metal contents of phytoplankton and labile particulate material in the north atlantic ocean abstract phytoplankton contribute significantly to global c cycling and serve as the base of ocean food webs phytoplankton require trace metals for growth and also mediate the vertical distributions of many metals in the ocean we collected bulk particulate material and individual phytoplankton cells from the upper water column

controls on the cadmium phosphate relationship in the tropical south pacific the relationship between dissolved cadmium cd and phosphate po4 3 can elucidate a biological role for cd in the ocean and help to evaluate the usefulness of cd as a tracer of past ocean circulation and nutrient distributions here we determine and analyze this relationship in the poorly studied region of the tropical south pacific the dissolved cd distribution is generally similar to po43 but a plot of cd versus po43 shows a clear concavity resulting from distinct cd po43 ratios in waters local to our transect and in waters formed distally in higher latitudes to determine the factors affecting the subsurface cd po43 ratio along our transect we used an ocean circulation model and a multilinear regression model to determine the preformed and regenerated components of dissolved cd and po43 we found that both the preformed and regenerated cd po43 ratios are low in the shallow locally formed water masses along the transect and significantly higher in the deeper and older water masses overall the regenerated preformed cd po43 ratio in the deep waters 1 000 m along our transect is 1 8 1 reflecting the basin wide average cd po43 fractionation factor during biological uptake however we find a lower fractionation factor in local waters of 1 1 0 6 we suggest that this locally lower biological fractionation factor is due to either the chemical speciation of cd or to a lower efficiency of cd assimilation by the picoplankton and nanoplankton species found in our study region

the search for fullerenes in rocks from the ries impact crater since their discovery fullerenes have been reported from various geological environments one group of these findings has been related to bolide impacts e g the sudbury crater and the k t and p t boundaries impact rocks of the ries crater germany including samples of suevites metamorphosed crystalline clasts and glass bombs have been collected in the otting altebrg and seelbronn quarries no fullerenes in concentrations above 1 ppb have been found in analyzed samples laser desorption time of flight mass spectrometry ld tof ms confirmed the absence of fullerenes in the analyzed samples these results support the concept that the ries impactor was a stony meteorite

limited impact of eolian and riverine sources on the biogeochemical cycling of cd in the tropical atlantic we present coupled cadmium cd concentrations and cd isotopic compositions expressed as 114cd in seawater profiles along the northeast southwest geotraces ga11 section in the tropical atlantic ocean the ga11 section encompasses three contrasting regions including the amazon river plume the north african dust plume and the guinea dome oxygen deficient zone odz given the long oceanic residence time of cd 104 to 105 yr local inputs such as atmospheric and riverine sources are generally considered to be of little importance for the open ocean cd budget and the limited cd isotope dataset available thus far has prevented any unambiguous conclusions on the importance of these processes the ga11 section is ideally located for assessing the influence of external natural and anthropogenic riverine and eolian inputs as well as internal processes on the cd mass balance in the tropical atlantic ocean as in previous cd isotope studies this dataset documents that both surface consumption regeneration of micronutrients within the water column and deep water mass mixing exert the prime control on the cycling of cd however we do observe some near surface samples with lower than expected 114cd signatures along the western section of the transect surface waters sampled at the margin of the amazon freshwater plume show no resolvable difference in cd and 114cd compared to waters outside of the plume suggesting that the amazon river is not an important source of cd to the open ocean although the eastern ga11 transect is directly downwind of the saharan dust plume atmospheric cd deposition accounts for 1 of the inferred upwelling flux indicating that atmospheric inputs to the surface north atlantic ocean even within the main saharan dust plume only have a relatively minor influence on the cd budget in the subsurface tropical atlantic 100 200 m water depth there is a clear deviation from a tight linear cd po4 correlation toward lower cd concentrations for a given po4 concentration our new cd data show that this cd po4 decoupling is likely a feature of the entire tropical atlantic and may possibly reflect po4 enrichment via preferential re mineralization of organically bound phosphorus alternatively the decoupling may arise from subsurface cd depletion caused by precipitation of cd sulphide within sinking organic particulate microenvironments as has been suggested in recent studies

cadmium chemical tracer of deepwater paleoceanography the oceanic distribution of cadmium resembles that of phosphorus because the cadmium content of foraminiferal shells is governed by the cadmium content of seawater planktonic and benthic fossil shells can be used to infer nutrient distributions within ancient oceans empirical studies demonstrate that cadmium in benthic foraminiferal shells is related to the bottom water composition through a proportionality constant d 2 9 this constant is the same for each of the species studied cibicidoides wuellerstorfi cibicidoides kullenbergi nuttallides umbonifera and uvigerina spp downcore cadmium data from high quality pacific and atlantic sediment cores suggest that the cadmium inventory of the ocean did not change significantly between the most recent glacial maximum and the present hence changes in the cadmium content of fossils at a site directly reflect changes in nutrient distributions due to altered oceanic circulation patterns studies of cadmium in pleistocene sediments show that deep ocean circulation patterns were significantly different during the most recent glacial maximum in the western north atlantic ocean the nutrient content of waters from 2500 to 3500 m was twice as high during glacials as during interglacial periods signifying an increase in the proportion of waters of antarctic origin in this depth interval and a decrease but not a cessation in the flux of north atlantic deep waters through this depth range below 3500 m the nutrient increase was greater indicating a higher proportion of antarctic bottom water above 2500 m the nutrient content was lower during glacial periods than it has been during interglacial times the cd content of high latitude north atlantic and southern ocean surface waters does not show a significant glacial interglacial change which argues against theories for changes atmospheric carbon dioxide that require changes in high latitude nutrient concentrations

occurrence of natural fullerenes in low grade metamorphosed proterozoic shungite from karelia russia abstract we report on the occurrence of fullerenes in proterozoic shungite 2 ga from the shungite mine kondopoga karelia russia 62 12 n 34 17 e the presence of fullerenes has been confirmed by mass spectrometry with peaks at 360 and 720 amu atomic mass unit powder x ray diffraction showing ten diffraction peaks corresponding to the fullerite structure with a 1 4201 5 nm and 13 c nuclear magnetic resonance nmr spectroscopic studies showing a peak at 143 2 ppm in the kondopoga shungite mine fullerenes occur in silty shales that have experienced greenshist facies metamorphism

origins of fullerenes in rocks this article is a technical comment and author response to the the discovery of naturally occuring fullerenes in shunga rock samples the commenting researchers did not find detectable amounts of fullerenes in a variety of carbon rich rocks they hypothesize that the fullerenes found in the shunga sample were probably a localized event the original researchers buseck and tsipursky provide a rebuttal with further comments including parallels to other minerological occurences all agreed that more data are needed 10 refs

biogeochemical cycling of cadmium isotopes along a high resolution section through the north atlantic ocean abstract cadmium cd is a bioactive trace element in the oceans with a nutrient like distribution that closely matches dissolved phosphate seawater dissolved stable cd isotope ratios 114cd are a relatively new parameter which show much promise for furthering our understanding of the biogeochemical cycling of cd in the oceans here we present a high resolution paired section of dissolved cd concentrations and dissolved 114cd from 21 open ocean stations along the us geotraces ga03 transect through the north atlantic ocean dissolved cd concentrations along the section are strongly influenced by water mass distribution and the cycling of cd the highest dissolved cd concentrations 400 540 pmol kg 1 are associated with antarctic sourced water masses whilst biological uptake in the surface ocean results in a strong vertical gradient in dissolved cd towards the surface reaching as low as 0 03 pmol kg 1 in western surface waters dissolved 114cd is also characterized by a vertical gradient from 0 2 in the deep ocean to 2 to 5 in the cd depleted surface ocean relative to nist srm 3108 this variability in 114cd can be ascribed to mixing of antarctic and north atlantic water masses together with fractionation due to in situ biological uptake of light cd in the very surface ocean subtle deviations from this overall pattern of dissolved cd concentration and dissolved 114cd are observed within low oxygen waters off north africa where a dissolved cd deficit relative to phosphate is associated with higher dissolved 114cd values together with elevated particulate cd and ba this suggests that cd sulfide precipitation is occurring within the water column of the north atlantic constituting a potentially important sink for isotopically light cd additionally the first measurements of dissolved 114cd within a hydrothermal plume at the mid atlantic ridge show that cd is scavenged from the dissolved phase leaving the remnant dissolved cd isotopically heavier constraining the significance of these marine sinks for dissolved cd is important not only for our understanding of the marine biogeochemical cycling of cd in the modern oceans but also for the successful application of the microfossil cd ca proxy and the development of 114cd as a tracer for past ocean biogeochemical cycling

testing for fullerenes in geologic materials oklo carbonaceous substances karelian shungites sudbury black tuff comment and reply reply buseck et al s 1992 1 discovery of fullerenes in fractures in a shungite sample enclosed in diabase from russian karelia has been followed by several substantiating reports see buseck 2002 2 p 785 as well as by conflicting reports e g ebbesen et al 1995 3 mossman et al

water mass analysis for the u s geotraces ga03 north atlantic sections we present the distributions of hydrographic properties potential temperature salinity dissolved oxygen and micromolar level inorganic macronutrients along two sections occupied in the subtropical north atlantic as part of the first u s geotraces ga03 survey during 2010 and 2011 the purpose of this work is to place subsequent papers in this special issue in a general context and to provide a framework in which the observed distributions of trace elements and isotopes can be interpreted using these hydrographic properties we use a modified optimum multiparameter water mass analysis method to diagnose the relative contributions of various water types along the sections and rationalize their distributions the water mass compositions appear largely consistent with what is understood from previous studies about the large scale circulation and ventilation of the north atlantic with perhaps one exception we found that the north atlantic deep water both east and west of the mid atlantic ridge is more strongly influenced by iceland scotland overflow water relative to denmark straits overflow water about 3 1 than inferred from other tracer studies typically 2 1 it remains unclear whether this is an artifact of our calculation or a real change in deep water composition in the decades between the determinations

cadmium regeneration within the north atlantic cadmium cd incorporated into the benthic microfossils has been widely used in reconstructing the past water circulation in the north atlantic this requires a major control by conservative mixing over regeneration process on the seawater cadmium distribution in the north atlantic through coupling the recently reported cd data at depths below 300 m with quantitative water mass analysis along the ga03 transect we tested two models for cadmium cycling within the north atlantic conservative mixing alone and conservative mixing plus regeneration which is termed as regenerative mixing the results show that the regenerative mixing model reproduces the observations slope 0 99 and r2 0 97 much better than the conservative mixing model slope 0 99 and r2 0 88 the regenerative mixing model was applied to estimate the amount of dissolved cadmium regenerated within the north atlantic this regionally regenerated cadmium contributes to 10 and 50 of the total cadmium in the north atlantic at depths 1000 m and 300 1000 m respectively indicating that the microfossil reconstructed seawater cd can be attributed to the mixing from the south atlantic to the north atlantic with high accuracy for depths below 1000 m while within 300 1000 m cadmium is more controlled by the regeneration process than the mixing process complicating the attribution of the microfossil reconstructed seawater cd to the changes in water mass geometry within this 300 1000 m depth range a regionally and vertically constant cd po43 regeneration ratio 262 pm mol kg was derived from the regenerative mixing model which is comparable with ratios estimated in the recent studies for the north atlantic

deep water mass geometry in the glacial atlantic ocean a review of constraints from the paleonutrient proxy cd ca 1 paleonutrient proxies currently provide the strongest constraints on the past spatial distribution of deep water masses we review the state of knowledge derived from the trace metal proxy cd ca for the atlantic ocean during the last glacial maximum lgm we compile published benthic foraminiferal cd ca data supplemented with new data to reconstruct meridional cd sections through the holocene and lgm atlantic holocene cd ca reflects the modern water masses north atlantic deep water nadw antarctic bottom water aabw and antarctic intermediate water aaiw reasonably well except for anomalously high values in the intermediate to mid depth far north atlantic lgm cd ca clearly shows that nadw was replaced by the shallower glacial north atlantic intermediate water gnaiw with significant northward expansion of aabw the boundary level between gnaiw and aabw was very abrupt occurring between 2200 and 2500 m modern water depth combined cd ca and cibicidoides d 13 c data allow us to also calculate the air sea signature of d 13 c d 13 cas the lgm atlantic can be explained entirely by mixing between high d 13 cas gnaiwand low d 13 cas aabw negative d 13 cas values in glacial aabw were likely caused by poor ventilation during formation probably associated with extensive sea ice coverage overall our knowledge base would benefit from improved data coverage in the south atlantic and southern ocean and a better understanding of ancillary effects on the cd ca proxy itself

cadmium zinc copper and barium in foraminifera tests the concentrations of cadmium zinc copper and barium have been determined on 2 mg samples of single species foraminifera populations cleaning techniques were tested using north atlantic core tops and followed by a detailed downcore study for the last 30 000 years in south atlantic core v22 174 raw foram tests cleaned by crushing followed by ultrasonic removal of fine grained material and dissolved in a ph 5 5 acetate buffer contain appreciable amounts of trace elements associated with ferromanganese and alumino silicate contaminants a reductive complexing cleaning treatment reduces ferromanganese contamination by 1 2 orders of magnitude acetate buffers at ph 5 5 complex iron and raise the solubility of ferromanganese oxides these buffers are unsuitable for separating carbonate lattice bound trace elements from the fraction associated with ferromanganese phases improved mechanical and ultrasonic reductive cleaning combined with a mild dissolution in distilled water under 1 atm pco2 reduces contaminant levels another order of magnitude the cd and zn concentrations order 10 8 mole cd mole ca and 10 5 mole zn mole ca of species with low surface area show an increase with decreasing isotopic temperatures this increase is consistent with the increasing concentrations of these metals from low values in surface waters to higher values at depth the variance of cd and zn over the last 30 000 years in the central south atlantic is consistent with the probable variability of the dissolved trace elements at the calcification levels of the species analyzed cu and ba are irreproducible and probably sensitive to residual contaminant phases the trace element content of the tests differs from levels observed in a recent coprecipitation study foraminifera may be a significant vector in zinc cycling in the ocean

the distributions of helium isotopes and tritium along the u s geotraces north atlantic sections geotraces gao3 abstract we present the distributions of helium isotopes in the form of helium isotope ratio anomaly relative to the atmospheric ratio and tritium along two sections occupied in the subtropical north atlantic as part of the first u s geotraces survey geotraces ga03 the general distributions of these isotopes are consistent with the continuing penetration and evolution of bomb produced tritium and its daughter isotope 3 he in the main thermocline and along the western boundary current system we combine these two distributions to compute a tritium 3 he age which is related to the elapsed time since the water was at the ocean surface although it is an indicator biased by the effects of mixing and influenced by the time history and spatial distribution of bomb tritium delivery to the ocean surface it still remains a useful measure of ventilation time scales aside from the continued propagation of the tritium 3 he transient into the ocean interior there are three notable features of interest in these distributions the first is the clear signature of upwelling in the water column near the coast of mauritania characterized by the upward bowing of isochrones in the thermocline and discernable 3 he excess at the ocean surface a simple 3 he mass balance calculation suggests an upwelling flux of order 1 8 10 6 m 3 s 1 1 8 sv along the mauritanian coast the second is a mid depth 1500 2000 m core of ventilated waters centered over the mid atlantic ridge an anticyclonic circulation of waters likely originating in the labrador sea the third notable feature is a volcanic 3 he plume at about 3500 m depth emanating from the tag hydrothermal area that is detectable as much as 500 km away on each side of the mid atlantic ridge we estimate a 3 he heat ratio of 7 10 18 mol j 1 and a 3 he flux from the tag site of 15 mmol y 1 since 3 he is a conserved tracer in the absence of measureable tritium the correlation of volcanic 3 he with other hydrothermally influenced teis e g fe can be used as a dilution tracer as probe of non conservative behavior in the water column also since the regional and global fluxes of volcanic 3 he are known the correlations can be used as a regional global flux gauge for hydrothermal input of those teis

processes controlling the distributions of cd and po4 in the ocean depth profiles of dissolved cd and po4 from a global data compilation were used to derive the cd p of particles exported from the surface layer and the results indicate lowest values in the north atlantic 0 17 0 05 highest in the southern 0 56 0 24 and intermediate in the south indian 0 31 0 14 and north pacific 0 36 0 08 ocean basins the cd p of exported particles in high nutrient low chlorophyll hnlc regions is twice that for particles exported in non hnlc regions as is the fractionation effect during biological uptake of cd and po4 and these trends primarily determine the spatial trends of dissolved cd po4 observed in the surface ocean in deep waters the lowest dissolved cd po4 of 0 23 0 07 is found in the north atlantic ocean and the result primarily of low cd po4 of north atlantic deep water 0 23 in contrast deep waters in the southern ocean have significantly higher dissolved cd po4 0 30 0 06 which is a result of the cd po4 of upwelled deep water from the south pacific and south indian 0 28 and the high cd p of degrading particles a multibox model that accounts for the impacts of particle degradation and thermohaline circulation in the deep sea yields dissolved cd and po4 interbasin trends close to observations model experiments illustrate the dependence of the dissolved cd po4 of the deep sea on the extent of hnlc conditions in the southern ocean and the impact on reconstructing paleo po4 concentrations from a cd proxy

cadmium in the north atlantic implication for global cadmium phosphorus relationship abstract dissolved cadmium cd distribution was determined in the tropical subtropical north atlantic along geotraces ga03 section us geotraces 2010 and 2011 cruises a pronounced mid depth cd maximum extends from the productive tropical eastern north atlantic where subsurface waters in the upper themocline are depleted in dissolved oxygen at this cd maximum cd depletion relative to phosphate po4 is observed in the cd vs po4 plot but the relative cd depletion is not present in the plot of cd po4 ratio vs depth the apparent relative cd depletion at the cd maximum appears to reflect a depth dependent variation of cd po4 ratio commonly observed in the world ocean such depth dependent variation of cd po4 ratio may result from the regeneration of cd from cd poor particulate organic carbon poc in the upper ocean and from cd rich poc in the deep ocean the vertical cd regeneration may lead to the observed difference in deep water cd po4 ratio between the north atlantic and north pacific if cd to phosphorus ratio in the poc flux to the deep ocean is higher in the pacific than in the atlantic

testing for fullerenes in geologic materials oklo carbonaceous substances karelian shungites sudbury black tuff comment and reply the presence of low concentrations of fullerenes has been reported from numerous terrestrial and meteoritic sources buseck 2002 1 in a recent paper mossman et al 2003 2 present mass spectra of carbonaceous substances using laser desorption ionization ldi and high resolution electron

black carbon in soils and sediments analysis distribution implications and current challenges this review highlights the ubiquity of black carbon bc produced by incomplete combustion of plant material and fossil fuels in peats soils and lacustrine and marine sediments we examine various definitions and analytical approaches and seek to provide a common language bc represents a continuum from partly charred material to graphite and soot particles with no general agreement on clear cut boundaries formation of bc can occur in two fundamentally different ways volatiles recondense to highly graphitized soot bc whereas the solid residues form char bc both forms of bc are relatively inert and are distributed globally by water and wind via fluvial and atmospheric transport we summarize chronologically the ubiquity of bc in soils and sediments since devonian times differentiating between bc from vegetation fires and from fossil fuel combustion bc has important implications for various biological geochemical and environmental processes as examples bc may represent a significant sink in the global carbon cycle affect the earth s radiative heat balance be a useful tracer for earth s fire history build up a significant fraction of carbon buried in soils and sediments and carry organic pollutants on land bc seems to be abundant in dark colored soils affected by frequent vegetation burning and fossil fuel combustion thus probably contributing to the highly stable aromatic components of soil organic matter we discuss challenges for future research despite the great importance of bc only limited progress has been made in calibrating analytical techniques progress in the quantification of bc is likely to come from systematic intercomparison using bcs from different sources and in different natural matrices bc identification could benefit from isotopic and spectroscopic techniques applied at the bulk and molecular levels the key to estimating bc stocks in soils and sediments is an understanding of the processes involved in bc degradation on a molecular level a promising approach would be the combination of short term laboratory experiments and long term field trials

lizardite versus antigorite serpentinite magnetite hydrogen and life the serpentinization of peridotite operates according to one or the other or a combination of two end member mechanisms in low temperature environments 50 300 c where lizardite is the predominant serpentine mineral olivine is consumed by reaction with h2o but its composition mg remains unchanged mg rich lizardite magnetite and dihydrogen gas brucite are products of the reaction at higher temperatures 400 600 c rates of mgfe diffusion in olivine are orders of magnitude faster with the result that the growth of mg rich antigorite can be accommodated by a compositional adjustment of olivine eliminating the need to precipitate magnetite and evolve hydrogen this latter end member mechanism probably best reflects the situation in the forearc mantle wedge

the relationship between cadmium and phosphate in the atlantic ocean unravelled abstract cadmium cd is not generally considered a nutrient element but behaves like a nutrient in the oceans and might play an important role in ocean biology after all the relationship between cd and the nutrient phosphate po4 has been studied for over 40 yrs but the debate on the driving mechanism and reason behind the kink a change in the steepness of the slope is ongoing using new data of high accuracy and spatial resolution covering the west atlantic ocean from north to south in combination with a robust extended optimum multiparameter eomp water mass model we show that mixing between different water masses is the dominant factor explaining the observed correlation and its kink regeneration of cd via remineralisation explains the smaller scale variability notably in the surface ocean observations imply the availability of cd in surface waters determines the cd uptake and thus the cd po4 remineralisation ratio this ratio is variable between different ocean regions notably between the northern and southern high latitude oceans due to their role in deep water formation both the northern and southern high latitude oceans are a driving factor in the atlantic and global cd and po4 relation outside the atlantic ocean the classical kink is not expected but the relationship is by no means linear most likely this is due to the interaction between low latitude surface waters and subsurface waters from high latitude origin but more data are required to assess this in detail

effect of cadmium sulphide precipitation on the partitioning of cd isotopes implications for the oceanic cd cycle abstract the biogeochemical cycling of cadmium cd and its isotopes in the surface ocean is dominated by biological uptake into phytoplankton while regeneration of the sinking particulate cd governs the shapes of cd profiles in the deeper ocean additionally the water mass circulation plays an important role in the redistribution of cd and its isotopes superimposed on this general cycle it has recently been argued that cadmium sulphide cds precipitation can occur in oceanic oxygen deficient zones odz this has been proposed to account for the decrease in cd po4 ratios and the positive cd isotope excursion in seawater compared to sinking particles to assess whether cds precipitation results in a fractionation of cd isotopes we performed cadmium sulphide precipitation experiments under controlled low oxygen conditions in low pure water and high ionic strength synthetic seawater water with variable reaction times and cadmium sulphide ratios enrichment in light cd isotopes is systematically observed in the precipitated cds phase in agreement with recent ab initio simulations of isotope effects associated with cd speciation in aqueous solution our experimental results follow a closed system rayleigh fractionation model with the fractionation factor cdsol cds for 112cd 110cd decreasing with increasing salinity from 1 00026 for pure water to 1 00014 for a salinity twice that of modern seawater indicating a salinity control on the magnitude of cd isotope fractionation we propose that this fractionation varying with salinity is controlled by isotope equilibrium between the various cd aqueous species present in solution with preferential involvement of free cd2 ion in cds formation the magnitude of cd isotope fractionation in seawater cdsol cds 1 00016 determined in our study is in accord with the cd isotope shift observed in modern oceanic odz and attributed to removal by cds our experiments show that cds precipitation could have significant local impact on the cycling of cd and further demonstrates the utility of cd isotopes as tracers of the sequestration of cadmium into sulphides in restricted euxinic basins such as the black sea

search for extractable fullerenes in clays from the cretaceous tertiary boundary of the woodside creek and flaxbourne river sites new zealand abstract when fullerenes were first discovered to form spontaneously in condensing carbon vapors kroto et al 1985 it was suggested that they might be widely distributed in the universe searches for fullerenes in meteorites see devries et al 1993 were unsuccessful but c 60 and c 70 were reported to occur on earth in samples of shungite a meta anthracite from a deposit near shunga russia buseck et al 1992 and in fulgurite a substance formed when lightning strikes certain soils or rocks daly et al 1993 the occurrence of fullerenes in shungite is particularly surprising since fullerene synthesis in the laboratory has always involved gas phase chemistry at temperatures over 1000 c such conditions may be attained during lightning strikes but shungite is believed to have formed from carbonaceous material creeping into fissures of a precambrian rock which metamorphosed under extreme pressures if the original carbonaceous material did not already contain fullerenes perhaps from wildfires they must have formed during the metamorphism by as yet unknown solid or liquid phase mechanisms

north atlantic thermohaline circulation during the past 20 000 years linked to high latitude surface temperature during a surface cooling event 10 000 to 12 000 years ago higher cd ca and lower 13c 12c ratios are observed in benthic foraminifera shells from rapidly accumulating western north atlantic sediments data from sediment cores show that marked nutrient depletion of intermediate waters occurs in association with reduced glacial north atlantic deep water flux it is proposed that cold high latitude sea surface temperatures enhance intermediate water formation at the expense of deep water formation

non rayleigh control of upper ocean cd isotope fractionation in the western south atlantic abstract we present seawater cd isotopic compositions in five depth profiles and a continuous surface water transect from 50 s to the equator in the western south atlantic sampled during geotraces cruise 74jc057 ga02 section leg 3 and investigate the mechanisms governing cd isotope cycling in the upper and deep ocean the depth profiles generally display high e 112 110 cd at the surface and decrease with increasing depth toward values typical of antarctic bottom water aabw however at stations north of the subantarctic front the decrease in e 112 110 cd is interrupted by a shift to values intermediate between those of surface and bottom waters which occurs at depths occupied by north atlantic deep water nadw this pattern is associated with variations in cd concentration from low surface values to a maximum at mid depths and is attributed to preferential utilization of light cd by phytoplankton in the surface ocean our new results show that in this region cd deficient waters do not display the extreme highly fractionated e 112 110 cd reported in some earlier studies from other oceanic regions instead in the surface and subsurface southwest sw atlantic when cd drops below 0 1 nmol kg 1 e 112 110 cd are relatively homogeneous and cluster around a value of 3 7 in agreement with the mean value of 3 8 3 3 2sd n 164 obtained from a statistical evaluation of the global ocean cd isotope dataset we suggest that cd deficient surface waters may acquire their cd isotope signature via sorption of cd onto organic ligands colloids or bacterial picoplankton extracellular functional groups alternatively we show that an open system steady state model is in good accord with the observed cd isotope systematics in the upper ocean north of the southern ocean the distribution of e 112 110 cd in intermediate and deep waters is consistent with the water mass distribution with the north south variations reflecting changes in the mixing proportion of nadw and either aabw or aaiw depending on the depth overall the sw atlantic cd isotope dataset demonstrates that the large scale ocean circulation exerts the primary control on e 112 110 cd cycling in the global deep ocean

impact of end member mixing on depth distributions of δ13c cadmium and nutrients in the n atlantic ocean abstract the po 4 13 c and cd depth distributions measured in the n atlantic ocean during recent geotraces and clivar cruises are a result of biological and circulation processes with in situ uptake and remineralization of organic matter dominating in the upper 300 m and mixing of water masses dominating in the thermocline and deep sea the observed slopes of the no 3 po 4 preindustrial 13 c po 4 and by analogy cd po 4 along isopycnals deviate significantly from that expected from redfield in the thermocline and deep sea and in each case the observed slope is similar to the slopes of the end member water masses being mixed the depth increase in the cd po 4 slope resulting from end member mixing explains the observed kink at 1 m po 4 in the cd po 4 relationship in the n atlantic the observation that the po 4 preindustrial 13 c cd relationship in the modern n atlantic is heavily influenced by end member mixing throughout most of the water column complicates the use of 13 c and cd as proxies of the paleocean s nutrient distribution because changes in the po 4 13 c cd composition of locally and remotely produced end members water masses would change the po 4 13 c and cd depth distributions in the paleo n atlantic ocean

deep atlantic ocean carbon storage and the rise of 100 000 year glacial cycles over the past three million years earth s climate oscillated between warmer interglacials with reduced terrestrial ice volume and cooler glacials with expanded polar ice sheets these climate cycles as reflected in benthic foraminiferal oxygen isotopes transitioned from dominantly 41 kyr to 100 kyr periodicities during the mid pleistocene 1 250 to 700 kyr ago ka because orbital forcing did not shift at this time the ultimate cause of this mid pleistocene transition remains enigmatic here we present foraminiferal trace element b ca cd ca and nd isotope data that demonstrate a close linkage between atlantic ocean meridional overturning circulation and deep ocean carbon storage across the mid pleistocene transition specifically between 950 and 900 ka carbonate ion saturation decreased by 30 mol kg 1 and phosphate concentration increased by 0 5 mol kg 1 coincident with a 20 reduction of north atlantic deep water contribution to the abyssal south atlantic these results demonstrate that the glacial deep atlantic carbon inventory increased by approximately 50 gt during the transition to 100 kyr glacial cycles we suggest that the coincidence of our observations with evidence for increased terrestrial ice volume reflects how weaker overturning circulation and southern ocean biogeochemical feedbacks facilitated deep ocean carbon storage which lowered the atmospheric partial pressure of co2 and thereby enabled expanded terrestrial ice volume at the mid pleistocene transition deep atlantic carbon storage increased and the meriodional overturning circulation weakened at the mid pleistocene transition to 100 000 year glacial interglacial cycles according to analyses of foraminifera trace elements and nd isotopes

geological fullerenes review and analysis abstract fullerenes have been reported from numerous terrestrial and meteoritic sources but only at low concentrations the occurrences are associated with localized energetic events such as lightning impacts of extraterrestrial objects and wildfires great interest has also been generated by a series of papers that report noble gases with anomalous isotopic compositions encapsulated within fullerenes in spite of all of the published work many unresolved questions remain about the identity and formation of fullerenes in geological environments