spatial variability of hydraulic conductivity and bulk density along a blanket peatland hillslope this article presents the results of a field investigation of saturated hydraulic conductivity ksat and bulk density bd in an atlantic blanket bog in the southwest of ireland starting at a peatland stream and moving along an uphill transect toward the peatland interior bd and ksat were examined at regular intervals saturated horizontal hydraulic conductivity khsat and vertical kvsat was estimated at two depths 10 20 and 30 40 cm below the peat surface whereas bd was estimated for the full profile we consider two separate zones one a riparian zone extending 10 m from the stream and a second zone in the bog interior we found that the ksat was higher 10 5 m s 1 in the bog interior than that in the riparian zone 10 6 m s 1 whereas the converse applied to bulk density with lowest density 0 055 g cm 3 at the interior and highest 0 11 g cm 3 at the riparian zone in general we found khsat to be approximately twice the kvsat these results support the idea that the lower ksat at the margins control the hydrology of blanket peatlands it is therefore important that the spatial variation of these two key properties be accommodated in hydrological models if the correct rainfall runoff characteristics are to be correctly modelled stream flow analysis over 3 years at the peatland catchment outlet showed that the stream runoff was composed of 8 base flow and 92 flood flow suggesting that this blanket peatland is a source rather than a sink for floodwaters copyright 2011 john wiley sons ltd

the geochemistry of major and selected trace elements in a forested peat bog kalimantan se asia and its implications for past atmospheric dust deposition abstract biogeochemical processes in a forested tropical peat deposit and its record of past atmospheric dust deposition were assessed using the vertical distribution of lithophilic and plant essential elements in a dated core profile from borneo se asia peat formation started 22 120 14c yr before present bp and ca mg mass ratios of the solid peat and very low ash contents indicate a strongly ombrotrophic character throughout the deposit implying that most of the inorganic fraction has been supplied exclusively by atmospheric inputs concentration profiles of mn sr and ca suggest a very minor influence of chemical diagenesis in the underlying sediments silicon ca mg p s and k show a strong and extended zone of enrichment in the top 200 cm of the profile indicating that biological accumulation mechanisms are much more extensive than in temperate peat bogs in the lower core sections where the element distribution is dominated solely by past atmospheric deposition average al ti ratios are similar to the upper continental crust ucc whereas fe is slightly enriched and si is strongly depleted this condition favors highly weathered tropical soil dust as the main inorganic mineral source significant correlation of al fe si s ca and ti with the lithophilic elements y and zr suggests that the distribution of these elements is controlled by sources of atmospheric mineral dust the ca mg ca k and mg k ratios of the collected rainwater samples are similar to the global average of continental rainwater and suggest a continental character for the site this is supported by the similarity of the average concentration of br mg ca and s to that in temperate continental and maritime bogs in switzerland and scotland the concentration profiles of si fe al and ti show distinct peaks within the profile implying enhanced dust deposition reduced rates of peat accumulation or possibly both owing to climatic changes during the holocene enhanced dust deposition between 10 830 and 9060 14c yr bp is tentatively interpreted as a younger dryas like event with dust fluxes of 10 8 mg m2 yr the variations in al ti and fe ti profiles suggest that mineral dust sources have been changing constantly during the holocene with local sources being dominant between 7820 and 9500 14c yr bp and long range transport derived most likely from china being important during the late pleistocene and early holocene and from 7820 14c yr bp to the present

the use of topographic scale models in predicting eolian dust erosion in hilly areas field verification of a wind tunnel experiment abstract eolian erosion of natural dust in an area of 53 ha situated in the northern negev desert is investigated in detail both in the wind tunnel erosion simulations on a topographic scale model and in the field the wind tunnel results and the field results show good agreement indicating that wind tunnel simulations of eolian dust erosion on scale models of complex topography may predict at least to an acceptable level the erosion sensitive areas in a hilly landscape of nearly uniform surface roughness the experiments also indicate that a restricted height distortion of scale models may be acceptable to determine the areas of highest erosion in addition wind tunnel blockage percentages up to 10 may be allowed to obtain acceptable erosion patterns on the model when surface roughness is more or less uniform eolian erosion of dry dusty sediments is almost entirely determined by macro topography if however surface roughness is highly variable over the field the initiation of eolian erosion is also largely a function of local micro topography

iodine 129 87sr 86sr and trace elemental geochemistry of northern appalachian basin brines evidence for basinal scale fluid migration and clay mineral diagenesis evidence for basin scale brine migration and clay mineral diagenesis in the northern appalachian basin was investigated using elemental and isotope 129i i 87sr 86sr geochemistry of formation waters collected from the middle to upper devonian section of the northern basin margin in western new york northwest pennsylvania and eastern kentucky one sample from each of the mississippian berea sandstone and the silurian medina sandstone were analyzed for comparison measured iodine ratios range between 28 to 1 890 10 15 and are anomalously high compared to cosmogenic iodine sourced from devonian age organic matter iodine 129 in the waters was largely derived from fissiogenic sources the spontaneous fission of 238u to produce 129i with estimated 129i i values up to 270 10 15 which occur locally in the organic rich shales there are three water samples that have values of 490 10 15 860 10 15 and 1 890 10 15 which are above the range for local fissiogenic 129i and may be accounted for by topographically driven basin scale fluid flow through a regionally high fissiogenic source relatively large uranium occurrences lie along the structural front of the appalachian basin in the blue ridge province and are situated within hypothesized flow paths parallel to the main compressional direction of the alleghanian orogeny estimated 129i i values for these uranium occurrences are in excess of 55 000 10 15 the strontium isotope composition and sr concentration of brines display a mixing trend between a highly radiogenic end member 0 7210 with low sr 51 mg l and a non radiogenic 0 7100 high sr 4789 mg l end member potassium and boron concentrations are notably depleted relative to evaporated paleozoic seawater the hypothesized source of appalachian basin brines the k rb values of formation waters are depleted relative to seawater values but in some cases are well above values indicative of water rock reactions the sr isotopic composition k and b depletion and intermediate k rb ratios are consistent with smectite diagenesis and paleo temperatures that are likely greater than approximately 150 c these temperatures may be high given the burial history of the study area and support the flow of formation waters from deeper within the basin the combined isotopic and elemental results of formation waters provide compelling evidence for basin scale fluid migration in the northern appalachian basin and are consistent with previously published evidence documented from the rock record including clay mineral diagenesis and ore deposition

spatial distribution of threshold wind speeds for dust outbreaks in northeast asia abstract asian windblown dust events cause human and animal health effects and agricultural damage in dust source areas such as china and mongolia and cause yellow sand events in japan and korea it is desirable to develop an early warning system to help prevent such damage we used our observations at a mongolian station together with data from previous studies to model the spatial distribution of threshold wind speeds for dust events in northeast asia 35 45 n and 100 115 e using a map of normalized difference vegetation index ndvi we estimated spatial distributions of vegetation cover roughness length threshold friction velocity and threshold wind speed we also recognized a relationship between ndvi in the dust season and maximum ndvi in the previous year thus it may be possible to predict the threshold wind speed in the next dust season using the maximum ndvi in the previous year

measuring physical and hydraulic properties of peat from x ray tomography abstract organic soils cover a large percentage of the canadian land mass in the form of peatlands 14 and other organic terrains including arctic and alpine tundra and taiga 25 sphagnum mosses are the dominant peat forming species in all of these terrains understanding the processes by which this material conducts retains and redistributes moisture and energy is crucial to the successful development of physically based methods of measuring and modelling their hydrological response sphagnum peat was sampled from scotty creek in the wetland dominated zone of discontinuous permafrost near fort simpson northwest territories canada physical properties of the peat samples were measured from standard methods and x ray tomographic images of sub samples were obtained at 5 levels of volumetric moisture content between 0 4 and 0 7 the volumetric moisture content measured using the tomographic images closely approximated the gravimetric measurements properties of the pore spaces were measured in both two and three dimensions the active porosities measured in 2d and 3d were very similar and matched closely with values reported in the literature specific surface area 3d however was larger than the specific perimeter 2d the 2d analysis suggests a relatively gradual transition from small to large pores while in 3d the distribution is dominated by a single large pore space whose volume and surface area are 3 orders of magnitude larger than the next largest pore and 99 of the total inter particle pore volume this single large pore space contains the flow network this study elucidated the volume and configuration of this network for discrete ranges of soil water pressure that typically occur in the field the flow network diminished from 17 6 to 9 0 of a sample volume as its volumetric moisture content lowered from 0 65 to 0 42 this volume loss was accommodated by the thinning and disaggregation of moisture films although as the sample lost moisture the flow network maintained a relatively even spatial distribution

effect of mine dewatering on the peatlands of the james bay lowland the role of marine sediments on mitigating peatland drainage the wetlands of the james bay lowland comprise one of largest wetland complexes in the world in part due to the properties thickness and hydraulic conductivity of the marine sediment ms that underlay them dewatering of an open pit diamond mine is depressurizing the surrounding silurian bedrock below the ms prior to mining it was assumed that these ms would largely isolate the overlying peatlands from the depressurized regional bedrock aquifer to assess this isolation we instrumented a 1 5 km long transect of wells and piezometers located within the zone of the mine s influence that crossed a sequence of bogs fens and bedrock outcrops bioherms results were differentiated between those areas with no ms near bioherms and those underlain by ms non bioherm along the transect between 2007 and 2010 at near bioherm and non bioherm locations average peat water tables declined 71 and 31 cm and hydraulic head declined 66 and 32 cm in bioherm and non bioherm locations respectively gradients varied from near zero 0 001 at the start of dewatering to 0 03 after 5 years in non bioherm areas and from 0 20 to 0 45 in near bioherm areas these gradients corresponded to fluxes groundwater recharge of approximately 0 26 mm day and 2 1 mm day in non and near bioherm areas respectively specific discharge recharge determined using the known mine dewatering rate and drawdown cone heads and areas corresponded well with measured recharge determined in the non bioherm transect locations a simple rearrangement of darcy s law used to calculate the specific discharge highlighted how the ratio of hydraulic conductivity to the thickness of the ms can be used to assess vulnerable areas therefore given the increasing development in ontario s far north considerable attention must be given to both the thickness and hydraulic conductivity of ms copyright 2013 john wiley sons ltd

estimating aerodynamic resistance of rough surfaces using angular reflectance abstract current wind erosion and dust emission models neglect the heterogeneous nature of surface roughness and its geometric anisotropic effect on aerodynamic resistance and over estimate the erodible area by assuming it is not covered by roughness elements we address these shortfalls with a new model which estimates aerodynamic roughness length z0 using angular reflectance of a rough surface the new model is proportional to the frontal area index directional and represents the geometric anisotropy of z0 the model explained most of the variation in two sets of wind tunnel measurements of aerodynamic roughness lengths z0 field estimates of z0 for varying wind directions were similar to predictions made by the new model the model was used to estimate the erodible area exposed to abrasion by saltating particles vertically integrated horizontal flux fh was calculated using the area not covered by non erodible hemispheres the approach embodied in dust emission models under the same model conditions fh estimated using the new model was up to 85 smaller than that using the conventional area not covered these fh simulations imply that wind erosion and dust emission models without geometric anisotropic sheltering of the surface may considerably over estimate fh and hence the amount of dust emission the new model provides a straightforward method to estimate aerodynamic resistance with the potential to improve the accuracy of wind erosion and dust emission models a measure that can be retrieved using bi directional reflectance models from angular satellite sensors and an alternative to notoriously unreliable field estimates of z0 and their extrapolations across landform scales

effects of checkerboard barriers on the distribution of aeolian sandy soil particles and soil organic carbon abstract sand barrier setup is an important measure to protect the topsoil against wind erosion salix psammophila checkerboard barriers are used widely in the mu us sandy land in order to ensure the safety of life and agricultural production to measure variations in soil structure and quality caused by barriers with different duration 7 years and 2 years the composition of aeolian sandy soil particles and the soil organic carbon soc distributions are studied the dunes with no barrier are used as controls ck analyzed by multi fractal parameters the topsoil samples are collected in the field and tested in the laboratory the predominant soil particles are fine sand medium coarse sand and clay and the contents of silt and very fine sand increase with extending barrier duration which shows a wider distribution range greater dispersion degree and larger soil particle heterogeneity the aeolian sandy particles particularly fine granular grains are deposited and accumulate at the bottom and top of dunes because of the barrier blocking effect the particle size distribution psd heterogeneity is the highest in 7 year barrier dunes and the lowest in the no barrier dunes the mean values of d0 capacity dimension of 7 year barrier dunes d1 entropy dimension of the no barrier dunes and d1 d0 of 2 year barrier dunes are maxima in addition the psd range and distribution increased with prolonged dune barrier duration as well as the changes of f shape of the multi fractal spectrum and width of multi fractal spectrum soc content increased with increasing barrier duration and decreasing d1 d0 the average soc contents of 7 year barrier dunes were the maximum and one of no barrier dunes had the minimum soc content and their difference was significant p correlations between the soc content and the psd multi fractal parameters of both 7 year and 2 year barrier dunes are significantly different p

chemical dilation and the dual porosity of humified bog peat abstract hydrochloric acid and calcium and sodium chloride salt solutions were passed through humified bog peat cores of 1 m length to determine values for the material properties governing solute transport hydraulic conductivity effective porosity and dispersivity chloride passed through the bulk peat cores about twice as fast as predicted from chloride breakthrough curves measured by selective ion probes inserted into the peat 30 cm downgradient from the source with continued experimentation chloride dispersion increased chloride also passed through the peat up to 12 times slower than predicted by conservative advection the retardation of the chloride fronts the faster bulk transport and the asymmetry of the breakthrough curves all indicate that humified bog peat is a dual porosity medium solutes both move preferentially through active macropore spaces and diffuse into dead pore space in the peat matrix neither the effective porosity nor the dispersivity of the peat could be precisely determined from the breakthrough curves because the hydraulic conductivity and discharge rates through the peat increased as much as five times when the chloride tracer solutions passed through the cores in initial experiments the shapes of the breakthrough curves were generally consistent with dispersivities of the order of centimeters similar to that observed for granular soils at the same length scale meters whereas they flattened considerably during later experiments suggesting dispersivities in the range of tens of centimeters we hypothesize that the interaction of the chloride tracer solutions with organic acid functional groups may cause macropores to dilate and micropores to close off

subsurface drainage from hummock covered hillslopes in the arctic tundra in the arctic tundra subsurface drainage occurs predominantly through the saturated zone within the layer of peat that mantles the hillslopes in plan view the peat cover is fragmented into a network of channels due to the presence of mineral earth hummocks in cross section the physical and hydraulic properties of the peat vary with depth and the water transmission characteristics e g hydraulic conductivity of the upper profile differ distinctly from those of the lower water flow through the peat is laminar therefore the friction factor f and the reynolds number nr are inversely related average values for the coefficientc of the relation f a c nr vary from 300 near the surface to 14 500 at depth this large difference in c confirms that the larger diameter soil pores of the living vegetation and lightly decomposed peat near the surface offer much less resistance to water motion than the finer grained peat deeper in the profile also the variability suggests that subsurface drainage is strongly affected by the position and thickness of the saturated zone within the peat matrix a first approximation for a model or simulation of the flow regime may consider a peat profile with depth varying resistance properties in respect to subsurface flow q 2000 elsevier science b v all rights reserved

geologic fluid inclusion and isotopic studies of the findlay arch district northwestern ohio the findlay arch district is a cluster of noneconomic carbonate hosted mineral occurrences centered in northwestern ohio the principal host rocks are vuggy dolostones that range in age from middle silurian to middle devonian reef complexes beds of nodular gypsum collapse breccias and fracture zones provided important stratigraphic and structural ore controls the main stage phases are brown yellow and purple fluorite sphalerite and galena the sphalerite galena ratios are 100 or higher early dolomite pyrite marcasite and celestite i are premain stage phases whereas saddle dolomite vug filling calcite celestite ii barite and strontianite are postmain stage phases t h and t m measurements of fluid inclusions in fluorite and sphalerite indicate that these minerals were precipitated from a warm na ca cl brine likely derived from the northern appalachian basin the flow path is inferred from westward diminishing salinity values that are documented in successive generations of inclusions the dominant thermal trend was aregional temperature plateau that peaked at about 110 degrees c thermal and salinity data imply that the flow system developed during the alleghenian orogeny when the burial depth of host rocks was at a maximum and when the brine was diluted isothermally as it migrated westward across the arch coexisting inclusions of oil and brine indicate that these fluids moved through the district together similar sulfur isotope compositions 0 9 to 4 8 and 3 4 to 0 6ppm in sphalerite and galena show that these sulfides are genetically related these data generally agree with sulfur compositions of late paleozoic seawater sulfate which is consistent with an alleghenian age for the findlay arch sulfur source lead isotope compositions of galena haden 1977 fall in the field of the appalachian ores and diagenetic galena indicating further that nonradiogenic paleozoic sedimentary rocks to the east were the likely source of lead minerals in vugs lack a radiogenic component of strontium nevertheless a basinal brine is required for the fluorite sphalerite mineralization because a rock capable of providing the salinity of the fluid inclusions was absent in the district the strontium isotope composition of this brine apparently was reset acquiring the signature of salina gypsum of upper silurian age a local source of strontium and sulfur is indicated for celestite i because its s and sr isotope compositions are nearly identical to those of the salina anhydrite brown calcite in veins associated with the bowling green fault zone contains strontium that is slightly radiogenic relative to vug filling calcite this along with the prehydrocarbon age of the brown calcite indicates that these early veins and the fiuorite sphalerite mineralization are not coeval

groundwater flow patterns in a large peatland abstract groundwater flow patterns and geochemistry were studied in the mer bleue bog near ottawa ontario canada groundwater flow patterns alternated between recharge i e head gradients producing flow from the surface of the peatland to the deeper peat and discharge i e head gradients indicating flow from the deeper peat towards the surface of the peatland during the summer of 1998 the patterns were controlled by changes in precipitation evapotranspiration and the differential head response of catotelm peat lower layer to changes in water table elevation above average rainfall in the spring created recharge patterns of groundwater flow in the peatland evapotranspiration exceeded precipitation for a three week period in mid summer decreasing head at the water table and reversing flow from recharge to discharge a sustained moisture deficit maintained a flow reversal for 32 days until a 46 mm rainfall raised the water table reversing the vertical hydraulic gradients and restoring recharge flow the mixing of meteoric water and deeper groundwater controls geochemical profiles diffusion modeling shows that the peatland is a long term recharge system however electrical conductivity and cation concentrations in peat pore waters increase up to 60 during a flow reversal and then decrease when recharge conditions are re established the redistribution of substrates from reversed flow is likely important to peatland biogeochemical function

structure of peat soils and implications for water storage flow and solute transport a review update for geochemists abstract global peatlands are a valuable but vulnerable resource they represent a significant carbon and energy reservoir and play major roles in water and biogeochemical cycles peat soils are highly complex porous media with distinct characteristic physical and hydraulic properties pore sizes in undecomposed peat can exceed 5 mm but significant shrinkage occurs during dewatering compression and decomposition reducing pore sizes the structure of peat soil consists of pores that are open and connected dead ended or isolated the resulting dual porosity nature of peat soils affects water flow and solute migration which influence reactive transport processes and biogeochemical functions advective movement of aqueous and colloidal species is restricted to the hydrologically active or mobile fraction of the total porosity i e the open and connected pores peat may attenuate solute migration through molecular diffusion into the closed and dead end pores and for reactive species also through sorption and degradation reactions slow diffusion limited solute exchanges between the mobile and immobile regions may give rise to pore scale chemical gradients and heterogeneous distributions of microbial habitats and activity in peat soils while new information on the diversity and functionalities of peat microbial communities is rapidly accumulating the significance of the geochemical and geomicrobial study on peat stands to benefit from a basic understanding of the physical structure of peat soils in this paper we review the current knowledge of key physical and hydraulic properties related to the structure of globally available peat soils and briefly discuss their implications for water storage flow and the migration of solutes this paper is intended to narrow the gap between the ecohydrological and biogeochemical research communities working on peat soils

anisotropy and depth related heterogeneity of hydraulic conductivity in a bog peat ii modelling the effects on groundwater flow anisotropy and heterogeneity of hydraulic conductivity k are seldom considered in models of mire hydrology we investigated the effect of anisotropy and heterogeneity on groundwater flow in bog peat using a steady state groundwater model in five model simulations four sets of k data were used the first set comprised measured k values from an anisotropic and heterogeneous bog peat these data were aggregated to produce the following simplified data sets an isotropic and heterogeneous distribution of k an isotropic and homogeneous distribution and an anisotropic and homogeneous distribution we demonstrate that where anisotropy and heterogeneity exist groundwater flow in bog peat is complex fine scale variations in k have the potential to influence patterns and rates of groundwater flow however for our data at least it is heterogeneity and not anisotropy that has the greater influence on producing complex patterns of groundwater flow we also demonstrate that patterns and rates of groundwater flow are simplified and reduced when measured k values are aggregated to create a more uniform distribution of k for example when measured k values are aggregated to produce isotropy and homogeneity the rate of modelled seepage is reduced by 28 we also show that when measured k values are used the presence of a drainage ditch can increase seepage through a modelled cross section our work has implications for the accurate interpretation of hydraulic head data obtained from peat soils and also the understanding of the effect of drainage ditches on patterns and rates of groundwater flow

surface deformations as indicators of deep ebullition fluxes in a large northern peatland 1 peatlands deform elastically during precipitation cycles by small 3 cm oscillations in surface elevation in contrast we used a global positioning system network to measure larger oscillations that exceeded 20 cm over periods of 4 12 hours during two seasonal droughts at a bog and fen site in northern minnesota the second summer drought also triggered 19 depressuring cycles in an overpressured stratum under the bog site the synchronicity between the largest surface deformations and the depressuring cycles indicates that both phenomena are produced by the episodic release of large volumes of gas from deep semi elastic compartments confined by dense wood layers we calculate that the three largest surface deformations were associated with the release of 136 g ch4 m 2 which exceeds by an order of magnitude the annual average chamber fluxes measured at this site ebullition of gas from the deep peat may therefore be a large and previously unrecognized source of radiocarbon depleted methane emissions from northern peatlands

sand transportation and reverse patterns over leeward face of sand dune abstract sand saltation has complex interactions with turbulent flow and dune form most models of wind blown sand consider ideal circumstances such as steady wind velocity and a flat surface and the bulk of data on wind flow and sand transport over an individual dune has focused mostly on the influence of dune shape or inter dune space on the wind flow neglecting the effect of morphology on sand saltation particularly airflow and sand transportation over the leeward slope wind flow structures over the leeward slope of sand dunes have a fundamental influence on the organization of sand dunes in order to understand sand dune dynamics lee face airflow and sediment transportation should be paid more attention previous field observations could not measure turbulent flow structure well because of the limited observation points and the influence of experiment structure on wind field in addition the reverse sand particles over leeward face could not be collected by sand trap in field numerous field observations could not measure turbulent flow structure because of the limited observation points and the influence of experimental structures on the wind field in addition the reverse transport of sand particles over leeward face could not be collected by sand traps in field therefore this paper aims to investigate the turbulent flow structure and sand transport pattern over the leeward slope a numerical model of sand saltation over slope terrain is constructed which also considers the coupling effects between air flow and sand particles the large eddy simulation method is used to model turbulent flow sand transport is simulated by tracking the trajectory of each sand particle the results show that terrain significantly alters the turbulent air flow structure and wind blown sand movement especially over the leeward slope here mass flux increases initially and then decreases with height in the reversed flow region in the direction of wind flow and the mass flux decreases with height in the reversed direction the height of 0 5 h is the height of vortex core in the reversed flow region the vortex core is a critical point in the flow region where few particles are transited in the reversed region the reversed mass flux of sand particles is 25 of the mass flux in the flow direction this research may contribute to scientific understanding of the mechanisms of sand motion and wind flow over leeward of dune and it is likely to be significant in desertification control

peat hydraulic conductivity in cold regions and its relation to pore size and geometry subsurface flow through peat plays a critical role in the hydrology of organic covered permafrost terrains which occupy a large part the continental arctic sub arctic and boreal regions hillslope drainage in these terrains occurs predominantly through the active flow zone between the relatively impermeable frost table and the water table above it the hydraulic conductivity profile within this zone controls the subsurface drainage of snowmelt and storm water peat hydraulic conductivity profiles were examined at three sites in north western canada each representing a widely occurring organic covered permafrost terrain type three independent measures of saturated hydraulic conductivity were used tracer tests constant head well permeameter tests and laboratory measurements of undisturbed samples at all three sites the conductivity profiles contained very high values 10 1000 m d 1 within the top ca 0 1 m where the peat is only lightly decomposed a large reduction with increasing depth below the ground surface in the transition zone and relatively low values in a narrow range 0 5 5 m d 1 below ca 0 2 m depth where the peat is in an advanced state of decomposition digital image analysis of resin impregnated peat samples showed that hydraulic conductivity is essentially controlled by pore hydraulic radius the strong dependence of hydraulic conductivity on hydraulic radius implies that peat soils subjected to similar degrees of decomposition and compaction have a similar hydraulic conductivity regardless of the location this explains the similarity of the depth conductivity profiles among all three terrain types copyright 2008 john wiley sons ltd

aeolian deposition of dust over hills the effect of dust grain size on the deposition pattern wind tunnel experiments were conducted to investigate the effects of topography on the grain size characteristics of aeolian dust deposits experiments were performed on three isolated hills having various size and aspect ratios the longitudinal profile of the median grain diameter was investigated for each hill the longitudinal dust deposition profile was also studied for nine grain size classes of between 10 and 104 m as were wind and dust concentration profiles in the atmosphere upwind of over and downwind of a hill the wind tunnel experiments show that the grain size characteristics of aeolian dust deposits are affected by topography most apparent is the occurrence of a zone of reduced grain size on the leeside of hills which extends from just upwind of the summit to a distance of several times the height of the hill slightly coarser than normal dust is deposited on the concave windward hill slope and in a zone downwind of the area of reduced grain size but the increase in grain size in these zones remains very small although the normalized dust deposition profile for a hill does not vary substantially as a function of grain size systematic trends are observed the most important tendencies are 1 a progressive extension in the downwind direction of a zone of decreased dust deposition on the leeside of a hill the coarser the grains the further downwind the zone of reduced deposition extends 2 a progressive increase in dust deposition immediately upwind of a hill the finer the grains the higher the deposition value upwind of a hill becomes both tendencies are explained by the difference in inertia of the grains which is controlled by grain size copyright 2005 john wiley sons ltd

aggregate scale spatial heterogeneity in reductive transformation of ferrihydrite resulting from coupled biogeochemical and physical processes abstract iron hydr oxides are ubiquitous in soils and sediments and play a dominant role in the geochemistry of surface and subsurface environments their fate depends on local environmental conditions which in structured soils may vary significantly over short distances due to mass transfer limitations on solute delivery and metabolite removal in the present study artificial soil aggregates were used to investigate the coupling of physical and biogeochemical processes affecting the spatial distribution of iron fe phases resulting from reductive transformation of ferrihydrite spherical aggregates made of ferrihydrite coated sand were inoculated with the dissimilatory fe reducing bacterium shewanella putrefaciens strain cn 32 and placed into a flow reactor the reaction cell simulates a diffusion dominated soil aggregate surrounded by an advective flow domain the spatial and temporal evolution of secondary mineralization products resulting from dissimilatory fe reduction of ferrihydrite were followed within the aggregates in response to a range of flow rates and lactate concentrations strong radial variations in the distribution of secondary phases were observed owing to diffusively controlled delivery of lactate and efflux of fe ii and bicarbonate in the aggregate cortex only limited formation of secondary fe phases were observed over 30 d of reaction despite high rates of ferrihydrite reduction under all flow conditions tested ferrihydrite transformation was limited in the cortex 70 85 mol fe remained as ferrihydrite because metabolites such as fe ii and bicarbonate were efficiently removed in outflow solutes in contrast within the inner fractions of the aggregate limited mass transfer results in metabolite fe ii and bicarbonate build up and the consummate transformation of ferrihydrite only 15 40 mol fe remained as ferrihydrite after 30 d of reaction goethite lepidocrocite and minor amounts of magnetite formed in the aggregate mid section and interior at low lactate concentration 0 3 mm after 30 d of reaction under high lactate 3 mm concentration magnetite was observed only as a transitory phase and rather goethite lepidocrocite and siderite were the dominant secondary mineralization products our results illustrate the importance of slow diffusive transport of both electron donor and metabolites concentrations and concomitant biogeochemical reactions within soils and sediments giving rise to heterogeneous products over small spatial m scale

anisotropy and depth related heterogeneity of hydraulic conductivity in a bog peat i laboratory measurements anisotropy and heterogeneity of hydraulic conductivity k are suspected of greatly affecting rates and patterns of ground water seepage in peats a new laboratory method termed here the modified cube method was used to measure horizontal and vertical hydraulic conductivity kh and kv of 400 samples of bog peat the new method avoids many of the problems associated with existing field and laboratory methods and is shown to give relatively precise measurements of k in the majority of samples tested kh was much greater than kv indicating that the bog peat was strongly anisotropic log10kh log10kv and log10 kh kv were found to vary significantly with depth although none of the relationships was simple we comment on the scale dependency of our measurements

high resolution measured and modelled three dimensional airflow over a coastal bowl blowout abstract blowouts are common landforms found within coastal dunes their dynamics are primarily driven by aeolian transport caused by surface wind stress though patterns of deflation and deposition within blowouts are poorly understood as near surface wind flow is complex three dimensional wind flows around blowouts have yet to be properly quantified especially within zones of separation re attachment and acceleration this has been largely due to inadequate measurement of airflow and a lack of suitable airflow models with this in mind we present results from a study that has quantified alongshore and oblique onshore wind flow dynamics over a bowl blowout on the belmullet peninsula ireland using ultrasonic three dimensional anemometry measuring at 50 hz and three dimensional computational fluid dynamic cfd modelling we measure and model for the first time in 3d a detailed picture of the heterogeneity of wind flow over this type of terrain during alongshore wind conditions wind speeds within the deflation basin were retarded by 50 compared to the foredune zone and flow separation restricted to a small zone in lee of the windward rim wind was directed into the deflation basin through a gap in a western erosional wall termed the blowout throat in oblique onshore wind airflow orientated with the blowout throat remained unchanged in direction and slowed by only 30 compared to wind speed on the foredune in lee of the erosional wall adjacent to the blowout throat small zones of flow separation occurred close to the erosional wall in both cases the highest variation in wind speed and direction occurred in zones of separation and attachment whilst flow increased in steadiness with height over the erosional walls the results illustrate that wind is manipulated according to localised topography within the bowl blowout itself resulting zones of potential sediment transport erosion and deposition are spatially complex and alter with wind direction the presence of a blowout throat has a significant influence on airflow patterns within a deflation basin modelled cfd and measured anemometer data demonstrated excellent comparisons for wind direction and speed allowing much greater spatial measurement resolution than physical instrumentation simulated turbulence did not correlate well with measured data highlighting the requirement for high frequency three dimensional anemometry in areas of complex flow

a field scale natural gradient solute transport experiment in peat at a newfoundland blanket bog a field scale natural gradient solute transport experiment conducted at a newfoundland blanket bog resulted in an asymmetrical plume owing to solute retardation in the dual porosity matrix an order of magnitude decrease in hydraulic conductivity 10 20 m downslope of the spill caused the transport rate to decrease and lateral dispersion to increase most transport occurred near the watertable and the transport rate increased as the watertable rose hydraulic conductivity between a depth of 0 and 0 2 m was 1 6 10 2 m s 1 whereas at a depth of 0 5 m it was 5 6 orders of magnitude lower owing to greater compaction and humification of the peat with depth at a depth of 0 4 0 45 m diffusion may have become the dominant transport mechanism in spite of the retardation process the solute front s rate of movement was relatively high about 2 3 m day 1 owing to a combination of the high watertable during the study and a relatively steep hydraulic gradient of 0 055 rain caused dilution and mixing of solute near the watertable evaporation did not have an appreciable effect on solute concentration which is attributable to the high transport rate

wind tunnel experiments of aeolian dust deposition along ranges of hills wind tunnel experiments of aeolian dust deposition on topographic scale models of ranges of hills were conducted different hill sizes and hill spacings were used and comparisons with the deposition patterns over single isolated hills were made dust profiles over ranges of hills differ from the profiles over identical but isolated hills on isolated hills the sedimentation maximum on the windward hillslope is always single and located on the concave part of the slope in the case of ranges of hills the maximum is either single or double with the second peak on the convex part of the windward slope in the latter case the local sedimentation maximum on the convex leeslope which is rather unimportant on isolated hills is much more developed in multiple hill topography also dust deposition on the leeslopes is significantly higher in multiple hill topography than on isolated hills dust patterns on ranges of hills may be affected by the dust shadow created by the most upstream located hill if hills succeed each other quickly they are located within the shadow zone and are protected from important dust deposition the plume of high air dust concentration that is created by a hill largely determines the dust pattern on the next hill as a result of the supply of dust from above by the descending plume areas that are normally devoid of dust now experience significant dust deposition

shallow horizontal groundwater flow in peatlands is reduced by bacteriogenic gas production 1 we tested the extent to which horizontal hydraulic conductivity kh below the water table in near surface peats is affected by the accumulation of biogenic gas bubbles we found 1 immediately after water table rise the peat is not saturated levels of initial undersaturation were between 1 and 9 percent 2 the production of biogenic gas bubbles below the water table causes large reductions typically more than a factor of two in kh

quantifying wind erosion at landscape scale in a temperate grassland nonignorable influence of topography abstract revised wind erosion equation rweq is widely applied to determining wind erosion and achieves reliable results however the spatial variability of wind erosivity and wind erosion has not been sufficiently investigated in previous studies in this paper rweq was used to determine wind erosion and its spatial variation at the landscape scale in the xilingele grassland which is a typical temperate grassland in north china suffering from increasing wind erosion problems based on field investigation and laboratory measurement land surface parameter data were obtained computational fluid dynamics cfd wind modelling was integrated to acquire the spatial variation of wind data which considers the influence of topography and land use these data were used to determine the five factors of rweq and wind erosion modulus results showed that the mean wind erosion modulus was 5 33 t ha 1 yr 1 and 97 16 of the area had light or no wind erosion which was mostly distributed in the low plains and the leeward areas however there were hotspots of wind erosion which were mainly distributed in the windward slopes and the summit areas there were no significant differences among the wind erosion moduli of different land uses but land use affected the influence of topography on wind erosion the maximum modulus varied greatly from 0 to 259 41 t ha 1 yr 1 for different land uses and the most severe wind erosion occurred in moderately grazed grassland mg followed by heavily grazed grassland hg arable land al lightly grazed grassland lg and ungrazed grassland ug statistical tests indicated that topography had a significant influence on wind erosion which was not detected in previous studies due to the lack of high resolution topography and wind data the combination of rweq and cfd wind modelling suggests that future wind erosion studies should further consider the important influence of topography to achieve sustainable development in temperate grassland rational grazing is critical and special attention should be paid to windward slopes and high elevation areas

fluid migration in a cratonic setting the fluid histories of two fault zones in the eastern midcontinent abstract a combined field petrographic fluid inclusion and stable isotope study was undertaken in two fault zones in the eastern midcontinent of the north american craton in order to determine their fluid histories because both the kentucky river fault zone in central kentucky and the bowling green fault zone in northwest ohio were active intermittently throughout much of the paleozoic it was thought that one or both may record the passage of the late paleozoic brine migration that affected large portions of the eastern midcontinent three fluid events were recognized in calcite veins of the kentucky river fault zone each tapped the same dominantly meteoric low salinity fluid reservoir but at different times as the fault zone was cooling t h 110 to 75 c at relatively shallow depths t h 115 to 60 c at a shallow depth

wind flow and sedimentation in artificial vegetation field and wind tunnel experiments abstract the flow dynamics within and immediately above an artificial plastic vegetation canopy are measured in the field and wind tunnel artificial plants created from wooden dowels and cable zip ties were arranged in a variety of arrays on pegboards where plant cover or lateral cover could be accurately controlled plant covers examined ranged from 12 to 60 wind velocity profiles and the bedforms incipient dunes that developed within and beyond the vegetation in a few hours were measured the results indicate that flow deceleration and drag increases within the canopy as plant density increases in general there is a marked reduction and inflection in velocity at the canopy top and a second major inflection in the velocity profiles occurs immediately below the base of the four arrays equal or 23 density tall vegetation allows flow to sweep under the canopy and local high speed maxima flows may develop leading to minimal sedimentation in those canopies but deposition downwind beyond the canopies short vegetation where the leaves fill the canopy close to the ground display significantly greater drag and rapid rates of sand deposition flow velocities above the canopy increase as plant cover or density increases due to flow compression and acceleration bedform development is strongly correlated with plant cover density or lateral cover and short plants such that shorter length higher bedforms develop in higher density and or shorter plants the relationship between plant cover density or lateral cover and within canopy velocity is non linear and a new tentative flow regime is proposed canopy flow which may occur between wake interference flow and skimming flow this study further confirms that plant density plays a defining role in determining bedform and dune morphology the results also apply to flow in semi arid grasslands