Search

Rice based cropping systems are the most predominantly grown systems in India contributing a major share to India's food grain production. However, systems i.e., rice-rice and rice-wheat brought us second generation sustainability issues over long run. Cowpea being a multi-role legume crop can be considered for the intensification of rice-based system with limited resources and its residue having lower C:N ratio can easily decompose in soil and enhance soil fertility. Following experiment was conducted at Institutional Research Farm, ICAR-National Rice Research Institute, Cuttack, Odisha during kharif, rabi and summer season during 2017-18 and 2018-19. The treatments were laid out in split plot design and consisted of three replications. The main plot consisted of two rice-based cropping systems i.e., rice-maize-cowpea (R-M-C) and rice-groundnut-cowpea (R-G-C), sub-plots consisted of five nutrient and residue management practices i.e., C-C-C, R-R-R, RI+R75-R-R, RI+R75-SM+R-R and RI+R75-SM+R-R50. The pooled value for the season 2017-18 and 2018-19 revealed that, RI+R75-SM+R-R and RI+R75-SM+R-R50 resulted higher yield i.e., pod yield, seed yield, stover yield, HI, nutrient content, nutrient uptake, economic return i.e., gross return, net return and B:C ratio, higher CH4 flux and lower N2O flux than R-R-R. Between two cropping systems, R-M-C cropping system recorded highest yield and is more feasible to take over R-G-C. Among nutrient management, RI+R75-SM+R-R recorded higher growth and yield but due to consistent residue retention and incorporation, even if using 50% of recommended dose of fertilizer in cowpea i.e., RI+R75-SM+R-R50 recorded similar growth, yield, economic return, and even higher B:C ratio than RI+R75-SM+R-R and recommended. Cowpea residue incorporation and 25% reduced dose of chemical fertilizer application in rice crop, rice straw mulch in rabi maize and 50% reduction in chemical fertilizer application in summer cowpea (RI+R75-SM+R-R50) received highest cowpea yield, and economic return and this system-based nutrient management should be recommended in R-M-C cropping system. [ABSTRACT FROM AUTHOR]

Abstract The performance of the solar air collector is experimentally investigated at the climate of North Eastern India. Various governing parameters considered for the present investigation are collector tilt angles (30⁰, 45⁰, and 60°), single and double glazing, mass flow rate (0.0039–0.0118 kg/s) and two different absorber plates (plain and corrugated). Results reveal that double glazing absorber plate always gives better performance both energy and exergy point of view, because of reduction of top loses. Increase in mass flow rate of air enhances the energy efficiency. An overall increment of the efficiency with the increase of mass flow rate and number of glazing is as high as 10.35–17.42%. Use of corrugated plate enhances the energy efficiency by 14%, because of improved turbulence effect and increment of the heat transfer area. The maximum enhancement of exergy efficiency for double glazing collector is 6.867% for mass flow rate 0.0118 kg/s compared to single glazing collector. Corrugated absorber plate show 30Pa higher pressure drop than plain absorber plate. Thermo-hydraulic efficiency is found to deviate by almost 6.35% from the corresponding thermal efficiency. Mass flow rate of air in the range of 0.0078–0.0094 kg/s is found to yield qualitative heat transfer. Highlights • Comparison of flat and corrugated plate solar air collector is presented. • Double glazing reduces losses and increase the thermal efficiency by 6.87%. • Increase in mass flow rate by 3 times results in 6%increase of efficiency. • Corrugated plate provides 14% higher efficiency than flat plate collector. • Mass flow rate of air enhances energy efficiency and reduce exergetic efficiency. [ABSTRACT FROM AUTHOR]

Abstract: In order to test the hypothesis that the ambient iron concentrations could regulate sulfate reducing activity (SRA) in mangrove areas, 10 cm cores were examined from test and reference sites. The test site at Diwar mangrove ecosystem is highly influenced by iron released by the movement of barges carrying iron ore during the non-monsoon seasons and the reference site at Tuvem is relatively pristine. The average iron concentrations were 17.9% (±8.06) at Diwar and 6.3% (±1.5) at Tuvem. Sulfate reducing rates (SRR) ranged from 50.21 to 698.66 nM cm−3 d−1 at Tuvem, and from 23.32 to 294.49 nM cm−3d−1 in Diwar. Pearson’s correlation coefficients between SRR and environmental parameters showed that at Tuvem, the SRR was controlled by SO4 −2 (r = 0.498, p < 0.001, n = 60) more than organic carbon (r = 0.316 p < 0.05, n = 60). At Diwar, the SRR was governed by the iron concentrations at an r-value of −0.761 (p < 0.001, n = 60), suggesting that ca.58% of the variation in SRR was influenced negatively by variations in ambient iron concentrations. This influence was more than the positive influence of TOC (r = 0.615, p < 0.001, n = 60). Laboratory experiments to check the influence of iron on SRR also supported our field observations. At an experimental manipulation of 50 ppm Fe3+ there was an increase in SRR but at 100 ppm an inhibitory effect was observed. At 1000 ppm Fe3+ there was a decrease in the SRR up to 93% of the control. Thus, our study showed that ambient iron concentrations influence SRR negatively at Diwar and counters the positive influence of organic carbon. Consequently, the influence could cascade to other biogeochemical processes in these mangrove swamps, especially the mineralization of organic matter to carbon dioxide by sulfate respiration. [Copyright &y& Elsevier]

Abstract: Two Gram (+) bacterial strains, BSB6 and BSB12, showing resistance and potential for Se(IV) reduction among 26 moderately halotolerant isolates from the Bhitarkanika mangrove soil were characterized by biochemical and 16S rDNA sequence analyses. Both of them were strictly aerobic and able to grow in a wide range of pH (4–11), temperature (4–40°C) and salt concentration (4–12%) having an optimum growth at 37°C, pH ∼7.5 and 7% salt (NaCl). The biochemical characteristics and 16S rDNA sequence analysis of BSB6 and BSB12 showed the closest phylogenetic similarity with the species Bacillus megaterium. Both the strains effectively reduced Se(IV) and complete reduction of selenite (up to 0.25mM) was achieved within 40h. SEM with energy dispersive X-ray and TEM analyses revealed the formation of nano size spherical selenium particles in and around the bacterial cells which were also supported by the confocal micrograph study. The UV–Vis diffuse reflectance spectra and XRD of selenium precipitates revealed that the selenium particles are in the nanometric range and crystalline in nature. These bacterial strains may be exploited further for bioremediation process of Se(IV) at relatively high salt concentrations and green synthesis of selenium nanoparticles. [Copyright &y& Elsevier]

Abstract: Biotite is a constituent Fe-bearing mineral of Delta subsoils in India and Bangladesh and has been hypothesized as a primary source of arsenic (As). The adsorption behavior of As onto structural Fe(II, III)-bearing biotite fractions (<50μm) was investigated in the pH range of 4–8 under a CO2-free, anoxic condition (O2 <1ppmv) using X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). The batch experiments indicate that As adsorption is strongly pH dependent and that As(V) adsorbs more efficiently than As(III). X-ray Absorption Near-Edge Structure (XANES) spectra show no oxidation or reduction of As by biotite after reaction with As(III) or As(V) solutions for 3days. Extended X-ray Absorption Fine Structure (EXAFS) spectroscopic results suggest that As(III) forms bidentate mononuclear edge-sharing (2E) and bidentate binuclear corner-sharing (2C) surface complexes at pH 7.7 as indicated by average As–Fe bond distances at 3.00±0.02Å and 3.37±0.03Å respectively. The surface speciation retrieved by XPS does not provide any evidence of reduction of As(V) on biotite after 30days further confirming the thermodynamic prediction and the XANES results. This study has therefore significant environmental implications for As contaminated areas, where biotite retards the release of As into reducing groundwater. The changes in soil redox conditions and weathering of biotite may likely contribute to the occurrence of high As in groundwater. [ABSTRACT FROM AUTHOR]

Hydrographic characteristics of the southwest coast of India and its adjoining Cochin backwaters (CBW) were studied during the summer monsoon period. Anomalous formation of anoxia and denitrification were observed in the bottom layers of CBW, which have not been previously reported elsewhere in any tropical estuarine systems. The prevalent upwelling in the Arabian Sea (AS) brought cool, high saline, oxygen deficient and nutrient-rich waters towards the coastal zone and bottom layers of CBW during the high tide. High freshwater discharge in the surface layers brought high amount of nutrients and makes the CBW system highly productive. Intrusion of AS waters seems to be stronger towards the upstream end (∼15 km), than had been previously reported, as a consequence of the lowering of river discharges and deepening of channels in the estuary. Time series measurements in the lower reaches of CBW indicated a low mixing zone with increased stratification, 3 h after the high tide (highest high tide) and high variation in vertical mixing during the spring and neap phases. The upwelled waters (O2 ⩽ 40 μM) intruded into the estuary was found to lose more oxygen during the neap phase (suboxic O2 ⩽ 4 μM) than spring phase (hypoxic O2 ⩽ μ10μM). Increased stratification coupled with low ventilation and presence of high organic matter have resulted in an anoxic condition (O2 = 0), 2-6 km away from barmouth of the estuary and leads to the formation of hydrogen sulphide. The reduction of nitrate and formation of nitrite within the oxygen deficient waters indicated strong denitrification intensity in the estuary. The expansion of oxygen deficient zone, denitrification and formation of hydrogen sulphide may lead to a destruction of biodiversity and an increase of green house gas emissions from this region. [ABSTRACT FROM AUTHOR]

Abstract: A microbial consortium DAS consisting three bacterial sp. originally obtained from dye contaminated sites of Solapur, India was selected because it was capable of decolorizing textile effluent and dye faster than the individual bacteria under static conditions. Identification of the isolates by 16S rRNA techniques revealed the isolates to be Pseudomonas species. The concerted metabolic activity of these isolates led to complete decolorization of textile effluent as well as Reactive Orange 16 (100mgl−1) within 48-h at pH 7 and 30°C. Studies involving Reactive Orange 16 (RO16) dye were carried with the bacterial consortium DAS to elucidate the mechanism of biodegradation. Induction of the laccase and reductase enzyme during RO16 decolorization indicated their role in biodegradation. The biodegradation of RO16 was monitored by using IR spectroscopy, HPLC and GC–MS analysis. Cytotoxicity, genotoxicity and phytotoxicity studies carried out before and after decolorization of the textile effluent revealed the nontoxic nature of the biotreated sample. [Copyright &y& Elsevier]

Abstract: Arsenic-enriched groundwater has been a pressing human health issue for more than a decade, with tens of millions of people worldwide being at risk of chronic As poisoning through the consumption of As-burdened groundwater. To elucidate the importance of dissolved S on the scale of As concentrations, the composition of groundwater samples from 926 locations spanning over the floodplains of three severely arsenic affected regions in Asia (Bengal-, Mekong-, Red River deltas), were assessed. A binary mixing model based on Cl− or B as conservative tracers implies that two types of water may be regarded as end-members with respect to groundwater composition in these deltas, namely surface derived water (approximated by river water) and saline water identical to residual sea water. Six redox zones were distinguished by comparing the model-calculated concentrations with the measured values. Only one zone (denoted methanogenic) had very high average As concentrations and they were significantly higher than in the other zones – for all three regions, regardless of applying Cl− or B as a tracer in the model. Average As concentrations±standard error in the methanogenic zone were 182±23μgL−1 (n =50%), 41±6μgL−1 (n =43%), and 61±20μgL−1 (n =24%) in the Mekong, Red River and Bengal delta, respectively. Arsenic levels were significantly lower in the SO4-reducing and the Fe-reducing zones, where averages were 23±7μgL−1 (n =27%, zone I), 14±3μgL−1 (n =48%, zone S) and 26±9μgL−1 (n =64%, zone S). These results suggest that a sufficient supply of inhibits the release of As to groundwater and that reduction may be as important as Fe reduction in controlling the enrichment of As in groundwater. [Copyright &y& Elsevier]

The article discusses research examining the role of indigenous microorganisms in the biodegradation of naturally occurring petroleum, iron reduction, and arsenite mobilization in aquifer sediments from West Bengal and other areas in Southeast Asia. The aquifers are used as a drinking water source and for irrigation by the local population. The team used a microcosm-based technique to test seven sediments from sites containing naturally occurring hydrocarbons. The sediments were incubated with synthetic groundwater and kept under anaerobic conditions for 28 days without external electron donation. The microbial mediation of arsenic and iron oxide Fe(III) and the preferential loss of n-alkanes during incubation are discussed.

The Arabian Sea contains one of the three major open-ocean denitrification zones in the world. In addition, pelagic denitrification also occurs over the inner and mid-shelf off the west coast of India. The major differences between the two environments are highlighted using the available data. The perennial open-ocean system occupies two orders of magnitude larger volume than the seasonal coastal system, however, the latter offers more extreme conditions (greater nitrate consumption leading to complete anoxia). Unlike the open-ocean system, the coastal system seems to have undergone a change (i.e., it has intensified) over the past few decades presumably due to enhanced nutrient loading from land. The two systems also differ from each other with regard to the modes of nitrous oxide (N2O) production: in the open-ocean suboxic zone, an accumulation of secondary nitrite (NO2-) is invariably accompanied by depletion of N2O whereas in the coastal suboxic zone high NO2- and very high N2O concentrations frequently co-occur, indicating, respectively, net consumption and net production of N2O by denitrifiers. The extents of heavier isotope enrichment in the combined nitrate and nitrite (NO3-+NO2-) pool and in N2O in reducing waters appear to be considerably smaller in the coastal region, reflecting more varied sources/sinks and/or different isotopic fractionation factors. [ABSTRACT FROM AUTHOR]