The Indian perspective of utilizing fly ash in phytoremediation, phytomanagement and biomass production

Coal-based power generation is a principal source of electricity in India and many other countries. About 15–30% of the total amount of residue generated during coal combustion is fly ash (FA). FA is generally alkaline in nature and contains many toxic metals like Cr, Pb, Hg, As and Cd along with many essential elements like S, B, Ca, Na, Fe, Zn, Mn and P. Dumped FA contaminates the biosphere by mobilization of its fine particles and hazardous metals. Despite the negative environmental impact of FA, coal continues to be a major source of power production in India and therefore FA disposal is a major environmental issue. To overcome this problem, FA dumping sites have been started as a potential resource for biomass production of tree species. Phytoremediation is a strategy that uses plants to degrade, stabilize, and remove contaminants from soils, water and waste FA. Phytomanagement of FA is based on the plants' root systems, high biomass, woody nature, native nature, and resistance to pH, salinity, and toxic metals. Recently Indian researchers mostly from the National Botanical Research Institute have been working on phytoremediation and revegetation of FA dykes, inoculation of bacterial strains for reducing FA stress and biomass production from FA dykes. Many international researchers have worked on reclamation, revegetation and utilization of FA. FA utilization saves resources, mainly land (topsoil), water, coal, limestone and chemical fertilizer. Safe utilization of FA is a major concern around the world and regulatory bodies are enforcing stringent rules for the proper management of FA. This article summarizes various viable avenues in India for FA utilization and environmental management.     

Comparison of carbon balances between continuous-cover and clear-cut forestry in Sweden

Continuous-cover forestry (CCF) has been recognized for the production of multiple ecosystem services, and is seen as an alternative to clear-cut forestry (CF). Despite the increasing interest, it is still not well described how CCF would affect the carbon balance and the resulting climate benefit from the forest in relation to CF. This study compares carbon balances of CF and CCF, applied as two alternative land-use strategies for a heterogeneous Norway spruce (Picea abies) stand. We use a set of models to analyze the long-term effects of different forest management and wood use strategies in Sweden on carbon dioxide emissions and carbon stock changes. The results show that biomass growth and yield is more important than the choice of silvicultural system per se. When comparing CF and CCF assuming similar growth, extraction and product use, only minor differences in long-term climate benefit were found between the two principally different silvicultural systems.     

Resources and international climate change policy gridlock

Few other policy zones are as complex as the issue of climate change.If the more pessimistic projections of climate change doom are correct,then the failure to address the issue is likely to be catastrophic and irreversible.The Inter-governmental Panel on Climate Change has predicted the potential extinction of many species and that the existence of small-island and other vulnerable countries will be threatened if business-as-usual greenhouse gas emissions continue.Climate change is a transboundary problem and requires unprecedented levels of cooperation between states and serious and sustained responses from major emitters.However,the growing demand and consumption of natural resources for continued energy security and cornucopian economic growth have undermined the outcomes of international climate change negotiations.It is argued here that there is a strong connection between the major emitters’positions at United Nations’climate talks,their possessions,dependence and consumption of natural resources,and the continued undermining of international climate change policy for unsustainable growth.This paper assesses the resource politics of the US,China,India,Canada,Russia,and Saudi Arabia and their positions at climate talks to show the link between lack of climate change policy progress and the positions of these main players.     

In vitro cytogenetic assessment of trichloroacetic acid in human peripheral blood lymphocytes

Trichloroacetic acid (TCA), a common water disinfection byproduct and a persistent metabolite of trichloroethylene (TCE), has been examined for its genotoxic potential in human lymphocytes. Chromosomal aberration (CA) and cytokinesis-block micronucleus (CBMN) assay were employed to assess the toxicity of TCA. Lymphocytes obtained from three healthy donors were exposed to 25, 50, and 100 μg/ml concentration of TCA separately. TCA exposure resulted in chromosomal anomalies and the formation of micronuclei in lymphocytes. Chromosome analysis revealed the dose-dependent and significant induction of CA. Chromatid break/chromosome break, fragments, and chromatid exchanges were commonly observed. Exposure of higher concentration (50 and 100 μg/ml) significantly inhibited mitotic index. Data obtained with CBMN assay indicated that the induction of micronucleus (MN) formation was greater than that of CA. At 25 μg/ml, TCA induced significant frequencies of MN as compared to control cells. Significant induction of MN at the lowest concentration indicates TCA may also interact with mitotic spindles. Lower percentage of CA and MN at 100 μg/ml as compared to 50 μg/ml indicates occurrence of severe cytotoxicity on exposure of 100 μg/ml TCA in lymphocytes. Collectively, results of both cytogenetic assays indicate that exposure of TCA can induce significant genotoxic and cytotoxic effects.     

Source Resolution of Fine Particulate Polycyclic Aromatic Hydrocarbons Using a Receptor Model Modified for Reactivity

This paper provides source contribution estimates from vehicular and meat-cooking emissions to particulate polycyclic aromatic hydrocarbon (PAH) and elemental carbon (EC) concentrations measured at two Los Angeles sites during a field study in 1989. The source concentration matrix for PAH was based on new data for vehicular emissions and literature data for meat-cooking operations. The chemical mass balance (CMB 7.0) receptor model was used, and source profiles were modified to reflect reactive decay of PAH in the atmosphere. The calculations indicate that the Pico Rivera site was dominated by auto emissions, which account for more than 90 percent of all the PAH (except chrysene), carbon monoxide (CO), and 61 percent of the EC concentrations. In contrast, emissions from meat cooking contributed significantly (20 to 75 percent) to the concentrations of four-ring PAH measured at a residential site at Upland. The five-ring and larger PAH were attributed to auto emissions at Upland as well.     

Characterisation and optimisation of three potential aerobic bacterial strains for kraft lignin degradation from pulp paper waste

Eight aerobic bacterial strains were isolated from pulp paper mill effluent sludge. Out of eight through nutrient enrichment technique three potential aerobic bacterial strains ITRC S(6), ITRC S(7) and ITRC S(8) were found capable to effectively degrade the kraft lignin (KL), a major byproduct of the chemical pulping process and main contributor to the colour and toxicity of effluent. Further, these potential strains (ITRC S(6), ITRC S(7) and ITRC S(8)) were biochemically characterised as Gram variable small rod, Gram negative rod and Gram positive rod respectively. Subsequently, 16S rRNA sequencing showed 95% base sequence homology and it was identified as Paenibacillus sp. (AY952466), Aneurinibacillus aneurinilyticus (AY856831), Bacillus sp. (AY952465) for ITRC S(6), IITRC S(7) and ITRC S(8), respectively. In batch decolourization experiments Bacillus sp. ITRC S(8) reduced the colour of lignin amended mineral salt medium, pH 7.6 by 65% after 6th d, at 30 degrees C, A. aneurinilyticus ITRC S(7) by 56% and Paenibacillus ITRC S(6) 43%. Under these conditions the three strains degraded the KL by 37%, 33% and 30%, respectively while the mixed culture of these three bacteria reduced colour by 69%, lignin by 40% and total substrate by 50% under same conditions. Biodegradation of the KL was not affected by low (<0.2 mg l(-1)) dissolved oxygen content; thus oxygen inhibition is more likely to be a metabolism-dependent event. Initially with 48 h incubation the decolourization was slow with decreased pH. Further incubation there was rapid decolourization with slight increase in pH at 6d compared with initial pH by increasing culture optical density. The lignin analysis from medium with HPLC indicated complete degradation rather than biotransformation with complete loss of absorbance peak at 280 nm.     

Tillage, cropping systems, and nitrogen fertilizer source effects on soil carbon sequestration and fractions

Quantification of soil carbon (C) cycling as influenced by management practices is needed for C sequestration and soil quality improvement. We evaluated the 10-yr effects of tillage, cropping system, and N source on crop residue and soil C fractions at 0- to 20-cm depth in Decatur silt loam (clayey, kaolinitic, thermic, Typic Paleudults) in northern Alabama, USA. Treatments were incomplete factorial combinations of three tillage practices (no-till [NT], mulch till [MT], and conventional till [CT]), two cropping systems (cotton [Gossypium hirsutum L.]-cotton-corn [Zea mays L.] and rye [Secale cereale L.]/cotton-rye/cotton-corn), and two N fertilization sources and rates (0 and 100 kg N ha(-1) from NH(4)NO(3) and 100 and 200 kg N ha(-1) from poultry litter). Carbon fractions were soil organic C (SOC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM). Crop residue varied among treatments and years and total residue from 1997 to 2005 was greater in rye/cotton-rye/cotton-corn than in cotton-cotton-corn and greater with NH(4)NO(3) than with poultry litter at 100 kg N ha(-1). The SOC content at 0 to 20 cm after 10 yr was greater with poultry litter than with NH(4)NO(3) in NT and CT, resulting in a C sequestration rate of 510 kg C ha(-1) yr(-1) with poultry litter compared with -120 to 147 kg C ha(-1) yr(-1) with NH(4)NO(3). Poultry litter also increased PCM and MBC compared with NH(4)NO(3). Cropping increased SOC, POC, and PCM compared with fallow in NT. Long-term poultry litter application or continuous cropping increased soil C storage and microbial biomass and activity compared with inorganic N fertilization or fallow, indicating that these management practices can sequester C, offset atmospheric CO(2) levels, and improve soil and environmental quality.     

Leaching mechanisms of Cr(VI) from chromite ore processing residue

Batch leaching tests, qualitative and quantitative x-ray powder diffraction (XRPD) analyses, and geochemical modeling were used to investigate the leaching mechanisms of Cr(VI) from chromite ore processing residue (COPR) samples obtained from an urban area in Hudson County, New Jersey. The pH of the leaching solutions was adjusted to cover a wide range between 1 and 12.5. The concentration levels for total chromium (Cr) and Cr(VI) in the leaching solutions were virtually identical for pH values >5. For pH values <5, the concentration of total Cr exceeded that of Cr(VI) with the difference between the two attributed to Cr(III). Geochemical modeling results indicated that the solubility of Cr(VI) is controlled by Cr(VI)-hydrocalumite and Cr(VI)-ettringite at pH >10.5 and by adsorption at pH <8. However, experimental results suggested that Cr(VI) solubility is controlled partially by Cr(VI)-hydrocalumite at pH >10.5 and by hydrotalcites at pH >8 in addition to adsorption of anionic chromate species onto inherently present metal oxides and hydroxides at pH <8. As pH decreased to <10, most of the Cr(VI) bearing minerals become unstable and their dissolution contributes to the increase in Cr(VI) concentration in the leachate solution. At low pH ( <1.5), Cr(III) solid phases and the oxides responsible for Cr(VI) adsorption dissolve and release Cr(III) and Cr(VI) into solution.     

Agriculture,dairy and fishery farming practices and greenhouse gas emission footprint: a strategic appraisal for mitigation

Rising global population would force farmers to amplify food production substantially in upcoming 3–4 decades. The easiest way to increase grain production is through expanding cropping area by clearing uncultivated land. This is attained by permitting deadly loss of carbon (C) stocks, jeopardizing ecosystem biodiversity and deteriorating environmental quality. We aim to propose key agronomical tactics, livestock management strategy and advance approaches for aquaculture to increase productivity and simultaneously reduce the environmental impacts of farming sector. For this, we considered three major sectors of farming, i.e. agriculture, fishery and dairy. We collected literatures stating approaches or technologies that could reduce GHG emission from these sectors. Thereafter, we synthesized strategies or options that are more feasible and accessible for inclusion in farm sector to reduce GHG emission. Having comprehensively reviewed several publications, we propose potential strategies to reduce GHG emission. Agronomic practices like crop diversification, reducing summer fallow, soil organic carbon sequestration, tillage and crop residue management and inclusion of N2-fixing pulses in crop rotations are some of those. Livestock management through changing animals’ diets, optimal use of the gas produced from manures, frequent and complete manure removal from animal housing and aquaculture management strategies to improve fish health and improve feed conversion efficiency could reduce their GHG emission footprint too. Adapting of effective and economic practices GHG emission footprint reduction potential of farming sector could make farming sector a C neutral enterprise. To overcome the ecological, technological and institutional barriers, policy on trade, tax, grazing practice and GHG pricing should be implemented properly.     

Fluoride removal studies using virgin and Ti (IV)-modified Musa paradisiaca (plantain pseudo-stem) carbons

The preparation of carbons in virgin and Ti-modified forms under controlled conditions at low temperature from plantain pseudo-stem (Musa paradisiaca) was achieved. These prepared carbons were characterized for instrumental studies such as BET, FTIR, XRD, SEM with EDS and TGA to understand the chemistry and modification. The determination of IEP and pH_ZPC established the presence of positive surface sites on the virgin (VMPC) and Ti-modified (TiMPC) carbons to facilitate the sorption of fluoride. The fluoride removal efficiency as a function of time, pH, dose, initial fluoride concentration, temperature, and co-ion intervention was studied. The maximum fluoride removal of about 81.2 and 97.7% was achievable with VMPC and TiMPC, respectively, after 20 min at the pH of 2.04 and continued for the equilibrium of 60 min. Temperature was found to be influential both by way of initial increase followed by a decrease in the fluoride uptake of MPCs. Regeneration was very consistent up to 7 cycles with the residual fluoride concentration below the WHO guide line of 1.5 mg L^?1. Highest intervention due to hydrogen carbonate ions was observed during the fluoride removal process. Kinetic (pseudo-first-order, pseudo-second-order, and intra-particle diffusion) and isotherm models (Langmuir, Freundlich, and DKR) were checked for their compliance with the present sorption system. These low temperature synthesized MPCs are found to be effective candidates in the process of fluoride abatement in water.