relative contribution of ionospheric conductivity and electric field to the auroral electrojets data from continuous scans of the chatanika radar beam along the magnetic meridian plane are used to determine the latitudinal profile of height integrated ionospheric conductivities and horizontal electric fields from which the latitudinal distribution of ionospheric currents is deduced the observations cover invariant latitudes between 62 and 68 where the ims alaska meridian chain of magnetometers was also in operation although the conductivities and the electric fields are interrelated the relative importance of the two in driving the eastward and westward auroral electrojet currents can be assessed it is found that for moderate and large current densities i e 0 2 a m the northward electric field strength increases as the magnitude of the eastward electrojet in the evening sector increases the height integrated hall conductivity stays generally at the level of 10 mhos even when the current density becomes as large as 1 a m however when the eastward electrojet is small substantial electric fields of 10 20 mv m may still exist as if the magnetosphere has a persistent voltage source there appear to be two distinct components to the westward electrojet in the midnight and early morning sestors 0300 mlt is dominated by a strong southward electric field

distribution of terrigenous lipids in marine sediments off northeastern taiwan surface sediments on the continental margin off northeastern taiwan have been analyzed for terrigenous lipids including n alkanes n fatty alcohols and sterols marine input to the sediments is particularly low based on the average n c17 n c29 alkane and n c16 n c28 fatty alcohol ratios 0 15 0 13 and 0 13 0 06 respectively this may be due to the fact that marine lipids are more prone to degradation than terrestrial ones the study area has the highest plant wax n alkane contribution average carbon preference index 3 9 1 2 among the coastal marine areas surrounding taiwan lateral particle transport from the southern east china sea shelf and river runoff from the east taiwan coast are considered to be the major contributors the distributions of plant wax n alkane and n alkanol concentrations normalized to total organic carbon toc in the study area generally show maximum values on the upper slope of the southernmost okinawa trough but not for phytosterols linear regression of toc versus plant wax n alkane concentrations show a weak relationship r 0 64 p 0 001 and an even weaker relationship r 0 42 p 0 05 between toc and plant wax n fatty alcohol concentrations is found this could be attributed to several factors 1 a complex input not a point source of terrigenous organic matter to the study area 2 toc also including marine organic matter 3 temporal variations in river flow due to flooding and 4 different rates of degradation for toc and individual biomarkers however in spite of those factors toc and phytosterol concentrations are positively linearly correlated r 0 85 p 0 001 implying that the dilution of phytosterols in terrigenous organic carbon with marine organic carbon with or without the phytosterols follows a nearly constant ratio which is remarkable in addition the predominant source of diploptene in the sediments does not appear to be of higher plant origin

static liquefaction as a possible explanation for the merriespruit tailings dam failure in 1994 the merriespruit gold tailings dam in south africa failed resulting in 17 deaths the post failure in vestigation provided no explanation as to why the catastrophic flow failure which contradicted all previous experiences of failures of gold tailings dams in south africa occurred the documented history of the dam describes insufficient freeboard provision and often poor pool control which is argued to have resulted in some areas of the dam having high in situ void ratios some of the undrained triaxial tests carried out on specimens obtained from zones adjacent to the failure scar exhibited nondilative behaviour laboratory triaxial tests that were conducted on reconstituted speci mens and are reported in a companion paper defined a series of steady state lines that were dependent on the particle size distribution of the tailings void ratios obtained from undisturbed samples taken during the post failure investiga tion are compared with these steady state lines and it is shown that an appreciable percentage of the specimens were likely to have been contractant the inference drawn is that a large volume of tailings was in a metastable state in situ and overtopping and erosion of the impoundment wall exposed this material resulting in static liquefaction of the tail ings and a consequent flow failure

cyclic shear response of fine grained mine tailings the mechanical response of three different types of fine grained mine tailings is examined using data from constant volume cyclic direct simple shear dss tests under cyclic dss loading fine grained tailings typically exhibit a cumulative decrease in effective stress along with progressive degradation of shear stiffness the observed shear strain development due to cyclic mobility is similar in form to that of the previously observed cyclic shear response for natural silts the cyclic resistance ratio crr of laterite tailings is observed to increase with an increase in the initial effective confining stress vc for this material the dilative tendency due to stress densification seems to have overridden the contractive tendency due to the increase in confining stress in contrast the crr of copper gold zinc tailings is insensitive to the initial effective confining stress suggesting a response similar to that of normally consolidated clay the postcyclic maximum shear strength ratio su pc v

the diurnal and latitudinal variation of auroral zone ionospheric conductivity the great spatial and temporal variability of auroral ionospheric conductivity significantly influences the ionospheric closure path for high latitude field aligned currents because these closure paths can extend to low latitudes changes in auroral zone conductivity can influence the global electric field distribution in this paper synoptic chatanika radar observations of auroral zone conductivity that cover 62 to 68 geomagnetic latitude are presented they are representative of quiet winter active winter and equinoctial conditions during the daytime the solar contribution to the height integrated conductivity is well represented by p h 5 10 cos1 2 where is the solar zenith angle the nighttime height integrated pedersen and hall conductivities p and h in the electron density trough are at times below our detection threshold of 0 5 mho following magnetic substorm onset enhanced conductivity regions move southward and intensify as the recovery phase begins the conductivity pattern recedes northward and diminishes the onset and cessation of precipitation associated with these events can be as abrupt as a few minutes in one example the behavior of p and h are examined in the vicinity of the harang discontinuity which was quite sharp 30 min in local time at the harang discontinuity on that day the ratio of h to p decreased indicating a softening of the precipitating energy distribution

new equations for swelling characteristics of bentonite based buffer materials compacted bentonite and sand bentonite mixtures are attracting greater attention as buffer material for repositories of high level nuclear waste this buffer material is expected to fill up the space between the canisters containing the waste and the surrounding ground by swelling to produce the specifications such as dry density sand bentonite mass ratio and dimensions of the buffer material the swelling characteristics of compacted bentonite and sand bentonite mixtures must be evaluated quantitatively new equations for evaluating the swelling behavior of compacted bentonite and sand bentonite mixtures are presented that can accommodate the influences of the sand bentonite mass ratio and the exchangeable cation composition of bentonite the new method for predicting swelling characteristics is presented by combining the new equations with the theoretical equations of the gouy chapman diffuse double layer theory and of the van der waals force which can evaluate the repulsive and attractive forces

a laboratory investigation of the dynamic properties of tailings the dynamic response of tailings from a gold mine located in western quebec was evaluated using cyclic laboratory testing these tailings are classified as nonplastic silt and sand specimens of the tailings were prepared as slurries consolidated to vertical effective stresses of 100 400 kpa and subjected to cyclic direct simple shear testing with cyclic stress ratio csr values between 0 075 and 0 15 the shear modulus reduction of the tailings under cyclic loading was found to be fairly similar to that described for clean sands in the literature the cyclic resistance ratio crr which reflects the liquefaction resistance of the samples was not significantly affected by the effective consolidation stress in the range considered here analysis of test results with the simplified method of liquefaction evaluation indicates that this method may be applicable to these tailings however other factors such as the possible effects of layering and ageing of the tailings in situ should also be consider

hydraulic conductivity of homogenized tailings from hard rock mines tailings produced by milling for one extraction from hard rock mines which range in size from clay to fine sand have relatively low hydraulic conductivity k the value of k must be known with a certain degree of certainty to analyze consolidation and seepage conditions in and around tailings ponds in this paper the authors present the results of a laboratory investigation on hydraulic conductivity of homogenized tailings from hard rock mines after describing some of the basic properties of four different materials including mineralogy grain size atterberg limits compaction characteristics and consolidation curves permeability test results are given the hydraulic conductivity value usually varies between 10 4 and 10 5 cm s the effect of various factors on this value including void ratio and grain size is then discussed in relation to predictive models it is shown that a modified version of the kozeny carman equation in which a tortuosity factor and a grain size distribution function are i

intense growth phase events of substorms over the past few decades several events of the intense growth phase preceding the expansion onset of substorms were reported we reexamine these events using an extensive set of data including ground based magnetograms at auroral latitudes solar wind data from the wind and imp 8 satellites and auroral uv images from the polar and viking satellites magnetograms show that the intense auroral electrojet is located in the early morning sector during these events a common feature among the corresponding solar wind conditions for these events is the existence of a period of southward interplanetary magnetic field imf preceded by a prolonged northward imf this intense growth phase however seems to be independent of the imf by polarity enhanced auroras in the early morning sector appear during the growth phase these auroras are consistent with relatively large geomagnetic disturbances during these events indicating that enhanced conductances combined with enhanced electric field caused by southward imf play an important role in the auroral electrojet during these intense growth phase events

the distribution and behaviour of 230th and 231pa at an ocean margin baja california mexico uranium th and pa isotopes were measured in sediments collected by box core along a transect normal to the baja california continental margin six cores were analyzed ranging in depositional environment from manganese nodule bearing pelagic red clay to hemipelagic sediments displaying mn reduction in the upper 5 cm in the hemipelagic cores solid phase mn peaks due to diagenetic remobilization occur within the upper layers which are well mixed with respect to unsupported sup 230 th and sup 231 pa the fact that sup 230 th and sup 231 pa are not concentrated at the mn peaks suggests that little mobility of these nuclides occurs within the sediment column unsupported sup 230 th sup 231 pa activity ratios in the biomixed layer of the sediments range from 10 9 to 6 6 generally decreasing towards the inshore stations the flux of sup 230 th and sup 231 pa across the sediment water interface is almost in balance with the theoretical water column supply in the most distal core but rapidly increases inshore this evidence from the sediment column confirms that enhanced sup 230 th and sup 231 pa removal occurs at ocean margins and that sup 231 pa is removed from the water column to the sediments in preference to sup 230 th

evolution of the hydraulic conductivity of reclamation covers over sodic saline mining overburden the evolution of the field saturated hydraulic conductivity of four covers located on a reclaimed saline sodic shale overburden from oil sands mining is presented three covers consisted of a surface layer of peat glacial topsoil over a mineral soil and one cover was a single layer of mixed peat and mineral soil measurements of the field saturated hydraulic conductivity of the cover and shale materials were made with a guelph permeameter between 2000 and 2004 the hydraulic conductivity of the cover materials in the multilayered covers increased by one to two orders of magnitude over the first few monitoring seasons the hydraulic conductivity of the single layer cover system which was placed three years before the multilayered covers marginally increased from 2000 to 2002 and then remained relatively unchanged the hydraulic conductivity of the shale underlying all four covers increased approximately one order of magnitude soil temperature measurements indicated that one freeze thaw cycle occurred

transport of stable isotopes of water and sulphate within reclaimed oil sands saline sodic mine overburden summary the reclamation of shale overburden dumps from oil sands mining requires the placement of reclamation covers comprised of salvaged organic and mineral soils the primary issues associated with the long term performance of these covers are their ability to store sufficient water to meet transpiration demands and the potential threat of salt ingress into the cover from the underlying shale the first issue has been addressed in previous studies so the objective of this study was to evaluate controls on salt ingress through observations and modelling of the transport of the stable isotopes of water and salt within reclaimed profiles at the south bison hills overburden dump located north of fort mcmurray alberta the water flow model was based on a dual porosity soil vegetation atmosphere model calibrated to observed field data this model was then used to simulate deuterium and sulphate transport within the soil profiles the optimized transport model for deuterium was used to estimate net percolation rates through the cover soil into the underlying shale this model was then used to assess the controls on sulphate migration including the rate of sulphate generation as a result of ongoing oxidation of the pyritic shale the model results indicate that the average net percolation rate is a function of topographic location ranging from 2 2 10 5 m d at slope locations to 20 8 10 5 m d at plateau locations during the unfrozen days these rates of net percolation should have produced observable patterns of salt flushing from the cover and upper shale however the observed sulphate levels could only be simulated by including a production term related to pyrite oxidation of the shale the simulated oxidation rates ranged from 0 4 to 5 65 mg l d similar to those estimated from previous laboratory and field investigations

asian dust input in the western philippine sea evidence from radiogenic sr and nd isotopes the radiogenic strontium sr and neodymium nd isotope compositions of the detrital fraction of surface and subsurface sediments have been determined to trace sediment provenance and contributions from asian dust off the east coast of luzon islands in the western philippine sea the sr and nd isotope compositions have been very homogenous near the east coast of the luzon islands during the latest quaternary yielding relatively least radiogenic sr sr 87 sr 86 0 70453 to 0 70491 and more radiogenic nd isotope compositions epsilon nd 0 5 3 to 5 5 these isotope compositions are similar to luzon rocks and show that these sediments were mainly derived from the luzon islands in contrast the sr and nd isotope compositions of sediments on the benham rise and in the philippine basin are markedly different in that they are characterized by overall more variable and more radiogenic sr isotope compositions sr 87 sr 86 0 70452 to 0 70723 and less radiogenic nd isotope compositions epsilon nd 0 5 3 to 2 4 the sr isotope composition in the huatung basin is intermediate between those of the east coast of luzon and benham rise but shows the least radiogenic nd isotope compositions the data are consistent with a two end member mixing relationship between luzon volcanic rocks and eolian dust from the asian continent which is characterized by highly radiogenic sr and unradiogenic nd isotope compositions the results show that asian continental dust contributes about 10 50 of the detrital fraction of the sediments on benham rise in the western philippine sea which offers the potentials to reconstruct the climatic evolution of eastern asia from these sediments and compare this information to the records from the central and northern pacific

coupled chemo hydro mechanical effects in one dimensional accretion of cemented mine fills abstract mine waste cement mixtures have been extensively used for filling underground mined out cavities worldwide as a sustainable solution to tailings disposal and for ground control the pressure that a mine fill imposes on its retaining structures would dictate the stability of a subsurface backfill system the pressure is influenced by the coupled consolidation and chemical shrinkage processes of a cemented mine fill various benchmark results have become available for understanding and predicting such coupled processes during the deposition of cemented mine fills in an ideal one dimensional 1d condition nevertheless there has been a paucity of studies where the coupled chemo hydro mechanical effects in their entirety are rationally considered in this paper the coupled chemo hydro mechanical behaviour of fluid saturated cemented mine fills during 1d accretion is investigated with a new chemo poroelasticity framework the present approach is conceptualized by extending biot s poroelasticity to accommodate the water volume changes induced by cement hydration the analyses performed in the study have brought new practical insights into the chemo poromechanical behaviour of accreting cemented mine fills in particular the study has shown quantitatively for the first time how the consolidation of a hydrating mine fill is dictated by the specific evolution of its properties rate of deposition as well as backfill mix design during sedimentation the study suggests that a case specific analysis with coupled numerical tools rather than the simple application of benchmark results is mandatory for rationally assessing the nonlinear consolidation process

on the use of the kozeny carman equation to predict the hydraulic conductivity of soils the saturated hydraulic conductivity of a soil can be predicted using empirical relationships capillary models statistical models and hydraulic radius theories a well known relationship between permeability and the properties of pores was proposed by kozeny and later modified by carman the resulting equation is largely known as the kozeny carman kc equation although the two authors never published together in the geotechnical literature there is a large consensus that the kc equation applies to sands but not to clays this view however is supported only by partial demonstration this paper evaluates the background and the validity of the kc equation using laboratory permeability tests test results were taken from publications that provided all of the information needed to make a prediction void ratio and either the measured specific surface for cohesive soils or the gradation curve for noncohesive soils the paper shows how to estimate the specific surface of a noncohesive soil from its g

modeling substorm current systems using conductivity distributions inferred from de auroral images images of auroral emissions observed with dynamics explorer 1 de 1 are used to calculate ionospheric conductivities over the polar region the combination of ground based magnetometer data and the inferred conductivities enables us to estimate on a global scale the distributions of ionospheric electric fields and currents and field aligned currents as well as the joule heating production rate with a time resolution of 12 min although our inference of the conductivity distribution requires further improvements the following conclusions may be drawn from this work 1 the westward electrojet is in general collocated with the region of high auroral luminosity while the region of relatively low luminosity in the evening sector is collocated with the eastward electrojet 2 the upward field aligned currents exist in the brightest auroral region on the poleward side of the evening auroral oval and on the equatorward side of the morning oval however the magnitudes of these upward currents are not in proportion to the auroral luminosities suggesting that the characteristic energies of precipitating electrons carrying the upward currents and generating the auroral luminosities may be different 3 a significant amount of ionospheric currents can flow in regions where there are no bright auroral emissions an example of this effect is found over the poleward half of the westward electrojet in the morning sector where the electric field is the main contributor to the ionospheric currents 4 the distribution of calculated field aligned currents displays many localized structures which characterize the development of the substorm current system previous satellite observations may represent gross time averages of such complicated distributions

scientific results of the u s ims ground based program the scientific results of the u s international magnetospheric study ims ground based program available to the author up to february 1982 are summarized included are results derived from 1 magnetometers of the ims meridian chains 2 incoherent scatter radars 3 a balloon campaign and 4 optical spectroscopic observations a large body of data obtained during the ims remains to be analyzed and published

geotechnical parameters and behaviour of uranium tailings the results of laboratory and in situ testing and test blasting the observations made on a test embankment and a description of actual construction practice associated with engineering studies fo

the stable isotopes of site wide waters at an oil sands mine in northern alberta canada abstract oil sands mines have large disturbance footprints and contain a range of new landforms constructed from mine waste such as shale overburden and the byproducts of bitumen extraction such as sand and fluid fine tailings each of these landforms are a potential source of water and chemical release to adjacent surface and groundwater and consequently the development of methods to track water migration through these landforms is of importance the stable isotopes of water i e 2 h and 18 o have been widely used in hydrology and hydrogeology to characterize surface water groundwater interactions but have not been extensively applied in mining applications or specifically to oil sands mining in northern alberta a prerequisite for applying these techniques is the establishment of a local meteoric water line lmwl to characterize precipitation at the mine sites as well as the development of a catalogue of the stable water isotope signatures of various mine site waters this study was undertaken at the mildred lake mine site owned and operated by syncrude canada ltd the lmwl developed from 2 years 2009 2012 of sample collection is shown to be consistent with other lmwls in western canada the results of the study highlight the unique stable water isotope signatures associated with hydraulically placed tailings sand or fluid fine tailings and overburden shale dumps relative to natural surface water and groundwater the signature associated with the snow melt water on reclaimed landscapes was found to be similar to ground water recharge in the region the isotopic composition of the shale overburden deposits are also distinct and consistent with observations made by other researchers in western canada on undisturbed shales the process water associated with the fine and coarse tailings streams has highly enriched 2 h and 18 o signatures these signatures are developed through the non equilibrium fractionation of imported fresh river water during evaporation from cooling towers used within the raw water process circuit this highly fractionated surface water eventually becomes part of the recycled tailings water circuit and as a consequence it undergoes further non equilibrium fractionation as a result of surface evaporation leading to additional enrichment along local evaporation lines

impact of desiccation on monotonic and cyclic shear strength of thickened gold tailings abstractvarious forms of thickened or high density tailings characterized by exhibition of a yield stress that facilitates deposition in gently sloped stacks are increasingly used for a variety of mining operations although this technology reduces reliance on containment by dams and the associated risk of catastrophic failure regulators are concerned with remobilization of such unbounded deposits by earthquakes or extreme rainfalls therefore the monotonic and cyclic shear strength of thickened tailings layers are of significant interest thickened tailings experience a particular stress history during deposition which may include desiccation rewetting and subsequent consolidation by burial under new tailings the effect of this stress history on their shear response is investigated using a norwegian geotechnical institute ngi type simple shear device samples are alternately mechanically overconsolidated or subjected to desiccation and subsequent rewetting because of burial by fresh tailings be

shear and dewatering behaviour of densified gold tailings in a laboratory simulation of multi layer deposition tailings may undergo desiccation stress history under varied climatic and depositional parameters while tailings substantially dewatered prior to deposition may experience desiccation under the gr

geo environmental site investigation for tunceli turkey municipal solid waste disposal site abstract the environmental and geological condition of a current solid waste disposal site in the city of tunceli turkey was investigated improper geological structure and soil properties of this unsanitary solid waste storage site as well as leachate from this site caused significant pollution in air soil and surface water natural soil characteristics and geology of the site are presented in this paper petrographic properties of vulcanized rubber rocks composed of tuff and volcanic sandstone at the bottom of storage sites and the mineralogical composition of the base composed of these rocks were examined permeability of the natural soil and index properties were determined using soil mechanics experiments moisture content specific gravity atterberg limit tests sieve analysis hydrometer analysis falling head permeability test and standard proctor test conducted on disturbed samples collected from excavated sites and the relationship between mineralogical composition and soil hydraulic behavior was investigated natural soil samples of six different parts of the site indicated that the soil class in four samples is silty sands sand silt mixtures one is clayey sands sand clay mixtures and one is clayey silts with slight plasticity the values obtained using permeability tests for subsoil samples vary from 10 5 to 10 8 cm s low permeability 10 7 and 10 8 cm s at the south part of the site increases to 10 5 cm s at the natural soil of the north side extensively faulted and fissured volcanic sandstone levels at the site give potential to waste leachate to reach deep levels the soil composition hydraulic conductivity topographic conditions and other location criteria in the current solid waste disposal site showed that the current disposal site is not suitable for this purpose

sedimentary processes in the inner new york bight evidence from excess210pb and239 240pu abstract particle reactive radionuclides were determined in sediments from the inner new york bight to trace transport and storage of fine grained sediments and associated reactive materials seven sediment cores 20 50 cm in length were analyzed for water content loss on ignition loi and excess 210 pb three of these were also analyzed for 239 240 pu excepting some depth horizons in a core from a dredge spoil dumpsite every sample analyzed contained excess 210 pb variations in the concentration of excess 210 pb with depth in the sediment at all stations correlated strongly with loi which apparently traces that fraction of the sediment which is active in removing reactive elements from the water column in the cores analyzed for 239 240 pu every sample contained finite pu and pu concentrations correlated strongly with excess 210 pb the radionuclide distributions may be simply viewed as products of steady state sediment accumulation or of mixing geochemically reasonable accumulation rates are very high 0 5 2 6 g cm 2 y and could probably only be sustained by offshore transport of dumped materials at the other extreme the relationships between excess 210 pb and loi are compatible with rapid mixing of a 210 pb carrier phase traced by loi into the pre existing substrate with little or no actual accumulation other non steady state processes such as sediment gravity flow could also explain the observed distributions measured sediment inventories dpm cm 2 of excess 210 pb and pu at these stations are greatly in excess of those supportable by direct atmospheric deposition lateral supply is required incorporation of sedimentary fines into the sand substrate could make the inner new york bight an important repository of reactive materials

variability of the chemical hydrography at the frontal region between the east china sea and the kuroshio north east of taiwan abstract the hydrography across the frontal region between the east china sea and the okinawa trough north east of taiwan observed during the summer of 1985 and 1988 and the early spring of 1987 was governed mainly by mixing across the front and the topographically induced upwelling of the modified kuroshio water in the okinawa trough during the periodic shelfward migration of the kuroshio the location of the front relative to the shelf break seemed to be temporally variable topographically induced upwelling was evident during the summer of 1988 and the early spring of 1987 when the front was located close to the shelf break it might not have occurred in the summer of 1985 when the front was further offshore the end member composition of the upwelling water was similar in both seasons it originated from about 300 m with a temperature and salinity of 13 c and 34 4 psu it was rich in nutrients and poor in oxygen with concentrations of nitrate phosphate silicate and oxygen of 16 1 18 and 160 m respectively this upwelling water is potentially a major source of nutrients to the east china sea the deep water in the okinawa trough at temperatures below 15 c did not participate in cross shelf mixing its chemical characteristics did not change significantly from year to year

comparison of the hydrological role of two reclaimed slopes of different ages in the athabasca oil sands region alberta canada establishing hydrological connectivity in reconstructed landscapes and understanding how this connectivity evolves over time is critical for the development of effective water management strategi

seasonal variations of the high latitude f region for strong convection we combined a plasma convection model with an inosphere atmospheric composition model in order to study the seasonal variations of the high latitude f region for strong convection our numerical study produced time dependent three dimensional ion density distributions for the ions no sup o sub 2 sup n sub 2 sup o sup n sup and he sup we covered the high latitude ionosphere above 42 sup 0 n magnetic latitude and at altitudes between 160 and 800 km for a time period of one complete day from our study we found the following 1 for strong convection the high altitude ionosphere exhibits a significant ut variation both during winter and summer 2 in general the electron density is lower in winter than in summer however at certain universal times the electron density in the dayside polar cap is larger in winter than in summer owing to the effect of the mid latitude winter anomaly in combination with strong antisunward convection 3 in both summer and winter the major region of low electron density is associated with the main or mid latitudde trough the trough is deeper and its local time extend is much greater in winter than in summer 4 typically the electron density exhibits a muchmore larger variation with altitude in winter than in summer 5 the ion composition and molecular atomic ion transition altitude are highly ut dependent in both summer and winter 6 the ion composition also displays a significant seasonal variation however at a given location the seasonal variation can be opposite at different universal times 7 high speed convection cells should display a marked seasonal variation with a much larger concentration of molecular ions near the f region peak in summer than in winter less

field determination of sulphide oxidation rates in mine tailings a field study was conducted to assess the rates of oxygen consumption in the vadose zone of sulphide mine tailings oxygen uptake rates were measured directly at the ground surface and were compared to rates of sulphate production in the tailings profile a nonreactive tracer gas was also used to assess effective diffusion coefficients in the shallow subsurface the 26 measurement sites were located within a 0 1 km2 area in tailings with a water table depth ranging from 0 6 m to ponding at the surface ambient oxygen consumption rates in the 8 year old tailings were compared to measurements through 0 2 m thick covers of fine sand and 0 2 m layers of fresh tailings replacing oxidized tailings at ground surface the oxygen flux across the tailings surface ranged from 0 1 to 250 mol o2 m 2 yr 1 for ambient oxidation conditions fresh tailings at the surface produced rates that were as much as twice the ambient rates the 0 2 m fine sand cover lowered rates by a factor of 100 below ambient rates sulphate production rates agreed well with oxygen consumption measurements independent diffusion flux measurements with a nonreactive gas exhibited an excellent correlation with oxygen uptake fluxes indicating the dominance of oxygen diffusion in the control of oxidation rates in the tailings spatial trends in oxidation rates were consistent with depth to the water table and temporal changes by as much as a factor of 2 were attributed to a 0 16 m variation in the depth to the water table over a 2 week period the results of this study support the use of simple fickian models to evaluate oxygen diffusion and oxidation rates in sulphide tailings

a predictive model for the water retention curve application to tailings from hard rock mines it is now commonly recognized that many geotechnical problems are related to the unsaturated behavior of soils such is the case for phenomena occurring at shallow depths in the so called vadose zone unsaturated flow is also very important for the management of milling wastes especially for seepage in and around tailings ponds suction properties constitute a key element for the functional representation of unsaturated flow conditions these are usually shown by the water retention curve which gives the relationship between volumetric water content theta and matric suction psi laboratory measurements have been performed on three different tailings from hard rock mines in the abitibi region to study the effect of various factors including grain size and porosity on the theta psi relationship the main results are presented in this paper the data are first analyzed using a well known descriptive model the experimental results are also used to estimate the air entry value according to vario

210pb activities in and fluxes to sediments of the washington continental slope and shelf abstract surface sediments of the washington coast have 210 pb activites which average 104 48dpm g for submarine canyon and slope regimes and 18 12dpm g for the continental shelf regime 210 pb sedimentary fluxes are also higher in canyons averaging 18 13dpm cm 2 per yr compared to 5 2 3 1 dpm cm 2 per yr for slope and 4 8 1 8dpm cm 2 per year for shelf regions these 210 pb activities and fluxes are 2 7 times greater than those reported for other coastal regions inputs from the atmosphere and the columbia river are not sufficient to supply the 210 pb but advection of seawater containing dissolved 210 pb produced in situ from 226 ra provides an input several times larger than the sedimentary fluxes the sedimentary 210 pb flux is limited by scavenging reactions rather than by supply of dissolved 210 pb calculations of maximum biological uptake and fluxes of 210 pb and selective chemical leaching experiments all show that the primary scavenging processes are due to hydrous mn and fe oxides rather than biological phases the pattern of higher 210 pb depositional fluxes in canyons than in nearby open slope areas of comparable water depth is most reasonably explained by enhanced scavenging of dissolved 210 pb near the sea floor rather than by processes operating throughout the water column relatively rapid removal of dissolved 210 pb from the near bottom nepheloid layer to slope and canyon sediments is shown by its mean residence time of less than two years in this layer

the distribution of 230th and 231pa in the deep sea surface sediments of the pacific ocean in order to determine the areal extent and distribution of 231pa sinks in the pacific ocean we have analyzed 34 deep sea surface sediment samples from widely distributed locations for their pa th and u isotopes while the 230thxs content varies by more than a factor often the 231paxs content is confined in a relatively narrow range with a mean value of 2 8 1 4 dpm g there is a positive correlation between 230thxs and 231paxs and using the regression line it is possible to calculate the 230thxs231paxs activity ratios in samples for which only 230th data are available we then constructed a map of 230thxs231paxs distribution using 230paxs231paxs 11 the production ratio in the water column as a criterion for identifying preferential 231pa sinks we have identified an area covering 30 40 of the pacific ocean this area includes most of the pacific margins the northwest pacific the antarctic ocean and perhaps the mid ocean ridge regions and is nearly coincident with that of high sediment accumulation rates this suggests that the paniculate flux is important for the removal of 231pa from the ocean two models for the removal of 231pa produced in the open ocean are 1 1 lateral transport into the vertical flux in regions of high particulate flux damaster 1979 andersonet al 1983a b or 2 2 uptake at the sediment water boundary the second model is more likely to be correct to distinguish unequivocally between the two proposed models we would need sediment trap data for the western north pacific

the determination of time stationary two dimensional convection patterns with single station radars at the present time most ground based radar estimations of ionospheric convection use observations from single station facilities this approach requires certain assumptions as to the spatial and or temporal uniformity of the convection in this paper the authors present a critical examination of the accuracy of these vector velocity determinations using realistic modeled flow patterns that are time stationary but not spatially uniform they find that under certain circumstances the actual and inferred flow fields show considerable discrepancy sometimes not even agreeing in the sense of flow direction specifically they show that the natural curvature present in ionospheric convection on varying spatial scales can introduce significant error in the velocity estimate particularly when the radius of curvature of the flow structure is less than or equal to the radar range to the scattering volume the presence of flow curvature cannot be detected by radars which determine velocities from measurements in two viewing directions and it might not be detected by radars using azimuth scanning techniques thus they argue that every effort should be made to measure the ionospheric convection by bidirectional or multidirectional observations of a common ionospheric volume and that a synthesis of coherent and incoherent radar observations from different sites ismore preferable to multidirectional single station observations using either radar alone these conclusions are applicable to any doppler measurement technique and are equally valid for high latitude wind patterns using fabry perot interferometer techniques less

strontium lead and zinc isotopes in marine cores as tracers of sedimentary provenance a case study around taiwan orogen abstract the active collision zone around taiwan orogen receives a variety of sedimentary inputs including terrigenous flux from taiwan and chinese rivers oceanic currents and atmospheric dust in order to determine the present day respective contributions of these different sources we analysed the pb and sr isotopic compositions of late quaternary sediments accumulated offshore east taiwan samples from the taiwan coastal range andesites sandstones conglomerate and peinan river terraces and suspended loads have also been analysed to constrain the mean taiwan isotopic signature mixing lines between the different sources of material indicate that the core located in the okinawa trough represents a mixture of about 60 of taiwan 30 of chinese loess and 10 of yangtze river contributions the southernmost core located close to luzon arc is influenced by taiwan 60 and volcanic material 40 the sr and pb isotopic compositions of samples cored in the manila trench and in the huatung basin are strongly influenced by the taiwan signature while the ryukyu trench core samples point to significant but variable contributions of chinese loess and yangtze river this work also reports zn isotopic variations in the silicate fraction of these marine core samples the overall variation in zn isotopic compositions expressed as 66zn is greater than 0 3 per mil for an analytical precision of 0 05 the zn isotopic signal for most of the marine core samples is similar to the literature data measured on sedimentary material except for the manila trench core samples and the older sample from the huatung basin they present values heavier by 0 2 0 3 close to those obtained on all taiwan rocks and peinan river particulates these results show 1 the particular characteristics of taiwan zn isotopic compositions on a large scale and 2 the possible use of zn isotopes as a tracer of material sources

chatanika radar and s3 2 measurements of auroral zone electrodynamics in the midnight sector measurements made by the incoherent scatter radar at chatanika alaska have been combined with s3 2 satellite data to study the relationships between conductivities electric fields and currents near the harang discontinuity three s3 2 passes were chosen for the study based on the quality of the radar and satellite data and the availability of supplementary ground and space based observations the radar measured electric fields and conductivities as a function of latitude and local time the satellite measured the latitudinal distribution of electric field and field aligned current during the three polar passes the dominant field aligned current in the midnight sector is upward equatorward of this current a downward sheet is observed which is the eastern end of the evening sector region 2 sheet poleward of the upward current are several sheets of varying directions and magnitudes these sheets are associated with active aurora during substorms the most intense electric fields were located at the poleward and equatorward boundaries of the upward current sheet a model is presented which demonstrates the self consistency of the observed relationships between conductivities electric fields and currents

nineteenth canadian geotechnical colloquium the soil water characteristic curve a historical perspective the constitutive relationship between water content or degree of saturation and suction is called the soil water characteristic curve the soil water characteristic curve provides a conceptual framework in which the behavior of unsaturated soils can be understood a historical review illustrates how the work of early researchers in soil science and geotechnical engineering laid the foundation for our current understanding of this relationship key elements of these early studies were a conceptual understanding of the soil water characteristic curve as a relationship between the mass or volume of water stored within the soil and the energy in the water phase it was on the basis of this conceptual model that current methods of measuring the soil water characteristic curve were developed interpretative models for the distribution and geometry of the water phase in an unsaturated soil based on the capillary model have provided a useful conceptual model for understanding the effects of soil texture gradatio

numerical investigation of the influence of waste rock inclusions on tailings consolidation the construction of waste rock inclusions wris in a tailings impoundment constitutes an alternative disposal technique that aims at improving the management of mine wastes this technique consists in strategically placing the wris inside the impoundment at the beginning and during its operation to form compartments or cells in which the tailings are stored such inclusions can serve various purposes in this paper the authors investigate the effects of drainage from wris on tailings consolidation during filling of the impoundment using experimental data from hard rock mines that provide the hydrogeological and geotechnical properties introduced in the numerical analyses the model used for the simulations represents a cross section of a portion of a tailings impoundment containing a wri the numerical calculations results illustrate how the wri affects the dissipation of the excess pore water pressures pwps during filling of the impoundment and help quantify the extent of the zone of influence

seasonal dependence of large scale birkeland currents the seasonal dependence of large scale birkeland currents has been determined from the analysis of vector magnetic field data acquired by the triad satellite in the northern hemisphere statistical characteristics of single sheet i e net currents and double sheet birkeland currents were determined from 555 triad passes during the summer and 408 passes during the winter more complicated multiple sheet current systems were not included in this study the average kp value for the summer events is 1 9 and for the winter events is 2 0 the principal results include the following 1 the single sheet birkeland currents are statistically observed more often than the double sheet currents in the dayside of the auroral zone during any season the single sheet currents are also observed more often in the summer than in the winter as much as 2 to 3 times as often depending upon the mlt sector 2 the intensities of the single and double sheet birkeland currents on the dayside from approximately 1000 mlt to 1800 mlt are larger during the summer in comparison to winter by a factor of about 2 3 the intensities of the double sheet birkeland currents in the nightside the dominant system in this local time do not show a significant difference from summer to winter 4 the single and double sheet currents in the dayside between 0600 and 1800 mlt appear at higher latitudes by about 1 to 3 during the summer in comparison to the winter these characteristics suggest that the birkeland current intensities are controlled by the ionospheric conductivity in the polar region the greater occurrence of single sheet birkeland currents during the summertime supports the suggestion that these currents close via the polar cap when the conductivity there is sufficiently high to permit it since the intensities of birkeland currents are larger during periods of greater ionospheric conductivity an important source but perhaps not the only source of these currents must be a voltage generator in the magnetosphere possibly related to the convective electric field

empirical high latitude electric field models electric field measurements from the dynamics explorer 2 satellite have been analyzed to extend the empirical models previously developed from dawn dusk ogo 6 measurements j p heppner 1977 the analysis embraces large quantities of data from polar crossings entering and exiting the high latitudes in all magnetic local time zones paralleling the previous analysis the modeling is based on the distinctly different polar cap and dayside convective patterns that occur as a function of the sign of the y component of the interplanetary magnetic field the objective which is to represent the typical distributions of convective electric fields with a minimum number of characteristic patterns is met by deriving one pattern model bc for the northern hemisphere with a y interplanetary magnetic field imf and southern hemisphere with a y imf and two patterns models a and de for the northern hemisphere with a y imf and southern hemisphere with a y imf the most significant large scale revisions of the ogo 6 models are 1 on the dayside where the latitudinal overlap of morning and evening convection cells reverses with the sign of the imf y component 2 on the nightside where a westward flow region poleward from the harang discontinuity appears under model bc conditions and 3 magnetic local time shifts in the positions of the convection cell foci the modeling above was followed by a detailed examination of cases where the imf z component was clearly positive northward neglecting the seasonally dependent cases where irregularities obscure pattern recognition the observations range from reasonable agreement with the new bc and de models to cases where different characteristics appeared primarily at dayside high latitudes the analysis of these differences for strong bz conditions using passes through different mlt zones led to finding that the deviations from both the bc and de models could be modeled by extending the evening cell foci toward and beyond noon with a deformation that roughly resembles a rotational twist of the extended evening cell the morning cell accommodation to the model bc deformation produces a narrow tongue of eastward convection near 75 invariant latitude on the dayside the model de deformation compresses the morning cell toward the night hours such that the sunward convection in the morning cell is diverted to polar latitudes in the 0400 to 0700 mlt sector in both cases the deformations of the two cell patterns lead to sunward convection in dayside polar regions while maintaining the integrity of the nightside convection pattern thus the nightside dilemmas that plague three and four cell models designed to explain sunward convection in polar regions under bz conditions do not appear

defining an appropriate steady state line for merriespruit gold tailings failure of the merriespruit gold tailings dam in 1994 in south africa was unusual in that never before had a gold tailings dam in south africa failed in such a catastrophic fashion conventional thinking was that gold tailings would always exhibit dilative characteristics upon loading primarily because of the method of deposition which allows significant consolidation to occur due to sun drying this paper demonstrates that the concept of a steady state line which separates dilative from contractive behaviour upon undrained loading is applicable to merriespruit tailings four particle size distributions of merriespruit tailings were tested to determine the influence of the percent finer than 75 m on the position of the steady state line the tailings with the greater percentage of fines gave a steady state line that plotted above all the others which translated to the requirement that a greater relative density was necessary to produce noncontractive behaviour than for the low fines tailings samples

ionospheric characteristics of a detached arc in the evening sector trough simultaneous measurements by the isis 2 satellite and the chatanika incoherent scatter radar have been used to identify the ionospheric characteristics of a detached arc in the evening sector trough region on 26 february 1977 at 0737 ut the isis 2 auroral scanning photometer detected a detached arc at 65 north geomagnetic latitude that extended from approximately 1900 mlt to 2100 mlt the arc was about 2 wide in latitude and was separated by about 3 from the equatorward edge of the diffuse aurora the ratio of observed emission intensity at 557 7 nm to that at 391 4 nm was low indicating a fairly hard electron distribution the isis 2 energetic particle detector observed energetic electron precipitation e 40 kev in the detached arc the chatanika radar found that the detached arc consisted of several narrow ionization enhancements with peak e region electron densities of about 1 105 cm 3 at 95 km altitude the major enhancements were about 20 km 0 2 wide in latitude and were spaced about 50 km 0 5 apart their widths and spacings were steady for about 40 minutes this persistent spatial pattern suggests the presence of an energetic electron precipitation mechanism that is periodic in latitude and extended in longitude

residence times of surface water and particle reactive 210pb and 210po in the east china and yellow seas 228ra 226ra 210pb and 210po were measured in the surface waters of the east china and yellow seas using mass balance equations for the ra isotopes we estimated the total flux of diffusion from sediments and desorption from suspended particles to be 0 1 dpm 226ra cm 2 a 1 and 1 dpm 228ra cm 2 a 1 and residence times to be 2 3 years for the waters on the east china sea shelf and 5 6 years for yellow sea waters box model calculations yielded generally congruent scavenging residence times for 210pb and 210po in the waters of 2 months on the shelf and 7 months in the kuroshio current these suggest that reactive heavy metals and pollutants discharged through rivers from the continent to the east asian continental shelf are largely deposited on the bottom sediments prior to transport to the pelagic ocean by lateral mixing

the behavior of inclined covers used as oxygen barriers covers with capillary barrier effects ccbe have been recently proposed as a viable option for gas migration barriers however the effect of geometry on ccbe performance has not been clearly demonstrated in this paper the results of a laboratory study performed with an original apparatus called the inclined box are presented the results obtained show that the hydraulic behavior of layered covers is influenced by the inclination of the slope generally the upper part of the slope contains less water than the lower part this means that the upper part is less efficient than the lower part for limiting gas migration the authors have also studied an existing site where a ccbe was built on a sloping surface after validation of the numerical model with in situ measured data the model was used to perform a parametric study to quantify the influence of the main ccbe parameters on its performance the results obtained confirm those measured in the lab and clearly show how geometry influences the performan

mine tailings dams characteristics failure environmental impacts and remediation on a global scale demand for the products of the extractive industries is ever increasing extraction of the targeted resource results in the concurrent production of a significant volume of waste material including tailings which are mixtures of crushed rock and processing fluids from mills washeries or concentrators that remain after the extraction of economic metals minerals mineral fuels or coal the volume of tailings is normally far in excess of the liberated resource and the tailings often contain potentially hazardous contaminants a priority for a reasonable and responsible mining organization must be to proactively isolate the tailings so as to forestall them from entering groundwaters rivers lakes and the wind there is ample evidence that should such tailings enter these environments they may contaminate food chains and drinking water furthermore the tailings undergo physical and chemical change after they have been deposited the chemical changes are most often a function of exposure to atmospheric oxidation and tends to make previously perhaps safely held contaminants mobile and available if the tailings are stored under water contact with the atmosphere is substantially reduced thereby forestalling oxygen mediated chemical change it is therefore accepted practice for tailings to be stored in isolated impoundments under water and behind dams however these dams frequently fail releasing enormous quantities of tailings into river catchments these accidents pose a serious threat to animal and human health and are of concern for extractive industries and the wider community it is therefore of importance to understand the nature of the material held within these dams what best safety practice is for these structures and should the worst happen what adverse effects such accidents might have on the wider environment and how these might be mitigated this paper reviews these factors covering the characteristics types and magnitudes environmental impacts and remediation of mine tailings dam failures

laboratory properties of mine tailings a vast amount and variety of mine tailings are produced around the world each day these mining wastes must be properly managed to evaluate mine tailings disposal technology the appropriate engin

a numerical study of steady state evaporative conditions applied to mine tailings the suction profile of a desiccating soil is dependent on the water table depth the soil water retention characteristics and the climatic conditions in this paper an unsaturated flow model whi

model for the prediction of shear strength with respect to soil suction experimental studies on unsaturated soils are generally costly time consuming and difficult to conduct shear strength data from the research literature suggests that there is a nonlinear increas

large scale patterns of auroral ionospheric convection observed with the chatanika radar ionospheric convection at auroral latitudes has been examined during a series of long duration experiments with the chatanika alaska incoherent scatter radar these experiments have been carefully designed to obtain maximum latitudinal coverage 56 75 while maintaining a temporal resolution of 30 min in order to resolve the effects of individual substorms on the convection pattern design criteria for the experiments are described together with presentation of observational data acquired during 400 hr of radar operations during various levels of geophysical disturbance the data accentuate the repeatability of the gross features of the auroral convection and its basic conformity to the two cell pattern predicted from the large scale magnetospheric circulation for moderate to active geomagnetic conditions uniform sunward convection with velocities of 800 1200 m s spans the 62 to 72 latitude band at both dawn and dusk in quieter circumstances the sunward convection continues in this region but has smaller speeds and is centered at higher latitudes little evidence of a throat in the dayside convection pattern is seen at latitudes below 75 except in very disturbed circumstances during several experiments coordinated operation of the chatanika and millstone hill massachusetts radars permitted the simultaneous observation of the auroral convection pattern at two different local times substorms affect the convection at all local times and appear to generally enhance the rate of convection without seriously changing its direction near midnight latitudinal displacements and expansions of the convection pattern during substorms may result in a local rotation or reversal of the direction of convection while near dawn and dusk convection velocities are enhanced and the region of sunward flow expands to lower latitudes

the impact of reclamation cover depth on the performance of reclaimed shale overburden at an oil sands mine in northern alberta canada multilayer covers are widely accepted reclamation designs in the oil sands region of northern alberta canada with an ultimate goal of revegetating to species characteristic of predisturbance native plant communities to determine the optimal depth of reclamation material required to reclaim overburden shale from an oil sands mine an evaluation was made of the long term performance of six reclamation soil cover depths all placed over overburden the measured soil water contents from different cover thicknesses at south bison hills located at the syncrude mine site north of fort mcmurray alberta were used to calibrate and validate a dual porosity model in hydrus 1d the calibrated and validated model was then used to evaluate the influence of cover thickness and climatic variability on plant available water for forest growth the frequency distributions of actual transpiration tr for six cover treatments with a range of leaf area index lai cases were developed these tr frequency distributions were then modified by coupling tr and lai the modified frequency distributions for annual tr for the six simulated cover thickness highlight the strong nonlinearity between the distributions of tr over a long term 60 years climate cycle in that incremental increases in cover thickness do not produce proportional increases in tr the results indicated that once the cover thickness exceeds 100 cm there is little incremental increase in the median value of tr over the 60 year climate cycle copyright 2014 john wiley sons ltd

variability of the harang discontinuity as observed by the chatanika radar and the ims alaska magnetometer chain the relative location of ionospheric parameters and ground magnetic perturbations in the vicinity of the harang discontinuity is examined for this purpose we use combined observations of the chatanika incoherent scatter radar and of the ims alaska meridian chain of magnetometers which were continuously measuring the crucial ionospheric parameters near the harang discontinuity when a sizeable substorm took place the harang discontinuity as defined by the reversal of the north south electric field is found to be located at 1 2 poleward of the discontinuity identified by the conventional method of using ground magnetic perturbations it is also found that the relative location of auroral conductivity enhancements is quite variable depending perhaps upon substorm time during relatively quiet times and the early stage of a substorm a conductivity enhancement occurs only on the poleward side of the harang discontinuity defined by the electric field reversal whereas the enhancement surges equatorward extending beyond the discontinuity during the maximum to recovery phase of a substorm

multi directional force displacement response of underground pipe in sand1 a methodology is presented to evaluate multi directional force displacement relationships for soil pipeline interaction analysis and design large scale tests of soil reaction to pipe lateral and u

plasma convection in the vicinity of the dayside cleft experiments conducted with the chatanika alaska incoherent scatter radar observed the ionospheric convection pattern equatorward of the noontime cleft there plasma transport is characterized by low speed convergence toward a meridian centered somewhat before noon and rotation of the flow into a poleward direction at higher latitudes for undisturbed conditions there is only weak convection at noon at these latitudes but the eastward electric field reaches a maximum of 15 mv m 2 4 hours before and after noon at latitudes between 70 and 74 during active conditions at the peak of the solar cycle the ionospheric cleft was located within the chatanika field of view on several occasions a longitudinally narrow region of rapid poleward convection near noon was not observed rather poleward flow occurred over a 3 4 hour spread of local time for disturbed conditions the prenoon and postnoon regions of plasma entry into the polar cap were enhanced and an eastward electric field of 25 mv m was seen across the 2 hours of local time around noon high density f region plasma was observed convecting poleward through the cleft from a source at lower latitudes in the afternoon sector such plasma seen at very high latitudes within the polar cap serves as a tracer of the convection pattern away from the cleft

colloquium 2004 hydrogeotechnical properties of hard rock tailings from metal mines and emerging geoenvironmental disposal approaches tailings are ground rock particles from which the valuable minerals or metals have been extracted an historical overview on hard rock mines shows that since the 1930s it has become current practice to pump the tailings into storage areas circumscribed by dykes made of the tailings themselves however numerous physical and chemical stability problems were observed mainly owing to the particular hydrogeotechnical and mineralogical properties of the tailings therefore modifications to the conventional methods were proposed but these were relatively costly not always efficient and sometimes difficult to implement new management methods that improve the physical and or chemical stability have hence been developed to reduce environmental risks associated with tailings storage namely densified tailings environmental desulphurization covers built with tailings and co disposal of tailings and waste rock even if many aspects need to be optimized these approaches can be considered today as interest

effect of waste rock inclusions on the seismic stability of an upstream raised tailings impoundment a numerical investigation over the years seismic activity has been a relatively common cause of tailings impoundment failure the flow of liquefied tailings from such ruptures can result in very severe consequences includ

boundary scavenging and deep sea sediment dating constraints from excess 230th and 231pa apparent sedimentation rates derived from excess 230th and 231pa in deep sea sediments accumulated during the last 25 000 years in the pacific ocean are mostly lower than the average rates determined by other independent such as 14c and 18o dating methods which may be a consequence of generally higher accumulation rates of aluminosilicate and carbonate during the last glacial that diluted the excess 230th and 231pa activities in glacial sediments the pattern of enhanced scavenging of nuclides in ocean margin areas i e boundary scavenging also changed from the glacial to the holocene fluxes of 230th and 231pa throughout the ocean varied over time responding to changes in the nature and intensity of boundary scavenging which in turn were influenced by changes in particle flux and particle composition the lower intensity of boundary scavenging of 231pa during the last glacial may also have contributed to the lower apparent sediment accumulation rates based on excess 231pa for cores in ocean margin areas

a simplified method to estimate saturated and unsaturated seepage through dikes under steady state conditions the seepage rate through homogeneous or zoned dikes includes saturated and unsaturated flow the latter is often neglected but should be considered to obtain the positions of the water table and the seepage face that may develop either on the downstream slope of a homogeneous dike or within the filter layer behind the core of a zoned dike different dikes with heights of 5 10 20 and 50 m have been analyzed numerically with a two dimensional finite element code the cases investigated include the most frequent types of small dikes designed to retain municipal or industrial wastewater solutions are proposed to solve numerically two difficulties related to the representation of saturated and unsaturated physical flow conditions one difficulty is treating a downstream seepage face the other is treating the passage of water from the core into a draining layer the paper presents simple expressions to predict the total saturated and unsaturated seepage flow rate through a dike and discusses precautions

submarine groundwater discharge sgd into the yellow sea revealed by 228ra and 226ra isotopes implications for global silicate fluxes abstract we estimated the magnitude of submarine groundwater discharge sgd into the yellow sea which is one of the largest continental shelves in the world using 226 ra and 228 ra isotopes on the basis of 228 ra and 226 ra mass balance models we estimated the advective flux of 226 ra through sgd to be 270 10 12 dpm yr 1 in the yellow sea using this 226 ra flux and the measured 226 ra activity in coastal groundwater the submarine discharge of groundwater mostly brackish groundwater was calculated to be at least 40 of the river water input 2 3 10 11 m 3 yr 1 then on the basis of the sgd and the concentration of si in coastal groundwater we estimated the flux of si through sgd to be 20 100 of that associated with river discharge 23 10 9 mol yr 1 this large sgd is likely to be due to the high tidal range up to 10 m and the wide distribution of sandy sediments in the yellow sea favorable for the recirculation of seawater through bottom sediments and rocks this result from such a large area implies that the si flux through sgd may be significant on a global scale

lead 210 sediment geochronology in a changing coastal environment abstract sediment accumulation rate studies utilizing excess 210 pb and 137 cs were conducted as part of recent investigations of biogeochemical cycling at a single site in cape lookout bight a rapidly changing coastal basin on the outer banks of north carolina u s a cores three meters in length reveal a depositional history for the bight interior characterized by a gradual transition in texture from coarse grained to fine grained material over the period 1946 1979 this transition is controlled by progressive enclosure of the bight by an active northerly migrating recurved spit the textural gradation is periodically interrupted by layers of well sorted sand associated with major storm events lead 210 data indicate that the upper meter of the sediment has accumulated at a rate of 3 35 to 4 71 g cm 2 yr 1 or approximately 8 4 to 11 8 cm yr 1 at o 0 84 below 120 cm depth dilution of clay and silt by low activity sand necessitates correction of the 210 pb profile in order to establish a geochronology grain size 210 pb distribution measurements at three depths reveal that the specific activity dpm g 1 of clay is 3 2 times that of silt and 24 7 times that of sand corrections of bulk sediment excess 210 pb activities based on these measurements lead to dates for textural changes which are consistent with charted changes in basin morphology and major storm events sixteen 137 cs measurements between 33 241 cm depth reveal a peak activity at 105 115 cm and indicate a minimum sedimentation rate of approximately 2 7 g cm 2 yr 1

neotectonic implications and regional stress field constraints on mud volcanoes in offshore southwestern taiwan abstract recently discovered numerous mud volcanoes mvs and mud diapirs mds in sw taiwan both onshore and offshore show eruption lineaments suspected to be related to neotectonic processes spatial and temporal distribution of the mvs eruption events shows an obvious switch of the lineament orientation from nne ne n s nw and e w trending in n s direction the mud volcanoes have experienced multi stage eruptions and should have occurred

evening harang and morning discontinuities in ionospheric electron drifts and their dependence on the interplanetary magnetic field observations made with scandinavian twin auroral radar experiment stare have revealed the existence of a discontinuity in the electron drift pattern at high latitudes during the morning hours the morning discontinuity appears to be equivalent to the evening or harang discontinuity but has the region of westward drifting electrons located poleward of the eastward drifting electrons the dependence of the discontinuity occurrence times on the sign of the azimuthal component by of the interplanetary magnetic field has been investigated we find the evening discontinuity generally occurs earlier for by 0 a similar behavior was not found for the morning discontinuity possibly due to the effects of the high level of magnetic activity kp 5 associated with observations of this discontinuity the average time separation between evening and morning discontinuities was 12 h 30 min it is tentatively proposed that the morning discontinuity is the footprint of the polar cleft in the ionosphere this would imply that the cleft during very disturbed magnetic conditions can extend down to 65 geomagnetic latitude

comparison of simultaneous chatanika and millstone hill observations with ionospheric model predictions as part of the mithras program the chatanika and millstone hill incoherent scatter radars made coordinated observations of the polar ionosphere on june 27 and 28 1981 we compare these data with predictions made by a high latitude ionospheric model qualitatively the same features are evident in both the model and the radar data fairly constant densities on the dayside with a mid latitude trough forming poleward of 65 degrees around 1900 mlt magnetic local time this trough is seen to extend equatorward with increasing mlt such that the minimum densities occurring in the trough appear just after midnight around 60 degrees dipole latitude these features are primarily understood in terms of different regions of convection further influenced by photoionization and vertical transport the only areas of major disagreement between the measurements and model are noted in the auroral oval and at a portion of the times during which substorms occurred quantitatively equally good agreement is obtained between the model predictions and the radar data the densities predicted by the model are usually within 25 of those measured by the radars although appreciable differences occur in some regions of the ionosphere at certain times

an empirical electric field model derived from chatanika radar data plasma convection velocity observations obtained with the chatanika alaska incoherent scatter radar have been used to prepare a quantitative empirical model of the convection electric field at auroral latitudes between 58 and 75 vector averaging of the individual days data and smoothing across 2 5 hours of local time were used to reduce substorm perturbations tables of the vector electric field components at 300 km altitude have been prepared for moderately disturbed kp 3 summer conditions resolution of the model is 0 5 of invariant latitude and one half hour of magnetic local time the model field is asymmetric with the afternoon convection cell dominant in magnitude and spatial extent and corresponds to conditions in which the cross polar cap potential is approximately 70 kv

hydroconsolidation and subsidence of loess studies from china russia north america and europe abstract various approaches to the widespread problem of the hydroconsolidation and subsidence of loess have been suggested these include considerations of rheology thermodynamics phase movements particle packing interparticle bonding pore structure and distribution catastrophe theory topology and simple structural frameworks chinese north american and most european investigators tend to concentrate on mechanisms of loess collapse the russian literature however retains an extra dimension two approaches the syngenetic and the epigenetic approach to the formation of subsiding loess have been defined in the literature most investigators follow a syngenetic approach which appears to be a consequence of the aeolian idea of loess deposition some russian writers in contrast promote an epigenetic approach in which collapsibility can develop in an originally noncollapsible material which can then suffer from hydroconsolidation and subsidence the basis of the phenomenon is a change in the packing structure of the major loess particles and this can be modelled using simple monte carlo methods to develop appropriate structures this paper aims to review the work done on this important subject serious investigation of hydroconsolidation and subsidence of loess began in the early nineteen forties fifty years ago and this has been reported in a piecemeal manner a detailed critical review of this diverse work is now overdue and this is presented herein in the light of recent work in the united kingdom an attempt is made to describe the process in a phenomenological and a structural sense inherent in this the role of n ya denisov as subsidence pioneer is considered

glacial to holocene changes in carbonate and clay sedimentation in the equatorial pacific ocean estimated from thorium 230 profiles uranium series nuclide concentrations have been measured on sediments from five box cores from an equatorial pacific transect 230thexcess activities show discontinuities at the holocene glacial boundary as dated by 14c the glacial sedimentation rates determined by 230th and 14c are 2 5 3 0 cm kyr the holocene rates from 230th are much lower than those dated by 14c 1 9 2 3 cm kyr because of carbonate dissolution 230th sedimentation fluxes exceed water column supply by factors of 1 2 1 8 in the holocene and 1 8 3 0 in the glacial sections a number of models have been applied to calculate carbonate dissolution rates the results show that carbonate dissolution rates in the holocene in g cm kyr equal 1 5 10 3 exp 1 4d where d is water depth in kilometers a point by point estimation of sediment fluxes through time show that clay accumulation rates in the area have been near constant at 0 1 0 2 g cm kyr over the past 20 kyr whereas carbonate accumulation rates have decreased dramatically from 0 6 1 0 g cm kyr in the glacial sections of the cores to 0 2 0 6 g cm kyr in the holocene the errors caused by the uncertainties in the age of the termination of the last glacial period have been investigated and results show that a range of 11 14 kyr leads to an error upper limit of about 30 in the estimation of caco3 dissolution rates the response time of caco3 and 230thex concentrations in the mixed layer of sediments due to an impulse of change in caco3 dissolution rate has also been discussed showing that the observed changes in carbonate dissolution may be explained in terms of a single or a continuous change depending upon the thickness of the mixed layer

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

electrostatic potential in the auroral ionosphere derived from chatanika radar observations a technique is described for determining the latitudinal variation of the electrostatic potential associated with the ionospheric convection electric field using the north south electric field component derived from radar convection velocity experiments the integral of e dl is taken northward along the magnetic meridian starting at low latitudes the radar data consist of up to 40 independent measurements of plasma convection spanning 15 of invariant latitude centered on chatanika alaska 65 with half hour temporal resolution it has been found that 1 the electric field contributions to the potential at and below 60 are small under most circumstances and 2 the latitudinal variation of the potential is smooth and regular permiting the potentials to be contoured across local time it is found from the experiments that the potential often varies uniformly over 10 latitude at dawn and dusk electric fields of 50 mv m are common it is also noted that the latitude of the greatest negative potential in the premidnight sector coincides with the harang discontinuity in ionospheric currents the potentials calculated from the measured plasma drifts exhibit a regular local time variation equipotential contours derived from the latitude local time potential field obtained with the long duration radar experiments while not providing a snapshot of the instantaneous pattern elucidate the large scale diurnal variation of the electrostatic potential at auroral latitudes from such contours it is found that a two cell convection pattern with varying degrees of asymmetry is consistently present at auroral latitudes that a cross polar cap potential drop of 70 120 kv is present in moderately disturbed conditions and that substorms perturb the potential pattern at all local times

ground based studies of ionospheric convection associated with substorm expansion the instantaneous patterns of electric fields and currents in the high latitude ionosphere are deduced by combining satellite and radar measurements of the ionospheric drift velocity along with ground based magnetometer observations for october 25 1981 for this purpose an updated version of the assimilative mapping of ionospheric electrodynamics technique has been used these global patterns are unobtainable from any single data set the period under study was characterized by a relatively stable southward interplanetary magnetic field imf so that the obtained electric field patterns do reflect in general the state of sustained and enhanced plasma convection in the magnetosphere during one of the satellite passes however an intense westward electrojet caused by a substorm intruded into the satellite de 2 and radar chatanika alaska field of view in the premidnight sector providing a unique opportunity to differentiate the enhanced convection and substorm expansion fields the distributions of the calculated electric potential for the expansion and maximum phases of the substorm show the first clear evidence of the coexistence of two physically different systems in the global convection pattern the changes in the convection pattern during the substorm indicate that the large scale potential distributions are indeed of general two cell patterns representing themore southward imf status but the night morning cell has two positive peaks one in the midnight sector and the other in the late morning hours corresponding to the substorm expansion and the convection enhancement respectively 40 refs 12 figs 1 tab less

predicting the saturated hydraulic conductivity of sand and gravel using effective diameter and void ratio this paper assesses methods to predict the saturated hydraulic conductivity k of clean sand and gravel currently in engineering the most widely used predictive methods are those of hazen and t

review and comparison of models for describing non equilibrium and preferential flow and transport in the vadose zone abstract in this paper we review various approaches for modeling preferential and non equilibrium flow and transport in the vadose zone existing approaches differ in terms of their underlying assumptions and complexity they range from relatively simplistic models to more complex physically based dual porosity dual permeability and multi region type models a relatively simple dual porosity flow model results when the richards equation is combined with composite double hump type equations for the hydraulic properties to account for both soil textural matrix and soil structural fractures macropores peds effects on flow the simplest non equilibrium flow model a single porosity model which distinguishes between actual and equilibrium water contents is based on a formulation by ross and smettem soil sci soc am j 64 2000 1926 that requires only one additional parameter to account for non equilibrium a more complex dual porosity mobile immobile water flow model results when the richards or kinematic wave equations are used for flow in the fractures and immobile water is assumed to exist in the matrix we also discuss various dual permeability models including the formulation of gerke and van genuchten water resour res 29 1993a 305 and the kinematic wave approach as used in the macro model of jarvis technical description and sample simulations department of soil science swedish university of agricultural science uppsala sweden 1994 51 both of these models invoke terms accounting for the exchange of water and solutes between the matrix and the fractures advantages and disadvantages of the different models are discussed and the need for inter code comparison is stressed especially against field data that are sufficiently comprehensive to allow calibration validation of the more complex models and to distinguish between alternative modeling concepts several examples and comparisons of equilibrium and various non equilibrium flow and transport models are also provided

simultaneous chatanika radar and s3 2 satellite measurements of ionospheric electrodynamics in the diffuse aurora simultaneous chatanika radar and s3 2 satellite measurements have been used to investigate the spatial variation of the auroral zone ionosphere near the equatorward edge of the diffuse aurora during early evening satellite passes on 2 days in february 1976 the equatorward boundary of the diffuse aurora was nearly overhead at chatanika the configurations of e region ionization and conductivity were nearly identical in both passes but the latitudinal variations of f region ionization were quite dissimilar during both passes the ionospheric electric field in the diffuse aurora was directed northward as a result the closing current of the field aligned current system was primarily a pedersen current and the eastward electrojet was larger than the northward ionospheric current although the morphology of ionospheric conductivity was very similar on the 2 days different patterns were observed for the latitudinal distribution of electric field and field aligned current

coherent radar estimates of average high latitude ionospheric joule heating the scandinavian twin auroral radar experiment stare and sweden and britain radar experiment sabre bistatic coherent radar systems have been employed to estimate the spatial and temporal variation of the ionospheric joule heating in the combined geographic latitude range 63 8 72 6 corrected geomagnetic latitude 61 5 69 3 over scandinavia the 173 days of good observations with all four radars have been analyzed during the period 1982 to 1986 to estimate the average ionospheric electric field versus time and latitude the ae dependent empirical model of ionospheric pedersen conductivity by spiro et al 1982 has been used to calculate the joule heating the latitudinal and diurnal variation of joule heating as well as the estimated mean hemispherical heating of 1 7 1011 w are in good agreement with earlier results average joule heating was found to vary linearly with the ae au and al indices and as a second order power law with kp the average joule heating was also examined as a function of the direction and magnitude of the interplanetary magnetic field it has been shown for the first time that the ionospheric electric field magnitude as well as the joule heating increase with increasingly negative southward bz

response of the dayside auroral and electrodynamic processes to variations in the interplanetary magnetic field the response of the dayside auroral and electrodynamic processes to variations in the interplanetary magnetic field imf is examined with multi instrument data from the viking and dmsp f7 satellites as well as ground magnetometer data the event selected which occurred on october 5 1986 was previously identified as a high latitude dayside form by murphree and elphinstone 1988 imf by was positive during most of the viking auroral uv observation whereas imf bz made a transient southward excursion followed by a sharp increase to 8 nt the results are summarized as follows 1 there were two auroral belts extending westward from the early afternoon sector the equatorward belt was persistent throughout the event and was embedded in the cps bps precipitation region whereas the poleward belt was in the open field line region and was associated with northward imf bz 2 a new auroral spot emerged in the afternoon sector just poleward of the previously active region delayed 10 min from the sudden increase in imf bz this time lag is ascribed to the travel time of the new imf orientation from the subsolar point to a solar wind magnetosphere interaction site tailward of the dayside cusp as well as to the response time of the dayside auroral acceleration process 3 the new auroral activity expanded both eastward and westward during the first few minutes and then expanded primarily westward across the noon meridian forming the poleward belt the speed of the westward extension in the second phase was comparable to the speed of the ionospheric convection 4 the dayside auroral process has a finite decay constant which is inferred to be at least 10 min 5 the response time of the midday ionospheric convection to imf variations is estimated to be a few to several minutes

comparative probabilistic assessment of the hydrological performance of reconstructed and natural watersheds the oil sands industry has committed to returning the mine sites to a productive condition the reconstructed soil covers must have sufficient available water holding capacity awhc to supply enough moisture over the growing season to promote vegetation in order to assess the sustainability of various soil cover alternatives a generic system dynamic watershed model entitled gsdw was used along with the available historical meteorological records to estimate the maximum soil moisture deficit and annual evapotranspiration fluxes a probabilistic framework was adopted consequently frequency curves of the maximum annual moisture deficit values are constructed and used to assess the probability that various reconstructed and natural watersheds can provide the associated moisture demands in general the study showed a tendency for the reconstructed watershed to provide less moisture for evapotranspiration than natural systems watersheds of various soil types layering thicknesses and topography were studied the gained knowledge was used to predict the possible performance of a hypothetical reclamation cover the results indicated that the hypothetical cover performed in a similar manner to the thickest existing soil cover which confirmed a high probability of that cover to survive under the same existing climatic conditions moreover this probabilistic framework was found to be useful for integrating information gained from natural watersheds e g the canopy of mature natural systems and transfer the results to the reconstructed system the results show that the canopy influenced the moisture deficit regime positively which signifies a greater possibility that reconstructed covers will adapt to vegetation type in brief the adopted approach enables better understanding of the response of reconstructed systems via multiple simulations of what if scenarios using different soil vegetation alternatives copyright 2010 john wiley sons ltd

altitudinal comparison of dayside field aligned current signatures by viking and dmsp f7 intermediate scale field aligned current systems dayside large scale and intermediate scale field aligned current fac signatures are examined with multi instrument measurements from viking and dmsp f7 at magnetic conjunctions the present paper reports four such conjunction events with an emphasis on an event that occurred on october 13 1986 in these four events both viking and dmsp f7 crossed prenoon fac systems approximately along meridians the altitude of dmsp f7 was 835 km whereas that of viking ranged from 8500 to 12 000 km the electric to magnetic field ratio measured by viking indicates that intermediate scale fac systems as well as large scale fac systems are often quasi stationary this is also supported by the comparison between the viking and dmsp f7 magnetic measurements the only obvious exception is the equatorward part of the october 13 event in which the viking and dmsp f7 measurements are better explained in terms of alfven waves in two other events the viking signature projected to the dmsp f7 altitude is significantly more structured than the dmsp f7 signature although the electric to magnetic field ratio observed by viking suggests that the associated facs were quasistationary this apparent discrepancy is possibly ascribed to the fact that viking stays longer in fac systems and therefore has more chance to observe temporal changes in facs however such temporal effects must operate longer than the alfven transit time so that fac systems become quasi stationary although the generation mechanism s of intermediate scale fac systems remains an open question possibilities include a localized shear of plasma convection and a localized merging between the solar wind and magnetospheric field lines

mean auroral e region plasma convection patterns measured by sabre large scale flows of convective plasma in the earth s magnetosphere driven by the external influence of the solar wind have long been known the electric fields associated with this convection are mapped along approximately equipotential field lines to low altitudes resulting in strong ionospheric flows considerable controversy surrounds the detailed pattern of the convective flow in the ionosphere its dependence on geomagnetic and interplanetary conditions and the resulting magnetospheric topology several observations1 2 suggest that this pattern rotates towards earlier local times during magnetically disturbed periods but empirically based modelling failed to detect such an effect and even suggested the counter rotation towards later local times3 since april 1982 a new radar auroral backscatter system sabre sweden and britain radar auroral experiment has been in operation in north ern europe4 which allows estimates to be made of plasma convection in the auroral e region over a large area 200 000 km2 l 4 6 with high spatial and temporal resolution here we present the flow patterns averaged over this period of radar operation for different levels of magnetic activity revealing a definite rotation of the whole convection pattern towards earlier local times with increasing activity

self weight consolidation of mixtures of mine waste rock and tailings mixtures of waste rock and tailings are compared with unmixed waste rock and tailings in a column study of self weight consolidation standard practice for surface mine waste disposal produces the two individual waste streams of waste rock and tailings waste rock dumps offer high strength and low compressibility characteristics but are prone to oxidation and metal leaching because of their high permeability and unsaturated conditions tailings deposits typically have low permeability and slow time rate consolidation properties but also have end land use issues and long term stability problems related to shear strength three mixtures of waste rock and tailings were loaded into columns and monitored for settlement drainage and pore water pressure response for 100 days a fourth column was built with waste rock only as a control mixtures with approximately 5 1 waste rock to tailings by dry mass were found to have a hydraulic conductivity similar to tailings alone and total settlements similar to waste r

sedimentation rates on the continental slope off eastern taiwan abstract 230th and 210pb were measured to determine sedimentation rate and mass flux for several cores collected from the continental slope off eastern taiwan in the slope northeast of taiwan at 490 m depth the sedimentation rate as determined from a box core by the excess 210pb method was 0 28 cm yr for the past 60 years in the deep slope off eastern taiwan the rates as determined from two piston cores by the excess 230th method were similar at about 2 3 cm kyr in gravity core located near lutao farther south the sedimentation rate dropped to 0 6 cm kyr these rates suggest that the river input and runoff from the east coast of taiwan contribute a significant mass of sediments to the slope off the east coast the sedimentation rate obtained on the northern continental slope is about 100 times greater than that on the slope off the east coast suggesting that the major sediment source for the former site is probably the east china sea shelf there are indications that the sediments from both the yangtze and yellow rivers are transported southward by the coastal current and then deflected eastward just north of taiwan when the coastal current encounters the north flowing taiwan warm current sediment traps deployed near the coring site on the northern slope yield an apparent particulate flux that varies periodically with time the flux ranges between 2 2 and 2 8 g m2 day the high variability of trapped particulate flux was found to be closely correlated with the tidal current the mass flux estimated from the sedimentation rate 0 28 cm yr and dry bulk density is about 11 g m2 day about four to five times higher than the trapped particulate flux this discrepancy may be mainly due to horizontal transport near bottom below the trap deployment depth an alternative interpretation for the high mass flux on the northeastern slope is that the sediments have been transported from north to south along the shelf break by the counter current just immediately to the west of the kuroshio

thirty ninth canadian geotechnical colloquium unsaturated soil mechanics bridging the gap between research and practice the majority of geoengineering applications occur in the unsaturated vadose zone which is the near surface region forming the connection between meteorological phenomena above and saturated grou

evaluation of the saturated unsaturated groundwater conditions of a thickened tailings deposit the method of thickened tailings disposal has been in use at an active copper zinc mine near timmins ontario for approximately 25 years the thickened tailings deposit that has been formed was in