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Journal of Environmental Science and Engineering(A) 2017年第3期6卷 149-154页

作者： Guillermo Espinosa jose-ignacio golzarri Physics Institute National Autonomous University of Mexico Mexico City 04510 Mexico

The aim of this study is to determine the indoor radon and thoron concentration distribution on three detection planes, inside of a controlled closed room with microclimate conditions with NTM （Nuclear Track Methodology）, using CR-39 Lantrack bared detectors. One hundred sixty two （162） 1.9 cm × 0.9 cm CR-39 polycarbonate chips were placed in each one of the three planes, 2.0 m × 2.0 m square structures, distributed uniformly in 18 columns and 18 lines, in each plane. After three months exposure to indoor radon and thoron inside of the closed room, with a main concentration value of 862 ± 49 Bq/m3, all the detectors were chemically etched in KOH-6.25M solution to 60 ± 1 ℃ for 18 h, following the well established protocols for indoor radon survey, by the Dosimetry Applications Laboratory of the Physics Institute, UNAM （National Autonomous University of Mexico） and later on read by DIAS （Digital Image Analysis System）.The results show that the radon and thoron concentration distribution is not homogeneous in anyone of the planes faces. The six faces of the three planes measured, have a very particular distribution. From the results, it can be observed that each side of each plane shows a peculiar distribution, with gradients of concentrations higher than 50% from one area to another of the same measured plane. These results can help to understand the dynamics of the radioactive gases,and their measurements.

关键词： Indoor radon radon nuclear tracks

Indoor Radon （^222Rn） Concentration Level Study in Child Care Centers and Kindergartens, Using Nuclear Track Methodology （NTM）

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Journal of Environmental Science and Engineering(A) 2016年第12期5卷 599-605页

作者： Guillermo Espinosa jose-ignacio golzarri Physics Institute National Autonomous University of Mexico Mexico City 04510 Mexico

As it is known, staying for long periods of time in a place with high concentration of radon is a health hazard. This health risk can be increased into adulthood, if at infant ages the young people grow inside places with important indoor radon levels. Causal associations between exposure level and lung cancer have been demonstrated in epidemiological studies around the world, suggesting that for younger age children groups, the risk coefficient of lung cancer for inhaled radon and their daughters is about a factor of 4 on children from recent born to 10 years old, and 2 for ages between 10 to 20 years old. The aim of this work is to determine the indoor radon levels where infants, from 3 months to 6 years old, remain long times in child care centers and kindergartens. Indoor radon （222Rn） concentration levels were measured in the child care centers and kindergartens of the 16 political administrative regions, covering 5% of the total in Mexico City. This study was conducted over a one-year period, divided into four three-month periods coinciding with the seasons. Nuclear Track Methodology was selected for the measurements, and a passive close-end-cup-device was designed specifically to be used in children places. In this study, the results of measurements of indoor radon concentration in child care centers and kindergartens in Mexico City are encouraging, finding indoor radon levels between 26 Bq/m^3 and 75 Bq/m^3 with an average value of 51 Bq/m^3. It can be considered that the indoor radon concentration levels are low in this type of buildings, due to the benign climate in the city, the architecture design of the constructions, and the ventilation habits of the population.

关键词： Indoor radon radon nuclear tracks kindergartens.

Assessment of Present and Future Radioactive Contamination at Global Scale

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Journal of Chemistry and Chemical Engineering 2012年第11期6卷 1010-1015页

作者： Juan Manuel Navarrete Miguel Angel ZUNiga Guillermo Espinosa jose ignacio golzarri Faculty of Chemistry National University of Mexico Mexico City 04510 Mexico Institute of Physics National University of Mexico Mexico City 04510 Mexico

As a result of more than two thousand nuclear tests performed since 1945, two war actions and few accidents in nuclear reactor, it does already exist a radioactive contamination at global scale. This contamination has been accumulated mainly in marine sediments, because sea is about 80% of planet surface, and solid fission products released by nuclear explosions are transported by wind first and then by rain to liquid and solid portions on earth, while gaseous fission products are diffused in the atmosphere. In this way, heavy, high yielding fission products, such as 137Cs, get marine sediments, where they are found mixed with heavy radioactive natural elements such as U, Th and their also radioactive decay products. But since alkaline are so abundant on earth, it is also found natural radioactive isotope 4~K, 0.0118% of isotopes forming K element, with half life 1.28 ~ l09, in the time range of planet age and elements origin. So, one easy way to assess both the importance and evaluation of radioactive contamination at global scale should be to establish a RCF （radioactive contamination factor） as a percentage of 137Cs contaminant radioactivity in marine sediments, compared to 4~K natural radioactivity present from the very beginning of earth, both expressed as Bq per gram of sediment. In the frame of these rather general considerations, a research project has started in Mexico whose varied purposes are： to characterize sea regions in both vast littorals in the country, by its natural 4~K radioactivity present in sea salts, as well as to determine if 137Cs traces produced by recent radioactive contamination have reached their coasts. Also, to assess the 137Cs traces already present in marine sediments as a result of more than two thousand nuclear test explosions performed till now, rather than contamination produced by four main accidents in nuclear reactors during the last 60 years. It is proposed a radioactive contamination factor obtained from samples taken up in

关键词： Contaminant natural radioactivity relation coefficient.

Study of the Opuntia ficus indica and Its Radioactive Potassium Content using the Gamma Spectrometry

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Journal of Environmental Science and Engineering(B) 2016年第4期5卷 167-172页

作者： Guillermo Espmosa jose-Ignaclo golzarri Edgar Padilla-Soriano Physics Institute National Autonomous University of Mexico (UNAM) Mexico City 04520 Mexico Chemistry Faculty National Autonomous University of Mexico (UNAM) Mexico City 04510 Mexico

Mexico is one of the largest producers of nopal （Opuntiaficus indica）. This ＂vegetable＂ is consumed on a daily basis by the Mexican population, being a source of food nutrients. Among its benefits, it is considered the content of potassium, which is essential for human life and health. In this study, it analyzes the content of potassium of the Mexican cactus （Opuntiaficus indica） grown in 5 different regions in the Mexican Basin, where 67% of the nopal is produced for human consumption. The used methodology is gamma spectrometry with Hyperpure Germanium detector （HPGe） and Multichannel Analyzer （MCA） with Maestro~ software. The results show interesting aspects on the concentration of potassium in the nopal. This concentration will primarily depend on：（a） the geological characteristics of the location where the nopal was grows; （b） that potassium concentrations may vary substantially from a region to another, with the same species of nopal as a reference and （c） that this concentration may also vary from one growing season to another.

关键词： Potassium nopal (Opuntiaficus indica) gamma spectrometry K-40 HPGe.

Mapping of Radon (<sup>220</sup>Rn and <sup>222</sup>Rn) Concentration Distribution in a Microclimate Condition Cellar Using Nuclear Track Methodology

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Journal of Environmental Protection 2019年第7期10卷 919-928页

作者： Guillermo Espinosa José-ignacio golzarri Alfonso M. Román-Sedano Fermín Castillo Instituto de Física Universidad Nacional Autónoma de México Circuito de la Investigación Científica Ciudad Universitaria Coyoacán Ciudad de México México Laboratorio de Espectroscopia Instituto de Ciencias Físicas Universidad Nacional Autónoma de México Cuernavaca México

This work presents the results of the Radon (220Rn and 222Rn) measurements made with 486 chips of CR-39 (Allyl Dyglicol Poly Carbonate) MASL? bared detectors, in a reticular mode distribution, inside of a cellar with average indoor radon concentration 862 ± 49 Bq/m3. The exposure time was 3 months, in microclimate condition of constant temperature, humidity, barometric pressure and no airflow. After these 3 months, all the detectors were chemically etched in KOH 6.25 M solution at 60°C ± 1°C for 18 hours, following a very well established protocol for indoor radon survey by the Dosimetry Applications Laboratory of the Physics Institute of the National Autonomous University of Mexico, and later read automatically by CADIS (Counting Automatically Digital Image System). The results show that each one of the nine measured planes is not homogeneous presenting important differences of indoor radon concentration values. Specifically, the Radon (220Rn and 222Rn) concentration levels vary for each measured point within the cellar. It is a very important observation to consider for the calculation of dose and radiological risk.

关键词： Indoor Radon Mapping Radon Distribution Nuclear Track Methodology NTM

Radioactive Contamination Factor(RCF)Obtained by Comparing Contaminant Radioactivity(^(137)Cs)with Natural Radioactivity(^(40)K)in Marine Sediments Taken up from Mexican Sea Waters

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World Journal of Nuclear Science and Technology 2014年第3期4卷 158-162页

作者： Manuel Navarrete Miguel A.Zúniga Guillermo Espinosa José I.golzarri Faculty of Chemistry National University of MexicoMexico CityMexico Physics Institute National University of MexicoMexico CityMexico

Radioactive contamination at planet scale started in 1945 when the first nuclear taste was performed in Alamo Gordo, New Mexico, followed by two war actions in Japan, a second test in Bikini, and more than 2000 tests were performed all over the world by different countries since then on. In this context, 10 main accidents in power and research nuclear reactors seem to be negligible in the general radioactive contamination at planet scale, which can be measured by comparing radioactivity of fission product 137Cs with that of natural 40K, both detected from marine sediments taken up at different places and depth. This paper shows 9 results obtained from Gulf of Mexico samples and one from Pacific North ocean, confirming the fact that this simple method works well enough to keep watching the process of radioactive contamination on earth, whatever may be the cause, to prove if it remains constant for a time, by equilibrium between contamination and decaying of 137Cs, it is decreasing at same rate than 137Cs radioactive decaying, or by the contrary, it is growing up and approaching at some extent the natural radioactivity from 40K.

关键词： Radioactive Contamination Factor Sea Sediments