the 7be 210pbxs ratio as an indicator of suspended sediment age or fraction new sediment in suspension reported here is a technique to use the 7be 210pbxs ratio as a measure of suspended sediment age or as an indicator of the fraction of the suspended sediment that is recently eroded from the landscape although both 7be and 210pbxs are delivered seasonally and stochastically to the landscape by precipitation the ratio of the two radionuclides varies substantially less the 7be 210pbxs ratios measured in three different catchments decrease in the following manner precipitation c 16 suspended sediments in rivers 6 7 suspended sediments in estuaries 4 6 sediment collected in sediment traps in the estuary c 1 surface sediment of the estuary c 0 5 decreases in the 7be 210pbxs ratio in suspended sediments can be interpreted to be the result of increased age of the sediment since 7be decays faster than 210pb alternatively a decrease in the 7be 210pbxs ratio in suspended sediments can be interpreted to be the result of dilution of newly tagged 7be rich sediment by 7be dead sediment for example by erosion of soil below the 7be enriched surface layer or by resuspension of 7be dead bottom sediment presented here is a model which uses the 7be 210pbxs ratio in suspended sediments to determine the time since the particles were tagged by precipitation derived radionuclides i e the age of the suspended sediment in addition an alternative model is presented to determine the fraction of the sediment that is newly tagged these two models are applied to three catchments old woman creek ohio weeks bay alabama and south slough oregon and yield similar findings at all three sites sediment ages increase from 0 in newly tagged material to 50 80 days in rivers to about 80 100 days in the estuaries to about 200 days in the sediment traps to about 300 days on surface bottom sediments alternatively the percentage new sediment decreases from 100 per cent in newly tagged material to about 35 50 per cent in rivers to 25 35 per cent in the estuary to less than 10 per cent in the sediment traps to 1 4 per cent on the surface of the bottom sediments

a global review of sediment source fingerprinting research incorporating fallout radiocesium 137cs abstract information on the main sources supplying deleterious sediment loads to river systems is needed to improve our understanding of soil erosion processes to better target erosion control measures in particular it is important to quantify the respective contributions of surface and subsurface sources to material degrading waterbodies radiocesium 137cs emitted during thermonuclear bomb testing 1950 1980 and nuclear accidents provides significant discrimination between surface material exposed to atmospheric fallout and subsurface material sheltered from it a systematic worldwide review of research articles n 123 that used 137cs to trace sediment sources showed that the united kingdom n 24 australia n 23 and the united states n 20 had the highest number of publications utilizing 137cs in a sediment tracing framework in contrast few studies were published for catchments in africa n 9 or south america n 2 in the northern hemisphere positive relationships were evident between 137cs activities in surface and subsurface sources and the proportion of thermonuclear bomb fallout however given the low proportions of fallout received in regions between 0 and 20 n and 0 20 s the potential application of 137cs tracing techniques may be limited in this area of the world as well as in agricultural regions with severe soil erosion i e chinese loess plateau and south africa in total 94 of the studies researching surface and subsurface sources that analysed 137cs as a potential tracing property included this parameter in end member mixing models the main challenges for the future of this technique are related to the access to ultra low background gamma spectrometry facilities and the development of surrogate tracers future research should ensure that basic catchment information and details on the sampling design are properly documented to ensure studies are reproducible moreover researchers should provide raw measurement data to help improve our global understanding of 137cs dynamics in soil erosion research

finite difference modeling experiments for seismic interferometry in passive seismic interferometry new reflection data can be retrieved by crosscorrelating recorded noise data the quality of the retrieved reflection data is among others dependent on the duration and number of passive sources present during the recording time the source distribution and the source strength to investigate these relations we set up several numerical modeling studies to carry out the modeling in a feasible time we design a finite difference algorithm for the simulation of long duration passive seismic measurements of band limited noise signatures in the subsurface novel features of the algorithm include the modeling of thousands of randomly placed sources during one modeling run the modeling experiments explore the dependency relation between the retrieved reflections and source signature length source positions number of sources and source amplitude variations from these experiments we observed that the positions of the passive sources and the length of the source signals are of direct influence on the quality of the retrieved reflections random amplitude variations among source signals do not seem to have a big impact on the retrieved reflections

erosion extension of indurated volcanic soils of mexico by aerial photographs and remote sensing analysis in the northern part of michoacan state in mexico between the patzcuaro and cuitzeo lakes we used aerial photographs and spot satellite data to define the spatial and temporal extensions of soil erosion over indurated volcanic material called tepetates segmentation techniques combined with graphic mask were applied over the aerial photographs in order to obtain the extension of eroded areas for 1975 1995 and 2000 an unsupervised classification was performed over various band combinations of spot the eroded areas were checked and improved with ground control points the results show that there are no more eroded areas today than 25 years ago there is however an evolution of the eroded areas some of them have disappeared while others have become larger a change in land use intensity explains the regression of eroded area in the north and the augmentation of eroded surfaces in the south the result obtained with spot imagery classification allows discrimination of four different erosion degrees where only one could be distinguish with aerial photographs however it is not possible to distinguish outcropping tepetates and outcropping andesit with spot as well additional socioeconomic studies and studies over spectral signatures of eroded materials in relation with their mineral contents are in process

determining the times and distances of particle transit in a mountain stream using fallout radionuclides abstract targeting of erosion and pollution control programs is much more effective if the time for fine particles to be transported through a watershed the travel distance the proportions of old and new sediment in suspension and the rate of erosion of the landscape can be estimated in this paper we present a novel technique for tracing suspended sediment in a mountain stream using fallout radionuclides sorbed to sediment atmospherically delivered 7 be 210 pb and 137 cs accumulate in the snowpack are released with its melting and sorb to fine particulates a portion of which are carried downslope into stream channels the half life of cosmogenic 7 be is short 53 4 days thus sediment residing on the stream bed should contain little of the radionuclide the different signatures of newly delivered sediment from the landscape with its 7 be tag and older untagged sediment from the channel is the basis for the tracing the total flux of such radionuclides compared to the inventory in the soil permits estimates of the rates of erosion of the landscape fine suspended particulates in the gold fork river id are transported downstream through the drainage in one or more steps having lengths of tens of kilometers length of the step decreases from about 60 km near the peak of the hydrograph to about 12 km near baseflow the percent of sediment in suspension that is new i e recently delivered from the landscape ranges from 96 to 12 the remaining sediment is resuspended older channel sediment residence times for particulates range from 1 6 days early in the hydrograph at the upper site to 103 days late in the hydrograph at the lowest elevation location rates of erosion of fine sediment calculated from the flux of radionuclides average 0 0023 cm year the long distance transport of fine particles suggests that delivery through the gold fork drainage to the basin outlet is fairly rapid once particles reach the channel and perhaps is also rapid in similar and smaller basins

joint isotopic mass balance a novel approach to quantifying channel bed to channel margins sediment transfer during storm events the important role of floodplains and the broader riparian zone in providing temporary storage for a large fraction of the annual sediment load of rivers is well established but this understanding is largely based on observations of the long term average behavior of the catchment here we combine measurements of the fallout radionuclides 7be and 210pb and the stable isotopes of hydrogen in water to quantify fine sediment mobilization and storage in a stream and its channel margins during individual intermediate sized storm events with recurrence intervals of a few months or less we demonstrate this method using five storm events in a small 15 km2 undeveloped gravel bedded tributary of the connecticut river usa we estimate that in each storm the mass of sediment deposited onto the margins accounts for almost 90 of the sediment mobilized from the bed with the remainder of the mobilized bed sediment transported downstream as suspended load the result that the bed is a net source of sediment to the stream and the margins a net sink is robust but estimates of the mass of material eroded from the bed and deposited on the margins are less certain the source of sediment to the bed remains unclear as consistent with earlier studies we observe only limited deposition of sediment to the bed during the storm events the suspended sediment is organic rich and thus its source may be associated with in channel organic decay between storm events understanding the coupled interactions between discharge magnitude and frequency and sediment resupply at the event time scale has important implications for stream restoration efforts seeking to connect the channel and the broader riparian zone and for the development of accurate sediment budgets and predictions of sediment flux from a watershed copyright 2015 john wiley sons ltd

geochemistry of daihai lake sediments inner mongolia north china implications for provenance sedimentary sorting and catchment weathering abstract to advance the understanding of sediment distribution catchment weathering hydraulic sorting and sediment provenance in a tectonically stable basin the geochemistry of surface sediment samples from daihai lake in north china is presented mud bulk sediments were analyzed for 10 major and 30 trace elements organic carbon and nitrogen and for 87sr 86sr ratios in silicate fraction acid insoluble ai and carbonates acid soluble as enrichment in fe2o3 cao mno mgo k2o and p2o5 and their positive correlation with al2o3 rb sr ratios and bivariate discrimination diagrams of k vs rb and th u vs th suggest low chemical weathering intensity under semiarid conditions in the daihai catchment accumulation of clays in deeper water sites by sedimentary sorting results in an evident distribution of sediment composition with the lake water depth although similar chondrite normalized ree rare earth element patterns of lake sediment samples with lree light rare earth element enrichment negative eu anomalies and an almost flat hree heavy rare earth element pattern may suggest similar sedimentary source rocks original sediment provenance can be recognized on the basis of their distinctive 87sr 86sr ai ratios and immobile th zr ti and nb trace element signature separating from weathering and sedimentary processes as well as from grain size effect

understanding the reverse time migration backscattering noise or signal reverse time migration backscattered events are produced by the cross correlation between waves reflected from sharp interfaces e g salt bodies these events along with head waves and diving waves produce the so called reverse time migration artefacts which are visible as low wavenumber energy on migrated images commonly these events are seen as a drawback for the reverse time migration method because they obstruct the image of the geologic structure which is the real objective for the process in this paper we perform numeric and theoretical analysis to understand the reverse time migration backscattering energy in conventional and extended images we show that the reverse time migration backscattering contains a measure of the synchronization and focusing information between the source and receiver wavefields we show that this synchronization and focusing information is sensitive to velocity errors this implies that a correct velocity model produces reverse time migration backscattering with maximum energy therefore before filtering the reverse time migration backscattered energy we should try to obtain a model that maximizes it

origin and consequences of cyclic ice rafting in the northeast atlantic ocean during the past 130 000 years deep sea sediment cores recovered from the northeast atlantic ocean were examined in order to elucidate the influence of the earth s orbital parameters on major ice rafting analyses of coarse grained ice rafted debris and planktonic foraminifers revealed a strong reaction to the precession signal since 130 000 yr b p dropstone layers have been deposited each half period of a precessional cycle 11 000 1000 yr ice rafting occurs during times of winter minimum summer maximum insolation and summer minimum winter maximum insolation in the first case high summer insolation forces meltwater discharge from the ice sheets into the polar seas which subsequently enhances formation of sea ice during the winter in the second case growth of continental ice enhances iceberg production which also leads to a salinity reduction of surface seawater both situations result in a southward penetration of polar water thus the marine record of dropstones documents ice rafting not only during weichselian stades but also during cold events within interstades the regularity of ice rafting yields a useful framework to calibrate and elucidate climatic changes not only in the region of the north atlantic ocean but also in remote areas such as the pacific ocean and the antarctic

surface water temperature salinity and density changes in the northeast atlantic during the last 45 000 years heinrich events deep water formation and climatic rebounds we developed a new method to calculate sea surface salinities sss and densities ssd from planktonic foraminiferal 18o and sea surface temperatures sst as determined from planktonic foraminiferal species abundances sst sss and ssd records were calculated for the last 45 000 years for biogeochemical oceanic flux study bofs cores 5k and 8k recovered from the northeast atlantic the strongest feature is the dramatic drop in all three parameters during the heinrich ice rafting events we modelled the possibility of deepwater formation in die northeast atlantic from the ssd records by assuming that the surface waters at our sites cooled as they flowed further north comparison with modelled north atlantic deepwater densities indicates that there could have been periods of deepwater formation between 45 000 and 30 000 14c years b p interrupted by iceberg meltwater input of heinrich event 3 and 4 at 27 000 and 38 000 14c years b p and during the holocene no amount of cooling in the northeast atlantic between 30 000 and 13 000 years could cause deep water to form because of the low salinities resulting from the high meltwater inputs from icebergs our records indicate that after each heinrich event there were periods of climatic rebound with milder conditions persisting for up to 2000 years as indicated by the presence of warmer and more saline water masses after these warm periods conditions returned to average glacial levels these short term cold and warm episodes in the northeast atlantic are superimposed on the general trend towards colder conditions of the last glacial maximum lgm heinrich event 1 appears to be unique as it occurs as insolation rose and was coeval with the initial melting of the fennoscandian ice sheet we propose that meltwater input of heinrich event 1 significantly reduced north atlantic deep water formation reducing the heat exchange between the low and high latitudes thus delaying deglaciation by about 1500 radiocarbon years 2000 calendar years

binge purge oscillations of the laurentide ice sheet as a cause of the north atlantic s heinrich events ice rafted debris in sediment cores from the north atlantic suggests that the laurentide ice sheet lis periodically disgorged icebergs in brief but violent episodes which occurred approximately every 7 000 years here i propose that heinrich events i e what these episodes are called were caused by free oscillations in the flow of the laurentide ice sheet which arose because the floor of hudson bay and hudson strait is covered with soft unconsolidated sediment that forms a slippery lubricant when thawed the proposed heinrich event cycle has two phases the growth phase occurs when the sediment is frozen and the lis is stranded immobile on a rigid bed the volume of the lis slowly grows during this phase at a rate dictated by snow accumulation the purge phase occurs when the basal sediment thaws and a basally lubricated discharge pathway i e an ice stream such as those which occur in west antarctica today developes through hudson strait the volume of the lis rapidly equilibrates to the reduced basal friction during this phase by dumping icebergs into the labrador sea the periodicity t k sl2g 2 7000 years of the proposed heinrich event cycle is a function of the thermal conductivity and diffusivity of ice k and respectively the atmospheric sea level temperature sl in degrees celsius and the excess geothermal heat flux defined by g g k where is the atmospheric lapse rate and g is the geothermal heat flux agreement between the predicted t and the apparent periodicity implied by the marine record is the main virtue of the free oscillation mechanism i propose an alternative mechanism in which heinrich events are forced by periodic variations in external climate is implausible because periodic atmospheric temperature perturbations are strongly attenuated with depth in an ice sheet

acoustic directional snapshot wavefield decomposition up down wavefield decomposition is effectuated by a scaled addition or subtraction of the pressure and vertical particle velocity generally on horizontal or vertical surfaces and works well for data given on such surfaces the method however is not applicable to decomposing a wavefield when it is given at one instance in time i e on snapshots such situations occur when a wavefield is modelled with methods like finite difference techniques for the purpose of for example reverse time migration where the entire wavefield is determined per time instance we present an alternative decomposition method that is exact when working on snapshots of an acoustic wavefield in a homogeneous medium but can easily be approximated to heterogeneous media and allows the wavefield to be decomposed in arbitrary directions such a directional snapshot wavefield decomposition is achieved by recasting the acoustic system in terms of the time derivative of the pressure and the vertical particle velocity as opposed to the vertical derivative in up down decomposition for data given on a horizontal surface as in up down decomposition of data given at a horizontal surface the system can be eigenvalue decomposed and the inverse of the eigenvector matrix decomposes the wavefield snapshot into fields of opposite directions including up down decomposition as the vertical particle velocity can be rotated at will this allows for decomposition of the wavefield into any spatial direction even spatially varying directions are possible we show the power and effectiveness of the method by synthetic examples and models of increasing complexity

chronology for climate change developing age models for the biogeochemical ocean flux study cores we construct age models for a suite of cores from the northeast atlantic ocean by means of accelerator mass spectrometer dating of a key core bofs 5k and correlation with the rest of the suite the effects of bioturbation and foraminiferal species abundance gradients upon the age record are modeled using a simple equation the degree of bioturbation is estimated by comparing modeled profiles with dispersal of the vedde ash layer in core 5k and we find a mixing depth of roughly 8 cm for sand sized material using this value we estimate that age offsets between unbioturbated sediment and some foraminifera species after mixing may be up to 2500 years with lesser effect on fine carbonate 10 mu m ages the bioturbation model illustrates problems associated with the dating of instantaneous events such as ash layers and the heinrich peaks of ice rafted detritus correlations between core 5k and the other cores from the bofs suite are made on the basis of similarities in the downcore profiles of oxygen and carbon isotopes magnetic susceptibility water and carbonate content and via marker horizons in x radiographs and ash beds

use of fallout tracers 7be 210pb and 137cs to distinguish the form of sub surface soil erosion delivering sediment to rivers in large catchments fallout radionuclides frns 137cs and 210pb are well established as tracers of surface and sub surface soil erosion contributing sediment to river systems however without additional information it has not been possible to distinguish sub surface soil erosion sources here we use the frn 7be half life 53 days in combination with 137cs and excess 210pb to trace the form of erosion contributing sediment in three large river catchments in eastern australia the logan river area 3700 km2 bowen river 9400 km2 and mitchell river 4700 km2 we show that the combination of 137cs excess 210pb and 7be can discriminate horizontally aligned sub surface erosion sources rilled and scalded hillslopes and the floors of incised drainage lines and gully badland areas from vertical erosion sources channel banks and gully walls specifically sub surface sources of sediment eroded during high rainfall and high river flow events have been distinguished by the ability of rainfall derived 7be to label horizontal soil surfaces but not vertical our results indicate that in the two northern catchments erosion of horizontal sub surface soil sources contributed almost as much fine river sediment as vertical channel banks and several times the contribution of hillslope topsoils this result improves on source discrimination provided previously and indicates that in some areas erosion of hillslope soils may contribute significantly to sediment yield but not as topsoil loss we find that in north eastern australia scalded areas on hillslopes and incising drainage lines may be sediment sources of comparable importance to vertical channel banks previous studies have used the combination of 137cs excess 210pb and 7be to estimate soils losses at the hillslope scale here we show that with timely and judicious sampling of soil and sediment during and immediately after high flow events 7be measurements can augment fallout 137cs and 210pb to provide important erosion source information over large catchments copyright 2013 john wiley sons ltd

baseflow control on sediment flux connectivity insights from a nested catchment study in central mexico in order to assess the extent of sediment connectivity between uplands and lowlands and to quantify the processes of in channel deposition and remobilization measurements of suspended sediment fluxes were conducted in a nested rural catchment of the mexican volcanic belt data were collected over one year at three upland sites 3 to 12 km2 and two downstream stations 390 630 km2 our results show that a structural discontinuity in the catchment i e abrupt slope decrease at the junction between piedmonts and the alluvial plain from 2 to 10 to 0 1 could be compensated by functional continuity during floods direct conveyance of fine sediment to the outlet occurred when a high stream transport capacity was reached erosion of the streambed was observed on various occasions and accounted for up to 50 of the flux leaving the catchment during one event conversely temporary in channel storage was apparent on other occasions amounting to up to 52 of the flux recorded upstream during one storm these two distinct behaviours were approximately equally distributed along the rainy season and strongly driven by the extent of coupling between surface and subsurface water this work indeed highlights the role of baseflow spatial variations in determining the extent of lowland sediment conveyance riverbed erosional processes occurred when large differences in pre event baseflow values i e at least a twofold longitudinal increase were observed between the 5 km distant lowland stations our findings outline the importance of systematically taking into consideration the baseflow parameter in research focusing on fine sediment transport across scales

runoff and erosion processes after a forest fire in mount carmel a mediterranean area in the mediterranean forest area of israel fires increase runoff and sediment yield rates relative to undisturbed forested land the september 1989 fire covered an area of 4 km2 in the main recreation area of mount carmel a typical mediterranean forest area the lithology is chalk and limestone and about 40 of the burnt area has steep slopes exceeding 30 three study plots were established in burnt and unburnt areas plots were located on 100 300 m2 areas with different slope exposures runoff and sediments were collected after each storm by a collector system a hydrometric station was established draining an area of 1 km2 in the burnt zone rainfall was measured by two recorders and several rain gauges at the experimental sites in the first rainfall season after the fire runoff and sediment yield were 500 and 100 000 times higher respectively in the burnt areas rainfall intensity is a dominant factor in runoff and sediment yield rates in the measured basin total runoff in the first year was 1 6 revegetation recovery of the area was rapid as shown by the results from the second season runoff decreased by one order of magnitude from an average of 10 mm to 1 5 mm sediment yield decreased by two orders of magnitude from 1200 g m 2 to 10 g m 2 the third season 1991 1992 was an exceptionally rainy year and therefore runoff and sediment yield increased but to less than in the first year runoff and sediment yield are related to vegetation cover rainfall intensity soil properties slope steepness and exposure and fire intensity logging activities after fire increase sediment yields through its effects on vegetation cover and soil fire severity increases the potential for erosion

rapid interglacial climate fluctuations driven by north atlantic ocean circulation recent data from the grip ice core1 3 in greenland suggest that the climate of the last eemian interglacial period was much less stable than that of the present interglacial rapid transitions between warm and cold periods were found to occur on timescales of just a few decades the north atlantic climate during the eemian period was also shown to be characterized by three states respectively warmer than similar to and colder than today1 2 recent data from the nearby gisp2 ice core have revealed some discrepancies with these findings which remain to be resolved4 5 here we present simulations using an idealized global ocean model which suggest that the north atlantic ocean has three distinct circulation modes each of which corresponds to a distinct climate state we find that adding a simple random component to the mean freshwater flux which forces circulation can induce rapid transitions between these three modes we suggest that increased variability in the hydrological cycle associated with the warmer eemian climate could have caused transition between these distinct modes in the north atlantic circulation which may in turn account for the apparent rapid variability of the eemian climate

suspended sediment dynamics in a southeast asian mountainous catchment combining river monitoring and fallout radionuclide tracers summary soil erosion is intense in mountainous tropical regions where heavy storms result in the supply of large quantities of sediment to rivers the origin and dynamics of suspended sediment were analysed in a catchment located in northern laos during the first erosive flood of the rainy season in may 2012 the catchment was equipped with 4 successive gauging stations draining areas ranging 0 2 11 6 km2 fallout radionuclides beryllium 7 7be unsupported pb 210 210pbxs and cesium 137 137cs were determined on rainfall overland flow stream water suspended sediment soil surface and subsurface samples with n 3 19 75 75 65 and 14 respectively assumptions underpinning the 7be labelling method were validated by implementing experiments in the laboratory i e rainwater 7be sorption to soil particles and in the field i e 7be 210pbxs activity ratio evolution in rainwater and related overland flow during a natural storm event radionuclide analyses provided a way to quantify variations in sediment dynamics and origin throughout the flood 1 a proportion of recently eroded sediment labelled by 7be and referred to as fresh sediment ranging between ca 8 35 in suspended loads 2 higher contributions of fresh sediment at the beginning of the flood rising stage 3 a progressive dilution of fresh sediment by particles remobilised from the riverbed channel 4 the dominance of particles originating from the soil surface ca 70 80 of total sediment load in upper parts and a much larger contribution of subsurface material ca 64 at the downstream station the original contribution of 7be labelled particles derived from collapsed riverbanks to sediment export was also demonstrated this pilot study supports the use of fallout 7be and 210pbxs in tropical catchments to constrain sediment dynamics it also puts forward the need to better characterize the sources of sediment in order to avoid possible misinterpretations

fallout 210pb as a soil and sediment tracer in catchment sediment budget investigations a review increasing anthropogenic pressures coupled with climate change impacts on natural resources have promoted a quest for innovative tracing techniques for understanding soil redistribution processes and assessing the environmental status of soil resources among the different existing tracers the fallout component of the radioisotope lead 210 also termed unsupported or excess lead 210 pb 210 ex when referring to its presence in soil or sediment arguably offers the broadest potential for environmental applications due to its origin and relatively long half life for more than five decades pb 210 ex has been widely used for dating sediments to investigate sedimentation processes and since the 1990s to provide information on the magnitude of soil and sediment redistribution the aim of this review is to provide a comprehensive evaluation and discussion of the various applications of pb 210 ex as a tracer in terrestrial and aquatic environments with particular emphasis on catchment sediment budget investigations this paper summarizes the state of the art related to the use of this tracer the main assumptions the requirements including the need for accurate analytical measurements and for parallel validation and the limitations which must be recognised when using this fallout radionuclide as a soil and sediment tracer lessons learned and current and future research needs in the environmental and radiochronological application of pb 210 ex are also presented and discussed c 2014 elsevier b v all rights reserved

patterns of ice rafted detritus in the glacial north atlantic 40 55 n the observation by heinrich 1988 that during the last glacial period much of the input of ice rafted detritus to the north atlantic sediments may have occurred as a succession of catastrophic events rekindled interest on the history of the northern ice sheets over the last glacial period in this paper we present a rapid method to study the distribution of these events both in space and time using whole core low field magnetic susceptibility we report on approximately 20 cores covering the last 150 to 250 kyr well defined patterns of ice rafted detritus appear during periods of large continental ice sheet extent although these are not always associated within their maxima most of the events may be traced across the north atlantic ocean for the six most recent heinrich layers hl two distinct patterns exist hl1 hl2 hl4 hl5 are distributed along the northern boundary of the glacial polar front over most of the north atlantic between 40 and 50 n hl3 is more restricted to the central and eastern part of the northern atlantic the nd sr isotopic composition of the material constituting different heinrich events indicates the different provenance of the two patterns hl3 has a typical scandinavia arctic icelandic young crust signature and the others have a large component of northern quebec and northern west greenland old crust material these isotopic results obtained on core su 9008 from the north american basin are in agreement with the study by jantschik and huon 1992 who used k ar dating of silt and clay size fractions of an eastern basin core me 68 89 these data confirm the large spatial scale of these events and the enormous amount of ice rafted detritus they represent

drivers of erosion and suspended sediment transport in three headwater catchments of the mexican central highlands quantifying suspended sediment exports from catchments and understanding suspended sediment dynamics within river networks is important especially in areas draining erodible material that contributes to the siltation of downstream reservoirs and to the degradation of water quality a one year continuous monitoring study of water and sediment fluxes was conducted in three upland subcatchments 3 0 9 3 and 12 0 km2 located within the cointzio basin in the central volcanic highlands of mexico michoacan state two subcatchments generated high sediment exports i e huertitas 900 1500 t km 2 y 1 and potrerillos 600 800 t km 2 y 1 whereas the third subcatchment was characterized by a much lower sediment yield i e la cortina 30 t km 2 y 1 such disparities in subcatchment behaviours were associated with the presence of severely gullied areas in huertitas and potrerillos rather than with rainfall erosivity indices an adapted classification of hysteretic patterns between suspended sediment concentration ssc and discharge was proposed because 42 of flood events contributing to 70 of sediment export were not discriminated by the classical clockwise anticlockwise typology this new classification allowed the identification of relationships in the hydrosedimentary responses of successive floods a stream transport capacity limit was also detected during hydrograph recession phases overall hydrosedimentary processes proved to be seasonally dependent sediment export was repeatedly limited by the stream transport capacity during the first part of the rainy season whereas a channel minimum erosivity threshold was frequently reached at the end of the season

sediment dynamics during the rainy season in tropical highland catchments of central mexico using fallout radionuclides tropical regions are affected by intense soil erosion associated with deforestation overgrazing and cropping intensification this land degradation leads to important on site e g decrease in soil fertility and off site e g reservoir siltation and water pollution impacts this study determined the mean soil particle and sediment residence times in soils and rivers of three subcatchments 3 12 km2 with contrasted land uses i e cropland forests and rangelands draining to a reservoir located in highlands of the transvolcanic mexican belt calculations were based on rainfall amount and river discharges as well as on fallout radionuclide measurements be 7 cs 137 and pb 210 conducted on rainfall precipitated samples soil sampled in the catchments and suspended sediment collected by automatic samplers in the river during most storms recorded throughout the 2009 rainy season calculations using a radionuclide two box balance model showed that the mean residence time of particles in soils ranged between 5000 1500 and 23 300 7000 years in contrast sediment residence time in rivers was much shorter fluctuating between 50 30 and 200 70 days the shortest mean residence times were measured in a hilly catchment dominated by cropland and rangelands whereas they were the longest in an undulating catchment dominated by forests and cropland calculation of the be 7 excess pb 210 in both rainfall and sediment allowed gaining insight on sediment dynamics throughout the rainy season the first heavy storms of the year exported the bulk of the sediment stock accumulated in the river channel during the previous year then during the rainy season the two steeper catchments dominated by cropland and rangelands reacted strongly to rainfall sediment was indeed eroded and exported from both catchments during single heavy storms on several occasions in 2009 in contrast the agro forested catchment with gentler slopes exported sediment at a constant and low rate throughout the rainy season overall land cover and flood type clearly proved to exert more control on sediment export than slope steepness and rainfall erosivity our results show the priority of stabilising old gully systems to prevent their extension by regressive erosion to cropland and to concentrate the implementation of on site erosion control measures in cropland and rangeland of the most reactive catchments

geochemical record of holocene to recent sedimentation on the western indus continental shelf arabian sea 1 we present a multiproxy geochemical analysis of two cores recovered from the indus shelf spanning the early holocene to recent 14 ka indus 23 is located close to the modern indus river while indus 10 is positioned 100 km further west the holocene transgression at indus 10 was over a surface that was strongly weathered during the last glacial sea level lowstand lower holocene sediments at indus 10 have higherendvalues compared to those at the river mouth indicating some sediment supply from the makran coast either during the deposition or via reworking of older sediments outcropping on the shelf sediment transport from makran occurred during transgressive intervals when sea level crossed the mid shelf the sediment flux from non indus sources to indus 10 peaked between 11 ka and 8 ka a hiatus at indus 23 from 8 ka until 1 3 ka indicates non deposition or erosion of existing indus shelf sequences higherendvalues seen on the shelf compared to the delta imply reworking of older delta sediments in building holocene clinoforms chemical index of alteration cia mg al and sr isotopes are all affected by erosion of detrital carbonate which reduced through the holocene k al data suggest that silicate weathering peaked ca 4 6 ka and was higher at indus 10 compared to indus 23 fine grained sediments that make up the shelf have geochemical signatures that are different from the coarser grained bulk sediments measured in the delta plain the indus shelf data highlight the complexity of reconstructing records of continental erosion and provenance in marine settings

temporal variability of suspended sediment sources in an alpine catchment combining river rainfall monitoring and sediment fingerprinting influence of the rainfall regime on erosion and transfer of suspended sediment in a 905 km 2 mountainous catchment of the southern french alps was investigated by combining sediment monitoring rainfall data and sediment fingerprinting based on geochemistry and radionuclide concentrations suspended sediment yields were monitored between october 2007 and december 2009 in four subcatchments 22 713 km 2 automatic sediment sampling was triggered during floods to trace the sediment origin in the catchment sediment exports at the river catchment outlet 330 pm 100 t km 2 yr 1 were mainly driven 80 by widespread rainfall events long duration low intensities in contrast heavy local and short duration storms generated high peak discharges and suspended sediment concentrations in small upstream torrents however these upstream floods had generally not the capacity to transfer the sediment down to the catchment outlet and the bulk of this fine sediment deposited along downstream sections of the river this study also confirmed the important contribution of black marls up to 70 to sediment transported in rivers although this substrate only occupies c 10 of the total catchment surface sediment exports generated by local convective storms varied significantly at both intra and inter flood scales because of spatial heterogeneity of rainfall however black marls marly limestones contribution remained systematically high in contrast widespread flood events that generate the bulk of annual sediment supply at the outlet were characterized by a more stable lithologic composition and by a larger contribution of limestones marls quaternary deposits and conglomerates which corroborates the results of a previous sediment fingerprinting study conducted on riverbed sediment

human impact on the environment in the ethiopian and eritrean highlands a state of the art abstract this review analyses the environmental evolution of the ethiopian highlands in the late quaternary the late pleistocene 20 000 12 000 14c years bp was cold and dry with 1 low lake levels in the rift valley 2 large debris fans on the flanks of lake abhe basin and 3 the blue nile transporting coarse bedload then a period with abundant and less seasonal rains existed between 11 500 and 4800 14c years bp as suggested by increased arboreal pollen high river and lake levels low river turbidities and soil formation around 5000 4800 14c years bp there was a shift to more arid conditions and more soil erosion many phenomena that were previously interpreted as climate driven might however well be of anthropic origin thick sediment deposits on pediments as well as an increase of secondary forest scrub and ruderal species in pollen diagrams are witnesses of this human impact one important aspect of the late quaternary palaeoenvironment is unclear changes in nile flow discharges and rift valley lake levels have been linked to changes in precipitation depth most authors do not take into account changes in land use in the highlands nor changes in the seasonality of rain both of which can lead to a change in runoff coefficients tufa and speleothem deposition around 14 000 years ago tend to indicate that at the end of the last glacial maximum lgm conditions might have been wetter than generally accepted the most important present day geomorphic processes are sheet and rill erosion throughout the country gullying in the highlands and wind erosion in the rift valley and the peripheral lowlands based on existing sediment yield data for catchments draining the central and northern ethiopian highlands an equation was developed allowing to assess area specific sediment yields sy 2595a 0 29 n 20 r 2 0 59 where sy area specific sediment yield t km 2 year 1 and a drainage area km2 with respect to recent environmental changes temporal rain patterns apart from the catastrophic impact of dry years on the degraded environment cannot explain the current desertification in the driest parts of the country and the accompanying land degradation elsewhere causes are changing land use and land cover which are expressions of human impact on the environment deforestation over the last 2000 3000 years was probably not a linear process in ethiopia studies on land use and land cover change show however a tendency over the last decades of increasing removal of remnant vegetation which is slowed down or reversed in northern ethiopia by a set aside policy ongoing land degradation requires urgent action at different levels of society soil and water conservation swc structures are now widely implemented local knowledge and farmer s initiatives are integrated with introduced swc techniques at various degrees impact assessments show clear benefits of the soil conservation measures in controlling runoff and soil erosion in high rain areas runoff management requires greater emphasis during the design of soil conservation structures in such areas investment in swc might not be profitable at farm level although benefits for society are positive this pleads in favour of public support the present land degradation in the ethiopian highlands has a particular origin which includes poverty and lack of agricultural intensification causes of these are to be found in the nature of past and present regional social relations as well as in international unequal development this review strengthens our belief that under improved socio economic conditions land husbandry can be made sustainable leading to a reversal of the present desertification and land degradation of the ethiopian highlands

thermohaline instability in the north atlantic during meltwater events stable isotope and ice rafted detritus records from core so75 26kl portuguese margin a benthic isotope record has been measured for core so75 26kl from the upper portuguese margin 1099 m water depth to monitor the response of thermohaline overturn in the north atlantic during heinrich events evaluating benthic 18o in ts diagrams in conjunction with equilibrium c fractionation implies that advection of mediterranean outflow water mow to the upper portuguese margin was significantly reduced during the last glacial 15 compared to 30 today the benthic isotope record along core so75 26kl therefore primarily monitors variability of glacial north atlantic conveyor circulation the 14c accelerator mass spectrometry ages of 13 54 07 and 20 46 12 ka for two ice rafted detritus ird layers in the upper core section and an interpolated age of 36 1 ka for a third ird layer deeper in the core are in the range of published 14c ages for heinrich events h1 h2 and h4 marked depletion of benthic 13c by 0 7 1 1 during the heinrich events suggests reduced thermohaline overturn in the north atlantic during these events close similarity between meltwater patterns inferred from planktonic 18o at site 609 and ventilation patterns inferred from benthic 13c in core so75 26kl implies coupling between thermohaline overturn and surface forcing as is also suggested by ocean circulation models benthic 13c starts to decrease 1 5 2 5 kyr before heinrich events hl and h4 fully increased values are reached 1 5 3 kyr after the events indicating a successive slowdown of thermohaline circulation well before the events and resumption of the conveyor s full strength well after the events benthic 13c changes in the course of the heinrich events show subtle maxima and minima suggesting oscillatory behavior of thermohaline circulation a distinct feature of thermohaline instability in numerical models inferrred gradual spin up of thermohaline circulation after hl and h4 is in contrast to abrupt wanning in the north atlantic region that is indicated by sudden increases in greenland ice core 18o and in marine faunal records from the northern north atlantic from this we infer that thermohaline circulation can explain only in part the rapid climatic oscillations seen in glacial sections of the greenland ice core record

runoff and soil erosion under rainfall simulation of andisols from the ecuadorian paramo effect of tillage and burning abstract in northern ecuador soils of high altitude grasslands paramos are mainly non allophanic andisols developed on holocenic volcanic ash these soils have a high water retention capacity and are the water tank of central ecuador to assess the effect of land use burning and tillage on soil hydrodynamic properties rainfall simulation was conducted at two different sites at pichincha near quito the simulation was conducted on a recent volcanic ash soil comparing natural tilled and burned plots at el angel the simulation was conducted on a mature non allophanic andisol comparing natural recently tilled and formerly cultivated plots on natural plots the infiltration rate was very high and sediment loss very low results for infiltration rate and runoff indicated that land use change on paramos increased runoff flow and reduced saturated hydraulic conductivity superficial reorganisation of the soil surfaces occurred on tilled plots at both sites this crusting process was fast and resulted in surfaces with very low conductivity at pichincha the same processes seemed to be slower at el angel the soil surface of recent andisols at pichincha was prone to crusting whereas the mature andisol at el angel with a lower bulk density was compacted when the kinetic energy of raindrops was high water repellency occurred after burning at pichincha and following long natural air drying after tillage in the non allophanic a horizon at el angel water repellency combined with the low bulk density of soil aggregates explain the intensity of sediment losses in the abandoned soils after cultivation bare fallow plots erosion occurred in these areas through floating hydrophobic and stable aggregates

separation of upgoing and downgoing waves in vertical seismic profiling by contour slice filtering the separation of upgoing waves and downgoing waves in vertical seismic profiling is effectively accomplished in the frequency wavenumber f k domain using a new technique of contour slice filtering the response of the filter has no straight edge or boundary and preserves the natural state of the spectra the cutoff contour level can be reduced as low as desirable to remove background noise and other unwanted signals in this sense it can also be viewed as a noise rejection filter the effectiveness of the process has been clearly demonstrated through synthetic and real examples its success with the upgoing waves depends on the degree of coherency of events in the vsp record to enhance the coherency and to avoid velocity aliasing we use a novel band pass frequency filter which is the result of convolving a boxcar spectral window with a frequency shifted gaussian function

beryllium 7 the cinderella of fallout radionuclide sediment tracers current concern for the sustainable management of soil resources and the many adverse effects of increased sediment loads on streams and river systems has generated a need for more information on rates and patterns of soil loss and an improved understanding of catchment sediment budgets traditional measurement techniques are frequently unable to meet the requirements and fallout radionuclides have been shown to offer considerable potential for tracing the mobilization transfer redistribution and storage of soil and sediment within catchments and river systems caesium 137 and lead 210 have been the most widely used fallout radionuclide sediment tracers but their half lives mean that the information that they provide is in most instances limited to the medium term e g 25 120 years the need for information on shorter timescales has directed attention to the potential for using beryllium 7 which has a considerable shorter half life for tracing soil and sediment redistribution over short timescales e g days weeks to date however there have been relatively few attempts to exploit this potential this situation is likely to be in part a reflection of the emphasis of early work on 137cs and 210pb and the more recent nature of work using 7be however it may also reflect the limitations and constraints imposed by the nature of 7be fallout and the short half life of this radionuclide this contribution explores recent work in using 7be as a sediment tracer and the constraints imposed by its origin and behaviour attention is directed to fallout inputs the application of 7be to tracing soil and sediment redistribution on slopes and on river floodplains its use as a source fingerprint and other related applications the likely future potential of 7be as a sediment tracer is assessed copyright 2012 john wiley sons ltd

decomposition of multicomponent seismic data into primary p and s wave responses1 inversion of multicomponent seismic data can be subdivided in three main processes 1 surface related preprocessing decomposition of the multicomponent data into primary p and s wave responses 2 prestack migration of the primary p and s wave responses yielding the angle dependent p p p s s p and s s reflectivity of the subsurface 3 target related post processing transformation of the reflectivity into the rock and pore parameters in the target this paper deals with the theoretical aspects of surface related preprocessing which consists of two steps 1 decomposition of the multicomponent data pseudo p and s wave responses into true p and s wave responses 2 elimination of the surface related multiple reflections and conversions

tracing sediment sources in a tropical highland catchment of central mexico by using conventional and alternative fingerprinting methods land degradation is intense in tropical regions where it causes for instance a decline in soil fertility and reservoir siltation two fingerprinting approaches i e the conventional approach based on radionuclide and geochemical concentrations and the alternative diffuse reflectance infrared fourier transform spectroscopy method were conducted independently to outline the sources delivering sediment to the river network draining into the cointzio reservoir in mexican tropical highlands this study was conducted between may and october in 2009 in subcatchments representative of the different environments supplying sediment to the river network overall cointzio catchment is characterized by very altered soils and the dominance of andisols and acrisols both fingerprinting methods provided very similar results regarding the origin of sediment in huertitas subcatchment dominated by acrisols where the bulk of sediment was supplied by gullies in contrast in la cortina subcatchment dominated by andisols the bulk of sediment was supplied by cropland sediment originating from potrerillos subcatchment characterized by a mix of acrisols and andisols was supplied in variable proportions by both gullies and rangeland cropland in this latter subcatchment results provided by both fingerprinting methods were very variable our results outline the need to take the organic carbon content of soils into account and the difficulty to use geochemical properties to fingerprint sediment in very altered volcanic catchments however combining our fingerprinting results with sediment export data provided a way of prioritizing the implementation of erosion control measures to mitigate sediment supply to the cointzio reservoir supplying drinking water to morelia city copyright 2012 john wiley sons ltd

sudden changes in north atlantic circulation during the last deglaciation sudden changes in the flow of warm atlantic surface waters into the norwegian sea occurred frequently during the last deglaciation typically involving shifts in sea surface temperature of 5 c in fewer than 40 years these led to equally large and rapid changes in atmospheric temperatures and to shifts in atlantic deep thermo haline circulation and ice sheet melting rates

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

provenance weathering and erosion records in southern okinawa trough sediments since 28ka geochemical and sr nd pb isotopic evidences abstract geochemical and sr nd pb isotopic compositions of the detrital sediments from odp hole 1202b and taiwan rivers were measured in this study aiming to reveal changes in sediment provenance in the southern okinawa trough sot since 28 ka and to examine the weathering and sediment transport processes in response to monsoon climate variability large variations in sr nd pb isotopic ratios at 11 9 ka suggest changes in detrital sediment provenance in the sot from a dominance of the paleo changjiang yangtze river and or continental shelf sediment during the late deglaciation and to west taiwan rivers since 9 5 ka volcanic rocks and eastern taiwan sediments have not significantly contributed to the sot the large shift in sediment provenance during the early holocene marks a major change in oceanic circulation mainly caused by the intrusion of the kuroshio current into the trough clay mineral and geochemical proxies suggest that the taiwan derived sediments accumulated during the early mid holocene climate optimum ca 9 5 4 ka might be tightly related to the reworking of older altered sediments from terraces and floodplains rather than having experienced more intense silicate weathering than in the late holocene 4 0 ka overall silicate weathering in taiwan was greatly inhibited by accelerating sediment production and transfer from land to ocean caused by monsoon intensification in holocene our study illustrates that the radiogenic isotopic and geochemical compositions of fine grained detrital sediments are sensitive tools for fingerprinting sediment sources and for reconstructing changes in oceanic currents and monsoon climate in river dominated east asian continental margin

evidence for massive discharges of icebergs into the north atlantic ocean during the last glacial period sediments in the north atlantic ocean contain a series of layers that are rich in ice rafted debris and unusually poor in foraminifera1 here we present evidence that the most recent six of these heinrich layers deposited between 14 000 and 70 000 years ago record marked decreases in sea surface temperature and salinity decreases in the flux of planktonic foraminifera to the sediments and short lived massive discharges of icebergs originating in eastern canada the path of the icebergs clearly marked by the presence of ice rafted detrital carbonate can be traced for more than 3 000 km a remarkable distance attesting to extreme cooling of surface waters and enormous amounts of drifting ice the cause of these extreme events is puzzling they may reflect repeated rapid advances of the laurentide ice sheet perhaps associated with reductions in air temperatures yet temperature records from greenland ice cores appear to exhibit only a weak corresponding signal moreover the 5 10 000 yr intervals between the events are inconsistent with milankovitch orbital periodicities raising the question of what the ultimate cause of the postulated cooling may have been

separated wavefield imaging using primary and multiple energy imaging with separated wavefields swim is an innovative depth imaging technology that uses upgoing and downgoing wavefields at the surface to deliver high resolution images of the subsurface it takes advantage of the extended illumination provided by surface multiple energy and thus it exploits data that the seismic industry historically has treated as unwanted noise the fundamental concept behind swim is based on using each receiver as a virtual source effectively expanding the surface coverage of the seismic experiment and enhancing the subsurface illumination particularly for shallow reflectors by effectively turning the streamer spread into a source and receiver array the resulting equivalent survey has spatial sampling that is much improved and a richer distribution of offsets and azimuths the improved spatial sampling enhances the angular illumination greatly at every image point therefore swim produces densely sampled angle gathers that provide greater opportunities for velocity model building and for improved interpretation of complex structures several issues need to be considered for proper imaging with swim migration imaging conditions attenuation of cross talk and acquisition design the latter must be addressed to support proper sampling of both upgoing and downgoing wavefields used for imaging a broad overview and examples of these subjects are presented applications to a deepwater wide azimuth waz survey from the gulf of mexico and a shallow water narrow azimuth naz data set from offshore malaysia demonstrate the enhanced areal illumination and improved imaging resolution from imaging using multiple reflection energy

magnetic fingerprinting of fluvial suspended particles in the context of soil erosion example of the canche river watershed northern france in northern france land use is dominated by agriculture erosion by runoff results in heavy loss of fertile soil into surface waters there is a need for cost effective tools to trace the sediment flux in catchments this study highlights the potential of environmental magnetism to provide rapid non destructive parameters to characterize the spatiotemporal runoff versus bedload signal in a watershed between 2015 and 2017 within the canche river watershed several spatiotemporal sampling campaigns of suspended particulate matter spm were undertaken and two distinct snapshot campaigns of flood events were conducted at key locations acquiring in addition hydrodynamical observations discharge turbidity sediment load etc agricultural soils and spm within the watershed have similar values for bulk magnetic concentration isothermal remanent magnetization irm the magnetic mineral assemblage of the spm is dominated by soft ferromagnetic sensu lato minerals during low water conditions and is enriched in high coercivity phases during high water stages associated with rainfall events low temperature remanence experiments identified goethite and hematite as the high coercivity phases irm acquisition component analysis of the room temperature results quantify the relative input of high versus low coercivity components focused on a given confluence site results from snapshot campaigns highlight the link between the enhanced runoff input of high coercivity particles during flood events and show that the s ratio parameter is an effective tool to trace erosion of topsoils

separation of p and s waves in combined p and sv observations with vertical and in line horizontal geophones recognition and separation of the individual p and s arrivals may form a considerable problem due to the geophone receiving characteristics p and s waves are observed on both horizontal and vertical geophones a new method of separating p and s waves is presented that inverts the geophone records for the receiving characteristics thereby separating the two wavetypes the filter coefficients are determined from the near surface p and s wave velocity and from the geometry of the geophone groups the p s separation filter was tested on synthetic data with good results even ps and sp converted reflections which are completely coinciding for horizontal reflectors could be well separated the filter appears to be stable and to have low sensitivity to noise in the data or to errors in the near surface p and s wave velocity the filter is superior to other separation methods which were applied to the same dataset for comparison this method can also be applied to vsp data

gully and sheet erosion on subtropical mountain slopes their respective roles and the scale effect abstract as most mountains in tropical and subtropical zones the western sierra madre suffers active present erosion which may create some constraints to the social and economic development in the area the objectives of this study of soil degradation in the western sierra madre are to determine the respective roles of gully and sheet erosion this research is based on field observations field measurements of runoff and soil losses at the plot as well as the watershed scales as an analysis of an exhaustive census of the few gullies located in an experimental area measured soil losses in the western sierra madre are high although there are few gullies most of the sediment yield seems to originate in widespread degraded areas where stoniness is the main evidence of a previous stage of erosion previously overgrazing and deforestation were determined as the factors of the appearance of new soil surface characteristics which explain the high runoff and sediment productions the soil compacted by cattle trampling reduces infiltration the decrease of the vegetation cover triggers a rise in the splash effect and thus a soil sealing these processes induce an increase in runoff and soil losses the main erosion type has been described as sheet erosion it is characterised by the removal of fine soil particles and the remains of gravels pebbles and blocks which constitute a pavement on the soil gullies generally appear on the bottom of wide valleys and depressions where soils are thick it is shown that sheet erosion is two orders of magnitude higher than gully erosion at the hillslope scale due to the spatial distribution of land use and the geological context such as the heavily degraded areas close to the main rivers the reduction of runoff and soil loss rates within the extension of a considered area commonly observed in hydrology only applies up to the elementary catchments scale 1 to 50 km 2 above this area runoff coefficient and soil loss rates increase

transport of the environmental radionuclides in an alpine watershed abstract the radionuclides137cs 210pb and7be have been examined in the alpine rho ne watershed switzerland during a period of two years in order to evaluate their usefulness as tracers of the removal and transport rate of top soil particles and particle reactive contaminants of atmospheric origin the specific activities of the radionuclides in fluvial suspension show a distinct seasonal pattern which depends on the hydrologic regime of the stream and the sources of the suspended matter input output budgets based on the atmospheric deposition and fluvial removal of three radionuclides in the alpine rho ne watershed are used to estimate their erosional residence times the simplest one box model yields mean residence times of about 800 and 1400 years for137cs and210pb respectively the removal rate of short lived7be suggests that a part of the watershed 0 6 2 3 of the total surface is exposed to a rapid erosion in which the mean residence time of the radionuclides is in the range of 1 220 days this has little influence on the calculated residence time of137cs but increases the estimated residence time of210pb in soil to over 1800 years the use of210pb 7be pair in fluvial output may be very helpful in the assessment of the impact of atmospheric pollutants on the water quality in rivers and lakes