In order to meet the proposed regulatory compliances for the protection of non-human species from the ionising radiation, a comprehensive dose-evaluation process for terrestrial and aquatic biota was worked out at Trombay. During this work, dose rate (external and internal) from ionising radiation to the terrestrial plants and marine organisms (mixed varieties of fish) was evaluated by estimating the concentration of anthropogenic ((137)Cs, (90)Sr) and natural radionuclides ((238)U, (232)Th and (40)K) in environmental matrices, such as soil, vegetation, sea water and sediment. The samples were processed as per the International Atomic Energy Agency protocol for the estimation of naturally occurring and anthropogenic radionuclides. The average values of radiation exposure to the terrestrial plants for (40)K, (90)Sr, (137)Cs, (232)Th and (238)U were 632.8 +/- 40.5, 167.4 +/- 48.2, 691.2 +/- 29.9, 48769 +/- 13203 and 1801 +/- 1495 microGy y(-1), respectively. In the case of marine organisms (fish), the maximum external exposure was 195 microGy y(-1) due to (40)K concentration in bottom sediment, whereas the minimum was 0.004 microGy y(-1) due to (137)Cs in sea water. Internal exposure to fish was maximum (700 microGy y(-1)) due to (40)K, whereas the minimum of 0.12 microGy y(-1) was due to (90)Sr. Considering the dose limit of 10 mGy d(-1) (3.65 Gy y(-1)), proposed by the US Department of Energy, evaluated radiation exposure (external + internal) and dose rate in the present study to the terrestrial plants and marine organisms are orders of magnitude less.

Uranium in groundwater samples collected from Punjab state, India was determined using radiometric methods (extractive liquid scintillation and Cerenkov counting). Experimental conditions were optimized by studying the effect of sample pH, quenching and amount of extracting agent added to the scintillation cocktail on recovery of uranium. To ensure the accuracy of results, both radiometric methods were compared with non radiometric method such as adsorptive stripping voltammetry and found to be very good agreement. The distinct advantage of proposed radiometric methods is almost 100 % effective especially extractive liquid scintillation for simultaneous measurement of alpha and beta emitting radionuclides with fast and simple sample preparation.

No abstract

Time-resolved coherent anti-Stokes Raman Scattering (CARS) is a nonlinear spectroscopic tool, which has gained importance with the development of ultrafast lasers due to its ability to probe ultrafast dynamical processes in molecules. Apart from the time resolution, the superiority of CARS over spontaneous Raman scattering derives from its high signal generation ability and coherent, laser like, signal emission. In this contribution, we describe the development of an experimental facility for the time-resolved coherent anti-Stokes Raman scattering spectroscopy and its application to study the vibrational dynamics of molecules containing nitro (NO 2 ) groups. fs-CARS experiments were carried out in neat liquids of nitrobenzene, nitromethane and their mixture. A detailed mapping of the dynamics initiated by the stimulated Raman process is achieved from the spectrum of the transient CARS signal. The CARS transient shows rich beating structure corresponding to frequencies as high as 10 THz. The Fourier transform of the transient allows accurate determination of the vibrational energy differences.This methodology is capable of providing the dephasing behaviour and spectral information of the molecular system at the same time.The results demonstrate that CARS spectroscopy with femtosecond time resolution and wavenumber-resolved detection is a powerful tool for the characterization of dynamics in the electronic ground state of molecules.