the speciation of marine particulate iron adjacent to active and passive continental margins abstract we use synchrotron based chemical species mapping techniques to compare the speciation of suspended 1 51 m marine particulate iron collected in two open ocean environments adjacent to active and passive continental margins chemical species mapping provides speciation information for heterogeneous environmental samples and is especially good for detecting spectroscopically distinct trace minerals and species that could not be detectable by other methods the average oxidation state of marine particulate iron determined by chemical species mapping is comparable to that determined by standard bulk x ray absorption near edge structure spectroscopy using chemical species mapping we find that up to 43 of particulate fe in the northwest pacific at the depth of the adjacent active continental margin is in the fe ii state with the balance fe iii in contrast particulate iron in the eastern tropical north atlantic which receives the highest dust deposition on earth and is adjacent to a passive margin is dominated by weathered and oxidized fe compounds with fe iii contributing 90 of total iron the balance is composed primarily of fe ii containing species but we detected individual pyrite particles in some samples within an oxygen minimum zone in the upper thermocline several lines of evidence point to the adjacent mauritanian continental shelf as the source of pyrite to the water column the speciation of suspended marine particulate iron reflects the mineralogy of iron from the adjacent continental margins since the solubility of particulate iron has been shown to be a function of its speciation this may have implications for the bioavailability of particulate iron adjacent to passive compared to active continental margins

relation between depositional environment and the elemental composition of early diagenetic siderite early diagenetic siderites from marine and fresh water depositional environments are characterized by distinctive compositional trends siderite from fresh water environments is often relatively pure i e greater than 90 mol feco sub 3 and commonly attains end member composition siderite from marine environments however is always extremely impure and has extensive substitution of mg up to 41 mol and to a lesser extent ca up to 15 mol for fe in the siderite lattice in addition marine siderite generally contains less mn and has a higher mg ca ratio than fresh water siderite this compositional variation appears to result from differences in the chemistry of early marine and meteoric pore waters inasmuch as early marine pore waters generally have a higher mg sup 2 ca sup 2 ratio and contain less mn sup 2 and fe sup 2 and more ca sup 2 and mg sup 2 than meteoric waters

estimates of atmospheric processed soluble iron from observations and a global mineral aerosol model biogeochemical implications 1 desert dust deposition to the ocean may be a significant source of biogeochemically important elements specifically iron the bioavailability of iron in the oceans requires it to be in a soluble form and because atmospheric iron in desert dust is typically insoluble understanding the atmospheric processes that convert insoluble iron to more soluble forms is essential understanding these relationships is especially important in remote ocean regions where iron may be the limiting nutrient observations of soluble iron from 2001 cruise based aerosol measurements over the atlantic and pacific oceans ranged from 0 to 45 mean of 4 9 in the fine mode 2 5 m in diameter and 0 to 87 mean of 2 10 in the coarse mode we test two simple hypotheses of soluble iron enhancement in the atmosphere using a global model of mineral aerosols the first method assumes that iron solubility increases as iron is exposed to solar radiation approximating photoreduction reactions that are important pathways for enhancement of soluble iron in the presence of acidic solutions the second process imitates cloud processing of iron by increasing the amount of soluble iron when the mineral aerosol comes into contact with a cloud both methods resulted in similar average magnitudes of percent soluble iron compared to observations but did not capture specific events or have sufficient variability perhaps because the model does not include aerosol interactions between species other than mineral dust or other processes that may be important

trends in the solubility of iron in dust dominated aerosols in the equatorial atlantic trade winds importance of iron speciation and sources 1 we present measurements of the solubility of fe ii and fe iii extracted from bulk and size fractionated african dust collected in summer trade winds at barbados west indies iron solubilities typically ranged from 1 to 3 fe iii dominates the iron solubility over the entire range of particle sizes at mineral dust concentrations below about 5 ug m3 fe ii believed to be largely derived from anthropogenic and biomass burning sources becomes increasingly important samples containing large soluble iron fractions and high fe ii fe iii ratios are associated with south atlantic back trajectories the gray coloration of the filters suggests that the source may be biomass burning in southern africa in general much of the variability in fe solubility is linked to fe ii concentration changes vanadium is often used as a tracer of anthropogenic impacts although many of our samples yielded v ti ratios much greater than average crustal abundances we could find no relationship between the enrichment of v and fe solubility our fe solubility results are quite similar to those obtained by others despite the fact that the measurements were made in diverse ocean regions and the protocols used were quite different in all cases this uniformity implies that the factors controlling aerosol iron solubility are largely inherent in the properties of the aerosols themselves and not the procedures used to extract the iron our results suggest that dust transport models that focus on the role of iron in ocean biogeochemistry must take into account aerosol origin in order to better model the solubility of iron

development and testing of a model for simulating weathering and trace elements release from fixated scrubber sludge utilized in abandoned coal mine reclamation site abstract in this paper we present the first approximation to a fully coupled model for simulating chemical reactions between engineered coal combustion byproducts specifically fixed scrubber sludge fss and ambient groundwater if fss is placed at a mine site as a hydrologic barrier over pyritic refuse it would interact with acidic mine water at the bottom and soil water at the top of the fss a coupled reactive transport model was developed for simulating reactions at the exposed edges of the fss over long time frames in our modeling emphasis was placed on the release and fate of toxic trace elements such as arsenic boron barium and zinc which are commonly present in fss the parameters associated with dissolution of trace element hosts were calibrated and optimized using data from column leachate experiments on core samples extracted from a reclaimed abandoned mine land site in indiana in an effort to evaluate the leaching potential of these trace elements reactive transport simulations were conducted and compared with historical chemistry data the model successfully reproduced many characteristics observed in the field such as initial rises in the concentrations of arsenic boron and zinc following by continuous decline toward steady state by the end of simulation also simulation results indicated that the weathering rate was slightly higher at the top of the fss where it is in contact with ambient soil water than at the bottom of the fss while the preliminary modeling results are promising comparisons between model calculations and historical data point to the fact that there must be other sources or mechanisms that accommodate rapid releasing of trace elements further model development will require explicit inclusion of mechanisms for sorption desorption of the potentially toxic elements

iron solubility driven by speciation in dust sources to the ocean particulate aerosols are thought to be the primary source of iron to the oceans but the factors determining their solubility and thus bioavailability are unclear x ray absorption analysis reveals that speciation controls the solubility of iron in three large sources of aerosol iron

hydrothermal vents as a kinetically stable source of iron sulphide bearing nanoparticles to the ocean hydrothermal vents emit metals such as iron to the ocean a chemical analysis of hydrothermal fluids suggests that up to 10 of the iron is present as stable iron bearing nanoparticles

determination of the effect of roof pressure on coal hardness and excavation productivity an example from a cayirhan lignite mine ankara central turkey mechanized longwall mines require a systematic excavation schedule to control roof stress excavation sometimes becomes easier when the cutting cycle is interrupted and the face is subjected to in situ strain because the excavation machine may perform more efficiently however under those circumstances it is important to determine the critical point at which this advantage overcomes the negative safety high roof pressure and productivity long wait aspects this study was conducted in a retreating longwall underground mine in which a mechanized excavation system is used to determine the most efficient extraction rate time dependent changes in the support pressures and coal hardness measurements made with the schmidt hammer method were determined at the coal face thus a time dependent relationship between the hardness of the coal face and roof pressure was established as a result of these analyses the optimum waiting time before excavation was determined for the mine in which the measurements were carried out in terms of support safety and excavation productivity

application of a chemical leach technique for estimating labile particulate aluminum iron and manganese in the columbia river plume and coastal waters off oregon and washington in order to determine the total concentration of bioavailable trace metals in seawater measurement of both the dissolved and labile particulate fractions is necessary comparison of labile particulate metal concentrations from various researchers is limited because of differing definitions of the fraction that is potentially available to phytoplankton on a time frame of generations a comparison experiment was conducted on coastal and riverine suspended particulate matter to determine the difference between several commonly used techniques that operationally define the labile particulate trace metal fraction furthermore we compared two leach techniques for surface transect samples from within the columbia river plume and water offshore of oregon and washington united states the particulate trace metal concentration in the leachate was determined by high resolution inductively coupled plasma mass spectrometry from this comparison one chemical leach was chosen to best define the labile particulate fraction of al fe and mn a weak acid leach 25 acetic acid at ph 2 with a mild reducing agent 0 02 m hydroxylamine hydrochloride and a short heating step 10 min 90 95 c this leach was applied to three surface transects within the columbia river plume these coastal waters were found to be rich in labile particulate trace metals that are directly delivered from the columbia river and indirectly supplied via resuspension from upwelling over a broad continental shelf

the magnitude timing and abruptness of changes in north african dust deposition over the last 20 000 yr reconstructions of eolian dust accumulation in northwest african margin sediments provide important continuous records of past changes in atmospheric circulation and aridity in the region existing records indicate dramatic changes in north african dust emissions over the last 20 ka but the limited spatial extent of these records and the lack of high resolution flux data do not allow us to determine whether changes in dust deposition occurred with similar timing magnitude and abruptness throughout northwest africa here we present new records from a meridional transect of cores stretching from 311 nt o 191n along the northwest african margin by combining grain size endmember modeling with 230 th normalized fluxes for the first time we are able to document spatial and temporal changes in dust deposition under the north african dust plume throughout the last 20 ka our results provide quantitative estimates of the magnitude of dust flux changes associated with heinrich stadial 1 the younger dryas and the african humid period ahp 11 7 5 ka offering robust targets for model based estimates of the climatic and biogeochemical impacts of past changes in north african dust emissions our data suggest that dust fluxes between 8 and 6 ka were a factor of 5 lower than average fluxes during the last 2 ka using a simple model to estimate the effects of bioturbation on dust input signals we find that our data are consistent with abrupt synchronous changes in dust fluxes in all cores at the beginning and end of the ahp the mean ages of these transitions are 11 870 2 ka 1s and 4 970 2 ka respectively

impact of sulphur and trace element geochemistry on the utilization of a marine influenced coal case study from the south wales variscan foreland basin abstract incremental channel samples through two high volatile a bituminous coal seams the amman rider and bute seams below and above the vanderbeckei marine band at the westphalian a b boundary have been analysed using proximate petrographic inductively coupled plasma mass spectrometry icp ms x ray fluorescence xrf and scanning electron microscopy with energy dispersive x ray sem edx techniques the results show that both coals are vitrinite rich and indicate a similar history of palaeomire development with a period of falling water tables towards the middle plies of each seam mean sulphur contents in the coal with the marine roof the amman rider seam 4 19 wt are almost 4 times higher than in the coal with a non marine roof the bute seam 1 09 wt implying that high sulphur contents are derived from sea water sulphate in both coals sulphur is predominantly in the form of pyritic sulphur both syngenetic framboidal and euhedral crystals and epigenetic vein and cleat fill pyrite are present relatively constant levels of organic sulphur at around 2 have been recorded in the amman rider seam sulphur levels in the basal and top plies of each seam are at least twice that of the ply with the lowest sulphur content in the seam reflecting the stages in palaeomire development most strongly influenced by sulphate containing waters thorium uranium ratios are below 2 9 in the coal with a marine roof the amman rider seam indicating an enrichment of u from sea water most marked at the top and bottom of the seam the seam without a marine roof shows th u ratios between 2 5 and 4 9 indicating mild marine enrichment of u the concentrations of environmentally significant trace elements eses are correlated with either the ash or sulphur contents or both the correlation between s and pb as cu ni in the coal with a marine roof implies an origin of these eses from sea water and their mode of occurrence in sulphide minerals most eses in this coal are present at levels at least twice that of the global average in coals the exceptions being pb and zn which have concentrations less than half the global average by contrast the coal without a marine roof and with lower sulphur contents has most eses present at concentrations less than a third of the global average the exceptions being ni and cu diagenetic hydrothermal activity is documented in the middle ply of the coal with a marine roof this hydrothermal system redistributed the sulphur pb and as in this ply the principal utilization of bituminous coals in the south wales coalfield is as feed coals in power station boilers the resultant concentration of most eses in the solid residues from power plant coal combustion theoretically can be alleviated by careful blending of feed coals with low and high ese contents

influence of anthropogenic combustion emissions on the deposition of soluble aerosol iron to the ocean empirical estimates for island sites in the north atlantic the results of several recent studies challenge the reigning paradigm that continental soil dust provides the only significant atmospheric source of dissolved iron to the surface ocean this evidence includes correlations between the operational solubility of aerosol iron and atmospheric loadings of black carbon and aluminum normalized vanadium and nickel each of which are associated with emissions from the combustion of fossil fuel oil these observations suggest that the relative solubility of aerosol iron hence the eolian flux of soluble iron to the surface ocean may be significantly impacted by anthropogenic oil combustion products using recent field data from the bermuda region we have developed an empirical method to estimate the solubility of aerosol iron using bulk aerosol concentrations of fe v and al we apply this method to a large body of published data from the aeroce program for north atlantic island sites on tenerife barbados bermuda and ireland where the relative proportions of anthropogenic aerosols range from minor to major respectively our aerosol iron solubility estimates suggest that anthropogenic emissions contribute approximately 70 and 85 of the annual dry deposition of soluble iron to the surface ocean near bermuda and ireland respectively implying that human activities have profoundly affected the iron budget of the north atlantic region the annual mean dry deposition of soluble iron at barbados and izana is dominated by soil dust the anthropogenic contribution at these two sites ranges from 12 to 30 and is highly dependent on the soil dust solubility of fe employed in the model the low end 12 estimate appears to be more representative of these high dust sites

iron mineralogy and speciation in clay sized fractions of chinese desert sediments iron released from asian desert dust may be an important source of bioavailable iron for the north pacific ocean and thereby may stimulate primary productivity however the fe species of the fine dusts from this source region are poorly characterized here we investigate iron species and mineralogy in the clay sized fractions 2 m the size fraction most prone to long distance transport as dust samples were analyzed by sequential chemical extraction x ray diffraction and diffuse reflectance spectrometry our results show that fe dissolved from easily reducible iron phases ferrihydrite and lepidocrocite and reducible iron oxides dominated by goethite are 0 81 wt and 2 39 wt respectively and fe dissolved from phyllosilicates extracted by boiling hcl dominated by chlorite is 3 15 wt dusts originating from deserts in northwestern china particularly the taklimakan desert are relatively enriched in easily reducible fe phases probably due to abundant fe contained in fresh weathering products resulting from the rapid erosion associated with active uplift of mountains to the west data about fe speciation and mineralogy in asian dust sources will be useful for improving the quantification of soluble fe supplied to the oceans especially in dust models

the contrasting biogeochemistry of iron and manganese in the pacific ocean abstract vertical and horizontal distributions of dissolved and suspended particulate fe and mn and vertical fluxes of these metals obtained with sediment traps were determined throughout the pacific ocean in general dissolved fe is low in surface and deep waters 0 1 to 0 7 nmol kg with maxima associated with the intermediate depth oxygen minimum zone 2 0 to 6 6 nmol kg vertical distributions of dissolved mn are similar to previous reports exhibiting a surface maximum a subsurface minimum a mn maximum layer coincident with the oxygen minimum zone and lowest values in deep waters near shore removal processes are more intense for dissolved fe than for dissolved mn dissolved mn in the surface mixed layer remains elevated much farther offshore than dissolved fe elevated near surface dissolved mn concentrations occur in the north pacific equatorial current suggesting transport from the eastern boundary near surface mixed layer dissolved mn concentrations are higher in the north pacific gyre reflecting enhanced northern hemisphere aeolian sources residence time estimates for the settling of refractory paniculate fe and mn from the upper water column are 62 220 days fe and 105 235 days mn in contrast residence times for the scavenging of dissolved fe and mn are 2 13 years fe and 3 74 years mn scavenging residence times for dissolved mn based on horizontal mixing in the surface mixed layer of the northeast pacific are 0 4 years nearshore to 19 years 1000 km offshore there is no evidence for in situ fe redox dissolution within sub oxic waters in the eastern tropical north pacific dissolved fe appeared to be controlled by dissolution from sub oxic sediments with oxidative scavenging in the water column or upper sediment layers however in situ mn dissolution within the oxygen minimum zone was evident

atmospheric transport of mineral dust from the indo gangetic plain temporal variability acid processing and iron solubility atmospheric transport of chemical constituents from the indo gangetic plain igp to the bay of bengal is a conspicuous seasonal feature that occurs during the late ne monsoon december march with this perspective aerosol composition and abundance of mineral dust have been studied during november 2009 to march 2010 from a sampling site kharagpur 22 3 n 87 3 e in the igp representing the atmospheric outflow to the bay of bengal the chemical composition of pm2 5 suggests the dominance of nss so42 6 9 24 3 g m 3 whereas the abundance of mineral dust varied from 3 to 18 g m 3 the concentration of aerosol iron fetot and its fractional solubility fews fews fetot 100 where fews is the water soluble fraction of fetot varied from 60 to 1144 ng m 3 and from 6 7 to 26 5 respectively a striking similarity in the temporal variability of total inorganic acidity tia no3 nss so42 and fews provides evidence for acid processing of mineral dust alluvium during atmospheric transport from the igp the contribution of tia to water soluble inorganic species nss so42 no3 wsis mass ratios of ca al and fe al and abundance of dust and fews in the igp outflow are similar to the aerosol composition over the bay of bengal with the rapid increase in anthropogenic activities over south and south east asia the enhanced fractional solubility of aerosol iron attributed to acid processing of mineral dust has implications to further increase in the air sea deposition of fe to the ocean surface

iceberg hosted nanoparticulate fe in the southern ocean mineralogy origin dissolution kinetics and source of bioavailable fe abstract sediments from icebergs and glaciers contain nanopartculate fe iii oxyhydroxides including ferrihydrite which form in aqueous oxic micro environments where fe ii bearing rock minerals oxidise and high degrees of supersaturation are promoted by freezing and thawing an ascorbic acid extraction dissolves only labile fe present in fresh loosely aggregated ferrihydrite that is directly or indirectly bioavailable glacial and iceberg sediments contain ferrihydrite aggregates that provide 0 04 to 0 17 fe soluble in ascorbic acid rather larger than the concentrations in a limited suite of atmospheric dusts the dissolution behaviour of labile fe from glacial and iceberg sediments by ascorbic acid is controlled by the access of reactant or removal of solute through micropores to or from active sites in the interior of ferrihydrite aggregates a first order kinetic model is presented to examine the rates at which bioavailable fe can be supplied by melting icebergs in the weddell sea the model utilizes rate constants from the literature for the processes which solubilise fe from nanoparticulate ferrihydrite dissolution photochemical reduction and grazing and the processes that remove fe nanoparticulates sinking scavenging and incorporation in faecal material and render them less reactive transformation aging model results demonstrate that icebergs can supply bioavailable fe to the weddell sea by the dissolution of nanoparticulate ferrihydrite despite loss removal of nanoparticles by sinking aging transformation scavenging and incorporation into faecal pellets at rates that are comparable to atmospheric dust dissolution enhanced by photochemical reduction and grazing provides the most rapid rates of bioavailable fe production

quantification of crystalline mineral matter in some turkish coals using interactive rietveld based x ray diffractometry quantitative x ray diffractometry using a rietveld based computational method siroquant has been carried out for a series of coal samples from the various turkish mines standard proximate and ultimate analyses were carried out chemical compositions of the high temperature ash hta of coal samples were determined by x ray fluorescence xrf spectrometry technique crystalline mineral matter and amorphous content of raw coal samples were estimated the ca si al s and fe concentrations are higher than those of the other major elements ti mn mg na p k in the studied coal samples the percentage of crystalline mineral matter for each sample varies from 16 5 to 36 1 of the coal samples the minerals in the sampled coals consist mainly of quartz clay minerals calcite pyrite and gypsum percentages of crystalline mineral matter in ash content remarkably decrease for the elbistan orhaneli and tufanbeyli lower rank coals

atmospheric iron deposition in the northwestern pacific ocean and its adjacent marginal seas the importance of coal burning this study applied a regional air quality model incorporated with an emission module to quantitatively differentiate the atmospheric iron sources originating from lithogenic dusts or coal burning fly ashes deposited in the northwestern pacific ocean and its marginal seas particular attention was paid to the high iron content of fly ashes emitted from steel and iron plants burning coals using the year 2007 as an example the modeling results exhibit large seasonal variations in iron deposition with highest deposition fluxes occurred during spring and autumn which are comparable to the seasonal fluctuation of chlorophyll a concentrations estimated by satellite images in the oceanic regions fly ash from coal burning accounted for 7 2 of the total iron deposited over the northwestern pacific ocean and 15 of that over the northern south china sea after considering the difference of iron solubility in the aerosols anthropogenic aerosol associated with coal burning would be the major bioavailable iron source in the surface water of the oceanic regions

mineralogy as a critical factor of dust iron solubility 1 to understand the impact of dust deposition on ocean primary productivity the evaluation of dust input is not sufficient and the soluble iron supply is also needed measurements of iron in aerosols suggest a much higher solubility than in soil implying substantial atmospheric processing of chemical or physical nature here we have investigated the effect of the mineralogy on iron solubility we have measured iron solubility from some minerals commonly found in dust clay feldspar and iron hydr oxides firstly we observe a greater solubility of iron resulting from clays 4 in comparison to iron hydr oxides 1 independently of specific surface of minerals secondly by considering amount of dissolved iron and the mineralogical composition of dust our results indicate that dissolved iron fraction mainly comes from clay dissolution in contrast to that assumed in some biogeochemical models in consequence it appears that iron solubility is closely linked to the mineralogical composition of aerosol

orbital and sea level changes regulate the iron associated sediment supplies from papua new guinea to the equatorial pacific abstract iron fe supplied to the equatorial pacific are thought to play a critical role in marine biogeochemical cycle and the related air sea co2 flux previous studies have shown that papua new guinea png is a major fe contributor for the western equatorial pacific however key issues of this fe supply including the exact sources transport processes and distribution range remain unclear especially its long term variability associated with hydroclimatic and paleoceanographic changes using a set of cores collected offshore the northern png and from the ontong java plateau ojp shown to situate along the pathway of fe delivery by undercurrents here we compile high resolution records to explore how the fe associated sediment supplies varied and distributed on orbital time scale during the past 400 ka the chronologic frameworks of these cores are established by using 14c datings and stratigraphic correlations of foraminiferal 18o records and carbonate contents the sedimentary fe and clay mineral smectite in the offshore png sites show a prominent precession cycle in phase with the march insolation change at 5 s such precessional predominance suggests the control of local precipitation and river runoff on the offshore deposition of the fe associated sediment for the ojp sites the proxies derived from terrigenous detrital component give a spectral pattern however prevailed by 100 ka cycle with secondary precessional highs the significant 100 ka cycle can best be attributed to glacial interglacial changes in oceanic transports likely caused by sea level regulated variability in the strength and or route of the coastal undercurrents off png this variability may have influenced the long distance transport of fe rich particulates from the png to the ojp and further eastwards via the equatorial undercurrent

schwertmannite in wet acid and oxic microenvironments beneath polar and polythermal glaciers glacial and iceberg sediments contain nanoparticulates of schwert mannite ferrihydrite and goethite formed where pyrite was oxidized by dissolved oxygen in aqueous subglacial environments schwertmannite typically found in acid mine drainage only forms at low ph by the oxidative weathering of pyrite stoichiometric models show that these conditions can be created in closed system microenvironments containing at least 10 4 m dissolved oxygen where volume ratios of water pyrite are 105 to 106 ferrihydrite is the only product at higher and lower volume ratios in these microenvironments the oxidation of pyrite to form schwertmannite is possible in several decades schwertmannite and ferrihydrite are metastable in contact with water and are transformed to goethite in 100 yr unless preserved in ice the presence of these nanoparticulates demonstrates the existence of transient acidic and oxic aqueous microenvironments where enhanced biochemical and or geochemical activity occurs beneath glaciers and ice sheets

soluble iron inputs to the southern ocean through recent andesitic to rhyolitic volcanic ash eruptions from the patagonian andes patagonia due to its geographic position and the dominance of westerly winds is a key area that contributes to the supply of nutrients to the southern ocean both through mineral dust and through the periodic deposits of volcanic ash here we evaluate the characteristics of fe dissolved into soluble and colloidal species from volcanic ash for three recent southern andes volcanic eruptions having contrasting features and chemical compositions contact between cloud waters wet deposition and end members of andesitic hudson volcano and rhyolitic chaiten volcano materials was simulated results indicate higher fe release and faster liberation rates in the andesitic material fe release during particle seawater interaction dry deposition has higher rates in rhyolitic type ashes rhyolitic ashes under acidic conditions release fe in higher amounts and at a slower rate while in those samples containing mostly glass shards fe release was lower and faster the 2011 puyehue eruption was observed by a dust monitoring station puyehue type eruptions can contribute soluble fe to the ocean via dry or wet deposition nearly reaching the limit required for phytoplankton growth in contrast the input of fe after processing by an acidic eruption plume could raise the amount of dissolved fe in surface ocean waters several times above the threshold required to initiate phytoplankton blooms a single eruption like the puyehue one represents more than half of the yearly fe flux contributed by dust

late triassic compositional changes of aeolian dusts in the pelagic panthalassa response to the continental climatic change abstract the carnian pluvial event cpe is considered as the drastic environmental change that occurred in the western tethys during the carnian late triassic although some studies have suggested that the cpe was a global event no studies have referred to pelagic environment related to the cpe to reveal the pelagic environment during the carnian x ray absorption fine structure xafs analysis was used to determine the iron fe species in chert samples collected from the ladinian carnian strata in the tamba mino ashio belt japan the x ray absorption near edge structure xanes analysis shows that all the red cherts contain hematite with a combination of clay minerals such as illite chlorite and smectite the existence of these minerals is identified using extended xafs exafs the xanes analysis of the green and the white cherts does not show any hematite signatures while the exafs analysis indicated increasing amounts of chlorite the stratigraphic change in the fe bearing compositions observed in this study can be divided into three stages i a stage where a relatively stable mineral composition chlorite illite hematite is observed in cherts deposited during the early carnian julian ii the abrupt change in mineral composition lack of chlorite and appearance of smectite observed in the middle area in the studied section and corresponding to the middle part of carnian late julian early tuvalian and iii the recovery of the previous stable mineral composition during the late carnian tuvalian these variations in the mineralogical composition of pelagic cherts can be interpreted to mean that the continental climate conditions changed during the carnian and different clay fractions were delivered to the pelagic region these data combined with the results of previous studies performed around the continental realm can be interpreted as follows i there was a relatively stable dry climate before the cpe ii there were increasing amounts of precipitation owing to the cpe and iii the climate returned to dry conditions similar to those prior to the cpe

redox conditions and trace metal cycling in coastal sediments from the maritime antarctic abstract redox sensitive trace metals mn fe u mo re nutrients and terminal metabolic products no 3 nh 4 po 4 3 total alkalinity were investigated for the first time in pore waters of antarctic coastal sediments the results of this study reveal a high spatial variability in redox conditions in surface sediments from potter cove king george island western antarctic peninsula particularly in the shallower areas of the bay the significant correlation between sulphate depletion and total alkalinity the inorganic product of terminal metabolism indicates sulphate reduction to be the major pathway of organic matter mineralisation in contrast dissimilatory metal oxide reduction seems to be prevailing in the newly ice free areas and the deeper troughs where concentrations of dissolved iron of up to 700 m were found we suggest a combination of several factors to be responsible for the domination of metal oxide reduction over sulphate reduction in these areas these include the increased accumulation of fine grained material with high amounts of reducible metal oxides a reduced availability of metabolisable organic matter and an enhanced physical and biological disturbance by bottom water currents ice scouring and burrowing organisms based on modelled iron fluxes we calculate the contribution of the antarctic shelf to the pool of potentially bioavailable iron feb to be 6 9 103 to 790 103 t yr 1 consequently these shelf sediments would provide an feb flux of 0 35 39 5 mg m 2 yr 1 median 3 8 mg m 2 yr 1 to the southern ocean this contribution is in the same order of magnitude as the flux provided by icebergs and significantly higher than the input by aeolian dust for this reason suboxic shelf sediments form a key source of iron for the high nutrient low chlorophyll hnlc areas of the southern ocean this source may become even more important in the future due to rising temperatures at the wap accompanied by enhanced glacier retreat and the accumulation of melt water derived iron rich material on the shelf

the shelf to basin iron shuttle in the black sea revisited continental shelf sediments are a major source of iron fe for phytoplankton in surface waters in this study we investigate the mechanisms that control release of fe from shelf sediments and its lateral transport shuttling in oxic and hypoxic waters on the northwestern black sea shelf we find that at two coastal stations near the outflow of the danube river high input of organic matter drives strong reductive dissolution of fe oxyhydr oxides henceforth termed fe oxides in surface sediments supporting high rates of fe release to oxygenated bottom waters 0 36 mmol m 2 d 1 we suggest that bioirrigation plays a key role in the release of fe from these sediments at four stations further offshore organic matter deposition is lower resulting in limited mobilization of fe2 in the sediment and low benthic fluxes of fe 0 2 m in the lower part of the water column likely through repeated deposition and resuspension of fe oxides from surface sediments using synchrotron based x ray spectroscopy and sequential chemical extractions we demonstrate that the suspended matter and surface sediments are enriched in easily reducible fe oxides mostly ferrihydrite and fe associated with clay the mobilization of fe in the coastal zone and subsequent lateral transport of these fe bearing particles results in higher ratios of fe al in surface sediments at outer shelf stations ca 1 2 to 2 wt wt 1 than at coastal stations ca 0 5 to 0 9 wt wt 1 however below the sediment surface layer fe al ratios are similar at all stations indicating limited burial of the laterally transported fe our results highlight the critical role of organic matter input associated biological activity and riverine fe input as drivers of fe shuttling on continental shelves we also show that in shelf areas where sediments receive low inputs of organic matter physical transport controls the ultimate fate of the shuttled fe

beyond the black sea paradigm the sedimentary fingerprint of an open marine iron shuttle we present iron fe concentration and fe isotope data for a sediment core transect across the peru upwelling area which hosts one of the ocean s most pronounced oxygen minimum zones omzs the lateral progression of total fe to aluminum ratios fet al across the continental margin indicates that sediments within the omz are depleted in fe whereas sediments below the omz are enriched in fe relative to the lithogenic background rates of fe loss within the omz as inferred from fet al ratios and sedimentation rates are in agreement with benthic flux data that were calculated from pore water concentration gradients the mass of fe lost from sediments within the omz is within the same order of magnitude as the mass of fe accumulating below the omz taken together our data are in agreement with a shuttle scenario where fe is reductively remobilized from sediments within the omz laterally transported within the anoxic water column and re precipitated within the more oxic water below the omz sediments within the omz have increased 56fe 54fe isotope ratios relative to the lithogenic background which is consistent with the general notion of benthic release of dissolved fe with a relatively low 56fe 54fe isotope ratio the fe isotope ratios increase across the margin and the highest values coincide with the greatest fe enrichment in sediments below the omz the apparent mismatch in isotope composition between the fe that is released within the omz and fe that is re precipitated below the omz implies that only a fraction of the sediment derived fe is retained near shore whereas another fraction is transported further offshore we suggest that a similar open marine shuttle is likely to operate along many ocean margins the observed sedimentary fingerprint of the open marine fe shuttle differs from a related transport mechanism in isolated euxinic basins e g the black sea where the laterally supplied reactive fe is quantitatively captured within the basin sediments we suggest that our findings are useful to identify omz type fe cycling in the geological record

impact of anthropogenic combustion emissions on the fractional solubility of aerosol iron evidence from the sargasso sea we report empirical estimates of the fractional solubility of aerosol iron over the sargasso sea during periods characterized by high concentrations of saharan dust summer 2003 and by low concentrations of aerosols in north american maritime north atlantic air masses spring 2004 and early summer 2004 we observed a strong inverse relationship between the operational solubility of aerosol iron defined using a flow through deionized water leaching protocol and the total concentration of aerosol iron whereby the operational solubility of aerosol iron was elevated when total aerosol iron loadings were low this relationship is consistent with source dependent differences in the solubility characteristics of our aerosol samples and can be described by a simple mixing model wherein bulk aerosols represent a conservative mixture of two air mass end members that carry different aerosol types saharan air which contains a relatively high loading of aerosol iron 27 8 nmol fe m 3 that has a low fractional solubility 0 44 and north american air which contains a relatively low concentration of aerosol iron 0 5 nmol fe m 3 that has a high fractional solubility 19 historical data for aerosols collected on bermuda indicate that the low iron loadings associated with north american air masses are typically accompanied by elevated v al fe al and v mn mass ratios in the bulk aerosol relative to saharan dust which are indicative of anthropogenic fuel combustion products the identification of similar compositional trends in our sargasso sea aerosol samples leads us to suggest that the elevated solubility of iron in the aerosols associated with north american air masses reflects the presence of anthropogenic combustion products which contain iron that is readily soluble relative to iron in saharan soil dust we thus propose that the source dependent composition of aerosol particles specifically the relative proportion of anthropogenic combustion products is a primary determinant for the fractional solubility of aerosol iron over the sargasso sea this hypothesis implies that anthropogenic combustion emissions could play a significant role in determining the atmospheric input of soluble iron to the surface ocean

chemical and physical characteristics of iron oxides in riverine and glacial meltwater sediments abstract the speciation and grain size distribution of iron have been examined in several riverine and glacial sediments in order to evaluate controls on the concentrations and modes of occurrence of iron oxides in weathering derived particulates three operationally defined fractions have been recognised relating to the reactivity of iron towards dissolved sulphide 1 highly reactive iron fe hr consisting of ferric oxides 2 poorly reactive iron fe pr consisting of magnetite and some sheet silicate iron and 3 unreactive residual silicate iron fe u the finer fractions of each riverine and glacial suite are enriched in fe hr and usually also have higher fe hr fet ratios however coarser fractions may also have elevated fe hr contents and relationships of fe hr to both surface area and al indicate that iron oxides dominantly occur in association with the surfaces of aluminosilicate minerals which are common in finer grained fractions but may also be relatively enriched in coarser fractions a similar range of fe hr surface loadings is evident in the riverine and glacial meltwater suites from 0 6 to 1 8 mg fe m 2 for the riverine sediments and 0 5 to 1 5 mg fe m 2 for the glacial meltwater sediments despite wide variations in catchment bedrock lithology and climatic conditions significantly lower iron oxide loadings 0 1 mg fe m 2 were found in subglacial sediments most fe hr is closely associated with organic c although the latter occurs as blebs or smears rather than continuous coatings e g ransom et al 1997 ransom b bennett r h baerwald r shea k 1997 tem study of in situ organic matter on continental margins occurrence and the monolayer hypothesis mar geol 138 1 9 electron microscope observations show that iron oxides may occur as nanoparticulate 10 20 nm spheres at the edges of sheet aluminosilicate minerals as crystalline oxides infilling surface pits in coarser grained aluminosilicate minerals and occasionally as discrete crystalline oxides the similar occurrences of iron oxides in both riverine and glacial environments indicates that the delivery of reactive iron oxides to the oceans during glacial interglacial cycles will be affected by the masses and grain size characteristics of sediments delivered by glacial and riverine fluxes rather than by differences in iron mineralogy these delivery rates will be modified by behaviour of the oxide nanoparticles during transport from the continents

biogenic iron oxyhydroxide formation at mid ocean ridge hydrothermal vents juan de fuca ridge here we examine fe speciation within fe encrusted biofilms formed during 2 month seafloor incubations of sulfide mineral assemblages at the main endeavor segment of the juan de fuca ridge the biofilms were distributed heterogeneously across the surface of the incubated sulfide and composed primarily of particles with a twisted stalk morphology resembling those produced by some aerobic fe oxidizing microorganisms our objectives were to determine the form of biofilm associated fe and identify the sulfide minerals associated with microbial growth we used micro focused synchrotron radiation x ray fluorescence mapping mu xrf x ray absorption spectroscopy mu exafs and x ray diffraction mu xrd in conjunction with focused ion beam fib sectioning and highresolution transmission electron microscopy hrtem the chemical and mineralogical composition of an fe encrusted biofilm was queried at different spatial scales and the spatial relationship between primary sulfide and secondary oxyhydroxide minerals was resolved the fe encrusted biofilms formed preferentially at pyrrhotite rich fe1 xs 0 x 0 2 regions of the incubated chimney sulfide at the nanometer spatial scale particles within the biofilm exhibiting lattice fringing and diffraction patterns consistent with 2 line ferrihydrite were identified infrequently at the micron spatial scale fe mu exafs spectroscopy and mu xrd measurements indicate that the dominant form of biofilm fe is a short range ordered fe oxyhydroxide characterized by pervasive edge sharing fe o6 octahedral linkages double corner sharing fe o6 linkages which are common to fe oxyhydroxide mineral structures of 2 line ferrihydrite 6 line ferrihydrite and goethite were not detected in the biogenic iron oxyhydroxide bio the suspended development of the bio mineral structure is consistent with fe iii hydrolysis and polymerization in the presence of high concentrations of fe complexing ligands we hypothesize that microbiologically produced fe complexing ligands may play critical roles in both the delivery of fe ii to oxidases and the limited fe iii oxyhydroxide crystallinity observed within the biofilm our research provides insight into the structure and formation of naturally occurring microbiologically produced fe oxyhydroxide minerals in the deep sea we describe the initiation of microbial seafloor weathering and the morphological and mineralogical signals that result from that process our observations provide a starting point from which progressively older and more extensively weathered seafloor sulfide minerals may be examined with the ultimate goal of improved interpretation of ancient microbial processes and associated biological signatures

a critical look at iron paleoredox proxies new insights from modern euxinic marine basins enrichments in reactive iron occur under euxinic marine conditions that is where dissolved sulfide is present in the water column these enrichments result primarily from the export of remobilized iron from the oxic shelf which is scavenged from the euxinic water column during syngenetic pyrite formation and deposited in the underlying sediments strongly elevated ratios of highly reactive iron to total iron fehr fet and total iron to aluminum fet al and high degrees of pyritization dop are each products of this enrichment process these paleoredox proxies are among the most faithful recorders of ancient euxinia contrary to previous arguments iron enrichment is decoupled from biogenic sediment inputs but it does appear to be a uniquely euxinic phenomenon in other words we can rule out a major contribution from preferential physical transport of fehr rich detrital sediment to the deep basin which could also operate under oxic conditions furthermore enrichment via the shuttling of iron remobilized from oxic shelves appears to be limited by inefficient transport and trapping processes in deep oxic basins elevated fet al ratios in the euxinic sediments also cannot be a product of internal enhancement of the reactivity of the detrital iron pool without net fehr addition these conclusions are supported by observations in the modern black sea orca basin and effingham inlet fet al ratios are unambiguous recorders of paleoredox even in sediments that have experienced high degrees of metamorphic alteration however this study suggests that high siliciclastic accumulation rates can swamp the enrichment mechanism resulting in only intermediate dop values for euxinic sediments and fet al ratios that mimic the oxic shelf such dilution effects are well expressed in black sea basinal turbidites and rapidly accumulating muds on euxinic basin margins under conditions of persistent euxinia varying extents of fehr enrichment can illuminate spatial and temporal gradients in siliciclastic sedimentation the magnitude of enrichment is a function of the source shelf to sink ocean basin areal ratio suggesting that iron proxies can also record ocean scale paleoenvironmental properties through muted enrichments at times of very widespread euxinia for the first time manganese data are interpreted in light of the redox shuttle model as for the iron data the black sea orca basin and effingham inlet show enrichments in total manganese in the deep euxinic basin suggesting export from the suboxic porewaters of the oxic shelf and scavenging and burial in the basin the black sea data reveal iron and manganese enrichment across the broad deep euxinic basin suggesting efficient lateral transport and deep water mixing tied to the physical properties of the water column

phase mineral and chemical composition of composite samples from feed coals bottom ashes and fly ashes at the soma power station turkey abstract the phase mineral and chemical composition of feed coals fcs and their bottom ashes bas and fly ashes fas produced in the soma thermo electric power station tps turkey was characterized fcs are high ash soma subbituminous coals abundant in moisture and ca and depleted in s the inorganic composition in decreasing order of significance of fcs includes calcite quartz kaolinite illite muscovite chlorite plagioclase gypsum pyrite montmorillonite k feldspar dolomite siderite ankerite opal and volcanic glass the results for 57 elements studied show that ca nb cs v li have significantly higher contents in fc ashes than the respective clarke values for coal ashes the water soluble residues isolated from fcs include gypsum calcite inorganic amorphous matter ca mg na k phase and opal these residues are enriched in na se s b mg mo sr ca k the phase mineral composition of bas and fas includes mainly glass quartz char mullite plagioclase calcite and portlandite and to a lesser extent illite muscovite melilite hematite anhydrite lime cristobalite kaolinite and magnetite minor amounts of k feldspar dolomite ankerite fe spinel gypsum and ca k na phase also occur in bas and fas fas are enriched in inorganic matter glass cristobalite mullite fe oxides lime and anhydrite and depleted in mineral matter char quartz clay minerals melilite portlandite and carbonates in comparison with bas only se is significantly enriched in bas and fas compared to fc ashes most of the trace elements in particular as bi cd ge pb sn tl and w are more abundant in fas while bas are more enriched in ca cs fe ho mn p sc se and tb significant percentages 11 59 of elements initially present in fcs namely s sb sn ta mo bi zn ni na lu tm b were emitted by stack emissions and not captured by the cleaning equipment in the soma tps some genetic features properties possible environmental concerns and potential utilization directions related to fcs bas and fas are also discussed

atmospheric transport of iron and its deposition in the ocean the atmospheric transport of continental weathering products is responsible for much of the mineral material and fe entering the open ocean and is probably the dominant source of nutrient fe in the photic zone in regions where other nutrients are present in high concentrations the flux of fe from the atmosphere may be a limiting factor in primary productivity due to the larger source regions for dust north of the equator 8 times more atmospheric fe is deposited in the northern hemisphere than in the southern hemisphere the mineral aerosol and fe transport and deposition are highly variable due to the episodic nature of dust generation and its transport and deposition processes between 10 and 50 of the total atmospheric fe entering the world ocean appears to dissolve i e it will pass through a 0 4 m pore size filter rapidly when the mineral matter enters the ocean much of the atmospheric fe is present as fe ii apparently produced as a result of photochemical reduction reactions taking place during atmospheric transport this readily soluble fe ii should be available immediately for use as a nutrient by phytoplankton atmospheric transport from the continents is estimated to supply 3 times as much dissolved fe to the oceans as that delivered via rivers

aeolian input of bioavailable iron to the ocean 1 atmospheric deposition of mineral dust supplies much of the essential nutrient iron to the ocean presumably only the readily soluble fraction is available for biological uptake previous ocean models assumed this fraction was constant here the variable solubility of fe in aerosols and precipitation is parameterized with a two step mechanism the development of a sulfate coating followed by the dissolution of iron hydr oxide on the dust aerosols the predicted soluble fe fraction increases with transport time from the source region and with the corresponding decrease in dust concentration the soluble fraction is 1 percent near sources but often 10 40 percent farther away producing a significant increase in soluble fe deposition in remote ocean regions our results may require more rapid biological and physicochemical scavenging of fe than used in current ocean models we further suggest that increasing so2 emission alone could have caused significant fe fertilization in the modern northern hemisphere oceans

mineralogical speciation of elements in an eastern canadian feed coal and their combustion residues from a canadian power plant systematic changes in mineralogy enrichment and depletion of selected elements and mineralogical speciation of selected elements in fly ash and bottom ash samples from the lingan power plant were compared to run of mine and pulverized feed coal from the sydney coalfield nova scotia eastern canada the analytical techniques used were an electron microprobe equipped with energy and wavelength x ray dispersive spectrometers x ray diffraction neutron activation scanning electron microscopy with energy dispersive x ray and incident light petrography three types of glasses feo rich fe al si o rich and or al si o rich were identified in the combustion residues they were formed as a result of the interaction of melted pyrite and clay minerals compared to the feed coal most elements were enriched 10 to20 times in the fly ash the concentration of the elements in both the fly ash and bottom ash are comparable to coal ash that is generated by the low temperature asher in the laboratory some chalcophile elements such as arsenic and lead occurred as a solid solution in pyrite in the feed coal and were concentrated in the float fraction density 2 81 g cm3 of the fly ash with non crystalline fe oxides x ray mapping of arsenic in the fly ash and bottom ash indicates that arsenic was evenly distributed as oxide within the feo and fe al si o rich glass and crystalline phases in the fly ash possibly in solid solution arsenic is associated with feo and fes crystalline phases in the bottom ash

intensive mixing along an island chain controls oceanic biogeochemical cycles 1 the subarctic pacific is a high nutrient low chlorophyll hnlc region in which phytoplankton growth is broadly limited by iron fe availability however even with fe limitation the western subarctic pacific wsp has significant phytoplankton growth and greater seasonal variability in lower trophic levels than the eastern subarctic pacific therefore differences in fe supply must explain the west to east decrease in seasonal phytoplankton growth the fe flux to the euphotic zone in the wsp occurs at a moderate value in that it is significantly higher than its value on the eastern side yet it is not sufficient enough to cause widespread macronutrient depletion that is hnlc status is maintained although we recognize several fe supply processes in the wsp the mechanisms that account for this moderate value of fe supply have not previously been explained here we demonstrate the pivotal role of tidal mixing in the kuril islands chain kic for determining the moderate value a basin scale meridional fe section shows that fe derived from sediments in the sea of okhotsk is discharged through the kic into the intermediate water masses 800 m of the western north pacific the redistribution of this fe rich intermediate water by intensive mixing as it crosses the kic is the predominant process determining the ratio of micronutrient fe to macronutrients e g nitrate in subsurface waters this ratio can quantitatively explain the differences in surface macronutrient consumption between the western and eastern subarctic as well as the general formation and biogeochemistry of hnlc waters of the subarctic north pacific

ocean chemistry a matter of mineralogy iron can stimulate productivity in many regions of the world ocean but only if it exists in a readily dissolvable form chemical analyses of typical aerosol particles show that the mineralogy of iron containing particles largely determines their solubility

micro investigation of epica dome c bottom ice evidence of long term in situ processes involving acid salt interactions mineral dust and organic matter abstract the epica dome c ice core edc reached a final depth of 3260 m at a maximum height of about 15 m above the ice bedrock interface in december 2004 we present here data gained from a detailed investigation of selected samples of the deeper part of the core located below 3200 m and referred to as bottom ice this part of the core has been poorly investigated so far mainly because there are significant challenges in interpreting paleo records that were very likely modified by long term in situ processes our study combines high resolution ion chromatography high resolution synchrotron x ray micro fluorescence micro xrf scanning and transmission electron microscopy our aim was to identify the long term physico chemical processes at work close to the bedrock to determine how they have altered the initial registers and ultimately to extract information on the very ancient antarctic environment the ubiquitous presence of nanometer iron oxide crystals at the surface of wind borne dust aggregates containing also large amount of organic matter raises the possibility that the consolidation of windborne dust clusters formed during ice recrystallization could be related to microbial iron reduction and thus to the progressive reactivation of dormant bacterial activity in warming ice inclusions of size and number density increasing with depth observed in the 12 last meters 3248 3260 m contain liquid and solid species among them marine biogenic acids numerous wind borne dust aggregates and clusters of large reversible calcium carbonate particles precipitated once the inclusion was formed and often covered by secondary gypsum the refreezing of slush lenses is discussed as a potential cause of the formation of such heterogeneous and complex mixtures in addition to the very fine micrometer size minerals windborne from extra antarctic continental sources and often accreted in large aggregates single medium size particles a few to ca 20 m and among them organic debris are commonly encountered their size surface shape and mineralogy suggest that aerosol transport from antarctic ice free areas played a significant role at the time edc bottom ice was formed concentrations and concentration ratios of biogenic sulfur species also advocate for the strengthening of peri antarctic meteorological patterns that favor the inland penetration of disturbed flow carrying local material very large well preserved mineral particles several tens of micrometers in diameter and biotope relics in deeper ice close to 3260 m likely come from the sub glacial environment

the continental margin is a key source of iron to the hnlc north pacific ocean here we show that labile particulate iron and manganese concentrations in the upper 500m of the western subarctic pacific an iron limited high nutrient low chlorophyll hnlc region have prominent subsurface maxima between 100 200 m reaching 3 nm and 600 pm respectively the subsurface concentration maxima in particulate fe are characterized by a more reduced oxidation state suggesting a source from primary volcagenic minerals such as from the kuril kamchatka margin the systematics of these profiles suggest a consistently strong lateral advection of labile mn and fe from redox mobilized labile sources at the continental shelf supplemented by a more variable source of fe from the upper continental slope this subsurface supply of iron from the continental margin is shallow enough to be accessible to the surface through winter upwelling and vertical mixing and is likely a key source of bioavailable fe to the hnlc north pacific

iron species determination to investigate early diagenetic reactivity in marine sediments iron speciation was determined in hemiplegic sediments from a high productivity area to investigate systematically the early diagenetic reactivity of fe a combination of various leaching agents 1 m hci dithionite buffered in citrate acetic acid hf h2so4 acetic cr ii was applied to sediment and extracted more than 80 of total fe subsequent fe species determination defined specific mineral fractions that are available for fe reduction and fractions formed as products of fe diagenesis to determine the fe speciation of sheet silicates we explored an extraction procedure hf h2so4 and verified the procedure by application to standard rocks variations of fe speciation of sheet silicates reflect the possible formation of fe bearing silicates in near surface sediments the same fraction indicates a change in the primary input at greater depth which is supported by other parameters the fe ii fe iii ratio of total sediment determined by extractions was compared with mossbauer spectroscopy at room temperature and showed agreement within 10 m6ssbauer spectroscopy indicates the occurrence of siderite in the presence of free sulfide and pyrite supporting the importance of microenvironments during mineral formation the occurrence of other fe ii bearing minerals such as ankerite ca fe mg carbonate can be presumed but remains speculative

cycling of lithogenic marine particles in the us geotraces north atlantic transect in this paper we present describe and model the first size fractionated 0 8 51 m 51 m water column particulate trace metal results from the us geotraces north atlantic zonal transect in situ pumping survey with a focus on the lithogenic tracer elements al fe and ti this examination of basin wide full depth distributions of particulate elements elucidates many inputs and processes some for bulk lithogenic material others element specific which are presented via concentration distributions elemental ratios size fractionation dynamics and steady state inventories key lithogenic inputs from african dust north american boundary interactions the mediterranean outflow hydrothermal systems and benthic nepheloid layers are described using the refractory lithogenic tracer ti we develop a 1 d model for lithogenic particle distributions and test the sensitivities of size fractionated open ocean particulate ti profiles to biotically driven aggregation disaggregation rates vertical sinking speeds and dust input rates we discuss applications of this lithogenic model to particle cycling in general and to poc cycling specifically

geological controls on the mineralogy and geochemistry of the beypazari lignite central anatolia turkey abstract the raw coal from the cayirhan mine beypazari basin turkey contains an average of 28 5 mineral matter consisting up to 80 zeolites the coal seam is split by a 1 m thick tuffaceous siltstone into the upper first tv and lower second tb seams which contain essentially different zeolites the first seam contains ca rich zeolites clinoptilolite heulandite whilst the second seam contains na rich zeolites analcime experimental work has shown that a na rich activation solution will produce na rich zeolites when the original volcanic glass is na rich but will produce ca rich zeolites when the volcanic material is ca rich it is thought that a na rich activation solution derived from contemporaneous volcanics in the beypazari basin reacted with volcanic tuffs of different chemical composition to produce the vertical variability in the mineral matter of the two seams trace element analyses of the raw coal showed that they are enriched in as b cr ni and zr when compared to world wide averages of coal they are also enriched in the major elements na and k these elements are probably also derived from a volcanic source barium and sr show a clear affinity for analcime whilst li cr ni cu zn co and ga show a clear affinity for clinoptilolite heulandite trace elements showing a positive correlation with the organic matter are mn b be ge y zr nb hf w and u manganese u th sc ge and hree heavy rare earth elements show correlations with phosphate trace elements showing correlation with both fe and s contents are co mo ta pb and iree intermediate rare earth elements arsenic and v seem to have mixed affinities with sulphides and zeolites and organic matter and zeolites respectively although a proportion of the as b and s are retained in the ash during coal combustion due to the sorption mechanism of cao derived from the clinoptilolite heulandite decomposition significant emissions of these elements may arise from the cayirhan thermal power station due to the anomalously high concentrations of these elements in the beypazari coal the high total alkali metal content of these coals exceeds the recommended maximum for steam coal but it is believed that sodium occurring in a mineralogical form such as analcime is not as likely to contribute to boiler fouling as organically associated sodium

triggering conditions and mobility of debris flows associated to complex earthflows landslides on black marl slopes of the french alps are in most cases complex catastrophic failures in which the initial structural slides transform into slow moving earthflows under specific hydrological conditions these earthflows can transform into debris flows due to their sediment volume and their high mobility debris flow induced by landslides are far much dangerous than these resulting from continuous erosive processes a fundamental point to correctly delineate the area exposed to debris flows on the alluvial fans is therefore to understand why and how some earthflows transform into debris flow while most of them stabilize in this paper a case of transformation from earthflow to debris flow is presented and analysed an approach combining geomorphology hydrology geotechnics and rheology is adopted to model the debris flow initiation failure stage and its runout postfailure stage using the super sauze earthflow alpes de haute provence france as a case study the objective is to characterize the hydrological and mechanical conditions leading to debris flow initiation in such cohesive material results show a very good agreement between the observed runout distances and these calculated using the debris flow modeling code cemagref 1 d the deposit thickness in the depositional area and the velocities of the debris flows are also well reproduced furthermore a dynamic slope stability analysis shows that conditions in the debris source area under average pore water pressures and moisture contents are close to failure a small excess of water can therefore initiate failure seepage analysis is used to estimate the volume of debris that can be released for several hydroclimatic conditions the failed volumes are then introduced in the cemagref 1 d runout code to propose debris flow hazard scenarios results show that clayey earthflow can transform under 5 year return period rainfall conditions into 1 km runout debris flow of volumes ranging between 2000 to 5000 m 3 slope failures induced by 25 year return period rainfall can trigger large debris flow events 30 000 to 50 000 m 3 that can reach the alluvial fan and cause damage

solid phase arsenic speciation in aquifer sediments a micro x ray absorption spectroscopy approach for quantifying trace level speciation abstract arsenic as is a geogenic contaminant affecting groundwater in geologically diverse systems globally arsenic release from aquifer sediments to groundwater is favored when biogeochemical conditions especially oxidation reduction redox potential in aquifers fluctuate the specific objective of this research is to identify the solid phase sources and geochemical mechanisms of release of as in aquifers of the des moines lobe glacial advance the overarching concept is that conditions present at the aquifer aquitard interfaces promote a suite of geochemical reactions leading to mineral alteration and release of as to groundwater a microprobe x ray absorption spectroscopy xas approach is developed and applied to rotosonic drill core samples to identify the solid phase speciation of as in aquifer aquitard and aquifer aquitard interface sediments this approach addresses the low solid phase as concentrations as well as the fine scale physical and chemical heterogeneity of the sediments the spectroscopy data are analyzed using novel cosine distance and correlation distance hierarchical clustering for fe 1s and as 1s xas datasets the solid phase fe and as speciation is then interpreted using sediment and well water chemical data to propose solid phase as reservoirs and release mechanisms the results confirm that in two of the three locations studied the glacial sediment forming the aquitard is the source of as to the aquifer sediments the results are consistent with three different as release mechanisms 1 desorption from fe oxyhydr oxides 2 reductive dissolution of fe oxyhydr oxides and 3 oxidative dissolution of fe sulfides the findings confirm that glacial sediments at the interface between aquifer and aquitard are geochemically active zones for as the diversity of as release mechanisms is consistent with the geographic heterogeneity observed in the distribution of elevated as wells

dissolved iron distribution in the western and central subarctic pacific hnlc water formation and biogeochemical processes it is well known that phytoplankton growth is broadly limited by iron fe availability in the subarctic pacific to investigate which fe sources control the amplitude of seasonal variation in biogeochemical parameters in the subarctic pacific we examined the spatial variation in the west to east distribution of dissolved fe dfe across the western and central subarctic pacific through the japanese geotraces program the vertical section profile of the western subarctic pacific gyre showed high dissolved fe concentrations from the bottom of the surface mixed layer to as deep as approximately 3000 m suggesting that fe rich intermediate water is transported laterally and distributed across the western subarctic gyre over 2000 km the section data also indicate that the influence of the western fe rich intermediate water does not reach the alaskan gyre fe index dfe observed po4 observed rfe p distribution clearly indicates that the western fe rich intermediate water is well explained by external sedimentary fe sources and water transport systems from a subpolar marginal sea the sea of okhotsk and the continental margin the spatial pattern of fe to nutrient stoichiometry supplied from the intermediate water to the surface in comparison with reported fe and nutrient demand in surface phytoplankton quantitatively explains the differences in surface macronutrient consumption between the western and eastern gyre as well as the formation of the high nutrient and low chlorophyll region in the whole subarctic pacific

estuarine removal of glacial iron and implications for iron fluxes to the ocean while recent work demonstrates that glacial meltwater provides a substantial and relatively labile flux of the micronutrient iron to oceans the role of high latitude estuary environments as a potential sink of glacial iron is unknown here we present the first quantitative description of iron removal in a meltwater dominated estuary we find that 85 of dissolved fe is removed in the low salinity region of the estuary along with 41 of total dissolvable iron associated with glacial flour we couple these findings with hydrologic and geochemical data from gulf of alaska goa glacierized catchments to calculate meltwater derived fluxes of size and species partitioned fe to the goa iron flux data indicate that labile iron in the glacial flour and associated fe minerals dominate the meltwater contribution to the fe budget of the goa as such goa nutrient cycles and related ecosystems could be strongly influenced by continued ice loss in its watershed

iron mobilization in mineral dust can anthropogenic so2 emissions affect ocean productivity 1 for fe contained in long range transported aeolian dust to act as a micronutrient for oceanic phytoplankton it must be first dissolved or mobilized we propose that fe mobilization can occur in mineral dust from east asia by the incorporation of so2 into the advecting dust plumes and subsequent acidification of the dust through heterogeneous so2 oxidation to test this hypothesis we consider a dust plume that originated from the gobi deserts and advected over the pacific ocean data collected over the yellow sea confirm that this plume contained high concentrations of dust and so2 significant gaseous hno3 concentrations indicate that the dust particles were acidified i e ph 2 at these ph s 1 2 of the fe contained in a deliquescent mineral dust particle would be mobilized within 3 5 days these results suggest a possible link between the rate of c fixation in so called high nitrate low chlorophyll regions of the pacific ocean and so2 emissions from east asia

biolabile ferrous iron bearing nanoparticles in glacial sediments abstract glaciers and ice sheets are a significant source of nanoparticulate fe which is potentially important in sustaining the high productivity observed in the near coastal regions proximal to terrestrial ice cover however the bioavailability of particulate iron is poorly understood despite its importance in the ocean fe inventory we combined high resolution imaging and spectroscopy to investigate the abundance morphology and valence state of particulate iron in glacial sediments our results document the widespread occurrence of amorphous and fe ii rich and fe ii bearing nanoparticles in arctic glacial meltwaters and iceberg debris compared to fe iii rich dominated particulates in an aeolian dust sample fe ii is thought to be highly biolabile in marine environments our work shows that glacially derived fe is more labile than previously assumed and consequently that glaciers and ice sheets are therefore able to export potentially bioavailable fe ii containing nanoparticulate material to downstream ecosystems including those in a marine setting our findings provide further evidence that greenland ice sheet meltwaters may provide biolabile particulate fe that may fuel the large summer phytoplankton bloom in the labrador sea and that fe ii rich particulates from a region of very high productivity downstream of a polar ice sheet may be glacial in origin

instability conditions of marly hillslopes towards landsliding or gullying the case of the barcelonnette basin south east france abstract black marl hillslopes in the french alps are strongly affected either by mass movements or by gully erosion due to their susceptibility to weathering processes this paper presents experimental data geomorphological geotechnical geomechanical and hydrological on the parameters of the material of three well known earthflows and of the two stratigraphic parts of the callovo oxfordian black marl the main objectives are to define the geomechanical behaviour of the various formations using different characterisations grain size distribution mineralogy retention capacity consolidation test direct shear test and triaxial test and to demonstrate how such soils can affect the stability of natural slopes particular care must be taken when interpreting the geomechanical tests on this evolving and very heterogeneous clay rich material there are strong relationships between the parent rock and the landslide materials this paper presents a conceptual model of the development of strength over a period of time and investigates the parameters of the material for use in slope stability analysis and risk assessment

mineralogical composition of african dust delivered by red rains over northeastern spain the african dust deposition mineralogy source regions and influence on rain chemistry were analyzed for a site in the montseny mountains catalonia northeastern spain for the period august 1 1983 through august 1 1994 dust deposition was highly variable two events collected on november 9 11 1984 and march 22 25 1991 accounted for 62 of the total dust input in the 38 red rain events recorded in the period the average annual dust deposition was 5 3 g m 2 se 2 6 three source regions in the african continent were identified with back trajectory analysis 1 western sahara 2 moroccan atlas and 3 central algeria events from the moroccan atlas predominated in terms of number of events amount of rainfall and dust deposition the meteorological situations during red rains were identified western sahara events occurred principally with a depression at high latitudes 50 n forming a trough in the north atlantic moroccan atlas events occurred with a depression in front of portugal and events from central algeria were associated with a depression over spain or north africa by order of abundance median of n 13 the minerals identified in the dust by x ray diffraction were as follows illite quartz smectite palygorskite kaolinite calcite dolomite feldspars differences in mineralogy between source regions were significant for smectite kaolinite quartz and dolomite smectite and kaolinite content was highest in the algerian events while quartz and dolomite content was lowest events from the moroccan atlas had the lowest smectite and kaolinite the red rain soluble chemistry was clearly influenced by the dissolution of calcite high alkalinity calcium concentration and basic ph and by marine components high na cl arid mg 2 concentrations because of the very alkaline character of red rains they had a strong weight on the annual mean ph of rainwater this was reflected by the significant relationship r 0 71 p 0 01 between the percentage of annual precipitation as red rain and annual mean precipitation ph red rains provided 25 45 of the annual dissolved input of the major ions in precipitation and 34 of the calcium required for holm oak quercus ilex l forest growth at the study site

water masses and currents in the upper tropical northeast atlantic off northwest africa recent current measurements in the tropical eastern north atlantic reproduce the components of the large scale flow field however the observations as well as the 1 12 flame model computations indicate that a lot of eddy scale variability is superimposed on the mean flow field despite of the disturbance by variability the signature of the guinea dome is well present in november 2002 the guinea dome transport from direct observations was about 2 8 sv above 25 8 kg m3 and 4 sv between 25 8 and 27 1 kg m3 the oxygen minimum in the shadow zone comprises the central water and the antarctic intermediate water aaiw layers and is located between the equatorial current system and the north equatorial current the north equatorial counter and undercurrents at 3 to 6 n are major oxygen sources for the central water layer of the low oxygen regions in the northeastern tropical atlantic a second northern north equatorial countercurrent nnecc band exists at 8 to 10 n the nnecc carries oxygen rich water from the southern hemisphere eastward but with an admixture of water from the northern hemisphere a float at 200 m depth was spreading eastward in the north equatorial undercurrent neuc at 28 w it shifted northward into the nnecc and then was trapped in the guinea dome region for more than 3 years the model indicates the region 22 to 32 w as the area of exchange between the necc neuc and the nnecc bands in the aaiw layer the northern intermediate countercurrent acts as oxygen source for the oxygen minimum zone

mineralogy and geochemistry of feed coals and their combustion residues from the cayirhan power plant ankara turkey abstract a total of 48 samples feed run of mine coals and their combustion residues fly ash and bottom ash were systematically collected twice a week over a 4 week period june 1998 from two boiler units i and ii of the cayirhan power plant 630 mw that burns zeolite bearing coals of late miocene age the feed coals are high in moisture 22 8 as received content and ash 44 9 yield and total s content 5 1 and low in calorific value 2995 kcal kg the mineralogy of the feed coals contains unusually high contents of the zeolites clinoptilolite heulandite and analcime which are distributed within the organic matter of coal other minerals determined are gypsum quartz feldspar pyrite dolomite calcite cristobalite and clays common minerals in the crystalline phase of the combustion residues are anhydrite feldspar quartz hematite lime and ca mg silicate minor and trace amounts of magnetite cristobalite maghemite gehlenite calcite and clinoptilolite heulandite are also present in the combustion residues trace element contents of the feed coals except for w fall within the estimated range of values for most world coals however the mean values of mn ta th u and zr are near maximum values of most world coals elements such as as bi ge mo pb tl w and zn are enriched more in the fly ash compared to the bottom ash