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31.
Evaluation of fertility indicators associated with arsenic-contaminated paddy fields soil 总被引:1,自引:0,他引:1
P. S. Chauhan S. K. Mishra S. Misra V. K. Dixit S. Pandey P. Khare M. H. Khan S. Dwivedi A. Lehri 《International Journal of Environmental Science and Technology》2018,15(11):2447-2458
Emerging environmental issues related to heavy metal contamination in rice draw great concern about the soil quality of paddy farming lands irrigated with groundwater. Investigating the functioning of soil microorganisms exposed to heavy metal contamination is imperative for agricultural soil manipulations. The current study accentuates the influence of heavy metals on microbial activity and community composition in arable soil of West Bengal State of India. The result revealed that the fertility indicators (activity of all soil enzymes) and growth-limiting factors (soil N and P) were negatively correlated with the heavy metal stress except the soil total organic content which demonstrated significant positive correlation with the heavy metals. In case of functional diversity of soil, all the considered diversity indices exhibited no specific pattern along with the availability of heavy metals. Further, despite the heavy metal contamination, we observed a very complex and indifferent pattern of bacterial community composition along the heavy metal contamination sites. Overall, we found that γ-Proteobacteria had been the most abundant bacterial community followed by Actinobacteria, Firmicutes, β-Proteobacteria and α-Proteobacteria. Commemorating all the results, we can infer that arsenic and other heavy metal contamination is deteriorating the soil quality and hence warrants immediate attention of concerned soil scientist and agronomists. 相似文献
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33.
Complex organic materials may exist as haze layers in the atmosphere of Titan and as dark coloring agents on icy satellite surfaces. Laboratory measurements of optical constants of plausible complex organic materials are necessary for quantitative evaluation from remote sensing observations, and to document the existence of complex organic materials in the extraterrestrial environments. The recent Cassini VIMS and CIRS observations provide new constraints on Titan’s haze properties in the mid-infrared wavelength region. Here, we present the optical constants (2.5–25 μm) of Titan tholins generated with cold plasma irradiation of a N2/CH4 (90/10) gas mixture at pressures of 0.26 mbar, 1.6 mbar, and 23 mbar. Our new optical constants of three types of Titan tholins suggest that no single Titan tholin in this study fulfills all the observational constraints of the Titan haze material. The discrepancy remains a challenge for future modeling and laboratory efforts that aim toward a better understanding of Titan’s haze material. 相似文献
34.
Anirudh Pradhan Rekha Jaiswal Kanti Jotania Rajeev Kumar Khare 《Astrophysics and Space Science》2012,337(1):401-413
We present two dark energy (DE) models with an anisotropic fluid in Bianchi type-VI
0 space-time by considering time dependent deceleration parameter (DP). The equation of state (EoS) for dark energy ω is found to be time dependent and its existing range for derived models is in good agreement with the recent observations.
Under the suitable condition, the anisotropic models approach to isotropic scenario. We also find that during the evolution
of the universe, the EoS parameter for DE changes from ω>−1 to ω=−1 in first model whereas from ω>−1 to ω<−1 in second model which is consistent with recent observations. The cosmological constant Λ is found to be a positive decreasing
function of time and it approaches a small positive value at late time (i.e. the present epoch) which is corroborated by results
from recent type Ia supernovae observations. The cosmic jerk parameter in our derived models is also found to be in good agreement
with the recent data of astrophysical observations. The physical and geometric aspects of both the models are also discussed
in detail. 相似文献
35.
Joseph D. Meiring Varsha P. Kulkarni James T. Lauroesch Celine Péroux Pushpa Khare Donald G. York Arlin P. S. Crotts 《Monthly notices of the Royal Astronomical Society》2008,384(3):1015-1033
We present chemical abundance measurements from medium-resolution observations of eight subdamped Lyα (sub-DLA) absorber and two strong Lyman-limit systems at z ≲ 1.5 observed with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph on the 6.5-m Magellan II Clay telescope. These observations were taken as part of an ongoing project to determine abundances in z abs ≲ 1.5 quasar absorption line systems focusing on sub-DLA systems. These observations increase the sample of Zn measurements in z abs ≲ 1.5 sub-DLAs by ∼50 per cent. Lines of Mg i , Mg ii , Al ii , Al iii , Ca ii , Mn ii , Fe ii and Zn ii were detected and column densities were determined. Zn ii , a relatively undepleted element and tracer of the gas-phase metallicity is detected in two of these systems, with [Zn/H]=−0.05 ± 0.12 and [Zn/H] > +0.86 . The latter one is however a weak system with N H I < 18.8 , and therefore may need significant ionization corrections to the abundances. Fe ii lines were detected in all systems, with an average Fe abundance of 〈[Fe/H]〉=−0.68 , higher than typical Fe abundances for DLA systems at these redshifts. This high mean [Fe/H] could be due to less depletion of Fe on to dust grains, or to higher abundances in these systems. We also discuss the relative abundances in these absorbers. The systems with high metallicity show high ratios of [Mn/Fe] and [Zn/Fe], as seen previously in another sub-DLA. These higher values of [Mn/Fe] could be a result of heavy depletion of Fe on to grains, unmixed gas, or an intrinsically non-solar abundance pattern. Based on cloudy modelling, we do not expect ionization effects to cause this phenomenon. 相似文献
36.
Nicolas Bruneau Juergen Grieser Thomas Loridan Enrica Bellone Shree Khare 《Natural Hazards》2017,85(2):649-667
Catastrophe risk models are used to assess and manage the economic and societal impacts of natural perils such as tropical cyclones. Large ensembles of event simulations are required to generate useful model output. For example, to estimate the risk due to wind-driven storm surge and waves in tropical cyclone risk models, computationally efficient parametric representations of the wind forcing are required to enable the generation of large ensembles. This paper presents new results on the impact of including explicit representations of extra-tropical transitioning in parametric wind models used to force storm surge and wave simulations in a catastrophe risk modelling context. Extra-tropical transitioning is particularly important in modelling risk on the Japanese coastline, as roughly 40 % of typhoons hitting the Japanese mainland are transitioning before landfall. Using both a historical and idealized track set, we compare maximum storm surge and wave footprints along the Japanese coastline for models that include, and do not include, explicit representations of extra-tropical transitioning. We find that the inclusion of extra-tropical transitioning leads to lower storm surge (10–20 %) and waves (5–15 %) on the southern Japanese coast, with significantly higher storm surge and waves along the northern coast (25–50 %). The results of this paper demonstrate that useful risk assessment of coastal flood risk in Japan must consider the extra-tropical transitioning process. 相似文献
37.
38.
Sagan C Khare BN Thompson WR McDonald GD Wing MR Bada JL Vo-Dinh T Arakawa ET 《The Astrophysical journal》1993,414(1):399-405
Polycyclic aromatic hydrocarbons (PAHs) are important components of the interstellar medium and carbonaceous chondrites, but have never been identified in the reducing atmospheres of the outer solar system. Incompletely characterized complex organic solids (tholins) produced by irradiating simulated Titan atmospheres reproduce well the observed UV/visible/IR optical constants of the Titan stratospheric haze. Titan tholin and a tholin generated in a crude simulation of the atmosphere of Jupiter are examined by two-step laser desorption/multiphoton ionization mass spectrometry. A range of two- to four-ring PAHs, some with one to four alkylation sites are identified, with net abundance approximately 10(-4) g g-1 (grams per gram) of tholins produced. Synchronous fluorescence techniques confirm this detection. Titan tholins have proportionately more one- and two-ring PAHs than do Jupiter tholins, which in turn have more four-ring and larger PAHs. The four-ringed PAH chrysene, prominent in some discussions of interstellar grains, is found in Jupiter tholins. Solid state 13C NMR spectroscopy suggests approximately equal to 25% of the total C in both tholins is tied up in aromatic and/or aliphatic alkenes. IR spectra indicate an upper limit in both tholins of approximately equal to 6% by mass in benzenes, heterocyclics, and PAHs with more than four rings. Condensed PAHs may contribute at most approximately 10% to the observed detached limb haze layers on Titan. As with interstellar PAHs, the synthesis route of planetary PAHs is likely to be via acetylene addition reactions. 相似文献
39.
A dark reddish-brown high-molecular-weight polymer is produced by long wavelength ultraviolet irradiation of abundant gases in reducing planetary atmospheres. The polymer i examined by paper chromatography, mass spectrometry, and infrared, visible, and ultraviolet spectroscopy. High carbon-number straight-chain alkanes with NH2 and, probably, OH and CO groups are identified, along with the previously reported amino acids. There are chemical similarities between this polymer and organic compounds recovered from carbonaceous chondrites and precambrian sediments. The visible and near-ultraviolet transmission spectrum of the polymer shows its absorption optical depth to be redder than λ?2 and perhaps similar in coloration to the clouds of Jupiter, Saturn, and Titan. The near-ultraviolet absorption coefficient is ~103 cm?1, and typical grain sizes ~30 μm. The nitrile content is small, and the polymer should be semitransparent in the 5 μm atmospheric window. Such polymers may be a common constituent of clouds in the outer solar system and on the early Earth. 相似文献
40.
Donald G. York Pushpa Khare Daniel Vanden Berk Varsha P. Kulkarni Arlin P. S. Crotts James T. Lauroesch Gordon T. Richards Donald P. Schneider Daniel E. Welty Yusra Alsayyad Abhishek Kumar Britt Lundgren Natela Shanidze Tristan Smith Johnny Vanlandingham Britt Baugher Patrick B. Hall Edward B. Jenkins Brice Menard Sandhya Rao Jason Tumlinson David Turnshek Ching-Wa Yip Jon Brinkmann 《Monthly notices of the Royal Astronomical Society》2006,367(3):945-978