a multi model analysis of the role of the ocean on the african and indian monsoon during the mid holocene we investigate the role of the ocean feedback on the climate in response to insolation forcing during the mid holocene 6 000 year bp using results from seven coupled ocean atmosphere general circulation models we examine how the dipole in late summer sea surface temperature sst anomalies in the tropical atlantic increases the length of the african monsoon how this dipole structure is created and maintained and how the late summer sst warming in the northwest indian ocean affects the monsoon retreat in this sector similar mechanisms are found in all of the models including a strong wind evaporation feedback and changes in the mixed layer depth that enhance the insolation forcing as well as increased ekman transport in the atlantic that sharpens the atlantic dipole pattern we also consider changes in interannual variability over west africa and the indian ocean the teleconnection between variations in sst and sahelian precipitation favor a larger impact of the atlantic dipole mode in this region in the indian ocean the strengthening of the indian dipole structure in autumn has a damping effect on the indian dipole mode at the interannual time scale

state of the art of modelling two phase flow in fractured rock two phase flow in fractured rock is an important phenomenon for a range of practical problems not the least of which is non aqueous phase liquid napl contamination of groundwater although multiphase systems have long been studied in the petroleum field in the hydrogeological field progress has only just reaches the point where models are being developed scale effect is one of the main issues of concern although models presented in this paper have the potential to provide useful predictions they can only be used to investigate a variety of possible scenarios with parameters being specified in the form of distribution of values the calibration and validation of all but the simplest of these models poses a formidable task with great demands on hydrogeologists and geophysicists to provide adequate data

scale dependence of soil permeability to air measurement method and field investigation this work investigates the dependence of soil permeability to air on sampling scale in near surface unsaturated soils a new dual probe dynamic pressure technique was developed to measure permeability in situ over different length scales and different spatial orientations in the soil soils at three sites were studied using the new technique each soil was found to have higher horizontal than vertical permeability significant scale dependence of permeability was also observed at each site permeability increased by a factor of 20 as sampling scale increased from 0 1 to 2 m in a sand soil vegetated with dry grass and by a factor of 15 as sampling scale increased from 0 1 to 3 5 m in a sandy loam with mature coast live oak trees quercus agrifolia the results indicate that standard methods of permeability assessment can grossly underestimate advective transport of gas phase contaminants through soils

distribution of uranium thorium and rare earth elements in the eye dashwa lakes pluton a study of some analogue elements abstract the distribution of u th and rare earth elements ree s in the eye dashwa lakes pluton near atikokan ontario is examined materials analysed include a unaltered granite b altered granite c highly altered granite adjacent to open fractures and d fracture filling minerals distinct distribution patterns are noted for u and some ree s among the four types of samples th shows higher concentrations in materials c and d compared with unaltered and altered granite the highly altered granite and some fracture fillings have greater concentrations of u th and ree s the large concentrations of u th and ree s in these materials are due to both sorption on selective materials and precipitation as mineral phases containing these elements the occurrence of uraninite bastnaesite and thorogummite coatings on fracture fillings are examples of this precipitation

the influence of changing orbital parameters and surface boundary conditions on climate simulations for the past 18 000 years abstract general circulation model experiments at 3000 year intervals for the past 18 000 years were made to estimate the magnitude timing and pattern of the climatic response to prescribed changes of orbital parameters date of perihelion axial tilt eccentricity and glacial age lower boundary conditions ice sheets land albedo sea ice and sea surface temperature the experiments used the community climate model ccm of the national center for atmospheric research ncar the response of monsoon circulations and tropical precipitation to the orbitally produced solar radiation changes was much larger than the response to changes of glacial age boundary conditions the continental interior of eurasia was 2 4 k warmer in summer and summer monsoon precipitation of north africa south asia was increased by 10 20 between 12 000 and 6000 yr bp before present when perihelion occurred during northern summer rather than in winter as now and the earth s axial tilt was larger than now southern hemisphe

a 13 000 year climate record from western tibet although the tibetan plateau is important in influencing the atmospheric circulation of the northern hemisphere1 3 there are only a few continuous palaeoclimate records available and these are limited to the plateau s northeastern margin4 6 here we present a 13 000 yr record from sumxi co western tibet constructed from both lake core and shoreline studies which shows that conditions in the early middle holocene were warmer and wetter than at present these results confirm model predictions of an intensified monsoon over the region at 9 000 yr bp owing to an orbitally induced increase in summer insolation7 8 we also find evidence for warm humid pulses at 12 500 and 10 000 yr bp in phase with the steps of the last deglaciation and for a return to cold dry conditions at 11 10 000 yr bp none of which can be explained by orbital variations the existence of the cold episode confirms that the cooling associated with the younger dry as event occurred in continental china6 9 and provides further evidence of the global nature of this event10

quantitative reconstructions of annual rainfall in africa 6000 years ago model data comparison precipitation are based on 85 pollen sites 14 c dated at 6000 500 years b p and distributed over the whole of africa to improve the reliability of the pollen based climate reconstruction two methods are used the modern analogues technique mat and the plant functional types pft methods we then conduct a model data comparison for five distinct regions allowing an evaluation of model outputs the sahara sahel the eastern sahara western equatorial africa east africa and madagascar the pollen inferred reconstructions are compared with 21 mid holocene simulations yielded by atmospheric general circulation models agcms and coupled ocean atmosphere vegetation models oavgcms the large scale feature of the hydrological changes is shown to be well captured by most of the models data show that during the mid holocene the sahara was considerably wetter than today 200 to 700 mm yr the results reinforce the conclusion that the agcms significantly underestimate this precipitation increase in the sahara whereas the oavgcm simulations are in accordance with the data our results show that vegetation and ocean feedbacks do not have a strong impact in the intertropical zone and that models fail to properly reproduce the climatic conditions in east africa and madagascar the model data comparison also suggests that the lengthening of the dry season during boreal winter in the west equatorial region is a robust feature although the pollen based reconstruction shows no change or only slight drying there

a large scale flow and tracer experiment in granite 1 experimental design and flow distribution this paper describes the stripa three dimensional experiment where water and tracer flow has been monitored in a specially excavated drift in the stripa mine several new experimental techniques and equipment were developed and used the experiment was performed in a specially excavated drift 100 m long at the 360 m level in granite the whole ceiling and the upper part of the walls were covered with 375 individual plastic sheets where the water flow into the drift could be collected eleven different tracers were injected at distances between 11 and 50 m from the ceiling of the drift the flow rate and tracer monitoring was kept up for more than 2 years the tracer breakthrough curves and flow rate distributions were used to study the flow paths velocities hydraulic conductivities dispersivities and channeling effects in the rock this paper describes the experimental techniques the fracture mapping the tracer and flow rate measurements and the results of the flow rate measurements the detailed observations made possible by the plastic sheeting technique have given some qualitative as well as quantitative information on flow rate distribution in fractured rock which previously has not been available these observations may be of importance for assessing the transport of dissolved species such as radionuclides through fractured rock

observations of preferential flow during a liquid release experiment in fractured welded tuffs author s salve rohit abstract to better understand preferential flow in fractured rock we carried out an in situ field experiment in the exploratory studies facility at yucca mountain nevada this experiment involved the release of 22 m3 of ponded water at a pressure head of 0 04 m over a period of 7 months directly onto a 12 m2 infiltration plot located on a fractured welded tuff surface as water was released changes in moisture content were monitored along horizontal boreholes located in the formation 19 22 m below distinct flow zones varying in flow velocity wetted cross sectional area and extent of lateral movement intercepted the monitoring boreholes there was also evidence of water being diverted above the ceiling of a cavity in the immediate vicinity of the monitoring boreholes observations from this field experiment suggest that isolated conduits each encompassing a large number of fractures develop within the fractured rock formation to form preferential flow paths that persist if there is a continuous supply of water in addition in fractured welded tuffs the propensity for fracture matrix interactions is significantly greater than that suggested by existing conceptual models in which flow occurs along a section of fracture surfaces an overriding conclusion is that field investigations at spatial scales of tens of meters provide data critical to the fundamental understanding of flow in fractured rock

mid holocene east asian summer climate as simulated by the pmip2 models abstract in the present study datasets derived from twelve coupled ocean atmosphere general circulation models oagcms in the paleoclimate modelling intercomparison project phase two were used to analyze the east asian summer climate during the mid holocene about 6000 calendar years ago on the whole the oagcms reproduced warmer and wetter summer climate conditions in east asia during the mid holocene the multi model ensemble showed that in east asia the regionally averaged summer surface air temperature sat increased by 0 89 c summer precipitation was 5 8 higher and an obviously strengthened southerly wind corresponded to a strong summer monsoon in the mid holocene when compared to preindustrial levels the data model comparison in china reveals a good agreement between the oagcms results and the reconstructed changes in the summer sat in east china during the mid holocene in north china the simulated sat anomalies are 0 5 c lower overall than reconstruction in contrast the oagcms fail to capture the strongest warming in the southern qinghai tibetan plateau on the other hand the simulated precipitation agrees well with proxy data except for in the central parts of china where the simulated summer precipitation disagrees in sign with reconstruction in addition there is a large spread among the simulations particularly over and around the qinghai tibetan plateau and inter model discrepancies are larger for precipitation than for sat as a whole

three dimensional characterization of a fractured granite and transport properties a three dimensional fracture network in a granite block is reconstructed from a series of experimental serial sections it is visualized and its most important geometrical characteristics are studied namely the orientation of the fractures the connectivity of the fractures the number of cycles per unit volume the distributions of surface areas and of the intersection lengths and the number of finite solid blocks isolated in the solid matrix by the network though the network mostly consists of two families of fractures it is interesting to note that a simple model of randomly oriented monodisperse hexagons often yields a good order of magnitude for the various geometrical properties which have been measured on the real block the flow properties are then studied examples of velocity field are provided as well as histograms of velocities the permeability tensor is determined and is found to be in good agreement with snow s formula finally dispersion is analyzed by means of a random walk method histograms of arrival times are provided and interpreted in terms of dispersion tensor

testing model simulations of the thermocline depth variability in the tropical atlantic from 1982 through 1984 abstract the multivariate model toning procedure of frankignoul et al has been extended to the general time series case thus allowing to test ocean model ability at simulating the interannual variability the method aims at distinguishing between model inadequacies and data uncertainties model performances are assessed from a misfit evaluated in a space of strongly reduced dimension with basis vectors issued from a double application of common principal component analysis the testing procedure has been used to investigate the ability of cane s linear multimode model at simulating the evolution of the 20 c isotherm depth in the equatorial atlantic during the 1982 1984 focal sequal experiment using monte carlo techniques and five different drag laws 25 equally plausible wind stress fields were constructed to represent the wind stress uncertainties consistently with the sample means and variances of the original ship measurements even during this well sampled period the forcing uncertainties were sub

mid holocene nao a pmip2 model intercomparison 1 the mid holocene 6000 years before present north atlantic oscillation nao from nine models in the paleoclimate modeling intercomparison project phase 2 is studied primarily through principal component analysis of winter time north atlantic sea level pressure slp modeled mid holocene nao and mean slp show small changes compared to pre industrial control runs with a shift in mean state towards a more positive nao regime for three of the models modeled nao variability shows little change with a small increase for some models in the fraction of time spent in the nao negative phase during the mid holocene proxy based reconstructions of the nao indicate a more positive nao regime compared to present day during the mid holocene we hypothesise that there was a small nao like shift in mean state during the mid holocene

long term weakening of the east asian summer and winter monsoons during the mid to late holocene recorded by aeolian deposits at the eastern edge of the mu us desert abstract the east asian summer monsoon easm and east asian winter monsoon eawm are major drivers of environmental conditions in east asia however due to the lack of high resolution eawm records the phase relationship between the easm and eawm during the holocene epoch is still debated here we use magnetic and grain size measurements from a sequence of aeolian sediments from the eastern edge of the mu us desert to track the history of the easm and eawm from 7 5 to 2 5 ka the results show that both the easm and eawm exhibit a similar long term weakening trend during this interval in view of the stable glacial boundary conditions and the significantly decreased rates of atmospheric co 2 rise since the mid holocene we suggest that orbitally induced insolation was the major cause of the weakening of both the easm and eawm decreasing summer insolation and increasing winter insolation reduced the thermal contrast between the ocean and the asian continent in both summer and winter time resulting in the weakening of both monsoon systems during the mid to late holocene

controls of mass recovery rates in single well injection withdrawal tracer tests with a single porosity heterogeneous conceptualization 1 a single well injection withdrawal swiw test is evaluated as a tool to assess a single porosity conceptualization for a transport system we have shown that there are cases in which matrix diffusion cannot be proven definitively from the results of swiw tests owing to uncertainties of aquifer properties drift during the resting phase of the test can carry a plume to areas where the flux is lower during the withdrawal phase leading to decreased mass recovery rates results of sensitivity studies on multiple stochastically generated heterogeneous transmissivity fields indicate that variance in transmissivity has a strong effect on drift and consequently mass recovery rates in addition to impacting drift directly the regional gradient has the potential to influence mass recovery rates by interfering with the pumping induced fluxes toward the well during withdrawal the kolmogorov smirnov test is used to evaluate whether simulated data using a single porosity conceptualization with plume drift significantly differ from swiw tracer test data from a fractured dolomite unit at the waste isolation pilot plant given the uncertainty in the variance of transmissivity it is unlikely that a single porosity conceptualization can match the field data matrix diffusion is a likely explanation for the observed gradual mass recovery rates

strong coherence between solar variability and the monsoon in oman between 9 and 6 kyr ago variations in the amount of solar radiation reaching the earth are thought to influence climate but the extent of this influence on timescales of millennia to decades is unclear a number of climate records show correlations between solar cycles and climate1 but the absolute changes in solar intensity over the range of decades to millennia are small2 and the influence of solar flux on climate is not well established the formation of stalagmites in northern oman has recorded past northward shifts of the intertropical convergence zone3 whose northward migration stops near the southern shoreline of arabia in the present climate4 here we present a high resolution record of oxygen isotope variations for the period from 9 6 to 6 1 kyr before present in a th u dated stalagmite from oman the 18o record from the stalagmite which serves as a proxy for variations in the tropical circulation and monsoon rainfall allows us to make a direct comparison of the 18o record with the 14c record from tree rings5 which largely reflects changes in solar activity6 7 the excellent correlation between the two records suggests that one of the primary controls on centennial to decadal scale changes in tropical rainfall and monsoon intensity during this time are variations in solar radiation

distribution of radon sources and effects on radon emanation in granitic soil at ben lomond california the abundance and distribution of radioelements on bulk and microscopic scales were investigated in residual granitic derived soil at a facility for investigating the movement of radon into structures in bulk soil samples ra concentrations range from 0 6 to 1 3 pci g and variations in ra th and k appear to be controlled mainly by heterogeneities inherited from the parent granitic rock which contains abundant dikes and inclusions u in soil and parent rock is concentrated in primary minerals mainly zircon and sphene and in secondary sites that are of greater importance for rn emanation the main u bearing secondary sites are weathered sphene grain boundary coatings weathered biotite and plagioclase as well as dense fe rich coatings and a ree phosphate mineral present in near vertical fracture zones in saprolite underlying shallow loam elevated u in these sites generally correlates with high ti al fe and or p preferential distribution of u and ra on grain boundaries and porous weathered minerals is reflected in relatively high rn emanation rates in the soil highest emanation occurs between 1 3 and 2 3 m depth where fine pedogenic phasesgibbsite and amorphous silica and fe ooh are most abundant it is related to fixation of ra by these phases which precipitate close to the surface and accumulate at these depths by illuviation separation of ra from u may occur locally given remobilization of u series elements from secondary sites and large differences between ra and u sorption capabilities of several phases present in the soil concentration of u along permeable fracture zones in saprolite suggests that contribution of soil gas rn from depth 2 m could be significant to rn availability near the surface

the influence of parent material on topsoil geochemistry in eastern england the topsoil of around 10 000 km2 in eastern england has recently been sampled intensely at 4609 sites to characterize its geochemistry the parent materials which include both solid geology and quaternary sediments range in age from permian to holocene the distributions of the concentrations of major and trace elements have been characterized geostatistically and the role of parent material on their spatial structure anisotropy and their spatial relationships coregionalization have been investigated analysis of variance with the sites grouped by major parent material type showed that this classi cation accounted for 14 to 48 per cent of the variance for the various elements global variograms of 13 elements al as ca cr cu fe mg mo ni p pb ti and u have been computed and modelled eleven of the variograms seem to comprise two structures both of which we modelled with spherical functions one of short range 3 5 to 9 km and the other with a range of 15 to 23 km the models included a nugget variance which varied from 27 per cent for as fe and mg to 63 per cent for p of the total the long range structures are related to the separations of the major parent materials the variograms of several elements showed appreciable anisotropy most notably that of mg anisotropy is evident at short ranges of less than 5 km this accords with the geological structure of the beds which dip from west to east so that their outcrops are elongated from north to south a linear model of coregionalization tted to the data emphasized several important geochemical associations which we interpret elements commonly associated with clay minerals mg al and the clay size fraction ti are dominated by the long range structure of the coregionalization whilst several trace elements as cr ni and u are spatially correlated with fe over short distances through adsorption of the former on the surfaces of fe oxyhydroxides the topsoil around large urban areas is enriched in lead but it is not clear whether anthropogenic sources are responsible for this metal s anomalous spatial relationships with other elements crown copyright 2003 reproduced with the permission of her majesty s stationery of ce published by john wiley sons ltd

the interpretation of a tracer experiment conducted in a single fracture under conditions of natural groundwater flow the development of conceptual models to describe the hydrogeology of sparsely fractured media requires the characterization of the properties of discrete fractures at the field scale in this study a tracer experiment conducted under conditions of natural groundwater flow in a discrete fracture in an interbedded shale and limestone sequence is interpreted this experiment which was initiated by injecting a small quantity of tracer into the fracture plane involved monitoring tracer movement using 27 boreholes within a 35 40 m area test data revealed a tracer plume which spread both longitudinally and transversely in the direction of mean groundwater flow the field breakthrough curves were interpreted using a two dimensional finite element transport model that incorporated longitudinal and transverse dispersion diffusion into the rock matrix and constant fracture aperture additional simulations which incorporated the effects of aperture variability were conducted in a monte carlo format by varying the spatial correlation and variance of the aperture field the constant aperture analysis found that the mean aperture determined from the tracer experiment was approximately 20 greater than the mean aperture measured by hydraulic methods values of matrix porosity ranging between 1 and 3 a constant longitudinal dispersivity of 0 1 m and a large range in transverse dispersivity from 0 01 to 0 22 m were required to simulate the data trends of increasing aperture and matrix porosity with distance were observed suggesting that tracer transport followed increasingly tortuous pathways although the variable aperture simulations were not fitted to the field data the aperture field having an isotropic spatial correlation length of 0 5 m and variance of 10 000 m2 provided simulated plumes that appeared to be most similar to the shape and concentration of the field plume evidence from the hydraulic measurement of the aperture distribution suggests that this is a reasonable estimate of the natural aperture field

hydrologic issues associated with nuclear waste repositories significant progress in hydrology especially in subsurface flow and solute transport has been made over the last 35 years because of sustained interest in underground nuclear waste repositories the present paper provides an overview of the key hydrologic issues involved and to highlight advances in their understanding and treatment because of these efforts the focus is not on the development of radioactive waste repositories and their safety assessment but instead on the advances in hydrologic science that have emerged from such studies work and results associated with three rock types which are being considered to host the repositories are reviewed with a different emphasis for each rock type the first rock type is fractured crystalline rock for which the discussion will be mainly on flow and transport in saturated fractured rock the second rock type is unsaturated tuff for which the emphasis will be on flow from the shallow subsurface through the unsaturated zone to the repository the third rock type is clay rich formations whose permeability is very low in an undisturbed state in this case the emphasis will be on hydrologic issues that arise from mechanical and thermal disturbances i e on the relevant coupled thermo hydro mechanical processes the extensive research results especially those from multiyear large scale underground research laboratory investigations represent a rich body of information and data that can form the basis for further development in the related areas of hydrologic research

diversity of channeling flow in heterogeneous aperture distribution inferred from integrated experimental numerical analysis on flow through shear fracture in granite 1 shear mode ii fractures with shear displacements of 1 and 5 mm were generated by direct shear on granite under normal stresses of 1 20 and 60 mpa fracture surface mapping showed that the surface roughnesses of the shear fractures decreased with increasing shear displacement and normal stress and were smaller than those of tensile fractures reported in our previous study fluid flow experiments on the shear fractures provided fracture permeabilities at a wide range of confining pressures of 10 100 mpa nonmonotonic permeability was usually observed to decrease with increasing confining pressure however the permeability changes were different between the shear fractures generated at the normal stress of 20 and 60 mpa in addition obvious permeability changes with shear displacement were observed for 60 mpa whereas no significant difference was observed for 20 mpa comparing the shear fractures with the tensile fractures having shear displacements revealed clear differences even for equivalent shear displacements numerical models that were constructed using the data of the fracture surface mapping by matching their permeabilities with the experimentally evaluated fracture permeabilities revealed the development of preferential flow paths i e channeling flows for the shear fractures providing a diversity of channeling flow in heterogeneous aperture distributions of rock fractures in the earth s crust

an evaluation of the simulated water balance of eurasia and northern africa at 6000 y bp using lake status data changes in the water balance of eurasia and northern africa in response to insolation forcing at 6000 y bp simulated by five atmospheric general circulation models have been compared with observations of changes in lake status all of the simulations show enhancement of the asian summer monsoon and of the high pressure cells over the pacific and central asia and the middle east causing wetter conditions in northern india and southern china and drier conditions along the chinese coast and west of the monsoon core all of the models show enhancement of the african monsoon causing wetter conditions in the zone between ca 10 20 n four of the models show conditions wetter than present in southern europe and drier than present in northern europe three of the models show conditions similar to present in the mid latitude continental interior while the remaining models show conditions somewhat drier than present the extent and location of each of the simulated changes varies between the models as does the mechanism producing these changes the lake data confirm some features of the simulations but indicate discrepancies between observed and simulated climates for example the data show 1 conditions wetter than present in central asia from india to northern china and mongolia indicating that the simulated asian monsoon expansion is too small 2 conditions wetter than present between ca 10 30 n in africa indicating that the simulated african monsoon expansion is too small 3 that northern europe was drier but the area of significantly drier conditions was more localized around the baltic than shown in the simulations 4 that southern europe was wetter than present apparently consistent with the simulations but pollen data suggest that this reflects an increase in summer rainfall whereas the models show winter precipitation and 5 that the mid latitude continental interior was generally wetter than present

recoil emanation theory applied to radon release from mineral grains abstract in this paper the recoil emanation theory is presented as a major mechanism for rn release from solid materials the basic theory is developed for rn emanation from geometrical shapes spheres and cylinders having variable thickness of precursor ra containing material subsequently a sphere pore model of emanation from mineral grains like those in rocks soils etc is developed in this model a surface of the grain is constructed as a superposition of in and out directed spherical caps and cylindrical pores the model incorporates processes like rn embedding pore overlap water effect and emanation from the edges using such a geometrical model it is shown how the rn emanating power measurements can give a clue to the ra distribution and surface properties of the samples in particular it is shown that for grains reasonably larger than the recoil range and for surface ra distribution the emanating power is independent of the grain size but the total ra concentration varies with the reciprocal of the grain size the opposite is true for ra distributed uniformly throughout the volume of the grain it is shown how the rn emanating power is related to the surface porosity of the grain also implications are made with respect to u transport in nature and with respect to low emanating power from lunar soil finally a failure of the emanation theory is discussed to reproduce emanation curves for the samples having high specific surface areas and ra distributed throughout the volume

holocene climate change in the western part of taihu lake region east china abstract the taihu lake basin is one of the most sensitive areas to climate change in the east asian summer monsoon easm influenced region there are significant differences regarding the interpretation of climate history for this area during the holocene due to a lack of high resolution paleoclimate records to better understand this scientific issue here we provide a new record of holocene climate change from the western part of taihu lake region east china a 4 m depth profile from gaochun has provided a 13 200 year record of climate change holocene climate change was reconstructed for the western part of taihu lake area based on various proxy records including pollen charcoal degree of humification doh and loss on ignition loi from the gaochun site the results indicate that climate during the late pleistocene 13 200 10 700 cal yr b p and early holocene 10 700 8000 cal yr b p was warm and humid alternated with several cold and dry intervals the late pleistocene and early holocene was a transitional period from cold dry to warm wet climates the middle holocene 8000 4400 cal yr b p was still warm and humid with a relatively stable climate the period between 8000 and 5300 cal yr b p was the holocene climate optimum hco during the late holocene 4400 0 cal yr b p the climate was cool but still humid in addition climate change at the western part of taihu lake during the late pleistocene and holocene was unstable containing several short term climate events such as younger dryas yd 8 2 ka and 4 2 ka events these abruptly occurred climate events were indicated by various paleoclimatic proxy indicators and can be compared with related records from other regions our findings suggest that the easm strength was strongest during the middle holocene between 8000 and 5300 cal yr b p which can be depicted as the period of hco

decoupled warming and monsoon precipitation in east asia over the last deglaciation our understanding of the continental climate development in east asia is mainly based on loess paleosol sequences and summer monsoon precipitation reconstructions based on oxygen isotopes delta o 18 of stalagmites from several chinese caves based on these records it is thought that east asian summer monsoon easm precipitation generally follows northern hemisphere nh summer insolation however not much is known about the magnitude and timing of deglacial warming on the east asian continent in this study we reconstruct continental air temperatures for central china covering the last 34 000 yr based on the distribution of fossil branched tetraether membrane lipids of soil bacteria in a loess paleosol sequence from the mangshan loess plateau the results indicate that air temperature varied in phase with nh summer insolation and that the onset of deglacial warming at similar to 19 kyr bp is parallel in timing with other continental records from e g antarctica southern africa and south america the air temperature increased from is c at the onset of the warming to a maximum of 27 degrees c in the early holocene similar to 12 kyr bp in agreement with the temperature increase inferred from e g pollen and phytolith data and permafrost limits in central china comparison of the tetraether membrane lipid derived temperature record with loess paleosol proxy records and stalagmite 5180 records shows that the strengthening of easm precipitation lagged that of deglacial warming by ca 3 kyr moreover intense soil formation in the loess deposits caused by substantial increases in summer monsoon precipitation only started around 12 kyr bp ca 7 kyr lag our results thus show that the intensification of easm precipitation unambiguously lagged deglacial warming and nh summer insolation and may contribute to a better understanding of the mechanisms controlling ice age terminations

a new regional mid holocene palaeoprecipitation signal of the asian summer monsoon the dongge cave speleothem 18o record which lies in the pearl river basin china has been interpreted as recording a regional decline in asian summer monsoon precipitation over the last 6 5 ka the same overall trend is seen in the bulk sedimentary organic 13corg record from a core in the pearl river estuary however the two records differ in detail and the regional nature of the dongge palaeoprecipitation signal has therefore been questioned our study re evaluates both records by constructing for the same estuarine core biomarker and compound specific 13c records which have better constrained terrestrial and marine end members than 13corg providing additional insights into the evolution of the asian summer monsoon the branched isoprenoidal tetraether bit index reflects the ratio of soil versus marine organic matter the bit record from the estuarine core co varies with the dongge cave 18o record suggesting the two share a common control which is likely to be driven by regional climate by contrast the sterols n alcohols and n fatty acid ratios show the same overall trend as dongge but parallel the 13corg record s variability between 6 5 and 2 ka indicating a partial decoupling between soil and land plant organic matter fluxes in the pearl river basin there is clear divergence between the biomarker and 13corg records from 2 ka to present analysis of the leaf wax 13c suggests that this results from an abrupt change in vegetation probably resulting from local anthropogenic cultivation two thousand years ago the basin scale of these estuarine records equates to up to 15 grid cells in typical earth system models used for simulating global climate this permits comparison of palaeoclimate model intercomparison project simulations of the mid holocene with spatially equivalent data relating to the summer asian monsoon for the first time

interpreting tracer breakthrough tailing from different forced gradient tracer experiment configurations in fractured bedrock 1 conceptual and mathematical models are presented that explain tracer breakthrough tailing in the absence of significant matrix diffusion model predictions are compared to field results from radially convergent weak dipole and push pull tracer experiments conducted in a saturated crystalline bedrock the models are based upon the assumption that flow is highly channelized that the mass of tracer in a channel is proportional to the cube of the mean channel aperture and the mean transport time in the channel is related to the square of the mean channel aperture these models predict the consistent 2 straight line power law slope observed in breakthrough from radially convergent and weak dipole tracer experiments and the variable straight line power law slope observed in push pull tracer experiments with varying injection volumes the power law breakthrough slope is predicted in the absence of matrix diffusion a comparison of tracer experiments in which the flow field was reversed to those in which it was not indicates that the apparent dispersion in the breakthrough curve is partially reversible we hypothesize that the observed breakthrough tailing is due to a combination of local hydrodynamic dispersion which always increases in the direction of fluid velocity and heterogeneous advection which is partially reversed when the flow field is reversed in spite of our attempt to account for heterogeneous advection using a multipath approach a much smaller estimate of hydrodynamic dispersivity was obtained from push pull experiments than from radially convergent or weak dipole experiments these results suggest that although we can explain breakthrough tailing as an advective phenomenon we cannot ignore the relationship between hydrodynamic dispersion and flow field geometry at this site the design of the tracer experiment can severely impact the estimation of hydrodynamic dispersion and matrix diffusion in highly heterogeneous geologic media

quantifying diffusive mass transfer in fractured shale bedrock a significant limitation in defining remediation needs at contaminated sites often results from an insufficient understanding of the transport processes that control contaminant migration the objectives of this research were to help resolve this dilemma by providing an improved understanding of contaminant transport processes in highly structured heterogeneous subsurface environments that are complicated by fracture flow and matrix diffusion our approach involved a unique long term steady state natural gradient injection of multiple tracers with different diffusion coefficients br he ne into a fracture zone of a contaminated shale bedrock the spatial and temporal distribution of the tracers was monitored for 550 days using an array of groundwater sampling wells instrumented within a fast flowing fracture regime and a slow flowing matrix regime the tracers were transported preferentially along strike parallel fractures with a significant portion of the tracer plumes migrating slowly into the bedrock matrix movement into the matrix was controlled by concentration gradients established between preferential flow paths and the adjacent rock matrix observed differences in tracer mobility into the matrix were found to be a function of their free water molecular diffusion coefficients the multiple tracer technique confirmed that matrix diffusion was a significant process that contributed to the overall physical nonequilibrium that controlled contaminant transport in the shale bedrock the experimental observations were consistent with numerical simulations of the multitracer breakthrough curves using a simple fracture flow model the simulated results also demonstrated the significance of contaminant diffusion into the bedrock matrix the multiple tracer technique and ability to monitor the fracture and matrix regimes provided the necessary experimental constraints for the accurate numerical quantification of the diffusive mass transfer process the experimental and numerical results of the tracer study were also consistent with indigenous contaminant discharge concentrations within the fracture and matrix regimes of the field site these findings suggest that the secondary source contribution of the bedrock matrix to the total off site transport of contaminants is relatively large and potentially long lived

last glacial maximum and holocene climate in ccsm3 abstract the climate sensitivity of the community climate system model version 3 ccsm3 is studied for two past climate forcings the last glacial maximum lgm and the mid holocene the lgm approximately 21 000 yr ago is a glacial period with large changes in the greenhouse gases sea level and ice sheets the mid holocene approximately 6000 yr ago occurred during the current interglacial with primary changes in the seasonal solar irradiance the lgm ccsm3 simulation has a global cooling of 4 5 c compared to preindustrial pi conditions with amplification of this cooling at high latitudes and over the continental ice sheets present at lgm tropical sea surface temperature sst cools by 1 7 c and tropical land temperature cools by 2 6 c on average simulations with the ccsm3 slab ocean model suggest that about half of the global cooling is explained by the reduced lgm concentration of atmospheric co2 50 of present day concentrations there is an increase in the antarctic circumpolar current an

reconstruction of climate and vegetation changes of lake bayanchagan inner mongolia holocene variability of the east asian monsoon a high resolution pollen and pediastrum record spanning 12 500 yr is presented for lake bayanchagan 115 21 e 41 65 n and 1355 m a s l southern inner mongolia individual pollen taxa pt mat and the pft affinity scores pft mat were used for quantitative climatic reconstruction from pollen and algal data both techniques indicate that a cold and dry climate similar to that of today prevailed before 10 500 cal yr b p the wettest climate occurred between 10 500 and 6500 cal yr b p at which time annual precipitation was up to 30 60 higher than today the early holocene increases in temperature and precipitation occurred simultaneously but mid holocene cooling started at approximately 8000 cal yr b p 1500 yr earlier than the drying vegetation reconstruction was based on the objective assignment of pollen taxa to the plant functional type the results suggest that this region was dominated by steppe vegetation throughout the holocene except for the period 9200 to 6700 cal yr b p when forest patches were relatively common inner mongolia is situated at the limit of the present east asian monsoon and patterns of vegetation and climate changes in that region during the holocene probably reflect fluctuations in the monsoon s response to solar insolation variations the early to middle holocene monsoon undoubtedly extended to more northern latitudes than at present

tracer tests and contaminant transport rates in dual porosity formations with application to the wipp transport of contaminants was analyzed for dual porosity formations in which advection occurs only through fractures but contaminants can diffuse into the rock matrix porosity transport was shown to occur in three distinct regimes fracture dual porosity and total porosity transport in the fracture transport regime contaminant transport is controlled by fracture porosity alone this was shown to end too quickly to have any significance for nuclear waste repositories like the waste isolation pilot plant wipp dual porosity transport in which contaminants are predominantly inside the matrix porosity and in the process of diffusing deeper into the rock was shown to be controlled by a single formation parameter called here the transport length which can be estimated from tracer tests although conventional two well tracer tests yield ambiguous values for fracture width and porosity they provide useable estimates of the transport length the effect on tracer tests of random heterogeneity and anisotropy in the formation was analyzed the arithmetic mean of inferred values from different tests is the correct average for the transport length and the harmonic mean is the correct average for the kinematic porosity data were analyzed from nine tracer tests in a dual porosity dolomite in the culebra formation above the wipp repository including one test repeated at a different flow rate the effect of dual porosity on the mean transport rate of contaminants potentially leaking from the wipp repository was shown to be negligible thus for off site transport at the wipp the formation is adequately modeled as a single porosity matrix only medium

mid holocene east asian summer monsoon strengthening insights from paleoclimate modeling intercomparison project pmip simulations abstract the east asian summer june july august monsoon easm is typically thought to have been stronger during interglacial periods based on spatially sparse proxy data on a large scale however whether this view is true and if so its underlying dynamic mechanisms remain unclear using all pertinent experiments within the paleoclimate modeling intercomparison project pmip here we present an analysis of the easm during the mid holocene 6000 years ago supporting the paleodata the mid holocene easm as measured by regionally averaged meridional wind at 850 hpa became stronger than the baseline period in 27 out of 28 pmip models with a demonstrable ability to simulate the modern easm climatology on average the easm strengthened by 32 across all the models and by a larger magnitude in 23 coupled models 35 than in five atmospheric models 20 it is proposed that an enhanced land sea thermal contrast and hence sea level pressure gradient between the east asian continent and adjacent oceans as a result of orbital forcing was responsible for the easm strengthening during the mid holocene

pedogeochemical models on prognosis and control of radon fluxes from humid tropical landscapes over granite the principal relationships between radon 222rn and 220rn exhalation intensities and the morpho dynamic elements of humid tropical landscapes have been established and analyzed with the objective of elaborating rn exhalation models which can be used on the scale of small habitational nuclei the current radioactive processes of generation emanation and migration of rn in relation to its exhalation rates on a landscape slope of granitic rock having normal u and th contents were correlated with the latosol podzolic soil association developed as a product of supergene processes during geological and pedological times and also with the water regime of an overlying phreatic aquifer this approach encompassing pedogeochemical models of radionuclide dispersion linked to soil systems and surface geochemistry was framed within a tridimensional interdisciplinary and systemic focus using concepts of nuclear physics climate and hydrogeology the characteristic signatures of elementary landscapes include 1 different landforms namely eluvial transeluvial and superaqual 2 residual soils having varying types thicknesses and perma porosities and 3 radioanomalies corresponding to different u and th concentrations secondary hosting minerals and also to different pedological ages considering these factors and their spatial relationships and on the basis of moisture content of soils it is postulated that the highest rn exhalation rates especially of 222rn are confined to superaqual and transeluvial landscapes in an eluvial landscape the rn fluxes are found to be less important even though gamma anomalies exist mainly due to the presence of resistant minerals containing u and th in short the products of supergene alteration organized in a sloping system can exhibit rn exhaling intensities higher than that measured on unaltered subjacent rock

large scale intrusion of shallow water into a vertical fracture zone in crystalline bedrock initial hydrochemical perturbation during tunnel construction at the aspo hard rock laboratory southeastern sweden on march 13 1991 construction of the entrance tunnel to the aspo hard rock laboratory opened a vertical fracture zone at a depth of 70 m this provides an opportunity to study geochemical changes resulting from shallow water inflow into a crystalline bedrock aquifer as anticipated during construction and operation of a deep repository for spent nuclear fuel chloride ion is a natural conservative tracer for mixing between the dilute cl 10 mg l 1 shallow groundwater and the saline cl 5000 mg l 1 native groundwater of the fracture zone a sharp dilution front corresponding to 80 dilution of the native groundwater indicated arrival of shallow groundwater in the entrance tunnel after 3 weeks in spite of this large input of shallow water the fracture zone remains predominantly anoxic major element hydrochemistry and carbon and oxygen stable isotope data indicate large inputs of alkalinity and biogenic co2 g input of organic carbon with shallow groundwater provides a possible energy and carbon source for anaerobic respiration there is no evidence for sulfate reduction and fe iii oxyhydroxide fracture minerals are the only other dominant electron acceptor observed

the relative mobility of u th and ra isotopes in the weathered zones of the eye dashwa lakes granite pluton northwestern ontario canada radioisotope activity ratios of weathered surface rocks from the eye dashwa lakes granite pluton show that in the 238u decay series 226ra has been leached more rapidly than the grandparent 234u and 238u isotopes the observation of 238th232th disequilibria in the 232th decay series shows that either 228th half life of 1 9 yrs or 228ra half life of 5 75 yrs have been removed from these rocks very rapidly indeed isotope ratios of separated mineral fractions appear to show that whereas uranium tends to be removed from all mineral fractions ra is strongly readsorbed onto feldspars presumably as these undergo alteration to clay minerals this necessitates making a distinction between intermineral mobility of u or ra and the net loss of u or ra from the whole rock an attempt has been made to model quantitatively the transport rate of ra though with little success failure of the modelling appears to indicate that the mobility of 228ra is higher than might be predicted by the mobility of 226ra that is the two isotopes are not strict analogues of one another in their response to initial weathering

tropical climate instability the last glacial cycle from a qinghai tibetan ice core an ice core record from the guliya ice cap on the qinghai tibetan plateau provides evidence of regional climatic conditions over the last glacial cycle 36 cl data suggest that the deepest 20 meters of the core may be more than 500 000 years old the 18 o change across termination i is 5 4 per mil similar to that in the huascaran peru and polar ice cores three guliya interstadials stages 3 5a and 5c are marked by increases in 18 o values similar to that of the holocene and eemian 124 000 years ago the similarity of this pattern to that of ch 4 records from polar ice cores indicates that global ch 4 levels and the tropical hydrological cycle are linked the late glacial stage record contains numerous 200 year oscillations in 18 o values and in dust nh 4 and no 3 levels

comparative study of 222rn 40ar 39ar and 37ar leakage from rocks and minerals implications for the role of nanopores in gas transport through natural silicates we have measured the leakage of radiogenic 222rn and 40ar and reactor produced 39ar and 37ar in samples of granites plagioclase orthoclase cleavelandite and hornblende to assess the role of nanopores in gas transport through them the 39ar and 37ar were produced by fast neutron irradiation of the samples in vacuum sealed ampoules the leakage of all three ar isotopes was barely measurable in contrast the leakage of 222rn ranged between 1 45 18 1 orders of magnitude higher than that of the ar isotopes the extremely low ar isotope leakage suggests that the samples studied are not permeated by extensive nanopore networks which intersect grain surfaces the relatively high 222rn loss from these samples therefore has to be attributed to preferential enrichment of 226ra 238u on grain surfaces or to the existence of u th accessory minerals in or around grain boundaries from which substantial quantities of 222rn escape

a large scale flow and tracer experiment in granite 2 results and interpretation water and tracer flow has been monitored in a specially excavated drift in the stripa mine several new experimental techniques and equipment were developed and used the whole ceiling and the upper part of the walls were covered with 375 individual plastic sheets where the water flow into the drift could be collected eleven different tracers were injected at distances between 11 and 50 m from the ceiling of the drift the flow rate and tracer monitoring was kept up for more than 2 years the tracer breakthrough curves and flow rate distributions were used to study the flow paths velocities hydraulic conductivities dispersivities and channeling effects in the rock in a companion paper the experimental design and performed experiments are described the present paper describes the interpretation of flow and tracer movement in the rock outside the drift the tracer movement was measured by the more than 160 individual tracer curves the tracer experiments have permitted the flow porosity and dispersion to be studied the possible effects of channeling and the diffusion of tracers into stagnant waters in the rock matrix and in stagnant waters in the fractures have also been addressed

effective radium concentration across the main central thrust in the nepal himalayas effective radium concentration ec ra of 622 rock samples from 6 different sites in the nepal himalayas was measured in the laboratory using radon accumulation experiments these sites located from lower dolpo in western nepal to eastern nepal are divided into 9 transects which cut across the main central thrust zone mct zone separating low grade meta morphic lesser himalayan sequence lhs units to the south and higher grade metamorphic greater himalayan sequence ghs units to the north this boundary remains difficult to define and is the subject of numerous debates ec ra values range from 0 03 0 03 to 251 6 4 0 bq kg a1 and appear to be representative of the formation and clearly related to the local lithology for example for the upper trisuli and langtang valleys site in central nepal the most studied place with 350 available ec ra values lhs rocks are characterized by a mean value of 5 3 1 3 bq kg a1 while ghs rocks of formations i and ii show significantly lower values with a mean value of 0 69 0 11 bq kg a1 thus leading to a lhs ghs ec ra ratio of 7 8 2 2 this behavior was systematically confirmed by other transects ratio of 7 9 2 2 in all other sites with a threshold ec ra value separating lhs from ghs of 0 8 bq kg a1 thus bringing forward a novel method to characterize within the mct shear zone which rocks belong to the ghs and lhs units in addition ulleri augen gneiss belonging to lhs rocks occurred in several transects and were characterized by high ec ra values 17 9 4 3 bq kg a1 easy to distinguish from the ghs gneisses characterized by low ec ra values at the bottom of the ghs thus providing a further argument to locate the mct the measurement of ec ra data thus provides a cost effective method which can be compared with neodymium isotopic anomalies or estimates of the peak metamorphic temperature this study therefore shows that the measurements of ec ra provides additional information to discriminate different geological formations and can be particularly useful in areas where geology mapping is not straightforward or still remains controversial

the dry holocene megathermal in inner mongolia the paleoclimate since 14 kyr bp 14c age was reconstructed based on a 16 22 m long sediment core collected from lake yanhaizi a saline lake located near the northern limit of the east asian summer monsoon in inner mongolia coarse sediments were deposited there during a shrinkage phase of the lake when sand dunes reactivated these sediments have low organic carbon contents but high maturity indices indicating that they were deposited in an arid environment by contrast based on high organic contents and low maturity indices fine sediments were deposited during periods of high lake stand in a humid environment it was in general dry between 8 0 and 4 3 kyr bp the above dry and wet phases are consistent with those recovered from the arid semiarid transition zone elsewhere but are unlike the widely perceived humid holocene megathermal reported in east china and the newly reconstructed record in the alpine retreat lake in taiwan the discrepancy may be due to a relative insensitivity to humidity changes in these two areas since they have both been under the total influence of the summer monsoon on the other hand much enhanced evaporation over higher monsoon precipitation at lake yanhaizi reduces the effective humidity in the warm climate near the northern boundary of the summer monsoon this also accounts for the fact the high temperature holocene megathermal as revealed in the okinawa trough and the northern south china sea is correlated to the dry phases at lake yanhaizi conversely the 4 2 kyr bp coldest period in the holocene corresponds to a wet phase at lake yanhaizi

response of the african monsoon to orbital forcing and ocean feedbacks in the middle holocene simulations with a climate model that asynchronously couples the atmosphere and the ocean showed that the increased amplitude of the seasonal cycle of insolation in the northern hemisphere 6000 years ago could have increased tropical atlantic sea surface temperatures in late summer the simulated increase in sea surface temperature and associated changes in atmospheric circulation enhanced the summer monsoon precipitation of northern africa by more than 25 percent compared with the middle holocene simulation with prescribed modern sea surface temperatures and provided better agreement with paleorecords of enhanced monsoons

the verification of millennial scale monsoon water vapor transport channel in northwest china summary long term changes of the asian summer monsoon water vapor transport play a pivotal role in the variability of monsoon precipitation paleo climate simulations have shown that there is an important monsoon vapor transport channel in western china previous studies mostly focused on the correlation between monsoon precipitation and intensity little research has been done on the verification of the water vapor channel compared with speleothem and lacustrine systems the hydrological cycle of land surface sediments is more directly related to the monsoon water vapor in this study we used carbonate 18 o and organic matter 13 c of the surface eolian sediments from the piedmont of the northern qilian mountains to verify the monsoon water vapor on the holocene millennial scale two surface sedimentary sections were selected to study paleo monsoon water vapor transport proxy data including carbonate 18 o and organic matter 13 c of surface eolian sediments as well as total organic matter and carbonate content were obtained from the two eolian sections we also synthesized transient simulations of the ccsm3 and the kiel climate models the pmip 3 0 project and trace isotopic simulations were also compared with the reconstructed monsoon water vapor transport our findings indicate that the strength of the holocene asian summer monsoon is consistent with the water vapor transport in western china that has significant impacts to long term monsoon precipitation in northern china this study verifies a significant millennial scale correlation between the monsoon strength and monsoon water vapor transport intensity along the eastern qinghai tibet plateau

unsaturated flow and transport through a fault embedded in fractured welded tuff 1 to evaluate the importance of matrix diffusion as a mechanism for retarding radionuclide transport in the vicinity of a fault located in unsaturated fractured rock we carried out an in situ field experiment in the exploratory studies facility at yucca mountain nevada this experiment involved the release of 82 000 l of water over a period of 17 months directly into a near vertical fault under both constant positive head at 0 04 m and decreasing fluxes a mix of conservative tracers pentafluorobenzoic acid pfba and bromide applied in the form of lithium bromide was released along the fault over a period of 9 days 7 months after the start of water release along the fault as water was released into the fault seepage rates were monitored in a large cavity excavated below the test bed after the release of tracers seepage water was continuously collected from three locations and analyzed for the injected tracers observations of bromide concentrations in seepage water during the early stages of the experiment and bromide and pfba concentrations in the seepage water indicate the significant effects of matrix diffusion on transport through a fault embedded in fractured welded rock

tracer transport in fractured crystalline rock evidence of nondiffusive breakthrough tailing extended tailing of tracer breakthrough is often observed in pulse injection tracer tests conducted in fractured geologic media this behavior has been attributed to diffusive exchange of tracer between mobile fluids traveling through channels in fractures and relatively stagnant fluid between fluid channels along fracture walls or within the bulk matrix we present a field example where tracer breakthrough tailing apparently results from nondiffusive transport tracer tests were conducted in a fractured crystalline rock using both a convergent and weak dipole injection and pumping scheme deuterated water bromide and pentafluorobenzoic acid were selected as tracers for their wide range in molecular diffusivity the late time behavior of the normalized breakthrough curves were consistent for all tracers even when the pumping rate was changed the lack of separation between tracers of varying diffusivity indicates that strong breakthrough tailing in fractured geologic media may be caused by advective transport processes this finding has implications for the interpretation of tracer tests designed to measure matrix diffusion in situ and the prediction of contaminant transport in fractured rock

holocene vegetation and climate dynamics of ne china based on the pollen record from sihailongwan maar lake abstract high resolution palynological analysis on annually laminated sediments of sihailongwan maar lake shl provides new insights into the holocene vegetation and climate dynamics of ne china the robust chronology of the presented record is based on varve counting and ams radiocarbon dates from terrestrial plant macro remains in addition to the qualitative interpretation of the pollen data we provide quantitative reconstructions of vegetation and climate based on the method of biomization and weighted averaging partial least squares regression wa pls technique respectively power spectra were computed to investigate the frequency domain distribution of proxy signals and potential natural periodicities pollen assemblages pollen derived biome scores and climate variables as well as the cyclicity pattern indicate that ne china experienced significant changes in temperature and moisture conditions during the holocene within the earliest phase of the holocene a large scale reorganization of vegetation occurred reflecting the reconstructed shift towards higher temperatures and precipitation values and the initial holocene strengthening and northward expansion of the east asian summer monsoon easm afterwards summer temperatures remain at a high level whereas the reconstructed precipitation shows an increasing trend until approximately 4000 cal yr bp since 3500 cal yr bp temperature and precipitation values decline indicating moderate cooling and weakening of the easm a distinct periodicity of 550 600 years and evidence of a mid holocene transition from a temperature triggered to a predominantly moisture triggered climate regime are derived from the power spectra analysis the results obtained from shl are largely consistent with other palaeoenvironmental records from ne china substantiating the regional nature of the reconstructed vegetation and climate patterns however the reconstructed climate changes contrast with the moisture evolution recorded in s china and the mid latitude semi arid regions of n china whereas a clear insolation related trend of monsoon intensity over the holocene is lacking from the shl record variations in the coupled atmosphere pacific ocean system can largely explain the reconstructed changes in ne china

radionuclide migration through fractured rock for arbitrary length decay chain analytical solution and global sensitivity analysis summary this study presents an analytical approach to simulate nuclide migration through a channel in a fracture accounting for an arbitrary length decay chain the nuclides are retarded as they diffuse in the porous rock matrix and stagnant zones in the fracture the laplace transform and similarity transform techniques are applied to solve the model the analytical solution to the nuclide concentrations at the fracture outlet is governed by nine parameters representing different mechanisms acting on nuclide transport through a fracture including diffusion into the rock matrices diffusion into the stagnant water zone chain decay and hydrodynamic dispersion furthermore to assess how sensitive the results are to parameter uncertainties the sobol method is applied in variance based global sensitivity analyses of the model output the sobol indices show how uncertainty in the model output is apportioned to the uncertainty in the model input this method takes into account both direct effects and interaction effects between input parameters the simulation results suggest that in the case of pulse injections ignoring the effect of a stagnant water zone can lead to significant errors in the time of first arrival and the peak value of the nuclides likewise neglecting the parent and modeling its daughter as a single stable species can result in a significant overestimation of the peak value of the daughter nuclide it is also found that as the dispersion increases the early arrival time and the peak time of the daughter decrease while the peak value increases more importantly the global sensitivity analysis reveals that for time periods greater than a few thousand years the uncertainty of the model output is more sensitive to the values of the individual parameters than to the interaction between them moreover if one tries to evaluate the true values of the input parameters at the same cost and effort the determination of priorities should follow a certain sequence

channeling with diffusion into stagnant water and into a matrix in series numerous field observations show that most water flow in fractured rocks takes place in only a small part of the fractures we call these channels solutes in the flowing water can diffuse in and out of stagnant water in the porous rock matrix that the flowing water contacts via the so called flow wetted surface fws in addition the solutes can diffuse into stagnant water in the fractures themselves and from this water further into the rock matrix for narrow channels with small fws the transport via the stagnant water in the fracture can considerably add to the exchange of solutes between flowing water and matrix water for sorbing solutes that interact with the micropore surfaces in the matrix the effect can be very strong some models that account for these processes are developed and solved using laplace transforms some examples are presented that show the effects of first diffusion into stagnant waters in fractures with subsequent diffusion into the rock matrix effects of slit like and tube like channels are considered as well as the presence of intersecting fractures the solutions are especially useful to model solute transport in complex three dimensional channels networks where wide and narrow or even tube like channels with widely varying flow rates combine into a multitude of different paths

importance of atmospheric inputs and fe oxides in controlling soil uranium budgets and behavior along a hawaiian chronosequence abstract a long term budget of uranium calculated for a chronosequence of hawaiian soils demonstrates the importance of mineral aerosol deposition as a geochemical pathway a series of sequential extractions on the same soils shows a strong association between fe oxides and uranium especially the amorphous and poorly crystalline fe oxides present in intermediate age soils 20 and 150 ka despite intense leaching conditions soil u contents were found to increase between 20 fold and 60 fold with age along the chronosequence from 9 to 17 g cm 2 at 0 3 ka sites to 344 543 g cm 2 at the 4100 ka site an open system transport function comparing u to an index least mobile element nb was used to calculate u gains or losses from the soils relative to the input from parent material weathering results show small losses or small gains 25 of u occurred in soils 150 ka and younger while gains of up to 531 u occurred in soils older than 150 ka highlighting the importance of mineral aerosol dust deposition at the older sites in the 4100 ka soil the ratio of dust derived u inputs to parent material derived u inputs is approximately 6 sequential extractions show that between 0 1 and 1 2 of the total u in the soils was extracted with ammonium acetate indicating that very little u exists as exchangeable cations a second extraction employing citrate dithionate and hydroxylamine hydrochloride was performed to extract u associated with fe oxides average percent occurrences for u in the fe oxide extraction for each profile are 7 at 0 3 ka 53 at 20 ka 40 at 150 ka and 17 at 4100 ka illustrating an increase with age to 20 ka followed by a subsequent decline this parallels the trend observed in amorphous fe oxide content suggesting that adsorption on amorphous fe oxides is the dominant control on u in the intermediate age soils

intercomparison of simulated global vegetation distributions in response to 6 kyr bp orbital forcing abstract the response of ten atmospheric general circulation models to orbital forcing at 6 kyr bp has been investigated using the biome model which predicts equilibrium vegetation distribution as a diagnostic several common features emerge a reduced tropical rain forest as a consequence of increased aridity in the equatorial zone b expansion of moisture demanding vegetation in the old world subtropics as a consequence of the expansion of the afro asian monsoon c an increase in warm grass shrub in the northern hemisphere continental interiors in response to warming and enhanced aridity and d a northward shift in the tundra forest boundary in response to a warmer growing season at high northern latitudes these broadscale features are consistent from model to model but there are differences in their expression at a regional scale vegetation changes associated with monsoon enhancement and high latitude summer warming are consistent with palaeoenvironmental observations but the simulated sh

timing and spatial distribution of mid holocene drying over northern china response to a southeastward retreat of the east asian monsoon 1 to determine the timing and spatial distribution of mid holocene drying over northern china the mineralogical and oxygen isotopic composition of authigenic carbonate from a closed lake at bayanchagan southern inner mongolia were measured further analysis and synthesis of the spatial geological data were performed results from lake bayanchagan show a significant drying at 6000 calendar years cal years b p indicated by dolomite precipitation and a striking rise in 18o values the synthesis of spatial data reveals a zonal distribution for timing of drying over northern china in the mid holocene which began at 9000 7000 cal years b p in deserts of north central china at 7000 5500 cal years b p drying extended into the desert steppe transitional zone and at 4500 cal years b p into northeastern and south central china this pattern indicates that the east asian summer monsoon has significantly retreated southeastward since the mid holocene which may be related to orbitally induced northern hemisphere insolation changes a retreat of 400 550 km is inferred for the front of the summer monsoon from 6500 to 4500 cal years b p

a holocene climatic record from arid northwestern china abstract the history of climatic changes during the interval 8500 3000 cal yr b p has been reconstructed from stratigraphical and chronological studies and the results of total organic carbon toc total inorganic carbon tic element composition pollen and stable isotope analyses of a section along the hongshui river in the southern tengger desert nw china the record suggests that from 8450 bottom of the studied section to 7500 yr b p the climate was characterized by instability from 7500 to 5070 yr b p the climatic conditions improved and can be divided into two parts a warm humid spell between 7290 and 6380 yr b p during which the average temperature was 3 4 c higher than that of today and a warm dry spell lasting from 5950 to 5720 yr b p the climate deteriorated between 6380 and 5950 yr b p from 5720 to 5070 yr b p the temperature decreased but humidity increased an abrupt temperature drop occurred between 5340 and 5290 yr b p that indicated the decline of the warmer and humid mid holocene climate from 5070 yr b p onward the climate oscillated significantly and there were three large temperature decreases coinciding with high mountain glacier advances between 5070 4670 yr b p 4300 3740 yr b p and 3410 3230 yr b p top of the section respectively the climatic fluctuations recorded in the southern tengger desert appear in phase with climatic changes recognized in the tibetan plateau suggesting that the period between 7290 and 6380 yr b p was the most warm humid spell one extremely dry event occurred at ca 3000 yr b p and subsequently the fluvial lacustrine depositional process terminated and wind action prevailed in the area both of these features can be attributed to the rapid strengthening and weakening of the summer monsoon circulation which are closely connected with global changes

an analogue validation study of natural radionuclide migration in crystalline rocks using uranium series disequilibrium studies abstract concentrations and isotope ratios of natural decay series radionuclides have been studied in three contrasting crystalline rock drillcore sections intersecting water conducting fractures deep in the bedrock radioactive disequilibria resulting from rock water interactions were observed in two of the cores these indicated u migration along distances of 40 cm or more on a time scale of 1 myr in conjunction with th immobility under the same conditions fracture surface minerals showed a high affinity for radionuclide retardation and a limit of 3 cm is suggested for the migration of radionuclides from fracture fluids into the saturated rock this limit may correspond to enhanced matrix porosities resulting from earlier hydrothermal activity along the same channels

solute transport in fractured rocks with stagnant water zone and rock matrix composed of different geological layers model development and simulations a model is developed to describe solute transport and retention in fractured rocks it accounts for the fact that solutes can not only diffuse directly from the flowing channel into the adjacent ro

evaluation of coupled ocean atmosphere simulations of the mid holocene using palaeovegetation data from the northern hemisphere extratropics we have used the biome4 biogeography biochemistry model and comparison with palaeovegetation data to evaluate the response of six ocean atmosphere general circulation models to mid holocene changes in orbital forcing in the mid to high latitudes of the northern hemisphere all the models produce a a northward shift of the northern limit of boreal forest in response to simulated summer warming in high latitudes the northward shift is markedly asymmetric with larger shifts in eurasia than in north america b an expansion of xerophytic vegetation in mid continental north america and eurasia in response to increased temperatures during the growing season c a northward expansion of temperate forests in eastern north america in response to simulated winter warming the northward shift of the northern limit of boreal forest and the northward expansion of temperate forests in north america are supported by palaeovegetation data the expansion of xerophytic vegetation in mid continental north america is consistent with palaeodata although the extent may be over estimated the simulated expansion of xerophytic vegetation in eurasia is not supported by the data analysis of an asynchronous coupling of one model to an equilibrium vegetation model suggests vegetation feedback exacerbates this mid continental drying and produces conditions more unlike the observations not all features of the simulations are robust some models produce winter warming over europe while others produce winter cooling as a result some models show a northward shift of temperate forests consistent with though less marked than the expansion shown by data and others produce a reduction in temperate forests elucidation of the cause of such differences is a focus of the current phase of the palaeoclimate modelling intercomparison project

transport of a tracer slug in a fractured permeable formation abstract this paper concerns the migration of a tracer slug injected into a fractured permeable formation basic transport processes are formulated dimensionless parameters governing transport phenomena in the domain are identified and their effects are determined a simplified conceptual model is employed for the quantitative evaluation of the physical phenomena associated with tracer migration in the domain the analytical approach applied in this study provides some basic characteristics concerning the build up and decay of tracer breakthrough curves characteristics of fracture networks incorporating a large number of fracture sectors are evaluated using a numerical finite difference scheme it is shown that various time and length scales characterize the phenomena involved in tracer slug migration in a fractured permeable formation it is found that in cross sections located at a small distance from the tracer injection point two maximum values of tracer concentration are expected in the breakthrough curves in cross sections located at comparatively large distances from the tracer injection point the breakthrough curves are similar to those characterizing an ideal porous media

uranium and microcracks in a 1 000 meter core redstone new hampshire the spatial distribution and mineralogical association of uranium in 30 samples of a 1 000 meter core from the redstone nh quarry were examined with fission track techniques backscattered electron imaging and energy dispersive x ray spectrometry with the following results for the conway and mount osceola granites 1 uranium occurs in microcracks sealed with siderite and or with ca re fluorocarbonate minerals the uranium contents of siderite and the re fluorocarbonates are 1 to 30 ppm and 500 1 500 ppm respectively 2 siderite and to a lesser extent re fluorocarbonate minerals occur as replacement minerals of amphibole and biotite the re fluorocarbonates are the main alteration minerals of allanite 3 the degree of alteration and the extent of uranium redistribution are greater in samples with major uraniferous microcracks 4 the contents of ca and mn are approximately constant for siderite in sealed cracks throughout the conway and mount osceola granites for the entire section penetrated by the corehole approximately 700 meters from these observations we conclude that an extensive set of fractures throughout a significant volume of the mount osceola and conway granties were the conduits through which hydrothermal fluids containing co2 uranium and res circulated microcracks facilitated fluid rock interactions resulting in alteration and uranium redistribution certain primary uraniferous accessory minerals i e allanite and ilmenorutile may have been the source for at least part of the uranium and res that now occur in secondary minerals in these granites

a tracer migration experiment in a small fracture zone in granite the water flow rate and tracer distribution has been studied in a fracture zone and averagely fractured rock in the stripa underground research laboratory the experimental site is located in granitic rock at a depth of 385 m below the ground surface a 50 m long drift with a diameter of 3 m was excavated the drift was intersected by a 6 m wide fracture zone the upper part of the drift was covered by 150 plastic sheets in which water was collected the water in the lower part of the drift was collected in sump holes different tracers were injected in seven locations at distances between 9 5 and 25 m from the drift more than 50 of the water was found in one sampling area in the drift and more than 90 in only eight sampling areas the recovery of the tracers was also concentrated in a few sheets most of the flow preferentially takes place in a few paths two sets of tracers were used in tandem one set of dyes which had previously been used in stripa and one set of lanthanide dtpa complexes although shown to be nonsorbing in long time high sensitivity laboratory tests the dyes were found to have a somewhat smaller recovery than the metal tracers this observation was used in an attempt to estimate the flow wetted surface into which the dyes can diffuse and sorb the flow porosity was estimated from the tracer residence times for all injection points the flow in the intersected fracture zone is not like that in a porous medium it is highly channeled

application of fracture flow hydrogeology to acid mine drainage at the bunker hill mine kellogg idaho abstract the mechanics of groundwater flow through fractured rock has become an object of major research interest during recent years this project has investigated the flow of groundwater through fractured precambrian metaquartzite rocks in a portion of the bunker hill mine near kellogg idaho groundwater flow through these types of rocks is largely dependent upon the properties of fractures such as faults joints and relict bedding planes groundwater that flows into the mine via the fractures is acidic and is contaminated by heavy metals which results in a severe acid mine drainage problem a more complete understanding of how the fractures influence the groundwater flow system is a prerequisite of the evaluation of reclamation alternatives to reduce acid drainage from the mine fracture mapping techniques were used to obtain detailed information on the fracture properties observed in the new east reed drift of the bunker hill mine the information obtained includes fracture type orientation trace length the number of visible terminations roughness waviness infilling material and a qualitative measure of the amount of water flowing through each fracture the hydrogeologic field data collected include routine measurements of the discharge from four individual structural features and four areas where large quantities of water are discharging from vertical rock bolts the depths to water in three piezometer nests at the ground surface the pressure variations in four diamond drillholes and constant discharge flow tests conducted on three of the diamond drillholes the field data indicate that relict bedding planes are the primary conduits for groundwater flow and suggest that the two major joint sets that are present connect water flowing through the discontinuous bedding planes the three minor joint sets that are present do not seem to have a significant impact on groundwater flow but along with the two major joint sets may store relatively large quantities of water it appears that rock bolt holes in the central portion of the drift primarily intersect relict bedding planes whereas rock bolt holes in the southeastern portion of the drift primarily intersect joints this probably is related to the shallower angle of dip of the bedding planes in the central portion of the drift it also appears that recharge from the surface directly above the mined out openings is the primary source of water in the upper workings of the mine and that the large seasonal head variations in the potentiometric surface are primarily responsible for the observed temporal variations in mine inflow infilling material may control the hydrogeologic character of the faults with those filled with gouge having low hydraulic conductivities and those filled with breccia having relatively high hydraulic conductivities in addition one of the faults may act as a positive constant head recharge hydrogeologic boundary a double porosity approach probably is the most appropriate for simulating the groundwater flow system in the vicinity of the new east reed drift finally grouting of a combination of breccia filled faults and relict bedding planes may offer the best hope for minimizing mine water inflow or recharge