chemical denudation in the yellow river and its geomorphological implications abstract chemical denudation plays an important role in regulating atmospheric co2 balance and modulating global climate with weekly collected water samples at three stations on the yellow river mainstem from july 2011 to july 2012 we investigate its chemical denudation characteristics on the basis of water geochemistry and discuss the geomorphological implications because of limited atmospheric inputs into the yellow river chemical weathering is of first importance in affecting the chemical compositions of its water geochemistry as a result of extensive carbonates within the watershed carbonate dissolution is the major source of the dissolved solids accounting for 28 33 7 of the total dissolved solids tds in contrast silicate weathering contributes only 9 9 10 9 with a mean tds concentration of 639 mg l 1 the tds flux into the ocean is estimated at 16 mt yr 1 corresponding to a specific chemical denudation rate of 21 3 t km 2 yr 1 comparative analysis with physical erosion suggests the dominance of physical erosion over chemical weathering in providing riverine loads rapid removal by physical erosion may have restrained the chemical denudation processes rock weathering consumes on average 2 3 mt of atmospheric co2 during the one year long sampling campaign accounting for 0 22 0 31 of the global annual co2 consumption through chemical weathering of the co2 consumed 74 is caused by carbonate weathering and 26 by silicate weathering indicating the predominance of carbonate weathering in consuming atmospheric co2 within the watershed

changes in the geochemical parameters of karst lakes over the past three decades the case of plitvice lakes croatia abstract one of the major reasons for the increase in global air temperature since the early 20th century is considered to be the increase in the atmospheric co 2 concentration karst relief is considered an important carbon sink but it can also be a natural source of carbon and co 2 emission aquatic systems in karst areas facilitate carbon exchange between the karst and the atmosphere often through groundwater geochemical carbonate rock dissolution carbon sink and in the form of secondary calcium carbonate precipitation possible carbon source the protected area of plitvice lakes national park located in the karst region of croatia was chosen as a case study on karst geochemical processes the lakes are also specific for their authigenic calcite precipitation in the form of tufa barriers and lake sediment physical and chemical data temperature ph ca 2 hco 3 mg 2 and co 2 concentrations calcite saturation index si calc calcite dissolution ionic ratio ir calc and mg ca ratio from water samples collected at 8 locations 2 springs 2 rivers and 4 lakes from 1981 to 2014 were studied the data were not collected systematically so long term changes have been mostly assessed through comparison between parameters from two selected periods 1981 1986 and 2010 2014 and through temporal correlations for each observed parameter in each calendar month for the 33 years studied an increase in air and water temperature ca 2 and hco 3 concentrations calcite saturation index si calc calcite dissolution ionic ratio ir calc and a decrease in the mg ca ratio were observed no statistically significant change was observed for ph or co 2 and mg 2 concentrations average discharge rates did not display any significant change over the past three decades however there was a change in their seasonal distribution the significant increase in ca 2 and hco 3 concentrations at lake locations were primarily caused by an increase in ca 2 and hco 3 values in the water of the springs simultaneously mg 2 concentrations remained constant which indicates higher levels of limestone calcite dissolution than dolomite dissolution one of the reasons for this could be higher air soil temperatures resulting in higher soil co 2 production which appears to result in the higher dissolution of calcite exclusively an increase in hco 3 concentrations at the springs implies that karst groundwater is a carbon sink furthermore the fact that the spatial decrease in hco 3 concentration in downstream waters was the same during the 1981 1986 and 2010 2014 periods implies that the entire observed karst lake system itself is a carbon sink temporal and spatial changes in si calc and ir calc values in surface waters were mainly attributed to an increase in the intensity of bioactivity which is in turn connected with an increase in water temperature

changing stress field in the middle segment of the tan lu fault zone eastern china abstract the tan lu active fault zone is an important tectonic boundary in east china minor structures associated with the fault show that the nature of displacement on the middle segment of the fault zone has changed in consecutive episodes since the cretaceous normal faulting during the cretaceous sinistral strike slip and reverse faulting at the end of the cretaceous or in the early tertiary and dextral strike slip and reverse faulting from the late tertiary to the present the regional orientation of the maximum principal compressive stress based upon the statistical study of minor shear fracture orientation is 6 s52 w in the late tertiary to quaternary this stress field may be related to the collision between india and tibet and the microspreading of the japan sea

seasonal diurnal and storm scale hydrochemical variations of typical epikarst springs in subtropical karst areas of sw china soil co2 and dilution effects summary two year continuous ph conductivity temperature and water stage of the two typical epikarst springs nongla spring and maolan spring about 200 km apart in subtropical karst areas of sw china were presented our primary study objective was to understand how karst systems respond hydrochemically to recharge at different time scales and what the biogeochemical processes and controlling factors in the sw china epikarst environment are a thermodynamic model was used to link the continuous data to monthly water quality data allowing the calculation of co 2 partial pressures and calcite dolomite saturation levels on a continuous basis marked seasonal diurnal and storm scale variations were observed for ph conductivity co 2 partial pressures and calcite dolomite saturation indexes of the springs indicating that both springs are dynamic and variable systems however the coefficients of variation of these hydrogeochemical features tends to be in the order of seasonal storm scale diurnal the seasonal and diurnal variations of these features higher conductivity and lower ph in summer and at daytime lower conductivity and higher ph in winter and at nighttime tend to co vary with temperature which influences the production of co 2 in soils thus being the driving force for the variations soil co 2 effect the storm scale fluctuations occur during the spring summer rainy days due to the storm events depending on the rainfall intensities however there are differences in magnitudes and direction of the variations of these features at very high rainfall intensity the dilution effect dominates the variations characterized by the decrease in both conductivity and calcite dolomite saturation of the springs while soil co 2 effect determines the variations at lower rainfall intensity characterized by increase in co 2 partial pressure and conductivity but decrease in ph and calcite dolomite saturation in a word the hydrodynamic aspects together with hydrobiogeochemical characteristics need to be taken into account to correctly explain the hydrochemical variations of the epikarst springs results from the study demonstrate the need to redesign hydrogeochemical sampling strategies for epikarst springs in karst areas with monsoon climate like sw china i e with remarkable seasonal matching fluctuations in temperature rainfall and vegetation

water geochemistry controlled by carbonate dissolution a study of the river waters draining karst dominated terrain guizhou province china concentrations of major ions and sr and sr isotopic compositions of two major river systems wujiang river and yuanjiang river in karst dominated regions and during winter were measured the rivers and their tributaries have high total dissolved solid concentrations with tz ranging from 2 1 to 6 3 meq l which are significantly higher than that of the global river average calcium and hco3 followed by mg2 and so42 dominate the chemical composition of major ions in the river waters both na k and cl si account for 5 10 of the cations and anions respectively the waters of the wujiang river have high sr2 concentrations and lower 87sr 86sr ratios 0 7077 0 7110 while those of the qingshuijiang river one of two major tributaries of the yuanjiang river system show higher sr isotopic ratios 0 7090 0 7145 and low sr concentrations the lithology and geography of the river basins largely control the chemical and isotopic compositions of these rivers analyses of the stoichiometry of the river waters show that the water chemistry is controlled by carbonate dissolution by both carbonic and sulfuric acid especially of the wujiang river and suggest an origin of sulfate mainly from atmospheric input because of coal combustion and or oxidation of sulfide minerals in the catchments we identify three main weathering sources limestone dolomite and silicates chemical and sr isotopic composition of wujiang river waters are characterized mainly by limestone weathering while those of the qingshuijiang river waters mainly by dolomite and silicate weathering chemical weathering rates of carbonate and silicate are estimated and the results indicate that the chemical weathering rates of carbonate in the catchments are remarkably high significantly higher than most large rivers it is considered that presence of sulfuric acid in the rock weathering overuse of land and deterioration of vegetation are most likely the key factors responsible for the high weathering rates of carbonate in the catchments

watershed scale chemical weathering in a merokarst terrain northeastern kansas usa abstract carbonate weathering in the merokarst landscape at the konza prairie near manhattan ks is governed by kinetically rapid reaction rates similar to other carbonate settings the geology of the site consists of repeating couplets of shale and limestone mantled by pleistocene loess on which most soils are built the headwater stream that is the subject of this study is intermittent and well connected to the secondary porosity in the limestone aquifers such that the water chemistry is groundwater dominated despite increasing in situ weathering rates shown by increasing solute concentrations long term 21 of 24 years decline in stream water discharge has reduced chemical denudation the current chemical denudation rate is 0 02 mm yr 1 limestone bedrock thickness 26 6 m is 38 of total bedrock thickness 70 m the present landscape would have taken 1 4 million years to dissolve at current weathering rates despite paleogeographic reconstructions suggesting exposure for the past 260 ma estimates of the time to erode younger strata using current physical and chemical denudation rates are 80 159 ma still much less than the age of the rocks an alternate source of material dust is proposed that may slow limestone weathering which in turn protects shales from physical erosion thereby slowing landscape evolution

effect of peripheral convection on tropical cyclone formation abstract the effect of peripheral convection on the formation and intensification of tropical cyclones has been studied earlier with diagnostic models and with prognostic models that do not resolve convection in this paper a prognostic axisymmetric model with explicit convection is used to study the effect of peripheral convection on tropical cyclone formation from a weak mesoscale vortex peripheral convection becomes stronger in the model if downdrafts extinguish deep convection in the core of the mesoscale vortex the subsequent concentration of convection in the core of the vortex and the onset of rapid intensification of the vortex occur simultaneously in model experiments relative humidity in the midtroposphere reaches a value of 90 within 100 km from the center of the vortex before the onset of rapid intensification occurs decreasing the sea surface fluxes of sensible and latent heat artificially in the outer region of the vortex decreases the amount of outer convection in the model this re

weathering and the global carbon cycle geomorphological perspectives abstract the links between the weathering of silicate minerals the global carbon cycle and climate change are complex and involve a whole range of often inter related tectonic climatic geomorphological and biological factors silicate weathering rates are known to have varied through geological time and increasingly sophisticated models now link such variation to the long term carbon cycle and climate change in order to improve the modelling further one key research need is for more and better datasets on weathering and the factors that control it as a contribution to this we review the nature of the weathering carbon cycle system the sources of evidence used to understand it and the challenges that remain in quantifying the feedbacks between weathering and the global carbon cycle we propose that increased understanding of geomorphological diversity of landscapes and processes and especially the dynamic relationships between weathering and erosion will aid clearer portrayal of the links between weathering and the long term carbon cycle

changes in the storage and sink of carbon dioxide in subsurface atmospheres controlled by climate driven processes the case of the ojo guarena karst system a comprehensive environmental monitoring program was conducted in the ojo guarena cave system spain one of the longest cave systems in europe to assess the magnitude of the spatiotemporal changes in carbon dioxide gas co2 in the cave soil atmosphere profile the key climate driven processes involved in gas exchange primarily gas diffusion and cave ventilation due to advective forces were characterized the spatial distributions of both processes were described through measurements of co2 and its carbon isotopic signal 13c co2 from exterior soil and cave air samples analyzed by cavity ring down spectroscopy crds the trigger mechanisms of air advection temperature or air density differences or barometric imbalances were controlled by continuous logging systems radon monitoring was also used to characterize the changing airflow that results in a predictable seasonal or daily pattern of co2 concentrations and its carbon isotopic signal large daily oscillations of co2 levels ranging from 680 to 1900 ppm day 1 on average were registered during the daily oscillations of the exterior air temperature around the cave air temperature these daily variations in co2 concentration were unobservable once the outside air temperature was continuously below the cave temperature and a prevailing advective renewal of cave air was established such that the daily averaged concentrations of co2 reached minimum values close to atmospheric background the daily pulses of co2 and other tracer gases such as radon 222rn were smoothed in the inner cave locations where fluctuation of both gases was primarily correlated with medium term changes in air pressure a pooled analysis of these data provided evidence that atmospheric air that is inhaled into dynamically ventilated caves can then return to the lower troposphere as co2 rich cave air

hydrochemical and pco2 variations of a cave stream in a subtropical karst area chongqing sw china piston effects dilution effects soil co2 and buffer effects the role of co2 in karst has been of interest for decades and emphasized by igcp 379 international geoscience programme unesco started in 1995 there are still open questions about the dynamics of carbon in karst systems particularly the flux of carbon between the surface and subsurface and between different components in the karst subsurface this research report focuses on the variations of hydrochemistry and pco2 partial pressures of carbon dioxide in subtropical karst groundwater using high resolution auto monitoring hydrochemical data 15 min intervals the aim of this study was to understand how hydrochemistry and pco2 in karst systems respond to recharge over different time scales and what the controlling factors are an auto monitoring hydrochemistry station was installed about 300 m upstream from the exit in the active stream channel of xueyu cave a typical subtropical karst cave four years of high resolution continuous ph specific conductivity spc temperature and water level data were collected a thermodynamic model was used to link the continuous data to monthly water quality data allowing the calculation of co2 partial pressures and calcite saturation sic levels on a continuous basis seasonal diurnal and storm scale variations were captured in the hydrochemistry and calculated pco2 records indicating that the cave stream is a dynamic and variable system seasonal features higher specific conductivity and lower ph in summer lower specific conductivity and higher ph in winter tend to covary with temperature which influences the production of co2 in soils thus being the driving force for the variations the soil co2 effect due to the buffer effect of a thick vadose zone and large void cave space diurnal variations are not obvious compared with epikarst springs in sw china storm scale fluctuations due to storm events occur during the summer rainy season piston flow effects dilution and soil co2 effects determine the variations in different storm events at the beginning of the rains the piston effect drives the variations characterized by increase in spc sic and ph in the cave stream and decrease in pco2 with heavy rainfall decrease in spc shows control by the dilution effect while decrease in sic and ph and increase in pco2 indicates the greater influence of soil co2 these results imply that the soil and cave voids are important factors influencing the hydrochemical evolution of karst groundwater future works need to use such high resolution technology widely for tracing the pco2 and hydrochemical variations in different karst aquifers

temperature driven meltwater production and hydrochemical variations at a glaciated alpine karst aquifer implication for the atmospheric co2 sink under global warming about two hydrological years of continuous data of discharge temperature electrical conductivity and ph have been recorded at the glarey spring in the tsanfleuron glaciated karst area in the swiss alps to understand how glaciated karst aquifer systems respond hydrochemically to diurnal and seasonal recharge variations and how calcite dissolution by glacial meltwater contributes to the atmospheric co2 sink a thermodynamic model was used to link the continuous data to monthly water quality data allowing the calculation of co2 partial pressures and calcite saturation indexes the results show diurnal and seasonal hydrochemical variations controlled chiefly by air temperature the latter influencing karst aquifer recharge by ice and snowmelt karst process related atmospheric co2 sinks were more than four times higher in the melting season than those in the freezing season this finding has implication for understanding the atmospheric co2 sink in glaciated carbonate rock terrains the carbon sink will increase with increasing runoff caused by global warming i e carbonate weathering provides a negative feedback for anthropogenic co2 release however this is a transient regulation effect that is most efficient when glacial meltwater production is highest which in turn depends on the future climatic evolution

hydrochemical variations during flood pulses in the south west china peak cluster karst impacts of caco3 h2o co2 interactions high resolution measurements of rainfall water level ph conductivity temperature and carbonate chemistry parameters of groundwater at two adjacent locations within the peak cluster karst of the guilin karst experimental site in guangxi province china were made with different types of multiparameter sonde the data were stored using data loggers recording with 2 min or 15 min resolution waters from a large perennial spring represent the exit for the aquifer s conduit flow and a nearby well measures water in the conduit adjacent fractured media during flood pulses the ph of the conduit flow water rises as the conductivity falls in contrast and at the same time the ph of groundwater in the fractures drops as conductivity rises as ca 2c and hco3 were the dominant 90 ions we developed linear relationships both r 2 0 91 between conductivity and those ions respectively and in turn

lithological and hydrological controls on water composition evaporite dissolution and glacial weathering in the south central andes of argentina 33 34 s lithological and hydrological influence on fluvial physical and chemical erosion was studied in a glacierized sedimentary basin with high evaporite presence suspended particulate matter spm total dissolved solids tds and major ion concentrations were analysed for 2 years of different hydrologic condition i 2009 2010 q 100 average and ii 2010 2011 q 60 average annual hydrograph was simple regime type with one peak in summer related to snow melting the intra annual spm and tds variations were directly and inversely associated to q respectively snow chemistry showed continental influence na ca2 0 17 and atmospheric input of tds was 1 of the total exported flux river water was highly concentrated in ca2 and so42 4 mmol l 1 and in na and cl 3 mmol l 1 ca2 so42 and na cl molar ratios were 1 and related to q directly and inversely respectively major ion relationships suggest that river chemistry is controlled by evaporite gypsum and halite dissolution having a summer input from sulfide oxidation and carbonate dissolution and a winter input from subsurface flow loaded with silicate weathering products this variation pattern resulted in nearly chemostatic behaviour for ca mg2 and so42 whereas na cl and sio2 concentrations showed to be controlled by dilution concentration processes during the 2009 2010 hydrological year the fluxes of water spm and tds registered in the snow melting high q season were respectively 71 92 and 67 of the annual total whereas for equal period in 2010 2011 56 of water 86 of spm and 54 of tds annual fluxes were registered the spm fluxes for 2009 2010 and 2010 2011 were 1 19 106 and 0 79 106 t year 1 whereas tds fluxes were 0 68 106 and 0 55 106 t year 1 respectively export rates for 2009 2010 were 484 t km2 year 1 for spm and 275 t km2 year 1 for tds these rates are higher than those observed in glacierized granite basins and in non glacierized evaporite basins suggesting a synergistic effect of lithology and glaciers on physical and chemical erosion copyright 2014 john wiley sons ltd

limestone weathering rates accelerated by micron scale grain detachment the weathering of carbonate rocks plays a critical role in the evolution of landscapes the erosion of buildings and monuments and the global scale shifting of carbon from the atmosphere to the ocean chemical dissolution is often assumed to govern the rates of weathering of carbonate rocks although some studies have suggested that mechanical erosion could also play an important role quantifying the rates of the different processes has proved challenging in part due to the high degree of variability encountered across different scales in both field and laboratory conditions to constrain the rates and mechanisms controlling long term limestone weathering we analyze a lidar scan of the western wall a roman period edifice located in jerusalem we find that extreme erosion rates in fine grained micritic limestone blocks are as much as two orders of magnitude higher than the average rates estimated for coarse grained limestone blocks at the same site atomic force microscope imaging of dissolving micritic limestone suggests that these elevated reaction rates are likely to be the result of rapid dissolution along micron scale grain boundaries followed by mechanical detachment of tiny particles from the surface our analysis indicates that such grain detachment could be the dominant erosional mode for fine grained carbonate rocks in many regions on earth

contribution of carbonate rock weathering to the atmospheric co2 sink to accurately predict future co2 levels in the atmosphere which is crucial in predicting global climate change the sources and sinks of the atmospheric co2 and their change over time must be determined in this paper some typical cases are examined using published and unpublished data firstly the sensitivity of carbonate rock weathering including the effects by both dissolution and reprecipitation of carbonate to the change of soil co2 and runoff will be discussed and then the net amount of co2 removed from the atmosphere in the carbonate rock areas of mainland china and the world will be determined by the hydrochem discharge and carbonate rock tablet methods to obtain an estimate of the contribution of carbonate rock weathering to the atmospheric co2 sink these contributions are about 0 018 billion metric tons of carbon a and 0 11 billion metric tons of carbon a for china and the world respectively further by the dbl diffusion boundary layer model calculation the potential co2 sink by carbonate rock dissolution is estimated to be 0 41 billion metric tons of carbon a for the world therefore the potential co2 source by carbonate reprecipitation is 0 3 billion metric tons of carbon a

karst biogeochemistry in china past present and future the dissolution and deposition processes of carbonate rock called co2 water carbonate rock interaction are controlled by complex interactions among the biosphere pedosphere atmosphere and lithosphere the interactions between biogenic activity and the co2 water carbonate rock system dissolution and precipitation of carbonate rocks element cycles and so forth had been named karst biogeochemistry in order to reveal their internal control mechanism over space and time chinese researchers undertook an in depth exploration of their interrelationships the main results of karst biogeochemistry in china can be summarized as follows i biogenic activity plays an important role in regulating dissolution and precipitation of carbonate rocks ii biogenic metabolic effects are involved in the positive or negative modulation of 13c 15n and the cycling of other elements iii co2 exchange during carbonate rock dissolution and precipitation which is mainly due to photosynthesis results in the accumulation of organic matter and iv primary karst biogeochemistry models have been established to evaluate carbon and nitrogen cycling in addition to these findings future studies should increasingly focus on the following topics i the apparent stability and transformation of dissolved organic carbon caused by microbial activities need to be clarified ii the temporal spatial scales of microbial biomineralization and the accompanying variances of karst biogeochemical cycles should be investigated to comprehensively understand the transformations and transport of substrates from biological activity in the co2 water carbonate rock system iii regional global scale models on karst biogeochemical cycles should be developed for the study of large small scale spatial and temporal variance on karst biogeochemical cycles iv new advanced techniques and methods are required and should be applied for the karst studies involving mathematics hydrochemistry isotope chemistry geology biology and so forth

chemical weathering in the upper reaches of xijiang river draining the yunnan guizhou plateau southwest china abstract chemical and strontium isotopic compositions of nanpanjiang river and beipanjiang river in the upper reaches of xijiang river draining the yunnan guizhou plateau southwest china were measured with a main purpose to understand the rock weathering and associated co 2 consumption rates in the karstic landform dominated area the chemical ion composition of the river water is characterized by dominance of ca 2 mg 2 and hco 3 and so 4 2 which account for more than 90 of total ion concentration 87 sr 86 sr ratios of nanpanjiang river water range between 0 7080 and 0 7140 while those of most beipanjiang river water vary within a limited range from 0 7075 to 0 7085 weathering of carbonate rocks dominate chemistry of major ions especially in the water of beipanjiang river whereas weathering of silicate minerals in the upper reaches of nanpanjiang river basin is obvious in addition to carbonate weathering mainly according to the sr isotopic composition of the river water analyses of the stoichiometry of the river water show that the water chemistry is controlled by carbonate dissolution not only by carbonic but also by sulfuric acid and indicate that sulfuric acid plays an important role in carbonate weathering the sulfate in river water is mainly from atmospheric input by coal combustion industries and from oxidation of sulfide minerals during weathering of coal containing strata and coal mining in the catchment the chemical weathering rates of silicate and carbonate and associated co 2 consumption rates by both carbonic and sulfuric acid and by only carbonic acid are respectively estimated the results show that chemical weathering rates of carbonate and silicate weathering in beipanjiang river basin are higher than those of nanpanjiang river basin showing linkages of geology and geography in the catchment to crustal weathering the involvement of sulfuric acid in carbonate weathering greatly enhances the carbonate weathering but lowers the co 2 consumption rates indicating that sulfide acid is an important agent to rock weathering and the role of sulfide acid should further be clarified in view of the regional and global budget of co 2

chemical weathering and co2 consumption in the xijiang river basin south china monthly samples of riverine water were collected and analyzed for the concentrations of major ions ca2 mg2 k na hco3 so42 cl no3 dissolved silicon and total dissolved solids tds at wuzhou hydrological station located between the middle and lower reaches of the xijiang river xjr from march 2005 to april 2006 more frequent sampling and analysis were carried out during the catastrophic flooding in june 2005 stoichiometric analysis was applied for tracing sources of major ions and estimating co2 consumption from the chemical weathering of rocks the results demonstrate that the chemical weathering of carbonate and silicate rocks within the drainage basin is the main source of the dissolved chemical substances in the xjr some 81 20 of the riverine cations originated from the chemical weathering processes induced by carbonic acid 11 32 by sulfuric acid and the other 7 48 from the dissolution of gypsum and precipitates of sea salts within the drainage basin the co2 flux consumed by the rock chemical weathering within the xjr basin is 2 37 x 10 11 mol y 1 of which 0 64 x 10 11 mol y 1 results from silicate rock chemical weathering and 1 73 x 10 11 mol y 1 results from carbonate rock chemical weathering the co2 consumption comprises 0 38 x 10 11 mol during the 9 d catastrophic flooding the co2 consumption from rock chemical weathering in humid subtropical zones regulates atmospheric co2 level and constitutes a significant part of the global carbon budget the carbon sink potential of rock chemical weathering processes in the humid subtropical zones deserves extra attention c 2008 elsevier b v all rights reserved

carbonate weathering related carbon sink fluxes under different land uses a case study from the shawan simulation test site puding southwest china abstract in the study of global climate change a major focus of research into the carbon cycle is to determine the fate of missing carbon sinks carbonate weathering related carbon sinks as a result of water carbonate co2 aquatic phototroph interactions may make a major contribution establishing optimal land uses which determine soil co2 concentrations and water supplies for carbonate dissolution may be a feasible and effective way to increase the sink potential elucidating both the hydrological and the hydrochemical behavior under different land uses is critical for rational planning of land use changes to increase the carbon sink given the complexity within natural karst catchments the shawan simulation test site was established at puding southwest china to simulate the influence of land uses with controlled carbonate test beds bare rock bare soil crop land grass land shrub land soil co2 concentrations hydrochemical parameters ph major ion concentrations and the spring artificial drain discharge were intensively measured from sept 1 2015 to aug 31 2016 to investigate the carbon and water responses to different land uses in different seasons in the vegetated land uses crop grass or shrub dic increased due to the increase of soil co2 resulting from stronger microbial activities and root respiration in summer and autumn growing seasons in the bare rock and soil cases there was also an increase in dic in summer and autumn due to decomposition of prior organic matter within soils and or rock pores the average dic concentration ranking high to low was grass land shrub land crop land bare soil bare rock soil co2 concentration was thus the dominant of dic concentration which is a key multiplier of carbon sink fluxes csf 0 5 dic rd where rd is depth of runoff dic is dic concentration and 0 5 because in carbonate dissolution only half of the hco3 is of atmospheric carbon origin however runoff depth ranked almost in reverse order i e from high to low bare rock bare soil crop land shrub land grass land the csf ranking from high to low was grass crop shrub bare rock bare soil a new parameter lcic land use change impact on csf is defined to compare the impacts of land use change on dic and rd and evaluate their combined effects on csf compared to bare rock the absolute values of lcic lcic s were 1 and csfs were larger for the three tanks with vegetation cover csf is smaller for bare soil lcic

effect of different land use land cover on karst hydrogeochemistry a paired catchment study of chenqi and dengzhanhe puding guizhou sw china summary rainfall spring stage water temperature ph and conductivity in the paired karst spring catchments of chenqi and dengzhanhe which shared the same climatic condition but different land use land cover lulc at puding guizhou province sw china were monitored by two high resolution multi parameter auto recordable instrument of ctdp300 during the hydrological year of september 2007 september 2008 other monthly hydrogeochemical and carbon isotopic 13c variations in the paired karst catchments during the same hydrological year were also investigated a thermodynamic model was used to link the continuous data to monthly hydrogeochemical data allowing the calculation of co2 partial pressure pco2 and calcite saturation index sic on a continuous basis the primary study objective was to understand how the karst processes and karst hydrogeochemistry respond to different lulc which is essential to assessing the karst related carbon cycle marked seasonal and storm scale variations were found for ph conductivity pco2 sic and 13c of the two springs indicating that both springs were dynamic and variable systems however there were differences in the magnitude and direction of the variations of these features between the two springs the higher pco2 and hco 3 concentration and lower ph sic and 13c in chenqi spring than those in dengzhanhe spring tend to be related to the difference in lulc between chenqi and dengzhanhe spring catchments in the chenqi spring catchment there was larger soil cover and the paddy land was located in the discharge area both of which produced and kept more co2 a major driving agent for the karst processes and lower 13c in the soil aquifer system while in the dengzhanhe spring catchment area there was larger bare carbonate rock occurrence and the paddy land was located mainly in the recharge area moreover the ph increased and pco2 decreased generally in chenqi spring after rainfall possibly due to more carbonate dissolution in the larger soil cover rich in limestone fragments in the spring catchment while the ph decreased and pco2 increased generally in dengzhanhe spring after rainfall all these differences show that soil cover and land use pattern played important roles in the karst processes in other words the karst hydrogeochemistry and the karst related carbon cycle could be regulated effectively by different lulc in addition the higher concentrations of ca2 so 4 2 mg2 and conductivity of dengzhanhe spring were due to the dissolution of more gypsum and dolomite minerals in the strata of dengzhanhe spring catchment therefore the karst hydrogeochemical parameters including ph conductivity hco 3 ca2 mg2 so 4 2 pco2 sic and 13cdic could serve as good indicators of different lulc and the other environmental changes

carbon flux and landscape evolution in epigenic karst aquifers modeled from geochemical mass balance this paper considers the contributions of epigenic karst processes as a major element of the carbon cycle and a significant agent of landscape evolution geochemical models developed from monitoring data and water samples are used to estimate the variation and magnitude of dissolved inorganic carbon dic flux in karst landscapes at several scales from local to global at the local scale the cumberland river watershed of southeast kentucky these geochemical models are also used to evaluate the potential role of sulfur in the production of dic and to compute an estimated rate of landscape erosion geochemical modeling using ionic species and modeled discharge reveal a variable rate of dic flux driven by large fluctuations in calcite saturation and discharge ratios of reaction products and principal component analyses pca suggest that some bedrock dissolution may be driven by the oxidation of reduced sulfur derived from brines entrained into the karst aquifers over the 3730 km2 of carbonate exposure in the cumberland river 25 8 62 4 gg yr of carbon dioxide co2 is conveyed from the atmosphere through the dissolution of carbonate at the global scale this translates to 123 296 tg yr of co2 delivered by karst processes into the aqueous system the bedrock portion of dic equates to a flux of 32 6 2 6 m3 35 2 2 8 m3 of bedrock during the period of study of which 29 was dolomite this translates to a landscape erosion rate of 13 1 17 9 mm ka in the 3 45 4 32 km2 of carbonate exposure in the studied watershed based upon 16 km of cave survey data spanning a vertical range of 72 to 75 m above base level this suggests that cave development in the watershed spans the plio pleistocene using the modeled erosion rates the ages of cave levels 4 03 5 71 3 08 4 56 1 57 2 43 1 01 1 67 0 45 0 91 and 0 45 ma are in good agreement with regional studies of plio pleistocene landscape evolution in the appalachian lowland plateaus copyright 2015 john wiley sons ltd

importance of suspended sediments and dissolved organic carbon to carbon exports in karst the vadu crisului karst basin in the pădurea craiului mountains romania abstract exports of dissolved inorganic carbon dic from karst aquifers are a significant contribution to the global carbon cycle contributions of particulate inorganic carbon pic and dissolved organic carbon doc in karst groundwater are often unaccounted for in carbon budgets this investigation considers field chemistry discrete samples and continuous monitoring data collected between october 2016 and december 2016 to quantitatively evaluate the net export of dissolved solutes total suspended sediments tss and doc within the vadu crisului karst basin in the p durea craiului mountains of northwest romania measurements of carbon isotopes 13c in dic and in bedrock specific ultraviolet absorption suva and carbon to nitrogen c n ratios were used to evaluate the relative contribution of different sources of carbon to the aqueous system 13cdic at the aquifer input trend toward an atmospheric signal in winter with lower doc concentrations and suva values and c n ratios corresponding to degraded carbon sources illustrating the reduction in microbial respiration in soil with cold temperatures at the spring 13cdic values trend more toward a soil based signal after storm events that bring increased doc concentrations with suva values corresponding to significantly degraded carbon dissolution in this karst basin is principally driven by the carbonate equilibrium reactions and direct meteoric recharge only accounts for 4 to 13 of observed discharge most recharge enters the karst basin through infiltration into dolines and epikarst on the zece hotare karst plateau and this results in a broadly stable chemical signature of spring water storm events do have a significant impact on mechanical erosion and chemical processes operating in the karst basin the addition of pic and tss flux increase landscape erosion rates by 1 1 to 1 2 and 7 9 to 8 3 respectively above the denudation rate computed by dissolved solutes 36 5 56 9 mm ka the modeled annual flux of dic from this karst basin 1 37 105 to 1 64 105 kg yr scales to a global co2 flux of 7 08 1011 to 1 06 1012 kg yr adding a modeled flux of doc increases the estimates of co2 flux by 12 to 22 a significant addition to the global carbon cycle

cave ventilation and rainfall signals in dripwater in a monsoonal setting a monitoring study from ne india detailed monitoring of subterranean microclimatic and hydrological conditions can delineate factors influencing speleothem based climate proxy data and helps in their interpretation multi annual monitoring of water stable isotopes air temperature relative humidity drip rates and pco2 in surface soil and cave air gives detailed insight into dripwater isotopes temperature and ventilation dynamics in mawmluh cave ne india water isotopes vary seasonally in response to monsoonal rainfall most negative values are observed during late indian summer monsoon ism with a less than one month lag between ism rainfall and drip response two dry season and two less well distinguishable wet season dynamic ventilation regimes are identified in mawmluh cave cave air temperatures higher than surface air result in chimney ventilation during dry season nights dry season days show reduced ventilation due to cool cave air relative to surface air and cold air lake development both high water flow and cooler than surface cave air temperatures result in air inflow during wet season nights wet season daytime ventilation is governed by river flow but is prone to stagnation and development of cold air lakes co2 monitoring indicates that pco2 levels vary at diurnal to annual scale mawmluh cave seems to act as co2 sink during part of the dry season while very likely additional data is needed to establish whether wet season cave air co2 levels rise above atmospheric values drip behavior is highly nonlinear related to effective recharge dynamics and further complicated by human influence on the epikarst aquifer