mobilization and speciation of arsenic from hydrothermally altered rock containing calcite and pyrite under anoxic conditions abstract the effects of water residence time and anoxic conditions on the mobilization and speciation of as in a calcite and pyrite bearing altered rock excavated during a road tunnel project has been evaluated using batch and column laboratory experiments higher infiltration rates i e shorter water residence times enhanced the leaching of as due to the higher ph values of the effluents and more rapid transport of dissolved as through the columns the concentration of as in the effluent also increased under anoxic conditions regardless of the water residence time this enhanced leaching of as under anoxic conditions could be attributed to a significant ph increase and decreased fe oxyhydroxide oxide precipitation compared to similar experiments done under ambient conditions processes that controlled the evolution of ph and the temporal release mechanisms of as under anoxic conditions were identical to those previously observed under ambient conditions the dissolution of soluble phases pyrite oxidation co precipitation and or adsorption desorption reactions speciation of as in the column experiments could partly be attributed to the ph dependent adsorption of as species onto fe oxyhydroxide oxide precipitates moreover apparent equilibrium of the total as and as iii concentrations was delayed under anoxic conditions in both batch and column experiments

megathrust splay faults at the focus of the prince william sound asperity alaska 1 high resolution sparker and crustal scale air gun seismic reflection data coupled with repeat bathymetric surveys document a region of repeated coseismic uplift on the portion of the alaska subduction zone that ruptured in 1964 this area defines the western limit of prince william sound differencing of vintage and modern bathymetric surveys shows that the region of greatest uplift related to the 1964 great alaska earthquake was focused along a series of subparallel faults beneath prince william sound and the adjacent gulf of alaska shelf bathymetric differencing indicates that 12 m of coseismic uplift occurred along two faults that reached the seafloor as submarine terraces on the cape cleare bank southwest of montague island sparker seismic reflection data provide cumulative holocene slip estimates as high as 9 mm yr along a series of splay thrust faults within both the inner wedge and transition zone of the accretionary prism crustal seismic data show that these megathrust splay faults root separately into the subduction zone decollement splay fault divergence from this megathrust correlates with changes in midcrustal seismic velocity and magnetic susceptibility values best explained by duplexing of the subducted yakutat terrane rocks above pacific plate rocks along the trailing edge of the yakutat terrane although each splay fault is capable of independent motion we conclude that the identified splay faults rupture in a similar pattern during successive megathrust earthquakes and that the region of greatest seismic coupling has remained consistent throughout the holocene

the use of documentary sources for reconstructing flood chronologies on the amalfi rocky coast southern italy documentary source materials are essential for retrospective reconstruction of flood events occurring in past centuries this paper presents methods of research and archiving of historical data from the 16th century to the present the quality and completeness of the various original sources were evaluated and carefully analysed in their historical context to avoid serious mistakes systematic investigation of about 3000 documents mainly found in national state archives and libraries allows us to identify and localize at least 106 flood events occurring along the amalfi coast southern italy for five centuries between the years 1500 and 2000 the collected data provide useful details on flood dynamics size of flooded areas flood duration damage level number of victims and induced geological effects when available in sufficient quantity the flood data allow determination of very useful parameters such as the severity class to identify large floods and their recurrence interval

arsenic toxicity of groundwater in parts of the bengal basin in india and bangladesh the role of quaternary stratigraphy and holocene sea level fluctuation arsenic toxicity in groundwater in the ganges delta and some low lying areas in the bengal basin is confined to middle holocene sediments dissected terraces and highlands of pleistocene and early holocene deposits are free of such problems arsenic rich pyrite or other arsenic minerals are rare or absent in the affected sediments arsenic appears to occur adsorbed on iron hydroxide coated sand grains and clay minerals and is transported in soluble form and co precipitated with or is scavenged by fe iii and mn iv in the sediments it became preferentially entrapped in fine grained and organic rich sediments during mid holocene sea level rises in deltaic and some low lying areas of the bengal basin it was liberated subsequently under reducing conditions and mediated further by microbial action intensive extraction of groundwater for irrigation and application of phosphate fertilizer possibly triggered the recent release of arsenic to groundwater this practice has induced groundwater flow mobilizing phosphate derived from fertilizer as well as from decayed organic matter which has promoted the growth of sediment biota and aided the further release of arsenic however the environment is not sufficiently reducing to mobilize iron and arsenic in groundwater in the ganges floodplains upstream of rajmahal thus arsenic toxicity in the groundwater of the bengal basin is caused by its natural setting but also appears to be triggered by recent anthropogenic activities

characterization and evaluation of arsenic and boron adsorption onto natural geologic materials and their application in the disposal of excavated altered rock construction of tunnels in hokkaido japan often excavates rocks containing substantial amounts of arsenic as and boron b when these rocks are exposed to the environment as and b are leached out that could potentially contaminate the surrounding soil and groundwater natural geologic materials contain minerals like al fe oxyhydroxides oxides that have as and b adsorption capabilities because these materials are widespread and readily available they could be utilized in the mitigation of as and b leached out from these sources this paper describes the ability of three natural geologic materials i e pumiceous tuffs partly weathered volcanic ashes and coastal marine sediments to sequester as and b from aqueous solutions and the actual leachate of a hydrothermally altered rock the adsorption of as fitted well with either the langmuir or freundlich isotherm while that of b followed the henry type model linear among the samples those containing substantial amorphous al and fe exhibited higher as adsorption however the distribution coefficient of b only had a moderate positive correlation with these amorphous phases the best adsorbent among these natural geologic materials was utilized in the adsorption layer of the column experiments adsorption of as was more effective the thicker the adsorption layer but this retardation was only temporary due to significant changes in the ph in contrast the adsorption layer only retarded the migration of b to a limited extent

the aqueous geochemistry of the berkeley pit butte montana u s a water levels in the berkeley pit butte montana are currently rising approximately 22m per year following the cessation of pumping in 1982 projections suggest that the pit may be filled to capacity at the 5520 ft 1682 m elevation by the year 2009 if remedial action is not implemented in addition as the water level in the pit continues to rise there is the potential for encroachment of contaminated water into the alluvial aquifer and subsequent transport of metals downgradient to silver bow creek geochemical measurements and aqueous samples collected during october 1987 indicate that water in the berkeley pit is moderately oxidizing eh 460mv below 30 m acidic ph 3 0 cafe sulfate solution the principal ions are al as ca cd cu fe k mg na so4 and zn which typically increase in concentration from the surface to the bottom of the pit arsenic occurs mainly as as v in total metal concentrations up to 1 mg l fe as fe iii in the top 3 m and as fe ii below this depth in concentrations up to 1000 mg l sulfate was measured in concentrations up to 6780 mg l from the deepest 130 m sample copper and zn were found in total metal concentrations of 202 and 512 mg l respectively at the 130 m sampling depth to verify the field eh measurements minteq was used to calculate a theoretical eh based on the fe ii fe iii couples the results suggest that the ratio fe ii fe iii is representative of the system eh when both species occur in measurable quantities 0 25mg l and when the minor species constitutes at least 5 of the total concentration data from this study were used in the geochemical computer code phreeqe to evaluate potential remediation of the water body through the addition of alkaline tailings fluid produced at the current milling operation on site five cases were evaluated two representative of conditions under ice cover pco2 not fixed and three open system simulations pco2 10 3 5 mineral controls included fe oh 3 gypsum caso4 2h2o jurbanite alohso4 and jarosite kfe3 so4 2 oh 6 the addition of three volumes of alkaline slurry to the existing volume of acidic fluid would raise the ph to 5 0 this option would take approximately 7 a at the current rate of production 11 6 million gallons per day 43 9 ml d at this time the fluid level would be approximately 20 m above the alluvial bedrock contact

geology of the sunbeam and grouse creek gold silver deposits yankee fork mining district eocene challis volcanic field idaho a volcanic dome and volcaniclastic hosted epithermal system the sunbeam and grouse creek epithermal gold silver deposits lie within the custer graben of the eocene challis volcanic field in central idaho the custer graben is a major northeast trending volcano tectonic depression that forms part of the trans challis fault system a 220 km long by 65 km wide zone defined by regional high angle faults grabens and cauldron subsidence features the relationship between the cauldrons and grabens along the trans challis fault zone northeast of the deposit area bears a strong resemblance to that observed in the east african rift system the challis volcanic field consists of a lower sequence of andesitic lavas and an upper sequence of quartz latitic and rhyolitic ash flow tuffs capping lacustrine and fluvial sedimentary rocks and late stage rhyolitic dikes domes and flows the sunbeam deposit is hosted by a subaerial rhyolitic flow dome complex and underlying pyroclastic rocks ore grades occur principally along dominant northeast and subordinate northwest trending fractures that are focused in silicified and argillized zones individual mineralized fractures manifested as either iron rich clayey zones with silicified cores and or margins or stockworks with anastomosing veinlets of silica and pyrite hydrothermal breccias are common and follow the regional structural fabric gold and silver occur primarily as electrum silver sulfides and sulfosalts are minor pyrite and arsenopyrite are the dominant sulfide minerals the silver to gold ratio is 6 1 argillically altered areas consist primarily of illite with less than 15 percent interlayered smectite pyrophyllite is present in the interior of the ore zones smectite exceeds 15 percent beyond the ore zones kaolinite is rare and alunite is absent oxidation is supergene in origin and forms a thin 12 to 30 m 40 100 ft cap to the deposits the grouse creek deposit is hosted by subaqueous volcaniclastic and pyroclastic rocks that are located within a subbasin immediately adjacent to and northwest of the sunbeam rhyolite flow dome the deposit is interpreted to be partly epigenetic and partly syngenetic ore occurs dominantly in silicified zones invading the same rhyolitic pyroclastic unit that hosts part of the sunbeam deposit in hydrothermal volcanic breccias and in the basal portion of the carbonaceous black shale which caps the sequence northeast and northwest trending fractures form the feeders for the hydrothermal system but have less influence on precious metal deposition than at the sunbeam deposit ore minerals are similar to those at the sunbeam deposit however the silver to gold ratio is roughly 43 1 argillic alteration and silicification encase the ore zones silicification is closely associated with ore grades whereas argillically altered rocks extend beyond the limits of ore grade propylitic alteration is widespread in the footwall of the ore zone regional structural and lithologic investigations and detailed geologic studies of both deposits indicate that the two deposits are contemporaneous but were deposited in different host environments the sunbeam deposit formed in a subaerial rhyolite flow dome that flanks the southern margin of the northeast trending rift valley lake in which the grouse creek deposit formed geochemical and mineralogical patterns in the host sedimentary sequence at the grouse creek deposit indicate that hydrothermal activity occurred during sediment accumulation most of the precious metals were deposited below the sediment water interface however warmer metal rich brines penetrated the sediment surface to form hydrothermal plumes which provided nutrients for biological blooms near the vent areas subsequent volcaniclastic sedimentation covered the deposit and its near surface manifestation the geologic environment of the custer graben and the sunbeam and grouse creek area bears strong resemblance to intracratonic rift environments such as the east africa rift system

geochemical evolution of a high arsenic alkaline pit lake in the mother lode gold district california the harvard orebody at the jamestown gold mine located along the melones fault zone in the southern mother lode gold district california was mined in an open pit operation from 1987 to 1994 dewatering during mining produced a hydrologic cone of depression recovery toward the premining ground water configuration produced a monomictic pit lake with alkaline ca mg hco3 so4 type pit water concentrations of as up to 1 200 g l and total dissolved solids tds up to 2 000 mg l in this study pit wall rocks were mapped and chemically analyzed to provide a context for evaluating observed variability in the composition of the pit lake waters in relationship to seasonal weather patterns an integrated hydrogeochemical model of pit lake evolution based on observations of pit lake volume water composition samples collected between 1998 2000 2004 and processes occurring on pit walls was developed in three stages using the computer code phreeqc stage 1 takes account of seasonally variable water fluxes from precipitation evaporation springs and ground water as well as lake stratification and mixing processes stage 2 adds co2 fluxes and wall rock interactions and stage 3 assesses the predictive capability of the model two major geologic units in fault contact comprise the pit walls the hanging wall is composed of interlayered slate metavolcanic and metavolcaniclastic rocks and schists the footwall rocks are chlorite actinolite and talc tremolite schists generated by metasomatism of greenschist facies mafic and ultramafic igneous rocks alteration in the ore zone provides evidence for mineralizing fluids that introduced co2 s and k2o and redistributed sio2 arsenian pyrite associated with the alteration weathers to produce goethite and jarosite on pit walls and in joints as well as copiapite and hexahydrite efflorescences that accumulate on wall rock faces during dry california summers all of these pyrite weathering products incorporate arsenic at concentrations from 100 up to 1 200 ppm in the pit lake ph and tds reach seasonal highs in the summer epilimnion ph is lowest in the summer hypolimnion arsenic and bicarbonate covary in the hypolimnion rising as stratification proceeds and declining during winter rains the computational model suggests that water fluxes alone do not account for this seasonal variability loss of co2 to the atmosphere interaction with pit walls including washoff of efflorescent salts during the first flush and seasonal rainfall and arsenic sorption appear to contribute to the observed pit lake characteristics

opposing gradients of permanent strain in the aseismic zone and elastic strain across the seismogenic zone of the kodiak shelf and slope alaska an industry acquired seismic reflection line from the aleutian arc to the alaska trench was prestack depth migrated and further constrained with wide angle ocean bottom hydrophone seismic velocity data and swath mapping from the seismic reflection image individual thrust slices the backstop and the forearc basin were resolved sufficiently well to balance the section tectonic shortening and age estimates provided rates of permanent contraction in five discrete segments over 150 km during the past 3 myr about 70 of the plate convergence is measured as contraction across the 40 km wide neogene accretionary prism which composes less than 10 of the forearc permanent contraction is minimal above the 1964 alaska earthquake aftershock zone indicating dominently elastic strain since elastic strain is poorly recorded in the geological record it was approximated from the historical record of the 1964 alaska earthquake the 1964 coseismic vertical deformation displays an inverse pattern to the permanent strain consistent with the earthquake cycle concept elastic deformation is dominant beneath the shelf and upper slope rapid permanent deformation is concentrated beneath the lower slope and a transition between them occurs beneath the middle slope

mobilization and speciation of arsenic from hydrothermally altered rock in laboratory column experiments under ambient conditions abstract this paper describes the mobilization and speciation of as found in hydrothermally altered rock under oxic column conditions the altered rock sample was obtained from a tunnel project located in the nakakoshi area of hokkaido japan whose geology is represented by slate shale and sandstone this area has undergone silicification pyritization and argillic alteration resulting in as enrichment of the rock results of the column experiments show that the infiltration rate bulk density and rock bed thickness affected the duration of water residence which in turn influenced the ph of the rock water system coexisting ions most notably ca2 at amounts greater than ca 50 mg l retarded the mobilization of as mobilization of as from the rock with time occurred in two stages stage 1 weeks 1 20 with higher as leaching and stage 2 weeks 20 76 characterized by nearly constant as release in addition pore water as concentrations revealed that the columns developed into two regions the top half where most of the leaching occurred and the bottom part dominated by adsorption thus the mechanism controlling the mobilization of as from the rock is a combination of one or more of the following processes dissolution of soluble as bearing fractions pyrite oxidation and adsorption reactions arsenite as iii was the dominant species in the effluent at the start of the experiment in columns with shorter water residence time and lower ph conditions

a review of the source behaviour and distribution of arsenic in natural waters the range of as concentrations found in natural waters is large ranging from less than 0 5 g l 1 to more than 5000 g l 1 typical concentrations in freshwater are less than 10 g l 1 and frequently less than 1 g l 1 rarely much higher concentrations are found particularly in groundwater in such areas more than 10 of wells may be affected defined as those exceeding 50 g l 1 and in the worst cases this figure may exceed 90 well known high as groundwater areas have been found in argentina chile mexico china and hungary and more recently in west bengal india bangladesh and vietnam the scale of the problem in terms of population exposed to high as concentrations is greatest in the bengal basin with more than 40 million people drinking water containing excessive as these large scale natural as groundwater problem areas tend to be found in two types of environment firstly inland or closed basins in arid or semi arid areas and secondly strongly reducing aquifers often derived from alluvium both environments tend to contain geologically young sediments and to be in flat low lying areas where groundwater flow is sluggish historically these are poorly flushed aquifers and any as released from the sediments following burial has been able to accumulate in the groundwater arsenic rich groundwaters are also found in geothermal areas and on a more localised scale in areas of mining activity and where oxidation of sulphide minerals has occurred the as content of the aquifer materials in major problem aquifers does not appear to be exceptionally high being normally in the range 1 20 mg kg 1 there appear to be two distinct triggers that can lead to the release of as on a large scale the first is the development of high ph 8 5 conditions in semi arid or arid environments usually as a result of the combined effects of mineral weathering and high evaporation rates this ph change leads either to the desorption of adsorbed as especially as v species and a range of other anion forming elements v b f mo se and u from mineral oxides especially fe oxides or it prevents them from being adsorbed the second trigger is the development of strongly reducing conditions at near neutral ph values leading to the desorption of as from mineral oxides and to the reductive dissolution of fe and mn oxides also leading to as release iron ii and as iii are relatively abundant in these groundwaters and so4 concentrations are small typically 1 mg l 1 or less large concentrations of phosphate bicarbonate silicate and possibly organic matter can enhance the desorption of as because of competition for adsorption sites a characteristic feature of high groundwater as areas is the large degree of spatial variability in as concentrations in the groundwaters this means that it may be difficult or impossible to predict reliably the likely concentration of as in a particular well from the results of neighbouring wells and means that there is little alternative but to analyse each well arsenic affected aquifers are restricted to certain environments and appear to be the exception rather than the rule in most aquifers the majority of wells are likely to be unaffected even when for example they contain high concentrations of dissolved fe

geochemical study of arsenic release mechanisms in the bengal basin groundwater 1 to investigate arsenic mobility in the bengal basin groundwater we sampled water wells and sediments throughout the region there are strong correlations among high levels of dissolved arsenic and iron ammonia and methane especially in samples from a single site laxmipur no linkage is seen between as and agricultural tracers such as phosphate the association of as and fe occurs because arsenic strongly adsorbs onto feooh particles in river water they flocculate with other fine grained particles at the freshwater saltwater transition zone subsequent bacterially mediated reduction of feooh in the clay releases the adsorbed arsenic weathering of as bearing mica plays a significant role in the as budget the correlated presence of as ch4 and nh4 in water supply wells is the result of diffusion out of organic rich clay into the more permeable zones arsenic is mainly released from recent sediments at 50 m depth deposited in the gbr floodplain as sea level rose throughout the holocene

the nexus between groundwater modeling pit lake chemogenesis and ecological risk from arsenic in the getchell main pit nevada u s a abstract the proliferation of mine pits that intersect the groundwater table has engendered interest in the environmental consequences of the lakes that form after cessation of dewatering the getchell main pit gmp in nevada hosts arsenic sulfide asxsy mineralization e g orpiment and realgar and ambient groundwater as up to 1 8 mg l 1 making groundwater inflow a potentially significant as source to the future pit lake predictive simulations using modflow surfact show that the gmp lake water level will recover to within 99 of the pseudo equilibrium stage within 100 years after the end of dewatering resulting in a 75 m deep terminal pit lake the juvenile gmp lake after 5 years will be a calcium sulfate ph 7 8 water body containing 920 mg l 1 tds and 0 6 mg l 1 as evolving towards a ph 7 9 1580 mg l 1 tds and 0 9 mg l 1 as water body after 100 years the predicted pit lake chemistry is consistent with earlier pit lake water quality after 16 years when the south and center pits precursors to the main pit were allowed to fill during a mining hiatus 1968 1984 the gmp mature pit lake chemistry was used to assess ecological risk to potential local receptors i e mallard duck cliff swallow golden eagle little brown bat spotted sandpiper deer mouse mule deer and cattle arsenic does not strongly bioaccumulate through the food chain at getchell hence pit lake as will not pose an unacceptable risk

hydrothermal arsenic enrichment in an active mountain belt southern alps new zealand abstract torlesse terrane greywackes and hydrothermal calcite associated with active fault systems in the main divide fault zone of new zealand s south island exhibit anomalous as concentrations relative to background values of similar rock types mass balance analysis of greywacke compositional data from the upper wilberforce valley of the main divide region demonstrate an average mass gain of as on the order of a factor of 6 above typical torlesse greywackes wilberforce mean 35 3 ppm 31 3 ppm n 44 torlesse mean 5 6 ppm 4 4 n 31 in addition hydride generated icp ms analyses of the weak acid soluble fraction of individual calcite rich veins and fault gouges in the main divide fault zone exhibit as concentrations mean 81 2 ppm 113 ppm n 17 in excess of a factor of 100 over hydrothermal calcite from other fault systems mean 1 7 ppm 4 0 n 29 stable isotopic analyses of these calcite veins show a wide range for both oxygen 18o 9 9 to 25 6 and carbon 13c 12 to 1 1 this observation suggests that the hydrothermal fluid source of these veins was of a mixed meteoric and highly exchanged fluid over a wide range of temperatures we suggest that the presence of high as concentrations in young hydrothermal calcite veins in the main divide region results from active transport of as rich deep crustal fluids upward along the fault zone this interpretation is consistent with both fluid flow tectonic models and geophysical observations which suggest that expansion in the main divide fault zone provides a conduit for the escape of deep exchanged fluids into the upper crust

the deglacial transition on the southeastern alaska margin meltwater input sea level rise marine productivity and sedimentary anoxia 1 oxygen isotope data from planktonic and benthic foraminifera on a high resolution age model 44 14c dates spanning 17 400 years document deglacial environmental change on the southeast alaska margin 59 33 32 n 144 9 21 w 682 m water depth surface freshening i e 18o reduction of 0 8 began at 16 650 170 cal years b p during an interval of ice proximal sedimentation likely due to freshwater input from melting glaciers a sharp transition to laminated hemipelagic sediments constrains retreat of regional outlet glaciers onto land circa 14 790 380 cal years b p abrupt warming and or freshening of the surface ocean i e additional 18o reduction of 0 9 coincides with the bolling interstade of northern europe and greenland cooling and or higher salinities returned during the allerod interval coincident with the antarctic cold reversal and continue until 11 740 200 cal years b p when onset of warming coincides with the end of the younger dryas an abrupt 1 reduction in benthic 18o at 14 250 290 cal years b p likely reflects a decrease in bottom water salinity driven by deep mixing of glacial meltwater a regional megaflood event or brine formation associated with sea ice two laminated opal rich intervals record discrete episodes of high productivity during the last deglaciation these events precisely dated here at 14 790 380 to 12 990 190 cal years b p and 11 160 130 to 10 750 220 cal years b p likely correlate to similar features observed elsewhere on the margins of the north pacific and are coeval with episodes of rapid sea level rise remobilization of iron from newly inundated continental shelves may have helped to fuel these episodes of elevated primary productivity and sedimentary anoxia

geochemical assessment of arsenic contamination in well water and sediments from several communities in the nawalparasi district of nepal arsenic contamination of well water is a serious issue in the nawalparasi district of the terai region in nepal a local investigation was carried out on 137 tube wells in 24 communities of the district in december 2011 the investigation revealed that the average arsenic concentration in the tube wells was 350 g l and that nearly 98 of the wells exceeded the who guideline arsenic level limit of 10 g l highly contaminated well water with more than 400 g l of arsenic was found within the limited depth ranges of 18 22 and 50 80 m high arsenic levels exceeding 500 g l were detected in shallower wells at patkhauli mahuawa thulokunwar and goini located between 27 517 and 27 543 n and between 83 648 and 83 748 e boring sampling at five communities of kashiya goini sanokunwar thulokunwar and mahuawa revealed two aquifers located at the two depths around 14 22 and 41 50 m in each community dark gray or black colored peaty clay layers rich in organic matter were distributed at depths of 18 21 m beside the upper aquifers with high arsenic concentration in each community positive correlations were shown between iron and arsenic in the sediments from the five communities it can be inferred that these results were caused by dissolution of iron oxyhydroxide molecules with arsenic from solid phases microbial metabolisms have a great potential to induce the dissolution and release arsenic attached on the solid phases into aqueous phases depending on the level of redox potential and ph

exhumation rates in the st elias mountains alaska abstract reprocessing and interpretation of seismic profiles from the gulf of alaska in the vicinity of the st elias mountains indicate that over 3000 km 3 of sediment were deposited on the ocean shelf since the end of the last glacial epoch approximately 10 000 years ago this estimate of the sediment volume does not include material moved out of the region by long shore currents transportation from the shelf to deeper waters or material trapped in fiords and basins on and near land thus an estimated sedimentation rate offshore of 7 9 mm year and the average erosion rate of 5 1 mm year from the st elias mountains derived from the estimated sedimentation rate represent minimum estimates we infer that these estimated rates are not typical of the approximately 5 m y history of mountain building in the area but rather they represent the result of efficient erosion by glaciers during this interglacial period

mineral control of arsenic content in thermal waters from volcano hosted hydrothermal systems insights from island of ischia and phlegrean fields campanian volcanic province italy this paper documents arsenic concentrations in 157 groundwater samples from the island of ischia and the phlegrean fields two of the most active volcano hosted hydrothermal systems from the campanian volcanic province southern italy in an attempt to identify the environmental conditions and mineral solution reactions governing arsenic aqueous cycling on ischia and in the phlegrean fields groundwaters range in composition from nacl brines which we interpret as the surface discharge of deep reservoir fluids to shallow depth circulating fluids the latter ranging from acid sulphate steam heated to hypothermal cold bicarbonate groundwaters arsenic concentrations range from 1 6 to 6900 g l 1 and from 2 6 to 3800 g l 1 in the phlegrean fields and on ischia respectively they increase with increasing water temperature and chlorine contents and in the sequence bicarbonate groundwatersbsteam heated groundwatersbnacl brines according to thermochemical modeling we propose that high as concentrations in nacl brines form after prolonged water rock interactions at reservoir t fo2 and fh2s conditions and under the buffering action of an arsenopyrite pyrite pyrrhotite rock assemblage on their ascent toward the surface nacl brines become diluted by as depleted meteoric derived bicarbonate groundwaters giving rise to hybrid water types with intermediate to low as contents steam heated groundwaters give their intermediate to high as concentrations to extensive rock leaching promoted by interaction with as bearing hydrothermal steam 2005 elsevier b v all rights reserved

geochemical modeling approach to predicting arsenic concentrations in a mine pit lake abstract between 1968 and 1983 the north pit at the getchell mine humboldt county nv filled with water to form a lake in 1983 water quality data were collected with the following results as concentrations of 0 29 to 0 59 mg l ph of 7 1 to 7 9 so 4 concentrations of 1490 to 1640 mg l and tds of 2394 to 2500 mg l using geochemical modeling techniques presented here pit lake waters have been theoretically allowed to react for 8 5 a the approximate time that the north pit had been completely full by 1983 modeling results predict ph of 7 9 to 8 2 so 4 concentrations of 1503 to 1644 mg l tds of 2054 to 2366 mg l and as concentrations ranging from 0 57 in the hypolimnion to 96 mg l in the epilimnion in the epilimnion model results do not match observed as concentrations suggesting that mechanisms such as precipitation of arsenate salts or adsorption to mineral surfaces may control as levels in an actual pit lake system adsorption to fe oxyhydroxide surfaces is questioned by the authors because of the low fe content in the getchell system but adsorption to al oh 3 gibbsite and clay mineral surfaces may be important in controlling natural as concentrations