Gas transport

A síntese e o comportamento mesomórfico de dois poliacrilatos quirais líquido cristalinos com cadeia lateral derivados do (S)-(-)-2-metil-1-butanol são descritos. Estes novos poliacrilatos quirais mostram dependência das temperaturas de transição de fase com a massa molar e o comprimento do espaçador. O poliacrilato contendo quatro unidades metilênicas no espaçador mostra fase nemática quiral, enquanto que o poliacrilato com espaçador contendo onze unidades metilênicas mostra fase esmética. Além disto, a fase nemática quiral foi encontrada para massa molar menor e fase esmética para massa molar maior. Experimentos de espalhamento de luz foram realizados em soluções diluídas do poliacrilato contendo onze unidades metilênicas em tetrahidrofurano e diclorometano. Valores de massa molar ponderal média, raio de giro e o segundo coeficiente virial foram determinados através de espalhamento de luz estático, enquanto que o coeficiente de difusão e o raio hidrodinâmico foram obtidos por espectroscopia de correlação de fótons. Uma comparação entre as técnicas indica que o comportamento da cadeia é típico de cadeia linear polidispersa em bom solvente. The synthesis and mesomorphic behavior of two chiral side chain liquid crystalline polyacrylates from (S)-(-)-2-methyl-1-butanol are described. These new polyacrylates show a dependence of the phase transition temperatures on both, molecular weight and spacer length. The polyacrylate with four methylene units in the spacer exhibits a chiral nematic phase whereas the polyacrylate with a spacer containing eleven methylene units presents a smectic phase. In addition, the chiral nematic phase appears for low molecular weight and smectic phase for high molecular weight polyacrylates. Light scattering experiments were performed in dilute solutions of the polyacrylate containing eleven methylene units in tetrahydrofuran and dichloromethane. Values for weight averaged molecular weight, radius of gyration and second virial coefficient were determined by static light scattering whereas the diffusion coefficient and the hydrodynamic radius of the chains were obtained by photon correlation spectroscopy. A comparison between both techniques indicates that the chain behavior can be taken as typical for a polydisperse linear chain in a good solvent.

The potentially significant role of the biogenic trace gas dimethylsulfide (DMS) in determining the Earth's radiation budget makes it necessary to accurately reproduce seawater DMS distribution and quantify its global flux across the sea/air interface. Following a threefold increase of data (from 15,000 to over 47,000) in the global surface ocean DMS database over the last decade, new global monthly climatologies of surface ocean DMS concentration and sea-to-air emission flux are presented as updates of those constructed 10 years ago. Interpolation/extrapolation techniques were applied to project the discrete concentration data onto a first guess field based on Longhurst's biogeographic provinces. Further objective analysis allowed us to obtain the final monthly maps. The new climatology projects DMS concentrations typically in the range of 1-7 nM, with higher levels occurring in the high latitudes, and with a general trend toward increasing concentration in summer. The increased size and distribution of the observations in the DMS database have produced in the new climatology substantially lower DMS concentrations in the polar latitudes and generally higher DMS concentrations in regions that were severely undersampled 10 years ago, such as the southern Indian Ocean. Using the new DMS concentration climatology in conjunction with state-of-the-art parameterizations for the sea/air gas transfer velocity and climatological wind fields, we estimate that 28.1 (17.6-34.4) Tg of sulfur are transferred from the oceans into the atmosphere annually in the form of DMS. This represents a global emission increase of 17% with respect to the equivalent calculation using the previous climatology. This new DMS climatology represents a valuable tool for atmospheric chemistry, climate, and Earth System models.

The aim of this work is to analyze the carbon monoxide (CO) transport in the human body submitted to several physical activity levels. A complete mathematical model of the human respiratory system was developed, considering the exchanges of CO, oxygen (O2) and carbon dioxide (CO2) in the lung, blood and tissues. The human body was divided in the following compartments: alveolar, pulmonary capillaries, arterial, venous, tissue capillary and tissues. The gas transport in the blood and tissues is represented by empirical equations. The physiological parameters were described in function of physical activity. The model was validated by comparing its results with experimental data of controlled CO exposition. The agreement was excellent. CO concentration curves for critical days of São Caetano do Sul city (SP, Brazil) atmosphere were used as model input. The simulation results for some physical activities show that the more intense the activity, the larger the blood carboxyhemoglobin (COHb) level variations. The COHb level was compared with a CO quality air criteria, which showed to be adequate for low and moderate physical activity levels.

The aim of this work is to analyze the carbon monoxide (CO) transport in the human body submitted to several physical activity levels. A complete mathematical model of the human respiratory system was developed, considering the exchanges of CO, oxygen (O2) and carbon dioxide (CO2) in the lung, blood and tissues. The human body was divided in the following compartments: alveolar, pulmonary capillaries, arterial, venous, tissue capillary and tissues. The gas transport in the blood and tissues is represented by empirical equations. The physiological parameters were described in function of physical activity. The model was validated by comparing its results with experimental data of controlled CO exposition. The agreement was excellent. CO concentration curves for critical days of São Caetano do Sul city (SP, Brazil) atmosphere were used as model input. The simulation results for some physical activities show that the more intense the activity, the larger the blood carboxyhemoglobin (COHb) level variations. The COHb level was compared with a CO quality air criteria, which showed to be adequate for low and moderate physical activity levels.

Phragmites australis wetlands act as a sink for greenhouse gases by photosynthetic assimilation of carbon dioxide (CO 2) from the atmosphere and sequestration of the organic matter produced in the wetland soil. The wetlands also act as a source for greenhouse gases by emission of sediment-produced methane (CH 4) to the atmosphere. In P. australis wetlands, the dominant mechanism of CH 4 release to the atmosphere is internal gas transport in the plants, primarily by pressurized convective gas flow. The time periods of carbon fixation and CH 4 release therefore vary seasonally and diurnally. The balance between net CO 2-assimilation and CH 4 emission determines if a wetland can be regarded as a net sink or a net source of greenhouse gases, and hence, the function of the wetland in relation to global climate change. On an annual basis up to 15% of the net carbon fixed by the wetlands may be released to the atmosphere as CH 4. Because of the different infrared absorption characteristics and atmospheric longevity of CH 4 and CO 2 , the warming effect of CH 4 in the atmosphere is about 21 times higher on a mass basis than CO 2 over a 100-year timescale. Thus, the immediate carbon balance, coupled with the different physical characteristics of the two gases, would suggest that although some wetlands function as a net sink for CO 2 , the wetlands still increase the greenhouse effect because of their release of CH 4. However, the short adjustment time for CH 4 in the atmosphere means that, over a longer time scale, the radiative forcing of CH 4 is less relative to CO 2 and the wetlands effectively become a sink for greenhouse gases. Wetlands may therefore be regarded as a source for greenhouse gases and so increase radiative forcing if evaluated on a short time scale (decades), but as a sink for greenhouse gases and thus attenuating radiative forcing if evaluated over longer time scales (>100 years).

Knowledge of heat and gas transport properties of the peat soils is important to simulate greenhouse gas behaviour and changes of soil(temperature in the wetlands. In this study, the heat and gas transport properties for differently(decomposed and variably saturated peat soils were measured in order to investigate the general analogies and differences between transport properties of the peat soils. As results, changes in liquid(phase tortuosity under different moisture conditions and volume shrinkage under dry conditions did not significantly affect the thermal conductivity, showing linear increase of thermal conductivity with moisture content. On the other hand, marked effects of soil(water blockage and volume shrinkage on the soil(gas diffusion coefficient under wet and dry conditions, respectively, were observed.

We present new simulation results for the packing of single-center and three-center models of carbon dioxide at high pressure in carbon slit pores. The former shows a series of packing transitions that are well described by our density functional theory model developed earlier. In contrast, these transitions are absent for the three-center model. Analysis of the simulation results shows that alternations of flat-lying molecules and rotated molecules can occur as the pore width is increased. The presence or absence of quadrupoles has negligible effect on these high-density structures.

The permeation of helium, oxygen and nitrogen in perfluorosulphonic acid ionomeric (PFSI) membranes with short and long side chains, namely Aquivion Ò and Nafion Ò 117, was studied in the relative humidity range between 0 and 90%, and at temperatures between 35 C and 65 C. The presence of humidity enhances, up to a factor of 100, the gas permeability in the membranes, due to the permeation of gas molecules in the hydrophilic domains: the enhancement is rather pronounced for O 2 and N 2 , and less marked for He permeability. The relative permeability increase, P gas /P gas,0 , shows a complex dependence on the relative humidity, as the water content in the membrane is itself a non linear function of this parameter. The water volume fraction in the membrane at each activity was accurately estimated from measurements of vapor-induced swelling, which indicate that the partial molar volume of water is smaller than its pure liquid value, in both membranes at 35 C. When plotted against water volume fraction, the gas permeability increases exponentially in the range between 2% and 20%; the slope of the curve is higher for Nafion Ò than for Aquivion Ò , as it is reasonable due to their different microstructures. The ideal selectivity of the two membranes for He over N 2 , O 2 over N 2 and He over O 2 , decreases markedly with increasing water content in the membrane.

The Netherlands has been a major gas producer and exporter for decades. This country implemented a gas hub policy to deal with diminishing resources. We study the effects of this policy using hourly data over the period 2006-2013. Storage and trading became more important, but transit hardly grew. The investments in the gas hub did not have clear effects in the short term.

A major concern resulting from the increased use and production of natural gas has been how to mitigate fugitive greenhouse gas emissions (predominantly methane) from natural gas infrastructure (e.g., leaky shallow pipelines). Subsurface migration and atmospheric loading of methane from pipeline leakage is controlled by source configurations and subsurface soil conditions (e.g., soil heterogeneity and soil moisture) and are further affected by atmospheric conditions (e.g., wind and temperature). However , the transport and attenuation of methane under varying subsurface and atmospheric conditions are poorly understood, making it difficult to estimate leakage fluxes from methane concentration measurements at and above the soil surface. Based on a series of controlled bench-scale experiments using a large porous media tank interfaced with an open-return wind tunnel, this study investigated multiphase processes controlling migration of methane from a point source representing a buried pipeline leaking at fixed flow rate (kg/s) under various saturation and soil-texture conditions. In addition, potential effects of atmospheric boundary controls, wind (0.5 and 2.0 m s −1) and temperature (22 and 35 • C), were also examined. Results showed the distinct effects of soil heterogeneity and, to a varying degree, of soil moisture on surface methane concentrations. In addition, results also showed the pronounced effects of wind and, to a lesser degree, of temperature on surface methane concentrations in the presence of varying soil and moisture conditions. The observed subsurface methane profiles were simulated using the mul-tiphase transport simulator TOUGH2-EOS7CA. Observed agreement between measured and simulated data demonstrates that for the conditions studied, multiphase migration of a multicomponent gas mixture (including methane) under density-dependent flow can be adequately represented with a Fickian advection-diffusion (or dispersion) model (ADM) framework. The dominant effect of saturation over the soil texture, could also be inferred from numerical characterization.

A multiscale, physically-based, reaction-diffusion kinetics model is developed for non-steadystate transport of simple gases through a rubbery polymer. Experimental data from the literature, new measurements of non-steady-state permeation and a molecular dynamics simulation of a gas-polymer sticking probability for a typical system are used to construct and validate the model framework. Using no adjustable parameters, the model successfully reproduces time-dependent experimental data for two distinct systems: (1) O 2 quenching of a phosphorescent dye embedded in poly(n-butyl(amino) thionylphosphazene), and (2) O 2 , N 2 , CH 4 and CO 2 transport through poly(dimethyl siloxane). The calculations show that in the pre-steady-state regime, permeation is only correctly described if the sorbed gas concentration in the polymer is dynamically determined by the rise in pressure. The framework is used to predict selectivity targets for two applications involving rubbery membranes: CO 2 capture from air and blocking of methane crossover in an aged solar fuels device.

We present new simulation results for the packing of single-center and three-center models of carbon dioxide at high pressure in carbon slit pores. The former shows a series of packing transitions that are well described by our density functional theory model developed earlier. In contrast, these transitions are absent for the three-center model. Analysis of the simulation results shows that alternations of flat-lying molecules and rotated molecules can occur as the pore width is increased. The presence or absence of quadrupoles has negligible effect on these high-density structures.

A recent hemodynamic model is extended and applied to simulate and explore the feasibility of detecting ocular dominance (OD) and orientation preference (OP) columns in primary visual cortex by means of functional magnetic resonance imaging (fMRI). The stimulation entails a short oriented bar stimulus being presented to one eye and mapped to cortical neurons with corresponding OD and OP selectivity. Activated neurons project via patchy connectivity to excite other neurons with similar OP in nearby visual fields located preferentially along the direction of stimulus orientation. The resulting blood oxygen level dependent (BOLD) response is estimated numerically via the model's spatiotemporal hemodynamic response function. The results are then used to explore the feasibility of detecting spatial OD-OP modulation, either directly measuring BOLD or by using Wiener deconvolution to filter the image and estimate the underlying neural activity. The effect of noise is also considered and it is estimated that direct detection can be robust for fMRI resolution of around 0.5 mm, whereas detection with Wiener deconvolution is possible at a broader range from 0.125 mm to 1 mm resolution. The detection of OD-OP features is strongly dependent on hemodynamic parameters, such as low velocity and high damping reduce response spreads and result in less blurring. The short-bar stimulus that gives the most detectable response is found to occur when neural projections are at 45 relative to the edge of local OD boundaries, which provides a constraint on the OD-OP architecture even when it is not fully resolved.

Laboratory experiments were conducted to investigate flow of discrete microbubbles through a water‐saturated porous medium. During the experiments, bubbles, released from a diffuser, moved upward through a quasi‐2‐D flume filled with transparent water‐based gelbeads and formed a distinct plume that could be well registered by a calibrated camera. Outflowing bubbles were collected on the top of the flume using volumetric burettes for flux measurements. We quantified the scaling behaviors between the gas (bubble) release rates and various characteristic parameters of the bubble plume, including plume tip velocity, plume width, and breakthrough time of the plume front. The experiments also revealed circulations of ambient pore water induced by the bubble flow. Based on a simple momentum exchange model, we showed that the relationship between the mean pore water velocity and gas release rate is consistent with the scaling solution for the bubble plume. These findings have important impl...

The tracer gas method is one of the common ways to evaluate the air exchange rate in a naturally ventilated barn. One crucial condition for the accuracy of the method is that both considered gases (pollutant and tracer) are perfectly mixed at the points where the measurements are done. In the present study, by means of computational fluids dynamics (CFD), the mixing ratio NH3/CO2 is evaluated inside a barn in order to assess under which flow conditions the common height recommendation guidelines for sampling points (sampling line and sampling net) of the tracer gas method are most valuable. Our CFD model considered a barn with a rectangular layout and four animal-occupied zones modeled as a porous medium representing pressure drop and heat entry from lying and standing cows. We studied three inflow angles and six combinations of air inlet wind speed and temperatures gradients covering the three types of convection, i.e., natural, mixed, and forced. Our results showed that few cases ...

A multiscale, physically-based, reaction-diffusion kinetics model is developed for non-steadystate transport of simple gases through a rubbery polymer. Experimental data from the literature, new measurements of non-steady-state permeation and a molecular dynamics simulation of a gas-polymer sticking probability for a typical system are used to construct and validate the model framework. Using no adjustable parameters, the model successfully reproduces time-dependent experimental data for two distinct systems: (1) O 2 quenching of a phosphorescent dye embedded in poly(n-butyl(amino) thionylphosphazene), and (2) O 2 , N 2 , CH 4 and CO 2 transport through poly(dimethyl siloxane). The calculations show that in the pre-steady-state regime, permeation is only correctly described if the sorbed gas concentration in the polymer is dynamically determined by the rise in pressure. The framework is used to predict selectivity targets for two applications involving rubbery membranes: CO 2 capture from air and blocking of methane crossover in an aged solar fuels device.

Preferential paths are often reported in connection with gas breakthrough experiments. These preferential paths may be explained, in a deformable soil skeleton, by the action of pressurised gas along a natural path. A natural path is defined in a spatially heterogeneous material by a set of connected spots of higher gas permeability. Along this path the soil will experience a marked desaturation and gas permeability will increase fast. The paper describes a procedure to simulate these effects. Soil heterogeneity is described by means of random fields, which describe the key soil properties for gas migration. Since actual data concerning soil variability at a small (sample) scale is very limited, a number of computer models of increased complexity have been developed. They maintain, however, a close relationship with the known macroscopic data of the average (homogeneous) sample. The effect of some hypothesis concerning the stochastic structure of soil variability and the role of the hydromechanical coupling has also been explored. Once the heterogeneous soil model is defined, a general purpose code for Thermo-Hydro-Mechanical analysis is subsequently used to perform the analysis. The soil is initially saturated and a non-wetting phase (gas) is forced through the saturated mass either at constant pressure or at a constant flow rate. The results of the different analyses are compared in order to advance in the basic understanding of gas migration through clay barriers. Finally, a discussion of the relevance of soil heterogeneity, on the basis of the analysis performed, is presented.

The use of inorganic composite membranes in chemical industries has received a lot of attention more recently due to a number of exceptional advantages including thermal stability and robustness. Inorganic membranes can selectively remove water from the reaction mixture during esterification reactions in order to enhance product formation. The characterisation of inorganic composite membranes used in this work including the determination of the pore diameter and specific surface area was performed using Liquid Nitrogen adsorption at 77 K. The membrane was modified once. The permeation test for the single gases including carbon dioxide (CO2), helium (He), nitrogen (N2) and argon (Ar) through the inorganic composite ceramic membrane was carried out at the gauge pressure range of 0.10 – 1.00 bar and at the temperature of 393 K. The order of the gas molecular weight was He < N2 < CO2 < Ar. The BET surface area of the dip-coated silica membrane showed a type IV isotherm characte...

A variety of liquid crystalline (LC) materials have been examined as potential membrane separation materials. The order present in the LC phases has measurable effects on solute sorption, diffusivity, permeability, and selectivity, and can thus be used to tune the transport and separation of different species. The current work has focused on polymer dispersed liquid crystal (PDLC), linear butadiene diol based side chain liquid crystalline polymer (LCP), and linear and crosslinked acrylate based LCP membranes. The focus was primarily on the separation of propylene and propane, a separation of significant industrial interest that is not easily achieved with current membrane technology. Polysulfone (Psf) and 4-cyano-4'-octylbiphenyl (8CB) were used to fabricate polymer dispersed liquid crystal (PDLC) membranes. Permeation properties for propane and propylene through polysulfone membranes with increasing LC concentrations were measured at temperatures above and below the glass transition temperature and in several LC phases. The plasticization of PSf by 8CB increased permeability and selectivity with increasing temperatures below the Tg, and membranes with higher LC concentrations exhibited a higher mixed gas permeability and selectivity for propylene. Permeability selectivity decreased across the smectic to nematic phase transition. Overall, selectivities were low, and membrane stability was a significant problem, especially at higher pressures. Thus, several LCP systems were studies as candidates for membrane gas separations. A side chain liquid crystalline poly(butadiene)diol with cyanobiphenyl mesogens was impregnated in a porous PTFE support for gas transport studies. Single gas sorption for propane and propylene in the LCP were investigated in the smectic A mesophase. Gas transport in the glassy state showed separation dominated by differences in gas diffusivity. Permeabilities and selectivities for

The potentially significant role of the biogenic trace gas dimethylsulfide (DMS) in determining the Earth's radiation budget makes it necessary to accurately reproduce seawater DMS distribution and quantify its global flux across the sea/air interface. Following a threefold increase of data (from 15,000 to over 47,000) in the global surface ocean DMS database over the last decade, new global monthly climatologies of surface ocean DMS concentration and sea-to-air emission flux are presented as updates of those constructed 10 years ago. Interpolation/extrapolation techniques were applied to project the discrete concentration data onto a first guess field based on Longhurst's biogeographic provinces. Further objective analysis allowed us to obtain the final monthly maps. The new climatology projects DMS concentrations typically in the range of 1-7 nM, with higher levels occurring in the high latitudes, and with a general trend toward increasing concentration in summer. The increased size and distribution of the observations in the DMS database have produced in the new climatology substantially lower DMS concentrations in the polar latitudes and generally higher DMS concentrations in regions that were severely undersampled 10 years ago, such as the southern Indian Ocean. Using the new DMS concentration climatology in conjunction with state-of-the-art parameterizations for the sea/air gas transfer velocity and climatological wind fields, we estimate that 28.1 (17.6-34.4) Tg of sulfur are transferred from the oceans into the atmosphere annually in the form of DMS. This represents a global emission increase of 17% with respect to the equivalent calculation using the previous climatology. This new DMS climatology represents a valuable tool for atmospheric chemistry, climate, and Earth System models.

The code DISGAS (model for passive DISpersion of GASes) is a Eulerian model for passive dispersion of diluted gas and fine dust particles. Turbulent diffusion is based on the K-theory and the wind field can be evaluated assuming either a uniform wind profile based on the Similarity Theory or using a terrain-following mass-consistent wind model. DISGAS can be used to forecast concentration of gas (or dust) over complex terrains. The inputs to the model are topography, wind observations from meteorological stations, atmospheric stability information, and gas flow rate from a discrete number of point sources. DISGAS is written in fortran 90. Here we describe the model and an application example.

Diplomski rad je izrađen: Sveučilište u Zagrebu Rudarsko-geološko-naftni fakultet Zavod za naftno-plinsko inženjerstvo i energetiku Pierottijeva 6, 10 000 Zagreb Sažetak Početak 21. stoljeća obilježio je trend rasta potrošnje prirodnog plina za dobivanje električne i/ili toplinske energije. Trend rasta pratio je porast svijesti o ekološkim kapacitetima Zemlje te o potrebi zaštite okoliša i održivog razvoja, a kao prateća pojava porastu potražnje, dogodio se i nagli skok količina plina transportiranog cjevovodima. Transportni sustav plina središnji je dio plinskog tržišta pa tako i tržišta plina u RH. Povezuje sve ostale djelatnosti iz plinskog sektora te omogućuje energetski tok plina od njegove proizvodnje do krajnjih potrošača koji su, zapravo i pokretači tržišta. Na tom putu odvijaju se brojni procesi te ugovaraju odnosi među sudionicima na tržištu, usklađeni s Uredbom CAM i Uredbom BAL te drugom pravnom stečevinom EU. Ugovaranje kapaciteta transportnog sustava, a potom i nominiranje istih tih kapaciteta preduvjet su za ostvarivanje poslovanja svih subjekata na tržištu, odnosno prijenosa i razvoda plina. Ugovaranjem kapacitetnih proizvoda koje operator transportnog sustava nudi, stječe se pravo na određeni tehnički kapacitet transportnog sustava, a nominiranjem se to pravo potvrđuje i ostvaruje. Po ostvarivanju transporta, obzirom na otvaranje hrvatskog plinskog tržišta i velik broj aktivnih sudionika, isporučena energija plina mora se i raspodijeliti po korisnicima sustava, što zbog izostanka dnevnih mjerenja na obračunskim mjestima nije nimalo lak zadatak. Plinacro je, kao operator hrvatskog transportnog sustava započeo testnu fazu novoizrađenog modela raspodijele isporučene energije plina, u svrhu učinkovitije i kvalitetnije usluge svim korisnicima, a time i optimiranja rada sustava kojeg vodi, nadzire i uravnotežuje čime stvara temelje za interakcije ostalih aktera na plinskom tržištu.

Opskrbljivači prirodnim plinom povećanje svoje zarade pronalaze u optimizaciji različitih procesa. Uz cijenu plina, krajnju cijena plina sadrži se od cijene transporta, cijene skladištenja i marže opskrbljivača. U ovom radu izrađen je program koji optimizacijom transportnih i skladišnih kapaciteta maksimalno povećava maržu opskrbljivača za plinsku godinu 2019./2020. za uvoz plina iz Austrije. Temeljem javno dostupnih informacija koje pružaju austrijski, slovenski, mađarski i hrvatski operatori transportnoga sustava dobiven je najjeftiniji način transporta plina iz Austrije u Hrvatsku. Na temelju cijena plina za pojedine proizvode u plinskoj godini 2019./2020. i cijena skladištenja izračunat je optimalan broj skladišnih jedinica.Natural gas suppliers find ways to increase their earnings in optimizing different processes. Besides the price of gas itself, the final price of gas includes the cost of transport, storage costs and the margin of the supplier. In this thesis, a program has b...

A short wetted-wall column was used to measure and correlate gas-phase mass transfer coefficients for various pure components evaporating counter current into an air stream. Mass transfer coefficients were also measured for binary mixtures. Both a smooth and a complex surface, similar to the surface of the structured packing Mellapak, were used in the study. The gas-phase mass transfer coefficients for the smooth surface were correlated with Sh g) 0.0044Re g Sc g 0.5 We l 0.111. The results for the complex surface were correlated with Sh g) 0.0036Re g 0.76 Sc g 0.5 Re l 0.41 Bo-0.13. Mass transfer coefficients for binary mixtures were compared with these gas-phase mass transfer coefficients. Enhanced mass transfer was observed for systems with large differences in pure-component surface tensions. This was not the case for binary systems with small differences in the pure-component surface tensions. Negligible liquidside resistance to mass transfer was found in all systems in this study. High-viscosity liquids deviated from the proposed correlations.

The aim of this work is to analyze the carbon monoxide (CO) transport in the human body submitted to several physical activity levels. A complete mathematical model of the human respiratory system was developed, considering the exchanges of CO, oxygen (O2) and carbon dioxide (CO2) in the lung, blood and tissues. The human body was divided in the following compartments: alveolar, pulmonary capillaries, arterial, venous, tissue capillary and tissues. The gas transport in the blood and tissues is represented by empirical equations. The physiological parameters were described in function of physical activity. The model was validated by comparing its results with experimental data of controlled CO exposition. The agreement was excellent. CO concentration curves for critical days of São Caetano do Sul city (SP, Brazil) atmosphere were used as model input. The simulation results for some physical activities show that the more intense the activity, the larger the blood carboxyhemoglobin (COHb) level variations. The COHb level was compared with a CO quality air criteria, which showed to be adequate for low and moderate physical activity levels.

A short wetted-wall column was used to measure and correlate gas-phase mass transfer coefficients for various pure components evaporating counter current into an air stream. Mass transfer coefficients were also measured for binary mixtures. Both a smooth and a complex surface, similar to the surface of the structured packing Mellapak, were used in the study. The gas-phase mass transfer coefficients for the smooth surface were correlated with Sh g) 0.0044Re g Sc g 0.5 We l 0.111. The results for the complex surface were correlated with Sh g) 0.0036Re g 0.76 Sc g 0.5 Re l 0.41 Bo-0.13. Mass transfer coefficients for binary mixtures were compared with these gas-phase mass transfer coefficients. Enhanced mass transfer was observed for systems with large differences in pure-component surface tensions. This was not the case for binary systems with small differences in the pure-component surface tensions. Negligible liquidside resistance to mass transfer was found in all systems in this study. High-viscosity liquids deviated from the proposed correlations.

A recent hemodynamic model is extended and applied to simulate and explore the feasibility of detecting ocular dominance (OD) and orientation preference (OP) columns in primary visual cortex by means of functional magnetic resonance imaging (fMRI). The stimulation entails a short oriented bar stimulus being presented to one eye and mapped to cortical neurons with corresponding OD and OP selectivity. Activated neurons project via patchy connectivity to excite other neurons with similar OP in nearby visual fields located preferentially along the direction of stimulus orientation. The resulting blood oxygen level dependent (BOLD) response is estimated numerically via the model's spatiotemporal hemodynamic response function. The results are then used to explore the feasibility of detecting spatial OD-OP modulation, either directly measuring BOLD or by using Wiener deconvolution to filter the image and estimate the underlying neural activity. The effect of noise is also considered and it is estimated that direct detection can be robust for fMRI resolution of around 0.5 mm, whereas detection with Wiener deconvolution is possible at a broader range from 0.125 mm to 1 mm resolution. The detection of OD-OP features is strongly dependent on hemodynamic parameters, such as low velocity and high damping reduce response spreads and result in less blurring. The short-bar stimulus that gives the most detectable response is found to occur when neural projections are at 45 relative to the edge of local OD boundaries, which provides a constraint on the OD-OP architecture even when it is not fully resolved.

The use of inorganic composite membranes in chemical industries has received a lot of attention more recently due to a number of exceptional advantages including thermal stability and robustness. Inorganic membranes can selectively remove water from the reaction mixture during esterification reactions in order to enhance product formation. The characterisation of inorganic composite membranes used in this work including the determination of the pore diameter and specific surface area was performed using Liquid Nitrogen adsorption at 77 K. The membrane was modified once. The permeation test for the single gases including carbon dioxide (CO2), helium (He), nitrogen (N2) and argon (Ar) through the inorganic composite ceramic membrane was carried out at the gauge pressure range of 0.10 – 1.00 bar and at the temperature of 393 K. The order of the gas molecular weight was He < N2 < CO2 < Ar. The BET surface area of the dip-coated silica membrane showed a type IV isotherm characte...

The use of inorganic composite membranes in chemical industries has received a lot of attention more recently due to a number of exceptional advantages including thermal stability and robustness. Inorganic membranes can selectively remove water from the reaction mixture during esterification reactions in order to enhance product formation. The characterisation of inorganic composite membranes used in this work including the determination of the pore diameter and specific surface area was performed using Liquid Nitrogen adsorption at 77 K. The membrane was modified once. The permeation test for the single gases including carbon dioxide (CO2), helium (He), nitrogen (N2) and argon (Ar) through the inorganic composite ceramic membrane was carried out at the gauge pressure range of 0.10 – 1.00 bar and at the temperature of 393 K. The order of the gas molecular weight was He < N2 < CO2 < Ar. The BET surface area of the dip-coated silica membrane showed a type IV isotherm characte...

Several non-volcanic sources in central Italy emit a large amount of carbon dioxide (CO 2). Under stable atmospheric conditions and/or in presence of topographic depressions, the concentration of CO 2 , 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 CO 2 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 animal are reached.

The Rome region contains several sites where endogenous gas is brought to the surface through deep reaching faults, creating locally hazardous conditions for people and animals. Lavinio is a touristic borough of Anzio (Rome Capital Metropolitan City) that hosts a country club with a swimming pool and an adjacent basement balance tank. In early September 2011, the pool and the tank had been emptied for cleaning. On 5 September, four men descended into the tank and immediately lost consciousness. On 12 August 2012, after a long coma the first person died, the second one reported permanent damage to his central nervous system, and the other two men recovered completely. Detailed geochemical investigations show that the site is affected by a huge release of endogenous gas (CO 2 ≈ 96 vol.% and H 2 S ≈ 4 vol.%). High soil CO 2 and H 2 S flux values were measured near the pool (up to 898 and 7.155 g•m −2 •day −1 , respectively), and a high CO 2 concentration (23-25 vol.%) was found at 50-70 cm depth in the soil. We were able to demonstrate that gas had been transported into the balance tank from the swimming pool through two hubs connected to the lateral overflow channels of the pool. We show also that the time before the accident (60 hr), during which the balance tank had remained closed to external air, had been largely sufficient to reach indoor nearly lethal conditions (oxygen deficiency and high concentration of both CO 2 and H 2 S). Plain Language Summary Rome volcanic region contains several sites where deep gas consisting mostly of carbon dioxide (CO 2) with 1-6% of hydrogen sulfide (H 2 S) is brought to the surface by faults, locally creating hazardous conditions. Lavinio is a touristic borough of Anzio (Rome province) located near the Tyrrhenian Coast. It hosts a country club with a swimming pool and an adjacent basement balance tank. In early September 2011, four men descended into the tank to clean it and immediately lost consciousness. After a nearly 1-year coma, the first man died and the second one suffered permanent damage to his central nervous system. Immediately after the accident, we carried out detailed geochemical investigations aimed at ascertaining the accident causes. The results show that the accident occurred because of a nearly lethal gas concentration indoor the emptied balance tank. The gas had been transported into the tank through two hubs connected to the overflow channels of the pool, where we measured very high concentration of both CO 2 and H 2 S. Geoscientific evidence indicates that the pool has been excavated in a severe gas-risk prone area, and it can be easily inferred that excavation works created new additional ways allowing gas to escape to the surface.

La Fossa quiescent volcano and its surrounding area on the Island of Vulcano (Italy) are characterized by intensive, persistent degassing through both fumaroles and diffuse soil emissions. Periodic degassing crises occur, with marked increase in temperature and steam and gas output (mostly CO 2 ) from crater fumaroles and in CO 2 soil diffuse emission from the crater area as well as from the volcano flanks and base. The gas hazard of the most inhabited part of the island, Vulcano Porto, was investigated by simulating the CO 2 dispersion in the atmosphere under different wind conditions. The DISGAS (DISpersion of GAS) code, an Eulerian model based on advection-diffusion equations, was used together with the mass-consistent Diagnostic Wind Model. Numerical simulations were validated by measurements of air CO 2 concentration inside the village and along the crater's rim by means of a Soil CO 2 Automatic Station and a Tunable Diode Laser device. The results show that in the village of Vulcano Porto, the CO 2 air concentration is mostly due to local soil degassing, while the contribution from the crater gas emission is negligible at the breathing height for humans and always remains well below the lowest indoor CO 2 concentration threshold recommended by the health authorities (1000 ppm). Outdoor excess CO 2 maxima up to 200 ppm above local background CO 2 air concentration are estimated in the center of the village and up to 100 ppm in other zones. However, in some ground excavations or in basements the health code threshold can be exceeded. In the crater area, because of the combined effect of fumaroles and diffuse soil emissions, CO 2 air concentrations can reach 5000-7000 ppm in low-wind conditions and pose a health hazard for visitors.

The Colli Albani volcanic area is affected by huge degassing of likely magmatic or mantle origin, as suggested by the gas He isotopic composition. Gas rising from a buried calcareous aquifer generates several surface emissions and accumulates also in permeable layers at various depths, from 10 to 350 m, beneath impervious formations. When reached by wells, these pressurized gas pockets cause hazardous blowouts of CO 2 and H 2 S, often in inhabited zone. Remedy requires the restoration of the drilled cap by cement injections, whose effectiveness can be conveniently assessed by monitoring both CO 2 soil diffuse flux and CO 2 and H 2 S air concentration. kind occurred at Colli Albani in the last 20 years (Fig. 1) and some of them have been described by Carapezza & Tarchini (2007) and Barberi et al. (2007). Three new gas blowouts from wells occurred in 2006–2008, two of which very near to houses and the remedy required complex well cementing operations whose effectiveness was checked by...

Three pilot studies were performed to assess application of the eddy covariance micrometeorological method in the Ž. measurement of carbon dioxide CO flux of volcanic origin. The selected study area is one of high diffuse CO emission 2 2 on Mammoth Mountain, CA. Because terrain and source characteristics make this a complex setting for this type of measurement, added consideration was given to source area and upwind fetch. Footprint analysis suggests that the eddy Ž 3 2. covariance measurements were representative of an upwind elliptical source area 3.8 = 10 m which can vary with mean y2 y1 Ž y2 wind direction, surface roughness, and atmospheric stability. CO flux averaged 8-16 mg m s 0.7-1.4 kg m 2 y1. day. Eddy covariance measurements of flux were compared with surface chamber measurements made in separate studies

Three pilot studies were performed to assess application of the eddy covariance micrometeorological method in the Ž. measurement of carbon dioxide CO flux of volcanic origin. The selected study area is one of high diffuse CO emission 2 2 on Mammoth Mountain, CA. Because terrain and source characteristics make this a complex setting for this type of measurement, added consideration was given to source area and upwind fetch. Footprint analysis suggests that the eddy Ž 3 2. covariance measurements were representative of an upwind elliptical source area 3.8 = 10 m which can vary with mean y2 y1 Ž y2 wind direction, surface roughness, and atmospheric stability. CO flux averaged 8-16 mg m s 0.7-1.4 kg m 2 y1. day. Eddy covariance measurements of flux were compared with surface chamber measurements made in separate studies

The Rome region contains several sites where endogenous gas is brought to the surface through deep reaching faults, creating locally hazardous conditions for people and animals. Lavinio is a touristic borough of Anzio (Rome Capital Metropolitan City) that hosts a country club with a swimming pool and an adjacent basement balance tank. In early September 2011, the pool and the tank had been emptied for cleaning. On 5 September, four men descended into the tank and immediately lost consciousness. On 12 August 2012, after a long coma the first person died, the second one reported permanent damage to his central nervous system, and the other two men recovered completely. Detailed geochemical investigations show that the site is affected by a huge release of endogenous gas (CO 2 ≈ 96 vol.% and H 2 S ≈ 4 vol.%). High soil CO 2 and H 2 S flux values were measured near the pool (up to 898 and 7.155 g•m −2 •day −1 , respectively), and a high CO 2 concentration (23-25 vol.%) was found at 50-70 cm depth in the soil. We were able to demonstrate that gas had been transported into the balance tank from the swimming pool through two hubs connected to the lateral overflow channels of the pool. We show also that the time before the accident (60 hr), during which the balance tank had remained closed to external air, had been largely sufficient to reach indoor nearly lethal conditions (oxygen deficiency and high concentration of both CO 2 and H 2 S). Plain Language Summary Rome volcanic region contains several sites where deep gas consisting mostly of carbon dioxide (CO 2) with 1-6% of hydrogen sulfide (H 2 S) is brought to the surface by faults, locally creating hazardous conditions. Lavinio is a touristic borough of Anzio (Rome province) located near the Tyrrhenian Coast. It hosts a country club with a swimming pool and an adjacent basement balance tank. In early September 2011, four men descended into the tank to clean it and immediately lost consciousness. After a nearly 1-year coma, the first man died and the second one suffered permanent damage to his central nervous system. Immediately after the accident, we carried out detailed geochemical investigations aimed at ascertaining the accident causes. The results show that the accident occurred because of a nearly lethal gas concentration indoor the emptied balance tank. The gas had been transported into the tank through two hubs connected to the overflow channels of the pool, where we measured very high concentration of both CO 2 and H 2 S. Geoscientific evidence indicates that the pool has been excavated in a severe gas-risk prone area, and it can be easily inferred that excavation works created new additional ways allowing gas to escape to the surface.

The Rome region contains several sites where endogenous gas is brought to the surface through deep reaching faults, creating locally hazardous conditions for people and animals. Lavinio is a touristic borough of Anzio (Rome Capital Metropolitan City) that hosts a country club with a swimming pool and an adjacent basement balance tank. In early September 2011, the pool and the tank had been emptied for cleaning. On 5 September, four men descended into the tank and immediately lost consciousness. On 12 August 2012, after a long coma the first person died, the second one reported permanent damage to his central nervous system, and the other two men recovered completely. Detailed geochemical investigations show that the site is affected by a huge release of endogenous gas (CO 2 ≈ 96 vol.% and H 2 S ≈ 4 vol.%). High soil CO 2 and H 2 S flux values were measured near the pool (up to 898 and 7.155 g·m −2 ·day −1 , respectively), and a high CO 2 concentration (23-25 vol.%) was found at 50-70 cm depth in the soil. We were able to demonstrate that gas had been transported into the balance tank from the swimming pool through two hubs connected to the lateral overflow channels of the pool. We show also that the time before the accident (60 hr), during which the balance tank had remained closed to external air, had been largely sufficient to reach indoor nearly lethal conditions (oxygen deficiency and high concentration of both CO 2 and H 2 S). Plain Language Summary Rome volcanic region contains several sites where deep gas consisting mostly of carbon dioxide (CO 2) with 1-6% of hydrogen sulfide (H 2 S) is brought to the surface by faults, locally creating hazardous conditions. Lavinio is a touristic borough of Anzio (Rome province) located near the Tyrrhenian Coast. It hosts a country club with a swimming pool and an adjacent basement balance tank. In early September 2011, four men descended into the tank to clean it and immediately lost consciousness. After a nearly 1-year coma, the first man died and the second one suffered permanent damage to his central nervous system. Immediately after the accident, we carried out detailed geochemical investigations aimed at ascertaining the accident causes. The results show that the accident occurred because of a nearly lethal gas concentration indoor the emptied balance tank. The gas had been transported into the tank through two hubs connected to the overflow channels of the pool, where we measured very high concentration of both CO 2 and H 2 S. Geoscientific evidence indicates that the pool has been excavated in a severe gas-risk prone area, and it can be easily inferred that excavation works created new additional ways allowing gas to escape to the surface.

Atmospheric dispersal of a gas denser than air can threat the environment and surrounding communities if the terrain and meteorological conditions favour its accumulation in topographic depressions, thereby reaching toxic concentration levels. Numerical modelling of atmospheric gas dispersion constitutes a useful tool for gas hazard assessment studies, essential for planning risk mitigation actions. In complex terrains, microscale winds and local orographic features can have a strong influence on the gas cloud behaviour , potentially leading to inaccurate results if not captured by coarser-scale modelling. We introduce a methodology for microscale wind field characterisation based on transfer functions that couple a mesoscale numerical weather prediction model with a microscale computational fluid dynamics (CFD) model for the atmospheric boundary layer. The resulting time-dependent high-resolution microscale wind field is used as input for a shallow-layer gas dispersal model (TWODEE-2.1) to simulate the time evolution of CO 2 gas concentration at different heights above the terrain. The strategy is applied to review simulations of the 1986 Lake Nyos event in Cameroon, where a huge CO 2 cloud released by a limnic eruption spread downslopes from the lake, suffocating thousands of people and animals across the Nyos and adjacent secondary valleys. Besides several new features introduced in the new version of the gas dispersal code (TWODEE-2.1), we have also implemented a novel impact criterion based on the percentage of human fatalities depending on CO 2 concentration and exposure time. New model results are quantitatively validated using the reported percentage of fatalities at several locations. The comparison with previous simulations that assumed coarser-scale steady winds and topography illustrates the importance of high-resolution modelling in complex terrains.

In central Italy, nonvolcanic CO2 is discharged froin many areas of focused degassing (vents and associated strong diffuse emission) and from high-pCO2 groundwater. We estimate that there are at least 100 CO2 vents in central Italy, many of which have a history of lethality to animals and humans. The gas vents are extremely efficient pathways for transporting large amounts of deeply derived CO2 from gas reservoirs to the surface. As CO2 fluxes from these vents were heretofore unmeasured, several complementary inethods were developed to measure the CO2 flux from seven of these vents, which cumulatively discharge 3.1x109 mol yr -• CO2 (472 t d-l). Considering all of the vents in central Italy, the total CO2 flux froin vents alone may be similaroto • the CO2 emission from the Taupo Volcanic Zone in New Zealand (-10•ømol yr-•; -1200 t ) and other areas of high heat flow.

The present work aims to assess the hazard for human health related to CO 2 anomalous concentrations in air emitted from dry gas vents located in the NE area of Mt. Amiata volcano (Tuscany, central Italy). A geochemical multi-methodological approach is adopted to determine the composition and the flux rate of the gas discharges in order to establish (1) the origin of the gas vents and (2) the behaviour of the discharged gases in the areas surrounding the emission sites. The gas vents are hosted within subcircular morphological depressions (∅∼10-30 m), which likely originated by the collapse of cavities formed at shallow depth in the ground by dissolution of Triassic anhydrite formations and recent travertine deposits. CaCO 3 and CaSO 4 dissolution is mainly related to the underground circulation of CO 2 -rich fluids whose hydrological pattern is regulated by local and regional tectonics. The CO 2 -rich (up to 996,070 μmol/mol) gases tend to accumulate within the topographic lows, thus creating a sort of CO 2 ponds, and the knowledge of their evolution in time and space is important to evaluate the related hazard. Consequently, a conceptual model of CO 2 diffusion in air is developed to understand the dynamic of the CO 2 accumulation/dispersion process based on (1) a 24-h continuous measurement of the CO 2 flux from one of the main emission sites and (2) the recording of the main meteoric parameters, i.e. air temperature, wind direction and speed to check their influence. The results indicate that the threshold of CO 2 concentrations considered dangerous for the human health is frequently overcome. Moreover, when meteoric conditions, i.e. low wind and cloudy weather, did not allow a rapid dispersion of the gas phase emitted from the dry vents, CO 2 -rich clouds periodically overflowed the morphological depressions for several tens of meters without any significant mixing with air. On the basis of these considerations, the monitoring of the output rate from the main gas emissions, combined with the continuous control of the local meteorological parameters, may be considered an efficient procedure to mitigate the CO 2 hazard deriving from dry gas vents. An improvement of the protocol can be achieved in case of installations of CO 2 sensors located in the most sensitive areas and Water Air Soil Pollut: Focus (connected to a telemetry system able to transmit the data in real time to the closest Civil Defence centre. The CO 2 degassing sites can also represent a tourist attraction after the installation of suitable metallic fences and a proper campaign of information about these natural phenomena.

The code DISGAS (model for passive DISpersion of GASes) is a Eulerian model for passive dispersion
of diluted gas and fine dust particles. Turbulent diffusion is based on the K-theory and the wind field can be
evaluated assuming either a uniform wind profile based on the Similarity Theory or using a terrain-following
mass-consistent wind model. DISGAS can be used to forecast concentration of gas (or dust) over complex
terrains. The inputs to the model are topography, wind observations from meteorological stations, atmospheric
stability information, and gas flow rate from a discrete number of point sources. DISGAS is written in fortran
90. Here we describe the model and an application example.

Naples is a large city located between two active volcanic areas: Campi Flegrei to the W and Vesuvius to the SE. The Solfatara crater, inside the caldera of the Campi Flegrei and nearest to the western quarters of the city, is a prodigious source of natural CO 2 with a mean emission rate of 1067 ton/d, i.e. seven times higher than that of Vesuvius (151 ton/d). This study shows that the area around the Solfatara and part of the urban area of Naples are affected by the volcanic plume when atmospheric circulatory patterns are dominated by the locally frequent sea breezes. Under these conditions the CO 2 content in the air increases above normal values, reaching more than 1000 ppm in proximity to the Solfatara crater to a few tens of ppm several kilometres from the source. Although these values do not indicate a health risk even under the most unfavourable atmospheric conditions, the volcanic source contributes to the total CO 2 burden from all urban emissions and hence to overall air quality. An emission rate ten times higher than the present one would lead to an air CO 2 concentration in excess of recommended health protection thresholds.

An Eulerian model for passive gas dispersion based on the K-theory for turbulent diffusion, coupled with a mass
consistent wind model is presented. The procedure can be used to forecast gas concentration over large and complex
terrains. The input to the model includes the topography, wind measurements from meteorological stations,
atmospheric stability information and gas flow rate from the ground sources. Here, this model is applied to study
the distribution of the CO2 discharged from the hot sources of the Solfatara Volcano, Naples, Italy, where the input
data were measured during a 15 day campaign in June 2001 carried out to test an Eddy Covariance (EC) station
by Osservatorio Vesuviano-INGV, Naples.

The city of Naples is nearest to the Solfatara crater (Campi Flegrei caldera) that is a prodigious source of natural CO2 [1]. In this study, the CO2 plume dispersion is simulated using the DisGas code [2], under the most significant local-scale wind and hydrodynamic conditions of the atmosphere. Results showed that the western quarters of the city, as well as the inhabited area around the Solfatara, are mantled by the volcanic plume when atmospheric circulatory patterns are dominated by the common winds blowing from the sea. Under these conditions the CO2 content in the air increases above normal values, reaching more than one thousand ppm in proximity to the Solfatara crater to a few tens of ppm several kilometres from the source (Figure 1). Simulated values satisfactory agreed with CO2 concentrations measured by two stations inside the crater. A complete discussion of these results is presented elsewhere [3].

Naples is a large city located between two active volcanic areas: Campi Flegrei to the W and Vesuvius to the SE. The Solfatara crater, inside the caldera of the Campi Flegrei and nearest to the western quarters of the city, is a prodi-gious source of natural CO 2 with a mean emission rate of 1067 ton/d, i.e. seven times higher than that of Vesuvius (151 ton/d). This study shows that the area around the Solfatara and part of the urban area of Naples are affected by the volcanic plume when atmospheric circulatory patterns are dominated by the locally frequent sea breezes. Under these conditions the CO 2 content in the air increases above normal values, reaching more than 1000 ppm in proximity to the Solfatara crater to a few tens of ppm several kilometres from the source. Al-though these values do not indicate a health risk even under the most unfavourable atmospheric conditions, the volcanic source contributes to the total CO 2 burden from all urban emissions and hence to overall air...

In central Italy, nonvolcanic CO2 is discharged froin many areas of focused degassing (vents and associated strong diffuse emission) and from high-pCO2 groundwater. We estimate that there are at least 100 CO2 vents in central Italy, many of which have a history of lethality to animals and humans. The gas vents are extremely efficient pathways for transporting large amounts of deeply derived CO2 from gas reservoirs to the surface. As CO2 fluxes from these vents were heretofore unmeasured, several complementary inethods were developed to measure the CO2 flux from seven of these vents, which cumulatively discharge 3.1x109 mol yr -• CO2 (472 t d-l). Considering all of the vents in central Italy, the total CO2 flux froin vents alone may be similaroto • the CO2 emission from the Taupo Volcanic Zone in New Zealand (-10•ømol yr-•; -1200 t ) and other areas of high heat flow.

An Eulerian model for passive gas dispersion based on the K-theory for turbulent diffusion, coupled with a mass consistent wind model is presented. The procedure can be used to forecast gas concentration over large and complex terrains. The input to the model includes the topography, wind measurements from meteorological stations, atmospheric stability information and gas flow rate from the ground sources. Here, this model is applied to study the distribution of the CO2 discharged from the hot sources of the Solfatara Volcano, Naples, Italy, where the input data were measured during a 15 day campaign in June 2001 carried out to test an Eddy Covariance (EC) station by Osservatorio Vesuviano-INGV, Naples.