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Author(s): Jiangyi Zhang [sup.1] [sup.2] , Zhifang Xu [sup.1] [sup.2] Author Affiliations: (1) grid.458476.c, 0000 0004 0605 1722, Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, [...], The accurate determination of arsenic species in waters is still an environmental challenge because of the rapid redox transformation of As. So, a procedure for on-site separation of As(III), As(V), methylarsonic acid, and dimethylarsinic acid in natural waters has been developed. The procedure involves passing a water sample through tandem cation- and anion-exchange resin columns in the field. Selective retention of arsenic species occurs in resin cartridges followed by selective elution. The eluate is collected and analyzed by inductively coupled plasma mass spectrometry. The standard reference material CASS-5 was diluted 10 times and analyzed directly to validate accuracy of measurements, and SLRS-2 was used to validate on-site separation procedure, respectively. The results agreed well with the certified values of standard reference materials. The proposed procedure was applied to the on-site separation of arsenic species from natural waters.

Author(s): Jiangyi Zhang [sup.1] [sup.2] , Zhifang Xu [sup.1] [sup.2] Author Affiliations: (1) grid.458476.c, 0000 0004 0605 1722, Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, [...], Direct determination of dissolved silicon (DSi) in atmospheric precipitation by ICP-MS is still a challenge because of the presence of serious mass interferences. In this work, a reliable method based on CH.sub.4-Ar mixed gas plasma DRC-ICP-MS was successfully used for the direct determination of DSi in atmospheric precipitation samples. The interfering ions (.sup.14N.sup.14N.sup.+, .sup.12C.sup.16O.sup.+) were directly removed by the reaction with carbon dioxide gas and could be reduced by up to 99% at m/z 28. In addition, the sensitivity of .sup.28Si.sup.+ was 2-fold improved by CH.sub.4 modifier that was introduced to the ICP plasma at 2 mL/min, and the background signal was decreased to 60%. Under the optimized conditions, the limit of quantification was 5 [mu]g/L, and the reproducibility (RSD) was generally less than 3%. The proposed method was assessed using surface water standard reference materials, and the measured values agreed well with the certified values.

We study the propagation rules of acoustic bright solitons in bubble-containing media, as well as the strong anti-interference ability of acoustic solitons; and the effects of nonlinearity, dispersion, and dissipation on the dynamic properties of acoustic solitons are also analyzed. Based on the bubble–liquid mixture model, a lossy nonlinear Schrödinger equation is obtained. The analytical expression of the enveloped bright-acoustic solitons in the bubbly liquids is derived, which can accurately capture the propagation law of the acoustic bright solitons in the physical system, even if there is viscous loss in the medium. The dissipation-induced dynamics of acoustic solitons is studied through analytical and numerical methods, and the balancing effects of nonlinearity and dispersion in the propagation of bright solitons are analyzed. Furthermore, the particle nature and dynamic stability of bright-acoustic solitons in bubble-containing media are emphasized through fully elastic collisions between solitons moving in the same and opposite directions. This process obeys the energy and momentum conservation laws. After the collision, solitons can maintain their original amplitude, speed, and shape and continue to propagate undisturbed. [ABSTRACT FROM AUTHOR]

Ozone (O3), an important and ubiquitous trace gas, protects lives from harmful solar ultraviolet (UV) radiation in the stratosphere but is toxic to living organisms in the troposphere. Additionally, tropospheric O3 is a key oxidant and a source of other oxidants (e.g., OH and NO3 radicals) for various volatile organic compounds (VOCs). Recently, highly oxygenated organic molecules (HOM s) were identified as a new compound group formed from the oxidation of many VOCs, making up a significant source of secondary organic aerosol (SOA). The pathways forming HOM s from VOCs involve autoxidation of peroxy radicals (RO2), formed ubiquitously in many VOC oxidation reactions. The main sink for RO2 is bimolecular reactions with other radicals, such as HO2 , NO , or other RO2 , and this largely determines the structure of the end products. Organic nitrates form solely from RO2 + NO reactions, while accretion products ("dimers") form solely from RO2 + RO2 reactions. The RO2 + NO reaction also converts NO into NO2 , making it a net source for O3 through NO2 photolysis. There is a highly nonlinear relationship between O3 , NOx , and VOCs. Understanding the O3 formation sensitivity to changes in VOCs and NOx is crucial for making optimal mitigation policies to control O3 concentrations. However, determining the specific O3 formation regimes (either VOC-limited or NOx -limited) remains challenging in diverse environmental conditions. In this work we assessed whether HOM measurements can function as a real-time indicator for the O3 formation sensitivity based on the hypothesis that HOM compositions can describe the relative importance of NO as a terminator for RO2. Given the fast formation and short lifetimes of low-volatility HOMs (timescale of minutes), they describe the instantaneous chemical regime of the atmosphere. In this work, we conducted a series of monoterpene oxidation experiments in our chamber while varying the concentrations of NOx and VOCs under different NO2 photolysis rates. We also measured the relative concentrations of HOMs of different types (dimers, nitrate-containing monomers, and non-nitrate monomers) and used ratios between these to estimate the O3 formation sensitivity. We find that for this simple system, the O3 sensitivity could be described very well based on the HOM measurements. Future work will focus on determining to what extent this approach can be applied in more complex atmospheric environments. Ambient measurements of HOMs have become increasingly common during the last decade, and therefore we expect that there are already a large number of groups with available data for testing this approach. [ABSTRACT FROM AUTHOR]

Particulate matter has major climate and health impacts, and it is therefore of utmost importance to be able to measure the composition of these particles to gain insights into their sources and characteristics. Many methods, both offline and online, have been employed over the years to achieve this goal. One of the most recent developments is the Vaporization Inlet for Aerosols (VIA) coupled to a nitrate Chemical Ionization Mass Spectrometer (NO 3 -CIMS), but a thorough understanding of the VIA–NO 3 -CIMS system remains incomplete. In this work, we ran a series of tests to assess the impacts from different systems and sampling parameters on the detection efficiency of highly oxygenated organic molecules (HOMs) in the VIA–NO 3 -CIMS system. Firstly, we found that the current VIA system (which includes an activated carbon denuder and a vaporization tube) efficiently transmits particles (> 90 % for particles larger than 50 nm) while also removing gaseous compounds (> 97% for tested volatile organic compounds – VOCs). One of the main differences between the VIA and traditional thermal desorption (TD) techniques is the very short residence time in the heating region, on the order of 0.1 s. We found that this short residence time, and the corresponding short contact with heated surfaces, is likely one of the main reasons why relatively reactive or weakly bound peroxides, for example, were observable using the VIA. However, the VIA also requires much higher temperatures in order to fully evaporate the aerosol components. For example, the evaporation temperature of ammonium sulfate particles using the VIA was found to be about 100–150 °C higher than in typical TD systems. We also observed that the evaporation of particles with larger sizes occurred at slightly higher temperatures compared to smaller particles. Another major aspect that we investigated was the gas-phase wall losses of evaporated molecules. With a more optimized interface between the VIA and the NO 3 -CIMS, we were able to greatly decrease wall losses and thus improve the sensitivity compared to our earlier VIA work. This interface included a dedicated sheath flow unit to cool the heated sample and provide the NO 3 -CIMS with the needed high flow (10 L min -1). Our results indicate that most organic molecules observable by the NO 3 -CIMS can evaporate and be transported efficiently in the VIA system, but upon contact with the hot walls of the VIA, the molecules are instantaneously lost. This loss potentially leads to fragmentation products that are not observable by the NO 3 -CIMS. Thermograms, obtained by scanning the VIA temperature, were found to be very valuable for both quantification purposes and for estimating the volatility of the evaporating compounds. We developed a simple one-dimensional model to account for the evaporation of particles and the temperature-dependent wall losses of the evaporated molecules, and we thereby estimate the concentration of HOMs in secondary organic aerosol (SOA) particles. Overall, our results provide much-needed insights into the key processes underlying the VIA–NO 3 -CIMS method. Although there are still some limitations that could be addressed through hardware improvements, the VIA–NO 3 -CIMS system is a very promising and useful system for fast online measurements of HOMs in the particle phase. [ABSTRACT FROM AUTHOR]

With the intensification of human activities, nitrate pollutants in groundwater are receiving increasing attention worldwide. Especially in the arid Nile Delta of Egypt, groundwater is one of the most valuable water resources in the region. Identifying the source of nitrate in groundwater with strong human disturbances is important to effective water resource management. This paper examined the stable isotopes (δ15N/δ18O-NO3 and δ2H/δ18O-H2O) and the hydrogeochemical parameters of the shallow groundwaters in the arid southeast of the Nile Delta to assess the potential sources and transformation processes of nitrate under severe urban and agricultural activities. The results revealed that the groundwaters were recharged by the Nile River. Meanwhile, the infiltration of irrigation water occurred in the west, while the mixing with the deep groundwater occurred in the east regions of the study area. The TDS, SO42−, NO3−, and Mn2+ concentrations of groundwaters (n = 55) exceeded the WHO permissible limit with 34.6%, 23.6%, 23.6%, and 65.5%, respectively. The NO3− concentrations in the shallow groundwaters ranged from 0.42 mg/L to 652 mg/L, and the higher levels were observed in the middle region of the study area where the unconfined condition prevailed. It extended to the deep groundwater and eastward of the study area in the groundwater flow direction. The δ15N-NO3 and δ18O-NO3 values suggested that the groundwater NO3− in the west and east regions of semi-confined condition were largely from the nitrification of soil organic nitrogen (SON) and chemical fertilizer (CF). In contrast, wastewater input (e.g., domestic sewage and unlined drains) and prevalent denitrification were identified in the middle region. The denitrification might be tightly coupled with the biogeochemical cycling of manganese. This study provides the first report on the groundwater NO3− dynamics in the Nile Delta, which generated valuable clues for effective water resource management in the arid region. [ABSTRACT FROM AUTHOR]

The multi-scheme chemical ionisation inlet 1 (MION1) enables rapid switching between the measurement of atmospheric ions without chemical ionisation and neutral molecules using various atmospheric pressure chemical ionisation methods. In this study, we introduce the upgraded version, the multi-scheme chemical ionisation inlet 2 (MION2). The new design incorporates enhanced ion optics, resulting in increased reagent ion concentration, ensuring a robust operation, and enabling the use of multiple chemical ionisation methods with the same ionisation time. In order to simplify the regular calibration of MION2, we developed an open-source flow reactor chemistry model called MARFORCE. This model enables quantification of the chemical production of sulfuric acid (H2SO4), hypoiodous acid (HOI), and hydroperoxyl radical (HO2). MARFORCE simulates the convection–diffusion–reaction processes occurring within typical cylindrical flow reactors with uniform inner diameters. The model also includes options to simulate chemical processes in the following two scenarios: (1) when two flow reactors with different inner diameters are connected and (2) when two flows are merged into one using a Y-shaped tee, although with reduced accuracy. Furthermore, the chemical mechanism files in the model are compatible with the widely used Master Chemical Mechanism (MCM), allowing for future adaptation to simulate other chemical processes in flow reactors. Furthermore, we conducted a comprehensive characterisation of the bromide (Br-) and nitrate (NO3-) chemical ionisation methods with different ionisation times. We performed calibration experiments for H2SO4 , HOI , and HO2 by combining gas kinetic experiments with the MARFORCE model. The evaluation of sulfur dioxide (SO2), water (H2O), and molecular iodine (I2) involved dilution experiments from a gas cylinder (SO2), dew point mirror measurements (H2O), and a derivatisation approach combined with a high-performance liquid chromatography quantification (I2), respectively. Our findings indicate that the detection limit is inversely correlated with the fragmentation enthalpy of the analyte–reagent ion (Br-) cluster. In other words, stronger binding (resulting in a larger fragmentation enthalpy) leads to a lower detection limit. Additionally, a moderately longer ionisation time enhances the detection sensitivity, thereby reducing the detection limit. For instance, when using the Br- chemical ionisation method with a 300 ms ionisation time, the estimated detection limit for H2SO4 is 2.9×104 molec. cm -3. Notably, this detection limit is even superior to that achieved by the widely used Eisele-type chemical ionisation inlet (7.6×104 molec. cm -3), as revealed by direct comparisons. While the NO3- chemical ionisation method remains stable in the presence of high humidity, we have observed that the Br- chemical ionisation method (Br- –MION2) is significantly affected by the air water content. Higher levels of air water lead to reduced sensitivity for HO2 and SO2 under the examined conditions. However, we have found that a sharp decline in sensitivity for H2SO4 , HOI , and I2 occurs only when the dew point exceeds 0.5–10.5 ∘ C (equivalent to 20 %–40 % RH; calculated at 25 ∘ C throughout this paper). For future studies utilising the atmospheric pressure Br- chemical ionisation method, including Br- –MION2, it is crucial to carefully consider the molecular-level effects of humidity. By combining approaches such as the water-insensitive NO3- –MION2 with Br- –MION2, MION2 can offer more comprehensive insights into atmospheric composition than what can be achieved by either method alone. By employing instrument voltage scanning, chemical kinetic experiments, and quantum chemical calculations, we have conclusively established that the presence of iodine oxides does not interfere with the detection of HIO3. Our comprehensive analysis reveals that the ions IO3- , HIO3⚫NO3- , and HIO3⚫Br- , which are detected using the Br- and NO3- chemical ionisation methods, are primarily, if not exclusively, generated from gaseous HIO3 molecules within atmospherically relevant conditions. [ABSTRACT FROM AUTHOR]

Ozone (O3), an important and ubiquitous trace gas, protects lives from harm of solar ultraviolet (UV) radiation in the stratosphere but is toxic to living organisms in the troposphere. Additionally, tropospheric O3 is a key oxidant, and source of other oxidants (e.g, OH and NO3 radicals) for various volatile organic compounds (VOC). Recently, highly oxygenated organic molecules (HOM) were identified as a new compound group formed from oxidation of many VOC, making up a significant source of secondary organic aerosol (SOA). The pathways forming HOM from VOC involve autoxidation of peroxy radicals (RO2), formed ubiquitously in many VOC oxidation reactions. The main sink for RO2 is bimolecular reactions with other radicals, HO2, NO or other RO2, and this largely determines the structure of the end products. Organic nitrates form solely from RO2 + NO reactions while accretion products ("dimers") solely from RO2 + RO2 reactions. The RO2 + NO reaction also converts NO into NO2, making it a net source for O3 through NO2 photolysis. There is a highly nonlinear relationship between O3, NOx, and VOC. Understanding the O3 formation sensitivity to changes in VOC and NOx is crucial for making optimal mitigation policies to control O3 concentrations. However, determining the specific O3 formation regimes (either VOC-limited or NOx-limited) remains challenging in diverse environmental conditions. In this work we assessed whether HOM measurements can function as a real-time indicator for the O3 formation sensitivity based on the hypothesis that HOM compositions can describe the relative importance of NO as a terminator for RO2. Given the fast formation and short lifetimes of the low-volatile HOM (timescale of minutes), they describe the instantaneous chemical regime of the atmosphere. In this work, we conducted a series of monoterpene oxidation experiments in our chamber while varying the concentrations of NOx and VOC under different NO2 photolysis rates. We also measured the relative concentrations of HOM of different types (dimers, nitrate-containing monomers, and non-nitrate monomers) and used ratios between these to estimate the O3 formation sensitivity. We find that for this simple system, the O3 sensitivity could be described very well based on the HOM measurements. Future work will focus on determining to what extent this approach can be applied in more complex atmospheric environments. Ambient measurements of HOM have become increasingly common during the last decade, and therefore we expect that there already are a large amount groups with available data for testing this approach. [ABSTRACT FROM AUTHOR]

In the past two decades, the research on acoustic metamaterials has flourished, which is also benefited from the development of additive manufacturing technology. The exotic physical phenomena and principles exhibited by acoustic metamaterials have attracted widespread attention from academia and engineering communities, which can be applied to noise reduction and acoustic nondestructive testing in industrial; invisible cloaking and camouflage in the military; medical ultrasound imaging in national health; acoustic stealth in defense security, detection in the ocean, communication, and other fields, i.e., acoustic metamaterials have important scientific research value and broad application prospects. This review summarizes the history and research status of acoustic metamaterials, focusing on the main research progress of metamaterials in nonlinear acoustic and acoustic coatings fields, including the research on acoustic coatings with cavities of our group. Finally, the future development direction of acoustic metamaterials is prospected, and the difficulties and challenges faced by the actual engineering of acoustic metamaterials are discussed, such as difficulties in mass production, hydrostatic pressure resistant property, omnidirectional wave control, high production costs, and so on. [ABSTRACT FROM AUTHOR]

Direct determination of dissolved silicon (DSi) in atmospheric precipitation by ICP-MS is still a challenge because of the presence of serious mass interferences. In this work, a reliable method based on CH4−Ar mixed gas plasma DRC-ICP-MS was successfully used for the direct determination of DSi in atmospheric precipitation samples. The interfering ions (14N14N+, 12C16O+) were directly removed by the reaction with carbon dioxide gas and could be reduced by up to 99% at m/z 28. In addition, the sensitivity of 28Si+ was 2-fold improved by CH4 modifier that was introduced to the ICP plasma at 2 mL/min, and the background signal was decreased to 60%. Under the optimized conditions, the limit of quantification was 5 μg/L, and the reproducibility (RSD) was generally less than 3%. The proposed method was assessed using surface water standard reference materials, and the measured values agreed well with the certified values. [ABSTRACT FROM AUTHOR]

We report experiments on high-amplitude sound wave propagation in an acoustic metamaterial composed of an air-filled waveguide periodically side-loaded by holes. In addition to the linear viscothermal and radiation losses, high amplitude sound waves at the locations of the side holes introduce nonlinear losses. The latter result in an amplitude-dependent reflection, transmission, and absorption, which we experimentally characterize. First, we evidence that nonlinear losses change the nature of the device from a reflective to an absorbing one, showing the possibility to use the system as a nonlinear absorber. Second, we study the second-harmonic generation and its beating phenomenon both experimentally and analytically. We find that when considering the propagation of both the fundamental and the second harmonic, nonlinear losses cannot be neglected. Our results reveal the role of nonlinear losses in the proposed device and also provide a quite accurate analytical model to capture the effect of such losses. [ABSTRACT FROM AUTHOR]

Major ions and Sr isotope compositions of waters in the Yalong River basin in the eastern Tibetan plateau were investigated to explore the sources of dissolved loads and the controls on chemical weathering rates. Measured radiogenic 87Sr/86Sr ratios of water samples are most likely derived from the weathering of metamorphic carbonates or the Precambrian silicate rocks. Quantitative analysis of water geochemistry shows that carbonate weathering dominates the chemical characteristics of the river water. The chemical weathering rate of the whole Yalong River basin is calculated to be 7.6 ton·km−2·year−1 by silicate weathering and 44.7 ton·km−2·year−1 by carbonate weathering, which consumes 158.5 × 103 and 885.0 × 103 mol·km−2·year−1 of atmospheric CO2, respectively. The highest carbonate weathering rate (116.3 ton·km−2·year−1) in the Yalong River basins is observed from the basin with the steepest catchment average slope. This highest magnitude of carbonate weathering is comparable to the rates from catchments in the southern Himalayas. Positive relationships are observed between silicate weathering rates and both climatic (precipitation and temperature) and topographic (relief and slope) controls. The combined climatic and tectonic effects increase silicate weathering and counterbalance the dilution effect. However, the relationship between silicate weathering rate and climatic and topographic controls varies with hydrologic conditions. The rate for low‐discharge catchments is more closely related to climatic parameters, while the rate for high‐discharge catchments is more closely related to local topography. Key Points: The highest carbonate weathering rate in the Yalong River basin is similar to that of tectonic active catchments in the southern HimalayasHigh 87Sr/86Sr ratios in rivers of the eastern Tibetan plateau are discovered, which come from meta‐carbonates or the Precambrian silicatesThe sensitivities of silicate weathering rates to climatic and topographic factors are variable with different hydrologic conditions [ABSTRACT FROM AUTHOR]

We study dark solitons, namely density dips with a phase jump across the density minimum, in a one-dimensional, weakly lossy nonlinear acoustic metamaterial, composed of a waveguide featuring a periodic array of side holes. Relying on the electroacoustic analogy and the transmission line approach, we derive a lattice model which, in the continuum approximation, leads to a nonlinear, dispersive and dissipative wave equation. The latter, using the method of multiple scales, is reduced to a defocusing nonlinear Schrödinger equation, which leads to dark soliton solutions. The dissipative dynamics of these structures is studied via soliton perturbation theory. We investigate the role—and interplay between—nonlinearity, dispersion and dissipation on the soliton formation and dynamics. Our analytical predictions are corroborated by direct numerical simulations. [ABSTRACT FROM AUTHOR]

Bisphenol A, an important compound that is classified as an environmental hormone, has been proven to have harmful effects on human health and ecology. A molybdenum disulfide/Au nanorod-modified glassy carbon electrode was prepared as an electrochemical sensor for the detection of bisphenol A using a simple and convenient approach. UV-Vis spectrophotometry and transmission electron microscopy were employed to characterize the composite. The electrochemical behavior of bisphenol A at the modified electrode was investigated via differential pulse voltammetry and cyclic voltammetry. The results show that bisphenol A exhibits a good electrochemical signal at the modified electrode under optimized conditions, and a good linear relationship was observed between the bisphenol A concentration and peak current within the range of 0.01-50 μM, with a detection limit of 3.4 nM. Furthermore, the fabricated electrodes showed good anti-interference, reproducibility and stability. The proposed electrochemical method was successfully applied for the detection of bisphenol A in milk and water samples, and its potential for applications in pollutant detection was demonstrated. [ABSTRACT FROM AUTHOR]

Understanding sources of recharge and mechanisms for hydrogeochemical evolution of groundwater in the Shule River basin, an arid inland river basin in northwestern China, is essential for successful water resource management. Sources of water and associated groundwater recharge processes were investigated using hydrogeological, hydrogeochemical, and isotopic methods. The study area was divided into three parts: Changma, the Shule valley, and the Beishan area. The hydrogeochemical and isotopic analysis results show that groundwater in Changma mainly originated from precipitation in the Qilian Mountains. Lateral flow from Changma is the primary recharge mechanism, while direct recharge by infiltration of precipitation can be neglected in the Shule valley. Minerals within the aquifer material (e.g., halite, calcite, dolomite, and gypsum) dissolve into water that recharges the groundwater system. Therefore, strong linear relationships were found between Na and Cl and between Ca+Mg and SO+HCO, with stoichiometry ratios of approximately 1:1 in both cases. Groundwater quality in the region is generally good, with low salinity and hardness. Local precipitation is the only source of recharge for groundwater in the Beishan area. Low groundwater velocity and dry climatic conditions suggest that dissolution of minerals from the aquifer material controls hydrogeochemical evolution. Water rarely travels from the Beishan area to the Shule valley; therefore, almost all the groundwater in the Shule valley originates from Changma. Global climate change and loss of glaciers in the Qilian Mountains may lead to a reduction of recharge; therefore, the groundwater resources of the Shule valley must be managed to sustain water supply. [ABSTRACT FROM AUTHOR]

Mercury is subject to severe tungsten oxide (WO) interference in the direct ICP-MS analysis for soil or sediment samples. In this study, a method based on ion molecule reaction (IMR) was used to eliminate the WO spectral interference in a dynamic reaction cell (DRC). Interfered ion (202WO+) was drastically oxidized to higher oxide ions (218WO2+or 234WO3+) by O2as the reaction gas in the DRC, while the analyte ion (202Hg+) cannot react with O2. Under the optimized O2flow rate (1.9 mL min−1) and DRC rejection parameter q (Rpq, 0.80), the background signal was reduced by up to 1000-fold at m/z202 and the limit of quantitation (LOQ, 10σ) for 202Hg was 1 ng g−1. The proposed method was applied to direct determination of Hg in a series of soil and sediment standard reference materials (SRMs) and the satisfactory results indicate that it has great potential for the determination of trace or ultra-trace level mercury in various environmental or geological samples. [ABSTRACT FROM AUTHOR]

Germanium/Silicon (Ge/Si) ratio is a common proxy for primary mineral dissolution and secondary clay formation yet could be affected by hydrothermal and anthropogenic activities. To decipher the main controls of riverine Ge/Si ratios and evaluate the validity of the Ge/Si ratio as a weathering proxy in the Tibetan Plateau, a detailed study was presented on Ge/Si ratios in the Yarlung Tsangpo River, southern Tibetan Plateau. River water and hydrothermal water were collected across different climatic and tectonic zones, with altitudes ranging from 800 m to 5000 m. The correlations between TDS (total dissolved solids) and the Ge/Si ratio and Si and Ge concentrations of river water, combined with the spatial and temporal variations of the Ge/Si ratio, indicate that the contribution of hydrothermal water significantly affects the Ge/Si ratio of the Yarlung Tsangpo River water, especially in the upper and middle reaches. Based on the mass balance calculation, a significant amount of Ge (11–88%) has been lost during its transportation from hydrothermal water to the river system; these could result from the incorporation of Ge on/into clays, iron hydroxide, and sulfate mineral. In comparison, due to the hydrothermal input, the average Ge/Si ratio in the Yarlung Tsangpo River is a magnitude order higher than the majority of rivers over the world. Therefore, evaluation of the contribution of hydrothermal sources should be considered when using the Ge/Si ratio to trace silicate weathering in rivers around the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

The standard addition method (SAM) is widely used to measure the isotopic compositions of natural samples, particularly those with a complex matrix. However, traditional SAM has limitations for isotope systems with significant variations in isotope composition due to its reliance on approximation in calculation and the requirement for a priori estimates of analyte isotopic compositions and accurate concentrations. To overcome the issues, our work proposes an improved SAM that explicitly calculates isotope ratio R (i.e., X E/ Y E, 34 S/ 32 S for example) instead of approximating R * (mass number of isotope X divided by total mass number of all isotopes of an element) with R in SAM. Additionally, the sample fraction within standard-sample mixture in improved SAM is determined using the isotope compositions of standards, sample-standard mixtures, and the mixtures of both standards, rather than relying on sample concentrations and volumes. Both improvements not only overcome the shortcomings of traditional SAM but also empowered the approach's ability to accurately determine sample concentrations. To validate its effectiveness, we applied the improved SAM to natural samples with substantial sulfur (S) isotope variation (1.94 to 27.19‰) and low S concentration (0.81 to 3.47 μg g -1 ). The calculated δ 34 S values and concentrations of these samples are consistent with direct measurements within the error ranges while reducing sample sizes to 20% of those required for direct measurement. Moreover, our method achieves higher accuracy in δ 34 S values compared with traditional SAM. Both comparisons affirm the reliability and superiority of improved SAM.