Reginald E. Masto

An appraisal of the potential use of fly ash for reclaiming coal mine spoil

Growing dependence on coal-fired power plants for electrical generation in many countries presents ongoing environmental challenges. Burning pulverized coal in thermal power plants (TPPs) generates large amounts of fly ash (FA) that must be disposed of or otherwise handled, in an environmentally-sound manner. A possible option for dealing with fly ash is to use it as an amendment for mine spoil or other damaged soil. It has been demonstrated through studies in India and other countries that FA alone or in combination with organic or inorganic materials can be used in a productive manner for reclamation of mine spoil. The characteristics of FA, including silt-sized particles, lighter materials with low bulk density (BD), higher water holding capacity, favorable pH and significant concentrations of many essential plant nutrients, make it a potentially favorable amendment for mine spoil reclamation. Studies have indicated that the application of FA has improved the physical, chemical and biological qualities of soil to which it is applied. The release of trace metals and soluble salts from FA could be a major limitation to its application. This is particularly true of fresh, un-weathered FA or acidic FA, although perhaps not a concern for weathered/pond ash or alkaline FA. Some potential contaminants, especially metals and other salt ions, could be immobilized and rendered biologically inert by the addition of certain inorganic and organic amendments. However, in view of the variability in the characteristics of FAs that are associated with location, feed coal, combustion conditions and other factors, the suitability of a particular FA for a specific soil/mine spoil needs to be critically evaluated before it is applied in order to maximize favorable results and eliminate unexpected consequences. FA generated in India tends to be mostly alkaline, with lower levels of trace elements than are often found in FAs from other countries. The concentrations of potential chemical stressors, predominantly metals, in Indian FAs are often less than established or proposed permissible limits and are thus better suited for soil application. A major logistic limitation to the use of FA could be the cost involved in transport of ash from production to utilization sites.

Soil quality index for evaluation of reclaimed coal mine spoil.

Success in the remediation of mine spoil depends largely on the selection of appropriate tree species. The impacts of remediation on mine soil quality cannot be sufficiently assessed by individual soil properties. However, combination of soil properties into an integrated soil quality index provides a more holistic status of reclamation potentials of tree species. Remediation potentials of four tree species (Acacia auriculiformis, Cassia siamea, Dalbergia sissoo, and Leucaena leucocephala) were studied on reclaimed coal mine overburden dumps of Jharia coalfield, Dhanbad, India. Soil samples were collected under the canopies of the tree species. Comparative studies on the properties of soils in the reclaimed and the reference sites showed improvements in soil quality parameters of the reclaimed site: coarse fraction (-20.4%), bulk density (-12.8%), water holding capacity (+0.92%), pH (+25.4%), EC (+2.9%), cation exchange capacity (+46.6%), organic carbon (+91.5%), N (+60.6%), P (+113%), K (+19.9%), Ca (+49.6%), Mg (+12.2%), Na (+19.6%), S (+46.7%), total polycyclic aromatic hydrocarbons (-71.4%), dehydrogenase activity (+197%), and microbial biomass carbon (+115%). Principal component analysis (PCA) was used to identify key mine soil quality indicators to develop a soil quality index (SQI). Selected indicators include: coarse fraction, pH, EC, soil organic carbon, P, Ca, S, and dehydrogenase activity. The indicator values were converted into a unitless score (0-1.00) and integrated into SQI. The calculated SQI was significantly (P<0.001) correlated with tree biomass and canopy cover. Reclaimed site has 52-93% higher SQI compared to the reference site. Higher SQI values were obtained for sites reclaimed with D.sissoo (+93.1%) and C.siamea (+86.4%).

Bioavailability and health risk of some potentially toxic elements (Cd, Cu, Pb and Zn) in street dust of Asansol, India

Street dust samples were collected from five different types of land use patterns (busy traffic zone, urban residential area, national highways, industrial area and sensitive area) in a medium sized industrial city Asansol, India. The samples were fractionated into ≤53µm and analyzed for potential toxic elements (PTEs) viz. Zn, Cd, Pb and Cu. The mean total concentration of Zn, Cd, Pb and Cu in the urban street dust samples were 192, 0.75, 110 and 132mgkg-1 respectively. Chemical speciation was performed for PTEs to evaluate the bio-available fractions. Cu was mostly associated with organic matter phase while Zn, Pb and Cd with residual phase. Mean mobility factor (MF) for heavy metals in Asansol was Zn (54.6%)>Pb (49.1%)>Cu (25.3%)>Cd (22.7%). Geo-chemical indices such as Enrichment Factor (EF), geo-accumulation index (Igeo) and contamination Factor (CF) were in the order of Pb>Cd>Zn>Cu. Cluster analysis was done to understand the similarities among the sites. The risks of all metals was calculated with mobile fraction, which indicated actual risk due to PTEs was less (HI<1).

Impacts of opencast coal mine and mine fire on the trace elements’ content of the surrounding soil vis-à-vis human health risk

Coal from its excavation, processing, and utilization creates environmental problems and health hazards. In these processes, the mobilization of potential organic and heavy metal contaminants affects the quality of soil and health of the inhabitants. Soil samples were collected from the nearby areas of an opencast coal mine (OCM) and a coal fire affected area (CFA) located in Jharia coalfield of Dhanbad, India. The control site was an abandoned land approximately 15 km away from the sources of contamination. These samples were analyzed for trace elements including Cr, V, Co, Ni, Cu, Zn, Ga, Rb, Zr, Ba, Th, and U. The soils of OCM were enriched with Cr and Ni and this is attributed to the mining activities in view of the absence of other sources of pollutants. In case of CFA, the soils were enriched with Cr, V, Ni, and Zn. However, the concentrations of Cr, Ni, and Zn in both the soils were well below the USEPA soil screening levels for human health risk assessment. The levels of Co and V exceeded the soil screening limits. Human exposure risks were evaluated for Co and V. The total intake of V concentration exceeded the EPAs reference dose, which may pose adverse health risks.

Evaluation of the co-application of fly ash and sewage sludge on soil biological and biochemical quality

Disposal of sewage sludge (SS) and fly ash (FA) is a multifaceted problem, which can affect environmental quality. FA has the potential to stabilize SS by reducing metal availability and making the SS suitable for application in the agricultural sector. An experiment was performed to evaluate soil biological quality changes with the combined amendment of SS and FA (fluidized bed combustion ash (FBCA) and lignite fly ash (LFA)). SS was amended with 0, 10, 30, 50 and 100%, (w/w) of FA, and then the FA–SS mixtures were incubated with red soil at 1:1 (v/v). Soil quality parameters such as pH, electrical conductivity, N, soil enzyme activities such as dehydrogenase (DHA), urease (URE), and catalase (CAT), and microbial biomass carbon (MBC) were evaluated at 20, 30, and 60 days of incubation. pH and EC increased with FA–SS dose; however, N decreased. DHA and URE were found to be increased with 10% LFA amendment; thereafter it decreased. However, URE increased up to 30% of FBCA. CAT and MBC increased with both FA amendments, even up to addition of 50% FA. Bioavailable Zn, Cu, and Co contents were decreased by the addition of FA. Principal component analysis showed that pH is the most influential factor. MBC appears to be a sensitive soil indicator for the effects that result from the addition of FA–SS. Phytotoxicity studies with Zea mays showed optimum performance at 30% FA. Addition of 10–30% FBCA or LFA to SS has a positive advantage on soil biological quality.

Potentially toxic elements in lignite and its combustion residues from a power plant

The presence of potentially toxic elements in lignite and coal is a matter of global concern during energy extraction from them. Accordingly, Barsingsar lignite from Rajasthan (India), a newly identified and currently exploited commercial source of energy, was evaluated for the presence of these elements and their fate during its combustion. Mobility of these elements in Barsingsar lignite and its ashes from a power plant (Bikaner-Nagaur region of Thar Desert, India) is presented in this paper. Kaolinite, quartz, and gypsum are the main minerals in lignite. Both the fly ash and bottom ash of lignite belong to class-F with SiO2 > Al2O3 > CaO > MgO. Both the ashes contain quartz, mullite, anhydrite, and albite. As, In, and Sr have higher concentration in the feed than the ashes. Compared to the feed lignite, Ba, Co, U, Cu, Cd, and Ni are enriched (10–5 times) in fly ash and Co, Pb, Li, Ga, Cd, and U in bottom ash (9–5 times). Earth crust–normalization pattern showed enrichment of Ga, U, B, Ag, Cd, and Se in the lignite; Li, Ba, Ga, B, Cu, Ag, Cd, Hg, Pb, and Se, in fly ash; and Li, Sr, Ga, U, B, Cu, Ag, Cd, Pb, and Se in bottom ash. Hg, Ag, Zn, Ni, Ba, and Se are possibly associated with pyrite. Leaching test by toxicity characteristic leaching procedure (TCLP) showed that except B all the elements are within the safe limits prescribed by Indian Standards.

The Impact of Fly Ash Amendment on Soil Carbon

Soils play an important role in carbon cycling. An important approach to terrestrial carbon sequestration is to make use of currently underutilized and waste/degraded lands. The addition of fly ash can ameliorate the adverse conditions of wastelands through a variety of mechanisms, besides helping in stabilization of the soil carbon. Carbon mineralization and humification studies were carried out with soil, fly ash, and their mixtures. Organic monomers included for the humification reactions were resorcinol, p-hydroxybenzoic acid, L-glycine, and L-serine. Results showed that the humification pattern was higher for Associate Cement Companies (0.154 λ485) and Khaparkheda (0.119 λ485) fly ashes, than soil (0.110 λ485). In the carbon mineralization experiment, the soil carbon stabilization enzyme peroxidase activity was higher at soil amended with fly ash (0.052 μM/g/h) than soil alone (0.013 μM/g/h). The dissolved organic carbon was almost two times lower in fly ash amended soil, which revealed the adsorption of carbon in fly ash. The adsorption of soluble organic compounds on the solid surfaces is one of the mechanisms of fixing of soil organic carbon. The cumulative CO2 liberation due to plant litter addition was not affected by fly ash. To conclude, fly ash is abundantly available and is considered as a waste in many thermal power plants, which could be sustainably utilized in the agriculture and forestry sectors, both under arable and waste degraded land for enhancing terrestrial carbon sequestration, besides increasing the plant growth and yield.

The Effect of Fly Ash Application on Phosphorus Availability in an Acid Soil

Fly ash has increasingly been used as soil amendment. The mobility of the plant nutrient, phosphorus (P), from fly ash into plant roots is limited due to various inherent locking of P in fly ash. Similarly, the phosphatic fertilizer added to acid soils is fixed and is not easily available to plants. The present study is focused on finding some important aspects of P fractions, P fixing capacity, and P adsorption behavior in acid soil and fly ash- soil mixtures to substantiate the beneficial effect of fly ash addition to acid soil in overcoming the P fixation. Fly ash collected from the fluidized bed combustion power plant of Tata Iron and Steel Company, Jamadoba, Dhanbad, India, and acid soil from Jamdoba village was mixed at different ratios for studying the behavior of P in soil and fly ash soil mixtures. In fly ash out of 3,140 mg kg−1 total P, only 2.89% (90.95 mg kg−1) was in loosely bound form, whereas in soil 54.45 mg kg−1 P (10.8%) out of the 504 mg kg−1 total P was in loosely bound form. Most of the P in fly ash (55.0%) was associated with Ca, while it was Fe-P (40.6%) in soil. The P adsorption maximum followed the order: fly ash (9,354 mg kg−1), 7:1 mix (8,850 mg kg−1), 3:1 mix (8,547 mg kg−1), soil alone (8,130 mg kg−1), and 1:1 mix (7,194 mg kg−1). The supply parameter calculated from the equilibrium phosphorus concentrations and adsorption data showed that the supply parameter increased with fly ash addition. Individually, P fixing capacity of the fly ash and soil was 75.6 and 65.68%, respectively, when both were mixed (1:1), the P fixing capacity decreased to 52.94% due to the synergistic interaction between soil and fly ash. Thus, though fly ash and acid soil is having difficulty with P availability, mixing enhanced the availability of P synergistically.

Exploratory Study of Archaebacteria and their Habitat in Underground, Opencast Coal Mines and Coal Mine Fire Areas of Dhanbad

Coal contains abundant microbial genera which include archaebacteria. The study of archaea kingdom in coal mines is a significant tool for knowing the relationship between coal and archaebacteria, the major role in geochemical cycle and application for further coal bio–beneficiation. The present study related to exploration of archaebacteria and their habitat in coal mining area of Dhanbad with reference to their ecology and nutrient availability that have evolve to grow under extreme conditions. Total six different sites such as two underground coal mines (Sudamdih shaft and Chasnalla underground mine), two opencast coal mines (Chandan project and Bhowra abandoned mine), Jharia mine fire and Sudamdih coal washery of Dhanbad was selected. Seven gram negative obligate anaerobic bacteria were isolated from the selected sites. The isolated species were rod and cocci shaped and the colony was round, smooth, off white in colour and with entire margin and little are cluster of cocci in shape. The isolated species were identified as Methanococcus spp, Methanobacterium spp and Methanosarcina spp. Apart from that two thermoacidophilic sulfur oxidizing bacteria Sulfolobus spp was also isolated from Jharia Coal Mine Fire. The physicochemical and biological characterization of the habitat was also studied for the entire selected area.

Tracing source, distribution and health risk of potentially harmful elements (PHEs) in street dust of Durgapur, India

Street dust samples from Durgapur, the steel city of eastern India, were collected from five different land use patterns, i.e., national highways, urban residential area, sensitive area, industrial area and busy traffic zone during summer, monsoon, and winter to analyze the pollution characteristics, chemical fractionation, source apportionment and health risk of heavy metals (HMs). The samples were fractionated into ≤ 53 µm and analyzed for potentially harmful elements (PHEs) viz. Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn. Summer season indicated higher concentrations of PHEs when compared to the other two seasons. Mean enrichment factor (EF), geo-accumulation index (Igeo), and contamination factor (CF) were high for Cd followed by Pb during all the three season in Durgapur. Chemical fractionation was executed in order to obtain distribution patterns of PHEs and to evaluate their bioavailable fractions in street dust samples. Mn was found to be highly bioavailable and bioavailability of the PHEs were in the order of Mn > Zn > Pb > Ni > Cd > Cu > Fe > Cr. Principal Component Analysis (PCA), cluster analysis, correlation analysis indicated the main sources of PHEs could be industrial, especially coal powered thermal plant, iron and steel industries and cement industries and vehicular. Multivariate analysis of variance (MANOVA) indicated that sites, seasons and their interaction were significantly affected by different PHEs as a whole. The health risk was calculated with total metal as well as mobile fraction of PHEs, which indicated that the actual non-carcinogenic risk due to bioavailable PHEs was less (HI < 1) when compared to total concentrations of PHEs. Carcinogenic risk was observed for total Cr in street dust (Child: 4.6E-06; Adult: 3.6E-06).