• NEANIAS Atmospheric Research Community

We report measurements of radon gas concentration in two deep gold mines in Ghana, viz Tarkwa Goldfields, and Prestea Goldfields. Radon concentrations measured underground at Tarkwa were in the range 56 Bq m-3 to 268 Bq m-3. Corresponding values for Prestea were 43 Bq m-3 to 878 Bq These results represent the first published data on underground radon concentration in deep gold mines in Ghana. Measurement of the radon gas was done by means of the solid-state nuclear track technique, with CR-39 plastic as a recording medium for the alpha particles from radon decay. The study is part of a nation-wide radon monitoring programme.

The L'Aquila seismic swarm culminated with the mainshock of April 6, 2009 (ML = 5.9). Here, we report and analyze the Large Volume Detector (LVD, used in neutrinos research) low energy traces (∼0.8 MeV), collected during the early-mid stages of the seismic sequence, together with the data of a radon monitoring experiment. The peaks of LVD traces do not correlate with the evolution and magnitude of earthquakes, including major aftershocks. Conversely, our radon measurements obtained by utilizing three automatic stations deployed along the regional NW-SE faulting system, seem to be, in one case, more efficient. In fact, the timeseries collected on the NW-SE Paganica fracture recorded marked variations and peaks that occurred during and prior moderate aftershocks (with ML > 3). The Paganica monitoring station (PGN) seems to better responds to active seismicity due to the fact that the radon detector was placed directly within the bedrock of an active fault. It is suggested that future networks for radon monitoring of active seismicity should preferentially implement this setting.

Since many years radon measurements became customary in a wide-spreading applications. Radon is used as geophysical tracer for locating buried faults and geological structures, in exploring for uranium, and for predicting earthquakes. It is also been used as tracer in the study of atmospheric transport processes and there have been many other application in meteorology, water research and medicine. In any case, the great majority of radon measurements are performed to evaluate the health risk due to radon daughters inhalation in indoor air. Indeed, for many years it is well known that radon and its decay products are the largest source of human exposure to environmental radiations. Since many epidemiological studies confirmed a correlation between lung cancer risk and radon exposure, most of the countries have introduced in their own legislation limits on the 222Rn indoor concentration in particular working places. Moreover, this specific exposition source shows peculiar mechanisms of dose assessment. In fact, the real responsible of the effective dose are the inhaled radon progeny whose behavior is strictly dependent on different air conditions. Thus, the main topics of investigation are the properties of radon progeny, its interaction with aerosol molecules and its deposition mechanism onto surfaces. In this contest, it is mandatory to carry out high-quality radon measurements which are guarantied by calibration facilities, suitable for the determination of calibration in a wide range of variability of all parameters involved and in many different experimental situations. In fact a large number methods have been developed for the radon measure in different situations and matrices and each of them requires a large variety of sampling technique and appropriate instruments. Thus, calibration procedures have to be settle for each measurements method, that account for the particular sampling and detecting processes. To calibrate correctly radon detectors, it is necessary to refer the instruments response to measurement standards, that are defined in term of different parameters, such as radon activity, radon activity concentration and so on. All of these standards have to be traceable to a reference 222Rn standard developed by the national metrology institutes. In this thesis it will be described the procedures involved in the development of a facility able to perform radon detector calibration as well as to carry out experiments for study the radon progeny behavior at controlled radon atmospheres. The radon sources are produced by emanation from a solid radium source, and an electrostatic cell is used as continuous monitor for the radon exposure determination inside a Radon chamber. This monitor, whose response is highly dependent from environmental air conditions, was characterized studying its response under different values of temperature, humidity and pressure using both an experimental and a numerical approach. The exposure chamber, equipped by a set of environmental sensors, can be used for the calibration of passive radon detector. Various tests have been carried out to study its reliability. In the first chapter the radon and its decays properties are described, including some important definitions. It follows a description of its measurements methods, related to the most used passive and active detectors. In the second chapter it will be illustrated the methods of the electrostatic collection for the active radon monitoring, that will be the technique used to control radon concentration in our facility with a suitable instrument (Ramona). In this context it will be described the physical factors that influence the 218Po+ collection as well as the experiments that have investigated the mechanism involved in its neutralizations. In this section we focus our attention on the use of the electrostatic collection technique to measure some important radon progeny physical parameters with both a theoretical and an experimental approach. Some remarks will be done about the importance of the characterization of the radon monitor against climatic parameters. In the following chapter, we will describe in detail the facility built for the Ramona calibration against temperature, humidity and pressure variation. It was also pointed out the importance of the traceability of the radon measurements to national standard and it will be described our metrology chain that refers to ENEA-INMRI primary radium source. In the fourth chapter we will illustrate the experimental results and the Monte Carlo methods used for the determination of the neutralization rates and to infer the electrostatic collection dependence on environmental parameters inside the radon monitor. The description of the radon chamber characteristics will be done in the fifth chapter. Here it will be also introduced new methods for the continuous radon monitoring in a small exposure volume. Conclusion and some perspective on the future radon studies with the developed radon facility will be outlined in the last chapter.

We used a network of stations to perform systematic radon surveys at Stromboli volcano. The time series of periodic measurements show that monthly average 222Rn emissions reflect changes in volcanic activity and exhibit increasing trends prior and during the last major eruptive cycles. Maps of radon emissions indicate that diffuse degassing is operative at Stromboli volcano. Concentrated degassing essentially occurs in the summit area and within a sector proximal to the two major NE trending faults. These sites were chosen for deploying the two real-time stations that are currently operating at Stromboli. In these devices, the 222Rn electronic dosimeters are connected to a radiomodem for wireless data transfer to a receiving station at the volcano observatory. Radon activity, soil temperature and atmospheric pressure data are sampled and instantaneously transferred via web so that they can be checked remotely. Collected time series reveal an overall inverse correlation between radon emissions and seasonal temperature variations. Radon emissions in sectors of diffuse degassing are modulated by tidal forces as well. Radon activities recorded at the summit station, located along the fracture zone where the gas flux is concentrated, are positively correlated with changes in atmospheric pressure and confirm the occurrence of the “atmospheric stack effect”. We finally emphasize that real-time radon monitoring is an innovative technique that may be systematically applied in volcano surveillance.

Radon gas has been declared a human carcinogen by the United States Environmental Protection Agency (USEPA) and the International Agency for Research on Cancer (IARC). Several studies carried out in Spain highlighted the high radon concentrations in several regions, with Galicia (northwestern Spain) being one of the regions with the highest radon concentrations. The objective of this work was to create a safe and low-cost radon monitoring and alert system, based on open source technologies. To achieve this objective, the system uses devices, a collection of sensors with a processing unit and a communication module, and a backend, responsible for managing all the information, predicting radon levels and issuing alerts using open source technologies. Security is one of the largest challenges for the internet of things, and it is utterly important in the current scenario, given that high radon concentrations pose a health risk. For this reason, this work focuses on securing the entire end-to-end communication path to avoid data forging. The results of this work indicate that the development of a low-cost, yet secured, radon monitoring system is feasible, allowing one to create a network of sensors that can help mitigate the health hazards that high radon concentrations pose.

Radon monitoring in the world literature is recognized as a promising method for predicting earthquakes. In the last decade on the Kamchatka Peninsula, the prospect of radon method to forecast subduction earthquakes has been quite convincingly demonstrated. The southern part of Sakhalin Island is a region of high seismic risk. The results obtained on Kamchatka give grounds to hope for the detection of precursor anomalies in the radon field (Rn) and for weaker, but also dangerous, small-focus earthquakes on Sakhalin Island. A network consisting of three points for monitoring volume activity of radon (VA Rn) in the air of the subsoil is currently operating in the test mode in the south of Sakhalin Island. In order to better understand the conditions of Rn migration to the surface, seismic survey was performed in the vicinity of the installed radiometers. Volume activity of radon is registered by α-radiation using the method of forced convection. The manifestation of weak seismic activity in the south of Kuril-Kamchatka and in the north of the Japanese seismic regions was reflected in the dynamics of the subsurface radon at two points. After testing the equipment and installing stationary points, it is planned to use radon monitoring data as an additional parameter to substantiate conclusions about the seismic hazard of the south of Sakhalin Island. Радоновый мониторинг в мировой литературе признан перспективным методом для прогноза землетрясений. В последнее десятилетие на полуострове Камчатка достаточно убедительно продемонстрирована перспективность радонового метода для прогноза субдукционных землетрясений. Южная часть острова Сахалин является регионом высокой сейсмической опасности. Результаты, полученные на Камчатке, дают основание надеяться на обнаружение предвестниковых аномалий в поле радона (Rn) и для более слабых, но не менее опасных, мелкофокусных землетрясений острова Сахалин. В тестовом режиме на юге острова Сахалин в настоящее время функционирует сеть из трех пунктов мониторинга объемной активности радона (ОА Rn) в воздухе подпочв. С целью лучшего представления об условиях миграции Rn к дневной поверхности в окрестности установки радиометров выполнены сейсморазведочные работы. Регистрация объемной активности радона ведется по α-излучению с использованием метода принудительной конвекции. Проявление слабой сейсмической активности на юге Курило-Камчатской и на севере Японской сейсмогенных областей нашло отражение в динамике подпочвенного радона на двух пунктах. После обкатки аппаратуры и установки стационарных пунктов планируется использовать данные радонового мониторинга в качестве дополнительного параметра для обоснования заключений о сейсмической опасности юга острова Сахалин. №5(25) (2019)