a high temperature hydrothermal deposit on the east pacific rise near 7 n abstract a seabeam survey of the east pacific rise epr led to the selection of several sites having structural characteristics favorable for hydrothermal activity dredging of such an area located at 7 n on the epr resulted in the recovery of sulfides oxides and fresh basalt chemical analyses and isotopic compositions showed that the recovered pyrites were probably precipitated directly from hot vent hydrothermal waters chemical analyses and isotopic composition of manganese iron oxides indicated that they too were of hydrothermal origin 210 pb pb measurements yielded ages of 90 10years for the deposits this site may still be undergoing hydrothermal activity

advances in marine chemistry 1979 1982 these four years saw advances in many areas further developments in sampling and analytical techniques have opened new avenues of exploration for trace elements and particulate matter the impact of the geosecs expedition was further felt in the field of marine chemistry as the results were still being published a major field effort occurred as a follow on to the geosecs work tto and intensive sampling was performed in the newly discovered submarine hydrothermal vent fields an important and unresolved controversy has arisen regarding the ability to measure preformed co2 in the seawater system in many respects the field of marine chemistry appears to be gaining a momentum spurred by both improvements in analytic techniques and an increasing social and economic relevance

budgets and behaviors of uranium and thorium series isotopes in santa monica basin sediments abstract nine natural decay series isotopes were measured in six box cores collected from a transect across the santa monica basin the 210 pb derived sedimentation rate decreases from 80 mg cm 2 yr at the slope to 20 mg cm 2 yr in the deep central basin sediment mixing prevails in sites underlying oxic waters but is subdued in the anoxic deep basin below the sill depth uranium contents in sediments are controlled by levels of authigenic u which are higher in the more reduced condition in the deep basin most of the authigenic u results from precipitation within the sediments the 232 th 228 th disequilibrium in sediments indicates that 228 ra is lost from the sediments from a depth of 10 cm upward modelling the distribution of excess 228 th and 234 th in the surficial layers of the deep basin sediments results in a mean sediment mixing coefficient of 0 2 cm 2 yr and a sedimentation rate close to that based on 210 pb there is no evidence of changing sedimentation rate in the central basin during the past century fluxes of excess 210 pb 230 th and 231 pa to the central santa monica basin sediments are much higher than what can be predicted from local supply advective input of open ocean waters coupled with enhanced scavenging of these reactive nuclides at the ocean margin is considered to be the primary cause

the application of uranium series disequilibrium concepts to sediment yield determination the determination of uranium series disequilibria in fluvial environments is proposed as a method of calculating catchment mass balances the technique is based on two main principles firstly 234u is more mobile than 238u especially during the early stages of weathering secondly uranium is far more mobile than either thorium or protactinium consequently teaching during weathering results in the loss of the uranium found in the fresh rock leaving the two immobile daughters behind the ratio of uranium carried by sediment to that dissolved us uw can therefore be determined from river water and sediment isotopic activity ratios fluxes of uranium can then be calculated from average concentrations in the water and the associated sediment from which a sediment yield can be inferred the witham catchment in lincolnshire has been used to test the proposed method a us uw ratio of between 5 and 7 is determined and a sediment yield of 2 51 2 12 tonnes yr 1 km 2 is proposed although some problems concerning environmental chemistry have arisen the validity of the approach is confirmed by the close correspondence between the results obtained and those inferred by earlier workers using more conventional methods

uranium and thorium isotopes in marine sediments off northeastern taiwan uranium and thorium isotopes have been determined on seven box cores collected aboard r v ocean researcher i within the lower continental slope area off northeast taiwan during may 1991 the goals are to obtain the downcore u and th concentrations and their isotopic compositions in the area and to evaluate their possible source s transport and deposition u 238 contents of the box cores are fairly uniform at about 1 3 dpm g ranging between 0 9 and 1 6 dpm g u 234 has activities between 1 2 and 2 dpm g with an average of 1 4 dpm g th 232 contents are also quite uniform at about 3 2 dpm g th 230 has values roughly between 1 5 and 2 3 dpm g averaging at 1 9 dpm g th 228 is essentially equal to th 232 in activity except for the very surface sediments where th 228 appears to be slightly higher than th 232 the u and th contents of the shale slate and black schist from taiwan are about 1 9 and 3 2 dpm g respectively with a uth ratio of 0 6 th 232 in the cored sediments has similar activities but u 238 has activities lower by about 0 6 dpm g on the average if these crustal rocks have provided their weathered debris or particles as sediments to the cored area then u 238 must have lost by about this amount or 30 in transit by dissolution into the seawater as th 230 in the cores has an average activity identical to the u 238 activity of the crustal rocks mentioned above secular equilibrium between u 238 u 234 and th 230 must have been established when the rocks were exposed to weathering and erosion and no net th 230 gain or loss occurred in transit thus both th 232 and th 230 have probably been retained by the detrital particles which form the cored sediments the excess th 230 defined as the th 230 in excess over the u 234 in activity is about 0 5 dpm g however this excess may be fictitious because it is probably caused by dissolution of uranium from the terrigenous particles in transit rather than scavenging of th 230 from the water column by these particles as the th 230 production from u 234 decay in the water column can only account for 2 12 of the calculated excess th 230 a reasonable explanation is that all the th 230 observed in the cores has been of detrital origin with little authigenic contribution from the water column the th 230th 232 activity ratios are quite constant at about 0 6 for both the cored sediments and the above mentioned crustal rocks suggesting that thorium has not been leached out in transit to final deposition this is further supported by the fact that identical activity ratio has also been observed in the settling particulates collected by traps deployed in the same area the th 228th 232 activity ratios are close to unity except for the top few centimeters where the ratios are greater than unity due to the th 228 derived from ra 228 decay in the water column under rapid deposition the penetration depth for this th 228 excess is about 4 cm which is consistent with the prediction based on the known sedimentation rates of about 0 3 0 5 cm yr

preservation of particulate non lithogenic uranium in marine sediments particulate non lithogenic uranium pnu excess u above detrital background levels found in marine particulate matter is formed in surface waters throughout the ocean previous studies have shown that pnu is regenerated completely prior to burial of particles in sediments within well oxygenated open ocean regions however the fate of pnu has never been examined in ocean margin regions or in anoxic basins here we evaluate the preservation of pnu in ocean margin sediments and within semi enclosed basins using samples from sediment traps deployed at multiple depths and surface sediments organic carbon fluxes at the sediment trap locations ranged from 0 1 to 4 3 g cm 2 kyr while the dissolved oxygen concentration in the water column ranged from 3 mt o 270 m preservation of pnu increases with decreasing dissolved oxygen concentration approaching 100 preservation at oxygen concentration 25 m pnu contributes as much as 40 to 70 of the total authigenic u in sediments in the santa barbara basin and seasonally anoxic saanich inlet and some 10 to 50 of the total authigenic u in sediments off the central california margin copyright 2002 elsevier science ltd

fluxes of uranium and thorium series isotopes in the santa barbara basin abstract samples from the manop santa barbara basin sediment trap intercomparison were analyzed for the isotopes of uranium thorium radium lead and polonium all of the traps showed approximately the same compositions and isotopic ratios indicating that they trapped similar materials the234th flux via falling particles was very close to the flux predicted from the production and scavenging rates of234th from the water column the210pb content of the trapped particles and the surface sediments were the same however the measured flux of210pb was seven times greater than the predicted flux predicted and measured fluxes of228th and210po were similarly out of balance to explain this apparent inconsistency we suggest as others have done that the santa barbara basin is an area where scavenging from the water column is intensified and where sediments deposited initially on the margins may be physically remobilized on a short time scale these two effects increase the apparent area from which the basin derives the longer lived isotopes but does not increase significantly the supply of the short lived234th

sources of land derived runoff to a coral reef fringed embayment identified using geochemical tracers in nearshore sediment traps geochemical tracers including ba co th 7be 137cs and 210pb and magnetic properties were used to characterize terrestrial runoff collected in nearshore time series sediment traps in hanalei bay kauai during flood and dry conditions in summer 2006 and to fingerprint possible runoff sources in the lower watershed in combination the tracers indicate that runoff during a flood in august could have come from cultivated taro fields bordering the lower reach of the river land based runoff associated with summer floods may have a greater impact on coral reef communities in hanalei bay than in winter because sediment persists for several months during dry periods sediment carried by the hanalei river appears to have been mobilized primarily by undercutting of low 7be low 137cs riverbanks composed of soil weathered from tholeiitic basalt with low ba and co concentrations following a moderate rainfall event in september high 7be sediment carried by the hanalei river was probably mobilized by overland flow in the upper watershed ba desorption in low salinity coastal water limited its use to a qualitative runoff tracer in nearshore sediment 210pb had limited usefulness as a terrestrial tracer in the nearshore due to a large dissolved oceanic source and scavenging onto resuspended bottom sediment 210pb scavenging does however illustrate the role resuspension could play in the accumulation of particle reactive contaminants in nearshore sediment co and 137cs were not affected by desorption or geochemical scavenging and showed the greatest potential as quantitative sediment provenance indicators in material collected in nearshore sediment traps

postdepositional enrichment of uranium in sediment from the bering sea abstract deep sea sediments were collected from the northern north pacific and the bering sea and separated into hcl soluble and hcl insoluble fractions these sediments were analyzed for their uranium and thorium concentrations and 234 u 238 u activity ratios by alphaspectrometry the mean concentration of total uranium in the oxic northern north pacific sediment was relatively low 1 25 ppm and showed little variation with sediment depth the concentration of total uranium in the surface sediment of the bering sea basin was also low 0 85 ppm similar to those of the northern north pacific sediment but it was higher 2 36 ppm in the strongly reducing sediment below 40 cm this increase in uranium concentration with depth is ascribed to higher quantities of hcl soluble uranium it is suggested that uranium diffuses through interstitial water and is postdepositionally precipitated during early diagenesis in the subsurface reducing environment a postdepositional precipitation rate of uranium in the bering sea basin sediment was estimated to be 28 g cm 2 103 yr 1 in the reducing bering sea basin sediment the concentration of total uranium in the layers enriched in manganese carbonate was 1 68 ppm which was slightly less than that of the other normal deep layer this depletion of uranium may be due to dilution with volcanic material of coarser texture

a sediment trap intercomparison study in the santa barbara basin four sediment traps of radically different design were deployed in the santa barbara basin for approximately 45 days the measured fluxes ranged from 370 to 774 g m 2 yr 1 for the different designs these values lie within flux measurements previously determined for the basin compared to the 25 year record 920 g m 2 yr 1 however all fluxes determined in this experiment are somewhat low because this experiment was conducted during a general period of high storm activity and runoff measurement of greater than average flux was expected it is probable that the higher flux recorded by the sediments results from a significant input of detritus into the basin by near bottom transport the chemical composition of trapped material was nearly identical in all four trap designs the deep cone design however had a significantly lower mn content since this trap was the only one in which reducing conditions were produced in the sample container reduction and mobilization of manganese after collection is believed to have occurred in spite of the very different designs tested the factor of two agreement in flux determination and the compositional similarity of the material collected is encouraging for future attempts to directly measure the flux of particulates in the ocean

anomalous isotopic concentrations in the sea off southern california measurements are reported of the 10be concentrations in 15 sediments from the sea off southern california the sedimentation patterns are modelled with a two component system one component having the high 10be concentration of pelagic sediment and the other the low concentration of continental runoff the pelagic component brought to the region by the california current with the pacific ocean as reservoir is very likely the source not only of anomalously high 10be deposition but also of similar effects with 2101pb 239 240pu and 241pu

210pb scavenging in the north atlantic and north pacific oceans the radionuclide210pb shows significant geographic variations in the extent of its removal from the open ocean water column this texture of scavenging is defined by mapping 1 the integrated deficiency of210pb in the water column relative to its supply from the atmosphere and from in situ decay of dissolved226ra and 2 inventories of excess210pb in deep sea sediments the ratio of210pb deficiency to its supply termed the scavenging effectiveness is 20 in the north equatorial pacific and 50 in the north atlantic this variation is related to the combined effects of uptake of210pb onto sinking particles and lateral transport of210pb to areas of more intense removal sediment inventories of excess210pb normalized to the210pb deficiency in the overlying water column permit evaluation of the relative importance of these effects in the north equatorial pacific virtually all of the210pb removed from the water column is present in the underlying sediments but in the mid latitude north atlantic the sediments comprise only about 50 of the210pb removed the deficiencies of210pb in the mid latitude north atlantic sediments south of 50 n are qualitatively offset by surpluses in high latitude sediments north of 50 n higher primary productivity and new production in the surface waters of the high latitude north atlantic and north equatorial pacific relative to the oligotrophic central north atlantic may account for the greater fluxes of210pb to bottom sediments in those areas

the geochemistry of plutonium in fresh and marine water environments abstract the chemical behaviour of plutonium in the hydrosphere is a subject of both great practical and intrinsic importance the production and eventual disposal of pu and other artificial radionuclides dictates that this be the case the main objective of this paper is to provide a synthesis and critical examination of currently published data and interpretations on the geochemistry of pu in natural waters and sediments where appropriate an attempt is made to reinterpret published data with the aim of establishing the relationships between geochemical and biological processes and the distribution concentration and speciation of pu particular attention is paid to the question of the potential for the chemical remobilization of pu from the solid to the aqueous phase approximately one third of the text deals with freshwaters mostly lakes while two thirds discusses the estuarine coastal and open ocean environments

influence of boundary scavenging and sediment focusing on 234th 228th and 210pb fluxes in the santa barbara basin abstract sediment trap samples were collected from the santa barbara basin to examine the flux of 234 th 228 th and 210 pb mean ratios of measured to predicted fluxes are 2 10 and 21 for 234 th 228 th and 210 pb respectively boundary scavenging may supply a portion of all three radionuclides however sediment focusing supplies additional 228 th and 210 pb but little 234 th sediment temporarily deposited on the shelf around the basin contains little excess 234 th due to its short half life 228 th and 210 pb fluxes to the sediments in the santa barbara basin are several times greater than predicted from their supply in the overlying water column these enhanced fluxes require lateral transport of 228 th and 210 pb to the basin through boundary scavenging and sediment focusing 234 th flux is poorly correlated with 228 th and 210 pb fluxes because individual radionuclide sources to the basin differ i e water column production boundary scavenging and or sediment focusing correlations between 228 th and 210 pb fluxes are high due to the strong influence of sediment focusing on both radionuclides there is a strong correlation between both the 228 th and 210 pb flux and total mass flux and lithogenic flux but a weak correlation with the other major sediment components e g organic carbon carbonate and biogenic opal in the santa barbara basin a large fraction of the total mass flux is lithogenic material 50 80 hence the strong correlation between 228 th and 210 pb fluxes and both total mass and lithogenic fluxes 234 th flux is poorly correlated with total mass and major sediment component fluxes

a three dimensional time dependent approach to calibrating sediment trap fluxes we conducted an experiment to test explicitly the accuracy of upper ocean sediment trap fluxes using the particle reactive radionuclide 234th t1 2 24 1 days two independent vertex style multitrap arrays were used for collection of sinking particles at 95 m and 97 m depths over a four day period in may 1992 at the u s joint global ocean flux study bermuda atlantic time series study bats site samples for total 234th were collected every 8 m between the surface and 96 m and immediately combined for analysis to obtain the vertically integrated activity of 234th we collected a total of 27 samples over the four day period the234th samples were collected daily at each of the two traps and every other day on a 6 6 km grid to characterize the entire source region for particles collected in the traps in situ flow sensors at one trap array indicated low horizontal shear at the trap mouth 5 10 cm s compared to normal values at bats the predicted 234th flux from the watercolumn profiles was not significantly different from zero 30 140 disintegrations per minute m2 d the measured trap 234th flux at both arrays was significantly higher 290 15 dpm m2 d we hypothesize that upper ocean traps at bermuda may overcollect during low flux periods and undercollect during high flux periods thus recording a biased signal of the true particle flux

transuranic nuclides in two coastal marine sediments off peru the fluxes of plutonium isotopes as well as their depth profiles are similar for northern and southern hemispheric varved sediments taken off western american coasts the inventories are in excess of the values predicted for atmospheric fallout in these anoxic sediments there is a general increase in concentration from depths to the near surface these observations are explainable on the bases that anoxic deposits have a substantially higher retentivity of sedimented materials compared to that of their bioturbated oxic counterparts and that there are inputs of resuspended materials previously deposited in the marine environment the 241am distributions are explained by ingrowth from 241pu assuming a substantial input of the parent from the u s thermonuclear tests during the 1950 s and the immobilization of both pu and am in the deposits

southern california inner basin sediment trap calibration the deployment of particle interceptor traps pits in the three inner basins of the southern california bight santa barbara santa monica and san pedro where preserved laminated bottom sediments occur provides a natural calibration between the parameters determined with the pits and those derived from the historical sedimentary deposits the accumulation rates and chemical composition of the pit materials compare favorably with these recently deposited bottom sediments the ratio of the measured particle collection rate to the sediment accumulation rate for these three basins averaged0 93 0 20 radionuclide 210pb 228th 232th and trace element fe cu zn cd pb compositions of the pit materials and surface sediments agree within generally 30 in each basin an application of pits as a sampling system in an outer basin san nicolas where the sedimentary record has been obscured by bioturbation is also presented to further demonstrate the utility of pits for spatial and temporal studies of various aspects of particle transport and sediment deposition based on the calibration of the pits in the three inner basins we conclude from the comparison of the radionuclide and trace element compositions between the pit materials and surface sediments from the san nicolas basin that recently deposited sedimentary material has been mixed by bioturbation with older material from the last several hundred years excess210pb and the228th 232th activity ratio in the pit material are 6 and 15 times higher than in the surface sediment total pb and1n hno3 leachable pb are 4 and 8 fold higher in the pit material

mixing and cycling of uranium thorium and 210pb in puget sound sediments abstract activity profiles of excess 234 th excess 210 pb 232 th 230 th 234 u and 238 u and 228 232 th ratios determined in eight box cores of sediment from six sites in central puget sound provide new insights into the dynamic nature of solid phase mixing in surface sediments the exchange of 228 ra and other soluble species across the sediment water interface and the cycling of u th and 210 pb in this coastal zone comparison of excess 234 th inventories in sediments with its production rate in the overlying water column indicates a mean residence time of at most 14 days for particles in the central puget sound water column surface sediment horizons with excess 234 th have no excess 228 th which might be used to ascertain sediment accumulation rates over the past decade instead deficiencies of 228 th due to loss of soluble 228 ra from pore water to the overlying water persist to 20 30 cm revealing that exchange of soluble chemicals between pore and overlying waters reaches these depths in the extensively bioturbated sediments of puget sound solid phase u isotope concentrations tend to increase by up to a factor of two with depth in sediments as a result of dissolved u being biologically pumped down into sediments where it is partially removed when conditions become mildly reducing 232 th and 230 th activities and 230 232 th ratios are constant with depth in sediments indicating constant detrital phase compositions and essentially no authigenic 230 th steady state 210 pb depositional activities in and fluxes to puget sound sediments average only about onehalf those for sediments of the open washington coast north of the columbia river mouth primarily because of a much lower supply of dissolved 210 pb in sea waters adverting into puget sound excess 234 th profiles in sediments reveal much more detail about the depth dependency dynamic nature and recent history of solid phase mixing processes than excess 210 pb profiles at least six of eight 234 th profiles show that mixing within the 210 pb defined surface mixed layer is depth dependent in three profiles 234 th derived mixing rates are fastest several centimeters below the sediment water interface indicating greater macro benthic activity at these depths depth dependent mixing coefficients derived from the best fit of a four layer advection diffusion decay model to the 234 th data are consistent with 210 pb profiles determined for the same sediments strongly suggesting that 234 th and 210 pb are mixed equivalently and in a multilayered manner

210pb derived chronology and the fluxes of 210pb and 137cs isotopes into continental shelf sediments east chukchi sea alaskan arctic abstract eleven sediment cores and eight sediment trap samples from the continental shelf of the eastern chukchi sea were analyzed for 210pb cs and 2226ra in selected samples the organic carbon content and stable carbon isotope ratios were also determined the excess 210pb 210pbxs concentrations in the 1 cm core tops are generally lower than those of surficial sediments of subarctic shelves and arctic lakes the sediment inventory derived depositional fluxes of 210ph vary between 0 09 and 0 38 dpm cm 2y 1 with a mean of 0 18 dpm cm 2 y 1 the apparent mass sediment accumulation rates which vary between 31 and 324 mg cm 2 y 1 with a mean value of 133 mg cm 2 y 1 are about an order of magnitude lower than the yearly particle flux obtained from the sediment trap experiments this difference between the relatively long term and short term yearly accumulation rates is likely due to the occasional resuspension of fine particles in the continental shelf areas and their advective transport to sites other than their initial deposition the sediment inventory of 137cs varied between 0 64 and 4 09 dpm cm 2 with a mean of 2 18 dpm cm 2 a comparison of this inventory with the expected fallout inventory of 137cs suggests that there had been no detectable input of 137cs to the study area from the former ussr nuclear dump sites

sensitivity of the phosphate cadmium carbon isotope relation in the ocean to cadmium removal by suboxic sediments reconstructions of past deep ocean nutrient concentrations rely largely on the carbon isotopic composition and cadmium content of shells of benthic foraminifera when comparing records of these two paleonutrient tracers a relation similar to the phosphate cadmium carbon isotope relation in the water column today is generally assumed we present new water column sediment and pore water data from the california continental margin which demonstrate that cd accumulation is enhanced in suboxic sediments these results suggest that the oceanic cd inventory is sensitive to changes in the areal extent and redox intensity of suboxic sediments and thus that the phosphate cadmium relation in the ocean could have been different in the past the magnitude of this effect and its evolution through time is presently hard to quantify because the oceanic cd budget is poorly constrained

a new concept for glacial geological investigations of surges based on high arctic examples svalbard abstract svalbard is a key area for the investigation of glacial surges and almost two centuries worth of field observations exists from this region studies have shown that the course of a surge and the associated formation of landforms are strongly influenced by basinal factors and that the broad range of variables involved can hamper interpretations and comparisons based on a review of surges in svalbard a new concept for glacial geological investigations has been developed that combines ice flows ice front movements and morphostratigraphy the concept is comprised of the following four elements 1 classification based on the configuration and characteristics of the receiving basin 2 division of the surge cycle into six stages 3 guidelines for morphological mapping and 4 use of an allostratigraphic approach for interpreting ice front movements in this context delineation of the active phase is critical which include the history of terminus movements and four main categories of receiving basins are recognized these are a terrestrial basins with deformable substrates b terrestrial basins with poorly deformable substrates c shallow water basins and d deep water basins the ice front movement history is reconstructed by coupling information from the proglacial moraines syn surge the supraglacial moraines post surge and the associated traces of meltwater to the surge stages i vi this approach has revealed a critical relationship between the termination of the active phase and three morphological elements namely the maximum ice front position the maximum moraine extent and the youngest proglacial moraine which are unique for each of the basins a d the concept is thus a novel and more precise approach for mapping the active phase and the active phase duration as shown by the 12 year long surge of fridtjovbreen where stage i was 30 months inception stage ii was 54 months ice front advance stage iii was 12 months stillstand and stage iv was 48 months retreat during active flow the glacier has been in quiescent phase stages v vi since 2002

medieval accumulation in the upper dniester river valley the role of human impact and climate change in the carpathian foreland research in the valleys of upper dniester strvja and stryj rivers in the eastern carpathian foreland documents the occurrence of 3 4 holocene floodplain terraces and several alluvial fills dating back to the late vistulian and the atlantic as well as the periods 3500 3000 bp 1850 1250 cal bc 2200 1700 bp 360 cal bc 390 cal ad 5th 6th 10th 12th and 14th 16th centuries ad flood phases distinguished in the upper dniester drainage basin correlate well with previously established phases of enhanced fluvial activity in the valleys of upper vistula the wisloka and the san in the western carpathian foreland an episode of tree fall during the 5th 6th century floods is the most conspicuous and is linked to the beginning of a wet climate phase 1500 1350 cal bp subsequent phases of greater fluvial activity from the 10th to the 12th and from the 14th to the 16th centuries record increasing human activity as well as correlation with wet and cool climate phases the first half of the 11th century and the beginning of the little ice age fluvial accumulation processes along the longitudinal profile of the upper dniester valley were affected not only by human activity and more humid climate phases but also by diverse neotectonic movements