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   

A comparison study between the newly-born ion effect and the thermal effect on the whistlers in the ionosphere     

G. C. Das  A. K. Sur 《Astrophysics and Space Science》1986,127(2):249-263

We have considered an ionospheric plasma model that includes the thermal effect along with the newly born ionic effect and derived a group travel time for the low-frequency whistlers with a view to employing it as a diagnostic tool in the ionosphere. The mathematical development shows that the thermal effect contribution varies with ( _i – )_–7/2 whereas that of the newly born ionic effect varies with _i – )_–5/2. Both the effects are discussed separately. It is concluded that the effects are reasonably countable in the ionosphere. The investigations finally conclude that both the effects should be taken into the whistler waves, otherwise the method might cause a discrepancy in the results, which could affect their accuracy.  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   

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   

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   

Stratification approach for forest cover type and landuse mapping using IRS-1A LISS-II data — A case study     

S. Sudhakar  R. K. Das  D. Chakraborty  B. K. Bardhan Roy  A. K. Raha  P. Shukla 《Journal of the Indian Society of Remote Sensing》1994,22(1):21-29

Indian Remote Sensing Satellite-1A (IRS-1A) LISS-II data of 24th Nov., 1988 was analysed digitally to differentiate three density classes viz. dense/closed forest, open forest and degraded forest within each vegetation type in the district, Jalpaiguri, West Bengal. Stratification approach was used to classify separately forest cover into pure sal forests, mixed forests, riverine forests along with man-made sal/teak plantations. In this approach the forested and non-forested areas were classified separately through supervised classification techniques using maximum likelihood algorithm using VAX 11/780 based VIPS-32 Image Processing software. Later the two classified outputs were composited to provide entire area of the district. The forest cover of the district was 1420.89 sq. km, (22.82 percent). Other broad landuse/landcover dominant in the district include agricultural areas.(45.20 percent) and tea gardens (10.49 percent). The accuracy of the classified output was estimated to be 90 percent for forested areas and 85 percent in case of other landuse/landcover classes.  相似文献   

Nature of variation of Antarctic O3 depletion and its correlation with solar UV radiation     

S. K. Midya  S. C. Ganda  G. Tarafdar  T. K. Das 《Earth, Moon, and Planets》1996,74(2):109-113

The purpose of this paper is to study the nature of variation of O₃ concentration of Antarctic Survey Stations and its correlation with solar ultraviolet radiation. Solar UV data for the period November 1978 to October 1984 are taken from Solar Geophysical Data Book. In absence of solar UV data for long period, a calibration curve between solar UV radiation and solar flare number (S.F.NO.) is drawn. (A straight line is obtained and correlation coefficient between two variables is 80%). The equation of straight line from least square principle becomes, UV flux = 0.2672 + 2.7578 × 10^?5 × S.F.NO. From this equation UV flux values for long period are calculated from known values of solar flare numbers. O₃ concentration of two Antarctic Survey Stations, Halley Bay (76? S, 27? W) and McMurdo (78? S, 166? E) are considered for analysis and following important results are obtained:

1. Yearly variations of O₃ concentrations and UV radiations are mainly controlled by their October concentrations.
2. Correlation coefficient between O₃ concentration and UV radiation is 62% for the month of October. For the other months it is poor.
3. It is concluded that dramatic decrease of O₃ concentration at Antarctica is independent of solar UV radiation and chemical processes are responsible for special depletion of O₃.

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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   

An enhanced image of the Pamir–Hindu Kush seismic zone from relocated earthquake hypocentres     

G. Pegler  & S. Das 《Geophysical Journal International》1998,134(2):573-595

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