the origin and mechanisms of salinization of the lower jordan river the chemical and isotopic 87 sr 86 sr 11 b 34 ssulfate 18 owater 15 nnitrate compositions of water from the lower jordan river and its major tributaries between the sea of galilee and the dead sea were determined in order to reveal the origin of the salinity of the jordan river we identified three separate hydrological zones along the flow of the river 1 a northern section 20 km downstream of its source where the base flow composed of diverted saline and wastewaters is modified due to discharge of shallow sulfate rich groundwater characterized by low 87 sr 86 sr 0 7072 34 ssulfate 2 high 11 b 36 15 nnitrate 15 and high 18 owater 2 to 3 values the shallow groundwater is derived from agricultural drainage water mixed with natural saline groundwater and discharges to both the jordan and yarmouk rivers the contribution of the groundwater component in the jordan river flow deduced from mixing relationships of solutes and strontium isotopes varies from 20 to 50 of the total flow 2 a central zone 20 50 km downstream from its source where salt variations are minimal and the rise of 87 sr 86 sr and so4 cl ratios reflects predominance of eastern surface water flows 3 a southern section 50 100 km downstream of its source where the total dissolved solids of the jordan river increase particularly during the spring 70 80 km and summer 80 100 km to values as high as 11 1 g l variations in the chemical and isotopic compositions of river water along the southern section suggest that the zarqa river 87 sr 86 sr0 70865 11 b25 has a negligible affect on the jordan river instead the river quality is influenced primarily by groundwater discharge composed of sulfate rich saline groundwater cl 31 180 mm so4 cl0 2 0 5 br cl2 310 3 87 sr 86 sr0 70805 11 b30 15 nnitrate 17 34 ssulfate4 10 and ca chloride rift valley brines cl 846 1500 mm br cl 6 8 10 3 87 sr 86 sr0 7080 11 b40 34 ssulfate4 10 mixing calculations indicate that the groundwater discharged to the river is composed of varying proportions of brines and sulfate rich saline groundwater solute mass balance calculations point to a 10 contribution of saline groundwater cl282 to 564 mm to the river a high nitrate level up to 2 5 mm in the groundwater suggests that drainage of wastewater derived irrigation water is an important source for the groundwater this irrigation water appears to leach pleistocene sediments of the jordan valley resulting in elevated sulfate contents and altered strontium and boron isotopic compo sitions of the groundwater that in turn impacts the water quality of the lower jordan river copyright 2004 elsevier ltd

spatial organization in the step pool structure of a steep mountain stream vogelbach switzerland 1 spatial organization in the step pool structure of a 1 58 km long section of the vogelbach a steep mountain stream average channel bed slope 0 17 m m in the alpthal basin switzerland is analyzed to evaluate the extent of randomness in the occurrence of steps and to isolate the potential hydraulic and topographic controls on step placement statistics of the observed step sequence are compared with those of random sequences generated by permutation from the observed step height distribution hydraulic and topographic controls on step placement are analyzed from step length and steepness distributions and relations between mean step properties and step height and channel gradient for both observed and random sequences results show that 1 observed step length distributions are statistically significantly different from randomly generated sequences 2 step steepness is significantly different in observed data because of a positive correlation between mean step length and height and it remains fairly constant for all step sizes 3 spatial organization in steps does not extend far beyond the nearest step and 4 the influence of channel gradient on step properties is insignificant and highly variable indicating that hydraulic rather than topographic controls are dominant for step placement in this stream although the vogelbach is a steep stream on the boundary between a cascading and step pool morphology where we would expect randomness to dominate spatial organization was nevertheless detected in many important aspects of the step pool geometry

characteristics of channel steps and reach morphology in headwater streams southeast alaska abstract the effect of timber harvesting and mass movement on channel steps and reach morphology was examined in 16 headwater streams of se alaska channel steps formed by woody debris and boulders are significant channel units in headwater streams numbers intervals and heights of steps did not differ among management and disturbance regimes a negative exponential relationship between channel gradient and mean length of step intervals was observed in the fluvial reaches

distribution of bedrock and alluvial channels in forested mountain drainage basins mountain river networks often consist of both bedrock and alluvial channels1 5 the spatial distribution of which controls several fundamental geomorphological and ecological processes6 7 the nature of river channels can influence the rates of river incision and landscape evolution1 2 as well as the stream habitat characteristics affecting species abundance and aquatic ecosystem structure8 11 studies of the factors controlling the distribution of bedrock and alluvial channels have hitherto been limited to anthropogenic badlands12 here we investigate the distribution of channel types in forested mountain drainage basins and show that the occurrence of bedrock and alluvial channels can be described by a threshold model relating local sediment transport capacity to sediment supply in addition we find that valley spanning log jams create alluvial channels hospitable to aquatic life in what would otherwise be bedrock reaches the formation of such jams depends critically on the stabilizing presence of logs derived from the largest trees in the riverside forests suggesting that management strategies that allow harvesting of such trees can have a devastating influence on alluvial habitats in mountain drainage basins

sources and dynamics of sulfur in weathered till western glaciated plains of north america abstract at three sites in the western glaciated plains warman and luck lake in saskatchewan canada and bow river in alberta canada thick 30 m till sequences contain 0 3 0 8 s by dry weight in the unweathered zone depths 2 5 15 m 65 90 of this s is cr reducible pyrite the remainder largely organic s is enriched in 34 s by 6 12 relative to the pyrite at the bow river site both pyrite and organic s are enriched in 34 s by up to 9 relative to samples of the same fractions from the warman and luck lake sites this may reflect a higher content of non marine parent material in southern alberta till at the warman site the sources and dynamics of sulfur in the weathered zone were investigated during weathering of the floral formation till sulfate was produced by the oxidation of pyrite and to a lesser extent by mineralization of organic s based on the distribution of so 4 in the landscape at warman three settings have been distinguished upland leached channel depression and saline ring the upland setting has a 9 m thick weathered zone which contains abundant so 4 mainly as secondary gypsum sulfate has been leached downward from the upper 2 m creating a peak accumulation of gypsum at 3 m sulfate has been leached from the entire 2 5 m deep weathered zone in the channel depression setting by seasonal infiltration of snow melt and lateral flow in contrast at 3 4 m depth in the weathered zone at the edge of the channel so 4 has accumulated as a saline ring here the gypsum s is up to 1 of the soil dry weight in the weathered zone of upland and saline ring settings the 34 s values of the so 4 in sediment extracts water soluble and groundwater 13 1 to 9 0 are very similar to those of the total s 12 0 to 11 4 and pyrite s 16 0 to 10 1 of unweathered floral formation till this indicates an in situ weathering source of the so 4 in contrast the 34 s of so 4 in sediment extracts and groundwater from the leached weathered zone of the upland and channel depression settings 7 7 to 4 5 is enriched in 34 s relative to unweathered floral formation till s this enrichment may be attributed to either 1 isotope fractionation during oxidation of pyrite and or 2 mineralization of residual organic s which is 34 s enriched after pyrite was weathered away

glacially induced organization of channel reach morphology in mountain streams 1 we examine the spatial distribution of channel reach morphologies in formerly glaciated mountain drainage basins of coastal british columbia canada using field and geographic information systems derived data we show that the local channel slope and the degree of colluvial alluvial coupling imposed by the glacial valley morphology dictate the spatial organization of channel types in particular the complex glacially induced channel long profile produces characteristic sequences of channel reaches that depart from the downstream succession colluvial boulder cascade step pool rapids riffle pool distinctive of simple unglaciated mountain streams typically the presence of one hanging valley in the river long profile produces and separates two full successions of channel types a headmost one characterized by an ephemeral seasonal hydrologic regime and a downstream one where water runoff is perennial we document that channel types are well separated in plots of slope versus shear stress area versus shear stress and slope versus relative roughness in agreement with these outcomes multivariate discriminant analyses coupled with principal component analysis of 98 study reaches yield a highly successful channel type classification when slope shear stress and relative roughness are considered success rates depending on whether or not boulder cascade reaches are pooled together with step pools are 88 and 75 respectively previous work in unglaciated settings has suggested that mountain channels have distinct bed morphology states that vary primarily with slope our study reveals that even in formerly glaciated valleys where slope is largely inherited from glacial times these distinct bed states exist and vary mostly with slope adding considerable strength to this empirical knowledge

geochemical evolution of groundwater in the carbonate aquifers of sierra de segura betic cordillera southern spain summary sierra de segura betic cordillera with a total area of over 3000 km 2 is the source of the two principal rivers in southern spain the guadalquivir and the segura due to the orographic effect of these mountains precipitations are considerably more abundant than in nearby lowland areas where the climate is semi arid sierra de segura is constituted of mesozoic and cenozoic sedimentary rocks among which there are thick limestone dolomitic formations which have given rise to extensive outcrops of permeable materials in geomorphological terms there is a large plateau intensively karstified that constitutes the main recharge area discharge takes place via a large number of springs of which the 50 most important add up to a mean spring flow of about 13 500 l s the active geochemical processes in aquifers of sierra de segura with their corresponding time sequence are dissolution of co 2 dissolution of calcite incongruent dissolution of dolomite dedolomitization exsolution of co 2 and precipitation of calcite more evolved water has higher temperature magnesium content and mg ca ratio therefore these parameters can be utilised as indicators of the degree of hydrochemical evolution in addition a good correlation between water temperature and magnesium concentration or mg ca ratio indicates that an increase in temperature accelerates the kinetics of the dissolution of dolomite finally the distribution of the temperatures in the vadose zone determined by atmospheric thermal gradient implies an apparent stratification of the predominant hydrochemical processes and of the groundwater physical and chemical characteristics

preservation of primary stable isotope signatures of peat forming plants during early decomposition observation along an altitudinal transect abstract the preservation of the primary stable isotope compositions of peat forming plants in peat was tested along a short

the frictional resistance characteristics of a bedrock influenced river channel much of the published literature relating to reach scale total ow resistance concentrates on alluvial rivers and little mention is made of the more extreme resistance found in bedrock in uenced river systems this paper presents the results of a detailed investigation of total ow resistance variation for ve channel types on the sabie river south africa cohesive mixed anastomosed uncohesive mixed anastomosed mixed pool rapid alluvial braided and alluvial single thread over a range of discharges manning s n and darcy weisbach f resistance coef cients are calculated using barnes methodology h h barnes us geological survey water supply paper 1849 1967 these data are analysed at the scales of channel type and morphologic unit and the resultant resistance values are compared with the literature generally the low ow friction values estimated for the bedrock in uenced channel types are higher than any reported flow resistance quanti cation of the alluvial channel type study sites on the sabie river produced values slightly higher than earlier studies of similar morphologies in situations where signi cant areas of irregular bedrock are exposed cohesive mixed anastomosed and mixed pool rapid channel types the high ow resistance coef cients at low discharges probably re ect energy dissipation due to hydraulic jumps and internal distortions however these values fall as discharge increases to values comparable to those recorded for step pool rivers it is suggested that the slightly elevated resistance coef cients recorded in the alluvial channel types are the result of the vegetation roughness component operating when the macro channel bar features are inundated copyright 2004 john wiley sons ltd

sulfuric acid as an agent of carbonate weathering constrained by δ13cdic examples from southwest china abstract rock weathering by carbonic acid is thought to play an important role in the global carbon cycle because it can geologically sequestrate atmospheric co 2 current model of carbon cycle evolution usually assumes that carbonic acid is the major weathering agent and that other acids are not important here we use carbon isotopic evidence and water chemistry of springs and rivers from the beipanjiang river basin guizhou province southwest china to demonstrate that sulfuric acid is also an important agent of rock weathering the 13 c of dissolved inorganic carbon dic in the water samples ranges from 13 1 to 2 4 and correlates negatively to hco 3 ca 2 mg 2 ratios and positively to so 4 2 ca 2 mg 2 ratios these relationships are interpreted as mixing diagrams between two reactions of carbonate weathering using carbonic acid and sulfuric acid as a proton donor respectively mixing proportions show that around 42 of the divalent cations in the spring water from guizhou are originated from the interaction between carbonate minerals and sulfuric acid it is shown that 40 of this sulfuric acid is derived from the atmosphere and has an anthropogenic origin the remaining 60 are derived from the oxidative weathering of sulfide minerals in sedimentary rocks our results show the positive action of sulfuric acid on the chemical weathering of carbonate particularly we show that sulfuric acid generated by coal combustion has increased by almost 20 the weathering rates of carbonate in southwest china this is a clear evidence that human activities are changing the weathering rates of rocks and demonstrates a negative feedback on the acidification of the ocean by greenhouse gases because of the involvement of sulfuric acid in weathering reactions 63 of the alkalinity exported by rivers is derived from carbonate instead of 50 when atmospheric co 2 is the only acid involved in chemical weathering of carbonate in the guizhou province the weathering of carbonate is thus at least transiently a net source of co 2 to the atmosphere when extrapolated at global scale sulfuric acid induced carbonate weathering could counterbalance a significant part of the co 2 consumed by silicate weathering this paper highlights the competition between silicate weathering by carbonic acid and carbonate weathering by sulfuric acid for the regulation of the atmospheric co 2 level

efflorescence as a source of hydrated sulfate minerals in valley settings on mars abstract a distinctive sulfur cycle dominates many geological processes on mars and hydrated sulfate minerals are found in numerous topographic settings with widespread occurrences on the martian surface however many of the key processes controlling the hydrological transport of sulfur including sulfur sources climate and the depositional history that led to precipitation of these minerals remain unclear in this paper we use a model for the formation of sulfate efflorescent salts mg ca na sulfates in the rio puerco watershed of new mexico a terrestrial analog site from the semiarid southwest u s to assess the origin and environmental conditions that may have controlled deposition of hydrated sulfates in valles marineris on mars our terrestrial geochemical results s 34 of 36 0 to 11 1 show that an ephemeral arid hydrological cycle that mobilizes sulfur present in the bedrock as sulfides sulfate minerals and dry wet atmospheric deposition can lead to widespread surface accumulations of hydrated sulfate efflorescences repeating cycles of salt dissolution and reprecipitation appear to be major processes that migrate sulfate efflorescences to sites of surface deposition and ultimately increase the aqueous so 4 2 flux along the watershed average 41 273 metric tons yr we suggest that similar shallow processes may explain the occurrence of hydrated sulfates detected on the scarps and valley floors of valles marineris on mars our estimates of salt mass and distribution are in accord with studies that suggest a rather short lived process of sulfate formation minimum rough estimate 100 to 1000 years and restriction by prevailing arid conditions on mars

catchment scale coupling between pyrite oxidation and calcite weathering abstract integrated time series of major element concentrations and flow rates from a small watershed white rock creek dallas tx are used to examine the general hydrogeochemical controls on calcite weathering and the specific role of trace pyrite oxidation in base cation export white rock creek is a perennial gaining stream occupying a catchment underlain by expanding clay soils and an uppermost fractured bedrock weathering zone which acts as a surface aquifer below which there is low permeability austin chalk seasonal variations in cation export are controlled predominantly by temperature effects on carbonate solubility dilution by variable amounts of rainfall and possibly organic activity creek water pco2 is 7 to 10 times atmospheric pco2 throughout the year and does not correlate with surface temperature non pyrite sulfate inputs are well constrained moreover integrated runoff and solute export from the basin are similar to global mean values pyrite although present only as a trace component accounts for a disproportionate amount of bedrock weathering 40 when oxidized to produce sulfuric acid irreversible dissolution of pyrite is insensitive to seasonal changes in temperature runoff and organic activity and probably reflects the slow movement of a weathering front at depth through the aquifer

controls on the δ34s and δ18o of dissolved sulfate in the quaternary aquifers of the north china plain summary the north china plain ncp is a typical cenozoic sedimentary basin and one of the largest alluvial plains in eastern asia it consists of piedmont alluvial plain central alluvial lacustrine plain and littoral alluvial plain from west to east where quaternary aquifer systems developed in different depths groundwater from these aquifers is the most important water resource and supports a population of 200 million in the ncp currently the quaternary groundwater is depleting fast due to both human and natural factors characterizing biogeochemical processes in groundwater is central to understanding groundwater chemistry to identify the sources of dissolved sulfate so 4 2 and address subsequent biogeochemical processes in groundwater we conducted a study of spatial distributions of 34sso4 and 18oso4 in the quaternary aquifers in the northern part of the ncp the so 4 2 34sso4 and 18oso4 along the west east groundwater flowpaths in the three alluvial plains are analyzed and examined the quaternary groundwater 20 c has a so 4 2 of 37 25 177 41 mg l with so 4 2 cl ratios ranging from 0 12 to 2 79 the 34sso4 and 18oso4 range from 4 9 to 30 9 and from 4 7 to 14 0 respectively supported by other geochemical and isotopic parameters such as total dissolved solids tds concentrations d and 18o of groundwater d and 18oh2o and 14c contents in groundwater our study concludes that 1 the shallow groundwater in the piedmont area is characterized by higher so 4 2 concentration of 153 22 mg l with 34sso4 of 10 0 14 5 and 18oso4 of 4 7 9 0 whereas the groundwater in the piedmont area is characterized by lower so 4 2 concentration of 37 25 mg l with 34sso4 of 4 9 7 3 and 18oso4 of 5 8 7 5 therefore the so 4 2 in the shallow groundwater is dominated by weathered sulfate minerals from the taihang mountains and sulfate derived from oxidation of sulfides in infiltration paths whereas the so 4 2 in the deep groundwater is dominated by atmospheric sulfate from precipitation and sulfate derived from decomposition of organic matter during its recharge processes 2 dissimilatory microbial sulfate reduction dmsr occurred in the deep confined aquifers in both central and littoral plains where 34sso4 and 18oso4 increase along the groundwater flowpaths and present specific patterns for each aquifer which imply variable contributions from dmsr processes 3 the deep confined aquifer in the littoral plain has a lower dmsr rate than the other aquifers probably due to the effect of its lower permeability on physical exclusion of bacteria from the aquifer matrix this study can provide a biogeochemical background for assessing groundwater evolution and its quality in the ncp

field measurements of three dimensional hydraulics in a step pool channel we investigated the effects of morphologic position and discharge on flow structure in a steep 0 10m m mountain channel by collecting three dimensional measurements of time averaged and turbulent velocity components with a sontek flowtracker handheld adv acoustic doppler velocimeter on a 30 m reach of a step pool channel in the colorado rockies velocity profiles were measured at morphologic positions characteristic of steep channels above steps step lips base of steps pools cascades runs and at five different discharges a marked three dimensionality of flow structure was documented in east st louis creek velocities in the streamwise component were the largest contributors to overall velocity vector magnitudes cross stream and vertical components contributed averages of 20 and 15 respectively to overall vector magnitudes turbulence intensities were especially multi dimensional however with large contributions to turbulent kinetic energy from the vertical component of velocity analysis of variance indicated that discharge and morphologic position significantly affected mean streamwise velocities with substantially higher velocities upstream from steps than in pools discharge and morphology effects on cross stream and vertical velocity components however were not significant discharge and morphologic position also significantly affected turbulence intensities for all flow components with the greatest turbulence intensities occurring in pools and at high discharges these results illustrate the strong discharge dependence of hydraulics in step pool channels where relative submergence of bedforms changes rapidly with discharge and the substantial spatial variation in hydraulics created by step pool sequences

natural and anthropogenic so4 sources in the arno river catchment northern tuscany italy a chemical and isotopic reconnaissance abstract the 34 s isotope signature of aqueous so 4 2 in the main river arno and principal tributaries was investigated along with major ion chemistry in order to check the pollution effects in the water network of a heavily industrialized and densely urbanized catchment extending in tuscany over an area of 8228 km 2 from the apennine ridge to the tyrrhenian sea major towns include florence and pisa analyses are presented for 29 water samples from the arno river and 36 water samples from the tributaries all collected in 1996 1997 during low flow hydrologic conditions samples from the arno are distributed from source to mouth and those from tributaries upstream from the confluence points the arno river solutes consist mainly of ca 2 and hco 3 but the proportions of na cl and so 4 2 increase downstream in keeping with the basically anthropogenic origin of the latter the 34 s so 4 2 signature also increases downstream with the most depleted values in the source zone the seawater ingression into the river is documented by distinctly higher chemical and isotopic parameters at about 13 km from the mouth in general the tributaries behave similarly to the arno for both their chemical and isotopic compositions with increasing 34 s na cl and so 4 2 downstream the 34 s of so 4 2 in natural inputs is estimated to range approximately between 15 and 4 from oxidation of pyrite disseminated in country rocks and between 15 and 23 from dissolution of evaporites whereas the 34 s of anthropogenic so 4 2 should be variable within the range 1 8

stabilizing self organized structures in gravel bed stream channels field and experimental observations stable reticulate structures which we call stone cells have been observed in cobble gravel channel beds with low bed material transport rates experiments show that such structures develop simultaneously with the armor layer during an extended period when flows do not exceed the shields threshold by more than 2 times so that bed material transport is low they are constructed by particles moving from less stable positions into more stable configurations against each other intermediate developments include clusters and stone lines they reduce sediment transport by orders of magnitude and are evidently a major stability promoting mechanism in gravel channels the timescale for their development suggests that the boundaries of many gravel bed channels are not in equilibrium with recent competent flows but reflect the history of recent dominant flows

geological and land use control on δ34s and δ18o of river dissolved sulfate the moselle river basin france abstract the upper part of the moselle river basin northeastern france shows contrasting lithology and topography granitic formations upstream in the vosges mountains and carbonate platform downstream on the lorraine plateau we measured concentration and isotopic composition of dissolved so 4 in the moselle river and its main tributaries in order to identify the sources of sulfate rainwater lichens s fertilizers and natural gypsum were also analyzed as potential sulfate sources along the moselle river dissolved so 4 concentrations and s o isotopes display relationships which suggest two major sources of sulfates 1 a low concentration and low delta values 34 s of 6 9 and 18 o of 6 9 component upstream and 2 a high concentration and high delta values 34 s of up to 17 and 18 o of up to 13 these are likely 1 atmospheric s input with some retention time in forest soils as carbon bonded sulfur and 2 sulfates from the dissolution of evaporites from the muschelkalk and keuper formations of the lorraine plateau the madon tributary drains a basin largely used for agriculture 35 of the land surface and formed by carbonate and evaporite rocks deviation from the general 34 s 18 o trend for dissolved so 4 was found to be seasonal and related to land use and agricultural practices and are interpreted as a significant input of sulfates from fertilizers used in the area isotope mixing models indicate that between 1 1 10 7 and 1 9 10 7 mol of anthropogenic so 4 are annually exported through the madon river these values compared well with the expected annual fertilizer spreading rates in the area and demonstrate the powerful source tracing done by using s isotopes in dissolved sulfates this implies that combining isotopic fingerprinting approach to knowledge of the catchment i e land use agricultural practices river flow would provide key information for decision makers in the context of river basin management

the effect of acid rain and altitude on concentration δ34s and δ18o of sulfate in the water from sudety mountains poland abstract the analyses of sulfate content 34s and 18o of dissolved sulfate and 18o of water were carried out in a 14 km2 crystalline massif located in the sudety mountains sw poland to 1 assess the amount of the sulfate delivered to the surface and groundwater systems by modern atmospheric precipitation 2 determine the effect of altitude on these parameters and 3 investigate their seasonal variations in april and november of 2002 august 2003 and march and september of 2005 samples of water were collected from springs and streams of the massif during these seasons sulfate contents and 18o so42 values varied from 5 80 to 18 00 mg l and from 3 96 to 8 23 respectively showing distinctively higher values of 18o so42 in wet seasons the 34s so42 values had a relatively narrow range from 4 09 to 5 28 and were similar to those reported for organic matter in soil and the canopy throughfall in the sudety mountains sulfate content 34s so42 18o so42 and 18o h2o values revealed a remarkable dependence on the altitude the calculated altitude effects for five season averages of these parameters were 1 00 mg l 100 m 0 18 100 m 0 27 100 m and 0 17 100 m respectively this dependence on the altitude resulted mainly from the mixing of sulfates of different origins such as anthropogenic sulfate sulfate produced in the soil within the weathered zone of the massif and that one from the tree canopy the oxygen isotope mass balance indicates that in the study area about one third of the sulfate delivered to the surface and groundwater by modern precipitation comes from anthropogenic pollution further interaction of meteoric water within the weathered rocks causes a continuous decrease of 18o so42 values resulting from biological transformation of the sulfate due to plant vegetation and decomposition of organic matter

the sources and budget for dissolved sulfate in a fractured carbonate aquifer southern sacramento mountains new mexico usa abstract climate change in the sw usa is likely to involve drier conditions and higher surface temperatures in order to better understand the evolution of water chemistry and the sources of aqueous so4 in these semi arid settings chemical and s isotope compositions were determined of springs groundwater and bedrock associated with a permian fractured carbonate aquifer located in the southern sacramento mountains new mexico usa the results suggest that the evolution of water chemistry in the semi arid carbonate aquifer is mainly controlled by dedolomitization of bedrock which was magnified by increasing temperature and increasing dissolution of gypsum anhydrite along the groundwater flow path the 34s of dissolved so4 in spring and groundwater samples varied from 9 0 to 12 8 reflecting the mixing of so4 from the dissolution of permian gypsum anhydrite 12 3 to 13 4 and oxidation of sulfide minerals 24 5 to 4 2 according to s isotope mass balance constraints the contribution of sulfide derived so4 was considerable in the high mountain recharge areas accounting for up to 10 of the total so4 load however sulfide weathering decreased in importance in the lower reaches of the watershed a smaller so4 input of 2 4 was contributed by atmospheric wet deposition this study implies that the 34s variation of so4 in semi arid environments can be complex but that s isotopes can be used to distinguish among the different sources of weathering here it was found that h2so4 dissolution due to sulfide oxidation contributes up to 5 of the total carbonate weathering budget while most of the so4 is released from bedrock sources during dedolomitization

the bed morphology of upland single thread channels in semi arid environments evidence of repeating bedforms and their wider implications for gravel bed rivers single thread gravel bed streams of moderate slope in the northern negev are characterized by three channel units bars exhibit steeper than average slopes and poorly sorted mixtures of small medium cobbles and coarse very coarse pebbles flats are associated with more gentle slopes and well sorted medium fine pebbles and granules and transitional units have intermediate slopes and grain size in general all three units are planar span the full channel width and have well defined boundaries bars and flats are more common than the transitional units and alternate downstream for distances of several hundred metres forming sequences that are reminiscent of the riffle pool structure commonly observed in humid temperate gravel bed rivers a notable contrast is the absence of significant bed relief bars lack crests and flats lack depressions the relative lack of bed relief in bar flat sequences is attributed to the high rate of sediment supply from the sparsely vegetated hillslopes which promotes the infilling of depressions and to the erosion of crests under conditions of intense transport this reduction of bed relief lowers channel roughness which in turn increases flow velocity and therefore the ability of the channel to transmit the large sediment loads it receives although our analyses pertain to a semi arid river system the results have wider implications for understanding the adjustment of channel bedform to high sediment loads in other fluvial environments copyright 2012 john wiley sons ltd

the role of morphology on the displacement of particles in a step pool river system abstract although studies of sediment transport in steep and coarse grained channels have been more numerous in recent years the dynamics of sediment transport in step pool river systems remain poorly understood this paper investigates displacements of individual clasts through spruce creek quebec canada a classic step pool channel and the effects of the channel morphology on the path length of the clasts passive integrated transponder tags pit were used to track the displacement of 196 individual particles over a range of discharges including the bankfull stage clasts were tracked after five sequences of flood events the results showed that the distance distributions match a two parameter gamma model equal mobility transport occurs for the particle size investigated during each sequence of flood events mean travel distance of the clasts can be estimated from excess stream power and the mobility of the clasts is more than an order of magnitude less than the model reported in riffle pool channels the dominant morphological length scale of the bed also controls the path length of the clasts these results confirm some preliminary observations on sediment transport in step pool channels

flow resistance estimation in mountain rivers examination of the flow resistance of high gradient gravel and boulder bed rivers using data collected in british mountain rivers with slopes of 0 4 4 shows that there are differences in resistance variation between mountain and lowland rivers and that between site variations do not necessarily reflect at a site variations comparison of data with the familiar resistance equation relating the dracy weisbach friction factor to the logarithm of relative submergence shows that the equation tends to overestimate the resistance in uniform flow the equation also tends to underestimate the rate of change of resistance at a site as discharge varies with high gradients the influences of nonuniform channel profile sediment size distribution channel slope and sediment transport are reviewed but the data do not allow any quantification of these effects instead an empirical approach based on the available data is presented allowing the friction factor to be calculated from the relative submergence with an error of up to n25 to n35 a summary of the field data is included

channel units in small high gradient streams on vancouver island british columbia descriptions and a classification are presented of channel units in very high gradient first order mountain channels bedrock cascades boulder cascades rapids chutes riffles glides and pools had distinct mean bed gradients of 0 49 0 45 0 20 0 12 0 09 0 06 and 0 03 respectively multiple pairwise comparisons showed that these gradients are significantly different except bedrock cascades were not different from boulder cascades and glides were not different from chutes riffles or pools channel width and entrenchment do not discriminate channel units in any consistent way but characteristic substrates occur constituent substrates of bedrock and boulder cascades are nominally apparent while chutes also are bedrock bound mixtures of boulders and cobbles constitute rapids while mixtures of cobbles and gravel constitute riffles glides and pools generally are composed of boulders cobbles and gravel in various proportions log steps sometimes delimit units particularly pools but wood is not a dominant element in these channels gradients of channel units in these small first order dominantly nonalluvial channels are significantly higher than correspondingly identified units in larger channels farther down the drainage system the reason for this distinction is supposed to be related to channel scale hence potential stream power

characteristics of log and clast bed steps in step pool streams of northwestern montana usa the role of log and clast steps was studied in 53 step pool reaches in 32 streams in northwestern montana in each reach 20 consecutive steps were sampled drainage areas ranged from 0 5 to 11 5 km2 mean step spacing was found to be proportional to channel gradient width of the bankfull channel and drainage area mean step height was proportional to the width of the channel no significant difference exists between clast and log steps with regard to step spacing and step height this suggested either that 1 woody debris is mobile in even the smallest channels in the study area or 2 channel flows arrange clast steps around immobile woody debris calculations of theoretical entrainment and transport of sediment suggest that the coarse clasts forming steps are capable of being entrained at bankfull discharge in most channels the presence of immobile log steps composed of living roots in the upstream reaches an increase in the percentage of log steps with gradient and a decrease in this percentage with the width of the bankfull channel and drainage area imply that woody debris is mobile primarily in the downstream reaches calculations of flow resistance suggest that most steps serve to maximize flow resistance these results support the second hypothesis that the height and spacing of clast steps are adjusted around immobile log steps to maintain consistent step characteristics

geospatial organization of fluvial landforms in a gravel cobble river beyond the riffle pool couplet abstract morphological units mu are landforms with distinct local form process associations at 1 10 channel widths scale that may be the fundamental building blocks describing the geomorphic structure of a river past research has disproportionately focused on the two mus of pool and riffle conjecturing that they are the central linked couplet in the process form association the goal of this study was to delineate and map spatially explicit fluvial landforms in two dimensional planview within a gravel cobble bed river using two dimensional hydrodynamic delineation and then to statistically examine mu geospatial patterns for indicators of deterministic geomorphic control this procedure is not discharge dependent like mesohabitat methods but gets at the geometry of underlying landforms statistical testing confirmed that eight delineated in channel mu types comprise a complex and diverse channel morphology in which pools and riffles are not directly coupled specifically gravel cobble river channels 1 exhibit nonrandom spatial organization of their longitudinally and laterally variable landform morphology 2 consist of a variety of mu types not just pools and riffles and 3 show distinct mu collocations and avoidances with riffles linked to chutes and runs while pools are linked to slackwaters and glides planview mu delineation with two dimensional hydrodynamic modeling provides a bottom up approach to understanding and linking channel morphology with ecosystem services and geomorphic processes and is being used to guide river management and rehabilitation strategies

early diagenetic dolomitization and dedolomitization of late jurassic and earliest cretaceous platform carbonates a case study from the jura mountains nw switzerland e france early diagenetic dolomitization is a common feature in cyclic shallow water carbonates throughout the geologic record after their generation dolomites may be subject to dedolomitization re calcification of dolomites e g by contact with meteoric water during emersion these patterns of dolomitization and subsequent dedolomitization frequently play a key role in unravelling the development and history of a carbonate platform on the basis of excellent outcrops detailed logging and sampling and integrating sedimentological work high resolution sequence stratigraphic interpretations and isotope analyses o c conceptual models on early diagenetic dolomitization and dedolomitization and their underlying mechanisms were developed for the upper jurassic lower cretaceous jura platform in north western switzerland and eastern france three different types of early diagenetic dolomites and two types of dedolomites were observed each is defined by a distinct petrographic isotopic signature and a distinct spatial distribution pattern different types of dolomites are interpreted to have been formed by different mechanisms such as shallow seepage reflux evaporation on tidal flats and microbially mediated selective dolomitization of burrows depending on the type of dolomite sea water with normal marine to slightly enhanced salinities is proposed as dolomitizing fluid based on the data obtained the main volume of dolomite was precipitated by a reflux mechanism that was switched on and off by high frequency sea level changes it appears however that more than one dolomitization mechanism was active pene contemporaneously or several processes alternated in time during early diagenesis percolating meteoric waters obviously played an important role in the dedolomitization of carbonate rocks that underlie exposure surfaces cyclostratigraphic interpretation of the sedimentary succession allows for estimates on the timing of early diagenetic de dolomitization these results are an important step towards a better understanding of the link between high frequency probably orbitally forced sea level oscillations and early dolomitization under mesozoic greenhouse conditions

dimensions of standing waves at steps in mountain rivers 1 oscillations of the water surface are common features of flows around critical conditions fr 1 and of both natural and structure induced undular hydraulic jumps the paper describes experimental tests and field data on the dimensions of standing waves created by artificial drops in steep gravel bed rivers the purpose of the research is to analyze what parameters affect the phenomenon to provide semiempirical formulations for wave dimensions and to assess whether previous models for undular hydraulic jumps and antidunes are reasonably predictive the dimensionless wavelength and wave amplitude were correlated to the froude number at the sill the first wavelength appears linearly related to the froude parameter whereas the amplitude of the first wave shows a less defined behavior possibly indicating that a maximum value occurs for sill froude numbers around 1 6 1 7 the corresponding wave steepness i e wave amplitude length results between 0 15 0 16 and this range also characterizes the point at which the dimensionless trough depth below the sill achieves a local maximum probably related to hydrodynamic conditions just before wave breaking the transition between roller and undular jumps at drops is then argued to likely represent a critical stage in step pool streams and the hydraulic and morphological implications of this finding are also discussed with particular emphasis on step stability and step wavelength

hydrogeochemical characteristics of surface water and groundwater in the karst basin southwest china groundwater is a very significant water source used for irrigation and drinking purposes in the karst region and therefore understanding the hydrogeochemistry of karst water is extremely important surface water and groundwater were collected and major chemical compositions and environmental isotopes in the water were measured in order to reveal the geochemical processes affecting water quality in the gaoping karst basin southwest china dominated by ca 2 mg 2 hco 3 and so 4 2 the groundwater is typically characterized by ca mg hco 3 type in a shallow aquifer and ca mg so 4 type in a deeper aquifer dissolution of dolomite aquifer with gypsiferous rocks and dedolomitization in karst aquifers are important processes for chemical compositions of water in the study basin and produce water with increased mg 2 ca 2 and so 4 2 concentrations and also increased tds in surface water and groundwater mg 2 ca 2 molar ratios in groundwater decrease slightly due to dedolomitization while the mixing of discharge of groundwater with high mg 2 ca 2 ratios may be responsible for mg 2 ca 2 ratios obviously increasing in surface water and mg 2 ca 2 ratios in both surface water and groundwater finally tending to a constant in combination with environmental isotopic analyses the major mechanism responsible for the water chemistry and its geochemical evolution in the study basin can be revealed as being mainly from the water rock interaction in karst aquifers the agricultural irrigation and its infiltration the mixing of surface water and groundwater and the water movement along faults and joints in the karst basin

controls on high sulfate concentrations in the upper floridan aquifer in southwest florida chemical profiles of groundwater in the upper floridan aquifer in southwest florida vary between an inland and a coastal site at the inland site sulfate concentrations increase with depth and chloride concentrations remain low at the coastal site sulfate concentrations are high and constant but chloride concentrations increase with depth the sulfate source at the inland site is gypsum dissolution whereas at the coastal site the sulfate source is predominantly gypsum dissolution overprinted by saltwater mixing mass transfer modeling in conjunction with isotopic data was used to evaluate hypothetical flow paths within the aquifer dedolomitization reactions gypsum and dolomite dissolution with calcite precipitation dominate along flow paths where sulfate concentrations increase the distribution of gypsum in the aquifer indicates that a deeply circulating flow path controls the chemical evolution of groundwater between the two sites fresh groundwater moves into deep zones in the aquifer where gypsum is found farther along the flow path in the discharge area this groundwater moves upward to shallower depths prior to the saltwater mixing zone saltwater mixing becomes more pronounced with both proximity to the coast and with increasing depth these results underscore the importance of evaluating vertical as well as lateral flow paths when quantifying geochemical reactions in a chemically stratified aquifer

time and the rivers flowing fluvial geomorphology since 1960 fluvial geomorphology has been the largest single subdiscipline within geomorphology for many decades fluvial geomorphic expertise is integral to understanding and managing rivers and to developing strategies for sustainable development this paper provides an overview of some of the significant advances in fluvial geomorphology between 1960 and 2010 with respect to conceptual models fluvial features and environments being studied tools used by fluvial geomorphologists geomorphic specialty groups within professional societies journals in which fluvial geomorphic research is published and textbooks of fluvial geomorphology during this half century fluvial geomorphology broadened considerably in scope from a focus primarily on physical principles underlying process and form in lower gradient channels with limited grain size range to a more integrative view of rivers as ecosystems with nonlinear behavior and great diversity of gradient substrate composition and grain size the array of tools for making basic observations analyzing data and disseminating research results also expanded considerably during this period as did the diversity of the fluvial geomorphic community

stable isotope geochemistry of sulfate in relation to hydrogeology in southern saskatchewan canada abstract isotope and chemical analyses were carried out on soil and water samples collected from testholes drilled into different stratigraphic layers at six locations in the assiniboia area southern saskatchewan to understand the origin and distribution of so 4 and sources of groundwater recharge the 34 s so 4 and 18 o so 4 values were mostly negative indicating oxidation of highly reduced sulfide in subsurface environments as the major source of so 4 in the soils and groundwaters however positive or near positive 34 s and 18 o values in some of the samples indicated that oxidation of sulfide with positive or near positive 34 s values or dissolution of a so 4 mineral such as evaporite gypsum may serve as alternate sources of s salt concentration and isotope compositions in the eastend sand were nearly uniform in comparison with till and shale layers total s content in the sediments varied from 0 7 to 3 2 g kg with greater accumulations in the till layer which were mostly 1 0 g kg the insoluble s fraction of the sediments was 4 s was the major form of s the 34 s and 18 o values of soluble so 4 and 18 o and d values of groundwaters provide supporting evidence of groundwater flow direction determined by other techniques the d and 18 o values of the groundwater samples varied between 131 and 119 and 15 2 to 11 4 respectively without any correlation with stratigraphy these data plot on a d vs 18 o line with a slope of 2 0 this departure from the meteoric water line with slope of 8 0 appears to be the result of evaporation or oxygen exchange with soil minerals the o isotope data suggest that exchange between so 4 and h 2 o is very slow under the conditions prevailing in the subsurface

an evaluation of the use of the chromous chloride reduction method for isotopic analyses of pyrite in rocks and sediment abstract the use of chromous chloride reduction as a preparation technique for isolation of pyrite sulphur for isotopic analysis has been assessed a small but consistent fractionation is introduced by reduction of pyrite to h 2 s enriching the yield in 34 s by 0 55 0 14

factors which determine the hydrogeochemical behaviour of karstic springs a case study from the betic cordilleras spain the cabra alcaide karstic massif situated in the south of spain constitutes an important part of the so called natural park of the subbetic sierras this aquifer system is drained by various springs which supply a population of some 100 000 inhabitants the feed areas of these springs show very different characteristics with respect to their geological structure size of the drainage area thickness of the vadose zone elevation and degree of karstification in addition the carbonate rocks lie over a clayey substratum which contains large masses of intercalated evaporites due to these conditions the hydrochemical composition of the springs is relatively variable in this study a hydrogeochemical characterization of the aquifer in both space and time is undertaken and the factors that determine it are discussed to achieve this 19 monthly samples were taken from the 6 most significant springs of the hydrogeological system the commencement of sampling coincided with the transition from a period of several years of severe drought and a very wet two year period which amplified considerably the hydrochemical and hydrodynamic response of the springs to the recharge identification of hydrogeochemical processes was performed by studying hydrographs the temporal evolution of physico chemical parameters ionic ratios mainly mg ca and by means of simple and multivariate statistical analyses the saturation status was established using the wateqf program and the mass transfer was quantified using phreeqc with the exception of the epikarstic subsystem i e the zarza spring the majority of the results indicate that the aquifer exhibits a diffuse flow model in which piston flow phenomena are seen closely linked to the most intense precipitation along the direction of flow hydrochemical trends are seen as the water type changes from ca hco3 to ca mg hco3 at the same time enrichment in some ions derived from the dissolution of evaporitic minerals of the impermeable substratum and dedolomitization processes occur in this way almost 90 of the water samples were oversaturated in calcite the majority of cases being a consequence of the dissolution of the gypsum of the substratum only in the epikarstic springs can it be considered that the oversaturation in calcite is due to loss of co2 from the emerging groundwater it is concluded that hydrodynamic aspects together with hydrogeochemical characteristics need to be taken into account to correctly explain the hydrochemical evolution of the karstic springs moreover the use of both approaches permits a more accurate establishment of the degree of aquifer karstification which in turn needs to be known in order to assess its vulnerability to contamination and to protect recharge zones

sulfide oxidation and sulfate reduction in a shallow groundwater system oderbruch aquifer germany abstract detailed groundwater monitoring was carried out over a period of two years in an anoxic river recharged aquifer of the oderbruch polder north eastern germany isotope data from wells located in a 5 km transect along the flow direction was used to determine sources and sinks of so 4 2 in the aquifer the so 4 2 originates from river water infiltration and from oxidative dissolution of fes 2 within the alluvial loam covering the aquifer sands a change of confined hydraulic conditions near the river to unconfined conditions in the central polder effects the hydrochemistry of the aquifer the confined areas are dominated by sulfate reduction increasing 34 s so 4 values suggest continuous but slow t 1 2 50 years sulfate reduction from the beginning of inflow onwards with 34 s so 4 values ranging from 1 8 to 44 7 versus cdt and an enrichment factor of 33 a zone with a strong sulfate depletion 34 s so 4 of up to 85 7 exists in a shallow microenvironment rich in solid phase organic carbon between river and levee in the unconfined areas of the central polder a so 4 2 plume with concentrations exceeding the original river water content indicates fes 2 oxidation by o 2 and or no 3 within the alluvial loam the lowered 34 s so 4 value reflects the input of the isotopically lighter so 4 2 from the sulfide

sulphur cycling in the drinking water catchment area of torgau mockritz germany insights from hydrochemical and stable isotope investigations the hydrochemical composition of groundwater and the isotopic composition of sulphur compounds in sediments 3 4 s of sulphide inorganic sulphate and groundwater 3 4 s 1 8 o of dissolved sulphate have been investigated to reveal the reasons for elevated concentrations of dissolved groundwater sulphate in the drinking water catchment area of torgau mockritz germany the three most important anthropogenic sources of sulphate identified in this study are historic atmospheric sulphate deposition predominantly of anthropogenic origin inorganic fertilization and dissolution of gypsum from waste dumps owing to their overlapping isotopic range no clear differentiation between the individual anthropogenic sources is possible sulphate from the oxidation of sedimentary sulphides however was recognized by its negative sulphur isotope signature 3 4 s 5 the mobilization of sulphate from different soil sulphur species is closely connected with variable isotopic fractionations resulting in a wide isotopic variation range for the sulphate entering the saturated zone generally sulphur and oxygen isotope ratios of the dissolved groundwater sulphate range from 19 to 37 vienna canon diablo troilite and from 2 to 19 vienna standard mean ocean water respectively sulphate from the majority of groundwater samples can be assigned to anthropogenic sources sulphate from sulphide oxidation is especially present in samples from the upper sampling level and the groundwater surface sulphate concentrations above 700 mg l 1 are mostly caused by the oxidation of sulphide sulphate that occurs in low and moderate concentrations dominantly originates from anthropogenic sources 3 4 s distribution patterns were used to locate the sources for the elevated sulphate concentrations in the raw water it was shown that the sulphate is not mobilized in the immediate vicinity of the production wells rather it originates in an area 1 5 km west of the intake the main mobilization mechanism there is the oxidation of reduced sedimentary sulphur species beyond its local significance this study presents a general example how changes in the sulphur cycle indicate major anthropogenically induced alterations of the hydrochemical situation in catchment areas

channel reach morphology in mountain drainage basins a classification of channel reach morphology in mountain drainage basins synthesizes stream morphologies into seven distinct reach types colluvial bedrock and five alluvial channel types cascade step pool plane bed pool rime and dune ripple coupling reach level channel processes with the spatial arrangement of reach morphologies their links to hillslope processes and external forcing by confinement ripar ian vegetation and woody debris defines a process based framework within which to assess channel condition and response potential in mountain drainage basins field investigations demonstrate character istic slope grain size shear stress and roughness ranges for different reach types observations consistent with our hypothesis that alluvial channel morphologies reflect specific roughness configurations ad justed to the relative magnitudes of sediment supply and transport ca pacity steep alluvial channels cascade and step pool have high ratios of transport capacity to sediment supply and are resilient to changes in discharge and sediment supply whereas low gradient alluvial channels pool rime and dune ripple have lower transport capacity to supply ra tios and thus exhibit significant and prolonged response to changes in sediment supply and discharge general differences in the ratio of transport capacity to supply between channel types allow aggregation of reaches into source transport and response segments the spatial distribution of which provides a watershed level conceptual model linking reach morphology and channel processes these two scales of channel network classification define a framework within which to in vestigate spatial and temporal patterns of channel response in moun tain drainage basins

a morpho statistical classification of mountain stream reach types in southeastern australia abstract the concepts of sediment transport capacity q c and sediment supply q s have shown promise in broadly differentiating mountain streams the important role of lithology in determining reach characteristics is also noted but as yet not fully included in existing process domain frameworks this study uses topographic and grain size surveys undertaken over 42 channel reaches with slopes between 0 01 and 0 20 m m to describe mountain stream morphology in southeastern australia reaches with two different lithologies are surveyed to specifically address the role of lithology in resultant channel morphology spatial autocorrelation analysis based on moran s i is used to detect the frequency and occurrence of in stream features such as bars and pools these data are combined with the grain size data to describe eight dominant reach morphologies most channel morphologies display broad characteristics similar to previous accounts of mountain streams although a number of intermediate morphologies affecting subtle variations in form and process where evident there was no significant longitudinal arrangement of the observed morphologies particularly with respect to catchment area and slope this is related to the strongly segmented longitudinal profiles characteristic of these streams where increasing catchment area does not result in a commensurate decrease in slope five of the eight channel morphologies identified are lithology dependent with respect to grain size and shape regime diagrams applied to quantify the physical controls on the different reach morphologies identified different q c q s domains for most morphologies however some lithology dependent morphologies could not be differentiated supporting the need to incorporate the effects of dominant grain shape or sphericity in assigning dimensionless critical shear stress values in determining q s overall the differences in mountain stream reach morphologies described in this study reflect the characteristic segmentation of the longitudinal profiles of these streams and contrasts in the supply and breakdown of parent material

a field investigation of the influence of sediment supply on step pool morphology and stability abstract the effect of the sediment supply on step pool morphology and stability was studied through the investigation of 42 step pool reaches eight in the vosges and 34 in the alps france step pool geometry step wavelength l and height h was measured for each reach and the data set split into two distinct groups comprising 25 connected to a sediment source step pool reaches and 17 disconnected step pool reaches the geometry analysis showed differences between the two groups with the shape factors k l hr and the h hr ratios hr is the residual pool depth being lower for disconnected step pools this was interpreted to result from progressively changing geometry over time with disconnected step pool geometry defining the probable asymptotic characteristic associated with this long term process the measured step pool dimensions were in good agreement with equations based on maximum flow resistance abrahams et al 1995 energy of a falling jet comiti et al 2005 and channel spanning deposition chartrand et al 2011 however the average shape factor for the comiti et al equation was k 17 instead of 8 as the authors had proposed the data set was extended to 255 values with data from the literature which confirmed this average value for k field evidence moss cover and stone imbrication indicate that connected step pools are mobile whereas disconnected step pools are stable this was investigated by a hydraulic analysis of threshold motion conditions for the boulder steps comparison with discharges measured at nearby gauging stations indicates that remobilization return periods are 20 50 years for connected step pools and even less when considering scouring effects and greater than 50 years for disconnected step pools this difference in step mobility was ascribed to the fact that with sediment supply the channel can freely adjust its local slope allowing a relatively efficient transfer downstream of large boulders by scouring effects

step pool evolution in the rio cordon northeastern italy the principle that formative events punctuated by periods of evolution recovery or temporary periods of steady state conditions control the development of the step pool morphology has been applied to the evolution of the rio cordon stream bed the rio cordon is a small catchment 5 km2 within the dolomites wherein hydraulic parameters of floods and the coarse bedload are recorded detailed field surveys of the step pool structures carried out before and after the september 1994 and october 1998 floods have served to illustrate the control on step pool changes by these floods floods were grouped into two categories the first includes ordinary events which are characterized by peak discharges with a return time of one to five years 1 8 5 15 m3 s 1 and by an hourly bedload rate not exceeding 20 m3 h 1 the second refers to exceptional events with a return time of 30 50 years a flood of this latter type occurred on 14 september 1994 with a peak discharge of 10 4 m3 s 1 and average hourly bedload rate of 324 m3 h 1 step pool features were characterized primarily by a steepness parameter c h ls s the evolution of the steepness parameter was measured in the field from 1992 to 1998 the results indicate that maximum resistance conditions are gradually reached at the end of a series of ordinary flood events during this period bed armouring dominate the sediment transport response however following an extraordinary flood and unlimited sediment supply conditions the steepness factor can suddenly decrease as a result of sediment trapped in the pools and a lengthening of step spacing the analogy of step spacing with antidune wavelength and the main destruction and transformation mechanism of the steps are also discussed copyright 2001 john wiley sons ltd

objective identification of pools and riffles this paper presents a new technique for objectively identifying pools and riffles the technique is termed the bed form differencing technique and as its data base has bed elevations surveyed at a fixed interval along the channel these elevations are differenced and the difference or elevation change values are used to identify pools and riffles where the cumulative elevation change since the last bed form exceeds a certain tolerance value a new bed form is considered to exist the type of bed form being determined by the direction of the elevation change analysis of a small stream in western new york suggests that the most realistic pool riffle sequence is obtained where the tolerance value is 0 75 times the standard deviation of the difference values the bed form differencing technique can be used to identify bed forms other than pools and riffles such as ripples and dunes by simply modifying the surveying interval to reflect the scale of the bed forms

sulfur biogeochemistry and isotopic fractionation in shallow groundwater and sediments of owens dry lake california groundwater and sediment samples 1 m depth at sites representative of different groundwater pathways were collected to determine the aqueous speciation of sulfur and the fractionation of sulfur isotopes in aqueous and solid phases in addition selected sediment samples at 5 depths from oxic to anoxic layers were collected to investigate the processes controlling sulfur biogeochemistry in sedimentary layers pyrite was the dominant sulfur bearing phase in the capillary fringe and groundwater zones where anoxic conditions are found low concentrations of pyrite b5 9 g kg 1 coupled with high concentrations of dissolved sulfide 4 81 to 134 7 mg l 1 and low concentrations of dissolved fe generally b 1m g l 1 and reducible solid phase fe indicate that availability of reactive fe limits pyrite formation the relative uniformity of down core isotopic trends for sulfurbearing mineral phases in the sedimentary layers suggests that sulfate reduction does not result in significant sulfate depletion in the sediment sulfate availability in the deeper sediments may be enhanced by convective vertical mixing between upper and lower sedimentary layers due to evaporative concentration the large isotope fractionation between dissolved sulfate and sedimentary sulfides at owens lake provides evidence for initial fractionation from bacterial sulfate reduction and additional fractionation generated by sulfide oxidation followed by disproportionation of intermediate oxidation state sulfur compounds the high salinity in the owens lake brines may be a factor controlling sulfate reduction and disproportionation in hypersaline conditions and results in relatively constant values for isotope fractionation between dissolved sulfate and total reduced sulfur d 2005 elsevier b v all rights reserved

recent 1999 2003 canadian research on contemporary processes of river erosion and sedimentation and river mechanics contributions by canadian fluvial geomorphologists between 1999 and 2003 are discussed under four major themes sediment yield and sediment dynamics of large rivers cohesive sediment transport turbulent flow structure and sediment transport and bed material transport and channel morphology the paper concludes with a section on recent technical advances during the review period substantial progress has been made in investigating the details of fluvial processes at relatively small scales examples of this emphasis are the studies of flow structure turbulence characteristics and bedload transport which continue to form central themes in fluvial research in canada translating the knowledge of small scale process related research to an understanding of the behaviour of large scale fluvial systems however continues to be a formidable challenge models play a prominent role in elucidating the link between small scale processes and large scale fluvial geomorphology and as a result a number of papers describing models and modelling results have been published during the review period in addition a number of investigators are now approaching the problem by directly investigating changes in the system of interest at larger scales e g a channel reach over tens of years and attempting to infer what processes may have led to the result it is to be expected that these complementary approaches will contribute to an increased understanding of fluvial systems at a variety of spatial and temporal scales

evaluating debris flow and anthropogenic disturbance on 10be concentration in mountain drainage basins implications for functional connectivity and denudation rates across time scales

hydrochemistry mineralogy and sulfur isotope geochemistry of acid mine drainage at the mt morgan mine environment queensland australia mineralogical hydrochemical and s isotope data were used to constrain hydrogeochemical processes that produce acid mine drainage from sulfidic waste at the historic mount morgan au cu mine and the factors controlling the concentration of so4 and environmentally hazardous metals in the nearby dee river in queensland australia some highly contaminated acid waters with metal contents up to hundreds of orders of magnitude greater than the australia new zealand environmental standards by pass the water management system at the site and drain into the adjacent dee river mine drainage precipitates at mt morgan were classified into 4 major groups and were identified as hydrous sulfates and hydroxides of fe and al with various contents of other metals these minerals contain adsorbed or mineralogically bound metals that are released into the water system after rainfall events sulfate in open pit water and collection sumps generally has a narrow range of s isotope compositions 34s 1 8 3 7 that is comparable to the orebody sulfides and makes s isotopes useful for tracing so4 back to its source the higher 34s values for no 2 mill diesel sump may be attributed to a difference in the source dissolved so4 in the river above the mine influence and 20 km downstream show distinctive heavier isotope compositions 34s 5 4 6 8 the dee river downstream of the mine is enriched in 34s 34s 2 8 5 4 compared with mine drainage possibly as a result of bacterial so4 reduction in the weir pools and in the water bodies within the river channel the so4 and metals attenuate downstream by a combination of dilution with the receiving waters so4 reduction and the precipitation of fe and al sulfates and hydroxides it is suggested here that in subtropical queensland with distinct wet and dry seasons temporary reducing environments in the river play an important role in s isotope systematics

channel morphology gradient profiles and bed stresses during flood in a step pool channel abstract the stability of a step pool channel is investigated on the basis of measurements during a median annual flood the study reaches range in gradient from 5 to 10 and the flow was 3 m3 s 1 in an 8 m wide channel the estimated shear stress based on the channel gradient was 102 pa which implies that the channel ought to move half meter class boulders calculations of the shear stress using flow resistance equations yield values of about 30 pa these figures imply that the largest boulders in the channel could be moved in fact the channel is stable the effective stress remains well below the threshold to move the large structure forming boulders the steps are stable structures that result from interlocking of the larger stones they are semi randomly located depending on the location of keystones that are deposited in the channel by debris flows or fall out of the banks the high variation in step pool wavelength step height residual pool depth and pool length is indicative of the random nature of step location and structure along a reach there is no convincing evidence that special conditions govern their formation

controls on δ 34 s and δ 18 o of dissolved sulfate in aquifers of the murray basin australia and their use as indicators of flow processes the usefulness of stable isotopes of dissolved so4 34s and 18o to study recharge processes and to identify areas of significant inter aquifer mixing was evaluated in a large semi arid groundwater basin in south eastern australia the murray basin the distinct isotopic signatures in the oxidizing unconfined murray group aquifer and the deeper reducing renmark group confined aquifer may be more sensitive than conventional chemical tracers in establishing aquifer connections 34s values in the unconfined murray group aquifer in the south and central part of the study area decrease along the hydraulic gradient from 20 8 to 0 3 the concomitant increasing so4 cl ratios as well as relatively low 18oso4 values suggest that vertical input of biogenically derived so4 via diffuse recharge is the predominant source of dissolved so4 to the aquifer further along the hydraulic gradient towards the discharge area near the river murray 34s values in the unconfined murray group aquifer increase and so4 cl ratios decrease due to upward leakage of waters from the confined renmark group aquifer which has a distinctly low so4 cl and high 34s 14 9 56 4 relatively positive 34s and 18oso4 values and low so4 cl in the renmark group aquifer is typical of so4 removal by bacterial reduction the s isotope fractionation between so4 and hs of 24 estimated for the confined aquifer is similar to the experimentally determined chemical fractionation factor for the reduction process but much lower than the equilibrium fractionation 70 even though the confined groundwater residence time is 300 ka years mapping the spatial distribution of 34s and so4 cl of the unconfined murray group aquifer provides an indicative tool for identifying the approximate extent of mixing however the poorly defined end member isotopic signatures precludes quantitative estimates of mixing fractions

bed morphology and generation of step pool channels flume experiments have been carried out to study the formation processes and the bed morphology of step pool channels from the experiments different step types and step configurations could be distinguished depending on the stream power these step types can be seen as an image of the generation mechanisms of step pool systems these results suggest that the bed roughness geometry develops towards a condition that provides the maximum possible bed stability for a given grain size distribution in contrast to a variety of other studies antidunes did not contribute to the generation of the step structures however the data of the presented study fits well into the region of antidune formation proposed by kennedy for sand bed rivers this observation points out that step pool field data located in the kennedy region do not inevitably prove that antidunes played a role in step development it is rather proposed that in kennedy s region of antidune formation there exist hydraulic conditions where the flow resistance is maximized it is suggested that such maximum flow resistance is associated with an optimal distance between the bedforms and their height independently of whether these are antidunes in sand and gravel bed rivers or step pool units in boulder bed streams the considerations of the kennedy region of antidune formation and the analysis of planform step types depending on stream power both suggest that steep channels have a potential for self stabilization by modifying the step pool structure towards a geometry that provides maximum flow resistance and maximum bed stability copyright 2008 john wiley sons ltd

isotopic evidence for processes of sulfur retention release in 13 forested catchments spanning a strong pollution gradient czech republic central europe sulfur isotope systematics were studied in 13 small catchments in the czech republic similar in topography v shaped valley and vegetation norway spruce the sites differed in elevation rainfall bedrock soil type and s pollution across the sites 34 5 values decreased in the order bulk deposition runoff spruce throughfall c horizon soil a b horizon soil 0 horizon soil bedrock means of 5 5 4 8 4 7 4 6 4 2 3 1 and 1 5 o respectively some of the sites had a net export of s while others accumulated s sites exporting s were located in the polluted north where atmospheric s input started to decrease in 1987 sites retaining s were located in the relatively unpolluted south sulfur isotope composition of runoff depended on whether the catchment accumulated or released s sites releasing s had runoff 34 s values lower than deposition in contrast sites retaining s had runoff 34 s values higher than deposition across the sites the 34 5 values of runoff were not correlated with 34 s values of bedrock indicating that the contribution of bedrock to s in runoff was negligible the 34 s values of runoff were strongly positively correlated with the 34 s values of soil sulfur present in the c horizon of soils was mainly derived from atmospheric deposition not bedrock sulfur isotope mass balances were constructed for each catchment making it possible to quantify the difference between 34 s values of the within catchment source sink of s and runoff s sulfur isotope mass balances indicated that the sink for the retained s at unpolluted sites and the source of the released s at polluted sites were isotopically fractionated by the same amount relative to runoff s inorganic and organic processes were considered as possible causes for this observation biological s cycling involves a variety of reactions some of which fractionate s isotopes in contrast adsorption desorption of inorganic sulfate in soil and weathering of s containing minerals do not fractionate s isotopes therefore the within catchment source sink of s must be largely a result of biological s cycling organic s cycling played an important role over a wide range of atmospheric s inputs from 13 to 130 kg s ha 1 yr 1

s and o isotopic character of dissolved sulphate in the cover rock aquifers of a zechstein salt dome abstract sulfur and o isotope analyses of dissolved so4 were used to constrain a hydrogeological model for the area overlying the gorleben rambow salt structure northern germany samples were collected from 80 wells screened at different depth intervals the study area consists of a set of two vertically stacked aquifer systems generally the isotope data show a good spatial correlation outlining well defined groundwater zones containing so4 of characteristic isotopic composition highly saline waters from deeper parts of the lower aquifer system are characterized by rather constant so4 isotopic compositions which are typical of permian zechstein evaporites 34s 9 6 11 9 18o 9 5 12 1 above this is a transition zone containing ground waters of intermediate salinity and slightly higher isotopic values average 34s 16 6 18o 15 3 the confined groundwater horizon on the top of the lower aquifer system below the low permeable hamburg clays is low in total dissolved solids and is characterized by an extreme 34s enrichment average 34s 39 1 18o 18 4 suggesting that bacterially mediated so4 reduction is a dominant geochemical process in this zone two areas of distinct isotopic composition can be identified in the shallow ground water horizons of the upper hydrogeological system sulfate in groundwaters adjacent to the river elbe and locknitz has a typical meteoric isotopic signature 34s 5 2 18o 8 2 whereas the central part of the area is characterized by more elevated isotopic ratios 34s 12 7 18o 15 6 the two major so4 pools in the area are represented by permian seawater so4 and a so4 of meteoric origin that has been mixed with so4 resulting from the oxidation of pyrite it is suggested that the s isotope compositions observed reflect the nature of the so4 source that have been modified to various extent by bacterial so4 reduction groundwaters with transitional salinity have resulted from mixing between brines and low mineralized waters affected by bacterial so4 reduction

a process based classification system for headwater streams in this paper we develop a classification system for small headwater streams predicated upon an understanding of the dominant physical processes acting in the channel and its basin and the conditions under which these processes operate the variables used to build the classification are hillslope gradient valley width as compared to channel width channel gradient channel depth and sediment size using physical laws and morphologic relationships we recognize domains in which various processes dominate channels within the same process domain can be expected to behave in a similar manner in transporting sediment and water and responding to and recovering from basin disturbance therefore we use the domains to recognize distinct channel types this classification system provides the foundation for building an approach for identifying basins and streams that are comparably sensitive to landuse

using dual isotopic data to track the sources and behaviors of dissolved sulfate in the western north china plain abstract this paper investigated the sources and behaviors of sulfate in groundwater of the western north china plain using sulfur and oxygen isotopic ratios the groundwaters can be categorized into karst groundwater kgw coal mine drainage cmd and pore water subsurface saturated water in interstices of unconsolidated sediment pore water in alluvial plain sediments could be further classified into unconfined groundwater ugw with depth of less than 30 m and confined groundwater cgw with depth of more than 60 m the isotopic compositions of kgw varied from 9 3 to 11 3 for 34 s so4 with the median value of 10 3 n 4 and 7 9 to 15 6 for 18 o so4 with the median value of 14 3 n 4 respectively indicating gypsum dissolution in karst aquifers 34 s so4 and 18 o so4 values of sulfate in cmd ranged from 10 8 to 12 4 and 4 8 to 8 7 respectively on the basis of groundwater flow path and geomorphological setting the pore water samples were divided as three groups 1 alluvial proluvial fan ii 1 group with high sulfate concentration median values of 2 37 mm and 1 95 mm for ugw and cgw respectively and positive 34 s so4 and 18 o so4 values median values of 8 8 and 6 9 for ugw 12 0 and 8 0 for cgw 2 proluvial slope ii 2 group with low sulfate concentration median values of 1 56 mm and 0 84 mm for ugw and cgw respectively and similar 34 s so4 and 18 o so4 values median values of 9 0 and 7 4 for ugw 10 2 and 7 7 for cgw and 3 low lying zone ii 3 group with moderate sulfate concentration median values of 2 13 mm and 1 17 mm for ugw and cgw respectively and more positive 34 s so4 and 18 o so4 values median values of 10 7 and 7 7 for ugw 20 1 and 8 8 for cgw in the present study three major sources of sulfate could be differentiated as following sulfate dissolved from ordovician to permian rocks 34 s so4 10 35 and 18 o so4 7 20 soil sulfate 34 s so4 5 9 and 18 o so4 5 8 and sewage water 34 s so4 10 0 and 18 o so4 7 6 kinetic fractionations of sulfur and oxygen isotopes as a result of bacterial sulfate reduction bsr were found to be evident in the confined aquifer in stagnant zone ii 3 and enrichment factors of sulfate sulfur and sulfate oxygen isotopes calculated by rayleigh equation were 12 1 and 4 7 respectively along the flow direction of groundwater at depths of 60 100 m the results obtained in this study confirm that detailed hydrogeological settings and identification of anthropogenic sources are critical for elucidating evolution of 34 s so4 and 18 o so4 values along with groundwater flow path and this work also provides a useful framework for understanding sulfur cycling in alluvial plain aquifers

dedolomitization and calcite cementation in the middle devonian winnipegosis formation in central saskatchewan canada limestone consisting of finely to medium crystalline calcite mosaics is present in the upper part of the winnipegosis formation on the east central margin of the elk point basin where the overlying prairie evaporite deposits have been removed this type of crystalline limestone is interpreted as dedolomite based on petrographic observations the 18o and 13c values of the winnipegosis dedolomite vary from 12 8 to 11 9 vpdb vienna pee dee belemnite and from 0 5 to 1 7 vpdb respectively both values are significantly lower than those for the corresponding dolomite the 87sr 86sr ratios of the dedolomite are significantly higher between 0 7082 and 0 7087 the spatial distribution and geochemical data of the winnipegosis dedolomite suggest that dedolomitization was related to an influx of fresh groundwater and dissolution of the prairie evaporite anhydrite during the latest mississippian to the early cretaceous when the basin was subjected to uplift and erosion the winnipegosis dedolomite displays a series of replacement fabrics showing progressive calcitization of dolomite including the occurrence of dedolomite restricted along fractures and adjacent areas dolomite patches floating in the dedolomite masses and massive dedolomite with sparsely scattered dolomite relicts however the characteristic fabrics resulting from dedolomitization documented in the literature have not been observed in the winnipegosis dedolomite coarsely to very coarsely crystalline subhedral to euhedral calcite cement is restricted in the dedolomite the petrographic features isotopic compositions and homogenization temperatures coupled with the burial history of the winnipegosis formation constrain the precipitation of the calcite cement from a mixing of basinal brines and fresh groundwater during late cretaceous to neogene time the more negative c isotopic signatures of the calcite cement 5 3 to 2 3 vpdb probably reflect a hydrocarbon derived carbon

sulfur isotope signatures in gypsiferous sediments of the estancia and tularosa basins as indicators of sulfate sources hydrological processes and microbial activity abstract in order to reconstruct paleo environmental conditions for the saline playa lakes of the rio grande rift we investigated sediment sulfate sources using sulfur isotope compositions of dissolved so 4 2 ions in modern surface water groundwater and so 4 2 precipitated in the form of gypsum sediments deposited during the pleistocene and holocene in the tularosa and estancia basins the major sulfate sources are lower and middle permian marine evaporites 34s of 10 9 14 4 but the diverse physiography of the tularosa basin led to a complex drainage system which contributed sulfates from various sources depending on the climate at the time of sedimentation as inferred from sulfur isotope mass balance constraints weathering of sulfides of magmatic hydrothermal and sedimentary origin associated with climate oscillations during last glacial maximum contributed about 35 50 of the sulfates and led to deposition of gypsum with 34s values of 1 2 to 2 2 which are substantially lower than permian evaporates in the estancia basin microbial sulfate reduction appears to overprint sulfur isotopic signatures that might elucidate past groundwater flows a rayleigh distillation model indicates that about 3 18 of sulfates from an inorganic groundwater pool 34s of 12 6 13 8 have been metabolized by bacteria and preserved as partially to fully reduced sulfur bearing minerals species elemental sulfur monosulfides disulfides with distinctly negative 34s values 42 3 to 20 3 compared to co existing gypsum 3 8 to 22 4 for the tularosa basin microbial sulfate reduction had negligible effect on 34s value of the gypsiferous sediments most likely because of higher annual temperatures 15 33 c and lower organic carbon content median 0 09 in those sediments leading to more efficient oxidation of h2s and or smaller rates of sulfate reduction compared to the saline playas of the estancia basin 5 28 c median 0 46 of organic carbon the white sands region of the tularosa basin is frequently posited as a hydrothermal analogue for mars high temperatures of groundwater 33 3 c and high 18o h2o values 1 1 in white sands however are controlled predominantly by seasonal evaporation rather than the modern influx of hydrothermal fluids nevertheless it is possible that some of the geochemical processes in white sands such as sulfide weathering during climate oscillations and upwelling of highly mineralized waters might be considered as valid terrestrial analogues for the sulfate cycle in places such as meridiani planum on mars

origin of step pool systems in mountain streams mountain streams very often present a step pool aspect antidune formation alone dispersion and sorting theory or velocity reversal as advocated for the origin of riffle pool sequences do not explain how steps and pools form experiments have been conducted to clarify their origin it was found that the step pool aspect appears after high flows had deformed the bed during the presented tests a self armoring process occurred which resulted in a stabilization of the bed when coarsening of the top layer was little classic antidunes resulted an important coarsening was accompanied by a structuring of the bed into roughness elements whose spacing did correspond to maximum flow resistance the substantial increase in resistance was an essential factor in bed stabilization

sulfur species and biosignatures in sulphur springs valles caldera new mexico implications for mars astrobiology abstract a biogeochemical so 4 2 cycle was investigated in the acid hot springs of valles caldera new mexico using s isotopes and distribution of amino acids in 2007 a major contribution of so 4 2 in this modern volcanic setting came from oxidation of h 2 s from hydrothermal sources which largely increased so 4 2 concentrations up to 2550 mg l 1 and decreased ph down to 2 27 in surface water a relatively small variation of 34 s among the analyzed s bearing minerals 2 1 to 4 0 fumarole h 2 s 1 7 to 4 6 and dissolved so 4 2 in modern surface and groundwater 2 5 to 7 9 indicates poor evidence of s isotope biosignatures related to microbial disproportionation of elemental s to h 2 s and so 4 2 which in turn are not effectively captured in the hydrothermal minerals of the studied volcanic setting this is mainly due to prevailing contribution of reduced s forms from magmatic hydrothermal sources and considerably smaller microbial activity in acid hot spring areas although hydrothermal gypsum and elemental s effectively trap amino acids their preservation lifetimes in s bearing hydrothermal minerals appear to be small the minimal lifetimes are inferred to be the result of increased temperatures and rapid recycling time of s materials in hydrothermal settings landed missions to the martian surface at sites inferred to have experienced active hydrothermal activity similar to the one studied in valles caldera e g elevated volcanic s flux may provide valuable insight into geological and geochemical processes that have influenced the martian surface but may provide minimal potential for recording either amino acid or s isotopic biosignatures of an extinct martian ecosystem

morphological patterns of headwater streams based in flysch bedrock examples from the outer western carpathians abstract a channel reach morphology of mountain headwater streams results from the balance between fluvial and hillslope processes a large dataset n 102 of channel reaches coming out from flysch mid mountains was evaluated and compared with streams occurring in other environments two new channel reach morphologies were distinguished with respect to their differences in the ratio of sediment supply to transport capacity bedrock cascades and step rapids the chaining of channel reach morphologies by gradient criteria and the parameters of channel gradient and bankfull width related to the basin area show similar trends when compared to other recent studies by contrast bankfull depth indicates its independence on increasing basin area significant downstream coarsening of bed material occurs only in alluvial stepped bed morphologies cascades step pools and step rapids mainly due to strong slope channel coupling processes moreover the specific ratio of bankfull width and d90 predicts the interlocking of boulder steps as well as well developed step pool morphology an amount of large woody debris is closely related to the activity of strict local forest management in evaluated channels as a significant decrease in large woody debris pieces is observed with increasing basin area

geochemical modeling of the madison aquifer in parts of montana wyoming and south dakota stable isotope data for dissolved carbonate sulfate and sulfide are combined with water compo sition data to construct geochemical reaction models along eight flow paths in the madison aquifer in parts of wyoming montana and south dakota the sulfur isotope data are treated as an isotope dilution problem whereas the carbon isotope data are treated as rayleigh distillations all reaction models reproduce the observed chemical and carbon and sulfur isotopic composition of the final waters and are partially validated by predicting the observed carbon and sulfur isotopic compositions of dolomite and anhydrite from the madison limestone the geochemical reaction models indicate that the dominant groundwater reaction in the madison aquifer is dedolomitization calcite precipita tion and dolomite dissolution driven by anhydrite dissolution sulfate reduction ca mg2 ina cation exchange and halite dissolution are locally important particularly in central montana the groundwater system is treated as closed to c02 gas from external sources such as the soil zone or cross formational leakage but open to c02 from oxidation of organic matter coupled with sulfate reduction and other redox processes occurring within the aquifer the computed mineral mass transfers and modeled sulfur isotopic composition of madison anhydrites are mapped throughout the study area carbon 14 groundwater ages adjusted for the modeled carbon mass transfer range from modem to about 23 000 years b p and indicate flow velocities of 7 7 ftlyr 2 1 26 5 rnlyr most horizontal hydraulic conductivities calculated from darcy s law using the average 14 c flow velocities are within a factor of 5 of those based on digital simulation the calculated mineral mass transfer and adjusted 14 c groundwater ages permit determination of apparent rates of reaction in the aquifer the apparent rate of organic matter oxidation is typically 0 12 jlidol uyr sulfate and to a lesser extent ferric iron are the predominant electron acceptors the kinetic biochemical fractionation of 34 s between sulfate and hydrogen sulfide is approximately 44 o at 25 c with a temperature variation of

isotopic studies of the upper and middle rio grande part 1 importance of sulfide weathering in the riverine sulfate budget abstract in order to characterize the sulfide derived so 4 fluxes in the rio grande we collected seasonally from 2009 to 2011 riverine agricultural drain and groundwater samples and analyzed them for their major element chemistries and the 34 s and 18 o of dissolved so 4 the observed variation of 34 s 4 to 8 and 18 o 2 to 7 in the rio grande mainly resulted from mixing between sulfide and sulfate derived so 4 of volcanic and sedimentary origin our s isotope mass balance suggests that the average sulfide derived so 4 flux usually accounted for 83 94 10 20 of the sulfate source in the upstream rio grande and decreased downstream to 45 51 because of increasing contributions of sulfate derived so 4 the sulfide derived so 4 was related to snow melt in the high elevation watersheds and recycling of surficial sulfate rich salts by episodic water activity in dry areas at lower elevations additionally elevated bedrock sulfide contents in volcanic and some sedimentary terrains of the studied area have been recognized as important factors contributing to sulfide derived so 4 in the rio grande

groundwater salinization processes and reversibility of seawater intrusion in coastal carbonate aquifers summary seawater intrusion swi has led to salinization of fresh groundwater reserves in coastal areas worldwide and has forced the closure of water supply wells there is a paucity of well documented studies that report on the reversal of swi after the closure of a well field this study presents data from the coastal carbonate aquifer in northeast china where large scale extraction has ceased since 2001 after salinization of the main well field the physical flow and concomitant hydrogeochemical processes were investigated by analyzing water level and geochemical data including major ion chemistry and stable water isotope data seasonal water table and salinity fluctuations as well as changes of 2 h 18 o values of groundwater between the wet and dry season suggest local meteoric recharge with a pronounced seasonal regime historical monitoring testifies of the reversibility of swi in the carbonate aquifer as evidenced by a decrease of the cl concentrations in groundwater following restrictions on groundwater abstraction this is attributed to the rapid flushing in this system where flow occurs preferentially along karst conduits fractures and fault zones the partially positive correlation between 18 o values and tds concentrations of groundwater as well as high no 3 concentrations 39 mg l suggest that irrigation return flow is a significant recharge component therefore the present day elevated salinities are more likely due to agricultural activities rather than swi nevertheless seawater mixing with fresh groundwater cannot be ruled out in particular where formerly intruded seawater may still reside in immobile zones of the carbonate aquifer the massive expansion of fish farming in seawater ponds in the coastal zone poses a new risk of salinization cation exchange carbonate dissolution and fertilizer application are the dominant processes further modifying the groundwater composition which is investigated quantitatively using hydrogeochemical models

the self organization of step pools in mountain streams abstract spontaneous autogenic self organization has been described in numerous geomorphic systems but it has not been investigated in detail with respect to coarse bedforms in general or step pools in particular in this paper we review the spatial organization of step pool systems and present example evidence of step pool development as an autogenic self organization process we then outline the mathematical language for defining spatially divergent self organization and test these ideas using two unique field examples from oregon andrews experimental forest and california baxter creek where step pools developed from planar beds in artificially manipulated channels results show that step pool development is consistent with a spatially divergent self organization phenomenon entropy increases as initially undifferentiated planar channels diverge into steps and pools then declines when a series of steps and pools of consistent size and spacing is established signifying stability in the system the self organization process is accompanied by increasing flow resistance and decreasing slope through increasing the vertical sinuosity of the step pool profile and creation of low or negative gradient pool areas suggesting a minimization of stream power the self adjustment of the step pool bed profile over time represents another manifestation of a general process that results in rhythmic patterns on the surface of earth

the morphologic structure of step pools in mountain streams abstract step pool sequences in streams in the santa monica mountains of southern california impart a characteristic morphologic structure that varies with slope but despite the strong association with slope that suggests a direct process control analysis of 464 step pools in 13 study reaches reveals the relationship to reflect correlation but not necessarily causality the direct control on step height is particle size whereas discharge is the probable causal process determining step wavelength because both particle size and discharge generally change with channel slope downstream a slope variation with step wavelength and height is the apparent indirect geometric result a conceptual model of process form linkages is proposed based on these results whereby the step pool morphology is produced by positive relationships between wavelength and discharge and between height and particle size the model offers new insights for explaining the step pool morphology and it is potentially useful in channeling future efforts toward the appropriate scales and variables

on the origin of step pool sequences in mountain streams this paper reports a field test of the prevailing antidune theory to explain the mechanisms of step pool formation in steep mountain streams the theory is supported by laboratory data but it has not received extensive field testing that would enable wide applicability to natural conditions data from the santa monica mountains of california are used to test the antidune model where step wavelength and reconstructed hydraulic conditions are compared with the formation domain predicted by experimental and theoretical studies results show general agreement between field and laboratory data step wavelength and hydraulic requirements are consistent with those of the antidune process of formation but results also suggest that true antidunes may be difficult to achieve in the steep headwaters where channels may be dominated by large roughness elements these findings strengthen the link between theory and observation in clarifying how step pools form they contribute to the basis for elucidating why step pools form in mountain streams

flow dynamics of groundwater and soil water in the former heap gessenhalde at the uranium mining area of ronneburg a stable isotope approach stable isotopes 2hwater 18owater as well as 18osulphate and 34ssulphate were used to study the flow system of shallow groundwater and soil water at the base area of a former leaching heap at the uranium mining area of ronneburg germany the flow paths and water retention times were estimated by comparison of 2h and 18o values in groundwater and soil water to the 2h and 18o signature of precipitation giving distinctive inputs of summer or winter precipitation the points of measuring the groundwater were divided into three categories with different flow conditions rapid flow stagnant conditions and a transition zone by hierarchical cluster analysis of 2h and 18o values of groundwater the transit time of groundwater in the rapid flow area is less than 6 months whereas water in the stagnant zone is stored for at least 1 year in soil water a clear response to different input signals is detectable only in the 30 cm horizon retention time is about 6 months whereas at deeper levels a mixing with older water is taking place the isotopic composition of the dissolved sulphate was used to identify oxidation of sulphides as the source of sulphate copyright 2010 john wiley sons ltd

drought induced pulses of so42 from a canadian shield wetland use of δ34s and δ18o in so42 to determine sources of sulfur abstract following summer drought periods pulses of elevated so 4 2 concentrations are frequently observed in streams draining forested catchments that contain wetlands delays in the recovery of freshwater streams and lakes in eastern canada from historically high levels of acidic precipitation have been partially ascribed to these periodic pulses of so 4 2 climate in eastern canada has also changed within the last 25 a with a documented increase in summer dryness and duration of droughts in small forested catchments in the turkey lakes watershed tlw so 4 2 concentrations in streams draining wetlands can be elevated by up to a factor of 7 during post drought discharge events compared to the annual average two neighbouring catchments one with a series of cascading wetlands and one without any wetlands were selected for comparison stable s and o isotope ratios were analyzed in samples of bulk precipitation streams and groundwaters to examine sources of so 4 2 in post drought pulses 34 s so 4 2 in the streams and groundwaters show that so 4 2 is retained in the wetland via so 4 2 reduction and stored in the upper peat profile nitrate is elevated in soil and groundwaters at tlw due to high rates of nitrification in forest soils and the presence of no 3 can be used to identify piezometers unaffected by so 4 2 reduction 18 o so 4 2 shows that higher concentrations of so 4 2 in deeper groundwater are likely due to oxidation of organic s and not a geologic source of reduced s following drought the low 34 s so 4 2 in streams is consistent with wetland retention by so 4 2 reduction and much lower than so 4 2 released by weathering in deep glacial till and bedrock high so 4 2 groundwaters and geologic sources do not contribute to the so 4 2 pulses in streams isotopic patterns over 6 a were similar pulses of so 4 2 in the wetland catchments following drought are a result of the oxidation of s previously reduced and stored in the wetland

the form and function of headwater streams based on field and modeling investigations in the southern appalachian mountains headwater streams drain the majority of most landscapes yet less is known about their morphology and sediment transport processes than for lowland rivers we have studied headwater channel form discharge and erosive power in the humid moderate relief valley and ridge and blue ridge provinces of the appalachian mountains field observations from nine headwater 2k m 2 drainage area mixed bedrock alluvial channels in a variety of boundary conditions demonstrate variation with respect to slope area channel initiation basic morphology slope distribution hydraulic geometry substrate grain size and role of woody debris these channels display only some of the typical downstream trends expected of larger lowland rivers variations are controlled mainly by differences in bedrock resistance from the formation level down to short wavelength outcrop scale variations hydrologic modeling on these ungauged channels estimates the recurrence of channel filling discharge and its ability to erode the channel bed two year recurrence discharge is generally larger and closer to bankfull height in the valley and ridge due to low soil infiltration capacity discharge that fills the channel to its surveyed bankfull form is variable generally exceeding two year flows at small drainage areas 0 5 km 2 and being exceeded by them at greater drainage areas this suggests bankfull is not controlled by the same recurrence storm throughout a channel or physiographic region stream power and relative competence are also variable these heterogeneities contrast relations observed in larger streams and illustrate the sensitivity of headwater channels to local knickpoints of resistant bedrock and armoring of channels by influx of coarse debris from hillslopes the general lack of predictable trends or functional relationships among hydraulic variables and the close coupling of channel form and function with local boundary conditions indicate that headwater streams pose a significant challenge to landscape evolution modeling copyright 2005 john wiley sons ltd

sour gas hydrothermal jarosite ancient to modern acid sulfate mineralization in the southern rio grande rift abstract as many as 29 mining districts along the rio grande rift in southern new mexico contain rio grande rift type rgr deposits consisting of fluorite barite sulfide jarosite and additional rgr deposits occur to the south in the basin and range province near chihuahua mexico jarosite occurs in many of these deposits as a late stage hydrothermal mineral coprecipitated with fluorite or in veinlets that crosscut barite in these deposits many of which are limestone hosted jarosite is followed by natrojarosite and is nested within silicified or argillized wallrock and a sequence of fluorite barite sulfide and late hematite gypsum these deposits range in age from 10 to 0 4 ma on the basis of 40ar 39ar dating of jarosite there is a crude north south distribution of ages with older deposits concentrated toward the south recent deposits also occur in the south but are confined to the central axis of the rift and are associated with modern geothermal systems the duration of hydrothermal jarosite mineralization in one of the deposits was approximately 1 0 my most 18oso4 oh values indicate that jarosite precipitated between 80 and 240 c which is consistent with the range of filling temperatures of fluid inclusions in late fluorite throughout the rift and in jarosite 180 c from pena blanca chihuahua mexico these temperatures along with mineral occurrence require that the jarosite have had a hydrothermal origin in a shallow steam heated environment wherein the low ph necessary for the precipitation of jarosite was achieved by the oxidation of h2s derived from deeper hydrothermal fluids the jarosite also has high trace element contents notably as and f and the jarosite parental fluids have calculated isotopic signatures similar to those of modern geothermal waters along the southern rift isotopic values range from those typical of meteoric water to those of deep brine that has been shown to form from the dissolution of permian evaporite by deeply circulating meteoric water jarosite 34s values range from 24 to 5 overlapping the values for barite and gypsum at the high end of the range and for sulfides at the low end most 34s values for barite are 10 6 to 13 1 and many 34s values for gypsum range from 13 1 to 13 9 indicating that a component of aqueous sulfate was derived from permian evaporites 34s 12 2 the requisite h2so4 for jarosite formation was derived from oxidation of h2s which was likely largely sour gas derived from the thermochemical reduction of permian sulfate the low 34s values for the precursor h2s probably resulted from exchange deeper in the basin with the more abundant permian so42 at 150 to 200 c jarosite formed at shallow levels after the ph buffering capacity of the host rock typically limestone was neutralized by precipitation of earlier minerals some limestone hosted deposits contain caves that may have been caused by the low ph of the deep basin fluids due to the addition of deep seated hf and other magmatic gases during periods of renewed rifting caves in other deposits may be due to sulfuric acid speleogenesis as a result of h2s incursion into oxygenated groundwaters the isotopic data in these sour gas jarosite occurrences encode a record of episodic tectonic or hydrologic processes that have operated in the rift over the last 10 my

anthropogenic sulfate loads in the rio grande new mexico usa abstract the sources of so 4 along a 550 km stretch of the rio grande in new mexico and western texas were investigated using stable s isotopes during 2007 and 2008 the 34 s of dissolved so 4 in the rio grande surface water varied over a narrow range from 1 6 to 0 9 which was consistent with the 34 s of local fertilizers 2 1 to 1 6 and was not consistent with paleozoic evaporite sources of so 4 in regional bedrock 7 6 to 12 9 this is likely due the fact that so 4 is the major component of n p k fertilizers used in the rio grande valley constituting about half of the total fertilizers by mass the so 4 cl ratios of the groundwater system are relatively low 0 06 to 3 compared to the fertilizer source suggesting that more cl is added to the rio grande from geological sources as compared to so 4 in the mesilla basin in southern new mexico we identified zones of mixing between recharging irrigation water with groundwater within the depth range of 50 200 m below the ground surface for this aquifer principal component analysis pca indicated that na k cl concentrations were largely attributable to geological sources and so 4 mg ca concentrations to anthropogenic sources here an additional anthropogenic source of so 4 with a 34 s of 2 7 was linked to anaerobic decomposition of manure on a horse farm in this case so 4 concentrations 800 mg l increased by about three times compared to background so 4 concentrations in groundwater 2 so 4 in fertilizer manufacturing anthropogenic so 4 fluxes to rivers and shallow aquifers from irrigation waters can be significant worldwide

alluvial architecture in headwater streams with special emphasis on step pool topography alluvial mountain streams exhibit a range of channel forms pool riffle plane bed step pool and cascades previous work suggested that these forms exist within discrete and progressively steeper slope classes measurements conducted at over 100 sites in west central and central idaho confirm that slope steepens progressively as one moves from pool riffle to plane bed to step pool and finally to cascades median slope for pool riffle topography is 0 0060 for plane beds 0 013 for step pools 0 044 and for cascades 0 068 there is substantial overlap in the slopes associated with these channel forms pool riffle topography was found at slopes between 0 0010 and 0 015 plane beds between 0 0010 and 0 035 step pools between 0 015 and 0 134 and cascades between 0 050 and 0 12 step pools are particularly striking features in headwater streams they are characterized by alternating steep and gentle channel segments the steep segments step risers are transverse accumulations of boulder and cobbles while the gentle segments pools contain finer material step wavelength is best correlated to step height which is in turn best correlated to the median particle size found on step risers this result differs from past studies that have reported channel slope to be the dominant control on step wavelength the presumed geometry and froude number associated with the features under formative conditions are consistent with the existence field for antidunes and by extension with the hypothesis that step pools are formed by antidunes copyright 2000 john wiley sons ltd

the role of sediment specific gravity and availability on cluster evolution the objective of this experimental study was to account for the role of sediment availability and specific gravity on cluster formation and cluster geometric characteristics spacing and size to isolate the effects of sediment availability and specific gravity on cluster evolution mono sized spheres were used to simulate the cluster evolutionary cycle overall twelve experimental runs were carried out in the laboratory flume six of these tests were performed by using glass spheres specific gravity sg 2 58 and the other six by employing an equal combination of glass and teflon spheres sg 2 12 of the same diameter to evaluate the role of specific gravity on cluster evolution the three sediment availability conditions that were investigated here simulated isolated gravel elements pool riffle sequences and densely packed gravel bed an advanced image analysis technique was employed to track the evolution of cluster microforms and provide quantitative information about the size and shape of clusters and the number of clusters per unit area the results of this study showed that 1 sediment availability affects the architecture and size of cluster microforms and 2 clusters consisting of mono sized sediments start disintegrating at twice the incipient conditions by performing complementary tests for the isolated gravel elements case it was found that the evolutionary cycle of individual clusters could be described as follows in order of increasing stress no cluster two particle cluster comet triangle rhomboid break up copyright 2003 john wiley sons ltd

origin of terrestrial gypsum dunes implications for martian gypsum rich dunes of olympia undae abstract the estancia white sands guadalupe and cuatrocienegas dune fields are among the largest known aeolian gypsum sand dune accumulations on earth and occupy closed drainage basins within the rio grande rift high sedimentation rates of lacustrine gypsum occur in topographic depressions within the closed basins the gypsum accumulations result from long term complex interaction between tectonism climate and a hydrologic cycle that involves geochemical recycling of sulfur from older sedimentary rocks flanking and underlying the basins gypsum precipitation in lacustrine environments is strongly controlled by local groundwater bedrock interaction the ranges of 34s values per mil vs vcdt for gypsum sand in the white sands dune field 12 1 to 13 9 guadalupe dune field 10 2 to 12 5 and cuatrocienegas dune field 14 6 to 15 9 indicate that the main sources of dissolved sulfate are evaporite strata of lower permian middle permian and cretaceous ages respectively a spatial increase of 34s values across the white sands dune field in the direction of prevailing winds matches well with a stratigraphically upward increase of 34s values recorded in lake otero an ancient lake in the basin strata this finding supports previous suggestions that white sands dune field evolved as a result of the step wise deflation of previously stored sediments in lake otero the modern gypsum dune fields are primarily wet eolian systems in which dune accumulation is controlled by a near surface groundwater table which promotes early cementation of the dune accumulations early cementation in the interdune surfaces and to a lesser degree on the dune surfaces reduces the amount of sand available for transport and slows rates of dune migration based on an average migration rate of 2 m year the time needed for a dune at white sands to migrate the downwind distance of the dune field is approximately 6500 years which matches well with other estimates of the initiation of the dune field at approximately 7000 years ago and indicates that white sands likely evolved as a wet aeolian system as on earth gypsum rich dune fields apparently are rare on mars gypsum has been identified only within the olympia undae dune field which encircles a portion of the martian north polar residual ice cap analogous to terrestrial gypsum dunes the gypsum within the olympia undae gypsum rich dunes might have originated from transport and deposition via aeolian processes in this model gypsum rich source sediment could have been formed by confined groundwater or surface water activity and later transported by the wind any subsequent gypsum precipitation in the source area could have been initiated by episodic melting of the martian polar ice cap it is likely that the gypsum was deposited in the olympia undae dunes after the main deflation events that led to formation of the siliciclastic components of the dune field

isotopic composition of sulfate as a tracer of natural and anthropogenic influences on groundwater geochemistry in an urban sandstone aquifer birmingham uk abstract development and management of urban groundwater resources is limited in practice by a lack of knowledge of the nature distribution and sources of groundwater contamination in an urban aquifer that may have had complex land use and abstraction history sulfate is associated with many of the solute sources to urban groundwater and in this study the use of dual isotope 18o and 34s fingerprinting of so 4 2 in groundwater to assess the contribution of different sources to urban groundwater is investigated groundwater 70 locations and surface water samples from the city of birmingham on the triassic sherwood sandstone aquifer have been analyzed for inorganic chemical and so 4 2 isotopic composition isotopic compositions of so 4 2 associated with various solute sources have also been determined sulfate derived from pyrite oxidation during recharge through quaternary drift deposits is characteristically depleted in 18o and 34s compared to other sources and is ubiquitous in unconfined zone groundwater though the contribution from this source has increased markedly following draw down induced by abstraction from the aquifer in unpolluted groundwaters other so 4 2 sources are dissolution of evaporite minerals confined zone and rainfall unconfined zone unfortunately so 4 2 isotopic composition cannot distinguish between made ground i e artificial man made ground usually demolition waste and sewage sources of so 4 2 which constitute the major contributions to so 4 2 in polluted urban groundwater at most sites contributions of so 4 2 from spilt industrial acids do have a distinctive isotopic composition seen at many metal working and former metal working sites estimates of solute contributions derived from these sources derived in this way provide a useful check on the calibration of aquifer and pollutant flux recharge models for urban groundwater

the influence of debris flows on channels and valley floors in the oregon coast range u s a debris flows are one of the most important processes which influence the morphology of channels and valley floors in the oregon coast range debris flows that initiate in bedrock hollows at heads of first order basins erode the long accumulated sediment and organic debris from the floors of headwater first and second order channels this material is deposited on valley floors in the form of fans levees and terraces in channels deposits of debris flows control the distribution of boulders the stochastic nature of sediment supply to alluvial channels by debris flows promotes cycling between channel aggradation which results in a gravel bed morphology and channel degradation which results in a mixed bedrock and boulder bed morphology temporal and spatial variability of channel bed morphology is expected in other landscapes where debris flows are an important process

geogenic arsenic in groundwaters in the western alps summary groundwater arsenic as of geogenic origin in the western alps is generally associated with aquifers in crystalline rock the external crystalline massifs ecm are in particular noted for occurrences of elevated concentrations of as in groundwaters the present study is based on as in groundwaters that have been measured in the ecm in both france and switzerland arsenic bearing sulfide minerals such as pyrite arsenian pyrite and arsenopyrite are the most likely sources of as leached within the crystalline ecm rocks while it is not known how as concentrations vary with time at all of the reported water sources we measured on a weekly basis the concentration of as at one thermal source over a period of one year and found the as concentrations to be variable however the cause of the variability is at present not understood even though many studies have applied 34 s so4 as a tool for understanding as mobilization in the ecm there is no consensus at present finally we present some perspectives on the possible effects of climate change and anthropogenic activities on as mobility in the ecm in particular droughts have the potential to increase as concentrations in groundwaters

characterising physical habitats and fluvial hydromorphology a new system for the survey and classification of river geomorphic units geomorphic units are the elementary spatial physical features of the river mosaic at the reach scale that are nested within the overall hydromorphological structure of a river and its catchment geomorphic units also constitute the template of physical habitats for the biota the assessment of river hydromorphological conditions is required by the european water framework directive 2000 60 wfd for the classification and monitoring of water bodies and is useful for establishing links between their physical and biological conditions the spatial scale of geomorphic units incorporating their component elements and hydraulic patches is the most appropriate to assess these links given the weakness of existing methods for the characterisation and assessment of geomorphic units and physical habitats e g lack of a well defined spatiotemporal framework terminology issues etc a new system for the survey and characterisation of river geomorphic units is needed that fits within a geomorphologically meaningful framework this paper presents a system for the survey and classification of geomorphic units gus geomorphic units survey and classification system aimed at characterising physical habitats and stream morphology the method is embedded into a multiscale hierarchical framework for the analysis of river hydromorphological conditions three scales of geomorphic units are considered i e macro units units sub units organised within two spatial domains i e bankfull channel and floodplain different levels of characterisation can be applied depending on the aims of the survey broad basic and detailed level at each level different complementary information is collected the method is applied by combining remote sensing analysis and field survey according to the spatial scale and the level of description required the method is applicable to most of fluvial conditions and has been designed to be flexible and adaptable according to the objectives e g reach characterisation assessment monitoring and available data e g image resolution the method supports integrated hydromorphological assessment at the reach scale e g the morphological quality index mqi and therefore contributes to better establishing links between hydromorphological conditions at the reach scale characteristic geomorphic units and related biological conditions

morphological effects of local scouring in step pool streams step pool morphology characterizes many high gradient streams in a variety of natural settings but formative processes and evolutionary dynamics are still poorly understood in this paper natural step pool geometry is compared with steep alluvial channels where grade control structures such as check dams and bed sills make the stream profile resemble a natural stepped stream along these channels local scouring due to falling jets forms plunge pools under each structure analogous to natural steps determining the formation of pools in order to test the hypothesis that natural pools are analogous to pools formed below grade control works with respect to their dimensions shape and formative dynamics 37 natural pools and 73 artificial pools were surveyed in 10 mountain streams of the eastern italian alps pools below grade control works featured a transitional zone between the scour hole and the downstream sloping bed marked by a depositional berm when geometric parameters such as maximum pool depth length and step berm distances are normalized to the jet virtual energy no statistically significant differences were detected between natural and artificial systems these results lend support to an upstream forced cascade model for step pool formation where the energy of falling jets controls the geometry of the pools and is therefore regarded as the most important scaling independent variable copyright 2005 john wiley sons ltd