Nabanita Naskar

Measurement of naturally occurring radioactive materials, 238U and 232Th: anomalies in photopeak selection

There are more than 200 photopeaks of various daughter radionuclides of 238U and 232Th series, some of which have been randomly used for quantitative measurement of U/Th in natural samples. It has been observed that arbitrariness in photopeak selection may fail to stipulate statistically consistent data. This paper judiciously selects set of three photopeaks from each series whose respective averages could present statistically reliable measurement of 238U and 232Th based on minimum relative standard deviation (RSD) under the selected photopeaks. RSD is also proposed as an important parameter in NORM measurement.

Measurement of naturally occurring radioactive material, 238U and 232Th: part 2—optimization of counting time

An effort has been made to optimize the counting time for low-level measurement of naturally occurring radioactive material (NORM) by considering the standard deviation between the activity values of different photopeaks and counting error. It is observed that at lower counting time, relative standard deviation (RSD) varies randomly, but attains a gradual trend with increasing time and also comes closure to the counting error. Therefore minimum counting time for low-level NORM measurement of 238U and 232Th would be the time required to stabilize the RSD values.

Measurement of naturally occurring radioactive materials, 238 U and 232 Th-part 3: is efficiency calibration necessary for quantitative measurement of ultra-low level NORM?

A well-calibrated and highly shielded HPGe detector with considerable relative efficiency is an efficient tool for measurement of naturally occurring radioactive material (NORM) present at ultra low-level in the environmental samples. Efficiency calibration is standard protocol required for quantitative estimation of the activity of any radioactive sample. In the present work it has been shown that in the case of ultra-low level NORM measurement, one can comfortably by pass efficiency calibration by using comparator method i.e., comparing the peak area counts of different photopeaks of standard and samples provided they are counted in same geometry and comparable composition.

Study of uranium toxicity using low-background gamma-ray spectrometry

The natural activity of 238U, 232Th and 40K present in soil, fertilizer and palaeosols besides animal fossils was determined using low background gamma ray spectrometry. The highest uranium activity level were found in animal fossils of geogenic origin compared to palaeosols, soils and fertilizers, a result of post-mortem uranium assimilation in these fossils via diagenetic processes. Hence, geogenic mobilization is likely a major cause of elevated uranium levels in Malwa region of Punjab, also known for higher than normal cancer incidence.

An Endophytic Bacterial Consortium modulates multiple strategies to improve Arsenic Phytoremediation Efficacy in Solanum nigrum

Endophytic microbes isolated from plants growing in contaminated habitats possess specialized properties that help their host detoxify the contaminant/s. The possibility of using microbe-assisted phytoremediation for the clean-up of Arsenic (As) contaminated soils of the Ganga-Brahmaputra delta of India, was explored using As-tolerant endophytic microbes from an As-tolerant plant Lantana camara collected from the contaminated site and an intermediate As-accumulator plant Solanum nigrum. Endophytes from L. camara established within S. nigrum as a surrogate host. The microbes most effectively improved plant growth besides increasing bioaccumulation and root-to-shoot transport of As when applied as a consortium. Better phosphate nutrition, photosynthetic performance, and elevated glutathione levels were observed in consortium-treated plants particularly under As-stress. The consortium maintained heightened ROS levels in the plant without any deleterious effect and concomitantly boosted distinct antioxidant defense mechanisms in the shoot and root of As-treated plants. Increased consortium-mediated As(V) to As(III) conversion appeared to be a crucial step in As-detoxification/translocation. Four aquaporins were differentially regulated by the endophytes and/or As. The most interesting finding was the strong upregulation of an MRP transporter in the root by the As + endophytes, which suggested a major alteration of As-detoxification/accumulation pattern upon endophyte treatment that improved As-phytoremediation.

Production and separation of no-carrier-added 181−184Re radioisotopes from proton irradiated tungsten target

Abstract Cross sections for the production of 181−184Re isotopes from proton irradiated thin natWO3 target at 20.9, 17.9, 14.9, 11.9 and 8.8 MeV projectile energies have been measured. An acceptable agreement between experimentally obtained data and available literature reports was found. The produced no-carrier-added (NCA) Re radionuclides have been separated from bulk tungsten target by liquid-liquid extraction (LLX) using trioctyl amine (TOA) and di-(2-ethylhexyl)phosphoric acid (HDEHP) dissolved in cyclohexane. A clear separation has been observed at 0.1 M and 1 M TOA with 0.1 M HNO3 concentration. However, by using HDEHP NCA Re radionuclides could not be separated from bulk W target without its contamination.