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 (F
) and grass-to-cow milk transfer coefficient (F
) 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 F
and the F
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 F
values were in the range 0.18-8.6, the geometric mean (GM) being 1.8. The correlations of F
values with a range of physicochemical parameters are presented. The GM values for F
were 2.2 × 10
d L
and 7.2 × 10
d L
for the two cows raised for this study, 2.6 × 10
d L
for those raised by the villagers, and 4.2 × 10
d L
for the dairy farm. The site-specific F
value for the region was determined as 3.2 × 10
d L
. 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
-5.4 × 10
) among the three categories of cows.
A study on exhalation rates of 222Rn and 220Rn and their enrichment pattern in different grain size fractions was carried out. Four different size fractions of the sand samples (1000-500 μm, ...500-250 μm, 250-125 μm, and <125 μm) collected from the beach placers of south west coast of India were analysed for 226Ra and 232Th activity concentrations (Bq kg−1) by gamma spectrometry. Automated continuous measurement technique using scintillation cell based monitors were used to measure the 222Rn and 220Rn concentrations. These measured values were then fitted to appropriate model to extract the mass exhalation and emanation coefficients. The 222Rn mass exhalation rate varied from 0.7 ± 0.2 mBq kg−1 h−1 to 11.0 ± 0.9 mBq kg−1 h−1 while that of 220Rn varied from 88.5 ± 4.8 Bq kg−1 h−1 to 3066 ± 14 Bq kg−1 h−1. Higher mass exhalation rates, for both radioactive gases, were observed in finer grain size fractions. However, this was in contrast to the emanation coefficient values. Interestingly, higher radioactive monazite rich beach samples exhibited low emanation coefficient values compared to the low radioactive soil and sand samples reported in the literature. Statistical analysis showed a positive correlation, with correlation coefficient R = 0.84 and R = 0.79, respectively, between mass exhalation rates of 222Rn, 220Rn with their respective radioactive predecessors for different grain size fractions.
•This study throws light on the relative contribution of the monazite minerals to 222Rn and 220Rn release in the environment.•Monazite rich samples have a low emanation coefficient and are not the highest contributor of 222Rn and 220Rn to the environment.•Radon and thoron emanation coefficient was higher in 1000–500 μm grain size fractions, which contained the least 226Ra and 228Ra activity (Bq kg−1).•Unlike 226Ra and 228Ra activity concentrations, 222Rn and 220Rn emanation coefficient did not increase with the finer grain size; rather, the opposite trend was observed.•The statistically significant correlation coefficient substantiated the dependency of 220Rn mass exhalation rate (Bq kg−1 h−1) and 228Ra activity (Bq kg−1), also between 222Rn mass exhalation rate (mBq kg−1 h−1) and 226Ra activity (Bq kg−1).
The air exchange rate (AER) is a critical parameter that governs the levels of exposure to indoor pollutants impacting occupants’ health. It has been recognized as a crucial metric in spreading ...COVID-19 disease through airborne routes in shared indoor spaces. Assessing the AER in various human habitations is essential to combat such detrimental exposures. In this context, the development of techniques for the rapid determination of the AER has assumed importance. AER is generally determined using CO2 concentration decay data or other trace gas injection methods. We have developed a new method, referred to as the “222Rn incremented method”, in which 222Rn from naturally available soil gas was injected into the workplace for a short duration (∼30 min), homogenized and the profile of decrease of 222Rn concentration was monitored for about 2 h to evaluate AER. The method was validated against the established 222Rn time-series method. After ascertaining the suitability of the method, several experiments were performed to measure the AER under different indoor conditions. The AER values, thus determined, varied in a wide range of 0.36–4.8 h−1 depending upon the ventilation rate. The potential advantages of the technique developed in this study over conventional methods are discussed.
•A new method was developed for air exchange rate (AER) determination referred to as the “222Rn incremented method”.•Radon from natural soil gas was used as tracer in the method.•The method is user friendly and enables rapid determination of AER.•The 222Rn incremented method was validated against the 222Rn time-series method.•The new method has many advantages over conventional methods.
Thorium (232Th), long lived (14.05 billion years) most stable thorium isotope, is thrice naturally abundant than uranium. 232Th occurs as rocky deposits and black monazite sands on the earth's crust ...geographically distributed in coastal South India and other places globally. Monazite sand comprises of cerium and large quantities of radioactive thorium. The environmental hazard lies in monazite rich area being termed as High Background Radiation Area (HBRA). In this study, we mimicked the HBRA under controlled chamber conditions using thorium oxalate as a thorium source for BALB/c mice exposure. Furthermore, sequential radio-disintegration of 232 Th leads to thoron (220Rn), the noble gas and other daughter products/progeny predominantly via alpha decay/emissions. Such progeny tend to attach to aerosol and dust particles having potential inhalation hazard followed by alpha emissions and damages that we evaluated in mouse lung tissues post thoron inhalation. Secondly, along with the radio disintegration and alpha emission, high energy gamma is also generated that can travel to various distant organs through the systemic circulation, as significant findings of our study as damages to the liver and kidney. The mechanistic findings include the damages to the hematological, immunological and cellular antioxidant systems along with activation of canonical NF-κβ pathway via double stranded DNA damage.
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•Thorium toxicity ascertained via inhaled thorium progeny deposition & organ damage.•Inhaled thorium progeny induced systemic, as well as, lung inflammation.•Highest progeny mean equivalent dose deposition was observed in lungs.•Progeny toxicity altered haematological, immunological & antioxidant machinery.•Oxidative stress induced double stranded DNA damage following activation of NF-κβ pathway.
•Strong linkage between rock magnetic parameters and the instrumental rainfall data.•The cyclic variation of rainfall during the past 2100 years.•The strong coherence between rock magnetic data and ...Total Solar Irradiance (TSI).•Similarities with other paleoclimatic records in the region and teleconnection between different climatic systems.
The present study is aimed at understanding the sub-decadal to decadal scale variability of rainfall in southern India based on a sedimentary record (dated using AMS 14C, 210Pb, 137Cs methods) from Madagadakere lake (MK) situated in the foothills of the Western Ghats. A strong linkage between sediment magnetic signature and the instrumental rainfall record for the past 115 years demonstrates that the environmental magnetic proxies are useful and have greater applicability in the paleomonsoonal reconstructions. Fluctuations in the mineral magnetic, grain size, and geochemical parameters of the studied sediment profile revealed that pedogenic activity and terrigenous sediment flux to the lake varied cyclically during the Late Holocene period in response to varying intensities of rainfall. The region experienced higher or increasing trend of rainfall during periods 2100–1900, 1600–1250, 1050–925, 680–600, and 350–270 cal. years B.P., with low rainfall/decreasing trend during intervening periods. The spectral analysis of magnetic parameters revealed significant periodicities of 291, 164, 101, 54, 48, 44, 41, 39, 105, 48, and 41 years, which are very well documented in other paleoclimatic records, and whose origin is ascribed unequivocally to variation in Total Solar Irradiance (TSI). We propose that the periods of higher values for concentration-dependent magnetic parameters (higher rainfall) can be attributed to the timings of the increased TSI, positive mode of Indian Ocean Dipole (IOD), northward migration of Intertropical convergence zone (ITCZ) and weakened El-Niño southern oscillation (ENSO) activity in the region, establishing the teleconnection between different climatic systems.
A walk-in type 222Rn calibration chamber of volume 22.7 m3, which has traceability to international standards, is established at the Centre for Advanced Research in Environmental Radioactivity, ...Mangalore University, India. It has a human-machine interface communication system, a programmable logic controller and sensor feedback circuit for controlling and data acquisition of relative humidity (RH) and temperature (T). An innovative method for the generation of desired 222Rn concentration (a few hundred Bq m-3 up to about 36 kBq m-3) using soil gas as a source was adopted. Leak rates of 222Rn from the chamber for the mixing fan ON and OFF conditions were determined to be 0.0011 and 0.00018 h-1 respectively. With the exhaust system fully turned on, the maximum clearance rate of the chamber was 0.58 ± 0.07 h-1. Excellent spatial uniformity in 222Rn concentration in the chamber was confirmed (with a mean value of relative standard deviation < 12%) through measurements at 23 locations using CR-39 film-based passive devices. Demonstration of calibration applications was performed using charcoal canister and PicoRad vials as the 222Rn adsorption devices. The study shows that gamma spectrometry is a convenient alternative approach to liquid scintillation analysis of PicoRad vials for 222Rn measurement.
Detailed studies were carried out to establish site-specific soil to grass transfer factors (Fv) and grass to cow milk transfer coefficients (Fm) for radioactive cesium (137Cs) and stable cesium (Cs) ...for Kaiga region, where a nuclear power station has been in operation for more than 10 years. The study included adopted cows, cows of local farmers, and cows from the dairy farm. A grass field was developed specifically for the study and 2 local breed cows were adopted and allowed to graze in this grass field. The soil and grass samples were collected regularly from this field and analyzed for the concentrations of 137Cs and stable Cs to evaluate the soil to grass Fv values. The milk samples from the adopted cows were analyzed for the 137Cs and stable Cs concentrations to evaluate Fm values. For comparison, studies were also carried out in dominant grazing areas in different villages around the nuclear power plant and the cows of local farmers which graze in these areas were identified and milk samples were collected and analyzed regularly. The geometric mean values of Fv were found to be 1.1 × 10−1 and 1.8 × 10−1 for 137Cs and stable Cs, respectively. The Fm of 137Cs had geometric mean values of 1.9 × 10−2 d L−1 and 4.6 × 10−2 d L−1, respectively, for adopted Cows 1 and 2; 1.7 × 10−2 d L−1 for the cows of local farmers, and 4.0 × 10−3 d L−1 for the dairy farm cows. The geometric mean values of Fm for stable Cs were similar to those of 137Cs. The Fm value for the dairy farm cows was an order of magnitude lower than those for local breed cows. The Fm values observed for the local breed cows were also an order of magnitude higher when compared to the many values reported in the literature and in the IAEA publication. Possible reasons for this higher Fm values were identified. The correlation between Fv and Fm values for 137Cs and stable Cs and their dependence on the potassium content (40K and stable K) in the soil and grass were also studied. In order to estimate the ingestion dose accurate data of the dietary habits of the population was necessary and this data was collected through a well planned demographic survey. The internal doses to a child due to the ingestion of 137Cs along with the milk of the local cows and from the dairy farm were found to be 0.29 μSv y−1 and 0.04 μSv y−1,while that to an adult were 0.39 μSv y−1 and 0.05 μSv y−1, respectively.
•This is a detailed study on Fv and Fm for 137Cs and stable Cs around the Kaiga nuclear power plant, India.•The geometric mean values of Fv were found to be 1.1 × 10−1 and 1.8 × 10−1 for 137Cs and stable Cs, respectively.•The Fm value for 137Cs for the local breed cows was estimated to be 2.4 × 10−2 d L−1.•The Fm value for dairy farm cows (4.0 × 10−3 d L−1) was an order of magnitude lower than those for local breed cows.•The reasons for the higher Fm values for 137Cs for the local breed cows are identified.
Radon (222Rn), thoron (220Rn), and their decay products contribute a major fraction (more than 50%) of doses received from ionisation radiation in public domain indoor environments and occupation ...environments such as uranium mines, thorium plants, and underground facilities, and are recognised as important radiological hazardous materials, which need to be controlled. This paper presents studies on the removal of 222Rn and 220Rn from air using coconut shell-based granular activated charcoal cylindrical adsorber beds. Experiments were conducted to evaluate the 222Rn and 220Rn adsorption characteristics, and the mitigation efficiency of coconut-based activated charcoal available in India. The performance parameters evaluated include breakthrough time (τ) and adsorption coefficient (K), and degassing characteristics of the charcoal bed of varying dimensions at different flow rates. While the breakthrough for 222Rn occurred depending on the dimension of the adsorber bed and flow rates, for 220Rn, the breakthrough did not occur. The breakthrough curve exhibited a stretched S-shape response, instead of the theoretically predicted sharp step function. The experiments confirm that the breakthrough time individually satisfies the quadratic relationship with respect to the diameter of the bed, and the linear relationship with respect to the length, as predicted in the theory. The K value varied in the range of 2.3–4.12 m3 kg−1 with a mean value of 2.99 m3 kg−1. The K value was found to increase with the increase in flow rate. Heating the charcoal to ∼100 °C resulted in degassing of the adsorbed 222Rn, and the K of the degassed charcoal and virgin charcoal were found to be similar with no deterioration in performance indicating the re-usability of the charcoal.
•222Rn and 220Rn removal from air using activated charcoal bed is demonstrated.•Breakthrough time and adsorption coefficient were evaluated.•A sustained mitigation factor exceeding 105 was demonstrated for 220Rn.•Degassing characteristics excellently demonstrate the reusability of charcoal.•Results would find application in designing 220Rn mitigation systems for workplaces.
Abstract
The paper describes a novel technique to harvest
222
Rn laden air from soil gas of natural origin as a highly efficient source of
222
Rn for calibration applications in a walk-in type
222
Rn ...calibration chamber. The technique makes use of a soil probe of about 1 m to draw soil gas, through a dehumidifier and a delay volume, using an air pump to fill the calibration chamber.
222
Rn concentration in the range of a few hundred Bq m
−3
to a few tens of kBq m
−3
was easily attained in the chamber of volume 22.7 m
3
within a short pumping duration of 1 h. A new technique referred to as “semi-dynamic mode of operation” in which soil gas is injected into the calibration chamber at regular intervals to compensate for the loss of
222
Rn due to decay and leak is discussed. Harvesting soil gas has many important advantages over the traditional methods of
222
Rn generation for calibration experiments using finite sources such as solid flow-through, powdered emanation, and liquid sources. They are: (1) soil gas serves as an instantaneous natural source of
222
Rn, very convenient to use unlike the high strength
226
Ra sources used in the calibration laboratories, and has no radiation safety issues, (2) does not require licensing from the regulatory authority, and (3) it can be used continuously as a non-depleting reservoir of
222
Rn, unlike other finite sources. The newly developed technique would eliminate the need for expensive radioactive sources and thereby offers immense application in a variety of day to day experiments—both in students and research laboratories.
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