Spatial distributions and dose assessment of natural radionuclides in rocks and soils of some selected sites in southwestern Nigeria

The activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K in rock and soil samples collected from Ondo and Ekiti States in southwestern Nigeria were measured by using gamma-ray spectrometer with a high-purity germanium (HPGe) detector. The mean activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K in the rock were 25.53, 61.12, and 554.20 Bq kg^?1 respectively, while that of the soil were 8.27, 17.37, and 151.72 Bq kg^?1 respectively. Results showed that the activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K were higher in the rocks than the soils of the areas studied. To assess the radiological impact of some radionuclides on the population in the region, the annual effective dose equivalent (AEDE), annual gonadal equivalent dose (AGED), and excess lifetime cancer risk (ELCR) were calculated. The mean values of the indoor and outdoor AEDE, and AGED were 88.08 µSv y^?1, 352.34 µSv y^?1, and 508.40 mSv y^?1, respectively for the rock samples, and 25.31 µSv y^?1, 101.25 µSv y^?1, and 145.80 mSv y^?1 respectively for the soil samples. The mean values obtained for AEDE and AGED for the soil were below ICRP recommended limits of 1 and 300 mSv y^?1, respectively. AGED for the rocks was higher than the maximum permissible limit.     

Risk assessment of natural radioactivity in surface water and sediments from a waterfall site in Osun State,Nigeria

Activity concentration of natural radionuclides in surface water and sediment from a waterfall site, Erin-Oke, Osun, Nigeria, has been determined by gamma spectrometry. The mean activity concentration of ⁴⁰K, ²²⁶Ra, and ²³²Th were estimated to be 61.015 ± 15.50, 8.165 ± 2.05 and 5.24 ± 1.57 Bq/l, respectively in water samples and 172.023 ± 35.433, 19.282 ± 4.95, and 17.089 ± 4.37 Bq/kg respectively in sediment samples. Total annual effective dose ingested by an individual ranges from 10.73 ± 3.36 to 15.18 ± 4.44 mSv/y, 2.50 ± 0.80 to 3.58 ± 0.96 mSv/y, and 2.30 ± 0.72 to 3.23 ± 0.93 mSv/y, with mean values of 13.25 ± 3.89, 3.10 ± 0.90, and 2.83 ± 0.83 mSv/y for infants, children, and adults, respectively. These values are greater than International Commission on Radiological Protection (ICRP) and the World Health Organization's recommended limit of 1.0 and 0.1 msv/y, respectively. Mean activity concentrations in sediment are 172.023 ± 35.433, 19.823 ± 4.95, and 17.089 ± 4.37 Bq/kg for ⁴⁰K, ²²⁶Ra, and ²³²Th, respectively, with mean absorbed dose of 26.91 nGyh^?1. This value is lesser than UNSCEAR world average value of 55 nGyh^?1. Health hazard index and radium equivalent for sediments showed lower values than absorbable limits.     

Natural radioactivity concentrations and dose assessment in coastal sediments along the East Coast of Tamilnadu,India with statistical approach

The present study was conducted to determine the activity concentration of ²³⁸U, ²³²Th and ⁴⁰K in coastal sediments samples from Poombuhar to Karaikal along East coast of Tamilnadu, India using gamma ray spectrometry. The average activity concentration for ²³⁸U, ²³²Th and ⁴⁰K were obtained as 36.82 (Bq kg⁻¹), 50.11(Bq kg⁻¹) and 320.38 (Bq kg⁻¹), respectively. These obtained results were used to calculate the radiological hazard parameters like radium equivalent activity (Ra_eq), absorbed gamma dose rate (D_R), the annual effective dose equivalent (AEDE), Annual gonadal dose equivalent (AGDE), Activity utilization index (AUI), External hazard index (H_ex), Internal hazard index (H_in), Gamma representative level index (RLI) and Excess lifetime cancer risk (ELCR). The computed radiological parameters values are compared with the internationally approved recommended values. The multivariate statistical method is used to simplify and organize large data sets to indicate natural associations between samples and variables.     

Natural radioactivity concentrations of 226Ra, 232Th,and 40K in commercial building materials and their lifetime cancer risk assessment in dwellers

Elevated radioactivity levels of ²²⁶Ra, ²³²Th, and ⁴⁰K in building materials were measured using gamma-ray spectrometry and their associated lifetime cancer risks were also determined. The mean activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K are 45.72 ± 0.55, 65.90 ± 8.89, and 487.32 ± 15.20 Bq kg^?1, respectively. Statistically, the principal component (PC) analysis indicates that higher loadings were recorded in Principal Component One (PC1) with large contribution from ²³²Th and ⁴⁰K. The leverage studies indicate that BN Ceramics (BNC) contributes more to the loadings in PC1 followed by Golden Crown Ceramic (GCC) sample. The mean values of 0.399 mSv y^?1 do not surpass the world average value of 0.7 mSv y^?1. The mean gamma index from the measured samples is 0.644, whereas a mean value of 0.271 for alpha index is noted in the samples. The activity utilization index (AUI) from the samples satisfied the AUI <2, which corresponded with the annual effective dose of <0.3 mSv y^?1, except interlock Site 2 and Gomez Spain tiles. Significantly, the mean value of excess lifetime cancer risk of 0.0014 is slightly lower than the world average value of 0.29 × 10^?3.     

Thoron levels in traditional Chinese residential dwellings

A survey on radon (²²²Rn), thoron (²²⁰Rn) and its decay products (²²⁰RnD) was conducted in Chinese traditional residential dwellings constructed with loam bricks or soil wall. The activity concentrations in 164 dwellings under investigation were 72.4±59.2 (arithmetic mean, AM) and 57.5±2.0 Bq m⁻³ (geometric mean, GM) for ²²²Rn, and 318±368 and 162±3.7 Bq m⁻³ for ²²⁰Rn, respectively. For ²²⁰RnD, 67 dwellings were studied. The AM of the ²²⁰RnD equilibrium equivalent concentration was 3.8±3.3 Bq m⁻³ with a maximum value of 15.8 Bq m⁻³. On the basis of these results, the average annual effective doses to the local residents due to radon and thoron exposure were 1.44–4.62 mSv. Thoron contributes 12.9–56.6% to the total doses. Preliminary results show that there is a relation between ²²⁰RnD in air and ²³²Th in soil. The correlation factors of outdoor and indoor were 0.88 and 0.40. The ²³²Th activity content of Chinese soil is estimated to be about two times the world average. The traditional residential dwellings with soil construction are still common in China. Further investigations on the ²²⁰Rn level in these dwelling with the aim of dose reduction are proposed.     

Radionuclides content in grape molasses soil samples from Central Black Sea region of Turkey

The activity concentrations of radionuclides in grape molasses soil samples collected from Zile (Tokat) plain in the Central Black Sea region of Turkey were measured by using gamma spectrometer with a NaI(Tl) detector. Also, the concentrations of ²²²Rn in soil samples and air were estimated essentially taking the activity concentrations of ²²⁶Ra measured in soil samples. Grape molasses soil samples with calcium carbonate content are used for sedimentation for making molasses in this region. The average activity concentrations of ²³²Th, ²²⁶Ra, ⁴⁰K, and ¹³⁷Cs were found as 62 ± 2, 68 ± 3, 479 ± 35, and 8.0 ± 0.3 Bq kg^?1, respectively. The average concentrations of ²²²Rn in soil samples and air were estimated to be 50 kBq m^?3 and 144 Bq m^?3. From the activity concentrations, absorbed gamma dose rate in outdoor air (D), annual effective dose from external exposure (E_E), annual effective dose from inhalation of radon (E_I), and excess lifetime cancer risk (ELCR) were estimated in order to assess radiological risks. The average values of D, E_E, E_I, and ELCR were found to be 90 nGy h^?1, 110 μSv y^?1, 1360 μSv y^?1, and 4 × 10^?4, respectively.     

Using the RESRAD Code to Assess Human Exposure Risk to 226Ra, 232Th,and 40K in Soil

This article evaluates the health risk raised by exposure to naturally occurring radionuclides in soil around Khak-Sefid, Ramsar, Iran, which is an area of high natural background radiation. A high purity germanium detector was used to determine levels of radionuclides in soil samples and the cancer morbidity risk for a hypothetical resident farmer was evaluated using the RESidual RADioactivity (RESRAD) code. The average activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K were found to be 13,201 ± 391, 27.9 ± 2.4, and 415.5 ± 16 Bq/kg, respectively. The maximum assessed cancer morbidity risks were calculated from external and internal exposure pathways as 4.73 × 10^?2 and 3.40 × 10^?2 for ²²⁶Ra, 1.41 × 10^?4 and 7.88 × 10^?5 for ²³²Th, and 1.3 × 10^?4 and 4.233 × 10^?4 for ⁴⁰K. The RESRAD calculations also showed total cancer morbidity risks from external gamma and plant ingestion pathways were more important than from other exposure pathways. A sensitivity analysis was also performed to determine the input parameter values in the risk assessment process. In general, due to the high calculated risk of ²²⁶Ra compared with ²³²Th and ⁴⁰K it can be the major source of concern for human heath in the study area.     

Study of radon/thoron exhalation rate,soil-gas radon concentration,and assessment of indoor radon/thoron concentration in Siwalik Himalayas of Jammu & Kashmir

In the present study, the soil-gas radon concentration was assessed at different depth intervals, i.e., 15 cm, 30 cm, 60 cm, and 100 cm from the 30 villages of Jammu &; Kashmir, India using RAD7, an electrostatic solid state alpha detector. The radon mass exhalation and thoron surface exhalation rate has also been measured in the selected 18 soil samples out of 30 of different grain sizes (i.e., 1 mm, 300 µm, 150 µm). The active radon and thoron concentrations were also assessed in the 20 villages. Both the exhalation rates and active radon/thoron concentration were measured using SMART Rn Duo, a portable radon monitor. The average values of soil-gas radon concentration were 210 ± 84 Bq m^?3, 1261 ± 963 Bq m^?3, 4210 ± 1994 Bq m^?3, and 671 ± 305 Bq m^?3 at the depth intervals of 15 cm, 30 cm, 60 cm, and 100 cm, respectively. The exhalation rate of radon and thoron from soil was found to decrease with the increase of grain size, as smaller soil particles make relatively more contribution to radon and thoron exhalations from the ground surface than larger soil particles. The measured Pearson's correlation coefficient was obtained as statistically significant between different quantities under two-tailed test.     

Measurement of <Superscript>131</Superscript>I activity in thyroid of nuclear medical staff and internal dose assessment in a Polish nuclear medical hospital

This paper presents results of ¹³¹I thyroid activity measurements in 30 members of the nuclear medicine personnel of the Department of Endocrinology and Nuclear Medicine Holy Cross Cancer Centre in Kielce, Poland. A whole-body spectrometer equipped with two semiconductor gamma radiation detectors served as the basic research instrument. In ten out of 30 examined staff members, the determined ¹³¹I activity was found to be above the detection limit (DL = 5 Bq of ¹³¹I in the thyroid). The measured activities ranged from (5 ± 2) Bq to (217 ± 56) Bq. The highest activities in thyroids were detected for technical and cleaning personnel, whereas the lowest values were recorded for medical doctors. Having measured the activities, an attempt has been made to estimate the corresponding annual effective doses, which were found to range from 0.02 to 0.8 mSv. The highest annual equivalent doses have been found for thyroid, ranging from 0.4 to 15.4 mSv, detected for a cleaner and a technician, respectively. The maximum estimated effective dose corresponds to 32% of the annual background dose in Poland, and to circa 4% of the annual limit for the effective dose due to occupational exposure of 20 mSv per year, which is in compliance with the value recommended by the International Commission on Radiological Protection.     

Fate of radiocesium in freshwater aquatic plants and algae in the vicinity of the Fukushima Daiichi nuclear power plant

The behavior of radiocesium (¹³⁷Cs) in aquatic plants (five species) and algae (three genera) grown in either a river (one sampling point) or pond (four sampling points) in the vicinity of the Fukushima Daiichi nuclear power plant was investigated. The ¹³⁷Cs concentration of <0.45-μm fractions of water taken from the river and ponds was between 5.01 × 10^?1 and 2.98 Bq/L, while that of sediment was between 4.85 × 10³ and 5.72 × 10⁴ Bq/kg dry weight. The ratio of ¹³⁷Cs concentration of sediment/water in ponds was ~10⁴. The sediment-to-plant transfer factor (TF) [(¹³⁷Cs concentration Bq/kg dry weight_plant) × (¹³⁷Cs concentration Bq/kg dry weight_sediment)^?1] was also measured. For aquatic plants, the highest value was 5.55 for Potamogeton crispus from the river, while the lowest was 3.34 × 10^?2 for P. distinctus from a pond. There were significant differences in values between aquatic plants belonging to the same genus. The water-to-plant TF [(¹³⁷Cs concentration Bq/kg dry weight_plant) × (¹³⁷Cs concentration Bq/L_water)^?1] of filamentous algae (Spirogyra sp.) and cyanobacteria (coexisting Anabaena sp. and Microcystis sp.) were 2.39 × 10³ and 1.26 × 10³, respectively. The ¹³⁷Cs concentration of cyanobacteria in pond water was 4.87 × 10^?1 Bq/L, which was the same order of magnitude as the ¹³⁷Cs concentration of pond water. Enrichment of ¹³⁷Cs in cyanobacteria was not observed.     

Measurement of activity concentrations of <Superscript>40</Superscript>K, <Superscript>226</Superscript>Ra and <Superscript>232</Superscript>Th for assessment of radiation hazards from soils of the southwestern region of Nigeria

Activity concentrations of the selected radionuclides ⁴⁰K, ²²⁶Ra and ²³²Th were measured in surface soil samples collected from 38 cities in the southwest region of Nigeria by means of gamma spectroscopy with a high-purity germanium detector. Measured activity concentration values of ⁴⁰K varied from 34.9 ± 4.4 to 1,358.6 ± 28.5 Bq kg⁻¹ (given on a dry mass (DM) basis) with a mean value of 286.5 ± 308.5 Bq kg⁻¹; that of ²²⁶Ra varied from 9.3 ± 3.7 to 198.1 ± 13.8 Bq kg⁻¹ with a mean value of 54.5 Bq kg⁻¹ and a standard deviation of 38.7 Bq kg⁻¹, while that of ²³²Th varied from 5.4 ± 1.1 to 502.0 ± 16.5 Bq kg⁻¹ with a mean value of 91.1 Bq kg⁻¹ and standard deviation of 100.9 Bq kg⁻¹. The mean activity concentration values obtained for ²²⁶Ra and ²³²Th are greater than the world average values reported by the United Nations Scientific Committee on Effects of Atomic Radiation for areas of normal background radiation. Radiological indices were estimated for the radiation/health hazards of the natural radioactivity of all soil samples. Estimated absorbed dose rates in air varied from 12.42 ± 2.25 to 451.33 ± 19.06 nGy h⁻¹, annual outdoor effective dose rates from 0.015 ± 0.003 to 0.554 ± 0.023 mSv year⁻¹, internal hazard index from 0.10 ± 0.03 to 3.02 ± 0.16, external hazard index from 0.07 ± 0.01 to 2.60 ± 0.11, representative level index from 0.19 ± 0.03 to 6.84 ± 0.29, activity index from 0.09 ± 0.02 to 3.42 ± 0.15, and radium equivalent activity from 26.95 ± 5.04 to 963.15 ± 41.87 Bq kg⁻¹. Only the mean value of the representative level index exceeds the limit for areas of normal background radiation. All other indices show mean values that are lower than the recommended limits.     

Feasibility of Phytoextraction to Clean Up Low-Level Uranium-Contaminated Soil

The potential to phytoextract uranium (U) from a sandy soil contaminated at low levels was tested in the greenhouse. Two soils were tested: a control soil (317 Bq ²³⁸U kg^-1) and the same soil washed with bicarbonate (69 Bq ²³⁸U kg^-1). Ryegrass (Lolium perenne cv. Melvina), Indian mustard (Brassica juncea cv. Vitasso), and Redroot Pigweed (Amarathus retroflexus) were used as test plants.

The annual removal of the soil activity with the biomass was less than 0.1%. The addition of citric acid (25 mmol kg^-1) 1 week before the harvest increased U uptake up to 500-fold. With a ryegrass and mustard yield of 15000 kg ha^-1 and 10000 kg ha^-1, respectively, up to 3.5% and 4.6% of the soil activity could annually be removed with the biomass.

With a desired activity reduction level of 1.5 and 5 for the bicarbonate washed and control soil, respectively, it would take 10 to 50 years to attain the release limit.

A linear relationship between the plant ²³⁸U concentration and the ²³⁸U concentration in the soil solution of the control, bicarbonate-washed, or citric acid-treated soil points to the importance of the soil solution activity concentration in determining U uptake and hence to the importance of solubilising agents to increase plant uptake.

However, citric acid addition resulted in a decreased dry weight production (all plants tested) and crop regrowth (in case of ryegrass).     

Statistical analysis of natural radioactivity data of clay samples in Tiruvannamalai,Tamilnadu, India

The activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K were determined in clay samples collected from Tiruvannamalai district, Tamilnadu using gamma ray spectrometry. The determined activity concentration ranges from BDL to 16 Bq Kg⁻¹, 18 to 192 Bq Kg⁻¹, 288 to 901 Bq Kg⁻¹ for ²²⁶Ra, ²³²Th and ⁴⁰K respectively. The concentration of these radionuclides is compared with world average values. Radiological risk evaluation was done by calculating radium equivalent activity (Ra_eq), absorbed gamma dose rate (D_R), annual effective dose rate (H_R), annual gonadal dose equivalent (AGDE), criteria formula (CF), representative level index (RLI), activity utilization index (AUI), gamma index (Iγ), alpha index ((Iα), the external hazard (Hex) and internal hazard (Hin) due to internal exposure to radionuclides distributed in clay samples. Multivariate statistical techniques were used to study the relation between activity concentration and radiation hazards of clay samples.     

Preliminary dose estimation from indoor radon for the medical staff of Radiation Oncology and Nuclear Medicine

The aim of this preliminary study was to measure the indoor radon activity concentration in the houses and offices of Radiation Oncology and Nuclear Medicine staff at Dokuz Eylül University and to assess the results from a radiological perspective. LR-115 type II solid-state nuclear track detectors were installed in the homes and hospital and were exposed for 2 months. LR-115 type II detectors were etched for 90 min in 10% (2.5 M) NaOH solution at 60°C and radon activity concentration was determined from observed microscopic track densities. It was observed that measured indoor radon concentration ranged between 18 and 624 Bq/m³ with a geometric mean of 95 Bq/m³ in hospital, and between 22 and 560 Bq/m³ with a geometric mean of 129 Bq/m³ in homes. Estimates of the annual effective dose received by medical staff who participated in the study ranged between 0.76 and 8.79 mSv. On average, the hospital building contributed 41% to the annual effective dose. The reported values for radon concentrations and the corresponding estimated annual effective equivalent doses were within the limits recommended by the International Commission on Radiological Protection as well as the Turkish Atomic Energy Commission recommended limits for workplaces and houses.     

Assessment of Natural Radioactivity Levels and Potential Radiological Risks of Common Building Materials Used in Bangladeshi Dwellings

The concentrations of primordial radionuclides (²²⁶Ra, ²³²Th and ⁴⁰K) in commonly used building materials (brick, cement and sand), the raw materials of cement and the by-products of coal-fired power plants (fly ash) collected from various manufacturers and suppliers in Bangladesh were determined via gamma-ray spectrometry using an HPGe detector. The results showed that the mean concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in all studied samples slightly exceeded the typical world average values of 50 Bq kg⁻¹, 50 Bq kg⁻¹ and 500 Bq kg⁻¹, respectively. The activity concentrations (especially ²²⁶Ra) of fly-ash-containing cement in this study were found to be higher than those of fly-ash-free cement. To evaluate the potential radiological risk to individuals associated with these building materials, various radiological hazard indicators were calculated. The radium equivalent activity values for all samples were found to be lower than the recommended limit for building materials of 370 Bq kg^-1, with the exception of the fly ash. For most samples, the values of the alpha index and the radiological hazard (external and internal) indices were found to be within the safe limit of 1. The mean indoor absorbed dose rate was observed to be higher than the population-weighted world average of 84 nGy h^–1, and the corresponding annual effective dose for most samples fell below the recommended upper dose limit of 1 mSv y^–1. For all investigated materials, the values of the gamma index were found to be greater than 0.5 but less than 1, indicating that the gamma dose contribution from the studied building materials exceeds the exemption dose criterion of 0.3 mSv y^-1 but complies with the upper dose principle of 1 mSv y⁻¹.     

Rumen microbes and microbial protein synthesis in Thai native beef cattle fed with feed blocks supplemented with a urea–calcium sulphate mixture

The influence of slow-release urea ( urea–calcium sulphate mixture; U–CaS) in feed blocks on rumen micro-organisms, predominant cellulolytic bacteria, microbial protein synthesis and ecology was studied in Thai native beef cattle. Four animals with an initial body weight of 100 ± 3.0 kg were randomly assigned to a 4 × 4 Latin square design with four dietary treatments (U–CaS in iso-nitrogen feed blocks at 0, 120, 150 and 180 g/kg dry matter (DM), respectively; U–CaS replaced urea). After 21 days of experimental feeding, rumen fluid was collected at 0 and 4 h after feeding. The mean intake of feed blocks and other feedstuffs offered (rice straw and concentrates) amounted to 0.3, 2.3 and 0.6 kg DM/day, respectively. Inclusion of U–CaS did not altered pH and temperature in the rumen. However, ruminal NH₃–N concentration decreased quadratically (p < 0.05) in response to U–CaS inclusion, with the lowest value at 180 g U–CaS per kg feed block. With inclusion of U–CaS, the populations of rumen bacteria increased quadratically (p < 0.05) and counts of fungal zoospores were linearly enhanced (p < 0.05), being highest at 180 g U–CaS per kg feed block. Supplementation of U–CaS increased the concentration of total bacteria linearly (p < 0.05) and of Fibrobacter succinogenes quadratically (p < 0.05), whereas Ruminococcus flavefaciens and Ruminococcus albus were not affected by dietary treatments. Microbial crude protein yield and efficiency of microbial nitrogen (N) synthesis were linearly increased with different levels of U–CaS addition. Furthermore, current data clearly indicate that inclusion of U–CaS in feed blocks can affect micro-organism diversity and major cellulolytic bacteria.     

Expression,characterization and mutagenesis of a novel glutamate decarboxylase from <Emphasis Type="Italic">Bacillus megaterium</Emphasis>

Objectives

To search for a novel glutamate decarboxylase (GAD) with an optimum pH towards near-neutrality in order to improve production of gamma-aminobutyric acid (GABA) in recombinant hosts.

Results

A novel glutamate decarboxylase, BmGAD, from Bacillus megaterium was overexpressed and purified. BmGAD was approximately 53 kDa by SDS-PAGE analysis. Its optimum activity was at pH 5 and 50 °C. BmGAD had a specific activity of 59 ± 5.2 U mg^?1 at pH 6, which is the highest value reported so far. The apparent Km and V_max values of BmGAD were 8 ± 0.5 mM and 150 ± 4.7 U mg^?1, respectively. Through site-directed mutagenesis, two BmGAD mutants (E294R and H467A) showed higher V_max values than that of wild-type, with the values of 210 ± 6.9 and 180 ± 4.1 U mg^?1 at pH 5 and 50 °C, respectively.

Conclusions

The unusual high activity of BmGAD at pH 6 makes it an attractive GABA-producing candidate in industrial application.

     

Patterns of saccular afferent innervation in sciaenids

In this study, saccular afferent arborization patterns in Atlantic croaker Micropogonias undulatus, red drum Sciaenops ocellatus and spot Leiostomus xanthurus were characterized. Leiostomus xanthurus showed the simplest configuration while M. undulatus displayed the most complex. In addition, hair‐cell densities at sites sampled along the rostro‐caudal axis of the saccular epithelia correlated with the observed patterns of arborization.     

Phycoremediation resultant lipid production and antioxidant changes in green microalgae Chlorella Sp.

In this investigation, we report on the treatment of tannery wastewater using microalgae Chlorella species to produce lipid and fatty acid as well as changes in antioxidant metabolism during the treatment. The variation in growth, production of pigments, antioxidant metabolism, lipid and fatty acids, and nutrient removal from wastewater during the remediation were observed. Surprisingly, a profuse growth was found in 50% diluted tannery wastewater (TW), which supported to accumulate high yield of lipid (18.5%) and unsaturated fatty acids (50.05%). The antioxidant activity of microalgae in both the concentrations (50% and 100% TW) were viz., lipid peroxidation 1.6 ± 0.1 and 2.3 ± 0.02nmol MDA mg^?1 protein, SOD 10.3 ± 0.4 and 15.7 ± 0.9 U mg^?1 protein, CAT 0.17 ± 0.036 and 0.52 ± 0.06 U mg^?1 protein, and APX 7.2 ± 0.8 and 11.2 ± 09 U mg^?1 protein respectively, which point out that the free radical scavenging mechanism against heavy metal stress. Maximum phycoremediation of heavy metals observed from both concentrations during the healthy growth period were Cr – 73.1, 45.7%, Cu – 90.4, 78.1%, Pb – 92.1, 52.2%, and Zn – 81.2, 44.6%, respectively. This study proved the potential use of Chlorella for heavy metal and nutrient removal from tannery wastewater. Moreover, an unaffected growth with high antioxidant activity of this species promises a sustainable lipid and fatty acid contents for biofuel production.     

Activity concentrations of <Superscript>226</Superscript>Ra, <Superscript>228</Superscript>Th,and <Superscript>40</Superscript>K in different food crops from a high background radiation area in Bitsichi,Jos Plateau,Nigeria

One of the three goals of the United Nations for sustainable food security is to ensure that all people have access to sufficient, nutritionally adequate, and safe food. Decades of tin mining in the Bitsichi area of the Jos Plateau, Nigeria, have left a legacy of polluted water supplies, impoverished agricultural land, and soil containing abnormally high levels of naturally occurring radioactive elements. In order to ascertain the radiological food safety of the population, different crops that constitute the major food nutritive requirements were collected directly across farmlands in the area. The activity concentrations of ²²⁶Ra, ²²⁸Th, and ⁴⁰K were determined in the food and soil samples using γ-ray spectrometry. Additionally, in situ gamma dose rate measurements were performed on the farms using a pre-calibrated survey meter. The corresponding activity concentrations in the food crops ranged from below detection limit (BDL) to 684.5 Bq kg⁻¹ for ⁴⁰K, from BDL to 83.5 Bq kg⁻¹ for ²²⁶Ra, and from BDL to 89.8 Bq kg⁻¹ for ²²⁸Th. Activity concentrations of these radionuclides were found to be lower in cereals than in tubers and vegetables. As for the soil samples, activity concentrations of these radionuclides varied from BDL to 166.4 Bq kg⁻¹, from 10.9 to 470.6 Bq kg⁻¹, and from 122.7 to 2,189.5 Bq kg⁻¹ for ⁴⁰K, ²²⁶Ra, and ²²⁸Th, respectively. Average external gamma dose rates were found to vary across the farms from 0.50 ± 0.01 to 1.47 ± 0.04 μSv h⁻¹. Due to past mining activities, the soil radioactivity in the area has been modified and the concentration level of the investigated natural radionuclides in the food crops has also been enhanced. However, the values obtained suggest that the dose from intake of these radionuclides by the food crops is low and that harmful health effects are not expected.