S. Tripathy

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.

Fractionation and bioavailability of metals and their impacts on microbial properties in sewage irrigated soil

A study was conducted to evaluate the effect of long-term irrigation of sewage contaminated with heavy metals like Cd, Cr, Cu and Pb on microbial and biochemical parameters of soils of West Bengal, India. The microbial parameters included microbial biomass carbon (MBC), microbial metabolic quotient; the biochemical parameters included fluorescein diacetate hydrolyzing activity, beta-glucosidase, urease, phosphatase, and aryl sulphatase activities. A sequential extraction technique was used to quantify water soluble, exchangeable, carbonate bound, Fe/Mn-oxide bound, organically bound, and residual metal fractions. Metal concentrations in the two most labile fractions (i.e., water soluble and exchangeable fractions) were generally low. Total metal concentrations at each site seemed to be associated with soil amorphous Fe and Al minerals. The MBC and the enzymes studied were significantly and negatively correlated with water soluble and exchangeable metals but not significantly correlated with other forms, indicating that water soluble and exchangeable forms exerted a strong inhibitory effect on the soil microbial and biochemical parameters. It was concluded that irrigating soils with metal contaminated sewage seemed to damage soil quality in the long term.

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.

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.

Influence of different forms of acidities on soil microbiological properties and enzyme activities at an acid mine drainage contaminated site

Assessment of microbial parameters, viz. microbial biomass, fluorescence diacetate, microbial respiration, acid phosphatase, beta-glucosidase and urease with respect to acidity helps in evaluating the quality of soils. This study was conducted to investigate the effects of different forms of acidities on soil microbial parameters in an acid mine drainage contaminated site around coal deposits in Jainta Hills of India. Total potential and exchangeable acidity, extractable and exchangeable aluminium were significantly higher in contaminated soil compared to the baseline (p<0.01). Different forms of acidity were significantly and positively correlated with each other (p<0.05). Further, all microbial properties were positively and significantly correlated with organic carbon and clay (p<0.05). The ratios of microbial parameters with organic carbon were negatively correlated with different forms of acidity. Principal component analysis and cluster analyses showed that the microbial activities are not directly influenced by the total potential acidity and extractable aluminium. Though acid mine drainage affected soils had higher microbial biomass and activities due to higher organic matter content than those of the baseline soils, the ratios of microbial parameters/organic carbon indicated suppression of microbial growth and activities due to acidity stress.

Mineralogy of Fe-Precipitates and Their Role in Metal Retention from an Acid Mine Drainage Site in India

Iron-rich precipitates from acid mine drainage (AMD) sites around the Jaintia Hills coalfield, India, were investigated. The ochreous precipitates mainly consist of schwertmannite, goethite, and jarosite. Sorption affinities suggest that Ni, Mn, Cr, Cd, Pb, and Zn are more significant in schwertmannite-bearing ochre than in more crystalline jarosite- and goethite-bearing ochres. The lower crystallinity and higher surface area of schwertmannite-bearing ochreous precipitate result in higher metal retention potential. Fe and Mn concentrations in water may also influence the sorption of metals in the precipitates. The results of the sequential extractions showed that metal mobility is mainly controlled by Fe and Mn oxyhydroxide phases. This information may aid understanding of the natural attenuation of trace metals by ochreous precipitates in AMD-contaminated water.ZusammenfassungEisenhaltige Ablagerungen von saurem Grubenwasser im Umfeld des Kohlereviers Jaintia Hills in Indien wurden untersucht. Die ockerartigen Ablagerungen bestehen hauptsächlich aus Schwertmannit, Goethit und Jarosit. Sorptionsverwandschaften deuten darauf hin, dass Ni, Mn, Cr, Cd, Pb und Zn häufiger in Schwertmannit bildenden Ockern vorkommen als in kristallinen Jarosit und Goethit bildenden Ockern. Die niedrigere Kristallinität und größere Oberfläche der Schwertmannit bildenden ockerartigen Ablagerungen resultieren aus dem höheren Metallrückhaltevermögen. Auch Fe und Mn Konzentrationen im Wasser können die Sorption von Metallen in den Ablagerungen beeinflussen. Die Ergebnisse der sequenziellen Extraktion zeigen, dass die Mobilität von Metallen vornehmlich durch Fe- und Mn-Oxihydrate kontrolliert wird. Diese Information kann zum Verständnis des natürlichen Abbauverhaltens von Spurenmetallen durch ockrige Ablagerungen in durch saures Grubenwasser verunreinigten Wässern beitragen.ResumenSe investigaron precipitados ricos en hierro desde drenajes ácidos de minas (AMD) en la zona de Jaintia Hills coalfield, India. Los precipitados ocres consisten principalmente de schwertmanita, goetita y jarosita. La sorción de Ni, Mn, Cr, Cd, Pb y Zn es más significativa en schwertmanita que en jarosita y en goetita. La menor cristalinidad y mayor área superficial de schwertmanita resulta en un mayor potencial de retención de metales. Las concentraciones de Fe y Mn en agua pueden también influir la sorción de metales en los precipitados. Los resultados de las extracciones secuenciales mostraron que la movilidad del metal es principalmente controlada por las fases de oxohidróxidos de Fe y Mn. Esta información podría ayudar a comprender la atenuación natural de metales trazas por precipitados ocres en aguas contaminadas con AMD.抽象文章研究了印度Jaintia Hill煤田酸性矿山废水中富铁沉淀物的特性。该赭黄色沉淀物主要由施氏矿、针铁矿和黄钾铁矾组成。含施氏矿的赭石与含结晶黄钾铁矾和针铁矿的赭石相比,Ni、Mn、Cr、Cd、Pb和Zn对前者具有更好的亲和性。低结晶度和大比表面积使含施氏矿赭黄色沉淀物具有较高金属阻滞潜力。水中Fe和Mn浓度也会影响沉淀物吸附金属离子能力。顺次提取试验结果表明金属迁移能力主要受铁、锰的氢氧化物形态控制。研究有助于深化理解酸性矿山废水中赭黄色沉淀物对微量金属元素的自然钝化作用。

L-asparaginase and L-glutaminase activities in submerged rice soil amended with municipal solid waste compost and decomposed cow manure.

The field study was conducted to evaluate the effect of municipal solid waste compost (MSWC) as a soil amendment on L-asparaginase (LA) and L-glutaminase (LG) activities. Experiments were conducted during the wet seasons of 1997, 1998 and 1999 on rice grown under a submerged condition, at the Agriculture Experimental Farm, Calcutta University at Baruipur, West Bengal, India. The treatments consisted of control, no input; MSWC, at 60 Kg N ha− 1; well-decomposed cow manure (DCM), at 60 Kg N ha− 1; MSWC (30 Kg N ha− 1) + Urea (U) (30 Kg N ha− 1); DCM (30 Kg N ha− 1) + U (30 Kg N ha− 1) and Fertilizer, (at 60:30:30 NPK kg ha− 1) through urea, single superphosphate and muriate of potash respectively). LA and LG activities alone and their ratio with organic-C (ratio index value, RIV), straw and grain yield were higher in DCM than MSWC-treated soils, due to higher amount of biogenic organic materials like water-soluble organic carbon, carbohydrate and mineralizable nitrogen in the former. The studied parameters were higher when urea was integrated with DCM or MSWC, compared to their single applications. The heavy metals in MSWC did not detrimentally influence the above-measured activities of soil. In the event of long term MSWC application, changes in soil quality parameters should be monitored regularly, since heavy metals once entering into soil persist over a long period.

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.