Chemical Denudation Research Articles

Anthropogenic impacts on the water chemistry of a transboundary river system in Southeast Asia

The Red River originating from Yunnan province, China is the second largest river in Vietnam in terms of length and discharge. Combination of water chemistry monitoring data of 4 years (2018–2022) from different sub-basins of the Red River (the Da, Lo, Thao, Tra Ly, and Day) with historical datasets indicates a decline in pH from 8.1 in 2000 to 7.7 in 2021, greater CO2 concentrations and a shift from waters naturally dominated by carbonate weathering to waters dominated by evaporite weathering. Such changes were most apparent in the delta area where heavy human activities have increased influxes of most dissolved chemicals, except SiO2. Evaporite weathering is particularly enhanced by mining and deforestation occurring in upstream regions of both China and Vietnam. Pyrite oxidation, alongside silicate weathering, is enhanced along the Red River Fault Zone but reduced in tributaries with a higher proportion of hydropower reservoirs. Longer water residence times in these large reservoirs (total volume > 2.7x1010 m3) located in the Da and Lo sub-basins have also increased primary productivity, leading to higher evasion/uptake of CO2 and SiO2, lower total dissolved solids (TDS), and higher pH. The total physical and chemical denudation rates of upstream mountain tributaries ranged between 0.107 ± 0.108 and 0.139 ± 0.137 mm yr−1, mainly due to reservoir implementation and instream aquatic biogeochemistry changes. Our findings demonstrate that anthropogenic activities are profound factors impacting the water chemistry of the Red River system.

Long-Term Changes in Water and Ion Flows of the Pechora River, the Longest Full-Water European Arctic River

Long-term series of annual and seasonal water flow and major ions in the Pechora River were analyzed. Long-term phases of increased and decreased water flow were identified, ranging in duration from 11 to 49 years, and the major characteristics of these phases were determined. Changes in the sequence and boundaries of contrast phases in the annual and snowmelt spring–summer flood runoff were found to coincide. The difference between the mean seasonal water runoff during the phases of increased and decreased flow varied from 12 to 41%. The ion flow values of contrast phases typically differed by 9 to 36%, which is less than for water flow. This is due to the inverse dependence between ion concentrations and water discharge. Such peculiar negative feedback stabilizes the rates of chemical denudation in the river catchments to some extent and, thus, the discharge of major ions into seas, even during significant variations in water.

Appearance of the rotifer community as a potential indicator of stable paleohydrological conditions in peatlands since the Late Glacial: a case study of three wetlands in Poland

In paleolimnological studies, rotifers are usually a very rare component in multiproxy research. These small invertebrates are identified from sediments by their loricas. Analysis of subfossil rotifers was conducted for sediment cores collected from three peatlands in within Poland: the Grel raised bog (S Poland, Carpathians, Orawa-Nowy Targ Basin), the Imszar raised bog (NE Poland, Podlasie Region), and the Podemszczyzna peatland (SE Poland, Sandomierz Basin). Results were compared with multiproxy analyses of peat deposits: pollen of aquatic and mire plants, non-pollen palynomorphs (NPPs), and geochemical analyses. Analysis of the rotifers indicated the occurrence of the bdelloid species Habrotrocha angusticollis (Murray, 1905). In all profiles of the studied peatlands, the occurrence of rotifers was not correlated with pollen of aquatic or mire plants or NPPs; they seem to be more related to geochemical indices. The highest densities of rotifers were found in profile sections without significant fluctuations of geochemical variables, i.e. those with higher Na/K (chemical denudation) ratios and stable redox conditions (Fe/Mn ratio). The study of subfossil rotifers supported by multiproxy analysis of peat deposits could be a useful tool for indication of periods with stable palaeohydrological conditions during the Late Glacial and Holocene.

Seasonal dynamics of karst surface dissolution based on a limestone tables experiment (Slovak karst)

Chemical denudation in karst is the basic process of karst relief formation. However, it is influenced by many factors of varying intensity that depend on the climatic conditions and characteristics of each given location. Based on measurable results of weight loss of limestone tablets, we monitored the intensity of chemical denudation in two areas of the Slovak Karst, Silica Plateau and Jasov Plateau that are situated in the most developed karst plateau region of Slovakia. Both experimental sites are similar in terms of geographical conditions, thus comparable between them. In each locality, we placed three sets of standardized tablets at a depth of 50 cm, 20 cm, and on the soil surface. The research began in December 2016 and has continued up to the end of 2021, with drying and weighing of the samples taking place each three months. The lowest weight loss was recorded on samples placed on the surface (in both sites) and the highest at the depth of 20 cm. This is due to biological activity in the soil during the growing season (2.65 - 2.82 mg/cm 2/year). The highest weight losses over time are observed at the turn of winter and spring, where the effect of snowfall and snow melting water plays an important role. The average dissolution rate in the spring season is between 3.78 and 4.12 mg/cm 2/year, whereas in winter is from 3.24 to 4.06 mg/cm 2/year.

Land use changes impact on selected chemical denudation element and components of water cycle in small mountain catchment using SWAT model

Land use changes are extremely important in the context of land and water management. This study examines impact of land use and land cover (LULC) changes on nitrate nitrogen, outflow and surface runoff in the agriculture catchment in the Polish Carpathians using the Soil and Water Assessment Tool (SWAT). The study covers 25-year (1995–2019) and was divided into three periods relating to different LULC patterns (1995–2004, 2005–2012, 2013–2019). The LULC maps used were based on aerial photos from 1997, 2009, and 2016. The SWAT was calibrated and applied to periods with variable LULC (in simulation 1) and by keeping the LULC constant during the period 1995–2019 (simulation 2; the LULC from 1997) to determine the impact of LULC changes on the analysed variables. The ongoing LULC changes were found to have resulted in a reduction of cultivated land area (by 72 %) and an increase of grassland (by 45 %), forest (by 2 %) and urbanised areas (by 17 %). The SWAT model achieved reasonable accuracy. The model results tend to overestimate the load of nitrate nitrogen and underestimate outflow and surface runoff. The LULC changes resulted in a decrease in outflow between 1995 and 2004 of 24 % in comparison to 2013–2019, and a decrease in surface runoff of 12 %. At the same time, there was a significant decrease in nitrate nitrogen load of 68 % (from 13.0 kg ha−1 in 1995–2004 to 4.2 kg ha−1 in 2013–2019). If the LULC of 2013–2019 was restored to 1997 conditions (as in simulation 2), the outflow and load of NO3-N would be higher by 16 % (12 % in simulation 1) and 67 % (55 % in simulation 1) in relation to the observed values. The impact of LULC on the analysed parameters was spatially differentiated between subbasins depending on the scale of the land use changes. The research conducted here indicates that planning and managing the effects of LULC changes is of key importance for sustainable development in terms of the quantity and quality of water.

Physical and biogeochemical drivers of solute mobilization and flux through the critical zone after wildfire

A nine-year time series of nutrient cation and anion concentration and efflux from three forested catchments in the Jemez River Basin Critical Zone Observatory (JRB-CZO) in northern New Mexico was used to quantify the pulse of chemical denudation resulting from varying levels stand-replacing wildfire intensity in May-June of 2013. The 3 years of pre-fire and 6 years of postfire data were also probed to shed light on the mechanisms underlying the pulsed release and the subsequent recovery. The initial large solute pulse released to the streams—K+, Ca2+, Mg2+, SO42-, Cl−, dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and total dissolved nitrogen (TDN)—was caused by leaching of hillslope ash deposits during the first monsoon storms post-fire. Debris flow following the wildfire likely redistributed much of the ash-containing sediments along streams and valley bottoms. Sustained elevated solute concentrations observed in the surface waters throughout the post-fire period relative to pre-fire baselines is consistent with these soluble materials being periodically flushed from the soils during wet seasons, i.e., snowmelt and summer monsoons. As microbial mediated reactions and biotic uptake—due to plant regrowth—recover after fire, nutrient ion export (e.g., NO3-, Cl− and SO42-) steadily decreased toward the end of the post fire period, but remained above pre-fire levels, particularly for NO3- and SO42-. Surface water concentrations of polyvalent cations (e.g., Al and Fe) decreased significantly after the fire. Our observations suggest that changes in organic matter composition after fire (e.g., increased humification index—HIX) and the presence of pyrogenic carbon may not favor organo-metal complexation and transport. Finally, differences in burn severity among the three watersheds presented in this study, provide insights of the relative impact of solute exports and resilience. The catchments that experienced high burn severity exhibited greater solute fluxes than the less severely burn. Moreover, despite these differences, toward the end of the post-fire period these surface waters presented low and similar solute effluxes, indicating system recovery. Nonetheless, magnitudes and rebounds were solute and process specific. The results of this study highlight the importance of surface and near surface physical and biogeochemical processes on the long-lasting geochemical denudation of forested catchments following wildfires of varying intensities.

The temporal and spatial complexity of carbonate deposition at Romincka forest cupola spring-fed fen (Central Europe) during the Holocene

Calcium carbonate records from alkaline fens provide valuable insights into past climate fluctuations. Yet, the climate is not the sole factor controlling tufa deposition. The present study aims to determine the drivers of postglacial tufa deposition at the exceptionally well-developed cupola alkaline fen located in the north-eastern Poland. Tufa deposition time frames and conditions are reconstructed using radiocarbon dating, geochemical, including loss on ignition and δ13C and δ18O, plant macrofossils, and mollusc analyses of two sediment sequences taken from the top and slope of the fen cupola. The exceptional in young-glacial area continuous Holocene-long history of CaCO3 precipitation was supported by a strong supply of artesian waters. The locally high endogenic heat flow density accelerated permafrost degradation and warranted the early start of artesian water circulation and tufa deposition ca. 11650 cal yr BP. Deposition of interlayered peat and tufa continued until ca. 4700 cal yr BP when the increasing height of the cupola disabled water outflow at the fen top, and peat with scattered CaCO3 started to accumulate. Seepages on the fen slopes supported deposition of interlayered peat and tufa on lower elevated parts of the mound until ca. 2300 cal yr BP. Colder and/or dryer episodes weakened the predominately intensive CaCO3 precipitation mainly at the top of the mound. Vegetation favoured tufa deposition (i) after the development of the soil, which enhanced chemical denudation of carbonate detritus from glacial deposits, (ii) during times of decreased evapotranspiration when the forest cover on the surrounding land diminished. Tufa deposition at the cupola top was limited between ca. 8450 and 4700 cal yr BP when trees entered the fen surface. The human impact on tufa deposition was likely limited except for the melioration of the surrounding area ca. 50 cal yr BP, after which CaCO3 precipitation eventually stopped.

Chemical denudation dynamic based on hydrochemical measurements in the area of Drienovecká jaskyňa Cave basin (Slovak karst, Slovakia)

Denudation is a fundamental process for the development of karst relief. It has different intensity in different geological and climatic condition and beside this many other partial factors influence the intensity and dynamic of the process during the year. In karst systems, there is often a positive correlation between water partial pressure of CO2 and denudation. The Drienovecká jaskyňa Cave spring represents typical active fluviokarstic spring and its catchment area is represented by Wetterstein and Waxenec limestones, and Drienovec conglomerates. This catchment study area is located at the contact of the conti-nental and oceanic climate, in terms of altitude at the border between the lowland and moun-tain climate. During three hydrological years we measured main karst water parameters that helped us bring first results on chemical denudation in the catchment area. The water from the spring is of calcium-magnesium-bicarbonate type. Hydrogeochemical analyses in-dicate that it is mostly water from an open hydrogeological structure. Water of the cave spring is oversaturated with respect to calcite, which is documented by the saturation index of calcite, whose values are higher than the solubility product of calcite. During the studied period, the dynamic of the chemical denudation rate is clearly observable with peaks in spring months in year 2014 and 2016. The average value of denudation rate for the entire period is 21.06 mg Ca2+. Factors that influence chemical denudation include, for example, type of carbonate rock, CO2 partial pressure, water and air temperature, chemical compo-sition of the aqueous solution, activity of soil organisms, vegetation and others. Water from melted snow can also play a significant role in changes in water chemistry and thus chemical denudation. URL: https://www.gcass.science.upjs.sk/

Chemical denudation in a small mountainous coastal river in the tropics: Insights from Kali River, Southwestern India

A study was conducted for the first time to understand the geochemical processes controlling the chemistry of the Kali River in tropical southwestern India and to determine its chemical denudation and net carbon dioxide consumption. The samples were collected from the source to the mouth of the river (15 stations) during monsoon (July 2018), post-monsoon (December 2018), and pre-monsoon (May 2019) seasons. The catchment experiences intense chemical weathering on account of heavy rainfall accompanied by runoff during the summer monsoon. Seasonal variations in silicate weathering processes are significantly controlled by runoff, and their rates are proportional to the discharge. The annual chemical denudation rate (CDR) calculated exclusively from the upstream catchment that are dominated by silicate rocks estimated to be 48.2 tons/km2/yr with a silicate weathering rate (SWR) of 41.3 tons/km2/yr and carbonate weathering rate (CWR) of 6.9 tons/km2/yr. The CDR is two times higher than the global mean average rate. The mean CO2 consumption rate (CCR) for silicate weathering is 2.9 × 105 mol. km−2 y−1, which is three-fold higher than the global average. Silicate rock weathering intensity (Re) values indicate the formation of the gibbsite. The Re does not show variations from upstream to downstream, implying the rapid transport of weathered material from the river catchment area. Intense rain, runoff, and temperature are the dominant climatic factors that accelerate weathering in the study area. This underscores the significance of small mountainous coastal rivers as drivers of intense chemical weathering in humid tropical environments, which removes the atmospheric CO2. This study adds to the existing database on chemical weathering and associated fluxes in granitic catchments across the globe.

Factors and Chemical Denudation Dynamics in the area of Drienovec Cave Basin (Slovak Karst, Slovakia)

Factors and Chemical Denudation Dynamics in the area of Drienovec Cave Basin (Slovak Karst, Slovakia)

The Long-Term Changes in Water and Ions Flux of Northern Dvina and Pechora

The long-term data sets of the annual and seasonal water flows and the major ions fluxes of the Northern Dvina River at the village of Ust-Pinega and Pechora River at the village of Ust-Tsilma were analyzed. Long-term phases of increased and decreased values of water runoff were identified, the duration of which ranged from 9 to 50 years, and their main characteristics were determined. The sequence and boundaries of the change in the contrasting phases of the annual water flow, the snowmelt flood flow and the summer-autumn flow on the Northern Dvina River and the annual water flow and snowmelt flood flow on the Pechora River practically coincided. The difference between the average annual and seasonal water flow in the phases of its increased and decreased values ranged from 11 to 41%, and the ion fluxes were in the range of 5–36%. The ion flux of contrast phases, as a rule, differs less than the water flow. This is due to the inverse nature of the dependence of the concentration of ions on the daily water discharges, because of which a kind of negative feedback is formed, stabilizing the intensity of chemical denudation in the wa- tersheds of these rivers and the flux of the main ions into the seas, even with noticeable fluctuations in water flow. Keywords: the Northern Dvina River, the Pechora River, water flow, ion flux, long-term phases of changes, cumulative deviation curves.

Chemical denudation and geochemical degradation of the relief in the Quadrilátero Ferrífero region, Brazil: An approach from an important hydrographic microbasin up to the geological unity

The Quadrilátero Ferrífero is one of the most important metallogenic provinces in the world, and most of these mineral resources are from geological units belonging to the Minas Supergroup. The present study investigates the chemical denudation and the lowering of the relief of the Bule Stream microbasin, which covers an area of 38 km2 and is composed almost entirely of units of the Minas Supergroup. As the study area has no anthropic influence, it can represent a natural background. Surface river water samples were collected at 15 points in the watershed in 4 periods: Dec/2015 and Apr/2018, representing the rainy period (summer), and in Aug/2016 and Aug/2017, representing the dry period (winter). Analyzes of their dissolved chemical compositions (Ca, Mg, Na, K, silica, and the main constituent metals) were performed, determining the total dissolved solids (TDS), in addition to flow and pH calculations. The main influencing source of water chemistry in the microbasin is rainfall, associated with the materials geological “flushing” process, in both periods. The main control factor for denudation is the lithological control and its erodibility, where an average of 246.4 tons of material removed and transported in the watershed per year was estimated. Ca, Mg and Si, the main constituents of rocks present in the microbasin, such as dolomite, phyllite, and quartzite, presented the highest denudational values. The ‘Colonia sector’, which drains a quartzite area, and the ‘west sector,’ which drains an area of carbonate rocks, presented the highest denudation rate values, verifying that the size of the drainage area of these sectors is not a considerable parameter determining the denudational behavior of the hydrographic basin. The extrapolation of denudation and degradation for the entire Minas Supergroup, considering no anthropic influence, provided values of 12,475.62 ton/yr of material removed through weathering with a relief degradation of 2.14 m/Ma.

Solute transport and solutional denu-dation rate of carbonate karst in the semi-arid Zagros region (southwes-tern Iran)

We conducted a one-year-long study of solute load measured three times per month in three neighboring subwatersheds (Alashtar, Khorram Abad, and Biranshahr) located in the Karkheh River basin in the Zagros region of southwestern Iran. Research was focused on the chemical composition of water (solute load), karst denudation rate, spatial and temporal variability, as well as comparison of solute load with suspended load. Results show that Ca-Mg-HCO3 is the dominant water type that reflects the lithological characteristics of the catchment areas. Lack of seasonal fluctuation of solute load and absence of dilution during high water levels but evident seasonal course of discharge defines the highest solute flux during the annual maximum of discharge in spring months. The highest solute flux is related to flood events. High annual variation of Na1 concentration compared to conservative Cl2 as well as Chloro-Alkali indexes (CAI and CAI2) suggests that Na1 adsorption and desorption during ion-exchange reactions occur in the regolith. This Na+ variability, to some extent, explains weak Ca21 and Mg21 dilution effect during high water levels. During the measurement period (2014-2015), solute flux calculated per catchment area amounted to 49-69 t km-2 a-1 (tons per km per year). The chemical composition of water and discharge shows by far the highest chemical denudation of limestones and dolomites (87−89 %), while dissolution of gypsum is of minor importance (11−13 %). As a result, the carbonate karst solutional denudation rate is between 0.010 and 0.040 mm a21 , where the higher values are more probable for longer periods due to the relatively low discharge during the spring of 2015. Comparison of dissolved and suspended loads indicates that the transport of suspended load is an order of magnitude less than transport of the dissolved load; the only exception is one flash flood event when suspended load exceeded the dissolved load. Besides a small decrease in solute flux as well as carbonate karst dissolution rates from NW to SE, no large hydrochemical differences between the three subwatersheds were detected.

МНОГОЛЕТНЯЯ ИЗМЕНЧИВОСТЬ ИОННОГО СТОКА КРУПНЫХ РЕК АРКТИЧЕСКОЙ ЗОНЫ РОССИИ

Studies of river ion runoff and its temporal variability are important. It affects coastal waters and is interrelated with climatic changes in the Arctic region. Long-term data on the chemical runoff of macrocomponents (chlorides, sulfates, hydrocarbonates, calcium and magnesium ions) at the outlet sections of large Arctic rivers in Russia - Pechora, Usa, Yenisei, Ob, Pur, Taz, Lena, Yana and Kolyma are given. The values of volumes and modules of chemical runoff were calculated on the basis of long-term (1980-2018) hydrological and hydrochemical information from the state observation system of Roshydrom-et. It is shown that the change in the absolute values of the chemical runoff is consistent with the water inflow. Greatest contribution to the ionic runoff is made by hydrocarbonates. The intra-annual change in the water inflow and the macrocomponents runoff occurs synchronously. There is a decisive role of water runoff in the formation of chemical runoff from the catchments of large Arctic rivers. Comparison of the chemical runoff modulus indicator made it possible to classify them into low, medium or high ionic runoff rivers. It was found that the maximum runoff of macrocomponents occurs from the catchment of the Usa river. It is may be due to active processes of chemical denudation and climate change.

Impacts of chemical weathering and human perturbations on dissolved loads of the Wei River, the Yellow River catchment

As the largest tributary of the Yellow River, the Wei River drains a basin mainly comprising two different geological settings, i.e., the Chinese Loess Plateau (CLP) in the north covered by Quaternary loess and the Qinling Mountains area in the south. Exploring the influence of natural weathering processes and human activities on river chemistry has high significance in understanding chemical transport from the Wei River to the Yellow River. The geochemical characteristics of the Wei River mainstream and its tributaries as well as chemical weathering were determined using a geochemistry and isotope dataset of high spatial resolution. The mainstream clearly exhibited a mixture of major elements and stable isotopes from tributaries on both the north and south banks, with values within the range of those of the tributaries. North-bank tributaries draining thick loess deposits showed higher contents of major elements and the enrichment of stable isotopes, reflecting the influence of geological setting on river chemistry. The dominant processes accounting for the water chemistry of the mainstream are evaporite (39–75%) and carbonate weathering (21–54%). Within the watershed, evaporite dissolution and silicate weathering are higher in the northern CLP area, whereas carbonate weathering is higher in the southern Qinling Mountain area. The CO2 consumption by the Wei River is 19.9 × 109 mol/yr, accounting for 32.5% of the total CO2 consumption by the middle reaches of the Yellow River. During the high-flow period, the chemical weathering flux of the Wei River was found to be within the range of northern rivers in China, while the chemical weathering rate was relatively high in the semi-arid region. This suggests that chemical denudation is a significant factor for the river chemistry of the CLP at least in the high-flow period.

Small peatland with a big story: 600-year paleoecological and historical data from a kettle-hole peatland in Western Russia

Peatlands are important records of past environmental changes. Based on a multiproxy analysis, the main factors influencing the evolution of a peatland can be divided into autogenic and allogenic. Among the important allogenic factors, apart from climate change, are deforestation and drainage, which are directly associated with human impact. Numerous consequences arise from these processes, the most important of which are physical and chemical denudation in the catchment and the related hydrological disturbances in the catchment and peatland. The present study determined how human activities and the past climatic variability mutually influenced the development of a small peatland ecosystem. The main goals of the study were: (1) to trace the local changes of the peatland history over the past 600 years, (2) to investigate their relationship with changes in regional hydroclimate patterns, and (3) to estimate the sensitivity of a small peatland to natural and human impact. Our reconstructions were based on a multiproxy analysis, including the analysis of pollen, macrofossils, Chironomidae, Cladocera, and testate amoebae. Our results showed that, depending on the changes in water level, the history of peatland can be divided into three phases as follows: 1/the phase of stable natural conditions, 2/phase of weak changes, and 3/phase of significant changes in the catchment. Additionally, to better understand the importance of the size of catchment and the size of the depositional basin in the evolution of the studied peatland ecosystem, we compared data from two peatlands – large and small – located close to each other. The results of our study indicated that “size matters,” and that larger peatlands are much more resilient and resistant to rapid changes occurring in the direct catchment due to human activities, whereas small peatlands are more sensitive and perfect as archives of environmental changes.

Ionic Runoff as a Way to Determine the Degree of Karst Denudation (Case Study Jasov Plateau, Slovak Karst, Slovakia)

Estimation of the catchment area of a karst spring is not possible in all areas for various reasons. The Slovak Karst is protected by the highest degree of protection and karst springs are used as a source of drinking water for the second largest city in Slovakia, Košice. From this reason, no results on ionic runoff or chemical denudation have been published from this area and the most appropriate way to obtain information about the denudation rate is to determine the ionic runoff. This paper provides an overview of ionic runoff results based on sampling and analysis of karst water from six springs in the period November 2013–October 2016 (three hydrological years) and periodic measurements. Springs have significantly fluctuated flow rates from 0 L/s in summer and autumn up to 192 L/s, and episodic events during the snow melting and heavy rain in the spring of 2013 are also known (more than 380 L/s). The total value of ionic runoff for the area of 40,847 m3/y.km2 is comparable with the Vracanska Plateau in Bulgaria, which lies at a similar altitude and with a similar amount of precipitation.

Glaciation enhanced chemical weathering in a cold glacial catchment, western Nyaingêntanglha Mountains, central Tibetan Plateau

The uplift of the Tibetan Plateau (TP) not only may enhance physical denudation and chemical weathering but also makes this area contain the largest glacier storage outside the polar regions. There is an argument on whether glaciation favours chemical weathering and carbon sequestration. To explore chemical weathering processes and intensities in the cold glacial region of the central TP, hydrochemistry of the river water in two catchments, i.e. the Qugaqiong and Qugaqie, was monitored from April to September 2018 with high-frequency sampling. These two catchments share similar geographical features except there are some cold glaciers in the upper reaches of the Qugaqie. The results of chemical composition show that the river water of the Qugaqie has a lower proportion of Ca2+ and HCO3− but higher SO42− and K++Na+ compared with the Qugaqiong. The seasonal variation of ionic concentration in the Qugaqie is significant but minor in the Qugaqiong. Those differences highlight the glacial impact in the Qugaqie compared with the non-glacierized Qugaqiong. Solutes in the glacial runoff of the Qugaqie mainly derive from sulfide oxidation. Its contribution to cations in the runoff of the Zhadang glacier and the Hanging glacier reaches 39% and 36%. The second most important contribution is carbonate dissolution (32% for both glacial runoffs). Silicate weathering provides fewer solutes and its contribution is only 20% and 11% in the two glacial runoffs, respectively. River water of the Qugaqiong shares similar hydrochemical characteristics with the non-glacial tributaries draining granodiorite/biotite adamellite in the Qugaqie. The contribution of sulfide oxidation to solutes in those rivers decreases to 10% while carbonate dissolution increases to 50%. Glacial comminution exposed trace sulfide minerals, thus made sulfide oxidation became pretty active due to this reaction is much faster than other mineral dissolution. The carbonate weathering rate (CWR) and silicate weathering rate (SWR) in the Qugaqie catchment are 9.7 t/km2/y and 6.7 t/km2/y. In comparison, values in the Qugaqiong catchment are 6.9 t/km2/y and 3.8 t/km2/y, respectively, which means CWR and SWR is 1.4 and 1.8 times higher in the Qugaqie catchment, respectively. Higher runoff and physical erosion rates are considered as the main reasons for higher chemical denudation rates in the Qugaqie catchment. The drainage system of the glaciers is dominated by the distributed pattern, which caused longer residences time of water, thus further promoted chemical weathering in the glacierized region. Our observation supports the idea that glaciation in the glacierized catchment of the central TP enhances chemical weathering, especially for SWR. Chemical denudation rates in the Qugaqie catchment remain at a moderate level compared with other glacierized catchments in the world and lithology and runoff are important factors to cause this spatial heterogeneity.

Buffering role of soil in chemical denudation in mountainous areas affected by windfall events – In light of experimental research

The important environmental effect of strong mechanical disturbances of the soil cover caused by windfall events can be an increase in chemical weathering and chemical denudation. The aim of the study was to examine how soils with different properties affect the rate of limestone weathering and to what extent do soils buffer ion leaching affecting chemical denudation. A laboratory experiment was performed to answer the questions listed above. Samples taken from typical soils developed on calcareous material in mountainous areas in the temperate climatic zone as well as relatively pure Jurassic limestone were collected for the purpose of the said experiment. Five trials were performed for every combination of soil material and limestone, which yields a total of 90 Eppendorf's conical tubes. Once a week deionized water was poured through each Eppendorf tube (with a hole in the bottom) and then collected. Rock samples and soil samples were analyzed before and after the experiment. The chemical composition of the soil solution (filtrate) was analyzed every five weeks.Our experiment showed that large differences in the degree of chemical weathering of limestone and in the chemical denudation of Ca2+, Mg2+, and K+ at the catchment scale may be expected in soils characterized by different properties. Accelerated chemical weathering of limestone causes Ca2+,Mg2+, and K+ denudation rates to increase, but the studied weathering process was not linearly correlated with denudation rates. The response depends on soil pH, amount of soil organic matter (SOM) in the soil, and the quantity of cations in of the soil exchange complex.Environmental disturbances occurring in mountain areas may lead to the exposure of limestone on the soil surface as a result of events such as windthrow. At least four response scenarios of the disturbed system may be distinguished, depending on soil properties, which are different for (1) soils with thick and very acidic, organic horizons, which is typical for areas under dwarf pine communities, (2) Calcaric Cambisols with thick and slightly acidic organic horizons typical for coniferous and broadleaf forests, (3) Calcaric Cambisols without a thick organic horizon, which is typical for meadows, (4) Rendzic Leptosols, whose soils are typical of calcareous grassland.

Elemental composition of biogenic sediments reveals palaeoclimatic changes during the Late Weichselian in a Central European river valley: A statistical approach

Five sections of sediment from mire infillings located in different part of the catchment small river valley in central Europe were studied by lithological and geochemical analysis in order to examine the response of aquatic ecosystems to the environment changes during Late Weischselian (LW). Differentiation of geochemical composition and grain-size properties in biogenic deposits is being considered as a result of change hydroclimatic conditions and geology structure in individual parts of the catchment. The principal component analysis (PCA) and clustered by hierarchical method (HCA) were chosen to create the lithogeochemical facies and their chronostratigraphy variability. Biogenic sediments of the studied river mires, regardless of the location in a given reach of the valley, are represents mainly by mineral or organic-mineral lithogeochemial facies with increased of lithophilic elements (Na, K and Mg). Similar chemical composition of gyttja and peat sediments in almost all periods of LW, indicate the strongly mechanical denudation processes in the Grabia River valley. The major process, conditioning the development of the mires (in it type and rate sedimentation), was the variable terrigenous material input which are related to its variable dynamic of floods. The higher than expected chemical denudation probably a result of specific groundwater flow direction and dissolving vari-grained sands and silts, which build plains in the central part of the study catchment. The number and thickness of individual lithogeochemical facies are caused by differences in the potential volume of the hydrologically active zone and geological conditions of the emerge or disappear permafrost.