geochemistry of eolian dust and its elemental contribution to lake qinghai sediment abstract located at the midpoint of the asian airborne dust corridor lake qinghai receives substantial dust annually which may impact the biogeochemical cycles of the system in order to determine quantitatively the flux and chemical contributions of dust to lake qinghai sediment dust samples were collected monthly at two sites surrounding the lake from june 2009 to may 2011 the results demonstrate similar chemical compositions of dust samples to the local loess implying strong representativeness of regional dust the average dust deposition flux is 265 7 55 0 g m 2 a constituting 56 6 11 7 of the modern sediment approximating to previous estimates 65 contributions of dust derived elements in the sediment differ substantially with a minimum of 16 7 for sr and a maximum of 83 9 for cu among these elements the contribution of lithophile elements na al k ti mn fe and rb is close to that of the bulk dust the contributions of mobile elements mg ca and sr are low only 16 7 sr 26 1 mg whereas potentially harmful metals cu zn and pb have high contributions 70 3 83 9 seasonal variations of elemental inputs indicate that springtime contributions dominate the annual dust fluxes for all elements into the sediment in agreement with the high dust flux in spring these observations not only quantify the contribution of dust to the sediment of lake qinghai but also highlight the important role of dust in the accumulation of various elements in the sediment especially for potentially harmful metals

relation between soil age and silicate weathering rates determined from the chemical evolution of a glacial chronosequence long term weathering rates rlt were determined from base cation depletion in soil profiles developed on six granitic glacial moraines varying in age from 0 4 to 297 ka in the wind river mountains wyoming weathering rates were found to decrease with soil age t according to the power law equation rlt 15 t 0 71 where rlt is in meq m 2 yr 1 and t is in ka comparable data from the literature are consistent with this function and it is similar to power law equations describing changes in laboratory weathering rates with time on the basis of our study we predict that for a catchment unaffected by anthropogenic inputs and in a steady state with respect to the organic and cation exchange pools rlt should be higher than present day weathering rates derived from stream fluxes rpd by a factor of about 3 4

subtropical denudation rates of granitic regolith along a hill ridge in longnan se china derived from cosmogenic nuclide depth profiles the denudation rates of granitic regolith are essential to our understanding of the geomorphic changes and landscape evolution of a region and for soil resource management we present denudation rates derived from four regolith profiles along a granitic slope in longnan southeastern china using depth profiles of in situ produced cosmogenic 10be and 26al the concentration ranges of 10be 26al and 26al 10be ratio were 2 98 104 1 72 105 atoms g 2 18 105 1 12 106 atoms g and 6 07 7 50 respectively analysis of the results shows that the surface lowering rates are 19 3 41 4 47 4 22 3 m ma for the four profiles from the foot of the hill to the top along the hillslope the mean denudation rate for the four profiles is 30 m ma this rate is lower than that derived by other methods in nearby areas and also lower than the mean global denudation rate in basins deduced from 10be levels in river sediment this suggests an unevenness of the erosion process on a basin scale the denudation rate at the ridge is twice that estimated for the summit and the foothill indicating that the hillslope has not reached its steady state thus the slopes below the ridge may become smoother and the ridge sharper in the long term landscape evolution the difference in topography may account for the variance among the profiles in addition bioturbation may have contributed to the lower concentration in the surface layer at the foot of the hill producing a higher denudation rate than the average for the basin the concentration of insoluble element zr in the soil surface layer and fresh bedrock suggests that chemical weathering accounts for about one third of the denudation rate

major element chemistry of the huai river basin china the chemistry of major ions ca mg na k hco3 so4 cl and si in the water of the huai river basin was studied based on samples from 52 sites from nine different water bodies in july 2008 ions and total dissolved solids tds displayed clear spatial patterns with lower concentrations in the south and higher in the north of the basin the same conditions were also found in the east line of south north water transfer project snwtp in this region the huai river main channel and hongze lake have moderate ion concentrations relative to the whole basin tds concentrations versus the weight ratios of na na ca and ternary ions demonstrate that the southern rivers shi r and pi r are mainly controlled by the weathering of carbonates whereas the northern water systems guo r shaying r nansi lake and its tributaries are dominated by the weathering of evaporites the huai river main channel hongze lake and the east line of snwtp are synergistically influenced by weathering of evaporites and carbonates yet hongze lake and the east line of snwtp are mainly controlled by evaporation and crystallization processes this study also confirmed that the huai river is the geographic division between southern and northern china most rivers of this basin have very high ionic composition relative to the global median and other world rivers the spatial patterns and ionic composition also suggest that intensive anthropogenic activities in northern areas of this basin are well characterized a comparison with who and chinese standards for drinking water indicates that the northern water systems of this basin are not suitable for use as drinking water sources and pollution control should be improved and enhanced in northern areas of the basin crown copyright c 2010 published by elsevier ltd all rights reserved

rates of weathering and soil formation abstract a new method for evaluation of rates of weathering and soil formation is proposed for the elements derived exclusively from rocks geochemical mass balances were assumed to exist between parent rocks soils and river waters on both global and regional scales seven geochemical mass balance equations which include the rate of weathering and soil formation as unknown quantities were set up using the mean contents of seven major elements al fe ca k mg na and si in the earth s crust soils and river waters respectively solutions of 21 sets of simultaneous equations made from the seven equations gave 21 sets of values of rates of rock weathering and soil formation reliability of the results were checked by the criterion that the rate of rock weathering is higher than that of soil formation and both of them have to be positive values the ranges of results which satisfied the criterion were 520 1310 mean 1100 kg ha 1 yr 1 for the rate of rock weathering and 370 1290 mean 700 kg ha 1 yr 1 for the rate of soil formation on a global scale the comparison with the reported value of the mean rate of erosion 906 kg ha yr 1 suggested that the results of the calculations were reliable by applying this method we could calculate the annual rate of soil formation not only on a global scale but also on a regional scale some regional examples in small watersheds were tested the rate of soil formation was 569 kg ha 1 yr 1 in hubbard brook watershed new hampshire usa and 2700 5700 kg ha 1 yr 1 in iu river watersheds in southwestern japan the rates of weathering and soil formation in watersheds are basic items of information for establishing sustainable watershed management practices to protect soil from degradation to control desertification and to minimize the effects of acid precipitation

atmospherically transported elements and deposition in the southeastern united states local or transoceanic abstract saharan dust is persistently transported and deposited in ecosystems of the western atlantic ocean this dust is an aggregate of clay and quartz particles cemented with fe oxides samples collected and analyzed from mali central africa the azores the caribbean and the eastern united states document the levels of minor and trace metals in the dust metal loadings particularly the toxic elements hg and as are significantly higher than average crustal rocks over the past decade the focus has been to understand the cycling of hg in south florida but as has received very little attention arsenic in the sediment deposited in the past decade in south florida averages 14 mg kg and appears to be correlated with al a proxy for dust the largest available aerosol data set containing as is the improve interagency monitoring of protected visual environments data set the average concentrations in aerosols collected during this program range from 17 mg kg in the virgin islands to 79 mg kg at chassahowitzka florida at chassahowitzka most of the as appears to be associated with organic c if it is assumed that the concentrations in mali dust and in the aerosols in the virgin islands are indicative of soil dust then the higher values at chassahowitzka may be derived from local or regional sources a simple calculation indicates that african dust supplies about 25 of the as deposited from aerosols in the southeastern united states comparison of the average yearly as concentrations measured in the virgin islands and everglades shows a negative relationship with the north atlantic oscillation nao this relationship demonstrates the influence of climate on the transport and deposition of aerosols to the southeastern united states

the fluvial geochemistry of the rivers of eastern siberia i tributaries of the lena river draining the sedimentary platform of the siberian craton abstract the response of continental weathering rates to changing climate and atmospheric pco 2 is of considerable importance both to the interpretation of the geological sedimentary record and to predictions of the effects of future anthropogenic influences while comprehensive work on the controlling mechanisms of contemporary chemical and mechanical weathering has been carried out in the tropics and to a lesser extent in the strongly perturbed northern temperate latitudes very little is known about the peri glacial environments in the subarctic and arctic thus the effects of climate essentially temperature and runoff on the rates of atmospheric co 2 consumption by weathering are not well quantified at this climatic extreme to remedy this lack a comprehensive survey has been carried out of the geochemistry of the large rivers of eastern siberia the lena yana indigirka kolyma anadyr and numerous lesser streams which drain a pristine high latitude region that has not experienced the pervasive effects of glaciation and subsequent anthropogenic impacts common to western eurasia and north america the scale of the terrain sampled in terms of area is comparable to that of the continental united states or the amazon orinoco and includes a similarly diverse range of geologic and climatic environments in this paper the chemical fluxes from the western region the very large ancient and geologically stable sedimentary basin precambrian to quaternary of the siberian platform will be presented and compared to published results from analogous terrains in the tropical basins of china while the range in the chemical signatures of the various tributaries included here 60 sampled is large this mainly reflects lithology rather than the weathering environment the areal chemical fluxes are comparable to those of the chinese rivers being dominated by the dissolution of carbonates and evaporites the net consumption of atmospheric co 2 by aluminosilicate weathering is minor as it is in the tropical basins it is much smaller than in active orogenic belts in similar latitudes e g the fraser and yukon but comparable to those of the mackenzie tributaries that drain the eastern slope of the rockies lithology exerts the dominant influence in determining the weathering yield from sedimentary terrains and for a largely carbonate evaporite terrain climate does not have a direct effect

an application of heavy mineral analysis to lithostratigraphy and reservoir modelling in the oseberg field northern north sea abstract three distinctive detrital garnet associations have been recognized in brent group sandstones of the oseberg area northern north sea by means of electron microprobe analysis these have lithostratigraphical significance with one association occurring in the etive and oseberg formations one in the ness formation and one in the tarbert formation the stratigraphic variation in garnet population reflects changes in provenance and in the pattern of distribution of clastic detritus although a detailed reconstruction of source areas is not possible on the basis of the available information differentiation of ness and etive oseberg formations by means of detrital garnet geochemistry has enabled the recognition of fluvial chanbel sandstones belonging to the ness formation which have cut down into the etive formation shoreline complex this provides direct evidence of communication between ness and etive oseberg adding an extra degree of sophistication to the geological input for reservoir simulation a strong permeability anisotropy can be modelled around the fluvial channels and a net sand volume can be modelled in agreement with channel orientation

characterization of the composition of dust fallout and identification of dust sources in arid and semiarid north china abstract a source analysis to characterize the composition of dust fallout in arid and semiarid north china an important source area of dust for east asia was performed monthly samples were obtained from april 2001 to march 2002 at 29 sites in sandy and gobi deserts steppes and loess areas and the following elements were analyzed ce co cs eu fe hf lu nd rb sc ta tb th as la na sb sm u yb al ca mg mn ti and v although the dust compositions differed it was difficult to determine the potential dust source areas based solely on the elemental fingerprints of the dust principal components analysis showed that at most sites sm sc la ce eu and th were most strongly correlated r 0 7 with other elements whereas crustal elements such as al fe and ti were only strongly correlated with the other elements at a few sites of the 26 elements that we analyzed maybe only sb was representative of anthropogenic pollution but pollutant sources were unclear because at most sites in different months the crustal derived elements and those derived from anthropogenic pollutants always appeared synchronously creating difficulties and high uncertainties in source identification

geochemistry of the pliocene red clay formation in the chinese loess plateau and implications for its origin source provenance and paleoclimate change abstract recent field observations and sedimentological studies suggest the eolian origin of the late tertiary red clay formation underlying the pleistocene loess soil sequence in the loess plateau thereby extending the wind blown record from 2 6 ma down to 7 0 ma in north central china to address the source provenance of the red clay major and trace element concentrations were analyzed on the samples from a north south loess transect of the loess plateau and a red clay section at jiaxian results show that there is a good agreement of both major and trace element compositions between the last glacial interglacial loess soil units and the jiaxian red clay record the ree distribution patterns of the loess soil and red clay samples are remarkably similar in shape with enriched lree and fairly flat hree profiles and clear negative eu anomaly the geochemical features of the red clay are also identical to those of upper continental crust these chemical characteristics provide further evidence for eolian sedimentation of the red clay from the relations both between na2o al2o3 and k2o al2o3 ratios and between u pb and th pb ratios the eolian loess and red clay materials must have been subject to thorough sedimentary differentiation and moderate chemical weathering in the source area the chemical similarity between soil unit s1 and the red clay implies that such an environment as occurred in the last interglacial period may have already formed in northwestern china during the late tertiary comparison of down section variations in elemental ratios with field observations of pedogenic development of the red clay suggests that cao al2o3 sr rb and sr ba are more sensitive to climate changes than magnetic susceptibility and can be used to reconstruct the climate history of the late cenozoic

control of dust emissions by geomorphic conditions wind environments and land use in northern china an examination based on dust storm frequency from 1960 to 2003 the degree to which dust emissions are controlled by geomorphic conditions wind environments and land use was investigated using the dust storm frequency dsf and data from more than 300 meteorological stations throughout northern china our analysis showed that most dust emissions originated in gobi deserts that developed in piedmont alluvial fans of the kunlun qilian and helan mountains dust emissions are low from other gobi desert regions such as the northern gurbantunggut and eastern taklimakan where high vegetation coverage restrained dust emissions or where dust size particles are not abundant after a long period of strong wind erosion sandy deserts with relatively high vegetation coverage or an extensive cover by mobile sands are not a major dust source although the highest dust emissions did not appear in regions with the highest wind energy dsf trends in each region from 1960 to 2003 were closely related to local wind activity dsf was low in regions with high levels of human activity where the mean dsf from 1960 to 2003 did not exceed 4 days year even from the 1960s to the early 1970s the period with the greatest dsf frequency did not exceed 8 days year which indicates that extensive land use did not contribute to dsf the low dsf in these areas might result from the fact that although land use could produce abundant fine soil fractions vegetation coverage and soil moisture remained higher than in the gobi deserts of arid china thereby decreasing dust storm occurrence

external supply of dust in the taklamakan sand sea northwest china reveals the dust forming processes of the modern sand sea surface abstract as one of the most important global dust sources the sand sea and neighboring areas contain multiple types of surfaces that release dust such as dry lakes and riverbeds degraded oases and gobi surfaces to understand the link between those active sources of dust and the dust formation process of the sand sea surface we investigated dust fallout characteristics at a height of 3 m and rare earth element ree geochemistry of different landforms in the taklamakan sand sea which has frequent dust events the seasonal fallout and concentrations of pm10 particles and monitoring results of their land surface concentrations show that the taklamakan sand sea is surrounded by dust sources and it s an important dust deposit area the particle size characteristics of dust sediment suggest that the dust conveying capacity of the taklamakan sand sea is much stronger than that of the gobi and degraded surfaces on the sand sea edge during sand dust storms the fine dust fraction

weathering processes and the composition of inorganic material transported through the orinoco river system venezuela and colombia abstract the composition of river borne material in the orinoco river system is related primarily to erosion regime which in turn is related to tectonic setting especially notable is the contrast between material derived from tectonically active mountain belts and that from stable cratonic regions for a particular morpho tectonic region the compositional suites of suspended sediment bed material overback deposits and dissolved phases are fairly uniform are are typically distinct from whose of other regions for each region a consistent set of chemical weathering reactions can be formulated to explain the composition of dissolved and solid loads in developing these formulations erosion on slopes and storage of solids in soils and alluvial sediments are important considerations compositionally verymature sediment is derived from areas of thick soils where erosion is transport limited and from areas where sediments are stored for extended periods of time in alluvial deposits compositionally immature sediments are derived from tectonically active mountain belts where erosion is weathering limited weathering limited erosion also is important in the elevated parts of the guayana shield within areas of sleep topography compared to the mountain belts sediments derived from elevated parts of the shield are more mature a greater degree of chemical weathering seems to be needed to erode the rock types typical of the shield the major element chemistry and mineral composition of sediment delivered by the orinoco river to the ocean are controlled by rivers that have their headwaters in mountain belts and cross the llanos a region of alluvial plains within the foreland basin the composition of sediments in rivers that drain the shield seems to be established primarily at the site of soil formation whereas for rivers that drain the mountain belts additional weathering occurs during s episodes of storage on alluvial plains as sediments are transported across the llanos to the main stem of the orinoco after mixing into the main stem there seems to be little subsequent alteration of sediment

drainage basin weathering and major element transport of two large chinese rivers huanghe and changjiang long term records show high concentrations of dissolved major elements in the changjiang yangtze river and the huanghe yellow river the huanghe drainage basin is characterized by intense weathering and erosion of carbonates and evaporites while weathering and erosion of carbonates and silicates over the drainage basin is the main source of major elements in the changjiang the rock soil composition and tectonics of the drainage basin are more important than atmospheric precipitation in affecting major element composition of these two rivers compared with other large rivers of the world the high suspended sediment and major element loads of the changjiang and huanghe reveal intense physical and chemical erosion over the chinese continent

the control mechanisms of erosion and weathering at basin scale from cosmogenic nuclides in river sediment the study of a sample of river sediment enables the determination of spatially averaged denudation rates that provide an exceptional perspective on erosion and weathering processes that have taken place within a landscape these measurements are done with in situ produced cosmogenic nuclides e g 10be 26al mostly in quartz from alluvial sediment cosmogenic nuclides are produced when secondary cosmic rays interact with the very uppermost layer of the earth s surface they are produced within a characteristic depth scale of about 1 m which means that the measured concentrations record an integrated denudation history while material passed through this depth interval depending on the denudation rate the resulting integration time scales are 103 to 105 years and one obtains a robust long term estimate of natural denudation that is relatively insensitive to short term changes the last 10 years have seen significant research activity using these methods and an array of fascinating tectono geomorphologic and geochemical insights are emerging amongst these is the ability to identify the physical and chemical processes with which a landscape responds to tectonic activity or climate change a compilation of world wide denudation rates in non glaciated areas that however does not yet include some of the world s most active mountain belts has resulted in the following findings some of which have been unexpected 1 no obvious relationship between precipitation or mean annual temperature and total denudation is apparent 2 topographic relief alone does not result in high rates of denudation 3 denudation rates are high in areas of landscape rejuvenation that is triggered and controlled by tectonic activity faulting escarpment formation and retreat rifting surface uplift 4 rates of weathering using a combination of cosmogenic nuclides and zirconium normalised cation loss balances co vary primarily with physical erosion rates and much less with temperature or precipitation 5 in some areas of high land use short term rates from river load gauging exceed those from cosmogenic nuclides by several orders of magnitude which serves to highlight the severity of geomorphic change caused by human action in the future the control mechanisms over denudation will be determined on all spatial scales ranging from the single soil section to entire river basins the same analysis can be done back through time on well dated terraces lake records and marine sediment cores which is possible with 10be for the past 1 2 my the rates obtained will be used to develop a quantitative understanding of tectonic geomorphologic and geochemical landscape processes which in turn is a prerequisite to design and calibrate models of the response of landscapes to tectonic climate and anthropogenic forcing

the origin of faceted garnets in sandstones dissolution or overgrowth faceted garnets from a wide range of geological ages environments and locations have been studied in polished grain mounts by a combination of backscattered electron microscopy and elemental mapping using energy dispersive x ray analysis in all cases the areas apparently showing positive relief on the faceted garnet surfaces are compositionally identical to the adjacent grain cores despite a wide variation in detrital garnet compositions in one case zoning within the grain core can be traced into the faceted areas on the grain surface thus faceted areas must be considered to form part of the original detrital grains together with previously published studies on experimental garnet etching thermodynamic conditions for garnet growth textural relationships between faceted garnets and authigenic and detrital phases and distribution of faceted garnets in the subsurface this paper provides conclusive proof that faceted garnet surfaces form as a result of dissolution not overgrowth

sedimentary fe mn oxyhydroxides as paleoceanographic archives and the role of aeolian flux in regulating oceanic dissolved ree in the marine environment authigenic ferromanganese fe mn oxides precipitate from seawater incorporating many dissolved trace elements such as nd pb whose isotopic composition is a direct proxy for ambient seawater thus isotopic studies of the fe mn oxyhydroxide component leached from sedimentary records can provide information on changes in erosional input or ocean circulation changes such studies may be complicated however by the presence of detrital material containing a fe mn oxide component which may mask the true seawater signal in addition the formation of fe mn oxyhydroxides in the marine environment remains poorly understood in particular the phase carbonates detrital particles that controls the delivery of authigenic fe mn oxides to the sediments has not yet been determined in this study we have analysed the ree and nd isotopic compositions of fe mn oxyhydroxide fractions dispersed in marine sediment cores from the cape and angola basins in the se atlantic cruise images ii for the angola basin deep sea core located at 1000 km south of the congo river mouth both the ree and nd isotopic compositions nd measured in recent fe mn oxyhydroxide fractions are typical of congo river borne fe mn oxides this shows that preformed fe mn oxides associated with detrital fractions can locally contaminate the seawater signal recorded by authigenic oxyhydroxides by contrast examination of ree distributions nd isotope data and mass accumulation rates in cape basin sediments shows paradoxically that the flux of fe mn oxides to sediments is controlled by aeolian particles from the nearby namib desert even though their ree and nd compositions point clearly to an authigenic origin it is proposed that partial dissolution of aeolian dust occurs in the water column releasing into solution its easily leachable fe mn component the dissolved fe2 and mn2 would then fuel the reprecipitation of authigenic fe mn oxyhydroxides scavenging additional dissolved trace elements from the ocean most probably from deep water masses in this case calculations suggest that aeolian deposition acts as a net sink for dissolved nd in the cape basin rather than a source and allows us to estimate the rate of removal of dissolved nd associated with atmospheric deposition yielding a global oceanic residence time for nd nd of between 500 and 1400 years

hydrogeochemistry of three watersheds the erlqis zhungarer and yili in northern xinjiang nw china abstract in the arid region of northern xinjiang one of the least studied areas in china three watersheds namely those of the yili zhungarer and erlqis have become the focus of attention due to rapidly increasing human population and water demands the hydrogeochemistry of natural water from the three watersheds was investigated the ionic chemistry of natural waters from these watersheds changes considerably on a regional scale the waters are neutral to alkaline in nature and most of them are soft fresh waters the total dissolved solid tds varies over two orders of magnitude with a mean value of 580 mg l about 1 2 times and 4 6 times those of the huanghe yellow river and the world spatial median respectively but only 40 and 0 8 of those of the tarim and the western alashan watersheds respectively much of the solutes and physicochemical parameters in these waters are under the highest desirable limits of the world health organization who for drinking purpose and a plot of sodium adsorption ratio versus ec shows that most waters are of good water quality for irrigation water rock interaction and saturation index si for selected minerals are evaluated the si of these natural waters is out of equilibrium undersaturated with respect to major carbonates calcite and dolomite and evaporites gypsum and halite the high concentrations of alkali earth metals alkalinity and the high ca mg na k and na cl ratios indicate that the release of major solutes in these waters is controlled largely by dissolution processes of carbonate and partly by silicate weathering while cation exchange reactions soil salt leaching and evaporation processes also play an important role the effects of local pollution are minimal in the montane and piedmont areas of these watersheds but are significant in the oases and central areas of the drainage basins

quantitative analysis of detrital modes statistically rigorous confidence regions in ternary diagrams and their use in sedimentary petrology abstract detrital modes are the basic type of quantitative data used in sedimentary petrology they represent estimates of the petrographic framework composition of sand or sandstone obtained by point counting of thin sections at present geological inferences from analysis of these numerical data are semi quantitative only because many of the data processing methods employed in sedimentary petrology lack a firm theoretical basis a review of existing methods reveals a number of fundamental statistical problems associated with the use of univariate statistics and the construction of so called hexagonal fields of compositional variation it is shown that these problems can be overcome by using multivariate methods that honour the non negativity and unit sum constraints on compositional data and incorporate the covariance structure spread in compositional data can be modelled on two levels 1 by regarding the grain as unit of observation and the total point count as a sample from a multinomial distribution 2 by regarding the total count as unit of observation and a set of counts as a sample from an additive logistic normal distribution numerical methods are presented for constructing statistically rigorous confidence regions in ternary diagrams by inversion of significance tests for these two distributions statistical analyses of the framework composition and heavy mineral assemblages of modern beach and river sands illustrate their use the case histories are followed by a brief overview of popular multivariate methods for reconstructing sediment provenance

rare earth elements of aeolian deposits in northern china and their implications for determining the provenance of dust storms in beijing this paper contributes to a better understanding of the source of dust storms in northern china and the relationship between these sources and other aeolian sediments in this region sediment samples in potential source areas were collected from the hunshandake sandy land heaven desert the loess deposits of the bashang area the mountainous basins and valleys north of beijing and from the badain jaran desert and hulunbaier sandy land fig 1 dust samples were collected in beijing during two dust storms in march 2002 and april 2006 the laboratory methods used in this study included measurements of abundance of trace elements in particular the rare earth elements rees mineral assemblages and grain size the ree contents eu and ce anomalies show clear differences between various deposits provenance is considered to be the key factor influencing ree patterns in the study areas the ree abundances and patterns indicate that the aeolian sand north of beijing such as in the heaven desert is mainly of local origin rather than from desert encroachment from the north the mineral grains carried in dust storms however are highly mixed and may come partly from local sources but mainly from distant desert regions in western china

geochemistry of the upper han river basin china 3 anthropogenic inputs and chemical weathering to the dissolved load abstract the study focuses on the chemical and trace element compositions of the dissolved load in the upper han river the water source area of the middle route of china s south to north water transfer project water samples were collected in the high flow period and analyzed for cations by inductively coupled plasma atomic emission spectrometer and anions by ionic chromatography respectively in order to understand the contributions of anthropogenic activities and rock weathering to river solutes as well as the associated co2 consumption in the carbonate dominated basin the river waters have a mean tz of 2674 eq l ranging from 1034 3 to 4611 6 eq l which is significantly higher than that of the global river waters calcium and hco3 followed by mg2 and so42 dominate the chemical composition of major species in the basin there are three major reservoirs carbonates silicates and agriculture urban effluents contributing to the dissolved load in the river chemical weathering rate is approximately 53 1 t km2 yr with respective carbonate and silicate weathering rates of 47 5 t km2 yr 19 8 mm kyr and 5 6 t km2 yr 2 1 mm kyr the co2 consumption is estimated to be 64 69 109 mol yr and 9 69 109 mol yr by carbonate and silicate weathering respectively the contribution of the anthropogenic inputs to the dissolved load is estimated to be 16 7 demonstrating the strong impacts of human activities on water chemistry

major ion chemistry of the ganga brahmaputra river system weathering processes and fluxes to the bay of bengal the ganga brahmaputra one of the world s largest river systems is first in terms of sediment transport and fourth in terms of water discharge a detailed and systematic study of the major ion chemistry of these rivers and their tributaries as well as the clay mineral composition of the bed sediments has been conducted the chemistry of the highland rivers upper reaches of the ganga the yamuna the brahmaputra the gandak and the ghaghra are all dominated by carbonate weathering ca mg and hco3 account for about 80 of the cations and anions in the lowland rivers the chambal the betwa and the ken hco3 excess over ca mg and a relatively high contribution of na k to the total cations indicate that silicate weathering and or contributions from alkaline saline soils and groundwaters could be important sources of major ions to these waters the chemistry of the ganga and the yamuna in the lower reaches is by and large dictated by the chemistry of their tributaries and their mixing proportions illite is the dominant clay mineral about 80 in the bedload sediments of the highland rivers kaolinite and chlorite together constitute the remaining 20 of the clays in the chambal betwa and ken smectite accounts for about 80 of the clays this difference in the clay mineral composition of the bed sediments is a reflection of the differences in the geology of their drainage basins the highland rivers weather acidic rocks whereas the others flow initially through basic effusives the ganga brahmaputra river system transports about 130 million tons of dissolved salts to the bay of bengal which is nearly 3 of the global river flux to the oceans the chemical denudation rates for the ganga and the brahmaputra basins are about 72 and 105 tons km yr 1 respectively which are factors of 2 to 3 higher than the global average the high denudation rate particularly in the brahmaputra is attributable to high relief and heavy rainfall

spatial and temporal analysis of water chemistry records 1958 2000 in the huanghe yellow river basin 1 the chemistry of major dissolved ions ca2 mg2 na k hco3 so42 cl and dissolved silica sio2 in the river water of the huanghe yellow river china was studied from historical records at 100 stations in the drainage basin for the period 1958 2000 not all the parameters were continuously monitored during the entire period this river system 750 000 km2 presents an exceptional temporal and spatial water chemistry variability compared to other major rivers the total dissolved solid tds concentration of the huanghe varied over 2 to 3 orders of magnitude throughout the basin with a median tds concentration of 452 mg l which is about 4 times the world spatial median value wsm in particular the concentrations of na k so42 and cl were 10 20 times higher than in other major world rivers similar to the changjiang yangtze river and many other himalayan rivers the tds at a given station is seasonally variable and inversely related to river runoff with a variation factor less than 2 0 despite a water dilution of fourfold to fivefold in the summer flood season in addition to chemical weathering of sedimentary rocks evaporation and fractional crystallization were found to be the major natural process controlling the major element chemistry of the huanghe owing to the abundance of loess and clastic rocks under arid and semiarid climates a persistent increasing trend from year to year has been observed in the concentrations of tds and all the salts except for hco3 at all main channel stations except for the uppermost lanzhou the rate of increase in the tds concentration was the highest in the middle reaches 10 52 mg l yr 1 at toudaoguai and remained to be unusually high in the lower reaches 5 5 mg l yr 1 at stations luokou and lijin the increasing trend coincided with a significant decrease in water discharge at most of the main channel stations in the past 40 years and is attributed to increasing regulations of reservoirs and intensive water withdrawal for irrigation and diversions as well as many other anthropogenic processes despite the increasing trend in tds concentrations the seaward tds flux to the sea by the huanghe has decreased dramatically from more than 20 109 kg yr in the 1960s to less than 10 109 kg yr at present due to the sharp decrease in water discharge sometimes completely dried up in the lower reaches of the river the significant decreases in sea ward fluxes of water and dissolved salts are expected to have profound physical ecological and socio economic impacts on the lower reaches of the river the coastal areas and the bohai sea

weathering and soil formation rates based on geochemical mass balances in a small forested watershed under acid precipitation in subtropical china abstract accurate weathering and soil formation rates in natural environment and their quantitative dependences on environmental factors remain poorly understood despite their significance in the understanding of biogeochemical cycling and for the development of sustainable land use strategies in the present study rates of weathering and soil formation on granite and their dependences on acid precipitation were studied in a small forested watershed fengxingzhuang fxz in subtropical china using geochemical mass balance equations and multiple regression analysis atmospheric input from wet and dry deposition and stream output through runoff were monitored from march 2007 to february 2010 the physical and chemical properties of soil and granite rock were also determined the results show that acid precipitation is very severe in the fxz forested watershed by bringing in h both directly from strong acids 741 mol ha 1 yr 1 and indirectly from nitrogen and sulfur transformations 831 mol ha 1 yr 1 which serves as an important driving force for weathering and soil formation the fxz forested watershed currently remains as a net sink for hydrogen ion inorganic nitrogen sulfur potassium and aluminum with a mean of 0 07 1 60 1 48 0 10 and 0 44 g m 2 yr 1 respectively and a net source for dissolved silicon sodium calcium and magnesium with a mean of 5 33 2 95 1 04 and 0 34 g m 2 yr 1 respectively based on geochemical mass balance equations the weathering rate of granite r in the fxz forested watershed is 1 04 0 65 t ha 1 yr 1 but varying according to the changes in environmental conditions such as rainfall amount air temperature and h input within different seasons correspondingly soil formation rate s is 0 95 0 69 t ha 1 yr 1 which equals to 0 066 0 048 mm yr 1 of soil depth suggesting a base for establishing the soil loss tolerance value in the granitic region of subtropical china acid precipitation significantly promotes weathering and soil formation by the input of rainfall and h although air temperature effects occur simultaneously a proposed model that quantitatively describes weathering and soil formation rates is a combined product of rainfall amount x 1 h input x 2 and air temperature x 3 resulting from multiple regressions r 0 00045 x 1 0 026 e 0 0022 x 2 0 012 e 0 0459 x 3 s 0 00035 x 1 0 029 e 0 002 x 2 0 016 e 0 0424 x 3 which improves the prediction from simple linear regression

mineralogical variation of sr nd isotopic and elemental compositions in loess and desert sand from the central loess plateau in china as a provenance tracer of wet and dry deposition in the northwestern pacific we determined sr and nd isotopic compositions and major trace and rare earth element ree compositions of evaporite and detrital minerals in loess and desert sand from the central loess plateau clp where 80 of the loess deposits in china are found the loess exhibited a narrow range of variation in 87sr 86sr 0 715 0 001 a sequential extraction experiment on the loess however showed that water and acetic acid hoac soluble minerals mainly halite and calcite hydrochloric acid hcl soluble minerals chlorite and phosphate and hcl insoluble minerals illite kaolinite smectite vermiculite feldspar and quartz have distinct 87sr 86sr ratios approximately 0 7111 0 0004 0 7141 0 0004 and 0 7195 0 0010 respectively the water and hoac soluble ratios were regionally uniform and were close to the 87sr 86sr value of river water from the huanghe yellow river and the maximum 87sr 86sr value of spring rainwater in japan suggesting selective solution of eolian halite and calcite into the chinese river water and into the japanese rainwater the mineralogical elemental and sr nd isotopic compositions of hcl soluble and insoluble minerals in the clp loess were different from those of the northern desert sand but were indistinguishable from those of its fine grained fraction supporting the view that the loess is composed of the fine grained fraction of desert sand that was transported to the southeast in the atmosphere the 87sr 86sr end and gd yb values of hcl insoluble minerals in the clp loess were almost identical to those of airborne dust soil minerals and deep sea sediments in the northwestern pacific considered to be of eolian origin suggesting dissolution of the loess evaporite minerals during atmospheric transportation these relationships demonstrate the usefulness of sr isotopes of water and hoac soluble minerals and sr and nd isotope ratios and ree compositions of acid insoluble minerals in loess as provenance markers for wet and dry deposition respectively

application of organic geochemistry to sequence stratigraphic analysis four corners platform area new mexico u s a abstract the sequence stratigraphic model of sedimentation postulates the existence of a time condensed section deposited at very low sedimentation rates occurring in the uppermost transgressive systems tract and the lowermost highstand systems tract this condensed interval has of often been equated with zones of increased hydrocarbon source potential and invoked as a petroleum source rock often in the absence of supporting geochemical data in this study isotopic molecular lithostratographic and paleontological data are presented for 51 outcrop samples from a cenomanian turonian section at red wash new mexico u s a interpretations are made within a sequence stratigraphic framework ramp model sedimentation rates are estimated in order to define the location of the codensed intervalm for comparison with the zone of best source potential approximately 80 m of section were sampled the interval of maximum flooding and westernmost progression of the cretaceous seaway shoreline as defined by paleontological data is stratigraphically immediately below the occurrence of discontinuities in total organic carbon content hydrogen index and fluoramorphinite concentration in the kerogen the overall transgressive event is accompanied by increases in relative concentrations of 24 n propylcholestane total steranes and rearranged steranes these changes are consistent with a simultaneous decrease in the ratio of terrigenous organic matter to marine algal input as westward flooding proceeded the simultaneous occurrence of discontinuities in kerogen related parameters and continuous trends in bitumen related parameters probably implies mobilization of soluble organic matter across the flooding event boundary sedimentation rate estimates for six intervals in the red wash section show that the best oil source rock potential occurs immediately above the condensed interval and maximum flooding surface within the highstand systems tract previous studies of cretaceous sections in other portions of the western interior basin have located the best source rock potential below the condensed zone we conclude that the equivalence between source rock occurence and condensed sections as applied through the sequence stratigraphic model requires modification before the model may be used to predict the location of oil source rocks in a ramp setting in this respect it is critical that the data in sequence stratigraphic studies be used to define the model and not allow the model to dictate the interpretation of the data

neutralization of atmospheric acidity by chemical weathering in an alpine drainage basin in the north cascade mountains the most important weathering reaction that neutralizes incoming atmospheric acidity in the south cascade lake basin is weathering of calcite which occurs in trace amounts in veins on joint surfaces and as a subglacial surficial deposit although the basin is underlain by igneous and high grade metamorphic rocks weathering of plagioclase is quantitatively negligible the principal silicate weathering reaction is alteration of biotite to vermiculite these conclusions are based on mass balance calculations involving runoff compositions and on mineralogical observations for predictive modeling of the effects of increased acid deposition it is essential to identify the relevant weathering reactions feldspar weathering is commonly not an important source of solutes in alpine basins underlain by granitic rocks 30 references 2 figures 1 table

major element chemistry of the changjiang yangtze river the chemistry of major elements ca mg na k hco3 so4 cl and si in the river water of the changjiang yangtze river was studied based on continuously monitored data at 191 stations in the drainage basin for the period 1958 1990 the results show that the total dissolved solid tds concentration of the changjiang varies over an order of magnitude throughout the basin 49 7 518 1 mg l with a medium tds concentration of 205 9 mg l about three times the global average in contrast the tds at a given main channel station varies only slightly in different seasons with a variation factor less than 2 0 despite a substantial water dilution in the summer flood season the major element chemistry of the changjiang is mainly controlled by rock weathering with the anion hco3 and the cation ca dominating the major ion composition due to the abundance of carbonate rocks in the basin a persistently increasing trend has been observed in the concentrations of so4 and to a lesser extent cl in the changjiang a signature of considerable anthropogenic impacts e g acid deposition flux calculations at datong the most downstream main channel station without tidal influence indicate that the changjiang transports ca 154 106 tons year of tds to the sea second only to the amazon in the world

dust sources in arid and semiarid china and southern mongolia impacts of geomorphological setting and surface materials abstract analysis of the geomorphological settings and surface materials in arid and semiarid china and southern mongolia revealed that the dominant dust sources are gobi deserts and alluvial fans adjacent to gobi deserts in the piedmonts of the kunlun qilian helan and gobi altai mountains these areas have persistent supplies of dust sized particles deposited by intermittent floods from the mountains and fine materials are also generated by weathering and aeolian processes acting on the coarse fractions of gobi surfaces clear spatial differences in mineral types and contents and in the salt contents of surface materials also strongly affected the intensity of dust emissions inconsistencies in monitoring simulation and calculation of dust emissions in previous studies of northern china and mongolia may have been caused by insufficiently detailed considerations of variations in the geomorphological setting where the geomorphological settings in these areas are not considered in sufficient detail deviations arise in the estimation and prediction of dust using current models although the present study did not quantify the persistence and replenishment of dust sources in the study area our conclusions about the importance of geomorphology can improve future studies of dust sources and controlling factors improve assessments of the effects of climate change on dust emissions and facilitate the interpretation of paleoclimate records

the fluvial geochemistry of the rivers of eastern siberia ii tributaries of the lena omoloy yana indigirka kolyma and anadyr draining the collisional accretionary zone of the verkhoyansk and cherskiy ranges fundamental to the global carbon cycle over geologic time scales is the control of atmospheric co2 by aluminosilicate weathering much of the information on the rates of this process comes from rivers in the tropics and subtropics to understand the possible climatic influences systematic studies are needed for the arctic subarctic regions this is the second in a series of papers addressing this problem by systematic studies of the pristine rivers of the russian far east the region to the east of the siberian platform huh et al 1998 is a geologically complex terrain formed by the mesozoic collision and accretion of the siberian and kolyma plates because of the arid continental climate it has not been glaciated in the recent past thus it is possible to study weathering processes in an arctic environment dominated solely by cryogenic interactions without contamination by heterogeneous components derived from scouring glaciers all the major rivers and their tributaries in this area have been sampled on expeditions to individual basins 100 samples on a reconnaissance basis at falling stage usually in july and august the total dissolved cation levels tz are moderate up to 3 100 eq and the major ion chemistry is indicative of ca aluminosilicate and carbonate weathering with significant contributions from black shales in some tributaries the si tz si na k and 87sr 86sr ratios indicate that the weathering is superficial i e only to cation rich secondary minerals the areal total dissolved solid fluxes range from 0 04 to 0 39 106 mol km2 yr up to an order of magnitude lower than for the amazon orinoco draining the andes in the tropics 0 6 4 1 106 mol km2 yr the co2 consumption by aluminosilicate weathering 18 230 103 mol km2 yr is also at the lower end of the range observed in the amazon orinoco headwaters 143 1 000 103 mol km2 yr however as the north american counterparts in similar latitudes and with comparable relief the mackenzie yukon and fraser draining the rockies also have high dissolved solids 0 2 2 9 106 mol km2 yr and co2 19 1 750 103 mol km2 yr fluxes these low values seem to be more a function of lithology than simply climate ice action in cold environments appears to overcome the inhibiting effects of the decreased temperatures and lack of precipitation in producing a high chemical yield but results in superficial weathering in the case of aluminosilicates

small scale 5 0 m vertical heterogeneity in mudstones implications for high resolution stratigraphy in siliciclastic mudstone successions 48 mudstone samples from the peterborough member oxford clay formation have been analysed to determine the small scale vertical and lateral lithofacies variability in this succession the samples were collected every 0 15 m from saxon and king9s dyke brickpits whittlesey peterborough uk over a short vertical interval 15 m the sampled interval spans the obductum to the grossouvrei subzones of the callovian upper jurassic lithofacies present were described using combined field logging optical and backscattered electron optical techniques the succession predominantly comprises silt rich mudstones with subordinate clay rich mudstones shell beds and shell pavements the individual units are variously composed of detrital clay quartz pyrite calcite with minor apatite kaolinite and glauconite in some units millimetre scale upward fining couplets are present elsewhere the original bedding structures have been destroyed by bioturbation comparison of successive thin sections reveals that upward coarsening is present on a metre scale and that shell enriched units are located close to the tops of these upward shoaling units comparison of samples collected laterally on a 0 01 1 0 m scale from the same level 3 0 m below the top of bed 14 indicates that there is lateral lithofacies variability the small scale 0 001 m couplets are interpreted to be beds deposited by waning flow currents significant breaks between these depositional events allowed a dysaerobic infauna to colonize the sediment the metre scale upward coarsening intervals which are capped by shell enriched units are interpreted to be parasequences the observed small scale lateral lithofacies variability is interpreted to be a product of small but significant vertical miscorrelation errors rather that systematic lateral facies changes these data suggest that producing reliable bed scale lateral correlations over distances of more than 1 km in this and successions like it will be very difficult

a new approach to provenance studies electron microprobe analysis of detrital garnets from middle jurassic sandstones of the northern north sea reading provenance from heavy mineral suites is hampered by the depletion of diagnostic but unstable heavy minerals through intrastratal solution a common phenomenon in deep sedimentary basins such as the north sea this paper demonstrates the potential of electron microprobe analysis in overcoming this problem by concentrating on the compositional variations shown by detrital garnets which are relatively resistant to intrastratal solution studies of the garnets from the brent group middle jurassic of the murchison and tern oilfields in the northern north sea reveal that three distinct areas supplied detritus association 1 which characterizes the broom formation in both areas and recurs higher in the sequence in the tern field is ascribed to an orkney shetland source the location of the areas supplying the garnets of association 2 best represented in murchison and association 3 common to both fields is less clear their ultimate sources clearly include high grade metamorphics and therefore probably lie on the norwegian landmass the orkney shetland platform or conceivably the scottish landmass but the possibility of recycling makes it difficult to judge their immediate provenances nevertheless the presence of three garnet associations indicates that the most widely accepted model of brent sedimentation with sands derived from a domal uplift in the outer moray firth and channelled northward along the viking graben is untenable

the effect of land plants on weathering rates of silicate minerals abstract land plants and their associated microbiota directly affect silicate mineral weathering in several ways by generation of chelating ligands by modifying ph through production of co2 or organic acids and by altering the physical properties of a soil particularly the exposed surface areas of minerals and the residence time of water in laboratory experiments far from equilibrium 1 mm oxalate a strong chelator of al has a negligible effect on the dissolution rate of alkali feldspars but some effect on calcic feldspars and olivine by analogy to oxalate the overall effect of organic ligands on the weathering rate of silicate minerals in nature is likely to be small except perhaps in microenvironments adjacent to roots and fungal hyphae the effect of ph on silicate mineral dissolution rate depends on ph below ph 4 5 the rate increases with decreasing ph in the circumneutral region the rate is ph independent and at ph values above around 8 the rate increases with increasing ph vegetation should thus cause an increase in weathering rate through the ph effect only where the ph is below 4 5 as an overall generalization the effect of plants on weathering rate through changes in soil solution chemistry is probably small for granitic rocks it may be greater for more mafic rocks it is the release of ca and mg from mafic rocks that has the greatest influence on the global co2 budget the effect of changes in soil physical properties on weathering rate can be major by binding fine particles plants can greatly increase weathering rates in areas of high physical erosion where erosion rates are lower the effect of plants is less clear on long timescales plants may decrease chemical weathering by binding secondary products and isolating unweathered minerals from meteoric water a major unknown in estimating the effect of the advent of land plants on weathering rates is the nature thickness particle size distribution permeability of the regolith on the pre silurian continents the indirect effect of vegetation through changing the regional distribution of precipitation may be as important as the direct effects

assessing detrital garnet chemical composition as a quantitative provenance tool a multivariate statistical approach abstract chemical analysis of detrital garnet is a widely utilized quantitative tool for determining the provenance of sediments the goal of this study is to investigate the ability of the compositions of detrital garnet to provide a direct linkage to the specific source rocks from which the garnet was derived to achieve this goal we analyzed detrital garnet isolated from alluvial samples collected from the french broad river and several of its tributaries a watershed that drains portions of the multiply deformed southern appalachian orogen usa to test whether potential linkages between detrital and potential source rock garnet could be achieved garnet crystals were chemically characterized from a wide variety of lithologies that crop out in the french broad watershed and thus are the most likely local sources of detrital garnet mahalanobis distances measured on canonical discriminant functions successfully differentiated garnet compositions among the 18 analyzed source rocks these metrics were then applied to 2 300 detrital garnet compositions to link each grain to its potential source rock approximately 94 of the detrital garnet crystals were linked to their potential source regions thus only 6 of the detrital crystals were treated as unclassified we interpret the unclassified high ca garnets to have been derived from minor sub map scale lenses and boudins of calc silicate or skarns from exposed ocoee or ashe metaclastic units within the french broad river watershed the unclassified high mn detrital garnet grains are interpreted to have been derived from the various felsic granitiods and pegmatites that intrude the region of study

fluvial geochemistry of the eastern slope of the northeastern andes and its foredeep in the drainage of the orinoco in colombia and venezuela abstract the fluvial geochemistry of the tributaries of the orinoco draining the eastern branch of the northern andes in colombia and venezuela is determined by lithology and ranges from rivers dominated by aluminosilicate weathering mainly of shales and mafic rocks to those bearing the signatures of dissolution of marine limestones and evaporites and of continental playa deposits these left bank tributaries of the orinoco provide the overwhelming proportion of the suspended and dissolved loads transported by the main stem although feeding only half the discharge however due to the extreme severity of weathering on the guayana shield the right bank tributaries supply about half the silica and 40 of the k carried by the orinoco there is a similar partitioning between the andes and the lowlands in the amazon drainage in contrast the mackenzie which drains the northern extremity of the continental arc of the western americas is completely dominated by the weathering of limestones and evaporites and transports very little silica this again appears to be a reflection of lithology since the yukon in similar latitudes and terrain has silica concentrations comparable to the tropical systems in addition a conservative deconvolution of the data gives estimates of the net consumption of atmospheric co 2 by aluminosilicate weathering that follows the same pattern thus the available evidence from the western americas indicates that exposure and lithology rather than the climatic variables temperature and runoff dominate the weathering yields in active orogenic belts these observations contradict the conventional view of weathering processes and their controls and are at complete variance with the assumptions parameterised in most models of the geochemical cycle

geochemistry of dissolved and suspended loads of the seine river france anthropogenic impact carbonate and silicate weathering this study focuses on the chemistry of the seine river system one of the major rivers in europe and constitutes the first geochemical investigation of both suspended and dissolved loads of this river the seine river drains a typical mesozoic cenozoic sedimentary basin the paris basin constituted of limestones mixed or interbedded with terrigenous sediments derived from the paleoreliefs bordering the mesozoic and cenozoic seas in the context of quantifying the global influence of carbonate and silicate weathering on atmospheric co2 consumption the seine river offers the possibility of examining weathering rates in a flat sedimentary environment under temperate climatic conditions one of the major problems associated with the seine river as with many temperate rivers is pollution we propose in this paper 2 approaches in order to correct the dissolved load of the seine river for anthropogenic inputs and to calculate weathering rates of carbonates and silicates the first uses the dissolved load of rivers and tries to allocate the different solutes to different sources a mixing model based on elemental ratios is established and solved by an inversion technique the second approach consists in using the suspended load geochemistry under steady state conditions we show that the geochemistry of suspended sediments makes it possible to estimate the amount of solutes released during the chemical weathering of silicates and thus to calculate weathering rates of silicates the total dissolved load of the seine river at paris can be decomposed into 2 of solutes derived from natural atmospheric sources 7 derived from anthropogenic atmospheric sources 6 derived from agriculture 3 derived from communal inputs and 82 of solutes derived from rock weathering during high floods the contribution of atmospheric and agriculture inputs predominates the weathering rate of carbonates is estimated to be 48 t km2 yr 25 mm 1000 yr only 10 of carbonates are transported in a solid form the rest being transported in solution co2 consumption by carbonate weathering approaches 400 103 mol km2 yr in the seine river at paris about 2 3 mg l of dissolved cations are found to originate from the chemical weathering of silicates by taking dissolved silica into accounts the total dissolved load derived from silicate weathering is about 6 7 mg l this value is minimal because biological uptake of silica probably occur in the seine river the chemical weathering rate of aluminosilicates is estimated to be 2 t km2 yr the ratio of physical over chemical weathering of silicates range between 1 and 3 and the total chemical and physical erosion rates of sedimentary silicates are about 2 3 mm kyr the co2 consumption by silicate weathering 15 24 103 mol km2 yr and is independent of dissolved silica concentration silicate consumption is thus 20 times less than carbonate consumption in the paris basin compared to the neighboring granitic areas the sedimentary region drained by the seine river has 2 to 3 times lower co2 consumption rates we attribute this difference to the cation depleted nature of the seine basin aluminosilicates which are of sedimentary origin at a world scale the chemical denudation rates found for the seine basin are very low and comparable to those given for tropical lowland rivers draining silicates such as the rivers of the congo and amazon basins in spite of huge climatic differences we attribute this similarity to the low mechanical denudation that characterizes these two types of regions

impacts of simulated acid solution on the disintegration and cation release of purple rock mudstone in southwest china abstract rock disintegration and cation release not only impact on terrestrial geomorphology but also provide nutrients for plants further fractal theory has been widely used to characterize the distribution of fragments in rocks for measuring the degree of disintegration yet the effects of an acidic environment on the trajectory of fractal dimensions of rock disintegration and cation release are not fully clear therefore to investigate the impacts of a solution s ph on disintegration and cation release from the purple rock in southwest china a series of laboratory experiments were performed by soaking the purple rocks in solutions with phs from 2 5 to 7 0 over 24 treatment cycles the results show that the lower the ph the fewer cycles required to obtain a stable fractal dimension the fractal dimension of purple rock under different ph values approached three after 24 treatment cycles until decay ratios the mass of decayed rock of 90 acidic treatment increased cation release especially when the ph value of the solution was below 3 5 compared with a deionised water soaking solution the amounts of k na ca2 and mg2 were increased by 4 92 1 27 1 12 and 1 08 times with ph values of 2 5 3 5 4 5 and 5 6 soaking solution respectively at the disintegration stage in addition the release of ca2 and mg2 were more sensitive to acid than that of k and na and ca2 weathering occupied the dominant position in the cation weathering rates moreover due to disintegration processes that transformed each rock sample into fragments fresh surfaces were exposed from which cations were liberated creating a significant p

glacial and interglacial patterns for asian dust transport abstract particle size distributions and depositional fluxes were investigated for present day asian dust and for the late quaternary loess palaeosol sequences from central china the regional scale transport of asian dust during interglacial stages is mainly attributable to non dust storm processes and is dominated by northwesterly surface winds conversely during glacial stages the impact of dust storms on the accumulation of loess is enhanced these regional effects are in contrast to the global dispersal of dust which is associated with transport by upper level westerly winds and is mainly the result of desert dust storms during both glacial and interglacial conditions temporal differences in the dust transport patterns to the loess plateau suggest that the variability in the coarse particle fraction 20 m during interglacial times is not directly attributable to the strong dust storms and dust fall events that have been linked to a strengthening of east asian winter monsoonal winds this is in contrast to the dust deposition rates which are strongly influenced by the monsoonal circulation

weathering processes in the ganges brahmaputra basin and the riverine alkalinity budget abstract we present river chemistry data for a network of rivers draining the western and central nepal himalaya our sampling locations cover the system from the sources of rivers in tibet to the gangetic plain water samples were collected throughout the year including the monsoon season for rivers in nepal and for the ganges and brahmaputra in bangladesh rivers draining the north himalaya are characterized by low discharge under a cold and arid climate main stream waters have 13 c dic near 0 and high so42 so42 hco3 ratios xso4 with values around 40 eq and high cl ca is the dominant cation ca2 cations 55 to 75 eq after correction of sodium by chloride dissolved sulfate is produced in waters from the tethian sedimentary series whereas chlorine is related to thermal waters dissolved sulfate is primarily derived from sulfide oxidation rather than evaporite dissolution 13 c dic values of up to 3 9 show that metamorphic co2 is an important weathering agent rivers of the north himalayan basins have about 50 of their alkalinity derived from carbonate dissolution 20 from biogenic activity and 30 from metamorphic co2 on the south flank of the himalaya rivers are more depleted in 13 c and have on average lower xso4 most rivers have 13 c dic and xso4 values compatible with a simple mixing between soil co2 and sulfate derived from sulfide oxidation during the monsoon discharge increases by a factor 20 but the total dissolved concentration is only slightly reduced xso4 and 13 c decrease while ca cations increases implying enhanced dissolution of pedogenic calcite as a whole the g b riverine flux of alkalinity derived from silicate weathering is around 2 7 1011 mol year modest at the global scale sulphuric acid controls 20 30 of the weathering reaction in the brahmaputra and 6 to 9 in the ganges na and k balance 60 to 65 of the silicate derived alkalinity flux and the long term co2 consumption by ganges and brahmaputra is near 6 4 1010 mol year the flux of metamorphic co2 converted to alkalinity via weathering reactions is ca 1 1010 mol year

atmospheric transport of iron and its deposition in the ocean the atmospheric transport of continental weathering products is responsible for much of the mineral material and fe entering the open ocean and is probably the dominant source of nutrient fe in the photic zone in regions where other nutrients are present in high concentrations the flux of fe from the atmosphere may be a limiting factor in primary productivity due to the larger source regions for dust north of the equator 8 times more atmospheric fe is deposited in the northern hemisphere than in the southern hemisphere the mineral aerosol and fe transport and deposition are highly variable due to the episodic nature of dust generation and its transport and deposition processes between 10 and 50 of the total atmospheric fe entering the world ocean appears to dissolve i e it will pass through a 0 4 m pore size filter rapidly when the mineral matter enters the ocean much of the atmospheric fe is present as fe ii apparently produced as a result of photochemical reduction reactions taking place during atmospheric transport this readily soluble fe ii should be available immediately for use as a nutrient by phytoplankton atmospheric transport from the continents is estimated to supply 3 times as much dissolved fe to the oceans as that delivered via rivers

climatic and geological factors contributing to the natural water chemistry in an arid environment from watersheds in northern xinjiang china a natural water hydrochemical investigation was carried out on three watersheds in northern xinjiang china to evaluate the climatic geological and anthropogenic influence on aqueous major element chemistry in an arid environment wide spatial variations are observed in the dissolved solids tds and water chemistry the hydrochemistry is typically carbonate and alkaline in nature with ca2 hco3 and so42 dominating the major ion composition four major water types ca hco3 ca nda non dominant anion ca so4 and ndc non dominant cation nda or na nda type are identified in terms of the piper model the water chemistry agrees well with the rock dominance mechanism with a tds value of 80 600 mg l and a na na ca2 ratio of 0 1 0 6 correlation analysis suggests that most of the ions derive from multiple sources stoichiometric analyses indicate that carbonate weathering is the primary source of dissolved ions followed by silicate weathering and evaporite dissolution the effects of local pollution have somewhat greater contribution on the oases and central areas of the zhungarer watershed most parts of the rivers show an increasing trend in the dissolved load toward the lower reaches which is primarily attributed to an evaporation process control along the water course variations in water chemistry show clear correlation with the regional lithological distribution topography and atmospheric precipitation using rainwater as a baseline contributions from atmospheric precipitation and rock weathering to the tributary chemistry are roughly evaluated to be in the range of 2 39 average 13 and 59 98 average 86 respectively implying a high effective control of regional geology on stream chemistry compared with that of atmospheric input c 2012 elsevier b v all rights reserved

mineralogy of aeolian dust reaching the north pacific ocean 1 sampling and analysis the mineral composition of the 2 m clay and 2 to 20 m silt size fractions of aerosol particles collected near the margins of the north pacific ocean was determined by x ray diffraction analysis although the same mineral phases are present in the two size fractions there are significant differences in the quartz plagioclase and kaolinite concentrations north pacific aerosols are primarily composed of illite in both size fractions in addition to kaolinite in the 2 m size class and quartz and plagioclase in the 2 to 20 m size class quartz and plagioclase are present in significantly higher amounts in the 2 to 20 m size fraction while kaolinite is greater in the 2 size class western north pacific aerosol particles contain significantly higher 2 m quartz than samples collected in the east and eastern north pacific aerosols have significantly higher concentrations of 2 m smectite than those from the west

heavy minerals and provenance of sands modeling of lithological end members from river sands of northern austria and from sandstones of the austroalpine gosau formation late cretaceous abstract provenance of sands and sandstones is evaluated by statistical analysis of heavy mineral data source rocks are distinguished by the modeling of lithological end members from detrital heavy mineral distributions using the version of extended q mode factor analysis of klovan and miesch 1976 two examples demonstrate this a heavy mineral data from modern river sands of the moldanubian region bohemian massif central europe in the northern part of austria show that the end member modeling estimates exactly the known source rocks b modeling of late cretaceous heavy mineral distributions of the austroalpine gosau formation confirms and clarifies a plate tectonic model of the alps by frisch 1979 the end members describe source rocks by variable combinations of different heavy minerals thus the frame of the sample space can be fitted optimally on the data structure the generally small number of end members facilitates a clear representation of results plate tectonic setting of source areas can be inferred by comparing the end member configuration to a simple tetrahedral graph which contains possible sources of clastic sediments for different stages of a plate tectonic cycle

geochemistry of the amazon 1 precipitation chemistry and the marine contribution to the dissolved load at the time of peak discharge analyses of precipitation and surface water are used to estimate the fluxes of marine cyclic salts through that part of the amazon river system draining past obidos 80 of the basin at the time of peak discharge in june amazon precipitation chemistry can be devided into two principal components marine and terrestrial the marine component determined from analyses of marine rain consists of na k mg ca and cl in approximately sea salt proportions with s doubly enriched the excess sulfur is probably derived from gas phase inputs the terrestrial component makes an important contribution of k ca s and n much of which can be related to biological emissions the emission of reduced sulfur in the marine and terrestrial environment and nitrogen in the terrestrial environment is responsible for a natural acid rain in the amazon region with a ph from 4 7 to 5 7 this is about one tenth the acidity of polluted urban rain the chloride content of lowland rivers which drain regions lacking significant geologic sources of chloride shows a systematic decrease in chloride with increasing distance from the ocean this trend is used to define the cyclic salt background for amazonian surface waters cyclic salts in general make only a minor contribution relative to terrestrial inputs to the chemistry of amazon basin rivers even those draining intensely weathered terrains an estimated 17 6 cl 6 9 na 1 3 mg 3 6 s 0 4 k and 0 1 ca of the dissolved load at obidos during peak discharge is cyclic

the mechanics and geological implications of dust transport and deposition in deserts with particular reference to loess formation and dune sand diagenesis in the northern negev israel

using pca to characterize and differentiate loess deposits in wisconsin and upper michigan usa abstract data on loess thickness as well as a variety of particle size fractions were determined for 875 samples taken from several loess sheets across wisconsin and upper michigan because the particle size characteristics of these samples varied widely within and between the loess sheets we used principal components analysis pca as a way of isolating the major textural components or signals that exist across the various loess sheets the purpose of this research was to examine and interpret these principal components or particle size signatures common to the different loesses in order to better understand the loess sheets character formation mechanisms and likely sources our initial assumption that many of these loesses varied markedly from the classical silty loess was supported by the particle size data and the pca although component 1 was interpreted as thick silty loess dominated by medium silts component 2 was mainly composed of very fine sand and coarse silt and is better viewed as coarse loess components 3 and 4 were less texturally homogeneous and may reflect mixing between the loess and the underlying sediment especially where the loess is

organic matter variations in a depositional sequence implications for use of source rock data in sequence stratigraphy variations in the amount and type of organic matter preserved in shelf sediments are predictable within a sequence stratigraphic framework these variations can be documented using routine petroleum source rock evaluation techniques the type and preservation of organic matter is related to the rate of allochthonous shelf sedimentation each depositional systems tract in a sequence has a distinct depositional style that affects changes in the amount of terrigenous influx therefore integration of source rock data with sedimentologic and regional stratigraphic results provides greater resolution in locating the critical surfaces that bound depositional systems tracts within the depositional sequence this integrated sequence stratigraphic approach has been applied to conventional cores of upper cretaceous strata in the san juan basin of new mexico fine grained marine sediments in transgressive systems tracts possess high total organic carbon and yield relatively high amounts of hydrocarbons during pyrolysis petrographically this organic matter is composed primarily of amorphous macerals both the lower juana lopez and the mancos shale above the tocito sandstone provide examples of organic matter deposited in the transgressive systems tract in contrast marine depositional systems of both the lowstand and highstand systems tracts contain less total organic carbon and less pyrolyzable hydrocarbons this methodologymore not only improves systems tract identification in fine grained basinward intervals but also reveals those portions of the depositional sequence that are most favorable for marine petroleum source rock formation less

increase in late neogene denudation of the european alps confirmed by analysis of a fission track thermochronology database abstract a sharp increase in deposited sediment volume since pliocene times has been observed worldwide and in particular around the european alps this phenomenon has been linked to a rise in denudation rates controlled by an increase of either climatic or tectonic forcing observation of in situ cooling histories for orogens is critical to assess the reality of the inferred increase in denudation rates and to determine whether this phenomenon is widespread or localized at active tectonic structures we exploit the unique density of fission track ages in the western european alps to reconstruct cooling isoage surfaces and to estimate exhumation rates on the orogen scale between 13 5 and 2 5 ma our novel technique is based on the association of isoage contours with age elevation relationships it uses map view interpolation enabling a spatio temporal analysis of exhumation rates over the entire western alps the resulting exhumation histories reconstructed for eight areas of the western alps display strong similarities in timing and rates with orogen wide average denudation rates inferred from sediment volumes this consistency validates the use of both techniques for the study of an orogen characterized by strong relief and high recent exhumation rates we conclude that exhumation rates in the western alps have increased more than twofold since late miocene times this increase may have been locally modulated by the distinct response of different tectonic units

evolution and variability of the asian monsoon system state of the art and outstanding issues the asian monsoon is comprised of the indian and east asian subsystems these two components are linked to one another in varying degrees by regions of strong sensible heating indo asian landmass and strong latent heat export the western pacific warm pool and the southern subtropical indian ocean variability within the indian and east asian subsystems interactions among them and the extent to which they interact with other climate phenomena e g enso are current topics of modern and paleoclimate research this work provides an overview of past and current paleomonsoon research on tectonic to interannual time scales with a primary focus on marine sediment records while past and current work has contributed greatly to our understanding of paleomonsoon variability at all time scales additional efforts are required to make further progress in two critical areas 1 additional efforts are needed in terms of proxy development and evaluation requiring concerted efforts at long term sediment trap deployments in key monsoon influenced regions as well as development of adequate and widely available core top databases these are necessary to assess the impact of modern oceanographic and seafloor processes on potential monsoon proxies 2 additional effort is also needed in acquiring a sufficient geographic distribution of downcore records to assess linkages among the subsystems and their role in the context of extratropical climate change these records should have high sedimentation rates including varved sections this requires substantial survey support to identify the most appropriate coring and drilling targets c 2004 elsevier ltd all rights reserved

metals in suspended sediments from the changjiang yangtze river and huanghe yellow river to the sea and their comparison thirty five samples of suspended sediments were collected at datong station and lijin station the basin wide control stations of the changjiang yangtze river and the huanghe yellow river during flood and dry seasons in 2000 and 2001 concentrations of 15 elements fe mg ca al na k ti mn ba sr pb cu zn v and ni in these samples were measured by icp aes the results indicated that fe al ti mn ba cu zn v and ni concentrations in the changjiang sediments in may flood season were quite close to those in november dry season whereas mg ca na k sr concentrations were slightly higher and pb was relatively lower in the dry season ti ba sr and zn concentrations in huanghe sediments varied little in august flood season and december dry season while mg ca al na and k concentrations were higher by approximately 30 and fe mn pb cu zn v and ni concentrations were lower in flood season concentrations of most metals except ca na and sr were much higher in changjiang sediments than those in the huanghe such differences of metal concentrations in sediments from these two rivers could be ascribed to their different sediment sources and weathering processes within their corresponding river basin particularly since the 1980s pb and zn concentrations in changjiang sediments have increased significantly due to the releases of waste contaminants from human activities while the variations for these two elements in the huanghe samples were very little due to the elevated river bed in the lower reaches