application of stochastic simulation to co2 flux from soil mapping and quantification of gas release 1 conditional sequential gaussian simulations sgs have been applied for the first time to the study of soil diffuse degassing from different volcanic and nonvolcanic systems the application regards five data sets of soil co2 fluxes measured with the accumulation chamber methodology at the volcanic areas of solfatara of pozzuoli italy vesuvio cone italy nisyros greece and horseshoe lake california and at the nonvolcanic degassing area of poggio dell olivo italy the sgs algorithm was used to generate 100 realizations of co2 flux for each area probabilistic summaries of these simulations together with the information given by probability plots were used 1 to draw maps of the probability that co2 fluxes exceed thresholds specific for a background flux i e to define the probable extension of the degassing structures 2 to calculate the total co2 output and 3 to quantify the uncertainty of the estimation the results show that the sgs is a suitable tool to model soil diffuse degassing producing realistic images of the distribution of the co2 fluxes that honor the histogram and variogram of the original data moreover the relation between the sample design and the uncertainty of estimation was investigated leading to an empirical relation between uncertainty and the sampling density that can be useful for the planning of future co2 flux surveys

variability in fault size scaling due to rock strength heterogeneity a finite element investigation abstract practical application of fault size scaling relationships usually involves extrapolation of a limited data set over a scale range beyond that observed or into adjacent unstudied areas here we investigate the validity of such extrapolations by considering the variability in the size frequency distributions of fault populations that develop under identical tectonic conditions using a numerical model to generate conjugate normal fault populations in cross section the deforming material is modelled using a strain softening von mises rheology with gaussian heterogeneity in yield strength distributed randomly throughout the mesh we present eight deformation experiments that differ only in the random spatial pattern of yield strengths we observe power law size frequency scaling i e n ax c where n is the cumulative number of faults and x is a measure of fault size but with a range of values of c the ensemble average value of c decreases with increasing percentage extension however for individual model runs the dependence of c on total strain shows significant variability that we can relate to small but important differences in fault growth and strain localisation at any particular strain the range of values of c is 10 times greater than the error estimate derived from least squares regression of the cumulative frequency data our results suggest therefore that large uncertainties should be associated with extrapolating fault population data from one scale or region to another even if the lithology and tectonic history are similar

comparative soil co2 flux measurements and geostatistical estimation methods on masaya volcano nicaragua we present a comparative study of soil co2 flux f rm co 2 measured by five groups groups 1 5 at the iavcei ccvg eighth workshop on volcanic gases on masaya volcano nicaragua groups 1 5 measured f rm co 2 using the accumulation chamber method at 5 m spacing within a 900 m2 grid during a morning am period these measurements were repeated by groups 1 3 during an afternoon pm period measured f rm co 2 ranged from 218 to 14 719 g m 2 day 1 the variability of the five measurements made at each grid point ranged from 5 to 167 however the arithmetic means of fluxes measured over the entire grid and associated total co2 emission rate estimates varied between groups by only 22 all three groups that made pm measurements reported an 8 19 increase in total emissions over the am results based on a comparison of measurements made during am and pm times we argue that this change is due in large part to natural temporal variability of gas flow rather than to measurement error in order to estimate the mean and associated co2 emission rate of one data set and to map the spatial f rm co 2 distribution we compared six geostatistical methods arithmetic and minimum variance unbiased estimator means of uninterpolated data and arithmetic means of data interpolated by the multiquadric radial basis function ordinary kriging multi gaussian kriging and sequential gaussian simulation methods while the total co2 emission rates estimated using the different techniques only varied by 4 4 the f rm co 2 maps showed important differences we suggest that the sequential gaussian simulation method yields the most realistic representation of the spatial distribution of f rm co 2 but a variety of geostatistical methods are appropriate to estimate the total co2 emission rate from a study area which is a primary goal in volcano monitoring research

considerations for measuring ground co2 effluxes with chambers abstract this paper considers the factors that influence ground co 2 fluxes as measured by the chamber method new data and published results are used to illustrate the effects of various factors on co 2 emissions from the ground these factors are pressure differences between the ambient air and the chamber wind speed within the chamber the chamber co 2 concentration relative to ambient air concentration and the accumulation of water vapor in the chamber a mathematical analysis of the accumulation of co 2 in the chamber in terms of diffusion and advection e g air flow out of the ground at geothermal degassing locations shows that the same protocol should be followed whether the mechanism of emission is purely by diffusion or by a combination of diffusion and advection the analysis also yields a simple way for estimating soil co 2 conductance and the soil co 2 concentration at the depth of insertion of the chamber into the ground

hydrothermal methane fluxes from the soil at pantelleria island italy abstract chemical and isotopic analyses of the main gas manifestations of the island of pantelleria italy were used to gain insight on the origin of the released methane results indicate that the most probable origin is through abiogenic reactions within the hydrothermal system methane and co 2 flux measurements from the soils were made with the accumulation chamber method in an area of about 0 015 km 2 within the main fumarolic area of the island favara grande the 23 measurements range from 34 to 3550 mg m 2 d 1 for ch 4 and from 0 6 to 379 g m 2 d 1 for co 2 the relationships between ch 4 and co 2 fluxes and the ch 4 co 2 ratios in the gases collected between the depths of 25 and 100 cm provide evidence for methanotrophic processes within the soils methane output for the surveyed area was calculated to be 2 5 t a 1 and extrapolated to about 5 10 t a 1 for the entire volcanic hydrothermal system of the island previous higher estimates of the ch 4 output at pantelleria etiope et al 2007 j volcanol geotherm res 165 76 86 were based on soil co 2 output and ch 4 co 2 ratios in fumarolic gases the present work provides the first direct ch 4 flux data and it suggests that methanotrophic activity in the soil could be substantial in reducing the ch 4 emission to the atmosphere

gas emissions and crustal deformation from the krýsuvik high temperature geothermal system iceland abstract the kr suvik volcanic system is located on the oblique spreading reykjanes peninsula sw iceland since early 2009 the region has been undergoing episodes of localized ground uplift and subsidence from april november 2013 we operated near real time monitoring of gas emissions in kr suvik using a multi component gas analyzer system multi gas collecting data on gas composition from a fumarole h2o co2 so2 h2s the dataset in this study comprises a near continuous gas composition time series the quantification of diffuse co2 gas flux analytical results for direct samples of dry gas seismic records and gps data gas emissions from the kr suvik geothermal system were examined and compared with crustal deformation and seismicity the gas emissions from the kr suvik system are h2o dominated with co2 as the most abundant dry gas species followed by smaller concentrations of h2s the average subsurface equilibrium temperature was calculated as 278 c this is consistent with previous observations made through sporadic spot sampling campaigns in addition the semi continuous multi gas dataset reveals higher variations in gas composition than previously reported by spot sampling the diffuse soil co2 flux is found to be variable between the three studied degassing areas in kr suvik ranging from 10 9 70 9 t day with the highest flux in hveradalir where the multi gas station is located the total flux is estimated as 101 t day comparison between multi gas and geophysical data shows that peaks of h2o rich emissions appears to follow crustal movements coinciding with the h2o rich peaks so2 is detected in minor amounts 0 6 ppmv allowing for calculations of h2o so2 co2 so2 and h2s so2 ratios this is the first time so2 has been detected in the kr suvik area the large variations in h2o co2 and h2o h2s ratios are considered to reflect variable degassing activity in the fumarole the activity of the fumarole appears less intense during intervals of low or no recorded seismic events the h2o co2 and h2o h2s ratios are lower presumably due to h2o condensation affecting the steam jet before reaching the multi gas inlet tube

hydrothermal fluid venting in the offshore sector of campi flegrei caldera a geochemical geophysical and volcanological study the ongoing unrest at the campi flegrei caldera cfc in southern italy is prompting exploration of its poorly studied offshore sector we report on a multidisciplinary investigation of the secca delle fumose sdf a submarine relief known since antiquity as the largest degassing structure of the offshore sector of cfc we combined high resolution morpho bathymetric and seismo stratigraphic data with onshore geological information to propose that the present day sdf morphology and structure developed during the initial stages of the last cfc eruption at monte nuovo in ad 1538 we suggest that the sdf relief stands on the eastern uplifted border of a n s trending graben like structure formed during the shallow emplacement of the monte nuovo feeding dike we also infer that the high angle bordering faults that generated the sdf relief now preferentially allow the ascent of hot brines with an equilibrium temperature of 179 c thereby sustaining hydrothermal degassing on the seafloor systematic vertical seawater profiling shows that hydrothermal seafloor venting generates a sizeable co2 ph and temperature anomaly in the overlying seawater column data for the seawater vertical profile can be used to estimate the co2 and energy heat outputs from the sdf area at 50 tons day 0 53 kg s and 80mw respectively in view of the cause effect relationship with the monte nuovo eruption and the substantial gas and energy outputs we consider that the sdf hydrothermal system needs to be included in monitoring programs of the ongoing cfc unrest this article is protected by copyright all rights reserved

geochemical evidence of magma intrusion inferred from diffuse co 2 emissions and fumarole plume chemistry the 2010 2011 volcanic unrest at taal volcano philippines we report herein significant increases in the diffuse co2 emission through the lake and soils of the taal volcano main crater philippines during a volcano seismic unrest period in april 2010 june 2011 monitoring of co2 emissions from the taal main crater lake and soils in the fumarole areas started in 2008 with a collaborative project between iter and phivolcs in august 2010 the total diffuse co2 emission from the taal main crater lake increased almost three times from a previously measured baseline emission value 1 000 t day 1 to 2 716 54 t day 1 this increase occurred during anomalous seismic activity which started in april 2010 the highest co2 emission value in the crater lake was measured in march 2011 at 4 670 159 t day 1 when the volcano was still showing signs of unrest significant changes in the co2 so2 co2 h2o and so2 h2s ratios in the fumarole gases suggest the occurrence of a magmatic injection several weeks before the onset of the volcano seismic unrest period these observed changes in the co2 emission rate and the fumarole gas composition as the result of magmatic activity were likely caused by magma moving from a deep reservoir to a shallow reservoir

structural pattern and co2 ch4 degassing of ustica island southern tyrrhenian basin brittle tectonics and ground degassing including fracture field soil gas and exhalation flux analyses of co2 and ch4 were studied at ustica island a pleistocene volcanic complex in the southern tyrrhenian sea the mesoscopic fracture pattern perfectly fits an e w trending left lateral strike slip master fault in agreement with the main morpho structural submarine alignment including ustica island and anchise seamount along the sw ne high angle normal arso fault geological evidence of reactivation with different kinematics left to right lateral displacements was recognised major co2 and ch4 degassing with fluxes up to 93 750 and 20 t km 2 a 1 respectively and soil gas concentrations of 11 3 and 5 7 ppm occur over the arso fault although this fault is mapped just in the sw sector of the island soil gas co2 anomalies point out its clear continuation up to the ne margin of the island these data together with those of previous geophysical and geochemical results from off shore ustica suggest that the arso fault is the local evidence of a more important active gas bearing structure this tectonic feature is interpreted as a reactivation of a preexistent sw ne trend inherited as a second order structure of the e w deep shear zone the reactivation is related to the interplay among different structures of the southern tyrrhenian basin

fumarole plume and diffuse co 2 emission from sierra negra caldera galapagos archipelago measurements of visible and diffuse gas emission were conducted in 2006 at the summit of sierra negra volcano galapagos with the aim to better characterize degassing after the 2005 eruption a total so2 emission of 11 2 t day 1 was derived from miniature differential optical absorption spectrometer mini doas ground based measurements of the plume emanating from the mini azufral fumarolic area the most important site of visible degassing at sierra negra volcano using a portable multigas system the h2s so2 co2 so2 and h2o so2 molar ratios in the mina azufral plume emissions were found to be 0 41 52 2 and 867 9 respectively the corresponding h2o co2 and h2s emission rates were 562 394 and 3 t day 1 respectively the total output of diffuse co2 emissions from the summit of sierra negra volcano was 990 85 t day 1 with 605 t day 1 being released by a deep source the diffuse to plume co2 emission ratio was about 1 5 mina azufral fumaroles released gasses containing 73 6 mol of h2o the main noncondensable components amounted to 97 4 mol co2 1 5 mol so2 0 6 mol h2s and 0 35 mol n2 the higher h2s so2 ratio values found in 2006 as compared to those reported before the 2005 eruption reveal a significant hydrothermal contribution to the fumarolic emissions 3he 4he ratios measured at mina azufral fumarolic discharges showed values of 17 88 0 25 ra indicating a mid ocean ridge basalts morb and a galapagos plume contribution of 53 and 47 respectively

subsoil co2 and ch4 and their advective transfer from faulted grassland to the atmosphere measurements of co2 and ch4 in 3 m deep groundwater soil gas and soil atmosphere fluxes were completed in two grasslands in central italy having the same soil conditions but different subsoil fault linked secondary permeability unfaulted grassland displays gas phase equilibrium between soil air and groundwater typical soil gas diffusion profiles and diffusive soil to atmosphere gas transfer on the basis of oxygen depletion assessment assuming a ratio of 1 1 between biogenic o2 consumption and co2 production the measured soil co2 concentrations are consistent with a normal production in the soil by biologic activity the faulted grassland instead has higher co2 and ch4 concentrations up to 6 and 10 ppmv in soil air and flux 1 2 ml m 2 s 1 and 1 3 l m 2 s 1 resulting from a combination of soil biologic and endogenous components with evidence of gas transfer from the saturated to the unsaturated zone and advective gas transfer from soil to the atmosphere the extra soil source in the faulted zone which is about 0 3 4 times the background soil biologic production is likely related to migrating crustal gas whatever the c gas origin and depth may be biogenic or abiogenic shallow or deep the present results demonstrate that the subsoil derived component occurring in the soil in areas with active tectonics cannot be ignored a priori in the assessment of the c terrestrial sources in particular the assumption that dryland soils are sinks for methane owing to methanotrophic consumption may be not true in areas affected by active and gas bearing faults accordingly it would be very important to assess at global scale the actual role in the carbon dioxide and methane cycle of soils within the active tectonic bounds

structural architecture releasing deep sourced carbon dioxide diffuse degassing at the caviahue copahue volcanic complex abstract the link between carbon dioxide diffuse degassing and its structural control was examined in the caviahue copahue volcanic complex over an area of approximately 10 km2 that encompasses five hydrothermal sites namely anfiteatro copahue town las maquinitas i las maquinitas ii and las maquinas both geochemical and structural approaches were applied in order to investigate the structural scenario releasing hydrothermal fluids in this area also the first isotopic analysis of soil co2 degassing in the andean region is presented the geochemical analysis shows well defined co2 diffuse degassing structures in copahue town las maquinitas i las maquinitas ii and las maquinas hydrothermal sites soil diffuse co2 is fed by multiple sources a deep magmatic hydrothermal source a biogenic source and a mixed source the structural analysis indicates the presence of an extensional regime that gives place to three structural trends consisting of ne sw trending normal faults nw se sinistral strike slip faults and ene wsw right lateral strike slip faults the comparison between diffuse degassing structures directions and faults directions suggests that there is a structural control on diffuse degassing diffuse co2 is released through an early extensional setting and it is emitted through normal faults strike slip faults and through areas with higher structural damage such as relay areas between fault segments and terminations of individual fault segments

satellite derived surface temperature and in situ measurement at solfatara of pozzuoli naples italy ground thermal anomalies in volcanic hydrothermal systems where the outflow of hot fluids gives rise to fumarolic fields soil degassing and hot soils have up to now rarely been investigated by using satellite here we report a comparison between surface temperature derived by satellite data and a large data set of measured soil temperatures and co2 fluxes for a volcanic hydrothermal system the solfatara of pozzuoli campi flegrei italy surface temperatures derived from aster advanced spaceborne thermal emission and reflection radiometer data are compared with soil temperatures and co2 fluxes from four surveys performed in 2003 2010 and in 2014 the good match between the spatial distributions of computed and measured temperatures suggests the adequacy of satellite data to describe the solfatara thermal anomaly while the correspondence between temperatures and co2 fluxes evidences the link between degassing and heating processes the aster derived surface temperatures 14 37 c are coherent with those measured in the soil 10 97 c at 10 cm depth considering the effect of the thermal gradients which characterize the degassing area of solfatara this study shows that satellite data can be a very powerful tool with which to study surface thermal anomalies and can provide a supplementary tool to monitor thermal evolution of restless volcanoes

diffuse co2 flux emission in two maar crater lakes from sao miguel island azores portugal abstract santiago and congro are two maar crater lakes located at sao miguel the largest island of the azores archipelago santiago lake is located on the sete cidades volcano at an altitude of 364 m presenting a surface area of 0 25 km2 and a maximum depth of 33 m congro lake is located on the congro fissural volcanic system at an altitude of 420 m and has a surface area of 0 04 km2 and a maximum depth of 22 m both lakes are monomictic in character with low mineralized waters of meteoric origin being the temperature in the range between 12 4 c winter period and 23 8 c summer period the main water type is na hco3 and the relative major ion composition is hco3 cl so42 f for anions and na k mg2 ca2 for cations four sampling surveys were carried out between 2013 and 2016 in each lake in order to estimate surface diffuse co2 degassing a total of 1612 and 713 co2 flux measurements were made with an accumulation chamber at santiago and congro lakes respectively the higher co2 fluxes were measured during the winter surveys 0 2 t d 1 in congro and 5 6 t d 1 in santiago while the lowest values 0 1 t d 1 and 0 2 t d 1 respectively in congro and santiago lakes were recorded in the summer these seasonal differences observed in both lakes are associated with the monomictic character of the lakes as the co2 is not able to ascend to the surface when the water column is stratified during the warmer period due to the physical processes that occur in both lakes the co2 emission is mostly associated to a biogenic origin but the higher co2 emissions measured in santiago lake suggest that a volcanic influence cannot be excluded as also shown through the heavier 13c isotopic measured in this water body the tectonic structures that cross santiago lake probably enable the observed degassing

geochemical evidences of seismo volcanic unrests at the nw rift zone of tenerife canary islands inferred from diffuse co 2 emission we report the results of 49 soil co2 efflux surveys by the accumulation chamber method at the north west rift nwr zone of tenerife island canary islands the surveys were carried out from 2000 to 2016 to evaluate the temporal and spatial variations of co2 efflux and their relationships with the volcanic and seismic activity at tenerife soil co2 efflux values ranged from non detectable 0 5 g m 2 day 1 up to 141 g m 2 day 1 with the highest values measured in may 2005 whereas total co2 emission rates ranged between 52 and 867 t day 1 metric tons per day isotopic analyses of soil gas in carbon dioxide 13c co2 suggest a mixing between organic and atmospheric co2 with a small contribution of deep seated co2 the main temporal variation in the total co2 output does not seem to be driven by external factors it shows a clear temporal correlation with the onsets of seismic activity subsurface magma degassing affecting the central part of the island is proposed as a cause for the observed changes in the total output of diffuse co2 emission as well as for the spatial distribution of soil co2 efflux

hazardous gas emissions from the flanks of the quiescent colli albani volcano rome italy abstract gas hazard was evaluated in the three most important cold gas emission zones on the flanks of the quiescent colli albani volcano these zones are located above structural highs of the buried carbonate basement which represents the main regional aquifer and the main reservoir for gas rising from depth all extensional faults affecting the limestone reservoir represent leaking pathways along which gas rises to the surface and locally accumulates in shallow permeable horizons forming pressurized pockets that may produce gas blowout when reached by wells the gas mainly composed of co 2 90 vol contains appreciable quantities of h 2 s 0 35 6 vol and both represent a potentially high local hazard both gases are denser than air and accumulate near ground where they may reach hazardous concentrations and lethal accidents frequently occur to animals watering at local ponds in order to evaluate the rate of degassing and the related hazard co 2 and h 2 s diffuse soil flux surveys have been repeatedly carried out using an accumulation chamber the viscous gas flux of some important discrete emissions has been evaluated and the co 2 and h 2 s air concentration measured by portable devices and by tunable diode laser profiles the minimum potential lethal concentration of the two gases 250 ppm for h 2 s and 8 vol for co 2 is 320 times higher for co 2 whereas the co 2 h 2 s concentration ratio in the emitted natural gas is significantly lower 15 159 this explains why h 2 s reaches hazardous even lethal concentrations more frequently than co 2 a relevant hazard exists for both gases in the depressed zones channels excavations particularly in the non windy early hours of the day

the co2 flux from hydrothermal systems of the karymsky volcanic centre kamchatka abstract the co 2 flux provided by the hydrothermal activity within the karymsky volcanic centre kamchatka was measured and the co 2 balance of the karymsky caldera lake was estimated in the framework of a deep carbon observatory dco project the karymsky volcanic centre located in the se of the kamchatka peninsula in the middle of the modern volcanic front consists of two calderas hosts a caldera lake and is characterized by hydrothermal activity that is manifested at several thermal fields within the akademii nauk an caldera which is filled by a caldera lake the akademii nauk springs discharge boiling water into the lake the lake is drained by the karymsky river that then crosses the caldera of the karymsky volcano karymsky caldera and drains the thermal field of co 2 rich karymsky springs the lake after the 1996 sublimnic eruption is in a steady state condition with the total dynamic co 2 budget of about 4 t day and has a total amount of co 2 stored inside of the lake of around 8000 t the thermal springs of the karymsky caldera drained by the karymsky river enrich the river in dissolved carbon species a total co 2 output of 320 t day from both karymsky centre calderas was estimated carrying around 130 t day carbon species expressed as co 2 as dissolved species hco 3 and co 2 aq and emitting to the atmosphere around 190 t day of co 2 as the diffusion flux from the soil and bubbling emanations from the springs

soil efflux and total emission rates of magmatic co2 at the horseshoe lake tree kill mammoth mountain california 1995 1999 abstract we report the results of eight soil co 2 efflux surveys by the closed circulation chamber method at the horseshoe lake tree kill hltk the largest tree kill on mammoth mountain the surveys were undertaken from 1995 to 1999 to constrain total hltk co 2 emissions and to evaluate occasional efflux surveys as a surveillance tool for the tree kills hltk effluxes range from 1 to 10 000 g m 2 day 1 grams co 2 per square meter per day they are not normally distributed station efflux rates can vary by 7 35 during the course of the 8 to 16 h surveys disturbance of the upper 2 cm of ground surface causes effluxes to almost double semivariograms of efflux spatial covariance fit exponential or spherical models they lack nugget effects efflux contour maps and total co 2 emission rates based on exponential spherical and linear kriging models of survey data are nearly identical similar results are also obtained with triangulation models suggesting that the kriging models are not seriously distorted by the lack of normal efflux distributions in addition model estimates of total co 2 emission rates are relatively insensitive to the measurement precision of the efflux rates and to the efflux value used to separate magmatic from forest soil sources of co 2 surveys since 1997 indicate that contrary to earlier speculations a termination of elevated co 2 emissions at the hltk is unlikely anytime soon the hltk co 2 efflux anomaly fluctuated greatly in size and intensity throughout the 1995 1999 surveys but maintained a n s elongation presumably reflecting fault control of co 2 transport from depth total co 2 emission rates also fluctuated greatly ranging from 46 to 136 t day 1 metric tons co 2 per day and averaging 93 t day 1 the large inter survey variations are caused primarily by external meteorological processes operating on time scales of hours to days the externally caused variations can mask significant changes occurring at depth a striking example is the masking of a degassing event generated at depth and detected by a soil gas sensor network in september 1997 while an efflux survey was in progress thus occasional efflux surveys are not an altogether effective surveillance tool for the hltk and making them effective by greatly increasing their frequency may not be practical

total co2 output from vulcano island aeolian islands italy 1 total co2 output from fumaroles soil gas bubbling gas discharges and water dissolved gases discharged from the island was estimated for vulcano island italy the co2 emission from fumaroles from the la fossa summit crater was estimated from the so2 crater output while co2 discharged through diffuse soil emission was quantified on the basis of 730 measurements of co2 fluxes from the soil of the island performed by using the accumulation chamber method the results indicate an overall output of 500 t day 1 of co2 from the island the main contribution to the total co2 output comes from the summit area of the la fossa cone 453 t day 1 with 362 t day 1 from crater fumaroles and 91 t day 1 from crater soil degassing the release of co2 from peripheral areas is 20 t day 1 by soil degassing palizzi and istmo areas mainly an amount comparable to both the contribution of water dissolved co2 6 t day 1 as well as to seawater bubbling co2 4 t day 1 measured in the istmo area presented data september 2007 refer to a period of moderate solphataric activity when the fumaroles temperature were 450 c and gas water molar ratio of fumaroles was up to 0 16 the calculated total co2emission allows the estimation of the mass release and related thermal energy from the volcanic hydrothermal system

correlated increase in co2 fumarolic content and diffuse emission from la fossa crater vulcano italy evidence of volcanic unrest or increasing gas release from a stationary deep magma body 1 the peculiarity of the quiescent la fossa volcano is the occurrence of crises characterized by strong increases of fumarole t and output and by chemical changes indicative of an increasing input of magmatic fluids several surveys carried out during a new crisis began in november 2004 indicate that the total diffuse co2 emission for the crater area increases by one order of magnitude during crises up to 1600 ton d 1 in december 2005 concern exists on the possibility that these crises be related to an unrest process leading to eruption the repetition along decades of the same gas compositional variations during crises their temporal coincidence with increases of the local shallow seismicity and the lack of any significant ground motion rather suggest that they correspond to moments of increasing volatile release from a stationary magma system

carbon dioxide emission and heat release estimation for pantelleria island sicily italy abstract detailed surveys of diffuse co2 flux soil temperature thermal gradients and sampling of high t fumaroles were carried out in the favare area and lake specchio di venere on pantelleria island spatial patterns of diffuse co2 emissions in the favare area reflect structural discontinuities faults fractures or cracks in the soil associated with the volcano tectonic structures of the young monastero caldera nne ssw to ne sw trending the estimated diffuse co2 output from two adjacent sites in the favare area 93 000 m2 is 7 8 t d 1 equivalent to 2 62 kt a 1 whereas that from the west shore of the lake 450 m2 is 0 041 t d 1 or 0 015 kt a 1 the extrapolation of diffuse co2 fluxes across the entire altered area of favare suggests that co2 emissions are 19 3 t d 1 the diffuse co2 flux correlates with shallow soil temperatures indicating a similar source for both the heat and volatiles from the underlying geothermal reservoir gas equilibria applied to fumarolic effluents define p t conditions for this reservoir at 2 6 bar and 120 160 c in good agreement with measurements from exploratory wells in these areas e g 135 c at a depth of 290 m using the co2 flux as a tracer for steam output and consequently for heat flow the calculated thermal energy for the shallow reservoir is 10 12 mw this represents the minimum geothermal potential of the reservoir on pantelleria island

fluid geochemistry and soil gas fluxes co2 ch4 h2s at a promissory hot dry rock geothermal system the acoculco caldera mexico abstract the acoculco caldera has been recognized by the mexican federal electricity company cfe as a hot dry rock geothermal system hdr and could be a potential candidate for developing an enhanced geothermal system egs apart from hydrothermally altered rocks geothermal manifestations within the acoculco caldera are scarce close to ambient temperature bubbling springs and soil degassing are reported inside the caldera while a few springs discharge warm water on the periphery of the caldera in this study we infer the origin of fluids and we characterize for the first time the soil degassing dynamic chemical and isotopic 18o d analyses of spring waters indicate a meteoric origin and the dissolution of co2 and h2s gases while gas chemical and isotopic compositions n2 he 3he 4he 13c 15n reveal a magmatic contribution with both morb and arc type signatures which could be explained by an extension regime created by local and regional fault systems gas geothermometry results are in agreement with temperature measured during well drilling 260 c 300 c absence of well developed water reservoir at depth impedes re equilibration of gases upon surface a multi gas flux survey including co2 ch4 and h2s measurements was performed within the caldera using the graphical statistical analysis gsa approach co2 flux measurements were classified in two populations population a representing 95 of measured fluxes is characterized by low values mean 18 g m 2 day 1 while the remaining 5 fluxes belonging to population b are much higher mean 5543 g m 2 day 1 this low degassing rate probably reflects the low permeability of the system a consequence of the intense hydrothermal alteration observed in the upper 800 m of volcanic rocks an attempt to interpret the origin and transport mechanism of these fluxes is proposed by means of flux ratios as well as by numerical modeling measurements with co2 ch4 and co2 h2s flux ratios similar to mass ratios of sampled gases were considered as reflecting advective transport a numerical model of co2 migration in the subsoil system under fully water and gas saturated conditions was performed using the tough2 code in order to reproduce semi quantitatively field measurements the main results show that high flux values produced by advective geothermal degassing can be very localized and that low and heterogeneous permeability conditions can induce low advective co2 flux values therefore in this case the populations discriminated by the gsa method should not be interpreted in terms of origin and or transport mechanism but rather in terms of permeability conditions

co2 fluxes of two lakes in volcanic caves in the azores portugal abstract this paper characterises diffuse co2 degassing from lakes located inside volcanic caves on the islands of terceira and graciosa in the azores archipelago portugal the algar do carvao lake is located inside a volcanic pit on terceira at an altitude of 92 m and has a surface area of 11 500 m2 and a maximum depth of 8 2 m the furna do enxofre lake is located inside a lava cave on graciosa at an altitude of 500 m and has a surface area of approximately 300 m2 and a maximum depth of 9 3 m the water temperature of both lakes is low with values ranging between 11 c and 13 c in both the winter and summer periods and no variations are observed along their water columns the electrical conductivity ranges from 585 s cm 1 to 687 s cm 1 in furna do enxofre and from 117 s cm 1 to 131 s cm 1 in algar do carvao reflecting a higher mineralisation in the former lake the ph values in furna do enxofre range between 6 50 and 6 58 which reflects the effect of co2 dissolution while in algar do carvao the ph values are more basic 7 42 8 53 the water types are mg hco3 for furna do enxofre and na hco3 for algar do carvao the mg enrichment in furna do enxofre is associated with water rock interactions which are enhanced by the acidic environment diffuse co2 flux measurements were made using the accumulation chamber method with a total of 37 measurements split into two surveys at algar do carvao and 71 measurements during a single survey at furna do enxofre the total co2 emitted from furna do enxofre was 6100 kg d 1 which was much lower than that emitted from algar do carvao 0 32 2 0 kg d 1 a volcanic origin was assigned to the lake on graciosa due to the 13c isotopic signature of the co2 conversely the co2 released in algar do carvao is derived from a biogenic co2 source considering the surface areas of the studied lakes the co2 flux is in the range of 1 5 6 7 t km 2 d 1 for algar do carvao and is 508 3 t km 2 d 1 for furna do enxofre

geochemical evidence of the renewal of volcanic activity inferred from co2 soil and so2 plume fluxes the 2007 stromboli eruption italy on 27 february 2007 a new eruption occurred on stromboli which lasted until 2 april it was characterized by effusive activity on the sciara del fuoco and by a paroxysmal event 15 march this crisis represented an opportunity for us to refine the model that had been developed previously 2002 2003 eruption and to improve our understanding of the relationship between the magmatic dynamics of the volcano and the geochemical variations in the fluids in particular the evaluation of the dynamic equilibrium between the volatiles co2 and so2 released from the magma and the corresponding fluids discharged from the summit area allowed us to evaluate the level of criticality of the volcanic activity one of the major accomplishments of this study is a 4 year database of summit soil co2 flux on the basis of which we define the thresholds low medium high for this parameter that are empirically based on the natural volcanological evolution of stromboli the so2 fluxes of the degassing plume and the co2 fluxes emitted from the soil at pizzo sopra la fossa are also presented it is noteworthy that geochemical signals of volcanic unrest have been clearly identified before during and after the effusive activity these signals were found almost simultaneously in the degassing plume so2 flux and in soil degassing co2 flux at the summit although the two degassing processes are shown to be clearly different the interpretation of the results will be useful for future volcanic surveillance at stromboli

carbon dioxide and hydrogen sulfide degassing and cryptic thermal input to brimstone basin yellowstone national park wyoming abstract brimstone basin a remote area of intense hydrothermal alteration a few km east of the yellowstone caldera is rarely studied and has long been considered to be a cold remnant of an ancient hydrothermal system a field campaign in 2008 confirmed that gas emissions from the few small vents were cold and that soil temperatures in the altered area were at background levels geochemical and isotopic evidence from gas samples 3 he 4 he 3r a 13 c co 2 3 however indicate continuing magmatic gas input to the system accumulation chamber measurements revealed a surprisingly large diffuse flux of co 2 277 t d 1 and h 2 s 0 6 t d 1 the flux of co 2 reduces the 18 o content of the overlying cold groundwater and related stream waters relative to normal meteoric waters simple isotopic modeling reveals that the co 2 likely originates from geothermal water at a temperature of 93 19 c these results and the presence of thermogenic hydrocarbons c1 c2 100 and 13 c ch 4 46 4 to 42 8 in gases require some heat source at depth and refute the assumption that this is a fossil hydrothermal system

soil co2 flux baseline in an urban monogenetic volcanic field the auckland volcanic field new zealand the auckland volcanic field avf is a dormant monogenetic basaltic field located in auckland new zealand though soil gas co2 fluxes are routinely used to monitor volcanic regions there have been no published studies of soil co2 flux or soil gas co2 concentrations in the avf to date or many other monogenetic fields worldwide we measured soil gas co2 fluxes and soil gas co2 concentrations in 2010 and 2012 in varying settings seasons and times of day to establish a baseline soil co2 flux and to determine the major sources of and controlling influences on auckland s soil co2 flux soil co2 flux measurements varied from 0 to 203 g m 2 day 1 with an average of 27 1 g m 2 day 1 higher fluxes were attributed to varying land use properties e g landfill using a graphical statistical approach two populations of co2 fluxes were identified isotope analyses of 13co2 confirmed that the source of co2 in the avf is biogenic with no volcanic component these data may be used to assist with eruption forecasting in the event of precursory activity in the avf and highlight the importance of knowing land use history when assessing soil gas co2 fluxes in urban environments

helium emission at cumbre vieja volcano la palma canary islands abstract we report herein the results of three soil helium surveys undertaken at cumbre vieja volcano la palma island canary islands helium content analyses at the surface environment of the volcano were carried out in the summers of 2002 2003 and 2004 to estimate the diffusion contribution of helium emission soil porosity was estimated indirectly from the granulometry data measured on a previous soil survey carried out in 1997 helium enrichments in the soil layer with respect to the air concentration measured on cumbre vieja indicate a strong structural control in the degassing processes of the volcano and the excess helium seems to be emitted mainly along both n s and n w rifts of the volcano 4 he flux values calculated following a pure diffusive model ranged between non detectable values and 1 0 mg m 2 d 1 in 2002 2003 and 2004 surveys total 4 he emission rate at cumbre vieja was estimated in the range of 18 38 kg d 1 isotopic composition of helium measured in soil gases along the n s volcanic rift of cumbre vieja showed small contributions of morb type helium increasing towards the southern part of the volcano a 3 he 4 he ratio of 9 95 0 12 r a was measured at a cold spring geothermal sample showing a 7 2 contribution of plume type helium 3 he emission results in the range of 0 6 0 7 mol yr support the hypothesis of contemporary degassing at cumbre vieja coming from magmas stored at different depths under la palma island

diffuse emission of carbon dioxide from cerro negro volcano nicaragua central america we report the first detailed soil co2 efflux survey carried out at cerro negro volcano nicaragua central america soil co2 efflux values ranged from 0 5 to 35 000 g m 2 d 1 spatial distribution of co2 efflux shows that volcanic gas is mainly released from the summit crater and the fissures opened during the august 1999 eruption the total co2 output of cerro negro is conservatively estimated to be 2 800 t d 1 based on a study area of 0 58 km contour maps of soil co2 efflux ground temperature and 13c co2 distributions support an important magmatic contribution for the total output of co2 at cerro negro volcano

co2 flux and chemistry of el chichon crater lake mexico in the period 2013 2015 evidence for the enhanced volcano activity the co2 flux from el chichon crater in the period from 2014 to 2015 increased by a factor of 3 from 260 t d 1 to 800 t d 1 compared to the 2007 2008 data the mechanism triggering the co2 flux from the lake surface has changed from being dominantly diffusive to mainly advective bubbling the cl concentration was steadily decreasing during the last two decades in the na cl boiling springs feeding the lake since 2013 for both lake and sp springs the cl concentration has increased up to the 2005 cl concentration levels a large degassing spot in the middle of the lake was found in april 2015 with a co2 flux of more than 10 000 g m 2 d 1 these observations are the evidence of the onset of a new stage of activity within the volcano hydrothermal system of el chichon volcano associated most probably with changes in the magmatic activity at depth

convective hydrothermal c02 emission from high heat flow regions abstract in addition to volatiles released from volcanoes the flux of co2 to the atmosphere from other sources e g metamorphism and subsurface magmatism represents an important aspect of the global carbon cycle we have obtained a direct estimate of the present day atmospheric co2 flux from convective hydrothermal systems within subaerial seismically active high heat flow regions geothermal systems of the salton trough california u s a and the taupo volcanic zone new zealand provide benchmarks for quantifying convective hydrothermal co2 fluxes from such regions co2 fluxes from the salton trough 109 mol yr 1 and the taupo volcanic zone 8 109 mol yr 1 were computed using data on convective heat flow and the temperatures and co2 concentrations of reservoir fluids the similarity in specific co2 flux 106 mol km 2 yr 1 from these two disparate geologic tectonic settings implies that this flux may be used as a baseline to compute convective hydrothermal co2 emission from other areas of high heat flow if this specific flux is integrated over high heat flow areas of the circum pacific and tethyan belts the total global co2 flux could equal or exceed 1012 mol yr 1 adding this flux to a present day volcanic co2 flux of 4 1012 mol yr 1 the total present day earth degassing flux could balance the amount of co2 consumed by chemical weathering 7 1012 mol yr 1

soil diffuse degassing and thermal energy fluxes from the southern lakki plain nisyros greece two diffuse soil co2 flux surveys from the southern lakki plain show that co2 is mainly released from the hydrothermal explosion craters the correspondence between high co2 fluxes and elevated soil temperatures suggests that a flux of hot hydrothermal fluids ascends towards the surface steam mostly condenses near the surface and the heat given off is conductively transferred to the atmosphere through the soil accompanied by a large co2 flux it was calculated that 68 t d 1 of hydrothermal co2 are released through the total surveyed area of 1 3 km admitting that a steam flux of 2200 t d 1 accompanies this co2 flux the thermal energy released through steam condensation amounts to 58 mw

active tectonic features and structural dynamics of the summit area of mt etna italy revealed by soil co2 and soil temperature surveying project cgl2005 07509 cli ministry of education and science of spain dpc ingv project flank istituto nazionale di geofisica e vulcanologia osservatorio etneo sezione di catania

co2 emissions from fogo intracaldera volcanic lakes sao miguel island acores a tool for volcanic monitoring abstract a geochemical study was carried out at fogo lake during june 2016 in one of the deepest lakes on sao miguel island as well as on small associated pond in order to identify possible anomalous degassing areas fogo lake is located inside the summit caldera of fogo volcano one of the three active central volcanoes that dominate sao miguel geology the hydrogeochemical profile carried out along the water column of the fogo lake suggests that the lake was thermally stratified corresponding to poorly mineralized and cold na cl type waters the same composition is found in the small pond but with a slight ca enrichment to measure the co2 flux at the lake surface the modified accumulation chamber method was used and a total of 1696 measurements were accomplished covering an area of approximately 1 56 km2 measured co2 flux values are relatively low ranging from 0 to 28 4 g m 2 d 1 mean 2 6 g m 2 d 1 and from 2 1 to 15 0 g m 2 d 1 mean 6 3 g m 2 d 1 respectively at fogo lake and at the small pond the very low values measured in the central area of fogo lake are associated with the monomictic character of the lake as the co2 is not able to ascend into the surface when the water column is stratified during the warmer period statistical analyses suggest that the co2 emission is associated with a single source of co2 probably biogenic a similar signature is pointed by the water 13c isotopic content the estimated total co2 emissions from the fogo lake was approximately 4 04 t d 1 much higher than the value observed at the small pond 0 19 t d 1

degassing regime of hekla volcano 2012 2013 hekla is a frequently active volcano with an infamously short pre eruptive warning period our project contributes to the ongoing work on improving hekla s monitoring and early warning systems in 2012 we began monitoring gas release at hekla the dataset comprises semi permanent near real time measurements with a multigas system quantification of diffuse gas flux and direct samples analysed for composition and isotopes 13c d and 18o in addition we used reaction path modelling to derive information on the origin and reaction pathways of the gas emissions hekla s quiescent gas composition was co2 dominated 0 8 mol fraction and the 13c signature was consistent with published values for icelandic magmas the gas is poor in h2o and s compared to hydrothermal manifestations and syn eruptive emissions from other active volcanic systems in iceland the total co2 flux from hekla central volcano diffuse soil emissions is at least 44 t d 1 thereof 14 t d 1 are sourced from a small area at the volcano s summit there was no detectable gas flux at other craters even though some of them had higher ground temperatures and had erupted more recently our measurements are consistent with a magma reservoir at depth coupled with a shallow dike beneath the summit in the current quiescent state the composition of the exsolved gas is substantially modified along its pathway to the surface through cooling and interaction with wall rock and groundwater the modification involves both significant h2o condensation and scrubbing of s bearing species leading to a co2 dominated gas emitted at the summit we conclude that a compositional shift towards more s and h2o rich gas compositions if measured in the future by the permanent multigas station should be viewed as sign of imminent volcanic unrest on hekla

multi scale observations of the variability of magmatic co2 emissions mammoth mountain ca usa abstract one of the primary indicators of volcanic unrest at mammoth mountain is diffuse emission of magmatic co 2 which can effectively track this unrest if its variability in space and time and relationship to near surface meteorological and hydrologic phenomena versus those occurring at depth beneath the mountain are understood in june october 2013 we conducted accumulation chamber soil co 2 flux surveys and made half hourly co 2 flux measurements with automated eddy covariance and accumulation chamber auto chamber instrumentation at the largest area of diffuse co 2 degassing on mammoth mountain horseshoe lake tree kill hltk estimated co 2 emission rates for hltk based on 20 june 30 july and 24 25 october soil co 2 flux surveys were 165 172 and 231 t d 1 respectively the average june october co 2 emission rate estimated for this area was 123 t d 1 based on an inversion of 4527 eddy covariance co 2 flux measurements and corresponding modeled source weight functions average daily eddy covariance and auto chamber co 2 fluxes consistently declined over the four month observation time wavelet analysis of auto chamber co 2 flux and environmental parameter time series was used to evaluate the periodicity of and local correlation between these variables in time frequency space overall co 2 emissions at hltk were highly dynamic displaying short term hourly to weekly temporal variability related to meteorological and hydrologic changes as well as long term monthly to multi year variations related to migration of co 2 rich magmatic fluids beneath the volcano accumulation chamber soil co 2 flux surveys were also conducted in the four additional areas of diffuse co 2 degassing on mammoth mountain in july august 2013 summing co 2 emission rates for all five areas yielded a total for the mountain of 311 t d 1 which may suggest that emissions returned to 1998 2009 levels following an increase from 2009 to 2011

soil gas radon emissions and volcanic activity at el hierro canary islands the 2011 2012 submarine eruption 1 soil gas radon 222rn and thoron 220rn activities have been continuously measured during the period of the recent volcanic unrest that occurred at el hierro canary islands at two different monitoring stations namely hie02 and hie03 significant increases in soil 222rn activity and 222rn 220rn ratio from the soil were observed at both stations prior to the 2011 2012 submarine eruption off the coast of el hierro showing the highest increases before the eruption onset and before the occurrence of the strongest seismic event m 4 6 statistical analysis showed that the long term temporal trend of filtered radon data matched closely that of seismic energy release during the volcanic unrest the observed increases of 222rn are related to the rock fracturing processes seismic activity and the magmatic co2 outflow increase as observed in hie03 station

estimation of the co2 flux from furnas volcanic lake sao miguel azores abstract a study on diffuse co 2 degassing was undertaken at furnas lake sao miguel island azores in order to estimate the total diffuse co 2 output and identify anomalous degassing areas over the lake furnas lake is located in furnas volcano the easternmost of the three active central volcanoes of the sao miguel island the lake has an area of 1 87 km 2 and a maximum length and width equal to 2025 and 1600 m respectively the maximum depth of the water column is 15 m and the estimated water storage is 14 10 6 m 3 lake water temperature is cold with temperature values between 13 c and 15 c in the winter period and 18 9 c to 19 3 c in early autumn and the variation along the water column suggests a monomictic character the major ion relative composition is in decreasing order na k ca 2 mg 2 for cations and hco 3 cl so 4 2 for anions and conductivity and ph measurements respectively in the range of 152 to 165 s cm 1 and 5 3 to 8 7 suggests that furnas has neutral diluted waters and can be classified as a non active lake diffuse co 2 flux measurements were made using the accumulation chamber method with a total of 1537 and 2577 measurements performed in two different sampling campaigns the total amount of diffuse co 2 emitted to the atmosphere was estimated between 28 and 321 t km 2 d 1 respectively in the second and first sampling campaigns corresponding to 52 and 600 t d 1 the main anomalous degassing area identified over the furnas lake during both surveys is probably associated to a wnw ese trending tectonic structure other secondary areas are also suggested to be tectonically influenced identified anomalous areas showed similarities to the ones observed during previous soil co 2 degassing studies

carbon dioxide diffuse emission and thermal energy release from hydrothermal systems at copahue caviahue volcanic complex argentina abstract the north western sector of caviahue caldera argentina close to the active volcanic system of copahue is characterized by the presence of several hydrothermal sites that host numerous fumarolic emissions anomalous soil diffuse degassing of co2 and hot soils in march 2014 measurements of soil co2 fluxes in 5 of these sites namely las maquinas las maquinitas i las maquinitas ii anfiteatro and termas de copahue allowed an estimation that 165 t of deeply derived co2 is daily released the gas source is likely related to a relatively shallow geothermal reservoir containing a single vapor phase as also suggested by both the geochemical data from the 3 deep wells drilled in the 1980s and gas geoindicators applied to the fumarolic discharges gas equilibria within the h c o gas system indicate the presence of a large probably unique single phase vapor zone at 200 210 c feeding the hydrothermal manifestations of las maquinas las maquinitas i and ii and termas de copahue a natural thermal release of 107 mw was computed by using co2 as a tracer of the original vapor phase the magmatic signature of the incondensable fumarolic gases the wide expanse of the hydrothermal areas and the remarkable high amount of gas and heat released by fluid expulsion seem to be compatible with an active magmatic intrusion beneath this portion of the caviahue caldera

methana the westernmost active volcanic system of the south aegean arc greece insight from fluids geochemistry abstract an extensive geochemical survey of the fluids released by the volcanic geothermal system of methana was undertaken gases were characterized based on the chemical and isotopic helium he and carbon c analysis of 27 samples carbon dioxide soil gas concentration and fluxes were measured at 179 sampling sites throughout the peninsula forty samples of thermal and cold groundwaters were also sampled and analysed to characterize the geochemistry of the aquifers gases of hydrothermal origin gave a preliminary geothermometric estimate of about 210 c the he isotope composition indicated mantle contributions of up to 40 and the c isotope composition of co 2 indicated that it predominantly 90 originated from limestone decomposition the groundwater composition was suggestive of mixing between meteoric and hydrothermally modified sea water endmembers and water rock interaction processes limited to simple rock dissolution driven by an increased endogenous co 2 content all of the thermal manifestations and anomalous degassing areas although of limited extent were spatially correlated with the main active tectonic system of the area the total co 2 output of the volcanic system has been preliminary estimated to be less than 0 05 kg s 1 although this value is very low compared to those of other volcanic systems anomalous co 2 degassing at methana which is currently restricted to limited areas and at present is the only volcanic risk of the peninsula is a potential gas hazard that warrants further assessment in future studies

dynamics of carbon dioxide emission at mammoth mountain california mammoth mountain a dormant volcano in the eastern sierra nevada california has been passively degassing large quantities of cold magmatic co2 since 1990 following a 6 month long earthquake swarm associated with a shallow magmatic intrusion in 1989 a search for any link between gas discharge and volcanic hazard at this popular recreation area led us to initiate a detailed study of the degassing process in 1997 our continuous monitoring results elucidate some of the physical controls that influence dynamics in flank co2 degassing at this volcano high coherence between variations in co2 efflux and variations in atmospheric pressure and wind speed imply that meteorological parameters account for much if not all of the variability in co2 efflux rates our results help explain differences among previously published estimates of co2 efflux at mammoth mountain and indicate that the long term annual co2 degassing rate has in fact remained constant since 1997 discounting the possibility of large meteorologically driven temporal variations in gas efflux at other volcanoes may result in spurious interpretations of transients that do not reflect actual geologic processes

monitoring gas and heat emissions at norris geyser basin yellowstone national park usa based on a combined eddy covariance and multi gas approach abstract we quantified gas and heat emissions in an acid sulfate vapor dominated area 0 04 km2 of norris geyser basin located just north of the 0 63 ma yellowstone caldera and near an area of anomalous uplift from 14 may to 3 october 2016 an eddy covariance system measured half hourly co2 h2o and sensible h and latent le heat fluxes and a multi gas instrument measured 1 hz frequency atmospheric h2o co2 and h2s volumetric mixing ratios we also measured soil co2 fluxes using the accumulation chamber method and temperature profiles on a grid and collected fumarole gas samples for geochemical analysis eddy covariance co2 fluxes ranged from 56 to 885 g m 2 d 1 using wavelet analysis average daily eddy covariance co2 fluxes were locally correlated with average daily environmental parameters on several day to monthly time scales estimates of co2 emission rate from the study area ranged from 8 6 t d 1 based on eddy covariance measurements to 9 8 t d 1 based on accumulation chamber measurements eddy covariance water vapor fluxes ranged from 1178 to 24 600 g m 2 d 1 nighttime h and le were considered representative of hydrothermal heat fluxes and ranged from 4 to 183 and 38 to 504 w m 2 respectively the total hydrothermal heat emission rate h le radiant estimated for the study area was 11 6 mw and le contributed 69 of the output the mean standard deviation of h2o co2 and h2s mixing ratios measured by the multi gas system were 9 3 3 1 parts per thousand 467 61 ppmv and 0 5 0 6 ppmv respectively and variations in the gas compositions were strongly correlated with diurnal variations in environmental parameters wind speed and direction atmospheric temperature after removing ambient h2o and co2 the observed variations in the multi gas data could be explained by the mixing of relatively h2o co2 h2s rich fumarole gases with co2 rich and h2o h2s poor soil gases the fumarole h2o co2 and co2 h2s end member ratios 101 7 and 27 1 respectively on average were invariant during the measurement period and fell within the range of values measured in direct fumarole gas samples the soil gas h2o co2 end member ratios 15 30 were variable and low relative to the fumarole end member likely resulting from water vapor loss during cooling and condensation in the shallow subsurface whereas the co2 h2s end member ratio was high 160 presumably related to transport of co2 dominated soil gas emissions mixed with trace fumarolic emissions to the multi gas station nighttime eddy covariance ratios of h2o to co2 flux were typically between the soil gas and fumarole end member h2o co2 ratios defined by multi gas measurements overall the combined eddy covariance and multi gas approach provides a powerful tool for quasi continuous measurements of gas and heat emissions for improved volcano hydrothermal monitoring

co2 degassing along the san andreas fault parkfield california the fluxes concentrations and carbon isotopic compositions of soil co2 were measured along the parkfield segment of the san andreas fault saf single or double peak co2 flux anomalies 18 g m 2 d 1 were observed along 12 of 16 fault crossing transects at five sites flux anomalies did not coincide with concentration anomalies flux anomalies paralleled the fault trace suggesting zones of high diffusivity permeability one flux anomaly may have been accentuated by a 0 3 mm creep event however values of 13c 23 7 to 21 6 and 14c 110 5 to 111 9 pmc for soil gas co2 are characteristic of co2 of biogenic origin the co2 flux anomalies are therefore consistent with fault related biogenic gas flow and do not yield evidence for degassing of deeply derived co2

diffuse carbon dioxide emissions from hidden subsurface structures at asama volcano japan we measured diffuse carbon dioxide co2 flux and soil temperature around the summit of asama volcano japan to assess the diffuse degassing structure around the summit area soil co2 flux was measured using an accumulation chamber method and the spatial distributions of co2 flux and soil temperature were derived from the mean of 100 sequential gaussian simulations results show that soil co2 flux was high on the eastern flank of kamayama cone and the eastern rim of maekake crater the outer cone these areas mostly correspond to high temperature anomalies the average emission rate of diffuse co2 was calculated to be 12 6 t day 1 12 2 14 6 t day 1 such diffuse emissions account for 12 of the total diffuse and plume co2 emissions from the summit area the diffuse co2 anomalies probably reflect permeable zones controlled by local topography and hidden fractures bordering maekake crater the permeable zones are connected to the low electrical resistivity zone inferred to indicate both a hydrothermal fluid layer and an upper sealed layer made of clay minerals magmatic gas from the main conduit ascends to the volcano surface through this fluid layer and the permeable zones these insights emphasize that the pathways and the connection between the pathways and the source of diffuse co2 combine to create the pattern of heterogeneous diffuse co2 emission seen at the surface only by using a combination of gas measurements and geophysical tools can we begin to understand the dynamics of this system as a whole

deep co2 emitted at furnas do enxofre geothermal area terceira island azores archipelago an approach for determining co2 sources and total emissions using carbon isotopic data abstract quantification of the co2 released by the volcanoes to the atmosphere is relevant for the evaluation of the balance between deep derived biogenic and anthropogenic contributions the current study estimates the co2 released from furnas do enxofre degassing area terceira island azores archipelago by applying an approach that integrates the flux of co2 from the soil with the 13c co2 values a deep derived co2 output of 2 54 t d 1 is estimated for an area of 23 715 m2 high biogenic derived co2 flux values 45 g m 2 d 1 associated with light carbon isotopic content 13c 28 1 1 are detected and explained by the type of vegetation that characterizes the study site carbon isotopic compositions of the co2 6 4 1 2 measured in olivine hosted fluid inclusions of the terceira basalts are presented for the first time and contribute to defining the mantle co2 signature differences between these values and heavier carbon isotope values from gas in fumaroles at furnas do enxofre 4 66 to 4 27 are explained by the carbon isotopic fractionation occurring when co2 reacts to form calcite in the geothermal reservoir at temperatures 180 c a clear correlation between the soil temperature and deep co2 fluxes is observed and the integration of the diffuse degassing information with the composition of the fumarolic emissions allows estimating a thermal energy flux of 1 1 mw

diffuse emission of carbon dioxide methane and helium 3 from teide volcano tenerife canary islands diffuse emission of co2 ch4 and he was investigated in the summit crater of teide volcano tenerife canary islands the results indicate that teide volcano releases abundant co2 not only from its active crater but also from its flanks as diffuse soil emanations the spatial distribution of these emanations correlates quite closely with that of geothermal anomalies and manifestations our flux measurements indicate a total output of 380 ton day 1 of co2 and 1 6 on day 1 of ch4 by diffuse degassing from the he co2 ratios and the co2 flux we estimate a diffuse he flux of 0 052 mol year 1 isotopic analysis of carbon in soil gas samples from sites of high soil co2 flux indicates a magmatic origin for the co2 also reported by high he 4he ratios of 5 50 and 5 87 ra the origin of methane is more uncertain with low 13c values suggesting a biogenic contribution

carbon dioxide earth degassing and seismogenesis in central and southern italy 1 we present the first regional map of co2 earth degassing from a large area most of central and south italy derived from the carbon of deep provenance dissolved in the main springs of the region the investigation shows that a globally significant amount of deeply derived co2 10 of the estimated global co2 emitted from subaerial volcanoes is released by two large areas located in western italy the anomalous flux of co2 suddenly disappears in the apennine in correspondence to a narrow band where most of seismicity concentrates here at depth the gas accumulates in crustal traps generating co2 overpressurized reservoirs which induce seismicity

heat flux from magmatic hydrothermal systems related to availability of fluid recharge abstract magmatic hydrothermal systems are of increasing interest as a renewable energy source surface heat flux indicates system resource potential and can be inferred from soil co 2 flux measurements and fumarole gas chemistry here we compile and reanalyze results from previous co 2 flux surveys worldwide to compare heat flux from a variety of magma hydrothermal areas we infer that availability of water to recharge magmatic hydrothermal systems is correlated with heat flux recharge availability is in turn governed by permeability structure lithology rainfall topography and perhaps unsurprisingly proximity to a large supply of water such as the ocean the relationship between recharge and heat flux interpreted by this study is consistent with recent numerical modeling that relates hydrothermal system heat output to rainfall catchment area this result highlights the importance of recharge as a consideration when evaluating hydrothermal systems for electricity generation and the utility of co 2 flux as a resource evaluation tool

methanotrophy in geothermal soils an overlooked process the example of nisyros island greece abstract a multidisciplinary field campaign was carried out at nisyros island greece hydrothermal gases were sampled and analysed and ch4 and co2 fluxes from the soils were measured with the accumulation chamber method the sampling area lakki plain covers an area of about 0 08 km2 and includes the main fumarolic areas of kaminakia stefanos ramos lofos and phlegeton flux values measured at 130 sites range from 3 4 to 1420 mg m 2 d 1 for ch4 and from 0 1 to 383 g m 2 d 1 for co2 the fumarolic areas show very different ch4 degassing patterns kaminakia showing the highest ch4 output values about 0 8 t a 1 from an area of about 30 000 m2 and phlegeton the lowest about 0 01 t a 1 from an area of about 2500 m2 the total output from the entire geothermal system of nisyros should not exceed 2 t a 1 previous indirect estimates of the ch4 output at nisyros based on soil co2 output and ch4 co2 ratios in fumarolic gases were more than one order of magnitude higher the present work further underscores the utmost importance of direct ch4 flux data because indirect methods totally disregard methanotrophic activity within the soil ten soil samples were collected for ch4 consumption experiments and for metagenomic analysis seven of the soil samples showed small but significant ch4 consumption up to 39 7 ng g 1 h 1 and were positive for the methanotrophs specific gene pmoa confirming microbial ch4 oxidation in the soil notwithstanding the harsh environmental conditions high temperature and h2s concentrations and low ph

review of the evolution of geochemical monitoring networks and methodologies applied to the volcanoes of the aeolian arc italy abstract fluids discharged from volcanic systems are the direct surface manifestation of magma degassing at depth and provide primary insights for evaluating the state of volcanic activity we review the geochemical best practice in volcanic surveillance based to a huge amount of monitoring data collected at different active volcanoes using both continuous and discontinuous approaches the targeted volcanoes belong to the aeolian arc located in the tyrrhenian sea italy and they have exhibited different activity states during the monitoring activities reported here la fossa cone on vulcano island has been in an uninterrupted quiescent stage characterized by variable solfataric activity in contrast stromboli island has shown a persistent mild explosive activity episodically interrupted by effusive eruptions in 1985 2002 2007 and 2014 panarea island which is the summit of a seamount rising from the seafloor of the southern tyrrhenian sea showed only undersea fluid release the only observable clues of active volcanism at panarea island have been impulsive changes in the undersea fluid release with the last submarine gas burst event being observed in november 2002 the geochemical monitoring and observations at each of these volcanoes has directly involved the volcanic plume and or the fumarole vents thermal waters and diffuse soil degassing depending on the type of manifestations and the level of activity encountered through direct access to the magmatic samples when possible and the collection of as much observable data related to the fluid release as possible the aim has been i to verify the thermodynamic equilibrium condition ii to discern among the possible hydrothermal magmatic marine and meteoric sources in the fluid mixtures iii to develop models of the fluid circulation supported by data iv to follow the evolution of these natural systems by long term monitoring and v to support surveillance actions related to defining the volcanic risk and the evaluation and possible mitigation of related hazards the examples provided in this review article show the close relationships among data analysis interpretation and modeling we particularly focus on describing the fieldwork procedures since any theoretical approach must always be verified and supported by field data rather than just by experiments controlled in laboratory indeed the natural systems involve many variables producing effects that cannot be neglected the monitored volcanic systems have been regarded as natural laboratories and all of the activities have focused on both volcanological research and surveillance purposes in order to ensure that these two goals have overlapped an appendix is also included that explains the scientific approach to the systematic activities regarding geochemical monitoring of volcanic activity

scent of a myth tectonics geochemistry and geomythology at delphi greece extensive geochemical investigation of water travertine soil and diffuse gas coupled with geo structural analysis provides new insights into local fault fluid interaction and allows us to pinpoint basic elements in the geological origin or geomythology of the delphic oracle still debated by geologists delphi hosted the most famous oracle of antiquity supposed to prophesy under the effects of intoxicating gas exhaling from a chasm in the ground co 2 h 2 s rich ethylene rich or ch 4 rich gases have been invoked to explain the mantic vapours although previous interpretations dismissed the results achieved by classical scholars this study fits together history archaeology mythology and geology in a single coherent frame we highlight that no hydrocarbon gas discharges are released at present to the surface in the area the lack of any geochemical anomaly indicates that the delphi active fault does not at present constitute a preferential route for the circulation of thermogenic deep fluids the mythological gas exhaling chasm can plausibly be related to episodic seismic ruptures in the ancient past which affected for a limited time gas pockets fed by a relatively deep confined hydrothermal system the delphi fault has produced shocks up to ms 6 7 1 august 1870 and similar seismic faulting events in the past could have episodically triggered co 2 h 2 s rich emissions

multivariate analysis of co2 h2s and ch4 diffuse degassing and correlation with fault systems in agua caliente tzitzio michoacan mexico abstract the quantitative relationships between soil gas flux anomalies and faults systems in agua caliente tzitzio geothermal system were analyzed statistically the main degassing features are related with thermal springs the data used in the multivariate analysis are geothermal gas fluxes and spatial structural data i e local fault strike exploratory data analysis eda and multivariate analysis of variance manova were implemented for the first time to statistically describe the relation between the location of degassing features and the presence of some local fault systems discriminating the direction of the main discharge channels and pointing to higher permeability faults the results show that there is a statistically significant correlation between diffuse degassing of co2 and ch4 and the n s and e w fault systems conversely h2s degassing does not show any correlation with the fault systems which may be related with the higher h2s reactivity compared with that of co2 and ch4 it is highly recommended to use eda and manova techniques in order to establish the main degassing directions in geothermal and volcanic areas

soil co2 emissions as a proxy for heat and mass flow assessment taupō volcanic zone new zealand the quantification of heat and mass flow between deep reservoirs and the surface is important for understanding magmatic and hydrothermal systems here we use high resolution measurement of carbon dioxide flux co2 and heat flow at the surface to characterize the mass co2 and steam and heat released to the atmosphere from two magma hydrothermal systems our soil gas and heat flow surveys at rotokawa and white island in the taup volcanic zone new zealand include over 3000 direct measurements of co2 and soil temperature and 60 carbon isotopic values on soil gases carbon dioxide flux was separated into background and magmatic hydrothermal populations based on the measured values and isotopic characterization total co2 emission rates co2 of 441 84 t d 1 and 124 18 t d 1 were calculated for rotokawa 2 9 km2 and for the crater floor at white island 0 3 km2 respectively the total co2 emissions differ from previously published values by 386 t d 1 at rotokawa and 25 t d 1 at white island demonstrating that earlier research underestimated emissions by 700 rotokawa and 25 white island these differences suggest that soil co2 emissions facilitate more robust estimates of the thermal energy and mass flux in geothermal systems than traditional approaches combining the magmatic hydrothermal sourced co2 emission constrained using stable isotopes with reservoir h2o co2 mass ratios and the enthalpy of evaporation the surface expression of thermal energy release for the rotokawa hydrothermal system 226 mwt is 10 times greater than the white island crater floor 22 5 mwt

diffuse emission and transport of gaseous elemental mercury gem in the mapamyum geothermal system western tibet china abstract mercury hg is a widely spread pollutant owing to its high mobility in the nature the rising input of hg into the atmosphere has resulted in enhanced hg pollution in both terrestrial and aquatic ecosystems the tibetan plateau which is known as the roof of the world is considered as a hg sensitive ecosystem the himalayan tibetan geothermal belt which is formed due to the collision between india and eurasia is an important potential source of hg to the atmosphere however previous studies to the emission and transport of geological hg in the tibetan plateau are still rare understanding emission and transport of hg in the tibetan plateau can provide important constraints on global hg budget and its pollution transport diffuse emission and transport of gaseous elemental mercury gem or hg0 in the mapamyum geothermal system mgf of western tibet was investigated and simulated by the closed chamber method and the hybrid single particle lagrangian integrated trajectory hysplit dispersion model the estimated annual output of gem in the mgf calculated over an area of 41 615 m2 was in the order of 6 1 10 4 ton he c isotope ratios of the geothermal samples were all within the range of typical crustal domain combing with the hydrothermal analysis it could deduce the hg0 in the mgf might derive from both deep lithosphere and the upper crust the gem diffused from the source region was mainly dispersed to the nw direction the maximum concentration of gem is mainly distributed around the mgf which is also the region with the largest deposition rate the simulated results of the hysplit dispersion model suggest that the gem emitted from the mgf would not significantly enhance the atmospheric hg concentration whereas the deposition and accumulation of gem around the source region is not negligible

co2 discharge from the bottom of volcanic lake rotomahana new zealand 1 from april 2010 to february 2011 co2 flux surveys were performed on lake rotomahana new zealand the area has been hydrothermally active with fumaroles and sublacustrine hydrothermal activity before and since the eruption of mt tarawera in 1886 the total co2 emission from the lake calculated by sequential gaussian simulation is 549 72 t d 1 two different mechanisms of degassing diffusion through the water air interface and bubbling are distinguished using a graphical statistical approach the carbon dioxide budget calculated for the lake confirms that the main source of co2 to the atmosphere is by diffusion covering 94 5 of the lake area mean co2 flux 25 g m 2 d 1 and to a lesser extent bubbling mean co2 flux 1297 g m 2 d 1 mapping of the co2 flux over the entire lake including over lake floor vents detected during the survey correlates with eruption craters formed during the 1886 eruption these surveys also follow regional tectonic patterns present in the southeastern sector of lake rotomahana suggesting a deep magmatic source 10 km for co2 and different pathways for the gas to escape to the surface the values of 13cco2 2 88 and 2 39 confirm the magmatic origin of co2

elevated carbon dioxide flux at the dixie valley geothermal field nevada relations between surface phenomena and the geothermal reservoir abstract in the later part of the 1990s a large die off of desert shrubs occurred over an approximately 1 km 2 area in the northwestern section of the dixie valley dv geothermal field this paper reports results from accumulation chamber measurements of soil co 2 flux from locations in the dead zone and stable isotope and chemical data on fluids from fumaroles shallow wells and geothermal production wells within and adjacent to the dead zone a cumulative probability plot shows three types of flux sites within the dead zone locations with a normal background co 2 flux 7 g m 2 day 1 moderate flux sites displaying excess geothermal flux and high flux sites near young vents and fumaroles a maximum co 2 flux of 570 g m 2 day 1 was measured at a location adjacent to a fumarole using statistical methods appropriate for lognormally distributed populations of data estimates of the geothermal flux range from 7 5 t day 1 from a 0 14 km 2 site near the stillwater fault to 0 1 t day 1 from a 0 01 km 2 location of steaming ground on the valley floor anomalous co 2 flux is positively correlated with shallow temperature anomalies the anomalous flux associated with the entire dead zone area declined about 35 over a 6 month period the decline was most notable at a hot zone located on an alluvial fan and in the sg located on the valley floor gas geochemistry indicates that older established fumaroles along the stillwater fault and a 2 year old vent in the lower section of the dead zone discharge a mixture of geothermal gases and air or gases from air saturated meteoric water asmw stable isotope data indicate that steam from the smaller fumaroles is produced by 100 c boiling of these mixed fluids and reservoir fluid steam from the senator fumarole sf and from shallow wells penetrating the dead zone are probably derived by 140 c to 160 c boiling of reservoir fluid carbon 13 isotope data suggest that the reservoir co 2 is produced mainly by thermal decarbonation of hydrothermal calcite in veins that cut reservoir rocks formation of the dead zone is linked to the reservoir pressure decline caused by continuous reservoir drawdown from 1986 to present these reservoir changes have restricted flow and induced boiling in a subsurface hydrothermal outflow plume extending from the stillwater fault southeast toward the dv floor we estimate that maximum co 2 flux in the upflow zone along the stillwater fault in 1998 was roughly seven to eight times greater than the pre production flux in 1986 the eventual decline in co 2 flux reflects the drying out of the outflow plume

a shallow layer model for heavy gas dispersion from natural sources application and hazard assessment at caldara di manziana italy several nonvolcanic sources in central italy emit a large amount of carbon dioxide co2 under stable atmospheric conditions and or in the presence of topographic depressions the concentration of co2 which has a molecular mass greater than that of air can reach high values that are lethal to humans or animals several episodes of this phenomenon were recorded in central italy and elsewhere in order to validate a model for the dispersion of a heavy gas and to assess the consequent hazard we applied and tested the code twodee 2 an improved version of the established twodee model which is based on a shallow layer approach that uses depth averaged variables to describe the flow behavior of dense gas over complex topography we present results for a vented co2 release at caldara di manziana in central italy we find that the model gives reliable results when the input quantity can be properly defined moreover we show that the model can be a useful tool for gas hazard assessment by evaluating where and when lethal concentrations for humans and animals are reached

spatial domain analysis of carbon dioxide from soils on vulcano island implications for co2 output evaluation abstract the carbon dioxide emissions of volcanoes have been targeted as effective contributors of co 2 to the atmosphere however different sources can be effective and active at the same time in the generation and release of co 2 in volcanic zones since isotopic fingerprinting of co 2 allows the precise identification of different sources coupling carbon isotope and co 2 flux measurements enables the evaluation of the mass contribution of each source to the carbon dioxide emissions this paper accounts for the first extensive spatial analysis of coupled measurements of carbon isotopologues of co 2 in the soil gases and co 2 fluxes discharged by soils on vulcano island an innovative method has been designed tested and fine tuned in the laboratory to measure 13 c co 2 values directly in field using a new type of laser based isotopologues analyzer namely a deltaray thermo fisher scientific the method can be used to determine the carbon isotope composition across the full range of co 2 concentrations in the soil gases 0 100 vol these data have been combined with measurements of the co 2 contents in the soil gases to distinguish co 2 from deep origins from co 2 of biogenic origin in the inhabited area of vulcano porto the method of evaluating the amount of deep origin co 2 in the soil gases is widely applicable in volcanic and geothermal zones for evaluation and monitoring purposes for both gas and volcanic hazards

recent activity of nisyros volcano greece inferred from structural geochemical and seismological data this study summarizes the results of structural geochemical and seismological surveys carried out at nisyros volcano aegean sea greece during 1999 2001 field mapping and mesostructural measurements at the summit caldera lakki plain indicate that faults follow two main strikes ne sw and n s the n s striking fault depicts extensional features accommodating the left lateral component of motion of the ne sw striking main faults the ne sw preferred strike of the lakki faults and of the mineral filled veins as well as the distribution and ne sw elongation of the hydrothermal craters indicate that tectonics plays a major role in controlling the fluid pathway in the nisyros caldera the same ne sw trend is depicted by co2 anomalies revealed through detailed soil co2 flux surveys thus indicating a structural control on the pattern of the hydrothermal degassing degassing processes account for a thermal energy release of about 43 mw most of which occurs at lofos dome an area that was affected by hydrothermal eruptions in historical times the seismic study was conducted in june 2001 using a deployment specifically aimed at detecting signals of magmatic hydrothermal origin our instruments recorded local and regional earthquakes a few local long period events lp and bursts of monochromatic tremor local earthquake activity is concentrated beneath the caldera at depths generally shallower than 6 km plane wave decomposition of tremor signal indicates a shallow 200 m source located in the eastern part of the caldera conversely lp events depict a source located beneath the central part of the caldera in the area of lofos dome at depths in the 1 2 km range in agreement with geochemical and structural measurements these data suggest that both the deeper and shallower part of the hydrothermal system are subjected to instability in the fluid flow regimes probably consequent to transient pressurization of the reservoir these instabilities may be related to input of hot fluids from the deeper magmatic system as suggested by the variations in geochemical parameters observed after the 1997 1999 unrest episode the significance of seismological and geochemical indicators as precursors of hydrothermal explosive activity at nisyros is discussed

gas emission from diffuse degassing structures dds of the cameroon volcanic line cvl implications for the prevention of co2 related hazards abstract in the mid 1980s lakes nyos and monoun violently released massive gas mainly magmatic co 2 killing about 1800 people subsequent geochemical surveys and social studies indicate that lakes nyos and monoun event is cyclic in nature and may occur anywhere in the about 37 other volcanic lakes located in the corridor of the cameroon volcanic line cvl this potential threat motivated us to check if alike nyos and monoun the internal dynamic of the other lakes is also controlled by inputs of deep seated derived co 2 and attempt to measure and provide comprehensive insights on the passive gas emission along the cvl this knowledge shall contribute to the prevention of volcanic lake related hazards in cameroon and the refinement of the global carbon cycle we used in situ fixation and dry gas phase sampling methods to determine co 2 origin and the concentration and the accumulation chamber technique to measure diffuse co 2 emission from nine lakes and on soil at nyos valley and mount manenguba caldera the results suggest that although in minor concentrations compared to nyos and monoun ranging from 0 56 mmol kg 1 to 8 75 mmol kg 1 the bottom waters of some lakes also contain measurable magmatic co 2 with 13 c varies from 4 42 to 9 16 vs pdb that finding implies that under certain circumstances e g increase to volcanic and or tectonic activities along the cvl the concerned lakes could develop a nyos type behavioural scheme the diffuse gas emission results indicate that the nine surveyed lakes release approximately 3 69 0 37 kt km 2 yr 1 of co 2 to the atmosphere extrapolation to the approximately 39 volcanic lakes located on the cvl yields an approximate co 2 output of 27 37 0 5 kt km 2 yr 1 representing 0 023 of the global co 2 output from volcanic lakes in addition to the precedent value the gas removal operation in lakes nyos and monoun released approximately 2 52 0 46 10 8 mol km 2 yr 1 co 2 to the atmosphere from january 2001 to march 2013 more than double the per area co 2 released by the yellowstone volcanic system the co 2 emission from soil was estimated to be 4 57 1 30 kt km 2 yr 1 the soil gas geochemistry of the mount manenguba caldera also indicates a dominant magma derived co 2 mean 13 c 8 6 vs vpdb

volatiles and energy released by purace volcano total co2 output of purace volcano colombia was estimated on the basis of fluids discharged by fumaroles soil gases and dissolved carbon species in the aquifer the soil co2 emission was computed from a field survey of 512 points of co2 soil flux measurements at the main degassing areas of purace volcano the co2 flux from purace s plume was estimated using an indirect method that used the so2 plume flux and co2 so2 ratio of the main high temperature fumarole the total output of co2 was estimated at 1500 t day the main contribution of co2 comes from the plume summit degassing and from soil degassing that emit 673 and 812 t day respectively the contributions of summit and soil degassing areas are comparable indicating an intermediate degassing style partitioned between closed and open conduit systems the estimated water vapor discharge as derived from the chemical composition of the fumaroles the h2o co2 ratio and the so2 plume flux allowed calculation of the total thermal energy fumarolic soil degassing and aquifer released from the purace volcanic system this was 360 mw

co2 output discharged from stromboli island italy abstract total co 2 output from soil gas and plume discharged from the stromboli island was estimated the co 2 emission of the plume emitted from the active crater was estimated on the basis of the so 2 crater output and c s ratio while co 2 discharged through diffuse soil emission was quantified on the basis of 419 measurements of co 2 fluxes from the soil of the whole island performed by using the accumulation chamber method the results indicate an overall output of 416 t day 1 of co 2 from the island the main contribution to the total co 2 output comes from the summit area 396 t day 1 with 370 t day from the active crater and 26 t day 1 from the pizzo sopra la fossa soil degassing area the release of co 2 from peripheral areas is 20 t day 1 by soil degassing scari area mainly the result of the soil degassing survey confirms the persistence of the highest co 2 degassing areas located on the north east crater side and scari area

cosmogenic 3he and 21ne measured in quartz targets after one year of exposure in the swiss alps abstract all currently used scaling models for terrestrial cosmogenic nuclide tcn production rates are based on neutron monitor surveys therefore an assumption underlying all tcn studies is that production rates are directly proportional to secondary cosmic ray intensities for all cosmogenic nuclides to test this crucial assumption we measured cosmogenic 3 he and 21 ne in artificial quartz targets after one year of exposure at mountain altitudes in the swiss alps the targets were inconel steel tubes containing 1 kg of artificial quartz sand 250 500 m degassed for one week at 700 c in vacuum prior to exposure from august 2006 until august 2007 ten of these targets were exposed at five locations in switzerland and italy zurich 556 m davos 1560 m santis 2502 m jungfraujoch 3571 m and monte rosa 4554 m additionally a sixth set of two blank targets was kept in storage and effectively shielded from cosmic ray exposure cosmogenic noble gases were measured at room temperature and at 700 c up to 9 of the cosmogenic 3 he was measured in the cold step indicating that 3 he diffuses out of quartz at room temperature on short time scales the remaining 3 he and all 21 ne were released at 700 c as shown by a repeat measurement at 800 c for the monte rosa target which yielded no additional cosmogenic helium and neon as expected the monte rosa target contained the highest cosmogenic nuclide content with 1 56 0 07 10 6 atoms of excess 3 he and 4 5 1 2 10 5 atoms of excess 21 ne all errors are 2 the raw measurements were corrected for non atmospheric blanks shielding roof container wall tritiogenic helium and solar modulation normalised to the average neutron flux over the past five solar cycles the 3 he 21 ne production rate ratio of 6 8 0 9 indicates that cosmogenic 3 he production by the container walls is negligible the main goal of the artificial target experiment was to determine the production rate attenuation length because all our targets had an identical design and were exposed under identical conditions all systematic errors cancel out in the calculation of an attenuation length our best estimates for the 3 he and 21 ne attenuation lengths are 134 8 5 9 g cm 2 and 135 25 g cm 2 respectively agreeing very well with currently used scaling models we conclude that tcn production rates are indeed proportional to neutron monitor count rates and that 3 he and 21 ne production rates follow the same altitudinal scaling relationships as the cosmogenic radionuclides finally the measurements were scaled to sea level and high latitude using the empirical attenuation length yielding weighted mean production rates of 107 6 6 6 at g yr for 3 he and 15 4 2 1 at g yr for 21 ne despite the significant uncertainties associated with the corrections for shielding solar modulation and especially the 3 he 3 h branching ratio these estimates are in good agreement with production rates derived from long term exposure experiments at natural calibration sites and physics based simulations

diffuse soil emission of hydrothermal gases co2 ch4 and c6h6 at solfatara crater campi flegrei southern italy abstract measurements of soil fluxes of hydrothermal gases with special emphasis on c 6 h 6 as well as chemical composition of mono aromatic compounds in fumaroles and air were carried out in april 2012 at the solfatara crater campi flegrei southern italy to investigate the distribution and behavior of these species as they migrate through the soil from their deep source to the atmosphere soil fluxes of co 2 ch 4 and c 6 h 6 exhibit good spatial correlation suggesting that diffuse degassing is mainly controlled by local fractures the calculated total output of diffuse c 6 h 6 from solfatara is 0 10 kg day 1 whereas fluxes of co 2 and ch 4 are 79 10 3 and 1 04 kg day 1 respectively a comparison between soil gas fluxes and fumarole composition reveals that within the crater soil ch 4 is significantly affected by oxidation processes which are more efficient for low gas fluxes being dependent on the residence time of the uprising hydrothermal gases at shallow depth benzene degradation mainly proceeding through oxidation via benzoate seems to be strongly controlled by the presence of a shallow so 4 2 rich aquifer located in the central and southwestern sectors of the crater suggesting that the process is particularly efficient when so 4 2 acts as terminal electron acceptor so 4 reduction relatively high c 6 h 6 c 7 h 8 ratios typical of hydrothermal fluids were measured in air close to the main fumarolic field of solfatara crater here c 6 h 6 concentrations whose detection limit is 0 1 g m 3 are more than one order of magnitude higher than the limit value for ambient air 5 g m 3 this suggests that hydrothermal fluids have a strong impact on air quality in the immediate surroundings of the fumarolic vents significant concentrations of endogenous mono aromatics were also detected in air samples collected from the northern and western sides of the crater where these gas compounds are mostly fed by diffuse degassing through the crater bottom soil

flux measurements of explosive degassing using a yearlong hydroacoustic record at an erupting submarine volcano at nw rota 1 are primarily h2o so2 and co2 instantaneous fluxes varied by a factor of 100 over the deployment using melt inclusion information to estimate the concentration of co2 in the explosive gases as 6 9 0 7 wt we calculate an annual co2 eruption flux of 0 4 0 1 tg a 1 this result is within the range of measured co2 fluxes at continuously erupting subaerial volcanoes and represents 0 2 0 6 of the annual estimated output of co2 from all subaerial arc volcanoes and 0 4 0 6 of the mid ocean ridge flux the multiyear eruptive history of nw rota 1 demonstrates that submarine volcanoes can be significant and sustained sources of co2 to the shallow ocean

gas geochemistry and co2 output estimation at the island of milos greece abstract twenty gas samples have been collected from the natural gas manifestations of milos island the majority of which is found underwater along its coast furthermore three anomalous degassing fumarolic areas kalamos paleochori and adamas have been recognized on land almost all the gases are co2 dominated with co2 ranging from 88 to 99 vol for the samples taken underwater while the on land manifestations show a wider range 15 98 due to air contamination methane reaches up to 1 0 vol h2 up to 3 2 vol and h2s up to 3 5 vol indicating a hydrothermal origin of the gases the isotope composition of he points out to mantle contributions up to 45 while the c isotope composition of co2 from 1 9 to 1 3 vs v pdb with most of the values around 0 5 suggests a prevailing limestone origin isotope composition of ch4 ranging from 18 4 to 5 0 vs v pdb for c and from 295 to 7 vs v smow for h points to a geothermal origin with sometimes evident secondary oxidation processes additionally co2 flux measurements showed high values in the three fumarolic areas up to 1100 1500 and 8000 g m2 d at kalamos paleochori and adamas respectively with the highest co2 flux values up to about 23 000 g m2 d being measured in the sea at kanavas with a floating chamber the south western part of the island was covered with a lower density prospection revealing only few anomalous co2 flux values up to 650 g m2 d the total output of the island 30 5 t d is typical of quiescent closed conduit volcanoes and comparable to the other volcanic geothermal systems of the south aegean active volcanic arc nisyros kos nea kameni methana and sousaki

the structure of a hydrothermal system from an integrated geochemical geophysical and geological approach the ischia island case study the complexity of volcano hosted hydrothermal systems is such that thorough characterization requires extensive and interdisciplinary work we use here an integrated multidisciplinary approach combining geological investigations with hydrogeochemical and soil degassing prospecting and resistivity surveys to provide a comprehensive characterization of the shallow structure of the southwestern ischia s hydrothermal system we show that the investigated area is characterized by a structural setting that although very complex can be schematized in three sectors namely the extra caldera sector ecs caldera floor sector cfs and resurgent caldera sector rcs this contrasted structural setting governs fluid circulation geochemical prospecting shows in fact that the caldera floor sector a structural and topographic low is the area where co2 rich 40 cm3 l hydrothermally mature log mg na ratios 150 g m 2 d 1 is clearly captured by electrical resistivity tomography ert and transient electromagnetic tem surveys as a highly conductive resistivity 10 000 mg l and poorly conductive meteoric derived tds 4 000 mg l waters are observed respectively we finally integrate our observations to build a general model for fluid circulation in the shallowest 0 5 km part of ischia s hydrothermal system

carbon dioxide and radon emissions from the soils of pantelleria island southern italy abstract in the period july 2005 october 2006 several soil gas prospections were performed on the island of pantelleria an active volcanic geothermal system at present in a quiescent state measured parameters were co2 concentrations and 220rn and 222rn activities at 50 cm depth and co2 fluxes from the soil the whole island was covered with a measurement density of 3 5 points km2 for co2 flux and concentration and 1 6 points km2 for rn further three main and seven minor areas of previously ascertained or expected exhalative activity were covered with a measurement density up to 100 points km2 the obtained results ranged from 0 038 to 95 vol for co2 concentration from 10 bq m3 to 164 000 bq m3 from 10 bq m3 to 750 000 bq m3 for 220rn and 222rn activities respectively and from

co2 and he degassing at el chichon volcano chiapas mexico gas flux origin and relationship with local and regional tectonics during 2007 2008 three co2 flux surveys were performed on el chichon volcanic lake chiapas mexico with an additional survey in april 2008 covering the entire crater floor including the lake the mean co2 flux calculated by sequential gaussian simulation from the lake was 1 190 march 2007 730 december 2007 and 1 134 g m 2 day 1 april 2008 with total emission rates of 164 9 5 march 2007 59 2 5 december 2007 and 109 6 6 t day 1 april 2008 the mean co2 flux estimated from the entire crater floor area was 1 102 g m 2 day 1 for april 2008 with a total emission rate of 144 5 9 t day 1 significant change in co2 flux was not detected during the period of survey and the mapping of the co2 flux highlighted lineaments reflecting the main local and regional tectonic patterns the 3he 4he ratio as high as 8 1 ra for gases in the el chichon crater is generally higher than those observed at the neighbouring transmexican volcanic belt and the central american volcanic arc the co2 3he ratios for the high 3he 4he gases tend to have the morb like values 1 41 109 and the co2 3he ratios for the lower 3he 4he gases fall within the range for the arc type gases the high 3he 4he ratios the morb like co2 3he ratios for the high 3he 4he gases and high proportion of morb co2 m 25 15 at el chichon indicate a greater depth for the generation of magma when compared to typical arc volcanoes

a magmatic source for fumaroles and diffuse degassing from the summit crater of teide volcano tenerife canary islands a geochemical evidence for the 2004 2005 seismic volcanic crisis the present work reports the results of 15 studies of diffuse co2 degassing performed at teide volcano crater canary island spain and the chemical and isotopic compositions of fluids discharged from a fumarolic field located at the top of the volcano as measured between 1991 and 2010 a higher contribution of magmatic gases accompanied by enhanced total diffuse co2 emissions were observed in relation with a seismic crisis that occurred in tenerife island between 2001 and 2005 with the main peak of seismic activity between april and june 2004 a significant pulse in total diffuse co2 emission was observed at the crater of teide up to 26 3 t day 1 in 2001 in december 2003 the chemical composition of the teide fumarole changed significantly including the appearance of so2 an increase in the hcl and co concentrations and in the c2h6 c2h4 and c3h8 c3h6 ratios and a decrease in the h2s ch4 and c6h6 concentrations and in the gas steam ratio a few months after a drastic decrease in seismic activity the so2 hcl and co concentrations and the c2h6 c2h4 and c3h8 c3h6 ratios strongly decreased whereas the ch4 and c6h6 concentrations and the gas steam ratios increased according to the trends shown by both the geochemical parameters and the seismic signals late in the observation period the risk of a rejuvenation of volcanic activity at teide is considered to be low the associated temporal changes in seismic activity and magmatic degassing indicate that geophysical and fluid geochemistry signals in this system are related future monitoring programs aimed at mitigating volcanic hazard on tenerife island should involve coupled geophysical and geochemical studies

carbon dioxide degassing and thermal energy release in the monte amiata volcanic geothermal area italy abstract the quaternary volcanic complex of mount amiata is located in southern tuscany italy and represents the most recent manifestation of the tuscan magmatic province the region is characterised by a large thermal anomaly and by the presence of numerous co2 rich gas emissions and geothermal features mainly located at the periphery of the volcanic complex two geothermal systems are located at increasing depths in the carbonate and metamorphic formations beneath the volcanic complex the shallow volcanic aquifer is separated from the deep geothermal systems by a low permeability unit ligurian unit a measured co2 discharge through soils of 1 8 109 mol a 1 shows that large amounts of co2 move from the deep reservoir to the surface a large range in 13ctdic 21 07 to 3 65 characterises the waters circulating in the aquifers of the region and the mass and isotopic balance of tdic allows distinguishing a discharge of 0 3 109 mol a 1 of deeply sourced co2 in spring waters the total natural co2 discharge 2 1 109 mol a 1 is slightly less than minimum co2 output estimated by an indirect method 2 8 109 mol a 1 but present day release of 5 8 109 mol a 1 co2 from deep geothermal wells may have reduced natural co2 discharge the heat transported by groundwater computed considering the increase in temperature from the infiltration area to the discharge from springs is of the same order of magnitude or higher than the regional conductive heat flow 200 mw m 2 and reaches extremely high values up to 2700 mw m 2 in the north eastern part of the study area heat transfer occurs mainly by conductive heating in the volcanic aquifer and by uprising gas and vapor along fault zones and in those areas where low permeability cover is lacking the comparison of co2 flux heat flow and geological setting shows that near surface geology and hydrogeological setting play a central role in determining co2 degassing and heat transfer patterns

diffuse emission of co2 from the fossa crater vulcano island italy numerous measurements of co2 degassing from the soil carried out with the accumulation chamber method indicate that in the period april july 1995 the upper part of the fossa cone released a total output of 200 t d 1 of co2 which corresponds to approximately 1000 t d 1 of steam these large amounts of fluids are of the same order of magnitude as those released by the high temperature fumarolic field located inside the crater the spatial distribution of soil gas fluxes shows that the main structures releasing co2 are the inner slopes of the crater and a nw se line located ne of the crater rim which correspond to the main direction of vulcano island active faults the comparison of the co2 maps with the soil temperature distribution derived from both direct measurements and airborne infrared images indicates the occurrence of extensive condensation of fumarolic steam within the upper part of the fossa cone whose total amount is comparable to the rainfall budget part of the condensate which originates from this process contributes to the recharge of the phreatic aquifer of porto plain modifying the chemical and isotopic composition of the groundwater

diffusive helium emissions as a precursory sign of volcanic unrest significant increases in helium emissions from the soil and 3 he 4 he ratios in groundwater on el hierro island canary islands spain were observed prior to the 2011 2012 submarine eruption off the coast of the island the changes of diffusive helium emissions rate were observed one month prior to the submarine eruption onset 12 october 2011 and the major increase preceded increases in seismic energy release during the volcanic unrest measured 3 he 4 he ratios in groundwaters from a well in el hierro island increased from 2 3 r a to 7 2 r a r a 3 he 4 he ratio in air 1 month prior to the eruption onset and reached a peak of 8 2 r a indicating a dominant magmatic contribution to the dissolved gases in ground waters 3 he 4 he values and diffusive helium emission studies have been extremely important for forecasting the onset of the volcanic unrest and subsequent volcanic eruption an aseismic exsolution of magmatic gases from magma bodies beneath el hierro island through fractures and vertical permeability structures increased the diffusive helium emission rate prior to episodes of seismic energy release associated with the volcanic unrest

quantification of carbon dioxide emissions of ciomadul the youngest volcano of the carpathian pannonian region eastern central europe romania abstract we provide the first high resolution co 2 flux data for the neogene to quaternary volcanic regions of the entire carpathian pannonian region eastern central europe and estimate the co 2 emission of the seemingly inactive ciomadul volcanic complex the youngest volcano of this area our estimate includes data from focused and diffuse co 2 emissions from soil the co 2 fluxes of focused emissions range between 277 and 8172 g d 1 corresponding to a co 2 output into the atmosphere between 0 1 and 2 98 t per year the investigated areas for diffuse soil gas emissions were characterized by wide range of co 2 flux values at apor baths ranging from 1 7 10 1 to 8 2 10 4 g m 2 d 1 while at l z re ti ranging between 1 43 and 3 8 10 4 g m 2 d 1 the highest co 2 focused gas fluxes at ciomadul were found at the periphery of the youngest volcanic complex which could be explained either by tectonic control across the brittle older volcanic edifices or by degassing from a deeper crustal zone resulting in co 2 flux at the periphery of the supposed melt bearing magma body beneath ciomadul the estimate of the total co 2 output in the area is 8 70 10 3 t y 1 and it is consistent with other long 10 kyr dormant volcanoes with similar age worldwide such as in italy and usa taking into account the isotopic composition of the gases that indicate deep origin of the co 2 emissions this yields further support that ciomadul may be considered indeed a dormant or pams volcano volcano with potentially active magma storage rather than an inactive one furthermore hazard of co 2 outpourings has to be taken into account and it has to be communicated to the visitors finally we suggest that co 2 output of dormant volcanic systems has to be also accounted in the estimation of the global volcanic co 2 budget

testing the tunable diode laser system in extreme environments measuring high and low co2 concentrations in both active volcanic and geothermal settings abstract measuring co2 emissions in geothermal and volcanic areas is sometimes difficult because of large areas to cover and sites often inaccessible measuring high levels of co2 concentration can provide information on hidden structure in geothermal areas and recording changes in co2 concentration on volcanic areas can help monitor the level of volcanic activity the purpose of this study was to use the tunable laser diode tdl absorption spectroscopy method to test levels of co2 concentrations at two extreme environments white island volcano the most active volcano of new zealand with large and concentrated gas fluxes and ngapouri geothermal area a small geothermal area in the taupo volcanic zone new zealand with relatively low and diffuse gas emissions in 2017 for the first time using tdl at white island co2 concentration measurements performed across the active fumarole fields had the highest co2 concentrations of 657 ppm tdl survey measurements were also conducted across fault strands near the ngapouri geothermal area and the results complemented co2 flux results obtained with the accumulation chamber method higher co2 concentrations were measured close to the mapped ngapouri splays with a maximum of 484 ppm the maximum co2 flux measured in the same area was 100 g m 2 day 1 however the highest co2 fluxes measured along the transects and by the mapped faults were less clear but the co2 concentrations increased closer to the fault splays advantages and disadvantages of using a tdl system have been described and compared to the accumulation chamber method the results from the tdl system demonstrated that co2 concentrations can be used as a tool with other geophysical tools for both detecting and highlighting geological structures where no obvious thermal activity is present and for monitoring purposes on active volcanoes

environmental influences on soil co2 degassing at furnas and fogo volcanoes sao miguel island azores archipelago abstract since october 2001 four soil co 2 flux stations were installed in the island of sao miguel azores archipelago at fogo and furnas quiescent central volcanoes these stations perform measurements by the accumulation chamber method and as the gas flux may be influenced by external variables the stations are equipped with several meteorological sensors multivariate regression analysis applied to the large datasets obtained allowed observing that the meteorological variables may influence the soil co 2 flux oscillations from 18 to 50 5 at the different monitoring sites additionally it was observed that meteorological variables mainly soil water content barometric pressure wind speed and rainfall play a different role in the control of the gas flux depending on the selected monitoring site and may cause significant short term spike like fluctuations these divergences may be potentially explained by the porosity and hydraulic conductivity of the soils topographic effects drainage area and different exposure of the monitoring sites to the weather conditions seasonal effects are responsible for long term oscillations on the gas flux before a reliable application of soil co 2 flux to seismic and or volcanic monitoring it is important to recognize those environmental influences on the gas flux in addition understanding the external meteorological influences on the gas flux may be important for the public health risk assessment since meteorological parameters may cause also significant indoor co 2 increases in a house at furnas village in furnas volcano caldera the values detected reached percentages as high as 20 8 due to significant decreases in the barometric pressure

sealing capacity of clay cap units above the cerro pabellon hidden geothermal system northern chile derived by soil co2 flux and temperature measurements abstract cerro pabellon is a hidden high enthalpy geothermal system reservoir temperature up to 250 c located in the pampa apacheta northern chile where the first geothermal power plant in south america is currently operating a fumarolic field located on the summit of apacheta volcano about 3 5 km w of pampa apacheta is the only evidence of the presence of a degassing magma connected to the surface co 2 soil flux and temperatures on a grid of 400 points were measured to understand the absence of any other thermal manifestations more than 90 of the measured co 2 flux values were below background estimated at 1 35 g m 2 day 1 whereas the associated soil temperatures mean value 19 4 c carried out at 10 cm depth were related at least partially to an endogenous though weak thermal anomaly no spatial correlation was observed between soil co 2 flux and temperature measurements suggesting a minimal role played by the volcano tectonic structures in the circulation of geothermal fluids soil temperature gradients measured on a grid of 85 points in the active fumarolic field where acid waters and magmatic gases are discharged revealed the only strong thermal anomaly temperatures up to 83 c of the area the thick argillic clay cap 300 m located above the geothermal reservoir has a pivotal role in preventing the resurgence of fluids whereas an efficient interaction between the rising magmatic fluids and the liquid dominated reservoir favours acidic gas scrubbing processes thus allowing the ascent of a steam depleted in magmatic compounds this steam interacts with the shallower discontinuous aquifer s below pampa apacheta with the consequent nearly complete dissolution of co 2 and h 2 s and heating of the shallow groundwater this results in low co 2 fluxes and extended slight thermal anomaly at the surface finally an integrated conceptual model using our results and available geological mineralogical geochemical and geophysical data of the cerro pabellon hidden geothermal system is presented with the aim of providing criteria for geothermal exploration of similar high enthalpy geothermal systems in the andes that also exhibit a lack of thermal surface features

soil co2 emissions at furnas volcano sao miguel island azores archipelago volcano monitoring perspectives geomorphologic studies and land use planning application accepted for publication in journal of geophysical research copyright 2010 american geophysical union