Experimental database on water equivalent factor (WEQp) and organically bound tritium activity for tropical monsoonal climate region of South West Coast of India

Environmental transfer parameters of strontium for soil to cow milk pathway for tropical monsoonal climatic region of the Indian subcontinent

The radionuclide transfer between compartments is commonly described by transfer parameters representing the ratio of concentrations of an element in two compartments for equilibrium conditions. This is a comprehensive study on the soil-to-grass transfer factor (Fv) and grass-to-cow milk transfer coefficient (Fm) for stable strontium (Sr) for soil-grass (pasture)-cow (Bos taurus) milk environmental pathway under field conditions for a high rainfall tropical monsoonal climatic region of the Indian subcontinent. The study was conducted in the vicinity of the Kaiga nuclear power plant (NPP), situated ~ 58 km inland of the West Coast of the Indian subcontinent. A grass field was developed exclusively for this study, and two cows of the native breed were raised to graze on it. The soil, grass, and milk were analyzed to evaluate the Fv and the Fm values for the stable Sr. For comparison, several pasture lands and the cows raised by the villagers and a dairy farm were also studied. The Fv values were in the range 0.18-8.6, the geometric mean (GM) being 1.8. The correlations of Fv values with a range of physicochemical parameters are presented. The GM values for Fm were 2.2 × 10-3 d L-1 and 7.2 × 10-3 d L-1 for the two cows raised for this study, 2.6 × 10-3 d L-1 for those raised by the villagers, and 4.2 × 10-3 d L-1 for the dairy farm. The site-specific Fm value for the region was determined as 3.2 × 10-3 d L-1. The concentration ratio (CR), defined as the ratio of Sr concentration in milk to that in feed under equilibrium conditions, exhibited less variability (1.8 × 10-2-5.4 × 10-2) among the three categories of cows.

NE-OBT and TFWT activity concentrations in wild plants in the vicinity of the PHWR nuclear power plant and control regions of the tropical monsoonal climatic region of the Indian subcontinent

The results of the first detailed study, involving a large number of samples, on water equivalent factor (WEQ_p), non-exchangeable organically bound tritium (NE-OBT) and tissue free water tritium (TFWT) activity concentrations in predominant plant species of the tropical monsoonal climatic region, are presented. A total of 369 samples from the vicinity of the PHWR nuclear power plant (NPP) at Kaiga, West Coast of India, and 47 samples of the control region (region not affected by local anthropogenic sources) were analysed. The WEQ_p varied in the range of 0.347-0.666 L kg^-1 with an overall mean value of 0.540 ± 0.045 L kg^-1. The NE-OBT activity concentration varied in the range of <9.8-60.9 Bq L^-1 of combustion water (mean = 24.6 ± 11.5 Bq L^-1) and that of TFWT in the range of 9.2-60.5 Bq L^-1 (mean = 30.7 ± 10.9 Bq L^-1) in the vicinity of the NPP. Rigorous statistical analysis of the data confirmed that (i) the activity concentrations of both forms of tritium decreased with the increase in the distance between the sampling location and NPP, and beyond 10 km, it was similar to that of the control region, (ii) the incorporation of tritium released from the NPP into wild plant leaves is not species-dependent, (iii) the NE-OBT activity concentration in the 5-10 km zone exhibited a dependence on the prevailing wind regime with respect to the NPP, but not in the 2.3-5 km zone which suggests that the transport of tritium, released into the atmosphere as the gaseous effluent, through diffusion is a dominating factor governing its activity concentration in the 2.3-5 km zone. The NE-OBT to TFWT specific activity concentration ratio (R-value) had a mean value of 0.82 ± 0.27 (range: 0.38-1.64) for samples collected from the vicinity of the NPP and 1.93 ± 0.50 (range: 1.35-3.19) for the control region. Recording higher NE-OBT activity concentration and R-value at the control region highlights the necessity of detailed studies to understand the mechanism of NE-OBT partitioning in the terrestrial environment.