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- Author or Editor: K. Pillai x
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Abstract
The study of physico-chemical and biotic processes in the environment is essential to understanding the behavior of transuranic nuclides and to assess their environmental impact. Dialysis, ion exchange, and co-precipitation techniques have been used to study speciation. The dissolved fraction of239,240Pu in coastal waters of Bombay harbor bay and in interstitial water from bottom sediments of the bay were found to be associated with organic matter. The desorption of Pu from sediments in coastal waters is influenced by salinity and carbonate. Studies indicate that, even from anoxic sediments, remobilization and the potential for migration is not significant.
Abstract
Preparation and purification of radioiodinated progesterone derivatives for the development of a radioimmunoassay of progesterone is described. We have standardized two procedures for preparing radioiodinated progesterone conjugate. In the first procedure125I labeled histamine was conjugated to progesterone 11 hemisuccinate by the mixed anhydride method. In the secod procedure, tyrosyl methyl ester was conjugated to progesterone 11 hemisuccinate and iodination of the conjugate was carried out. Purification of the iodinated products was carried out by solvent extraction and thin layer chromatography techniques. The radiochemical purity of the tracers prepared by both methods were more than 95%. Labeled progesterone derivatives prepared were used for developing a radioimmunoassay procedure. The non-specific binding of the tracer was about 2–3%, while up to 80% binding could be obtained in the presence of excess antibody. The radioiodinated tracer could be used up to four months in the assay.
Abstract
The standardisation of a direct radioimmunoassay for progesterone using an125I labeled progesterone prepared by iodinating the tyrosine methyl ester (TME) conjugated to a progesterone hemiphthalate derivative and an antibody prepared using progesterone linked to bovine serum albumin through 11α hemisuccinate derivative is described. The hemiphthalate derivative of progesterone was prepared by reacting 11α-hydroxy progesterone with phthalic anhydride which was then conjugated to TME by using isobutyl chloroformate. The conjugate was iodinated with125I using chloramine-T as oxidising agent and purified by thin layer chromatography. Radiochemical purity of the tracer was >95% in all batches. The tracer gave 70–75% binding with excess antibody. Assays were optimised with 8-anilino-1-naphthalene sulphonic acid (ANS) and sodium salicylate as blocking agents to release the progesterone from binding proteins. The assay optimised with sodium salicylate as blocking agent has a sensitivity of 0.25 ng/ml and a working range of 0.25–50 ng/ml, whereas the assay with ANS has a sensitivity of 0.75 ng/ml and a working range of 0.75–100 ng/ml. Serum samples were analysed and compared with the values obtained with a homologous bridge assay.
Abstract
The procedures developed and standardised for estimation of ultra trace quantities of Pu and Am in environmental samples involve matrix dependent sample preparation, preconcentration of the nuclides by coprecipitation on iron hydroxide and or bismuth phosphate, ion exchange, electrodeposition and counting by alpha spectrometry. Isotopic analysis of Th in chicken bone using oxalate precipitation, ion exchange, electrodeposition and alpha spectrometry has indicated higher build up of228Th in chicken bone from monazite areas possibly from metabolized228Ra.
Abstract
Neutron activation analysis was used to determine129I in soil and grass samples around a reprocessing plant. The method involved wet oxidation of samples, using chromic acid, followed by distillation, collection of iodine in alkaline solution, loading on Dowex-1, irradiation and post-irradiation purification steps. The -activity of130I isotope of the purified samples was measured for quantitative determination of129I. The experimental results showed that129I and the129I/127I atomic ratio in soil samples varied from 1.09×10–4 to 5.33×10–3 pCi g–1 and 0.10×10–6 to 6.12×10–6, respectively. Further, the geometric mean of soil-to-plant transfer factor (Bv) for129I was found to be 0.16 which was comparable with other published values.
Abstract
A sequential radiochemical scheme for the separation of Pu and Am (along with Cm) from environmental materials is given. Optimum conditions for coprecipitation of these elements on bismuth phosphate and the influence of Fe and Th content of the sample on the recovery of Am were studied. Internal tracers242Pu and243Am were used as tracers for Pu and Am, respectively, and estimates were made by alpha-spectrometry. Average recoveries obtained from sea water were 85% and 77% for Pu and Am, respectively. Lower recoveries (<50%) were obtained for Am in sediments.
Abstract
Desorption studies of137Cs from marine sediments by artificial sea water and artificial sea water devoid of individual major cations such as Na, K, Ca, Mg and Sr indicated that only Na and K were effective in the desorption of137Cs. Studies with various ionic strengths ranginf from 0.01 to 1.6M KCl and NaCl solutions showed that KCl desorbs constantly about 45%137Cs at and above an ionic strength of 0.1. In case of NaCl, the percent desorption increases linearly with ionic strength. The difference in desorption by K and Na is attributed to the contraction of the clay mineral layers by K ion and expansion of the layers by Na ion.
Abstract
Sea water is observed to be a good desorbing agent for137Cs from marine sediments. Investigations on the sites of137Cs binding and their abundance by desorption over extended periods indicated that, whatever the time of contact of sorption,137Cs has three modes of desorption: fast component with desorption half-time of 30–50 min, medium component with desorption half-time of 25–50 h and slow component with desorption half-time of 31–112 days. These are expected to be sites of ion exchange, slower exchange and trapped Cs in the clay mineral layer lattices.
Abstract
A simple method employing neutron activation and radiochemical separation was developed for simultaneous determination of the concentrations of232Th(Th) and238U(U) in biological materials. Using this method, it is possible to detect 0.05 and 0.2 ng of Th and U, respectively, in the samples. This method was applied to determine the daily dietary intake of these two nuclides by the population living in the high background areas of India (Monazite area), where the soil contains very high levels of these two nuclides. The comparison of the daily intakes by the population living in high and normal background areas showed significantly higher intake of these two nuclides by the high background population.
Abstract
Geochemical association of plutonium in the coastal environment of Trombay has been studied. A sequential leaching method was employed for chemical partitioning of plutonium in sediments. The results show that 95±15% of plutonium was extracted by different leaching reagents out of which 85±14% was associated with organic matter and hydrous oxide and 9±4% with residual fraction.The presence of significant fraction of Pu bound with organic matter of the sediment is an important factor in determining the extent to which an element becomes available to bottom feeding biota and so enters the aquatic food chain.