M. A. Powell

Leachability of elements from sub-bituminous coal fly ash from India

Environmental concerns regarding the potential contamination of soil, surface and ground water due to the presence of soluble metal species in the ash pond leachate is of great importance. Serial batch leaching was carried out simulating the rainwater condition of the study area to understand the behaviour of elements during leaching. The leachates were analysed for the elements Al, Ca, K, Mg, Na, P, S, Si, As, Ba, Fe, Mn, Mo, Ti, V, Pb, Zn, Co, Cr, Cu, Ni and Cd by inductively coupled plasma optical emission spectrometer (ICP-OES). It was found that Cd, Co, Cr and Ni did not leach from the ash while Cu and Pb concentrations were insignificant in the leachate regardless of liquid to solid (L/S) ratio. Most of the elements showed maximum concentrations at lower L/S ratio and then decreased with increasing L/S. The total cumulative concentrations of As, Mn and Mo were found to be higher than the World Health Organization (WHO) recommended values for drinking water while the concentrations of Fe, Mn and As exceeded the maximum allowable concentrations prescribed by the United States Environmental Protection Agency (USEPA). The pre and the post leached ash samples were analysed for morphology, specific surface area and mineralogical changes. Analysis of post-leached fly ash indicated changes in the specific surface area and morphology but no change in mineralogy.

Authigenic mineralization and detrital clay binding by freshwater biofilms: The Brahmani river, India

Epilithic biofilms, growing on submerged boulders, were collected upstream and downstream of sites of industrial discharge into the Brahmani River, Orissa State, India. Transmission electron microscopy (TEM) showed that the outer cell walls of attached bacteria in all samples were often encrusted with fine‐grained (<1 μm) inorganic precipitates. The density of mineralization ranged from a few epicellular grains to complete encrustation by clayey materials. Energy‐dispersive x‐ray spectroscopy (EDS) and selected‐area electron diffraction (SAED) indicated that the most abundant inorganic phase was a complex, poorly ordered, (Fe, Al)‐silicate of variable composition, containing minor amounts of potassium. No trace metals were detected in the authigenic precipitates. Bacterial cells were also found to entrap or adsorb detrital minerals such as kaolin, mica, quartz, iron oxide, and gibbsite onto their outer surfaces. Because epilithic microbial biofilms have a very large and highly reactive surface area, bindi...

Sorption and distribution of adsorbed metals in three soils of India

Abstract The mobility and bioavailability of heavy metals depends on the metal retention capacity of soil and also on the geochemical phases with which metals are associated. Laboratory batch experiments were carried out to study the sorption and distribution of Cd, Ni and Pb in 3 soils differing in their physicochemical properties from India: Oxyaquic Haplustalf (SL1), Typic Haplustalf (SL2) and Typic Haplustert (SL3). The heavy metal adsorption was studied by isotherms and the distribution coefficient ( K D ) for each metal was obtained from the linear regressions of the concentration of metal remaining in equilibrium solution and the amount adsorbed. In general, the sorption capacity for all the metals decreased in the order: SL3>SL2>SL1. Among metals, the sorption capacity in all the soils decreased in the order: Pb>>Ni>Cd. Distribution of sorbed metals at various equilibrating concentrations was studied by sequential extraction. Results showed significant differences in the distribution of metals in these soils. At higher additions (such as 200 μM l −1 ) most of the metals were extracted in their more mobile fractions, exchangeable and/or inorganic in contrast to their original partitioning in soils, where they were preferentially associated with the less mobile residual fraction. Largest percentages of metals extracted in the exchangeable fraction corresponded to those soil–metal systems with smaller K D values, e.g. Cd, Ni and Pb in SL1 and Cd and Ni in SL2. In neutral and alkaline soils (SL2, pH=7.1, and SL3, pH=8.6) Pb was predominantly extracted from the inorganic fractions and this corresponded to higher K D values for Pb in these soils. The predominance of metals associated with the exchangeable fraction together with low K D values indicates higher mobility of metals retained in the acidic soil (SL1, pH=5.2) compared with the others.

Arsenic Uptake by Rice and Accumulation in Soil Amended with Municipal Solid Waste Compost

Effect of municipal solid waste compost (MSWC) on arsenic content of submerged rice paddies was studied. Experiments were conducted during the three consecutive wet seasons from 1997 to 1999 on rice grown under submergence, at the Experimental Farm of Calcutta University, India. A sequential extraction method was used to determine the various arsenic fractions in MSWC and cow dung manure (CDM). Arsenic (As) was significantly bound to the organic matter and iron (Fe) and manganese (Mn) oxides in MSWC and CDM. Arsenic content in rice straw was higher than rice grain. Arsenic bound with Fe and Mn oxides best correlated with straw As (r = + 0.99**) and grain As (r = + 0.99**) content. The As bound with organic matter followed next (r = + 0.98** for straw, and r = + 0.94* for grain) with the exchangeable part being also significant with straw (r = + 0.94*). In CDM, the As content of rice grain correlated best with water soluble As (r = + 0.96**) while the straw As content was best correlated with exchangeable As (r = + 0.99**) followed by As bound with organic matter (r = + 0.98**). MSWC effectively served as binding agent for native soil arsenic thereby moderating the rapid arsenic mobilization to the crop rhizosphere.

Delineation of groundwater contamination around an ash pond: Geochemical and GIS approach

The study has investigated the levels of metal contamination in groundwater due to particulate matter fallout and leaching from ash pond and assigned contamination indices for the adjacent localities around an ash disposal site with application of geographic information systems (GIS). Fe, Ba, Cu, Mn, S, Pb, V, and Zn were found to be the major contaminants in groundwater. Enrichment factors (EF) of these elements with respect to the United States Environmental Protection Agency (USEPA) maximum contaminant levels show high values for Mn, Fe, and Pb in groundwater. The zone of attenuation for Ba, Fe, Cu, Mn, S, and Zn in groundwater is about 600-900 m from the ash pond, while Pb did not show any significant attenuation even at a distance of 1200 m. Tube wells around Rankasingha and Kukurhanga villages are most contaminated whereas open wells of Lachhmanpur, Kaniapada, and Kurudul villages showed higher degrees of contamination.

Trace element geochemistry of river sediment, Orissa State, India

Abstract Geochemical analyses of bottom sediment from rivers flowing through Orissa State, India indicated that trace element concentrations were extremely variable, and commonly higher than crustal abundance. The highest elemental concentrations were associated with the Brahmani River, followed by the Baitarani and Mahanadi Rivers. Although all three rivers drain similar, geology, the Brahmani River catchment is heavily industrialized, and sediment collected downstream from industry confirms that anthropogenic activity influenced its chemical composition. A similar pattern was observed in sediments collected downstream from towns in the Mahanadi and Baitarani catchments. In both examples, the clay size fraction was shown to be the most highly reactive component of the sediments. Comparisons between metal concentrations from the upper to lower stretches of the three river systems indicated no net accumulation downstream. Apparently, trace elements discharged into the river system tend to be short-lived in the water column, rapidly settling out or becoming adsorbed into the bottom sediment. Although for much of the year, the trace metals may remain locally incorporated as bottom sediment, during monsoonal episodes, where bedload transport can be significant, the effects of pollution may expand over regional distances.

Geochemistry and Mineralogy of Fly-Ash from the Mae Moh Lignite Deposit, Thailand

The concentration of 21 elements in fly ash from three boilers (75 MW, 150 MW and 300 MW) at the EGAT power plant, Mae Moh, Thailand, were determined by instrumental neutron activation analysis (INAA). The concentration of 10 major elements was determined by x-ray fluorescence (XRF). Arsenic, Co, Cr, Ni, Mo and Sb generally increase in concentration going from bottom ash (BA) through the sequence of electrostatic precipitator ashes (ESPA) and reach maxima of As (352 ppm), Co (45 ppm), Cr (105) ppm, Mo (32 ppm), Ni (106 ppm) and Sb (15 ppm) in the ESPA. Cerium, Cs, Fe, Hf, La, Sc, Ta, Tb and Yb did not exhibit concentration trends or are variable except in the case of one boiler (unit 6), which showed an increase going from BA to ESPA. Only Br decreased in composition going from BA to ESPA. Rubidium, Sm, U and Th showed marked variation in trends. Scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) was used to identify element assemblages within discrete particles and particl...

A global crisis: Energy in the future

We are beginning to consider the concept of sustainable (renewable) energy when we develop new technologies. Our present technologies are not sustainable. We are living on capital. Given that one hour of sunlight could provide our annual needs for one year, the future must be with solar energy. Geothermal energy sources, using the normal thermal gradient of Earth, are also impressive. There is no sign thatHomo sapiens has the wisdom to use fission energy given the potential abuses of this technology. One thing is certain, if we continue to burn fossil carbon to supply the worlds increasing energy demands, the consequences will be devastating for all life.

Coal Utilization in India: Mobilization of Selected Elements to the Surface Environment

Abstract The concentrations of 20 elements in two suites of coal samples from India were determined by RABBIT neutron activation analysis (NAA) and x-ray fluorescence spectroscopy (XRF). Sulphur was determined by Leco and ash was determined in the lab at approximately 550°C. One group of samples was collected from feed coals at 11 power plants representing approximately 15% of all the coal burned in India: Korba, Madhya Pradesh (6 plants); Talcher, Orissa (1); Neyveli, Tamil Nadu (2); and Delhi (2). Effective coal concentration (ECC) is defined here as the total amount of a given element mobilized yearly due to coal utilization. For the above plants the ECC are (metric tons/year): ash (7.896 × 106), Al (1.031 × 106), Ba (3,768), Ca (1.03 × 105), Cl (2,229), Co (72), Cr (580), Dy (148), l (108), ln (1), Mg (4.02 × 105), Mn (1.921), Na (6,834), Ni (317), Rb (325, only 10 plants included), S (2.06 × 105), Si(2.017 × 106), Sr(l,325), Ti(77,340), V(1,128), andZn (642). A second set of channel samples was colle...

Heavy Metals Adsorption and Their Distribution in Three Soil Types of India: Effect of Coal Fly Ash and Sewage Sludge Amendment

Even though both coal fly ash and sewage sludge are rich sources of bio-essential nutrients, one of the major limiting factors in their use either individually or in mixture proportions as for amendment into agricultural soil is the presence of various metals likely to be potentially toxic at their elevated concentrations. This study evaluated the adsorption and distribution behaviours of selected metals in three different soils from India amended with mixtures of ash and sludge in various proportions at a maximum application rate of 52t ha−1 and incubated up to 90 days at near field capacity moisture level. The properties of amended soils were affected significantly by sludge than the ash and the Freundlich distribution coefficients (KDs) of metals were marginally higher compared to their respective controls. The degree of impact of amendment on soil properties, distribution coefficients of metals and their adsorption affinity sequences, based on KDs, within and across soil types were determined. Sequential extraction indicated that, the concentrations of native metals in each soil type tends to be less in highly mobile and moderately mobile fractions than the resistant; and changed marginally following amendment while the distribution patterns remained more or less undisturbed. The sequential extraction of adsorbed metals at various equilibrating concentrations of their addition indicated shifts in the distribution patterns in each soil type. However, the changes in the partitioning of adsorbed metals were wide and clearly noticeable only at higher loadings and the metals showed propensity to accumulate preferentially in more mobile fractions, depending on the type of soil surface and substrate. The results indicated that at low rate of application, ash and sludge, though capable of changing the soil properties and its metal adsorption capacities to certain extent; they had no major influence on metal distribution patterns in the amended soils which mainly depended on the soil properties, type of metal and its concentration.