Soligo, Michele

New analyses of marine terraces in the Tyrrhenian Sea margin of Basilicata - northern Calabria (southern Italy) have been carried out. In the study area, c. 25 km in length, an impressive flight of marine terraces occurs, with the highest terraces reaching ~160 m a.s.l. Detailed geomorphological-stratigraphical analyses on remnants of paleoshorelines located within 60 m a.s.l. have shown that the rocky coast of the investigated coastal stretch has been affected by multiple relative sea-level fluctuations, during which reworking of older shorelines has occurred. Dating of the coral Cladocora caespitosa and speleothems, either predating or postdating single paleoshorelines, has allowed the construction of a chronological framework for the identified relative sea-level markers, and their correlation with MIS 7, MIS 6e and distinct peaks of MIS 5. A mean uplift rate of c. 0.25 mm/y since the Last Interglacial has been quantified, one order of magnitude larger than previous estimates. The uplift rate value has been used to infer the elevations of MIS 5a, 5c and 6e sea level peaks, which are higher than those reported in most sea level curves worldwide, although consistent with several findings from the western Mediterranean. Our results demonstrate that a mere sequential correlation may be misleading in the interpretation of flights of marine terraces and indicates that multiple age controls are crucial to unravelling the complex interaction between uplift and sea-level fluctuations in uplifted coastal areas. The reconstructed MIS 5a, 5c and 6e sea level paleo-elevations, besides contributing to the assessment of late Quaternary sea-level fluctuations in the Mediterranean Sea, may contribute to constrain coeval ice sheets volume variations.

In the frame of Radon rEal time monitoring System and Proactive Indoor Remediation (RESPIRE), a LIFE 2016 project funded by the European Commission, the contribution of building materials of volcanic origin to indoor radon concentration was investigated. First, total gamma radiation and related outdoor dose rates of geological materials in the Caprarola area (Central Italy) were measured to defi ne main sources of radiation. Second, Rn-222 and Rn-220 exhalation rates of these rocks used as building materials were measured using an accumulation chamber connected in a closed loop with a RAD7 radon monitor. Among others, the very porous “Tufo di Gallese” ignimbrite provided the highest values. This material was then used to construct a scale model room of 62 cm × 50 cm × 35 cm (inner length × width × height, respectively) to assess experimental radon and thoron activity concentration at equilibrium and study the effects of climatic conditions and different coatings on radon levels. A fi rst test was carried out at ambient temperature to determine experimental Rn-222 and Rn-220 equilibrium activities in the model room, not covered with plaster or other coating materials. Experimental Rn-222 equilibrium was recorded in just two days demonstrating that the room “breaths”, exchanging air with the outdoor environment. This determines a dilution of indoor radon concentration. Other experiments showed that inner covers (such as plasterboard and different kinds of paints) partially infl uence Rn-222 but entirely cut the short-lived Rn-220. Finally, decreases in ambient temperature reduce radon exhalation from building material and, in turn, indoor activity concentration.

This paper presents a detailed geological map at the 1:20,000 scale of the Tocomar basin in the Central Puna (north-western Argentina), which extends over an area of about 80 km2 and displays the spatial distribution of the Quaternary deposits and the structures that cover the Ordovician basement and the Tertiary sedimentary and volcanic units. The new dataset includes litho-facies descriptions, stratigraphic and structural data and new 234U/230Th ages for travertine rocks. The new reconstructed stratigraphic framework, along with the structural analysis, has revealed the complex evolution of a small extensional basin including a period of prolonged volcanic activity with different eruptive centres and styles. The geological map improves the knowledge of the geology of the Tocomar basin and the local interplay between orogen-parallel thrusts and orogen-oblique fault systems. This contribution represents a fundamental support for in depth research and also for encouraging geothermal exploration and exploitation in the Puna Plateau region.

Rock substrates beneath active volcanoes are frequently subjected to temperature changes caused by the input of new magma from the depth and/or the intrusion of magma bodies of variable thickness within the subvolcanic rocks. The primary effect of the influx of hot magma is the heating of surrounding host rocks with the consequent modification of their physical and chemical properties. To assess mobilization in subvolcanic thermal regimes, we have performed radon (220Rn) thermal experiments on a phonolitic lava exposed to temperatures in the range of 100-900°C. Results from these experiments indicate that transient Rn signals are not unequivocally related to substrate deformation caused by tectonic stresses, but rather to the temperature-dependent diffusion of radionuclides through the structural discontinuities of rocks which serve as preferential pathways for gas release. Intense heating/cooling cycles are accompanied by rapid expansion and contraction of minerals. Rapid thermal cycling produced both inter- and intra-crystal microfracturing, as well as the formation of macroscopic faults. The increased number of diffusion paths dramatically intensified Rn migration, leading to much higher emissions than temperature-dependent transient changes. This geochemical behaviour is analogous to positive anomalies recorded on active volcanoes where dyke injections produce thermal stress and deformation in the host rocks. An increased Rn signal far away from the location of a magmatic intrusion is also consistent with microfracturing of subsurface rocks over long distances via thermal stress propagation and the opening of new pathways.

Naturally occurring 222Rn is increasingly recognized as a powerful environmental tracer in hydrology. Radon-in-water concentrations can be measured in the field by stripping radon from a water sample into a gas volume and measuring the respective radon-in-gas concentration using a portable radon-in-gas monitor. Alternatively, radon is firstly extracted from the water body by diffusion through a radon exchanger such as polypropylene (PP) tubing and then is measured using a radon-in-gas monitor, connected in closed-loop to the PP membrane. The paper discusses results of field experiments in which the Radon-in-Water Probe (Durridge co.), a 2.2 m long PP tubing, connected to a RAD7 monitor (method A), is used to determine dissolved radon concentration in four water bodies characterised by different water flow velocity and radon concentration. The efficiency of this method is validated by comparison with two established methods, gamma-ray spectrometer + charcoal canister (method B) and RAD7 monitor + Big Bottle RAD H20 accessory (method C). Relative efficiency of method A is directly proportional to water flow velocity, ranging from about 0.50 ± 0.05 at 0.01 m/s to about 0.92 ± 0.08 at 0.57 m/s. A minimum of 2–3 h are needed to collect enough records to asymptotically fit radon-in-gas data and obtain equilibrium radon concentration, which is then converted into radon-in water concentration, considering the temperature-dependency of radon partition coefficient between water and air. Equilibrium condition is reached after about 6–8 h. No correlation was found between relative efficiency and radon concentration. An equation is proposed to correct radon data as a function of water flow velocity, even for poorly moving water bodies. The DURRIDGE Water Probe is useful to monitor radon-in-water levels, without the potential risk of radon loss during water sampling and sample handling. However, it must be pointed out that duplicate or triplicate sampling using other methods similarly permit to evaluate whether radon loss is an issue.

An integration of laboratory radon and thoron exhalation data with gamma radiation mapping is applied to assess the geogenic radon and the exposure of people to natural radiation in a highly-urbanized city (Roma, Italy). The study area is a protected territory where ignimbrites from Colli Albani volcano and alluvial sediments largely crop out. A map of total gamma radiation, a gamma transect across Caffarella valley and 9 vertical gamma profiles have been carried out, showing that the main control of gamma levels is, of course, the lithological nature, without neglecting the simultaneous effect of other parameters such as slope morphology, erosion/weathering processes, occurrence of sinkholes or underground tunnels. The surveys allowed to distinguish the medians of ignimbrites (from 816 ± 16 cps to 936 ± 19 cps) from that of alluvial materials (611 ± 14) cps), but showed also that alluvial sediments with anomalously high radioactivity (769 ± 14 cps) can be locally recognized, providing valuable information on the interaction between sedimentation and erosion in fluvial valleys. Total gamma activity was converted into absorbed gamma dose rate ranging from 0.33 to 0.38 μSv/hr. Outdoor Annual Effective Dose Equivalents were also estimated between 0.58 and 0.67 mSv y-1. Laboratory radon and thoron exhalation rates of collected material are positively correlated with gamma radiation. Volcanic and alluvial sediments are well-discriminated. The correlation between the two variables is evident, but not robust because of the variable concentration of 40 K, which is not contributing to radon and thoron exhalation rates. Anomalous data of soil samples located at the foot of a slope can be interpreted as due to reworking and accumulation processes. Similar gamma radiation data documents analogous concentration of radon and thoron parent-nuclides, but coexisting different radon and thoron exhalation rates provides an additional information on different grain size distributions which can be considered as a proxy for soil gas permeability. The integration of gamma mapping and radon and thoron exhalation measurements is a very useful tool to assess people exposure to natural radiation, in terms of dose rates and potential indoor radon. Gamma mapping, which provides data on the radiation source (the bedrock) is fast and not expensive. It allows to obtain very detailed pictures of a study area, but it needs to be combined with laboratory determination of radon and thoron release in order to definitely and correctly interpret variations of gamma signal. Furthermore, laboratory determination of soil radon exhalation gives information on the release of radon and is a good proxy for soil gas permeability. It has the great advantage over in-situ measurements of gas flow not to be influenced by seasonal pedoclimatic parameters and is affected by lower analytical uncertainties. These data are thus reproducible and precise and can be used to estimate potential radon hazard, which is the main source of exposure and thus the most important parameter for human protection from environmental radioactivity.

Radon isotopes (222Rn, 220Rn) are noble, naturally occurring radioactive gases. They originate from the alpha decay of radium isotopes (226Ra, 224Ra), which occur in most materials in the environment, i.e. soil, rocks, raw and building materials. Radon is also found in ground and tap water. The two radon isotopes are chemically identical, but they have very different halflives: 3.82 days for radon (222Rn) and 56 seconds for thoron (220Rn). Thus, they behave very differently in the environment. Both isotopes are alpha-emitters; their decay products are polonium, bismuth and lead isotopes. The main source of radon in air (indoor or outdoor) is soil, where radon concentrations are very high and reach tens of Bq/m3. Radon release from soil into the atmosphere depends on radium (226Ra) concentration in soil, soil parameters (porosity, density, humidity) and weather conditions (e.g. air temperature and pressure, wind, precipitation). Outdoor radon concentrations are relatively low and change daily and seasonally. These changes may be used to study the movement of air masses and other climatic conditions. Radon gas enters buildings (homes, workplaces) through cracks, crevices and leaks that occur in foundations and connections between different materials in the building. This is due to temperature and pressure differences between indoors and outdoors. Indoor radon is the most important source of radiation exposure to the public, especially on ground floor. Radon and its decay products represent the main contributor to the effective dose of ionising radiation that people receive. Radon is generally considered as the second cause of increased risk of lung cancer (after smoking). The only way to assess indoor radon concentration is to make measurements. Different methods exist, but the most common one is to use track-etched detectors. Such detectors may be used to perform longterm (e.g. annual) measurements in buildings. The exposure time is important because indoor radon levels change daily and seasonally. Moreover, radon concentration shows a high spatial variation on a local scale, and is strongly connected with geological structure, building characteristics and ventilation habits of occupants. A European map of indoor radon concentration has been prepared and is displayed. It is derived from survey data received from 35 countries participating on a voluntary basis.

Radon monitoring represents an important investigation tool for environmental changes assessment and geochemical hazard surveillance. Despite anomalous radon emissions are commonly observed prior to earthquakes or volcanic eruptions, radon monitoring alone is not yet successful in correctly predicting these catastrophic events because contrasting radon signals are unexpectedly measured by lithologically distinct areas. This contribution aims to summarize and integrate natural and laboratory studies pertaining to the transport behavior of radon in different rock types experiencing variable stress and thermal regimes at subvolcanic conditions. The final purpose is to ignite novel and pioneer experimental researches exploring the causes and consequences of radon anomalous emissions, in order to elucidate in full the relationship between the physicochemical changes in substrate rocks and the radon signal.