Natural radioactivity levels in topsoil from the Pearl River Delta Zone, Guangdong, China

Radon and thoron exhalation rate in the soil of Western Haryana, India

This study reports the exhalation rates of radon and thoron from surface soil collected from 60 rural sites of district Hisar, Haryana, India. The exhalation rates of Rn²²² (radon) and Rn²²⁰ (thoron) were measured by portable SMART RnDuo (AQTEK SYSTEMS) using a mass accumulation chamber which was equipped with a scintillation material-coated cell. Dose rates due to natural gamma radiations ranged from 0.526 to 1.139 mSv y^-1. The Rn²²² mass exhalation rate in soil samples varied from 0.14 to 94.65 mBq kg^-1 h^-1. Thoron surface exhalation rates ranged from 46.42 to 619.88 Bq m^-2 h^-1. This study gives an idea about the differences in Rn²²² and Rn²²⁰ exhalation at different locations which may be due to variations in geological features of the locations and characteristics of the topsoil. The findings show that usage of study area soil as building material is safe.

Distributional Characteristics and Source Identification of Cadmium in Soils of the Pearl River Delta, China

The results of the Multi-Purpose Geochemical Survey in the Pearl River Delta (PRD) show that the pollution is serious. In this study, the influence of geological genesis, soil-forming process, and human activities on soil quality in PRD is analyzed, and the influence factors, genesis and spatial distributional characteristics of cadmium (Cd) in different soil depths are studied by inverse distance weighted (IDW) and hot spot analysis. The results show that the spatial distribution of Cd is significantly different in PRD and high-value is mainly concentrated in the central cities of Guangzhou-Foshan-Jiangmen-Zhongshan-Zhuhai. Moreover, hot spots with higher Cd content in deep are mainly along Beijiang, Dongjiang, and Pearl River Estuary (PRE). Overall, our findings suggest that the high background value areas formed by marine-land and fluvial sediments as well as intensive human activities that make PRD become an area under the dual restriction of geological genesis and human activities, pollution control cannot be ignored.

STATISTICAL ESTIMATION OF RADIOLOGICAL HAZARDS FROM RADIONUCLIDE CONTENTS IN BUILDING MATERIALS

Thirteen (13) types of building tiles and Sharp sand commonly used for building purposes were collected for their radionuclide contents analysis using gamma ray spectrometry. The average value of the Radium equivalent activity is 208.81 Bq/kg for all samples considered was found to be lower than the recommended safe limit of 370 Bq/kg. Similarly, both external and internal hazard indices (Hex and Hin) were noted to have mean values of 0.57 and 0.73, respectively, which were lower than the recommended safe standard of 1. More so, the average absorbed gamma dose rate was observed to be 94.31 nGy/h, much higher than the recommended safe limit of 59 nGy/h.

Natural and anthropogenic radionuclides in urban soil around non-nuclear industries (Northern Al Jubail), Saudi Arabia: assessment of health risk

The residential areas are located around one of the oldest and largest non-nuclear industrial cities in Saudi Arabia, Arabian Gulf. Therefore, it is important to study the radioactivity levels in the urban soil in order to estimate the potential risk of radiation in environment and for public. The activity concentrations of ²²⁶Ra, ²³²Th, ⁴⁰K, and ¹³⁷Cs in urban soil around non-nuclear industries were measured using gamma ray spectrometric technique. The mean values of activity concentrations were found to be 7.64 ± 0.4, 3.76 ± 0.2, 174 ± 3.7, and 0.391 ± 0.03 (Bq/kg) for ²²⁶Ra, ²³²Th, ⁴⁰K, and ¹³⁷Cs, respectively. Radium equivalent activity (Ra_eq), gamma absorbed dose rate in air (D), and annual effective dose equivalent (E) for outdoor were calculated. The mean values of these radiological parameters were found to be less than the allowed limits in soil. The obtained results were compared with other studies from Arabian Gulf and other regions of the world. Consequently, the direct gamma radiation exposure from the urban soil in the study area was found to be safe for public. Additionally, the present study is the first in this area which could be used as a baseline for radioactivity levels in soil nearby industrial areas of the Arabian Gulf region.

Significant chemical fluxes from natural terrestrial groundwater rival anthropogenic and fluvial input in a large-river deltaic estuary

The shores of the Pearl River estuary are home to 35 million people. Their wastes are discharged into the large river delta-front estuary (LDE), one of the most highly polluted systems in the world. Here we construct a radium reactive transport model to estimate the terrestrial groundwater discharge (TGD) into the highly urbanized Pearl River LDE. We find the TGD comprises only approximately 0.9% in term of water discharge compared to the river discharge. The TGD in the Pearl River LDE delivers significant chemical fluxes to the coast, which are comparable to the fluvial loadings from Pearl River and other world major rivers. Of particular importance is the flux of ammonium because of its considerable role in Pearl River estuary eutrophication and hypoxia. Unlike the ammonium in many other aquifers, the ammonium in the Pearl River aquifer system is natural and originated from organic matter remineralization by sulfate reduction in the extremely reducing environment. The TGD derived NH₄⁺ is as much as 5% of the upstream Pearl River fluvial loading and 42% of the anthropogenic inputs. This high groundwater NH₄⁺ flux may greatly intensify the eutrophication, shift the trophic states, and lead to alarming hypoxia within the affected ecosystems in the Pearl River LDE. The large TGD derived chemical fluxes will lead to deterioration of water and will potentially affect human health.

A suggestion to radiological hazards characterization of 226Ra, 232Th, 40K and 137Cs: spatial distribution modelling

Spatial distribution modelling has been proposed to characterize the radiological hazards associated with concentration of natural ²²⁶Ra, ²³²Th, ⁴⁰K and artificial ¹³⁷Cs radionuclides in the nature. These elements have been determined for the sediment samples of the Bafa Lake with the aim of radiation hazard evaluation via a high purity germanium detector gamma spectrometry. Their activity concentrations in sediments are in the ranges of 29.87 ± 2.2-72.56 ± 11 Bq kg^{- 1} dry weight (dw), 31.57 ± 3.5-66.48 ± 8.3 Bq kg^{- 1} (dw), 332.01 ± 12-1092.37 ± 21 and 0.65 ± 0.04-3.96 ± 0.78 Bq kg^{- 1} (dw), respectively. In order to determine the radiological hazard associated with the radioactivity in the samples, the external terrestrial gamma dose rate in air, annual effective dose rate, the radium equivalent activity and the external hazard index are calculated and compared with the data from literature. Moreover, the spatial modelling distributions are obtained visually for radiological hazards characterization of these elements, which are very dangerous in terms of radiological and environmental pollution in the nature. These visual distributions give meaningful information for future researches on the migration of radionuclides in the environment.

Radon concentration in drinking water and supplementary exposure in Baita-Stei mining area, Bihor county (Romania)

The radon concentration was measured in the drinking water of public water supply and private wells located in the mining area of BăiŢa-Ştei, Bihor County, Romania. The measurements were performed using the LUK-VR system based on radon gas measurement with Lucas cell. The results show that the radon concentrations are within the range of 1.9-134.3 kBq m(-3) with an average value of 35.5 kBq m(-3) for well water, 18.5 kBq m(-3) for spring water and 6.9 kBq m(-3) for tap water. Comparing with previous data from the whole of Transylvania, the average value is two times higher, proving this zone to be a radon-prone area. From the results of this study the effective dose to the population is between 4.78 and 338.43 µSv y(-1). These doses are within the recommended limits of the world organisations.

Assessment of the vertical distribution of natural radionuclides in a mineralized uranium area in south-west Spain

Low-level alpha spectrometry techniques using semiconductor detectors (PIPS) and liquid scintillation (LKB Quantulus 1220™) were used to determine the activity concentration of (238)U, (234)U, (230)Th, (226)Ra, (232)Th, and (210)Pb in soil samples. The soils were collected from an old disused uranium mine located in southwest Spain. The soils were sampled from areas with different levels of influence from the installation and hence had different levels of contamination. The vertical profiles of the soils (down to 40 cm depth) were studied in order to evaluate the vertical distribution of the natural radionuclides. To determine the origin of these natural radionuclides the Enrichment Factor was used. Also, study of the activity ratios between radionuclides belonging to the same radioactive series allowed us to assess the different types of behaviors of the radionuclides involved. The vertical profiles for the radionuclide members of the (238)U series were different at each sampling point, depending on the level of influence of the installation. However, the profiles of each point were similar for the long-lived radionuclides of the (238)U series ((238)U, (234)U, (230)Th, and (226)Ra). Moreover, a major imbalance was observed between (210)Pb and (226)Ra in the surface layer, due to (222)Rn exhalation and the subsequent surface deposition of (210)Pb.

Reference levels of natural radioactivity and (137)Cs in and around the surface soils of Kestanbol pluton in Ezine region of Çanakkale province, Turkey

The aim of the study was to conduct a systematic investigation on the natural gamma emitting radionuclides ((226)Ra, (232)Th and (40)K) as well as (137)Cs in the surface soils from Kestanbol/Ezine plutonic area in Çanakkale province as part of the environmental monitoring program on radiologic impact of the granitoid areas in Western Anatolia. The activity measurements of the gamma emitters in the surface soil samples collected from 52 sites distributed all over the region has been carried out, by means of HPGe gamma-ray spectrometry system. The activity concentrations of the relevant radionuclides in the soil samples appeared in the ranges as follows: (226)Ra was 20-521 Bq kg(-1); (232)Th, 11-499 Bq kg(-1)and; (40)K, 126-3181 Bq kg(-1), yet the (137)Cs was much lower than 20 Bq kg(-1)at most. Furthermore, based on the available data, the radiation hazard parameters associated with the surveyed soils were calculated. The present data also allowed evaluation of some correlations that may exist in the investigated natural radionuclides of the soil samples from the plutonic area in Çanakkale province. It is concluded from the above that the concerned region did not lead to any significant radiological exposure to the environment.

Natural radioactivity and external dose assessment of surface soils in Vietnam

In this study, natural radioactivity in surface soils of Vietnam and external dose assessment to human population, deduced from activities of (226)Ra, (232)Th and (40)K nuclides, were determined. From 528 soil samples collected in 63 provinces of Vietnam, including five centrally governed cities, the average activities were obtained and equal to 42.77 ± 18.15 Bq kg(-1) for (226)Ra, 59.84 ± 19.81 Bq kg(-1) for (232)Th and 411.93 ± 230.69 Bq kg(-1) for (40)K. The outdoor absorbed dose rates (OADRs) in air at 1 m above the ground level for 63 provinces were calculated, and their average value was 71.72 ± 24.72 nGy h(-1), with a range from 17.45 to 149.40 nGy h(-1). The population-weighted OADR of Vietnam was 66.70 nGy h(-1), which lies in the range of 18-93 nGy h(-1) found in the World. From the OADRs obtained, it was estimated that the outdoor annual effective dose and indoor annual effective dose to the population were 0.082  and 0.458 mSv, which are higher than the corresponding values 0.07 and 0.41 mSv, respectively, of the World. The radium equivalent activity Ra(eq) and the external hazard index H(ex) of surface soils of Vietnam are lower than the corresponding permissible limits of 370 Bq kg(-1) and 1, respectively. Therefore, soil from Vietnam is safe for the human population when it is used as a building material.