The imprint of thermally induced devolatilization phenomena on radon signal. Implications for the geochemical survey in volcanic areas

Thermal gradients due to magma dynamics in active volcanic areas may affect the emanating power of the substrate and the background level of radon signal. This is particularly effective in subvolcanic substrates where intense hydrothermal alteration and/or weathering processes generally form hydrous minerals, such as zeolites able to store and release great amounts of H2O (up to ∼25 wt.%) at relative low temperatures. To better understand the role played by thermally induced devolatilization reactions on the radon signal, a new experimental setup has been developed for measuring in real time the radon emission from a zeolitized volcanic tuff. Progressive dehydration phenomena with increasing temperature produce radon emissions two orders of magnitude higher than those measured during rock deformation, microfracturing and failure. In this framework, mineral devolatilization reactions can contribute significantly to produce radon emissions spatially heterogeneous and non-stationary in time, resulting in a transient state dictated by temperature gradients and the carrier effects of subsurface gases. Results from these experiments can be extrapolated to the temporal and spatial scales of magmatic processes, where the ascent of small magma batches from depth causes volatile release due to dehydration phenomena that increase the radon signal from the degassing host rock material

Indoor/outdoor air exchange affects indoor radon – the use of a scale model room to develop a mitigation strategy

Abstract. Indoor/outdoor air exchange on indoor radon concentration was investigated. We evaluated the effect of air extraction versus air introduction at different flow rates on equilibrium 222Rn activity concentrations in a scale model room of 62 cm × 50 cm × 35 cm (inner length x width × height), made of a porous, radium and thorium-rich lithoid ignimbrite (Tufo di Gallese) from Vico volcano (Lazio, central Italy). Experiments were carried either with the inner walls of the chamber covered with a plasterboard shield or without any inner coating. Air introduction was always more effective than air extraction to reduce indoor 222Rn and, in both cases, higher flow rates produced higher 222Rn decreases. The presence of the plasterboard enhanced 222Rn reduction when outdoor air was introduced in the chamber. Main results were that, with plasterboard, maximum reductions of 89.5 % and 25.0 % were obtained introducing and extracting air, respectively; without plasterboard, we found maximum radon decreases of 33.2 % and 26.6 %, namely with air introduction or extraction. The diffusion of 222Rn through the walls of the scale model room was modelled with a modified version of Fick's second law, where a term considering air flow velocity was added. These findings suggested that the combined use of proper coatings on the inner walls of a house and outdoor air introduction at suitable rates are a good strategy to approach radon mitigation actions

Use of commercial biochar for river water purification in the Lazio region, Italy

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Endokarst costero, niveles marinos y tectónica: el ejemplo de la costa oriental de Mallorca

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Dataciones Th/U de espeleotemas freáticos controlados por el nivel marino, procedentes de cuevas costeras de Mallorca

[cat] Actualment és possible constatar la formació d'espeleotemes freàtics en la superfície dels llacs salobrosos de nombroses coves costaneres de l’illa de Mallorca (Espanya); la seva presència registra amb precisió l’altura mitjana del nivell marí en el moment de la deposició d'aquests carbonats freàtics. Per tant, els dipòsits antics d'espeleotemes freàtics poden ser utilitzats per a reconstruir les fluctuacions de la Mediterrània durant el Pleistocè ja que existeixen, en diverses coves de l’àrea en estudi, abundants alineacions elevades d'aquests espeleotemes que delimiten paleonivells assolits per les aigües freàtiques. S'han datat alguns espeleotemes freàtics, usant el mètode Th/U, amb la intenció de determinar la posició del nivell marí durant el Pleistocè mitjà i superior. Han estat reconegudes tres estabilitzacions altes de la Mediterrània a diferents altures -entre 1,4 i 2,5 metres per damunt de l’actual nivell de fa mar -en coves localitzades en distints sectors de la costa oriental de Mallorca. Les esmentades estabilitzacions es remunten a edats entorn dels 83, 108 i 124 ka B.P. i poden ser relacionades amb diversos events menors dins de l’estadi 5 del registre marí d’isòtops d'oxigen. Així mateix, s'inclouen en aquesta nota algunes dades mineralògiques sobre els espeleotemes datats. Es poden observar diferències d'altura de fins 1 metre en mostres pertanyents al mateix paleonivell marí. Hi són particularment ben documentades les corresponents al subestadi isotòpic 5e, el qual es presenta registrat a altituds majors en les localitats mes septentrionals. Aquestes anomalies altimètriques han de ser explicades en base a una deformació tectònica recent de l’àrea investigada.[eng] Phreatic speleotherns form today at the surface of the brackish pools existing inside littoral caves of Mallorca island (Spain); their occurrence directly identifies the height of the sea level at the time of carbonate deposition. Therefore, ancient phreatic speleothems can be used to reconstruct Mediterranean fluctuations during the Pleistocene, since many raised alignments of these deposits are present in several caves of the studied area. Some phreatic speleothems have been dated using the Th/U method in order to determine the position of the sea level during the Middle and Upper Pleistocene. Three high sea-stands have been recognized at different heights -bemeen 1.4 and 2.5 meters above current sea level- in caves located in various sectors of the eastern coast of Mallorca. They date back to around 83, 108 and 124 ka B P and can be related to several minor events within stage 5 of the marine oxygen isotope record. Some mineralogical data about the analyzed samples are also included in this paper. Differences in height of about 1 meter can be observed in samples corresponding to the same sea paleolevel. Those which are particularly well-documented pertain to substage 5e, with higher elevations towards the northernmost localities. These altimetrical disturbances could be explained in terms of a tectonic tilt of the investigated area

Sea level change at Capo Caccia (NW Sardinia) and Mallorca (Balearic Islands) during oxygen isotope substage Se, based on Th/U datings of phreatic overgrowths on speleothems

Sea level changes during Last Interglacial (substage Se) have been documented in two sites of the Western Mediterranean area: Mallorca Island (Balearic Archipelago) and Capo Caccia area (NW Sardinia). Past sea stands have been recorded by overgrowths of phreatic crystallizations developing around previously formed vadose speleothems. These carbonate coatings have been U-series dated, mostly using multicollector inductively coupled mass spectrometry. Two high sea stands have been recognised along the eastern coast of Mallorca at about 1.5 - 3 metres a.p.s.l, from 135 to 109 ka B.P., with a rapid episode of regression around 125 ka. The average duration of the older high stand episode can be estimated at 9.5 ka and that of the younger at 12.8 ka. So far only the younger stand has been found in Capo Caccia area at 4.3 m a.p.s.l., with a minimum duration of 3 ka. The difference in elevation of late Se high stand, recorded at Mallorca and Capo Caccia, can be only partly justified by neotectonic activity and is probably the result of different responses of the two areas, (owing to their different crustal thickness) to the change in the water loading characterising the glacial-interglacial cycles.Els canvis del nivell de la mar durant el darrer interglacial (subestadi isotòpic Se) han estat documentats en dues àrees de la Mediterrània occidental: l'illa de Mallorca (Illes Balears) i la zona de Capo Caccia, a I' Alguer (NW de Sardenya). A les coves costaneres d'aquestes illes, antigues estabilitzacions del nivell marí es troben enregistrades mitjançant sobrecreixements de cristal·litzacions freàtiques que es desenvoluparen al voltant d'espeleotemes vadosos preexistents. Aquests recobriments de carbonats s'han datat amb el mètode de les sèries de l'Urani, majoritàriament usant tècniques MC-ICPMS (multicollector inductively coupled mass spectrometry). Al llarg de la costa oriental de Mallorca, ha estat possible reconèixer dos episodis transgressius que assoleixen 1,5 - 3 m per sobre de I' actual nivell marí, ocorreguts entre 135 i 109 ka BP, separats per una ràpida regressió al voltant dels 125 ka. La durada de la pulsació transgressiva més antiga pot ésser estimada en 9,5 ka, mentre que la duració de la més recent seria de 12,8 ka. Fins al moment, tans sols la transgressió més recent es troba documentada a l'àrea de Capo Caccia a +4,3 m amb una durada mínima de 3 ka. La diferència d'altitud de l'episodi transgressiu més recent dins el subestadi Se, enregistrat a Mallorca i a Capo Caccia (Sardegna), pot ésser tan sols parcialment justificada per l'activitat neotectònica i és probablement el resultat de respostes diferents de les dues àrees (atribuïbles a les distintes gruixes de l'escorça continental) als canvis en la càrrega d'aigua marina que caracteritzen els cicles climàtics pleistocènics

Evaluating radon loss from water during storage in standard PET, bio-based PET, and PLA bottles

h i g h l i g h t s Radon loss from water during storage in polyethylene terephthalate (PET) and polylactic acid (PLA) bottles was evaluated. Surface/volume ratio and thickness of plastic materials were studied. A correction for dissolved radium concentration was applied to estimate gas loss. Proper corrections for degassing efficiency of aerators were developed. The interference of H 2 O on radon daughter electrostatic collection was quantified. a r t i c l e i n f o a b s t r a c t Polyethylene terephthalate (PET) and polylactic acid (PLA) bottles were tested to evaluate radon loss from water during 15 days of storage. PET bottles (lower surface/volume-ratio vials) lost 0.4e7.1% of initial radon, whereas PLA bottles lost 3.7% of it. PET bottles with volume of 0.5 L, lower surface/weight ratio, and hence higher thickness display proportionally reduced radon loss. Corrections for dissolved radium are needed during analyses. Formulas for calculating degassing efficiency and water interference on electrostatic collections are developed

Groundwater monitoring in the archaeological site of Ostia Antica (Rome, Italy): first results

The archaeological site of Ostia Antica hosts the ruins of the ancient roman city called Ostia founded in the VII century B.C. near the mouth of Tiber River. The area was strategically important for Rome, not only for the control of the river, but also for some salt marshes (Ostia Pound). During the XIX century, the whole area was reclaimed and the salt production stopped. Nowadays drainage canals and pumps avoid the flood of zones placed below sea level, keeping dewatering below the ground surface. In February 2014, the site was largely flooded after an exceptional rainfall event and the Superintendence for Archaeological Heritage of Rome ordered the closure for 15 days. Few months later (July 2014) a groundwater monitoring project started with the aim of studying the aquifer response to local rainfall and prevent future damage and groundwater flooding. The activity consisted in water-table monitoring, groundwater electrical conductivity (EC) and temperature continuous measurements, coupled with chemical analysis of major ions. Preliminary results shows the link between water table fluctuations and rainfall distributions. The average elevation of the archaeological area is about 2,5 m a.s.l. and the local water-table depth is of about 0,5 m a.s.l.; groundwater flows from the Tiber River to the reclaimed area according to regional flowpath. Groundwater sampled from three wells is Ca-HCO3 freshwater (600 - 1000 μS/cm), while the sample collected from a well located close to ancient salt storage warehouse (now Ostia Antica museum), is Na-Cl brackish water (about 4000 μS/cm). The chemical evolution of groundwater from summer to winter suggested a possible lateral inflow from the Tiber River, affected by salt-wedge intrusion. The inflow of Ca-Cl, SO4 Tiber's water with an intermediate salinity could determine salinization of Ca-HCO3 freshwaters and refreshing of Na-Cl brackish water