubility of atmospheric iron from anthropogenic aerosols and other sources. We report here an investigation of iron dissolution for three FA samples in acidic aqueous solutions and compare the solubilities with that of Arizona test dust (AZTD), a reference material for mineral dust. The effects of pH, simulated cloud processing, and solar radiation on iron solubility have been explored. Similar to previously reported results on mineral dust, iron in aluminosilicate phases provides the predominant component of dissolved iron. Iron solubility of FA is substantially higher than of the crystalline minerals comprising AZTD. Simulated atmospheric processing elevates iron solubility due to significant changes in the morphology of aluminosilicate glass, a dominant material in FA particles. Iron is continuously released into the aqueous solution as FA particles break up into smaller fragments. These results suggest that the assessment of dissolved atmospheric iron deposition fluxes and their effect on the biogeochemistry at the ocean surface should be constrained by the source, environmental pH, iron speciation, and solar radiation.

Industrial wastes as low-cost potential adsorbents for the treatment of wastewater laden with heavy metals

Industrial wastes, such as, fly ash, blast furnace slag and sludge, black liquor lignin, red mud, and waste slurry, etc. are currently being investigated as potential adsorbents for the removal of the heavy metals from wastewater. It was found that modified industrial wastes showed higher adsorption capacity. The application of low-cost adsorbents obtained from the industrial wastes as a replacement for costly conventional methods of removing heavy metal ions from wastewater has been reviewed. The adsorption mechanism, influencing factors, favorable conditions, and competitive ions etc. on the adsorption of heavy metals have also been discussed in this article. From the review, it is evident that certain industrial waste materials have demonstrated high removal capacities for the heavy metals laden with wastewater. However, it is to be mentioned that adsorption capacities of the adsorbents vary depending on the characteristics of the adsorbents, the extent of chemical modification and the concentration of adsorbates. There are also few issues and drawbacks on the utilization of industrial wastes as low-cost adsorbents that have been addressed. In order to find out the practical utilization of industrial waste as low-cost adsorbents on the commercial scale, more research should be conducted in this direction.

Identification of Chemical Compounds in Fly Ash by X-Ray Absorption Spectroscopy and Proton-Induced X-Ray and Gamma-Ray Emission Analyses

Proton-induced X-ray emmision and proton-induced gamma-ray emission analyses have been used to determine the elemental content of four oil fly ash samples collected from the flue line of an oil-fired power plant. X-ray absorption spectroscopy was used to characterize the vanadium and nickel compounds present in the fly ash. Vanadium was present primarily as VOSO4·3H2O and nickel was present as a mixture of NiSO4 and NiO.

Environmental feasibility of using coal ash as a fill material to raise the ground level

Batch leach tests (BLTs) and column leach tests (CLTs) were conducted on bottom ash (BA), lagoon ash (LA), soil (S), and bottom ash-soil (BA-S) and lagoon ash-soil (LA-S) mixtures to evaluate the environmental feasibility of using these as fill materials to raise the ground level at construction sites. For the BLTs, the leachability of the elements (i.e., Cr, Mn, Ni, and Zn) generally increased with decreasing pH from 6.3 to 3.0. In addition, the concentration of all the elements analyzed in the leachates increased with decreasing the liquid-to-solid (L/S) ratio. Freezing-thawing cycles had no significant effect on the leachability of the elements found in the BLTs. The initial concentrations of the leachates from the CLTs were higher than those of the leachates from the BLTs regardless of the materials tested due to the lower L/S ratio. The initial concentrations of As, Ni, Mn, Se, Cl-, and SO4(2-) in the leachates from the CLTs for the LA, BA, and LA-S and BA-S mixtures exceeded the drinking water standards (DWSs), which suggests that these materials may pose a risk to groundwater when these materials are used in areas where there is little dilution.

Effects of leachant temperature and pH on leachability of metals from fly ash. A case study: Can thermal power plant, province of Canakkale, Turkey

Lignite powered electric generation plants result in increasing environmental problems associated with gaseous emissions and the disposal of ash residues. Especially, low quality coals with high ash content cause enormous quantities of both gaseous and solid fly ash emissions. The main problem is related to the disposal of fly ash, which, in many cases, contains heavy metals. It is known that toxic trace metals may leach when fly ash is in contact with water. In this study, fly ash samples obtained from the thermal power plant in the town of Can in Turkey were investigated for leachability of metals under different acidic and temperature conditions. The experimental results show that a decrease in pH of the leachant favors the extraction of metal ions from fly ash. A significant increase in the extraction of arsenic, cadmium, chromium, zinc, lead, mercury, and selenium ions from the ash is attributed to the instability of the mineral phases. These heavy metals concentrations increase with respect to increasing acidic conditions and temperature. Peak concentrations, in general, were found at around 30 degrees C.

Methods for speciation of metals in soils: a review

The inability to determine metal species in soils hampers efforts to understand the mobility, bioavailability, and fate of contaminant metals in environmental systems, to assess health risks posed by them, and to develop methods to remediate metal contaminated sites. Fortunately, great strides have been made in the development of methods of species characterization and in their application to the analysis of particulates and mixtures of solid phases in physics, analytical chemistry, and materials science. This manuscript highlights a selection of the analytical methods available today offering the greatest promise, briefly describes the fundamental processes involved, examines their limitations, points to how they have been used in the environmental and geochemical literature, and offers some suggested research directions in the hope of stimulating further investigation into the application of these powerful tools to the problems outlined above.

The surface chemistry of leaching coal fly ash

The utilization of coal fly ash in the construction and non-construction areas has seen a rapid growth in the last decade. As production outweighs the utilization of fly ash, its disposal as a dilute or dense slurry is still practiced in coal fired power stations. In this review the surface chemistry of leaching coal fly ash is presented to highlight the role of mass transfer in providing resistance and consequently delayed leaching of elements, when fly ash is disposed or used for value addition.

Pulmonary effects of ultrafine coal fly ash inhaled by guinea pigs

Guinea pigs were exposed to ultrafine coal fly ash produced in a laboratory furnace. The average mass median aerodynamic diameter and the average mass concentration of Illinois no. 6 fly ash produced in all exposure conditions were 0.21 microns and 5.8 mg/m3, respectively. In guinea pigs exposed to Illinois no. 6 fly ash, total lung capacity (TLC), vital capacity (VC), and diffusing capacity for carbon monoxide (DLco) were significantly reduced below the control values immediately, 2 h, and 8 h postexposure. The diffusing capacity was still 10% below the control 96 h after exposure. The total sulfate in the Illinois no. 6 fly ash as determined using ion chromatography is 1105 +/- 120 micrograms/m3. Animals exposed to the Montana lignite fly ash at comparable concentration and particle size did not show alteration in diffusing capacity. The data suggest that part of the sulfate present in the fly ash of Illinois no. 6 could be in the form of sulfuric acid and is responsible for the adverse effects observed in the exposed animals. The sulfuric acid in the fly ash of Montana lignite is neutralized by its high alkali content and produces no change in lung functions.

The leachability and chemical speciation of selected trace elements in fly ash from coal combustion and refuse incineration

A laboratory leaching test has been used to predict the potential mobility of As, Se, Pb and Cd in landfilled fly ash produced by coal combustion and refuse incineration. These waste residues also formed the basis of a speciation study in which the valency states of As and Se and the chemical forms of Pb and Cd have been determined. Selenium displayed the greatest leachability in each ash type, despite being present at relatively low concentrations in both materials. Substantial amounts of other trace elements were also leached, particularly Pb and Cd from refuse ash and As from coal ash. Chemical associations of Pb and Cd were examined by a sequential extraction procedure. In coal fly ash, both elements were mostly present in the residual fraction, while in refuse ash these elements were mainly associated with the exchangeable fraction. Water-soluble extracts of coal fly ash contained As exclusively as As(V); high background interference prevented the detection of water-soluble As in refuse ash. Selenium was present largely as Se(IV) in aqueous extracts of both ash types. The value of speciation techniques and leaching tests as predictors of environmental behaviour is discussed in conjunction with results of routine trace element determinations and plant uptake studies.