Rajnarayan Saha

Metal accumulation and its effects in relation to biochemical response of vegetables irrigated with metal contaminated water and wastewater.

Agricultural application of metal contaminated water resulted in elevated concentrations of metals in irrigated soil and vegetables. Metal enrichment in irrigated soil is in the sequence of Cr>Fe>Pb>Mn>Zn>Cu>Cd. High metal translocation was observed from soil to plants with varied accumulation pattern in different species. Fe, Mn, Cu, Zn, Cr showed higher translocation to the aerial parts, while Cd, Pb exhibits their restricted mobility and concentrated in roots and stems. Hyperaccumulation of metals in vegetative parts resulted significant decrease (p<0.05) in total chlorophyll and soluble sugars, with elevated (p<0.05) protein and proline content in cultivated vegetables. Oxidative stress due to high metal concentrations significantly induced (p<0.05) the antioxidant-enzyme activity. Peroxidase (52-206%) and catalase (40-106%) activity was noticeably higher in all the examined species, while enhanced activity of ascorbate peroxidase (70-78%) was observed in pea and spinach.

In vitro model reaction of sulfur containing bio-relevant ligands with Pt( ii ) complex: kinetics, mechanism, bioactivity and computational studies

cis-[Pt(MAMP)Cl2] 1 and its hydrolysed product cis-[Pt(MAMP)(H2O)2]2+ 2 (where MAMP = 2-[(N-methylamino)methyl]pyridine) were synthesised and characterised by spectroscopic methods. Kinetic and mechanistic studies were followed on complex 2 with thiols; L-cysteine (L-cys) and N-acetyl-L-cysteine (N-ac-L-cys). The thiol substituted products [Pt(MAMP)(L-cys)] 3 and [Pt(MAMP)(N-ac-L-cys)] 4 formation mechanisms were proposed and characterized. Their bonding modes were also confirmed spectroscopically and theoretically. At pH 4.0, the interactions of complex 2 with the ligands show two distinct consecutive steps: the first step is dependent and the second is independent of [ligand]. The association equilibrium constant (KE) for the outer sphere complex formation and rate constants for both steps have been evaluated. The activation parameters (ΔH‡ and ΔS‡) for both the steps were calculated using the Eyring equation and an associative mechanism is proposed for both the reactions. Structural optimization, HOMO–LUMO energy calculation, and Natural Bond Orbital (NBO) analysis of complexes 2–4 were investigated with Density Functional Theory (DFT). The complexes bind strongly to DNA and change its electrophoretic mobilization pattern in agarose gel. For theoretical understanding of the binding interaction of complex 2 with B-DNA, a molecular docking study was performed. Anticancer properties of all the three complexes 2–4 were probed on both HeLa and Hep G2 cell lines which shows remarkable activity of 70–75% compared to cisplatin at 50.0 μM concentration. Significant growth inhibition by the complexes in both Gram positive and Gram negative bacteria was observed. The water soluble complexes 2–4 may be further investigated and might be considered as chemotherapeutic agents.

Effects of metal stress on biochemical response of some aquatic macrophytes growing along an industrial waste discharge channel

Abstract The present research work focused on the metal translocation in the soil-plant system and subsequent metal stress on biochemical response of aquatic macrophytes growing along an industrial waste discharge channel. The bottom sediment of the effluent channel is highly contaminated with metals. High transfer factor (TF) for most of the metals indicated higher metal uptake by aquatic macrophytes of which Typha sp. was found to be the most suitable. Average TF was in the order of Fe (4.82) > Mn (3.91) > Cu (3.59) > Cd (2.29) > Zn (2.22) > Cr (1.83) > Pb (1.80). Hyper accumulation of metals within plants resulted in significant reductions in total chlorophyll, soluble sugar with an increase in protein and proline content. The investigation also demonstrated that exposure to high concentrations on metals resulted in enhanced activity of catalase (61.82–90.91%) and peroxidase (37.08–70.23%) in all examined macrophytes with a reduced (27.58–43.4%) or unchanged ascorbate peroxidase activity depending on plant species.

Temporal changes and depth wise variations in pit pond hydrochemistry contaminated with industrial effluents with special emphasis on metal distribution in water-sediment system.

The investigation showed pronounced temporal and vertical variations of pit lake-water chemistry contaminated with industrial effluents. An intermixing layer of few meters at a depth of 5-8 m usually separates an upper oxic epilimnion with alkaline pH from deeper sub-oxic/anoxic zone with relatively lower pH. Metal concentrations were in higher magnitude at anoxic zone in comparison to surface layer. Most of the parameters including metals showed higher concentrations during summer, while least concentrations were observed during monsoon. In shallow sediments, metals were mainly in insoluble-residual form, while redox metals were fractionated as oxihydroxide-reducible form. Geoaccumulation of metals in bottom sediments were Fe>Cr>Pb>Cu>Cd>Mn>Zn. Toxicity assessment showed that pit pond water is highly contaminated (C(d)=7.52) and moderate pollution load (PLI=2.272) in shallow sediments, with metal evaluation index (HEI) value of 11.08 and 15.91 respectively.

Assessment of Arsenic Toxicity and Tolerance Characteristics of Bean Plants (Phaseolus Vulgaris) Exposed to Different Species of Arsenic

ABSTRACT Experiments were conducted to evaluate the arsenic toxicity, its accumulation and phytoremediation potential of bean plants (Phaseolus vulgaris) grown in soils contaminated with different species of arsenic such as arsenite (As(III)), arsenate (As(V)) and dimethylarsinic acid (DMA). Bean plants were grown in soils amended by aqueous solutions of 20 and 50 mg kg−1 of As (III), As(V) or DMA. Arsenic species negatively affected the yield and growth of the plant. The study demonstrated arsenic accumulation in the plant parts. The concentration of arsenic compounds in the shoots decreased in the order arsenate > arsenite > dimethylarsinic acid while in the roots as arsenite > arsenate > dimethylarsinic acid. Most arsenic is accumulated in the roots with limited transfer to shoots. Thus, bean plants can be considered as an arsenic excluder and has the potential for phytostabilization of arsenic contaminated sites. The study also reveals that removal of arsenic by boiling the vegetables with excess of water is not possible.

Facile one pot synthesis of zinc oxide nanorods and statistical evaluation for photocatalytic degradation of a diazo dye

In the present work zinc oxide nanorods (ZNRs) have been synthesized to estimate its photocatalytic degradation potential on an industrially used diazo dye and optimization of the total treatment process has been designed. Response surface methodology (RSM) has been used to model the operational parameters for this photocatalytic degradation. The crystallite size (101 plane) of the synthesized ZNR has been found to be 20.99 nm having a band gap energy of 3.45 eV. At elevated pH, the rate of degradation of the photocatalyst was found to be higher than that of acidic pH. The independent variables of the model are time (9.6-122 min), pH (2-12.2), catalyst dose (0.2-0.4 g/L) and dye concentration (88-512 mg/L). It was seen that the degradation efficiency was significantly affected by the initial dye concentration and the pH, the optimal values of the parameters being a pH of 10.67, an initial concentration of 150 mg/L and ZnO dose of 0.37 g/L, the time taken being 88.52 min. The actual degradation efficiency of the dye reached 96.9% at optimized condition, which is quite close to the predicted value of 98.07%.

Severe wear behaviour of alumina balls sliding against diamond ceramic coatings

At present alumina is the most widely used bio-ceramic material for implants. However, diamond surface offers very good solid lubricant for different machinery, equipment including biomedical implants (hip implants, knee implants, etc.), since the coefficient of friction (COF) of diamond is lower than alumina. In this tribological study, alumina ball was chosen as the counter body material to show better performance of the polycrystalline diamond (PCD) coatings in biomedical load-bearing applications. Wear and friction data were recorded for microwave plasma chemical vapour deposition (MWCVD) grown PCD coatings of four different types, out of which two samples were as-deposited coatings, one was chemo-mechanically polished and the other diamond sample was made free standing by wet-chemical etching of the silicon wafer. The coefficient of friction of the MWCVD grown PCD against Al2O3 ball under dry ambient condition was found in the range of 0.29–0.7, but in the presence of simulated body fluid, the COF reduces significantly, in the range of 0.03–0.36. The samples were then characterized by Raman spectroscopy for their quality, by coherence scanning profilometer for surface roughness and by electron microscopy for their microstructural properties. Alumina balls worn out (14.2 × 10−1 mm3) very rapidly with zero wear for diamond ceramic coatings. Since the generation of wear particle is the main problem for load-bearing prosthetic joints, it was concluded that the PCD material can potentially replace existing alumina bio-ceramic for their better tribological properties.

Dissimilitude behaviour of Cu2O nano-octahedra and nano-cubes towards photo- and electrocatalytic activities

We demonstrate how the morphology of a simple metal-oxide system (e.g., Cu2O) controls catalytic activity. Cu2O catalysts were synthesized with a highly uniform nanocube and nano-octahedra morphology under PVP surfactant-assisted reaction conditions. A series of structural, morphological, optical and electrical characterizations are done to optimize the growth of nanostructures with different morphologies. Finally, the nanostructures are exploited as photo- and electrocatalysts. Interestingly, we find dissimilitude behaviour of nano-octahedra and nano-cube samples towards photo and electrocatalytic activities. The nano-octahedra samples are ∼57% more photocatalytically active (half-life timeoctahedra ∼ 10.7 minutes) than the nanocube samples, which is one of the highest reported photocatalytic efficiencies reported to date. However, the same nano-octahedra samples show lower electrocatalytic activity towards oxygen reduction reaction (ORR) as compared with the nanocube sample.

A multi-responsive thiosemicarbazone-based probe for detection and discrimination of group 12 metal ions and its application in logic gates

A new simple 3-in-1 multi-response thiosemicarbazone-based chemosensor has been synthesized and characterized. The probe not only exhibited high sensitivity towards the most familiar and abundant group 12 metal ions, viz., Zn2+, Cd2+ and Hg2+, in MeCN–H2O (1 : 1, v/v) medium but also can efficiently distinguish them through significant changes in their absorption and emission spectral behavior. The selectivity response was found to follow the order Hg2+, Cd2+, Zn2+ due to the different degrees of stability of their respective complexes, which was further established by TDDFT calculations and interference studies. The binding affinities of the probe towards these metal ions were investigated by absorption, fluorescence emission, fluorescence lifetime, mass spectral and 1H NMR spectral measurements. The effects of solvent polarity on the probe molecule were also examined. Due to the observation of different binding affinities and the ensuing significant changes in absorbance at different wavelengths by a combination of different inputs, L can be judiciously applied for the construction of some basic logic gates (AND, OR, NOT, IMPLICATION and INHIBIT).

Dynamics of Metal Distribution in Cultivated Soil and Vegetables in Vicinity to Industrial Deposition: An Inference to Chemical Contamination of Food Chain

The present study demonstrates accumulation and distribution of heavy metals Fe, Cr, Cd, Pb & Cu in cultivated soil and vegetables, and its potential implication to health risk via consumption of contaminated vegetables. Deposition of atmospheric metals results significant enrichment of metal contents Pb=1.6, Cu=1.4 & Cd=15.9 in cultivated soil. Elevated metal content in soil facilitate higher metal accumulation in growing vegetables through root uptake and also by leaf absorption. Results show noticeably higher metal translocation >1 from soil to roots TFr and shoots TFs, followed by higher metal accumulation in leafy shoots except R. sativa. In sampled vegetables, estimated hazard quotient HQ for individual metal does not exceed the safe limit, but integrated hazard quotient IHQ in L. esculanta is above the safe limit 1.33 and incredibly close in R. sativa 0.97 and S. oleracia 0.93 to cause health hazard.