<Superscript>226</Superscript>Ra, <Superscript>232</Superscript>Th and <Superscript>40</Superscript>K activities in soils of Cuihua Mountain National Geological Park,China

Gamma activity from the naturally occurring radionuclides namely, ²²⁶Ra, ²³²Th, the primordial radionuclide ⁴⁰K was measured in the soil of Cuihua Mountain National Geological Park, China using γ-ray spectrometry technique. The mean activity of ²²⁶Ra, ²³²Th and ⁴⁰K were found to be 27.2 ± 6.5, 43.9 ± 6.2 and 653.1 ± 127.6 Bq kg⁻¹, respectively. The concentrations of these radionuclides were compared with the typical world values and the average activities of Chinese soil. The radium equivalent activity, the air absorbed dose rate, the annual effective dose rate, and the external hazard index were evaluated and compared with the internationally approved values. All the soil samples have Ra_eq lower than the limit of 370 Bq kg⁻¹ and H _ex less than unity. The overall mean outdoor terrestrial gamma dose rate is 66.3 nGy h⁻¹ and the corresponding outdoor annual effective dose is 0.081 mSv.     

Radiological hazards of coal and ash samples collected from Xi’an coal-fired power plants of China

The natural radiological characteristics and their respective annual effective dose (AED) rates, produced by ²²⁶Ra, ²³²Th and ⁴⁰K in coal, fly ash and bottom ash from two large coal-fired power plants (CFPPs) of Xi’an were determined by means of γ-ray spectrometry. The average activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in all ash samples (fly ash and bottom ash samples) from the two CFPPs were 67.6, 74.3 and 225.3 Bq kg⁻¹, respectively. The results are compared with data from other locations. To evaluate the radiological hazards of the natural radioactivity, the radium equivalent activity (Ra_eq), air absorbed dose rate (D), AED and external hazard index (H _ex) are compared with internationally accepted values. Ra_eq and H _ex of all samples except three fly ash samples were less than the limits of 370 Bq kg⁻¹ and unity, respectively. The average D and AED for ash samples were 86.8 nGy h⁻¹ and 0.11 mSv y⁻¹, respectively, which exceed the world average and Xi’an average values.     

Measurement of natural radioactivity in sand samples collected from the Baoji Weihe Sands Park, China

The activity concentrations and the gamma-absorbed dose rates of the primordial naturally occurring radionuclides ²²⁶Ra, ²³²Th and ⁴⁰K were determined for sand samples collected from the Baoji Weihe Sands Park, China, using γ-ray spectrometry. The natural radioactivity concentration of sand ranges from 10.2 to 38.3 Bq kg⁻¹ for ²²⁶Ra, 27.0 to 48.8 Bq kg⁻¹ for ²³²Th and 635.8 to 1,126.7 Bq kg⁻¹ for ⁴⁰K with mean values of 22.1, 39.0 and 859.1 Bq kg⁻¹, respectively. The concentrations of these radionuclides are compared with the typical world values and the average activity of Chinese soil. The measured activity concentration of ²²⁶Ra and ²³²Th in sand is lower than the world average while that of ⁴⁰K is higher. . To evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity, the external hazard index, the absorbed dose rate, and the effective dose rate have been calculated and compared with internationally approved values. The radium equivalent activity values of all sand samples are lower than the limit of 370 Bq kg⁻¹. The values of the external hazard index are less than unity. The mean outdoor air absorbed dose rate is 69.6 nGy h⁻¹ and the corresponding outdoor effective dose rate is 0.085 mSv y⁻¹.     

Natural radioactivity of bricks and brick material in the Salihli-Turgutlu area of Turkey

Some of the rocks and soil-originated materials used in building construction are the serious natural radiation sources. Soil-originated bricks and roof-tiles and their raw material in the Salihli-Turgutlu area were tested in situ for natural radiation levels using a gamma-ray spectrometer. The concentrations of the radioelements ⁴⁰K, ²³⁸U and ²³²Th and air-absorbed radiation rates were measured for soil, raw material heaps, brick and roof-tile stacks and waste brick heaps. The radium-equivalent activity Ra_eq of the raw material varied between 187.9 and 216.4 Bq kg^?1. The external radiation hazard index H_ex values ranged between 0.51 and 0.58. For building material and its products, recommended Ra_eq and H_ex levels are 370 Bq kg^-1 and 1.0, respectively. On the other hand, both Ra_eq and H_ex values for waste brick heaps, containing broken brick pieces, coal pieces and ash, were higher than the recommended levels, i.e. Ra_eq values varied from 473.8 to 651.0 Bq kg^-1 and H_ex values were within the range 1.15–1.76. The annual dose rate and radium-equivalent activity values of the brick and roof-tiles were below the level of criteria. Annual dose rate ranged between 0.42 and 0.62 mSv y^?1 and radium equivalent activity was in the range 172.9–245.2 Bq kg^?1. The external and internal radiation hazard indices were all below the value of 1.0 for the Salihli-Turgutlu area bricks and roof-tiles. Results of this study were compared with results of previous studies. Natural radiation levels of construction raw material of study area are generally higher than of those of previous studies.     

Annual cycle of radionuclide contamination on tide-washed pasture in the Mersey Estuary, NW England

The radionuclide burden of vegetation comprising a tide-washed pasture at Ince Marsh in the Mersey Estuary, U.K., derives mainly from adhered external particulates originating as suspended sediments in estuarine water. Radionuclide concentrations are dominated by the growth cycle of the vegetation, with the highest winter levels of contamination activity an order of magnitude greater than the lowest levels in mid-summer. A secondary effect due to sediment transfer during periods of severe flooding produces subsidiary features on this dominant seasonal profile. Radionuclide concentrations on vegetation are in the range¹³⁷Cs=8–191,¹³⁴Cs=0.3–0.9,²⁴¹Am=0.6–46,²³⁸Pu=0.1–1.5, and^239/240Pu=0.8–44 Bq kg⁻¹. These ranges reflect the relative concentrations of radionuclides in estuarine sediment (¹³⁷Cs=615,²⁴¹Am=202, and^239/240Pu=104 Bq kg⁻¹) rather than the values in filtered estuary water (¹³⁷Cs=0.4,²⁴¹Am=0.001, and^239/240Pu=0.001 Bq 1⁻¹). Median K_d values for these radionuclide species are Cs=1,400, Am=200,000, and Pu=80,000 1 kg⁻¹).     

Gamma radiation measurements of naturally occurring radioactive samples from commercial Egyptian granites

Due to the widespread use of granites as building and ornamental materials, measurements of natural radioactivity for a total 27 selected samples of commercial granites used in Egypt were carried out by using a high pure germanium detector. The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K of commercial granites ranged from 25 to 356, 5 to 161, and 100 to 1,796?(Bq?kg^?1), respectively. The concentrations of these radionuclides are compared with the international recommended values. To evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity, the absorbed dose rate, the effective dose rate, and the hazard index have been calculated. The radium equivalent activity Ra_eq varied from 41 to 669?(Bq?kg^?1) which exceeds the permitted value (370?Bq?kg^?1) and the internal hazard index H _in varied from 0.2 to 2.8 which is higher than 1. The absorbed dose rate due to the natural radioactivity in the samples under investigation ranged from 19 to 310?(nGy?h^?1). The total effective dose rates per person indoors were determined to be 0.09 to 1.5?(mSv?year^?1).     

Analysis of terrestrial naturally occurring radionuclides in soil samples from some areas of Sirsa district of Haryana,India using gamma ray spectrometry

The activity concentration and the gamma-absorbed dose rates of the terrestrial naturally occurring radionuclides (²³²Th, ²²⁶Ra and ⁴⁰K) were determined in soil samples collected from ten different locations of Sirsa district of Haryana, using HPGe detector based on high-resolution gamma spectrometry system. The range of activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in the soil samples from the studied areas varies from 19.18 Bq kg⁻¹ (Moriwala) to 40.31 Bq kg⁻¹ (Rori), 59.43 Bq kg⁻¹ (Pipli) to 89.54 Bq kg⁻¹ (Fatehpur) and 223.22 Bq kg⁻¹ (Moriwala) to 313.32 Bq kg⁻¹ (SamatKhera) with overall mean values of 27.94, 72.75 and 286.73 Bq kg⁻¹ respectively. The absorbed dose rate calculated from activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K ranges between 8.84 and 18.58, 37.02 and 55.78, and 9.24 and 12.97 nGy h⁻¹, respectively. The total absorbed dose in the study area ranges from 60.40 to 82.15 nGy h⁻¹ with an average value of 70.12 nGy h⁻¹. The calculated values of external hazard index (H _ex) for the soil samples of the study area range from 0.36 to 0.49 with an average value of 0.42.     

Estimation of radiation exposure in soils and organic (animal) and inorganic (chemical) fertilizers using active technique

In this study, activity concentrations of ⁴⁰K, ²²⁶Ra and ²³²Th in fertilized soil samples and different organic and inorganic fertilizers used in agricultural soil were analysed using gamma-ray spectrometry NaI (Tl) detector in order to access the implications of extended use of fertilizers in 2–3 years. The concentrations of radionuclides in some granular fertilizer brands were discovered to be higher for ⁴⁰K, ²²⁶Ra and ²³²Th than those obtained in leafy fertilizer, animal fertilizer and fertilized soil samples. From the results, the highest overall mean concentrations of the specific activities of ⁴⁰K, ²²⁶Ra and ²³²Th were 2301.8 (granular fertilizer), 42.5 (leafy fertilizer) and 327.1 (animal fertilizer) in Bq kg^?1, while the lowest values observed in the specific activities of the same radionuclides were 357.7 (leafy fertilizer), 28.1 (animal fertilizer) and 36.5 (animal fertilizer). The radiological hazards of the radium equivalent (Ra_eq), normative value (NRN), outdoor radium equivalent (Ra_eq-out), external hazard index (H _ext), internal hazard index (H _in), dose rate, annual effective dose rate, activity utilization index and concentration accumulation index (CAI) and Ra_FZ due to the presence of these radionuclides in the investigated samples were calculated. Nevertheless, some of the fertilizer brands have higher concentration values than the recommended limit, and the values of hazard indices of fertilizer brands used in the selected teaching and research farms were within acceptable limit. Therefore, the fertilized soil samples in the studied farms are safe.     

Radiological hazard assessment for building materials incorporating phosphogypsum made using Eshidiya mine rock in Jordan

The mean activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K in Eshidiya phosphogypsum samples were measured as 351.4 ± 23.4, 3.8 ± 0.3, and 120.7 ± 8.3 Bq kg^?1, respectively. The results show that the mean values of activity concentration of ²²⁶Ra, ²³²Th, and ⁴⁰K are in the lower range of typical values reported for phosphogypsum samples collected worldwide. Radiological hazard indices such as the radium-equivalent activity (Ra_eq), the gamma index (I _γ ) alpha index (I _α ), the absorbed gamma dose rate (D _in), and the corresponding annual effective dose (E _in) were assessed for building materials for dwellings. The results of assessment exhibit that all phosphogypsum samples are higher than the recommended safe limit for building materials for dwellings, except for the radium-equivalent activity (Ra_eq). Overall assessment, it can be concluded that the possibility of using Eshidiya phosphogypsum in building materials in proportions lower than 100 % will be safe. The mixture of phosphogypsum with normal gypsum can dilute the concentrations of natural radionuclides allowing the use of the mixed building materials to be safe from a radiological point of view.     

Gamma radiation levels in the villages of South Konkan,Maharashtra, India

Ambient gamma radiation study was carried out in South Konkan using thermo luminescent dosimeters (TLDs). A statistical analysis was carried out to understand the distribution of gamma radiation in the study area. The annual effective doses (AEDs) received by the local population from the selected villages were 0.31 and 0.09 mSv year^?1 for indoor and outdoor locations, respectively. For indoor conditions, the maximum dose rate occurred for winter season and the minimum occurred in monsoon season while for outdoor conditions the maximum dose rate occurred in spring season and minimum occurred in the monsoon season. The terrestrial radioactivity in the corresponding villages was measured by a HpGe detector. The radiation hazard indices like absorbed dose rate in air (D), radium equivalent activity (Ra_eq), external hazard index (H _ex) and internal hazard index (H _in), and AED were calculated using soil radioactivity data. The minimum absorbed dose rate in air (33.97 nGy h^?1) corresponds to the Dale village and the maximum (101.86 nGy h^?1) corresponds to the Mithgawane village. Radiation hazard indices as Ra_eq, H _ex, and H _in were found to be within the limit. The average AED from natural radionuclides was found to be lower than the worldwide value. The AEDs of this study were compared with previous studies carried out worldwide. A positive correlation was observed for the absorbed dose rate in air and the activity concentration of U-238, Th-232, and K-40. A positive correlation between activity concentrations of U-238, Th-232, and K-40 was also observed. The comparison between the AEDs calculated using absorbed dose measured by TLDs and the values calculated from soil’s gamma spectrometry showed some variation in the villages of South Konkan.     

Radioactivity in sediments and gross alpha–beta activities in surface water of Fırtına River, Turkey

The concentrations and distribution of natural and artificial radionuclides in sediment and water samples collected from Fırtına River in the Eastern Black Sea region of Turkey were investigated with an aim of evaluating the environmental radioactivity and radiation hazard. Natural gross α and gross β activities were determined for 21 different water samples, and the activity concentrations were obtained for ²²⁶Ra, ²¹⁴Pb, ²¹⁴Bi, ²²⁸Ac, ²⁰⁸Tl, ⁴⁰K and ¹³⁷Cs in 20 different sediment samples. The obtained results showed that natural gross α and gross β activity concentrations in water samples range from 12.4 ± 3.4 to 66.2 ± 9.2 mBq l⁻¹ and from 27.9 ± 3.3 to 133.3 ± 4.1 mBq l⁻¹, respectively. The mean activity concentrations were 32.6 ± 3.8 mBq l⁻¹ for gross α and 69.9 ± 4.4 mBq l⁻¹ for gross β. Generally, the gross β activities were higher than the corresponding gross α activities. The average concentrations of ²³⁸U and ²³²Th daughter products vary from 11 to 167 Bq kg⁻¹ and from 16 to 107 Bq kg⁻¹, respectively. The concentrations of ⁴⁰K and ¹³⁷Cs vary from 51 to 1,605 Bq kg⁻¹ and from 0.8 to 42 Bq kg⁻¹, respectively. Sediment characterization was also investigated using grain size, thin section and XRD analysis.     

Evaluation of radiation dose due to naturally occurring radionuclides in rock samples of different origins collected from Azad Kashmir

The state of Azad Kashmir is rich in three types of rocks, namely, sedimentary, metamorphic, and igneous rocks. These rocks contain extensive deposits of graphite, marble, limestone, quartzite, granite, dolerite, and sandstone, which are widely used for the construction of dwellings in Azad Kashmir and Pakistan. Therefore, knowledge about the presence of natural radioactivity in these materials is desirable to assess the radiological hazards associated with it. In this context, 30 rock samples were collected from different geologic formations of the Muzaffarabad Division, Azad Kashmir. After processing the samples, the specific activities of ²²⁶Ra, ²³²Th, and ⁴⁰ K in them were measured using a P-type coaxial high-purity germanium detector. The observed highest dose rate values for sedimentary, metamorphic, and igneous rocks have been found to be 83.16 ± 1.08, 135.87 ± 1.18, and 115.98 ± 1 nGy ⋅ h^–1, respectively. The radium equivalent activity (Ra_eq) varied from 23.76 ± 1.15 for dolerite sample (igneous rock) to 293.69 ± 2.60 Bq ⋅ kg^–1 for marble (metamorphic rock). The Ra_eq values of all rock samples are lower than the limit mentioned in the Organization for Economic Cooperation and Development (OECD, 1979) report (370 Bq ⋅ kg^–1, equivalent to γ-dose of 1.5 mSv ⋅ y^–1). The values of external (H_ex) and internal hazard indices (H_in) are less than unity. The mean outdoor and indoor annual effective dose equivalents are 0.073 mSv ⋅ y^–1 and 0.29 mSv ⋅ y^–1, respectively. The mean (over all types of rock samples) annual effective dose equivalent is reported as 0.36 mSv ⋅ y^–1.     

Assessment of natural radioactivity in aquifer medium bearing uranium ores in Koprubasi,Turkey

Koprubasi, located within Manisa Province near the Izmir, is the biggest uranium mine where uranium ores originate from Neogene aged altered sandstone and conglomerate layers. The main objective of this study is to determine the radiation hazard associated with radioactivity levels of uranium ores, and the rocks and sediments around Koprubasi. In this regard, measured activity levels of ²²⁶Ra, ²³²Th and ⁴⁰K were compared with world averages. The average activity levels of ²²⁶ Ra, ²³²Th and ⁴⁰K were measured to be 5369.75, 124.78 and 10.0 Bq/kg in uranium ores, 24.32, 52.94 and 623.38 Bq/kg in gneiss, 46.24, 45.13 and 762.26 Bq/kg in sandstone and conglomerate, 73.11, 43.15 and 810.65 Bq/kg in sediments, respectively. All samples have high ²²⁶Ra and ⁴⁰K levels according to world average level. As these sediments are used as construction materials and in agricultural activities within the study area, the radiation hazard are calculated by using dose rate (D), annual effective dose rate (He), radium equivalent activity (Ra_eq) and radiation hazard index (I_yr). All the samples have Ra_eq levels that are lower than the world average limit of 370 Bq/kg. On the other hand, D, He and I_yr values are higher than world average values. These results indicate that the uranium ores in the Koprubasi is the most important contributor to the natural radiation level. The radioactivity levels of sediments and rocks make them unsuitable for use as agricultural soil and as construction materials. Moreover, it is determined that shallow groundwater in sediments and deep groundwater in conglomerate rocks and also surface water sources in the Koprubasi have high ²²⁶Ra content. According to environmental radioactive baseline, some environmental protection study must be taken in Koprubasi uranium site and the environment.     

Ra/Ra and Ra/Ba ratios to track barite formation and transport in the water column

We measured ²²⁸Ra_ex/²²⁶Ra_ex and ²²⁶Ra_ex/Ba_ex ratios in suspended and sinking particles collected at the Oceanic Flux Program (OFP) time-series site in the western Sargasso Sea and compared them to seawater ratios to provide information on the origin and transport of barite (BaSO₄) in the water column. The ²²⁸Ra_ex/²²⁶Ra_ex ratios of the suspended particles down to 2000 m are nearly identical to those of seawater at the same water depth. These ratios are much lower than expected if suspended barite was produced in surface waters and indicate that barite is produced throughout the mesopelagic layer. The ²²⁸Ra_ex/²²⁶Ra_ex activity ratios of sinking particles collected at 1500 and 3200 m varied mostly between 0.1 and 0.2, which is intermediate between the seawater ratio at these depths (<0.03) and the seawater ratios found in the upper 250 m (0.31-0.42). This suggests that excess Ba (i.e., Ba_ex = Ba_total − Ba_lithogenic), considered to be mainly barite, present in the sinking flux is a mixture of crystals formed recently in the upper water column, formed several years earlier in the upper water column, or formed recently in deeper waters. We observe a sizeable temporal variability in the ²²⁸Ra_ex/²²⁶Ra_ex ratios of sinking particles, which indicates temporal variability in the relative proportion of barite crystals originating from surface (with a high ²²⁸Ra_ex/²²⁶Ra_ex ratio) and mesopelagic (with a low ²²⁸Ra_ex/²²⁶Ra_ex ratio) sources. However, we could not discern a clear pattern that would elucidate the factors that control this variability. The ²²⁶Ra/Ba ratios measured in seawater are consistent with the value reported from the GEOSECS expeditions (2.3 dpm μmol⁻¹) below 500 m depth, but are significantly lower in the upper 500 m. High ²²⁶Ra_ex/Ba_ex ratios and elevated Sr concentrations in suspended particles from the upper water column suggest preferential uptake of ²²⁶Ra over Ba during formation of SrSO₄ skeletons by acantharians, which must contribute to barite formation in shallow waters. Deeper in the water column the ²²⁶Ra_ex/Ba_ex ratios of suspended particles are lower than those of seawater. Since ²²⁸Ra_ex/²²⁶Ra_ex ratios demonstrate that suspended barite at these depths has been produced recently and in situ, their low ²²⁶Ra_ex/Ba_ex ratios indicate preferential uptake of Ba over Ra in barite formed in mesopelagic water.     

Contamination assessment of copper,lead, zinc and chromium in dust fall of Jinan,NE China

To assess the pollution of heavy metal in dust fall, nine dust fall samples were collected during the heating period and non-heating period from Jinan, a city in northeastern China. The samples were analyzed for Cu, Pb, Zn and Cr and the contamination level of heavy metals was assessed on the basis of the geo-accumulation index (I _geo). The results indicated that all of the four investigated metals accumulated significantly in the dust fall of Jinan, and the metal concentrations were much higher than background values. During the heating period, the mean values for Cu, Pb, Zn and Cr in the dust fall were 354.9, 688.5, 2,585.5 and 478.6 mg kg⁻¹. During the non-heating period, the mean values for Cu, Pb, Zn and Cr in the dust fall were 228.2, 518.2, 1,933.9 and 96.3 mg kg⁻¹, respectively. The I _geo values calculated based on background values revealed that the contamination level of heavy metal in the dust fall ranges from moderately contaminated to heavily contaminated, and it mainly originates from traffic and industry. In this work, the dust fall residue compared to the standard reference was also chosen as the background value to calculate the I _geo value. This method is useful for situations in which the background value is difficult to obtain.     

Influence of humic acids on the accumulation of copper and cadmium in <Emphasis Type="Italic">Vallisneria spiralis</Emphasis> L. from sediment

Physiological responses and metal accumulation in Vallisneria spiralis L. exposed to copper and cadmium contaminated sediment were examined at different metal concentrations and the influence of humic acids on copper and cadmium accumulation was also studied. The plants of V. spiralis accumulated high amount of copper and cadmium. The maximum accumulation of 396 and 114 mg kg⁻¹ DW copper were found in the roots and shoots, respectively, at 614 mg kg⁻¹ DW after 21 days’ copper exposure; they were 63.8 and 48.0 mg kg⁻¹ DW for cadmium at 88.69 mg kg⁻¹ DW. The plants showed decrease in chlorophyll content with the increasing concentration of copper/cadmium in sediment. With addition of humic acids from 3.09 to 7.89 g kg⁻¹ DW, both copper and cadmium accumulation in V. spiralis were significantly inhibited (p < 0.01). The cadmium concentrations of roots and shoots of plant decreased 26.4–50.3 and 14.3–33.0% under cadmium treatments, respectively; copper accumulation decreased much more with 44.0–77.0 and 35.0–62.7%, respectively. It was concluded that V. spiralis appeared to be an ideal candidate for the phytoremediation of copper and cadmium polluted sediments, and humic acids had an important role in regulating copper and cadmium bioavailability and toxicity in sediments.     

Vulnerability of headwater catchment resources to incidences of <Superscript>210</Superscript>Pb excess and <Superscript>137</Superscript>Cs radionuclide fallout

Recent identification of elevated excess ²¹⁰Pb (≤302.6 mBq L⁻¹) and ¹³⁷Cs (≤111.3 mBq L⁻¹) activity in drinking water wells up to 20 m depth indicates some transport of airborne radionuclide fallout beyond soils in the Shaker Village catchment, Maine. Estimated airborne mass loading ²¹⁰Pb_ex fluxes of about 0.9 mBq m⁻³, canvass this headwater catchment and may be sufficient to pose risks to unprotected shallow wells. Inventories of ²¹⁰Pb_ex and ¹³⁷Cs in pond sediments indicate maximum median activities of 943 mBq g⁻¹ and 40.0 mBq g⁻¹, respectively. Calculated ²¹⁰Pb_ex fluxes in the catchment soils range from 0.62–0.78 Bq cm⁻² year⁻¹ and yield a mean residence time of near 140 years. Measured ¹³⁷Cs activity up to 51.1 mBq g⁻¹ occurs in sediments at least to 5 m depth. Assumed particle transport in groundwater with apparent ⁸⁵Kr ages less than 5 years BP (2005) may explain the correlation between these particle-reactive radionuclides and elevated activity in some drinking water wells.     

Speciation and phytoavailability of heavy metals in sediments in Nanjing section of Changjiang River

Heavy metal pollution and their fractionations in the sediments of Changjiang River in Nanjing Reach was monitored for cadmium (Cd), lead (Pb), zinc (Zn), chromium (Cr), and copper (Cu). Moreover, the biological enrichment of metals by riverine plants was studied. The results demonstrated there were highly significant variations among different sampling stations for the concentrations of tested metals. The highest range was for Cu (38.8–120.4 mg kg⁻¹), followed by Cr (74.4–120.0 mg kg⁻¹), Zn (80.9–121.1 mg kg⁻¹), Ni (26.0–55.5 mg kg⁻¹), Pb (15.8–46.7 mg kg⁻¹) and Cd (0.28–0.48 mg kg⁻¹). Cd was the element with highest biological enrichment factor (BEF). The highest BEF of Cd in Erigeron bonariensis reached 3.0, indicating a significant Cd enrichment in this aquatic plant. In addition, 60% of Cd was found in reducible fraction and exchangeable and acid-soluble fraction, which was consistent with its high mobility. The consistency of Cd fraction in sediment and suspended particle indicated they came from the same source. Accumulated Cd concentration calculated according to the release curve showed significant relativity with the total Cd concentration in the sediment.     

Assessment of the radiological hazards of sand sediments collected from streams and streamlets of the uranium deposit areas in West Khasi Hills District,Meghalaya, India

Primordial radionuclides in sand sediments that are often used as constructing materials are one of the sources of radiation hazard in dwellings. Activity concentrations of the primordial radionuclides of ⁴⁰K, ²²⁶Ra and ²³²Th have been measured in sand sediments collected from streams and streamlets lying within and around the uranium mineralization deposit blocks of Kylleng-Pyndensohiong, Mawthabah Areas of West Khasi Hills District, Meghalaya, India. The technique of gamma-ray spectroscopy using a NaI(Tl) detector with a PC-based multi channel analyser was applied for determination of the activity concentrations. The activity of the sand sediments obtained in this study ranges from 95.3 to 1,088.8 Bq kg⁻¹ for ⁴⁰K; 38.3 to 784.1 Bq kg⁻¹ for ²²⁶Ra and 78.0 to 316.1 Bq kg⁻¹ for ²³²Th. Sand sediments from two sampling locations lying within the mineralization zone show highest concentrations of these radionuclides. The radiological hazards of the sand sediments were calculated using various models given in the literature. The radium equivalent activity was found to be higher than the accepted standard criterion value of 370 Bq kg⁻¹ and the values of external and internal hazard indices were also found to be higher than unity in these two sampling locations. Besides these two sampling locations, a sampling location lying at a nearby distance from the mineralization zone also exhibits hazard indices values greater than unity.     

Radionuclides measurements and mineralogical studies on beach sands, East Rosetta Estuary, Egypt

Radiometric measurements were carried out for the beach sands from East Rosetta estuary to determine the activity concentrations of 238 U, 226 Ra, 232 Th, and 40 K, using a Hyper Pure Germanium spectrometer, to estimate the dose rates and radiation hazard indices. The average specific activities are 778.20 Bq/kg for 238 U; 646.89 Bq/kg for 226 Ra; 621.92 and 627.85 Bq/kg for the 222 Rn daughters 214 Pb and 214 Bi respectively. The average specific activity of 232 Th is 1510.25 Bq/kg, while the calculated specific activity for 40 K has an average of 8.41 Bq/kg. The average specific activity of 235 U is 38.61 Bq/kg. The average absorbed dose rate is 1211.36 nGy/h, 20 times higher than the estimated average global primordial radiation of 60 nGy/h and 6 times higher than that of the world range (10-200 nGy/h). The radium equivalent (Ra eq ) values are from 6 to 9 times the recommended value. The internal and external hazard indices (H int , H ex ) indicate that their values are from 6 to 11 times the permissible values of these indices. These higher values may be due to the presence of economic heavy minerals containing radionuclides as zircon and monazite as well as some trace minerals, thorite and uranothorite. The mineralogical study indicates the beach sands contain heavy minerals, zircon, monazite, rutile, ilmenite, leucoxene, magnetite and garnet. The average abundance of zircon is 0.175 wt% ranging from 0.125 wt% to 0.239 wt%, while it is 0.004wt% ranging from 0.001 wt% to 0.007 wt% for monazite. The average abundance is 0.087 wt% for rutile; 2.029 wt% for ilmenite; 1.084 wt% for magnetite; 0.384 wt% for leucoxene and 0.295 wt% for garnet.