A study of the technologically modified sources of 222Rn and its environmental impact in an Indian U mineralised belt

These investigations present qualitative and quantitative assessments of the 222Rn contributing potential of the technologically modified sources, e.g. mine exhausts and tailings piles, arising due to the mining and processing of uraniferous minerals at Jaduguda, India. The overall geometric mean of the 222Rn flux from low-grade uranium (U) mill tailings being 1.19 Bq m-2 s-1, requisite attenuation of 37.8% to the recommended limit of 0.74 Bq m-2 s-1 can be attained by a typical clay coverage of 20 cm. Theoretically, feasible options for selection of overburden materials for stabilisation of the tailings piles are examined. Extrapolation studies with a turbulent diffusion model yield an atmospheric dispersion pattern of 222Rn in reasonable correspondence with the prevailing concentrations, especially for locations beyond a 4 km radius. The overall 222Rn contribution of the U complex to the ambient air is the same as that contributed by the adjoining land mass of 2.75 km radius in this mineralised terrain.     

Market segmentation and industry overcapacity considering input resources and environmental costs through the lens of governmental intervention

Environmental Science and Pollution Research - The problems with China’s regional industrial overcapacity are often influenced by local governments. This study constructs a framework that...     

Performance evaluation of isoproturon-degrading indigenous bacterial isolates in soil microcosm

Isoproturon (IPU)-degrading soil bacteria were isolated from herbicide-applied wheat fields. These isolates were identified using cultural, morphological, biochemical and 16S rRNA sequencing methods. 16S rRNA sequences of both the bacterial isolates were compared with NCBI GenBank data base and identified as Bacillus pumilus and Pseudoxanthomonas sp. A soil microcosm study was carried out for 40 days in six different treatments. Experimental results revealed maximum 95.98% IPU degradation in treatment 6 where bacterial consortia were augmented in natural soil, followed by 91.53% in treatment 5 enriched with organic manure as an additional carbon source. However, only 14.03% IPU was degraded in treatment 1 (control) after 40 days. In treatments (2–4), 75.59%, 70.92% and 77.32% IPU degradation was recorded, respectively. IPU degradation in all the treatments varied significantly over the control. 4-Isopropylaniline was detected as IPU degradation by-product in the medium. The study confirmed that B. pumilus and Pseudoxanthomonas sp. performed effectively in soil microcosms and could be employed profitably for field-scale bioremediation experiments.     

Application of remote sensing for assessment of change in vegetation cover and the subsequent impact on climatic variables

Environmental Science and Pollution Research - The impacts of vegetation cover changes (VCCs) and land use land cover changes (LULCCs) on climate variabilities need to be addressed while...     

An overview on the production of pigment grade titania from titania-rich slag.

To recover pigment grade TiO2, operating plants all over the world use chemical processes. Slag-based technology is considered to be attractive because of low waste generation and low chemical cost due to high titanium content and is poised to replace the conventional technology. This paper provides a review of the slag-based technology with the specific aim to produce leachable slag and achieving high titania yield from recovered wastes. Leachable oxides of the lower oxidation state, such as TiO and Ti2O3, facilitate the leaching process. However, during smelting these oxides increase the viscosity of the slag. Formation of titanium carbide or carbonitride is also not desirable as it leads to resistance to the leaching of titanium. This report highlights the problems and their possible solutions to obtain leachable slag.     

Feasibility of bioleaching integrated with a chemical oxidation process for improved leaching of valuable metals from refinery spent hydroprocessing catalyst

Bioleaching is considered an eco-friendly technique for leaching metals from spent hydroprocessing catalysts; however, the low bioleaching yield of some valuable metals (Mo and V) is a severe bottleneck to its successful implementation. The present study reported the potential of an integrated bioleaching-chemical oxidation process in improved leaching of valuable metals (Mo and V) from refinery spent hydroprocessing catalysts. The first stage bioleaching of a spent catalyst (coked/decoked) was conducted using sulfur-oxidizing microbes. The results suggested that after 72 h of bioleaching, 85.7% Ni, 86.9% V, and 72.1% Mo were leached out from the coked spent catalyst. Bioleaching yield in decoked spent catalyst was relatively lower (86.8% Ni, 79.8% V, and 59.8% Mo). The low bioleaching yield in the decoked spent catalyst was attributed to metals’ presence in stable fractions (residual + oxidizable). After first stage bioleaching, the integration of a second stage chemical oxidation process (1 M H₂O₂) drastically improved the leaching of Ni, Mo, and V (94.2–100%) from the coked spent catalyst. The improvement was attributed to the high redox potential (1.77 V) of the H₂O₂, which led to the transformation of low-valence metal sulfides into high-valence metallic ions more conducive to acidic bioleaching. In the decoked spent catalyst, the increment in the leaching yield after second stage chemical oxidation was marginal (<5%). The results suggested that the integrated bioleaching-chemical oxidation process is an effective method for the complete leaching of valuable metals from the coked spent catalyst.

     

Growth, biomass production and photosynthesis of Cenchrus ciliaris L. under Acacia tortilis (Forssk.) Hayne based silvopastoral systems in semi arid tropics

The growth, biomass production and photosynthesis of Cenchrus ciliaris was studied under the canopies of 17 yr old Acacia tortilis trees in semi arid tropical environment. On an average the full grown canopy of A. tortilis at the spacing of 4 x 4 m allowed 55% of total Photosynthetically Active Radiation (PAR) which in turn increased Relative Humidity (RH) and reduced under canopy temperature to -1.75 degrees C over the open air temperature. C. ciliaris attained higher height under the shade of A. tortilis. The tiller production and leaf area index decreased marginally under the shade of tree canopies as compared to the open grown grasses. C. ciliaris accumulated higher chlorophyll a and b under the shade of tree canopies indicating its shade adaptation potential. The assimilatory functions such as rate of photosynthesis, transpiration, stomatal conductance, photosynthetic water use efficiency (PN/TR) and carboxylation efficiency (PN/CINT) decreased under the tree canopies due to low availability of PAR. The total biomass production in term of fresh and dry weight decreased under the tree canopies. On average of 2 yr C. ciliaris had produced 12.78 t ha(-1) green and 3.72 -t ha(-1) dry biomass under the tree canopies of A. tortilis. The dry matter yield reduced to 38% under the tree canopies over the open grown grasses. The A. tortilis + C. ciliaris maintained higher soil moisture, organic carbon content and available N P K for sustainable biomass production for the longer period. The higher accumulation of crude protein, starch, sugar and nitrogen in leaves and stem of C. ciliaris indicates that this grass species also maintained its quality under A. tortilis based silvopastoral system. The photosynthesis and dry matter accumulation are closely associated with available PAR indicating that for sustainable production of this grass species in the silvopasture systems for longer period about 55% or more PAR is required.