Sediment and heavy metal accumulation in the Cauvery basin   总被引：2，自引：0，他引：2  

A. L. Ramanathan  V. Subramanian  B. K. Das 《Environmental Geology》1996,27(3):155-163

Eleven cores were collected from the Cauvery basin. Radiometric dates were used to determine modern sediment accumulation rates. Sediment accumulation rates ranged from 0.4 to 4 mm yr^–. Heavy metal concentration decreases with the increase of depth. The heavy metal concentrations at certain depths are attributed to the irregular input of metals and their remobilization. Heavy metal accumulations have been computed using sediment accumulation rates, and accumulation rates show an additional anthropogenic input of metals and sediments in the recent past. Factor analysis and correlation analysis show the diverse source and accumulation mechanism influencing the metal distribution in the basin.  相似文献   

Hydromagnetic turbulence in cometary plasmas     

N. N. Rao  U. N. Rao  A. C. Das 《Earth, Moon, and Planets》1988,43(2):155-163

An instability associated with the magnetosonic wave driven unstable due to coupling with electron and ion drift modes has been considered as a potential source for driving the hydromagnetic turbulence observed in Giacobini-Zinner (G-Z) Cometary plasma. The instability has good growth rate for propagation perpendicular to plasma inhomogeneities and exists for all wave numbers. The wave period for waves propagating perpendicular to the gradients is about a few times ion-gyroperiod and higher values of plasma beta ( _e lead to stronger instability.  相似文献   

Coastal Pollution Mitigation with Lime and Zero Valent Iron     

John L. Daniels  Gautham P. Das  Maria Teresa Serrano Hernandez  Sunyoung Bae 《Marine Georesources & Geotechnology》2006,24(3):183-191

The Taiwan Strait region has many miles of coastline, and the Taiwan Straits Tunnel (TST) project faces many potential pollution problems as construction proceeds through sensitive areas. Conventional approaches for pollution mitigation require further examination. The recent development of nanoscale particle technology has shown distinct advantages for contaminant attenuation and ground improvement. This paper is focused on trace metals and is part of the overall effort to develop the nanoscale particle technology. Trace metals in ground and surface waters represent a continued threat to human and ecological health. One of the difficulties in removing toxic concentrations of trace metals from solution is the variable oxidation state and amphoteric nature of multiple constituents. In particular, while cationic metals (e.g., Pb²⁺, Cd²⁺, Ni²⁺) may be rendered less mobile under high pH conditions, anionic metals (e.g., AsO₄^3-, CrO₄^2-, SeO₄^2-)may become more mobile. The objective of this research was to evaluate the sorption of both cationic and anionic trace elements, including arsenic (As), cadmium (Cd), chromium (Cr) and selenium (Se) under batch conditions. Mixtures of a local residual soil were tested alone and in combination with lime and zero valent iron. It was hypothesized that lime would raise the pH and precipitate positively charged metals while zero valent iron would create reducing conditions favorable to the immobilization of negatively charged metals. Results indicate that the use of lime and/or zero valent iron can increase the sorption capacity of soil. Compared to the baseline soil, sorption capacity increased with addition of lime for arsenic and cadmium while it decreased for chromium and selenium. In the case of zero valent iron addition, sorption capacity increased for cadmium, chromium and selenium, while showing no change for arsenic. When both lime and zero valent iron were used, the sorption capacity increased for all metals tested. These results suggest that the combined use of lime and zero valent iron may serve as an alternative treatment technology for removing trace metals from contaminated water systems.  相似文献   

On the numerical evaluation of theH-functions of transfer problems in multiplying media     

S. R. Das Gupta  Z. Islam  B. Majee 《Astrophysics and Space Science》1980,72(1):71-78

Extensive tables of the values ofH-functionsH ⁰(z, ) andH ₁ ⁰ (z, ) appropriate for the problems of radiative transfer in multiplying media characterized by >1, have been constructed correctly to the sixth decimal place for values of in the range 1.05–10. This accuracy has been attained with the aid of a 32-point Gaussian quadrature.  相似文献   

Propagation of Rayleigh waves in soils     

Sushil Chandra Das Gupta 《Pure and Applied Geophysics》1953,25(1):13-16

Summary Propagation of Rayleigh type waves in soils is considered in this paper. It is a well known fact that soils do not behave like an ordinary isotropic elastic medium where the ratio of Young's modulus to the modulus of rigidity is much less than that in sandy soils. Considering the velocity of Rayleigh type wave as less than that of distortional wave (which is an observed fact) a probable value of this ratio is determined, and also assuming the value of this ratio based on some experimental data, the velocity of wave propagation in the medium is deduced.  相似文献   

Exact solution of the equation for the problem of diffuse reflection and transmission with a scattering function ω0(1 +x cos⊙) by the method of laplace transform and theory of linear singular integral equation     

Rabindra Nath Das 《Astrophysics and Space Science》1978,57(2):409-417

Neutrinos couple through a weak neutral current to the density of matter, in particular to the neutron density. Density fluctuations, or phonons, in the neutron fluid may be emitted or absorbed by neutrinos passing through the matter. At high densities, temperatures and neutrino energies the neutrino mean free paths for phonon emission and absorption can be 10⁶ cm. Significant changes in the neutrino momentum and energy accompany these processes. We present a model calculation for neutrino scattering by phonons, and representative numerical results for the neutrino mean free path and mean energy and momentum changes fork _B T andE _v both ranging from 1 to 27 MeV.Research supported by the National Research Council of Canada.  相似文献   

Exact solution of the equation of radiative transfer for semi-infinite plane-parallel isotropic scattering atmosphere with scattering albedo ω0 ≤ 1 by a method based on Laplace transform and Wiener-Hopf technique     

Rabindra Nath Das 《Astrophysics and Space Science》1978,57(2):419-427

By performing the one-sided Laplace transform on the scalar integro-differential equation for a semi-infinite plane-parallel isotropic scattering atmosphere with a scattering albedo ₀ 1, an integral equation for the emergent intensity has been derived. Application of the Wiener-Hopf technique to this integral equation will give the emergent intensity. The intensity at any optical depth for a positive scattering angle is also derived by inversion. The intensity at any optical depth for a negative scattering angle is also derived in terms of Cauchy's principal value using Plemelj's formulae.  相似文献   

Exact solution of the transport equation for radiative transfer with scattering albedo ωO < 1 using the Laplace transform and the Wiener-Hopf technique and an expression ofH-function     

Rabindra Nath Das 《Astrophysics and Space Science》1979,60(1):49-58

We have considered the transport equation for radiative transfer to a problem in semi-infinite non-conservative atmosphere with no incident radiation and scattering albedo ₀ < 1. Usint the Laplace transform and the Wiener-Hopf technique, we have determined the emergent intensity and the intensity at any optical depth. We have obtained theH-function of Dasgupta (1977) by equating the emergent intensity with the intensity at zero optical depth.  相似文献   

A comparative study of Hα-flares of different visual features in relation to radio bursts and sunspots     

M. K. Das Gupta  T. K. Das  S. K. Sarkar 《Solar physics》1979,64(2):323-328

Solar H-flares now reported with their distinctive visual features have been statistically examined for a period of about eight years in relation to their different characteristics, flare-burst and flare-sunspot association. Important results obtained are: (i) Integrated intensity changes from the highest to the lowest values in the order F, H, E, and D flare type, whereas, impulsiveness in the order H, F, E, and D type, (ii) Flare-burst association is frequency dependent and is highest and lowest for H and D types respectively in almost all the frequencies, (iii) Most of the flares of D, E, and F types are associated with sunspots of _p , _p , and configurations having field strength 1500–2500 G, while that of H type with _p and configurations having field strength 1000–2000 G.  相似文献   

Multiple forecasts of kharif rice in orissa state-four year experience of fasal pilot study     

N. K. Patel  M. Chakraborty  S. Dutta  C. Patnaik  J. S. Parihar  S. C. Moharana  A. Das  B. K. Sarangi  G. Behera 《Journal of the Indian Society of Remote Sensing》2004,32(2):125-143

Considering the requirement of multiple pre-harvest crop forecasts, the concept of Forecasting Agricultural output using Space, Agrometeorology and Land based observations (FASAL) has been formulated. Development of procedure and demonstration of this technique for four in-season forecasts for kharif rice has been carried out as a pilot study in Orissa State since 1998. As the availability of cloud-free optical remote sensing data during kharif season is very poor for Orissa state, multi-date RADARSAT SCANSAR data were used for acreage estimation of kharif rice. Meteorological models have been developed for early assessment of acreage and prediction of yield at mid and late crop growth season. Four in-season forecasts were made during four kharif seasons (1998-2001); the first forecast of zone level rice acreage at the beginning of kharif crop season using meteorological models, second forecast of district level acreage at mid growth season using two-date RADARSAT SCANSAR data and yield using meteorological models, third forecast at late growth season of district level acreage using three-date RADARSAT SCANSAR data and yield using meteorological models and revised forecast incorporating field observations at maturity. The results of multiple forecasts have shown rice acreage estimation and yield prediction with deviation up to 14 and 11 per cent respectively. This study has demonstrated the potential of FASAL concept to provide inseason multiple forecasts using data of remote sensing, meteorology and land based observations.  相似文献