Hydrochemistry and carbon isotope characteristics of Nujiang River water:Implications for CO_(2) budgets of rock weathering in the Tibetan Plateau

The Tibetan Plateau is one of the most complicated geographical units worldwide in terms of its tectonic and environmental background.Although a hotspot for continental weathering and carbon cycling studies,accurate determination of the weathering carbon budget is challenging in this area,especially sink and source flux quantification and the controlling mechanisms.Compared with other major rivers on the plateau,the Nujiang River is characterized by less human disturbance and maintains a relatively pristine state.This study investigates the high spatiotemporal resolution hydrochemistry and dual-carbon isotope composition(δ~(13)C_(DIC)andΔ~(14)C_(DIC))of river water in the Nujiang River Basin.The results revealed that the solutes and dissolved inorganic carbon in the river water are predominantly derived from rock weathering by carbonic and sulfuric acids,mainly due to the carbonate weathering process,and significantly enhanced by deep carbon sourcing from hot springs in the fault zone.The average contributions of geological and modern carbon in the main stream of the Nujiang River are 35.2%and 64.8%,respectively,and sulfide oxidation contributes>90%of sulfate ions in the river water.After considering the involvement of sulfuric acid generated by sulfide oxidation during rock weathering,the calculated consumption fluxes of atmospheric CO_(2) by silicate and carbonate weathering in the watershed were decreased by approximately 52.0%and 37.4%,respectively,compared with those calculated ignoring this process.Rock weathering of the Nujiang River Basin is a“CO_(2) sink”on a short time scale,while the participation of sulfuric acid makes it a“CO_(2) source”on a geological time scale.The high-frequency observations of ion concentrations,elemental ratios,and calculated contributions of different rock weathering materials indicate that carbonate rock weathering is more sensitive to temperature and runoff variations than silicate rock weathering,with the solute contribution from carbonate weathering increasing significantly during monsoon period.The material input from different rock types is dominated by the hydrological pathways and water-rock reaction times in the basin.This study reveals the river solute origins and weathering CO_(2) sequestration effect in response to a monsoonal climate in one of the most representative pristine plateau watersheds in the world,which is of great importance for elucidating the weathering control mechanisms and CO_(2) net sourcesink effect in plateau watersheds.

Dynamic response and failure process of horizontal-layered fractured structure rock slope under strong earthquake

Rock slope with horizontal-layered fractured structure(HLFS)has high stability in its natural state.However,a strong earthquake can induce rock fissure expansion,ultimately leading to slope failure.In this study,the dynamic response,failure mode,and spectral characteristics of rock slope with HLFS under strong earthquake conditions were investigated based on the large-scale shaking table model test.On this basis,multiple sets of numerical calculation models were further established by UDEC discrete element program.Five influencing factors were considered in the parametric study of numerical simulations,including slope height,slope angle,bedding-plane spacing and secondary joint spacing as well as bedrock dip angle.The results showed that the failure process of rock slope with HLFS under earthquake action is mainly divided into four phases,i.e.,the tensile crack of the slope shoulder joints and shear dislocation at the top bedding plane,the extension of vertical joint cracks and increase of shear displacement,the formation of step-through sliding surfaces and the instability,and finally collapse of fractured rock mass.The acceleration response of slopes exhibits elevation amplification effect and surface effect.Numerical simulations indicate that the seismic stability of slopes with HLFS exhibits a negative correlation with slope height and angle,but a positive correlation with bedding-plane spacing,joint spacing,and bedrock dip angle.The results of this study can provide a reference for seismic stability evaluation of weathered rock slopes.

Comparing mineral weathering and elemental transport between earth's critical zone with different parent rocks in Yanshan Mountain,Hebei province,China

Bedrock weathering performs a significant influence on the evolution of Earth’s critical zone.Carbonate rock(dolostone),metamorphic rock(gneiss),and sedimentary rock(sandstone)geological formations in Yanshan Mountain,Hebei Province,are taken as objects to probe the controlling of geological formations on weathering characteristics,migration,and enrichment of elements as well as structure of Earth’s critical zone under the identical climate conditions through geological field survey,analysis on minerals component,element distribution in the weathering profile.The dolostone geological formation(DGF)is lithologically dominated by dolostone,characterized by the strongest and predominant chemical weathering.During bedrock weathering and pedogenesis,DGF is marked by significant depletion of CaO,Mg O,S,Mn,Mo and enrichment of N,K,Fe_(2)O_(3),and Zn with concentrations of P,Cu,and B keeping stable.Shortage of soil-forming materials and significant loss are driven by soil erosion,which results in thin regolith and soil.The soil thickness is less than 10 cm,and the regolith thickness is less than 30 cm.The vegetation community is predominantly rock arbor or brush,which is calcivorous and tolerant of barrenness.Plagiogneiss is a dominant rock type of gneiss geological formation(GGF),characterized by the weakest weathering and fast chemical and physical weathering rate.GGF is masked by significant depletion of P,K,CaO,MgO,Fe_(2)O_(3),Mn,Cu and enrichment of N,S,Mo,and B,with contents of Zn keeping stable.Both soil and regolith developed in GGF are relatively thick for one of the reasons that biotite expands during weathering.The soil thickness is more than 50 cm,and the regolith thickness ranges from 100 to 200 cm.The vegetation community is predominantly high-quality economic forests and various arbors because of the enrichment of nutrients in GGF.Sandstone is primarily a rock type of sandstone geological formation(SGF),characterized by moderate weathering degree and slow chemical weathering rate.SGF is marked by significant depletion of P,K,CaO,MgO,Fe_(2)O_(3),and enrichment of N,S,Mn,Cu,Zn,and Mo,with fluctuant changes of Zn and B.The thickness of soil developed in SGF varies between that of DGF and GGF.The soil thickness ranges from 30 to 50 cm,and the regolith thickness ranges from 50 to 100 cm.Chinese pines are widely spread on the shady slopes of SGF.Research provides theoretical support for screening dominant ecological resource areas,ecological industry development and ecological protection and restoration for Yanshan Mountain,Hebei Province.

Digital monitoring of rotary-percussive drilling with down-the-hole hammer for profiling weathered granitic ground

Rock and geotechnical engineering investigations involve drilling holes in ground with or without retrieving soil and rock samples to construct the subsurface ground profile.On the basis of an actual soil nailing drilling for a slope stability project in Hong Kong,this paper further develops the drilling process monitoring(DPM)method for digitally profiling the subsurface geomaterials of weathered granitic rocks using a compressed airflow driven percussive-rotary drilling machine with down-the-hole(DTH)hammer.Seven transducers are installed on the drilling machine and record the chuck displacement,DTH rotational speed,and five pressures from five compressed airflows in real-time series.The mechanism and operations of the drilling machine are elaborated in detail,which is essential for understanding and evaluating the drilling data.A MATLAB program is developed to automatically filter the recorded drilling data in time series and classify them into different drilling processes in sub-time series.These processes include penetration,push-in with or without rod,pull-back with or without rod,rod-tightening and rod-untightening.The drilling data are further reconstructed to plot the curve of drill-bit depth versus the net drilling time along each of the six drillholes.Each curve is found to contain multiple linear segments with a constant penetration rate,which implies a zone of homogenous geomaterial with different weathering grades.The effect from fluctuation of the applied pressures is evaluated quantitatively.Detailed analyses are presented for accurately assess and verify the underground profiling and strength in weathered granitic rock,which provided the basis of using DPM method to confidently assess drilling measurements to interpret the subsurface profile in real time.

Geochemistry of the upper Permian sandstones in the Dalong Formation in the South Yellow Sea Basin,East China:implications to provenance,weathering,and tectonic setting

To reconstruct the paleoenvironment,the petrography and geochemical compositions of the upper Permian Dalong Formation(Fm)(P_(3)d)sandstones in the Central Uplift,South Yellow Sea Basin,was investigated,after which the provenance,tectonic setting,weathering conditions,and diagenetic history were determined.The Dalong Fm is mainly composed of sandstones with a few mudstones and limestones.The petrographic analysis showed that the P_(3)d sandstones are in low maturity and could be classified into feldspar sandstone and lithic sandstone on average framework composition of Q_(63)F_(16)L_(21).The major and trace element results show that Dalong Fm sandstones are enriched in Rb and depleted in Cr and Ni compared with the upper continental crust(UCC).The chemical weathering intensity is weak to low moderate in the source area as indicated by the chemical index of alteration(CIA)and other results from a variety of methods.The diagenetic process included three main stages:eodiagenesis,mesodiagenesis,and telodiagenesis.Tectonic discrimination plots show that the source areas were an active continental margin(ACM)and a passive continental margin(PCM),which may have been related to the northward movement of the Lower Yangtze Plate(LYP)and the collision between the LYP and the North China Plate(NCP).

DEM investigation of weathered rocks using a novel bond contact model

The distinct element method（DEM） incorporated with a novel bond contact model was applied in this paper to shed light on the microscopic physical origin of macroscopic behaviors of weathered rock, and to achieve the changing laws of microscopic parameters from observed decaying properties of rocks during weathering. The changing laws of macroscopic mechanical properties of typical rocks were summarized based on the existing research achievements. Parametric simulations were then conducted to analyze the relationships between macroscopic and microscopic parameters, and to derive the changing laws of microscopic parameters for the DEM model. Equipped with the microscopic weathering laws, a series of DEM simulations of basic laboratory tests on weathered rock samples was performed in comparison with analytical solutions. The results reveal that the relationships between macroscopic and microscopic parameters of rocks against the weathering period can be successfully attained by parametric simulations. In addition, weathering has a significant impact on both stressestrain relationship and failure pattern of rocks.

Estimating the properties of weathered bedrock and pile-rock interaction from the geological strength index

The effect of variable rock mass properties on pile-rock interaction poses a great challenge to the design of stabilizing piles and numerical analysis of pile-rock interaction. The paper presents a novel method to estimate the properties of weathered bedrock, which can be applied to routine design of landslide-stabilizing piles for collivial landslides. The Ercengyan landslide located in the Three Gorges Reservoir, China, is the area of interest for this study. A geological investigation and triaxial tests were conducted to estimate the basic parameters, including Geological Strength Index(GSI), uniaxial compressive strength σ_(ci) and Hoek-Brown constant m_i of intact bedrock in the study area. Hoek-Brown criterion was used to estimate mechanical properties of the weathered rock, including elastic modulus E_m, cohesion c, friction angle Φ, and normal ultimate lateral resistance p_(max). A parametric study was performed to evaluate the effect of parameterizations of GSI, σ_(ci) and m_i on the bedrock properties and p-y curves. The estimated rock mass properties were used with PLAXIS 2D software to simulate pile-rock interaction. Effect of GSI on stress at the pile-rock interface and in the rock, pile bending moment, pile shear force, and p-y curve were analysed.

Compacting Deformation Engineering Characteristics of Weathered Soft Rock Mixture in Subgrade

The engineering characteristics of weathered soft rock are important contents of soft rock mechanics. They also play a significant role in compacting deformation, which has been known to exert a significant amount of influence on the stability of highway filling subgrade engineering. In an effort to investigate this aspect of the problem, compacting tests and unconfined compressive strength tests have been carried out on weathered argillaceous slate and pelitic siltstone rocks, which are broken and graded before the test. The testing results indicate that the relationships of both between stress and strain and between axial strain and tangent modulus are exponential relationships; the size of the grain plays some influence on the deformation modulus, whereas the water content impacts the compressive strength greatly, which shows quadratic function; the unconfined compressive strength is linear with the dry density of loose soft rock mixtures. Therefore, the water content must be controlled in both the design and the construction of subgrade engineering of soft rock filling, and at the same time some effective measures should be taken to reach the requirement of compaction.

Prediction of Young’s modulus of weathered igneous rocks using GRNN,RVM,and MPMR models with a new index

Young’s modulus(YM)of intact rock is an important parameter in the assessment of engineering behaviours of rock masses,and it cannot always be obtained in an economical and practical manner in laboratory experiments.The main purpose of this study is to examine the capability of the minimax probability machine regression(MPMR),relevance vector machine(RVM),and generalised regression neural network(GRNN)models for the prediction of YM.The other aim is to determine the usefulness of a new index,the n-durability index(ndrb),which is based on porosity and the slake durability index.According to the regression analysis performed in this study,the n-durability index as an explanatory parameter performs better than the P-wave velocity(Vp),porosity,and slake durability index in the models,considering the results herein as well as the existing literature.According to regression error characteristic curves,Taylor diagrams,and performance indices,the best prediction model is MPMR,while the worst is the GRNN model.Although GRNN is the worst of the soft computing models,its performance is slightly better than that of the multiple linear regression(MLR)model.According to the results of the study,the MPMR and RVM models with ndrb and Vp are successful tools that can predict the YM of igneous rock materials to different degrees.

The Fate of Chromium in Weathered Ultramafic Rocks and Their Derivitative Soils in Cuba: Clues from Spectroscopic Studies

In its cationic,trivalent form,Chromium(Cr)it is a micronutrient,and exhibits low environmental mobility.In hexavalent form,however,it is a human carcinogen and also highly mobile.Climate is a key environmental factor controlling weathering rates and stability of primary and secondary Cr-bearing minerals.Knowledge of Cr oxidation state and mineral residence is therefore essential to estimating the risk posed by Cr in serpentinites,chromite mine wastes,and soils developed on these parent materials.X-ray absorption spectroscopy(XAS)is currently the best available technique for determination of the relative abundance of Cr(III)and Cr(VI)in situ(that is,without digestion of solid phases).A brief review of relevant XAS studies of is presented below,focusing on studies in tropical climates1,as they will be most relevant to eastern Cuba’s extensively serpentinized ophiolite belt.Cr(III)-bearing spinels are usually the dominant and most refractory Cr host in ultramafic rocks.Previous XAS studies2 indicate that in tropical climates,Cr-spinels weather rapidly to form Cr(III)-bearing secondary Fe(III)(hydr)oxides(goethite,hematite).Manganese(Mn)is also enriched in ultramafic rocks2;as Mn(IV),it can also co-precipitate with Fe(III)(hydr)oxides,or form its own secondary(hydr)oxides.A previous study found up to 20%Cr(VI)in in a tropical,serpentine soil that contained substantial Mn,and a strong correlation between the*amounts of Cr(VI)and Mn(IV)in the soil profile2.Theresults of several XAS studies suggest that a close association of Mn(IV)and Cr(III)in secondary Fe(hydr)oxides is necessary for oxidation of Cr(III)to Cr(VI)via electron transfer reactions with Mn(IV);however,additional XAS studies have shown that organic matter3and Cr-bearing aluminosilicates4 may also be important sources of Cr(III)to the environment under specific conditions.The stability and fate of Cr has not been studied in detail for these two host phase types,to the best of our knowledge.Access to XAS facilities to perform Cr geochemical experiments is limited and will only become more so in the future.We are working to develop and apply(micro)Raman spectroscopy to evaluate Cr oxidation state and mineral residence(in crystalline and amorphous materials).In addition to standard Raman scattering,we are employing resonance Raman(785 nm laser)to enhance signal from Cr(VI)-bearing phases and laser-stimulated photoluminescence to identify Cr(III)associated with Al-rich alteration products

Hydrochemistry of Rara Lake: A Ramsar lake from the southern slope of the central Himalayas,Nepal

High-altitude Himalayan lakes act as natural storage for environmental evidence related to climate change and environmental factors.A great number of lakes are distributed in the southern slope area of the central Himalayas;however,research concerning the hydrochemical processes of these lakes is still insufficient.Herein,we present a comprehensive study on the water chemistry of the lake waters and the inlet stream waters from Rara Lake in western Nepal based upon samples collected in November 2018.The p H,dissolved oxygen,chlorophyll-aconcentration(chl-a),water temperature,electric conductivity(EC)and total dissolved solids(TDS)were measured in situ,and the concentrations of major ions(Ca^(2+),Mg^(2+),K^(+),Na^(+),Cl^(-),SO_(4)^(2-),and NO_(3)^(-))were analyzed in the laboratory.The results revealed that the water in Rara Lake is slightly alkaline,with p H values ranging from 7.6-7.98.The cations,in decreasing order of concentration in the lake water,are Ca^(2+)>Mg^(2+)>K^(+)>Na^(+)with average concentrations of20.64 mg·L^(-1),11.78 mg·L^(-1),1.48 mg·L^(-1) and 0.72 mg·L^(-1),respectively;the order and concentrations for the anions is HCO_(3)^(-)>SO_(4)^(2-)>Cl^(-)>NO_(3)^(-),with average concentrations of 122.15 mg·L-1,2.15 mg·L-1,0.46mg·L-1 and 0.55 mg·L-1,respectively.The dominant cation and anion in the lake water are Ca2+and HCO3-and they account for 48.14%and 71.8%of the totals,respectively.The range of lake water TDS is from 95mg·L^(-1) to 98 mg·L^(-1),with an average of 96.85 mg·L^(-1).The high ratio of(Ca^(2+)+Mg^(2+))to total cations and the low ratio of(Na^(+)+K^(+))to total cations indicate that Rara Lake receives ions from rock weathering,especially from carbonate rocks.Similarly,Gibbs boomerang diagrams and Piper diagrams also support the hydrochemistry of Rara Lake as being dominated by rock-weathering patterns.Likewise,other statistical analysis tools,such as Principal Component Analysis(PCA)and correlation strongly suggest the dominance of weathering of calcium and magnesium bicarbonate rocks as the major source of ions in Rara Lake.However,several traces of anthropogenic inputs into the lake were noticed,and the hypolimnion in the lake appears to be oxygen deficient,which may not be an issue at present but cannot be ignored in the future.

Origin of Boron in the Gas Hure Salt Lake of Northwestern Qaidam Basin, China: Evidence from Hydrochemistry and Boron Isotopes

The Gas Hure Salt Lake(GHSL) in the northwestern Qaidam Basin, western China, is rich in boron(B) resources, but its B-resource origin is hardly known. Hydrochemical compositions and B isotope characteristics of different waters were collected around the GHSL, including the river water, stream water, spring water, salt-lake brine, intercrystalline brine, well water, drilling brine, and solar pond brine. The hydrochemical signatures suggest that silicates, carbonates and evaporates are the main B-bearing rocks during the water dynamic. The reservoir estimation of B resources shows that the Kulamulekesay River(KLMR) and the Atekan River(ATKR) contribute annually 18.3 tons and 22.84 tons of B, respectively, with a total amount of 11.72 × 10^(4) tons of B during the past 5.7 ka. In comparison with the known B reservoir(32.96 × 10^(4) tons) in the GHSL, a significant amount of B in the GHSL was probably recharged from deep fluids and sediments around the GHSL. The B concentration and B-enrichment degree are shaped by the evaporation process, which are highly elevated at the carnallite and bischofite stages.

Indexing the engineering properties of residual soils in the southern slopes of Mashhad,NE Iran

Residual soils are weathering products of rocks that are commonly found under unsaturated conditions.The properties of residual soils are a function of the degree of weathering.A series of index properties,engineering properties and geophysics survey examinations were performed on residual soils from two major geological formations in Iran.In the present research,the index properties of residual soils in the south of Mashhad city in Iran are investigated.Natural and artificial trenches were analyzed for evaluating the weathering profiles and collecting soil samples.Disturbed and undisturbed samples were obtained from each of the soil profile horizons resulting from weathering of different parent rocks.Subsequently,physical properties and mechanical properties of the soil samples were determined in accordance with ASTM standards.Also,the mineralogical composition,chemistry,and texture of the soil were evaluated in 51 profiles.The field observations showed the difference in the weathering profile of residual soils deposited on various rocks(igneous,sedimentary,and metamorphic).These profiles mainly consisted of two horizons includingresidual soil on top and saprolite at the bottom.The results of laboratory tests and geotechnical data showed that the properties of residual soil samples change by depth.Moreover,depending on the type of origin rock,the properties are different in various types of residual soils.In most of the samples,the moisture content of soil horizons was also increased by depth.Based on the unified soil classification(USCS),the soils of the upper horizons appeared to be classified as ML(Lean silt)and CL(Lean clay)while the soils of the lower horizons(saprolite zone)fall in SC(clayey sand),SM(silty sand),and SW(wellgraded sand)classes.Moreover,the results demonstrated that the particle size of the soil was increased by depth.Comparison of results of the geotechnical tests showed that properties of residual soils are changed by variations of depth,weathering level,and type of parent rock.Considering the concentration of the number of lines and the concentration of the points of intersection,the length and dimension fractal of lineaments in the southeastern part of the study area,it is evident that this zone possesses weathering severity and soil thickness.Fieldwork data from this zone have also verified the severity of weathering conditions.The analysis of lineaments trends in different parts of the study area indicated that the lineaments with the NW-SE trend have a strong effect on weathering development.The weathering depth depends on the orientation of bedding joints with respect to the slope in the study area.Slope inclination and soil thickness are controlled by weathering and erosion processes.

Chemical Characteristics and Influencing Factors of Surface Water in the Heihe River Basin of the Qinling Mountains

From April to October in 2017,water samples were collected from the Heihe River basin of the Qinling Mountains,and hydrochemical eigenvalues were analyzed. The comprehensive character description method,Gibbs plot,triangular diagrams of anions and cations,correlation analysis and factor analysis were used to analyze the chemical composition of surface water and its influencing factors. The results show that the runoff of the Heihe River basin was weakly alkaline with low mineralization. HCO_3^- content was the highest in all anions,while Ca^(2+) content was the highest in all of the cations. The hydrochemical type of the water body was HCO_3^--Ca^(2+). The main factor influencing the composition of chemical ions in the river water of the Heihe River basin was the weathering of calcite and other carbonate rocks. At the same time,the weathering of silicate rocks also had a certain influence on the hydrochemical composition of the basin.

Grouting techniques for the unfavorable geological conditions of Xiang'an subsea tunnel in China

One of the major challenges during subsea tunnel construction is to seal the potential water inflow. Thepaper presents a case study of Xiang＇an subsea tunnel in Xiamen, the first subsea tunnel in China. Duringits construction, different grades of weathered geomaterials were encountered, which was the challengingissue for this project. To deal with these unfavorable geological conditions, grouting was adoptedas an important measure for ground treatment. The grouting mechanism is first illustrated by introducinga typical grouting process. Then the site-specific grouting techniques employed in the Xiang＇ansubsea tunnel are elaborated. By using this ground reinforcement technique, the tunneling safety of theXiang＇an subsea tunnel was guaranteed. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

Comparison of surface water chemistry and weathering effects of two lake basins in the Changtang Nature Reserve,China

The geochemistry of natural waters in the Changtang Nature Reserve,northern Tibet,can help us understand the geology of catchments,and provide additional insight in surface processes that influence water chemistry such as rock weathering on the Qinghai–Tibet Plateau.However,severe natural conditions are responsible for a lack of scientific data for this area.This study represents the first investigation of the chemical composition of surface waters and weathering effects in two lake basins in the reserve（Lake Dogaicoring Qiangco and Lake Longwei Co）.The results indicate that total dissolved solids（TDS）in the two lakes are significantly higher than in other gauged lakes on the Qinghai–Tibet Plateau,reaching 20–40 g/L,and that TDS of the tectonic lake（Lake Dogaicoring Qiangco）is significantly higher than that of the barrier lake（Lake Longwei Co）.Na＋and Cl-are the dominant ions in the lake waters as well as in the glacier-fed lake inflows,with chemical compositions mainly affected by halite weathering.In contrast,ion contents of inflowing rivers fed by nearby runoff are lower and concentrations of dominant ions are not significant.Evaporite,silicate,and carbonate weathering has relatively equal effects on these rivers.Due to their limited scope,small streams near the lakes are less affected by carbonate than by silicate weathering.

Experimental Study on Mechanical Properties of Weathered Rock Covered by Loess

Based on dynamic triaxial test, the mechanical properties of the weathered rock covered by loess were studied. The cohesion value of weathered mudstone is far below that of the weathered sandstone, while the internal friction angle values are basically equivalent, about 30. Compared with the undisturbed sample, the cohesion value of remodeling weathered rock sample decreases significantly. With the increase of moisture content, the strength of weathered mudstone is obviously decreased due to the influence of the water softening efect. This results illustrate that the bearing stratum is not easily afected by external disturbance in comparison to weathered mudstone. In the engineering, in order to ensure the good mechanical properties of the soil, more attention should be paid to keeping the water content constant, even to reducing the water content. The experiments show that the relations between shear stress and strain of weathered rock were nonlinear and the behavior of weathered rock can be expressed by the hyperbolic model. The initial modulus of undisturbed weathered rock, under the same consolidation conditions, is much greater than that of remodeling samples. Meanwhile, the initial dynamic elastic modulus of sandstone is also greater than that of the mudstone. The dynamic shear modulus ratios of the undisturbed sandstone, the undisturbed mudstone, as well as the remodeling mudstone have the normalization characteristics with the increase of dynamic shear strain. The damping ratio of mudstone is larger than that of the sandstone, and the damping ratio of remolding sample is also greater than that of the undisturbed mudstone. The mudstone has the bad mechanical properties as bearing stratum.

A carbon-neutrality-capactiy index for evaluating carbon sink contributions

The accurate determination of the carbon-neutrality capacity(CNC)of a region is crucial for developing policies related to emissions and climate change.However,a systematic diagnostic method for determining the CNC that considers the rock chemical weathering carbon sink(RCS)is lacking.Moreover,it is challenging but indispensable to establish a fast and practical index model to determine the CNC.Here,we selected Guizhou as the study area,used the methods for different types of carbon sinks,and constructed a CNC index(CNCI)model.We found that:(1)the carbonate rock chemical weathering carbon sink flux was 30.3 t CO_(2)km^(-2)yr^(-1).Guizhou accounted for 1.8%of the land area and contributed 5.4%of the carbonate chemical weathering carbon sink;(2)the silicate rock chemical weathering carbon sink and its flux were 1.44×10^(3)t CO_(2)and 2.43 t CO_(2)km^(-2)yr^(-1),respectively;(3)the vegetation-soil ecosystem carbon sink and its flux were 1.37×10^(8)t CO_(2)and 831.70 t CO_(2)km^(-2)yr^(-1),respectively;(4)the carbon emissions(CEs)were 280 Tg CO_(2),about 2.8%of the total for China;and(5)the total carbon sinks in Guizhou were 160 Tg CO_(2),with a CNCI of 57%,which is 4.8 times of China and 2.1 times of the world.In summary,we conducted a systematic diagnosis of the CNC considering the RCS and established a CNCI model.The results of this study have a strong implication and significance for national and global CNC determination and gap analysis.

Spatial-temporal patterns of major ion chemistry and its controlling factors in the Manasarovar Basin, Tibet

The Manasarovar Basin in southern Tibet, which is considered a holy land in Buddhism, has drawn international academic attention because of its unique geographical environment. In this study, based on actual measurements of major ion concentrations in 43 water samples collected during the years 2005 and 2012, we analyzed systemically the spatialtemporal patterns of water chemistry and its controlling factors in the lake and inflowing rivers. The results reveal that the water in the Manasarovar Basin is slightly alkaline, with a pH ranging between 7.4-7.9. The amounts of total dissolved solids （TDS） in lake and river waters are approximately 325.4 and 88.7 mg/l, respectively, lower than that in most of the surface waters in the Tibetan Plateau. Because of the long-term effect of evaporative crystallization, in the lake, Na^＋ and HCO3^- have the highest concentrations, accounting for 46.8% and 86.8% of the total cation and anion content. However, in the inflowing rivers, the dominant ions are Ca^2＋ and HCO3^-, accounting for 59.6% and 75.4% of the total cation and anion content. The water exchange is insufficient for such a large lake, resulting in a remarkable spatial variation of ion composition. There are several large inflowing rivers on the north side of the lake, in which the ion concentrations are significantly higher than that on the other side of the lake, with a TDS of 468.9 and 254.9 mg/l, respectively. Under the influence of complicated surroundings, the spatial variations in water chemistry are even more significant in the rivers, with upstreams exhibiting a higher ionic content. The molar ratio between （Ca^2＋＋Mg^2＋） and （Na^＋＋K^＋） is much higher than 1.0, revealing that the main source of ions in the waters is carbonate weathering. Although natural processes, such as rock weathering, are the major factors controlling main ion chemistry in the basin, in the future we need to pay more attention to the anthropogenic influence.

Soil C, N and P stocks and stoichiometry under different vegetation on the surface of the Leshan Giant Buddha

The accumulation of soil organic matter and nutrients is an important pathway in effectivelyunderstanding the mechanisms of plant settlement and rock weathering, while the characteristics ofsoil organic carbon (C), nitrogen (N) and phosphorus (P) under different vegetation remain unclear.In this study, the stocks and stoichiometry of soil organic C, N and P were determined in differentpositions and types of vegetation on the surface of the Leshan Giant Buddha. We found that the totalstocks of soil organic C, N and P were 1689.77, 134.6 and 29.48 kg, respectively, for the Buddha.The stocks of soil organic C, N and P under vascular plants were higher than those under othervegetation, with highest values observed under herb. Higher stocks per unit area (m2) of soil organicC, N and P were found on the left and right arms, shoulders, and two platforms. These results providea full primary picture in understanding soil organic C, N and P accumulation and distribution on thesurface of the Buddha, which could supply the fundamental data on weathering management of theBuddha and other similar open-air stone carvings.