Multiple environmental factors influence 238U, 232Th and 226Ra bioaccumulation in arbuscular mycorrhizal-associated plants

Ecological consequences of low-dose radioactivity from natural sources or radioactive waste are important to understand but knowledge gaps still remain. In particular, the soil transfer and bioaccumulation of radionuclides into plant roots is poorly studied. Furthermore, better knowledge of arbuscular mycorrhizal (AM) fungi association may help understand the complexities of radionuclide bioaccumulation within the rhizosphere. Plant bioaccumulation of uranium, thorium and radium was demonstrated at two field sites, where plant tissue concentrations reached up to 46.93 μg g^{-1 238}U, 0.67 μg g^{-1 232}Th and 18.27 kBq kg^{-1 226}Ra. High root retention of uranium was consistent in all plant species studied. In contrast, most plants showed greater bioaccumulation of thorium and radium into above-ground tissues. The influence of specific soil parameters on root radionuclide bioaccumulation was examined. Total organic carbon significantly explained the variation in root uranium concentration, while other soil factors including copper concentration, magnesium concentration and pH significantly correlated with root concentrations of uranium, radium and thorium, respectively. All four orders of Glomeromycota were associated with root samples from both sites and all plant species studied showed varying association with AM fungi, ranging from zero to >60% root colonisation by fungal arbuscules. Previous laboratory studies using single plant-fungal species association had found a positive role of AM fungi in root uranium transfer, but no significant correlation between the amount of fungal infection and root uranium content in the field samples was found here. However, there was a significant negative correlation between AM fungal infection and radium accumulation. This study is the first to examine the role of AM fungi in radionuclide soil-plant transfer at a community level within the natural environment. We conclude that biotic factors alongside various abiotic factors influence the soil-plant transfer of radionuclides and future mechanistic studies are needed to explain these interactions in more detail.

Soil radon gas in some soil types in the rainy season in Ho Chi Minh City, Vietnam

Field experiments on soil radon and radium concentrations were carried out in eighteen locations in Ho Chi Minh City, Vietnam. Soil radon depth profiles (10-100 cm) of loam, sand and clay soil samples in the rainy season were measured using RAD7 radon detector. Mean concentrations of ²²²Rn and ²²⁶Ra were found to be 28.6 ± 2.0 Bq.kg^-1 and (1.56 ± 0.06) × 10⁴ Bq.m^-3 in clay soil while they are 31.2 ± 2.5 Bq.kg^-1 and (1.15 ± 0.05) × 10⁴ Bq.m^-3 in loam soil. They are 30.7 ± 2.0 Bq.kg^-1 and (9.37 ± 0.52) × 10³ Bq.m^-3 in sandy soil, respectively. Values of radon diffusion length and diffusion coefficient for different soils were obtained using semi-empirical fit method linked to the poor diffusion of gas in clay soil (0.2 × 10^-6 m² s^-1), the moderate diffusion coefficient (0.9 × 10^-6 m² s^-1) in loam and good diffusion of radon gas in sandy soil (1.4 × 10^-6 m² s^-1). An unexpectedly unclear linear relation was found between soil radon concentration and radium content. The grain size smaller than 0.1 mm was dominant reason for the lowest (0.15 ± 0.01) and highest (0.40 ± 0.03) values emanation coefficient for sand and clay soil, respectively. A strong positive correlation was found between radon concentration and soil pH level leads to soil pH is an indirect dynamic parameter affecting the migration of radon in soil.

Influence of soil conditions on the distribution coefficients of 226Ra in natural soils

In order to clarify some of the assumptions and approximations about the use of the distribution coefficient K_d for ²²⁶Ra in soils, a systematic study has been performed using centrifugation to extract the soil solution. The separated fractions of the soil solution have different kinetics with respect to the sorption process in the soil, which may in turn condition the final chemical composition and even the speciation of the radionuclides in solution. In the experimental design of this study three factors were considered: the moisture level in the incubation process, incubation time and the speed of centrifugation. Also, three levels were chosen for each factor. In order to analyze the influence of the structural characteristics of the soil, this study was performed with three textural fractions: coarse sand, fine sand, and silt and clay, obtained from an only soil. Also, the soil was naturally enriched with radionuclides of the ²³⁸U series. An analysis of variance (ANOVA) was performed in order to assess the influence of the factors studied on the distribution coefficient of ²²⁶Ra. The results indicate that different behaviors can be observed depending on the structural characteristic of the soil. In the case of particle size, the soil with the largest grain size showed that the incubation process parameters influence the equilibrium level achieved, while in the case of the smallest edaphic particles, radium is not homogeneously distributed in the soil solution and the K_d value is dependent on the speed of centrifugation.

Radium geochemical monitoring in well waters at regional and local scales: an environmental impact indicator-based approach

To assess radium (²²⁶Ra) as a potential indicator of impact in well waters, we investigated its behavior under natural conditions using a case study approach. ²²⁶Ra geochemistry was investigated in 67 private wells of southeastern New Brunswick, Canada, a region targeted for potential shale gas exploitation. Objectives were to i) establish ²²⁶Ra baseline in groundwater; ii) characterize ²²⁶Ra spatial distribution and temporal variability; iii) characterize ²²⁶Ra partitioning between dissolved phase and particulate forms in well waters; and iv) understand the mechanisms controlling ²²⁶Ra mobility under natural environmental settings. ²²⁶Ra levels were generally low (median = 0.061 pg L^-1, or 2.2 mBq L^-1), stable over time, and randomly distributed. A principal component analysis revealed that concentrations of ²²⁶Ra were controlled by key water geochemistry factors: the highest levels were observed in waters with high hardness, and/or high concentrations of individual alkaline earth elements (i.e. Mg, Ca, Sr, Ba), high concentrations of Mn and Fe, and low pH. As for partitioning, ²²⁶Ra was essentially observed in the dissolved phase (106 ± 19%) suggesting that the geochemical conditions of groundwater in the studied regions are prone to limit ²²⁶Ra sorption, enhancing its mobility. Overall, this study provided comprehensive knowledge on ²²⁶Ra background distribution at local and regional scales. Moreover, it provided a framework to establish ²²⁶Ra baselines and determine which geochemical conditions to monitor in well waters in order to use this radionuclide as an indicator of environmental impact caused by anthropogenic activities (e.g. unconventional shale gas exploitation, uranium mining, or nuclear generating power plants).

223Ra-Dichloride in castration-resistant metastatic prostate cancer: improving outcomes and identifying predictors of survival in clinical practice

Purpose

We first assessed whether the pattern of referrals to a nuclear medicine clinic improved as experience with ²²³Ra-dichloride increased, and whether referral patterns affected patient outcomes, and second assessed the value of bone scintigraphy, total alkaline phosphatase (tALP) and lymphadenopathy as prognostic factors in patients receiving ²²³Ra-dichloride.

Methods

A total of 57 patients eligible to receive ²²³Ra-dichloride over a 2-year period (March 2014 to March 2016) were retrospectively assessed and prospectively followed (median follow up 298 days). ²²³Ra-Dichloride was administered at 4-week intervals for a maximum of six injections. The numbers of patients in years 1 and 2 referred in relation to extent of bone disease (EOBD) category and overall survival (OS) were determined. The prognostic factors EOBD category, baseline tALP (tALP_BL), tALP response, greatest percentage reduction in tALP from baseline in any treatment cycle (ALP_max; among patients with elevated ALP_BL), and the presence of lymphadenopathy were assessed as predictors of OS.

Results

The proportion of patients with EOBD1 was higher in year 2 than in year 1 (29% and 4%, respectively), and in year 2 there was a lower rate of symptomatic skeleton-related events, a higher proportion of patients completing six cycles, and longer (albeit nonsignificant) OS (p = 0.55). There were significant differences in OS between EOBD4 patients and those in all other groups and between EOBD1 and EOBD3 patients (p < 0.05). OS was longer in patients with normal tALP_BL than in those with elevated tALP_BL (p = 0.01), in ALP responders than in nonresponders (p < 0.05), and in patients without lymphadenopathy than in those with lymphadenopathy (p = 0.29). OS was correlated with ALP_max (r² = 0.24).

Conclusion

A collaborative multidisciplinary referrals pathway, together with increased experience with ²²³Ra-dichloride, led to improved outcomes. In patients with elevated tALP_BL, tALP dynamics may be useful for monitoring response and predicting OS. Imaging and prognostic markers may therefore be of value for individualizing ²²³Ra-dichloride treatment and planning retreatment; however, further studies are required.

Chemical reactivity of natural peat towards U and Ra

Peat is a complex material with several organic constituents that contribute to its high capacity to retain metals. In the context of uranium mining, peat can accumulate high concentrations of uranium and its decay products such as radium. Hence, interaction with peat appears to be a key factor in the understanding of the geochemical mechanisms controlling the fate of these products. This study aims to determine the sorption properties of two trace elements, U(VI) and ²²⁶Ra, on natural organic matter from peat. The presented method was applied to both natural peat samples originating from a mining context, with various contents of organic matter (from 40 to 70%) and detrital loads, and wetland peat with a more than 98% composition of organic matter. In the present study, considering peat material as a sorbent, its reactivity towards metals and other contaminants can be described as that of an ion-exchanger. A relatively simple model of ion-exchange based on the sorption properties of carboxylic sites has been applied with success to describe the sorption of uranium and radium. In the general overview of the different mechanisms able to control the mobility of these radionuclides in a uranium mining context, organic matter is likely one of the main contributors to radionuclide scavenging even under oxic conditions.

Radium and other alpha emitters in prostate cancer

²²³Radium (²²³Ra) is the first alpha-emitting therapy proven effective in human cancer. Prospective randomized trials indicate that ²²³Ra, which concentrates after intravenous injection in areas of osteoblastic metastatic disease, can prolong survival in bone-dominant castrate resistant prostate cancer patients. Though radium isotopic therapy is conceptually critical to demonstrate that alpha emitters can be safe and effective, ²²³Ra has inherent limitations given its restriction to bone metastatic disease. To overcome this limitation, targeted alpha therapy (TAT) is now being actively evaluated in prostate cancer, and other neoplasms. Key to TAT in prostate tumors in current studies is the overexpression of prostate specific membrane antigen (PSMA), a folate hydrolase expressed on the cell surface of malignant adenocarcinomas of the prostate. Using PSMA targeting (small molecules or antibodies), alpha emitting agents such as ²²⁵Actinium (²²⁵Ac) or ²¹³Bismuth (²¹³Bi) can be delivered to PSMA expressing tumors regardless of their metastatic location. Initial results from TAT in prostate cancer are highly promising and rapid development of these agents is anticipated in the years ahead assuming adequacy of isotope availability and appropriate clinical trial design. TAT may be develop as an independent approach, or synergize with a variety of other approaches including external beam radiation, hormonal therapies, chemotherapies, various radiation sensitizers, DNA repair inhibitors, and/or immune modulators. Clinical investigation opportunities in this field will rapidly increase in the years ahead.

Lingering radioactivity at the Bikini and Enewetak Atolls

We made an assessment of the levels of radionuclides in the ocean waters, seafloor and groundwater at Bikini and Enewetak Atolls where the US conducted nuclear weapons tests in the 1940's and 50's. This included the first estimates of submarine groundwater discharge (SGD) derived from radium isotopes that can be used here to calculate radionuclide fluxes in to the lagoon waters. While there is significant variability between sites and sample types, levels of plutonium (^239,240Pu) remain several orders of magnitude higher in lagoon seawater and sediments than what is found in rest of the world's oceans. In contrast, levels of cesium-137 (¹³⁷Cs) while relatively elevated in brackish groundwater are only slightly higher in the lagoon water relative to North Pacific surface waters. Of special interest was the Runit dome, a nuclear waste repository created in the 1970's within the Enewetak Atoll. Low seawater ratios of ²⁴⁰Pu/²³⁹Pu suggest that this area is the source of about half of the Pu in the Enewetak lagoon water column, yet radium isotopes suggest that SGD from below the dome is not a significant Pu source. SGD fluxes of Pu and Cs at Bikini were also relatively low. Thus radioactivity associated with seafloor sediments remains the largest source and long term repository for radioactive contamination. Overall, Bikini and Enewetak Atolls are an ongoing source of Pu and Cs to the North Pacific, but at annual rates that are orders of magnitude smaller than delivered via close-in fallout to the same area.

Spatial variations of 226Ra, 228Ra, 134Cs, and 137Cs concentrations in western and southern waters off the Korean Peninsula in July 2014

We examined the spatial distributions of ²²⁶Ra, ²²⁸Ra, ¹³⁴Cs, and ¹³⁷Cs concentrations (activities) in seawater off the western and southern Korean Peninsula in July 2014. Radium-228 (and ²²⁶Ra) concentrations in water samples varied widely from 5 to 14 mBq/L (2-4 mBq/L), showing a negative correlation with salinity, particularly at the surface off the western Korean Peninsula. This indicates that the seawaters in this area are fundamentally comprised of ²²⁸Ra-poor and high-saline Kuroshio Current water and ²²⁸Ra-rich and low-saline water (e.g., continental shelf water), with various mixing ratios. Although Fukushima Dai-ichi Nuclear Power Plant (FDNPP)-derived ¹³⁴Cs was below the detection limit (<0.08 mBq/L) in waters off the western Korean Peninsula, low level ¹³⁴Cs (0.1-0.2 mBq/L) was detected in waters off the southern Korean Peninsula accompanied by higher ¹³⁷Cs concentrations (1.6-1.9 mBq/L) relative to that off the western Korean Peninsula. Combined with the lower radium concentrations, the detection of ¹³⁴Cs is explained by mixing of FDNPP-derived radiocesium-contaminated Kuroshio Current water.

Geological and hydrogeochemical controls on radium isotopes in groundwater of the Sinai Peninsula, Egypt

Radium isotopes (²²⁶Ra and ²²⁸Ra) were analyzed in 18 groundwater samples from the Nubian Sandstone Aquifer System (NSAS) and the shallow alluvial aquifers overlying the basement complex of the Sinai Peninsula, Egypt. Groundwater samples from deep Nubian aquifer wells (total depths 747 to 1250m) have ²²⁶Ra and ²²⁸Ra activities ranging from 0.168 to 0.802 and 0.056 to 1.032Bq/L, respectively. The shallower Nubian aquifer wells (63 to 366m) have ²²⁶Ra and ²²⁸Ra activities ranging from 0.033 to 0.191 and 0.029 to 0.312Bq/L, respectively. The basement shallow alluvial aquifers have ²²⁶Ra and ²²⁸Ra activities ranging from 0.014 to 0.038 and 0.007 to 0.051Bq/L, respectively. Combined Ra activities in most wells were generally in excess of the US Environmental Protection Agency (EPA), the European Union (EU), and the World Health Organization (WHO) maximum contaminant levels (MCL) for drinking water. Radium in groundwater is produced mainly by decay of parent nuclides in the aquifer solids, and observed activities of dissolved Ra isotopes result from a combination of alpha-recoil, adsorption/desorption, co-precipitation/dissolution processes. The observed correlation between Ra activities and salinity indicates that adsorption/desorption processes may be the dominant factor controlling Ra mobility in Sinai groundwater. Radium activities in central and northern Sinai are generally higher than those in southern Sinai, consistent with a gradual increase in salinity and water-rock interaction with increasing groundwater age. Barite is approximately saturated in the groundwater and may limit maximum dissolved Ra concentration. The results of this study indicate that Sinai groundwater should be used with caution, possibly requiring Ra removal from water produced for domestic and agricultural consumption.

Radionuclides as natural tracers of the interaction between groundwater and surface water in the River Andarax, Spain

The identification of specific aquifers that supply water to river systems is fundamental to understanding the dynamics of the rivers' hydrochemistry, particularly in arid and semiarid environments where river flow may be discontinuous. There are multiple methods to identify the source of river water. In this study of the River Andarax, in the Southeast of Spain, an analysis of natural tracers (physico-chemical parameters, uranium, radium and radon) in surface water and groundwater indicates that chemical parameters and uranium clearly identify the areas where there is groundwater-surface water interaction. The concentration of uranium found in the river defines two areas: the headwaters with U concentrations of 2 μg L^-1 and the lower reaches, with U of 6 μg L^-1. Furthermore, variation in the ²³⁴U/²³⁸U isotopic ratio allowed us to detect the influence that groundwater from the carbonate aquifer has on surface water in the headwaters of the river, where the saline content is lower and the water has a calcium bicarbonate facies. The concentration of ²²⁶Ra and ²²²Rn are low in the surface waters: <1.6 × 10^-6 μg L^-1 and <5.1 × 10^-12 μg L^-1, respectively. There is a slight increase in the lower reaches where the water has a permanent flow, greater salinity and a calcium-magnesium-sulphate facies. All this is favoured by the influence of groundwater from the detritic aquifer on the surface waters. The results of this study indicate the utility in the use of physico-chemical and radiological data conjointly as tracers of groundwater-surface water interaction in semiarid areas where the lithology of aquifers is diverse (carbonate and detritic) and where evaporitic rocks are present.

Applications of radon and radium isotopes to determine submarine groundwater discharge and flushing times in Todos os Santos Bay, Brazil

Todos os Santos Bay (BTS) is the 2nd largest bay in Brazil and an important resource for the people of the State of Bahia. We made measurements of radon and radium in selected areas of the bay to evaluate if these tracers could provide estimates of submarine groundwater discharge (SGD) and flushing times of the Paraguaçu Estuary and BTS. We found that there were a few areas along the eastern and northeastern shorelines that displayed relatively high radon and low salinities, indicating possible sites of enhanced SGD. A time-series mooring over a tidal cycle at Marina do Bonfim showed a systematic enrichment of the short-lived radium isotopes ²²³Ra and ²²⁴Ra during the falling tide. Assuming that the elevated radium isotopes were related to SGD and using measured radium activities from a shallow well at the site, we estimated groundwater seepage at about 70 m³/day per unit width of shoreline. Extrapolating to an estimated total shoreline length provided a first approximation of total (fresh + saline) SGD into BTS of 300 m³/s, about 3 times the average river discharge into the bay. Just applying the shoreline lengths from areas identified with high radon and reduced salinity results in a lower SGD estimate of 20 m³/s. Flushing times of the Paraguaçu Estuary were estimated at about 3-4 days based on changing radium isotope ratios from low to high salinities. The flushing time for the entire BTS was also attempted using the same approach and resulted in a surprisingly low value of only 6-8 days. Although physical oceanographic models have proposed flushing times on the order of months, a simple tidal prism calculation provided results in the range of 4-7 days, consistent with the radium approach. Based on these initial results, we recommend a strategy for refining both SGD and flushing time estimates.

Constraining the temporal variations of Ra isotopes and Rn in the groundwater end-member: Implications for derived SGD estimates

Submarine groundwater discharge (SGD) has been recognized as an important supplier of chemical compounds to the ocean that may influence coastal geochemical cycles. Radium isotopes (²²³Ra, ²²⁴Ra, ²²⁶Ra_,²²⁸Ra) and radon (²²²Rn) have been widely applied as tracers of SGD. Their application requires the appropriate characterization of both the concentrations of tracers in the discharging groundwater and their distribution in the coastal water column. This study evaluates the temporal evolution of Ra isotopes and ²²²Rn concentrations in a dynamic subterranean estuary of a microtidal Mediterranean coastal aquifer that experiences large displacements of the fresh-saltwater interface as a necessary initial step in evaluating the influence of SGD in coastal waters. We show that changes in groundwater salinities due to the seaward displacement of the fresh-saltwater interface produced large variations in Ra activities in groundwater (by a factor of ~19, ~14, ~6, and ~11 for ²²³Ra, ²²⁴Ra, ²²⁶Ra and ²²⁸Ra, respectively), most importantly during rainfall events. In contrast, the ²²²Rn activities in groundwater oscillated only by a factor of 3 during these rainy periods. The large temporal variability in Ra activities hampers the characterization of the SGD end-member when using Ra isotopes as tracers, and thus presents a challenge for obtaining accurate SGD estimates. This study emphasizes the need to understand the hydrodynamics of coastal aquifers to appropriately constrain the Ra isotopes and ²²²Rn concentrations in groundwater and when applying both tracers in dynamic microtidal coastal systems.

The potential of 223Ra and 18F-fluoride imaging to predict bone lesion response to treatment with 223Ra-dichloride in castration-resistant prostate cancer

PURPOSE

The aims of this study were to calculate bone lesion absorbed doses resulting from a weight-based administration of 223Ra-dichloride, to assess the relationship between those doses and corresponding 18F-fluoride uptake and to assess the potential of quantitative 18F-fluoride imaging to predict response to treatment.

METHODS

Five patients received two intravenous injections of 223Ra-dichloride, 6 weeks apart, at 110 kBq/kg whole-body weight. The biodistribution of 223Ra in metastatic lesions as a function of time after administration as well as associated lesion dosimetry were determined from serial 223Ra scans. PET/CT imaging using 18F-fluoride was performed prior to the first treatment (baseline), and at week 6 immediately before the second treatment and at week 12 after baseline.

RESULTS

Absorbed doses to metastatic bone lesions ranged from 0.6 Gy to 44.1 Gy. For individual patients, there was an average factor difference of 5.3 (range 2.5-11.0) between the maximum and minimum lesion dose. A relationship between lesion-absorbed doses and serial changes in 18F-fluoride uptake was demonstrated (r2 = 0.52). A log-linear relationship was demonstrated (r2 = 0.77) between baseline measurements of 18F-fluoride uptake prior to 223Ra-dichloride therapy and changes in uptake 12 weeks after the first cycle of therapy. Correlations were also observed between both 223Ra and 18F-fluoride uptake in lesions (r = 0.75) as well as between 223Ra absorbed dose and 18F-fluoride uptake (r = 0.96).

CONCLUSIONS

There is both inter-patient and intra-patient heterogeneity of absorbed dose estimates to metastatic lesions. A relationship between 223Ra lesion absorbed dose and subsequent lesion response was observed. Analysis of this small group of patients suggests that baseline uptake of 18F-fluoride in bone metastases is significantly correlated with corresponding uptake of 223Ra, the associated 223Ra absorbed dose and subsequent lesion response to treatment.

Influence of chronic low-dose/dose-rate high-LET irradiation from radium-226 in a human colorectal carcinoma cell line

PURPOSE

To evaluate potential damages of chronic environmentally relevant low-dose/dose-rate high-LET irradiation from a naturally occurring alpha-emitting radionuclide (radium-226, ²²⁶Ra) on a human colorectal carcinoma HCT116 p53^+/+ cell line.

METHODS

Clonogenic survival assays and mitochondrial membrane potential (MMP) measurement with a sensitive fluorescent MMP probe JC-1 were performed in HCT116 p53^+/+ cells chronically exposure to low doses/dose rates of ²²⁶Ra with high-LET. Comparisons were made with the human non-transformed keratinocyte HaCaT cell line and acute low-dose direct low-LET gamma radiation.

RESULTS AND CONCLUSION

The chronic low-dose/dose-rate alpha radiation (CLD/DRAR) did not reduce the clonogenic survival of HCT116 p53^+/+ cells over the period of 70 days of exposure. Only one significant reduction in the HCT116 p53^+/+ cells' clonogenic survival was when cells were grown with 10,000mBq/mL ²²⁶Ra for 40 days and progeny cells were clonogenically assessed in the presence of 10,000mBq/mL ²²⁶Ra. The cumulative doses that cells received during this period ranged from 0.05 to 46.2mGy. The mitochondrial membrane potential (MMP) dropped initially in both HCT116 p53^+/+ and HaCaT cells in response to CLD/DRAR. The MMP in HCT116 p53^+/+ cells recovered more quickly at all dose points than and that in HaCaT cells until the end of the exposure period. The highest dose rate of 0.66mGy/day depolarized the HaCaT's mitochondria more consistently during the exposure period. The faster recovery status of the MMP in HCT116 p53^+/+ cells than that in HaCaT cells was also observed after exposure to acute low-dose gamma rays. Overall, it was found that CLD/DRAR had little impact on the MMP of human colorectal cancer and keratinocyte cell lines.

Natural radionuclide dose and lifetime cancer risk due to ingestion of fish and water from fresh water reservoirs near the proposed uranium mining site

Ten sampling locations in Nagarjuna Sagar Dam have been selected to assess the suitability of the reservoir water for human consumption. The sediment, water, and fish samples were collected and analyzed for radionuclide (²³⁸U, ²³²Th, ²¹⁰Po, ²²⁶Ra, ²¹⁰Pb) and physicochemical parameters like pH, TOC, total hardness, alkalinity, DO, cation exchange capacity, and particle size. The spatial variations among the radionuclides (²³⁸U, ²³²Th, ²¹⁰Po, ²²⁶Ra, ²¹⁰Pb) in water and bottom sediments of Nagarjuna Sagar Dam were determined. The uranium concentration in the sediment and water was in BDL (<0.5 ppb). The maximum permissible limits in water samples of the analyzed radionuclides are ²³⁸U-10 Bq/l, ²¹⁰Po-0.1 Bq/l, ²²⁶Ra-1 Bq/l, and ²¹⁰Pb-0.1 Bq/l. The radionuclides in our water samples were approximately 50 times far below the recommended limit. The ingestion of water and fish would not pose any significant radiological impact on health or cancer risk to the public, implicating that the fishes from Nagarjuna Sagar Dam reservoir are safe for human consumption except the fisherman community.

Influence of soil structure on the "Fv approach" applied to 238U and 226Ra

The soil-to-plant transfer factors were determined in a granitic area for the two long-lived uranium series radionuclides ²³⁸U and ²²⁶Ra. With the aim to identify a physical fraction of soil whose concentration correlates linearly with the plant concentration, the soil compartment was analyzed in various stages. An initial study identified the soil compartments as being either bulk soil or its labile fraction. The bulk soil was subsequently divided into three granulometric fractions consisting of: coarse sand, fine sand, and silt and clay. The soil-to-plant transfer of radionuclides for each of these three texture fractions was analyzed. Lastly, the labile fraction was extracted from each textural part, and the activity concentration of the radionuclides ²³⁸U and ²²⁶Ra was measured. In order to assess the influence of soil texture on the soil-to-plant transfer process, we sought to identify possible correlations between the activity concentration in the plant compartment and those found in the different fractions within each soil compartment. The results showed that the soil-to-plant transfer process for uranium and radium depends on soil grain size, where the results for uranium showed a linear relationship between the activity concentration of uranium in the plant and the fine soil fraction. In contrast, a linear relation between the activity concentration of radium in the plant and the soil coarse-sand fraction was observed. Additionally, the presence of phosphate and calcium in the soil of all of the compartments studied affected the soil-to-plant transfer of uranium and radium, respectively.

Nasopharyngeal radium irradiation: The lessons of history

In the Netherlands, nasopharyngeal radium irradiation was started in 1945. The indications included refractory symptoms of otitis media with effusion and other adenoid-related disorders after adenoidectomy. It was considered a safe and effective therapy. Its use decreased sharply in 1958, following a worldwide media avalanche around the dramatic events in the treatment of a 5-year-old child in Utrecht, enhancing the widespread fear of radioactivity. This case history illustrates the powerful role of the media in medical decision-making.

Radon in the soil air of Estonia

Several investigations in Estonia during 1996¬-1999 have shown that permissible level (200 Bq/m³) of radon (222Rn) in indoor air is exceeded in 33% of the inspected dwellings. This makes Estonia one of the five countries with highest radon risk in Europe (Fig 1). Due to correlation between the soil radon risk level and radon concentration in houses, small scale radon risk mapping of soil air was carried out (one study point per 70-100 km²). It turned out that one-third of Estonian mainland has high radon risk potential, where radon concentration in soil air exceeds safe limit of 50 kBq/m³. In order to estimate radon content in soil air, two different methods developed in Sweden were used simultaneously. Besides measuring radon content from soil air at the depth of 80 cm with an emanometer (RnM), maximum potential content of radon in soil (RnG) was estimated based on the rate of eU (226Ra) concentration in soil, which was acquired by using gamma-ray spectrometer. Mapping and following studies revealed that simultaneously measured RnG and RnM in study points may often differ. To inspect the cause, several monitoring points were set up in places with different geological conditions. It appeared that unlike the RnG content, which remains close to average level in repeated measurements, the RnM content may differ more than three times periodically. After continuous observations it turned out that concentration of directly measured radon depended on various factors being mostly controlled by mineral composition of soil, properties of topsoil as well as different factors influencing aeration of soil. The results of Rn monitoring show that reliable level of radon risk in Estonian soils can only be acquired by using calculated Rn-concentration in soil air based on eU content and directly measured radon content of soil air in combination with interpreting specific geological and geochemical situations in the study points.

Removal naturally occurring radionuclides from drinking water using a filter specifically designed for Drinking Water Treatment Plants

The occurrence of naturally occurring radionuclides in drinking water can pose health hazards in some populations, especially taking into account that routine procedures in Drinking Water Treatment Plants (DWTPs) are normally unable to remove them efficiently from drinking water. In fact, these procedures are practically transparent to them, and in particular to radium. In this paper, the characterization and capabilities of a patented filter designed to remove radium from drinking water with high efficiency is described. This filter is based on a sandwich structure of silica and green sand, with a natural high content manganese oxide. Both sands are authorized by Spanish authorities to be used in Drinking Water Treatment Plants. The Mn distribution in the green sand was found to be homogenous, thus providing a great number of adsorption sites for radium. Kinetic studies showed that the ²²⁶Ra adsorption on green sand was influenced by the content of major cations solved in the treated water, but the saturation level, about 96-99%, was not affected by it. The physico-chemical parameters of the treated water were unaltered by the filter. The efficiency of the filter for the removal of ²²⁶Ra remained unchanged with large water volumes passed through it, proving its potential use in DWTP. This filter was also able to remove initially the uranium content due to the presence of Fe₂O₃ particles in it, although it is saturated faster than radium.

Radionuclides: Accumulation and Transport in Plants

Application of radioactive elements or radionuclides for anthropogenic use is a widespread phenomenon nowadays. Radionuclides undergo radioactive decays releasing ionizing radiation like gamma ray(s) and/or alpha or beta particles that can displace electrons in the living matter (like in DNA) and disturb its function. Radionuclides are highly hazardous pollutants of considerable impact on the environment, food chain and human health. Cleaning up of the contaminated environment through plants is a promising technology where the rhizosphere may play an important role. Plants belonging to the families of Brassicaceae, Papilionaceae, Caryophyllaceae, Poaceae, and Asteraceae are most important in this respect and offer the largest potential for heavy metal phytoremediation. Plants like Lactuca sativa L., Silybum marianum Gaertn., Centaurea cyanus L., Carthamus tinctorius L., Helianthus annuus and H. tuberosus are also important plants for heavy metal phytoremediation. However, transfer factors (TF) of radionuclide from soil/water to plant ([Radionuclide]plant/[Radionuclide]soil) vary widely in different plants. Rhizosphere, rhizobacteria and varied metal transporters like NRAMP, ZIP families CDF, ATPases (HMAs) family like P1B-ATPases, are involved in the radio-phytoremediation processes. This review will discuss recent advancements and potential application of plants for radionuclide removal from the environment.

Anthropogenic and naturally occurring radionuclide content in near surface air in Cáceres (Spain)

The anthropogenic (¹³⁷Cs, ⁹⁰Sr, ^239+240Pu and ²⁴¹Am) and naturally occurring radionuclide (⁴⁰K, ^234,238U, ^228,230,232Th, ²²⁶Ra and ²¹⁰Pb) content in near surface air present seasonal variations related to natural processes, such as soil erosion, resuspension of fine particles of soil and radon exhalation from soil (²¹⁰Pb). The objective is to analyze seasonal variations of their concentrations and compare with radiological events (Fukushima fallout and wild fire) in a location without any known source of anthropogenic radionuclides. The ²¹⁰Pb, ⁴⁰K, and ¹³⁷Cs presented annual variations, with maximum activity levels in summer. Solar radiation and rainfall were correlated with ²¹⁰Pb and ⁴⁰K. The ^234,238U, ^228,230,232Th, ²²⁶Ra, ¹³⁷Cs and ⁹⁰Sr presented positive correlation with monthly mean values of temperature. The ratio ⁹⁰Sr/¹³⁷Cs was within the range of those reported for soils in Spain. Finally, the maximal effective dose rate was estimated to be 37 and 88 μSv/y for infants and adults, respectively, well below 1 mSv/y reference level. The main contributor to effective dose was ²¹⁰Pb, about 92%, followed by: ²¹⁰Pb ≫ ^228,230,232Th > ²²⁶Ra, ^234,238U > ⁷Be, ^239+240Pu > ⁴⁰K, ⁹⁰Sr > ¹³⁷Cs > ²²Na.

(210)Po in drinking water, its potential health effects, and inadequacy of the gross alpha activity MCL

Polonium-210 ((210)Po) is a naturally-occurring, carcinogenic member of the (238)U decay series and the granddaughter of (210)Pb. It has a half life of 138.4days and is rarely found in drinking water at levels exceeding 5mBq/L because it strongly binds to aquifer sediment. When the current US Maximum Contaminant Level (MCL) covering (210)Po was promulgated in December 2000, very little was known about its occurrence and the processes responsible for mobilizing it. More is now known about the processes that mobilize (210)Po from sediments and a review of recent occurrence data show that it may not be as rare in the US as the US Environmental Protection Agency (USEPA) thought in 2000. Worldwide, only about 2200 analyses for (210)Po in drinking water were identified, with activities exceeding 500mBq/L being found only in Finland, India, Sweden, and the US. The median of 400 (210)Po analyses from the US is 4.75mBq/L and >10% of the samples exceed 500mBq/L. Current compliance-monitoring regulations in the US essentially guarantee that (210)Po contamination will not be detected except in very contaminated wells. Major problems with the US Gross Alpha Activity MCL include the volatility of (210)Po and extended holding times and sample-compositing methods that can allow the majority of (210)Po in a sample bottle to decay before analysis. In light of new information, the radionuclide rule should be changed and direct measurements of (210)Po should be made in all public-water supply wells to rule out its presence. Much of the important biological and toxicological research on (210)Po is more than four decades old and new laboratory research using modern tools is needed. Biological and epidemiological investigations of known contaminated areas are needed to assess the effect (210)Po exposure is having on animals and humans consuming the water.

Radium isotope ((223)Ra, (224)Ra, (226)Ra and (228)Ra) distribution near Brazil's largest port, Paranaguá Bay, Brazil

This work investigates the (223)Ra, (224)Ra, (226)Ra and (228)Ra isotope distribution in river, estuarine waters and sediments of the Paranaguá Estuarine Complex (PEC). The stratification of the Ra isotopes along water columns indicate differing natural sources. In sediments, the radium isotope activities was inversely proportional to the particle size. The highest concentrations of (223)Ra, (224)Ra, (226)Ra and (228)Ra in the water column were found in the bottom more saline waters and towards the inner of the estuary. These relatively high concentrations towards the bottom of the estuary may be attributed to the influence of tidally driven groundwater source and desorption from particles at the maximum turbidity zone. The apparent river water ages from the radium isotope ratios, (223)Ra/(224)Ra and (223)Ra/(228)Ra, indicate that the principal rivers that flow into the estuary have residence times from between 6 and 11days.