mercury emissions and stable isotopic compositions at vulcano island italy abstract sampling and analyses methods for determining the stable isotopic compositions of hg in an active volcanic system were tested and optimized at the volcanic complex of vulcano aeolian islands italy condensed gaseous fumarole hg fum t plume gaseous elemental hg g 0 and plume particulate hg p ii were obtained at fumaroles f0 f5 f11 and fa the average total hg emissions based on hgt so2 in condensed fumarolic gases and plumes range from 2 5 to 10 1 kg y 1 in agreement with published values ferrara r mazzolai b lanzillotta e nucaro e pirrone n 2000 volcanoes as emission sources of atmospheric mercury in the mediterranean basin sci total environ 259 1 3 115 121 aiuppa a bagnato e witt m l i mather t a parello f pyle d m martin r s 2007 real time simultaneous detection of volcanic hg and so2 at la fossa crater vulcano aeolian islands sicily geophys res lett 34 l21307 plume hg p ii increases with distance from the fumarole vent at the expense of hg g 0 and indicates significant in plume oxidation and condensation of fumarole hg fum t relative to the nist srm 3133 hg standard the stable isotopic compositions of hg are 202hg fum t 0 74 0 18 2sd n 4 for condensed gaseous fumarole hg fum t 202hg g 0 1 74 0 36 2sd n 1 for plume gaseous elemental hg g 0 at the f0 fumarole and 202hg p ii 0 11 0 18 2sd n 4 for plume particulate hg p ii the enrichment of hg p ii in the heavy isotopes and hg g 0 in the light isotopes relative to the total condensed fumarolic hg fum t gas complements the speciation data and demonstrates a gas particle fractionation occurring after the gas expulsion in ambient t atmosphere a first order rayleigh equilibrium condensation isotope fractionation model yields a fractionation factor cond gas of 1 00135 0 00058

near bed mass flux profiles in aeolian sand transport high resolution measurements in a wind tunnel vertical profiles of the streamwise mass flux of blown sand in the near bed 17 mm region are analysed from high resolution measurements made using an optical sensor in a wind tunnel this analysis is complemented by detailed measurements of mass flux and mean velocity profiles throughout the boundary layer depth 0 17 m using passive chambered sand traps of small dimensions and armoured thermal anemometers respectively the data permit a preliminary analysis of the relations between the observed forms of the profiles of near bed fluid stress and horizontal mass flux within a carefully conditioned boundary layer profiles of mass flux density are found to be characterized by three regions of differing gradient with transitions at about 2 mm and 19 mm above the bed the exponential decay of mass flux with height is confirmed for elevations above 19 mm and when plotted as a function of u 2 g a parameter of mean vertical trajectory height in saltation the gradient of mass flux in this region scales with the wake corrected friction velocity u where u 0 30 m s 1 a separate near bed region of more intense transport below 19 mm is identified which carries 80 per cent of the total mass flux this region is evident in some previous field and wind tunnel data but not in profiles simulated by numerical models ventilated passive sand traps underestimate mass flux in this region by 37 per cent at slow or moderate wind speeds a third significant region below 2 mm is observed these regions are likely to be related to grain populations in successive saltation low energy ejections and intermittent bed contact respectively optical measurements reveal locally high grain concentrations at some elevations below 5 mm these heights scale with transport rate mass flux gradient and wind speed copyright 1999 john wiley sons ltd

thermal areas on kilauea and mauna loa volcanoes hawaii abstract active thermal areas are concentrated in three areas on mauna loa and three areas on kilauea high temperature fumaroles 115 362 c on mauna loa are restricted to the summit caldera whereas high temperature fumaroles on kilauea are found in the upper east rift zone mauna ulu summit fumaroles 562 c middle east rift zone 1977 eruptive fissure fumaroles and in the summit caldera solfataric activity that has continued for several decades occurs along border faults of kilauea caldera and at sulphur cone on the southwest rift zone of mauna loa solfataras that are only a few years old occur along recently active eruptive fissures in the summit caldera and along the rift zones of kilauea steam vents and hot air cracks also occur at the edges of cooling lava ponds on the summits of lava shields along faults and graben fractures and in diffuse patches that may reflect shallow magmatic intrusions

water geochemistry and soil gas survey at ungaran geothermal field central java indonesia abstract a soil gas survey for radon rn thoron tn co 2 and mercury hg and the chemical analysis of hot spring waters were undertaken in the ungaran geothermal field central java indonesia the results of soil gas surveys indicate fault systems trending nne ssw and wnw ese particularly high co 2 concentrations 20 and high hg concentrations were detected in vicinity of the fumaroles emanometries of rn tn and co 2 also conclusively identified the presence of a fracture zone for the migration of geothermal fluid the hg results infer that the up flow zone of high temperature geothermal fluids maybe located in the north of fumaroles in the gedongsongo area near the collapse wall chemistry of thermal springs in the up flow zone are acid ph 4 and show a ca mg so 4 composition the thermal waters are mainly ca mg hco 3 and ca na so 4 hco 3 types near the fumarolic area and are mixed na ca cl hco 3 waters in the south east of gedongsongo the 18 o between 5 3 and 8 2 and between 39 and 52 indicate that the waters are essentially meteoric in origin a conceptual hydro geochemical model of the gedongsongo thermal waters based on the soil gas isotope and chemical analytical results was constructed

electromagnetic prospecting for groundwater in precambrian terrains in the republic of upper volta the autorite des amenegements des valees des voltas avv is establishing new rural settlements in the volta valleys first a survey of available water supplies is performed economic aquifers in precambrian terrains are deep 15 50 m and usually occur in fractured zones accompanying faults such zones can be identified on aerial photographs but their precise location on the ground is virtually impossible by visual means because of the small size of the aquifers a location error of 5 m can make the difference between a productive well and a dry hole traditionally resistivity profiling has been used as the means of locating the fractured zones in the field our studies suggest that the task can be performed faster cheaper and more accurately by vlf and em methods because of the limited choice of transmitting stations reccivable in upper volta the vlf method is not sufficiently sensitive to detect conductors with a strike between 45 and 105 the results obtained with a multifrequency horizontal loop em hlem system were satisfactory in all investigated areas during the 1980 field season 35 target areas were surveyed of the 24 holes drilled so far 23 are productive the weathered layer is a source of distinctive hlem anomalies which are characteristic of the underlying rocks therefore different interpretational procedures had to be developed for granitic and volcano sedimentary areas despite the high background level of in phase and quadrature components which varied with thickness and conductivity of the weathered layer aquifers could be detected at a depth greater than 30 m attempts were made to interpret the hlem results quantitatively using two models a three layer medium and a valley discontinuity the latter model is more realistic but more scale modelling will have to be performed to permit development of viable interpretational procedures meanwhile phasor diagrams based on drilling and resistivity sounding data can be used to estimate the aquifer depth

the status of research on the development and characteristics of mass flux density profiles above wind eroded sediments a literature review the mass flux density profile above wind eroded sediments mfdp plays an important role in defining the characteristics and impacts of wind sand flows and therefore has great theoretical and practical significance as a result it has been extensively studied from the perspectives of geography mechanics physics and engineering this paper reviews the research work that has been conducted since bagnold s pioneering efforts summarizes the research achievements discusses the problems that have not yet been solved and proposes future research directions this field of research has progressed from field observations to theoretical analyses and numerical simulations accompanied by increasing sophistication in the research and the research scope includes land with mobile sands wind eroded farmland gravel gobis and degraded grasslands many mathematical functions have been proposed to describe mfdp including exponential power modified exponential modified power and polynomial functions this variation results from differences in the study conditions and in the parameters included in a given model and on differences between wind tunnel experiments and field observations however there are the limitations of both wind tunnel experiments and theoretical derivations and the key parameters of the profile lack a clear physical meaning which limits the practical application of these functions future research must aim to solve these problems

first simultaneous mercury and major volatiles characterization of atmospheric hydrothermal emissions at the pisciarelli s fumarolic system campi flegrei italy abstract hydrothermal systems with active surface expressions are important natural source of atmospheric mercury here we report on the first simultaneous assessment of gaseous elemental mercury gem and major volatiles h2s and co2 fluxes from the fumarolic system of pisciarelli currently the most active at the campi flegrei caldera cfc naples italy this was achieved via a gps synchronized lumex and multigas survey which extends similar investigations reported elsewhere gem concentrations measured in the fumarolic emissions were consistently above background air level close to the degassing area mean 8 3 ng m 3 on average and ranged up to 12 000 ng m 3 our data evidenced pulsed sequences of gem increases in the fumarole plume closely matched by temporally consistent increases in co2 and h2s r2 0 9 supporting the idea that major volatiles such as co2 acts as potential carrier in transporting gem within the magmatic hydrothermal systems the slope of the best fit calculated for the dispersion of our data provides a gem co2 molar ratio of 1 1 10 8 and a gem h2s of 5 10 6 respectively these ratios are comparable to those reported for both low 100 c and high t 250 c fumaroles from non explosive volcanic hydrothermal degassing systems elsewhere we adopted an ad hoc method that combines video footages and gas measurements to obtain high precision concentration maps of gas emissions used to estimate the total atmospheric gem co2 and h2s flux of about 0 0113 225059 and 511 t y 1 respectively the human health risk assessment related to the gem emissions at pisciarelli confirms that except for the degassing fumarolic area all the main sites affected by the plume dispersion always remain well below the safe threshold recommended by the health authorities

mercury bearing black shales and human hg intake in eastern finland impact and mechanisms migration of hg from black shales to the aquatic ecosystems and local residents was studied comprehensively with samples of black shales 627 samples surface waters 22 organic stream sediments 40 organic lake sediments 172 noble crayfish 72 and human hair 225 the black shales exhibited elevated c s ni cu zn cd and hg concentrations gneiss granite mica schist and quartzite with very low heavy metal contents are encountered just next to the black shales offering good reference areas for comparison there are no local anthropogenic hg sources in the study areas black shale areas were reflected as elevated ni cu zn and cd and low ca in glacial till surface waters organic stream sediments and lake sediments mercury behaved differently in surface waters than the other heavy metals there was no correlation between the hg concentration of the surface waters and the hg concentration of the underlying bedrock median values for total hg and methyl hg in stream water were 1 6 and 0 2 ng l respectively in the black shale area and 2 0 and 0 3 ng l in the adjacent reference area with hg poor bedrock even though hg concentrations in surface waters were not elevated in the black shale areas relative to the reference areas mean hg concentrations of the muscle of noble crayfish astacus astacus were higher in black shale area lakes than in lakes in the reference areas the explanation of this correlation probably is not hg flux from the bedrock to watercourses as a more easily eroded rock than granites quartzites and mica schists black shale tends to occur in topographic depressions in glaciated terrain lakes in the black shale areas are typically surrounded by peatlands and the catchment areas from which they collect humic material rich in hg may be extensive the total hg concentrations in hair ranged from 0 04 to 12 1 g g the distribution of hair hg content did not appear to correlate with the distribution of black shales in the present study the main route of hg to humans was via fish even though hg contents were higher in crayfish and fish in the black shale area lakes people consumed fish not only from the lakes next to their residence but also from lakes situated in the reference areas among the non fish eaters in one black shale area the use of dug well water as well as the consumption of local potatoes and mushrooms slightly increased the hg in hair this contribution may reflect the heavy metal load of the natural black shale environment

changing mercury anomalies in long valley california indication for magma movement or seismic activity mercury anomalies in soils in geothermal areas form as a result of vapor transport comparison of the hg distribution of long valley measured in 1975 and again in 1982 indicates that a new hg anomaly formed in the inyo crater zone in the intervening period two models can explain this new anomaly 1 geothermal water has reached shallow levels as a result of increased permeability created by seismic activity or 2 addition of a co sub 2 rich magnetic vapor to the geothermal system at depth caused vapor exsolution in zones where it did not occur before if the hg anomaly in the inyo crater zone is related to the addition of magmatic vapors the site of the new anomaly may overlie young intruding magma 26 references 5 figures

a 14 500 year record of the accumulation of atmospheric mercury in peat volcanic signals anthropogenic influences and a correlation to bromine accumulation a 14 500 calendar year record of mercury accumulation rates has been obtained from an ombrotrophic peat bog in the swiss jura mountains the range of natural pre industrial mercury accumulation rates varied from 0 3 to 8 0 w gm 32 yr 31 during the late glacial and holocene climatic and volcanic signals were evident in the mercury record mercury accumulation rates increased by a factor of ca 5 during the younger dryas cold period short term spikes in mercury accumulation rates which correspond in time to known volcanic eruptions occur during the late boreal and older atlantic periods when volcanic influences on mercury deposition appear to have been intensified due to increased atmospheric humidity a correlation of mercury to bromine accumulation is observed throughout the preanthropogenic period during the holocene mercury accumulation only exceeded the range of this correlation for a few short periods of elevated mercury deposition which correspond to known volcanic eruptions during the older atlantic during historical times mercury accumulation rates have exceeded the range of the correlation of mercury to bromine continuously since ca 1330 ad this excess in mercury accumulation is interpreted as an indication of pollution during the industrial period mercury accumulation rates reached 107 6 w gm 32 yr 31 of which 84 was mercury that exceeded the correlation range mercury accumulation rates peaked again during the 1970s with 78 8 wg m 32 yr 31 early 20th century pollution appears to have been dominated by non swiss emissions from coal burning whereas swiss mercury emissions appear to have been the dominant pollution source during the mid and late 20th century current mercury accumulation rates at the site are similar to those ca 10 years ago with modern deposition rates being ca 15 times their prehistorical average anthropogenic emissions of reactive brominated compounds could be contributing to increased atmospheric deposition rates of mercury a 2002 elsevier science b v all rights reserved

summit outgassing as indicated by radon mercury and ph mapping kilauea volcano hawaii abstract surface geochemical mapping of rn hg and ph on the summit of kilauea volcano hawaii has shown some of the characteristics of outgassing rn concentrations measured in shallow ground gas are highest 10 to 155 units i e up to 0 016 nci l222rn over deep structures associated with the summit caldera low 1 to 5 units over the upper rift zones which are underlain by shallow intrusions and low to negative 1 to 3 units over most of the volcanically inactive peripheral areas high rn concentrations were measured over peripheral well developed structures such as the kaoiki and koae fault systems 45 and 12 units respectively the pattern of rn values broadly suggests the existence of a summit wide convection system interrupted locally by specific permeable structures the low ph 3 5 to 5 6 of soils over the caldera is suggested to be largely due to the sulfurous component of the ground gas the low concentrations of hg 5 to 80 ppb in these soils are postulated as being partly a function of subsurface complexing of hg with the abundant sulfur the shallow intrusions below the upper rift zones appear to have outgassed much of their sulfur content so soils in these areas are only slightly acid 5 6 to 6 2 allowing the accumulation of hg to concentrations of several thousands of ppb these conditions change during extrusive and intrusive events with the increases in shallow subsurface temperatures and volatiles in ground gas producing an increase in rn concentration and a decrease in soil hg due to volatilization after such events rn concentration decreases and soil hg increases significantly

elemental mercury at submarine hydrothermal vents in the bay of plenty taupo volcanic zone new zealand hot springs in active geothermal areas such as yellowstone national park the geysers geothermal field in california and the taupo volcanic zone in new zealand are notably enriched in the trace metals au ag as sb and hg such near surface hot springs have formed many of the world s important deposits of gold and silver and some of the largest deposits of mercury the majority of these are associated with continental geothermal systems in subaerial environments here we report the discovery of active mercury depositing hot springs in a submarine setting at nearly 200 m water depth within the offshore extension of the taupo volcanic zone of new zealand these vents contain the first documented occurrence of elemental mercury on the sea floor and provide an important link between offshore hydrothermal activity and mercury depositing geothermal systems on land the discovery has implications for mercury transport in sea floor hydrothermal systems and underscores the importance of submarine volcanic and geothermal activity as a source of mercury in the oceans

influence of sieving time on the efficiency and accuracy of grain size analysis of beach and dune sands grain size is a fundamental property of sediments and is commonly used to describe sedimentary facies and classify sedimentary environments among the various conventional techniques utilized to determine grain size frequency distributions sieving is the most widely applied procedure the accuracy of such analyses is among other factors strongly dependent on the sieving time however despite a substantial amount of research in this field optimal sieving times for different types of sediments have to date not been established in this article the influence of sieving time on grain size analyses of medium grained microtidal and mesotidal beach and dune sands has been determined to assess the precision of important textural parameters such as median grain size sorting skewness and kurtosis an error analysis was carried out for different sieving times 2 5 10 15 and 20 minutes after calibrating the analytical and sampling methodologies significant deviations were registered when sieving time was less than 10 minutes however such deviations were very small and grain size distributions remained almost identical for sieving times of 10 minutes and longer relative errors being as low as 0 in some cases

an airborne tensor vlf system from concept to realization1 radio signals from very low frequency vlf transmitters distributed world wide have been used for several decades to study the lateral variations of the electrical conductivity in the upper few hundred metres of the earth s crust traditionally in airborne applications the total magnetic fields from one or two transmitters are measured to form the basis for construction of maps that primarily show those conductive structures that are parallel or subparallel to the direction to the transmitters the tensor vlf technique described in this paper makes use of all signals available in a predefined frequency band to construct transfer functions relating the vertical magnetic field and the two horizontal magnetic field components these transfer functions are uniquely determined for a particular measuring site and contain information about the lateral conductivity variations in all directions first experiences with real field data acquired during a test survey in sweden show that maps of the so called peaker the spatial divergence of the transfer functions give an image of the conducting structures most of the structures can be correlated to small valleys filled with conducting sediments or valleys underlain by conductive fracture zones in the crystalline rocks

first combined flux chamber survey of mercury and co2 emissions from soil diffuse degassing at solfatara of pozzuoli crater campi flegrei italy mapping and quantification of gas release abstract there have been limited studies to date targeting gaseous elemental mercury gem flux from soil emission in enriched volcanic substrates and its relation with co 2 release and tectonic structures in order to evaluate and understand the processes of soil air exchanges involved at solfatara of pozzuoli volcano the most active zone of campi flegrei caldera italy an intensive field measurement survey has been achieved in september 2013 by using high time resolution techniques soil air exchange fluxes of gem and co 2 have been measured simultaneously at 116 points widely distributed within the crater quantification of gas flux has been assessed by using field accumulation chamber method in conjunction with a lumex ra 915 portable mercury vapor analyzer and a licor for co 2 determination respectively the spatial distribution of gem and co 2 emissions correlated quite closely with the hydrothermal and geological features of the studied area the highest gem fluxes from 4 04 to 5 9 10 5 g m 2 d 1 were encountered close to the southern part of the crater interested by an intense fumarolic activity and along the se sw tectonic fracture 1 26 10 6 6 91 10 5 g gem m 2 d 1 conversely the lowest values have been detected all along the western rim of the crater characterized by a weak gas flux and a lush vegetation on a very sealed clay soil which likely inhibited mercury emission range 1 5 10 7 7 18 10 6 g gem m 2 d 1 results indicate that the gem exchange between soil and air inside the solfatara crater is about 2 3 orders of magnitude stronger than that in the background areas 10 8 10 7 g m 2 d 1 co 2 soil diffuse degassing exhibited an analogous spatial pattern to the gem fluxes with emission rates ranging from about 15 to 20 000 g co 2 m 2 d 1 from the outermost western zones to the south eastern sector of the crater the observed significant correlation between gem and co 2 suggested that in volcanic system gem volatilizes from substrate in a similar manner to the release of co 2 the quantitative estimation of the total amount of co 2 and gem released from the solfatara crater gave values of about 304 13 and 3 7 0 2 10 6 t d 1 respectively finally based on our dataset and previous work we propose that an average gem co 2 molar ratio of 2 10 8 n 9 is best representative of hydrothermal degassing taking into account the uncertainty in global hydrothermal co 2 emissions from sub aerial environments 10 12 mol yr 1 we infer a global volcanic gem flux from hydrothermal environments of about 8 5 t yr 1 although this value has to be considered as a lower limit for the global emission of gem from these sources we suggest that on a local scale hydrothermal activity can be regarded as a significant source of gem than previously recognized to the atmospheric pool

mercury concentration speciation and budget in volcanic aquifers italy and guadeloupe lesser antilles abstract quantifying the contribution of volcanism to global mercury hg emissions is important to understand the pathways and the mechanisms of hg cycling through the earth s geochemical reservoirs and to assess its environmental impacts while previous studies have suggested that degassing volcanoes might contribute importantly to the atmospheric budget of mercury little is known about the amount and behaviour of hg in volcanic aquifers here we report on detailed investigations of both the content and the speciation of mercury in aquifers of active volcanoes in italy and guadeloupe island lesser antilles in the studied groundwaters total hg thg concentrations range from 10 to 500 ng l and are lower than the 1000 ng l threshold value for human health protection fixed by the world health organization who 1993 who guidelines for drinking water quality http www who int water sanitation health gdwq index htlm positive co variations of thg with sulphate indicate that hg so4 rich acid groundwaters receive a direct input of magmatic hydrothermal gases carrying mercury as hg0 gas increasing thg in a volcanic aquifer could thus be a sensitive tracer of magmatic gas input prior to an eruption since the complex behaviour and toxicity of mercury in waters depend on its chemical speciation we carefully determined the different aqueous forms of this element in our samples we find that dissolved elemental hg0 aq and particulate bound hg hgp widely prevail in volcanic aquifers in proportions that highlight the efficiency of hg adsorption onto colloidal particles moreover we observe that dissolved hg0aq and hg ii forms coexist in comparable amount in most of the waters in stark contrast to the results of thermodynamic equilibrium modelling therefore chemical equilibrium between dissolved mercury species in volcanic waters is either prevented by natural kinetic effects or not preserved in collected waters due to sampling storage artefacts finally we provide a first quantitative comparison of the relative intensity of aqueous transport and atmospheric emissions of mercury at mount etna a very active basaltic volcano

equations for the near surface mass flux density profile of wind blown sediments the erosion of sediment by wind and the resulting mass flux density profile is thought to be described by a mathematical function that bears information on the mechanisms responsible for the movement of individual particles by the wind and such functions have been studied extensively in this study several functions are evaluated that have been proposed to describe the variation in mass flux density with height of wind blown sediment with the flux containing a mixture of particles in suspension and saltation based on detailed field data at four land types in the minqin area of north western china where severe wind erosion occurs high resolution mass flux density measurements at 50 heights collected at 20 mm intervals to a height of 1 m above the surface were obtained using vertically segmented samplers three kinds of functions fit the measured flux density profiles reasonably well but a three parameter modified exponential function is preferred because it contains fewer coefficients to be defined and provides a reasonably good fit to the measured mass flux density profiles this and previous conclusions suggest that the decay with height of mass flux density of sediments dominated by saltation particles as in the present study tends to follow a modified exponential function law but a modified power function law replaces the modified exponential function law when the height extends to a level high enough to be dominated by suspension particles copyright 2011 john wiley sons ltd

mercury as a proxy for volcanic activity during extreme environmental turnover the cretaceous paleogene transition abstract the usually low geological background concentrations of hg makes this trace element suitable for identifying accumulation pulses in sediments that can be tentatively related to weathering processes and thus to climatic changes intense volcanism has witnessed the cretaceous paleogene transition ktb and was perhaps responsible for dramatic climatic changes and decrease in biodiversity and mass extinction we have used hg concentrations as a proxy for volcanic activity and atmospheric hg and co2 buildup across the ktb at three localities in the salta basin argentina hg contents display several spikes across the ktb with a maximum value of 250 ng g 1 in three drill cores across the ktb in the paraiba basin northeastern brazil hg contents increase from the late maastrichtian to early danian and hg spikes predate the ktb perhaps as a record of volcanic activity before but very close to this transition at stevns klint denmark hg contents reached almost 250 ng g 1 within a 5 cm thick clay layer the fiskeler member fish clay that comprises the ktb some co variation between hg and al2o3 contents has been observed in all of the studied sections across the ktb suggesting that hg is probably adsorbed onto clays thermo desorption experiments in selected samples from the yacoraite formation showed hg 2 as the major species present which is in agreement with a volcanic origin combined hg and c isotope chemostratigraphy may become a powerful tool for the eventual assessment of the role of volcanic activity during extreme climatic and biotic events such as those during the ktb

real time simultaneous detection of volcanic hg and so2 at la fossa crater vulcano aeolian islands sicily 1 measuring hg so2 ratios in volcanic emissions is essential for better apportioning the volcanic contribution to the global hg atmospheric cycle here we report the first real time simultaneous measurement of hg and so2 in a volcanic plume based on lumex and multigas techniques respectively we demonstrate that the use of these novel techniques allows the measurements of hg so2 ratios with a far better time resolution than possible with more conventional methods the hg so2 ratio in the plume of f0 fumarole on la fossa crater vulcano island spanned an order of magnitude over a 30 minute monitoring period but was on average in qualitative agreement with the hg so2 ratio directly measured in the fumarole mean plume and fumarole ratios being 1 09 10 6 and 2 9 10 6 respectively the factor 2 difference between plume and fumarole compositions provides evidence for fast hg chemical processing the plume

saltating particles over flat beds measurements of ejection and impact velocities trajectory lengths and maximum rise heights of sand grains median diameters 118 and 188 m in saltation over a flat sand bed in a wind tunnel have been obtained from the digitization of multiple image photo graphs the mean angle of ejection is found to be about 30 o from the horizontal rather than 90 o with mean vertical ejection velocity of about 2u where u is the friction velocity trajectories of saltating grains have been computed using the measurements of the initial ejection velocities and the mean velocity profile of the air flow

mercury isotopic composition of hydrothermal systems in the yellowstone plateau volcanic field and guaymas basin sea floor rift abstract to characterize mercury hg isotopes and isotopic fractionation in hydrothermal systems we analyzed fluid and precipitate samples from hot springs in the yellowstone plateau volcanic field and vent chimney samples from the guaymas basin sea floor rift these samples provide an initial indication of the variability in hg isotopic composition among marine and continental hydrothermal systems that are controlled predominantly by mantle derived magmas fluid samples from ojo caliente hot spring in yellowstone range in 202hg from 1 02 to 0 58 0 11 2sd and solid precipitate samples from guaymas basin range in 202hg from 0 37 to 0 01 0 14 2sd fluid samples from ojo caliente display mass dependent fractionation mdf of hg from the vent 202hg 0 10 0 11 2sd to the end of the outflow channel 202hg 0 58 0 11 2sd in conjunction with a decrease in hg concentration from 46 6 pg g to 20 0 pg g although a small amount of hg is lost from the fluids due to co precipitation with siliceous sinter we infer that the majority of the observed mdf and hg loss from waters in ojo caliente is due to volatilization of hg0 aq to hg0 g and the preferential loss of hg with a lower 202hg value to the atmosphere a small amount of mass independent fractionation mif was observed in all samples from ojo caliente 199hg 0 13 1 0 06 2sd but no significant mif was measured in the sea floor rift samples from guaymas basin this study demonstrates that several different hydrothermal processes fractionate hg isotopes and that hg isotopes may be used to better understand these processes

the effect of wind speed and bed slope on sand transport this paper reports on a wind tunnel study of the effects of bed slope and wind speed on aeolian mass transport the use of a sloping wind tunnel has enabled estimation of the friction angle to be about 40 for saltating particles in the range 170 540 m a formula relating dimensionless mass transport to friction speed and bed slope is proposed and mass transport data for five uniform sand samples and one non uniform sand sample are shown to fit the equation well in particular the relationship reveals an overshoot in mass transport slightly above threshold collisions a feature also evident when previous experimental data is re examined as the number of mid air collisions between the saltating particles increases greatly with wind speed the overshoot may occur as a result of increasing energy losses resulting from the collisions finally it is demonstrated that data for saltating snow shows a similar overshoot in the dimensionless transport rate

fumarole compositions and mercury emissions from the tatun volcanic field taiwan results from multi component gas analyser portable mercury spectrometer and direct sampling techniques gas emissions from tatun volcanic group northern taiwan were studied for the first time using a multi component gas analyser system multi gas in combination with giggenbach flask methods at fumaroles and mud pools at da you keng dyk and geng tze ping gzp co 2 s molar ratios observed at dyk ranged from 3 17 similar ratios were observed using a multi gas sensor box of 8 16 so 2 at gzp was low higher concentrations were observed at dyk where so 2 h 2 s ratios were close to 1 for both methods a lower co 2 h 2 s ratio was measured via giggenbach flask sampling 7 2 than was found in the plume using the gas sensor at gzp 9 2 this may reflect rapid oxidation of h 2 s as it mixes with background air gaseous elemental mercury gem levels were observed in the fumarole gases using a portable mercury spectrometer these are the first such measurements of mercury at tatun mean gem concentrations in the fumarole plumes were 20 ng m 3 with much higher concentrations observed close to the ground mean gem 130 and 290 ng m 3 at dyk and gzp respectively the gem in the fumarole plume was elevated above concentrations in industrial urban air in northern taiwan and the increase in gem observed when the instrument was lowered suggests high levels of mercury are present in the surrounding ground surface the gem co 2 10 8 and gem s 10 6 ratios observed in the fumarole gases were comparable to those observed at other low temperature fumaroles combining the hg co 2 ratio with a previous co 2 flux value for the area the annual gem flux from the tatun field is estimated as 5 50 kg year 2008 elsevier b v all rights reserved

erosion profiles due to particles entrained by wind application of an eolian sediment transport model erosion by impacts of particles entrained in the wind scales with the kinetic energy of impacting grains a recent model of eolian sediment transport permits calculation of expected erosion patterns in objects of simple geometry the modeling of vertical erosion profiles in turn provides an exacting test of the transport model realistic distributions of liftoff velocities for saltating grains give rise to kinetic energy flux profiles characterized by a strong maximum as much as 1 4 m above the bed during strong winds kinetic energy flux due to suspended grains also peaks above the bed the height and strength of the maxima depend very strongly on the grain size distribution as grain size diminishes increased particle deflection by the air flow around an obstacle reduces delivery of kinetic energy to the surface for both saltating and suspended grains kinetic energy flux scales with the fifth power of the wind shear velocity erosion profiles in man made obstacles are well modeled with only slight modification of the saltation model to account for the relatively high elasticity of actual deflationary surfaces lending considerable support for the model the modeling also elucidates several aspects of ventifaction as small ventifacts 1 2 m in diameter and the lower portions of larger ones are predominantly eroded by saltating grains upwind surface irregularities are quickly damped leading to facets that dip upwind and sharply truncate lee surfaces sandblasting by suspended grains dominates along the upper portions of large ventifacts where grain paths are partially deflected by the obstacle and may lead to radially symmetrical flutes and grooves

estimations of mercury fluxes emitted by mount etna volcano a sampling and measuring device which enables the assessment of atmospheric particulate and gaseous mercury concentrations has been tested on mount etna volcano particulate matter is collected on a whatman gf c of 1 0 m pore size gaseous mercury species on a au column the analysis is carried out in two steps 1 the mercury species collected on the filter or the au column are transferred to a fixed analytical au column 2 mercury liberated from this column during the second step is detected with a mercury vapour monitor average concentrations of gaseous and particulate mercury in ambient sampling sites on mount etna are 3 8 ng m 3 and 0 49 ng m 3 respectively average concentrations of gaseous and particulate mercury in the plume of bocca nuova on mount etna are 15 ng m 3 and 24 ng m 3 respectively an estimation of the total mercury discharge from mount etna amounts to 2 5 10 2 tons day 1

atmospheric mercury emissions from substrates and fumaroles associated with three hydrothermal systems in the western united states 1 this paper quantifies atmospheric mercury hg emissions from substrates and fumaroles associated with three hydrothermal systems lassen volcanic center california lvc yellowstone caldera wyoming yc and dixie valley nevada dv substrate hg fluxes were measured using field chamber methods at thermal and nonthermal sites the highest hg fluxes up to 541 ng m 2 h 1 were measured at thermal active areas fluxes from altered and unaltered nonthermal sites were 98 at yc substrate hg emissions were dominated 50 to 90 by acidically altered thermal areas substrate emissions at dv were low and primarily from nonthermal areas 66 to 75 fumarole emissions at lvc 91 146 kg yr 1 and yc 0 18 1 6 kg yr 1 for mud volcano were estimated by applying hg h2o and hg co2 ratios in hydrothermal gas samples to h2o and co2 emissions applying total area average emissions from substrates and thermal features at lvc yc and dv to similar systems across the conterminous united states yearly atmospheric hg emissions from active hydrothermal systems are projected to be 1 3 2 1 mg

collateral variations between the concentrations of mercury and other water soluble ions in volcanic ash samples and volcanic activity during the 2014 2016 eruptive episodes at aso volcano japan abstract during 2014 2016 the aso volcano located in the center of the kyushu islands japan erupted and emitted large amounts of volcanic gases and ash two episodes of the eruption were observed firstly strombolian magmatic eruptive episodes from 25 november 2014 to the middle of may 2015 and secondly phreatomagmatic and phreatic eruptive episodes from september 2015 to february 2016 bulk chemical analyses on total mercury hg and major ions in water soluble fraction in volcanic ash fall samples were conducted during the strombolian magmatic eruptive episodes total hg concentrations averaged 1 69 0 87 ng g 1 n 33 with a range from 0 47 to 3 8 ng g 1 in addition the temporal variation of total hg concentrations in volcanic ash varied with the amplitude change of seismic signals in the aso volcano the volcanic tremors are always observed during eruptive stages and quiet interludes and the amplitudes of tremors increase at eruptive stages so the temporal variation of total hg concentrations could provide an indication of the level of volcanic activity during the phreatomagmatic and phreatic eruptive episodes on the other hand total hg concentrations in the volcanic ash fall samples averaged 220 88 ng g 1 n 5 corresponding to 100 times higher than those during the strombolian eruptive episode therefore it is possible that total hg concentrations in volcanic ash samples are largely varied depending on the eruptive type in addition the ash fall amounts were also largely different among the two eruptive episodes this can be also one of the factors controlling hg concentrations in volcanic ash

mercury gas emissions from la soufriere volcano guadeloupe island lesser antilles abstract quantifying mercury hg emissions from active volcanoes is of particular interest for better constraining the global cycle and environmental impact of this highly toxic element here we report on the abundance of total gaseous tgm hg 0 g hg ii g and particulate hg p mercury in the summit gas emissions of la soufriere andesitic volcano guadeloupe island lesser antilles where enhanced degassing of mixed hydrothermal magmatic volatiles has been occurring since 1992 from the southern summit crater we demonstrate that hg in volcanic plume occurs predominantly as gaseous mercury with a mean tgm hg p mass ratio of 63 combining the mean tgm h 2 s mass ratio of the volcanic plume 3 2 10 6 measured close to the source vent with the h 2 s plume flux 0 7 t d 1 determined simultaneously allows us to estimate a gaseous mercury emission rate of 0 8 kg yr 1 from la soufriere summit dome somewhat lower tgm s tot mass ratio in fumarolic gases from the source vent 4 4 10 7 suggests that plume chemical composition is not well represented by the emission source fumaroles due to chemical processes prior to or upon discharge current mercury emission from la soufriere volcano represents a very small contribution to the estimated global volcanic budget for this element

modeling and inversion of magnetic and vlf em data with an application to basement fractures a case study from raigarh india we present modeling of magnetic and very low frequency electromagnetic vlf em data to map the spatial distribution of basement fractures where uranium is reported in sambalpur granitoids in the raigarh district chhattisgarh india radioactivity in the basement fractures is attributed to brannerite u ti fe complex and uranium adsorbed on ferruginous matter the amplitude of the 3d analytical signal of the observed magnetic data indicates the trend of fracture zones further the application of euler 3d deconvolution to magnetic data provides the spatial locations and depth of the source fraser filtered vlf em data and current density pseudosections indicate the presence of shallow and deep conductive zones along the fractures modeling of vlf em data yields the subsurface resistivity distribution of the order of less than 100 ohm m of the fractures the interpreted results of both magnetic and vlf em data agree well with the geologic section obtained from drilling

field evaluation of some sand transport models fluorescent tracer procedures originally developed for research on fluvial sediment movement were used to monitor the movement of three commercially purchased sands in a natural dune environment results were compared with estimates of transport rates from three theoretical models estimates from models by bagnold 1941 and hsu 1971 were larger by as much as one order of magnitude than the rates observed in the tracer study the model of a a kadib 1965 provided closer correspondence to observed transport rates for medium sand mean diam 0 653 mm but underestimated rates for coarse sand mean diam 0 992 mm

rapid oxidation of mercury hg at volcanic vents insights from high temperature thermodynamic models of mt etna s emissions a major uncertainty regarding the environmental impacts of volcanic hg is the extent to which hg is deposited locally or transported globally an important control on dispersion and deposition is the oxidation state of hg compounds hg 0 is an inert insoluble gas while hg ii occurs as reactive gases or in particles which deposit rapidly and proximally near the volcanic vent using a new high temperature thermodynamic model we show that although hg in etna s magmatic gases is almost entirely hg 0 i e gaseous elemental mercury significant quantities of hg ii are likely formed at etna s vents as gaseous hgcl2 when magmatic gases are cooled and oxidised by atmospheric gases these results contrast with an earlier model study and allow us to explain recent measurements of hg speciation at the crater rim of etna without invoking rapid 1 min low temperature oxidation processes we further model hg speciation for a series of additional magmatic gas compositions compared to etna hg ii production i e hg ii hgtot is enhanced in more hcl rich magmatic gases but is independent of the hg hbr and hi content of the magmatic gases hg ii production is not strongly influenced by the initial oxidation state of magmatic gases above nno although production is hindered in more reduced magmatic gases the model and results are widely applicable to other open vent volcanoes and may be used to improve the accuracy of chemical kinetic models for low temperature hg speciation in volcanic plumes

mercury content and speciation in the phlegrean fields volcanic complex evidence from hydrothermal system and fumaroles abstract mercury is outstanding among the global environmental pollutants of continuing concern although degassing of active volcanic areas represents an important natural source of mercury into the atmosphere still little is known about the amount and behaviour of hg in volcanic aquifers especially regarding its chemical speciation in order to assess the importance of mercury emissions from active volcanoes thermal waters were sampled in the area surrounding la solfatara pozzuoli bay this is the most active zone of the phlegrean fields complex coastal area north west of naples with intense hydrothermal activity at present day studied groundwaters show total hg thg concentrations range from 56 to 171 ng l and are lower than the 1000 ng l threshold value for human health protection fixed by the world health organization who 1993 we also carefully discriminated the different aqueous species of hg in the collected water samples besides original data on hg determination in gaseous manifestations at la solfatara crater are also reported we measured volcanogenic mercury concentration and hg s tot ratio both in the volcanic plume and in fumarolic condensates in order to better constrain hg reactivity once emitted into the atmosphere data on hg s tot reveal that there is no significant difference between hg volcanic composition at the venting source fumaroles and in near vent diluted volcanic plumes 1 6 10 5 and 1 9 10 5 respectively suggesting that there is limited hg chemical processing in volcanic fumarole plumes at least on the timescales of a few seconds investigated here combining the mean fumaroles hg co 2 mass ratio of about 1 3 10 8 molar ratio 2 1 10 9 with the hydrothermal soil diffuse co 2 degassing of the area the annual hg flux from la solfatara is estimated as 7 kg y 1 0 007 t y 1 current mercury emission from la solfatara volcano represents a very small contribution to the estimated global volcanic budget for this element and the estimated hg flux is considerably lower than that estimated from open conduit active basaltic volcanoes

global mercury flux from volcanic and geothermal sources abstract the global hg flux from natural sources is poorly known we present data on hg levels in volcanic fumaroles that in combination with sulfur analyses and published so 2 flux data lead to new global hg flux estimates the volcanogenic hg flux from passively degassing volcanoes is small 30 mg hg yr the flux from erupting volcanoes is much larger but less well constrained we estimate it at about 800 mg yr these data are interpreted as evidence for early hg degassing from magmas geothermal sources contribute roughly 60 mg yr hg to the atmosphere an estimate based on average hg contents of hot springs and global convective heat transport total natural hg emissions from land amount to 1290 mg yr including a revised soil vapor flux of 400 mg yr estimates of anthropogenic contributions to the atmospheric hg budget vary between 3000 and 11 500 mg yr and are substantial compared to our natural hg flux estimate

bioindication of volcanic mercury hg deposition around mt etna sicily mt etna is a major natural source of hg to the mediterranean region total mercury concentrations hg tot in castanea sativa sweet chestnut leaves sampled 7 13 km from etna s vents during six campaigns in 2005 2011 were determined using atomic absorption spectroscopy hg tot in c sativa was greatest on etna s se flank reflecting hg deposition from the typically overhead volcanic plume hg tot also showed hg accumulation over the growing season increasing with leaf age and recent eruptive activity hg tot in c sativa was not controlled by hg tot in soils which instead was greatest on etna s nw flank and was correlated with the proportion of organic matter in the soil org an elevated hg tot org ratio in soils on etna s se flank is indicative of increased hg deposition this ratio was also found to decrease with local soil ph suggesting that hg deposited to the low ph and organic poor soils on etna s se flank may not be retained but will instead be released to groundwater or re emitted to the atmosphere these results show that the deposition of volcanic hg

aeolian sand transport above three desert surfaces in northern china with different characteristics shifting sand straw checkerboard and gravel field observations aeolian sand transport results from interactions between the wind and the ground surface and is a key link between microscale mechanisms responsible for the movement of individual grains of sand and macroscopic mechanisms that govern the flow of windblown sand as a result many studies have been performed to study aeolian transport but a few studies have simultaneously compared the effects of the surface characteristics on aeolian transport in the same region in this study we designed three experimental areas to provide a comparison of the transport rates under different types of boundary layer conditions shifting sand straw checkerboard and gravel with different sediment availability but under the same wind regime the study was conducted at the shapotou aeolian experiment site chinese academy of sciences where we studied the sand transport rate and mass flux density profiles using synchronous experimental data the surface characteristics dramatically affected aeolian transport the mass flux density profile above the open shifting sand surface and straw checkerboard reached its maximum value near the surface and followed an exponential decay function for the gravel surface the maximum transport occurred at a certain height above the ground but above that height followed an exponential decay curve the transport rate was greatest above the open shifting sand reaching up to 465 times the rate above the straw checkerboard with intermediate values above the gravel surface the average saltation height was highest above the gravel covered surface and lowest above the straw checkerboard surface

a steady state model of wind blown sand transport a model for steady state eolian saltation is presented in which computation of sand grain trajectories in the wind and of the wind velocity profile modified by saltating grain drag forces is combined with experimental data on grain bed collisions in an iterative simulation scheme which resembles the time development of natural saltation qualitative features of eolian saltation are reproduced in the simulations including a height in the saltating layer at which the wind velocity remains roughly constant with changing free stream friction velocity and an approximate separation of the saltating population into successively hopping grains and reptating or creeping grains the numerical solutions give rise to more general arguments in support of the conclusions that fluid entrainment of grains is unimportant in steady state saltation that the mass flux profile obeys roughly an inverse power law dependence on height and that the vertically integrated mass flux dependence on the free stream friction velocity

fast imaging of subsurface conductors using very low frequency electromagnetic data the study presents a fast imaging technique for the very low frequency data interpretation first an analytical expression was derived to compute the vertical component of the magnetic field at any point on the earth s surface for a given current density distribution in a rectangular block on the subsurface current density is considered as exponentially decreasing with depth according to the skin depth rule in a particular block subsequently the vertical component of the magnetic field due to the entire subsurface was computed as the sum of the vertical component of the magnetic field due to an individual block since the vertical component of the magnetic field is proportional to the real part of very low frequency anomaly an inversion program was developed for imaging of the subsurface conductors using the real very low frequency anomaly in terms of apparent current density distribution in the subsurface imaging results from the presented formulation were compared with other imaging techniques in terms of apparent current density and resistivity distribution using a standard numerical forward modelling and inversion technique efficacy of the developed approach was demonstrated for the interpretation of synthetic and field very low frequency data the presented imaging technique shows improvement with respect to the filtering approaches in depicting subsurface conductors further results obtained using the presented approach are closer to the results of rigorous resistivity inversion since the presented approach uses only the real anomaly which is not sensitive to very small isolated near surface conducting features it depicts prominent conducting features in the subsurface

distribution of mercury in sediments from kagoshima bay japan and its relationship with physical and chemical factors kagoshima bay is located on the south coast of kyushu island japan submarine fumaroles present in the northern area have been identified as a natural source of mercury in the bay the aim of the present work is to study the spatial distribution of mercury in the bottom sediments of the bay and its relationship with major physicochemical properties that might affect the transport of mercury in the ecosystem surrounding this area sediment core samples were collected in the north and central areas in surveys performed during 2011 and 2013 the individual core samples were sliced and processed for the analysis of total mercury t hg chemical composition total organic carbon toc particle size and magnetic susceptibility the horizontal distribution of t hg indicates that fumaroles are the primary source of hg in the area the results indicate a key role of organic matter binding to hg in the area to the west of the fumaroles the relationship between hg and toc is characterized by two linear trends that correspond to the upper and lower sections of the cores from the physicochemical properties it was suggested that the two distinct linear relations might be caused by a change of the volcanic activity at the aira caldera which is located at the northern part of the bay the extent of the bay impacted by the hg generated from the hydrothermal vents has decreased in recent years and is limited to the vicinity of the emission point

effect of source width and tidal elevation changes on aeolian transport on an estuarine beach data from a moderate energy meso tidal beach on the east side of delaware bay new jersey usa revealed the significance of both beach width as a source for aeolian transport and the effect of tidal rise on source width wind speeds averaged over 17 1 min recorded 6 m above the crest of a 0 5 m high dune ranged from 11 6 to 12 7 m s 1 during the experiment the highest observed rate of transport on the beach was 0 0085 kg m 1 s 1 monitored at rising low tide when the average wind speed was 11 6 m s 1 across 0 35 mm diameter surface sediments the wind direction was oblique to the shoreline creating a source width of 34 m the reduction in the width of the beach as a source for aeolian transport during rising tide was approximately arithmetic whereas the reduction in volume of sediment trapped was exponential aeolian transport effectively ceased when source width was less than 8 m wind conditions moisture content of the surface sediments and presence of binding salts did not appear to vary dramatically and no coarse grained lag deposit formed on the surface of the beach the decrease in rate of sediment trapped through time in the tidal cycle is attributed to differences in source width sediment deposited in the litter behind the active beach by strong winds during the rising tide was eroded during the high water period by the high waves and storm surge generated by these winds and net losses of sediment were observed despite initial aeolian accretion

magnitude of lead flux to the atmosphere from volcanoes pb s tl s and bi s ratios were measured in eruptive and fumarolic volcanic gases and indexed to the global flux of volcanic s to characterize approximate global volcanic emissions of these three metals to the atmosphere which are about 1200 tons pb yr 600 tons tl yr and 4000 tons bi yr this volcanic pb input is similar to the magnitude of natural soil dust pb input which is about 1400 tons pb yr during the holocene interglacial both are negligible compared to annual industrial inputs of 300 000 tons pb yr which maintain the present tropospheric reservoir of pb however polar ice records indicate that thousands of years ago the atmospheric pb reservoir was only 1 of its present size which means that volcanic pb was the source of about half the pb in the atmosphere during preindustrial holocene times

correlation of geoelectric data with aquifer parameters to delineate the groundwater potential of hard rock terrain in central uganda knowledge of aquifer parameters is essential for management of groundwater resources conventionally these parameters are estimated through pumping tests carried out on water wells this paper presents a study that was conducted in three villages tumba kabazi and ndaiga of nakasongola district central uganda to investigate the hydrogeological characteristics of the basement aquifers our objective was to correlate surface resistivity data with aquifer properties in order to reveal the groundwater potential in the district existing electrical resistivity and borehole data from 20 villages in nakasongola district were used to correlate the aquifer apparent resistivity e with its hydraulic conductivity ke and aquifer transverse resistance tr with its transmissivity te ke was found to be related to e by text log k text e 0 002 rho text e 2 692 similarly tr was found to be related to t by text tr 0 07t text e 2260 using these expressions aquifer parameters tc and kc were extrapolated from measurements obtained from surface resistivity surveys our results show very low resistivities for the presumed water bearing aquifer zones possibly because of deteriorating quality of the groundwater and their packing and grain size drilling at the preferred ves spots was conducted before the pumping tests to reveal the aquifer characteristics aquifer parameters to and ko as obtained from pumping tests gave values 29 424 7 m2 day 374 3 m day 9 801 1 m2 day 437 0 m day 31 852 4 m2 day 392 9 m day the estimated aquifer parameter tc and kc when extrapolated from surface geoelectrical data gave 7 142 9 m2 day 381 9 m day 28 200 0 m2 day 463 4 m day 19 428 6 m2 day 459 2 m day for tumba kabazi and ndaiga villages respectively interestingly the similarity between the kc and ko pairs was not significantly different we observed no significant relationships between the tc and to pairs the root mean square errors were estimated to be 18 159 m2 day and 41 4 m day

vlf survey of the weathered layer in southern india the electrical properties of the weathered layer were investigated by means of geonics vlf em 16 16r equipment in two areas of the andhra pradesh state the resistivity and thickness of the weathered layer were found to be variable even over a small survey area in the area underlain by precambrian granite gneiss most of the recorded vlf em anomalies were caused by variations in the resistivity of the weathered layer changes in thickness were well reflected in the vlf emr curves the second area was underlain by cretaceous basalts and dolerites quantitative interpretation of the vlf emr data with a simple one dimensional model yielded considerable detail about the weathered layer for the granitic area a prior estimate of at least one resistivity parameter of the ground is required if this is not already available a limited amount of direct current resistivity surveying can provide the required information a study of the emr data from the basaltic area revealed the presence of a thin highly conductive layer between the weathered layer and the bedrock the parameters of this layer were found to be variable making it necessary to use a set of diagrams for quantitative interpretation due to the presence of this highly conductive layer the emr data contain little information on the bedrock resistivity our field studies suggest that the vlf emr method can be used as a fast and inexpensive tool for mapping of the weathered layer in tropical regions with hard rock geology such mapping is of considerable importance because the weathered layer is an important source of groundwater

metal residence sites in lavas and tuffs from volcan popocatepetl mexico implications for metal mobility in the environment volcan popocatepetl is a quaternary stratovolcano located 60 km southeast of mexico city the summit crater is the site of recent ash eruptions excess degassing and dacite dome growth the modern cone comprises mainly pyroclastic flow deposits airfall tephras debris flows and reworked deposits of andesitic composition it is flanked by more mafic monogenetic vents in least degassed fallout tuffs and mafic scoria transition metals are concentrated in phases formed before eruption during eruption and after eruption preeruptive minerals occur in both lavas and tephra and include oxides and sulfides in glass and phenocrysts the magmatic oxides consist of magnetite ilmenite and chromite the sulfides consist of both fe ni 1 xs mss and cu fe sulfide iss syn and posteruptive phases occur in vesicles in both lavas and tephra and on surfaces of ash and along fractures the mineral assemblages in lavas include cu fe sulfide and fe ti oxide in vesicles and fe sulfide and cu fe sulfide in segregation vesicles assemblages in vesicles in scoria include fe ti oxide and rare fe cu sn sulfide vesicle fillings of fe ti oxide ni rich chromite fe sulfide cu sulfide and barite are common to two pumice samples the most coarse grained of the vesicle fillings are cu fe sulfide and cu sulfide which are as large as 50 in diameter the youngest plinian pumice also contains zn fe sulfide as well as rare ag cu sulfide ag fe sulfide ag bromide ag chloride and au cu telluride the assemblage is similar to those typically observed in high sulfidation epithermal mineralization the fine grained nature and abundance of syn and or posteruptive phases in porous rocks makes metals susceptible to mobilization by percolating fluids the abundance of metal compounds in vesicles indicates that volatile exsolution prior to and or during eruption played an important role in releasing metals to the atmosphere

vertical profiles of aeolian sand mass flux abstract vertical profiles of the horizontal mass flux of blown sand are investigated experimentally using a passive vertical array in a wind tunnel considering lower sampling efficiency of the sand trap in the near bed region this investigation is complemented by the measurements of the longitudinal profiles of mass flux made using a horizontal sand trap the experiments were conducted with two test sands and five different stream velocities in the upper part of the vertical profile the measured data exhibit an exponential decay distribution with a positive deviation occurring in the near bed region the measured longitudinal profiles are similar to the measured vertical profiles linking both profiles and the modes of sand transport it is possible that saltating sand grains give rise to the well known exponential decay distribution of mass flux and that creeping and reptating grains force a deviation from it a simple equation applicable for both the vertical and the longitudinal sand mass flux variations is introduced and the parameters are estimated from experimental data

particle geochemistry of volcanic plumes of etna and mount st helens particles in volcanic plumes include vapor condensates and reaction products of ash with vapors or condensed liquids in addition to abundant silicate particles in the 1980 mount st helens plume we detected abundant na k cl crystals as well as ca sulfates the latter commonly as overgrowths on ash or anthropogenic particles many of the chloride particles contained zinc and cadmium high temperature fumarolic incrustations showed strong enrichments of arsenic zinc alkalis and iron at etna we did not detect chloride crystals but found abundant al fe and ca sulfates sulfuric acid droplets were ubiquitous in both plumes bulk analyses of fumarole incrustations at etna showed an enrichment in the rare earth elements ree the chemical and textural data of the plume particles indicate that chloride particles form relatively early and react later with sulfuric acid droplets to form sulfates at etna aluminum as well as some ree are probably transported as volatile fluorine compounds the differences in plume chemistry between etna and mount st helens are most likely related to differences in f cl ratios of the vapors based on the abundance of particulate chlorine in plumes we suggest that only a small fraction of the total chlorine released during an eruption might reach the stratosphere in the vapor phase

airborne aerosol measurements in the quiescent plume of mount st helens september 1980 atmospheric particulate matter and condensed volatile species were collected in the quiescent plume of mount st helens volcano in sept 1980 using air filter systems mounted aboard a nasa turbo prop p 3 aircraft concentrations of 27 elements were determined by instrumental neutron activation analysis and ion chromotagraphy the volatile elements cl br f zn w in s cd se sb hg as and au were enriched relative to bulk ash emitted during the earlier eruptions by factors of 50 to 20 000 particulate s concentrations were approx 3 mu g m sup 3 and accounted for 6 of the total plume sulfur gas phase hg concentrations were 2 5 to 16 ng m sup 3 fluxes of elements were estimated by normalizing elemental concentrations to the concurrently measured total sulfur flux emission rates vary from 3500 kg day for particulate cl to 3 kg day for au with substantial quantities of the enriched elements zn as hg sb se and cd also being released estimated global fluxes of these elements from volcanoes to the atmosphere are in reasonable agreement with other literature estimates

isotope geochemistry of mercury in source rocks mineral deposits and spring deposits of the california coast ranges usa abstract we present here the first study of the isotopic composition of mercury in rocks ore deposits and active spring deposits from the california coast ranges a part of earth s crust with unusually extensive evidence of mercury mobility and enrichment the franciscan complex and great valley sequence which form the bedrock in the california coast ranges are intruded and overlain by tertiary volcanic rocks including the clear lake volcanic sequence these rocks contain two types of mercury deposits hot spring deposits that form at shallow depths the franciscan complex and great valley sequence contain clastic sedimentary rocks with higher concentrations of mercury than volcanic rocks of the clear lake volcanic field mean mercury isotopic compositions 202hg for all three rock units are similar although the range of values in franciscan complex rocks is greater than in either great valley or clear lake rocks hot spring and silica carbonate mercury deposits have similar average mercury isotopic compositions that are indistinguishable from averages for the three rock units although 202hg values for the mercury deposits have a greater variance than the country rocks precipitates from spring and geothermal waters in the area have similarly large variance and a mean 202hg value that is significantly lower than the ore deposits and rocks these observations indicate that there is little or no isotopic fractionation

mercury content in atlantic sediments as a new indicator of the enlargement and reduction of northern hemisphere ice sheets the total mercury content of quaternary sediments over the last 1 1 ma from iodp site u1308 drilled in the north atlantic ocean has changed varying with periodicities of 100 000 and 41 000 years the hg content of the sediment increased during glacial periods associated with increases in ice rafted debris ird and correlates positively with the total organic carbon toc content and inversely with the absolute abundance of surface dwelling nannoplankton species toc total nitrogen ratios and 13corg values of toc indicate that the toc deposited during glacial periods was marine and associated with increased hg deposition these observations suggest that marine hg is incorporated into the organic matter produced by deep dwelling phytoplankton in the lower photic zone mercury and ird bearing icebergs flowed out to this area during glacial periods melt increasing the hg content of photic water and depositing ird on the ocean floor where increased marine hg during glacial periods was consumed by deep dwelling phytoplankton therefore the change in the sediment hg content from the north atlantic ocean is controlled by climatic change and can be used as a chemical indicator of northern hemisphere ice sheet variability

wind blown sand on beaches an evaluation of models five models for predicting rates of aeolian sand transport were evaluated using empirical data obtained from field experiments conducted in april 1994 at a beach on inch spit co kerry republic of ireland measurements were made of vertical wind profiles to derive shear velocity estimates beach slope and rates of sand transport sediment samples were taken to assess characteristics of grain size and surface moisture content estimates of threshold shear velocity were derived using grain size data after parsing the field data on the basis of the quality of shear velocity estimation and the occurrence of blowing sand 51 data sets describing rates of sand transport and environmental conditions were retained mean grain diameter was 0 17 mm surface slopes ranged from 0 02 on the foreshore to about 0 11 near the dune toe mean shear velocities ranged from 0 23 m s 1 just above the observed transport threshold to 0 65 m s 1 rates of transport ranged from 0 02 kg m 1 h 1 to more than 80 kg m 1 h 1 these data were used as input to the models of bagnold bagnold r a 1936 the movement of desert sand proc r soc london a157 594 620 kawamura kawamura r 1951 study of sand movement by wind translated 1965 as university of california hydraulics engineering laboratory report hel 2 8 berkeley zingg zingg a w 1953 wind tunnel studies of the movement of sedimentary material proc 5th hydraulics conf bull 34 iowa city inst of hydraulics pp 111 135 kadib kadib a a 1965 a function for sand movement by wind university of california hydraulics engineering laboratory report hel 2 8 berkeley and lettau and lettau lettau k and lettau h 1977 experimental and micrometeorological field studies of dune migration in k lettau and h lettau eds exploring the world s driest climate university of wisconsin madison ies report 101 pp 110 147 correction factors to adjust predictions of the rate of transport to account for the effects of slope and moisture content were calculated using the models of bagnold bagnold r a 1973 the nature of saltation and bed load transport in water proc r soc london ser a 332 473 504 and belly belly p y 1964 sand movement by wind u s army corps eng cerc tech mem 1 washington d c 38 pp respectively none of the models was able to produce a strong correspondence between measured and predicted rates of transport best results were obtained using the bagnold and zingg models and the kadib model was the least viable of this group the influence of sediment moisture content appeared to be the critical factor in degrading model viability overall none of the models is adequate for general applications to coastal aeolian environments where moisture content complications tend to override the predictive competence of the simple transport formulations c 1998 elsevier science b v

emergence of oblique dunes in a landscape scale experiment the dynamics of dune evolution under bimodal wind regimes are poorly understood owing to a lack of long term wind records and the limitations of most experimental set ups a 4 year landscape scale experiment in the tengger desert mongolia demonstrates that the orientation of oblique dune crests is controlled by the wind regime