Lithium isotopic composition of the carbonate type salt lake in Tibet and its implication for origin and hydrological processes

The implementation of the carbon peaking and carbon neutrality strategy has led to a steady increase in the supply of lithium resources. Brine is one of the important sources of lithium, and the extraction of Li from carbonate-type brine is particularly straightforward. Research into the source of materials and hydrological processes of brine is crucial for the sustainable development of lithium in carbonate-type brine. As a fluid-mobile and metallogenic element, lithium has a significant mass difference between its stable isotopes (7Li and 6Li), leading to isotopic fractionation. In this study, we analyzed the hydrochemistry and Li isotope compositions of samples collected from a Li-rich salt lake (Bangor Co) in the Qinghai-Tibetan Plateau. The samples included lake brines, recharge rivers, cold springs, and salt minerals (hydromagnesites). The Li content in the various types of water varied significantly, ranging from 0.06 mg/L to 198.10 mg/L, showing a variation of 4 orders of magnitude. Water samples exhibit a wide range of delta 7Li values, varying from 4.89 parts per thousand to 16.02 parts per thousand. Notably, the lowest and highest values are observed in cold springs. Additionally, the concentrations and delta 7Li values in hydromagnesite differ across various relative ages. The hydrochemistry indicated that the recharge water is influenced by rock weathering, but the lake brine is influenced by evaporation concentration. The analysis of trace elements and Li isotopic data reveals that rock weathering, geothermal systems, salt minerals, and freshwater, primarily from early geothermal activities and the redissolution of carbonate minerals, contribute to the Li in salt lake brine. Boron isotopes and lithium isotopes of lake brines are found to vary differently. The delta 7Li in brine is increased significantly by adsorption of hydromagnesite. And 11B gradually accumulates in hydromagnesite. This study has demonstrated that hydromagnesite plays a crucial role in influencing the characteristics of Li in brine

Plant litter decomposition is regulated by its phosphorus content in the short term and soil enzymes in the long term

Plant litter decomposition plays a vital role in soil carbon (C) cycling and nutrient release, significantly influencing agricultural resource utilization and soil fertility management. Litter quality-defined by its C, nitrogen (N), and phosphorus (P) contents, as well as C:N:P stoichiometry-is a key factor regulating its decomposition. However, the influence of litter C:P ratios on plant litter decomposition, particularly in relation to changes in soil C:N:P stoichiometry, microbial biomass, and extracellular enzyme activities, remains unclear, especially in agroecosystems. In this study, the effects of litter C:P ratios on its decomposition were investigated using C-13-labeled plant litter with naturally occurring gradients of C:P ratios (ranging from 377 to 1,288) in an 84-day incubation experiment. After 84 days, cumulative (CO2)-C-13 emissions derived from litter accounted for approximately 50 % of total CO2 emissions. Litter with higher P content increased (CO2)-C-13 emissions, whereas higher litter C:P ratios suppressed emissions, indicating that litter with lower C:P ratios decomposed more rapidly in the short-term (14 days). In contrast, elevated soil exoenzymatic C:P and N:P ratios stimulated (CO2)-C-13 emissions during long-term decomposition (84 days). These findings suggest that litter P content primarily regulates short-term decomposition, while soil enzyme activity plays a key role in long-term decomposition. Overall, this study highlights the pivotal role of P limitation in litter decomposition, particularly in the early stages, and underscores the potential benefits of P fertilization in enhancing decomposition rates, thereby improving resource efficiency and soil fertility in agroecosystems

Determination of low-level 90Sr in large volumes of seawater

The release of radioactive substances into the environment, particularly the discharge of contaminated water from the Fukushima Daiichi Nuclear Power Plant, has raised public concern. 90Sr, a highly hazardous radionuclide, remains a significant challenge for accurate determination in environmental seawater due to its low concentration. In this work, an effective co-precipitation of 90Sr with SrCO3 and CaCO3 was established for preconcentration of 90Sr from a large volume of seawater up to 45 L by using an appropriate concentration of (NH4)2CO3 instead of Na2CO3 followed by removal of calcium by hydroxide precipitation. A chemical yield of (88 +/- 2)% was achieved for strontium from 45 L of seawater, and the decontamination factors for most radionuclides were higher than 104. The 90Y ingrown from 90Sr decay was used for the determination of 90Sr, and sulfate precipitation was employed to remove radionuclides of Sr, Ba, Ra, and Pb, and the Y was further purified by hydroxide precipitation. The chemical yield of Y was higher than 90% in this step, and the counting efficiency of 90Y by liquid scintillation counting reached 100%. The detection limit for 90Sr was estimated at 0.11 mBq/L for 45 L seawater, an order of magnitude lower than surface seawater levels without direct human nuclear contamination. The method was validated by the standard addition method and successfully applied to determine 90Sr in seawater collected from China seas. The developed method is simple and cost-effective compared to the reported methods and robust for routine analysis of seawater for 90Sr

Vegetation-Driven Spatial Heterogeneity of Land Surface Temperature Changes on the Chinese Loess Plateau

A comprehensive understanding of the processes and mechanisms driving Holocene temperature changes is crucial for resolving the ongoing Holocene temperature controversy. Here, we reconstructed land surface temperature (LST) variations over the past 27,000 years in two loess-paleosol profiles from the Chinese Loess Plateau based on soil bacterial lipid signatures. By combining our data with other published records derived from the same proxy, we identify notable spatial inconsistencies in LST trends across geographically proximate areas with distinct vegetation cover, despite the expectation that air temperature trends should be consistent. By integrating modern meteorological data, we propose that rainfall-induced changes in surface vegetation dynamics are a key factor contributing to this divergence. This contributes to our understanding of past climate dynamics in East Asia and underscores the importance of considering vegetation effects when interpreting paleoclimate data and resolving controversies over Holocene temperature trends

Distinct Assembly Patterns of Soil Bacterial and Fungal Communities along Altitudinal Gradients in the Loess Plateau's Highest Mountain

A critical issue in microbial ecology is quantifying the relative contributions of deterministic and stochastic processes to microbial community assembly, and predicting ecosystem function by understanding the ecological processes of community composition is an integral part. However, the mechanisms driving microbial community assembly along altitudinal gradients in mountain ecosystems remain largely unexplored. Here, we used high-throughput sequencing to examine the structural characteristics and diversity maintenance mechanisms of soil bacterial and fungal communities along an altitudinal gradient (2632-3661 m) in Mahan Mountain, the highest peak of the Loess Plateau. Proteobacteria, Acidobacteriota and Actinobacteriota dominated the bacterial communities, while Ascomycota, Basidiomycota and Mortierellomycota were the predominant fungal groups. Although elevation did not significantly affect bacterial and fungal alpha diversity, notable shifts in community structure were observed along the altitudinal gradients. Bacterial communities were predominantly shaped by deterministic processes, leading to pronounced structural and compositional differentiation across altitudes. In contrast, fungal community assembly was primarily determined by a combination of deterministic and stochastic processes, leading to small pronounced structural divergence. The interplay of topography, climate, and soil conditions influenced the altitudinal distribution and community structure of soil bacteria in this mountain ecosystem

Health risk assessment of source-specific elemental carbon (using dual carbon isotopes) and heavy metals in the Tibetan Plateau

We assessed the health risks associated with atmospheric heavy metals (HMs: Mn, Zn, Co, Cu, V, Ni, and metalloid As) and elemental carbon (EC) at three sampling sites across the Tibetan Plateau (TP). The highest annual concentrations of HMs (80.7 ng m-3) were observed in the northeastern TP (Qinghai Lake), while the highest annual concentration of EC (1.9 mu g m-3) was found in the southwestern TP (Ngari). Mn and As were major contributors to the Hazard Quotient (HQ) and the incremental lifetime cancer risk (ILCR). Peak HQ and ILCR values were observed during the winter seasons. The HI (Hazard Index) of HMs for children exceeded safety thresholds. Health risk assessments for EC indicated no significant non-carcinogenic risk (non-CR) but significant carcinogenic risk (CR) effects in the TP. Higher risks of HMs were found during the dust-rich period (DRP) compared to the normal period (NOP), while EC posed lower health risks during the DRP. Based on dual carbon isotope analyses, the source-specific contributions of EC to health risks were attributed to biomass burning (30.4 %), coal combustion (28.7 %), and liquid fossil fuel combustion (41.0 %), respectively. These findings improved our understanding of the health effects associated with dust exposure and the source-specific health risks of EC in the remote areas

A synthesis on the spatial patterns and driving factors of water-holding capacity of forest litter layer across China

Forest litter layers play a crucial role in regulating hydrological processes and conserving ecosystem water, yet their spatial patterns and key drivers at regional scales remain unclear. By analyzing data from 1062 sampling sites across China using machine learning, we identified the distribution and controlling factors of forest litter mass, litter water-holding rate (LWHR), and litter water-holding amount (LWHA). Our findings reveal that (1) the mean storage of undecomposed and semi-decomposed litter was 6.2 and 10.3 t ha- 1, respectively, with a mean LWHR of 247.8 % and LWHA of 34.3 t ha- 1; (2) LWHR varied significantly among forest types, being highest in deciduous forests (285.7 %) and lowest in evergreen needleleaf forests (223.5 %); (3) LWHA was greatest in deciduous needleleaf forests (59.7 t ha- 1) and lowest in bamboo forests (17.4 t ha- 1); (4) both LWHR and LWHA decreased with latitude, indicating regional differences in litter water retention; and (5) climate and topography were the primary drivers of litter water-holding capacity, influencing litter production, accumulation, and decomposition. Our findings provide a scientific basis for forest management strategies aimed at enhancing water conservation, particularly in regions vulnerable to climate change and water shortages. The results also offer a reference for global forest ecosystems, highlighting the importance of litter layers in sustaining water resources and informing policy decisions on forest conservation and watershed management

Source-Specific Mass Absorption Efficiencies of Char-EC and Soot-EC Improve Accuracy in Black Carbon Radiative Effect Estimation

Optical properties of elemental carbon (EC) are critical for climate modeling due to its strong light absorption. Elemental carbon consists of char-EC and soot-EC, which differ in mass absorption efficiency (MAE). However, the MAEs of these forms remain underexplored primarily due to the limited methods available for measurement, limiting the accuracy of EC climate impact assessments and leading distortions of EC radiative effect in the temporal and spatial distribution. In this study, we derived MAEs for char-EC and soot-EC using combined modeling methods based on observational data, revealing key differences. Soot-EC generally has higher MAEs than char-EC, except from biomass burning. Meteorological factors, such as relative humidity, also influence the MAEs of char-EC and soot-EC differently. The differences in sources and aging process lead to changes in the mass concentration and MAE of char-EC and soot-EC over time. Ignoring these differences can lead to discrepancies in the radiative effect from -9.1% to 18.7%. This study underscores the importance of considering the char-EC and soot-EC in accurate EC radiative effect estimates, and implies that optimizing the management of different black carbon emission sources would mitigate global warming to varying extents due to the divergence of the char/soot emission ratio and their MAE

Towards an understanding of dynamics of blue-ice moraines: A case study in the Grove Mountains, East Antarctica

Knowledge regarding former behavior of the East Antarctic Ice Sheet (EAIS) is crucial for assessing global sealevel change and understanding the global climate system. Yet, it remains challenging to examine pre-Last Glacial Maximum (LGM) glacial histories of the EAIS due to the limitations of the traditional geologic records. Recent studies suggest that blue ice areas (BIAs) and associated deposits (e.g. supraglacial moraines) have a potential to overcome this problem. However, the relationship between blue-ice evolution and climate changes is not yet well examined. In this study, we investigate two types of BIAs in the Grove Mountains, EAIS, on the basis of surface exposure dating of erratic boulders and cobbles on blue-ice moraines at Mount Harding and Escarpment. Here, we present 27 new ages, including single (10Be; n = 10) and paired (10Be and 26Al, n = 17) exposure-ages. The newly-obtained ages, along with previously-published 10Be data (n = 40), indicate that the studied BIAs have been relatively stagnant since the LGM, and that blue-ice moraines formed in a closed system are much older than those built in the absence of a barrier. Also, the compilation implies multiple phases of preLGM ice flow that corresponded to global cold periods. We suggest that there was likely a response of blue-ice evolution to Antarctic glaciations on orbital timescales