Sea to land transfer of anthropogenic radionuclides to the North Wales coast, Part II: aerial modelling and radiological assessment

Modelling calculations have been performed to predict the radiological impact of the sea to land transfer pathway to members of the public in North Wales from 1952 to 2004. The radionuclides of interest were (99)Tc, (137)Cs, (239,240)Pu and (241)Am and the exposure routes considered were food consumption, external and inhalation. The consumption of locally grown terrestrial food in the early to mid 1980s was the most significant source of exposure to all of the groups considered, with (239,240)Pu being the radionuclide contributing most to the dose. A maximum dose of 1.46muSvy(-1) was calculated for adult members of the critical consumption group in 1985, with doses for 2004 reducing to 0.59muSvy(-1). Despite the conservative approach of the dose calculations, the dose rate values are very low, less than 0.15% of the annual limit of 1000muSvy(-1) for the UK public from controlled radiation sources (excluding medical).     

Occurrence and behaviour of radionuclides in the Moselle River—Part I: Entry of natural and artificial radionuclides

Various sources contribute to the radioactive contamination of the Moselle River, among which the French NPP Cattenom with four units of 1300 M We represents the most important. Appropriate operational precautions were taken in order to monitor the nuclide transfer on different pathways under normal and accidental conditions and the effectiveness of these measures has been tested using natural (²¹⁴Pb/²¹⁴Bi, ⁷Be, ⁴⁰K) and artificial radionuclides. (³H, ⁵⁸Co, ⁶⁰Co, ¹³¹I, ¹³⁷Cs) as tracers. Measurements of suspended matter have revealed that the inputs of natural nuclides exceed the discharges of the NPP Cattenom. In 1992 the annual loads of ⁷Be and ⁴⁰K in suspended matter at Palzem amounted to 21 and 130 GBq year⁻¹, whereas the emission rates of ⁶⁰Co and ¹³⁷Cs were about 2.6 and 1.0 GBq year⁻¹. The total nuclide load of ¹³⁷Cs at Palzem reached 6.2 GBq year⁻¹, which is about six times the quantity emitted by the NPP Cattenom in the same year. This excess is due to the accident at Chernobyl and to a lesser extent to prior atmospheric weapons tests.     

Distribution of radionuclides in the guano sediments of Xisha Islands, South China Sea and its implication

Several natural and anthropogenic radionuclides (²¹⁰Pb, ²²⁶Ra and ¹³⁷Cs) in guano-phosphatic coral sediments and pure guano particles collected from Ganquan, Guangjin, Jinqing and Jinyin Islands of the Xisha archipelago, South China Sea, were analyzed. The Constant Initial Concentration (CIC) model and the Constant Rate of Supply (CRS) model were applied for age calculation. The average supply rate of ²¹⁰Pb was 126 Bq m⁻² a⁻¹, very close to the flux of northern hemisphere average (125 Bq m⁻² a⁻¹). The activities of anthropogenic radionuclides in the sediments were very low, indicating that human nuclear tests did not notably impact this region. The main source of radionuclides in the sediments was from atmospheric precipitation, and the organic matter derived from plant and produced by nutrient-rich guano could further enhance them.     

Elevated concentrations of primordial radionuclides in sediments from the Reedy River and surrounding creeks in Simpsonville, South Carolina

A gamma-ray survey and analysis of 16 riverbed samples from the Reedy River watershed near Simpsonville, SC were conducted and compared with national and international studies of primordial radionuclides. The study reported here follows on a recent discovery of anomalously high uranium concentrations in several private well waters in the area. An HPGe spectrometer was used for quantification of gamma emitting radionuclides in the sediments. All sediments contained radionuclides from the uranium and thorium series as well as (40)K. Uranium-238 concentrations in sediment samples ranged from 11.1 to 74.2Bqkg(-1). The measured radionuclide concentrations were compared with data from UNSCEAR and NURE reports. The river and stream sediment data were augmented by in situ NaI(Tl) gamma-ray spectrometer measurements. Comparisons between the ex situ and in situ measurements indicate equivalently distributed uranium in the surface soils and stream sediments, the source of which is likely attributed to the monazite belts that are known to exist in the area.     

Radionuclide concentrations in soil and lifetime cancer risk due to gamma radioactivity in Kirklareli,Turkey

The objective of this study is to evaluate and map soil radionuclides' activity concentrations and environmental outdoor gamma dose rates (terrestrial and cosmic) in Kirklareli, Turkey. The excess lifetime cancer risks are also calculated. Outdoor gamma dose rates were determined in 230 sampling stations and soil samples were taken from 177 locations. The coordinates of the readings were determined by the Global Positioning System (GPS). The outdoor gamma dose rates were determined by Eberline smart portable device (ESP-2) and measurements were taken in air for two minutes at 1 m from the ground. The average outdoor gamma dose rate was 118 ± 34 nGy h^?1. Annual effective gamma dose of Kirklareli was 144 μSv and the excess lifetime cancer risk of 5.0 × 10^?4. Soil samples were analyzed by gamma spectroscopy. The average ²²⁶Ra, ²³⁸U, ²³²Th, ¹³⁷Cs, and ⁴⁰K activities were 37 ± 18 Bq kg^?1, 28 ± 13 Bq kg^?1, 40 ± 18 Bq kg^?1, 8 ± 5 Bq kg^?1 and 667 ± 281 Bq kg^?1, respectively. The average soil radionuclides' concentrations of Kirklareli were within the worldwide range although some extreme values had been determined. Annual effective gamma doses and the excess lifetime risks of cancer were higher than the world's average.     

Soil-fungi transfer coefficients: Importance of the location of mycelium in soil and of the differential availability of radionuclides in soil fractions

Soil-fungus transfer coefficients are usually defined as the ratio between the content of the fruiting bodies and that of the soil. Since, however, the methodology of how to determine the soil content is not firmly established, there exist a variety of definitions in the literature. We analyzed the 137Cs, 90Sr, 40K, and 226Ra content of mushroom and soil samples from two pine-wood ecosystems in Spain. The location of the mycelium in the soil profiles of these ecosystems was determined by means of the ergosterol concentration. The results showed the mycelium to generally be localized in the surface layer of soil (0-5 cm). We also carried out a speciation procedure for this layer of soil to determine the different degrees of association of the radionuclides in the soil. The results led us to propose some variations to the traditional definition used in quantifying radionuclide transfer. With these modifications, we were able to analyze Cs-K competition in several species of mycorrhizal and saprophytic fungi.     

Cosmogenic 7Be deposition in North Wales: 7Be concentrations in sheep faeces in relation to altitude and precipitation

Beryllium-7 (7Be) is a cosmogenic radionuclide with a half-life of 53.3 days produced mostly in the stratosphere by cosmic ray spallation of nitrogen and oxygen and entering the lower troposphere by atmospheric circulation processes. Most of the nuclide is removed by rainout during precipitation, so given that rainfall generally increases with altitude, it was considered probable that 7Be deposition would also be greater at higher altitudes. The aim of this study was to determine if there is any relationship between 7Be concentrations, altitude and precipitation by measuring 7Be activity within sheep faeces. An area of North Wales and Northwest England was selected for study, extending from the Dee Estuary at sea level to Snowdon at 1065 m. The results obtained showed a significant increase in 7Be activity with increasing altitude and precipitation consistent with predictions based on the existing literature.     

Persistent organic pollutant residues in the sediments and mollusks from the Bohai Sea coastal areas,North China: An overview

The Bohai Sea costal area is one of the most developed zones of China and the sewage water from populous and developed cities, including Beijing, Tianjin, Qinhuangdao and Dalian is discharged into the Bohai Sea. Additionally, its semi-enclosed characteristic restricts water exchange, which leads to high accumulation of pollutants in the environment. This overview presents the residues of 6 classes of Persistent Organic Pollutants (POPs), including PAHs, DDTs, HCHs, PCBs and PCDD/Fs, in the sediments and mollusks of the Bohai Sea through analyzing previous literatures. In the sediments, the highest PAH concentrations were detected in the vicinities of Qinhuangdao, while the northeast corner of the Bohai Bay possessed the highest levels of DDTs and PCBs. The investigations on HCHs and PCDD/Fs distributions on the whole sea scale have not been reported. In mollusks, PAH concentrations were in the same order of magnitude in the whole Bohai Sea, so were DDTs, HCHs and PCBs, while the outlier maximum values of PCDDs and PCDFs occurred in Yingkou. In general, the POPs residues in mollusks collected from Shandong Province were higher than the other areas. The compositions of DDTs, HCHs and PCBs in sediments indicated their recent usage. By comparing POP concentrations in sediments with the recommended criterions, it was shown that some individual PAH compounds occasionally associated with adverse biological effects in the vicinities of the Liaodong Bay and Qinhuangdao, and the Liaohe River Estuary were heavily contaminated with DDTs, but PCBs were all below the thresholds. In order to reveal the transference and transformation of POPs in the environment, further studies concerning with their behavior, fate and bioaccumulation in the different trophic levels should be programmed. Moreover, laws and regulations should be enforced to ban the illegal usage of POPs-containing pesticides to guarantee health of the environment and human.     

Variation of the activity concentrations and fluxes of natural (210Po, 210Pb) and anthropogenic (239,240Pu, 137Cs) radionuclides in the Strait of Gibraltar (Spain)

The activity concentrations and fluxes of natural (210Pb, 210Po) and anthropogenic (239,240Pu, 137Cs) radionuclides have been determined in the different water masses crossing the Strait of Gibraltar. New data have been gathered during four multidisciplinary and multinational sampling campaigns, performed between 1997 and 1999 within the framework of the CANIGO-FLUGIST Project. Mean activity concentrations of 210Po (1.53+/-0.34 Bq m(-3), n = 30) and 210Pb (1.16+/-0.50 Bq m(-3), n = 31) in the Atlantic water entering the Mediterranean basin are about double those measured in the Mediterranean outflow, namely 0.84+/-0.34 Bq m(-3) (n = 22) for 210Po and 0.66+/-0.34 Bq m(-3) (n = 22) for 210Pb. The opposite trend is observed for 231,240Pu, with average concentrations of 9.9+/-3.0 mBq m(-3) (n = 29) in the incoming Atlantic flow and 22.0+/-3.0 mBq m(-3) (n = 22) in the outpouring Mediterranean water. In the case of 137Cs, the same concentrations were quantified in the waters moving inwards (2.52+/-0.28 Bq m(-3), n = 27) and outwards (2.14+/-0.52 Bq m(-3), n = 21) from the Mediterranean Sea. On this basis, the Mediterranean basin experiences a net annual input flux of 14 TBq of 210Pb and 19 TBq of 210Po, and a net annual loss of 0.34 TBq of 239,240Pu, while--at present--137Cs input and output fluxes appear to be balanced.     

Heavy metals in the aquatic environment of the Southern Adriatic Sea, Italy: macroalgae, sediments and benthic species

Samples of sea urchins (Paracentrotus lividus), holothurians (Holothuria polii), green algae (Ulva lactuca. Codium vermilara and Enteromorpha prolifera) and sediments were collected from different coastal zones of the South Adriatic Sea (Italy). The occurrence of metals in macroalgae is poor especially if compared with that reported in other coastal areas affected by human activities, with the exception of Fe that showed high mean values (405 microg g(-1) dry wt.). Likewise, relationships between metal concentrations in holothurians and sediments were found, demonstrating that H. polii could serve as bioindicator for Hg and Cu.     

Occupational exposure to radon and natural gamma radiation in the La Carolina, a former gold mine in San Luis Province, Argentina

Radon and gamma radiation level measurements were carried out inside the La Carolina mine, one of the oldest gold mining camps of southern South America, which is open for touristic visits nowadays. CR-39 track-etch detectors and thermoluminescent dosimeters of natural CaF₂ and LiF TLD-100 were exposed at 14 points along the mine tunnels in order to estimate the mean ²²²Rn concentration and the ambient dose equivalent during the summer season (November 2008 to February 2009). The values for the ²²²Rn concentration at each monitoring site ranged from 1.8 ± 0.1 kBq m⁻³ to 6.0 ± 0.5 kBq m⁻³, with a mean value of 4.8 kBq m⁻³, indicating that these measurements exceed in about three times the upper action level recommended by ICRP for workplaces. The correlations between radon and gamma radiation levels inside the mine were also investigated. Effective doses due to ²²²Rn and gamma rays inside the mine were determined, resulting in negligible values to tourists. Considering the effective dose to the mine tourist guides, values exceeding 20 mSv of internal contribution to the effective doses can be reached, depending on the number of working hours inside the mine.     

Levels of 137Cs in muddy sediments of the seabed of the Bay of Cadiz, Spain. Part I. Vertical and spatial distribution of activities

This is the first of a two-part paper. This first part describes a detailed study conducted of the spatial and vertical distribution of the concentration of the radionuclide (137)Cs, utilising columns of sediment extracted from the seabed of the Bay of Cadiz (Spain) as specimens. The activity concentrations have been measured by means of gamma spectrometry using a HPGe detector and (137)Cs is used as an indicator of the sedimentation and contamination processes in the zone. At the same time the relationship between the levels of activity found and other hydrodynamic and sedimentological variables characteristic of the zone have been studied. The experimental results obtained will also serve to develop a model of the distribution of (137)Cs, which will be presented in the second part of this paper.     

交易费用三维度属性作用机理及交易方式选择意愿——佛山市南海区集体建设用地市场实证分析

基于广东省南海区的问卷调研,采用Tobit模型分析资产专用性、交易的不确定性和交易频率对农村集体建设用地交易费用的影响,采用Probit模型分析交易费用对市场交易方式选择的影响。(1)集体建设用地市场交易费用的研究结果:资产专用性中承租人不是本地人、受教育程度越高的人力资本资产专用性较高,会产生更高的交易费用;模型中需求方物质资产专用性没有影响;土地资产专用性中的地块离镇中心距离越近的资产专用性更高,因而其交易费用相对较高。交易的不确定性中交易行为的不确定性中交易对象为村集体,其交易费用更低;签订合同可以减少不确定性,降低履约风险,从而达到减少交易费用的目的;没有政府干预更倾向于采用接近市场的形式,交易费用低;交易环境的不确定性中采用竞标方式决定价格其交易费用较低,而采用协议方式其交易费用较高;办理了《房屋产权证》的交易其交易费用更低,产权明晰是市场有效运作的前提。(2)市场交易方式选择的研究结果:交易费用较高的情况下,承租方倾向于选择出让的交易方式;资产专用性中企业员工人数和产业状态均显著正向影响交易方式的选择,地块更靠近镇中心,企业更愿意选择出让的方式;交易的不确定性中交易行为的不确定性具有正向显著影响的因素包括交易对象、合同年限、合同是否公证;交易环境的不确定性中价格决定方式、是否知道南海区试点及南海区流转政策三个变量都显著正向影响交易方式的选择;交易频率显著正向影响交易费用,二次或多次转租的承租方会更愿意选择出租的方式进行交易。研究结论:交易费用的三个分析维度对交易费用的影响不尽一致,应根据其影响的差异性来制定相关政策,以达到降低市场交易费用的目的。